Synthesis and properties of o-containing chevrel phases,AxMo6S6O2 (A=Co,Ni, Cu and Pb)

Oxygen containing Chevrel phases, A_xMo₆S₆O₂ (A_x=Co₂,Ni₂,Cu₂,Pb) and Mo₆S₆O₂ have been synthesized and electrical and superconducting properties examined. These exhibit physical properties quite akin to the corresponding -S₈ phases. However, differences in ionic size and electronegativity between O and S bring about subtle changes in T_c and T_t after O-incorporation.     

Solubility of Compounds AI I(BVUO6)2·nH2O in Aqueous Solutions (AI I = Mn, Fe, Co, Ni, Cu, Zn, Cd; BV = P, As)

The solubility of uranophosphates and uranoarsenates of 3(4)d transition elements in dilute HCl solutions was determined. The equilibrium constants and Gibbs energies of the process, and also the Gibbs energies of formation of these compounds were calculated from the experimental data.     

Nouvelles pyrochlores Cd2M2F6S (M = Mn,Fe, Co,Ni, Cu,Zn)

New pyrochlores of formula Cd₂M₂F₆S have been prepared and studied (X-rays and magnetic measurements). All these compounds, except Cd₂Cu₂F₆S are cubic. Their structure is explained as formed by two sublattices (Cd₂S) and (M₂F₆).     

Physical Chemistry of the Compounds AI I(BVUO6)2·nH2O (AI I = Mn, Ni, Co, Zn, Cd; BV = P, As)

The ion exchange between an aqueous solution of a bivalent metal chloride (A^{I I} = Mn, Ni, Co, Zn, Cd) and crystalline phases HB^VUO₆·4H₂O (B^V = P, As) was studied. The exchange constants and standard Gibbs energies of formation of the crystalline compounds A^{I I}(B^VUO₆)₂·nH₂O were calculated.     

反应时间对Ba_2Co_(0.4)Zn_(1.0)Cu_(0.6)Fe_(12)O_(22)(Co_2Y)铁氧体性能的影响

采用化学共沉淀法制备Y型平面六角铁氧体(Ba2Co0.4Zn1.0Cu0.6Fe12O22)前驱体,并通过激光粒度分析仪(LPS)、扫描电子显微镜(SEM)、X射线衍射仪(XRD)、振动样品磁强计(VSM)和E4991A精密阻抗分析仪等手段研究了共沉淀反应时间对粉体及烧结样品的粒径、表面形貌、晶体结构和磁性能的影响。结果表明,当共沉淀反应时间为90 h时,得到的前驱体粉体粒径分布均匀,平均粒径约为1μm。在900℃烧结后能够得到较纯相的Y型平面六角铁氧体。烧结样品的相对密度超过95%,频率为1 GHz时,起始磁导率μi≈3.7,品质因数Q≈5.8,共振频率fr2.5 GHz,截止频率在3 GHz左右。     

Synthesis and Physical Properties of (Cu,M)Ba2Ca3Cu4Oz (M=C,Mg,Ni,Al,Zn,Tl)

We have synthesized the single phase samples of Cu _x C _0.1 Ba ₂ Ca ₃ Cu ₄ O _z (x=0.20.9). Transport and magnetic measurements and iodometric titration analysis were carried out for these materials. From these results we discuss the correlation between T _c , the Hall number, copper valence and oxygen content. The effect of the substituted M ions on T _c in (CuC, M)-l234 (M=Ni,Zn,Al,TI,Mg) is also discussed. We propose a unique selective carrier-doping mechanism in (Cu,C)- and (CuC,Mg)-1234 systems.     

Structural determination of some MPS3 layered phases (M = Mn,Fe, Co,Ni and Cd)

The structures of most of the MPS₃ phases (M = Mn, Fe, Co, Ni, Cd) were determined from single crystal analysis. They show the expected CdCl₂ structural type, some weak disorder on the cationic sites being detected on NiPS₃ and CoPS₃. Fair stoichiometry is inferred for the phases since no interslab cation could be seen in the Van der Waals' gap of the structures. Polytypism may occur in the case of NiPS₃.     

Synthesis and electrical properties of mixed tetrahedral cluster phases,A(Mo2Re2)S8, A=Fe,Ni,Zn,Cu and Ga

Quaternary phases, A(Mo₂Re₂)S₈, A=Fe,Ni,Zn,Cu and Ga containing mixed tetrahedral (Mo₂Re₂) clusters have been synthesized and electrical properties examined in the range 77–300K. The compounds possess cubic symmetry and are n-type semiconductors except when A=Cu, which is metallic exhibiting p-type behavior. Isostructural GaMo₄S₈ is an n-type semiconductor.The type of bonding in these materials is discussed.     

巨磁电阻材料A0.05Co0.95Cr2S4(A=Zn、Ni、Cd、Fe)的输运行为及磁性能研究

过渡金属尖晶石型硫化物具有包括超巨磁电阻(CMR)效应在内的多种物理性能, 其CMR效应机理的研究对开发巨磁电阻材料有重要价值。目前, 铬基硫族尖晶石的CMR效应尚未深入研究。本论文通过固相反应法制备A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Cd、Fe)样品, 研究磁性和非磁性元素掺杂对CoCr₂S₄晶体结构和磁性能的影响。XRD检测表明, 掺杂的A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Cd、Fe)均呈现纯的尖晶石结构, 掺杂导致的晶胞参数变化与掺杂元素的离子半径成比例。磁电阻测定表明A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Fe)均具有巨磁电阻效应。掺杂削弱了铁磁相互作用, 导致A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Cd、Fe)的居里温度T_C降低。在0.01 T下, A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Cd、Fe)的零场冷却(ZFC)和加场冷却(FC)曲线均呈现磁性不可逆现象。A_0.05Co_0.95Cr₂S₄(A=Zn、Ni、Cd、Fe)呈现典型的亚铁磁性磁滞回线, 其中Zn_0.05Co_0.95Cr₂S₄的矫顽场最大。     

Flux growth of crystals of MNb2O6 (M = Ni,Co, Mn,Fe)

The growth of crystals of MNb₂O₆ (M = Ni, Co, Mn, Fe) from fluxed melts is described. With M = Ni and Co, platinum crucibles were used, but with M = Mn and Fe, growth was carried out under nitrogen in molybdenum and iron crucibles respectively.     

Thermodynamics of AII(BVUO6)2·nH2O (AII is Ni or Cu, BV is P or As)

The standard enthalpies of formation of nickel and copper uranophosphates and uranoarsenates at T = 298.15 K were determined. The temperature dependence of the isobaric heat capacity of these compounds in the range from 80 to 300 K was measured. Based on the results obtained, the standard entropies and Gibbs functions of formation of the compounds were evaluated. The thermodynamic characteristics of synthesis and dissolution of the compounds were evaluated.     

LaNi4M(M=Ni、Co、Fe)的晶体和电子结构

根据密度泛函理论,采用总体能量-超软赝势平面波技术,分析了LaNi5和20%Ni分别被Co和Fe代换后的晶体结构、总体能量、电子态密度以及Mulliken布居电荷.由理论计算得到的晶体结构参数与实验值符合得比较好.取代后合金的晶体结构变化趋势与取代元素的原子半径变化趋势一致.Co和Fe代换可改变合金的电子结构,降低合金的稳定性.Co-d或Fe d带的位置及其中的电子数影响合金的稳定性.Co或Fe更倾向于取代3g位,且Co取代比Fe取代稳定.合金生成热的理论计算值与实验值较为接近.     

Structure and magnetic properties of LiMVO4 (M = Co,Ni, Cu) spinels

The two-dimensional antiferromagnetic correlations found for LiCuVO₄ below 30 K have been explained by considering the ordered distribution of lithium and copper in the octahedral sites.     

Synthesis and Properties of Willemite,Zn2SiO4, and M2+:Zn2SiO4 (M = Co and Ni)

Fine particles of willemite, -Zn₂SiO₄, were prepared by both solution combustion and sol-gel methods. Both processes yield single-phase, large-surface area (26- and 78-m²/g), sinteractive willemite powders. Thermal evolution of crystalline phases was studied using X-ray powder diffraction patterns. The combustion method favors low-temperature formation of willemite compared to the sol-gel method. The powders, when uniaxially pressed and sintered at 1300°C, achieved 78–80% theoretical density. The microstructures of the sintered body show the presence of equiaxed 0.5- to 4-m grains. Blue pigments of willemite doped with Co²⁺ and Ni²⁺ were also prepared by the combustion process.     

Comparative study on the doping effect of 3d elements in Bi1.5Pb0.2Sr2Ca2Cu2.8M0.2O y (M=Sc,Ti, V,Cr, Mn,Fe, Co,Ni, or Zn)

With XRD,R-T, and acχ measurements a comparative study on the doping effects of 3d elements in Bi_1.5Pb_0.2Sr₂Ca₂Cu_2.8M_0.8O _y (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Zn) has been carried out. The effects of the former five members are significantly different, both on phase formed and onT _c , from the latter four. It seems that the effect on phase stabilization correlates with the valency of the doped cation. In connection with the instability of the 2223 phase, the correlation has been discussed.     

Ti-Cr-Mn-M(M-V、Fe、Ni、Cu)合金的储氢性能

为改善Ti(Cr-Mn)2 AB2型合金的储氢性能,采用A侧过化学计量和过渡金属部分替代Mn进行多元合金化,系统研究了Tix(Cr-Mn-M)2(x=1.0,1.1;M=V、Fe、Ni、Cu)合金的储氢性能.研究结果表明,V、Fe、Ni、Cu部分替代Mn进行多元合金化后,合金主相仍保持C14(MgZn2)型Laves相,合金晶胞体积增大.合金化元素部分替代Mn后合金的活化性能得到明显改善,合金吸放氢量增大,吸放氢压力滞后减小.除Fe使合金放氢平台压力有所升高外,其余合金化元素均使合金的吸放氢平衡压力有不同程度的降低,这是由于合金的晶胞体积增大所致.在所形成的合金中,以Ti1.1Cr1.2Mn0.5CuO0.3的综合性能最好,其室温下吸放氢量分别达到1.95%和1.72 9,6(质量分数).采用该合金与自制的轻质高压储氢容器(工作压力为40MPa)复合组成金属氢化物复合式高压储氢器,对其储氢密度的计算结果表明,当储氢合金的填充量(体积分数)达到0.20时,该复合式储氢器总的体积储氢密度将提高57%.     

Heterogeneous equilibria in the system uranoborate MII(BUO5)2 · nH2O-aqueous solution (MII=Mn, Co, Ni, Zn)

Solutions of uranoborates M^II(BUO₅)₂·nH₂O (M^II=Mn, Co, Ni, Zn) in aqueous mineral acids at 25°C are studied. Based on experimental data on the solubility of uranoborates in hydrochloric acid, a quantitative model of the system crystalline uranoborate-aqueous solution is suggested. The model is used to predict the state of the investigated heterogeneous systems under various conditions, and also to estimate the standard thermodynamic functions of the indicated series of uranoborates.