Laboratory X-ray Diffractometer Research Articles

IBARAKI Materials Design Diffractometer for J-PARC

Ibaraki prefecture, the local government of the area for J-PARC site, has decided to build a versatile powder diffractometer (IBARAKI Materials Design Diffractometer) to promote industrial applications for neutron beams in J-PARC. This diffractometer is designed to be a high throughput one enabling materials scientists to use it like the chemical analytical instruments in their material development processes. It covers in d range 0.18 < d ( Å ) < 5 with Δ d / d = 0.16 % at the high-resolution scattering detector bank, and covers 5 < d ( Å ) < 800 with gradually changing resolution. Typical measuring time to obtain a ‘Rietveld-quality’ data is several minutes for the sample size of laboratory X-ray diffractometer. To promote industrial application, a utilization system for this diffractometer is required. We will establish a support system for both academic and industrial users who are willing to use neutron but have not been familiar with neutron diffraction.

Negative thermal expansion in silicalite-1 and zirconium silicalite-1 having MFI structure

In situ high temperature X-ray diffraction (HTXRD) studies on monoclinic silicalite-1 (S-1, silica polymorph of ZSM-5) and an orthorhombic metallosilicate molecular sieve, zirconium silicalite-1 (ZrS-1) with MFI structure (Si/Zr=50) have been carried out using a laboratory X-ray diffractometer with an Anton Parr HTK 1600 attachment. While the structure of the S-1 collapsed at 1123K forming α-cristobalite. S-1 and ZrS-1 showed a complex thermal expansion behavior in the temperature range 298–1023K, ZrS-1 was stable. Powder X-ray diffraction (PXRD) data taken in this region have shown strong negative lattice thermal expansion coefficient, αV=−6.75×10−6 and −17.92×10−6K−1 in the temperature range 298–1023K−1 for S-1 and ZrS-1 samples, respectively. The thermal expansion behavior of S-1 and ZrS-1 is anisotropic, with the relative strength of contraction along a axis is more than that along b and c axes. Three different thermal expansion regions could be identified in the overall temperature range (298–1023K) studied, corroborating with the three steps of weight loss in the TG curve of ZrS-1 sample. While the region between 298 and 423K, displays positive thermal expansion coefficient with αV=2.647×10−6 and 4.24×10−6K−1, the second region between 423 and 873K shows strong negative thermal expansion (NTE) coefficient αV=−7.602×10−6 and −15.04×10−6K−1, respectively, for S-1 and ZrS-1 samples. The region between 873 and 1023K, shows a very strong NTE coefficient with αV=−12.08×10−6 and −45.622×10−6K−1 for S-1 and ZrS-1, respectively, which is the highest in the whole temperature range studied. NTE seen over a temperature range 298–1023K could be associated with transverse vibrations of bridging oxygen atoms in the structure which results in an apparent shortening of the Si–O distances.

Dehydrated and Cs+-Exchanged MFI Zeolites: Location and Population of Cs+ from In Situ Diffraction Data as a Function of Temperature and Degree of Exchange

H-MFI type zeolitic materials of different Si/Al ratios have been completely or partially cesium-exchanged (cesium content ranging from 0.7 to 7.7 Cs/unit-cell (uc)). Examined with synchrotron X-ray powder diffractometry, an anhydrous sample with the Cs6.6H0.3Al6.9Si89.1O192 chemical composition revealed at ambient temperature the presence of five discrete Cs locations: Cs1 located in the channel intersection near a 10-ring window of the zigzag channel; Cs2 and Cs2', both located in the straight channel but 1.23 A apart; Cs3 and Cs3', both located in the zigzag channel and rather close to each other (2.51 A). The populations of the Cs species amounted to 2.61/0.81/1.85/0.86/0.47/uc for Cs1/2/2'/3/3', respectively. The continuous but multimodal nature of the C2 split site is well-described by a joint-probability density function. The 10-ring of the straight channel in the framework is highly elliptical (epsilon = 1.218). The populations for the same sites were also determined at higher temperatures: 131, 237, 344, and 450 degrees C. At 450 degrees C, Cs2' has migrated toward the center of the channel intersection, and the site separation between Cs2 and Cs2' has lengthened to 2.23 A. Using a temperature-controlled laboratory X-ray diffractometer, similar studies were carried out on partially or almost totally Cs-exchanged samples from various sources with differing Cs contents. They show that over the 0.7 to 4 Cs/uc range all the individual Cs populations vary linearly as a function of total Cs/uc present. At higher total Cs/uc content (4 to approximately 7 Cs/uc) solely Cs1 continues to do so. For Cs2+Cs2' and Cs3+Cs3', the variation is almost linear over the whole concentration range. Computer simulations using a 6-exp-1 Buckingham-type atom-atom van der Waals interaction model yield six possible Cs sites in the actual Cs6.6MFI framework structure. Four of them lie very close to those determined from difference Fourier maps using the room temperature data. A fifth one is close to the Cs2' species after thermal migration at 450 degrees C, and the sixth one is close to the center of the channel intersection. However, this latter site is observed experimentally only in the case of hydrated CsMFI phases. In the anhydrous Cs6.6MFI phase at room temperature, the shortest Cs-framework oxygen distance is Cs3'-O25 = 3.08 A, and the next shortest distances are Cs1-O26 = 3.37, Cs2-O11 = 3.34, Cs2'-O22 = 3.47, and Cs3-O20 = 3.34 A. The framework T(Si,Al) sites most involved in these contacts are the T9, T11, T12, T10, and T3 sites. This implies that these sites are prime candidates for Si/Al substitution.

Stress relaxation of shot-peened UDIMET 720Li under solely elevated-temperature exposure and under isothermal fatigue

The aim of this experimental study was to quantify the changes that occur to the residual-stress state and the near-surface work-hardened zone as a function of depth in a shot-peened UDIMET 720Li Ni superalloy following solely thermal exposure and in combination with strain-controlled fatigue loading at two strain amplitudes. Residual-stress measurements were performed using the sin2 ψ method on a laboratory X-ray diffractometer as a function of depth by successive electrochemical removal of material. It was found that the as-peened variation in diffraction-peak width (X-ray) with depth correlated well with the recorded hardness profile. A hardness increase in excess of 50 pct was recorded close to the surface. Regarding solely thermal exposure, it was found that the near-surface compressive stresses were relieved to some extent at all temperatures (350 °C to 725 °C) after short-term exposure, being reduced by up to 50 pct at the highest temperatures (650 °C to 725 °C). The isothermally fatigued samples strained at 0.6 pct amplitude displayed similar stress-relaxation behavior to the thermally loaded samples, indicating that at such small strains, stress relaxation is controlled predominantly by thermal relaxation processes. In contrast, stress relaxation following strain-controlled fatigue at 1.2 pct strain is governed by a combination of thermal and mechanical processes. The mechanically induced relaxation component is anisotropic, being significantly greater along the loading axis than transverse to it. Unsurprisingly, with increasing temperature, the thermal contribution to stress relaxation becomes increasingly important and the degree of in-plane anisotropy of stress relaxation lessens.

Silicon strip detector applied to X-ray diffractometer: Angular resolution and counting rate

The silicon strip detector (128 strips with 100 μm strip pitch) was mounted at the arm of laboratory X-ray diffractometer with 230 mm instrument radius. With the use of a LaB 6 standard sample we demonstrate the angular resolution of 0.05° at low angles for classical Bragg–Brentano configuration. Experiments with a large LiF single crystal makes it possible to experimentally determine the detector limit range of linearity (30 000 cps/strip) and maximum counting range (100 000 cps/strip).

Miniaturized multipurpose cell for in situ investigation of sputtered thin films with x-ray techniques

The design of a miniaturized sputter deposition chamber for the in situ study of thin film growth processes with x rays is reported. X-ray diffraction experiments, grazing incidence x-ray reflectometry, as well as x-ray fluorescence analysis are possible. Due to its compact design and low weight, the chamber can be used in conjunction with conventional x-ray reflectometers and laboratory x-ray diffractometers as well, i.e., very detailed in situ studies of reactive and nonreactive sputtering processes and the resulting film properties are possible. The construction of the chamber is described in detail and first results obtained in situ with different techniques are presented, indicating that experiments that were previously restricted to synchrotron radiation facilities are now possible even with laboratory equipment.

Powder pattern indexing using the weighted crosscorrelation and genetic algorithms.

X-ray diffraction is a powerful technique for investigating the structure of crystals and crystalline powders. Unfortunately, for powders, the first step in the structure elucidation process, retrieving the unit cell parameters (indexing), is still very critical. In the present article, an improved approach to powder pattern indexing is presented. The proposed method matches peak positions from experimental X-ray powder patterns with peak positions from trial cells using a recently published method for pattern comparison (weighted crosscorrelation). Trial cells are optimized with Genetic Algorithms. Patterns are not pretreated to remove any existing zero point shift, as this is determined during optimization. Another improvement is the peak assignment procedure. This assignment is needed for determining the similarity between lines from trial cells and experiment. It no longer allows calculated peaks to be assigned twice to different experimental peaks, which is beneficial for the indexing process. The procedure proves to be robust with respect to false peaks and accidental or systematic absensences of reflections, and is successfully applied to powder patterns originating from orthorhombic, monoclinic, and triclinic compounds measured with synchrotron as well as with conventional laboratory X-ray diffractometers.

Polycrystalline X-ray Diffraction Technique with a DAC

Fundamental techniques of polycrystalline x-ray diffraction measurement at high pressure using a diamond anvil cell are described. We point out several unusual conditions specific to a sample compressed in the DAC, give a detailed description of a laboratory x-ray diffractometer for high-pressure study and its performance, and briefly introduce a high-pressure synchrotron x-ray diffraction technique.

Structure of the polymer–salt co-ordination complex [(CH2CH2O)n]∶ KCF3SO3, obtained from powder diffraction data

The crystal structure of the polymer–salt complex [(CH2CH2O)n]∶KCF3SO3 has been obtained from powder diffraction data collected on a laboratory X-ray diffractometer. Profile refinement was employed in the structure elucidation, based on a model of the previously known structure of [(CH2CH2O)n]∶NaCF3SO3.

Ab initio structure determination of norbornene from powder diffraction data using molecular packing analysis method

The previously unknown crystal structre of the low temperature ordered phase of norbornene was solved from a set of powder diffraction data with severe preferred orientation collected on a laboratory X-ray diffractometer by first predicting the starting model by means of molecular packing analysis method, which was then refined against the experimental data by means of Rietveld method.

Ab initio solution of a complex crystal structure from powder-diffraction data using simulated-annealing method and a high degree of molecular flexibility

The previously unknown crystal structure of the polymer/salt complex poly(ethylene oxide):${\mathrm{NaSO}}_{3}$${\mathrm{CF}}_{3}$ was solved from a powder-diffraction pattern collected on a laboratory x-ray diffractometer. The solution was performed starting from a random arrangement of constituent molecular fragments in the unit cell using a full-profile-fitting technique and a simulated-annealing method for finding the global minimum of the figure-of-merit function. Unlike the only other structure solution using this approach, the procedure was successful only when the highest degree of flexibility was applied to stereochemically constrained species.

X-ray scattering studies of FeSi2 films epitaxially grown on Si(111)

A laboratory x-ray diffractometer for surface and thin-film studies is presented. Ex situ structural characterization of FeSi2 films epitaxially grown on Si(111) is reported. Both specular and nonspecular reflectivities are measured on β-FeSi2 films grown by solid-phase epitaxy and reactive deposition epitaxy techniques. A detailed comparison is performed of the electron density profile of the films normal to the surface, as well as of their surface roughness. In-plane diffraction is also measured at grazing incidence. For the β-FeSi2 sample investigated, the (110) epitaxy on Si(111) is clearly shown. For a film grown by molecular-beam-epitaxy codeposition at 550 °C, the existence of a new metastable phase which is in registry with silicon along the Si〈1̄ 10〉 direction and slightly out of registry, (3.0±1.0)% compressed along the Si〈112̄〉 direction, is reported.

Investigation and rationalisation of hydrogen bonding patterns in sulfonylamino compounds and related materials: crystal structure determination of microcrystalline solids from powder X-ray diffraction data

The crystal structures of three sulfonylamino compounds have been solved ab initio using powder diffraction data collected using a conventional laboratory X-ray diffractometer, and refined using Rietveld profile-refinement techniques. 4-Toluenesulfonamide (1) is monoclinic, P21/n, with a= 7.7030(3), b= 16.4656(7), c= 6.5861(3)Å, β= 92.411(2)°; benzenesulfonylhydrazine (2) is monoclinic, P21/c, with a= 8.0924(2), b= 8.6082(2), c= 11.7122(4)Å, β= 108.591(2)°; and 4-toluenesulfonylhydrazine (3) is monoclinic, P21/n, with a= 18.6021(6), b= 5.6406(2), c= 8.5356(3)Å, β= 106.222(2)°. The structures of 1 and 2 were solved from powder X-ray diffraction data by direct methods, using the SHELXS and SIR88 programs respectively; the structure of 3 was solved from powder X-ray diffraction data by the combined maximum entropy and likelihood method. The hydrogen bonding patterns in these crystals, and in the crystal structures of some related sulfonylamino compounds, are analysed and classified according to recently developed methods based on graph set analysis. For 1, the hydrogen bonding is described by the graph set C(4)C(4); for 2, the graph set for the first-order network is N1=C(5)S(5)C(4), and there are second-order networks R44(14) and R44(18); for 3, the first-order network is N1=C(5)S(5)C(4).