Surface finishing of complex geometries through conductive solid bodies under vibration

Abstract

A system and method for surface finishing, comprising a container including at least one electrically conductive device, acting as a first electrode, at least partially arranged inside the container; an electric source providing an electric potential difference between the at least one surface to be treated, at least partially arranged within the container and acting as a second electrode, and the at least one electrically conductive device; the two electrodes connected through a solid-particle based electrolyte that enables ion exchange between the at least one surface to be treated and the a solid-particle based electrolyte when current is applied; and at least one device adapted with means for generating vibrations, and thereby inducing a relative motion between the solid-particle based electrolyte and the at least one surface to be treated.

Description

[0001] SURFACE FINISHING OF COMPLEX GEOMETRIES THROUGH CONDUCTIVE SOLID BODIES UNDER VIBRATION

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to the field of surface finishing. More particularly, the disclosure relates to homogeneous surface finishing of parts with different sizes and complex shapes, such as concavities or inner channels.

[0004] BACKGROUND

[0005] In the field of surface finishing, achieving a uniform, high-quality finish on parts of varying shapes and sizes presents a significant challenge. Surface finishing processes, such as polishing, are commonly used to improve the aesthetics, functionality, and durability of parts by creating smooth, defect-free surfaces. However, the diversity in geometries, contours, and dimensions of the parts being treated makes it difficult to utilize a single, flexible polishing system that can provide homogeneous results across different applications.

[0006] Traditional liquid electropolishing techniques that employ ultrasonic vibrations to generate cavitation have long been used to eliminate oxides and salts during surface treatment processes. These methods create cavitation through liquid agitation, which has historically presented challenges in achieving uniform polishing, particularly in complex geometries or hard to reach areas. The collapse of microbubbles in cavitation, while essential to traditional ultrasonic electropolishing, often struggles to create sufficient impact on the surface to be polished, especially in hard-to-reach areas or intricate geometries. Due to the small scale of these effects, the energy generated by microbubble implosions may not be effectively transferred to the workpiece surface, limiting the uniformity of material removal.

[0007] Traditional polishing methods often require specialized equipment, tools, or configurations for each type of part or application. For example, complex or irregular surfaces may demand custom tooling, while larger or smaller parts might need different polishing media, techniques, or machines. This lack of versatility complicates the finishing process and increases production time and cost, as operators need to adjust or replace equipment for different tasks. Additionally, inconsistent surface finishes may result when the polishing system is not adequately adapted to the specific shape or size of the part, leading to quality issues such as uneven gloss, texture variations, or defects like scratches. Traditional solid-particle based electropolishing methods, which use electrically conductive solid bodies, have proven effective in achieving good surface finishes and homogeneity. However, these methods face significant limitations, particularly when addressing concavities or inner channels, where the solid electrolyte’s limited mobility and lack of aerodynamic control present major challenges. This limitation is especially pronounced with large, irregularly and complex shaped parts. The inability of these methods to conform to complex surface results in suboptimal finishes in areas that require precise treatment, such as narrow spaces or recessed regions.

[0008] Given these shortcomings, there is an urgent need for a surface finishing system capable of overcoming these challenges by ensuring that solid-particle based electrolytes can efficiently reach and operate within complex geometries, regardless of their size or shape. Such a system should address the aerodynamic and mobility limitations of current technologies, particularly in difficult-to-reach areas like concavities and internal channels, where traditional methods fall short. By developing a more flexible and dynamic approach to the handling of solid-particle based electrolytes, this innovation would provide consistent, high-quality results across diverse applications, offering a reliable solution for manufacturers working with large, irregular components.

[0009] In conventional electrochemical processes, vibration and ultrasonic vibrations have been employed to enhance surface finishing by mitigating issues like cavitation, which can otherwise lead to surface damage. These techniques leverage ultrasonic cavitation to improve surface roughness and mechanical properties, as seen in hybrid methods that combine electrochemical polishing with ultrasonic cavitation.

[0010] There is a need for surface finishing that is potentially uniform and effective. There is also a need for surface finishing that may be used in challenging geometries.

[0011] SUMMARY

[0012] The present invention tackles this critical need by providing systems and methods and specifically designed to ensure uniform and effective surface finishing, even, but not necessarily, in challenging geometries. This system delivers superior results by addressing the limitations posed by current methods, particularly in terms of electrolyte mobility and adaptability to complex shapes, enhancing efficiency, reducing costs, and ensuring high- quality finishes across a broad range of parts.

[0013] The present invention provides methods and systems for surface finishing that utilizes free electrically conductive solid bodies in an electrolytic medium, combined with controlled vibrations, including ultrasonic vibrations at different amplitudes, to achieve a uniform, high-quality surface finish. This invention addresses the need for flexible surface finishing methods and systems capable of adapting to various part shapes and sizes, offering consistent results even on intricate geometries, such as concave surfaces or inner channels.

[0014] One aspect of the present invention refers to a method for finishing a surface comprising: arranging a solid-particle based electrolyte inside of a container; immersing within said electrolyte at least part of an electrically conductive device and at least part of a surface to be treated; applying an electrical potential difference between said electrically conductive device, and a surface to be treated, by connecting them to an electric source, generating an ion transport between the surface to be treated and said solid-particle based electrolyte when current is applied; providing at least a vibration, and thereby inducing a relative motion between the solid-particle based electrolyte and the at least one surface to be treated.

[0015] In another aspect, the invention provides a system for performing surface finishing, the system comprising a container being an structural enclosure defining a treatment chamber in which a solid-particle-based electrolyte is contained; an electrically conductive device arranged within the treatment chamber; a workpiece support structure adapted to position a workpiece such that at least a portion of its surface is exposed to the solid- particle-based electrolyte; and an electric source configured to supply a potential difference between the electrically conductive device and the workpiece surface to enable electrochemical interaction with the electrolyte. The system further comprises a vibration source or vibration apparatus, including components operatively coupled to the enclosure, to the electrolyte, or to the workpiece support, the vibration source being configured to deliver controlled vibratory energy to modulate the mechanical interaction and ion transport occurring within the solid-particle-based electrolyte during the finishing process.

[0016] In a further aspect, the present invention provides an system for finishing a surface, comprising a container adapted to hold a solid-particle-based electrolyte; at least one electrically conductive device positioned such that a portion of the device is arranged within the solid-particle-based electrolyte; and a workpiece having at least one surface to be treated, arranged so that at least a portion of said surface is immersed within the solid- particle-based electrolyte. The system further includes an electric source operatively connected to the electrically conductive device and to the workpiece surface, the electric source being configured to establish an electrical potential difference that enables ion transport between the solid-particle-based electrolyte and the surface to be treated. The system additionally comprises at least one vibration source or vibration apparatus configured to apply vibrational energy to induce relative motion between the solid-particle- based electrolyte and the surface to be treated, thereby enhancing the effectiveness of the surface finishing operation.

[0017] A solid-particle based electrolyte according to the present invention refers to an electrolyte including solid particles retaining a liquid electrolyte making them electrically conductive, referencing certain aspects of the International Application No. PCT / ES2017 / 070247 (published as WO 2017 / 186992 A1). The environment allocated on an interstitial space between the solid bodies can include either a conductive and a non- conductive fluid, miscible or immiscible in the conductive solution retained by the solid bodies, or any possible combination of said mentioned aspects, as mentioned on the previously referenced application, and in combination to aspects referenced on the International Application No. PCT / ES2021 / 070864 (published as WO 2022 / 123096 A1). In further embodiments, a solid-particle-based electrolyte may be contained in or combined with a moderative medium, in particular a moderative fluid, more in particular a moderative liquid. In the present invention a moderative medium present on the interstitial space between the solid bodies is to be understood as any fluid, either gas, liquid, superfluid or any other possible fluid presenting a lower electrical conductivity of that presented by the electrically conductive solid particles.

[0018] This invention is particularly suited for applications requiring the finishing of complex internal geometries, such as conical or tubular parts used in the pharmaceutical industry and extends to complex shapes like those found in internal barrels, where controlled vibrational patterns can precisely polish interior surfaces.

[0019] Other potential use includes large or high-value-added parts that require precision polishing and products requiring a mirror-like polishing with high uniformity, enhancing its appeal for luxury products, custom manufacturing and urban furniture. The system's versatility makes it ideal for large pieces, where achieving a consistent high-gloss finish across expansive surfaces or within intricate zones is essential. This method is best suited for industries where mass production is not a priority, focusing instead on high-precision or custom applications that necessitate stable processing conditions for optimal results.

[0020] The present invention relates to surface finishing of conductive materials, in particular to metallic materials. More in particular the present invention encompasses the polishing of metallic alloys, such as Steels, Stainless steels, High carbon steels, Cast Iron, Inconel Alloys, Cobalt chrome, cupper alloys, brass, aluminum alloys, metal matrix composites, tungsten carbides, etc. This method is also beneficial for achieving a high gloss on large surfaces or in otherwise inaccessible zones, further expanding its market to include industries dealing with intricate or delicate pieces, like high-precision machining or custom manufacturing.

[0021] The surface finishing process in this invention can modify surface characteristics like roughness, gloss, waviness, and the presence of oxides or contaminants. These modifications may involve smoothing, polishing, precision finishing, deburring, corrosion protection, or altering surface chemistry and morphology. Additionally, the process can relieve residual stress, provide passivation, or enhance corrosion resistance.

[0022] A feature of the invention is the introduction of vibration to delocalize and enhance the mobility of the solid bodies, allowing them to frictionally engage with the surface being treated. The vibrations ensure that the conductive particles are uniformly distributed and in continuous relative motion, providing better contact and polishing efficiency, particularly in challenging areas. This vibration-based method, by controlling the movement, packing factor, and viscosity of the solid bodies, ensures that they reach all parts of the surface, delivering a homogeneous finish even on complex and irregular geometries that has been not reached using conventional processes.

[0023] The application of vibrations, facilitates a uniform adaptation of the polishing process across various surfaces. The vibrations prevent the solid bodies from forming static clusters while maintaining effective electrical bridges between the cathode and anode, generating defects or uneven surface finishing results over the surface. Different configurations of vibration power and the ratio of electrically conductive solid bodies to a non-conductive medium, moderative fluid or liquid moderative medium present on the environment of the interstitial space between the free electrically conductive solid bodies ensure optimal polishing conditions. The vibration power, amplitude and frequency required to foment a successful result will depend on the packing force or pressure of the solid particles, as well as their particle size and size distribution.

[0024] In several embodiments, a system according to the present invention includes a container that houses both the electrolytic medium and at least one electrically conductive device, with an electric potential applied between the device and the part being polished. Vibrational energy enhances the movement of the solid bodies, ensuring thorough and even surface treatment. This combination of electrical potential and vibration provides a highly adaptable system that can easily be adjusted to accommodate different part geometries by modifying the vibration parameters, making the process efficient, versatile, and capable of delivering superior results.

[0025] A vibration source or an apparatus for providing vibrations and generating relative motion between the free electrically conductive solid bodies within a fluid, which serves as an electrolyte, comprises, in certain embodiments, a vibration-inducing device, whereas in other embodiments other devices are employed. Examples include vibratory motors that generate oscillations through eccentric rotating masses, electromechanical or electromagnetic vibrators configured to deliver controlled linear or radial vibration, and vibration tables or platforms capable of transmitting uniform vibratory energy to the entire container. Alternative vibration sources may further include piezoelectric transducers, magneto-strictive elements, or other electromechanical actuators configured to impart controlled oscillatory motion to the container, the solid-particle-based electrolyte, or the medium itself. The generated vibrations can be applied directly to the solid bodies, to the moderative medium in which they are suspended, to the part being polished, or to various points within the processing receptacle, depending on the specific polishing or cleaning requirements. In several embodiments, where the vibration source has positioned at the bottom of the receptacle, results on an efficient vibration transmission to the surface of the part. However, other configurations are also possible to optimize cavitation effects, such as placing the vibration source on the part holder, on the receptacle sidewalls, or in a combination of bottom and side positions. This flexibility enables precise control over the frictional interaction between the solid bodies and the surface, enhancing their adaptability to complex geometries. By fine-tuning the amplitude and frequency of the vibrations, the system adjusts the mobility and packing density of the solid bodies, ensuring thorough and uniform coverage across the surface. This approach yields consistent, high-quality polishing results, particularly in hard-to-reach areas like concave surfaces or inner channels, where traditional methods often fall short.

[0026] When the vibration source is placed at greater depth from the surface of the electrolyte tank, in some embodiments it is necessary to increase the amplitude of the vibrations. This is because, the vibration waves must travel a greater distance through the electrolyte to transfer sufficient energy. Higher amplitude vibrations allow the energy to propagate more effectively.

[0027] On the other hand, when the vibration system is closer to the surface, in particular embodiments, there is no need to use such large amplitudes. In these cases, lower amplitude vibrations are sufficient to induce cavitation on the surface of the part without having to cover large distances and face high compression environments. The frequency of the vibrations is adjusted based on the depth of the vibration system's location within the electrolyte to ensure effective action across the entire surface to be treated.

[0028] This invention significantly improves upon traditional surface finishing methods by offering a flexible, efficient solution for achieving mirror-like finishes on a wide range of parts, regardless of their shape or size, while ensuring uniformity and high-quality results. An aspect of the present invention relates to a surface finishing method and system capable of a wide range of surface modifications, such as smoothing, polishing, precision finishing, deburring, rounding, and removing oxides or contaminants. The method allows for various enhancements, including improvements in surface roughness, gloss, tension, and residual stresses, while also offering corrosion resistance, surface passivation, and chemical or morphological changes. The invention applies to a wide variety of surfaces, including those made from materials such as steel, stainless steel, copper, titanium, nickel, and aluminum alloys.

[0029] A system and / or method according to some embodiments are / is configured to use free electrically conductive solid bodies suspended in an electrolytic medium, which are moved, by controlled vibrations, across the surface to be treated. These conductive particles, in several embodiments, are made from materials like polymeric ion-exchange resins or other conductive substances that retain the electrolytic solution, enabling ionic exchange reactions with the metal surface. The vibrations ensure efficient contact between the conductive particles and the surface, facilitating a homogeneous surface finish even on complex or large parts.

[0030] In some embodiments, the liquid retained by the solid particles is electrolytic, and its conductivity can be enhanced with acids or other agents, although the invention also allows for reduced-acid or acid-free configurations, reference made on the International Application No. PCT / ES2022 / 070649 (published as WO 2023 / 067214 A1), where acid-free configuration using electrically conductive solid bodies are used for polishing composite materials. This reduces environmental hazards typical of acid-based surface finishing, making the process safer and more suitable for facilities that do not handle acids. The fluid’s composition can be adjusted to include lubricating solids, which modify viscosity and provide additional control over the electropolishing process. In other embodiments, the fluid may also consist of a gas, offering further flexibility in medium selection.

[0031] The term "free electrically conductive solid bodies" refers to electrically conductive particles that may be made from materials capable of retaining liquid, such as polymers, minerals, ceramics, organic compounds, or even plant-derived materials, with a preference for polymeric substances. In particular, ion-exchange resins that hold electrolytic solutions are used to facilitate ionic exchange reactions with metallic surfaces.

[0032] The invention also contemplates the use of free conductive solid bodies in various forms, such as microporous or gel-like structures, which enhance fluid exchange and provide precise surface treatment. These particles may contain functional groups, such as acidic or chelating groups, allowing for specific interaction with metal ions during polishing. In some particular embodiments, the solid bodies comprise an ion exchange resin, which can be cationic or anionic, strong or weak, depending on the application. The system supports different electrolytes, including aqueous solutions of sulfuric acid, sulfonic acids, such as methanesulfonic acid (MSA), phosphoric acids, ionic liquids, deep eutectic solvents, inorganic or organic salt solutions or other electropolishing agents, giving the user flexibility in choosing from any preexisting liquid electrolyte.

[0033] The conductive particles themselves may be made from materials like acidic cationic resins, anion exchange resins, or chelating resins that facilitate metal ion exchange. In particular, sulfonated divinylbenzene (S-DVB) styrene copolymers and other similar materials may be used for their resistance to acids and oxidative processes. These particles can also feature functional groups like sulfonic or carboxylic groups for metal ion retention, or chelating groups for selective interaction with transition metals.

[0034] Conductive particles may have various shapes, including spherical, rhomboidal, pyramidal, or cylindrical, and may encapsulate electrolytes such as aqueous solutions of acids like hydrofluoric, sulfuric, methanesulfonic, phosphoric, or citric acids. In some embodiments, these particles contain different electrolytes in concentrations ranging from 0.1% to 70% by weight, depending on the specific surface finishing requirements. The porous or gel-like structures of these particles enhance fluid exchange and surface contact, leading to improved control over surface roughness and other finishing parameters.

[0035] In various possible embodiments of the invention, the movement, viscosity, and packing factor of the solid bodies are controlled by applying vibrations to different components of the system.

[0036] The packing factor represents a feature of the electrolyte which influences the efficiency of the process. It affects the interaction between the solid bodies and the liquid medium. In this context, a solid-to-liquid phase ratio in volume used in an electrolyte is 7:5 of electrically conductive solid bodies to moderative medium present on its environment, particularly presenting a supernatant layer when a non-conductive liquid is used. This ratio is important for achieving the desired packing density, ensuring that the vibrational energy and cavitation effects are distributed effectively across the electrolyte. In several particular embodiments of the invention a ratio between the volume of the solid bodies and a moderation fluid present on its environment comprises ratios from 10:1 to 1 :10, in particular from 2:1 to 1 :5, and more in particular from 1 :1 to 1 :2.

[0037] Vibrations are closely related to the viscosity of the electrolytic medium, as the viscosity determines the flow resistance and the propagation of vibrational waves through the fluid. In highly viscous moderative fluids, the movement of the solid bodies and the cavitation effects generated by the vibrations are less efficient, as the fluid resists shear forces more strongly. However, the viscosity can be optimized to create a synergetic effect, especially when working with non-Newtonian fluids comprised in the moderative medium. These fluids, whose viscosity changes under stress and / or, can enhance the cavitation process when subjected to controlled vibrations, as their response to shear forces can be tailored for specific polishing or cleaning effects. In particular embodiments of the invention a moderative medium on the interstitial space of the solid bodies presents a viscosity ranging from 0.5 to 10000 mPa-s at 25 °C, in particular from 1 to 2000 mPa-s at 25 °C, more in particular from 10 to 100 mPa s at 25 °C.

[0038] Some examples of elements comprised on a moderation fluid according to the present invention includes water, oils, aliphatic hydrocarbon chains from 5C to 25C, Polyethylenic, glycerol, fatty acids, isopropanol, among others. The present invention also allows for mixtures between the elements listed before and others possible elements, such as fatty alcohols and surfactants, creating an emulsion and modifying the resulting properties.

[0039] Properties of each non-Newtonian liquids present on the electrolytes environment, such as shear-thinning or shear-thickening behaviors, can act as either dampers or resonators in the system. Depending on the fluid's response, it can either amplify or reduce the vibrational energy, influencing the effectiveness of the polishing process.

[0040] In some embodiments, the moderative medium present within the solid-particle- based electrolyte may exhibit non-Newtonian behavior, allowing its viscosity and flow properties to vary as a function of the applied shear rate or vibrational energy. By selecting or formulating such a medium, the transmission and dissipation of vibrational energy through the electrolyte can be dynamically adjusted during operation, thereby influencing both the mechanical and electrochemical interactions between the particles and the surface being treated. The non-Newtonian character of the moderative medium thus provides an additional parameter for controlling the polishing or surface finishing process.

[0041] Non-Newtonian behaviors suitable for use in the present invention may include shear-thinning (pseudoplastic), shear-thickening (dilatant), thixotropic, or rheopectic characteristics, among others. A shear-thinning medium, such as one based on polymeric gels, aqueous suspensions of carboxymethyl cellulose, or certain silicone-based fluids, may reduce its viscosity under vibration or shear, facilitating deeper penetration of the electrolyte and improved wetting of intricate geometries, inner cavities, or small-diameter channels. In contrast, a shear-thickening or dilatant medium, such as those containing dispersed colloidal silica, cornstarch suspensions, or other particulate-polymer systems, can increase its viscosity under higher vibration amplitudes, enhancing the transmission of mechanical energy and providing localized polishing intensity where stronger agitation is beneficial. In further embodiments, thixotropic or rheopectic moderative media may be employed to achieve time-dependent viscosity control, allowing gradual adaptation of the medium’s rheological state to the process dynamics. Thixotropic materials, which temporarily decrease in viscosity under prolonged vibration, can enhance electrochemical uniformity by maintaining consistent particle dispersion during extended treatment cycles. Conversely, rheopectic materials that increase in viscosity over time may be used to stabilize the polishing medium once optimal fluid distribution has been achieved. The selection and tuning of the non-Newtonian properties, through composition, particle concentration, or polymer chain structure, can thus be tailored to optimize both the vibrational energy transfer and the electrochemical effectiveness of the surface treatment, particularly when processing complex geometries or components with internal cavities.

[0042] In particular embodiments the moderation fluid, e.g., used in the system or in the method, may be at least partially comprised within the conductive solid bodies and can act at some point as an electrolytic medium.

[0043] To optimize the electropolishing process, the fluid’s viscosity and aerodynamics are engineered to ensure effective movement and recirculation within the container, aiding in cooling the conductive particles. The fluid may also contain lubricating solids to further adjust viscosity and improve process control. This enhances the electrical conductivity of the system, accelerating the surface finishing process by increasing the frequency of electrical bridges between the conductive ends of the system, leading to reduced finishing times while maintaining precision.

[0044] The interstitial gaps between the solid particles may be filled with non-conductive fluids such as hydrocarbons, mineral oils, or silicone oils, depending on the application. Other additives like surfactants, abrasive particles, or moderator particles may be incorporated to reduce surface tension, aid material removal, or prevent excessive wear during polishing. Additional interstitial components might include substances like fatty acids, glycols, sulfoxides, sulfonic surfactants, ethoxylated alcohols or deep eutectic solvents to further enhance the functionality of the system.

[0045] Elastic elements, such as elastic particles capable of transmitting, or absorbing, vibrations, are included to modulate the vibrational energy within the polishing medium, and in some embodiments, a set of electrically conductive free solid bodies possess these elastic characteristics, enhancing the adaptability and control of the vibrational effects in the polishing process. In some cases, these elastic elements or elastic particles are the same electrically conductive solid bodies of the solid-particle based electrolyte.

[0046] In certain embodiments, the elastic elements incorporated within the polishing medium may be formed from polymeric materials or composites that exhibit high resilience and reversible deformation under mechanical stress. Suitable examples include silicone rubber, polyurethane elastomers, natural or synthetic rubber, thermoplastic elastomers (TPE), and cross-linked polyethylene. These materials are capable of effectively transmitting and modulating vibrational energy, enabling controlled deformation and energy return during each vibration cycle. When used as part of the solid-particle-based electrolyte or as discrete elastic inclusions, such materials can improve the adaptability of the medium to surface irregularities and enhance the uniformity of the polishing action by distributing mechanical forces more evenly.

[0047] In addition to the elastic elements, the system may also incorporate materials or structures designed primarily for damping, that is, for dissipating mechanical energy and reducing excessive vibrational amplitudes. The inclusion of damping elements can serve to stabilize the dynamic behavior of the polishing medium, preventing resonance effects or uncontrolled particle agitation that could otherwise lead to surface defects or non-uniform finishing. These damping components may be interspersed among the solid-particle electrolyte or embedded within the container or support structure to regulate the transmission of vibratory energy throughout the system.

[0048] Examples of suitable polymeric materials for damping elements include viscoelastic compounds and high-loss polymers such as polyvinyl chloride (PVC), ethylene-vinyl acetate (EVA), nitrile rubber (NBR), butyl rubber (HR), and certain modified polyolefins or composite formulations incorporating internal damping additives. These materials are characterized by their ability to convert part of the vibrational energy into heat through internal friction, thereby attenuating vibration amplitudes and providing a more stable and controlled polishing environment. The use of such damping materials is particularly advantageous in applications involving delicate, thin-walled, or high-precision components, where excessive vibration could compromise dimensional accuracy or surface integrity.

[0049] In the context of the present invention, whether an element behaves predominantly as an elastic component or as a damping component is determined by its dynamic mechanical properties, particularly its storage modulus (E'), which quantifies elastic energy storage, and its / oss modulus (E") or / oss factor (tan 5 = E7E'), which quantifies energy dissipation. Materials having a low loss factor, typically tan 5 < 0.1 , behave substantially as elastic elements capable of storing and returning vibrational energy with minimal internal dissipation. Conversely, materials having a higher loss factor, typically tan 5 > 0.3, function predominantly as damping elements that absorb and dissipate mechanical energy through viscoelastic losses. Intermediate values (tan 5 between 0.1 and 0.3) may provide a mixed or tunable elastic-damping response depending on operating frequency and deformation amplitude. In certain embodiments, the selection of an elastic or damping element is determined by specifying a target range of storage modulus E', for example between 0.5 MPa and 20 MPa for highly compliant elastic inclusions, or a target range of loss modulus E", for example between 0.1 MPa and 10 MPa for damping inclusions intended to attenuate vibrations. By defining the functional role of these components through their dynamic mechanical property values, the system allows precise tuning of vibration transmission, attenuation, or redistribution within the solid-particle-based electrolyte to optimize the resulting surface finishing process.

[0050] In some embodiments, the vibration system may operate across a broader frequency spectrum encompassing sonic and sub-ultrasonic ranges, for example from approximately 10 Hz up to 100 kHz. Lower-frequency vibrations, typically within the range of 10 Hz to 1 kHz, can be employed to induce macroscopic agitation and bulk movement of the solid-particle electrolyte, promoting effective mixing and renewal of the moderative fluid within the interstitial spaces. Mid-range sonic vibrations, extending from about 1 kHz to 20 kHz, may enhance the mechanical loosening and redistribution of the conductive particles, assisting in the uniform exposure of the surface to the electrochemical environment. When combined with higher ultrasonic frequencies between 20 kHz and 100 kHz, these lower- frequency oscillations can generate a synergistic effect wherein the coarse agitation improves particle mobility and liquid replenishment, while the ultrasonic component refines surface finishing through controlled cavitation and localized ion transport. This multifrequency or broadband excitation allows the system to address different stages or requirements of the finishing process, ranging from initial surface smoothing to final micropolishing, thereby extending the versatility and adaptability of the method to a wide variety of materials and geometries.

[0051] The disclosed surface finishing method employs controlled vibrations, in some embodiments including ultrasonic frequencies ranging from 25 kHz to 40 kHz, with variation extending from 20kHz to 50kHz, to enhance the efficiency of electropolishing. Frequencies around 20 to 30 kHz are typically used for more intensive cavitation, as the relatively large bubbles generated at these levels produce a higher energy impact on the surface. In contrast, frequencies from 30 to 50 kHz can provide more controlled cavitation, which is better suited for more fragile materials or components with complex geometries requiring higher precision without compromising material integrity.

[0052] The vibration source, responsible for generating vibratory movement in the polishing process and operating at the previously mentioned frequencies, can exhibit movement amplitudes within a range from 0.1 mm to 40 mm, more specifically between 0.5 mm and 5 mm, and even more precisely from 0.5 mm to 1 mm. These amplitudes allow for adjusting the intensity of the vibration according to the process requirements, providing optimal control to achieve a uniform and effective surface finish.

[0053] In some embodiments, the plurality of electrically conductive solid bodies forming the solid-particle-based electrolyte may have either homogeneous or heterogeneous sizes and shapes, including but not limited to spherical, angular, irregular, or elongated geometries. A homogeneous particle configuration can provide predictable and uniform contact behavior, facilitate consistent ion transport and control polishing effects. In contrast, a heterogeneous combination of particle sizes and shapes can improve packing efficiency, enhance dynamic redistribution under vibration, and promote uniform current flow across complex surface geometries. The selection between homogeneous or heterogeneous particle distributions may therefore be determined according to the desired balance between surface uniformity, polishing rate, and adaptability to the component’s topology.

[0054] In certain embodiments, a relationship is established between the size of the solid particles constituting the solid-particle-based electrolyte and the amplitude of the vibrations applied to the system. The ratio between the mean particle diameter and the vibration amplitude may range from approximately 0.1 % to 10000%, more typically from 1% to 1000%, and even more specifically between 10% and 200%. When the vibration amplitude is small relative to the particle size, the mechanical interaction among particles remains predominantly compressive, favoring stable electrical contact and consistent ion transport pathways. Conversely, when the vibration amplitude approaches or exceeds the characteristic particle dimension, the solid-particle bed experiences partial fluidization or dynamic rearrangement, increasing local mixing and exposing new conductive surfaces for electrochemical exchange. By appropriately selecting the particle size distribution in relation to the applied vibration amplitude, it becomes possible to tailor the process toward either enhanced material removal rates or improved surface uniformity, depending on the desired finishing outcome. This controlled interplay between particle size and vibratory amplitude thus provides an additional mechanism to fine-tune both the mechanical and electrochemical effects of the surface finishing operation.

[0055] In certain embodiments, the vibration amplitude applied may be modulated or oscillated according to a predetermined waveform, such as sinusoidal, triangular, or pulsed variations, in order to dynamically alter the mechanical behavior of the solid-particle electrolyte bed. This modulation induces periodic changes in the packing density of the solid particles, thereby intermittently modifying the electrical contact between the particles and the surface being treated. As a result, both the ion transport phenomena and the localized current density at the treated surface can be precisely controlled, enabling selective enhancement or attenuation of the electropolishing effect in specific regions or time intervals. The oscillatory adjustment of amplitude thus provides an additional degree of control over the aggressiveness of the surface finishing process and allows fine-tuning of the surface roughness and gloss level.

[0056] Similarly, in another embodiments, the vibration frequency may be varied or modulated during operation, either continuously or stepwise, to influence the cavitation behavior and the fluid dynamics of a moderative liquid present within the interstitial spaces of the solid-particle bed. By periodically shifting the frequency within a defined range, for example between 20 kHz and 50 kHz, it becomes possible to alternate between regimes of intensive cavitation, favoring rapid material removal, and regimes of controlled cavitation, which promote smoother surface refinement and enhanced uniformity. Such frequency modulation also assists in maintaining homogeneous distribution of the moderative liquid and prevents the formation of localized stagnation zones, contributing to improved process consistency and reduced surface defects.

[0057] In yet another embodiment, simultaneous or coordinated modulation of both amplitude and frequency may be implemented according to a predefined control algorithm, allowing adaptive surface treatment responsive to real-time process conditions, such as temperature, current density, or surface potential variations. This approach enables a selfoptimizing surface treating environment that can balance efficiency, precision, and material preservation according to the specific requirements of the component under treatment.

[0058] The phenomenon of resonance, diffraction, and wave interference as vibrations pass through an aperture is also part of some configurations of the present invention by directing a vibratory energy with precision. A resonator is to be also understood in the present application as a fiscal element capable of guiding the vibration direction differently to its original transmission impulse by the vibration source, in some cases trough the desired path or target, by wave resonance effects. As the wavefront encounters an opening aperture, it undergoes diffraction, spreading out and partially attenuating its amplitude, which reduces its intensity. This diffraction effect, combined with the natural wave interference that occurs, results in a more homogeneous distribution of energy. By shaping and guiding the waves, this approach allows for controlled, focused vibrations, effectively channeling the energy towards the target area. This directed resonance, diffraction, and interference enable uniform treatment of complex surfaces, enhancing the quality of processes such as polishing and cleaning in localized zones while minimizing the impact on surrounding areas. In some cases, in order to control an energy loss during the wave diffraction effect, some elastic or damping elements are to be introduced at the vicinity of aperture. If vibration energy loss is to be avoided, an element / s with higher elastic properties than that presented on a used electrolytic medium can be introduced. By contrast id vibration energy loss is to be promoted, an element / s with higher damping properties than that presented on a used electrolytic medium can be introduced. This element can be either a physical element or a fluid element forming part of the environment between the solid particles, such as a non-Newtonian fluid.

[0059] The resonators' capacity to generate stable, customizable ultrasonic waves allows for effective cleaning of contaminants, such as salts and oxides, and enhances polishing by inducing localized cavitation. This cavitation effect can be beneficial in applications where non-abrasive, high-precision finishing is required, as it enables the removal of unwanted layers without damaging the underlying material. Furthermore, the welded connection of these resonators enhances the efficiency and stability of the vibrations, similar to those achieved in liquid electropolishing, making them suitable for challenging industrial applications that demand both reliability and adaptability.

[0060] In certain embodiments, multiple resonators may be arranged in a coordinated configuration to generate interference patterns of vibrational energy across the solid- particle-based electrolyte and the surface being treated. By controlling the phase, frequency, and orientation of each resonator, constructive and destructive interference regions can be intentionally formed, producing spatial variations in the vibration amplitude of the electrically conductive solid particles. Such interference patterns may resemble two- slit interference phenomena, creating periodic or localized zones of intensified or diminished vibratory energy over the treated surface. These controlled distributions of vibrational amplitude enable selective modulation of the electrochemical and mechanical effects occurring at the surface, allowing the formation of surface treatment gradients or patterns according to predefined geometries. In this manner, it becomes possible to achieve variable surface finishes (e.g., ranging from high-polish to matte regions) on a single component, or to direct enhanced polishing energy to critical functional zones while preserving other areas from excessive material removal.

[0061] The introduction of conductive or non-conductive particles with elastic or damping properties into the polishing system provides a novel method for controlling vibration transmission. These particles can be tailored to either enhance or dampen the vibrations, depending on the specific needs of the process. Conductive particles, such as metallic or carbon-based materials, can facilitate better transmission of vibrations across the medium, ensuring consistent polishing in areas that may otherwise experience uneven vibrational energy. Non-conductive, elastic particles, on the other hand, such as rubber or polymer- based spheres, in some embodiments act as buffers, absorbing excessive vibrations to prevent damage to sensitive components or surface irregularities. This selective control of vibration transmission allows for fine-tuning of the process, improving surface homogeneity and polishing efficiency, particularly in complex geometries where direct vibrational impact might otherwise be difficult to achieve.

[0062] An aspect of the present invention relates to a method comprising: arranging a solid-particle based electrolyte including at least a plurality of free electrically conductive solid bodies inside of a container, preferably including an elastic or damping element for vibration transmission control; arranging at least one electrically conductive device at least partially inside the container, preferably along with a moderative fluid allocated on an interstitial space of the solid bodies including non-Newtonian viscous properties; generating an electric potential between an at least one surface to be treated and the at least one electrically conductive device bough in contact to the solid-particle based electrolyte; generating a vibration to a solid-particle based electrolyte, to the part to be treated or bough, preferably on an ultrasonic frequency range and with an amplitude of the same order of the used conductive solid bodies, and; while the electrolytic medium and an at least one electrically conductive device are both arranged inside the container, surface finishing the at least one surface to be treated by providing relative motion between at least some of the free electrically charged conductive solid bodies and the at least one surface so that at least some of the free electrically conductive solid bodies contact the at least one surface, thereby surface finishing the at least one surface.

[0063] The system can work with various types of vibrational movements, such as linear, orbital, transversal, and longitudinal, depending on the specific requirements of the surface being treated. This flexibility in vibrational modes ensures that each surface receives a tailored, efficient, and precise treatment.

[0064] Piezoelectric transducers can be used in some embodiments of the invention, that include ceramic piezoelectric resonators (e.g., PI ceramics), which produce controlled, high- frequency vibrations when subjected to an electric field. By adjusting the frequency and amplitude of the vibrations, the system can adapt to various materials and surface requirements, ensuring consistent cavitation effects across complex geometries.

[0065] Additionally, the system can be applied in both gas and liquid media, creating sonic waves that affect the solid and liquid phases. Although sound waves on their own may not generate the same high-intensity cavitation as ultrasonic waves, they can still produce localized pressure changes, for example, capable of forming small bubbles or microcavitation under certain conditions. An aspect of certain particular embodiments of the invention lies in the combination of ultrasonic vibrations with lower-frequency agitation, creating a synergy between the two. While traditional polishing methods use either ultrasonic waves or mechanical agitation separately, this invention carefully calibrates the amplitudes and frequencies to ensure the vibrations reach the targeted areas without dampening their effect. In some cases, if only ultrasonic waves or agitation were applied alone, the piece would likely suffer pitting or other forms of corrosion, as it’s crucial to introduce additional movement between the piece and the electrolyte.

[0066] Moreover, finding the right balance between frequencies and amplitudes is important for preventing the ionic conductivity from being cut off at the particle bridge, a non-trivial task in complex surface treatments. To achieve this, the system must avoid damping the waves while maintaining the frequencies and amplitudes applied, which are specifically tuned to ensure uninterrupted transmission of vibrational energy through the electrolyte. By carefully calibrating the vibrational frequencies and the amplitude of movement in the vibrating device, the system maximizes the energy transfer to the surface without diminishing the wave intensity.

[0067] In certain embodiments, the means for generating vibrations are configured to produce oscillatory motion with an amplitude selected in relation to the size of the free electrically conductive solid bodies within the electrolyte. In particular, the vibration amplitude may be on the order of between approximately 10% and 1000% of the characteristic dimension of the solid bodies, more in particular between 20% and 500%, more in particular between 50% and 200%. By selecting amplitudes within this range, the vibration can induce controlled relative motion between the solid bodies and the surface to be treated, promoting effective mechanical interaction, enhancing particle rearrangement, and optimizing ion transport for improved surface finishing performance. This range allows for both moderate agitations, preserving stability of the particle bed, and more vigorous motion, increasing localized polishing or material removal as required by the specific application.

[0068] Cavitation can potentially disrupt the connectivity among free solid bodies that are connected through with each other through contact. This disconnection may occur if the cavitation effects are too intense, temporarily interrupting ionic communication between particles and generating shadow zones where polishing is less effective. In the case of direct current parameters, the connectivity between particles might be more stable due to the continuous current flow, which reduces interruptions in conductivity. However, at higher frequencies, the rapid oscillations can exacerbate disconnections, as the alternating current cycles amplify the cavitation forces, potentially cutting off contact between particles more frequently. This can diminish the overall conductivity and, consequently, the polishing efficiency in areas where the particles become separated.

[0069] Furthermore, the fluid’s viscosity plays a role in either dampening or transmitting cavitation effects, adding another layer of control for managing particle connectivity within the electrolyte medium.

[0070] Air bubbles generated by cavitation also pose a challenge, as they could prevent the polishing action from taking place. Adjusting the power, whether through changes in amplitude or frequency, helps counteract this issue, ensuring the desired level of surface treatment is achieved across a variety of conditions.

[0071] Vibrations can be effectively transmitted to reach the targeted area, particularly in complex geometries or deep cavities. The ability of the vibration to reach these areas depends on finding the optimal power level, which involves carefully adjusting either the amplitude, the frequency, or both, to maintain consistent energy transfer. Simply increasing power may not guarantee improved reach; excessive amplitude or frequency adjustments could lead to energy dissipation or unintended resonance effects that prevent the vibrations from focusing on the desired zone. Fine-tuning these parameters is essential for ensuring that the vibration energy is delivered precisely and efficiently to achieve the intended results.

[0072] BRIEF DESCRIPTION OF THE DRAWINGS

[0073] To complete the description and in order to provide for a better understanding of the disclosure, a set of drawings is provided. Said drawings form an integral part of the description and illustrate embodiments of the disclosure, which should not be interpreted as restricting the scope of the disclosure, but just as examples of how the disclosure can be carried out. The drawings comprise the following figure:

[0074] Figure 1-A shows a system in accordance with some embodiments.

[0075] Figure 1-B shows a system in accordance with some embodiments.

[0076] DETAILED DESCRIPTION

[0077] Figures 1-A and 1-B show a system in accordance with some embodiments, describing a system for surface finishing, wherein the vibration energy is applied to the workpiece being treated (Fig. 1-B) or to other elements of the system (Fig. 1-A), comprising:

[0078] A container (3) comprising at least one electrically conductive device, acting as a first electrode (5), at least partially arranged inside the container; an electric source (1) providing an electric potential difference between the at least one surface to be treated (2), at least partially arranged within the container (3) and acting as a second electrode (2), and the at least one electrically conductive device (5); the two electrodes (5, 2) connected through a solid-particle based electrolyte (4) that enables ion exchange between the at least one surface to be treated (2) and the a solid-particle based electrolyte (4) when current is applied; and at least one device adapted with means for generating vibrations (6, 7, 8 and 9) to either a set of free electrically conductive solid bodies, to an environment between said solid bodies, or to a surface to be treated, and thereby inducing a relative motion between the solid-particle based electrolyte (4) and the at least one surface to be treated (2).

[0079] A device adapted with means for generating vibrations (6), can be located on the walls of the container (3), or on the surface of the workpiece itself (8) when placed inside the container. In several particular embodiments, the generators are coupled to vibration resonators, which preferably have a conical shape, although they can present different geometries. A vibration device can also be used in a holder (9), allowing it to provide vibration along all three axes, thereby enhancing the surface finishing process with multidirectional vibration, or it can act as an agitator, performing this dual functionality.

[0080] In the context of the present invention, elements (6), (7), (8), and (9) are to be understood as components associated with the generation and transmission of vibratory energy within the solid-particle based electrolyte and / or the surface being treated, and are part or constitute the vibration source or vibration apparatus. Elements (6), (8), and (9) function as vibration-generating elements, whereas element (7) operates as a vibrationtransmission element. In particular, element (6) corresponds to a vibration generator adapted or mounted onto the container (3); element (7) corresponds to a transmission component or interface configured to convey vibratory energy directly to the workpiece surface (2); element (8) represents a vibration generator integrated or attached to the workpiece itself when positioned within the container; and element (9) corresponds to a vibration generator arranged on a holder or support structure that secures the workpiece or, in certain embodiments, is coupled to the electrically conductive device (5).

[0081] In another embodiment, the system may further comprise an additional vibration apparatus positioned directly within the solid-particle-based electrolyte, such that the element is in direct physical contact with the free electrically conductive solid bodies. This vibration apparatus may be partially or fully immersed in the electrolyte and configured to transmit vibratory energy directly into the free electrically conductive solid bodies bed or, in certain embodiments, indirectly through the moderative medium present between said solid bodies. Through either direct mechanical contact or vibratory propagation via the moderative medium, this configuration enhances localized agitation, improves particle mobility, and increases the intensity or precision of the surface finishing effect at selected regions within the container.

[0082] In a particular embodiment, the first electrode (5) shape is a mesh and adapted to that of the container (3), although it may adopt different configurations. Preferably, the material used for the first electrode is selected from graphite and iridized or platinated titanium, although it can be made of any other conductive material.

[0083] Said system as represented in Figure 1 , present additional vibration elements (i.e., present additional vibration elements such as the container, or the workpiece) configured for adding different vibration configurations, including amplitudes, frequencies, distances, etc. By adjusting different vibration elements, it is possible to obtain a better control over the obtained finishing result.

[0084] The solid-particle based electrolyte used on the example represented on Figure 1 comprises: o 50 % in volume (300 L) of electrically conductive particles made of:

[0085] • 98 % wt. of spherical particles with a heterogeneous particle size distribution ranging between 0.3 - 1.1 mm in diameter of sulfonated gel styrene divinylbenzene particles in an acid format after being dried up to get a constant moisture of 35 - 45 wt. % with respect to the total weight of the solid bodies.

[0086] • 2 % of methanesulfonic acid at a concentration of 70% wt. o 50 % in volume (300 L) of a non-conductive fluid made of:

[0087] • 73.8 % wt. of a mixture of aliphatic hydrocarbons with a carbon chain between 12-15 C containing less than 2% of aromatic groups, and 2.7% by weight of octanoic acid 90 - 99 % purity.

[0088] • 1.48 % wt. of ethoxylated alcohol with an ethoxylation of 2.5 mol and 10 carbons.

[0089] • 22.14 % wt. of water

[0090] • 1 .85 of methanesulfonic acid at a concentration of 70% wt.

[0091] • 0.74 % wt. of sodium natural sulfonate.

[0092] The ratio between electrically conductive particles and a non-conductive fluid has an effect on the turbulence, packing factor and to the conductivity of the medium under work conditions. In a particular embodiment of the invention, the ratio in volume between the electrically conductive particles and the non-conductive fluid is 1 : 10 to 2: 1 , in particular from 1 :5 to 1 :1 , more in particular from 1 :2 to 1 :1. In this particular embodiment, the container (3) is a cube of a size of 2m. In other possible configurations of the inventions, the container adopts other shapes, such as cylindrical or prismatic, and sizes, ranging in some cases from 0.01 m3to 100 m3.

[0093] The deepness under which the apparatus for providing vibrations to a set of free electrically conductive solid bodies within a fluid is allocated at 1 m from the surface. The deepness can be adjusted in order to control the vibration transmission. In a particular embodiment it is located at the bottom of the receptacle, in others between a profundity of 50 % and 90 % with respect to the height of the surface, more in particular between 70 % and 80%.

[0094] An apparatus for providing vibrations and generating relative motion between the free electrically conductive solid bodies within a fluid, which serves as an electrolyte (4), is, in certain embodiments, a vibration-inducing device, though other systems may also be employed. In one embodiment, the vibration source may consist of an electromechanical actuator, such as a piezoelectric transducer, a magnetostrictive element, or an eccentric rotating mass (ERM) motor, configured to impart controlled oscillatory motion to the container or to the medium itself. Such a vibration device can be operated over a broad frequency range extending from sonic to ultrasonic levels, typically between 10 Hz and 100 kHz, and in particular between 20 kHz and 50 kHz for ultrasonic operation. The amplitude of vibration may similarly be adjusted according to process requirements, thereby enabling precise control of the relative motion between the solid particles and the surface being treated, enhancing both the mechanical and electrochemical effects of the surface finishing process. A polished par on the example is a blade of 20 cm of diameter, made out of stainless steel. The used parameters are a DC at 30 V, with a current of 5 A. After a polishing process of 30 min, the roughness has been decreased homogeneously from Ra = 1 pm to a Ra = 0.3 pm, achieving a mirror finish.

[0095] In several particular embodiments the agitation of the electrolyte presents a synergy with the required vibrations. By modifying the packing factor of the solid particles, it is possible to control the vibration transmission. I several particular embodiments, changing the packing factor includes generating a motion or agitation on the solid-particle based electrolyte, such as introducing a moving turbine at the bottom of the receptacle.

[0096] In different embodiments of the invention, other electrical parameters or polarities can be used to achieve the desired result.

[0097] In one aspect, the invention provides a solid-particle-based electrolyte comprising a plurality of electrically conductive free solid bodies. A set of electrically conductive solid bodies comprises or retains an electrolyte liquid, which may be contained within the particle due to its porosity, molecular structure, or gel-like characteristics. The electrolyte liquid may be retained by mechanisms including permeation, absorption, adsorption, or interlaminar retention. The electrically conductive free solid bodies may be composed of materials capable of retaining liquids, such as polymeric, mineral, ceramic, organic, inorganic, or hybrid materials, preferably of polymeric nature. In particular embodiments, the electrically conductive free solid bodies comprise or consist of polymeric ion-exchange resins. Suitable materials include strong and weakly acidic cationic resins, strong and weakly basic anionic resins, and chelating resins.

[0098] In some embodiments, the electrolyte of one or more (e.g., one, some, all) electrically conductive free solid bodies of the first plurality of electrically conductive free solid bodies is inside the electrically conductive free solid bodies.

[0099] Liquid retention in the electrically conductive free solid bodies can occur due to porosity of the material or due to molecular structure such as a gel-like structure. Possible retention mechanisms within the scope of the present disclosure include: permeation, absorption, adsorption, retention in the interlaminar space.

[0100] The electrically conductive free solid bodies may be of any material capable of retaining liquid, such as, for example, polymeric materials, mineral, ceramic, organic compounds, inorganic compounds, of plant origin, and are preferably of polymeric material.

[0101] Electrically conductive free solid bodies of a polymeric material may simply be referred to herein as polymeric particles.

[0102] Suitable polymeric materials may be, e.g., ion exchange resins. In some embodiments, the electrically conductive free solid bodies are of a material selected from: strong and weakly acidic cationic resins, strong and weakly basic anion exchange resins and chelating resins, and more preferably are cationic exchange resins, as such resins contribute to capturing metal ions extracted in the electropolishing processes.

[0103] In some embodiments, the electrically conductive free solid bodies comprise strong acid cationic (SAC) resins such as sulfonated styrene-divinylbenzene copolymers, poly(perfluorosulfonic acid), or perfluoro vinyl ether polymers with sulfonic acid side chains. These resins contain sulfonic acid groups with a pKa of approximately -2, ensuring full ionization and high conductivity across a broad pH range, including acidic conditions. Other examples include phenol-formaldehyde sulfonic acid resins and sulfonated polyacrylic resins. In alternative embodiments, weak acid cationic (WAC) resins such as poly(acrylic acid) or crosslinked poly(acrylic acid) are used, featuring carboxylic acid groups with a pKa between 4.5 and 6.0, suitable for mildly acidic to neutral environments.

[0104] Further embodiments include chelating resins containing functional groups such as iminodiacetic acid, aminophosphonic acid, thiourea, or 2-picolylamine, capable of selectively binding metal ions during surface finishing. Additional embodiments utilize strong base anionic (SBA) resins having quaternary ammonium groups (-NR4+) or weak base anionic (WBA) resins incorporating primary, secondary, or tertiary amines (-NH2, -NHR, - NR2). These resins enable the retention and controlled exchange of anionic or cationic species depending on the environment and the treated material.

[0105] In preferred embodiments, the polymeric material comprises sulfonated divinylbenzene-styrene (S-DVB) copolymers exhibiting excellent chemical resistance to acids and oxidants, favoring ion exchange and metal ion retention. Alternative polymeric matrices include copolymers derived from acrylic or methacrylic acid, acrylamides, cyanoacrylates, or alkyl acrylates, optionally functionalized with chelating or acid groups such as sulfonic, carboxylic, aminophosphonic, or thiourea groups. Depending on the specific polymer type and functionalization, the chemical and physical properties of the electrically conductive free solid bodies can be adjusted to suit the desired polishing or surface finishing operation.

[0106] The electrically conductive free solid bodies may take various geometrical forms, including spherical, cylindrical, rhomboidal, conical, pyramidal, or irregular (e.g., broken or crushed) shapes. A particle size may range between 10 pm and 20 mm, preferably between 200 pm and 1300 pm. The particle size is determined using standard sieving or equivalent analytical techniques.

[0107] An electrolyte liquid retained within the solid bodies may include aqueous or nonaqueous solutions of conductive media, such as hydrofluoric acid, sulfuric acid, phosphoric acid, methanesulfonic acid, hydrochloric acid, citric acid, ionic liquids, or deep eutectic solvents. In some embodiments, the liquid electrolyte concentration is between 0.1 % and 70% by weight. A retained electrolyte may also be deionized, distilled, or tap water.

[0108] In additional embodiments, the electrolyte further includes abrasive particles or abrasive composites. The abrasive particles may have densities between 2.5 and 5.5 g / cm3and hardness values between 3 and 10 on the Mohs scale, preferably between 7.5 and 9.25. Abrasive materials include alumina, zirconia, boron carbide, silicon carbide, cerium oxide, or diamond dust. The abrasive particles may be used alone or as composite particles incorporating charged polymers such as polyacrylic acid (PAA), polyethyleneimine (PEI), or polydiallyldimethylammonium chloride (PDDA), with 30-80% by weight of abrasive powder and 5-20% polymer. These composites enhance electrostatic stability, adhesion, and dispersion during polishing.

[0109] In ion exchange technology, resins are categorized as strong or weak based on the ionization characteristics of their functional groups, influenced by their pKa values, which determines their ion-exchange behavior in varying pH environments. Strong ion-exchange resins possess functional groups that remain fully ionized across a wide pH range, making them effective in diverse conditions. In contrast, weak ion-exchange resins have functional groups with higher pKa values, meaning their ionization, and thus their ion-exchange capacity, is more pH-sensitive. Generally, resins having groups with a pKa of up to 3 may be regarded strong acidic cationic resins also referred to as strong acid cation (SAC) resins.

[0110] Resins having groups with a pKa of above 3 and up to about 6 may be regarded as a week acid cation (WAC) resins. Resins having groups with a pKa from 7 to about 10 may be regarded as weak base anion (WBA) resins, and resins having groups with a pKa higher than 10, e.g., about 12 or 13 may be regarded as strong base anionic (SBA) resins.

[0111] Chelating resins may have groups with a range of different pKas depending on the nature 15 of the chelating group of the resin, e.g., with a pKa ranging from 1 to 10. In some embodiments, electrically conductive free solid bodies are of or comprise a SAC resin, in particular a SAC such as styrene-divinylbenzene with a macroporous or gel structure, having sulfonic acid (-SO3H) groups as functional components. These sulfonic acid groups have a pKa of approximately -2, ensuring they remain fully ionized across a broad pH range, including in highly acidic environments. This enables consistent cation exchange performance. Particular examples include Poly(perfluorosulfonic acid) resins, Perfluoro vinyl ether polymers with sulfonic acid groups, and Polytetrafluoroethylene (PTFE) with sulfonic acid side chains, which are highly resistant to pH fluctuations. Other strong acid cation resins include Phenol-formaldehyde sulfonic acid resin, sulfonated phenolic polymers, and crosslinked polyacrylic resins with sulfonic acid functional groups, all of which maintain high efficiency in both acidic and neutral conditions due to their low pKa values.

[0112] In some embodiments, electrically conductive free solid bodies are of or comprise a WAC resin, in particular a WAC such as Poly(acrylic acid) or Crosslinked poly(acrylic acid) resins. These resins feature carboxylic acid (-COOH) groups with a pKa typically in the range of 4.5 to 6.0, making them pH-sensitive and more suitable for environments that are moderately acidic to neutral. They are less effective in strongly acidic solutions due to partial ionization at low pH. Other WAC resins include Poly(acrylic acid-co-divinylbenzene), Poly(methacrylic acid), and crosslinked iminodiacetic acid-functionalized resins, all of which 35 exhibit ion-exchange properties optimized for pH levels where carboxyl groups are ionized, ensuring effective cation capture and release in more controlled pH conditions.

[0113] In some embodiments, electrically conductive free solid bodies are of or comprise chelating resins, which enhance the selectivity for metal ions through functional groups such as iminodiacetic acid and aminophosphonic acid. These groups form stable chelates with specific metal ions. Iminodiacetic acid has a pKa of approximately 2.5 and 9.5, allowing for selective metal ion capture at different pH levels, while aminophosphonic acid has a pKa around 1 .5 and 6.5, making it ideal for selectively recovering metals like 5 calcium and other multivalent ions from complex solutions. Examples of such resins include Poly(styrenedivinylbenzene) resin functionalized with these chelating groups, crosslinked iminodiacetic acid or aminophosphonic acid resins, and thiourea-functionalized styrene- divinylbenzene resins. These resins are particularly useful for selective metal recovery in mixed or harsh 10 chemical environments, providing high specificity even in the presence of competing ions.

[0114] In some embodiments, free electrically conductive solid bodies are of or comprise a SBA resin, in particular an SBA which utilizes functional groups like quaternary ammonium (- NR4+) that remain fully ionized across a wide pH range. These resins have a pKa greater than 12, ensuring consistent performance in both neutral and highly alkaline environments, where they can effectively exchange anions such as sulfate, nitrate, and chloride. SBA resins are highly stable and do not lose their ion-exchange capacity even in extreme pH conditions, making them ideal for processes requiring strong anion capture. Particular examples of SBA resins include crosslinked poly(styrene-divinylbenzene) resins functionalized with quaternary ammonium groups, and other resins with similar high-pKa ammonium-based functional groups. These resins are particularly suitable for applications involving the removal or recovery of strong acid anions from highly alkaline or near-neutral solutions.

[0115] In some embodiments, free electrically conductive solid bodies are of or comprise a WBA resin, in particular a WBA which includes functional groups such as primary, secondary, or 25 tertiary amines (-NH2, -NHR, -NR2) that exhibit a pKa in the range of 7 to 10, meaning they are only partially ionized in moderately acidic to neutral pH environments. WBA resins are effective in absorbing weak acid anions, such as organic acids or carbonates, in environments where strong base anions are not as prevalent. Unlike SBA resins, WBA resins become less effective in strongly alkaline conditions, where their functional groups 30 are not ionized, and they tend to lose their capacity in highly basic environments. Typical examples of WBA resins include crosslinked poly(styrene- divinylbenzene) resins functionalized with amine groups and copolymers of acrylic or methacrylic acids. These resins are commonly used in applications where selective removal of weak acid anions is required, especially in solutions with pH levels that can be easily controlled for optimal ion exchange.

[0116] In some embodiments, the free solid bodies of polymeric material are of a sulfonated divinylbenzene S-DVB and styrene copolymer, since it is a material resistant to acid and the oxidative action of the process. The material has the ability to act as an ion exchanger, which favors the extraction of metal from the surface to be surface finished (e.g., polished) by storing the ions. Alternatively, the polymeric material free solid bodies are of a copolymer containing units derived from acrylic acid or methacrylic acid. This includes derivatives with different functional groups such as acrylic acid, acrylamide, cyanoacrylate, alkyl acrylates, among others, and the corresponding methacrylate analogs.

[0117] In some embodiments, electrically conductive free solid bodies are of polymeric materials including functional groups that are capable of capturing or retaining the metal ions generated during the process, such as acid, amino, or chelating groups, including the groups as described above. These functional groups can be of the acidic type, such as sulfonic or carboxylic groups. These acidic functional groups are especially useful in this application as they have good chemical resistance and are capable of retaining a wide variety of metal ions. In some embodiments, the polymeric materials include functional groups that are of the chelating type such as, for example, iminodiacetic, aminophosphonic, polyamine, 2-picolylamine, thiourea, amidoxime, isothiouronium, bispicolilamine, among others. These chelating groups have a high selectivity over the transition metals versus alkali or alkaline earth metals, which allows them to be more flexible in the formulation and does not require the use of distilled water.

[0118] Depending on the specific type of polymer and functional groups included, the exact composition of the electrically conductive, electrically conductive free solid bodies may vary and may be adjusted. As a mode of example, in some embodiments, electrically conductive free solid bodies are of a cationic resin of a gel copolymer styrene-divinylbenzene (DVB), which may preferably be sulfonated.

[0119] The electrically conductive free solid bodies may take various shapes, including spherical, rhomboidal, pyramidal, cylindrical or broken or crushed particles. Any combination of different shapes is within the scope of the present disclosure.

[0120] Said previously described electrically conductive solid bodies may contain electrolytes liquids to make them electrically conductive, such as aqueous solutions of hydrofluoric acid (HF), sulfuric acid, sulfonic acids such as methanesulfonic acid (MSA), phosphoric acid, carboxylic acids, citric acid, hydrochloric acid, ionic liquids or deep eutectic solvents.

[0121] In some cases, the electrically conductive solid bodies may contain different electrolytes liquids, such as MSA and sulfuric acid, in varying concentrations from 0.1% to 70% by weight.

[0122] In some embodiments, the electrolyte liquid retained by the electrically conductive solid bodies to make them conductive is an aqueous solution, such as water, such as tap water, drinking water, distilled water or in particular, deionized water.

[0123] In some embodiments, a solid particle-based electrolyte according to the present disclosure comprises a fluid included within the environment. Preferably the fluid medium is liquid and non-significantly conductive compared to the solid bodies, but other configurations are possible, such as including a gas, emulsions, etc. The conductivity of a liquid present on the environment according to some embodiments, can be enhanced with acids or other agents, though the disclosure also allows for reduced-acid or acid-free configurations. This reduces the environmental hazards associated with traditional acidbased surface finishing, making the process safer and more suitable for facilities that do not handle acids. Additionally, the fluid’s composition can be adjusted to include lubricating solids, enhancing the process by modifying the viscosity and providing further control over the electropolishing process.

[0124] Electrically conductive free solid bodies of the first plurality of electrically conductive free solid bodies may selectively remove material from the surface(s) of the object, thereby enabling targeted roughness reduction.

[0125] In some embodiments, a size of one or more electrically conductive free solid bodies of the first plurality of electrically conductive free solid bodies is between 10 pm and 20 mm, in particular between 50 pm and 2000 pm, preferably between 200 pm and 1300 pm. In some embodiments, spheric particles of sulfonated PST-DVB present a diameter between 0.1 and 2 mm, preferably between 0.3 and 1.2 mm.

[0126] The particle size may be determined by methods known in the art. The maximum particle size may be determined by establishing the size of the smallest sieve through which a 100 percent of the particles in a plurality of particles pass.

[0127] In some embodiments, a solid-particle based electrolyte according to the present invention provides an electrically conductive abrasive composite material combining an ionexchange resin and an abrasive powder. The resin may be sulfonated styrene- divinylbenzene or quaternary ammonium-based polymers, and the abrasive may be silica, alumina, cerium oxide, or nanodiamonds. This dual-function composite provides simultaneous abrasive and electrochemical polishing action.

[0128] In some embodiments, one or more abrasive particles (e.g., one, some or all) of the at least one abrasive particle have a density ratio DR fulfilling the following: 7 > DR > 0.7, and / or a mass ratio MR fulfilling the following: 2 > MR > 0.2; where DR=p_ap / p_res , where p_ap is a density of the abrasive particles, and p_res is a density of the electrically conductive free solid bodies or a resin thereof; and where MR=m_ap / m_res , the particles (or resin thereof) including the electrolyte; and where MR=m_ap / m_res , where m_ap is a mass of the abrasive particles, and m_res is a mass of the resin of the electrically conductive free solid bodies.

[0129] As a mode of example, the density of abrasive particles (p_ap) may be from 2.5 to 5.5 g / cm3, in particular from 3.0 to 5.0 g / cm3, yet more in particular from 3.5 to 4.5 g / cm3.

[0130] A combination of a first plurality of electrically conductive free solid bodies and at least one abrasive particle may be homogeneous or heterogeneous. In some embodiments, the combination is a mixture of a first plurality of electrically conductive free solid bodies and a second plurality of abrasive particles, which mixture may be homogeneous or heterogeneous.

[0131] In some embodiments, the combination is a mixture of a first plurality of electrically conductive free solid bodies and a single abrasive particle, which mixture is heterogeneous. In such a combination the single abrasive particle may be a fixed element or a loose element present in, e.g., a container containing the first plurality of electrically conductive free solid bodies.

[0132] In some embodiments, a combination of the first plurality of electrically conductive free solid bodies and the at least one abrasive particle is a homogeneous mixture.

[0133] The density and the mass of the electrically conductive free solid bodies, in particular a resin of the electrically conductive free solid bodies, respectively referred to as pres, and mresrefers to the particles, or resin thereof, including the electrolyte contained therein.

[0134] The hardness of abrasive particles may be from 3 to 10 in the mohs scale, in particular from 5 to 9.75 mohs, more in particular from 6 to 9.5 mohs, and yet more in particular from 7.5 to 9.25 mohs.

[0135] The geometry of abrasive particles may typically include edges, owing to their surface and / or their shape. For instance, abrasive particles may be prismatic, e.g., of triangular base or other geometrical base; cylindric; cubic; rhombic; pyramidal; conic; and / or spheric.

[0136] The material of abrasive particles may be synthetic (i.e., manufactured) and / or natural (i.e., naturally sourced, e.g., mined minerals). In some embodiments, the abrasive particles are preferably synthetic abrasive particles. Some natural abrasive particles (e.g., zirconia alumina, diamond dust, etc.) may also be manufactured, and synthetic versions of naturally sourced abrasive particles may be preferred due to difficult availability and higher costs of the naturally sourced abrasive particles. Additionally, or alternatively, synthetic particles may be preferred as they may be more effective as abrasives, since they may be free of impurities that natural abrasive particles may comprise.

[0137] In some embodiments, abrasive particles (synthetic and / or natural) of the at least one abrasive particle are selected from alumina (aluminum (III) oxide: AI2O3), e.g., in the form of corundum, emery (impure corundum), and ceramic aluminum oxide, including white AI2O3, brown AI2O3 and gray AI2O3; zirconia (zirconium dioxide); zirconia alumina (a combination of aluminum (III) oxide and zirconium dioxide); iron(lll) oxide (e.g., ceramic iron oxide); borazon (cubic boron nitride or CBN); boron carbide; glass powder; steel abrasive; silicon carbide (carborundum); calcite (calcium carbonate); diamond dust; novaculite; pumice; sand; garnet; sandstone; rotten stone (Tripoli); powdered feldspar; staurolite; and slag (a by-product of processes for smelting ores and recycling metals, comprising a mixture of metal oxides and silicon dioxide).

[0138] In some embodiments, the at least one abrasive particle comprises the second plurality of abrasive particles comprising more than one type of abrasive particles, e.g., two, three or more different types of abrasive particles.

[0139] Embodiments of the disclosure include at least one abrasive particle or a second plurality of abrasive particles wherein the abrasive particles comprise or are of charged polymers combined with abrasive powders, also referred to herein as abrasive composites or abrasive composite particles. Abrasive powders may include powders particularly suited for specific applications such as in polishing, and chemical-mechanical planarization (CMP). For instance, the abrasive composites may include powders such as silica, alumina, cerium oxide, zirconium dioxide, silicon carbide, titanium dioxide, and nanodiamonds, dispersed in a charged polymer matrix. The charged polymer enhances the dispersion, electrostatic stability, and adhesion to substrates of abrasive particles comprising the same. Examples of charged polymers include polyacrylic acid (PAA), polyethyleneimine (PEI), polydiallyldimethylammonium chloride (PDDA), and poly(sodium acrylate).

[0140] In some particular embodiments, the abrasive composites typically comprise between 30% and 80% by weight of the abrasive powder and between 5% to 20% by weight of the charged polymer, any remaining percentage up to 100 % by weight, if necessary, consists of a solvent, such as water or alcohol, to form a stable colloidal suspension. The at least one abrasive composite particle varies in size from 2 nm to 500 nm, depending on the hardness and polishing requirements of the application. Densities of the abrasive composite particle(s) range from 2 to 7 g / cm3, and may be of, e.g., 2.6 g / cm3for abrasive composites comprising silica powder, 3.97 g / cm3for abrasive composites comprising alumina powder, and 5.6 g / cm3abrasive composites comprising for zirconium dioxide powder. The choice of a specific abrasive powder and / or charged polymer allows for tailored material properties and ultimately different removal rates. Some particular embodiments relate to abrasive composite particles with 60-70 wt.% silica combined with 10-20 wt.% PAA for semiconductor polishing, 50-65 wt.% alumina with 5-10 wt.% PDDA for hard substrates, and 40-60% cerium oxide with 5-15 wt.% PEI for optical glass polishing.

[0141] In some embodiments, the at least one particle having both electrically conductive and abrasive properties comprises a composite material exhibiting both abrasive and electrical conductivity properties simultaneously, also referred to herein as electrically conductive abrasive composite material. In some embodiments, the electrically conductive composite material comprises an ion-exchange resin, and an abrasive powder. The ionexchange resin includes a resin such as those described above, e.g., sulfonated polystyrene divinylbenzene, or other ion-exchange resins including sulfonated polyacrylate, aminomethylated polystyrene, or quaternary ammonium-based resins. These resins provide a solid structure with controlled ion conductivity and tunable surface charge.

[0142] The abrasive powder includes an abrasive powder such as those described above, in particular a powder having charged abrasive particles such as silica, alumina (AI2O3), cerium oxide, zirconium dioxide, silicon carbide, titanium dioxide, or nanodiamonds.

[0143] In further embodiments, the solid-particle-based electrolyte may be contained in or combined with a fluid medium. The fluid medium may be liquid, gaseous, or a combination of both, and is preferably non-significantly conductive relative to the solid bodies. The fluid medium may include organic liquids such as mineral or silicone oils, paraffins, or hydrocarbon mixtures with carbon chains of 12-16 atoms and less than 2% aromatic content. The viscosity of the liquid medium may range between 0.5 and 50 cP at 40°C, preferably between 20 and 26 cP.

[0144] A medium may further comprise additives such as fatty acids, alcohols, glycols, sulfoxides, ionic liquids, deep eutectic solvents, or phenolic compounds to modulate surface tension and improve polishing behavior. Fatty acids from C6-C30, alcohols such as ethylene glycol or fatty alcohols (C8-C28), and organic compounds containing sulfonic, sulfate, nitro, phosphate, or amine groups may be used. These additives modulate the electrochemical behavior of the electrically conductive free solid bodies, stabilize the medium, and improve the control of particle-surface interactions during polishing.

[0145] In further embodiments, a solid-particle-based electrolyte may be contained in or combined with a moderative medium, in particular a moderative fluid, more in particular a moderative liquid. A fluid medium may be liquid, gaseous, or a combination of both, and is preferably non-significantly conductive relative to the solid bodies. The fluid medium may include organic liquids such as mineral or silicone oils, paraffins, or hydrocarbon mixtures with carbon chains of 12-16 atoms and less than 2% aromatic content. The viscosity of the liquid medium may range between 0.5 and 50 cP at 40°C, preferably between 20 and 26 cP.

[0146] A medium may further comprise additives such as fatty acids, alcohols, glycols, sulfoxides, ionic liquids, deep eutectic solvents, or phenolic compounds to modulate surface tension and improve polishing behavior. Fatty acids from C6-C30, alcohols such as ethylene glycol or fatty alcohols (C8-C28), and organic compounds containing sulfonic, sulfate, nitro, phosphate, or amine groups may be used. These additives modulate the electrochemical behavior of the electrically conductive free solid bodies, stabilize the medium, and improve the control of particle-surface interactions during polishing.

[0147] In additional embodiments, the electrolyte further includes abrasive particles or abrasive composites. The abrasive particles may have densities between 2.5 and 5.5 g / cm3and hardness values between 3 and 10 on the Mohs scale, preferably between 7.5 and 9.25. Abrasive materials include alumina, zirconia, boron carbide, silicon carbide, cerium oxide, or diamond dust. The abrasive particles may be used alone or as composite particles incorporating charged polymers such as polyacrylic acid (PAA), polyethyleneimine (PEI), or polydiallyldimethylammonium chloride (PDDA), with 30-80% by weight of abrasive powder and 5-20% polymer. These composites enhance electrostatic stability, adhesion, and dispersion during polishing.

[0148] In some embodiments, the invention provides an electrically conductive abrasive composite material combining an ion-exchange resin and an abrasive powder. The resin may be sulfonated styrene-divinylbenzene or quaternary ammonium-based polymers, and the abrasive may be silica, alumina, cerium oxide, or nanodiamonds. This dual-function composite provides simultaneous abrasive and electrochemical polishing action.

[0149] In another aspect, the invention provides a method for surface treatment or polishing of a metallic or conductive object using the described solid-particle-based electrolyte. The method comprises placing the object in contact with the electrolyte, applying an electrical potential difference between the object and an electrode, and moving the electrically conductive free solid bodies relative to the object. The process selectively removes surface irregularities and contaminants via controlled electrochemical dissolution.

[0150] In some embodiments, a solid particle-based electrolyte according to the present disclosure comprises a fluid included within the environment. Preferably the fluid medium is liquid and non-significantly conductive compared to the solid bodies, but other configurations are possible, such as including a gas, emulsions, etc. The conductivity of a liquid present on the environment according to some embodiments, can be enhanced with acids or other agents, though the disclosure also allows for reduced-acid or acid-free configurations. This reduces the environmental hazards associated with traditional acidbased surface finishing, making the process safer and more suitable for facilities that do not handle acids. Additionally, the fluid’s composition can be adjusted to include lubricating solids, enhancing the process by modifying the viscosity and providing further control over the electropolishing process.

[0151] In some embodiments, a “non-significantly conductive” fluid is understood as a medium whose intrinsic electrical conductivity is substantially lower than that of the solid conductive bodies or of a conventional liquid electrolyte. Specifically, the fluid without electrically conductive free solid bodies may contain dissolved or suspended ionic species in such concentrations that its electrical conductivity is equal to or below approximately 10% of that exhibited by a fluid containing both a liquid electrolyte and electrically conductive free solid bodies. In certain embodiments, the fluid may be substantially free of electrolyte liquid, such as acids or salts, or may contain only trace amounts thereof. In alternative configurations, the fluid without electrically conductive free solid bodies may present a conductivity between about 1 % and 99% of that of the corresponding electrolyte-containing medium, preferably between 10% and 50%, and more preferably between 25% and 35%. The fluid composition may therefore contain less than 10% by weight of liquid electrolyte, in some cases below 5%, or even less than 1 %, and may, in certain embodiments, be entirely acid-free. This definition allows for safe operation of the system without the need for specialized acid-handling facilities, while maintaining adequate electrochemical functionality when used in conjunction with the electrically conductive free solid bodies.

[0152] The fluid without electrically conductive free solid bodies may contain certain amounts of liquid electrolyte in a concentration such that its electrical conductivity decreases to equal or below 10% compared to the fluid with liquid electrolyte and the electrically conductive free solid bodies. In some instances, the fluid may be entirely free of electrolyte liquid, such as an acid.

[0153] In some embodiments, the fluid without electrically conductive free solid bodies presents a conductivity of between 1 - 99% of that of the fluid with liquid electrolyte and electrically conductive free solid bodies, in particular, between 10 - 50 %, more in particular between 25 - 35 %.

[0154] The method or the system allows surface finishing without requiring transport of the container to facilities capable of handling acids, as the fluid contains less than 10%, in some cases below 5%, or even less than 1 %by weight of liquid electrolyte, such as acids. In certain cases, the fluid is completely acid-free.

[0155] The absence or reduced presence of acid agents renders the method or the system suitable for use in various facilities, even those not designed for handling acids, thus eliminating the need to transport containers to specialized locations. Surface finishing can therefore be performed on-site, reducing the production of harmful vapors, fumes, or particles typically generated by large amounts of acid. Such particles, when excessive, often require neutralization or passivation of the treated surface to extend the surface to be treated lifespan.

[0156] In some embodiments, the fluid on the medium consists of a liquid, while in others it may be a gas. The fluid serves as a medium that facilitates the movement of conductive solid bodies relative to the surface, creating an electrical potential difference between the electrically conductive free solid bodies and the surface to be treated. The fluid's viscosity and aerodynamics ensure effective motion and recirculation inside the container, thus aiding the electropolishing process. When in liquid form, the fluid also helps cool down the electrically conductive free solid bodies during electropolishing due to heat generated by ohmic effects, such as joule effect.

[0157] A medium on the interstitial gaps or a moderative medium or moderative fluid between the electrically conductive free solid bodies in a solid-particle based electrolyte according to the present invention, can include non-conductive fluids, which may include hydrocarbons such as mineral oils, paraffins, or silicone oils, more specifically, a mixture of aliphatic hydrocarbons with a carbon chain between 12-15 C containing less than 2% of aromatic groups. Other non-conductive fluids, such as certain synthetic oils and inert gases, are also utilized in some embodiments depending on the application. Additionally, various elements are incorporated, in some embodiments, into the solid-particle based electrolyte to further enhance its functionality. These may include surfactants to reduce surface tension, abrasive particles to aid in material removal during polishing, or moderator particles to control the polishing rate and prevent excessive wear or damage to the material being treated. In particular embodiments, other components that are included on the interstitial space between solid bodies are one or more of: fatty acids, glycols, sulfoxides, ionic liquids, deep eutectic solvents, phenols and fatty alcohols.

[0158] In some embodiments, medium on the interstitial gaps between the electrically conductive free solid bodies comprises an oil, such as, e.g., a mixture of aliphatic hydrocarbons with a carbon chain between 12-16 C.

[0159] In some embodiments, the fluid includes a lubricating solid that adjusts the viscosity of the fluid and / or the surface, allowing greater control over the electropolishing process

[0160] The selection of fluid viscosity is therefore another configurable variable to maintain the necessary dynamic conditions for transient packing factors. Some liquid environments where the solid bodies are allocated in particular embodiments of the present disclosure have a dynamics viscosity’s at 40°C of between 0.5 to 50 cP (i.e. , centipoise); in particular, between 15 to 30 cP; more in particular, between 20 to 26 cP.

[0161] Using organic compounds in the moderative medium comprising hydrophilic groups, such as carboxyl groups (e.g., fatty acids); hydroxyl groups (e.g., alcohols); sulfonic, or sulfate, sulfone or thiol groups; nitro or nitrate groups; phosphate groups; and / or amine groups, may be useful additives in surface finishing processes and in particular electropolishing methods using electrically conductive free solid bodies.

[0162] In some embodiments, the moderative medium includes organic compounds comprising hydrophilic groups, such as fatty acids, alcohols and other organic compounds comprising sulfonic or, sulfate, sulfone or thiol groups, nitro or nitrate groups, phosphate groups, or amine groups, preferably fatty acids and alcohols, and more preferably fatty acids, for surface finishing at least one surface of an object.

[0163] In a method as described herein known methods have been modified by using an organic compound comprising hydrophilic groups, such as organic compounds comprising carboxyl groups (e.g., a fatty acid) and / or hydroxyl groups (e.g., an alcohol) and other organic compounds comprising sulfonic or, sulfate, sulfone or thiol groups, nitro or nitrate groups, phosphate groups, or amine groups, in particular a fatty acid and / or an alcohol, in the medium comprising electrically conductive free solid bodies. In a method as described herein the plurality of electrically conductive free solid bodies in the medium bear the weight of interacting with the surface of the object to achieve the surface finishing as previously described. However, the presence of the organic compound comprising hydrophilic groups such as a fatty acid, an alcohol and other organic compounds comprising sulfonic or .sulfate, sulfone or thiol groups, nitro or nitrate groups, phosphate groups, or amine groups, has been found to modulate the interaction of the electrically co An organic compound comprising hydrophilic groups may be an organic compound comprising a carboxyl group (such as a fatty acid) and / or a hydroxyl group (such as an alcohol). The fatty acid may be selected from C3 to C50 fatty acids, e.g., C4 to C50 fatty acids in particular from C6 to C30 fatty acids, more in particular from C8 to C28 fatty acids. The alcohol may be selected from a C2 to C50 alcohol, in particular a C2 to C10 alcohol, comprising one or more hydroxyl groups. In particular, the alcohol may be a glycol, comprising two hydroxyl groups and may preferably be ethylene glycol. The alcohol may also be a fatty alcohol such as from C4 to C50 fatty alcohols, in particular from C6 to C30 fatty alcohols and more in particular from C8 to C28 fatty alcohols.

[0164] Organic compounds comprising sulfonic, or sulfate, sulfone or thiol groups may be selected from sulfonic acids, such as alkylbenzene sulfonic acids and their salts, including sodium dodecylbenzenesulfonate (SDBS) and sodium toluenesulfonate; and sulfate esters and their salts, such as sodium lauryl sulfate (SLS) and ammonium SLS.

[0165] Organic compounds comprising nitro or nitrate groups may be selected from alkyl nitrates, and nitroalkanes, including nitromethane or nitroethane.

[0166] Organic compounds comprising phosphate groups may be selected from aryl phosphates such as triphenyl phosphate (TPP), tricresyl phosphate (TCP); alkyl phosphates such as diethyl phosphate or tributyl phosphate; and phosphate esters such as monoalkyl or dialkyl phosphate esters.

[0167] Fatty acids as used herein has the meaning commonly used in the art. In particular, a fatty acid is understood by a person skilled in the art a carboxylic acid consisting of a hydrocarbon chain and a terminal carboxyl group. Fatty acids may be naturally occurring or derived from naturally occurring products such as fatty acids derived from esters in fats and oils. Fatty acids may also be synthetic.

[0168] Organic compounds comprising carboxyl groups are compounds known in the art having one or more -COOH groups, in their neutral form or ionic form (e.g., used as a salt), preferably comprising one carboxyl group, such as fatty acids. Fatty acids for surface finishing an object may be used, e.g., in a method as described herein in their neutral form or a salt, e.g. of an alkali or an alkaline earth metal ion. For instance, a fatty acid salt may be selected from a sodium, potassium, calcium and magnesium fatty acid salt.

[0169] Organic compounds comprising hydroxyl groups are compounds known in the art having one or more -OH groups, preferably comprising one or two carboxyl groups, such as alcohols and mono- or di-alcohols. Alcohols as used herein has the meaning commonly used in the art. In particular, alcohols are hydrocarbons comprising one or more hydroxyl groups as described above, and may particularly be selected from glycols (such as ethylene glycol) and fatty alcohols (which are similar to fatty acids in that they have a hydrocarbon chain and a terminal hydroxyl group, instead of a carboxyl group of the fatty acids).

[0170] Organic compounds comprising sulfonic or, sulfate, sulfone or thiol groups are compounds known in the art, having one or more -S(=O)2-OH groups (also represented as -SO3H) or -OS(=O)2-OH, -S(=O)2-, or -SH, respectively, in their neutral form or ionic form used as, e.g., a salt, preferably comprising one sulfonic or, sulfate, sulfone or thiol group. Sulfonic or sulfate groups may be particularly preferred.

[0171] Organic compounds comprising nitro or nitrate groups are compounds known in the art, having one or more -NO2 or -ONO2 groups respectively, preferably comprising one nitro or nitrate group.

[0172] Organic compounds comprising phosphate groups are compounds known in the art, having one or more -OP(=O)O2H2 groups, in their neutral form or ionic form, e.g., used as a salt, preferably comprising one phosphate group

[0173] Organic compounds comprising amine groups are compounds known in the art, and may typically be primary, secondary or tertiary amines, having one or more -NH2, -NH-R or -NR2 groups respectively, in their neutral form or ionic form, e.g., used as a salt.

Claims

1. CLAIMS1. A system for surface finishing at least one surface, comprising: a container (3) including at least one electrically conductive device, acting as a first electrode (5), at least partially arranged inside the container (3); the at least one surface (2) at least partially arranged inside the container (3); a solid-particle based electrolyte (4) arranged inside the container (3); an electric source (1) providing an electric potential difference between the at least one surface to be treated (2), at least partially arranged within the container (3) and acting as a second electrode (2), and the at least one electrically conductive device (5); the first and second electrodes (5, 2) being configured to be electrically connected through a solid-particle based electrolyte (4) that enables ion exchange between the at least one surface to be treated (2) and the solid-particle based electrolyte (4) when current is applied; and at least one device adapted with means for generating vibrations (6, 7, 8 and 9), and thereby inducing a relative motion between the solid-particle based electrolyte (4) and the at least one surface to be treated (2).

2. A system according to claim 1 , wherein the means for generating vibrations are configured for transmitting vibrations through direct physical contact against a set of free electrically conductive solid bodies of the solid-particle based electrolyte (4).

3. A system according to any of the preceding claims, wherein the means for generating vibrations are configured for transmitting vibrations through direct physical contact against a moderative medium present within an environment between the set of solid bodies of the solid-particle based electrolyte (4).

4. A system according to any of the preceding claims, wherein the means for generating vibrations are configured for applying vibrations to a surface to be treated.

5. A system according to any of the preceding claims, wherein the means for generating vibrations is configured to generate vibrations with a frequency ranging from 10 kHz to 100 kHz.

6. A system according to any of the preceding claims, wherein the means for generating vibrations is configured to generate vibrations with an amplitude is between 10% and 1000% the size of the solid bodies.

7. A system according to any of the preceding claims, where the amplitude of the vibrations generated is between 0.1 mm and 40 mm, more specifically between 0.5 mm and 5 mm.

8. A system according to any of claims 1 to 7, wherein the solid bodies comprise a sulfonic ion exchange resin.

9. A system according to any of claims 1 to 8, wherein the size of the solid bodies is between 0.1 and 2 mm, preferably between 0.3 and 1.2 mm.

10. A method for finishing a surface, comprising: arranging a solid-particle based electrolyte (4) inside of a container (3); immersing within said electrolyte (4) at least part of an electrically conductive device (5) and at least part of a surface to be treated (2); applying an electrical potential difference between said electrically conductive device (5), and a surface to be treated (2), by connecting the electrically conductive device and the surface to an electric source (1), generating an ion transport between the surface to be treated and said solid-particle based electrolyte (4); providing at least a vibration and thereby inducing a relative motion between the solid-particle based electrolyte (4) and the at least one surface to be treated (2).

11. A method according to claim 10, wherein the vibration is applied to a set of free electrically conductive solid bodies of the solid-particle based electrolyte (4).

12. A method according to any of claims 10 to 11 , wherein the means for generating vibrations is configured to generate vibrations with a frequency ranging from 10 kHz to 100 kHz.

13. A method according to claim 12, wherein the means for generating vibrations is configured to generate vibrations with a frequency ranging from 1 kHz to 10 kHz.

14. A method according to any of claims 10 to 13, wherein the vibration is applied to the surface to be treated.

15. A method according to any of claims 10 to 14, wherein a vibration amplitude is of the order of the size of the solid bodies.

16. A method according to claim 15, wherein the size of the solid bodies is between 0.1 and 2 mm, preferably between 0.3 and 1.2 mm.

17. A method according to any of claims 10 to 16, comprising arranging a vibration generator adapted to a configuration of at least one resonator arranged within the container.

18. A method according to claim 17, wherein at least one resonator that is configured to generate interference patterns of vibrational energy across the solid-particle-based electrolyte and the surface being treated.

19. A method according to any of claims 10 to 18, wherein the vibration is generated by ceramic piezoelectric transducers.

20. The method according to any of claims 10 to 19, wherein the solid-particle-based electrolyte comprises at least one particle having elastic properties with a loss factor tan 5 < 0.1 and / or a storage modulus E' between 0.5 MPa and 20 MPa.

21. The method according to any of claims 10 to 20, wherein the solid-particle-based electrolyte comprises at least one particle having damping properties with a loss factor tan 5 > 0.3 and / or a loss modulus E" between 0.1 MPa and 10 MPa.

22. The method according to any of claims 10 to 21 , wherein the solid-particle based electrolyte contains at least a substance to enhance the vibration selected from the following: surfactants, rheology modifiers, viscosity enhancers, non-Newtonian fluids, or stabilizing agents.

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