Failure mechanisms and toughness of Al2O3 ductile-particle toughened ceramics and SiC fibre-ceramic composites

The development of high performance ceramics and ceramic composites often relies on assumptions about their behaviour during loading and at failure. A crucial influence on the mechanical properties of these materials is the degree of sub-critical cracking, which post mortem investigations cannot adequately reveal. Hence a clear picture of the dynamic micromechanisms of cracking is required if applications of fracture and damage mechanics to theoretical models is to be meaningful.

Theoretical and numerical investigation of SiC JFET and MOSFET at 6.5 kV

This paper presents a preliminary theoretical and numerical investigation of 4H-SiC JFET and MOSFET at 6.5 kV. To improve the on-state/breakdown performance of the JFET, buried layers in conjunction with a highly doped buffer layer have been used. Trench technology has been employed for the MOSFET. The devices were simulated and optimized using MEDICI[I] simulator. From the comparison between the two devices, it turns out that the JFET offers a better on-state/breakdown trade-off, while the trench MOSFET has the advantage of MOS-control.

Microwave power effects on the properties of phosphorus-doped SiC:H films prepared using ECR-CVD

There has been a growing interest in hydrogenated silicon carbide films (SiC:H) prepared using the electron cyclotron resonance-chemical vapour deposition (ECR-CVD) technique. Using the ECR-CVD technique, SiC:H films have been prepared from a mixture of methane, silane and hydrogen, with phosphine as the doping gas. The effects of changes in the microwave power (from 150 to 900 W) on the film properties were investigated in a series of phosphorus-doped SiC:H films. In particular, the changes in the deposition rate, optical bandgap, activation energy and conductivity were investigated in conjunction with results from Raman scattering and Fourier transform infra-red (FTIR) analysis. It was found that increase in the microwave power has the effect of enhancing the formation of the silicon microcrystalline phase in the amorphous matrix of the SiC:H films. This occurs in correspondence to a rapid increase in the conductivity and a reduction in the activation energy, both of which exhibit small variations in samples deposited at microwave powers exceeding 500 W. Analysis of IR absorption results suggests that hydrogen is bonded to silicon in the Si-H stretching mode and to carbon in the sp3 CHn rocking/wagging and bending mode in films deposited at higher microwave powers.

Comments on "micro-scale abrasive wear testing of PVD coatings on curved substrates"

Previously published expressions for the wear volume in the micro-scale abrasion test for curved specimen surfaces (K.L. Rutherford and I.M. Hutchings, Tribology Letters 2 (1996) 1-11) were based upon erroneous assumptions about the wear-scar geometry. Accurate volumes have now been computed, and the errors in the use of the original analytical equations are shown to be negligibly small (<0.5% error) for all practical cases. © J.C. Baltzer AG, Science Publishers.