Mechanism of the reduction of zirconium and titanium oxides by calcium hydride

Meerson, G.A.; Kolchin, O. P.

doi:10.1007/bf01514612

Cited by 13 publications

(6 citation statements)

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“…The free energy of formation of NdFeO 3 was calculated from Δ H ° and Δ S ° of formation values; Δ H ° and Δ S ° were assumed to be constant with temperature. For free energy change of reduction (Δ G ) calculations, a mechanism similar to that suggested by Meerson et al was considered. The reduction of the Nd−Fe−B oxides (M n O m , M = Nd, Fe, B) by CaH 2 involved the following reactions (eqs −): CaH 2 ↔ Ca + 2 H M n O m + mCa ↔ nM + mCaO M + xH ↔ MH x 2 H ↔ H 2 ↑ …”

Section: Resultsmentioning

confidence: 99%

Sol−Gel Based Chemical Synthesis of Nd₂Fe₁₄B Hard Magnetic Nanoparticles

et al. 2010

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Nd2Fe14B hard magnetic nanoparticles were synthesized by chemical synthesis techniques. Nd−Fe−B gel was prepared using NdCl3·6H2O, FeCl3·6H2O, H3BO3, citric acid, and ethylene glycol (EG) by a Pechini type sol−gel method. This gel was subsequently annealed to produce mixed oxide powders. Nd2Fe14B nanoparticles were prepared from these oxides by a reduction−diffusion process. The phase analysis, structure, and magnetic properties were determined by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), and vibrating sample magnetometer (VSM) techniques. The mechanism of Nd2Fe14B formation was investigated by differential scanning calorimetry (DSC), XRD, and thermodynamic free energy change data. Our experimental and modeling results showed that the reduction−diffusion of the Nd−Fe−B mixed oxide was a three step process. The reduction of Fe2O3 to Fe and B2O3 to B occurred at 300 °C. NdH2 and Fe was formed from Nd2O3 and NdFeO3 at 620 °C. The Nd2Fe14B phase was formed from NdH2, Fe, and B at 692 °C. The coercivity of as-synthesized powder was 6.1 kOe. The Henkel plot showed that this powder was exchange coupled; removal of CaO by washing led to dipolar interactions and a decrease in coercivity.

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Section: Resultsmentioning

confidence: 99%

Sol−Gel Based Chemical Synthesis of Nd₂Fe₁₄B Hard Magnetic Nanoparticles

et al. 2010

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“…The undesirable CaO phase in this reaction can be eliminated by washing with water for several times to obtain the desired nanoparticles [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

“…It has been shown that solid state reduction of metal oxides with calcium or calcium hydride is a successful method to prepare of metals (Zr and Ti [8]) and alloys (NiTi [9] and Fe-B [10][11][12][13][14][15]) nanoparticles. The undesirable CaO phase in this reaction can be eliminated by washing with water for several times to obtain the desired nanoparticles [8][9][10].…”

Section: Introductionmentioning

confidence: 99%

Mechanochemical synthesis of nanocrystalline Fe and Fe–B magnetic alloys

Mohammadi

Ghasemi

Tavoosi

2016

Journal of Magnetism and Magnetic Materials

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“…Calcium hydride has several industrial applications and is widely used as a desiccant in laboratory practice for extracting moisture from crystal hydrates, hydrocarbons, ethers and other solvents [40,41]. It is also commonly used as a reducing agent for the synthesis of metallic powders such as Ti, Zr, Nb, Ta, Mo and W from their oxides and halides [42,43].…”

Section: Introductionmentioning

confidence: 99%