Heterogeneity along the height in disc specimens of raphite/tungsten powder mixtures with sub-stoichiometric carbon atom ratios heated by concentrated solar beam to 1600°C

Nobumitsu Shohoji; Teresa Magalhães; Fernando de Almeida Costa; Luis G. Rosa; Jorge  Cruz Fernandes; José Rodriguez; Inmaculada Cañadas; Diego Martinez

Informações chave

Autores:

Nobumitsu Shohoji; Teresa Magalhães; Fernando de Almeida Costa (Fernando de Almeida Costa Oliveira); Luis G. Rosa (Luís Manuel Guerra da Silva Rosa); Jorge Cruz Fernandes (José Jorge Lopes da Cruz Fernandes); José Rodriguez; Inmaculada Cañadas; Diego Martinez

Publicado em

2010

Resumo

Compositional heterogeneity along the thickness of compacted disc specimens of graphite / tungsten powder mixtures with sub-stoichiometric carbon atom ratios (0.35, 0.50 and 1.00) heated by concentrated solar beam to 1600ºC was characterised by X-ray diffraction. Top surface of any examined test piece was consisted purely of mono-carbide WC while the bottom surface showed different constitution depending on the net initial C/W ratio of the test piece; almost pure metallic W for the C/W = 0.35 specimen, dominant metallic W associated with small proportion of W2C for the C/W = 0.50 and dominant W2C with trivial proportion of WC for the C/W = 1.0. In the intermediate zone between the top and the bottom layers, the constitution held virtually constant depending on the nominal C/W ratio of the starting material: co-existing metallic W and W2C for the C/W = 0.35, pure W2C for the C/W = 0.50 and predominant WC with trace W2C for the C/W = 1.00. Unlike for the top surface of the C/W = 0.35 test piece heated in a solar furnace to 1900ºC reported earlier, no evidence of formation of nano-meter scale WC whisker was detected for the top surface in any sample heated to 1600ºC in the present work.