1,721,082 research outputs found
Improving SOFC Ceramic Components: A Multi-faceted Scientific and Technological Challenge
No full text
Synthesis of Zr diboride-Zr nitride composite powders by self-propagating high-temperature synthesis from zirconium, boron and hexagonal boron nitride.
No full textPreparation of nano-size ZrB2 powder by self-propagating high-temperature synthesis
Full text linkPreparation of nano-size ZrB2 powder by SHS has been investigated. Zr and B elemental powders were mixed with 10-50 wt.% NaCl, and prepared pellets were reacted under argon. Adiabatic temperatures were calculated by HSC software. Increasing NaCl content led to a continuous decrease in adiabatic temperatures and reaction wave velocity. Products were subjected to XRD, SEM and FESEM analyses. Average crystallite size of ZrB2, which was 303 nm without NaCl, decreased to 32 nm with 40% NaCl addition. Distinct decrease in ZrB2 particle size was also observed from SEM analyses. 30% NaCl addition was found to be optimum for ensuring a stable SHS reaction and providing the formation of nano-size ZrB2 particles. It was revealed from particle size distribution measurements that ZrB2 powder obtained by 30 wt.% NaCl addition contained particles mostly finer than 200 nm. A mechanism, similar to solution-precipitation was proposed for the particle size refining effect of NaCl
Self-propagating high-temperature synthesis of ZrB2 or TiB2 reinforced Ni–Al composite powder
No full textThe self-propagating high-temperature synthesis (SHS) of 0-40 wt.% ZrB(2) or 40 wt.% TiB(2) reinforced Ni-Al matrix composite powders has been investigated. The SHS reactions were conducted starting from elemental powders of Zr, Ti, Ni, Al, and amorphous B. For all initial compositions, the product contained only the NiAl and ZrB(2) or TiB(2) compounds without any trace of cross-reaction phases. The powder, obtained by grinding the reacted pellet, contained ZrB(2) or TiB(2) homogeneously dispersed in the NiAl matrix. The dimension and distribution of the reinforcement phase make the powder suitable as precursor for thermal spray applications. After sintering of the composite powder up to 85% of theoretical density, microhardness was measured. The microhardness of pure NiAl was 394 +/- 37 HV(0.2). It increased considerably by the addition of the boride phases. Samples containing 40 wt.% ZrB(2) and TiB(2) attained values of 812 +/- 94 and 967 +/- 104 HV(0.2), respectively
Transition Metal Silicides: Growth in Metal-Silicon Diffusion Couples
No full textAn original kinetic model to calculate the diffusion coefficients of the metals in silicides layers and to study the kinetics of growth of the layers themselves is discussed
Reactive growth of silicides in M (Nb, Ta, V) - Si bulk diffusion couples
No full textThe reactive growth of silicides in M (Nb, Ta, V) - Si bulk diffusion couples as observed by Scanning electron Microscopy is discussed. A quantitative model to obtain the diffusion coefficients of the metals in the silicides layers is presented
Energetics of aluminum vacancies and incorporation of foreign trivalent ions in gamma-Al2O3: An atomistic simulation study
No full text
- …
