3M干银法x射线系统

3M公司推出Inspex Ⅱ型x射线系统,使用3M干银法技术和Trimax增感屏,能产生高质量射线照片。     

Magnetic properties of (Fe1−x M x )7Se8

The temperature dependence of the magnetization of the quenched and slowly cooled samples of Fe₇Se₈ and (Fe_1–x M _x )₇Se₈ samples with M = cobalt and nickel and x=0.02, 0.05 and 0.08 are given. All the thermomagnetic curves obtained belong to the Weiss ferrimagnetic type. Discontinuities indicating a magnetic transformation to antiferromagnetic order were obtained for some samples. The magnetic moment at 0 and 78 K (M ₀ and M₇₈) dependence on nickel and cobalt concentrations are given. The temperature dependence of the reciprocal susceptibility in the paramagnetic range was studied, and the asymptotic Curie points are given. The values of the effective magnetic moment, _eff, and the number of unpaired electrons were calculated. The thermal variation of the electrical conductivity of the host material, Fe₇Se₈, is given.     

Magnetic and Mössbauer investigation of PbFe12−x Ga x O19 hexagonal ferrites

Magnetic and Mö ssbauer measurements have been performed on polycrystalline samples of Ga substituted M-type hexagonal ferrites having compositions PbFe_12–x Ga _x O₁₉ (0 < x < 11). The saturation magnetisation (_S) at 0 K falls with increasing x, from 20 _B for x = 0 to 4.32 _B for x = 6. The Curie temperature tends to zero at x 9, indicating that the compounds with x > 9 are paramagnetic at all temperatures. The magnetic moments of the non substituted Fe³⁺ ions in the spin-up predominant sublattice do not have the same temperature dependence, because of the presence of non magnetic Ga³⁺ ions in the neighbouring lattice sites. For x < 3, the Mössbauer data show that there is no significant deviation from collinear magnetic order. The decrease of _S(0) for x < 3 agrees with the collinear model and the distribution of gallium in all the five available sublattices. At x > 3, the faster decline of the saturation magnetisation can be attributed to the onset of non collinear magnetic order.     

Microstructure Effects on the Superconducting Properties of YBa2Cu3 – x M x O7 – δ (M = Ag, Hg)

The properties of YBa₂Cu_{3 – x} Ag _x O_{7 –} and YBa₂Cu_{3 – x} Hg _x O_{7 –} (0 < x 0.5) solid solutions were studied. The solute concentration is shown to have a significant effect on the superconducting transition temperature, density, and grain size of the solid solutions. The difference in the composition dependences of the properties of the solid solutions is interpreted in terms of the crystal-chemical behavior of the Ag and Hg ions.     

Study of Electronic and Magnetic Properties of Zn1−x M x O (M = Mn and Cr) by ab initio Calculations

The electronic structure and ferromagnetic properties of Zn_1?x M _x O (M = Mn and Cr) have been investigated by using the Korringa–Kohn–Rostoker (KKR) method combined with the coherent potential approximation (CPA). The half-metal behavior is observed for different doping concentrations. The gap energies are deduced for different dilution x values. The magnetic moment of each atom and the total magnetic moment are computed. A special attention is paid to the discussion of the mechanism of ferromagnetism in these components.     

Synthesis and Properties of La2(Mo1 – x M x )2O9 (M = Nb, Ta) Ionic Conductors

La₂(Mo_{1 – x} M _x )₂O₉ (M = Nb, Ta; 0 < x 0.2) solid solutions were prepared, and their physicochemical and electrical properties were studied. Second harmonic generation measurements indicate that the solid solutions have a noncentrosymmetric structure and undergo a structural phase transition accompanied by a sharp increase in ionic conductivity, similar to that of La₂Mo₂O₉. The transition temperature is found to decrease with increasing Nb or Ta content. The introduction of 5 wt % Nb increases the 800°C conductivity of the material.     

Fluctuation Conductivity of RE1−2x Ca x M x Ba2Cu3O7−δ (RE=Nd,Y and M=Pr,Th) Superconductors

Polycrystalline samples of RE_1?2x Ca _x M _x Ba₂Cu₃O_7?δ with RE=Nd, Y and M=Pr, Th (with 0.0≤x≤0.10), superconductors were prepared by the standard solid-state method. Resistivity was measured as a function of temperature and doping concentration x. Excess conductivity was analyzed using the modified Lawrence-Doniach (LD) expressions. The fluctuation regions, crossover temperatures, coherence lengths, and effective layer thickness were obtained and the values were compared for both samples. For both samples, it was found that with increasing doping, the crossover temperatures were reduced, while the coherence length decreased. The upper critical field and critical current density were increased with increasing doping concentration due to the introduction of disorder and the enhancement of flux pinning by charge neutral doping. Furthermore, the coherence lengths of the Nd-based samples are larger than that for the Y-based samples by a factor 2. It was found that the value of critical current density in Nd(CaPr)-123 is higher than Y(CaTh)-123, from which it is suggested that CaPr doping is more effective than CaTh doping.     

The relationship between the mean dopant-ion radii and conductivity of co-doped ZnO systems, Zn1−x−y M x M′ y O (M, M′ = Al, In, Ga, Y)

The conductivities of the Zn_1–x–y M _x M _y O (M, M = Al, In, Ga, Y) and Zn_1–x M _x O (M = Al, In, Ga) systems were measured from room temperature to 1173 K in order to elucidate a dominant parameter of the conducting mechanism. The conductivity at 873 K first increased with the dopant content. However, it showed a maximum value at a given dopant content, and then gradually decreased. For the samples with the same dopant content, their conductivity at 873 K was strongly dependent on the mean dopant-ion radii, and reached a maximum value at around 0.51 Å of the mean dopant-ion radii. The results suggested that the conductivity of the system would be influenced not only by the dopant content, but also by the mean dopant-ion radii. It was found that the co-doped ZnO system of Zn_0.995Al_0.003In_0.003O had a conductivity higher than that of the other usual mono-doped system.     

浅谈Ф3x12M水泥磨机提高产量的几项措施

我公司水泥生产线有两台水泥磨机,一台洛阳矿山机器厂生产的中心传动Ф3．2x11M水泥磨机,另一台是沈阳水泥机器厂生产的Ф3x12M、该磨机传动电动1400wk磨机分两仓,粗磨仓为阶梯衬板,细磨仓为波纹衬板,研磨体装载量为100t,设计台时产136—45t／h（入磨粒度小于25mm）,由于受到各种不良因素的影响,磨机台时产量不稳定。为此我攻关小组先后采取了一系列措施,经过1年的努力,使磨机系统生产正常,产量大幅度提高。     

M（t）={x∈Xg（x,t）≤0}下半连续的几个定理

本文引入一类比拟凸更广泛的弧拟凸和一致严格弧拟凸函数族的定义。对度量空间X×T上的集值映射。 M(t)={x∈X|g_1(x,t)≤0,(?)i∈J={1,2,…,m}}1,(?)i∈T中g_i(·,t)是拟凸拟凹或在t。∈T是一致严格弧拟凸函数时M(t)的下半连续性(Berge意义)进行了讨论,得到和[5]中关于g_i(·,t)是凸弱解析函数时相应的结论。     

Electrical and Thermal Transport Properties of Transition Metal Substituted in Electron-Doped La0.9Te0.1Mn1?x M x O3 Compounds (M=Cr and Al)

Systematical studies of resistivity ??(T), thermopower S(T), and thermal conduction ??(T) have been performed on the electron-doped manganites La_0.9Te_0.1Mn_1?x Cr(Al) _x O₃ (0.05??x??0.20). The Cr005 and Al005 samples exhibit an insulator-metal transition in the ??(T) curves, however, other samples present insulating behaviors in the whole measured temperature. The S(T) data increases with decreasing temperature and develop a peak at $T_{S}^{P}$ for all samples, with decreasing temperature further, another characteristic temperature $T_{s}^{m}$ is observed. The fits of ??(T) and S(T) data in the high temperature region are presented, and the result shows that the electron conduction is governed by the VRH mechanism for Al-doped samples and the SPC mechanism for Cr-doped ones. As to thermal conduction ??(T), it is suggested that it comes from two sides, one is the phonon-phonon scattering due to disorder and the other is the spin-phonon interaction.     

Mössbauer spectroscopic studies of the crystallization of amorphous Fe80B20−x Si x (x=0, 2, and 8) alloys

The crystallization process of amorphous Fe₈₀B_20–x Si _x (x=0, 2, and 8) ferromagnetic alloys has been studied by using ⁵⁷Fe Mössbauer spectroscopy and X-ray diffraction studies. Results for samples heat treated at different temperatures for different times show that the crystallization of Fe₈₀B_20–x Si _x samples having x=0 and 2 leads to -Fe and t-Fe₃B, while for x=8, it leads to -Fe, t-Fe₂B, and perhaps Fe-Si. It is further observed that the addition of silicon to the Fe-B system improves the thermal stability of the system.     

Mössbauer study of Li0.5Fe2.5−x Al x O4: cation distribution and noncollinear spin alignment

Based on⁵⁷Fe Mössbauer spectroscopic investigations of Li_0.5Fe_2.5–x Al _x O₄ (x=0.3 and 0.8) conducted at 4.2 K under an external magnetic field of 40 kG, the exact cation distribution has been worked out. Both the compositions show spin canting for the octahedral sites, with the Yaffet Kittle angle _yk20° forx=0.3 and _yk27° forx=0.8. The Al³⁺ ions show some preference for the octahedral sites but the derived cation distribution is quite different from that reported earlier on the basis of magnetization studies. The reported compensation temperature forx=0.8 has not been observed. The origin of the central quadrupole doublet along with the magnetic sextet and the role of canted spin alignment towards the possible observance of compensation point, are discussed.     

Effect of Synthesis Conditions on the Lithium Nonstoichiometry and Properties of La2/3 – x Li3x □4/3 – 2x M2O6 (M = Nb, Ta) Perovskite-like Solid Solutions

The effects of the nominal composition and synthesis conditions on the lithium nonstoichiometry of La_{2/3 – x} Li_{3x 4/3 – 2x} Nb₂O₆ (I) and La_{2/3 – x} Li_{3x 4/3 – 2x} Ta₂O₆ (II) solid solutions are studied. The results demonstrate that lithium losses can be reduced from 26–30 to 14–15 mol % in system I and from 15 to 4 mol % in system II. It is shown that the disturbance of electroneutrality caused by Li nonstoichiometry in the solid solutions is eliminated via the formation of oxygen vacancies in positions O(1) (1f: 1/2 1/2 0) and O(2) (1h: 1/2 1/2 1/2) of the cation-deficient perovskite structure. The optimal lithium ion conductivity is offered by solid solutions with /3x 2.6 and x 0.136–0.143.     

XRD, Magnetic and M?ssbauer Spectral Studies of?Ag x Ni1?x Fe2O4 Ferrite Nanoparticles

Nanophase Ag _x Ni_1?x Fe₂O₄ (x=0,0.2) ferrites were prepared by glycothermal method. The NiFe₂O₄ (x=0) nanosized sample was also produced by high-energy ball milling for comparison of properties. Structural investigations of the samples were carried out by X-ray diffraction. The experiment reveals that pure Ag-Ni ferrite materials with grain sizes of about 8 nm can be obtained after annealing at relatively low temperature of about 500?°C. The nanosized compounds produced by glycothermal reaction indicate superparamagnetic behavior. A higher value of coercive field (910 Oe) is observed in x=0 milled sample with similar particle size. The zero field cooled (ZFC) and field cooled (FC) magnetization measurements reveals spin glass like behavior of the nanosized compounds.     

Thermodynamic properties of Ca1 − x Er x F2 + x and Ca1 − x Yb x F2 + x heterovalent solid solutions

The heat capacity of single crystals of the Ca_{1 ? x} Er _x F_{2 + x} (x = 0.05, 0.10) and Ca_0.95Yb_0.05F_2.05 fluorite solid solutions was determined by adiabatic calorimetry in the temperature range 55–300 K. The results were used to obtain temperature dependences of the Debye characteristic temperature, entropy, and enthalpy for the solid solutions.     

Pb1−x Bi x /Bi/Pb1−x Bi x Josephson junction

A superconductor/semimetal/superconductor (S/SM/S) Josephson junction has been developed. We have used an alloy of Pb_1–x Bi _x (0x 0.6) as the superconductor and Bi as the semimetal. By irradiating at X-band microwave of 10 GHz, Shapiro steps were observed for various bismuth barrier thicknesses inÅ and bismuth weight ratiosx. Finally, we obtained the empirical relationship for barrier thickness, below which microwaves could be detected for various bismuth weight ratiosx at the temperature of 4.2 K.     

Lattice-matched epitaxial Pb1 − x Mn x Se/PbSe1 − x S x heterojunctions

This paper examines the possibility of producing lattice-matched p-n heterojunctions based on epitaxial n-Pb_{1 ? x} Mn _x Se (x = 0.02) and p-PbSe_{1 ? x} S _x (x = 0.04) films. The heterojunctions have been grown by molecular beam epitaxy in a single processing cycle, without breaking the vacuum, using a compensating Se vapor source in the growth process. Optimal conditions have been found for the growth of structurally perfect (W _1/2 = 90″-100″) epitaxial films and fabrication of lattice-matched heterojunctions based on such films, photosensitive in the IR spectral region.     

High-Pressure Studies on Superconductivity in LaFeAsO1−x F x and SmFeAsO1−x F x

The pressure dependence on the superconducting transition temperature (T _c ) was investigated for the iron-based superconductors LaFeAsO_1−x F _x and SmFeAsO_1−x F _x . The T _c ’s increase largely for LaFeAsO_1−x F _x with a small increase of pressure, while a sharp decrease of T _c was observed for SmFeAsO_1−x F _x . The electrical resistivity measurements reveal pressure-induced superconductivity for undoped LaFeAsO and SmFeAsO. These pressure effects seem to be related to an anisotropic decrease of the lattice constants under high pressure from the x-ray diffraction measurements up to 10 GPa for the LaFeAsO_1−x F _x system.     

The dielectic response of K x Al x Ti8−x O16 and K x Mg x/2 Ti8−x/2 O16

Materials of the hollandite structure with the general formulae K_x Al_x Ti_8–x O₁₆ and K_x Mg_x/2 Ti_8–x/2 O₁₆ have been synthesized in the composition range 1.6x2.0 and their dielectric properties have been measured in the temperature range 77 to 800 K and the frequency range 10^–3 to 10⁶ Hz. The observed response shows a whole range of features characteristic for both charge carrier and dipolar polarization processes and these are seen as being associated with the one-dimensional transport in channels in the hollandite structure. At low temperatures the dominant response is the universal dielectric relation in which the loss follows the law x() ^n–1, with the exponent n<1 and equal specifically to approximately 0.7. This is followed at 120 to 180 K by a distinct loss peak superimposed on the above law, and finally at higher temperatures by a region of strong dispersion which is associated with strongly interacting many-body processes between charged carriers restricted by defects to move in limited regions of the channels.