Surface-modified multi-scale heterogeneous graphite filler, method of preparation and use

Abstract

This invention relates to the field of graphite surface modification technology, and more particularly to a surface-modified multi-scale heterogeneous graphite filler, its preparation method, and its application. The filler includes a graphite filler on which an anatase crystalline titanium oxide film is deposited using atomic layer deposition (ALD). The anatase crystalline titanium oxide film exhibits higher intrinsic chemical stability, effectively isolating the graphite filler from direct contact with external corrosive electrolytes. Furthermore, ALD deposition can be performed at relatively low temperatures of 100-300°C, significantly improving the graphite filler's resistance to galvanic corrosion, dynamic friction and wear, and high-temperature oxidation while fully preserving its inherently excellent sealing performance. This fills the gap in the insufficient electrochemical corrosion resistance of flexible graphite fillers and solves the problem in existing technologies where surface modification of graphite fillers is difficult to effectively overcome the poor electrochemical corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of graphite surface modification technology, specifically to a surface-modified multi-scale heterogeneous graphite filler, its preparation method, and its application. Background Technology

[0002] In the grand process of industrial development, the process industry occupies a pivotal position, encompassing numerous key areas such as petrochemicals, aerospace, and nuclear power. Within the various equipment and systems of the process industry, the performance of sealing components, such as valve stem packing for control valves and mechanical seal rings for pumps, directly affects the safe and stable operation of the entire system and its energy efficiency. However, these components often face extreme conditions such as high temperatures (up to 600K or higher), high pressures (medium pressures of 0.3-0.6 MPa and above), highly corrosive media (acids, alkalis, and salt solutions), and dynamic friction and wear, leading to prominent valve stem seal leakage problems.

[0003] Graphite materials, especially flexible graphite, are widely used in sealing applications in process industries due to their excellent thermal conductivity, self-lubricating properties, chemical inertness, and good compression resilience, making them a crucial material for ensuring the normal operation of process industry systems. However, intrinsic graphite materials exhibit significant drawbacks in complex electrochemical environments: First, their porous structure and low electrochemical potential make them highly susceptible to galvanic corrosion in electrolyte environments when used as mating pairs for metal valve stems, disrupting the smoothness and fit of the sealing surface. Second, during continuous dynamic friction, the graphite surface is prone to wear, and wear debris can clog pores or alter the surface morphology, leading to a decline in sealing performance. Furthermore, graphite is at risk of oxidation and strength reduction in high-temperature, oxygen-rich environments. These factors collectively result in the short lifespan and frequent maintenance of traditional graphite packings under highly corrosive and high-parameter operating conditions, becoming a bottleneck in system reliability.

[0004] To improve the mechanical strength and durability of graphite fillers, existing technologies mainly focus on macroscopic composites and structural design, but their effectiveness in improving the wear and corrosion resistance of graphite surfaces is limited. In terms of macroscopic composites, a common method is to incorporate metal wires into graphite materials. By uniformly integrating the metal wires into the graphite matrix, the high strength and tensile properties of the wires enhance the overall tensile and extrusion resistance of the graphite filler. However, the introduction of metal wires may scratch the surfaces of the mating metals, and the contact between dissimilar metals may exacerbate galvanic corrosion, accelerating the corrosion rate of both the metal wires and the graphite material, thus reducing the service life of the sealing components. In terms of structural design, various graphite fillers with special cross-sectional shapes, such as V-shapes and rhomboid shapes, are designed. These specially shaped fillers can better adapt to changes in the shape of the sealing surface during the sealing process, increasing the contact area and improving the sealing effect. Simultaneously, using sealing structures combining multiple materials is also an effective improvement method. For example, combining flexible graphite with aramid packing, PTFE, and other materials fully utilizes the advantages of each material. However, the compatibility and bonding strength between different materials remain a key issue. If the materials do not bond well, delamination and detachment can easily occur during use, leading to seal failure. Furthermore, organic additives such as PTFE are prone to degradation at high temperatures, producing harmful gases that not only affect sealing performance but may also pollute the environment.

[0005] Given the limitations of macroscopic modification, recent research has shifted towards surface engineering modification of graphite fillers, aiming to directly construct a corrosion-resistant functional coating on the material surface to improve its various properties. Existing surface coating technologies include chemical vapor deposition (CVD), slurry coating, and electrophoretic deposition. However, CVD typically requires high temperatures (>500℃), and graphite materials are prone to oxidation and changes in their internal microstructure at high temperatures, thus affecting their sealing performance. While slurry coating is relatively simple, the uniformity of the coating and its adhesion to the substrate are difficult to control effectively. Furthermore, due to the porous structure of graphite surfaces, the slurry is difficult to fill the pores uniformly during coating, resulting in a thick, uneven coating that affects adhesion to the substrate, thus impacting sealing performance and service life. Electrophoretic deposition requires a high conductivity substrate, but the conductivity of graphite materials can vary depending on the preparation process and composition, increasing the difficulty of implementing the electrophoretic deposition process. In addition, the coating formed by electrophoretic deposition generally lacks density and cannot effectively block the penetration of corrosive media, offering limited protection to graphite materials. Plasma electrolytic oxidation technology is mainly applicable to valve metals, but not to non-valve metals such as graphite. Therefore, it cannot be used for the surface modification of graphite fillers.

[0006] Therefore, developing a low-temperature, uniform, and efficient surface modification method suitable for graphite fillers to significantly improve their corrosion resistance while maintaining their inherent excellent sealing properties is of great significance for extending the service life of sealing components of key equipment and ensuring the safe and stable operation of industrial systems. Summary of the Invention

[0007] To address the problem that surface modification of graphite fillers in existing technologies cannot effectively overcome the poor electrochemical corrosion resistance of graphite fillers, this invention provides a surface-modified multi-scale heterogeneous graphite filler, its preparation method, and its application.

[0008] To achieve the above objectives, the present invention employs the following technical solution: The present invention provides a surface-modified multi-scale heterogeneous graphite filler, comprising a graphite filler, wherein an anatase crystalline titanium oxide film is deposited on the surface of the graphite filler by atomic layer deposition technology.

[0009] Optionally, the graphite filler is a flexible graphite sheet, flexible graphite paper, graphite ring, or graphite packing seal.

[0010] Optionally, the thickness of the anatase crystalline titanium oxide film is 100-300 nm.

[0011] The present invention also provides a method for preparing surface-modified multi-scale heterogeneous graphite fillers as described above, comprising: The surface of the graphite filler is pretreated to obtain surface-activated graphite filler; Atomic layer deposition (ALD) was employed, using titanium and oxygen source precursors as reaction precursors. By alternating pulsed gas inlet and inert gas purging cycles, an anatase crystalline titanium oxide film was grown in situ on the surface of activated graphite filler, resulting in surface-modified multi-scale heterogeneous graphite filler.

[0012] Optionally, the method for pretreating the surface of the graphite filler to obtain surface-activated graphite filler is as follows: The surface of the graphite filler is polished to remove surface slag and protrusions, resulting in polished graphite filler. The polished graphite filler was ultrasonically cleaned in anhydrous ethanol and dried to obtain surface-activated graphite filler.

[0013] Optionally, the titanium source precursor is titanium isopropoxide, and the temperature of titanium isopropoxide is 60-80℃; the oxygen source precursor is hydrogen peroxide.

[0014] Optionally, the inert gas is nitrogen with a purity of ≥99.999%.

[0015] Optionally, the deposition temperature of the atomic layer deposition process is 200-300℃, and the sequence of the single pulse gas inlet and inert gas purging cycle is as follows: titanium source precursor pulse gas inlet, first inert gas purging, oxygen source precursor pulse gas inlet, and second inert gas purging.

[0016] Optionally, during a single pulse intake and inert gas purging cycle: the pulse intake time for the titanium source precursor is 1-2 s, the first inert gas purging time is 10-15 s, the pulse intake time for the oxygen source precursor is 0.1-0.3 s, and the second inert gas purging time is 10-15 s; the number of alternating pulse intake and inert gas purging cycles is 2000-3000.

[0017] The aforementioned surface-modified multi-scale heterogeneous graphite fillers are used as sealing components in process industries.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a surface-modified multi-scale heterogeneous graphite filler, comprising a graphite filler on which an anatase crystalline titanium oxide film is deposited using atomic layer deposition (ALD). The anatase crystalline titanium oxide film exhibits higher intrinsic chemical stability, is strongly bonded by Ti-O bonds, and is less prone to dissolution or ion exchange in electrolyte environments, thus avoiding the introduction of additional corrosion potential differences. This significantly inhibits or eliminates galvanic corrosion, protecting the flatness and fit accuracy of the sealing surface. Simultaneously, the surface of the anatase crystalline film is atomically saturated, exhibiting high chemical inertness and low active sites for corrosion reactions. Furthermore, the anatase crystalline titanium oxide film possesses a long-range ordered atomic arrangement and a close-packed lattice structure, with dense grain boundaries effectively eliminating amorphous seepage channels. Its ion diffusion coefficient is significantly lower than that of amorphous titanium oxide films. As a corrosion barrier layer, it exhibits excellent density and integrity, effectively isolating the graphite filler from direct contact with external corrosive electrolytes (acids, alkalis, and salt solutions), blocking the electronic pathways and ion migration paths required for galvanic corrosion. Furthermore, atomic layer deposition (ALD) can be performed at lower temperatures of 100-300℃, significantly lower than traditional chemical vapor deposition (typically >500℃). This effectively avoids oxidation, deformation, or mechanical property damage to porous, layered graphite structures caused by high temperatures. The low-temperature deposition also avoids thermal stress caused by the mismatch in thermal expansion coefficients of the graphite filler, resulting in a low-stress, high-bonding interface between the film and the substrate. This ensures the long-term stability of the modified graphite filler under dynamic sealing conditions. Thus, while fully preserving the inherent excellent sealing performance of graphite filler, it significantly improves the graphite filler's resistance to galvanic corrosion, dynamic friction and wear, and high-temperature oxidation. This fills the gap in the insufficient electrochemical corrosion resistance of flexible graphite fillers and is expected to significantly extend the service life of sealing components of critical valves, pumps, and other equipment operating in high-temperature, high-pressure, and highly corrosive media environments in the petrochemical, aerospace, and other fields, thereby improving the safety and reliability of system operation.

[0019] This invention also provides a method for preparing surface-modified multi-scale heterogeneous graphite fillers as described above. This method involves pretreating the surface of the graphite filler to obtain surface-activated graphite filler, and then using atomic layer deposition (ALD) to grow anatase crystalline titanium oxide thin films in situ on the surface of the surface-activated graphite filler. This achieves the preparation of surface-modified multi-scale heterogeneous graphite fillers. By optimizing the ALD process, low-temperature surface modification of the graphite filler is achieved, retaining the intrinsic structural properties of the graphite filler while improving its corrosion resistance. The self-limiting surface reaction unique to ALD technology endows it with excellent wrap-around coating properties (i.e., three-dimensional conformal coverage), enabling the anatase crystalline titanium oxide thin film to form a uniform, pinhole-free, and highly dense protective layer on the surface of complex porous graphite fillers, and even in the internal pores and edges of the filler. This layer is firmly bonded to the graphite filler and effectively blocks the penetration of corrosive media. With strong process controllability and good repeatability, the ALD process parameters (such as temperature, pulse time, and number of cycles) are precisely controllable, enabling nanometer-level precision control of film thickness and structure. This ensures the uniformity of product performance and the repeatability of the preparation process, making it suitable for industrial applications and of significant practical value for promoting the technological advancement of sealing components in the process industry.

[0020] The aforementioned surface-modified multi-scale heterogeneous graphite packing is used as a sealing component in process industries. Because this surface-modified multi-scale heterogeneous graphite packing retains the excellent sealing performance inherent in graphite packing, the introduction of anatase crystalline titanium oxide film simultaneously significantly improves resistance to galvanic corrosion. This results in sealing components made using this surface-modified multi-scale heterogeneous graphite packing exhibiting advantages such as good sealing performance, good environmental adaptability, long service life, high safety, and low maintenance costs, making it a promising candidate for applications in petrochemical, aerospace, and nuclear power industries. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the preparation method of a surface-modified multi-scale heterogeneous graphite filler according to the present invention.

[0022] Figure 2 This is a schematic diagram illustrating the specific process of preparing a surface-modified multi-scale heterogeneous graphite filler according to the present invention.

[0023] Figure 3 The images shown are physical images of the surface-modified multi-scale heterogeneous graphite fillers prepared in Examples 1-3 of the present invention. Among them, a is a comparison image of the sheet-like surface-modified multi-scale heterogeneous graphite filler prepared in Example 1 before and after corrosion, b is a physical image of the annular surface-modified multi-scale heterogeneous graphite filler prepared in Example 4, and c is a physical image of the packing surface-modified multi-scale heterogeneous graphite filler prepared in Example 3.

[0024] Figure 4 The morphology and elemental characterization of the titanium oxide thin film deposited on the flexible graphite sheet in Example 1 of the present invention are shown, where a represents the surface SEM morphology and bd represents the EDS energy dispersive spectroscopy analysis.

[0025] Figure 5 XPS results for the sheet-like surface-modified multi-scale heterogeneous graphite filler prepared in Example 1 of this invention; Figure 6 The XRD results are for the sheet-like surface-modified multi-scale heterogeneous graphite filler prepared in Example 1 of this invention. Figure 7 The results of electrochemical corrosion performance tests before and after surface modification of the multi-scale heterogeneous graphite filler in Example 1 of this invention are as follows: Figure 8 This is a curve comparing the intrinsic electrochemical corrosion performance of the multi-scale heterogeneous graphite filler with different coating thicknesses and the graphite filler itself with different coating thicknesses in Example 1 of the present invention.

[0026] Figure 9 The results are the bonding performance test results of the graphite packing before and after coating in Example 3 of the present invention. Detailed Implementation

[0027] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0028] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0029] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0030] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0031] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0032] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0033] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0034] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0035] Atomic layer deposition (ALD) is a thin film deposition technique based on self-limiting surface chemical reactions. It boasts significant advantages such as uniform and dense films, controllable thickness (down to the nanometer scale), low-temperature deposition, excellent step coverage, and three-dimensional wrap-around deposition capabilities. ALD technology has been used to deposit protective films such as Al2O3 and TiO2 on the surfaces of complex and precision components. Studies have shown that TiO2 films possess good chemical stability, high hardness, and certain corrosion resistance. However, existing TiO2 films are often amorphous, and the surface of amorphous TiO2 contains a large number of unsaturated coordination atoms (such as Ti...). 3+ Defects and oxygen vacancies—these highly active sites readily adsorb OH groups. - Cl - Corrosive ions (OH-) act as initiators of localized corrosion reactions. Furthermore, the long-range disorder of amorphous TiO2 atoms, coupled with numerous microscopic pores and coordination defects, easily creates penetrating channels, allowing corrosive ions (OH-) to easily penetrate the surface. - Cl - It can rapidly diffuse along the defects to the graphite matrix interface, failing to effectively provide electrochemical corrosion protection for the graphite filler.

[0036] To address the above issues, this invention provides a surface-modified multi-scale heterogeneous graphite filler, comprising a graphite filler on which an anatase crystalline titanium oxide film is deposited by atomic layer deposition.

[0037] Preferably, the graphite filler is a flexible graphite sheet, flexible graphite paper, graphite ring, or graphite packing seal; the thickness of the anatase crystalline titanium dioxide film is 100-300 nm, more preferably 150-250 nm.

[0038] Anatase crystalline titanium dioxide film is used as a protective layer for graphite filler. The surface of the anatase crystalline film is atomically saturated and chemically inert, which can significantly reduce the active sites of corrosion reaction. Moreover, the anatase crystalline film has a long-range ordered atomic arrangement and a close-packed lattice structure, with dense grain boundaries between grains, which effectively eliminates the seepage channels of amorphous materials. Its ion diffusion coefficient is much lower than that of amorphous materials. As a corrosion barrier layer, its density and integrity are significantly better than those of amorphous materials, which can better protect the graphite filler from electrochemical corrosion.

[0039] See Figure 1 and Figure 2 This invention provides a method for preparing surface-modified multi-scale heterogeneous graphite fillers as described in any one of claims 1-3, characterized in that it comprises: S1: The surface of the graphite filler is pretreated to obtain surface-activated graphite filler, specifically as follows: The surface of the graphite filler is polished to remove surface slag and protrusions, resulting in polished graphite filler. The polished graphite filler is ultrasonically cleaned in anhydrous ethanol and then dried to obtain surface-activated graphite filler. Preferably, the polished graphite filler is ultrasonically cleaned in anhydrous ethanol for 10-20 minutes, the surface is dried with nitrogen gas before drying, and then dried at 80-100℃ for 30-60 minutes.

[0040] S2: Using atomic layer deposition (ALD) with titanium and oxygen source precursors as reaction precursors, and alternating pulsed gas injection and inert gas purging cycles, an anatase crystalline titanium oxide film is grown in situ on the surface of activated graphite filler to obtain surface-modified multi-scale heterogeneous graphite filler. The titanium source precursor is titanium isopropoxide, and its temperature is 60-80℃; the oxygen source precursor is hydrogen peroxide; and the inert gas is nitrogen with a purity ≥99.999%. The deposition temperature of the ALD process is 200-300℃, more preferably... 220℃; the sequence of single pulse intake and inert gas purging cycles is as follows: titanium source precursor pulse intake, first inert gas purging, oxygen source precursor pulse intake, and second inert gas purging; during the single pulse intake and inert gas purging cycle: the titanium source precursor pulse intake time is 1-2s, the first inert gas purging time is 10-15s, the oxygen source precursor pulse intake time is 0.1-0.3s, and the second inert gas purging time is 10-15s; the number of alternating pulse intake and inert gas purging cycles is 2000-3000 times.

[0041] The aforementioned surface-modified multi-scale heterogeneous graphite packing is used as a sealing component in process industries. Because this surface-modified multi-scale heterogeneous graphite packing retains the excellent sealing performance inherent in graphite packing, the introduction of anatase crystalline titanium oxide film simultaneously significantly improves resistance to galvanic corrosion. This results in sealing components made using this surface-modified multi-scale heterogeneous graphite packing exhibiting advantages such as good sealing performance, good environmental adaptability, long service life, high safety, and low maintenance costs, making it a promising candidate for applications in petrochemical, aerospace, and nuclear power industries.

[0042] Example 1 Graphite filler pretreatment: Select flexible graphite sheets (thickness 0.5mm, size 10mm×10mm, density 1.0g / cm³). 3 The graphite sheet was prepared using a carbon content ≥99.5% as the matrix. The graphite sheet was placed in anhydrous ethanol and ultrasonically cleaned for 15 minutes to remove surface oil and processing residues. It was then transferred to deionized water and ultrasonically cleaned for 15 minutes to remove ethanol residues. After removal, the surface was purged with high-purity nitrogen (99.999% purity) until no obvious liquid traces remained. It was then placed in a vacuum oven and dried at 80℃ for 60 minutes to fully remove adsorbed moisture. After cooling, it was placed in a clean petri dish and sealed for later use.

[0043] ALD deposition of anatase crystalline titanium oxide thin films: A thermal atomic layer deposition system was used. The chamber was baked and degassed before deposition, and the background vacuum was evacuated to <10 mbar.

[0044] Deposition parameters: Titanium source precursor: titanium isopropoxide (TTIP, purity 99.99%), source bottle heating temperature 70℃; Oxygen source precursor: hydrogen peroxide (H2O2, 30% by mass), room temperature; Carrier gas / purge gas: High-purity nitrogen (99.999% purity), flow rate 150 sccm; Deposition temperature: 220℃; Single ALD cycle timing: Titanium source precursor pulse inlet: 2s; First nitrogen purging: 10s (to fully remove excess precursor and byproducts); Oxygen source precursor pulse inlet: 0.2s; Second nitrogen purging: 10s; Total number of cycles: 2500; Expected growth rate: 0.08nm / cycle.

[0045] Comparison of the prepared sheet-like surface-modified multi-scale heterogeneous graphite filler before and after corrosion, see [link / reference]. Figure 3 'a' in 'a'; See Figure 4 a. SEM surface morphology: The film is continuous and dense, without pinholes, cracks or peeling areas; cross-sectional morphology: The film thickness is uniform, about 205 nm (consistent with 2500 cycles × 0.082 nm / cycle); the interface between the graphite filler and the TiO2 film is clear, with no obvious diffusion layer or interface delamination.

[0046] X-ray photoelectron spectroscopy was used with a monochromatic AlKα X-ray source (hν = 1486.6 eV) and a beam diameter of 400 μm. The full-spectrum scan pass energy was 200 eV with a step size of 1.0 eV; the high-resolution narrow-spectrum scan pass energy was 50 eV with a step size of 0.1 eV. Charge correction was performed using the C1s binding energy of surface contaminant carbon (284.8 eV) as an internal standard.

[0047] See Figure 4 XPS full-spectrum scanning of the sample surface revealed that Ti, O, and C were the main elements present, while no other precursor residues such as N and Cl were detected. (See also...) Figure 5 The C1s signal mainly originates from the graphite filler and trace amounts of surface adsorbed carbon. No Ti-C bond characteristic peak (approximately 281.5 eV) was observed, indicating that the film is a pure phase TiO2 without carbide inclusions.

[0048] X-ray diffraction (XRD) analysis: Cu Kα radiation (λ = 1.5406 Å) was used, with a scanning range of 2θ = 20–80°. See also Figure 6 The results showed that obvious diffraction peaks appeared at 2θ=25.3°, 48.1° and 55.2°, which correspond to the (101), (200) and (211) crystal planes of anatase TiO2, respectively; the film was highly crystalline and the preferred orientation was the (101) crystal plane.

[0049] Electrochemical testing system: Electrolyte: H3BO3-NaOH buffer solution (pH=9.0), simulating an alkaline sealed working environment; Testing method: Potentiodynamic polarization curve (scan rate 0.5 mV / s, potential range -0.4~+0.6 V vs. SCE); Electrode structure: Three-electrode system, the sample is the working electrode (exposed area 0.94985cm²), the reference electrode is a saturated calomel electrode (SCE), and the counter electrode is a platinum sheet.

[0050] Test results: See Figure 7 and Figure 8 Uncoated graphite filler: Corrosion current density icorr = 1.141 μA / cm -2 Corrosion potential Ecorr = -0.105 V; 64 nm thick titanium dioxide film on graphite sheet: corrosion current density icorr = 0.613 μA / cm² -2 Corrosion potential Ecorr = -0.122V; corrosion current density decreases by approximately 46.28%; for a 160nm thick titanium dioxide film on a graphite sheet: corrosion current density icorr = 0.134μA / cm². -2 The corrosion potential Ecorr = -0.093V, and the corrosion current density decreased by approximately 88.26%. This indicates that the TiO2 film effectively blocked the penetration of the corrosive medium into the substrate.

[0051] Example 2 Unlike Example 1, the background vacuum level before deposition was <10 mbar.

[0052] Deposition parameters: Titanium source precursor: titanium isopropoxide (TTIP, purity 99.99%), source bottle heating temperature 70℃; Oxygen source precursor: hydrogen peroxide (H2O2, mass fraction 30%), room temperature; Carrier gas / purge gas: high-purity nitrogen (99.999% purity), flow rate 150 sccm; deposition temperature: 220℃; single ALD cycle sequence (fast cycle mode): titanium source precursor pulse inlet: 1.0s (shorter than Example 1); sequential nitrogen purging: 10s; oxygen source precursor pulse inlet: 0.1s (shorter than Example 1); nitrogen purging: 10s; total number of cycles: 2800; the total time of a single cycle was shortened from 22.2s in Example 1 to 21.1s, and the total deposition time was reduced by about 5%.

[0053] X-ray diffraction (XRD) analysis: obvious anatase phase characteristic peaks appeared at 2θ=25.3°, 48.1°, and 55.1°, corresponding to the (101), (200), and (211) crystal planes, respectively; no rutile or brookite phase characteristic peaks were observed, indicating that the film has a pure anatase structure; compared with Example 1, the peak positions are consistent and the crystallinity is comparable, indicating that the fast cycling process did not affect the crystal phase structure of the film.

[0054] 2) Scanning electron microscope (SEM) observation: The film is continuous and dense, with the surface composed of uniformly packed nanocrystals, without pinholes, cracks or peeling areas.

[0055] X-ray photoelectron spectroscopy (XPS) analysis revealed the presence of Ti, O, and C elements on the sample surface. The C1s signal primarily originated from the graphite filler and trace amounts of adsorbed carbon on the surface. The absence of Ti-C bond characteristic peaks indicates that the film is a pure-phase TiO2 film without carbide inclusions.

[0056] Electrochemical testing system: Same as in Example 1.

[0057] Test results: Uncoated graphite substrate: Corrosion current density icorr = 1.141 μA / cm -2 ; Corrosion current density of the graphite substrate after coating: icorr = 0.593 μA / cm -2 The corrosion current density decreased by 48.0%. Compared with Example 1 (film thickness 160 nm, reduction of 88.26%), the corrosion current density decreased less in this example, which is related to the slight effect of the fast cycling process on the film density, but it is still significantly better than the uncoated substrate.

[0058] Example 3 Expanded graphite packing (braided structure, 3mm×3mm cross-section, 20mm length), a typical sealing component; the packing was placed in anhydrous ethanol and ultrasonically cleaned for 20 minutes (intensified cleaning to penetrate the braided interior) to remove processing oil and debris; it was then transferred to deionized water and ultrasonically cleaned for 10 minutes; after removal, it was purged with high-purity nitrogen and placed in a vacuum oven at 100℃ for 2 hours to fully remove adsorbed moisture from the braided interior; after cooling, it was sealed for later use.

[0059] ALD deposition of anatase crystalline titanium oxide films: Deposition parameter adjustments (optimized for complex woven structures). Deposition temperature: 250℃ (increasing the temperature to enhance surface reactivity and improve coverage within the woven structure); Number of cycles: 2500; Single cycle sequence: Titanium source precursor pulse inlet: 2.0s (extending the pulse time to ensure precursor penetration into the woven structure), nitrogen purging: 15s, oxygen source precursor pulse inlet: 0.2s, nitrogen purging: 15s, carrier gas flow rate: 200sccm (enhancing the precursor delivery capacity into the woven structure); other parameters are the same as in Example 1, see physical image. Figure 3 c in the text.

[0060] X-ray diffraction (XRD) analysis showed that the characteristic peaks of the anatase phase (101), (200), and (211) were clearly visible, with the (211) peak located at 2θ≈55.2°, indicating a crystallinity superior to that of Example 2; there were no rutile phase or impurity peaks, and the film was a pure anatase structure.

[0061] Surface morphology observed by scanning electron microscopy (SEM): The fibers and weave gaps on the packing surface are covered by a continuous TiO2 film, with no exposed graphite areas and no cracks in the film layer; Cross-sectional observation: SEM observation after slicing the packing shows that the film is uniformly deposited along the fiber surface and the internal pores of the weave, with a thickness of about 220 nm, indicating that ALD achieves excellent three-dimensional conformal coverage.

[0062] X-ray photoelectron spectroscopy (XPS) analysis: XPS showed Ti, O, and C elements, with no other impurities. High-resolution Ti2p spectrum: Ti2p 3 / 2 Binding energy 458.7 eV, Ti 2p 1 / 2 The binding energy is 464.4 eV, titanium is in the +4 valence state, and there are no lower valence states. The O1s high-resolution spectrum shows a main peak at 529.9 eV (lattice oxygen). The O / Ti atomic ratio is calculated to be 2.02, close to the ideal stoichiometry. The C signal disappears rapidly after etching, and the Ti / O ratio remains constant, indicating a pure film and a clean interface.

[0063] Test method: Cut the packing and expose 1cm. 2 Electrochemical tests were performed on the area under the same conditions as in Example 1, and the remaining parts were encapsulated.

[0064] Test results: Uncoated packing: Corrosion current density icorr = 1.824 μA / cm -2 After coating, the packing corrosion current density icorr = 0.905 μA / cm -2 The corrosion current density decreased by 50.38% after coating; the polarization curve showed that the corrosion potential shifted positively after coating, the passivation range was significantly widened, and the corrosion resistance was greatly improved.

[0065] To evaluate the bonding strength between TiO2 film and graphite packing, a universal testing machine was used to perform tensile tests on packing samples before and after coating, and the film-substrate bonding force was recorded.

[0066] Test method: Clamp both ends of the packing into the testing machine fixture, tensile rate 5 mm / min; 5 parallel samples are tested in each group, and the average value is taken; the bonding force is defined as the stress value when the film layer begins to peel or break during the tensile process.

[0067] Enhanced cohesion: See Figure 9The adhesion strength increased from 5.372 MPa before coating to 7.683 MPa after coating, an increase of 43.0%. The significant improvement in adhesion strength indicates that the TiO2 film deposited by ALD formed a good interfacial bond with the graphite packing. Atomic layer deposition achieved highly uniform coverage in the porous woven structure, with the film continuously deposited along the fiber surface and the internal pores of the weave, avoiding local bonding weaknesses caused by uneven coverage. The deposition temperature of 250℃ is significantly lower than that of traditional CVD processes (usually >500℃), which greatly reduces the thermal stress caused by the mismatch in the thermal expansion coefficients of graphite and TiO2, thereby reducing the driving force for film peeling at the source.

[0068] Example 4 A flexible graphite sealing ring (outer diameter 30mm, inner diameter 20mm, thickness 2mm, density 1.0g / cm³) was selected. 3 The graphite ring (with a carbon content ≥ 99.5%) was used as the matrix. This ring structure, with its inner and outer cylindrical surfaces and end faces, allows for a comprehensive examination of the conformal covering capability of ALD technology on complex-shaped substrates. The graphite ring was placed in anhydrous ethanol and ultrasonically cleaned for 15 minutes to remove surface oil and processing residues; it was then transferred to deionized water and ultrasonically cleaned for 15 minutes to remove ethanol residues; after removal, it was purged with high-purity nitrogen (99.999% purity) until no obvious liquid traces remained on the surface, paying particular attention to purging the internal pores of the ring; it was then placed in a vacuum oven and dried at 80℃ for 60 minutes to fully remove adsorbed moisture; after cooling, it was placed in a clean petri dish and sealed for later use.

[0069] ALD deposition of anatase crystalline titanium oxide thin films (pulse time optimization): A thermal atomic layer deposition system was used. To ensure uniform deposition on the inner and outer surfaces of the ring-shaped substrate, the graphite ring was placed flat on the sample holder, ensuring that the ring hole axis was parallel to the gas flow direction to facilitate precursor diffusion to the inner wall. The chamber was baked and degassed before deposition, and the base vacuum was evacuated to <10 mbar. Deposition parameters: Deposition temperature: 220℃; Single ALD cycle sequence (pulse time optimization): Titanium source precursor pulse inlet: 2.0 s (extending the pulse time to ensure sufficient diffusion of the precursor to the inner wall of the ring hole); Nitrogen purging: 12 s (thoroughly removing excess precursor and byproducts); Oxygen source precursor pulse inlet: 0.3 s (extending the pulse time to ensure oxygen saturation reaction on the inner wall); Nitrogen purging: 12 s (thorough purging); Total cycles: 2800; Expected growth rate: 0.075 nm / cycle (equivalent growth rate of the ring-shaped substrate), target thickness approximately 210 nm. Other parameters are the same as in Example 1; see the physical image below. Figure 3 b.

[0070] To comprehensively evaluate the uniformity of the thin film on the surface of the annular substrate, samples were taken from the outer cylindrical surface, inner wall and end face of the graphite ring for characterization.

[0071] X-ray diffraction (XRD) analysis: A small amount of film was scraped from the outer surface of the graphite ring for XRD analysis. Cu Kα radiation (λ=1.5406 Å) was used, and the scanning range was 2θ=20~60°. The XRD pattern showed that the characteristic peak of the anatase phase appeared at 2θ=25.3°, corresponding to the (101) crystal plane. There were no diffraction peaks of rutile or brookite phases, indicating that the film was a pure anatase structure.

[0072] Scanning electron microscopy (SEM) observation: SEM observations were performed on the outer cylindrical surface, inner hole wall, and end face of the graphite ring. Outer cylindrical surface morphology: The film is continuous and dense, with a surface composed of uniformly packed nanocrystals, free of pinholes, cracks, or spalling areas. Inner hole wall morphology: The inner wall surface is also covered by a continuous film, with grain sizes comparable to the outer surface. The film is dense, indicating that the ALD precursor effectively diffused into the ring pores and completed the saturation reaction. End face morphology: SEM of the end face shows that the film uniformly covers the axial end face of the ring, with no thinning or exposure at the edges. X-ray photoelectron spectroscopy (XPS) analysis: XPS analysis was performed on the outer surface and inner pore wall surface of the graphite ring to evaluate the consistency of the thin film chemical state.

[0073] Test conditions: Same as in Example 1.

[0074] Surface XPS analysis: XPS full spectrum showed the presence of Ti, O, and C elements on the sample surface, with no precursor residues such as N and Cl. The C1s signal mainly originated from the graphite filler and trace amounts of adsorbed carbon on the surface.

[0075] Electrochemical testing system: Same as in Example 1. The graphite ring was cut to expose 1 cm of its outer surface. 2 The area was tested, and the rest was encapsulated.

[0076] Test results: Uncoated graphite ring: Corrosion current density icorr = 1.490 μA / cm -2 The graphite ring after coating has a corrosion current density of icorr = 0.823 μA / cm. -2 The corrosion current density decreased by 44.77% after coating; the corrosion potential shifted significantly to the positive side after coating, which also indicates that the TiO2 film effectively blocked the corrosive medium.

[0077] In summary, this invention not only pioneers a new application of ALD-TiO2 films in the field of graphite sealing and corrosion protection, but also demonstrates significant advancements not found in comparative patents in areas such as direct low-temperature growth of crystalline films, conformal coverage of complex substrates, and non-destructive modification. The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A surface-modified multiscale heterogenous graphite filler, characterized in that, It includes graphite filler, on the surface of which an anatase crystalline titanium oxide film is deposited by atomic layer deposition technology.

2. The surface-modified, multiscale hetero-graphite filler of claim 1, wherein, The graphite filler is a flexible graphite sheet, flexible graphite paper, graphite ring, or graphite packing seal.

3. The surface-modified, multiscale hetero-graphite filler of claim 1, wherein, The thickness of the anatase crystalline titanium oxide film is 100-300 nm.

4. A method for preparing surface-modified multi-scale heterogeneous graphite filler as described in any one of claims 1-3, characterized in that, include: The surface of the graphite filler is pretreated to obtain surface-activated graphite filler; Atomic layer deposition (ALD) was employed, using titanium and oxygen source precursors as reaction precursors. By alternating pulsed gas inlet and inert gas purging cycles, an anatase crystalline titanium oxide film was grown in situ on the surface of activated graphite filler, resulting in surface-modified multi-scale heterogeneous graphite filler.

5. The method for preparing surface-modified multi-scale heterogeneous graphite fillers according to claim 4, characterized in that, The method for pretreating the surface of graphite filler to obtain surface-activated graphite filler is as follows: The surface of the graphite filler is polished to remove surface slag and protrusions, resulting in polished graphite filler. The polished graphite filler was ultrasonically cleaned in anhydrous ethanol and dried to obtain surface-activated graphite filler.

6. The method for preparing surface-modified multi-scale heterogeneous graphite filler according to claim 4, characterized in that, The titanium source precursor is titanium isopropoxide, and the temperature of titanium isopropoxide is 60-80℃; the oxygen source precursor is hydrogen peroxide.

7. The method for preparing surface-modified multi-scale heterogeneous graphite filler according to claim 4, characterized in that, The inert gas is nitrogen with a purity of ≥99.999%.

8. The method for preparing surface-modified multi-scale heterogeneous graphite filler according to claim 4, characterized in that, The deposition temperature using the atomic layer deposition process is 200-300℃, and the sequence of the single pulse gas inlet and inert gas purging cycle is as follows: titanium source precursor pulse gas inlet, first inert gas purging, oxygen source precursor pulse gas inlet, and second inert gas purging.

9. The method for preparing surface-modified multi-scale heterogeneous graphite filler according to claim 4, characterized in that, During a single pulse intake and inert gas purging cycle: the pulse intake time for the titanium source precursor is 1-2 s, the first inert gas purging time is 10-15 s, the pulse intake time for the oxygen source precursor is 0.1-0.3 s, and the second inert gas purging time is 10-15 s; the number of alternating pulse intake and inert gas purging cycles is 2000-3000 times.

10. The application of the surface-modified multi-scale heterogeneous graphite packing according to any one of claims 1-3 as a sealing component in the process industry.

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