Calcium carbonate particles with different morphologies were fabricated by the precipitation reaction of sodium carbonate with calcium chloride in the absence and presence of the copolymer poly (styrene-alt-maleic aci...
详细信息
Calcium carbonate particles with different morphologies were fabricated by the precipitation reaction of sodium carbonate with calcium chloride in the absence and presence of the copolymer poly (styrene-alt-maleic acid) (PSMA) at 80°C, respectively. The as-prepared products were characterized with SEM, XRD, Infrared and BET surface areas. The results showed that the pH of solution and the concentration of PSMA and CaCO3 significantly influenced the morphologies of CaCO3 particles. Various crystal morphologies of calcium carbonate, such as plates, rhombohedras, rods, ellipsoids, dumbbells, peanuts, spheres etc., could be obtained depending on the experimental conditions.
In this paper, transparent Li2O-Al2O 3-SiO2 system glass-ceramic with low expansion was prepared by melting method, using SiO2, Al2O3 Li2CO3 as raw materials, a small amount of alkaline-earth metal oxide, clarify addi...
详细信息
In this paper, transparent Li2O-Al2O 3-SiO2 system glass-ceramic with low expansion was prepared by melting method, using SiO2, Al2O3 Li2CO3 as raw materials, a small amount of alkaline-earth metal oxide, clarify additive and nucleating agent (TiO2, ZrO 2). The glass-ceramic was nucleated and crystallized under different temperature and time, according to the DTA. The results show that the glass-ceramic of Li2O-Al2O2-SiO2 system could be obtained by being nucleated at 550°C for 2 hours and crystallized at 550°C for 1 hour. The system was fully compact. The crystal size in the glass-ceramics was small and homogenous, and its main crystalloid was β-quartz. The expansion coefficient of the glass-ceramics was 2.262×10-7/°C(0 [similar to] 900°C)and the density was 2.5 g/cm3.
As has been discussed, research on the electronic structure between organic and inorganic atoms in hybrid compounds has become important. In our study, DV—Xα method was employed to calculate the electronic structure...
As has been discussed, research on the electronic structure between organic and inorganic atoms in hybrid compounds has become important. In our study, DV—Xα method was employed to calculate the electronic structure of the hybrid compound. The information obtained from the calculation included orbit charge, bonding order, Fermi energy, density of the state, etc. The influence of organic and inorganic parts on the energy band structure of the hybrid compound was discussed based on the calculation results of Fermi energy and density of state. The chemical bonding between organic and inorganic parts in the hybrid compound was also analyzed in detail according to the orbital charges and bond orders.
With the preparation of organic-inorganic layered perovskite-type compounds (C4H9NH3)2MCl4 (M = Mn, Cu) in solutions, X-ray diffraction (XRD), scanning electron microscopy (SEM),thermal gravimetry (TG) and differentia...
With the preparation of organic-inorganic layered perovskite-type compounds (C4H9NH3)2MCl4 (M = Mn, Cu) in solutions, X-ray diffraction (XRD), scanning electron microscopy (SEM),thermal gravimetry (TG) and differential scanning calorimetry (DSC) have been used to characterize the obtained powders. XRD patterns demonstrate that the two compounds have obvious layered structures and SEM pictures reveal that both (C4H9NH3)2MCl4 and (C4H9NH3)2CuCl4 take on obvious sheet-like microstructure. TG&DSC curves indicate that (C4H9NH3)2CuCl4 decomposes at much lower temperature than (C4H9NH3)*** is ascribed to weakening interactions between its organic and inorganic components, which is presumably due to the Jahn-Teller distortion of [CuCl6] octahedra.
The Small Punch Creep Tests (SP-C tests) are simulated by a Finite Element Method (FEM). The objective of the present study is to establish a foundation for the SP-C test method by investigating the deformation and st...
详细信息
The Small Punch Creep Tests (SP-C tests) are simulated by a Finite Element Method (FEM). The objective of the present study is to establish a foundation for the SP-C test method by investigating the deformation and stress state of the SP-C test specimen. The emphasis is placed on the dependence relation of the creep strain and the stress on the measurable quantities, such as applied loads and the central deflections. Simulation works are conducted for two different materials, one is the tungsten-alloyed 9% Cr ferritic steel and the other is 12Cr1MoV steel. The numerical results for the central deflection versus time curves are quantitatively similar to the experimental results obtained on tungsten-alloyed 9% Cr ferritic steels. From the numerical results, the relationship between the central deflection and the equivalent creep strain is approximately independent of load, temperature, and material properties. The magnitude of the equivalent stress in the central region of the SP-C specimen shows no significant change with respect to time at the secondary creep stage, an approximate equation is proposed for the assessment of the equivalent stress in the SP-C specimen. As a farther result, the high temperature creep properties of the 12Cr1MoV steel and tungsten-alloyed 9% Cr ferritic steel are appraised by numerical simulation. The results are in good agreement with the results from the standard test method. The results indicate that the small punch test technique is an effective method for the evaluation of the high-temperature creep properties of materials.
Poly-2-acrylamido-2-methyl propane sulfonic acid( PAMPS) proton exchange membrane and cross-linking PAMPS were prepared for PEM fuel cell. The water content, dimensional change, mechanical property, high temperature w...
详细信息
Poly-2-acrylamido-2-methyl propane sulfonic acid( PAMPS) proton exchange membrane and cross-linking PAMPS were prepared for PEM fuel cell. The water content, dimensional change, mechanical property, high temperature water retentivity and proton conductivity of the membranes were investigated. It was found that the PAMPS membrane had high proton conductivity (0.32 S/cm), but high dimensional change and low mechanical property. After cross-linking, the membranes had high water retentivity in high temperature and high proton conductivity (3% MBA, 0.076 S/cm), but low dimensional change and high mechanical property(3% MBA, 23.6 MPa).
By the polyol reduction process, the nanometer spherical cobalt particles with fcc structure and a crystal size of 10-13 nm, are prepared using the reagents of cobaltous salt as precursor and 1,2-propanediol as reduci...
详细信息
By the polyol reduction process, the nanometer spherical cobalt particles with fcc structure and a crystal size of 10-13 nm, are prepared using the reagents of cobaltous salt as precursor and 1,2-propanediol as reducing agent. XRD, TEM are applied to characterize the phase and morphology of the as-prepared products. The magnetic characterizations of the nanometer β-Co particles are studied by VSM. They are ferromagnetic at room temperature but with small coercivity (6.282 × 103 A/m).
The numerical simulation for the Small Punch creep (SP-C) tests is conducted using a Finite Element method. The objective of the present study is to obtain the deformation states of the SP-C specimen and to estimate t...
详细信息
ISBN:
(纸本)0878499709
The numerical simulation for the Small Punch creep (SP-C) tests is conducted using a Finite Element method. The objective of the present study is to obtain the deformation states of the SP-C specimen and to estimate the feasibility of SP-C test method for high-temperature creep properties. The emphasis is put on the relationship between the equivalent creep strain and the central deflection of the SP-C specimen. The time history of central deflection and equivalent creep strain is obtained by finite element method and the effects of the load, temperature and material properties on the relationship of central deflection and equivalent creep strain are discussed. From the numerical results, the relationship between the central deflection and the equivalent creep strain is approximately independent of load, temperature, and material properties. As a farther result, the high temperature creep properties of the 12CrlMoV steel are appraised by numerical simulation. The results are in good agreement with the results from the standard test method. The results indicate that the small punch test technique is an effective method for the evaluation of the high-temperature creep properties of materials.
The mechanical properties, thermal properties, electrical properties and oxidation behavior at high temperature of Ti3SiC2 with solute Al synthesized by hot pressing the mixture powder with the molar ratio 2TiC/Ti/Si/...
详细信息
The mechanical properties, thermal properties, electrical properties and oxidation behavior at high temperature of Ti3SiC2 with solute Al synthesized by hot pressing the mixture powder with the molar ratio 2TiC/Ti/Si/0.2Al were studied in this paper. The compressive strength, flexural strength, fracture toughness and Vicker's hardness were 854 MPa, 420 MPa, 5.8 MPa·m1/2 and 3.5-5.0 GPa;at 25°C and 800°C, the electrical conductivities were 4.3 × 106 S/m and 1.0 × 106 S/m, respectively. The thermal expound coefficient was 9.0 × 10-6 /K. The solute Al altered the oxidation mechanism of Ti3SiC2-The oxide layers consisted of a mass of α-Al2O3 formed by the outward diffusion of Al, instead of the outward diffusion of Ti, were observed on oxidized samples as a dense and adhesive protect scale. The oxidation mechanism varied with the additive aluminum, which greatly improved the oxidation resistance of Ti3SiC2.
A numerical study is presented that simulates small punch creep (SP-C) tests using a finite-element method (FEM). The objective of the present study is to develop a miniaturized testing methodology for high-temperatur...
详细信息
暂无评论