X-ray Diffraction Apparatus Research Articles

Advancing the understanding of metal additive manufacturing via physical simulation and in situ transmission electron microscopy: a viewpoint

The complex microstructure evolution and heterogeneities in metal additive manufacturing (AM) continue to delay the adoption of AM parts by additional industries. Achieving uniform and superior properties in AM parts requires better fundamental understanding of the microstructural evolution. A suitable pathway to gain such understanding is via in situ techniques such as high-speed X-ray imaging, high-resolution infrared cameras, or via synchrotron and neutron diffraction. However, these methods are complex and resource intensive. Modeling may be a more economical avenue, yet, to make these models more robust and reliable, data from in situ techniques are often required. We believe that in some cases, physical simulation methods originally developed for research on conventional processing such as forging, rolling, and welding may provide similar insights. This viewpoint article discusses existing experimental methods for tracking the microstructure evolution during AM in lab-scale settings, focusing on Ni-based superalloys as a case study. The proposed physical simulation methods include the Gleeble thermo-mechanical simulator, dilatometry, and the arc-melting heat treatment technique. These methods can also be integrated into various X-ray, synchrotron, and neutron diffraction set-ups. We discuss how insights derived from thermo-kinetic modeling can underpin the experimental observations from physical simulations. Last, in situ transmission electron microscopy is evaluated as a powerful method with unparalleled resolution for observing the microstructure evolution directly during simulated AM processes. We believe that these methods can be extended to other alloy systems, enhancing scientific understanding, and streamlining the efficient development of AM parts with superior and more uniform properties, promoting the more widespread adoption of AM.

A miniature X-ray diffraction setup on ID20 at the European Synchrotron Radiation Facility.

We describe an ultra-compact setup for in situ X-ray diffraction on the inelastic X-ray scattering beamline ID20 at the European Synchrotron Radiation Facility. The main motivation for the design and construction of this setup is the increasing demand for on-the-fly sample characterization, as well as ease of navigation through a sample's phase diagram, for example subjected to high-pressure and/or high-temperature conditions. We provide technical details and demonstrate the performance of the setup.

Diamagnetic to Ferromagnetic Like Transition of Non-Stoichiometry Barium Titanate (BaTiO3-x) Prepared by Sol-gel Method

The oxygen vacancy properties are significant, creating ferromagnetic properties of material in metal oxide systems like dilute magnetic semiconductors. An aqueous sol-gel method has been used in the present study to synthesize non-stoichiometry BaTiO3-x polycrystalline. In an attempt of examining the oxygen deficiency consequences on the magnetic properties, the gel samples were sintered (1000◦C) at various times (6, 12, 18, and 24 hours) under a vacuum environment. This study employs an X-ray diffraction apparatus in terms of characterizing segments and structures of the samples. It also investigates morphology and element distribution on the surface of the samples exploiting an Electron microscope where Energy dispersive spectroscopy is supplied. For the purpose of characterizing the magnetic properties of the samples, it applies vibrating sample magnetometers. The chemical state of the element and its corresponding bond to other elements was identified using X-ray photoelectron spectroscopy. Single-phase compounds were observed. The crystal system is tetragonal, but the crystal parameters are different. Increase sintering time leads to increase crystallite size and decrease in micro strain. Moreover, sintering in a vacuum environment results in oxygen deficiency and leads to the atomic ratio of Ba/Ti change as the sintering time increases. The Ba/Ti ratio change affects the transformation from diamagnetic to ferromagnetic-like. The elements (Ba, Ti and O) chemical state is shown and its bonding to the corresponding element along with the X-ray photoelectron spectroscopy pattern of the BTX2 sample. The element of oxygen binds to Ti and Ba while Ba element exists in two chemical states.

In-situ cryogenic X-ray diffraction analysis of Poly(dimethylsiloxane) oil and film

Understanding the phase transitions and crystallographic characteristics of polysiloxane materials poses a significant challenge. To address this issue, a custom cryogenic chamber has been developed and integrated with a laboratory X-ray diffraction apparatus, enabling the execution of in-situ temperature-dependent X-ray diffraction (XRD) analyses across the cooling and heating cycles. Through the utilization of diverse sample holders, the real-time monitoring of crystallization and melting phenomena in both linear poly(dimethylsiloxane) (PDMS) oil and crosslinked PDMS film has been made feasible. Notably, high-quality X-ray diffraction data, encompassing 13 diffraction lines, are successfully acquired for the first time for linear PDMS oil at 153K. Subsequent crystallographic examination has revealed a tetragonal unit cell characterized by lattice parameters a = b = 8.3379 Å, c = 11.9284 Å, and space group I 41, suggesting the adoption of a fourfold helical conformation by two polymer chains, each comprising four monomer units, within the lattice structure. This improved and versatile X-ray instrumentation presents clear advantages over conventional commercial powder X-ray diffractometers, which is anticipated to provide a promising in-situ characterization approach for investigating the low-temperature behaviors of liquid or oil materials.

A modular table-top setup for ultrafast x-ray diffraction.

We present a table-top setup for femtosecond time-resolved x-ray diffraction based on a Cu Kα (8.05keV) laser driven plasma x-ray source. Due to its modular design, it provides high accessibility to its individual components (e.g., x-ray optics and sample environment). The Kα-yield of the source is optimized using a pre-pulse scheme. A magnifying multilayer x-ray mirror with Montel-Helios geometry is used to collect the emitted radiation, resulting in a quasi-collimated flux of more than 105 Cu Kα photons/pulse impinging on the sample under investigation at a repetition rate of 10Hz. A gas ionization chamber detector is placed right after the x-ray mirror and used for the normalization of the diffraction signals, enabling the measurement of relative signal changes of less than 1% even at the given low repetition rate. Time-resolved diffraction experiments on laser-excited epitaxial Bi films serve as an example to demonstrate the capabilities of the setup. The setup can also be used for Debye-Scherrer type measurements on poly-crystalline samples.

Synthesis of β-tricalcium phosphate by modifying the heating process of a dental casting mold.

This study investigated a novel method for artificial synthesis of β-tricalcium phosphate (β-TCP). The binder of the phosphate-bonded investment was replaced with calcium oxide instead of magnesium oxide and sintered in an electric furnace. The water/powder mixing ratio for hardening was determined using preliminary experiments. Thermal analysis was performed to check the thermal behavior of the sample tested. In addition, the fired sample was analyzed using an X-ray diffraction apparatus to identify the compounds after sintering. The hardened sample exhibited multiple compounds, including unreacted components, post which, new compounds were generated by heating. Peaks of calcium pyrophosphate and β-TCP were confirmed at 800ºC and 1,300ºC, respectively. β-TCP could be easily synthesized within the limited study by sintering at 1,300ºC both monoammonium phosphate and calcium oxide. Experimental results suggest that β-TCP can be easily synthesized by simulating the conventional dental casting process.

A MHz X-ray diffraction set-up for dynamic compression experiments in the diamond anvil cell.

An experimental platform for dynamic diamond anvil cell (dDAC) research has been developed at the High Energy Density (HED) Instrument at the European X-ray Free Electron Laser (European XFEL). Advantage was taken of the high repetition rate of the European XFEL (up to 4.5 MHz) to collect pulse-resolved MHz X-ray diffraction data from samples as they are dynamically compressed at intermediate strain rates (≤103 s-1), where up to 352 diffraction images can be collected from a single pulse train. The set-up employs piezo-driven dDACs capable of compressing samples in ≥340 µs, compatible with the maximum length of the pulse train (550 µs). Results from rapid compression experiments on a wide range of sample systems with different X-ray scattering powers are presented. A maximum compression rate of 87 TPa s-1 was observed during the fast compression of Au, while a strain rate of ∼1100 s-1 was achieved during the rapid compression of N2 at 23 TPa s-1.

Characterization of Titanium dioxide (TiO2 ) Nanoparticles Biosynthesized using Leuconostoc spp. Isolated from Cow’s Raw Milk

Nanotechnology is a continually expanding field for its uses and applications in multiple areas i.e. medicine, science, and engineering. Biosynthesis is straightforward, less-toxicity, and cost-effective technology. TiO2 NPs biosynthesis has attained consideration in recent decades. In this study, probiotic bacteria were isolated from cow’s raw milk samples, and then were identified by using the Vitek2 system; as Leuconostoc spp. included Leuconostoc mesenteroides subsp. mesenteroides (Leu.1), Leuconostoc mesenteroides subsp. cremoris (Leu.4), and Leuconostoc pseudomesenteroides (Leu.14). All Leuconostoc spp. isolates showed an ability for TiO2 NPs bio-production, after being incubated at anaerobic conditions (30 o C/ 24 h) in DeMan Regosa and Sharpe (MRS) broth medium. The biosynthesized TiO2 nanoparticles were characterized using the following apparatuses: UV-Vis spectroscopy, X-ray diffraction (XRD) apparatus, Atomic Force Microscopy (AFM), Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FE-SEM) in addition to Energy Dispersive X-ray analysis (EDX) spectra. The characterized biosynthesized TiO2 NPs were spherical-shaped, nanostructure anatase crystals with an average size range of 53.35-59.41 nm. The UV absorption spectrum was observed at the wavelength 344-248 nm; the topography AFM 2D and 3D images result showed the height and roughness of biosynthesized TiO2 NPs that were in the range of 1.137-18.88 nm. Absorption peaks in the FTIR spectra were located in a region typical of TiO2 NPs, and biosynthesized TiO2 nanoparticles’ main IR topographies (408.21- 445.80) cm-1 belonged to anatase Titania (Ti-O-Ti) bridge.

A unique laboratory experimental setup for single-crystal X-ray diffraction under electric field

A unique laboratory experimental setup for single-crystal X-ray diffraction under electric field

The Radon transform as a tool for 3D reciprocal-space mapping of epitaxial microcrystals.

This work presents a new approach suitable for mapping reciprocal space in three dimensions with standard laboratory equipment and a typical X-ray diffraction setup. The method is based on symmetric and coplanar high-resolution X-ray diffraction, ideally realized using 2D X-ray pixel detectors. The processing of experimental data exploits the Radon transform commonly used in medical and materials science. It is shown that this technique can also be used for diffraction mapping in reciprocal space even if a highly collimated beam is not available. The application of the method is demonstrated for various types of epitaxial microcrystals on Si substrates. These comprise partially fused SiGe microcrystals that are tens of micrometres high, multiple-quantum-well structures grown on SiGe microcrystals and pyramid-shaped GaAs/Ge microcrystals on top of Si micropillars.

Thermal decomposition kinetics of FAPbI3 thin films

In the realm of organic-inorganic-hybrid metal-halide perovskites, ${\mathrm{FAPbI}}_{3}$ is seeing increasing attention as a potentially more stable alternative to ${\mathrm{MAPbI}}_{3}$. To add to our previous paper, where we studied the reaction kinetics of the thermal decomposition of ${\mathrm{MAPbI}}_{3}$, here we analyze the compositional change and crystal phase evolution during the thermal decomposition of ${\mathrm{FAPbI}}_{3}$ thin films. To this end, we prepare the perovskite using thermal coevaporation and monitor the growth and thermal decomposition in vacuum with an in situ x-ray diffraction setup. The experimental procedure has been carried out via three approaches: producing a partially decomposed sample with the help of a graded temperature profile, using a temperature ramp and a set of isothermal decomposition experiments. From this data we analyze and calculate the stoichiometry and phase changes, the activation energy $E$ and the frequency factor $A$ of the thermal decomposition process, in addition to the thermal expansion coefficient during heating. We compare our results to the ones obtained for ${\mathrm{MAPbI}}_{3}$ thin films by the same experimental method, confirming the enhanced thermal stability of ${\mathrm{FAPbI}}_{3}$.

A combined rotating disk electrode-surface x-ray diffraction setup for surface structure characterization in electrocatalysis.

Characterizing electrode surface structures under operando conditions is essential for fully understanding structure-activity relationships in electrocatalysis. Here, we combine in a single experiment high-energy surface x-ray diffraction as a characterizing technique with a rotating disk electrode to provide steady state kinetics under electrocatalytic conditions. Using Pt(111) and Pt(100) model electrodes, we show that full crystal truncation rod measurements are readily possible up to rotation rates of 1200 rpm. Furthermore, we discuss possibilities for both potentiostatic as well as potentiodynamic measurements, demonstrating the versatility of this technique. These different modes of operation, combined with the relatively simple experimental setup, make the combined rotating disk electrode-surface x-ray diffraction experiment a powerful technique for studying surface structures under operando electrocatalytic conditions.

Role of orientation relationship for the formation of morphology and preferred orientation in NiAl-(Cr,Mo) during directional solidification

In order to reveal the role of orientation relationship for the formation of morphology and preferred orientation in directionally solidified NiAl-(Cr,Mo) eutectic alloys, a unique in-situ X-ray diffraction setup was utilized. Comprehensive analyses of the solidification front during processing demonstrate that the eutectic alloys crystallize with preferred crystallographic orientation of both phases with respect to the growth direction. These orientations of the eutectics prevail during growth of the fibrous or lamellar colonies and subsequent cooling as determined by ex-situ microstructural analysis. Depending on the composition and growth velocity, different preferred orientations were obtained resolving the ambiguity in literature regarding the reported components, e.g. strong 〈001〉 and 〈111〉 directions parallel to the growth direction but also additional minor 〈110〉 components. By the aid of in-situ experiments excluding the superimposed effect of different thermal expansion of the phases in comparison to previous experiments, a correlation between the evolving preferred orientation and lattice mismatch during solidification was found for alloys with low Mo content. Remarkably, no change in morphology between fibers and lamellae was associated to the transitions in preferred orientation. For larger Mo contents, two distinct orientation relationships between the A2 (Cr,Mo) solid solution and the B2 NiAl intermetallic phase were identified by ex-situ microstructural analysis, namely (1) cube-on-cube and (2) a 60° rotation about 〈111〉 in different colonies of one and the same sample. The morphology of these colonies were fibrous and lamellar, respectively. For the 60° relationship, the growth direction of both phase is unique, namely 〈111〉. Thus, morphology and preferred orientation are determined by the orientation relationship in this case.

Room temperature strengthening mechanisms, high temperature deformation behavior and constitutive modeling in an Al-3.25Mg-0.37Zr-0.28Mn-0.19Y alloy

To improve the ambient strength and high temperature ductility, a novel Al-3.25Mg-0.37Zr-0.28Mn-0.19Y (wt.%) alloy has been fabricated by multidirectional forging and warm rolling. Microstructures and mechanical properties were investigated by light microscope, X-ray diffraction apparatus, transmission electron microscope, and tensile tester. The ultimate tensile strength, yield strength, and elongation of 354.67 ± 0.04, 254 ± 3 MPa, and 18.47% were achieved in the processed alloy, respectively, at room temperature. The maximum superplasticity of 412.5% was demonstrated in this fine-grained (grain size of 8.80 ± 1.06 μm) alloy at 793 K and 8.33 × 10−4 s−1. An ambient strengthening sequence was obtained: grain boundary strengthening > dislocation strengthening > Orowan strengthening > solid solution strengthening. The occurrence of Portevin–Le Chatelier effect or serrated flow in as-annealed alloy was confirmed by theoretical model estimation and experimental evidence. Microstructural evolution and flow stress curves confirmed that dynamic recovery and dynamic grain growth occurred at elevated temperatures; Sotoudeh-Bate curves were discovered at higher temperatures and lower strain rates. Solute Mg, dynamic grain growth, and flow localization were responsible for the formation of Sotoudeh-Bate curves. Modified Johnson–Cook constitutive equation considering dislocation variables and power-law constitutive equation were established. In this fine-grained alloy at 793 K and 8.33 × 10−4 s−1, the number of dislocations inside a grain was 6, the stress exponent was 2, the grain size exponent was 2, and the average activation energy for deformation was 140.10 kJ/mol. These pieces of evidence demonstrated that grain boundary sliding accommodated by intragranular dislocation controlled by lattice diffusion governs the rate-controlling process.

The reproducible normality of the crystallographic B-factor

Reproducibility determines the utility of a measurement. In structural biology the reproducibility permeate areas such as mechanics, data measurement, data analysis and refinement. In order to access the reproducibility of the combined contribution of these sources in uncertainties of protein crystallography we evaluated four groups of parameters from data collection to final structural model. We used lysozyme as a model, with 20 datasets collected at 1.6 Å resolution using two dissimilar x-ray diffraction setups and refined through a single automatic pipeline without arbitrary interpretation. Besides statistical differences in some structural parameters, the reproducibility of the final refined models allowed the determination of positional uncertainty, in good agreement with the Luzzati coordinate error. While the raw B-factor was found non-reproducible, an empirical scaling/normalization resulted in reproducible B-factors. The validity of this empirical scaling was corroborated by the reproducibility of normalized B-factors of independently solved datasets from proteins (insulin and myoglobin) from varying space groups available from structural database. The reproducibility of normalized B-factor may reposition this displacement parameter in the analysis of chemical (ligands, pH) and physical (pressure, temperature, space groups) variables.

Cover Picture: Tailoring Preferential Orientation in BaTiO3‐based Thin Films from Aqueous Chemical Solution Deposition (Chem. Methods 2/2022)

The Front Cover shows our in-situ X-ray diffraction setup for analysing the crystallization process in oxide thin films made by chemical solution deposition. By adjusting the process parameters, the nucleation and growth conditions are changed and the degree of preferred orientation and epitaxi in the oxide films can be tailored. This change is illustrated by the change in microstructure of the polycrystalline films with random orientation (left) towards highly oriented cube-on-cube grown films (right) where the film unit cell follows that of the substrate. This effect can be observed experimentally by the appearance of spot reflection instead of full diffraction rings on the detector. More information can be found in the Full Paper by Kristine Bakken et al.

SDPD-SX: combining a single crystal X-ray diffraction setup with advanced powder data structure determination for use in early stage drug discovery

A method for routine molecular crystal structure determination on very small (typically <0.1 mg) amounts of crystalline material using powder X-ray diffraction data from a laboratory-based single-crystal diffractometer is reported.

Experimental investigation of n-heptane unsteady-state pyrolysis coking characteristics in microchannel

Coke deposition is considered a challenging problem during hydrocarbon pyrolysis. To get more insights into pyrolysis coking characteristics in the regenerative cooling channels, the unsteady-state experiments of n-heptane were performed in a 2.0 mm (internal diameter) passivated STS304 tube at 873–1073 K and 1.0 MPa with a feeding flow rate of 1.0 mL/min during pyrolysis for 5–60 min. The unsteady-state and spatial coke distributions were obtained. Results showed three distinct stages of coking, namely, catalytic coking, the transition stage, and pyrolytic coking. Coke samples obtained under different temperatures were characterized by element analyzer, scanning electron microscope (SEM), thermogravimeter coupled with a Fourier transform infrared spectroscopy (TG-FTIR), X-ray diffraction (XRD), and Raman spectra apparatus. The coke could be classified into two or three types according to its oxidative activity, and was composed of aromatic carbon and aliphatic hydrocarbons. The morphology of the coke transitions from filamentous to spherical with temperature and pyrolysis time. The C/H ratio of coke increased with the temperature in the catalytic coking stage, but decreased in the pyrolytic coking stage. High H contents and extensive defects of the coke observed at high temperatures could attributed to the generation of large amounts of pyrolytic coke and high coking rate, which resulting a lower degree of dehydrogenation. The presence of metallic substances in the coke verifies the catalytic effect at the beginning of coking and indicates the occurrence of carburization corrosion.

Importance of methylammonium iodide partial pressure and evaporation onset for the growth of co-evaporated methylammonium lead iodide absorbers

Vacuum-based co-evaporation promises to bring perovskite solar cells to larger scales, but details of the film formation from the physical vapor phase are still underexplored. In this work, we investigate the growth of methylammonium lead iodide (MAPbI_3) absorbers prepared by co-evaporation of methylammonium iodide (MAI) and lead iodide (PbI_2) using an in situ X-ray diffraction setup. This setup allows us to characterize crystallization and phase evolution of the growing thin film. The total chamber pressure strongly increases during MAI evaporation. We therefore assume the total chamber pressure to be mainly built up by an MAI atmosphere during deposition and use it to control the MAI evaporation. At first, we optimize the MAI to PbI_2 impingement ratios by varying the MAI pressure at a constant PbI_2 flux rate. We find a strong dependence of the solar cell device performance on the chamber pressure achieving efficiencies > 14% in a simple n-i-p structure. On the road to further optimizing the processing conditions we vary the onset time of the PbI_2 and MAI deposition by delaying the start of the MAI evaporation by t = 0/8/16 min. This way, PbI_2 nucleates as a seed layer with a thickness of up to approximately 20 nm during this initial stage. Device performance benefits from these PbI_2 seed layers, which also induce strong preferential thin film orientation as evidenced by grazing incidence wide angle X-ray scattering (GIWAXS) measurements. Our insights into the growth of MAPbI_3 thin films from the physical vapor phase help to understand the film formation mechanisms and contribute to the further development of MAPbI_3 and related perovskite absorbers.

Reaction kinetics of the thermal decomposition of MAPbI3 thin films

Despite their outstanding optoelectronic properties, metal halide perovskites have not yet seen widespread use in commercial applications. This is mostly due to their lack of stability with respect to several external factors, e.g., humidity, heat, light, and oxygen. Even though extensive studies have been carried out over the last decade, a lot of questions regarding their thermal stability still remain, and various publications have put forth different approaches for measuring and quantifying the conditions of their decomposition. However, differences in the experimental setups and in the reported values make comparisons of the reported results challenging. We show an approach, where ${\mathrm{MAPbI}}_{3}$ thin films are thermally decomposed in high vacuum within a temperature range from $220{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ to $250{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, while monitoring changes in the crystal structure using an in situ x-ray diffraction setup. This process reveals the complete phase evolution of the thin films from ${\mathrm{MAPbI}}_{3}$ into ${\mathrm{PbI}}_{2}$. The time resolved data was then evaluated in view of the reaction kinetics using three different approaches. First, an Arrhenius fit was applied to $lnk$ over $1/T$, where the rate constant $k$ was determined by fitting a first order exponential decay onto the decreasing peak area of the most prominent diffraction peaks. Secondly, a model fitting approach was used, where the data was tested against a set of different reaction models. Lastly, a model free isoconversional approach was applied. By doing this, we succeed in characterizing the decomposition and determine the kinetic triplet, consisting of the activation energy $E$, the frequency factor $A$, and the reaction model $f(\ensuremath{\alpha})$. With the help of the kinetic triplet the decomposition reaction can be expressed in a physically meaningful way and allows us to predict the decomposition dynamics of ${\mathrm{MAPbI}}_{3}$ thin films for varying temperatures.