Precise X-ray Research Articles

Facile synthesis of triple Ni-Mo-W alloys and their catalytic properties in chemical vapor deposition of chlorinated hydrocarbons

The utilization of chlorine-containing organic wastes remains an actual problem. In the present research, sponge-like porous Ni-Mo-W alloys were prepared and used as catalysts for the catalytic chemical vapor deposition of 1,2-dichloroethane. The synthesis of the alloys was performed via a facile approach of high-temperature reductive thermolysis of the preliminarily prepared multicomponent precursors. The formation of alloys of exact composition was proven by precise X-ray diffraction analysis. The catalytic activity of the alloys in the decomposition of 1,2-dichloroethane was studied in a flow-through reactor at 600 °C for 2 h. The simultaneous presence of Mo and W in the composition of the Ni-based alloys was shown to have a synergetic effect on the process efficiency. The diameter of these fibers was found to be comparable with the size of metal particles formed as a result of initial alloys self-disintegration under the action of the aggressive reaction medium.

Radiation damage of a two-dimensional carbon fiber composite (CFC)

Carbon fiber composites (CFC) are, among other applications, already in use as low-impedance collimating elements for intercepting TeV-level protons machines, like the CERN Large Hadron Collider. Towards a comprehensive understanding of these materials’ properties and behavior, a series of radiation damage campaigns have been undertaken in order to quantitively investigate the response of AC-150 K CFC to high proton fluences. The CFCs dimensional changes, stability, micro-structural evolution, and structural integrity below and above 5 × 1020 p/cm2 fluence threshold were studied. The irradiating particles were protons of kinetic energies in the range of 130–200 MeV. The effects of the irradiation temperature (~90–180 °C and 280–500 °C) combined with the proton fluence on the dimensional stability and the microstructural evolution of this anisotropic two-dimensional composite structure were studied using precision dilatometry and X-ray diffraction. Our results shed light on the fluence-based limitations for these composite materials. Furthermore, we compare these results with reference unirradiated graphite, and we discuss the similarities and differences in the dimensional changes and post-irradiation annealing properties.

Annealing-induced phase transformations and hardness evolution in Al–Cu–Al composites obtained by high-pressure torsion

Multilayered bulk Al–Cu–Al metal-matrix composite was fabricated by means of high-pressure torsion and subsequent annealing. The resulting composite had a heterogeneous structure consisting of ductile aluminum matrix and hard intermetallic inclusions with a gradient decrease in grain size and layer thickness when moving from the center to the periphery of the sample. Precipitation of $$\hbox {Al}_{2}\hbox {Cu}$$ intermetallic phase was revealed at the edge of the sample in the as-deformed state. Post-deformation annealing initiated the emergence of AlCu and $$\hbox {Al}_{\mathrm {4}}\hbox {Cu}_{\mathrm {9}}$$ intermetallic precipitates with increased hardness compared to strain-induced $$\hbox {Al}_{\mathrm {2}}\hbox {Cu}$$ particles. The growth kinetics of intermetallic compounds was obtained using precise X-ray phase analysis. It was found that the initial growth of intermetallic phases at temperatures 150–210 $$^{\circ }$$ C depends on time $$t^{1/2}$$ , indicating the bulk diffusion-controlled growth. The growth activation energy of Al $$_2$$ Cu and AlCu phases was calculated to be 0.48 and 0.33 eV, respectively. The results obtained contribute to an understanding of the kinetics of annealing-induced growth of intermetallic phases and the corresponding evolution of strength characteristics in Al–Cu–Al composites. It was revealed that thermal treatment regimes resulting in enhanced mechanical properties are associated with moderate time and temperature of annealing, which allows avoiding partial dissolution of strengthening phases. The applied approach of phase kinetics analysis can become the basis for the development of new energy-efficient heat treatment modes of in situ Al-based composites allowing to govern their heterogeneity type and tailoring the mechanical properties of the material.

Precision X-ray diagnosis of osteoporosis in representatives of risk groups for the appearance and development of varicose disease of the lower limbs

Precision X-ray diagnosis of osteoporosis in representatives of risk groups for the appearance and development of varicose disease of the lower limbs

Influence of Neutron Irradiation on the Characteristics of Phase Transitions in Multifunctional Materials with a Perovskite Structure (A Review)

Exposure to neutron radiation is an efficient way to enter dosed amounts of defects into the crystal and real structures of advanced inorganic materials. Thus-gained experimental data are of importance for both fundamental radiation materials science and for finding ways of usefully modifying the effect of radiation on the properties of practically important multifunctional materials with the perovskite structure. The review considers the specificity of the effect of exposure to neutron radiation on the parameters of crystal and real structures and on the multifunctional (ferroelectric, superconducting, nonlinear optical, magnetic, and other) properties of crystals of the perovskite family that experience various structural phase transitions. The review dwells on the effect of radiation defects on variations of the local and macroscopic properties of crystals, reflected in the anomalies of these properties in phase-transition regions. Ferroelectric perovskite crystals are shown to be particularly susceptible to defects. The main types of radiation-induced structural states are considered, including their formation mechanisms and patterns. Correlation relations between the structural alteration upon radiation exposure and the evolution of phase-transformation temperatures are considered. It is shown that variable irradiation parameters (dose, radiation annealing, impurity content, and concentration of a certain type of initial defects) offer a means to control the kinetics of radiation rearrangement and, ultimately, the radiation resistance of the structure. In addition, taking these factors into account, one can provide conditions for the generation of almost any metastable structural state, close to those formed in intact (non-irradiated) crystals at the pre-transition stage, that would be stable at room temperature. The study of effects of neutron irradiation by precision X-ray structural analysis shows that the structural states that occur under radiation exposure are stable over a wide temperature range, including room temperature, and the stability of metastable states, as a rule, increases with the radiation fluence. These radiation-induced states are actually new structural states, intermediate between low-temperature and high-temperature polymorphs of perovskite crystals. The analysis of literature data implies that the radiation-induced structural rearrangement, amorphization, and decomposition of the initial compound are in many cases competing processes, the activity of which depends on the neutron irradiation fluence and temperature. A decrease in exposure temperature often slows down the decomposition and suppresses the attendant deformation of the crystal, which is essential for the implementation and identification of structural alterations in irradiated crystals.

Centrosymmetric and acentric whitlockite-type phosphates and vanadates among Ca3(VO4)2-Ca3(PO4)2-Y2O3 compositions

Identifications and studies of whitlockite-type phases for the first time are fulfilled in the cation-anion mixed phosphate-vanadate ferroelectric systems Ca10.5(V1-x P x O4)7, Ca9Y(V1-x O4)7, Ca10.5-1.5x Y x (VO4)7 and Ca10.5-1.5x Y x (PO4)7. These systems are the sections of a more extensive multi-component system Ca3(VO4)2 - Ca3(PO4)2 - Y2O3, but are all built on the basis of well-known individual compounds of the type of mineral whitlockite. The solid solutions formed between them are also of ferroelectric whitlockite-type, but some compositions are not ferroelectric, and according to the nonlinear optical phase analysis possess centrosymmetric structure. Ferroelectric phase transitions were detected in the region of 1000–1300 K by the method of dielectric spectroscopy. A precision X-ray study of some compositions of solid solutions using synchrotron radiation revealed a significant deviation in the cationic-anionic arrangement from being completely disordered. Partial ordering of structural tetrahedral groups of PO4 3- and VO4 3- determines a significant increase in nonlinear optical activity in the mixed anions whitlockite-type compounds.

On the accuracy and precision of X-ray and neutron diffraction results as a function of resolution and the electron density model.

X-ray diffraction is the main source of three-dimensional structural information. In total, more than 1.5 million crystal structures have been refined and deposited in structural databanks (PDB, CSD and ICSD) to date. Almost 99.7% of them were obtained by approximating atoms as spheres within the independent atom model (IAM) introduced over a century ago. In this study, X-ray datasets for single crystals of hydrated α-oxalic acid were refined using several alternative electron density models that abandon the crude spherical approximation: the multipole model (MM), the transferable aspherical atom model (TAAM) and the Hirshfeld atom refinement (HAR) model as a function of the resolution of X-ray data. The aspherical models (MM, TAAM, HAR) give far more accurate and precise single-crystal X-ray results than IAM, sometimes identical to results obtained from neutron diffraction and at low resolution. Hence, aspherical approaches open new routes for improving existing structural information collected over the last century.

Electrochemical Phase Formation of Metals and Alloys at Chemically Identical Solid or Liquid Cathode: Part 3. Alloys in the Form of Intermetallic Compounds

In order to provide further evidence on the existence of the phenomenon of electro-chemical phase formation in metals and alloys via a supercooled liquid state stage, a set of experiments were carried out to reveal the predicted structural features in alloys during electrochemical phase formation at chemically identical solid or liquid cathode. In the third part of the research, the results of the precision X-ray phase analysis for the interface between an electrodepositing alloy in the form of intermetallic compounds and a cathode of Wood’s alloy that persisted in either a solid or a liquid condition are discussed. The phenomenon in question was proved by the following experimental results: (1) alloys electrodepositing as intermetallic compounds at a solid metallic cathode showed formation of intermetallics involving components of the depositing alloy and, in parallel, cathode elements and alloy components; (2) on replacing a solid cathode with a chemically identical liquid one for alloys electrodepositing as intermetallic compounds, occurrence of additional intermetallics enriched in the major alloy component and cathode elements was observed.

Dosimetric characterization of an X-ray irradiator for use with cells

PurposeThis study aims to characterize an X-ray irradiator (CellRad™, Precision X-ray Inc., North Branford, CT) for use with cells using its internal parallel-plate ionization chamber by evaluating the linearity and repeatability of dose and dose rates delivered by the machine. MethodologyUsing the on-board software modules for X-ray irradiation, dose linearity and repeatability tests were performed at the following setting: 130 kVp, 5.0 mA, and 33.0 cm source-to-shelf distance. Four (4) setups with distinct combinations of 0.5-mm Al added filtration and turntable rotation settings were employed. The measurements obtained from the internal ionization chamber were analyzed using statistical tests. ResultsThe X-ray irradiator can generate temporally linear and repeatable doses from aluminum-filtered (0.5 mm) and unfiltered X-ray beams (130 kV, 5.0 mA). At a 33.0-cm source-to-shelf distance, the computed dose rates indicate that the X-ray irradiator can deliver 1.345 ± 0.046 Gy/min and 6.718 ± 0.11 Gy/min at the specified tube and shelf settings, with and without the 0.5 mm Al added filter, respectively. An acceptable level of repeatability of the dose is achieved after at least 20 s of irradiation time. The automatic dose control function of the irradiator was also found to measure accumulated doses within ±5% of the target dose for all the setups employed in this study. The results also revealed that turntable rotation has no significant effect on the dose measured by the internal dosimeter for both filtered and unfiltered beams. On the other hand, adding a 0.5-mm Al filtration significantly alters the beam by decreasing the measured dose rate to only 20% of that of the unfiltered beam. Conclusions and recommendationsThis study demonstrates that the X-ray irradiator can generate and measure precise radiation doses that vary linearly with irradiation time. The available irradiation modules in the on-board software can be used to deliver doses within ±5% of the target dose, although irradiation time should be at least 20 s to achieve acceptable dose repeatability. Further dosimetric calibration and output verification using external dosimetry system(s) should be conducted for the complete dosimetric characterization of this X-ray irradiator.

Ultra-high precision x-ray polarimetry with artificial diamond channel cuts at the beam divergence limit

This work demonstrates the realization of a highly pure linear polarization state of x-rays using a pair of polarizers each made of four diamond crystals. With these polarizers, the authors reach the limit where the purity of the polarization is determined by the divergence of the beam.

Ordering Phase Transition with Symmetry-Breaking from Disorder over Non-Equivalent Sites: Calorimetric and Crystallographic Study of Crystalline d-Sorbose

Phase transitions in the crystalline state of chiral sorbose were examined using precise heat capacity calorimetry and X-ray crystallography. The calorimetry established heat capacity below room temperature. Besides the known transition (main transition) at 199.5 K, the calorimetry detected plural thermal anomalies assignable to new phase transitions (around 210 K) and a glass transition (at ca. 120 K). The X-ray diffraction at low temperatures established the crystal structure of the lowest temperature phase. The identification of the broken symmetry upon the main transition solves an apparent contradiction that the structural disorder reported previously does not contribute seemingly to the symmetrization.

Electrochemical Phase Formation of Metals and Alloys at Chemically Identical Solid or Liquid Cathode: Part 2. Alloys in the Form of Substitutional Solid Solutions

The existence of the phenomenon of electrochemical phase formation in metals and alloys via a supercooled liquid state stage has been discussed. In the second part of the research, the results of the precision X-ray phase analysis for the interface between electrodepositing alloy in the form of a substitutional solid solution and a cathode of Wood’s alloy that persisted in either a solid or a liquid condition are considered. It was found that the phenomenon under study here is proved by the following experimental data: (1) the formation of intermetallics between solid metallic cathode elements and the solvent in the alloy electrodepositing as substitution solid solution, and enhancement of these processes accompanied by the development of additional intermetallics enriched in cathode elements on replacing a solid cathode with a chemically identical liquid one; (2) with alloys electrodepositing as substitution solid solution at a solid metallic cathode, the formation of intermetallics including cathode elements and the alloy solute element building no distinct phase; and (3) on replacing a solid cathode with a chemically identical liquid one, enhanced intermetallic formation involving metallic cathode elements and the electrodepositing alloy solute building no distinct phase plus emergence of additional intermetallics enriched in cathode elements.

Development of a position–velocity–time-modulated two-dimensional ion beam figuring system for synchrotron x-ray mirror fabrication

With the rapid evolution of synchrotron x-ray sources, the demand for high-quality precision x-ray mirrors has greatly increased. Single nanometer shape accuracy is required to keep imaging capabilities at the diffraction limit. Ion beam figuring (IBF) has been used frequently for ultra-precision finishing of mirrors, but achieving the ultimate accuracy depends on three important points: careful alignment, accurate dwell time calculation and implementation, and accurate optical metrology. The Optical Metrology Group at National Synchrotron Light Source II has designed and built a position-velocity-time-modulated two-dimensional IBF system (PVT-IBF) with three novel characteristics: (1) a beam footprint on the mirror was used as a reference to align the coordinate systems between the metrology and the IBF hardware; (2) the robust iterative Fourier transform-based dwell time algorithm proposed by our group was applied to obtain an accurate dwell time map; and (3) the dwell time was then transformed to velocities and implemented with the PVT motion scheme. In this study, the technical aspects of the PVT-IBF systems are described in detail, followed by an experimental demonstration of the figuring results. In our first experiment, the 2D RMS in a $ 50\;{\rm mm} \times 5\;{\rm mm} $50mm×5mm clear aperture was reduced from 3.4 to 1.1 nm after one IBF run. In our second experiment, due to a 5 mm pinhole installed in front of the source, the 2D RMS in a $ 50\;{\rm mm} \times 5\;{\rm mm} $50mm×5mm clear aperture was reduced from 39.1 to 1.9 nm after three IBF runs, demonstrating that our PVT-IBF solution is an effective and deterministic figuring process.

Studies of kaonic atoms at the DAΦNE collider: from SIDDHARTA to SIDDHARTA-2

The DAΦNE electron-positron collider of the Laboratori Nazionali di Frascati of INFN is a worldwide unique low-energy kaon source and for this reason is suitable for low-energy kaon physics like kaonic atoms and kaon-nucleons/nuclei interaction studies. Kaonic atoms are atomic systems where an electron is replaced by a negatively charged kaon, containing the strange quark, which interacts in the lowest orbits with the nucleus also by the strong interaction. As a result, their study offers the unique opportunity to perform experiments equivalent to scattering at vanishing relative energy. This allows to study the strong interaction between the antikaon and the nucleon or the nucleus “at threshold”, without the need of ad hoc extrapolation to zero energy, as in scattering experiments. The most precise kaonic hydrogen measurement to date, together with an exploratory measurement of kaonic deuterium, were carried out by the SIDDHARTA collaboration at the DAΦNE electron-positron collider of LNF-INFN, by combining the excellent quality kaon beam delivered by the collider with new experimental techniques, as fast and precise Silicon-Drift X-ray Detectors. The measurement of kaonic deuterium will be realized in the near future by SIDDHARTA-2, a major upgrade of SIDDHARTA.

A Mail Audit Independent Peer Review System for Dosimetry Verification of a Small Animal Irradiator.

Dedicated precision orthovoltage small animal irradiators have become widely available in the past decade and are commonly used for radiation biology research. However, there is a lack of dosimetric standardization among these irradiators, which affects the reproducibility of radiation-based animal studies. The purpose of this study was to develop a mail-based, independent peer review system to verify dose delivery among institutions using X-RAD 225Cx irradiators (Precision X-Ray, North Branford, CT). A robust, user-friendly mouse phantom was constructed from high-impact polystyrene and designed with dimensions similar to those of a typical laboratory mouse. The phantom accommodates three thermoluminescent dosimeters (TLDs) to measure dose. The mouse peer review system was commissioned in a small animal irradiator using anterior-posterior and posterior-anterior beams of 225 kVp and then mailed to three institutions to test the feasibility of the audit service. The energy correction factor for TLDs in the mouse phantom was derived to validate the delivered dose using this particular animal irradiation system. This feasibility study indicated that three institutions were able to deliver a radiation dose to the mouse phantom within ±10% of the target dose. The developed mail audit independent peer review system for the verification of mouse dosimetry can be expanded to characterize other commercially available orthovoltage irradiators, thereby enhancing the reproducibility of studies employing these irradiators.

Mass determination of the charged pion, using high precision X-ray spectroscopy

X-ray transitions in pionic nitrogen were measured using a curved crystal spectrometer. From the transition energy, calibrated with the help of the copper Ka1,2 electronic transition, a value for the charged pion mass of (139.57071± 0.00053) MeV/c2 was deduced. In order to reduce the uncertainty of the charged pion mass in the level of 1 ppm, we propose the determination of pionic transition energy based on the more precisely known energies and line shapes of muonic transitions.

VIP-2 - Testing spin-statistics for electrons with high sensitivity

The VIP-2 (VIolation of the Pauli Exclusion Principle) experiment conducted at the Gran Sasso underground laboratory (LNGS) of INFN is searching for possible tiny violations of standard quantum mechanics in copper atoms with extremely high sensitivity. We investigate atomic transitions with precision X-ray spectroscopy in order to test the Pauli Exclusion Principle (PEP) and therefore the spin-statistics theorem. We present the experimental method for the search for “anomalous” (i.e. Pauli-forbidden) X-ray transitions in copper atoms, produced by “new” electrons, which could have a tiny probability to undergo a Pauli-forbidden transition to the 1s ground state already occupied by two electrons. We describe the VIP-2 experimental setup and its recent optimisations. Presently VIP-2 is taking data at LNGS. The goal of VIP-2 is to test PEP for electrons with unprecedented accuracy, down to a limit in the probability that PEP is violated at the level of 10−31 (and using a more elaborate analysis even 10−40). We present current experimental results.

Negative volume thermal expansion of monoclinic Cu2-2xZn2xV2O7 in the temperature range from 93 to 673 ​K

Negative volume thermal expansion was found for the monoclinic structure of the solid solution β-Cu2-2xZn2xV2O7 in a wide temperature range from 93 to 673 ​K: αV· ​= ​−31.4(2) · 10−6 ​K−1 for β-Cu1.6Zn0.4V2O7, αV· ​= ​−12.6(4) · 10−6 ​K−1 for β-Cu0.8Zn1.2V2O7. Precision X-ray studies of β-Cu2-2xZn2xV2O7in situ made it possible to detail the changes in the linear and angular parameters of the structure upon heating. The obtained data set revealed the defining role of changes the symmetry-nonfixed angle of rotation of the vanadium-oxygen tetrahedra in the [V2O7] orthogroups at the initiation of the hinged deformations, leading to the compression of the structure.

Kaonic Deuterium Measurement with SIDDHARTA-2 on DA$\Phi $NE

The interaction of antikaons with nucleons and nuclei in the low-energy regime represents an active research field in hadron physics with still many important open questions. The investigation of light kaonic atoms is, in this context, a unique tool to obtain precise information on this interaction. The most precise kaonic hydrogen measurement to date, together with an exploratory measurement of kaonic deuterium, were carried out by the SIDDHARTA Collaboration at the DAΦNE electron–positron collider of LNF-INFN, by combining the excellent quality kaon beam delivered by the collider with new experimental techniques, as fast and precise Silicon-Drift X-ray detectors. The measurement of kaonic deuterium will be realized in the near future by SIDDHARTA-2, a major upgrade of SIDDHARTA.

Electrochemical Phase Formation of Metals and Alloys at Chemically Identical Solid or Liquid Cathode: Part 1. Metals

The existence of the phenomenon of electrochemical phase formation in metals and alloys via a supercooled liquid state stage is discussed. In dealing with that subject in terms of emergence and ultrarapid solidification of a deeply supercooled metallic liquid represented by a multitude of liquid atomic clusters, an idea was put forth that an identity of the state of aggregation between the cathode and the electrodepositing metal/alloy at the cathode???deposit interface must facilitate phase transformations at the interface. It was assumed that replacing a solid cathode with a chemically identical liquid one would lead to a wider spectrum of intermetallics formed due to interactions of the electrodepositing metal with elements of the liquid metallic cathode. Precision X-ray phase characterization was performed for the interface between the electrodepositing metal and a cathode of Wood???s alloy that persisted in either a solid or a liquid condition through the electrodeposition process. Relying on the data obtained, it was concluded that the phenomenon in point is proved by the formation enhancement of intermetallic compounds involving metallic cathode elements and the electrodepositing metal plus evolvement of additional intermetallics enriched in cathode elements, on replacing a solid cathode with a chemically identical liquid one.