It is well known that the lattice waves in alloy can be looked upon as the superposition of a series of plane waves with different wave vectors. Because of these plane wave′s diffraction action for X photon, there ar...It is well known that the lattice waves in alloy can be looked upon as the superposition of a series of plane waves with different wave vectors. Because of these plane wave′s diffraction action for X photon, there are two satellites (sidebands) around X ray main diffraction peak. With the wavelength and asymmetric factor α y of rectangle wave of the distribution of concentration introduced, the amplitude of modulation wave appearing along some crysallographic direction can be expressed clearly in the form of a sum of several diffraction wave vectors in the reciprocal space, and the diffracted intensity can be obtained. The X ray diffraction angle of sidebands strongly depends on the distribution of the wavelength. Fig.1b gives the simulated X ray diffraction profiles. It shows that when we fix the average modulated wavelength and change the distribution of wavelength, the angle difference between the satellite and main diffraction peak varies correspondingly. The simulated diffraction profiles are in good agreement with experimental results [1] (Fig.1a). The more diffuse the distribution of wavelength is, the nearer the sidebands are to main peak, and vice versa. In addition, the intensity and position of satellite are obviously restricted by the asymmetric factor of wave shape. Any lattice wave propagating in crystal can be resolved along coordinate axes. On the basis of the principle of superposition, all compositions of the lattice wave have diffraction profiles of themselves. Add two diffraction patterns perpendicular to each other on the reciprocal plane which is normal to the projected direction, we get the simulated TEM diffraction pattern of spinodal decomposition. Fig.2a is the TEM pattern by Kubo H [2] , Fig.2b and 2c are the simulated TEM patterns by Kubo H [2] and Khachaturyan A G [3] respectively. Our simulated TEM pattern (Fig.2d) is in good agreement with Fig.2a.展开更多
Bamboo-structured boron nitride （BN） nanotubes with thorn-like morphology were synthe-sized by thermal chemical reaction using amorphous boron powders and NiO nanoparticles as precursors under the flow of NH3 at 110...Bamboo-structured boron nitride （BN） nanotubes with thorn-like morphology were synthe-sized by thermal chemical reaction using amorphous boron powders and NiO nanoparticles as precursors under the flow of NH3 at 1100 oC. The structural and morphological charac-teristics of BN nanotubes were investigated by X-ray diraction and transmission electron microscopy. The results showed that the thorn-like nanostructures attaching to the stems of bamboo-structured BN nanotubes were the hexagonal BN nano akes. Based on the diffu-sion of solid B and vapor B2O2, a possible growth mechanism of these novel thorn-like BN nanotubes was primarily proposed.展开更多
The hot deformation behavior of Ti-6Al-4V （TC4） titanium alloy was investigated in the temperature range from 650℃ to 950℃ with the strain rate ranging from 7.7×10^-4 s^-1 to 7.7×10^-2 s^-1. The hot tens...The hot deformation behavior of Ti-6Al-4V （TC4） titanium alloy was investigated in the temperature range from 650℃ to 950℃ with the strain rate ranging from 7.7×10^-4 s^-1 to 7.7×10^-2 s^-1. The hot tension test results indicate that the flow stress decreases with increasing the deformation temperature and increases with increasing the strain rate. XRD analysis result reveals that only deformation temperature affects the phase constitution. The microstructure evolution under different deformation conditions was characterized by TEM observation. For the deformation of TC4 alloy, the work-hardening is dominant at low temperature, while the dynamic recovery and dynamic re-crystallization assisted softening is dominant at high temperature.展开更多
2017 aluminum alloy plates with an ultrafine grained （UFG） structure were produced by equal channel angular processing （ECAP） and then were joined by underwater friction stir welding （underwater FSW）. X-ray diff...2017 aluminum alloy plates with an ultrafine grained （UFG） structure were produced by equal channel angular processing （ECAP） and then were joined by underwater friction stir welding （underwater FSW）. X-ray diffractometer （XRD）, transmission electron microscope （TEM）, scanning electron microscope （SEM） and microhardness tester were adopted to investigate the microstructural and mechanical characteristics of the FSW joint. The results indicate that an ultrafine grained microstructure with the mean grain size of-0.7 Ixm is obtained in the weld nugget by using water cooling. However, The FSW joint exhibits softening compared with the ultrafine grained based material and the heat affected zone （HAZ） has the lowest hardness owing to the coarsening of the strengthening precipitates.展开更多
The auto-evolved ultrafine copper powders were synlhesized via a novel electrodeposition route performed by ultrasonic dispersion of the electrolyte. The properties of the samples obtained were characterized by X-ray ...The auto-evolved ultrafine copper powders were synlhesized via a novel electrodeposition route performed by ultrasonic dispersion of the electrolyte. The properties of the samples obtained were characterized by X-ray powder diffractometry （XRD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM） and laser size distribution analyzer （SL） respectively. The formation mechanisms of the powders and the efficiency of the elctrodeposition were discussed. The results show that the as-prepared powders are high-purity copper nanoparticles with the fcc structure taking a mixture of fishbone-like and irregular shapes When the concentration of Cu^2＋ increases from 0.03 to 0.09 mol/L, the average size of copper particles increases from 0.92 to 1.80 μm, and current efficiency of electrodeposition linearly changes from 66.5% to 91.3%.展开更多
The synthesis of high purity intermetallic FeAI nanoparticles using the flow-levitation （FL） method was reported. Iron and aluminium droplets were levitated stably at about 2 230℃. The morphology, clystal structure...The synthesis of high purity intermetallic FeAI nanoparticles using the flow-levitation （FL） method was reported. Iron and aluminium droplets were levitated stably at about 2 230℃. The morphology, clystal structure and chemical composition of FeAI nanoparticles were investigated by transmission electron microscopy （TEM）, high-resolution TEM, X-ray diffraction and energy dispersive spectrometry. The results show that the average particle size of these nanoparticles is about 34.5 nm. Measurements of the d-spacing from X-ray diffraction and electron diffraction studies confirm that the intermetallic nanoparticles have the same crystal structure （B2） as the bulk FeA1. A thin oxidation coating is formed around the particles when being exposed to air. Based on the XPS measurements, the surface coating of the FeAI nanoparticles is composed of Fe2O3 and FeAl2O4. Besides, hysteresis curve reveals that saturation magnetization （Ms） of FeA1 is 1.66 A/m2, and the coercivity is about 1.214×10^3 A/re.展开更多
The dispersibility of vermiculite is the key factor that affects the application of vermiculite.In this paper,the milled natural vermiculite was pillared by organic quaternary ammonium salts.Then the pillared vermicul...The dispersibility of vermiculite is the key factor that affects the application of vermiculite.In this paper,the milled natural vermiculite was pillared by organic quaternary ammonium salts.Then the pillared vermiculite was ground and homogenized under the existence of dispersive agent to form a stable vermiculite hydrosol system.Small angle X-ray diffraction(SA-XRD),fourier transform infrared spectroscopy(FTIR),and thermogravimetric analyses(TGA)were used to characterize the structure and thermal property of the vermiculite.The results indicate that the exfoliated vermiculite is successfully obtained.The analyses of laser particle size analyzer,transmission electron microscope(TEM),and Tyndall phenomenon analyzer demonstrate that the vermiculite hydrosol prepared is a stable hydrosol system.展开更多
Mesoporous zirconia was synthesized by a new and simple method. Zirconium n-propoxide was used as the zirconium source. A small, inexpensive nonsurfactant, triethanolamine, was used as the template. The template was r...Mesoporous zirconia was synthesized by a new and simple method. Zirconium n-propoxide was used as the zirconium source. A small, inexpensive nonsurfactant, triethanolamine, was used as the template. The template was removed by thermal treatment in air and supercritical fluid extraction using CO2. The structure of the resulting materials was characterized by X-ray diffraction, transmission electron microscopy, and N2 adsorption-desorption analyses. The materials are found to have narrowly distributed average pore diameters and wormhole-like pore channels. However, higher surface area and larger pore volume are exhibited after supercritical fluid extraction with CO2. The removal of the template by thermal treatment also leads to condensation and mild shrinkage of the zirconia framework.展开更多
A yttrium-containing high-temperature titanium alloy(Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting(SEBM). The resulting microstructure and...A yttrium-containing high-temperature titanium alloy(Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting(SEBM). The resulting microstructure and textures were studied using scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and electron backscattered diffraction(EBSD) and compared with the conventionally manufactured form. A notable distinct difference of microstructures is that additive manufacturing by SEBM enables homogeneous precipitation of fine Y2O3 dispersoids in the size range of 50-250 nm throughout the as-fabricated alloy, despite the presence of just trace levels of oxygen(7×10-4, mass fraction) and yttrium(10-3, mass fraction) in the alloy. In contrast, the conventionally manufactured alloy shows inhomogeneously distributed coarse Y2O3 precipitates, including cracked or debonded Y2O3 particles.展开更多
文摘It is well known that the lattice waves in alloy can be looked upon as the superposition of a series of plane waves with different wave vectors. Because of these plane wave′s diffraction action for X photon, there are two satellites (sidebands) around X ray main diffraction peak. With the wavelength and asymmetric factor α y of rectangle wave of the distribution of concentration introduced, the amplitude of modulation wave appearing along some crysallographic direction can be expressed clearly in the form of a sum of several diffraction wave vectors in the reciprocal space, and the diffracted intensity can be obtained. The X ray diffraction angle of sidebands strongly depends on the distribution of the wavelength. Fig.1b gives the simulated X ray diffraction profiles. It shows that when we fix the average modulated wavelength and change the distribution of wavelength, the angle difference between the satellite and main diffraction peak varies correspondingly. The simulated diffraction profiles are in good agreement with experimental results [1] (Fig.1a). The more diffuse the distribution of wavelength is, the nearer the sidebands are to main peak, and vice versa. In addition, the intensity and position of satellite are obviously restricted by the asymmetric factor of wave shape. Any lattice wave propagating in crystal can be resolved along coordinate axes. On the basis of the principle of superposition, all compositions of the lattice wave have diffraction profiles of themselves. Add two diffraction patterns perpendicular to each other on the reciprocal plane which is normal to the projected direction, we get the simulated TEM diffraction pattern of spinodal decomposition. Fig.2a is the TEM pattern by Kubo H [2] , Fig.2b and 2c are the simulated TEM patterns by Kubo H [2] and Khachaturyan A G [3] respectively. Our simulated TEM pattern (Fig.2d) is in good agreement with Fig.2a.
文摘Bamboo-structured boron nitride （BN） nanotubes with thorn-like morphology were synthe-sized by thermal chemical reaction using amorphous boron powders and NiO nanoparticles as precursors under the flow of NH3 at 1100 oC. The structural and morphological charac-teristics of BN nanotubes were investigated by X-ray diraction and transmission electron microscopy. The results showed that the thorn-like nanostructures attaching to the stems of bamboo-structured BN nanotubes were the hexagonal BN nano akes. Based on the diffu-sion of solid B and vapor B2O2, a possible growth mechanism of these novel thorn-like BN nanotubes was primarily proposed.
文摘The hot deformation behavior of Ti-6Al-4V （TC4） titanium alloy was investigated in the temperature range from 650℃ to 950℃ with the strain rate ranging from 7.7×10^-4 s^-1 to 7.7×10^-2 s^-1. The hot tension test results indicate that the flow stress decreases with increasing the deformation temperature and increases with increasing the strain rate. XRD analysis result reveals that only deformation temperature affects the phase constitution. The microstructure evolution under different deformation conditions was characterized by TEM observation. For the deformation of TC4 alloy, the work-hardening is dominant at low temperature, while the dynamic recovery and dynamic re-crystallization assisted softening is dominant at high temperature.
基金Projects(50774059, 51074119) supported by the National Natural Science Foundation of China
文摘2017 aluminum alloy plates with an ultrafine grained （UFG） structure were produced by equal channel angular processing （ECAP） and then were joined by underwater friction stir welding （underwater FSW）. X-ray diffractometer （XRD）, transmission electron microscope （TEM）, scanning electron microscope （SEM） and microhardness tester were adopted to investigate the microstructural and mechanical characteristics of the FSW joint. The results indicate that an ultrafine grained microstructure with the mean grain size of-0.7 Ixm is obtained in the weld nugget by using water cooling. However, The FSW joint exhibits softening compared with the ultrafine grained based material and the heat affected zone （HAZ） has the lowest hardness owing to the coarsening of the strengthening precipitates.
基金Project(08JJ3104) support by Hunan Provincial Natural Science Foundation of China
文摘The auto-evolved ultrafine copper powders were synlhesized via a novel electrodeposition route performed by ultrasonic dispersion of the electrolyte. The properties of the samples obtained were characterized by X-ray powder diffractometry （XRD）, transmission electron microscopy （TEM）, scanning electron microscopy （SEM） and laser size distribution analyzer （SL） respectively. The formation mechanisms of the powders and the efficiency of the elctrodeposition were discussed. The results show that the as-prepared powders are high-purity copper nanoparticles with the fcc structure taking a mixture of fishbone-like and irregular shapes When the concentration of Cu^2＋ increases from 0.03 to 0.09 mol/L, the average size of copper particles increases from 0.92 to 1.80 μm, and current efficiency of electrodeposition linearly changes from 66.5% to 91.3%.
基金Project(10804101) supported by the National Natural Science Foundation of China
文摘The synthesis of high purity intermetallic FeAI nanoparticles using the flow-levitation （FL） method was reported. Iron and aluminium droplets were levitated stably at about 2 230℃. The morphology, clystal structure and chemical composition of FeAI nanoparticles were investigated by transmission electron microscopy （TEM）, high-resolution TEM, X-ray diffraction and energy dispersive spectrometry. The results show that the average particle size of these nanoparticles is about 34.5 nm. Measurements of the d-spacing from X-ray diffraction and electron diffraction studies confirm that the intermetallic nanoparticles have the same crystal structure （B2） as the bulk FeA1. A thin oxidation coating is formed around the particles when being exposed to air. Based on the XPS measurements, the surface coating of the FeAI nanoparticles is composed of Fe2O3 and FeAl2O4. Besides, hysteresis curve reveals that saturation magnetization （Ms） of FeA1 is 1.66 A/m2, and the coercivity is about 1.214×10^3 A/re.
基金National High Technology Research and Development Program(863 Program),China(No.2007AA03Z336)Program for New Century Excellent Talents in University,China(No.NCET-07-0174)
文摘The dispersibility of vermiculite is the key factor that affects the application of vermiculite.In this paper,the milled natural vermiculite was pillared by organic quaternary ammonium salts.Then the pillared vermiculite was ground and homogenized under the existence of dispersive agent to form a stable vermiculite hydrosol system.Small angle X-ray diffraction(SA-XRD),fourier transform infrared spectroscopy(FTIR),and thermogravimetric analyses(TGA)were used to characterize the structure and thermal property of the vermiculite.The results indicate that the exfoliated vermiculite is successfully obtained.The analyses of laser particle size analyzer,transmission electron microscope(TEM),and Tyndall phenomenon analyzer demonstrate that the vermiculite hydrosol prepared is a stable hydrosol system.
基金Supported by the Natural Science Foundation of Ningxia ProvinceInnovation Team Projects in Ningxia Teachers University
文摘Mesoporous zirconia was synthesized by a new and simple method. Zirconium n-propoxide was used as the zirconium source. A small, inexpensive nonsurfactant, triethanolamine, was used as the template. The template was removed by thermal treatment in air and supercritical fluid extraction using CO2. The structure of the resulting materials was characterized by X-ray diffraction, transmission electron microscopy, and N2 adsorption-desorption analyses. The materials are found to have narrowly distributed average pore diameters and wormhole-like pore channels. However, higher surface area and larger pore volume are exhibited after supercritical fluid extraction with CO2. The removal of the template by thermal treatment also leads to condensation and mild shrinkage of the zirconia framework.
基金Projects(2014KTZB01-02-03,2014KTZB01-02-04)supported by Shaanxi Science and Technology Coordination and Innovation Program,ChinaProject(DP120101672)supported by Australian Research Council(ARC)Discovery Grant,ARC Centre of Excellence for Design in Light Metals,Australia
文摘A yttrium-containing high-temperature titanium alloy(Ti-6Al-2.7Sn-4Zr-0.4Mo-0.45Si-0.1Y, mass fraction, %) has been additively manufactured using selective electron beam melting(SEBM). The resulting microstructure and textures were studied using scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD) and electron backscattered diffraction(EBSD) and compared with the conventionally manufactured form. A notable distinct difference of microstructures is that additive manufacturing by SEBM enables homogeneous precipitation of fine Y2O3 dispersoids in the size range of 50-250 nm throughout the as-fabricated alloy, despite the presence of just trace levels of oxygen(7×10-4, mass fraction) and yttrium(10-3, mass fraction) in the alloy. In contrast, the conventionally manufactured alloy shows inhomogeneously distributed coarse Y2O3 precipitates, including cracked or debonded Y2O3 particles.
