Author(s):
Shohoji, Nobumitsu ; Magalhães, Teresa ; Oliveira, Fernando Almeida Costa ; Rosa, Luís Guerra ; Fernandes, Jorge Cruz ; Rodriguez, Jose ; Cañadas, Inmaculada ; Martinez, Diego
Date: 2010
Persistent ID: http://hdl.handle.net/10400.9/1070
Origin: Repositório do LNEG
Subject(s): Tungsten carbides; Solar furnace; X-ray diffraction; Heat treatment; Temperature gradient; Tungsten carbides; Tungsten carbides; Solar furnace; Solar furnace; X-ray diffraction; X-ray diffraction; Heat treatment; Heat treatment; Temperature gradient; Temperature gradient
Description
Compositional heterogeneity along the thickness of compacted disc specimens of graphite/tungsten powder mixtures with substoichiometric carbon atom ratios (0.35, 0.50 and 1.00) heated by concentrated solar beam to 1600 C 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 metallicWfor the C/W ¼ 0:35 specimen, dominant metallicWassociated with small proportion ofW2C for the C/W ¼ 0:50 and dominantW2C with trivial proportion of WC for the C/W ¼ 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 metallicWandW2C for the C/W ¼ 0:35, pureW2C for the C/W ¼ 0:50 and predominant WC with traceW2C for the C/W ¼ 1:00. Unlike for the top surface of the C/W ¼ 0:35 test piece heated in a solar furnace to 1900 C reported earlier, no evidence of formation of nano-meter scale WC whisker was detected for the top surface in any sample heated to 1600 C in the present work.
