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Welcome to Dongguan many hardware Ceramics Co., Ltd., a manufacturer specializing in zirconia ceramics.

Ceramic dispensing valve ceramic plunger ceramic suction disc sucker

Specializing in alumina ceramic and zirconia ceramics processing and customization

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Dongguan many many hardware Ceramics Co., Ltd.
Contact: Mr. Han
Mobile phone: 13288886353
Tel: 0769-82926445
QQ:304871063
Mailbox: Duoxuduo2006@163.com
Website: bjyjpf.cn
Address: No. 6 Chuang Road, Shang Sha first industrial area, Changan Town, Dongguan.

95 alumina
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The main component of alumina ceramics is Al2O3. Ceramics with a Al2O3 content of more than 75% are usually referred to as high alumina ceramics. 95 alumina ceramics are the most widely used ceramics in structural ceramics. Because of its excellent electrical performance at high frequency, its dielectric loss is small, volume resistivity is high, strength is high, hardness is large, coefficient of linear expansion is small, and its wear resistance and heat resistance are also good. In general, the use of 95% alumina ceramics is more economical and practical. 99% to 99.9% alumina ceramics are used for occasions with high performance requirements.

95 the specific performance of alumina ceramics.

Electrical properties of 1 and 95% aluminum oxide

1. The volume resistivity of volume resistivity insulation refers to the ratio of the DC electric field intensity to the current density in the volume current direction of the sample. In the formula, EV/jv is the intensity of DC electric field, and JV is the current density of CM. 95% alumina ceramic is an excellent electronic insulating material with high volume resistivity. In the national standard GB/T5593 - 1999, it is specified that when the temperature is 100 degrees, the temperature is higher than 1 * 1013 ohm cm; at 300 C, it is more than 1 * 1010 cm; when 500 degrees C, it is more than 1 1 108 cm. In fact, the volume resistivity of 95 porcelain produced in China is 1-2 orders of magnitude higher than those mentioned above. Instruments for testing volumetric resistance usually use a high resistance meter.

2, DC breakdown strength, electrical breakdown strength of electrical insulation material refers to the change under the action of an applied DC electric field, mainly due to internal structural changes. When the electric field intensity reaches a certain value, it will further change its internal structure and cause insulation breakdown. According to the national standard, the 95% alumina ceramic is subjected to voltage test under DC condition. When the DC voltage is applied to the sample, the breakdown of the sample will be made. The breakdown voltage value is equal to the average thickness of the sample, which is called DC breakdown strength. The unit is KV/mm. The provisions of the national standard are 18KV/mm. In fact, we usually reach 30 to 40 km / mm.

3. A parameter for dielectric polarization of dielectric permittivity under alternating electric field. It is the ratio of capacitance of a capacitor filled with some insulating material to that of a capacitor with the same electrode size in a vacuum medium. It represents an inherent characteristic of materials. According to GB, the dielectric constant of 95% alumina ceramics is 9-10 when the test frequency is 1MHz.

4. Dielectric loss tangent dielectric loss indicates that the material is polarized or absorbed under the action of alternating electric field, resulting in the loss of electric energy. The magnitude of dielectric loss is expressed by the tangent value of dielectric loss angle. According to the national standard 1MHz, the requirement of 95% alumina ceramics reaches 4 * 10-4 when the frequency is at the same time.

Two, 95% alumina thermal properties

1, the average linear expansion coefficient of ceramic at elevated unit temperature relative elongation, that is, the average linear expansion coefficient is one of the main performance indicators of 95% alumina ceramics. According to the national standard, the test temperature is 20-500 C, the A is 6.5 * 10 - 6 - 7 5 * 10-6/ C, and the A is 6.5 * 10 - 6 - 8 * 10-6/ C at the test temperature of 20-800 C. As ceramic parts are usually sealed with metal parts, the expansion coefficient is required to match the expansion coefficient of metal materials.

2, thermal shock resistance refers to the ability of ceramic materials to withstand rapid cooling and rapid heating. 95% alumina ceramics have good thermal shock resistance and can withstand high temperature and rapid cooling without heat damage. The national standard is to put 10 ceramic samples in a heating furnace at 800 + 10 degrees Celsius for 30 minutes, then put them on the asbestos board and cool them to room temperature. Then the samples are put into the 800 degree heating furnace. According to the above regulations, they are carried out for 10 times. Finally, they are immersed in the red magenta solution of 1% concentration for 3 minutes. If the 10 specimens are not cracked and cracked, the performance is qualified.

Three, 95% alumina mechanical properties

Mechanical performance refers to the ability of materials to be destroyed without mechanical damage. The tensile strength, flexural strength and compressive strength are usually determined according to the direction of the force and the point of force. 95% the tensile strength of alumina ceramics is generally more than 160Mpa, usually higher than the best sealing strength. There is no technical specification for the tensile strength and compressive strength of 95% alumina ceramics in the national standard of the standard. The national standard GB/T5593 - 1999 stipulates that the flexural strength of 95% alumina ceramics is 280MPA.  

Four, 95% other properties of alumina

1. Bulk density of 95% alumina ceramic bulk density has a great relationship with the choice of raw materials and porcelain manufacturing technology. In the national standard 3.60g/cm3 / T 95%, the volume density of alumina ceramics is above that. In fact, the forming method of porcelain is different. The density of 95% alumina ceramics is quite different. Usually, the density is 3.60-3.70 g/cm3 when molding by hot die-casting and grouting. When isostatic pressing is formed, 3.70 g/cm3; gel forming can reach 3.73 g/cm3.

2, airtight 95% alumina ceramics for microwave devices, vacuum switches and so on, require high vacuum tightness. In the electronic industry standard SJ/T, the leakage rate of seals is QK or less than 1 x 10-11Pa.M3/S., which also stipulates that the leakage rate of ceramic must meet the above standards.

3, chemical stability 95% alumina ceramic chemical stability is characterized by its ability to resist various chemical reagents. The ability of acid resistant agents to be etched is called acid resistance, and the ability of alkali resistant agents to be etched is called alkali resistance. According to the national standard, the sample is placed in 1:9 hydrochloric acid or 10% sodium hydroxide solution, and the solution is heated to 100 degrees C for 1H. The requirement of acid resistance is Kh or less than 7mg/cm2, and the alkaline resistance requirement is Kn or less than 0.2mg/cm2.

4. The microstructure of ceramic microstructure ceramics refers to the combination of crystalline phase (main crystalline phase, sub crystalline phase), glass phase, gas phase, grain boundary, content, distribution, shape, particle size distribution, uniformity, defect, interphase material, domain structure and so on. The microstructure is closely related to the process of porcelain making, and directly affects the performance of ceramics. It is a research method to improve the quality of ceramics and improve the technology.

Sealing performance of five, 95% alumina ceramic metal

95% alumina ceramics, as a kind of structural ceramics, must be sealed with metal to form a component. In particular, 95% alumina ceramics used in microwave devices and vacuum development tubes usually assess ceramic metal sealing performance as an important indicator. Contents of the examination: ceramic metal sealing requires high strength and good tightness. In the electronics industry standard SJ/T "ceramic tube shell for vacuum switch tubes", it is stipulated that the average sealing strength is sealed by standard porcelain when the sigma A is equal to 90Mpa, and when the three point method is used, the sigma A is equal to or greater than 90Mpa. The air tightness of the sealing piece and helium leak rate Qk is less than 1 * 10-11PaM3/S.