Porous silicon nitride

Potassium loaded on a porous silicon nitride has been reported as a superbase catalyst. With appropriate pre-treatment, the catalyst was found to be highly active for 2,3-dimethylbut-l-ene isomerisation yielding 2,3-dimethylbut-2-ene in close to 100% selectivity. In order for high activity to be demonstrated, 30 wt% potassium amide was loaded by impregnation. A trace of Fc203 was also added on impregnation. A silicon nitride synthesised via a silicon diimide precursor which was pre-treated at 1000°C was found to be best and the catalyst was activated by heating in vacuo. The possibility that this resulted in active potassium nitride species via ... 

Kawai, C., and Yamakawa, A., Machinability of high-strength porous silicon nitride ceramic, J. Ceram. Soc. Jap., 106(11) 1135-1137 (1998). 

Carbon as fugitive additive for porous silicon nitride processing... 

In addition to dense monolithic ceramics, porous silicon nitrides are gaining more importance in technological applications [24], Some porous silicon nitrides with high specific surface area have already been applied as catalysis supports, hot gas filters and biomaterials [25], There is an emerging tendency to facilitate silicon nitride as biomaterial, because of specific mechanical properties that are important for medical applications [25], Moreover, in a recent study it was shown that silicon nitride is a non-toxic, biocompatible ceramic which has the ability to propagate human bone cells in vitro [25], Bioglass and silicon nitride composites have already been realized to combine... 

Yang, J.-F., Deng, Z.-Y., Ohji, T., Fabrication and characterisation of porous silicon nitride ceramics using Yb203 as sintering additive, J. Eur. Ceram. Soc., 23, 2003, 371-378. 

Non-oxide ceramic materials such as silicon carbide has been used commercially as a membrane support material and studied as a potential membrane material. Silicon nitride has also the potential of being a ceramic membrane material. In fact, both materials have been used in other high-temperature structural ceramic applications. Oxidation resistance of these non-oxide ceramics as membrane materials for membrane reactor applications is obviously very important. The oxidation rate is related to the reactive surface area thus oxidation of porous non-oxide ceramics depends on their open porosity. The generally accepted oxidation mechanism of porous silicon nitride materials consists of two... 

Kaskel, S Schlichle, K. Porous silicon nitride as a superbase catalyst. Journal of Catalysis. 2001 201.270-274. 

T. Fukasawa, Z, Y, Deng, and M. Ando, Synthesis of Porous Silicon Nitride with Unidirectionally Aligned Channels Using Freeze-drying Process, J. Am. Ceram. Soc., 85 [9] 2151-2155 (2002),... 

Yao DX, Zeng YP (2011) High flexural strength porous silicon nitride prepared via nitridation of silicon powder. J Inorg Mater 26 422-426... 

Fibrous Crain-Aligned Porous Silicon Nitrides... 

Although, in structural materials, the pores are generally beheved to cause a deterioration in mechanical reliability, this is not always true. Rather, the pores may cause an improved or even unique mechanical performance of the material which cannot be attained in the dense counterpart, especially when the porous microstructure is carefully tailored. Two examples of porous silicon nitrides are described in the... 

Fibrous Grain-Aligned Porous Silicon Nitrides 371... 

Porous Silicon Nitride Through Tape-Casting... 

Figure 8.21 Microstructures of porous silicon nitride with large fibrous grain alignment (porosity 14%). Reprinted with permission from Ref [50] 2000, Blackwell Publishing, Inc.

Porous Silicon Nitride Through Sinter-Forging... 

Figure 8.26 Fracture surfaces of porous silicon nitride with fine fibrous grain alignment fabricated through a sinter-forging technique. The porosity is 24%. Illustration courtesy of Naoki Kondo et al.

The fracture energy, strength, fracture strain and lightweight nature of the porous silicon nitrides introduced here, compared to two conventional dense materials, are shown graphically in Figure 8.27. Here, PSN-A and -B are porous materials fabricated... 

R. B. Zhang, D. N. Fang, Y. M. Pei, L. C. Zhou, Microstructure, mechanical and dielectric properties of highly porous silicon nitride ceramics produced by a new water-based freeze casting, Ceram. Int, 38,4373-4377 (2012). 

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