传统的碳化硅电热元件烧结工艺主要通过二次烧结来实现，烧成周期长，能耗过大，烧结过程中生成的CO对环境污染大，不利于自动控制，同时，烧制成的电热元件电阻离散性大，对成品率有很大的影响。一次烧结工艺周期短、能耗小、污染小、烧成制度利于控制、成品率高，但制品的性能尤其是密度不如传统工艺的好。本实验针对一次烧结工艺的这种不足，对碳化硅电热元件的一次烧结工艺进行了进一步研究。 由于碳化硅电热元件一次烧结的致密度不高，研究了颗粒级配模型，并与实验相结合来确定恰当的颗粒级配来提高电热元件的生坯密度。因为碳化硅电热元件的烧结收缩性差、烧成密度低、强度低等缺点，研究了不同种类和不同含量的添加剂对电热元件性能的影响。通过研究不同的成型工艺成形所制备的电热元件的性能，来选取恰当的成型方式。进一步研究了碳化硅电热元件的导电机理、烧结机理及结晶性，以达到改善电热元件性能的目的。 通过实验研究发现，多粒度颗粒体系的级配效果好，粗颗粒粒径越大，级配效果越显著，最佳生坯密度为2.068g/cm3，配比为5.6:0.8:1.6:2。对含有添加剂的电热元件的研究发现，单种添加剂中Al2O3对密度、强度影响最大，添加剂含量为0.5%时密度为2.314g/cm3，强度为36.14MPa；Fe2O3对电阻率影响最大，添加剂含量为0.5%时电阻率为0.634Ω•cm。两种添加剂体系中Fe2O3+Al2O3对电热元件性能的改善最大，最佳配方时密度为2.359 g/cm3，强度为41.27MPa。经过对不同成型工艺的研究发现，等静压成型中，物料受力最均匀，压制出的制品密度性能高，缺陷比通过单向加压和挤压成型的制品少。通过对碳化硅电热元件导电机理的研究发现，添加Al2O3的引起电热元件杂质离子导电；添加Fe2O3的引起电热元件电子导电。进一步对其烧结机理研究发现，本实验中不含有添加剂、添加了H3BO3或石油焦的烧结都属于固相烧结；添加了Al2O3、Fe2O3的烧结属于部分液相烧结。 通过XRD、SEM和能谱分析得出，H3BO3的加入促进了SiO2的生长，Al2O3和石油焦则促进了a-SiC的生长。同时证明了晶界间有非化学计量化合物的存在。 经过系统的实验研究发现，SiC电热元件密度提高4%左右，抗折强度和电阻率都有明显的改善；能耗降低了1~2倍，成品率提高30~40%。

Traditional sintering technology for silicon carbon electric heating element mainly uses second sintering process, which has longer sintering cycle, causes higher energy consumption, produces CO polluting air and is disadvantageous to automatic control, besides, the sintered electric heating element has great resistance discreteness, which has very huge influence on finished product rate. First sintering technology has shot sintering cycle, low energy consumption and slight pollution, benefits the sintering system control, improves finished product rate, but doesn’t have high properties especially density than the traditional technology. According to the shortcoming, further study on the first sintering technology for silicon carbide electric heating element is done in this experiment. Considering low tightness of the first sintering electric heating element, it has researched the model of grain composition and confirms proper grain composition with experiment to improve the green density of electric heating element. Because it has bad sintering contractility, low density and low intensity, etc, on silicon carbide electric heating element, the influence upon additives with different type and content to the electric heating element performance influence has been studied. Proper molding way has been selected through researching electric heating element properties of different molding technology. Besides, electric conductivity mechanism, sintering mechanism and crystallinity have been further researched to improve electric heating element properties. Through experimental study, it discovers that the graded effect of multi- granularity grain system is good, as coarse granule particle size increasing, the gradation effect gets better. The best green density is 2.068g/cm3, the allocated proportion is5.6:0.8:1.6:2. According to the research on electro-heating element including additives, discovers that the greatest influence to the density and the intensity is Al2O3 when the additive level is 0.5% ，the density is 2.314g/cm3 and the intensity is 36.14MPa, besides, the most tremendous influence to the electronic resistivity is Fe2O3 When the additive level is 0.5% and the electronic resistivity is 0.634Ω•cm in the mono-additives.Fe2O3+Al2O3 take the biggest improvement to the electric heating element in two kinds of additives when the density is 2.359 g/cm3 and the intensity is41.27MPa. Through researching on the differently formation craft, discovers that, when taking shape through the equal static pressure, material’s stress is the evenest, the product density is high and the flaw is less than the other formation way. Al2O3 causes the electric heating element impurity ionic conduction; Fe2O3 causes the electric heating element electron conduction through the research on the electric heating element electric conduction mechanism. By further investigations of the sintering mechanism, discovers that the mechanism of without additives, adding H3BO3 or petrol coke in this experiment belongs to the solid-phase sintering one, but adding Al2O3, Fe2O3 to the electric heating element partially belongs to the liquid phase sintering one. Through XRD, SEM and the power spectrum analysis, the added H3BO3 promotes the SiO2 growth, Al2O3 and the petrol coke promote the a-SiC growth. Simultaneously proves the non-stoichiometric compound exists between the grain boundaries. After the systematic experiment study, it discovers that the SiC electric heating element density enhances about 4%, the flexural strength and the electrical resistivity all have the visible improvement, besides, the energy consumption is reduced 1~2 times and the finished product rate was increased 30~40%.