Corrosion-resistant conductive material and method for making same

Abstract

The application discloses a kind of corrosion-resistant conductive materials and preparation method thereof.Corrosion-resistant conductive material is with SiO2 and platinum or gold as main component a kind of new material.The material utilizes ammonia, acetic acid as catalyst, tetraethyl orthosilicate (TEOS) as SiO2 source, glycerol as anti-cracking agent, platinum or gold powder as conductor material.Catalysis using ammonia makes the solubility of silicon-hydroxyl compound increase, then two-step catalysis using acetic acid makes silicon-hydroxyl compound polymerize into colloidal particles.Add glycerol as anti-cracking agent to the prepared colloid, add appropriate amount of micron-sized platinum or gold powder, stir and mix uniformly.The prepared colloid is spin-coated on different substrates such as silicon wafer, and heat treatment is carried out using a rapid annealing furnace, to prepare a new type of corrosion-resistant conductive material.The method is simple, has very good plasticity, has oxidation resistance, corrosion resistance to strong acid and salt water, can work in seawater for a long time, the resistance does not change, and the adjustable range of resistivity is very large.

Description

Technical Field

[0001] This invention relates to the field of functional materials, specifically to a corrosion-resistant conductive material and its preparation method; more particularly, it relates to a method for preparing a novel corrosion-resistant conductive material with SiO2 and platinum as the main components using ethyl orthosilicate (TEOS) or butyl orthosilicate and platinum powder or gold powder with micron or nano-sized particles. Background Technology

[0002] In today's marine exploration engineering field, various instruments and devices are required, often involving various circuits. Since these devices operate year-round in seawater, ordinary conductive metals cannot withstand the corrosion. While materials like platinum or gold have good corrosion resistance, they can usually only be prepared into relatively thin films using electron beam evaporation or sputtering. However, many marine exploration devices are deep-hole or tubular instruments, making the fabrication of electrodes or circuits inside extremely difficult and impossible using conventional thin-film deposition methods such as evaporation, sputtering, or electroplating. If corrosion-resistant materials like platinum or gold are prepared into a paste or colloid similar to silver paste, spin-coated into the inside of deep holes or glass tubes, and then cured by heat treatment, the desired effect can be achieved.

[0003] This novel corrosion-resistant conductive material and its preparation method, with SiO2 and platinum (gold) as the main components, are groundbreaking and have not been reported in China before. Summary of the Invention

[0004] The purpose of this invention is to provide a corrosion-resistant conductive material and its preparation method. This invention employs a sol-gel method, hydrolyzing tetraethyl orthosilicate (TEOS) or tetrabutyl orthosilicate to form a colloid. Glycerin is added as a crack inhibitor, and then micron- or nano-sized platinum powder (or gold powder) is added as a conductor. After uniform mixing using a glass rod or ultrasonic vibration, the mixture is heat-treated using a rapid annealing furnace, nitrogen oven, muffle furnace, etc., to prepare a new corrosion-resistant conductive material. The conductivity of this material can be adjusted according to the proportion of platinum powder mixed into the colloid. This invention offers a simpler method, and the prepared electrode material is resistant to strong acids and salts, facilitating the fabrication of micron-sized electrodes inside deep-hole or tubular instruments. It is particularly suitable for use as an electrode material in various detection instruments operating year-round in seawater, demonstrating very practical application prospects.

[0005] This invention is achieved through the following technical solution:

[0006] This invention provides a corrosion-resistant conductive material comprising SiO2 and conductive metal powder, which is prepared by the following method: hydrolyzing silicate esters to form a sol, adding conductive metal powder with micron or nano-sized particles as a conductor material, mixing evenly, and then performing heat treatment to decompose the silicate esters into silicon dioxide, thereby obtaining the corrosion-resistant conductive material.

[0007] Furthermore, the conductive metal powder includes one of gold powder and platinum powder. The conductive metal used in this invention is a metal that is resistant to strong acid corrosion and is not easily oxidized; metals such as iron and aluminum are not suitable, and gold powder and platinum powder are the best choices.

[0008] Furthermore, the resistivity of the corrosion-resistant conductive material is adjustable in the range of 2000–0.01 Ω·cm. The resistivity can be adjusted according to the proportion of conductive particle powder mixed in the colloid (the ratio of platinum (gold) atoms to silicon dioxide molecules). Under conditions of -30℃ to 90℃, the resistivity of the film is adjustable in the range of approximately 2000–0.01 Ω·cm.

[0009] Furthermore, hydrolysis utilizes a two-step catalysis process involving both alkali and acid to hydrolyze silicates into colloids.

[0010] Furthermore, the silicate ester is a sol-gel ester, including one of tetraethyl orthosilicate (TEOS) and tetrabutyl orthosilicate. More preferably, the silicate ester is tetraethyl orthosilicate (TEOS).

[0011] Further, the alkali catalysis specifically involves adding ammonia and deionized water to silicate esters, mixing and stirring, and then heat-treating to obtain an alkali-catalyzed slurry. The purpose of alkali catalysis is to increase the solubility of silicon-hydroxy compounds. The volume ratio of ammonia, deionized water, and silicate esters in the alkali catalysis is 1:2:10 to 1:3:10. The ammonia is 15-28% concentration. The heat treatment temperature is 50-80℃, and the heat treatment time is 36-120 hours.

[0012] Furthermore, the acid catalysis specifically involves adding an organic acid to an alkaline catalytic slurry, followed by heat treatment to polymerize the silicon-hydroxy compound into larger colloidal particles, thus obtaining a sol. The heat treatment temperature is 50–80°C, and the heat treatment time is 8–12 hours. The volume ratio of acid used in the acid catalysis to ammonia used in the alkaline catalysis is 1:1 to 1:2. The organic acid includes one of acetic acid, formic acid, and oxalic acid. The organic acid is acetic acid with a concentration of 8%–12%.

[0013] The role of heat preservation in acid and base catalysis: to ensure the hydrolysis rate, allowing for more complete hydrolysis and colloidal coagulation. Among alkalis, only ammonia water is suitable due to its high volatility; other alkalis are not suitable.

[0014] Furthermore, an anti-cracking agent, glycerol, is added before the conductive metal powder is added. Glycerol is added to the silicate sol after acid and alkali catalysis as an anti-cracking agent. Its function is to reduce the capillary stress that causes silica cracking during the drying process, as organosilicon materials often crack. These organic alcohols decompose into carbon dioxide and water vapor at high temperatures and do not introduce pollution.

[0015] Furthermore, the particle size of the conductive metal powder is 10 nm to 50 μm. The amount of conductive metal powder added is 0.1 to 10 times the mass of the sol.

[0016] Furthermore, the sol containing the conductive metal powder needs to be stirred with a glass rod or ultrasonically vibrated to mix it evenly.

[0017] Furthermore, the heat treatment is divided into three stages. The prepared colloid needs to be processed using a rapid annealing furnace, a nitrogen oven, a muffle furnace, etc. The three heat treatments must be carried out sequentially. The preparation process first removes deionized water, then decomposes the organic matter at high temperature, transforming the colloid into a solid.

[0018] Furthermore, the first heat treatment is carried out at a temperature of 100–120°C for 5–15 minutes to remove deionized water.

[0019] Furthermore, a second heat treatment is performed at 250–300°C for 5–15 minutes to remove volatile chemical reagents.

[0020] Furthermore, a third heat treatment is performed at 450–600°C for 5–15 minutes, during which the silicates decompose into silicon dioxide. If the temperature is too low, the silicates will not decompose; if the temperature is too high, the glass substrate will soften and cannot withstand the excessively high temperature.

[0021] This invention also provides an application of the aforementioned corrosion-resistant conductive material in strong acid environments and marine exploration. The corrosion-resistant conductive material prepared by this invention can be spin-coated onto substrates such as silicon wafers, glass sheets, sapphire, and mica sheets to prepare electrodes or circuits for detection devices, or electrodes and circuits of any shape can be coated inside a glass tube using tools such as syringes. It can also be heat-treated and soldered very firmly with external platinum or gold wire leads.

[0022] The technical principle of this invention lies in utilizing the property that silicate esters can generate large colloidal particles through hydrolysis under acid and alkali catalysis. These large colloidal particles can adsorb micron- and nano-sized platinum (gold) powder particles. After uniform mixing, during heat treatment, the silicate esters decompose into corrosion-resistant solid silica, which binds the platinum (gold) powder particles together, resulting in a material that is both conductive and possesses excellent ductility.

[0023] Compared with existing metal thin film preparation technologies, this invention has the following outstanding features:

[0024] 1) This invention does not require vapor deposition or sputtering equipment, and the method is simple.

[0025] 2) The corrosion-resistant conductive material prepared by this invention has very good plasticity.

[0026] 3) The corrosion-resistant conductive material prepared by this invention can achieve the desired thickness by adjusting the spin coating speed.

[0027] 4) The corrosion-resistant conductive material prepared by this invention is very convenient to be soldered to external platinum or gold wire leads, and can be cured by heat treatment.

[0028] 5) The corrosion-resistant conductive material prepared by this invention has resistance to oxidation, strong acid and salt water corrosion, and its resistance remains unchanged when working in seawater for a long time.

[0029] 6) The resistivity of the corrosion-resistant conductive material prepared by this invention can be adjusted over a very large range. Attached Figure Description

[0030] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0031] Figure 1 SEM image of a cross section of the material prepared in this invention;

[0032] Figure 2 The results are from the EDS test in Example 1;

[0033] Figure 3 This is a diagram showing the uniform distribution of platinum powder in the conductive film of Example 1. Detailed Implementation

[0034] To make the content, technical solutions, and advantages of this invention clearer, the invention is further described below in conjunction with specific embodiments. The embodiments are only for illustrating the invention and are not intended to limit the invention to the following examples. The specific implementation methods of this invention are described in detail below with reference to test data graphs.

[0035] This invention discloses a novel corrosion-resistant conductive material and its preparation method; the material is a novel material with SiO2 and platinum as the main components. The material utilizes ammonia and acetic acid as catalysts, tetraethyl orthosilicate (TEOS) as the SiO2 source, glycerol as a crack inhibitor, and micron-sized platinum powder as the conductor material. The solubility of silicon-hydroxy compounds is increased by the catalysis of ammonia, and then the silicon-hydroxy compounds are polymerized into colloidal particles by a two-step catalysis using acetic acid. Glycerol is added to the prepared colloid as a crack inhibitor, and an appropriate amount of micron-sized platinum powder is added and stirred until homogeneous. The prepared colloid is spin-coated onto different substrates such as silicon wafers and heat-treated using a rapid annealing furnace to prepare a novel corrosion-resistant conductive material.

[0036] This invention utilizes the decomposition of tetraethyl orthosilicate (TEOS) to prepare silicon dioxide. By adding micron-sized platinum powder to the precursor, the material acquires conductivity and corrosion resistance. The novel corrosion-resistant conductive material prepared by this invention can be spin-coated onto planar substrates such as silicon wafers and sapphire to prepare thin films of different thicknesses, or it can be spray-coated into electrodes of different shapes inside glass tubes using a syringe. This invention's method is simpler, faster, and more efficient. The prepared conductive material exhibits excellent resistance to strong acids and salts, showing particular advantages in the fabrication of electrodes and circuits for deep-sea exploration instruments.

[0037] Example 1

[0038] This embodiment uses ordinary glass as a substrate, and tetraethyl orthosilicate (TEOS) and 100nm platinum powder particles as raw materials. 25% ammonia and 8% acetic acid are used as catalysts, and 5% glycerol is used as an anti-cracking agent. The specific steps are as follows.

[0039] 1. Cleaning the substrate: Soak the glass slide in concentrated sulfuric acid and hydrogen peroxide (10:1) for 10 minutes, take it out, rinse it clean, and then dry it in a nitrogen oven.

[0040] 2. Sol preparation: Take 20 mL of tetraethyl orthosilicate (TEOS), add 5 mL of ammonia and 50 mL of deionized water into a clean beaker, mix thoroughly, seal with plastic wrap, and place in a 50°C oven for 72 hours.

[0041] 3. Remove the alkaline-catalyzed reagent from the oven, add 2 mL of acetic acid, seal it, and place it in a 50°C oven for 12 hours.

[0042] 4. Add 8 mL of 5% glycerol solution.

[0043] 5. Add 50g of platinum powder with a particle size of 100nm, and use ultrasonic vibration for 10 minutes to fully mix the platinum powder and colloid.

[0044] 6. Take 2ml of the mixed colloid and drop it onto a clean glass slide. Adjust the spin coater speed to 800r / min. To increase the film thickness and reduce the film resistance, repeat the spin coating process multiple times (3 times).

[0045] 7. Place the glass slide carrying the colloidal material into an annealing furnace and perform three heat treatments in an air atmosphere.

[0046] 8. The first heat treatment temperature is 100℃, and the deionized water is removed in 10 minutes.

[0047] 9. The second heat treatment is carried out at 250℃ for 10 minutes to remove volatile chemical reagents.

[0048] 10. The third heat treatment is carried out at 500℃ for 10 minutes. The silicate esters decompose into silicon dioxide and are fixed together with the platinum powder.

[0049] The cross-sectional SEM image of the prepared conductive thin film is as follows: Figure 1 As shown, the EDS test results are as follows: Figure 2 As shown, the distribution of platinum powder in the material is as follows: Figure 3 As shown.

[0050] Example 2

[0051] This embodiment uses a single polished P-type (100) silicon wafer as the substrate, and tetrabutyl orthosilicate and 100nm platinum powder particles as raw materials. 25% ammonia and 8% acetic acid are used as catalysts, and 5% glycerol is used as an anti-cracking agent. The specific steps are as follows.

[0052] 1. Cleaning the substrate: Soak the silicon wafer in concentrated sulfuric acid and hydrogen peroxide (10:1) for 10 minutes, take it out, rinse it clean, and then dry it in a nitrogen oven.

[0053] 2. Sol preparation: Take 15 mL of butyl orthosilicate, add 5 mL of ammonia water and 50 mL of deionized water into a clean beaker, mix thoroughly, seal with plastic wrap and place in a 50℃ oven for 12 hours.

[0054] 3. Remove the alkaline-catalyzed reagent from the oven, add 2 mL of acetic acid, seal it, and place it in a 50°C oven for 12 hours.

[0055] 4. Add 8 mL of 5% glycerol solution.

[0056] 5. Add 50g of platinum powder with a particle size of 100nm, and use ultrasonic vibration for 10 minutes to fully mix the platinum powder and colloid.

[0057] 6. Take 2ml of the mixed colloid and drop it onto a clean silicon wafer. Adjust the speed of the spin coater to 800r / min. To increase the film thickness and reduce the film resistance, repeat the coating process twice.

[0058] 7. Place the silicon wafer carrying the colloidal material into an annealing furnace and perform three heat treatments in an air atmosphere.

[0059] 8. The first heat treatment temperature is 100℃, and the deionized water is removed in 10 minutes.

[0060] 9. The second heat treatment is carried out at 250℃ for 10 minutes to remove volatile chemical reagents.

[0061] 10. The third heat treatment is carried out at 650℃ for 10 minutes, during which the silicate esters decompose into silicon dioxide and are fixed together with the platinum powder.

[0062] Comparative Example 1

[0063] This comparative example provides a corrosion-resistant conductive material, and the preparation method is basically the same as that in Example 1, except that no alkaline catalytic treatment is performed.

[0064] Uncatalyzed tetraethyl orthosilicate has low solubility in deionized water and a slow hydrolysis rate. It produces few colloidal particles, which are insufficient to bind large amounts of platinum powder particles, preventing the preparation of continuous films; the resulting product consists of scattered particles.

[0065] Comparative Example 2

[0066] This comparative example provides a corrosion-resistant conductive material, and the preparation method is basically the same as that in Example 1, except that acid catalysis treatment is not performed.

[0067] Uncatalyzed tetraethyl orthosilicate cannot polymerize into large colloidal particles; instead, the colloidal particles are small with a low viscosity. When platinum powder is added, it precipitates to the bottom, preventing the preparation of a homogeneous colloidal mixture.

[0068] Comparative Example 3

[0069] This comparative example provides a corrosion-resistant conductive material, and the preparation method is basically the same as that of Example 1, except that the third step of heat treatment is not performed.

[0070] Without the third step of treatment, tetraethyl orthosilicate cannot be completely decomposed into corrosion-resistant and stable silica solid.

[0071] Comparative Example 4

[0072] This comparative example provides a corrosion-resistant conductive material, and the preparation method is basically the same as that in Example 1, except that the added conductive metal material is titanium powder or silver powder.

[0073] When the added conductive materials are titanium powder or silver powder, the resistance of the prepared electrode material is easily oxidized, and the resistance gradually increases over time, and it may even become an insulator.

[0074] Performance testing:

[0075] 1. Oxidation resistance test: The corrosion-resistant conductive material prepared in this invention was heated in air at 500°C for 30 minutes and then cooled to room temperature. The resistance did not change before and after heating.

[0076] 2. Strong acid resistance test: The corrosion-resistant conductive material prepared in this invention was immersed in 35% hydrochloric acid, 45% sulfuric acid, and 45% nitric acid solutions for 30 minutes respectively. The resistance did not change before and after immersion.

[0077] 3. Salt water corrosion resistance test: The corrosion-resistant conductive material prepared in this invention was soaked in 15% salt water for 360 hours (15 days), and the resistance did not change before and after soaking.

[0078] 4. Shapeability: It can be coated with the desired shape and thickness on the inside or outside of silicon wafers, glass sheets, sapphire sheets, mica sheets or tubes.

[0079] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A corrosion-resistant conductive material, characterized in that, The corrosion-resistant conductive material comprises SiO2 and conductive metal powder, and is prepared by the following method: hydrolyzing silicate esters to form a sol, adding conductive metal powder with micron or nano-sized particles as a conductor material, mixing evenly, and then performing heat treatment to decompose the silicate esters into silicon dioxide, thereby obtaining the corrosion-resistant conductive material. The hydrolysis is carried out using a two-step catalysis of base and acid to hydrolyze silicates into colloids; The alkaline catalysis process involves adding ammonia and deionized water to silicates, mixing and stirring, and then heat-treating to obtain an alkaline catalytic slurry. Acid catalysis specifically involves adding organic acid to an alkaline catalytic slurry, heat treatment, and polymerizing silicon-hydroxy compounds into colloidal particles to obtain a sol. The conductive metal powder includes one of gold powder and platinum powder, and the particle size of the conductive metal powder is 10nm to 50um; the silicate ester is one of ethyl orthosilicate and butyl orthosilicate.

2. The corrosion-resistant conductive material according to claim 1, characterized in that, The resistivity of the corrosion-resistant conductive material can be adjusted within the range of 2000 to 0.01 Ω·cm.

3. The method for preparing the corrosion-resistant conductive material according to claim 1, characterized in that, The heat treatment is divided into three heat treatments. The first heat treatment is at a temperature of 100-120 °C for 5-15 minutes to remove deionized water. The second heat treatment is at a temperature of 250-300 °C for 5-15 minutes to remove volatile chemical reagents. The third heat treatment is at a temperature of 450-600 °C for 5-15 minutes to decompose silicates into silicon dioxide.

4. The application of the corrosion-resistant conductive material as described in claim 1 in strong acid environments and marine exploration.

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