27results about How to "Solve the mechanical properties" patented technology

The invention provides a preparation method of a bipolar plate of a redox flow battery, which comprises the following steps: adding a coupling agent into resin and graphite powder, so that one end of the coupling agent is wound with the resin, the other end of the coupling agent is chemically crosslinked with the treated graphite powder to form a crosslinked net-shaped three-dimensional structure, and meanwhile, adding a conductive polymer to increase a conductive path between flexible graphite; the high-density graphite paper on the upper side and the lower side of the bipolar plate can prevent electrolyte of the flow battery from entering the bipolar plate, and the situation that the performance of the bipolar plate is reduced due to the fact that resin is in direct contact with the electrolyte is avoided.

The invention belongs to the technical field of electrocatalysis, and particularly relates to a preparation method of a nickel-iron-based transition metal boride / black phosphorus composite oxygen evolution reaction electrocatalyst. The invention provides a preparation method of a ferronickel-based transition metal boride / black phosphorus composite oxygen evolution reaction electrocatalyst, which is characterized by comprising the following steps: synthesizing a quasi-two-dimensional ethylenediamine modified black phosphorus nanosheet (eda-BP) by a hydrothermal method, and carrying out ultrasonic treatment on the surface of the obtained eda-BP to obtain the ferronickel-based transition metal boride / black phosphorus composite oxygen evolution reaction electrocatalyst. The nickel-iron-based transition metal boride / black phosphorus composite oxygen evolution reaction (OER) electrocatalyst (Ni < x > FeyB / eda-BP) is prepared by loading nickel-iron-based transition metal boride (Ni < x > FeyB) through an in-situ chemical reduction method, so that modification of a two-dimensional black phosphorus electrocatalyst is realized; the problems of instability of a quasi-two-dimensional black phosphorus catalyst, serious Fe loss of a nickel-iron-based catalyst, poor reaction kinetics and the like are solved to a great extent, and under the synergistic effect of the two parts, the electro-catalytic oxygen evolution reaction activity and the electro-catalytic stability of the composite catalyst are remarkably improved. The preparation method of the nickel-iron-based transition metal boride / black phosphorus composite oxygen evolution reaction electrocatalyst provides a new thought and a new way for designing and developing a novel efficient and stable oxygen evolution reaction electrocatalyst.

The invention belongs to the technical field of secondary batteries, and discloses a negative pole piece, a preparation method of the negative pole piece and a quick-charge type lithium ion battery. The negative electrode plate comprises a negative electrode current collector, a bottom coating layer coated on the surface of the negative electrode current collector and an upper coating layer coated on the surface of the bottom coating layer, the active substance in the material of the bottom coating and the active substance in the material of the upper coating are respectively and independently graphite negative electrode materials, and the OI value of the active substance in the material of the bottom coating and the OI value of the active substance in the material of the upper coating are respectively and independently smaller than or equal to 15. Graphite with different OI values is adopted for layered coating, the ion impedance of the pole piece is reduced, the rate capability of the pole piece is improved, and the problem that the energy density and the rate capability cannot be considered at the same time due to insufficient electrolyte wettability, insufficient dynamic performance and poor conductivity caused by thickening of the negative pole piece is solved.

The invention relates to a hydrated borate micromolecule with a boron-nitrogen coordination bond, a derivative resin material and a preparation method of the hydrated borate micromolecule. The preparation method comprises the following steps: S1, synthesizing boron-nitrogen coordination micromolecules: dissolving and reacting boric acid, a derivative thereof and a polyfunctional group amine compound at room temperature through a solution reaction to obtain the boron-nitrogen coordination micromolecules; the borate micromolecule NCBW-X with intramolecular boron and nitrogen coordination is formed; s2, the NCBW-X micromolecule can be used for curing epoxy resin and synthesizing materials such as phenolic resin through end-NH2 and end-OH on two sides, the NCBW-X improves the mechanical property of each system through a rigid eight-membered ring, boron-nitrogen coordination of the NCBW-X can generate hydration, the environmental endurance is improved on the premise of retaining the original dynamic nature of boric acid ester of the NCBW-X, and the service life of the NCBW-X micromolecule is prolonged. Meanwhile, due to the dynamic reversibility of the NCBW-X, the NCBW-X is used for curing epoxy resin, and materials such as phenolic resin and the like are improved to a certain extent in the aspects of self-repairing and recycling.

The invention belongs to the field of basalt fiber photovoltaic supports, and discloses an energy-consuming basalt fiber photovoltaic support without trepanning connection, which is characterized in that a plurality of groups of energy-consuming connecting pieces are arranged on a stand column, and each energy-consuming connecting piece comprises a buckle, an energy-consuming assembly and a pre-embedded connecting steel plate; the buckle is used for fixing the basalt fiber supporting structure and providing stable inclined supporting force and vertical supporting force for the basalt fiber purline; the energy dissipation assembly consumes external load energy through friction, and the anti-seismic and wind-resistant performance of the support is enhanced; the whole support is connected without opening holes, stress is effectively dispersed, local stress concentration is avoided, and the material performance is kept; the energy dissipation assembly enables the support to be in rigid connection under the load and then to be in flexible connection, energy is consumed, load transmission is limited, and rod pieces are prevented from falling off and cracking. By adopting the bracket, the problems of mechanical property reduction and stability caused by trepanning are solved, the durability and the safety of the bracket are remarkably improved, and the bracket is widely applicable to different geographical and climatic conditions.

The invention relates to the technical field of coatings, and provides a single-component polyurea coating, which is prepared from the following raw materials in parts by weight: 150 to 200 parts of polyether polyol, 60 to 80 parts of isocyanate, 20 to 35 parts of polyamine, 60 to 80 parts of filler, 0.5 to 1 part of defoaming agent, 1 to 3 parts of catalyst and 10 to 20 parts of thixotropic agent. The thixotropic agent is modified bentonite, the modified bentonite is obtained by modifying bentonite through a modifier, and the modifier is hydroxyl polydimethylsiloxane and isocyanate propyl triethoxy silane. According to the technical scheme, the problems of poor mechanical property and adhesive force of a single-component polyurea coating in the prior art are solved.

This invention discloses a transition metal phosphide catalyst, its preparation method, and its application, belonging to the field of electrocatalysis technology. The process includes: firstly, dissolving nickel salt, lanthanum salt, urea, and ammonium fluoride in deionized water to synthesize a nickel-lanthanum layered hydroxide nanosheet precursor via a hydrothermal method; secondly, preparing a lanthanum-doped nickel phosphide catalyst using a phosphating reaction; and thirdly, utilizing a lanthanum doping strategy to modulate the electronic structure of nickel phosphide and improve its electrocatalytic reaction performance. This lanthanum-doped nickel phosphide material exhibits good catalytic activity when used to catalyze hydrogen evolution and sulfide ion oxidation reactions. In an integrated two-electrode electrolyzer for sulfide ion oxidation-assisted hydrogen production, it outputs 10 mA cm⁻¹. ‑2 This invention achieves the goal of producing hydrogen and high-value-added sulfur products with low energy consumption by requiring a relatively low voltage of 0.525 V at a current density. It has advantages such as simple preparation process, controllable operating conditions, and low raw material costs, possessing the potential for large-scale production and serving as a high-performance catalyst for electrocatalytic hydrogen production and sulfur ion oxidation reactions.

The invention relates to a laser modification method of transparent ceramic and the transparent ceramic obtained by the method, and the method combines laser pretreatment (LPP) and laser shock peening (LSP) to improve the laser damage resistance (LIDT) and mechanical stability of the transparent ceramic. The technical scheme comprises step-by-step surface and deep layer laser treatment, LPP is executed preferentially to eliminate surface microdefects and improve optical transmittance and damage threshold, and then the mechanical damage resistance of the interior of the material is enhanced through the LSP technology under the condition that the laser energy density is kept lower than the safety threshold. Through strict LIDT and mechanical property tests, technological parameters are fed back and adjusted, and the performance of the transparent ceramic is comprehensively improved. The process is suitable for high-performance optical elements and laser systems requiring high optical transparency and excellent mechanical properties. The innovation not only obviously prolongs the service life of the material, but also reduces the maintenance cost, and has wide application prospects.

The application relates to the technical field of food packaging, in particular to a degradable food packaging bag and a preparation process thereof. The packaging bag comprises two base films and a functional adhesive layer which is compounded between the two base films. The base film is made of raw materials including the following components in parts by mass: polybutylene adipate terephthalate 50-70 parts; polylactic acid 20-35 parts; corn starch 10-25 parts; and a compatilizer 2-6 parts. The functional adhesive layer is made of raw materials including the following components in parts by mass: water-based polyurethane emulsion 100 parts; hydrophobic silicon dioxide particles 3-15 parts; chitosan derivative modified micron zinc oxide 5-20 parts; and a plasticizer 1-5 parts. The application provides a method which considers the degradation, antibacterial property and mechanical property, and has the effects of being safer and more reliable.

The invention relates to the technical field of cable materials, and provides a low-smoke halogen-free flame-retardant cable material and a preparation method thereof.The cable material is prepared from, by weight, 16-20 parts of ethylene-vinyl acetate copolymer, 4-6 parts of polyolefin elastomer, 6-8 parts of polyethylene, 5-7 parts of compatilizer, 60-70 parts of composite flame retardant and 1-2 parts of antioxidant; the composite flame retardant is prepared from sepiolite, N, N '-diacryloylethylenediamine and an inorganic flame retardant. According to the technical scheme, the problems of poor flame retardance and mechanical property of the cable material in the prior art are solved.

The invention relates to the technical field of winding wires, and proposes an insulated submersible motor winding wire and a preparation method thereof. The insulated submersible motor winding wire includes a wire core, a film layer, and an insulating layer from the inside to the outside. The wire core is composed of a conductor and a coating. The conductor is a copper wire, the coating is a nickel coating, the film layer is a polyester film, and the insulating layer includes the following raw materials by weight: 60-70 parts of polyethylene, 20-30 parts of filler, 1-3 parts of silane coupling agent, 1-2 parts of lubricant, and 2-3 parts of antioxidant; the filler includes bentonite and modified alumina, and the modified alumina is obtained by modifying alumina with nitride. Through the above technical scheme, the problem of poor mechanical properties and insulation of the winding wire in the related art is solved.

The present invention relates to an ultra-black composite coating based on carbon nanomaterials and a preparation method thereof, and belongs to the technical field of coatings. The preparation method of the present invention comprises the following steps: S1, dissolving carbon nanoparticle color paste, multi-walled carbon nanotube color paste, and graphene color paste in water and stirring evenly, and then adding a binder, a metal oxide filler, a thickener, a defoamer, and an auxiliary agent and stirring evenly to obtain a composite ink; S2, using a spraying technology or an ink direct writing 3D printing technology to make a composite coating on the surface of a substrate with the composite ink; S3, freezing the composite coating with liquid nitrogen through a self-adsorption flat plate freezer, and then freeze-drying it through a freeze dryer, and obtaining the ultra-black composite coating based on carbon nanomaterials through plasma surface treatment, and constructing a flexible, large-area ultra-black composite coating with a vertically ordered micro-nano honeycomb light-trapping structure based on carbon nanomaterials.

The invention relates to the technical field of winding wires, and provides an insulating submersible motor winding wire and a preparation method thereof.The insulating submersible motor winding wire sequentially comprises a wire core, a film layer and an insulating layer from inside to outside, the wire core is composed of a conductor and a plating layer, the conductor is a copper wire, the plating layer is a nickel plating layer, and the film layer is a polyester film; the insulating layer comprises the following raw materials in parts by weight: 60-70 parts of polyethylene, 20-30 parts of filler, 1-3 parts of a silane coupling agent, 1-2 parts of a lubricant and 2-3 parts of an antioxidant; the filler comprises bentonite and modified aluminum oxide, and the modified aluminum oxide is obtained by modifying aluminum oxide through nitride. According to the technical scheme, the problem that the winding wire is poor in mechanical property and insulativity in the prior art is solved.

The invention relates to the technical field of composite materials, and provides a prefabricated breathable coiled material and a preparation method thereof.The prefabricated breathable coiled material sequentially comprises a surface layer and a bottom layer from top to bottom, and the surface layer is prepared from, by weight, 30-40 parts of SEBS, 15-22 parts of polypropylene, 15-25 parts of first filler, 25-30 parts of softener, 1-3 parts of antioxidant and 1-3 parts of maleic anhydride grafted polypropylene; the bottom layer is prepared from the following raw materials in parts by weight: 15 to 22 parts of SEBS, 30 to 40 parts of polypropylene, 20 to 30 parts of second filler, 25 to 30 parts of softening agent and 1 to 3 parts of maleic anhydride grafted polypropylene; the first filler and the second filler are both calcium-containing compounds. According to the technical scheme, the problems of poor air permeability, wear resistance and mechanical property of the prefabricated coiled material in the prior art are solved.

The present invention relates to the technical field of flame retardant materials, and discloses a flame retardant low-density polyethylene composite material, a preparation method thereof and an application thereof. The composition for preparing the composite material comprises the following components in percentage by mass: 55-85% low-density polyethylene, 10-25% modified ammonium polyphosphate and 5-20% carbon-forming agent; wherein the modified ammonium polyphosphate is ammonium polyphosphate coated with an organosiloxane compound and a silicone gel. Low-density polyethylene, modified ammonium polyphosphate and a carbon-forming agent are melt-blended to obtain a flame retardant low-density polyethylene composite material. The present invention utilizes ammonium polyphosphate coated with an organosiloxane compound and a silicone gel and a carbon-forming agent to form an intumescent flame retardant system, and prepares an intumescent flame retardant low-density polyethylene composite material by melt blending. The oxygen index of the product can meet the flame retardant requirements and reduce the amount of smoke released, while solving the problem that the addition of flame retardants in the prior art will greatly reduce the mechanical properties of the material.

The invention provides a polynorbornene interpenetrating polymer network cross-linked anion exchange membrane as well as a preparation method and application thereof. According to the invention, the polynorbornene-based interpenetrating polymer network cross-linked anion exchange membrane is prepared from polynorbornene, allylphenol quaternary ammonium salt and polythiol under the irradiation condition of an ultraviolet lamp. The polynorbornene-based interpenetrating polymer network cross-linked anion exchange membrane has a smooth and transparent surface, has excellent conductivity, stability and mechanical properties, overcomes the problem of tradeoff between conductivity and stability of a common AEM, and can be applied to alkaline fuel cell equipment, alkaline electrolyzed water equipment, electrodialysis equipment, waste acid recovery equipment, carbon dioxide reduction equipment and the like.

A biomimetic mother-of-pearl interlocking structure hydrophobic hemp fiber-based radiation cooling membrane and its preparation method are disclosed, belonging to the field of radiation cooling technology. To address the problems of environmentally unfriendly raw materials, high cost, complex preparation processes, and low cooling efficiency in existing radiation cooling materials, this invention provides a preparation technology for a hemp fiber-based biomimetic radiation cooling membrane and a flexible fabric coating. Using industrial hemp recycled fibers as the core green matrix, through synergistic design of material innovation, structural innovation, and process innovation, it comprehensively solves the technical defects of existing radiation cooling materials, providing a new green solution for the large-scale application of radiation cooling technology in multiple scenarios. This radiation cooling membrane, using recycled industrial hemp fibers as the matrix, combines the characteristics of being environmentally friendly, having a biomimetic interlocking structure, and providing high-efficiency radiation cooling. The preparation process is simple and can be mass-produced, meeting the application needs of multiple fields such as building energy conservation, outdoor equipment manufacturing, electronic equipment thermal management, and agricultural greenhouse film control.

The invention discloses a high-performance fiber polymer material and a spinning preparation method thereof, and relates to the technical field of spinning preparation, and the spinning preparation method of the high-performance fiber polymer material comprises the following steps: S1, preparing a polystyrene solution, a nano silicon dioxide suspension and a chitin and chitosan mixed acetic acid solution; s2, preparing a polydopamine solution, a nano titanium oxide suspension liquid, a carbon nano tube and a graphene dispersion liquid; s3, preparing a core layer solution and a shell layer solution; s4, carrying out defoaming treatment on the core layer solution and the shell layer solution; s5, preparing a high-performance fiber polymer material; s6, cleaning and drying the high-performance fiber polymer material; and S7, carrying out tensile property test on the high-performance fiber polymer. The fiber polymer material with a core layer structure is prepared, and the fiber polymer material is alternately subjected to thermocuring and photocuring, so that the processability and the mechanical property of the fiber polymer material are optimized.

The invention discloses a method for modifying a Prussian blue sodium battery positive electrode material by a solvothermal method and a positive electrode material prepared by the method, pentacarbonyl iron Fe (CO) 5 is used as a raw material, and the Prussian blue sodium battery positive electrode material coated and modified by an iron elementary substance is prepared by the solvothermal method. The purpose of improving the electrochemical performance of the Prussian blue sodium battery positive electrode material is achieved. The iron elementary substance is insoluble in water and is not easy to react with water, and the iron elementary substance coating layer can prevent the base material from being in direct contact with water, so that the water absorption of the base material is reduced, and the processability of the Prussian blue sodium battery positive electrode material is improved. The existence of the iron elementary substance can avoid direct contact between the substrate and an electrolyte, so that the side reaction of an electrochemical interface is inhibited, the interface stability of the material is improved, and the cycle performance of the material is improved. The elementary iron has extremely high conductivity, and the elementary iron is coated on the surface of the base material, so that the problems of poor electrochemical kinetics and stability caused by inherent low conductivity of the Prussian blue sodium battery positive electrode material can be solved, and the rate capability of the material is further improved.

The invention discloses a mineral admixture suitable for a phosphorus-based solid waste roadbed material and a preparation method thereof, the mineral admixture is prepared by taking carbide slag and Portland cement clinker as raw materials, spraying a small amount of additive on the surface of the raw materials, carrying out ball milling on the uniformly mixed materials in a ball mill for 25-30 minutes, and sieving with a 200-mesh sieve. The mineral admixture prepared by the invention can effectively solidify soluble phosphorus in the phosphorus-based solid waste roadbed material, stimulate the activity of phosphorus slag and generate C-S-H gel and AFt in a hydration process, so that the mechanical property and water resistance of the phosphorus-based solid waste roadbed material are remarkably improved. Besides, the mineral admixture takes the carbide slag as a main raw material, the preparation method is simple, the energy consumption is low, and the utilization of phosphatized industrial solid wastes in road engineering is promoted.

The application provides a bone filling net bag with a double-material filling structure, which comprises an inner layer net bag and an outer layer net bag wrapped outside the inner layer net bag; a first filling cavity is formed in the inner layer net bag, and the first filling cavity is used for filling polymethyl methacrylate bone cement; an annular gap between the inner layer net bag and the outer layer net bag forms a second filling cavity, and the second filling cavity is used for filling artificial bone material; a connecting pipe is arranged on the outer surface of the inner layer net bag, the connecting pipe is connected with the first filling cavity and the second filling cavity, and is used for guiding the polymethyl methacrylate bone cement to enter the second filling cavity from the first filling cavity. The synergistic design of the structure and the material enables the implanted body to form a gradient composite interface of 'bone cement-artificial bone-host bone' in microcosm, realizes the unity of immediate stability and long-term fusion in macrocosm, and reduces the risk of postoperative implant loosening and re-fracture.

The invention provides polypropylene fiber concrete and a preparation method thereof, and belongs to the technical field of concrete, the polypropylene fiber concrete is prepared by uniformly mixing 320-330 parts by weight of recycled aggregate, 610-620 parts by weight of fine aggregate, 380-390 parts by weight of cement, 1.2-1.5 parts by weight of polypropylene fiber, 1.5-2.0 parts by weight of glass powder, 0.8-1.0 part by weight of nano silicon dioxide, 5-7 parts by weight of a water reducing agent and 170-180 parts by weight of water. Through the synergistic effect of the nano silicon dioxide, the glass powder and the polypropylene fiber, the problems that the mechanical property and the freeze-thaw resistance become poor due to the fact that the recycled aggregate is used for preparing the concrete are effectively solved, recycling of the recycled aggregate is well achieved, and the compression resistance and the freeze-thaw resistance of the prepared polypropylene fiber concrete are improved.

The invention provides a workpiece performance optimization method and system, electronic equipment and a storage medium. The method comprises the steps that microstructure features of a workpiece in the LPBF forming process are extracted, and the mechanical property of the workpiece is determined according to the microstructure features; in response to a to-be-optimized area of which the mechanical property does not meet a preset condition on the workpiece, determining optimization process parameters of the to-be-optimized area according to a process optimization model; wherein the process optimization model represents a corresponding relationship among process parameters, microstructure characteristics and mechanical properties, and the process optimization model is constructed according to simulation data and / or experimental data; and optimizing the region to be optimized by adopting the optimization process parameters. The structure uniformity of all structural domains of the workpiece can be further improved, the problems of inconsistent microstructure distribution and mechanical property fluctuation caused by complex workpiece structure and non-uniform heat input are solved, and the defect occurrence rate of the workpiece is reduced.

The invention belongs to the field of inorganic non-metallic materials, and particularly relates to a preparation method of an anti-ablation coating for a composite material blade of a hydrogen-burning gas turbine, the anti-ablation coating is coated on a gas runner surface of a ceramic matrix composite material blade, and the anti-ablation coating is composed of a packaging layer, a chemical barrier layer, a water-oxygen-resistant layer and a heat insulation layer from inside to outside in sequence, the anti-ablation coating is prepared by adopting a composite technology of slurry dipping, plasma spraying and vibration finishing treatment, and the protection requirement of the ceramic matrix composite blade in a 1600 DEG C hydrogen combustion environment can be met. The preparation method of the anti-ablation coating of the composite material blade of the hydrogen gas turbine has the advantages of convenience in construction, excellent aerodynamic characteristics, good hydrogen ablation resistance and CMAS corrosion resistance, long service life and the like.

The invention discloses a method for preparing a modified Prussian blue sodium battery positive electrode material and the positive electrode material prepared by the method. The invention belongs to the field of sodium ion batteries, and particularly relates to a method for preparing a modified Prussian blue sodium battery positive electrode material through CuFeS2 coating and the positive electrode material prepared by the method. The method comprises the following steps: dropwise adding an S < 2-> salt solution into a Prussian blue sodium battery positive electrode material suspension containing Fe < 3 + > and Cu < 2 + > under a stirring condition, and enabling Fe < 3 + > and Cu < 2 + > to react with S < 2->; and further performing hydrothermal reaction to form high-crystallinity CuFeS2 which is coated on the surface of the Prussian blue sodium battery positive electrode material. CuFeS2 coating realizes the purpose of reducing the water absorption of the Prussian blue sodium battery positive electrode material, and solves the problem of poor electrochemical kinetics and stability caused by inherent low conductivity and sensitivity to electrolyte of the Prussian blue sodium battery positive electrode material at the same time; the electrochemical performance of the modified Prussian blue sodium battery positive electrode material is improved.

The invention discloses an antistatic PE water supply pipe and a preparation method thereof, and belongs to the technical field of plastic pipes. The copolymerized ionic liquid formed by polymerization has higher thermal stability, so that the thermal stability and the antistatic property of the PE water supply pipe are greatly improved, the gaseous silicon dioxide has plasticizing property, and the bis (2, 2, 6, 6-tetramethyl-4-piperidyl) sebacate can have a synergistic effect with the antioxidant and the antistatic agent, so that the antistatic property of the PE water supply pipe is improved. The antistatic property and the anti-aging property of the PE water supply pipe are greatly improved. According to the invention, the antistatic PE water supply pipe is prepared by taking 3-methyl-5-(2-methallyl) pyridine tetrafluoroborate and quaternary ammonium salt copolymerized ionic liquid as an antistatic agent and gaseous silicon dioxide loaded bis (2, 2, 6, 6-tetramethyl-4-piperidyl) sebacate as a toughening anti-ultraviolet filler; and the material has excellent antistatic, anti-ultraviolet aging and mechanical properties.

This invention relates to the field of electronic materials technology and discloses a low-temperature curing copper-silver composite paste for TGV interconnects and multilayer RDL fabrication and its preparation method. The aim is to address how to suppress the destructive effect of intrinsic copper oxidation on the conductive network during TGV via metallization in an air atmosphere at 200-300°C. This is achieved by using a dense silver layer to coat copper powder to form silver-coated copper composite particles, suppressing the oxidation of the copper core during the heating process. The low-temperature sintering activity of nano-silver powder forms conductive silver bridges before the silver layer dehumidifies, connecting adjacent silver-coated copper particles. A high-temperature resistant resin with a glass transition temperature higher than 260°C after curing is selected as the binder. After curing, the resin is distributed in a discontinuous island-like pattern between the particles, applying compressive stress to enhance contact and simultaneously resisting multilayer wiring processes. The synergistic effect of these three stages allows the sintering reaction to form a stable conductive network in an air atmosphere at 200-300°C, and it is compatible with photosensitive polyimide insulating layers, making it suitable for additive manufacturing of multilayer RDLs for glass via circuit boards.