密堆六方纳米ZnO的X射线衍射表征与研究

X射线衍射(XRD)实验发现密堆六方纳米ZnO的hk0、h-k=3n的衍射线, 仅存在微晶宽化, 而h-k=3n±1的衍射线, 无l=偶数、l=奇数的层错选择宽化效应. 为了表征这种纳米ZnO的晶粒大小和层错几率, 提出了分解纳米ZnO微晶-层错二重宽化效应的最小二乘法. 计算结果表明: 密堆六方纳米ZnO的晶粒大小和层错几率与制备方法、原料配比等有关.     

Structural investigations of the phenyl methacrylate and methyl methacrylate copolymer system

The compositions of the copolymers of phenyl methacrylate and methyl methacrylate synthesized by free radical polymerization have been determined by nuclear magnetic resonance spectroscopy. X-ray diffraction analysis was employed for structural investigations. The results are discussed in terms of degree of amorphousness, interchain separation and mean crystallite size.     

Metrological characterization of X-ray diffraction methods for determination of crystallite size in nano-scale materials

Crystallite size values were determined by X-ray diffraction methods for 210 TiO₂ (anatase) nanocrystalline powders with crystallite size from 3 nm to 35 nm. Each X-ray diffraction pattern was processed using different free and commercial software. The crystallite size calculations were performed using Scherrer equation and Warren–Averbach method. Statistical treatment and comparative assessment of the obtained results were performed for the purpose of an ascertainment of statistical significance of the obtained differences. The average absolute divergence between results obtained with using Scherrer equation does not exceed 0.36 nm for the crystallites smaller than 10 nm, 0.54 nm for the range 10–15 nm and 2.4 nm for the range > 15 nm. We have also found that increasing the analysis time improves statistics, however does not affect the calculated crystallite sizes. The values of crystallite size determined from X-ray data were in good agreement with those obtained by imaging in a transmission electron microscope.     

An electron microscopy and X-ray diffraction study of the microstructures of melt-drawn polyethylene films

Electron microscopy and X-ray diffraction have been used to study microstructures of melt-drawn polyethylene films. During the drawing process, uniplanar structures are formed which consist of crystals with theirb andc axes in the film plane. On annealing the films, the crystal size and orientation increase. Quantitative measures of the crystal thickness, lateral crystallite size and long period were obtained from bright-field and dark-field electron micrographs as well as from wide and small angle X-ray diffraction of stacked layers of the films.     

Structural characterization of lead sulfide thin films by means of X-ray line profile analysis

X-ray diffraction patterns of chemically deposited lead sulphide thin films have been recorded and X-ray line profile analysis studies have been carried out. The lattice parameter, crystallite size, average internal stress and microstrain in the film are calculated and correlated with molarities of the solutions. Both size and strain are found to contribute towards the broadening of X-ray diffraction line. The values of the crystallite size are found to be within the range from 22–33 nm and the values of strain to be within the range from 1·0 × 10⁻³–2·5 × 10⁻³.     

Crystallinity enhances light transmissivity through low-density polyethylene sheets

The effect of the crystalline structure (crystallinity and crystallite size) on the light transmissivity in low-density polyethylene sheets has been studied. Wide-angle X-ray diffraction, DSC, and UV/visible spectroscopy techniques have been used. The increase in crystallinity enhanced the light transmissivity in the visible region, but no significant effect in the UV region was obtained. The crystallite size showed no clear relation to transmissivity.     

Preparation and characterization of ATO nanoparticles by various coprecipitation

A series of Sb doped SnO₂ (ATO) nanoparticles, with Sb doping levels 0–20 at.% has been prepared by two different coprecipitation routes. Effect of preparation process, Sb doping concentration and calcination temperature on the crystallinity and morphology of ATO nanoparticles were investigated and analyzed. The prepared nanoparticles were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, selective area electron diffraction, X-ray diffraction and energy dispersive X-ray spectroscopy. Results indicated that the prepared ATO nanoparticles were tetragonal, and isostructural with rutile lattice structure as known from bulk SnO₂. The ATO nanoparticles prepared via process I (homogeneous coprecipitation) presented obviously weaker crystallinity, smaller average crystallite size and harder agglomeration than that prepared via process II (heterogeneous coprecipitation). The crystallinity and average crystallite size of ATO nanoparticles prepared via process II increased with increasing calcination temperatures and reducing Sb doping concentrations, respectively. The increased crystallinity, dispersibility and average crystallite size for ATO nanoparticles prepared via process II may be due to the formation of ATO crystal nuclei, leading to an improved formation dynamics of ATO nanoparticles.     

The effect of temperature on microstrains and crystallite growth in alumina

The effects of temperature on the microstrains and crystallite growth in milled alumina have been examined, using a modern method of X-ray diffraction profile analysis. The microstrains may be relieved by annealing at temperatures between 600 and 1000° C, and this relief is accompanied by crystallite size growth. Isotropy was observed with regard to the residual stresses and cleavage properties, in the milled crystals.     

An X-ray diffraction and Mossbauer study of nano-crystalline Fe2O3–Cr2O3 solid solutions

A series of gels with nominal composition Fe_2−xCr_xO₃ (x=0–2) was prepared at room temperature by an inorganic sol–gel route and studied by X-ray diffraction and Mossbauer spectroscopy. The gels dried at 105°C were found to be X-ray amorphous, but Mossbauer studies revealed the gels to be nano-crystalline solid-solution particles of the composition above, with super-paramagnetic properties. Further heating to 600°C gave crystalline X-ray patterns which allowed lattice parameter and crystallite size calculations to be made. It was found that lattice parameters and crystallite sizes decreased with increasing chromia content, and that at the higher chromia/iron ratios, a partially collapsed Mossbauer pattern results, indicating reductions in crystallite size and hyperfine field with increasing chromia content. This revised version was published online in November 2006 with corrections to the Cover Date.     

Novel synthesis of nanocrystalline CeO2 by mechanochemical and water-in-oil microemulsion methods

Nanocrystalline cerium dioxide (CeO₂) had been synthesized by two different methods which were mechanochemical and water-in-oil microemulsion. Effects of synthesis conditions on properties of nanocrystalline cerium dioxide were investigated. X-ray diffraction (XRD) was used to characterize the phase and crystallite size of synthesized cerium dioxide nanoparticles. XRD results showed that face centered cubic CeO₂ nanoparticles with crystallite size in nanometer scale were formed. The crystallinity increased with increasing annealing temperature. The average specific surface area of the particles was probed using gas adsorption-desorption measurements. The average particles size was calculated from the specific surface area and was determined to be 5.2 nm for microemulsion samples and 6.9 nm for mechanochemical samples. These results showed that properties of synthesized cerium dioxide could be tailored by adjusting the synthesis conditions.     

Texture and surface morphology effects on tetragonal phase stabilization in ZrO2 films deposited by metal-organic chemical vapor deposition

Tetragonal zirconia coatings (ZrO2) without doping any trivalent impurities have been deposited by metal-organic chemical vapor deposition (MOCVD) on (100) Si single crystals, using Zr(thd)4 precursor. The surface and cross-section morphologies were observed with Field-Emission-Gun Scanning Electron Microscopy (FEG-SEM). The crystalline structures were characterized by grazing incident X-ray diffraction (GIXRD). Crystallographic textures of these films were studied for both {011}t and {110}t planes by pole figure recording by X-ray diffraction under a 4-circle goniometer. The internal stresses were measured with the use of sin2 psi method. In order to study the relationship of microstructures and tetragonal phase stabilization in ZrO2 films, annealing experiments were taken at different temperature. The results show that the critical crystallite size for tetragonal to monoclinic phase transformation is different for samples with different initial microstructures. Besides the critical crystallite size and the residual stress, the texture and crystallite morphology of the ZrO2 films are responsible for the stabilization of the metastable tetragonal phase.     

Preparation and characterization of Ln2Zr2O7 microspheres by an inorganic sol-gel route

Free-flowing Ln₂Zr₂O₇ microspheres (Ln=lanthanide) were prepared by an aqueous inorganic sol-gel route without any intermediate phase formation. The gel spheres obtained at room temperature were shown by X-ray diffraction to be amorphous but calcination to 750 °C produced fully crystalline fluorite phases. On calcination to 850 °C, pyrochlore phases were formed with suitable lanthanides. The microspheres were characterized by X-ray diffraction and scanning electron microscopy with energy dispersive analysis of X-rays to give accurate determination of structure, composition and crystallite size.     

Synthesis and photocatalytic activity of nano-sized iron oxides

Nano-sized iron oxide powder with average crystallite sizes 35, 100 and 150 nm was prepared by thermal evaporation and co-precipitation techniques. The synthesized powders were characterized by X-ray diffraction analysis technique, transmission electron microscope (TEM) and scanning electron microscope (SEM). The prepared powders were tested as catalysts for the photo catalytic decomposition of Congo red dye. The effect of crystal size of iron oxides on the rate of decomposition of Congo red dye was investigated in visible light as well as in the absence of light. The experimental results show that both iron oxides with crystallite size 35 and 150 nm cause complete decomposition of Congo red dye while iron oxide particles with crystallite size 100 nm were unable to decompose the dye.     

X-ray diffraction and fourier transform infrared analysis of nanophase apatite coatings prepared by electrocrystallization

The concept of biological fixation of artificial joint prosthesis by using bioactive calcium phosphate coatings has generated considerable interest in recent years. This paper reports an electrocrystallization process for fabricating stoichiometric and non-stoichiometric hydroxyapatite (HA) coatings with nanometer size crystals similar to biogenic apatite. X-ray diffraction and Fourier Transform Infrared (FTIR) spectroscopy were used to characterize the structure and chemical composition of the HA coatings.As-deposited coatings at 65°C were poorly crystalline, Ca-deficient HA with a crystallite size of about 35 nm and exhibited apatitic characteristics similar to bone apatite. Post-treatment of coatings in steam at 125°C followed by calcining at 425°C resulted in the transformation of the initial phase to a well-defined stoichiometric HA with a crystallite size of about 100 nm.     

A Raman spectroscopic study of structural evolution of electrochemically deposited ZnO films with deposition time

Zinc oxide thin films were fabricated on ITO substrates by electrodeposition method. The electrolyte used was a 0.2 M zinc nitrate aqueous solution. The substrates were maintained at room temperature and the deposition performed for different times between 10 and 30 min. X-ray diffraction measurements indicated the formation of polycrystalline ZnO film with hexagonal wurtzite structure. The structure and crystallinity of the films was also confirmed by Raman spectroscopy. Further, the degree of disorder was estimated both from the phonon correlation length calculated from the Raman spectra using the spatial correlation model and from the intensity ratios of the phonons. The variation with deposition time followed the same trend as the crystallite sizes obtained from X-ray diffraction. X-ray photoelectron spectroscopy measurements indicated oxygen deficiency in the films. A combination of annealing and optimum deposition time improves the quality of the electrodeposited ZnO films.     

Investigation of microstructural characteristics of nanocrystalline 12YWT steel during milling and subsequent annealing by X-ray diffraction line profile analysis

The variations of dislocation density, character of dislocations, and crystallite size as a function of milling time and post-heat-treating temperature were investigated for 12YWT nanocomposite ODS ferritic steel using X-ray diffraction line profile analysis. The modified Williamson–Hall and the modified Warren–Averbach methods, which are based on the dislocation model of the strain anisotropy, were utilized to characterize the microstructural parameters of the nanocomposite material and the matrix alloy. The presence of nano-oxide particles in the ODS steel caused an initially sharp decrease in the average crystallite size; however, with increasing milling time, the crystallite size of the unreinforced alloy reached the comparable value of that of the reinforced material. The subsequent heat treating on the powders milled for 80 h showed that the presence of Y₂O₃ dispersoids increased the recrystallization temperature and suppressed the grain growth up to 800 °C in the 12YWT alloy as compared to the matrix alloy which occurred about 700 °C. The results of X-ray diffraction line profile analysis also showed that the contribution of edge components of the dislocations increased at the initial milling stages, while the screw components tended to increase after 40-h milling time.     

Simulation of texture and crystallite microstrain development during compression and tension of an Al alloy and comparison to experimental results

Cold compression textures, tension textures and crystallite microstrains of an AlMg₃ aluminum wrought alloy were simulated using the Taylor–Bishop–Hill theory and an elastic unloading model. The results of the simulations are compared to inverse pole figures determined by X-ray diffraction and _ψ vs sin²ψ-curves determined using synchrotron radiation. It is shown that the texture evolution has a strong influence on the crystallite microstrains and produces non-linear microstrain curves, which can be interpreted and evaluated using the results of the simulations.     

The influence of deposition temperature on the crystalline and electrical properties of thin silver films

Silver films were evaporated onto glass substrate under ultrahigh vacuum conditions and investigated using X-ray diffraction analysis and electrical measurements. The influence of the deposition temperature on the crystallite size, the surface roughness and the electrical properties was studied by analysing the width, intensity and fine structure of the diffraction peaks and the film resistivity.     

Synthesis of CuS and PbS nanocrystals on the basis of PE/NBR polymer/elastomeric composites for their applications

In this research work, we have presented a chemical method to elaborate the PbS, CuS nanocrystals embedded in a polymer composites matrix. We have used polyethylene and nitrile butadiene rubber PE/NBR as a support for synthesis of lead sulfide (PbS) and copper sulfide (CuS) nanocrystals. The size control and morphology of these (PbS and CuS) nanoparticles have been applied by the method of “layer by layer”. The obtained nanoparticles were characterized by X-ray diffraction (XRD), UV–Vis and Atomic Force Microscopy (AFM). UV–Vis spectroscopy was used to determine simple optical responses, getting the biggest transmittances of CuS and PbS nanoparticles. Measured size of CuS nanoparticles is approximately 5.5–90 nm in different dose. X-ray diffraction (XRD) study confirmed the formation of cubic phase of PbS nanocrystals into the composite matrix. The size of PbS was estimated ∼9 nm. The surface morphology and crystallite sizes were determined by Atomic Force Microscopy measurements.     

Effects of ball milling intensity on structural changes in mixed 50Ni–50Ti powders during mechanical alloying process

Abstract

Mixed 50Ni–50Ti powders were milled in an attritor high energy ball mill and the structural evolution of the milled powders characterised by X-ray diffraction analysis. The microstrain, crystallite size, and lattice parameters of the nickel and titanium crystals were measured. The results show that increases in the rotational velocity and the total ball volume/tank volume ratio leads to a decrease in the crystallite size and rapid changes in the microstrain and lattice parameters, which enhance the amorphisation rate, thereby reducing the time required to obtain afully amorphous phase.

MST/2079