Thermite assisted synthesis of ZrB2 and ZrB2–SiC through B4C reduction of ZrO2 and ZrSiO4 in air

Krishnarao, R. V.; Sankarasubramanian, R.

doi:10.1007/s40145-017-0226-4

Cited by 9 publications

(3 citation statements)

References 28 publications

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“…In addition, there may be some residual amorphous carbon impurity in the final UB 4 products. It is worthwhile noting that C is typical impurity in metal borides synthesized by boro/carbothermal reduction …”

Section: Resultsmentioning

confidence: 99%

Boro/carbothermal reduction synthesis of uranium tetraboride and its oxidation behavior in dry air

et al. 2018

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Uranium tetraboride (UB4) was successfully synthesized by boro/carbothermal reduction of UO2 with B4C and carbon as combined reduction agents under flowing argon. The effects of processing temperature and mole ratios of starting materials on phase evolution were studied. XRD results demonstrated that UB4 was obtained with 3.75 mol% B4C in excess based on the UO2/B4C/C molar ratios of 1:1:1 at 1500°C. SEM observation revealed that submicrometer‐sized quasi‐spherical UB4 particles cemented together to be an aggregate. The laser particle size analysis showed that the particle size was in the range of 1‐10 μm. The oxidation behavior of UB4 was also investigated by TG and XRD. The oxidation of UB4 started at about 500°C and it showed better oxidation resistance than other basic uranium nuclear fuels (UO2, UC, UN and U3Si2). The oxidation chemical process of UB4 was presented as a three‐step process: (a) the formation of U3O8 and B2O3 oxidation products; (b) the formation of UB2O6 intermediate product by the interaction of U3O8 and B2O3; (c) the decomposition of UB2O6 to get U3O8.

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Section: Resultsmentioning

confidence: 99%

Boro/carbothermal reduction synthesis of uranium tetraboride and its oxidation behavior in dry air

et al. 2018

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“…Zircon (ZrSiO 4 ), a low-cost and high-abundance material, intended to decompose into highly active ZrO 2 and SiO 2 in situ, has been proved to be favorable for enhancing the synthetic reactions of ZrB 2 -SiC powders [10,11]. Moreover, the theoretical phase composition of the final product, resulting from ZrSiO 4 , was ZrB 2 -26 wt % SiC, which was among the as-reported optimal composition range for the preparation of the bulk counterpart, with promising mechanical properties and oxidation resistance [12,13].…”

Section: Introductionmentioning

confidence: 99%

Highly Efficient and Low-Temperature Preparation of Plate-Like ZrB2-SiC Powders by a Molten-Salt and Microwave-Modified Boro/Carbothermal Reduction Method

et al. 2018

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To address the various shortcomings of a high material cost, energy-intensive temperature conditions and ultra-low efficiency of the conventional boro/carbothermal reduction method for the industrial preparation of ZrB2-SiC powders, a novel molten-salt and microwave-modified boro/carbothermal reduction method (MSM-BCTR) was developed to synthesize ZrB2-SiC powders. As a result, phase pure ZrB2-SiC powders can be obtained by firing low-cost zircon (ZrSiO4), amorphous carbon (C), and boron carbide (B4C) at a reduced temperature of 1200 °C for only 20 min. Such processing conditions are remarkably milder than not only that required for conventional boro/carbothermal reduction method to prepare phase pure ZrB2 or ZrB2-SiC powders (firing temperature of above 1500 °C and dwelling time of at least several hours), but also that even with costly active metals (e.g., Mg and Al). More importantly, the as-obtained ZrB2 particles had a single crystalline nature and well-defined plate-like morphology, which is believed to be favorable for enhancing the mechanical properties, especially toughness of their bulk counterpart. The achievement of a highly-efficient preparation of such high-quality ZrB2-SiC powders at a reduced temperature should be mainly attributed to the specific molten-salt and microwave-modified boro/carbothermal reduction method.

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“…In our previous work, B 4 C reduction of ZrO 2 to form impurity (ZrC, C)-free ZrB 2 was reported [19]. Further, composite powders of ZrB 2 -SiC with particle sizes ranging from sub-micron to nanometer have been produced by rapid heating a mixture of ZrO 2 +B 4 C+Si, in an air furnace [19] and in air without using any furnace [20].…”

Section: Introductionmentioning

confidence: 99%

ZrB2–SiC based composites for thermal protection by reaction sintering of ZrO2+B4C+Si

Krishnarao¹,

Bhanuprasad²,

Reddy³

2017

J Adv Ceram

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Synthesis and sintering of ZrB 2 -SiC based composites have been carried out in a single-step pressureless reaction sintering (PLRS) of ZrO 2 , B 4 C, and Si. Y 2 O 3 and Al 2 O 3 were used as sintering additives. The effect of ratios of ZrO 2 /B 4 C, ZrO 2 /Si, and sintering additives (Y 2 O 3 and Al 2 O 3 ), was studied by sintering at different temperatures between 1500 and 1680 ℃ in argon atmosphere. ZrB 2 , SiC, and YAG phases were identified in the sintered compacts. Density as high as 4.2 g/cm 3 , micro hardness of 12.7 GPa, and flexural strength of 117.6 MPa were obtained for PLRS composites. Filler material was also prepared by PLRS for tungsten inert gas (TIG) welding of the ZrB 2 -SiC based composites. The shear strength of the weld was 63.5 MPa. The PLRS ZrB 2 -SiC composites exhibited: (i) resistance to oxidation and thermal shock upon exposure to plasma flame at 2700 ℃ for 600 s, (ii) thermal protection for Cf-SiC composites upon exposure to oxy-propane flame at 2300 ℃ for 600 s.

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Thermite assisted synthesis of ZrB2 and ZrB2–SiC through B4C reduction of ZrO2 and ZrSiO4 in air

Cited by 9 publications

References 28 publications

Boro/carbothermal reduction synthesis of uranium tetraboride and its oxidation behavior in dry air

Boro/carbothermal reduction synthesis of uranium tetraboride and its oxidation behavior in dry air

Highly Efficient and Low-Temperature Preparation of Plate-Like ZrB2-SiC Powders by a Molten-Salt and Microwave-Modified Boro/Carbothermal Reduction Method

ZrB2–SiC based composites for thermal protection by reaction sintering of ZrO2+B4C+Si

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