微波消解-ICP-AES法测定茶叶中钾、钠、磷、硫、铁、锰、铜、锌、钙、镁方法研究

通过优化微波消解条件,并根据不同元素性质,调谐ICP-AES工作条件至最佳,实现了茶叶中K、Na、P、S以及Fe、Mn、Cu、Zn、Ca、Mg 10种元素的同时测定。10种元素测定结果 RSD%为0.67(Cu)～5.57(Na),回收率为84.0%(Na)～101.5%(Fe),检出限为0.001(Mn)～0.029(S)μg·g-1,表明该方法准确可靠,能够满足茶叶中K、Na、P、S、Fe、Mn、Cu、Zn、Ca、Mg分析要求。     

CCS,CCUS,CCRS,CMC系统集成

二氧化碳捕集—封存、生产生活中的节能减排和可再生能源的开发是实施低碳经济的三个核心举措。近年来提出的碳捕集—利用—封存和碳捕集—再利用—封存是更为积极的CO2减排应对策略。人类在未来必须要把宝贵的碳元素同时作为资源和能源载体循环利用,进行全程管理。     

Dry Autoclaving for the Nanofabrication of Sulfides,Selenides, Borides,Phosphides, Nitrides,Carbides, and Oxides

This review compiles various nanostructures fabricated by a distinct “dry autoclaving” approach, where the chemical reactions are carried out without solvents; above the dissociation temperature of the chemical precursor(s) at elevated temperature in a closed reactor. The diversity to fabricate carbides (SiC, Mo₂C, WC), oxides (VOx‐C, ZnO, Eu₂O₃, Fe₃O₄, MoO₂), hexaborides (LaB₆, CeB₆, NdB₆, SmB₆, EuB₆, GdB₆), nitrides (TiN, NbN, TaN), phosphides (PtP₂, WP), sulfides (ZnS, FeS/C, SnS/C, WS₂, WS₂/C), and selenides (Zn_1‐xMn_xSe/C, Cd_1‐xMn_xSe/C), with various shapes and sizes is accounted with plausible applications. This unique single‐step, solvent‐free synthetic process opens up a new route in the growing nanomaterials science; owing to its considerable advantages on the existing approaches.     

Optical properties of the metals Al, Co, Cu, Au, Fe, Pb, Ni, Pd, Pt, Ag, Ti, and W in the infrared and far infrared

Infrared optical constants collected from the literature are tabulated. The data for the noble metals and Al, Pb, and W can be reasonably fit using the Drude model. It is shown that -epsilon1(omega) = epsilon2(omega) approximately omega(2)(p)/(2omega(2)(tau)) at the damping frequency omega = omega(tau). Also -epsilon1(omega(tau)) approximately - (1/2) epsilon1(0), where the plasma frequency is omega(p).     

Elastic, structural, bonding, and defect properties of zinc-blende BN, AlN, GaN, InN and their alloys

Simple tight-binding simulations, incorporating only the Herman–Skillman atomic term values, are shown to provide valuable information about the bonding, elastic and structural properties of zinc-blende group III-nitrides. Our calculated values of the elastic parameters (viz., bulk modulus, elastic stiffness constants, Kleinman's internal displacement parameter, Keating force constants, etc.) for BN, AlN, GaN, and InN are shown to exist well within the range of values derived from more sophisticated methods. Despite the crude approximations used, the tight-binding method has clearly provided the meaningful trends to the local distortions around isoelectronic impurities and has described reasonably well the bond length variations as a function of composition in ternary alloys.     

Vacuum Carbosilicothermic Reduction of Zirconium,Hafnium, Vanadium,Niobium, Tantalum,and Chromium Oxides

Inorganic Materials - This paper reports on vacuum carbosilicothermic reduction of zirconium(IV), hafnium(IV), vanadium(V), niobium(V), tantalum(V), and chromium(III) oxides at a temperature of...     

Synthesis and structure of dodecamolybdates of tetravalent cerium,thorium, uranium,neptunium, and plutonium

A series of isostructural compounds of the composition Na₇H[EMo₁₂O₄₂]·12H₂O, where E(IV) = Ce, Th, U, Np, or Pu, were synthesized and structurally characterized. In the [EMo₁₂O₄₂]^8– heteropolyanion (HPA), the central E(IV) atom is surrounded by six Mo₂O₉ groups, each constituted by two octahedra sharing a common face. The coordination polyhedron (CP) of the central atom is a weakly distorted icosahedron with the mean E(IV)–О bond lengths of 2.498, 2.529, 2.500, 2.490, and 2.488 Å for Ce, Th, U, Np, and Pu, respectively. In the structure of the compounds Na₇H[EMo₁₂O₄₂]·12H₂O, there are two crystallographically independent sodium atoms: Na(1) and Na(2). The oxygen surrounding of the Na(1) atom is formed by the terminal oxygen atoms of two heteropolyanions adjacent along [001], and its coordination polyhedron is an octahedron. The surrounding of the Na(2) atom (a six-vertex polyhedron) is formed by three terminal oxygen atoms of three Mo₂O₉ groups belonging to the same HPA and by three water molecules. The coordination polyhedra of the Na(2) atoms are linked with each other via common oxygen atoms of O_w(2) water molecules to form a chain “winding” around the 3₁ screw axis. The heteropolyanions and Na⁺ cations in the crystal form a framework constructed in a fashion characteristic of Dexter–Silverton type anions, with the coordination via three terminal oxygen atoms of three Mo₂O₉ groups. Excess negative charge of HPA is compensated by the proton localized on one of the six bridging O atoms. In the Mo₂O₉ doubled octahedra, the Mo–O bonds with the О atoms bonded to E(IV) and forming the edge of the common face are sensitive to the kind of the central atom.     

Elastic properties of thorium ceramics ThX (X = C,N, O,P, As,Sb, S,Se)

The elastic constants (C ₁₁, C ₁₂, and C ₄₄) of all the known cubic binary phases of thorium with non-metals, ThX (X = C, N, O, P, As, Sb, S, Se), have been calculated using the full-potential linearized augmented plane wave (FLAPW) method with an exchange-correlation potential in the generalized gradient approximation (GGA). Numerical estimates of elastic parameters of the corresponding polycrystalline ceramics (bulk compression modulus, shear modulus, Young’s modulus, Poisson’s ratio, and Lamé’s coefficients) are obtained and analyzed for the first time.     

Thermophysical Properties of Sulfides of Lanthanum, Praseodymium, Gadolinium, and Dysprosium

The temperature dependence of the thermal conductivity, electrical conductivity, thermoelectromotive force, and thermal expansion coefficient for sulfides of lanthanum, gadolinium, praseodymium and dysprosium of the composition Ln_{3 – x} V _x S₄ is investigated in the temperature range from 300 to 1200 K. It is shown that the transfer phenomena and thermoelectrical properties of the investigated compositions depend on the concentration of current carriers, cation vacancies, and mobility. Gadolinium sulfide is found to have the highest thermoelectrical efficiency. The scattering from ions of rare-earth elements has a noticeable effect on the magnitude and temperature dependence of the lattice thermal conductivity and electrical resistance.     

ICP-AES法测定超高强度钢中Mn,Si,Al,Ti,Nb,La杂质元素

介绍了采用ICP-AES测定超高强度钢中Mn,Si,Al,Ti,Nb,La的方法.研究了超高强度钢中基体元素,常见元素对六种杂质元素分析谱线的光谱干扰情况;选择了合适的分析谱线;工作曲线线性良好;根据钢中共存元素的含量范围,进行了加入回收实验和精密度、准确度实验,测量结果满足分析要求.     

Structural transformations, reactions, and electronic properties of fullerenes, onions, and buckytubes

We describe the results of extensive quantum molecular dynamics calculations of the properties of fullerenes and microtubules. The topics to be discussed include: (i) stability of C₆₀ isomers and barriers to isomerization; (ii) reactivity of C₆₀ and C₅₈ with C₂ and C₃, and its implications on the formation and growth of fullerenes; and (iii) atomic and electronic structure and doping of semiconducting microtubules. We also discuss the structures, stabilities and atomic transformations of large multishell fullerenes and offer an explanation for the formation of spheroidal “onions” under high fluence electron irradiation conditions. The last results, which involved calculations for up to 15 000 atoms, were obtained using classical three-body potentials.     

Electrospray ionization mass spectrometry of tetracycline, oxytetracycline, chlorotetracycline, minocycline, and methacycline

The effects of mobile-phase additives and analyte concentration on electrospray ionization mass spectra of a series of tetracyclines were investigated in both positive and negative ion modes. Only [M + H](+) and [M - H](-) ions were observed. The greatest sensitivity as [M + H](+) ions was obtained with 1% acetic acid and the greatest sensitivity as [M - H](-) ions was obtained using 50 mM ammonium hydroxide. Sensitivities in the positive ion mode were greater than those in the negative ion mode. The sensitivity as [M + H](+) showed no systematic variation with pH; however, the sensitivity as [M - H](-) did increase with increasing pH. A larger linear range was observed for [M - H](-) than for [M + H](+) ions. Both [M + Na](+) and [M + H](+) ions were observed with 0.5 mM sodium acetate and sodium iodide, but no adduct ions were observed with ammonium acetate. Some M(2)H(+) ions were observed at higher concentrations. Cluster ions, Na(NaOAc)(n)(+) or Na(NaI)(n)(+), but no sample ions were observed using 5 mM salts. The data suggest that mechanisms in addition to solution ionization are involved in the formation of the ESI sample ions. The utility of mobile phases containing 1% HOAc or 50 mM NH(4)OH was demonstrated for chromatographic separations.     

浅谈三氯化氮的性质、危害、预防及去除

阐述了氯碱生产中的三氯化氮的性质、危害、形成,着重介绍了三氯化氮的预防措施及去除方法.     

Wear protection of steels by boriding, vanadizing, nitriding, carburising, and hardening

The wear behaviour of the differently treated steel surface was examined under conditions of adhesion, tribooxidation, abrasion and surface fatigue. Like and unlike surface pairs were tested, in the absence and presence of a lubricant.In adhesive wear the best pairing is two nitrided surfaces, except over long periods of running when borided surfaces could be better. Vanadized surfaces are superior intribooxidative and abrasive wear situations. It surface fatigue is acting, casehardening is the best means to reduce wear.     

Theory of curved, clamped, piezoelectric film, air-borne transducers

Differential equations in the cylindrical coordinate system have been solved to calculate vibration mode of a curved, clamped, piezoelectric multilayer film. Type I has two clamps at straight ends with uniform film curvature, and Type II has the same two clamps with nonuniform curvature in which the radii are different for the central region and for side regions. The solutions include a uniform displacement term, flexural waves with sinusoidal terms, and a hyperbolic cosine term. By numerical computations, the vibration modes and frequency response of displacement are shown, as are various transducer performances. Mechanical losses of the layer materials were taken as complex Young's moduli with Q values assumed to be constant with frequency. Numerical calculations for 28-/spl mu/m PVDF with 25-/spl mu/m polyester enforcement have shown that (1) the resonance frequency is not necessarily proportional to the inverse of curvature radius as classical theory describes, and, furthermore, resonance diminishes for a certain range of radii, forming a stop band; (2) a back air cavity thinner than 150 /spl mu/m significantly increases the resonance frequency; (3) Type II generates much higher output pressure than Type I; (4) receiver sensitivities for Type I and Type II are not much different; and (5) the effect of radiation impedance is small leading to /spl sim/7% output reduction.     

Powder X-Ray Reference Patterns of Sr2RGaCu2Oy (R = Pr,Nd, Sm,Eu, Gd,Dy, Ho,Er, Tm,and Y)

X-Ray Rietveld refinements were conducted on a series of eleven lanthanide phases, Sr₂RGaCu₂O_y (2112 phase, R = Pr, Nd, Sm, Eu, Gd, Dy, Ho, Y, Er, Tm, and Yb) that are structurally related to the high T_c superconductor Ba₂YCu₃O₇ (213). In the 2112 structure, instead of square planar Cu-O chains, tetrahedral GaO4 chains were found to run in a zig-zag fashion along the diagonal of the basal 213 ab-direction. Reference powder patterns for these compounds were prepared by using the Rietveld decomposition technique. The unit cell volume of these compounds follows the expected trend of the lanthanide contraction. The lattice parameters range from a = 22.9694(3) Å, b = 5.5587(2) Å, and c = 5.44743(7) Å for R = Pr, to a = 22.8059(2) Å, b = 5.46031(5) Å, and c = 5.37773(5) Å for R = Yb. An electon diffraction study of the Sm- and Er-analogs showed characteristic diffuse streaks along the b-axis, suggesting some disorder within the GaO₄ chains.     

Design,Processing, Microstructure,Properties, and Applications of Advanced Intermetallic TiAl Alloys

After almost three decades of intensive fundamental research and development activities, intermetallic titanium aluminides based on the ordered γ‐TiAl phase have found applications in automotive and aircraft engine industry. The advantages of this class of innovative high‐temperature materials are their low density and their good strength and creep properties up to 750 °C as well as their good oxidation and burn resistance. Advanced TiAl alloys are complex multi‐phase alloys which can be processed by ingot or powder metallurgy as well as precision casting methods. Each process leads to specific microstructures which can be altered and optimized by thermo‐mechanical processing and/or subsequent heat treatments. The background of these heat treatments is at least twofold, i.e., concurrent increase of ductility at room temperature and creep strength at elevated temperature. This review gives a general survey of engineering γ‐TiAl based alloys, but concentrates on β‐solidifying γ‐TiAl based alloys which show excellent hot‐workability and balanced mechanical properties when subjected to adapted heat treatments. The content of this paper comprises alloy design strategies, progress in processing, evolution of microstructure, mechanical properties as well as application‐oriented aspects, but also shows how sophisticated ex situ and in situ methods can be employed to establish phase diagrams and to investigate the evolution of the micro‐ and nanostructure during hot‐working and subsequent heat treatments.     

Heterogeneous Equilibria in Aqueous Solutions of Uranovanadates Ak(VUO6)k·nH2O (Ak = H,Na, K,Rb, Cs,Tl, Mg,Ca, Sr,Ba, Co,Ni, Cu,Pb)

The state of mineral-like uranovanadates of mono- and bivalent metals in aqueous solutions was studied. Based on experimental solubility data, the reaction equilibria in the crystal uranovanadate-aqueous solution system were described quantitatively, which, in turn, allowed evaluation of the solubility products of uranovanadates and their standard Gibbs energies of formation and prediction of the solubility of these compounds in aqueous solutions of various compositions under the isobaric-isothermal conditions.     

ICP-AES同时测定磷灰石中的K、Na、Ca、Mg、Ti等元素

研究了电感耦合等离子体原子发射光谱(ICP-AES)同时测定磷灰石中的K、Na、Ca、Mg、Ti等元素。确定了各元素的检出限,回收率在97%-104%之间,RSD小于1.5%,该方法用于样品测定,结果令人满意。