CdS thin films on LiNbO3 (1 0 4) and silicon (1 1 1) substrates prepared through an atom substitution method

CdS thin films on LiNbO₃ (1 0 4) and silicon (1 1 1) substrates were prepared through an atom substitution technique using cadmium nitrate as a reactant in an H₂S atmosphere at 230 °C. X−ray diffraction, scanning electron microscopy and transmission microscopy results indicate that the CdS film grows on LiNbO₃ oriented along the [0 0 1] axis in form of crystallized nanoplates, while that deposited on silicon forms randomly oriented nanoparticles. Investigation of the precursor thin film suggests that CdS forms from the O in the CdO precursor thin film being substituted by S from H₂S in the surrounding environment, which is designated as an atom substitution process. This novel method involving an atom substitution reaction between the CdO precursor thin film and its environment can provide a new low cost approach to the preparation of chalcogenide or other compound thin films. A schematic illustration and corresponding mechanism describing the details of this method are proposed.     

Reactivity of ZrCl4 and HfCl4 with silylamines and thermal decomposition of the compounds [MCl4{NH(R)(SiR′3)}] (M = Zr,Hf, R = tBu,R′ = Me; R = SiR′3 = SiMe3, SiMe2H)

The Lewis acid/base adducts [MCl₄{NH(R)(SiR′₃)}] (M = Zr, Hf; R = tBu, R′ = Me; R = SiR′₃ = SiMe₃, SiMe₂H) were synthesized by the 1:1 reaction of MCl₄ with NH(R)(SiR′₃) in dichloromethane solution at room temperature. The decomposition of [MCl₄{NH(R)(SiR′₃)}] proceeds with the elimination of R′₃SiCl, as shown by thermogravimetric analysis. Pyrolysis of the compounds at 620 °C under inert conditions (N₂, vacuum) afforded powders of composition [ClMN] or [Cl₂MNH]. Preliminary low pressure chemical vapour deposition experiments show that [MCl₄{NH(R)(SiR′₃)}] deposits thin films of metal nitride contaminated with metal oxide.     

Chemical solution deposited silver tantalate niobate, Ag x (Ta0.5Nb0.5)O3? y , thin films on (111)Pt/Ti/SiO2/(100)Si substrates

Silver tantalate niobate films are candidates for temperature stable microwave dielectrics. In this work, a chemical solution deposition synthesis method was developed for Ag _x (Ta_0.5Nb_0.5)O_3−y films on Pt-coated Si substrates. Stable solutions with a range of silver stoichiometries were prepared using 2-methoxyethanol and pyridine as solvents, from AgNO₃ and Nb and Ta ethoxide precursors. It was extremely difficult to prepare phase-pure perovskite films of Ag(Ta_0.5Nb_0.5)O₃ on Pt-coated Si subtrates; instead a mixture of perovskite and natrotantite phases was identified. Such mixed phase films had dielectric constant ɛ _r and dielectric loss tanδ values ranging from 200±20 to 270±25 and 0.006±0.002 to 0.002±0.001 at 100 kHz, respectively, depending on the firing temperature. For Ag₂(Ta_0.5Nb_0.5)₄O₁₁, Ag_0.8(Ta_0.5Nb_0.5)O_2.9, Ag_0.85(Ta_0.5Nb_0.5)O_2.925 and Ag_0.9(Ta_0.5Nb_0.5)O_2.95 films, mainly the natrotantite phase was observed. The ɛ _r values of these films were between 70±10 and 130±15 with tan δ values of 0.008±0.002 at 100 kHz.     

MgO/Al2O3吸附剂对CO2动态吸附性能的研究

以γ- Al₂O₃为载体,采用等体积浸渍法制取MgO/Al₂O₃吸附剂,利用BET、XRD等表征手段对吸附剂进行表征;并通过固定床测量穿透曲线的方法研究其对CO2动态吸附性能的影响,考察了MgO负载量、吸附温度、气体流量等因素对吸附剂吸附CO₂性能的影响,同时还通过多次吸脱附实验考察MgO/Al₂O₃吸附剂的稳定性和再生能力。结果表明,MgO负载量为10%的吸附剂,吸附温度在50℃左右,流量为45mL/min动态吸附量最大;经数次循环后材料的结构性质和吸附性能未见明显变化,可再生性能比较优异,是一种潜在的可工业化应用的CO₂吸附剂。     

Influence of MgO in the CO2 – steam reforming of methane to syngas by NiO/MgO/ α-Al2O3 catalyst

Simultaneous steam and CO₂ reforming of methane to syngas (H₂and CO) over NiO/MgO/a-Al₂O₃ catalyst have been investigated at different MgO wt.%. The catalyst has been characterized by temperature-programmed reduction and XRD techniques. Addition of MgO reduced the carbon deposition and energy consumption. The stability and less coking on MgO-promoted catalysts are attributed to the lewis basicity of MgO.     

Ferroelectric perovskite-type barium copper niobate: BaCu1/3Nb2/3O3

A perovskite-type BaCu_1/3Nb_2/3O₃ was prepared by high temperature reaction using BaCO₃, CuO and Nb₂O₅. The X-ray powder diffraction pattern of this compound was indexed with the tetragonal cell with the lattice parameters of a=4.0464(4) and c=4.1807(4) Å (c/a=1.033). This compound had the tetragonal perovskite-type structure in which the B site was occupied statistically by Nb and Cu atoms. From high temperature X-ray powder diffraction patterns this compound had a phase transition from the tetragonal to cubic symmetry in the temperature range of 500-600 °C. The P-E and S-E hysteresis loops occurred at room temperature and the apparent maximum in the temperature dependence of the dielectric constant was observed at 520 °C. The temperature dependence of the inverse of magnetic susceptibility exhibited paramagnetic behavior.     

Study of the acid-base properties of Ga2O3/Al2O3 by using test reactions

Two test reactions: conversions of propan-2-ol and 2-methyl-3-butyn-2-ol were applied for the investigation of the acid-base properties of Ga₂O₃-Al₂O₃ materials. Both test reactions lead to consistent conclusions on the overall acid-base properties of the materials studied. It has been found that the deposition of gallium oxide on the surface of γ-Al₂O₃ enhances the overall basicity.     

H2O + Fe(NO3)3 + Ni(NO3)2 ternary system isotherms at 0 °C and 30 °C

H₂O + Ni(NO₃)₂ binary system were investigated in the temperature range from −25 °C to 55 °C. The solid-liquid equilibria of the ternary system H₂O + Fe(NO₃)₃ + Ni(NO₃)₂ were studied using a synthetic method based on conductivity measurements. Tow isotherms were established at 0 °C and 30 °C, and the appearing stable solid phases are iron nitrate nonahydrate (Fe(NO₃)₃·9H₂O), iron nitrate hexahydrate (Fe(NO₃)₃·6H₂O), nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) and nickel nitrate tetrahydrate (Ni(NO₃)₂·4H₂O).     

Preparation and characterization of MgO/Al2O3 mixed oxides support for hydrotreating catalysts

The characteristics of pure MgO, Al₂O₃ and three binary mixtures of MgO-Al₂O₃ were studied by determining their BET surface areas, micropore surface area, total pore volume, adsorption-desorption isotherms, the x-ray diffractogram, surface acidity and catalytic functionality for cumene cracking.The XRD results show that the incorporation of alumina into the magnesia beyond 50% renders it amorphous. Furthermore, the mixed oxide containing 50% magnesia and 50% alumina had the highest BET surface area of 200 m²/g and is the only mixed oxide with bimodal pores.The results of the acidity measurements and cumene cracking functionality indicates that strong acid sites are found only in mixed oxides containing more than 50% alumina.     

Enthalpy of mixing in 0.8[xB2O3-(1 − x)P2O5]-0.2Na2O glasses at 298 K

0.8[xB₂O₃-(1 − x)P₂O₅]-0.2Na₂O (with 0 ≤ x ≤ 1) glasses have been characterized by solution calorimetry at 298 K in acid solvent. The experimental data showed a strong negative departure of the enthalpy of mixing from the ideality described by the equation (in kJ/mol): ΔH = x(1 − x)(−660.2 + 570x). The results were interpreted on the basis of the structural data. Enthalpies of mixing were consistent with sub-regular solution behaviour.     

Phase and structural characterization of Sr2Nb2O7 and SrNbO3 thin films grown via pulsed laser ablation in O2 or N2 atmospheres

The influence of substrate temperature, process gas, deposition pressure, and substrate type on the phase selection, orientation/epitaxy, and growth morphology of thin films in the SrNbO_y (y≈3.0 or 3.5) family was investigated. Pulsed laser deposited films (from a Sr₂Nb₂O₇ target) obtained in both oxygen and nitrogen atmospheres upon various substrates were characterized with X-ray diffraction, energy dispersive spectroscopy, atomic force microscopy, and transmission electron microscopy. In oxygen atmospheres, films adopted the (110)-layered perovskite structure of the target. Higher temperatures, lower pressures of oxygen, and use of (110)-oriented SrTiO₃ substrates lead to highly crystalline, epitaxial films of Sr₂Nb₂O₇. The use of nitrogen atmospheres resulted in cubic perovskite SrNbO₃ formation: epitaxial, textured, or polycrystalline films were obtained depending on the substrate; no nitrogen incorporation could be observed on the anion sublattice. On SrTiO₃, the cubic perovskite films followed a cube-on-cube epitaxy and planar defects were observed to occur on the (110) perovskite planes.     

Y2O3:Eu (5 mol%) with Ag nanoparticles prepared by citrate precursor

Y₂O₃:Eu³⁺ (5 mol% Eu³⁺) and Y₂O₃:Eu³⁺ (5 mol% Eu³⁺) containing 1 mol% of Ag nanoparticles were prepared by heat treatment of a viscous resin obtained via citrate precursor. TEM and EDS analyses showed that Y₂O₃:Eu³⁺ (5 mol% Eu³⁺) is formed by nanoparticles with an average size of 12 nm, which increases to 30 nm when Ag is present because the effect of metal induced crystallization occurs. Ag nanoparticles with a size of 9 nm dispersed in Y₂O₃:Eu³⁺ (5 mol% Eu³⁺) were obtained and the surface plasmon effect on Ag nanoparticles was observed. The emission around 612 nm assigned to the Eu³⁺ (⁵D₀→⁷F₂) transition enhanced when the Ag nanoparticles were present in the Y₂O₃:Eu³⁺ luminescent material.     

Alkaline earth metal poly(hydrogen fluorides) hexafluoroarsenates(V) and hexafluorophosphate(V): M2(H2F3)(HF2)2(AF6) (M = Ca, A = As; M = Sr, A = As, P)

New compounds of the type M₂(H₂F₃)(HF₂)₂(AF₆) with M = Ca, A = As and M = Sr, A = As, P) were isolated. Ca₂(H₂F₃)(HF₂)₂(AsF₆) was prepared from Ca(AsF₆)₂ with repeated additions of neutral anhydrous hydrogen fluoride (aHF). It crystallizes in a space group P4₃22 with a = 714.67(10) pm, c = 1754.8(3) pm, V = 0.8963(2) nm³ and Z = 4. Sr₂(H₂F₃)(HF₂)₂(AsF₆) was prepared at room temperature by dissolving SrF₂ in aHF acidified with AsF₅ in mole ratio SrF₂:AsF₅ = 2:1. It crystallizes in a space group P4₃22 with a = 746.00(12) pm, c = 1805.1(5) pm, V = 1.0046(4) nm³ and Z = 4. Sr₂(H₂F₃)(HF₂)₂(PF₆) was prepared from Sr(XeF₂)_n(PF₆)₂ in neutral aHF. It crystallizes in a space group P4₁22 with a = 737.0(3) pm, c = 1793.7(14) pm, V = 0.9744(9) nm³ and Z = 4. The compounds M₂(H₂F₃)(HF₂)₂(AF₆) gradually lose HF at room temperature in a dynamic vacuum or during being powdered for recording IR spectra or X-ray powder ray diffraction patterns. All compounds are isotypical with coordination of nine fluorine atoms around a metal center forming a distorted Archimedian antiprism with one face capped. This is the first example of the compounds in which H₂F₃⁻ and HF₂⁻ anions simultaneously bridge metal centers forming close packed three-dimensional network of polymeric compounds with low solubility in aHF. The HF₂⁻ anions are asymmetric with usual F?F distances of 227.3-228.5 pm. Vibrational frequency (ν₁) of HF₂⁻ is close to that in NaHF₂. The anion H₂F₃⁻ exhibits unusually small F?F?F angle of 95.1°-97.6° most probably as a consequence of close packed structure.     

Preparation, crystal structures, EPR and reflectance spectra of two new charge-transfer salts, [CpFeCpCH2N(CH3)3]4[XMo12O40] · nCH3CN (n = 0 for X = P or n = 1 for X = Ge)

Two new charge-transfer salts, [CpFeCpCH₂N(CH₃)₃]₄[PMo₁₂O₄₀] · CH₃CN (1) and [CpFeCpCH₂N(CH₃)₃]₄[GeMo₁₂O₄₀] (2), were synthesized by the traditional solution synthetic method and their structures were determined by single-crystal X-ray analysis. Salt 1 belongs to the triclinic space group P1, and salt 2 belongs to the triclinic space group . There exist the complex interactions of the cationic ferrocenyl donor and Keggin polyanion in the solid state. The solid state UV-Vis diffuse reflectance spectra indicate the presence of a charge-transfer band climbing from 450 nm to well beyond 900 nm for 1, a charge-transfer band from 460 to 850 nm with λ_max = 630 nm for 2.The EPR spectra of salts 1 and 2 at 77 K show a signal at g = 2.0048 and 1.9501, respectively, ascribed to the delocalization of one electron in reduced Keggin ion in salt 1 and the Mo^VI in [GeMo₁₂O₄₀]⁴⁻ is partly reduced to Mo^V owing to the charge-transfer transitions taking place between the ferrocenyl donors and the POM acceptors. The two compounds were also characterized by IR spectroscopy and cyclic voltammetry.     

Study of oxygen adsorption on β-Si3N4(0 0 0 1) by the density functional theory

The density functional theory (DFT) B3LYP method is used to theoretically investigate the interaction of O₂ with the β-Si₃N₄ surface (0 0 0 1) at 1200 °C. All the calculations have been performed at the 6-31G^∗ basis set level using H-saturated cluster. From the total energy minimization, the chemisorption on the center of the molecule lying above an Si site and the molecular axis paralleling to the surface is the most stable. After adsorption, the O–O bond is easier to dissociate compared to the free O₂. The electron transferred from the substrate to the O₂ molecule occupies the O₂ anti-bonding orbital, thus leading to a weakening off the bond strength, which is reflected by the elongated O₂ bond length. The changing trend of the O–O population and vibrational frequency is consistent with the change of the O–O bond length. The significant chemisorption energy and the short adsorption bond length indicate that the oxidation occurs on the β-Si₃N₄(0 0 0 1) surface at 1200 °C more easily.     

铂沉积对Ga2O3-SiO2纳米粒子光催化性能的提高（英文）

Ga2O3‐SiO2 nanoparticles were prepared by a sol‐gel method and Pt was then immobilized on their surface via photo‐assisted deposition (PAD). The produced samples were characterized using X‐ray diffraction (XRD), ultraviolet and visible spectroscopy, photoluminescence emission spectroscopy, and surface area measurements. The catalytic performances of the Ga2O3‐SiO2 and Pt/ Ga2O3‐SiO2 samples were evaluated for the degradation of cyanide using visible light. XRD and EDX results showed that the Pt was well dispersed within the Ga2O3‐SiO2 phase and was detected on the surface of the catalyst, which confirmed the successful loading of Pt ions by the PAD method. BET results revealed that the surface area of Ga2O3‐SiO2 was higher than that of Pt/Ga2O3‐SiO2 . 0.3 wt% Pt/Ga2O3‐SiO2 exhibited the highest photocatalytic activity for degradation of cyanide under visible light. The catalyst could be reused with no loss in activity for the first 10 cycles.     

CO oxidation over Au/Al2O3catalysts modified by MgO

Summary Au/Al₂O₃catalysts modified by MgO were tested in CO oxidation using temperature programmed technique. Contrary to Au/Al₂O₃the modified Au/MgO-Al₂O₃catalysts showed high activity in the sub-ambient and ambient temperature ranges.     

Preparation, morphology and properties of nano-sized Al2O3/polyimide hybrid films

Nano-sized Al₂O₃/polyimide (PI) hybrid films based on 4,4′-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) were prepared by incorporation with different content of nano-sized Al₂O₃ via in situ polymerization. The TEM and SEM micrographs indicated that the Al₂O₃ particles were homogenously dispersed in the polyimide matrix by means of the ultrasonic treatment and the addition of coupling agent. The mechanical properties and thermal stability of the pure PI film can be improved by adequate addition of Al₂O₃. The PI hybrid film was strengthened and toughened simultaneously by the introduction of the well-dispersed Al₂O₃ particles. The PI hybrid films showed improved electrical aging performance as compared with pure PI film. Especially, the PI hybrid films with 10 wt.% of Al₂O₃ content exhibited obviously enhanced electrical aging performance with the time to failure of 3.4 times longer than that of pure PI film. The improved electrical aging performance of the hybrid film was attributed to the nano-sized Al₂O₃ particles highly dispersed in the hybrid film, which confirmed by the investigation of the morphology and the surface composition of PI hybrid film before and after electrical aging.     

Enthalpy of mixing in 0.8[xB2O3-(1 − x)SiO2]-0.2K2O melts at 973 K

0.8[xB₂O₃-(1 − x)SiO₂]-0.2K₂O (with 0 ≤ x ≤ 1) glasses were synthesized by melt quenching techniques. DSC curves of the glasses exhibit only one glass transition. Calorimetric measurements of heats of dissolution in lead borate at 973 K indicated small negative enthalpies of mixing. Consequently phase separation was not observed over the whole composition range. The results are in good agreement with the structural data available in the literature.     

Thermodynamic properties on quaternary aqueous solutions of chlorides charge-type 1-1*2-1*2-1: XCl + MgCl2 + CaCl2 + H2O with (X ≡ Na; NH4)

In this investigation, the quaternary aqueous solutions of chlorides charge-type 1-1*2-1*2-1 with a cation (Na⁺; NH₄⁺; Mg²⁺; Ca²⁺) have been studied using the hygrometric method at 298.15 K. The water activities of the systems NH₄Cl + MgCl₂ + CaCl₂ + H₂O and NaCl + MgCl₂ + CaCl₂ + H₂O are measured at total molalities from 0.60 mol kg⁻¹ to saturation for different ionic-strength fractions NH₄Cl or NaCl, y = 0.20, 0.50, 0.80, and z ratio ionic-strength for other solutes, with z = 0.20, 0.50 and 0.80 for each y. The obtained data allow the deduction of osmotic coefficients.