Degree Of Structural Disorder Research Articles

Signatures of Structural Disorder in the Developing Drosophila Germband Epithelium

Epithelial cells generate functional tissues in developing embryos through collective movements and shape changes. In some morphogenetic events, a tissue dramatically reorganizes its internal structure—often generating high degrees of structural disorder—to accomplish changes in tissue shape. However, the origins of structural disorder in epithelia and what roles it might play in morphogenesis are poorly understood. We study this question in the germband epithelium, which undergoes dramatic changes in internal structure as cell rearrangements drive elongation of the embryo body axis. Using two order parameters that quantify volumetric and shear disorder, we show that structural disorder increases during body axis elongation and is strongly linked with specific developmental processes. Both disorder metrics begin to increase around the onset of axis elongation, but then plateau at values that are maintained throughout the process. Notably, the disorder plateau values for volumetric disorder are similar to those for random cell packings, suggesting this may reflect a limit on tissue behavior. In mutant embryos with disrupted external stresses from the ventral furrow, both disorder metrics reach wild-type maximum disorder values with a delay, correlating with delays in cell rearrangements. In contrast, in mutants with disrupted internal stresses and cell rearrangements, volumetric disorder is reduced compared to wild type, and shear disorder depends on specific external stress patterns. Together, these findings demonstrate that internal and external stresses both contribute to epithelial tissue disorder and suggest that the maximum values of disorder in a developing tissue reflect physical or biological limits on morphogenesis. Published by the American Physical Society 2024

Electronic transport in reactively sputtered Mn3GaN films prepared under optimized nitrogen flow

Abstract Mn-based nitrides with antiperovskite structures have several properties that can be utilized for antiferromagnetic spintronics. Their magnetic properties depend on the structural quality, composition and doping of the cubic antiperovskite structure. Such nitride thin films are usually produced by reactive physical vapor deposition, where the deposition rate of N can only be controlled by the N2 gas flow. We show that the tuning of the N content can be optimized using low temperature resistivity measurements, which serve as an indicator of the degree of structural disorder. Several Mn3GaN x films were prepared by reactive magnetron sputtering under different N2 gas flows. Under optimized gas flow conditions, we obtain films that exhibit a metal-like temperature dependence of the resistivity, a vanishing logarithmic increase of the resistivity towards zero, the highest resistivity ratio, and a lattice contraction of 0.4% along the growth direction when heated above the Néel temperature T N . The retarded formation of an additional magnetic phase appearing at a temperature T ∗ ≪ T N gives rise to a large thermal hysteresis of the resistivity and anomalous Hall effect.

Computational insights into the structural, thermodynamic and transport properties of CaF2-MgF2 binary fluoride system at high temperatures

The structural, thermodynamic and transport properties of the CaF2-MgF2 molten salt system were investigated with ab initio molecular dynamics (AIMD), system-specific neural network interatomic potentials (NNIPs) and universal PreFerred Potentials (PFP). We trained an NNIP model using AIMD data as input and used this potential to efficiently simulate the interactions within a large supercell in a temperature range of 1273–1773 K. The Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) code was employed to validate our trained NNIP model. The Matlantis software with universal PFP is also presented to prove its feasibility for MD calculations and can be considered as a useful alternative simulation tool for higher-order systems where existing potentials are not readily available. We calculated structural and thermodynamic properties including radial distribution function (RDF), angular distribution function (ADF), specific heat capacity, ionic self-diffusivity, and viscosity. Our results indicate that the system exhibited a high degree of structural disorder, with the Ca, Mg, and F ions forming a liquid solution. Using PFP, the positions of the first peak in RDFs for Ca-F and Mg-F pairs are only slightly left-shifted (<0.05 Å), and the estimated viscosity of the melt decreases from 4.613 mPa·s to 1.846 mPa·s with an increase in temperature from 1273 K to 1773 K, in agreement with the NNIP trained specifically for CaF2-MgF2. Our results provide valuable insights into the properties of the CaF2-MgF2 system at high temperatures and serve as predictive models for the development of new electrolytes that could be used for silicon epitaxy by adding silica.

Regulating Anderson localization with structural defect disorder

Abstract Localization due to disorder has been one of the most intriguing theoretical concepts that evolved in condensed matter physics. Here, we expand the theory of localization by considering two types of disorders at the same time, namely, the original Anderson’s disorder and the structural defect disorder, which has been suggested to be a key component in recently discovered two-dimensional amorphous materials. While increasing the degree of both disorders could induce localization of wavefunction in real space, we find that a small degree of structural defect disorder can significantly enhance the localization. As the degree of structural defect disorder increases, localized states quickly appear within the extended phase to enter a broad crossover region with mixed phases. We establish two-dimensional diagrams for the wavefunction localization and conductivity to highlight the interplay between the two types of disorders. Our theoretical model provides a comprehensive understanding of localization in two-dimensional amorphous materials and highlights the promising tunability of their transport properties.

Atomic Structure Amorphization and Electronic Structure Reconstruction of FeCoNiCrMox High-Entropy Alloy Nanoparticles for Highly Efficient Water Oxidation.

The complexity of the multielement interaction in high-entropy alloys (HEAs) may provide more active sites to adapt different catalytic reaction steps in oxygen evolution reaction (OER). Investigating the correlation between structure and performance of HEAs electrocatalysts is both essential and challenging. In this work, FeCoNiCrMox HEAnanoparticles are successfully fabricated utilizing a unique nanofabrication method called inert gas condensation. With the increase of high-valence metal component Mo, the atomic structure amorphization and electronic structure reconstruction are unveiled. According to the X-ray photoelectron spectroscopy valence spectra, the d-band center of FeCoNiCrMox is ascending, and thus enhancing the adsorption energy. Synchrotron pair distribution function analysis reflects the degree of structural disorder and reveals a robust correlation with the intrinsic OER activities of the electrocatalysts. FeCoNiCrMo1.0 high-entropy metallic glass nanoparticles exhibit an outstanding OER performance with an ultralow overpotential of 294.5mV at a high current density of 100mAcm-2. This work brings fundamental and practical insights into the modulation mechanism of metal components of HEAs catalysts for developing OER.

Real-time emissivity measurements on solid phase formation and its degree of structural disorder during solidification of SrAl2Si2O8 from molten state

An in-situ real-time study on solid phase formation and its degree of structural disorder could shed light on the mechanisms of solidification from the liquid and allow insight into the creation of materials designed to possess enhanced properties and facilitate their production and application. The implementation of a Rapid Scan technique on a FT-IR emissometer designed to allow the observation of materials under extreme temperature conditions allows following the liquid to solid-state phase transition mechanisms through time-resolved emissivity spectra acquired at a speed of 20 spectra per second. The cooling rate of the material can be modified by controlling the laser-heating system. This technique has been validated on SrAl2Si2O8 feldspar, a material which displays structural disorder. The technique is sufficiently accurate to determine small changes in the linewidths of spectra obtained at different cooling rates, suggesting that structural order is increased at slower cooling speeds and confirming the Al/Si ordering dependence on thermal history.

Dynamic pressure-induced amorphous transition and crystallization behavior of 4-methylpyridine

The phase transitions of 4-methylpyridine (4MP) were studied under static pressure and dynamic pressure by in situ Raman spectroscopy. Under static compression, 4-methylpyridine underwent three phase transitions: a liquid to crystal I transition at 0.44 GPa; followed by transformation into crystal II at 2.17 GPa and crystal III at 10.36 GPa. Under dynamic compression, 4-methylpyridine was compressed into an amorphous phase as the pressure increased from 0.36, 0.38, and 0.33 GPa to 4.42, 6.80, and 11.53 GPa within 5 ms, respectively. Through the fitting of partial Raman peak linewidth with pressure, the compression rate has a significant effect on the disorder degree of crystal structure. During the pressure relief process, the amorphous 4-methylpyridine transformed into a new crystal Ⅰ’ at 2.40 GPa, and then returned to the initial liquid state at roughly 0.58 GPa. The phase transitions of 4-methylpyridine dynamic pressure can be explained by the faster compression rate that drives systems to break chemical equilibrium and generate a new phase.

Pyrochlore-type lanthanide titanates and zirconates: Synthesis, structural peculiarities, and properties

This contribution provides a thorough examination of the structural characteristics of pyrochlore-type lanthanide titanates and zirconates Ln2Ti2O7 and Ln2Zr2O7, across various length scales. This paper also examines their processing, interesting physical properties (electrical, magnetic, and thermal characteristics), and responses to high pressure and ion irradiation. Brief sections on the elemental oxides' crystal chemistry, pertinent phase diagrams, and energetics of defect formation are also provided. Pyrochlore-type Ln2Ti2O7 and Ln2Zr2O7 stand out as truly multifunctional materials. Moreover, they have emerged as fascinating materials due to magnetic geometrical frustration, arising from the ordering of magnetic Ln3+ and non-magnetic Ti4+ (or Zr4+) cations into separate, interpenetrating lattices of corner-sharing tetrahedra. This results in a diverse array of exotic magnetic ground states, such as spin-ice (e.g., Dy2Ti2O7 or Ho2Ti2O7) or quantum spin ice (e.g., Tb2Ti2O7), observed at both low and room temperatures. They also exhibit varied electrical and electrochemical characteristics. Some members such as Gd2Zr2O7, function as fast ion conductors with a conductivity (σ) of ≈10−2 S·cm−1 at 800 °C and activation energy (Ea) ranging from 0.85 to 1.52 eV, depending on the degree of structural disorder. Others, such as Gd2TiMoO7, are mixed ionic-electronic conductors with σ ≈ 25 S·cm−1 at 1000 °C, making them promising candidate materials for applications in energy conversion and storage devices and oxygen separation membranes. Their exceptionally low thermal conductivity (e.g., κ ∼ 1.1–1.7 W·m−1·K−1 between 700 and 1200 °C for Ln2Zr2O7), close to the glass-like lower limit of highly disordered solids, positions them as valuable materials for thermal barrier coatings. They can also effectively accommodate actinides (e.g., Pu, Np, Cm, Am) in solid solutions and sustain prolonged exposure to radiation due to alpha-decay events, while preserving the integrity of the periodic atomic structure. Proposed as major components in actinide-bearing ceramics, they contribute to the long-term immobilization and disposal of long-lived waste radionuclides from nuclear programs. Some of these properties are displayed simultaneously, opening avenues for new applications. Despite the wealth of data available in the literature, this review highlights the need for a better understanding of order/disorder processes in pyrochlore-type materials and the influence of the structural length scale on their physical and chemical properties. Recent experimental evidence has revealed that pyrochlore short-range structure is far more complex than originally thought. Moreover, pyrochlore local structure is now believed to include short-range, lower symmetry, ordered domains, such as the orthorhombic weberite-type of structure. Notably, short- and long-range structures appear decoupled across different length scales and temperature regimes, and these differences persist even in well-ordered samples. We believe that the pyrochlore structure offers a unique opportunity for examining the interplay between chemical composition, defect chemistry, and properties. In Memoriam: Rodney C. Ewing, Fondly Remembered.

Correlating Structural Disorder in Metal (Oxy)hydroxides and Catalytic Activity in Electrocatalytic Oxygen Evolution

AbstractUnderstanding the correlation between the structural evolution of electrocatalysts and their catalytic activity is both essential and challenging. In this study, we investigate this correlation in the context of the oxygen evolution reaction (OER) by examining the influence of structural disorder during and after dynamic structural evolution on the OER activity of Fe−Ni (oxy)hydroxide catalysts using operando X‐ray absorption spectroscopy, alongside other experiments and theoretical calculations. The Debye–Waller factors obtained from extended X‐ray absorption fine structure analyses reflect the degree of structural disorder and exhibit a robust correlation with the intrinsic OER activities of the electrocatalysts. The enhanced OER activity of in situ‐generated metal (oxy)hydroxides derived from different pre‐catalysts is linked to increased structural disorder, offering a promising approach for designing efficient OER electrocatalysts. This strategy may inspire similar investigations in related electrocatalytic energy‐conversion systems.

Correlating Structural Disorder in Metal (Oxy)hydroxides and Catalytic Activity in Electrocatalytic Oxygen Evolution.

Understanding the correlation between the structural evolution of electrocatalysts and their catalytic activity is both essential and challenging. In this study, we investigate this correlation in the context of the oxygen evolution reaction (OER) by examining the influence of structural disorder during and after dynamic structural evolution on the OER activity of Fe-Ni (oxy)hydroxide catalysts using operando X-ray absorption spectroscopy, alongside other experiments and theoretical calculations. The Debye-Waller factors obtained from extended X-ray absorption fine structure analyses reflect the degree of structural disorder and exhibit a robust correlation with the intrinsic OER activities of the electrocatalysts. The enhanced OER activity of in situ-generated metal (oxy)hydroxides derived from different pre-catalysts is linked to increased structural disorder, offering a promising approach for designing efficient OER electrocatalysts. This strategy may inspire similar investigations in related electrocatalytic energy-conversion systems.

Phospholipid-induced secondary structural changes of lysozyme polymorphic amyloid fibrils studied using vacuum-ultraviolet circular dichroism.

The hallmark of amyloidosis, such as Alzheimer's disease and Parkinson's disease, is the deposition of amyloid fibrils in various internal organs. The onset of the disease is related to the strength of cytotoxicity caused by toxic amyloid species. Furthermore, amyloid fibrils show polymorphism, where some types of fibrils are cytotoxic while others are not. It is thus essential to understand the molecular mechanism of cytotoxicity, part of which is caused by the interaction between amyloid polymorphic fibrils and cell membranes. Here, using amyloid polymorphs of hen egg white lysozyme, which is associated with hereditary systemic amyloidosis, showing different levels of cytotoxicity and liposomes of DMPC and DMPG, changes in the secondary structure of the polymorphs and the structural state of phospholipid membranes caused by the interaction were investigated using vacuum-ultraviolet circular dichroism (VUVCD) and Laurdan fluorescence measurements, respectively. Analysis has shown that the more cytotoxic polymorph increases the antiparallel β-sheet content and causes more disorder in the membrane structure while the other less cytotoxic polymorph shows the opposite structural changes and causes less structural disorder in the membrane. These results suggest a close correlation between the structural properties of amyloid fibrils and the degree of structural disorder of phospholipid membranes, both of which are involved in the fundamental process leading to amyloid cytotoxicity.

Uncovering the structural stability of Magnaporthe oryzae effectors: a secretome-wide in silico analysis

Rice blast, caused by the ascomycete fungus Magnaporthe oryzae, is a deadly disease and a major threat to global food security. The pathogen secretes small proteinaceous effectors, virulence factors, inside the host to manipulate and perturb the host immune system, allowing the pathogen to colonize and establish a successful infection. While the molecular functions of several effectors are characterized, very little is known about the structural stability of these effectors. We analyzed a total of 554 small secretory proteins (SSPs) from the M. oryzae secretome to decipher key features of intrinsic disorder (ID) and the structural dynamics of the selected putative effectors through thorough and systematic in silico studies. Our results suggest that out of the total SSPs, 66% were predicted as effector proteins, released either into the apoplast or cytoplasm of the host cell. Of these, 68% were found to be intrinsically disordered effector proteins (IDEPs). Among the six distinct classes of disordered effectors, we observed peculiar relationships between the localization of several effectors in the apoplast or cytoplasm and the degree of disorder. We determined the degree of structural disorder and its impact on protein foldability across all the putative small secretory effector proteins from the blast pathogen, further validated by molecular dynamics simulation studies. This study provides definite clues toward unraveling the mystery behind the importance of structural distortions in effectors and their impact on plant-pathogen interactions. The study of these dynamical segments may help identify new effectors as well. Communicated by Ramaswamy H. Sarma

Mechanism of elemental segregation around extended defects in high-entropy alloys and its effect on mechanical properties

Elemental segregation around extended defects is common in high-entropy alloys (HEAs) composed of multi-principal elements, which profoundly impacts their mechanical properties. In HEAs, the driving force for segregation usually competes with chemical short-range ordering (CSRO) formation, making it challenging to elucidate the segregation mechanisms. In this study, we systematically investigate the chemical composition changes around extended defects, including dislocations, stacking faults, and grain boundaries (GBs) in CoNiCrFe HEAs, to explore the chemical-structure-mechanical relationship utilizing hybrid Monte Carlo and molecular dynamic (MC/MD) simulations and theoretical analysis. We find a pronounced Cr enrichment and Co/Ni/Fe depletion around all defects considered in this work. A correlation between the degree of structural disorder and the chemical segregation/depletion phenomenon in the proximity of extended defects has been uncovered. Our results show that due to the extreme chemical complexity in HEAs, CSRO inevitably contributes to the elemental rearrangement and affects segregation. Consequently, the segregation behavior in HEAs is mainly controlled by interactions between different atomic pairs, and the segregation entropy also plays a dominant role. By decoupling the strengthening contribution from elemental segregation and CSRO, we demonstrate and highlight that the strengthening in HEAs can be modulated by elemental segregation. The positive impact of element segregation on interfacial properties - improved ultimate tensile strength and elongation, has been evidenced through experimental comparisons of CoNiCrFe with different Fe additions. This work elucidates the mechanism of heterogenous elemental distributions in HEAs where elemental segregation and CSRO coexist, paving the way for manipulating their mechanical properties by modulating the compositional variations.

Effect of multi-component at the A site on the phase and sintering resistance of high entropy rare earth zirconates

A series of high entropy rare earth zirconate ceramics, (5A0.2)2Zr2O7, with single- or dual-phase structures were synthesized using the solid-state reaction method. The cations at the A site varied in terms of average ionic radius RA, atomic mass MA, radius (size) disorder δR, and mass disorder δM. Our results demonstrate that increasing the structural disorder degree promotes the transition from an ordered pyrochlore structure to a defective fluorite structure, and leads to poor sintering resistance. The structural disorder degree of the high entropy zirconates could be increased by decreasing the ionic radius ratio RA/RZr, increasing the size disorder δR and introducing Ce4+ at the A site. Meanwhile, large size disorder leads to strong partitioning of rare earth ions and deviation of the lattice constant from the predicted value. The presence of Ce4+ ions at A site could significantly increase the structural disorder degree and promote the sintering process, and the underlying mechanisms are proposed and discussed.

Exploring the Relationship Between Halide Substitution, Structural Disorder, and Lithium Distribution in Lithium Argyrodites (Li6-xPS5-xBr1+x).

Lithium argyrodite superionic conductors have recently gained significant attention as potential solid electrolytes for all-solid-state batteries because of their high ionic conductivity and ease of processing. Promising aspects of these materials are the ability to introduce halides (Li6-xPS5-xHal1+x, Hal = Cl and Br) into the crystal structure, which can greatly impact the lithium distribution over the wide range of accessible sites and the structural disorder between the S2- and Hal- anion on the Wyckoff 4d site, both of which strongly influence the ionic conductivity. However, the complex relationship among halide substitution, structural disorder, and lithium distribution is not fully understood, impeding optimal material design. In this study, we investigate the effect of bromide substitution on lithium argyrodite (Li6-xPS5-xBr1+x, in the range 0.0 ≤ x ≤ 0.5) and engineer structural disorder by changing the synthesis protocol. We reveal the correlation between the lithium substructure and ionic transport using neutron diffraction, solid-state nuclear magnetic resonance (NMR) spectroscopy, and electrochemical impedance spectroscopy. We find that a higher ionic conductivity is correlated with a lower average negative charge on the 4d site, located in the center of the Li+ "cage", as a result of the partial replacement of S2- by Br-. This leads to weaker interactions within the Li+ "cage", promoting Li-ion diffusivity across the unit cell. We also identify an additional T4 Li+ site, which enables an alternative jump route (T5-T4-T5) with a lower migration energy barrier. The resulting expansion of the Li+ cages and increased connections between cages lead to a maximum ionic conductivity of 8.55 mS/cm for quenched Li5.5PS4.5Br1.5 having the highest degree of structural disorder, an 11-fold improvement compared to slow-cooled Li6PS5Br having the lowest degree of structural disorder. Thereby, this work advances the understanding of the structure-transport correlations in lithium argyrodites, specifically how structural disorder and halide substitution impact the lithium substructure and transport properties and how this can be realized effectively through the synthesis method and tuning of the composition.

AGE FEATURES OF REMODELING OF ARTERIES OF THE PROSTATE GLAND AT ETHANOL INTOXICATION

Chronic alcohol intoxication leads to damage of almost all organs and systems, the degree of structural and functional disorders of which in this pathology is different and depends on the duration and severity of intoxication. Organs of the reproductive system are always involved in the pathological process with long-term effects of alcohol on the body. Age-related remodeling of prostate arteries in ethanol intoxication has not been studied enough.&#x0D; The aim of the study: morphologically study the age-related features of prostate artery remodeling under conditions of ethanol intoxication.&#x0D; Materials and methods. The prostate arteries of 60 white rats were morphologically studied, which were divided into 4 groups: 1 group – 15 intact animals aged 8 months; group 2 – 15 rats aged 24 months; group 3 – 15 8-month-old animals with ethanol intoxication; Group 4 – 15 24-month-old rats with the indicated simulated pathology. A 30% ethanol solution was injected intragastrically at the rate of 2 ml per 100 g of animal weight for 28 days once a day. Animals were euthanized by bloodletting under anesthesia. The external and internal diameters of small-caliber arteries, the thickness of the intima, media, adventitia, intimo-medial, intimo-adventitous, adventitio-medial, Vogenvort and Kernogan indices, and the relative volumes of damaged endotheliocytes were determined on the micropreparations of the prostate. Quantitative morphological indicators were processed statistically.&#x0D; Research results. The wall of arteries thickens, their lumen narrows, the thickness of the media and adventitia increases, and the studied indices change significantly in ethanol intoxication in the prostate. The thickness of the media in young animals with a pronounced statistically significant difference increased by 49.2 %, in old animals by 50.2 % (p&lt;0.001), and the Wogenvoort index changed by 1.56 and 1.6 times, respectively (p &lt;0.001). The lumen of the studied vessels in young rats was statistically significantly (p&lt;0.001) reduced by 16.6%, in old rats by 35.0%, the Kernoghan index by 12.7 % and 13.0 % (p&lt;0.001), which indicated a marked decrease in vascular permeability and deterioration of blood supply to the organ. The relative volume of damaged endotheliocytes in the small-caliber arteries of the prostate gland during long-term ethanol intoxication in young rats was equal to (24.80±0.18) %, and in animals of the older age group – (47.60±0.21) %. Light-optically, pronounced vascular disorders, hemoptysis, expansion of mainly venous vessels, perivisceral and stromal edema, foci of dystrophically, necrobiotically, apoptically altered endotheliocytes, epitheliocytes of glandular structures, focal infiltrates and growth of connective tissue were observed in the prostate gland during chronic alcohol intoxication. Swelling of endotheliocytes, their dystrophy, necrobiosis, desquamation and proliferation were also noted.&#x0D; Conclusions. Ethanol intoxication leads to thickening of walls of arteries of the prostate gland, narrowing of their lumen, atrophic processes in the intima, an increase of thickness of media, adventitia, disruption of the relationship between them, apoptotic, dystrophic and necrobiotic changes in endotheliocytes, endothelial dysfunction, hypoxia, dystrophy, necrobiosis cells and stromal structures, infiltration and sclerosis. The degree of structural rearrangement of prostate arteries dominates in experimental animals of the older age group.

X-Ray Diffraction in Mineralogical Research

A brief account of role of X-ray diffraction (XRD) in mineralogical research with special reference to radioactive and atomic minerals is given. Aspects of research methodology such as sample preparation, analysis time, limitations, search match methods for identification, and complimentary techniques are also given. The most common applications of XRD in mineralogical researches related to radioactive/atomic minerals include identification of primary and secondary uranium and associated ore and gangue minerals, determination of the oxidation grade of uraninites, identification of Th, Nb, Ta, Sn, Be, Li, Zr, Hf, Ti, rare-earth elements (REE) minerals, investigations on degree of structural disordering in Nb-Ta minerals, X-ray crystallographic and substitutional solid solution studies, clay minerals, triclinicity of K-feldspar, metamict minerals and influence of the degree of metamictisation on uranium beneficiation, characterisation of leached residue, beneficiated, heat-treated products, metallurgical slags and other mineralogical studies. The results of mineralogical research are used for elucidating physicochemical conditions and geologic processes that prevailed during mineral formation

X-Ray Diffraction in Mineralogical Research

A brief account of role of X-ray diffraction (XRD) in mineralogical research with special reference to radioactive and atomic minerals is given. Aspects of research methodology such as sample preparation, analysis time, limitations, search match methods for identification, and complimentary techniques are also given. The most common applications of XRD in mineralogical researches related to radioactive/atomic minerals include identification of primary and secondary uranium and associated ore and gangue minerals, determination of the oxidation grade of uraninites, identification of Th, Nb, Ta, Sn, Be, Li, Zr, Hf, Ti, rare-earth elements (REE) minerals, investigations on degree of structural disordering in Nb-Ta minerals, X-ray crystallographic and substitutional solid solution studies, clay minerals, triclinicity of K-feldspar, metamict minerals and influence of the degree of metamictisation on uranium beneficiation, characterisation of leached residue, beneficiated, heat-treated products, metallurgical slags and other mineralogical studies. The results of mineralogical research are used for elucidating physicochemical conditions and geologic processes that prevailed during mineral formation

Silver Tungstate Obtained via Successive Seed Crystal Growth: Structural, Morphological, Optical, and Photocatalytic Properties

Synthesis routes and parameters such as synthesis time, precursor molar ratio, pH, and temperature are critical for generating oxides of various sizes and morphological aspects. However, there is no information on how to prepare silver tungstate (Ag2WO4) crystals of different shapes and sizes under laboratory conditions and without using sulfating agents. In this study, we attempted to fill this gap by preparing α-Ag2WO4 crystals of various sizes and morphologies using the coprecipitation method in a 3 h interval at room temperature and without using sulfating agents. The powder X-ray diffraction analysis confirmed that all crystals had an orthorhombic structure, whereas Fourier-transform infrared spectroscopy revealed the degree of structural disorder in the bonds between the atoms in the materials. Scanning electron microscopy revealed that the α-Ag2WO4 crystals had different sizes (5.37-26.83 μm) and morphologies (tetragonal prism, rod, and cypress leave-like rod), whereas ultraviolet-visible diffuse reflectance spectroscopy analysis indicated the optical band gap energy (2.92-3.05 eV), calculated using the method proposed by Kubelka and Munk. Catalytic tests revealed that the synthesized samples with the smallest crystals (AW1) and a tetragonal prism morphology degraded dye more efficiently (apparent rate constant (k) = 5.86 × 10−3 min−1) than other samples.

Optimization of the structural and optical properties of ALD grown ZnO thin films for photocatalytic applications: thickness dependence

Thin films of ZnO with different thicknesses (ranging from 8 to 40 nm) have been prepared by plasma-enhanced atomic layer deposition. Grazing incidence x-ray diffraction shows the nano-crystalline structure of the films with high degree of disorder. The films have also lattice oxygen and non-lattice oxygen where the film with 20 nm thickness has the highest percentage of the non-lattice oxygen. These films have indirect optical transitions. The energy gap increases slightly with decreasing the film thickness (2.96, 3.03 and 3.16 eV for the thicknesses 40, 20 and 8 nm, respectively). These films have strong photocatalytic activity to treat the water from the organic dyes such as Levafix Brilliant Red. The film with thickness 20 nm has the optimum photocatalytic activity and the lowest contact angle with water. The photoinduced super-hydrophilic nature of ZnO film (20 nm) renders this film suitable for antifogging application. The high photocatalytic activity and super-hydrophilicity are due to the low recombination rate of charge carriers accompanied to the excess of oxygen vacancies and the high degree of structural disorder.