CN1160031A - Fused quartz ceramic material - Google Patents

Abstract

The invention belongs to the field of heat-resistant ceramics. It is especially suitable for preparing various high-strength heat-resistant ceramic parts. In the fused silica ceramic material of the present invention, _SiO2 is used as the base and 1-8% BN is added to increase the crystallization temperature of the material to 1400 ° C. In order to improve the bending strength of the material, 10 - 20% of either short carbon fibers Csf or silicon carbide whiskers SiCw. Compared with the prior art, the material of the invention not only has better overall performance, but also has obvious improvement of the crystallization temperature.

Description

A kind of fused silica ceramic material

The invention belongs to the field of heat-resistant ceramics. It is especially suitable for preparing various high-strength heat-resistant ceramic parts.

Fused silica is a high-purity _SiO2 material, which has the characteristics of low density, small thermal expansion coefficient, dielectric properties, thermal shock resistance and chemical stability, etc., so the application fields of fused silica and its composite materials very broad. For example, in the fields of chemical industry and light industry, it is made into acid-resistant containers, hot plates, heat insulation materials, etc. In the metallurgical and coking industry, it can be used to prepare various coke oven doors, combustion nozzles, ladle casting ports, blast furnace hot air pipe linings, etc. In the field of aerospace, high-tech components such as missile antenna windows, radomes, missile end caps and space shuttle heat-resistant tiles can be manufactured. However, fused silica material is mainly used in an amorphous state, and is a thermodynamically unstable material. Generally, it begins to crystallize at 1200°C. Once fused silica begins to crystallize, the strength of the material will decrease and the thermal shock resistance will be obvious. Therefore, it is very important to add components that inhibit crystallization to the fused silica material and increase the crystallization temperature of the material. It is pointed out in Chinese patent CN85103433A that adding quantitative components of Al ₂ O ₃ and La ₂ O ₃ can make the crystallization temperature of high silica glass 30-40°C higher than that of quartz. In addition, there are other articles introducing the use of TiO ₂ , B ₂ O ₃ , P ₂ O ₅ etc. as additives, all of which have the effect of inhibiting crystallization, but the effect is not ideal. It increases the crystallization temperature of fused silica to about 1300°C , can not meet the user's requirements.

The purpose of the present invention is to propose a fused silica ceramic material with good comprehensive performance and high crystallization temperature.

According to the purpose of the present invention, the specific chemical composition of the fused silica ceramic material proposed by us is (weight%): BN1-8%, and the rest is _SiO2 . In addition, 10-20% of short carbon fiber Csf or silicon carbide whisker SiCw can also be added to the composition of the fused silica ceramic material of the present invention. _SiO2 in the fused silica ceramic material of the present invention is a matrix element, but because the crystallization temperature of the fused silica material is relatively low, it is only 1100°C-1200°C. Therefore, the purpose of adding BN element in the material of the present invention is to increase the crystallization temperature of the material itself. BN element has low density, small thermal expansion coefficient, good thermal shock resistance, high temperature chemical inertness, dielectric properties close to fused silica, and little change with temperature, so BN is suitable for use as an additive in the material of the present invention. The principle of increasing the crystallization temperature of the material itself is that BN is a strong covalent bond compound, which exists in the form of molecules in the network structure of fused silica, thus complicating the network structure and reducing the chance of atomic rearrangement into crystals, achieving an increase The purpose of crystallization temperature. Other additives are weak covalent bond compounds or ionic bond compounds, which are easy to replace Si-O bonds to form new network structures or metal ions are distributed in the silicon-oxygen tetrahedral network, so the inhibition of devitrification is not obvious.

The preparation method of the fused silica ceramic material of the present invention is to weigh an appropriate amount of amorphous _SiO2 raw material powder and BN powder into a wet mill within the designed composition range, use alcohol as the ball milling medium, and ball mill the wet mixed raw materials The weight ratio of balls and alcohol is 1:2:4, the wet mixing time of ball milling is 10-24 hours, and the powder is taken out and dried after ball milling. If it is to prepare a composite material, 10-20% of any one of the reinforcing and toughening raw materials Csf or SiCw can be added and mixed uniformly. Then press the uniformly mixed powder according to the molding requirements and sinter at high temperature. The sintering temperature is 1350-1400°C, and the sintering time is 20-60 minutes. It can also be directly sintered by hot pressing. The hot pressing temperature and time are the same as above, and the hot pressing pressure 5 ~ 15MPa.

Compared with the prior art, the fused silica ceramic material of the present invention has significantly improved crystallization temperature of the material, and its comparison results are shown in Table 1:

Table 1 The material of the present invention is compared with the crystallization temperature of the prior art additive BN of the present invention TiO ₂ Al ₂ O ₃ Al ₂ O ₃ ＋ La ₂ O ₃ B ₂ O ₃ Quartz glass Crystallization temperature 1400°C 1300°C 1230°C 1300°C 1250°C 1200℃

Adding reinforcing and toughening additives to the material of the present invention can also obviously change the mechanical and thermal properties of the material, and its various properties are shown in Table 3.

Example

According to the composition range of the fused silica ceramic material designed in the present invention, we have prepared four kinds of materials with different composition contents in total. 1 ^# and 2 ^# are only adding BN additives with different contents, and 3 ^# and 4 ^# are adding BN at the same time. Different contents of reinforcing and toughening phases were added. The specific composition content is shown in Table 2. The preparation method of this embodiment is to adopt hot pressing and sintering at 1400° C. for 30 minutes, and the pressure is 10 MPa. Then various performance tests were carried out on each material, and the test results are shown in Table 3. Table 2 The composition comparison (weight %) of the embodiment material of the present invention serial number BN Csf SiCw SiO ₂ 1 3% - - Remain 2 6% - - Remain 3 5% 10% - Remain 4 5% - 15% Remain

The detection performance of each material in the embodiment of table 3 Performance serial number Density (%) Bending strength (MPa) Coefficient of thermal expansion (×10 ^-S /K) Wire ablation rate (mm/s) Thermal shock resistance Crystallization temperature 1 99.5 41.6 0.52 0.317 ΔT＞1350℃ >1400℃ 2 99.2 48.0 0.55 0.337 ΔT＞1350℃ >1400℃ 3 98.7 97.2 0.57 0.207 ΔT＞1400℃ >1400℃ 4 98.3 329.8 1.0 0.372 ΔT＞1300℃ >1400℃

Claims (2)

1, a kind of fused quartz ceramic material is characterized in that the concrete Chemical Composition of this material is (weight %) BN1-8%, and all the other are SiO ₂

2,, it is characterized in that to add in the composition of this material any raw material among 10-20%Csf or the SiCw according to the described material of claim 1.