Thermal expansion of kyanite at ambient pressure:An X-ray powder diffraction study up to 1000℃

The thermal expansion coefficients of kyanite at ambient pressure have been investigated by an X-ray powder diffraction technique with temperatures up to 1000 ℃. No phase transition was observed in the experimental temperature range. Data for the unit-cell parameters and temperatures were fitted empirically resulting in the following thermal expansion coefficients： αa = 5.8（3） × 10^-5, αb = 5.8 （1）× 10^-5, αc = 5.2（1）× 10^-5, and αv = 7.4（1） × 10^-3 ℃ 1 in good agreement with a recent neutron powder diffraction study. On the other hand, the variation of the unit-cell angles α, β and γ of kyanite with increase in temperature is very complicated, and the agreement among all studies is poor. The thermal expansion data at ambient pressure reported here and the compression data at ambient temperature from the literature suggest that, for the kyanite lattice, the most and least thermally expandable directions correspond to the most and least compressible directions, respectively.

Ab initio Structure Determination of [Co(NH_3)_5Br]Br_2 Using Conventional X-ray Powder Diffraction

The crystal structure of [Co(NH3)5Br]Br2 has been determined ab initio from the conventional X-ray powder diffraction data. The approximate structure with all 7 indeyendent non-H atoms was solved by direct methods. The final orthorhombic unit-cell parameters after Rietveld refinement are: a=13.6927, b=10.7071, c=6.9400A, V=1017.47A3, F30=93(0.0075,43), M20=49, Z=4. Space group is Pnma. The structure agreement factors are: Rp=0.066,Rwp=0.090, RF=0.041, RB=0.042.

Rietveld Refinement and X-ray Powder Diffraction Data of GdAlSi

The X-ray powder diffraction data of the compound GdAlSi was studied by means of X-ray diffraction technique and refined by Rietveld method. The compound GdAlSi has tetragonal α-ThSi_2-type structure, space group I4_1/amd (No.141), Z=4, the lattice parameters a=041234 (1) nm, c=1.44202(1) nm. The Smith and Snyder figure of merit [5] F_N is F_ 30=2521(36). The R-factors of Rietveld refinement are R_p=0.098 and R_ wp=0.128. The X-ray powder diffraction data are given. The field dependence of the magnetization measured at room temperature and the temperature variation of the inverse magnetic susceptibility of the compound GdAlSi were also presented.

X-ray Powder Diffraction Pattern of Bi_4(SiO_4)_3

In cooperation with figure-of-merits the Rietveld analysis can appraise both angular and intensity data of powder diffraction. In this work, X-ray diffraction pattern of Bi4(SiO4)3 was redetermined with intensity figure-of-merits, which qualify agreement between observed and calculated relative intensities. F30 is 158.90 (0.0059, 32), intensity figure of merit Rint is 8.7, I20(17), 8.0. The values of figure-of-merits show that the data of JCPDS cards are distorted. Both the experimental and calculated peak positions and heights are listed in detail.

IDENTIFICATION AND SIMULATION OF X-RAY POWDER DIFFRACTION PATTERN

A new method for pattern identification and simulation of X-ray powder diffraction data is described, which can give definite phase composition of the unknown rapidly and correctly. The method is implemented in Microsoft Fortran 77 for the IBM PC/XT/AT personal computer or their compatibles.

X-RAY POWDER DIFFRACTION STUDY FOR RE COMPOUND GdNiSn

The compound GdNiSn has been studied by X-ray powder diffraction technique.The crystal structure and the X-ray diffraction data for this compound at room temperature are reported.The compound GdNiSn is orthorhombic with lattice parameters a=7.2044(1)A,b=7.6895(6)A,c=4.4772(4)A,space group Pna2_(1) and 4 formula units of GdNiSn in unit cell.The Smith and Snyder figure of index F_(30) for this compound is 35(0.015,59).

CRYSTAL STRUCTURE AND X-RAY POWDER DIFFRACTION DATA FOR RE COMPOUND HoNiSb

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SYNTHESIS AND X-RAY POWDER DIFFRACTION DATA OF A NEW COMPOUND:K_6FeNb_(15)O_(42)

A new compound K6FeNb15O42 was prepared for the first time by solid state reaction in K2O-Fe2O3-Nb2O5 ternary system. The X-ray powder diffraction data of the title compound was measured. K6FeNb15 O42 crystallizes in the hexagonal system with unit cell parameters, a = 9. 1320(4) A ,c = 12. 0670(9) A , and space group P63/mcm (193) , z = 1. The calculated and measured densities are 4. 489 g/cm3 and 4. 485 g. cm3, respectively.

SYNTHESIS AND X-RAY POWDER DIFFRACTION DATA OF A NEW COMPOUND:K_6FeNb_(15)O_(42)

A new compound K6FeNb15O42 u(?) prepared for the first time by solid state reaction in K2O-Fe2O3-Nb2O5 ternary system. The XRD data of the title compound was determined. K6FeNb15O42 crystallizes the hexagonal system with unit cell parameters a=9. 1320(4) A,c=12. 0670(9) A, and space group P63/mcm(193) , 2=1. The calculated and measured densities are 4. 489 g/ cm3 and 4. 485 g. cm3, respectively.

Investigation on the 773 K isothermal section of La-Fe-Sn ternary systems by X-ray powder diffraction

The 773 K isothermal section of the La-Fe-Sn ternary system was investigated and constructed by X-ray powder diffraction（XRD）.The existence of two reported ternary intermetallic compounds,La6Fe13Sn and La3FeSn6,is confirmed in this work.Compared with other R-Fe-Sn phase diagrams（R = Pr and Sm）,the binary alloys Fe3Sn and Fe5Sn3 are not present.The compound Fe3Sn2 was observed from the XRD pattern of Fe3Sn2 samples,but it is not an equilibrium phase at 773 K and decomposes into Fe and FeSn phases completely for a longer heat treated time.Up to now,the crystal structure data of La2Sn3 has not been reported,so the X-ray pattern of La2Sn3 was only estimated.The phase relationship for this compound was drawn by a dotted line.

X-Ray Powder Diffraction: Why Not Use CuKβ Radiation?

CuKβ radiation with a wavelength of λ = 1.3923 ? is recommended for crystal structure determination from X-ray powder diffraction using the Rietfeld method. A highly sensitive image plate detector is able to collect enough intensity to record a brilliant X-ray powder pattern in a reasonable time, compared to CuKα1 radiation used today. Especially atomic displacement coefficients could be determined more precisely with the much greater number of reflections recorded. A double-radius Guinier camera attached to a micro-focus rotating anode tube ensures increased brilliance besides high resolution. A simple construction specification is presented to make smart cylindrically bent Ge(111) or Si(111) X-ray monochromators that deliver focused CuKβ radiation. The highly linear response of image plate detectors allows removing of fluorescence radiation simply as background of the pattern. The proposed equipment is a cost-efficient alternative to a liquid gallium-metal-jet X-ray source with maximum power load and a similar wavelength of λ(GaKα1) = 1.34013 ?.

Microstructures and micromechanical behaviors of high -entropy alloys investigated by synchrotron X-ray and neutron diffraction techniques: A review

High-entropy alloys(HEAs)possess outstanding features such as corrosion resistance,irradiation resistance,and good mechan-ical properties.A few HEAs have found applications in the fields of aerospace and defense.Extensive studies on the deformation mech-anisms of HEAs can guide microstructure control and toughness design,which is vital for understanding and studying state-of-the-art structural materials.Synchrotron X-ray and neutron diffraction are necessary techniques for materials science research,especially for in situ coupling of physical/chemical fields and for resolving macro/microcrystallographic information on materials.Recently,several re-searchers have applied synchrotron X-ray and neutron diffraction methods to study the deformation mechanisms,phase transformations,stress behaviors,and in situ processes of HEAs,such as variable-temperature,high-pressure,and hydrogenation processes.In this review,the principles and development of synchrotron X-ray and neutron diffraction are presented,and their applications in the deformation mechanisms of HEAs are discussed.The factors that influence the deformation mechanisms of HEAs are also outlined.This review fo-cuses on the microstructures and micromechanical behaviors during tension/compression or creep/fatigue deformation and the application of synchrotron X-ray and neutron diffraction methods to the characterization of dislocations,stacking faults,twins,phases,and intergrain/interphase stress changes.Perspectives on future developments of synchrotron X-ray and neutron diffraction and on research directions on the deformation mechanisms of novel metals are discussed.

X-ray Powder Diffraction Data and Rietveld Refinement for NdCoGe_3

オ-ray powder diffraction data and crystal structure of RE compound NdCoGe3 were studied by using X-ray powder diffraction and refined by the Rietveld profile fitting method. The compound has the tetragonal BaNiSn3type structure, space group I4mm (No.107) a=0.42961(2) nm, c=098147(4) nm, V=0.018114 nm3, Z=2 and Dx=7.717 g·cm-3. The figure of merit FN for the powder data is F30=623 (0.0107, 45). Structure refinement was performed with 110 reflections and led to Rp=11.78% and Rwp=16.56%.

Quantification of flupirtine maleate polymorphs using X-ray powder diffraction

Flupirtine maleate, a pharmaceutical compound for treating psychotic disease in clinics, has seven polymorphs. Form A, with better crystal stability and bioavailability, has been widely used as the pharmaceutical crystal form. Unfortunately, it is usually found in a polymorphic mixture with form B. In this study, pure crystal forms of A and B were prepared and characterized by X-ray powder diffraction （XRPD）, Fourier transform infrared spectroscopy （FT-IR） and thermal analysis. An XRPD-based method for the quantitative determination of the amount of the flupirtine maleate polymorphs form A and form B was also established through a systematic optimization of instrumental parameters. The results of the analytical methodology validation showed that the XPRD method had a broad quantitative range of 0- 100% （w/w）, good linear relationship, with R2= 0.999, excellent repeatability and precision and low limits of detection （LoD） of 0.15% （w/w） and quantification （LoQ） of 0.5% （w/w）. The results also showed that the single-peak method was not as good as the whole pattern in reducing the influence of the preferred orientation, but this can be compensated for by a systematic optimization of instrumental parameters and validating the analytical methodology to reduce errors and obtain a good, repeatable, sensitive, and accurate method. This XRPD method can be used to analyze mixtures of flupirtine maleate polymorphs （forms A and B） quantitatively and control the quality of the bulk drug.

Intensity correlation properties of x-ray beams split with Laue diffraction

Beam splitting is one of the main approaches to achieving x-ray ghost imaging, and the intensity correlation between diffraction beam and transmission beam will directly affect the imaging quality. In this paper, we investigate the intensity correlation between the split x-ray beams by Laue diffraction of stress-free crystal. The analysis based on the dynamical theory of x-ray diffraction indicates that the spatial resolution of diffraction image and transmission image are reduced due to the position shift of the exit beam. In the experimental setup, a stress-free crystal with a thickness of hundredmicrometers-level is used for beam splitting. The crystal is in a non-dispersive configuration equipped with a double-crystal monochromator to ensure that the dimension of the diffraction beam and transmission beam are consistent. A correlation coefficient of 0.92 is achieved experimentally and the high signal-to-noise ratio of the x-ray ghost imaging is anticipated.Results of this paper demonstrate that the developed beam splitter of Laue crystal has the potential in the efficient data acquisition of x-ray ghost imaging.

Direct observation of shock-induced phase transformation in polycrystalline iron via in situ x-ray diffraction

Phase transition of polycrystalline iron compressed along the Hugoniot is studied by combining laser-driven shock with in situ x-ray diffraction technique.It is suggested that polycrystalline iron changes from an initial body-centered cubic structure to a hexagonal close-packed structure with increasing pressure(i.e.,a phase transition fromαtoε).The relationship between density and pressure for polycrystalline iron obtained from the present experiments is found to be in good agreement with the gas-gun Hugoniot data.Our results show that experiments with samples at lower temperatures under static loading,such as in a diamond anvil cell,lead to higher densities measured than those found under dynamic loading.This means that extrapolating results of static experiments may not predict the dynamic responses of materials accurately.In addition,neither the face-centered cubic structure seen in previous molecular-dynamics simulations or twophase coexistence are found within our experimental pressure range.

A Novel High Temperature Apparatus for in situ Synchrotron X-ray Diffraction Studies of Molten Salt

This study demonstrates the design and application of a novel high temperature rotatory apparatus for insitu synchrotron X-ray diffraction studies of molten salts,facilitating investigation into the interaction between various structural materials and molten salts.The apparatus enables accurate detection of every phase change during hightemperature experiments,including strong reaction processes like corrosion.Molten salts,such as chlorides or fluo⁃rides,together with the structure materials,are inserted into either quartz or boron nitride capillaries,where X-ray diffraction pattern can be continuously collected,as the samples are heated to high temperature.The replacement re⁃action,when molten ZnCl2 are etching Ti3AlC2,can be clearly observed through changes in diffraction peak intensity as well as expansion in c-axis lattice parameter of the hexagonal matrix,due to the larger atomic number and ionic ra⁃dius of Zn2+.Furthermore,we investigated the high-temperature corrosion process when GH3535 alloy is in FLiNaK molten salt,and can help to optimize its stability for potential applications in molten salt reactor.Additionally,this high temperature apparatus is fully compatible with the combined usage of X-ray diffraction and Raman technique,providing both bulk and surface structural information.This high temperature apparatus has been open to users and is extensively used at BL14B1 beamline of the Shanghai Synchrotron Radiation Facility.

Investigation on the 773K isothermal section of Ho-Ni-Si ternary phase diagram by X-ray powder diffraction and magnetic property of Ho3NiSi2 alloy

The isothermal section of the Ho-Ni-Si system at 773 K was constructed by X-ray powder diffraction(XRD)in this work.The system contains sixteen known type structure compounds TiNiSi-type HoNiSi,BaAl4-type HoNi2Si2,CeNiSi2-type HoNiSi2,U1Co3Si5-type Ho2Ni3Si5,SmNiGe3-type HoNiSi3,Ce3 Ni6Si2-type Ho3Ni6Si2,ThMn12-type HoNi10Si2,YPd2Si-type HoNi2Si,YNi5Si3-type HoNi5Si3,YNi4Si-type HoNi4Si,Gd3NiSi2-type Ho3NiSi2,YNi6Si6-type HoNi6Si6.AlB2-type Ho2NiSi3,AlB2-type Ho3Ni2Si4,AlB2-type Ho4NiSi7,Gd3Ru4Al12-type Ho8Ni31Si11,and one unknown type structure compound Ho5Ni2Si3.At the same time,one unknown structure new phase Ho37Ni3Si60 was observed.In ternary compounds,Ho2NiSi3 and Ho4NiSi7 have the solid solution phenomena;the solid solution ranges are about Ho33.3Ni18.7-9.7Si-48.0-57.0 and Ho33.Ni-8.3-2.6Si-58.3-64.1,respectively.At the same time,quasi-binary solid solutions were detected at 773 K for Ho2Ni17,HoNi5,Ho2Ni7,HoNi3,HoNi2,HoNi,HoSi.Other binary compounds of the Ho-Ni-Si system do not show any visible solubility.The magnetic property studies show that Ho3NiSi2 compound has two successive magnetic phase transitions in a low field:a spinreorientation transition at TSR=10 K and a second order ferromagnetic(FM)-paramagnetic(PM)transition at Tc=37 K.

Rietveld refinement of powder X-ray diffraction,microstructural and mechanical studies of magnesium matrix composites processed by high energy ball milling

This research reports the processing of magnesium matrix composites reinforced with silicon carbide(SiC)and aluminium oxide(Al_(2)O_(3))using powder metallurgy technique through high energy milling.Samples of Mg-SiC and Mg-Al_(2)O_(3)composites subjected to high energy ball milling for different vol%of secondary particles 20,30 and 40%of SiC and Al_(2)O_(3)are studied by X-Ray diffraction technique.The rietveld method as implemented in the Fullprof program is applied in order to determine the quantities of the resulting crystalline phases and amorphous phases at each stage of the mechanical treatment.Microstructural examination is carried out using Scanning Electron Microscope(SEM).In addition,crystal structural analysis using appropriate size and strain models is performed in order to handle the distinctive anistrophy that is observed in convinced crystallographic directions for the magnesium composite.The results are furnished in terms of crystalline domains size enlargement of the magnesium composites phases upon prolonged milling duration and discussed in the light of up to date views and theories on crystal growth of nanocrystaline materials.The hardness of the composite samples is calculated by Vickers’s Hardness tester.Further,dry sling wear test and corrosion test are performed for the fabricated composites.Composite with 30%secondary particles incorporated magnesium composites exhibits better wear and corrosion resistance than the other composites.

Application of chemical fractionation and X-ray powder diffraction to study phosphorus speciation in sediments from Lake Hongfeng,China

Based on the techniques of sequential extraction and X-ray powder diffraction(XRD) ,the distribution characteristics of phosphorus speciation were investigated in 13 sediment samples from Lake Hongfeng,an important drinking water source for Guiyang with a typical karstic limestone environment.The total phosphorus(TP) concentrations in the sediments ranged from 973.36 to 2334.18 mg/kg with a mean concentration of 1635.87 mg/kg(dry weight) ,and it was evident that the phosphorus level in the sediments was high compared with other eutrophic lakes such as Lake Chaohu and Lake Xihu.The results of the two methods,sequential extraction and XRD,demonstrated the presence of different phosphorus species in the lake sediments.Being compatible with local geophysical characteristics,the results of sequential extraction techniques indicate that the average percentages of dissolved phosphorus(DP) ,aluminum-bound phosphorus(Al-P) ,iron-bound phosphorus(Fe-P) ,calcium-bound phosphorus(Ca-P) and organic phosphorus(OP) in the sediments were 0.40%,7.06%,5.07%,45.48%and 38.49%,respectively.Notably,the concentrations of inorganic phosphorus(IP) were higher than those of OP,and the IP consisted primarily of Ca-P.The high concentrations of Ca-P may temporarily control the release of phosphorus from the sediments because it is a relatively stable,inert and non-bioavailable phosphorus fraction.The results of XRD analysis indicated that,among phosphorus species,AlPO4 was found in all sediment samples at relatively high concentrations.Moreover,the TP concentrations in the sediments were high;thus the release potential and bioavailability of phosphorus in the sediments was important.Further statistical analyses of the results revealed significant correlations between phosphorus species in the sediments with two extractable principal components and four selectable cluster levels allowing interpretation of possible origins of phosphorus loading and transformation mechanisms of phosphorus species.Furthermore,available remediation measures were briefly assessed for the lake while considering its distinct environmental features.