LaB6-ZrB2共晶复合材料的组织特征及控制

用电弧炉和电子束悬浮区熔炉法制备了ＬａＢ６ＺｒＢ２共晶复合材料，并用ＳＥＭ和ＴＥＭ方法对其显微组织进行了研究。结果表明，ＬａＢ６ＺｒＢ２形成纤维状共晶组织，控制凝固条件可得到定向排列的组织，ＬａＢ６基体上均匀分布着直径为０２～１２μｍ的ＺｒＢ２纤维，纤维长度可达１００μｍ以上。对于固液界面为平面生长的试样，其结晶学取向关系为［００１］ＬａＢ６∥［００１］ＺｒＢ２，（１１０）ＬａＢ６∥（０１０）ＺｒＢ２。     

Electrosynthesis of hafnium diboride from cryolite-alumina melts containing hafnium and boron oxides

Electrosynthesis of hafnium diboride from cryolite-alumina melts containing hafnium and boron oxides is studied. Thermodynamic estimation and voltammetric measurements show this process to occur in one-stage. Hafnium diboride coatings on nickel are obtained by electrolysis.__________Translated from Elektrokhimiya, Vol. 41, No. 4, 2005, pp. 448–451.Original Russian Text Copyright © 2005 by Devyatkin.     

Reply to the comment from Mamedov

Here, I present the reply to the comments from Mamedov regarding numerical solution of Bloch–Gruneisen function to determine the contribution of electron–phonon interaction in polycrystalline superconductor. Reply to the comments from Mamedov is discussed one by one.     

Superconductivity and x—ray photoemission study of MgB2 thin films

Highly c-axis oriented MgB2 thin films with Tc^onset of 39.6K were fabricated by magnesium diffusing into pulsedlaser-deposited boron precursors.The estimation of critical current density Jc,using hysteresis loops and the Bean model,has given the value of 10^7A/cm^2(15K,0T),which is one of the highest values ever reported.The x-ray photoemission study of the MgB2 thin films has revealed that the binding energies of Mg 2p and B 1s are at 49.4eV and 186.9eV,which are close to those of metallic Mg and transition-metal diborides,respectively.     

H?TiO oder TiB2?? – eine Korrektur

H? TiO or TiB₂? – A Correction Reinvestigations of “H? TiO” single crystals and the comparison with measurements of TiB₂ crystals have shown that “H? TiO” in fact is titanium diboride.     

One-step synthesis of VB2 powder by epoxy-assisted borothermal reduction of V2O5

Vanadium diboride was directly synthesized by borothermal reduction of V₂O₅ with the addition of epoxy resin as a reducing agent for the low-temperature reduction of vanadium(V) to vanadium(IV), which leads to the gradual removal of oxygen by the formation of CO gas. The slow rate of gas release prevents destruction of green body, which usually occurs during conventional borothermal reduction. This makes it possible to directly obtain VB₂ powder with an average particle size of 200–300 nm without need to prepare intermediate lower vanadium oxides.     

Preparation and microstructure evolution of diboride ultrafine powder by sol–gel and microwave carbothermal reduction method

Titanium diboride ultrafine powder was prepared from sucrose, tetrabutyl titanate and boric acid by the sol–gel and microwave carbothermal reduction method. The influence of reaction temperature, ratio of Ti to C and Ti to B on the synthesis of titanium diboride was studied. The results indicated that the carbothermal temperature, the content of carbon and the amount of H₃BO₃ show obvious effects on the formation of TiB₂. 1,300 °C was the optimum synthesis temperature and pure TiB₂ could be prepared. The microstructure of prepared TiB₂ was investigated by field emission-scanning electron microscopy (FE-SEM), which results showed that the crystalline size of the prepared titanium diboride at 1,300 °C was about 3–5 μm. The quantities of the crystalline phases of the powders prepared at different temperatures were analyzed by Rietveld refinement method. An erratum to this article can be found at     

Preparation and some properties of ScB2 single crystals

ScB₂ single crystals were grown by inductive floating zone melting. The ScB₂ structure was refined on single crystal and powder data, the latter obtained from parts of single crystals which were prepared by controlled crushing. The ScB₂ structure corresponds to the AlB₂ structure type, sp. gr. P6/mmm, No. 191 (R₁=0.0191, wR₂=0.0474), lattice parameters are equal to a=0.314820(3) nm, c=0.351483(5) nm, c/a=1.117, X-ray density is 3.670 g/cm³. The measured hydrostatic density is 3.666 g/cm³ which correspond to the Sc_0.99B₂ composition. The ScB₂ Young modulus value is equal to 480 GPa and the Debye characteristic temperature is 1020 K.     

Critical Comment on “Numerical solution of Bloch–Gruneisen function to determine the contribution of electron–phonon interaction in polycrystalline MgB2 superconductor” by Intikhab A. Ansari [Physica C: Superconductors, 470 (2010) 508–510]

We present critical comments on the recent paper [Intikhab A. Ansari, Physica C: Superconductors, 470 (2010) 508] concerning numerical methods for solving Bloch–Gruneisen function and its applications to MgB₂ superconductor. It is demonstrated that the presented in this work the formulas and examples are not original and they are quite identical the formulas already established in our article [B.A. Mamedov, I.M. Askerov, Physics Letters A, 362 (2007) 324].     

On the electronic and structural properties of aluminum diboride Al0.9B2

Single crystals of aluminum diboride (space group P6/mmm, No. 191) a=3.0050(1) Å, c=3.2537 (8)  Å; Z=1) were prepared by the aluminum flux method. Crystal structure refinement shows defects at the aluminum site and resulted in composition Al_0.894(9)B₂≈Al_0.9B₂. The defect structure model is confirmed by the measured mass density ρ_exp=2.9(1) g/cm³ in comparison with a calculated value ρ_x=3.17 g/cm³ for full occupancy of the aluminum position. The results of ¹¹B NMR measurements support the defect model and are in agreement with the structure obtained by X-ray diffraction methods. Electrical resistivity measured on a single crystal parallel to its hexagonal basal plane with ρ(300 K)−ρ(2 K)=2.35 μΩ cm shows temperature dependence like a typical metal. Charge is dominantly carried by holes (Hall-coefficient R=+2×10⁻¹¹ m/C). Respective, p-type conductivity is confirmed by theoretical calculations. Chemical bonding in aluminum diboride is discussed using the electron localization function.