共查询到20条相似文献,搜索用时 31 毫秒
1.
《Materials Chemistry and Physics》1987,16(1):67-77
The acid-base and oxidizing properties and the structures of ZrOn prepared with ammonia or urea and ZrO2 treated with sulfuric acid or ammonium sulfate have been investigated. The treatment of ZrO2 with so42− caused the remarkable increases in the phase transition temperature to monoclinic form, the surface area and the acid strength and the appearance of the oxidizing property. The acid strength was higher for ZrO2 treated with H2SO4 than for ZrO2 treated with (NH4)2SO4, though the surface area was the reverse. The difference between ammonia and urea as precipitating reagents caused no difference in crystallography and acid strength, but the surface areas of ZrO2-A and ZrO2-A-H2SO4 prepared with ammonia were higher than those of ZrO2-U and ZrO2-U-H2SO4 prepared with urea, respectively. 相似文献
2.
Cu2O·TeO2 and CuI·Cu2O·TeO2 glasses were synthesized and characterized by complex impedance measurement, Raman spectroscopy, X-ray photoelectron spectroscopy, and atomic force microscopy techniques. Samples of the binary and the ternary systems are found to have both Cu+ and Cu2+ with their relative concentration being composition dependent. Bonds like -O-Cu2+-O-, leading to the formation of bridging oxygen are found to form in the binary system. Structural units like (Te3O8
4–)n are also found to form when Cu2O content is high in the binary system. Phase separation is observed in the ternary system. The glass structure and hence the ionic conduction behavior are found to depend upon chemical composition. When CuI content exceeds 60 mol%, the crystalline phase of -Cul gets stabilized at room temperature, thus causing the enhancement in conductivity. 相似文献
3.
Uranosilicates of the general formula MI
I[HSiUO6]2·2H2O (MI
I = Sr, Ba) were prepared by hydrothermal synthesis. Previously unknown intermediate crystal hydrates were separated and studied by X-ray diffraction (XRD), IR spectroscopy, and thermal analysis. Polymorphic transitions -Sr[HSiUO6]2 -Sr[HSiUO6]2 and -Ba[HSiUO6]2 -Ba[HSiUO6]2 were revealed at 700 and 780°C, respectively. 相似文献
4.
Journal of Superconductivity and Novel Magnetism - We have investigated the electrical and magnetic properties of the compounds LaPt2As, LaPt2As2, and BaPt2As2 prepared by conventional solid-state... 相似文献
5.
Guangsi GUO Guangtai WANG Zhitong SUI)Department of Materials Science Engineering Shenyang Institute of Technology Shenyang China)School of Materials Metallurgy Northeastern University Shenyang China 《材料科学技术学报》2004,20(1):68-70
The pure intermetallic compounds (Tb1-x;Dyx)Fe2 are super-magnetostriction materials, which were produced from DyFe2 and TbFe2 in this paper. The thermodynamic possibility and kinetic feasible conditions for DyFe2 and TbFe2 preparation by reduction-diffusion in Ca-Dy2O3-Fe and Ca-Tb4O7-Fe systems were analyzed and the products of DyFe2 and TbFe2 were confirmed by XRD. The contracting core model was applied to describe the reduction-diffusion process in which the diffusion is a rate-controlled step. The apparent activation energies of DyFe2 and TbFe2 processes are 45 and 39 kJ/mol respectively. 相似文献
6.
Titanium dioxide nanostructures have been synthesised by annealing the Pd loaded titanium foil at 680°C under the atmosphere of Ar or Ar–H2 gas mixture. The microstructure and production of titanium dioxide are found to depend critically on the concentration of Pd catalyst and the Ar–H2 atmosphere. The catalyst of Pd and the introduction of 5%H2 gas are the key factor for the formation of the long (about 100?μm in the average) and smooth titanium dioxide nanowires at low temperature. Scanning electron microscope and X-ray diffraction show that they are all rutile phase. The further result shows that the titanium dioxide nanowires possess good crystallinity and high surface photovoltage response. 相似文献
7.
E. Yu. Peresh O. V. Zubaka S. V. Kun I. V. Galagovets I. E. Barchii M. Yu. Sabov 《Inorganic Materials》2001,37(8):849-852
The composition stability limits of the compounds Tl2TeBr6, Cs2TeBr6, and Rb2TeBr6were determined from differential thermal analysis, microstructural, and microhardness data. The congruently melting composition was found to differ from the stoichiometric composition for Tl2TeBr6and Cs2TeBr6and to coincide with it for Rb2TeBr6. Single crystals of the compounds studied were prepared using growth charges with the congruently melting compositions, and their properties were investigated. 相似文献
8.
M.B. Gaifullin Yuji Matsuda N. Chikumoto J. Shimoyama K. Kishio R. Yoshizaki 《Journal of Low Temperature Physics》1999,117(5-6):1229-1233
Josephson plasma resonance for underdoped Bi
2
Sr
2
CaCu
2
O
8+
and Bi
2
Sr
2
CuO
6+
have been measured by sweeping the microwave, frequency continuously. The resonance enables us to determine the superfluid density and quasiparticle conductivity in the c-axis accurately. We show that the. superfluid response and the low energy excitations out of the condensate in the c-axis of these materials are very different from those in the ordinary Josephson multilayer tunnel junctions. The Josephson coupling energy in single layer Bi
2
Sr
2
CuO
6+
is more than 5000 times smaller than is predicted in interlayer tunneling model. 相似文献
9.
Chemically prepared electrolytic γ-MnO2 and an electrodeposited MnO2 doped with Ce(III)were subjected to physicochemical studies. X-ray diffractometry, density measurements, chemical analysis and thermal analysis were used to determine the structure and chemical disorder present.The samples prepared chemically(CMD) or electrochemically (EMD) showed a variable amount of de Wolff disorder(Pr) and microtwinning (Tw). Manganese dioxide prepared in the presence of Ce(III) showed appreciable decrease in de Wolff defect and a large amount of microtwinning. Thermal analysis showed a loss of weight due to the physically adsorbed and the structural(OH)water, from which the activation energy was calculated. Chemical composition and formulae calculated on the bases of cation vacancy model, cleared that Ce(III)-doped sample has a remarkable increase in the vacancies population associated with higher structural water content. This leads to lower activation energy of water release, and consequently it is supposed to acquire higher electrochemical activity. 相似文献
10.
J. Wei Q.Z. Chen M.M. Stevens J.A. Roether A.R. Boccaccini 《Materials science & engineering. C, Materials for biological applications》2008,28(1):1-10
Biocompatibility and bioactivity of polymer matrix composites containing titanium dioxide (TiO2) nanoparticles were investigated. The solvent casting method was used to prepare poly (d,l-lactic acid) (PDLLA) films with 0 and 20 wt.% TiO2 nanoparticles and with 20 wt.% TiO2 mixed with 5 wt.% micrometre-sized (< 5 μm) Bioglass® particles. The samples were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy Dispersive X-ray (EDX) analyses. A Zygo® light interferometer was used to examine the surface roughness of the samples. The bioactivity and the surface reactivity of the materials were determined by investigating the formation of hydroxyapatite (HA) on the surface of samples upon immersion in simulated body fluid (SBF) for up to 28 days. Heterogeneous distributed HA crystals were found on composite films containing TiO2 after 21 days exposure to SBF. Cell cytotoxicity and viability were determined by using live/dead and MTS assay on osteoblast-like MG-63 cells. The PDLLA films containing different concentrations of TiO2 and Bioglass® particulate inclusions showed no effect on cell viability in live/dead assay after incubation period of 7 days. All three groups of samples demonstrated significant increase in relative metabolic activity in MTS assay after 7 days incubation (while a slower proliferation rate was obtained for cells on the PDLLA film containing both TiO2 and Bioglass® compared to the Thermanox® control). The bioactive behaviour of the nanocomposites may make them attractive materials for fabrication of tissue engineering scaffolds. 相似文献
11.
Preparation and Properties of Nano-TiO_2 Powders 总被引:1,自引:0,他引:1
This paper reports the preparation of nano-TiO2 (about 10 nm) powder by the method of precipitation. In detail, some breparation conditions were investigated in order to find out how to control the grain size and reduce the agglomeration of powders. Also, the reflex spectra of nano-scale powders with different grain size were studied. It tvas found that the wave length and width of reflex spectra are connected with the grain size of nano-TiO2 powders 相似文献
12.
The 2 × 2 matrix formalism proposed by Bovard is extended to absorbing inhomogeneous thin films for propagating the electromagnetic field. The contribution of each order into multiple reflections inside the film is analyzed. 相似文献
13.
ZrO2–SiO2 composite powder has been prepared by a wet chemical route using zirconyl chloride and fumed silica as starting materials and subsequently sintered by the hot-pressing method to obtain a ZrO2–SiO2 ceramic. The mechanical properties of the silica matrix have been much increased by the addition of 20 vol% zirconia. The microstructural features of the composite are observed by transmission electron microscopy (TEM) and high-resolution electron microscopy (HREM). The stabilibity of tetragonal zirconia in the matrix is attributed to the particle-size effect, and to the constraint effect of the silica matrix and that of the interphasic reaction layer. The increase in mechanical properties is discussed in relation to the residual stress and the enhanced elastic modulus caused by the incorporated ZrO2 particles. 相似文献
14.
15.
Xiaowei Mu Hui Pan Ping He Haoshen Zhou 《Advanced materials (Deerfield Beach, Fla.)》2020,32(27):1903790
Metal–CO2 batteries, especially Li–CO2 and Na–CO2 batteries, offer a novel and attractive strategy for CO2 capture as well as energy conversion and storage with high specific energy densities. However, some scientific issues and challenges existing restrict their practical applications. Here, recent progress of crucial reaction mechanisms on cathodes in Li–CO2 and Na–CO2 batteries are summarized. The detailed reaction pathways can be modified by operation conditions, electrolyte compositions, and catalysts. Besides, specific discussions from aspects of catalyst design, stability of electrolytes, and anode protection are presented. Perspectives of several innovative directions are also put forward. This review provides an intensive understanding of Li–CO2 and Na–CO2 batteries and gives a useful guideline for the practical development of metal–CO2 batteries and even metal–air batteries. 相似文献
16.
Motoki Shimada Hisashi Tamaki Eiji Higuchi Hiroshi Inoue 《Journal of Materials Science》2013,48(20):7312-7319
To improve kinetics for hydrogen absorption of Mg and hydrogen desorption of MgH2, ternary composites were prepared from MgH2, Ni and Si or Ni2Si by a mechanochemical technique. The X-ray diffraction spectra of the resultant ternary composites after the initial hydrogen desorption treatment at 400 °C in vacuum suggested that in all composites the nanocrystalline Mg2Ni would be formed in the intergrain region between Mg and Ni components, while in the MgH2–Ni–Si composite the nanocrystalline Mg2Si would also be formed in the intergrain region between Mg and Si components. However, Ni2Si did not form any alloys with Mg. The hydrogen absorption rate at 250 °C for the MgH2–Ni–Ni2Si composite was comparable to that for the MgH2–Ni and MgH2–Ni–Si composites, while the hydrogen desorption rate at 250 °C decreased in the order of MgH2–Ni > MgH2–Ni–Ni2Si > MgH2–Ni–Si. In contrast, the hydrogen desorption rate at 220 °C for the MgH2–Ni–Ni2Si composite was faster than that for the MgH2–Ni composite, suggesting that Ni2Si was a key material in the improvement of hydrogen desorbability at lower temperatures. Moreover, the most plausible reaction model and the rate-determining process for hydrogen absorption and desorption at 250 °C were determined. 相似文献
17.
We determine the scattering rate from microwave measurements for an optimally doped Bi-2212 single crystal, using a simple two-fluid model with a d-wave symmetry order parameter. In the superconducting state, the calculated scattering rate is three orders of magnitude smaller than that determined from ARPES experiments. A similar anomalously large decrease in the scattering rate is also required to explain the data within a gap-quasiparticle scenario for other HTS, such as YBa2Cu3O7–. The results suggest that the assumption of normal excitations vanishing at low T is invalid and an additional charge mode is responsible for the microwave absorption. 相似文献
18.
The oxidation state of the Mn activator in 2MgO · GeO2, 2MgO · GeO2 · MgF2 was shown to be 4+. The observed luminescence behavior of these phosphors was accounted for by a large crystal-field splitting.
The2T1 and2E excited states of Mn4+ were found to be close in lifetime (100-120 ώs). The slower luminescence decay in magnesium fluorogermanate is attributable
to the energy transfer between the activator and electron traps through the conduction band. 相似文献
19.
E. P. Zaretskaya I. A. Victorov V. F. Gremenok A. V. Mudryi 《Technical Physics Letters》2001,27(1):49-51
Single-phase films of CuInS2x Se2(1−x) solid solutions with a chalcopyrite structure were deposited by laser evaporation of CuInS2x Se2(1−x) crystal targets (0≤x≤1). The structural and optical characteristics of the films depend on the chalcogen concentrations. 相似文献
20.
Nakamori Ryogo Kawano Naoki Nakauchi Daisuke Kato Takumi Fukushima Hiroyuki Takebuchi Yuma Shinozaki Kenji Yanagida Takayuki 《Journal of Materials Science: Materials in Electronics》2022,33(26):20470-20478
Journal of Materials Science: Materials in Electronics - 1Eu2O3–3BaO–20Nb2O5–76TeO2 glass and the corresponding glass-ceramics were synthesized with the aim to investigate the... 相似文献