La synthèse des poudres céramiques non-oxydes par réduction carbothermique

Bachelard, R.

doi:10.1051/mattech/198775120461

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“…The carbothermal reduction of metal oxide by carbon black is the most conventional way to produce low cost oxycarbide powders in large amount with good reproducibility. [1][2][3] Other methods of synthesis such as sol-gel [4][5][6] or polymer-derived ceramic 7 routes are not really promising although they provide to nano-sized carbide particles with a nearstoichiometric composition and low oxygen content. Unfortunately, these latter routes provide obvious agglomeration which lead to heterogeneous microstructure aer sintering due to their different sinterability.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of zirconium oxycarbide powders using metal–organic framework (MOF) compounds as precursors

et al. 2015

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ZrC x O y oxycarbides were synthesized for the first time by using Metal-Organic Framework (MOF) compounds as precursors. These MOFs, based on zirconium carboxylates, are derived from the UiO-66 type structure. Three different Zr-MOF compounds were synthesized, differing by their C/Zr ratio, due to the use of terephthalic acid (C/Zr=8, or UiO-66), naphtalene-2,6-dicarboxylic acid (C/Zr=12) and biphenyl-4,4'-dicarboxylic acid (C/Zr=14 or UiO-67). The oxycarbides crystallites obtained through appropriate thermal treatments (under Ar atmosphere) of the Zr-MOF precursors show an average size of few hundred microns. They are surrounded by an outer rim of turbostratic carbon, which thickness is directly relevant to the C/Zr ratio coming from the nature of the organic linker. The composition of the oxycarbides obtained was estimated on the basis of the cell parameters refined from the powder XRD patterns. The oxycarbides synthesized from naphtalene-2,6dicarboxylic acid and biphenyl-4,4'-dicarboxylic acid are close to ZrC 0.925 O 0.075 , while that of the oxycarbide obtained from terephthalic acid precursor is ZrC 0.944 O 0.056 . It results that the carbon richer oxycarbide product is observed for the UiO-66 precursor synthesized with terephthalic acid, and exhibiting the lower C/Zr ratio of the series. The composition of the oxycarbide powders is shown to be directly relevant to the mechanisms of decomposition of the Zr-MOF compound involved during heating.

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