Nitride microstructure

Hirao K, Imamura H, Watari K, Brito ME, Toriyama M, Kanzaki S (1999) Seeded Silicon Nitride Microstructure and Performance. In Niihara K, Sekino T, Yasuda E,... 

Lewis HM (1993) Sialons and Silicon Nitrides Microstructural Design and Performance. In Chen IW, Becher PF, Mitomo M, Petzow G, Yen TS (eds) Silicon Nitride Ceramics - Scientific and Technological Advances, Mat Res Soc Symp Proc 287, MRS, Pittsburgh, p 159... 

K. Hirao, H. Imamura, K. Watari, M. E. Brito, M. Toriyama and S. Kanzaki, Seeded Silicon Nitride Microstructure and Performance , Key Engineering Materials, 161-163, 1999, 469-474,... 

England, K. M., and Mazunder, J., Kinetics and Microstructure of Laser Chemical Vapor Deposition of Titanium Nitride, SPIEProc., 2703 552-562 (Feb. 1996)... 

Mingwu, Bai, Koji, Kato, Noritsugu, Umehara, Yoshihiko, Miyake, Xu, Junguo, and Hiromitsu, Tokisue, "Dependence of Microstructure and Nanomechanical Properties of Amorphous Carbon Nitride Thin Films on Vacuum Annealing, Thin SoZ/dFz Zms, Vol. 376,2000, pp. 170-178. 

As a result of the microstructure SEM investigations (fig. 1 and 2) it was established that the diffusion layer was a combination of surface layers of nitride phases and zone of internal saturation. 

Figure 1. The electron-microscopic images of microstructure (on the left) and eutectic (a) of the phases formed in the Fe-foils after PPD and nitriding at T=853 K during 15 minutes, their electron-diffractions (b, c, d)...

Figure 2. The electron-microscopic images of microstructure formed in the Fe-0.5 %Ni foils after deformation and nitriding at T=623 K during 5 minutes...

Matsuoka T (2005) Progress in nitride semiconductors from GaN to InN - MOVPE growth and characteristics. Superlattices and Microstructures 37(1), 19-32... 

In some instances, subtle changes in the precursor architecture can change the composition and microstructure of the final pyrolysis product. For example, pyrolysis of —[MeHSiNH] — leads to amorphous, silicon carbide nitride (SiCN) solid solutions at >1000°C (see SiCN section). At ca 1500 °C, these material transform to SisN SiC nanocomposites, of interest because they undergo superplastic deformation20. In contrast, chemically identical but isostructural — [F SiNMe] — transforms to Si3N4/carbon nanocomposites on heating, as discussed in more detail below21. 

Keywords Silicon nitride ceramics, Phase relations, Processing, Microstructure, Properties... 

An improved nitridation process of Si in a rotary tube furnace allows a better control of the exothermic reaction, avoids overheating and agglomeration [192], is faster and results in smaller crystallites. Those powders have an improved sintering behaviour and after sintering a more favourable microstructure compared to powders produced by a batch process [192], Recently successful fast nitridation in a fluidised bed reactor was realised in laboratory experiments [194]. 

In conclusion, it can be stated that Si3N4 ceramics are polyphased materials including mainly /fss, ass, secondary phases (mainly oxide nitrides, in ceramic literature generally called oxynitrides) and an amorphous phase, all having characteristic morphologies and can be arranged in a manifold of microstructures (Sect. 6). 

Silicon nitride ceramics are not merely only one material but several classes of materials. All of them are multiphased, i.e., they exhibit a heterogeneous microstructure which has formed during sintering (Sect. 6). Therefore in all classes a large variety of properties is predominant and as a consequence also a large variety of potential applications (Sect. 10). Often little variations in the powders and the processing parameters cause remarkable changes in the microstructure which have a pronounced effect on properties (Sects. 6 and 7). 

Nevertheless, the microstructure cannot be directly correlated to the initial /1-content in the starting powder. The experimentally determined particle density in sintered samples indicates that only a part of the initial /I particles are able to grow [283]. The number of growing /1-particles depends on a critical particle diameter dcrit (Fig. 18). Particles below dcrit will dissolve in the oxide nitride liquid during phase transformation and reprecipitate on the overcritical /1-particles according to an anisotropic Ostwald ripening process [284, 292, 293]. 

Hydrogen or ammonia in the reaction atmosphere increase the a content, the fineness of microstructure, and the strength, they reduce the dependence of the nitridation process on variations in green density and powder properties... 

Table 15. Influence of processing variables during nitridation on the conversion rate, microstructure and properties of RBSN [541-546, 549, 550]...

Fast nitridation, coarse microstructure, high a content... 

Accelerated nitridation, increased /1-content More homogenous reaction. High a-content, fine microstructure, high strength and KIC Coarse microstructure, low strength and KIC... 

Parr NL, Martin GF, May ERW (1960) Preparation, Microstructure and Mechanical Properties of Silicon Nitride. In Popper P (ed) Special Ceramics. Heywood, London, p 102... 

Kim HD, Han BD, Park DS (2001) Process to obtain Bimodal Microstructure in Silicon Nitride. Paper presented at 25th Annual Conference on Composites, Advanced Ceramics, Materials, and Structures. Am Ceram Soc, Cocoa Beach, Fl... 

Becher PF, Hwang SL, Lin HT, Ticgs TN (1994) Microstructural contributions to the fracture resistance of silicon nitride ceramics. In Hoffmann MJ, Petzow G (eds) Tailoring of Mechanical Properties of Si3N4 Ceramics, NATO ASI Ser E Vol. 276, Kluwer Academic Publishers, Dordrecht, p 87... 

Nishimura N, Masuo E, Takita K (1991) Effect of Microstructural Oxidation on the Strength of Silicon Nitride after High Temperature Exposure. In Carlsson T, Johansson T, Kahlman T (eds) Proc 4th Int Symp Ceram Mater Components for Engines. Elsevier, London, p 1139... 

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