An investigation on the formation mechanism of nano CrB2 powder in the Mg–B2O3–Cr2O3 system

Torabi, Omid; Golabgir, Mohammad Hossein; Tajizadegan, Hamid

doi:10.1016/j.ijrmhm.2015.02.015

Cited by 9 publications

(1 citation statement)

References 23 publications

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“…Оптимальными параметрами синтеза являются температура 1700 °С, сравнительно длительное время (2,5 ч). При металлотермическом методе восстановителем может служить магний [9]. Характерной особенностью металлотермических процессов является необходимость очистки целевых продуктов от соединений металлов-восстановителей (в данном случае оксида MgO).…”

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Synthesis of finely dispersed chromium diboride from nanofibrous carbon

Krutskii

Dyukova²,

Kuzmin

et al. 2018

Izv. vysš. učebn. zaved., Čern. metall.

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The paper presents experimental data on synthesis of finely dispersed powder of chromium diboride. Chromium diboride was prepared by reduction of chromium oxide Cr2O3 with nanofibrous carbon (NFC) and boron carbide in the induction furnace under argon atmosphere. NFC is a product of catalytic decomposition of light hydro carbons. The main characteristic of a NFC is high specific surface area (~150,000 m2/kg), which is significantly higher than that of soot (~50,000 m2/kg). The content of impurities in NFC is about 1 wt %. Boron carbide used as a reagent is characterized by high dispersity (at the level of ~2 μm) and insignificant content of impurities – no more than 1.5 wt %. Based on analysis of state diagram of the Cr – B system, composition of the charge and upper temperature limit of diboride formation reaction were determined for obtaining chromium diboride in powder state. According to the results of thermodynamic analysis, the temperature of beginning of reaction for chromium oxide Cr2O3 reduction by carbon and boron carbide was determined at various CO pressures. Composition and characteristics of chromium diboride were studied using X-ray phase analysis, inductively coupled plasma atomic emission spectrometry (AES-ISP), scanning electron microscopy using local energy-dispersive X-ray microanalysis (EDX), low-temperature adsorption of nitrogen, followed by determination of specific surface area by BET method, sedi mentation analysis, synchronous thermogravimetry and differential scanning calorimetry (TG/DSC). The material obtained at optimal parameters is represented by a single phase – chromium diboride CrB2 . The content of impurities in chromium diboride does not exceed 2.5 wt %. The powder particles were predominantly aggregated. The average size of the particles and aggregates is equal to 7.95 μm within a wide range of size distribution. The specific surface area of a single-phase sample is 3600 m2/kg. Oxidation of chromium diboride begins at a temperature of 430 °C and when the temperature reaches 1000 °C, the degree of oxidation is approximately 25 %. Optimum synthesis parameters are the ratio of reagents according to stoichiometry to obtain chromium diboride at a temperature of 1700 °C and holding time of 20 min. It is shown that for this process nanofibrous carbon is an effective reducing agent and that chromium oxide Cr2O3 is almost completely reduced to diboride CrB2 .

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Synthesis of finely dispersed chromium diboride from nanofibrous carbon

Krutskii

Dyukova²,

Kuzmin

et al. 2018

Izv. vysš. učebn. zaved., Čern. metall.

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Mechanochemical Synthesis of High Crystalline Cerium Hexaboride Nanoparticles from CeO₂‐B₂O₃‐Mg Ternary System

Torabi

Naghibi

Golabgir

et al. 2016

J Chinese Chemical Soc

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High crystalline cerium hexaboride (CeB 6 ) nanoparticles (NPs) were synthesized using mixture of magnesium (Mg), cerium oxide (CeO 2 ) and boron oxide (B 2 O 3 ) via the mechanochemical process at room temperature. Based on the results, magnesiothermic reduction of B 2 O 3 occurred after about 2 h of milling in a mechanically induced self-sustaining reaction (MSR). The significant amount of heat produced by the reduction reaction resulted in CeO 2 reduction to elemental Ce which finally reacted with elemental B and formed CeB 6 compound. According to XRD analyses, the degree of crystallinity and lattice parameter of the product was calculated about 93% and 4.1458 Å, respectively. The morphology observations revealed that the synthesized CeB 6 had semi-cubic shape with the range of size 25-60 nm. The synthesis of CeB 6 during the thermal treatment was studied by simultaneous thermal analysis (STA) technique. It was found that the reduction of B 2 O 3 took place after melting of Mg meanwhile, no CeB 6 phase achieved even up to 1100°C.

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Mechanochemical processing and microstructural characterization of pure Fe 2 B nanocrystals

Şimşek

Baris

Kalkan

2017

Advanced Powder Technology

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An investigation on the formation mechanism of nano CrB2 powder in the Mg–B2O3–Cr2O3 system

Cited by 9 publications

References 23 publications

Synthesis of finely dispersed chromium diboride from nanofibrous carbon

Synthesis of finely dispersed chromium diboride from nanofibrous carbon

Mechanochemical Synthesis of High Crystalline Cerium Hexaboride Nanoparticles from CeO₂‐B₂O₃‐Mg Ternary System

Mechanochemical processing and microstructural characterization of pure Fe 2 B nanocrystals

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An investigation on the formation mechanism of nano CrB2 powder in the Mg–B2O3–Cr2O3 system

Cited by 9 publications

References 23 publications

Synthesis of finely dispersed chromium diboride from nanofibrous carbon

Synthesis of finely dispersed chromium diboride from nanofibrous carbon

Mechanochemical Synthesis of High Crystalline Cerium Hexaboride Nanoparticles from CeO2‐B2O3‐Mg Ternary System

Mechanochemical processing and microstructural characterization of pure Fe 2 B nanocrystals

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Product

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Mechanochemical Synthesis of High Crystalline Cerium Hexaboride Nanoparticles from CeO₂‐B₂O₃‐Mg Ternary System