Diffraction Peak Profile Research Articles

Dislocation structure and crystallite size distribution in plastically deformed Ti determined by X-ray peak profile analysis

Abstract Ultrafine-grained titanium produced by equal channel angular pressing and subsequent cold rolling is studied by X-ray diffraction. It is found that a texture exists in which the hexagonal basal planes are parallel to the longitudinal axis of the billet. The crystallite size distribution and the dislocation structure are determined by X-ray diffraction peak profile analysis. The median and the variance of the crystallite size distribution are obtained as m = 39 nm and σ = 0.14, respectively. The dislocation model of anisotropic broadening of peak profiles enables to determine the active slip systems. It was found that all three possible hexagonal Burgers vectors of dislocations exist, with the composition of 66% <a> type, 33% <c> type and 1% <c + a> type.

Austenite stabilization kinetics in early stages of austempering treatment in TRIP-aided steel using in-situ neutron diffraction technique

The transformation and stabilization behaviors of the austenite (γ) phase during bainite transformation in the early stages of austempering treatment of low-alloy transformation-induced plasticity-aided bainitic ferrite (TBF) steel were investigated by in-situ neutron diffraction measurement and microstructure observation. Neutron diffraction peak profile analysis with a short time range resolution showed the changes in the phase fractions and the lattice constants of the α and γ phases in TBF steel during rapid cooling and austempering treatment. The γ phase with a low carbon concentration (γ(low-C)-Fe) immediately disappeared before the austempering time of 300 s. This indicates a remarkable increase in the lattice constant of the γ with a high carbon concentration (γ(high-C)-Fe) because of the bainite transformation of γ(low-C)-Fe and carbon partitioning to γ(high-C)-Fe. When the austempering time increased from 300 s to 3600 s, the volume fraction of γ(high-C)-Fe monotonically decreased and the lattice constant was hardly changed.

Effects of Voigt diffraction peak profiles on the pair distribution function.

Powder diffraction and pair distribution function (PDF) analysis are well established techniques for investigation of atomic configurations in crystalline materials, and the two are related by a Fourier transformation. In diffraction experiments, structural information, such as crystallite size and microstrain, is contained within the peak profile function of the diffraction peaks. However, the effects of the PXRD (powder X-ray diffraction) peak profile function on the PDF are not fully understood. Here, all the effects from a Voigt diffraction peak profile are solved analytically, and verified experimentally through a high-quality X-ray total scattering measurement on Ni powder. The Lorentzian contribution to the microstrain broadening is found to result in Voigt-shaped PDF peaks. Furthermore, it is demonstrated that an improper description of the Voigt shape during model refinement leads to overestimation of the atomic displacement parameter.

Austenite Stabilization Kinetics in Early Stage of Austempering Treatment in Trip-Aided Steel Using In-Situ Neutron Diffraction Technique

The transformation and stabilization behaviors of the austenite (γ) phase during bainite transformation in the early stages of austempering treatment of low-alloy transformation-induced plasticity-aided bainitic ferrite (TBF) steel were investigated by in-situ neutron diffraction measurement and microstructure observation. Neutron diffraction peak profile analysis with a short time range resolution showed the changes in the phase fractions and the lattice constants of the α and g phases in TBF steel during rapid cooling and austempering treatment. The γ phase with a low carbon concentration (γ2-Fe) immediately disappeared before the austempering time of 300 s. This indicates a remarkable increase in the lattice constant of the γ with a high carbon concentration (γ1-Fe) because of the bainite transformation of γ2-Fe and carbon partitioning to γ1-Fe. When the austempering time increased from 300 s to 3600 s, the volume fraction of γ1-Fe monotonically decreased and the lattice constant was hardly changed.

Line profile analysis of synchrotron X-ray diffraction data of iron powder with bimodal microstructural profile parameters

Room-temperature synchrotron X-ray diffraction and subsequent detailed line profile analysis of Fe powder were performed for microstructural characterization. The peak shapes of the diffraction pattern of Fe were found to be super-Lorentzian in nature and the peak widths were anisotropically broadened. These peak profile features of the diffraction pattern are related to the microstructural parameters of the material. In order to elucidate these features of the diffraction pattern, detailed line (peak) profile analyses were performed using the Rietveld method, modified Williamson–Hall plots and whole powder pattern modelling (WPPM), and related microstructural parameters were determined. Profile fitting using the Rietveld and WPPM methods with a single microstructural (unimodal) model shows systematic deviation from the experimentally observed diffraction pattern. On the basis of Rietveld analysis and microstructural modelling it is revealed that the microstructure of Fe consists of two components (bimodal profile). The microstructural parameters of crystallite/domain size distribution, dislocation density, nature of dislocations and phase fraction were evaluated for both components. The results obtained using different methods are compared, and it is shown that diffraction peak profile analysis is capable of modelling such inhomogeneous bimodal microstructures.

Retracted] XRD Peak Profile Analysis of SiC Reinforced Al2O3 Ceramic Composite Synthesized by Electrical Resistance Heating and Microwave Sintering: A Comparison

Al2O3 with 10 wt.% of SiC ceramic composite is synthesized at 1500°C by electrical resistance heating sintering with a holding time of 5 hours and microwave sintering methods with a holding time of 15 minutes. The samples generated by the two methods are characterized using powder X‐ray diffraction and field emission scanning electron microscopy (FESEM). Experiments with both samples showed that the existence of the α‐Al2O3 and β‐SiC phases in both samples was verified by the findings of XRD pattern on both samples. Microstructure study illustrates that the Al2O3 matrix particles have spherical‐like shape and their average matrix particle size is 67 ± 5 nm for electrical resistance heating sintered sample and 38 ± 5 nm for microwave sintered sample. The lattice strain and crystallite size of Al2O3 matrix were measured using Williamson–Hall (W‐H) methods, which were achieved via the use of XRD peak broadening, based on a diffraction pattern. Three modified W‐H models were used to compute other parameters, including strain (ε) and stress (σ), as well as energy density (u). These models were the uniform deformation model (UDM), the uniform deformation energy density model (UDEDM), and the uniform deformation stress model (UDSM). The average crystallite sizes of α‐Al2O3 attained from these three models of Williamson–Hall (W–H) methods and FESEM analysis are correlated and found very close to each other. In all three models of the W‐H technique, X‐ray diffraction peak profile examination of electrical resistance heating‐sintered and microwave‐sintered Al2O3/10 wt. % SiC ceramic composite reveals that the microwave‐sintered sample has finer crystallite size with less strain.

New Ternary Compounds of the Composition Cu2SnTi3 and Their Crystal Structures

A new ternary compound Cu2SnTi3 has been synthesized by vacuum sintering at 900 °C. The atomic structures of CaCu5- and InNi2-like Cu2SnTi3 are calculated using density functional theory methods. The X-ray diffraction (XRD) analysis and selected area diffraction (SAD) patterns of the new ternary compound Cu2SnTi3 are considered to verify the atomic structures of CaCu5- and InNi2-like Cu2SnTi3. The results reveal that the InNi2-like Cu2SnTi3 model has the lowest total energy of −35.239 eV, representing the trigonal crystal structure. The orthorhombic crystal structure of the CaCu5-like Cu2SnTi3 model has the second lowest total energy of −33.926 eV. Our theoretical X-ray diffraction peak profiles of InNi2-like (CaCu5-like) Cu2SnTi3 are nearly identical to experimental one, leading to an error below 2.0% (3.0%). In addition, the hexagonal crystal structure of the CaCu5-like Cu2SnTi3 model has the highest total energy of −33.094 eV. The stability of the Cu2SnTi3 in terms of energy follows the order: the trigonal, orthorhombic, and hexagonal crystal structure.

Correlation RTOF diffractometry at long-pulse neutron source: II. Analysis of frequency windows and diffraction peak profiles

Neutron RTOF diffractometry is a special correlation technique, combining the use of a fast Fourier chopper for modulation of the incident neutron beam intensity and the reverse time-of-flight (RTOF) method for data acquisition. This approach allows one to achieve a high-resolution level of the instrument over a wide range of interplanar spacing dhkl at a relatively short flight distance between the chopper and the sample position. Recently, a new high-performance DAQ system for recording RTOF data in a list mode was implemented on high-resolution Fourier diffractometers operating at the long-pulse neutron source – the IBR-2 reactor – in FLNP JINR (Dubna, Russia). One of the most important features of list-mode data acquisition is the possibility to analyze real frequency window of the Fourier chopper and compensate the chopper phase mismatch, which is crucial for obtaining diffraction peaks with a symmetric Gaussian profile. This paper discusses the experience of using list-mode DAQ for analysis of real frequency windows reconstructed from pickup signal events. In addition, a comparison of various frequency windows and their influence on the diffraction peak shape is performed.

Influences of annealing temperature on properties of Fe2+:ZnSe thin films deposited by electron beam evaporation and their applications to Q-switched fiber laser**Project supported by the National Natural Science Foundation of China (Grant No. 11574221) and the Graduate Student’s Research and Innovation Fund of Sichuan University, China (Grant No. 2018YJSY008).

Fe2+:ZnSe thin films are prepared on sapphire substrate at room temperature by electron beam evaporation and then annealed in vacuum (about 1 × 10–4 Pa) at different temperatures. The influences of thermal annealing on the structural and optical properties of these films such as grain size and optical transmittance are investigated. The x-ray diffraction patterns show that the Fe2+:ZnSe thin film is preferred to be oriented along the (111) plane at different annealing temperatures. After the film is annealed, the full-width-at-half-maximum ( FWHM ) of the x-ray diffraction peak profile (111) of the film decreases and its crystal quality is improved. Scanning electron microscope images show that the films are more dense after being annealed. Finally, the sample is used as a saturable absorber in ZBLAN fiber laser. The annealed Fe2+:ZnSe thin films can be used to realize stable Q-switching modulation on ZBLAN fiber laser. The results demonstrate that the Fe2+:ZnSe thin film is a promising material for generating the high-power pulses of mid-infrared Q-switched fiber lasers.

Inclusion of the Phytoalexin trans-Resveratrol in Native Cyclodextrins: A Thermal, Spectroscopic, and X-Ray Structural Study.

The aim of the study was to determine the feasibility of complexation between the antioxidant trans-resveratrol (RSV) and underivatized cyclodextrins (CDs) using a variety of preparative methods, including physical mixing, kneading, microwave irradiation, co-evaporation, and co-precipitation techniques. Products were characterized using differential scanning calorimetry (DSC), simultaneous thermogravimetric/DSC analysis (TGA/DSC), Fourier transform infrared (FT-IR) spectroscopy, and powder X-ray diffraction (PXRD). With α-CD and RSV, sample amorphization was revealed by PXRD and FT-IR, but no definitive inclusion complexation was evident. Similar results were obtained in attempts to complex RSV with β-CD. However, complex formation between γ-CD and RSV was evident from observation of an endo-/exothermic effect appearing in the DSC trace of the product from kneading and was further corroborated by FT-IR and PXRD methods. The latter technique indicated complexation unequivocally as the diffraction peak profile for the product matched that for known isostructural γ-CD complexes. Single crystal X-ray analysis followed, confirming the predicted complex between γ-CD and RSV. A combination of 1H NMR and TGA data yielded the complex formula (γ-CD)3·(RSV)4·(H2O)62. However, severe disorder of the RSV molecules prevented their modeling. In contrast, our previous studies of the inclusion of RSV in methylated CDs yielded crystals with only minor guest disorder.

Structural and physical parameters of sol-gel spin coated ZnO thin films: Effect of sol concentration

Zinc oxide thin films are deposited by sol–gel spin coating on glass substrates for varying sol concentrations and the effect is studied on a range of structural and physical parameters which are determined by X-ray diffraction and X-ray peak profile analysis. The diffraction peaks confirms the formation of ZnO with hexagonal wurtzite phase. The film with highest sol concentration shows preferred c-axis orientation. The crystallinity of the films increases with increase in concentration of the sol. The X-ray peak broadening analysis was employed to estimate the physical parameters such as strain, stress and energy density corresponding to major diffraction peaks by the Williamson-Hall (W-H) method with three different models namely uniform deformation model, uniform stress deformation model and uniform deformation energy density model. To the best of our knowledge studies of ZnO thin films deposited with various sol concentrations using these models have not been reported. The deposited ZnO thin films may be used in solar cells to enhance their efficiency.

Study of the structure of fibrous carbon materials using X-ray diffractometry

New possibilities for diagnosing the structure of carbon materials by X-ray diffraction analysis are described. The studies were performed on an X-ray diffractometer D8 ADVANCE (filtered Cu K α radiation) using carbon fibers (CF) differed in the mode of heat treatment (~2300 to ~3000°C). It is shown that when studying the structure of fibrous carbon materials characterized by a large depth of X-rays penetration, it is necessary to limit the thickness of the object under study to ~0.1 mm to provide the self-focusing condition for the entire sample volume engaged in formation of the diffracted beam. The material of high modulus carbon fibers can be heterogeneous and contain coherent scattering regions wherein the crystal structure parameters are somewhat different and experimentally observed diffraction peaks 002, 004, and 006 become asymmetric and are not described by the Gauss, Lorentz, or Voigt functions. Thus, the standard method used for determination of the average value of the interplanar spacing and the size of coherent scattering regions does provide reliable information on the real structure of the material. The profile of the asymmetric diffraction peak 002 was analyzed using the Origin program thus providing information about fine (heterogeneous) structure of the carbon fiber material which largely determines the physicomechanical properties. The data on 002 diffraction peak profiles of carbon fibers before and after removal of the Cu K α 2 component are presented. The data on decomposition of the experimentally observed asymmetric 002 diffraction peaks into symmetric peaks described by the Gaussian, Lorentz, and Voigt functions are compared. The most preferable is the decomposition into the components described by the Gaussian or Voigt functions.

Comparative study of crystallite size using Williamson-Hall and Debye-Scherrer plots for ZnO nanoparticles

ZnO nanoparticles at different pH were synthesised by a sol-gel technique from zinc acetate dihydrate at a calcination temperature of 450 °C. The synthesized ZnO nanoparticles were characterised by x-ray diffraction (XDR) peak profile analysis, high-resolution scanning electron microscopy and Fourier transform infrared spectroscopy. The effects of solution pH on the crystallite size using Williamson-Hall and Debye–Scherrer were determined. The XRD analysis of the zincite phase structure of ZnO nanoparticles was obtained in the form of spheres for all the samples. The average crystallite sizes of ZnO nanoparticles decrease with increasing pH. The crystallite sizes of ZnO nanoparticles were investigated using Williamson-Hall analysis and Scherrer’s formula. The parameters such as dislocation density and lattice strain were computed for the diffraction peaks of XRD in the range of 2θ = 10–90°. The results showed that the crystallite sizes calculated from Scherrer’s equation and Williamson-Hall analysis from XRD are not inter-correlated. Both methods give a wide deviation of crystallite size. Also, it was found that the crystallite sizes using both methods decrease with an increase in pH. Smaller crystallite sizes were estimated using the Scherrer’s formula. Thus, it is deduced that the equation fitted well for the synthesised ZnO nanoparticles.

Structural and electrochemical properties of lithiated conical carbon nanotubes as anode materials for lithium ion accumulating systems

AbstractInteraction of conical carbon nanotubes with lithium during their electrochemical treatment was studied by galvanostatic measurements. The presence of reversible and irreversible reactions during the Li insertion into conical carbon nanotubes was established. The structural changes occurring in the conical walls of the conical carbon nanotubes in consequence of the lithium intercalation were investigated by using X-ray diffraction. The results obtained show that the lithiation of conical carbon nanotubes is partially reversible and leads to a change in the diffraction peak profile (2θ = 26°) corresponding to the interplanar distance in conical carbon nanotubes. Such changes are associated with the lithium insertion into the interplanar spaces of conical carbon nanotubes.

Estimation of lattice strain in alumina\u2013zirconia nanocomposites by X-ray diffraction peak profile analysis

Zirconia nanoparticles were synthesized by a solution combustion technique. Zirconia nanoparticles were grown inside alumina templates to control the crystal size. The alumina templates were characterized by pores of sizes of approximately 6–8 nm. X-ray diffraction line profile analysis using Williamson–Hall method and Warren and Averbach revealed that the alumina templates were characterized by negligible defect-related effect of lattice distortion. Rietveld structure refinement did not reveal any gross difference with the literature reported values for cell parameters ‘a’ and ‘c’ and fractional atomic coordinates x and z for Al and O atoms indicating no large-scale bond deformation. The template X-ray reflections in the nanocomposites are skewed in nature which indicates some distortion of the templates might have taken place. The distortion is, however, plastic in nature which is evident from the higher level of lattice distortion viz. 0.2% of lattice microstrain.

Application of Different Diffraction Peak Profile Analysis Methods to Study the Structure Evolution of Cold-Rolled Hexagonal α-Titanium

This paper presents a comparison between the “classical” and the modified Williamson–Hall and Warren–Averabach methods applied to an analysis of the microstructure of $$\alpha$$-titanium. The microstructural parameters of cold-rolled titanium specimens were retrieved from analysis of the X-ray diffraction (XRD) peaks. The high-quality XRD patterns were received at the P07 beamline (The High Energy Materials Science) at the German electron synchrotron. The dependence of the crystallite size, the inhomogeneous microstrains, the average dislocation density, the dislocation cut-off radius and some other parameters on the plastic strain were estimated. The results clearly indicate that, due to the consideration of the dislocation contrast effect, the modified models are a much better fit to the experimental data in comparison with the “classical” models. The results of hardness and corrosion resistance measurements of Ti samples can be explained based on the results obtained from the XRD analysis.

Stacking Fault Energy, Dislocation Density, and Twin Fault Probability Determined by Neutron Diffraction Peak Profile Analysis in CrCoNi Based Medium Entropy Alloys

Neutron diffraction peak profile analysis was used to determine stacking fault energy (SFE), dislocation density, and twin fault probability (Ptw) in CrCoNi and CrCoNiFe medium entropy alloys at 293K and 140K. The CrCoNi shows higher Ptw (up to 3.8%) and dislocation density (up to 9.7 x 1015 m-2) than CrCoNiFe (1.3% and 3.4 x 1015 m-2, respectively) at 293K. Meanwhile, at 140K, the Ptw in CrCoNiFe increases significantly to 4.4%. The dominant twinning deformation is due to the lower SFEs of CrCoNi (16.1 mJ/m2) at 293K and CrCoNiFe (7.4 mJ/m2) at 140K compared to 32.1 mJ/m2 for CrCoNiFe at 293K.

Spin State of Cobalt Ions and the Magnetic Properties of Heavily Ba‐Substituted Cobaltites with Perovskite Structure

The evolution of the magnetic and magnetotransport properties and of the crystal structure in the cobaltites La0.45Ba0.55CoO3‐δ and La0.4Ba0.6CoO3‐δ depending on the oxygen content is investigated by various methods. The oxygen content decrease leads to a stabilization of the oxidation state 3+ of the cobalt ions and to a transition from ferromagnetic conducting state into an insulating antiferromagnetic long‐range one. Application of a magnetic field gradually transforms the antiferromagnetic state into a ferromagnetic one. This transition is accompanied by a large magnetoresistance effect. There is no obvious temperature dependence of the average cubic unit cell parameter, however, temperature evolution of diffraction peak profiles suggests a phase separation scenario apparently due to a spin crossover. It is assumed that the ferromagnetic component corresponds to the collective intermediate spin state of cobalt ions while antiferromagnetic phase corresponds to a mixed high/low spin state.

Electric field-induced strain in core-shell structured BiFeO3[sbnd]K0.5Bi0.5TiO3[sbnd]PbTiO3 ceramics

A coherent core-shell structure in 0.24BiFeO3-0.56K0.5Bi0.5TiO3-0.20PbTiO3 ceramics, with Tm around 385 °C, was revealed using a combination of characterisation methods including scanning and transmission electron microscopy. The core regions consist of a cubic matrix with minor monoclinic phase with limited coherence length, while the shell regions are a tetragonal phase with characteristic long-range ordered ferroelectric domain structures. The electric field-induced strains for both core and shell regions were investigated by conducting an in-situ poling study using high energy synchrotron X-ray diffraction (XRD). A methodology is developed to evaluate both intrinsic (lattice strain) and extrinsic (domain switching) contributions for each phase based on diffraction peak profile fitting for multiple reflections.It is shown that there were no significant variations in the cubic and tetragonal phase fractions under an electric field in the range from −6 to +6 kV mm−1. An irreversible strain ∼0.04% was attributed mainly to ferroelectric domain switching in the tetragonal shell regions, while a reversible lattice strain ∼0.12% was identified in the pseudo-cubic core, leading to significant levels of intra-granular stress. Strain anisotropy, dependent on the crystallographic orientation of different grain families, was also evident. Macroscopic strain measurements, conducted using a novel digital image correlation (DIC) method, demonstrated the formation of typical ‘butterfly’-type strain-electric field loops and were consistent with the total strain values calculated from the XRD results.

Syntheses and Characterization of Intermetallic Nanostructures Based on Mn

The nanocrystalline powders of Mn50Ni41Sn9 were prepared by ball milling using a PM 200-type RETSCH planetary ball mill. The morphological, microstructural, and structural characterizations of the nanostructured powders were carried out by scanning electron microscope, x-ray diffraction, first using the Williamson–Hall relation for the refinement of the diffraction peak profiles. The high-temperature thermal and magnetic properties of nanocrystalline alloy Mn50Ni41Sn9 were characterized at different temperatures using a vibrating sample magnetometer; differential scanning calorimetry was used to determine the transformation temperature and thermodynamic values in the Mn50Ni41Sn9 alloy.