Additive for silicon nitride sintered bodies

Abstract

The invention discloses an additive for silicon nitride sintered bodies, which is prepared from the following components by weight percent: 29.5-65.2 percent of sintering aid and 34.8-70.5 percent of activating composite oxide, wherein the activating composite oxide is a compound formed by combining lithium oxide (Li2O), yttrium oxide (Y2O3), silicon dioxide (SiO2) and aluminium-containing compound. After the additive is added into a silicon nitride sintered body, the inter-granular phase components of a silicon nitride heating element is changed, the refractoriness of the silicon nitride sintered body sintered at normal pressure is enhanced, the mechanical property of the heating element at high temperature is improved and a heating element of the silicon nitride sintered body with the use temperature of 1,200-1,400 DEG C is obtained, the thermoconductivity is 21-32 W*m <-1>*K<-1>, the linear expansibility is 3.1*10<-6>-3.8*10<-6> / DEG C(40-800DEG C) and the density is over 98 percent. The invention realizes the normal-pressure low-temperature rapid-firing sintering of the silicon nitride heating element.

Description

technical field

[0001] The invention relates to a heating element additive for a silicon nitride sintered body. Background technique

[0002] Silicon nitride is an atomic crystal compound composed of nitrogen and silicon through strong covalent bonds. The heat of formation is 733.6kJ / mol. Compared with the combination of two nitrogen atoms to form nitrogen (N 2 ) is much lower than the 941.69kJ / mol released, so even if the sintering temperature is reached under the condition of no sintering aid, α-silicon nitride will decompose to generate nitrogen and free silicon without sintering. In the prior art, the decomposition of silicon nitride is suppressed by applying pressure or adding sintering aids to realize sintering. Commonly added sintering aids are oxides of rare earth elements, such as yttrium oxide and lanthanum oxide, which can effectively prevent the decomposition of Si3N4 during sintering.

[0003] CN1229829A discloses a silicon nitride heating element and its manu...

Examples

Embodiment 1-10

[0033] The preparation method of embodiment 1-10:

[0034] (1) Raw material configuration: According to the ingredients in Table 1, add absolute ethanol and silicon nitride balls, ball mill for 1 hour, and dry under the protection of nitrogen.

[0035] (2) Green body preparation: Process the mold according to the shape requirements of the heating element (150mm×30mm×5mm), and prepare the green body by using dry powder compression molding.

[0036] (3) Microwave sintering process: the green body enters the microwave sintering furnace continuously, and is continuously sintered under the protection of flowing nitrogen. The sintering temperature of the furnace body is shown in Table 1, and the atmosphere in the furnace is 102,325-102500Pa flowing nitrogen. The green body is sintered in this temperature range and released after cooling.

technical field

[0001] The invention relates to a heating element additive for a silicon nitride sintered body. Background technique

[0002] Silicon nitride is an atomic crystal compound composed of nitrogen and silicon through strong covalent bonds. The heat of formation is 733.6kJ / mol. Compared with the combination of two nitrogen atoms to form nitrogen (N 2 ) is much lower than the 941.69kJ / mol released, so even if the sintering temperature is reached under the condition of no sintering aid, α-silicon nitride will decompose to generate nitrogen and free silicon without sintering. In the prior art, the decomposition of silicon nitride is suppressed by applying pressure or adding sintering aids to realize sintering. Commonly added sintering aids are oxides of rare earth elements, such as yttrium oxide and lanthanum oxide, which can effectively prevent the decomposition of Si3N4 during sintering.

[0003] CN1229829A discloses a silicon nitride heating element and its manu...

Examples

Embodiment 1-10

[0033] The preparation method of embodiment 1-10:

[0034] (1) Raw material configuration: According to the ingredients in Table 1, add absolute ethanol and silicon nitride balls, ball mill for 1 hour, and dry under the protection of nitrogen.

[0035] (2) Green body preparation: Process the mold according to the shape requirements of the heating element (150mm×30mm×5mm), and prepare the green body by using dry powder compression molding.

[0036] (3) Microwave sintering process: the green body enters the microwave sintering furnace continuously, and is continuously sintered under the protection of flowing nitrogen. The sintering temperature of the furnace body is shown in Table 1, and the atmosphere in the furnace is 102,325-102500Pa flowing nitrogen. The green body is sintered in this temperature range and released after cooling.

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