Acid-Base Properties of Alumina-Supported M2O3 (M=B, Ga, In) Catalysts

The acid-base properties of -Al₂O₃ and alumina-supported B₂O₃, Ga₂O₃ and In₂O₃ have been determined by microcalorimetry of ammonia and sulfur dioxide adsorption. From the adsorption of NH₃, it was found that the addition of B₂O₃ on alumina leads to an increase of the number of acid sites, while Ga₂O₃ and In₂O₃ additives caused a decrease in the acidity of alumina. Using SO₂ as a probe molecule to study the basicity, the number of surface basic sites on alumina was found to be strongly decreased by the addition of boron oxide, while it was only slightly affected by the addition of gallium oxide and decreased by the addition of indium oxide. The differential heats of adsorption are discussed as a function of the coverage by the probe molecules. The electronic properties of the oxides are examined in order to explain the acid-base properties of the supported oxides.     

Effect of BiMO3 (M=Al,In, Y,Sm, Nd,and La) doping on the dielectric properties of BaTiO3 ceramics

In this study, in order to enhance the energy storage density, 10% BiMO₃ doping is performed in BaTiO₃ ceramics (M=Al, In, Y, Sm, Nd, La) by a traditional solid-state method. The effects of different M³⁺ radii on the structural characteristics, dielectric properties, and energy storage are investigated systematically. The locations of the M-ions gradually shift from B-site substitutions to A-site substitutions with the increase in the ionic radius, which affect the structural characteristics and the dielectric properties. When 80<R_M3+<95.5 pm, the ceramic has a cubic phase which shows the highest energy density; while out of this range, the dielectric properties of the ceramics are degraded. Specially, the change rate of permittivity of the Sm substituted composition reaches 70% at 100 kV/cm, which might be good for high frequency tunable device application. Typically, combined with the suppression of nonlinearity, polarization maximum (P_m) and remnant polarization (P_r), 0.9BaTiO₃–0.1BiInO₃ exhibits the maximum energy density of 0.753 J/cm³ and the highest energy efficiency of 89.4%, which exhibits slim P-E hysteresis loops for energy storage applications.     

M2(Si,Al)4(N,C)7 (M = La,Y,Ca) carbonitrides: II. The crystal structure of Ca0.8Y1.2Si4N6.8C0.2

A new (Ca,Y)Si₄(N,C)₇ phase has been characterised lying between the two end-members Y₂Si₄N₆C and CaYSi₄N₇. This phase is similar to BaYbSi₄N₇, which is made up of a network of [N(SiN₃)₄] structural units linked together in a three-dimensional network, with the large cations located in the interstices, but (Ca,Y)Si₄(N,C)₇ is a disordered variant, with nitrogen atoms partially occupying two sets of equivalent sites related by the combined operations of rotation and tilt. The crystal of (Ca,Y)Si₄(N,C)₇ used for structure determination contained Ca and Y in the atomic ratio 2:3, the excess positive charge in the cation sites being balanced by the partial replacement of nitrogen by carbon in the central non-metal site of the [N(SiN₃)₄] unit. Powder diffraction data are listed for Ca_0.8Y_1.2Si₄N_6.8C_0.2, which is hexagonal with a=5.9874(4), c=9.7849(8) Å at ambient temperature. The crystal structure has been determined from single crystal data; Z=2; S.G. P6₃mc (no. 186); R_int=0.0274, R1=0.0384, wR2=0.0993 for all data.     

Endohedral metallofullerenes M@C82 (M=La, Y): synthesis and transport properties

Endohedral metallofullerenes M@C_2n (M=La, Y) were synthesized by the arc-discharge method using optimum electric arc parameters. It was also shown that an organic solvent (N,N-dimethylformamide) is successfully used in selective extraction of M@C_2n. We identified the resulting products by mass spectrometry, electron spectrophotometry, EPR and X-ray fluorescence spectroscopy. The resulting N,N-dimethylformamide extracts of La@C_2n and Y@C_2n are shown to be free of empty fullerenes and appear as a mixture of endometallofullerenes M@C_2n whose main ingredient is M@C₈₂ (∼80 wt%). Transport properties of the extracts of La@C₈₂ and Y@C₈₂ were studied using pressed pellets. It was found that oxygen and heat treatment affect conductivity of endometallofullerenes. Heat treatment results in a three-order increase of conductivity from 10⁻⁵ upto 10⁻² Ohm⁻¹ cm⁻¹     

Compositional Effects on the Properties of Si-Al-RE-Based Oxynitride Glasses (RE = La, Nd, Gd, Y, or Lu)

A series of silicon-aluminum oxynitride-glass compositions containing selected rare-earth (RE) additions were prepared to examine the effects of specific RE, as well as Si:Al:RE and N:O ratio, on properties. The properties that were characterized included density, thermal expansion coefficient (α), glass-transition temperature ( T _g), hardness ( H ), and Young's modulus ( E ). The compositions (in equivalent percent) selected included: 55 Si-20 RE-25 Al oxide and 80 O-20 N oxynitride, and 45 Si-30 RE-25 Al oxide and 70 O-30 N glasses. The results show that the density increased significantly with an increase in the RE atomic mass and slightly with an increase in N:O ratio. For each of the fixed Si-Al-RE-O-N compositions, the E , H , and T _g values were each increased by substituting smaller RE ions, whereas the α value was decreased. For each specific cation composition and RE, increasing the N:O ratio systematically led to a decrease in the α values but an increase in the E , H , and T _g values. The observed response in the glass properties to changes in composition appears to reflect modifications in the bonding within the glass network.     

M2(Si,Al)4(N,C)7 (M=La,Y,Ca) carbonitrides: I. Synthesis and structural characterisation by XRD and NMR

A series of new nitrides and carbonitrides has been identified with crystal structures similar to those of the hexagonal quaternary nitrides of the type (Ba,Sr,Eu)YbSi₄N₇. The large divalent cations in these structures can be replaced by trivalent cations such as Ln and/or Y, if valency balance is preserved by the simultaneous substitution of carbon for nitrogen in the unique [4]-coordinated anion site. This has been demonstrated by carbon-13 magic-angle spinning NMR spectra which for the yttrium member of this series shows a peak at 36.7 ppm corresponding to carbon atoms occupying the central non-metal atom site in the characteristic [C(NSi₃)₄] structural unit. The resulting compounds have compositions of the types La₂Si₄N₆C, Y₂Si₄N₆C or (La,Y)₂Si₄N₆C; the crystal structure of a related mixed (Ca,Y) derivative of composition (Ca,Y)₂Si₄(N,C)₇ is reported in Part II of this series. When the two large cations are different, the hexagonal symmetry characteristic of the (Ba,Sr,Eu)YbSi₄N₇ compounds is maintained; when both cations are the same, lower symmetries are observed. The powder diffraction pattern of La₂Si₄N₆C indexes on an orthorhombic unit cell with a=6.0360(7), b=10.1246(9), c=10.5664(11) Å and the crystal structure has been determined. An alternative way of achieving valency balance without incorporation of carbon is to replace some of the silicon by aluminium; related derivatives of the type M₂Si₃AlN₇, where M=La, Y or mixed La,Y have been prepared and their unit cell dimensions are reported.     

Separation and Recovery of Silver(I) Ions from Base Metal Ions by Thiourea- or Urea-Formaldehyde Chelating Resin

Abstract

In the present work, thiourea-formaldehyde (TF) and urea-formaldehyde (UF) chelating resins have been synthesized and they have been used in the adsorptions of Ag(I), Cu(II), and Zn(II) metal ions by batch and column methods. The effect of initial acidity of Ag(I) solution and the adsorption capacities of TF and UF resins by batch method and the separation of Ag(I) ions from Cu(II) and Zn(II) base metal ions by the column method were examined experimentally. The adsorption capacities of TF and UF resins were found as 58.14 and 47.39 mg Ag(I)/g by batch method and 30.7 and 4.66 mg Ag(I)/g, 0.80 and 0.121 mg Cu(II)/g, and under 0.002 mg Zn(II)/g by the column method, respectively. It was found that Ag(I) ions showed higher affinity towards TF resin than UF resin, compared with Cu(II) or Zn(II) ions, and Ag(I) could be separated more effectively by TF resin from Cu(II)and Zn(II) ions.     

Quantitative Separations of La(III) from Alkaline Earth Metal Ions Using a New,Poorly Crystalline Inorganic Ion Exchanger: Niobium Molybdate

Abstract

During our systematic studies of niobium compounds (1–4) as ion-exchange materials, it was found that niobium molybdate has a high thermal stability and can be more easily converted into a poorly crystalline form than the tin (5), thorium (6), titanium (7), and chromium (8) molybdates studied in our laboratories. We therefore decided to investigate the ion-exchange behavior of this material. The results are given below.     

Separation of Metal Ions on Titanium(IV) Tungstate Papers

Abstract

Papers impregnated with titanic tungstate have been used to chromatograph 52 cations in 45 aqueous and mixed solvents. Experimentally, a large number of complex cation separations have been achieved easily and rapidly—Au³⁺, Tl³⁺, Ag⁺, Mo⁶⁺, K⁺, Rb⁺, CS⁺, Ni²⁺, Sb²⁺, Bi³⁺, Be²⁺, and Tl⁺ can be easily separated from numerous metal ions. Several quaternary, ternary, and binary separations have also been achieved, and some important separations are discussed.     

Separation of Metal Ions on Titanium(IV) Molybdate Papers

Abstract

Papers impregnated with titanic molybdate have been used to chromatograph various cations in sodium nitrate solutions of 0.1 to 4 M concentrations. Various important separations are listed. The movement of the cations is proportional to the activity of the developing medium. Various plots are made to discuss the theoretical behavior of movement of cations on these papers.     

核壳纯丙乳液的结构形态对Tg及MFT影响的研究

研究了核壳纯丙乳液聚合中乳液结构对其玻璃化转变温度、最低成膜温度的影响，以及单体种类、核壳比、核壳设计Tg对乳液性能的影响，还通过TEM、AFM研究了乳液颗粒形态及核壳乳液成膜后的表面形态。     

Coatings on textiles for Cu(In,Ga)Se2 photovoltaic cell formation on textile carriers: Preparation of Cu(In,Ga)Se2 solar cells on glass‐fiber textiles

Results are presented on the construction of a thin‐layer photovoltaic cell on glass‐fiber fabric. The unevenness of the fabric was first smoothed by the application of a high‐temperature stable resin before photovoltaic layer deposition. We obtained an efficiency of light‐to‐current conversion of more than 8%. This constitutes a remarkably high value for a photovoltaic cell on a flexible substrate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Structure and lithium-ion mobility in Li1.5M0.5Ge1.5(PO4)3 (M = Ga,Sc, Y) NASICON glass-ceramics

This work reports structural and lithium-ion mobility studies in NASICON single- or multiple phase Li_1+xM_xGe_2−x(PO₄)₃ (M = Ga³⁺, Sc³⁺, Y³⁺) glass-ceramics using solid-state NMR techniques, X-ray powder diffraction, and impedance spectroscopy. X-ray powder diffraction data show the successful incorporation of Ga³⁺ and Sc³⁺ into the Ge⁴⁺ octahedral sites of the NASICON structure at the levels of x = 0.5 and 0.4, respectively. The glass-to-crystal transition was further characterized by multinuclear NMR and electrical conductivity measurements. Among the studied samples, the gallium-containing glass-ceramic presented the highest DC conductivity, 1.1 × 10⁻⁴ S/cm at room temperature, whereas for the Sc-containing samples, the maximum room temperature conductivity that could be reached was 4.8 × 10⁻⁶ S/cm. No indications of any substitution of Ge⁴⁺ by Y³⁺ could be found.     

双对二甲氨基苯甲醛缩连氮的合成及其对金属离子的识别

以水合肼和对二甲氨基苯甲醛为原料设计合成了双对二甲氨基苯甲醛缩连氮(1),经元素分析、1H-NMR及质谱对其结构进行了表征。在甲醇-水(V/V=4:1)混合溶剂中采用UV-Vis光谱法和荧光光谱法研究了化合物1对H+、Li+、Na+、K+、Mg2+、Ca2+、Mn2+、Co2+、Ni2+、Zn2+、Cd2+、Hg2+及Cu2+的选择性识别性能。结果表明,化合物1的紫外-可见光谱仅对H+有特殊的选择敏感性;其荧光光谱对H+、Mn2+和Co2+有显著的识别传感能力,三种离子均可有效地猝灭化合物1的荧光。根据Stern-Volmer公式,Mn2+和Co2+对化合物1荧光的影响属于动态猝灭过程。     

Studies of the Size-Selective Extraction of Alkali Metal Ions by the Synergistic Extraction System,Crown Ether-DI(2-Ethylhexyl) Phosphoric Acid-Benzene

Abstract

In order to take practical advantage of the size-selective cation-coordinating ability of the cyclic polyethers (crown ethers), experiments seeking a means of avoiding the problem of solubilizing a mineral-acid anion in a nonpolar organic diluent were performed. Mixtures of several known extractants and crown ethers were tried. Results presented indicate that organic soluble cation exchangers mixed in solution with crown ethers produce a synergistic extractant mixture that largely exhibits the size-selective properties expected of the crown ether. Data are presented for the extraction of macro concentrations of alkali metals by di(2-ethylhexyl) phosphoric acid—dicyclohexyl-18-crown-6 mixtures at a single pH, and at nonloading condition(σ metal cone < 0.04 M) as a function of pH, 2 to 6. In both cases potassium is synergized most strongly presumably because of its best fit to the crown ether cavity. Other data indicate, however, that the size-fit principle is not as consistent for all alkali metal ions and crown ethers as for potassium and dicyclohexyl-18-crown-6. Other effects such as competition for ion hydration and aqueous-phase distribution of the complex may have important effects that have not been elucidated.     

分散剂对柠檬酸络合法制备氧化镧钇亚微米粉体的影响

以硝酸镧、硝酸钇和柠檬酸为原料,采用柠檬酸络合法制备氧化镧钇亚微米粉体,分别探讨了PEG400和油酸作为分散剂时对粉体物相、微观形貌以及粒径分布的影响规律.结果发现,无论是以PEG400还是油酸作为分散剂,煅烧后获得的粉体中只存在Y2O3单相,且粉体粒径随着煅烧温度的升高而变大;PEG400的最佳添加量为4wt％,此时粉体在1100℃煅烧后的一次粒径D50在85 nm左右;油酸的最佳添加量为2wt％,此时粉体在1100℃煅烧后的一次粒径D50在75 nm左右;使用油酸作为分散剂明显比使用PEG400作为分散剂的团聚峰平缓,说明油酸的分散效果比PEG400的分散效果更为优异.     

金属离子对面包酵母合成ATP的影响机制初探

对Mg2+, K+和Na+在面包酵母酶系合成ATP过程中的影响机制进行了初步研究. 发现Mg2+对ATP的合成影响很大,当Mg2+浓度为40 mmol/L时,ATP合成量达到最大值,为6.07 mmol/L;高浓度磷酸钾缓冲液会抑制ATP的合成,进一步研究发现高浓度K+对ATP合成具有明显抑制作用,但K+完全缺乏时,也不利于腺苷的转化;Na+可通过激活腺苷酸激酶的活性来促进ATP合成,同时激活腺苷脱氨酶的活性,其存在会使底物腺苷向肌苷转化.     

Column Chromatographic Separation of Hg(ll), La(lll), Ce(lll), and In(lll) from Other Metal Ions in NH4CI-CH3COOH Medium by Cation Exchange

Abstract

Cation exchange equilibrium distribution coefficients (K) with the (Dowex 50W-X8) H⁺ form have been determined for 21 metal ions in media consisting of mixtures of 0.7 mol/dm³ acetic acid and varying concentrations (0.16, 0.32, 0.48, 0.64, 0.96, and 1.28 mol/dm³) of ammonium chloride. The distribution coefficients were determined by the batch technique for finding the conditions for the mentioned separations. The column chromatographic separations achieved were all quantitative. The results of the resolution of the synthetic binary and ternary mixtures along with the elution curves are presented.     

Influence of Internal Stresses on the Glass Transition Temperature of Filled Polymers

Abstract

It is assumed that, in a system of filler in polymer, an internal stress distribution is associated with a shift in the glass transition temperature of the polymer. Experimental results supporting this theory are presented.     

Phase stability,microstructure, and dielectric properties of quaternary oxides In12Ti10A2BO42 (A: Ga or Al; B: Mg or Zn)

Quaternary oxides In₁₂Ti₁₀Al₂MgO₄₂ (ITAM), In₁₂Ti₁₀Al₂ZnO₄₂ (ITAZ), In₁₂Ti₁₀Ga₂MgO₄₂ (ITGM), and In₁₂Ti₁₀Ga₂ZnO₄₂ (ITGZ), were synthesized by the solid-state reaction method and the dielectric behavior is reported. The samples were submitted to different sintering temperatures (1473-1773 K) for 24 hours and the phase stability and microstructure were analyzed by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). It is found that the phase decomposition occurs above of 1573 K. Microstructure images showed an increase in the grains size as sintering temperature was raised. The dielectric permittivity as a function of temperature and frequency showed acceptable dielectric constant (15-30) and low dielectric loss (tan δ << 1) values in a wide range of temperature. The band gap obtained by the optical spectrum analysis is about 3.5 eV indicating good dielectric insulating compounds. Furthermore, the electrical conductivity, the activation energy, and the conduction mechanisms are analyzed and discussed in a whole range of temperature. The good dielectric values, ε′ (15-20) and tan δ (~0.004), and their behavior (almost independent of the frequency and temperature) almost constant within a wide range of temperature make these quaternary oxides interesting in electroceramic applications.