CN102352143B - Glass coating and film technology for reducing platinum rhodium alloy bushing plate loss - Google Patents

Abstract

The glass coating for reducing the loss of platinum-rhodium alloy bushing plate provided by the present invention is composed of glass component and Suzhou soil, the weight ratio of glass component and Suzhou soil is 9-15:1, and the coating process adopts sol-gel Coating method, the process is simple, the raw materials for coating are cheap and the utilization rate is high; small-sized (nano-scale) oxide particles can be obtained, with high specific surface area and high activity; high coating uniformity, easy to prepare multiple groups Uniform oxide coating.

Description

Glass coating and coating process to reduce loss of platinum-rhodium alloy bushing plate

technical field

The invention relates to a glass coating composition with high temperature resistance, erosion resistance and simple operation, that is, a glass coating and a coating process for reducing loss of a platinum-rhodium alloy bushing.

Background technique

The content of platinum group metals in the ore is generally very low, only a few grams per ton. Platinum and rhodium metal is one of the strategic resources that China is extremely short of. Platinum rhodium precious metals are widely used in the glass fiber industry for their high temperature corrosion resistance, good oxidation resistance at high temperatures, creep resistance under high temperature load conditions, and small wetting angle to glass liquid. in production.

The prices of precious metals in the international market continued to rise, among which the prices of platinum and rhodium reached record monthly average prices of 300,000 yuan/kg and 1.42 million yuan/kg respectively in May this year. A large part of the investment in fiberglass plants is used to purchase platinum and rhodium precious metals. Due to long-term high temperature conditions, platinum and rhodium are easily oxidized to form oxides that volatilize from the exposed surface of the metal. Some people have studied that the loss of rhodium in production is greater than that of platinum.

Glass fiber is mainly used in the production of composite materials. The excellent performance of glass fiber composite materials is more and more widely used, which will lead to an increase in the output of glass fiber. Therefore, it is imperative to reduce platinum and rhodium volatilization in the glass fiber production process. Attempts have been made to make breakout boards from alternative materials, but have failed. The reason for this is that these bushings are expensive to manufacture and have a short service life. Therefore, the cost of glass fiber manufacturing is increased, and the product quality is lowered. However, the search for alternative materials has not stopped. The work that has been published recently is to use platinum metal to cover stainless steel to make the leakage plate, insert the leakage nozzle made of platinum tube into the hole formed by stamping in the bottom plate, and integrate it by isobaric pressing, but the effect is not very satisfactory. The use of platinum and rhodium in the fiberglass industry seems inevitable at present.

Engineering ceramics have excellent chemical stability, high temperature oxidation resistance and heat insulation performance. Using these characteristics, thermal spraying method is used to spray engineering ceramics as coating materials on the surface of metal workpieces to improve the material's corrosion resistance, wear resistance, and Oxidation and heat insulation properties have been applied in engineering, but corrosion resistance, wear resistance, oxidation resistance and heat insulation properties are often accompanied by working environments with rapid cooling and hot temperatures. Therefore, the thermal shock resistance of the coating is also the key to give full play to the above characteristics of the coating material, so that the ceramic coating can be widely used in engineering. According to literature reports, the current research on thermal shock resistance of coatings is mainly below 850°C. Under this research condition, it is generally accepted by researchers that the thermal shock resistance of coatings mainly depends on the expansion of the coating and the substrate. The mismatch of the coefficients, based on this view, the ceramic layer that is currently selected to withstand thermal shock in the industry uses ZrO ₂ as the spraying material, which is relatively similar to the expansion coefficient of the metal substrate, but the high price of ZrO ₂ spraying powder makes the cost of the workpiece obvious. raised. Coating a layer of glass ceramics on the metal surface can reduce the contact between the metal and the outside air and protect the metal well, which provides a way for us to study how to reduce the volatilization of platinum and rhodium at high temperatures.

Contents of the invention

In view of the above situation, the present invention has designed and tested a kind of high temperature resistance, erosion resistance, and easy-to-operate glass coating composition, that is, the glass coating and coating process that reduces the loss of platinum-rhodium alloy drain plate, and it can be used to reduce platinum Rhodium bushing loss.

The choice of coating components is based on the protective effect of the coating system on the substrate as an inert melt film shielding protection mechanism. At high temperatures, the bonding effect of the molten glass phase makes the coating bond to the substrate, blocking the pores of the coating and making the coating more dense. Prevent or slow down the diffusion process and reduce the erosion of the substrate by the corrosive medium to achieve the purpose of protecting the substrate. Glass frit material is used as a binder, mixed with Suzhou soil to adjust the high-temperature viscosity and coating performance of the coating, and prevent the coating from peeling off from the substrate when too much glass phase is quenched.

The glass coating for reducing the loss of the platinum-rhodium alloy bushing plate provided by the invention is composed of glass components and Suzhou soil, and the weight ratio of the glass components and Suzhou soil is 9-15:1. Preferably, the weight ratio of the glass component to Suzhou soil is 9-11:1. More preferred weight ratios are 9, 11, 13 or 15:1.

The preferred scheme of the glass coating is that the composition of the glass component is: 45-55 parts of SiO ₂ , 35-45 parts of Al ₂ O ₃ , 6-12 parts of Na ₂ O, and CaO is 1 to 4 parts, 0.5 to 3 parts of MgO, 0.1 to 0.6 parts of Li ₂ O, and 0 to 1 part of La ₂ O ₃ , all by weight.

The aforementioned glass coating, the preferred solution is that _SiO2 is 47-51 parts, _Al2O3 is _35-38 parts, _Na2O is 6-10 parts, CaO is 1.5-3 parts, and MgO is 1-2.5 parts. parts, Li ₂ O is 0.3-0.5 parts, and La ₂ O ₃ is 0.5-0.8 parts.

The preferred version of the glass coating is that the amount of CaO is 1-4 parts.

The coating process of the glass coating that reduces the loss of the platinum-rhodium alloy bushing provided by the invention, the steps are as follows:

(1) Preparation of sol: Weigh the glass component and Suzhou soil in proportion, mix and stir with deionized water and absolute ethanol until transparent, take it out after 4-8 hours in a water bath at 32-37°C, and store at room temperature for later use;

(2) Slotted plate coating: first clean the leaky plate, then scrub it with alcohol, apply a film on the homogenizer, drop the prepared sol in the center of the rotating sample, and the sol will form a film evenly under the action of centrifugal force;

(3) Put the coating film sample into the resistance furnace to dry, complete the first coating film, repeat the above steps, and carry out the second coating film on the sample.

The preferred method of the coating process is that in step (1), the sol that has been stirred until transparent is taken out after 6 hours in a water bath at 35°C, and stored at room temperature for later use.

The preferred method of the coating process is that the drying mechanism is: 3°C/min in the range of 0-200°C, 5°C/min in the range of 200-1400°C, and heat preservation for 2 hours when the temperature rises to 1400°C.

The preferred method of the film coating method is that in step (2) after film formation on both sides of the sample, dip an appropriate amount of sol with absorbent cotton and gently wipe the corners and uncoated parts of the sample to form a uniform coating.

In the present invention, _SiO2 mainly plays the role of the glass network skeleton, which can reduce the thermal expansion coefficient of the glass and improve the thermal stability and heat resistance of the glass. However, when the content is too high, the melting temperature will be significantly increased, and may cause crystallization. Al ₂ O ₃ belongs to the intermediate oxide, and the content of Al 2 O 3 exceeds a certain limit, and the viscosity of the glass liquid will increase. Al ₂ O ₃ inhibits phase separation and improves the chemical and thermal stability of the glass. Na ₂ O is the outer body of the glass network. Sodium ions reside in the holes in the glass structure. Na ₂ O can provide free oxygen to increase the O/Si ratio in the glass structure and cause bond breaking, thereby reducing the viscosity of the glass and making the glass easy to Melting is a good co-solvent for glass, and Na ₂ O cannot be introduced too much. In this glass component, the molecular ratio of Na ₂ O and Al ₂ O ₃ is greater than 1, and Al ₂ O ₃ forms aluminum-oxygen tetrahedrons and forms a continuous structural network with silicon-oxygen tetrahedrons, which improves the thermal stability and Thermal expansion coefficient. CaO mainly plays a role of stability, reduces the viscosity of the glass at high temperature, and promotes the melting and clarification of the glass. When the CaO content is high, the crystallization tendency of the glass increases. Therefore, when the CaO content in the glass system is 1 to 5 parts , the effect is superior. MgO is the outer body of the network, which can improve the formation performance of glass, reduce the crystallization tendency and crystallization speed of glass, and improve the performance of glass. MgO can replace an appropriate amount of CaO to improve the performance of glass coating. When the substitution amount is 1-2.5 parts , the effect is superior. Li ₂ O has a strong fluxing effect and can be introduced as an essential component, either in the form of spodumene or as a pure industrial raw material.

Suzhou soil is used to adjust the high-temperature viscosity and coating performance of the coating, and prevent the coating from peeling off from the substrate when the excessive glass phase is rapidly cooled. It is produced in Yangshan, Suzhou, Jiangsu Province, China, hence the name. There are two types of beneficiation, manual and mechanical, high-quality products, white in appearance, fine and smooth in texture, and the whiteness after burning can reach more than 90%, so it is also called Suzhou White Clay. High-quality Suzhou soil is often selected by hand, with few impurities. The main minerals are tubular halloysite and flaky kaolinite, which are rare natural high-quality raw materials for special ceramics. The main substance contained in Suzhou soil is 37%-39% alumina, 46%-48% silica, 1730°C refractoriness, and low plasticity. It is mainly used to make ceramics, and can also be used as a binder for refractory materials.

Aiming at the characteristics of complex operation of metal surface coating, the present invention adopts sol-gel coating method, which has simple equipment and process, cheap raw materials for coating and high utilization rate; small-sized (nano-scale) oxide particles can be obtained, With high specific surface area and high activity; high coating uniformity, easy to prepare multi-component uniform oxide coating.

In addition, the technology of the present invention is also embodied in:

1. Under high temperature conditions, the problem of bonding between the glass coating and the platinum-rhodium bushing plate interface is solved.

2. The glass coating coated on the surface of the platinum-rhodium bushing not only significantly reduces the volatilization of platinum-rhodium precious metals, but also does not affect the production process of glass fiber.

Detailed ways

Specific examples are listed below to further explain and illustrate the technical solutions in this patent, but are not limited thereto.

The raw materials used in the examples can be purchased from the market. For example, the Suzhou soil used is purchased from Shenyang Yinshan Kaolin Co., Ltd. In terms of appearance, the Suzhou soil is mostly reddish, white or yellow. Yellow Suzhou soil contains more calcium, and reddish Suzhou soil often contains more iron, which is unfavorable for glass fiber production. In the present invention, white Suzhou soil is used.

Platinum-rhodium alloy bushing is one of the main devices in glass fiber production. It is shaped as a trough container. During the drawing process, molten glass flows into the bushing, adjusted to a suitable temperature by it, and then flows out through the nozzle on the bottom plate. At the exit, it is drawn into continuous glass fiber by a high-speed rotating wire drawing machine. Wherein the loss amount of 6kg platinum-rhodium bushing plate work one year is about 60g, but the obtained data in the embodiment is significantly lower than this.

Embodiment 1 , glass coating and coating process for reducing loss of platinum-rhodium alloy bushing plate

Preparation of sol: Weigh glass chemical components and white Suzhou soil according to the mass ratio of 15:1, mix and stir with distilled water and absolute ethanol, stir the solution until transparent, take it out after 6 hours in a water bath at 35°C, store at room temperature, and wait for use . The weighed amount of glass chemical components is shown in Table 1:

Table 1 Glass chemical composition (parts by weight)

Experiment number 1 2 3 4 5 6 SiO ₂ 45 47 49 51 53 55 Al ₂ O ₃ 39.5 38 37.5 37 35.5 35 Na ₂ O 11.5 10.5 8.5 7.5 6.5 6 CaO 2 2.1 1.9 2.2 1.5 1 MgO 1.2 1.3 1 1.1 2.4 2 Li ₂ O 0.3 0.5 0.4 0.5 0.3 0.4 La ₂ O ₃ 0.5 0.6 0.7 0.7 0.8 0.6

Put the coating film sample into a self-made resistance furnace for drying. The drying mechanism is: 3°C/min in the range of 0-200°C, 5°C/min in the range of 200-1400°C, and hold for 2 hours when the temperature rises to 1400°C . The above is the first film coating, repeat the above steps, and carry out the second film coating on the sample.

According to the above operation, a platinum-rhodium alloy bushing plate coating was prepared. After working for one year, the breakout plate was disassembled and weighed. The specific results are shown in Table 2.

Table 2 Loss of bushing plate/g

Experiment number 1 2 3 4 5 6 loss 55.2 51.2 49.4 52.6 55.7 57.3

Example 2 , the glass chemical components and white Suzhou soil were weighed according to the mass ratio of 13:1, and the glass chemical components were weighed according to Table 1, and the experiment numbers were 7, 8, 9, 10, 11, and 12. The specific implementation method is the same as that of Example 1. After working for one year, the bushing was disassembled and weighed. The specific results are shown in Table 3.

Table 3 loss of bushing plate/g

Experiment number 7 8 9 10 11 12 loss 40.7 31.5 33.2 35.8 36.5 43.6

Example 3 , the glass chemical components and white Suzhou soil were weighed according to the mass ratio of 11:1, and the glass chemical components were weighed according to Table 1, and the experiment numbers were 13, 14, 15, 16, 17, and 18. The specific implementation method is the same as that of Example 1. After working for one year, the bushing was disassembled and weighed. The specific results are shown in Table 4.

Table 4 Loss of bushing plate/g

Experiment number 13 14 15 16 17 18 loss 29.4 31.3 26.5 27.7 25.2 30.1

Example 4 , the glass chemical components and white Suzhou soil were weighed according to the mass ratio of 9:1, the glass chemical components were weighed according to Table 1, and the experiment numbers were 19, 20, 21, 22, 23, and 24. The specific implementation method is the same as that of Example 1. After working for one year, the bushing was disassembled and weighed. The specific results are shown in Table 5.

Table 5 loss of bushing plate/g

Experiment number 19 20 twenty one twenty two twenty three twenty four loss 24.1 23.4 19.7 22.9 23.2 23.8

Claims (3)

1. reduce the preparation method of the glass coating of platinum rhodium bushing loss, it is characterized in that step is as follows:

(1) colloidal sol preparation: take by weighing glass ingredient and Suzhou soil in proportion, mix to transparently with deionized water, dehydrated alcohol, take out behind the 32-37 ℃ of water-bath 4-8h, room temperature preservation is stand-by; The part by weight of glass ingredient and Suzhou soil is 9-11:1; The composition of described glass ingredient is: 45～55 parts SiO ₂, 35～45 parts Al ₂O ₃, 6～12 parts Na ₂O, CaO are 1～4 part, and MgO is 0.5～3 part, 0.1～0.6 part Li ₂O, 0～1 part La ₂O ₃, be weight part;

(2) bushing coating: earlier bushing is cleaned, clean with alcohol, film at sol evenning machine, the colloidal sol for preparing is dropped in the center that rotates sample, colloidal sol is even film forming under action of centrifugal force; Pick an amount of colloidal sol wiping sample edges and corners and uncoated place gently with absorbent cotton after the film forming of sample two sides, make it form uniform coating;

(3) sample of will filming is put into resistance furnace and is dried, and finishes and films for the first time, repeats above-mentioned steps, sample is carried out filming the second time, dryer is made as: 3 ℃/min in 0～200 ℃ of scope, 5 ℃/min in 200～1400 ℃ of scopes, insulation 2h when temperature rises to 1400 ℃.

2. preparation method according to claim 1 is characterized in that, step (1) will be stirred to transparent colloidal sol and take out behind 35 ℃ of water-bath 6h, and room temperature preservation is stand-by.

3. preparation method according to claim 1 is characterized in that, SiO ₂Be 47～51 parts, Al ₂O ₃Be 35～38 parts, Na ₂O is 6～10 parts, and CaO is 1.5～3 parts, and MgO is 1～2.5 part, Li ₂O is 0.3～0.5 part, La ₂O ₃It is 0.5～0.8 part.