Effect of sulphur addition on the properties of FeTi alloy for hydrogen storage

Addition of sulphur to the Fe-Ti alloy was found to produce a marked improvement in the properties of the alloy for hydrogen storage. The most effective composition was FeTi_1.05S_0.02, which had a low activation temperature (80–100 °C), a short incubation time (10–30 h) and a good equilibrium plateau pressure over a wide concentration range of absorbed hydrogen. The degree of pulverization for this alloy after the absorption-desorption cycle test was comparatively moderate. The sulphur added to the alloy was converted into Ti₂S which was precipitated in a network structure with strips about 5 μm wide separated by spaces of dimensions about 20–50 μm.     

Hard magnetic properties of rapidly quenched Nd4−xDyxFe77.5B18.5 alloys

Effects of the substitution of dysprosium for neodymium on the magnetic properties of rapidly quenched Nd₄Fe_77.5B_18.5 alloy were studied. The Curie and crystallization temperatures of amorphous Nd_4−xDy_xFe_77.5B_18.5 alloys were found to have a small dependence on the dysprosium concentration x. The as-quenched samples were magnetically soft but developed a coercive field of 0.1–3.6 kOe after crystallization by annealing at 600–810°C. The highest energy product in the samples studied was found to be 13 MG Oe. X-ray diffraction and thermomagnetic measurements on the optimal annealed samples showed a multi-phase structure mainly consisting of Fe₃B in addition to (Nd, Dy)₂Fe₁₄B and small amounts of α-Fe. The hard magnetic properties in crystallized Nd_4−xDy_xFe_77.5B_18.5 alloys originate from the presence of the hard magnetic 2: 14: 1 phase.     

Investigation of the CeFe binary system

The CeFe binary system was investigated and an FeCe binary phase diagram was proposed. This system consists of

• 1.(i) two peritectic reactions, γ-Fe + L → Ce₂Fe₁₇ and Ce₂Fe₁₇ + L → CeFe₂, occurring isothermally at 1063°C and 925°C respectively;
• 2.(ii) a eutectic reaction, L → CeFe₂ + Ce, occurring isothermally at 592°C with eutectic containing 83.3 at.% Ce (92.6 wt.% Ce);
• 3.(iii) a peritectoid reaction, γ-Fe + Ce₂Fe₁₇ → α-Fe(Ce), occurring isothermally at 922 °C.

The solid solubility of cerium in iron in the temperature range 850–900 °C was found to be less than 0.04 at.% (0.1 wt.%). The Curie temperature of α-Fe(Ce) was slightly lowered with increasing cerium content in solid solution.     

Effect of hydrogen reduction temperature on the microstructure and magnetic properties of Fe–Ni powders

The effect of hydrogen reduction temperature on the properties of Fe–Ni powders was described. The mixed powders of Fe-oxide and NiO were prepared by chemical solution mixing of nitrates powders and calcination at 350 °C for 2 h in air. The calcined powders formed small agglomeration with an average particle size of 100 nm. The microstructure and magnetic properties were investigated by using X-ray diffractometry, thermogravimetry, differential thermal analyzer, and vibrating sample magnetometer. Microstructure and thermal analysis revealed that the Fe-oxide and NiO phase were changed to FeNi₃ phase in the temperature range of 245–310 °C, and by heat-up to 690 °C the FeNi₃ phase was transformed to γ-FeNi phase. The reduced powder at 350 °C showed saturation magnetization of 76.3 emu/g and coercivity of 205.5 Oe, while the reduced powders at 690 °C exhibited saturation magnetization of 84.0 emu/g and coercivity of 14.0 Oe. The change of magnetic properties was discussed by the observed microstructural features.

     

Influence of Fe concentration on the properties of the electrodeposited Zn–Fe coatings

Electrodeposition of Zn–Fe alloys on a copper substrate from a sulfate bath with different Fe²⁺ concentration (0.05, 0.10 and 0.20 mol L^?1) at room temperature was investigated using cyclic voltammetry. The influence of the Fe²⁺ content in the plating bath on the surface morphology, structural and magnetic properties of the coatings were characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and Vibrating Sample Magnetometer (VSM). The results show that the morphology of Zn–Fe films changes with different Fe²⁺ concentration. The EDS analysis demonstrated that the Fe content of the coatings increased with increasing the Fe concentration in the bath. XRD measurements shows the presence of ?Zn (hcp), δ1ZnFe (hcp) and the ΓZnFe (bcc) phases with a (101) preferential orientation in all the electrodeposited films. The magnetic analysis of Zn–Fe films indicated that the saturation magnetization was largely enhanced in comparison to pure Zn, especially with 0.2 at. % Fe, while the coercivity decreased.     

Structure and magnetic properties of Ho2Co17−xMx pseudobinary compounds

The homogeneity range of the pseudobinary system Ho₂Co_17−xM_x (M ≡; Ni, Fe, Mn, Cr, V, Ti, Cu, Al) and the dependence of the lattice constants and the Curie temperature on composition were studied. Although Ho₂Co₁₇, Ho₂Ni₁₇ and Ho₂Fe₁₇ have identical crystal structures and similar lattice constants, the homogeneity range for the Th₂Ni₁₇-type compound in the Ho₂Co_17−xNi_x and Ho₂Co_17−xFe_x systems is limited to x < 5. The curves of Curie temperature versus composition have maxima at x values of 1, 3 and 0.9 for the systems Ho₂Co_17−xNi_x, Ho₂Co_17−xFe_x and Ho₂Co_17−xCu_x respectively. This suggests that the effect of nickel, iron and copper on the Co-Co exchange interaction in the cobalt sublattice at low concentrations may be different from that at high concentrations.     

On the reactivity of less common halopseudohalogens towards metalcarbon- and metalmetal-bonded compounds

Freshly generated solutions of iodine azide (IN₃) and iodine isocyanate (INCO) in acetonitrile or carbon tetrachloride add oxidatively to tertiaryaryl derivatives of group VB elements, Ar₃M (Ar = Ph, p-tolyl, p-ClC₆H₄ or p-FC₆H₄, and M = As, Sb or Bi) and diaryltellurium(II), Ar₂Te (Ar = Ph or p-CH₃OC₆H₄) at −10°C to −5°C to give stable covalent monomeric products, Ar₃MIX and Ar₂TeIX, respectively (where X = N₃ or NCO). The mode of bonding of the pseudohalide group to M has been established by solid-state IR spectra. Ar₃MI(N₃) failed to react with CS₂ but reaction with PhNCY (Y = O or S) gave cyclic tetrazole derivatives. Contrasting behaviour was also observed in the metathetic reaction of Ar₂MIX and Ar₂TeIX with silver pseudohalides [AgX′ (X′ = NCO or NCS)]. The tetraorgano compounds, R₄M (M = Sn or Pb, and R = Ph or p-tolyl), and Bu₃SnPh failed to react with IN₃ and Bu₃SnPhINCO but IN₃ cleaved one tin-aryl bond from Ar₄Sn in the presence of AlCl₃. Addition of IN₃ and INCO across the olefinic bond of Ph₃SnCH₂CHCH₂ is preferred to tin-allyl bond cleavage. Reactions of hexaaryldileads with IN₃ and INCO under appropriate conditions proceeded with the cleavage of a PbPb bond. Parallel reactions of cyanogen halides (CNI and CNBr) resulted in the formation of corresponding triaryllead halides and pseudohalide derivatives.     

Determination of the stability and magnetic properties of Fe–Pd nitride using the generalised gradient approximation (GGA)

In this study, an electronic structure calculation of the substituted nitride PdFe₃N was conducted, and a posterior understanding of its structural and magnetic properties was obtained. A first principle method was applied to study the lattice parameter variation in relation to the energy of solid formation. After the equilibrium parameter was found, some properties of the ground state, such as the magnetic moment and the bulk modulus, were calculated. Preliminary observations show that the material properties of γ′-Fe₄N vary significantly with the insertion of the palladium atom in the matrix as well as when the material is subjected to applied pressure. The density of states shows a strong interaction between the s states of nitrogen and, primarily, the s and p states of iron, presenting a weak interaction with the palladium atoms. The analysis of such properties illustrates why these nitrides have a promising future for use in technological applications.     

Infrared spectra of aluminogermanate- and aluminate-sodalites and a re-examination of the relationship between TO bond length,TOT angle and the position of the main i.r. absorption band for compounds with framework structures

Cell parameters and i.r. data are presented for 6 aluminogermanate-sodalites, 11 aluminate-sodalites and for Na₈(Ga₆Ge₆O₂₄)Br₂ and Na₈(Ga₈Si₆O₂₄)Br₂. Apart from the borate-sodalites the framework absorption bands of the sodalite family can be grouped into three sets: ν_as TOT between 800 and 1000 cm⁻¹, ν_s TOT between 500 and 800 cm⁻¹ and δ OTO between 300 and 500 cm⁻¹ (T =tetrahedral framework cation). The aluminogermanate-sodalites have one ν_as TOT mode and two v_s TOT and δ OTO modes. Cubic aluminate-sodalites with ∼ 9 Å cells are similar but with only one δ OTO mode; aluminate-sodalites without cubic ∼9 Å cells showed broadening of the v_as TOT mode, which has several maxima and additional v_s TOT bands. Compounds with framework structures having AlO, (Al, Ge)O, (Al, Si)O, (Ga, Ge)O, GeO and SiO framework bonds, when grouped into those with TOT angles close to either 125° or 145°, show good correlations between the wave numbers of their main absorption bands and their mean TO distances.     

Improvement of magnetic properties by hot rolling of sintered powder alloy in the Fe–Cr–Co system

A method to produce a technically suitable, hard-magnetic material of composition Fe–26% Cr–16% Co–2% Mo–2% W from a powder raw material was proposed. A distinguishing feature of the method is a reduced temperature of sintering of powder compacts (1200°C). The sintered samples are subjected to hot rolling. The magnetic and strength characteristics of the thus obtained magnetic material are on the level of those of alloys produced by powder metallurgy at a sintering temperature of about 1400°C and their cast analogs. Data on the magnetic hysteresis and strength properties of the synthesized material were presented.     

Profile analysis of infrared absorption of NH stretching band

The shape of the infrared NH stretching band of N-methyl aniline in different solvents has been studied. Carbon tetrachloride, tetrachloroethylene, carbon disulfide, benzene, anisole, chloroform, dioxane and di-n-butyl ether were used as solvents. Band shapes observed show self-association of N-methyl aniline in dioxane, di-n-butyl ether and chloroform solutions.Moments analysis and time autocorrelation function calculations have been performed. The frequencies of the band maximum are more sensible to the solvent than the half band width and the band shape. Moments values depend strongly on the integration interval. The correlation function shows non-exponential decays in a short time range (0–0.16 ps) for any solutions, and this indicates that the molecular motions do not obey a simple rotational diffusion model. Exponential decays show at times longer than 0.16 ps. Relaxation times are linearly related with the solvents viscosity.     

Synthesis and spectroscopic studies of organotin compounds containing the SnS bond

The preparation of a number of organotin(IV) compounds, containing SnS bonds, is described. Their ¹³C and ¹H NMR and IR spectra are presented. In cases where either SnS or SnN may be expected, Mössbauer spectra show two sets of peaks consistent with these possibilities.     

New oxyborates in the MgMnBO system

Two new oxyborate compounds were synthesized during a study of the phase relationships between the pinakiolite-ludwigite series of compounds. The structural topologies of these previously unreported materials have been determined experimentally by comparing calculated with observed electron microscope images. Both of these structures are very similar to each other, and also closely related to pinakiolite which consists of flat walls of edge-sharing octahedra connected to zigzag chains of octahedra by triangular BO₃ groups. The two new structures contain similar infinite walls which are separated by slabs of octahedra that are wider than the zigzag chains found in pinakiolite. A new series of structurally related oxyborate compounds can be envisaged and are described.     

Thermodynamic properties of the Zr0.8Ti0.2(MnxCr1−x)FeH2 system

The effects of the substitution of chromium by manganese in Zr_0.8Ti_0.2(Mn_xCr_1−x)Fe Laves phase alloys on the pressure-composition-isotherm (PCT) relations, especially on the plateau slopes and hysteresis, were systematically investigated by PCT measurements. There is no dependence of the hydrogen storage capacity on composition as manganese is substituted for chromium. Increasing manganese substitution increases the extent of hysteresis but decreases the degree of the plateau slopes as well as the hydride stability. This is caused by the more sensitive change in the equilibrium pressures for hydride formation than for hydride decomposition in the two-phase region as the alloy composition x varies. It is suggested from the above results that the compositional dependence of the PCT relations of the Zr_0.8Ti_0.2(Mn_xCr_1−x)FeH₂ system originates from the difference in nature of the hysteresis behavior between ZrMn₂-type and ZrCr₂-type Laves phase alloy systems, since the hysteresis energies show a drastic change around x = 0.5. The difference in hysteresis nature is probably related to the difference in mechanical properties of the alloy itself, i.e. between ZrCr₂-type and ZrMn₂-type Laves phases.     

Nd1.1Fe4B4和Nd2Fe14B的标准生成自由能

Nd-Fe-B合金是迄今为止所发现的具有最大磁能积的永磁材料,目前关于Nd-Fe-B体系的磁学性质、晶体结构及相图已有多篇文献报道。但是,该体系中两个最重要的化合物Nd_(1.1)Fe_4B_4和Nd_2Fe_(14)B的标准生成自由能还没有文献报道。本文报道了用CaF_2单晶为固体电解质构成原电池,对Nd_(1.1)Fe_4B_4和Nd_2Fe_(14)B的标准生成自由能进行测定的结果。     

Synthesis and properties of trifluoromethylating steroid compounds

Trifluoromethyl steroids la,b; 2a,b; 3a,b have been synthesized by starting from estren 3,17-dicarbonyl-3,3-dimethyl ether (4) and dl-18-methyl-2(3)l5(10)-estra-diene-17-carbonyl-3-methyl ether (5),and by using trimthyltrifluoromethylsilane as the trifluoromethylating agent under the catalysis of tetrarnethylam-monium fluoride.The overall yields were 82%,76%; 54%,62%; and 27%,25%,respectively The α-configura tion of trifluoromethyl group of 17-position was determined by X-ray crystal diffraction method Compounds 1a,2a and 3a showed high affinity for rat uterus PRc.The test of biological activities of compounds 1b,2b and 3b is proceeding.     

Extended Fe₄ butterfly complexes: theoretical analysis of magnetic properties and magnetostructural maps

The inclusion of additional metal atoms in Fe? butterfly complexes drastically modifies their magnetic properties. Exchange interactions of a Fe?Y? complex have been calculated using theoretical methods based on density functional theory. The calculated values are in good agreement with experimental data showing that the change in the nature of bridging ligands induces a dramatic decrease of the antiferromagnetic wing-body interaction while the body-body interaction between the two central iron atoms is ferromagnetic. Finally, we propose a new tool to facilitate the understanding of the magnetic properties in polynuclear iron complexes. Magnetostructural maps allow us to correlate the calculated exchange coupling constants with metal-metal distances for the dinuclear or polynuclear iron complexes that we have studied.     

Optimizing the sensitivity and radiological properties of the PRESAGE® dosimeter using metal compounds

The aim of this study is to investigate the radiation-modifying effects of incorporating commercially available bismuth-, tin- and zinc-based compounds in the composition of the PRESAGE^® dosimeter, and the feasibility of employing such compounds for radiation dose enhancement. Furthermore, we demonstrate that metal compounds can be included in the formulation to yield water-equivalent PRESAGE^® dosimeters with enhanced dose response. Various concentrations of the metal compounds were added to a newly developed PRESAGE^® formulation and the resulting dosimeters were irradiated with 100 kV and 6 MV photon beams. A comparison between sensitivity and radiological properties of the PRESAGE^® dosimeters with and without the addition of metal compounds was carried out. Optical density changes of the dosimeters before and after irradiation were measured using a spectrophotometer. In general, when metal compounds were incorporated in the composition of the PRESAGE^® dosimeter, the sensitivity of the dosimeters to radiation dose increased depending on the type and concentration of the metal compound, with the bismuth compound showing the highest dose enhancement factor. In addition, these metal compounds were also shown to improve the retention of the post-response absorption value of the PRESAGE^® dosimeter over a period of 2 weeks. Thus, incorporating 1–3 mM (ca. 0.2 wt%) of any of the three investigated metal compounds in the composition of the PRESAGE^® dosimeter is found to be an efficient way to enhance the sensitivity of the dosimeter to radiation dose and stabilize its post-response for longer times. Furthermore, the addition of small amounts of the metal compounds also accelerates the polymerization of the PRESAGE^® dosimeter precursors, significantly reducing the fabrication time. Finally, a novel water-equivalent PRESAGE^® dosimeter formula optimized with metal compounds is proposed for clinical use in both kilovoltage and megavoltage radiotherapy dosimetry.