不同金属氧化物在原位生成技术改性HNBR中的作用研究

分别采用氧化镁(MgO)、氧化钙(CaO)、氧化锌(ZnO)与丙烯酸(AA)原位生成丙烯酸盐改性氢化丁腈橡胶(HNBR),研究不同金属氧化物对原位生成技术改性HNBR的影响.采用傅里叶红外光谱分析3种原位生成不同丙烯酸盐改性HNBR的结构;采用扫描电子显微镜观测丙烯酸盐在HNBR中的分布;并采用平衡溶胀法表征了未改性H...     

Morphology control of titanium oxides by tetramethylammonium cations in hydrothermal conditions

The effect of tetramethylammonium cations (TMA⁺) on TiO₂ crystal morphology in hydrothermal conditions has been studied. The as-synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) methods. The morphologies including besom-like particle, nanosheet and nanotube have been observed. The different ways TMA⁺ cations in the hydrothermal bases affect the crystal growth manner are suggested to be responsible for the different morphologies of the as-synthesized samples.     

Investigation of transition metal oxides by ultrasonic microscopy

Ultrasonic microscopy is now well established in non-destructive testing and has become a versatile method for investigating solid materials. It may serve both as imaging technique for large scale inspection of sample homogeneity and also as measuring device for a local determination of elastic properties. Our investigations of single crystalline vanadium dioxide nicely demonstrate this capability of flexible use and are exemplary for the beneficial effect of ultrasonic microscopy on materials research, in general. Here we focus on three different subjects: the detection of odd phases in as-grown single crystals, the inspection of structural transformations accompanying the metal–insulator transition and the investigation of elastic properties performed on small crystallites.     

Abiotic oxidation of catechol by soil metal oxides

The mechanism of catechol oxidation by soil metal oxides is investigated in a slurry reactor. This abiotic transformation is shown to consist in a three-step process. The first step is a heterogeneous reaction. Catechol undergoes fast, partial oxidation at the expenses of Fe and Mn oxides contained in the soil. In the second step, reduced Fe and Mn are released into the aqueous solution and immediately complexed by catechol. Metal-catecholate complexes are stable at the very low dissolved-oxygen concentration levels attained under nitrogen sparging. The third step is a homogenous reaction. The highly reactive intermediate produced by catechol partial oxidation initiates catechol polymerisation. Under nitrogen sparging, the polymerisation process ends rather rapidly, thus yielding only partial conversion of the phenol and producing low-molecular weight, water-soluble polymers. Further oxidation of the metal-catecholate complexes formed in the second step only occurs under air sparging. Thus, reactive intermediates are formed at much higher concentration levels than those attained when nearly no oxygen is present in solution. The polymerisation proceeds at a much faster rate until, under the experimental conditions adopted, complete catechol conversion is attained and high-molecular-weight, insoluble polymers are produced.     

Dichloromethane treatment by mesoporous metal catalysts

Dichloromethane (DCM) is one of the most commonly used solvents in industry. DCM easily accumulates and breaks down slowly; it is recognized as being carcinogenic. This research uses the sol-gel method to synthesize Mesoporous Mobil Catalytic Material Number 41 (MCM-41), Fe-MCM-41 and Pt-MCM-41 catalysts, and discusses the effectiveness of using these self-made catalysts to treat DCM. The qualities of each catalyst are identified using XRPD, BET, and SEM–EDS characteristic analyses. These results are then analyzed using the reaction kinetics theory. Results show that removal efficiency increases with the increase in temperature and concentration, and decreases with the increase in reaction chamber flow rates. Adsorption of DCM using mesoporous metal catalysts conforms to the Langmuir isotherm adsorption model. It was found that the best correlation results were observed for a Pt-MCM-41 catalyst.     

Strain effects in low-dimensional transition metal oxides

Transition metal oxides offer a wide spectrum of properties which provide the foundation for a broad range of potential applications. Many of these properties originate from intrinsic coupling between lattice deformation and nanoscale electronic and magnetic ordering. Lattice strain thus has a profound influence on the electrical, optical, and magnetic properties of these materials. Recent advances in materials processing have led to the synthesis of low-dimensional single-crystal transition metal oxides, namely, epitaxial ultra-thin films and free-standing nano/microwires. Unlike bulk materials, these systems allow external tuning of uniform strain in these materials to tailor their properties and functionalities.This paper provides a comprehensive review of recent developments in studies of strain effects in transition metal oxide ultra-thin films and nano/microwires. In epitaxial thin films, biaxial strain is developed as a result of lattice mismatch between the film and the substrate. By choosing different substrates, a wide range of strain can be established at discrete values that allows for exploration of new phase space, enhancement of order parameters, creation of complicated domain textures, and stabilization of new phases. On the other hand, continuous tuning of uniaxial strain is possible in nano/microwires, where a variety of phase transitions and their dynamics could be probed at the single or few-domain scale. We focus on the work of strain-controlled electromechanical response in piezoelectric oxides and strain-induced metal–insulator transitions as well as domain physics in strongly correlated electron oxides. Related nanoscale device applications such as strain sensing and power generation will be highlighted as well.     

Passivation of pyrite oxidation with metal cations

Under the influence of anodic potentials greater than 0.5V against SCE (saturated calomel electrode), pyrite slurried in acidic electrolytes is oxidized to water soluble ferric and sulphate ions. Experiments were conducted in a stirred Pyrex reactor provided with three electrodes, the anode being a platinum mesh. The rate of reaction of pyrite corrosion was observed to increase with electrolysis time. The autocatalytic reaction is brought about by the ferric ions produced during the course of the reaction. The rates of reaction, however, can be depressed by adding small quantities of copper and silver ions (both of these have lower redox potentials than that of the Fe²⁺/Fe^3– couple) to the electrolyte. It is suggested that addition of these cations results in the formation of an electrochemically inactive sulphur layer on the surface of pyrite particles.[/p]     

Electrical conductivity of platinum metal — nonplatium metal double oxides

The authors have determined an electrical conductivity type for 145 platinum metal-nonplatinum metal double oxides such as Ln₂M₂O₇ pyrochlores, AMO₃ perovskites, ARh₂O₄ spinels, Rh MO₄ rutiles, M_xPd₃O₄ and M_xPt₃O₄ bronzes, etc. It was shown that conductivity type is a certain function of the d-electron configuration of platinum metal ion in the double oxide, namely the double oxide with d⁴ or d⁵ electron configuration for platinum metal ion exhibits metallic conductivity while the oxide with d⁶ or d⁸ electron configuration for the ion is a semiconductor.     

Room temperature synthesis of crystalline metal oxides

Crystalline titanium dioxide powders have been synthesized as either rutile or anatase from aqueous solutions at low temperatures (T≤100°C) and atmospheric pressure. First, a sol is prepared by the hydrolysis of a titanium alkoxide in an acidic solution. The sol is subsequently heated at different rates to produce the different crystalline phases of titanium dioxide. Powder characterization was carried out using X-ray diffraction, scanning electron microscopy and high resolution transmission electron microscopy. In general, the precipitate size was observed to be between 50 and 100 nm. Possible mechanisms involved in determining the crystal variants are discussed. This revised version was published online in November 2006 with corrections to the Cover Date.     

Interaction of poly-N-vinylpyrrolidone with hydrated metal oxides

On the basis of data of IR spectroscopy and powder diffraction analysis, an aqueous solution of poly-N-vinylpyrrolidone was shown to interact with hydrated alumina and zirconia synthesized from corresponding metal chlorides by means of sol-gel technology. A change was shown in the nature of polymer interaction with individual components and their binary mixture at different annealing temperatures. Different mechanisms of formation of intermediate substances in the synthesis of alumina and zirconia from hydrosols in the presence of a water-soluble polymer were assumed with respect to the nature of synthesized sols. The phase composition of oxides in the course of crystallization is affected by poly-N-vinylpyrrolidone and its hydrolysis products formed by electrochemical synthesis of metal oxide hydrosols.     

Low-frequency kinetics of high-T c metal oxides

A microscopic explanation of the low-frequency kinetic properties of metal oxides is proposed. It is based on a strong electron-phonon interaction, which forms a charged Bose liquid of small bipolarons. The large value, the nonKorringa temperature dependence above T _c, and the absence below T _c of the coherent peak of the nuclear spin relaxation, as well as an unexpected coherent peak of the low frequency dynamic conductivity and the linear T-dependence of the resistivity are explained.     

On the stereochemistry of cations in the doping block of superconducting copper oxides

Metal-oxygen complexes containing Cu, Tl, Hg, Bi, and Pb cations are electronically active in superconducting copper oxides by stabilizing single phases with enhancedT _c, whereas other metal-oxygen complexes deteriorate copper oxide superconductivity. Cu. Tl, Hg, Bi, and Pb in their actual oxidation states are closed-shelld ¹⁰ or inerts ² pair ions. Their electronic configurations have a strong tendency to polarize the oxygen environment. The closed shelld ions with low-lyingnd ¹⁰nd ⁹(n+1)s excitations form linear complexes through hybridization polarizing the apical oxygens. Comparatively lownd ⁹(n+1)s excitation energies distinguish Cu^1+,3+, Tl³⁺, Hg²⁺, from other closed-shelld ¹⁰ ions deteriorating copper oxide superconductivity, e.g., Zn²⁺.     

选择表面工艺改性的CIPs涂层及其氧化物的吸波性能

针对吸波涂层氧化腐蚀现象,提出一种基于选择表面的周期结构涂层维修工艺。利用腐蚀法,在以羰基铁粉(CIPs)为吸收剂的吸波涂层表面制备CIPs及其氧化物涂层。用扫描电子显微镜(SEM)对腐蚀后颗粒的形貌进行了分析。测试了8~18GHz下混合颗粒的复介电常数和复磁导率,并用等效介质理论计算氧化涂层的参数。分析腐蚀和维修工艺对反射损耗(RL)的影响。结果表明:当CIPs涂层表面被氧化时,随着氧化涂层厚度的增加,涂层的吸波性能减弱,反射损耗增量值约为2dB。当涂层厚度为0.8mm时,维修效果不理想,若涂层厚度增加至1mm,且氧化涂层厚度为0.1mm时,维修效果较好,体现为10~18GHz频率范围内的吸波带宽增加,反射损耗相应减小约为2dB。