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This article provides a concise discussion of thermodynamic and kinetic contributions to microstructure stabilization by dopant atoms located at interfaces in metallic nanocrystalline materials and an overview of recent molecular dynamics simulations used to study the behavior of dopant-modified interfaces in nanocrystalline copper. Molecular dynamics simulations show that antimony dopant atoms randomly positioned at copper grain boundaries can retard grain growth, in agreement with proposed thermodynamic and kinetic predictions. Simulations of uniaxial tensile deformation show a maximum in the flow strength at a grain size of 15 nm and that antimony dopants at the grain boundaries do not appreciably impact the nucleation of partial or full dislocations during uniaxial tensile deformation in nanocrystalline copper. [ABSTRACT FROM AUTHOR]

In this work we have synthesized FePtP films using sodium hypophosphite as source material for phosphorous. The surface morphology, crystalline structure, grain size and magnetic properties of the plated films prepared at various current densities, bath temperature and concentration of phosphorous source material (NaH2PO2) have been compared. The results shows that the structural & magnetic properties of this thin film depends on the phosphorus content in the film. When the bath temperature increases the phosphorus content decreases & hence coercivity increases. Also coercivity increases after annealing. Reasons for variation in magnetic properties and structural characteristics were discussed. [ABSTRACT FROM AUTHOR]

In this study, empirical constitutive relations of materials with different crystalline structures through severe plastic deformation are introduced. Here, for each material, an optimized empirical relation is chosen by fitting some empirical relations on the results achieved from a dislocation-based constitutive model. In this work, four modes of empirical relations are fitted on the results of modified Estrin–Toth–Molinari–Brechet constitutive model for four materials with different crystalline structures (Al, Cu, Ta, and Zr). The obtained relations for the materials can be usable in commercial finite element codes. [ABSTRACT FROM AUTHOR]

TiO2 nanotube arrays were synthesized by anodization of Ti metal sheets followed by thermal annealing at elevated temperatures from 400 to 600 °C. Scanning electron microscopic measurements showed that dense arrays of nanotubes were produced with the inner diameter about 100 nm, wall thickness 35 nm, and length about 10 μm. X-ray diffraction measurements showed that the as-prepared nanotubes were largely amorphous, whereas thermal annealing led to the formation of well-defined anatase crystalline phase. More interestingly, at 470 °C, the brookite crystalline phase also started to emerge, which became better defined at 500 °C and disappeared eventually at higher temperatures, a phenomenon that has not been observed previously in TiO2 nanotube arrays prepared by anodization. The impacts of the TiO2 nanocrystalline structure on the photocatalytic activity were then examined by using the reduction of methylene blue in water as an illustrating example. Upon exposure to UV lights, the visible absorption profiles of methylene blue exhibited apparent diminishment. Based on these spectrophotometric measurements, the corresponding pseudo-first-order rate constant was estimated, and the sample thermally annealed at 500 °C was found to exhibit the highest activity. The strong correlation between the TiO2 crystalline characteristics and photocatalytic performance suggests that the synergistic coupling of the anatase and brookite crystalline domains led to effective charge separation upon photoirradiation and hence improved photocatalytic activity, most probably as a consequence of the vectorial displacement at the nanoscale junctions between these crystalline grains that impeded the dynamics of electron–hole recombination. These results demonstrate the significance of nanoscale engineering in the manipulation of oxide photocatalytic performance. [ABSTRACT FROM AUTHOR]

The presence of crystalline inclusions in plasma cell myeloma is a rare phenomenon and cases have been reported with rod, needle, and rectangular shaped crystals. Here, we present a case of IgG lambda restricted plasma cell myeloma with rhomboid shaped intracellular crystalline inclusions and extracellular crystal depositions in the bone marrow. Since rhomboid crystal depositions can be seen in other clinical conditions such as pseudogout, this case invites consideration of plasma cell myeloma in the differential diagnosis of patients with rhomboid crystalline deposition in the bone marrow and in sites/organs other than the bone marrow. [ABSTRACT FROM AUTHOR]

The article offers information on a study which examines the protein interaction component within a specific sub-compartment of a eukaryotic flagellum. It states that the trypanosome flagellum contains a para-crystalline extra-axonemal structure which is known as paraflagellar rod. As mentioned, study was conducted by using two yeast hybrids, RNAi and 2D DiGE which helps in defining a protein-protein interaction network taking place in this structure. It concludes that protein interaction data can be generated for insoluble protein complexes.

Mixtures containing the desired weight ratios of α-Fe2O3 and γ-AlOOH were homogenized in the planetary mill, then pressed into tablets and heated up to 1200 °C. All samples were characterized by X-ray diffraction, Mössbauer spectroscopy, Field emission scanning electron microscopy and Energy dispersive X-ray analysis. Two types of solid solutions of general formula α-(AlxFel-x)2O3 a were found; one solid solution was closely related to α-Fe2O3, the other toα-Al2O3. The terminal solid solubility limits, r = 27.0 ± 0.5 mole ratio of α-Al2O3 in α-Fe2O3 and r = 9.0 ± 0.5 of α-Fe2O3 in α-Al2O3, were determined. The Mössbauer spectra showed a broadening of spectral lines and a decrease in the hyperfine magnetic field of α-Fe2O3 with incorporation of Al3+ ions in the α-Fe2O3 structure. For mole fractions between x = 0.40 and 0.70, the Mössbauer spectra were considered as the superposition of a sextet and quadrupole doublet(s). In this concentration range the samples showed an almost constant value of hyperfine magnetic field. For x = 0.90 and 0.93, the Mössbauer spectra were considered as a superposition of two quadrupole doublets, whereas for x = 0.95 the superposition of two quadrupole doublets and one singlet was considered. The origin of this singlet with the isomer shift close to zero is not clearly understood. FE-SEM showed a strong sintering effect on the particles in all samples in the α-(AlxFel-x)2O3 system. [ABSTRACT FROM AUTHOR]

3,4,5-Trimethoxy N-(salicylidene) aniline was synthesized and characterized by IR spectroscopy, ¹H NMR and x-ray single crystal analysis. UV-visible spectroscopy was used for physicochemical tests. X-ray data reveals that the crystalline network cohesion of this compound is essentially assured by CH/pi type hydrogen bounds. It crystallized in the orthorhombic Pbcn space group. Electronic spectroscopy shows that the title compound doesn't present photochromic property but thermochromic one. Intermolecular interactions analysis confirms for this compound a thermochromic structural predisposition. [ABSTRACT FROM AUTHOR]

Phase change materials (PCMs) can exist in at least two different phases (an amorphous and one or more crystalline phases), and they can be switched repeatedly between these phases. The different phases have distinctly different physical properties such as electrical conductivity, optical reflectivity, mass density or thermal conductivity. These differences and the repeatability of the switching give these materials the ability to store information. Rewritable compact discs, digital versatile discs, and Blu-ray™ discs store information in thin films of PCMs, using the difference in reflectivity between the phases as the storage mechanism. A novel solid-state memory technology that applies the difference in electrical resistivity is currently being developed, and possible future applications include reconfigurable logic. This article reviews the unique set of properties of PCMs and their current and future applications. [ABSTRACT FROM AUTHOR]

This paper reports recent theoretical perspectives and experimental results on microstructural evolution during sintering in terms of the interface structure, which is either rough (atomically disordered) or faceted (atomically ordered). The paper presents theoretical predictions and calculations of grain growth during liquid-phase sintering based on crystal growth theories. It is shown that various types of grain growth behavior, which may be normal, abnormal, or stagnant, can appear as a result of the coupling effects of the maximum driving force for growth and the critical driving force for appreciable growth. The predictions are also shown to be valid in the case of solid-state sintering. A number of experimental observations showing the effect of some critical processing parameters have been found to be in excellent agreement with the predictions. Principles of microstructure development (grain growth control) during sintering are suggested. In addition, the effect of the interface structure on densification is briefly described and discussed. [ABSTRACT FROM AUTHOR]

Atmospheric pressure plasma technologies are a potential substitution for wet chemical and vacuum processes in the production of crystalline silicon solar cells, leading to a simplified in-line processing chain. In this contribution, a plasma chemical etching technology is presented as a basic step for a future continuous production process. A linearly extended DC arc discharge is used for activation of the etching gases. An Ar-N2 mixture is fed through the plasma source; etch gases are injected into the afterglow plasma, near the substrate. Controlled purge gas systems prevent the contamination of the reaction zone with air or moisture as well as the release of reaction products. The plasma source was studied by a noninvasive in-line monitoring of the DC arc phenomena. Silicon etching rates can be controlled by the etch gas composition and the plasma conditions. Fourier Transform infrared spectroscopy of the waste gas was applied to monitor the current etching rates. First industrial tests confirmed standard efficiencies of the cells after edge isolation by atmospheric pressure plasma etching. [ABSTRACT FROM AUTHOR]

The results of investigation of the temperature fields arising in the process of cutting of crystalline materials are presented. The temperature distributions in the cutting zone and in the neighboring regions were determined with the use of an infrared thermograph. It is shown that, in the process of cutting of sapphire, the temperature reaches a maximum at a certain distance before the cutting zone. With time the temperature of the sapphire increases monotonically or passes through a maximum depending of the load applied. The kinetic dependence of the temperature of diamond also passes through a maximum. It has been established that the temperature of diamond crystal subjected to cutting under hard conditions increases markedly, which can lead to the separation of large parts, probably because of the growth of fatigue cracks due to the intense heating of the material. [ABSTRACT FROM AUTHOR]

Abstract: The problem of a screw dislocation interacting with a core–shell nanowire (coated nanowire) containing interface effects (interface stresses) is first investigated. The interaction energy and the interaction force are calculated. The interaction force and the equilibrium position of the dislocation are examined for variable parameters (interface stress and material mismatch). The influence of the core–shell nanowire and the interface stresses on the interaction between two screw dislocations is also considered. The results show that the impact of the interface stresses on the motion and the equilibrium position of the dislocation near the core–shell nanowire is very significant when the radius of the nanowire is reduced to nanometer scale. [Copyright &y& Elsevier]

Coupling of polarized light to thin opal films was examined to characterize their crystalline structure and diffraction processes in them. Photonic stop bands were observed in transmission (reflection) spectra and attributed to diffraction from the {111} crystallographic planes of the twinned fcc structure. Weakening and collapses of stop bands for linearly polarized light demonstrated a strong anisotropy of light propagation in the films. Reflection spectra of the films under the s-polarized light illumination highlighted an unusual behavior of light scattering. Multiple Bragg diffraction accompanied by leakage and inflow of energy to major diffraction lobes has been detected and described in detail. [ABSTRACT FROM AUTHOR]

Stable crystalline phosphorus ylides were obtained in excellent yields from the 1:1:1 addition reaction between triphenylphosphine and dialkyl acetylenedicarboxylates in the presence of phenylhydrazone derivatives, such as 1-benzylidene-2-phenylhydrazine, 1-(3-chlorobenzylidene)-2-phenylhydrazine, 1-(2,4-dinitrobenzylidene)-2-phenylhydrazine, 1-(4-nitrobenzylidene)-2-phenylhydrazine, 1-(2-fluorobenzylidene)-2-phenylhydrazine, 1-(4-fluorobenzylidene)-2-phenylhydrazine and 1-(2,4-dichlorobenzylidene)-2-phenylhydrazine. These stable ylides exist in solution as a mixture of two geometrical isomers as a result of the restricted rotation around the carbon-carbon partial double bond resulting from the conjugation of the ylide moiety with the adjacent carbonyl group. [ABSTRACT FROM AUTHOR]

[Display omitted] • Innovative passivating contact using poly-Si/quantum well/c-Si contact. • Quantum well suppresses dopant diffusion from the poly-Si layer into c-Si bulk. • Excellent passivation quality achieved with iV oc of 742 mV and J o of 1.1 fA/cm2. Herein, we propose a quantum well comprising a stack of SiO x /nanocrystalline silicon (nc-Si)/SiO x layers between a polycrystalline silicon (poly-Si) layer and a crystalline silicon wafer (c-Si) for enhancing the passivation quality through the poly-Si/c-Si passivating contact for c-Si solar cells. A large number of dopants can diffuse deeply into c-Si from a heavily doped poly-Si layer during high-temperature annealing, reducing the surface passivation quality. The quantum well with the double SiO x layer plays a significant role as a double barrier, thus suppressing this. The formation of the nc-Si phase sandwiched between the SiO x layers can support carrier transport, i.e., the tunnelling of carriers through the SiO x layers for collection. Moreover, a highly doped poly-Si/quantum well/c-Si contact exhibits considerable improvement in the passivation quality, achieving a high iV oc of 742 mV and low J o of 1.1 fA/cm2, compared with a reference poly-Si/c-Si passivating contact (iV oc = 707 mV, J o = 32.5 fA/cm2). The results indicate the effectiveness of the innovative passivating contact concept and pave the way for further improvements in the performance of c-Si solar cells. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the structural and spatial considerations in the N,N'-Diacyl- and Bis(alkoxycarbonyl)bispidinone series. It discourses on the structural distinctiveness and involution to other compounds of the bispidinone framework which believed to have been eluded notice. It offers details which considers the experiments and procedures where the given compound is further elaborated.

Carbon-rich silicon carbonitride (SiCN) ceramics derived from polysilylcarbodiimides represent a novel class of materials where the incorporation of a high amount of carbon was demonstrated to be beneficial for ultrahigh-temperature resistance against crystallization. Calorimetric measurements of heat of oxidative dissolution in a molten oxide solvent show that these amorphous SiCN ceramics produced at 1000° or 1100°C possess a small positive or near zero enthalpy of formation relative to their crystalline constituents, namely silicon nitride, silicon carbide, and graphite. The enthalpy of formation does not change strongly with increasing SiC mole fraction. Because the enthalpies of formation from crystalline constituents are at most slightly positive, and the entropies of formation are expected to be significantly positive because of disorder in the amorphous phase, it is likely that the free energies of formation from silicon carbide, silicon nitride, and graphite are negative and the high-temperature persistence of amorphous SiCN ceramics may originate from thermodynamic stabilization. However, this stabilization is less pronounced than that for SiCO polymer-derived ceramics studied earlier. [ABSTRACT FROM AUTHOR]

Abstract: Three thermostable neutral cellulases from Melanocarpus albomyces, a 20-kDa endoglucanase (Cel45A), a 50-kDa endoglucanase (Cel7A), and a 50-kDa cellobiohydrolase (Cel7B) heterologously produced in a recombinant Trichoderma reesei were purified and studied in hydrolysis (50°C, pH 6.0) of crystalline and amorphous cellulose. To improve their efficiency, M. albomyces cellulases naturally harboring no cellulose-binding module (CBM) were genetically modified to carry the CBM of T. reesei CBHI/Cel7A, and were studied under similar experimental conditions. Hydrolysis performance and product profiles were used to evaluate hydrolytic features of the investigated enzymes. Each cellulase proved to be active against the tested substrates; the cellobiohydrolase Cel7B had greater activity than the endoglucanases Cel45A and Cel7A against crystalline cellulose, whereas in the case of amorphous substrate the order was reversed. Evidence of synergism was observed when mixtures of the novel enzymes were applied in a constant total protein dosage. Presence of the CBM improved the hydrolytic potential of each enzyme in all experimental configurations; it had a greater effect on the endoglucanases Cel45A and Cel7A than the cellobiohydrolase Cel7B, especially against crystalline substrate. The novel cellobiohydrolase performed comparably to the major cellobiohydrolase of T. reesei (CBHI/Cel7A) under the applied experimental conditions. [Copyright &y& Elsevier]

Ceramic lasers have advantages such as better optical homogeneity, cheaper production, and more freedom in shape compared with monocrystalline lasers. However, equal or better laser performances are required. Interface segregation is important as ceramics contain a high number of interfaces, segregation to which may locally alter the concentration of luminescent dopants, which in turn may influence laser performance. The present work applies atomistic simulation techniques to investigate the segregation of neodymium (Nd) dopants to surfaces and mirror twin grain boundaries in yttrium aluminum garnet (YAG). These results allow a better understanding of interfacial segregation and its influence on laser performance of Nd:YAG ceramics. [ABSTRACT FROM AUTHOR]

The present paper describes an opto-electronic humidity sensor based on thin film of zinc oxide prepared by pulsed laser deposition method. Being optical in nature it gives electromagnetic disturbance-free monitoring. The sensing element is a right-angled isosceles prism with its base coated with ZnO thin film. Films have been characterized by XRD, SEM, and optical transmission. Film grown with substrate at room temperature is amorphous whereas that grown at elevated temperature is single crystalline with grain size 38.52 nm. Film deposited at room temperature is sensitive to humidity over a wide range i.e. 5–90RH% while that deposited at elevated temperature is found to be insensitive to humidity. The sensor shows better sensitivity for higher range of humidity. The response and recovery time of the sensor element have also been evaluated. This sensor configuration can be used for on-line applications and in-situ monitoring. [ABSTRACT FROM AUTHOR]

Polycrystalline silicon obtained by the crystallization of thin amorphous silicon films has been an important material for microelectronics technology during the last decades. Many properties are improved in crystallized amorphous silicon compared to the as-deposited polysilicon such as larger grain size, smoother surface, and higher-carrier mobility. In this work, the crystallization of amorphous silicon is investigated by combining transmission electron microscopy (TEM) observations and molecular dynamics calculations. TEM observations on a series of specimens have shown that the majority of the silicon grains are oriented with a $$ {\left\langle {110} \right\rangle} $$ zone axis normal to the surface. In order to understand the crystallization mechanism molecular dynamic simulations were performed. It is found that the $$ {\left\langle {110} \right\rangle} $$ c/amorphous interface exhibits the lowest reduced interfacial energy density while the $$ {\left\langle {111} \right\rangle} $$ c/amorphous has the lowest reduced energy differences per unit interfacial area. The most energetically unfavorable interface is $$ {\left\langle {001} \right\rangle} $$ c/amorphous. [ABSTRACT FROM AUTHOR]

We make a systematic study on the time history interfacial conditions in multiscale computations for crystalline solids in one space dimension. The exact interfacial condition is derived rigorously. For a class of approximate time history kernel functions, the error is estimated. In particular, a cut-off of the exact kernel function is a special case. Moreover, an effective numerical algorithm is proposed for the convolution. [ABSTRACT FROM AUTHOR]

The dissociation of CO serves both as a model test reaction on single crystals and as a relevant reaction step for industrial methanation. We combined extensive density functional theory calculations, ultra-high vacuum experiments on well-defined single crystals, and catalytic activity measurements on supported catalysts in a study of the dissociation mechanism of CO on Ni surfaces. We found that this process is highly structure-sensitive and also is sensitive to the presence of hydrogen: Under ultra-high vacuum, with no hydrogen present, the dissociation proceeds through a direct route in which only undercoordinated sites (e.g., steps) are active. Under methanation conditions, the dissociation also proceeds most favorably over undercoordinated sites, but through a COH species. [Copyright &y& Elsevier]

Mechanical properties of Ti/Al–7Si assemblies produced by insert moulding were studied with a classical push-out test and a variant that is the circular-bending test. Special care has been taken for controlling both the reactivity at the Ti/Al–7Si interface and the metallurgical health of the Al–7Si matrix. Mechanical tests until complete debonding have been completed with interrupted tests, metallographic characterizations and FEM analysis of elastic stress state. A mean shear strength of the interface of about 120 MPa was obtained. When the Ti insert is solely fretted in the matrix, without chemical interaction between Ti and the Al–7Si alloy, the mean shear strength is significantly lower (48 MPa). This result clearly shows that chemical interaction at the interface (formation of a thin TiSi layer at the Ti side and a thick Al3Ti(Si) layer at the Al–7Si alloy side) improves the mechanical properties of the assembly. It is also shown that the failure sequence is characterized both by crack propagation from bottom to top and matrix yielding from top to bottom. Actually, interface damaging begins by crack initiation at the specimen bottom face (not at the top face and under the indenter) in a nearly pure mode I solicitation at a radial tensile stress of about 100 MPa. [ABSTRACT FROM AUTHOR]

Four interface models for crystalline oxynitride on (001)Si substrates are proposed and investigated. All four models are proposed to model thin oxynitride films on Si substrates, according to experimental findings and theoretical studies on amorphous oxynitride films and nitrogenated SiO2. State-free insulating interfaces were obtained by expanding the bulk oxynitride cell by approximately 12% and 1% along the [100] and [010] axes, respectively, and interfacing it with (001)Si. Results demonstrate state-free insulating interfaces for all models with, however, valence-band offsets slightly above or below 1 eV. The significant decrease in the valence-band offsets is mainly attributed to the significant expansion of the oxynitride's lattice constant to lattice-matched (001)Si, as well as to the high concentration of nitrogen atoms in the oxynitride bulk. [ABSTRACT FROM AUTHOR]

The thermal properties, crystalline structure and shape memory effects of poly( l-lactide) (PLLA) and poly( l-lactide-co-ε-caprolactone) (PCLA) copolymers are systematically investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and tensile tests. The effects of the deformation strain on the shape recovery rate and recovery stress are also revealed. The polymers have the PLLA crystal and the amorphous phase, which are served as the fixed phase and reversible phase, respectively. The shape recovery rate and the recovery stress are significantly affected by the compositions and the deformation strain. With the increase of the deformation strain, the shape recovery rate decrease and higher shape recovery rate can be obtained in the polymers which have higher ε-CL content. However, the variation of recovery stress with the deformation strain is quite different and the maximum recovery stress of all polymers exceeds 3 MPa. [ABSTRACT FROM AUTHOR]

The thermal behaviour of the animal by-product meat and bone meal (MBM) has been investigated in order to assess how it is affected structurally and chemically by incineration. Initially composed of intergrown collagen and hydroxyapatite (HAP), combustion of the organic component is complete by 650 °C, with most mass loss (50–55%) occurring by 500 °C. No original proteins were detected in samples heated at 400 °C or above. Combustion of collagen is accompanied by an increase in HAP mean crystallite size at temperatures greater than 400 °C, from 10 nm to a constant value of 120 nm at 800 °C or more. Newly formed crystalline phases appear beyond 400 °C, and include β-tricalcium phosphate, NaCaPO4, halite (NaCl) and sylvite (KCl). Crystallite thickness as judged by small angle X-ray scattering (SAXS) increases from 2 nm (25–400 °C) to 8–9 nm very rapidly at 550 °C, and then gradually increases to approximately 10 nm. The original texture of HAP within a collagen matrix is progressively lost, producing a porous HAP dominated solid at 700 °C, and a very low porosity sintered HAP product at 900 °C. [ABSTRACT FROM AUTHOR]

Novel bulk glassy samples of the pseudoternary chalcohalide Ge–S–AgI system have been prepared. Glasses have been obtained by monotemperature synthesis in evacuated ampoules and standard melt-quenching technique. The glass-forming region in the system determined by X-ray diffraction is situated in the S-rich region on the Ge–S side (S/Ge = 1.2, 1.5, 2 and 3) with AgI content up to 20 mol.%. Some physicochemical properties of the amorphous materials and their compositional dependence have been investigated. In addition, the theoretical average coordination number (Z), the total constraints per atom (Nco), the radial (Na) and axial (Nb) strength of the bonds have been calculated and related to the experimental results. [ABSTRACT FROM AUTHOR]

Interfaces are often believed to play a role in the mechanical behavior of mineralized biological and biomimetic materials. This motivates the micromechanical description of the elasticity and brittle failure of interfaces between crystals in a (dense) polycrystal, which serves as the skeleton of a porous material defined one observation scale above. Equilibrium and compatibility conditions, together with a suitable matrix-inclusion problem with a compliant interface, yield the homogenized elastic properties of the polycrystal, and of the porous material with polycrystalline solid phase. Incompressibility of single crystals guarantees finite shear stiffness of the polycrystal, even for vanishing interface stiffness, while increasing the latter generally leads to an increase of polycrystal shear stiffness. Corresponding elastic energy expressions give access to effective stresses representing the stress heterogeneities in the microstructures, which induce brittle failure. Thereby, Coulomb-type brittle failure of the crystalline interfaces implies Drucker–Prager-type (brittle, elastic limit-type) failure properties at the scale of the polycrystal. At the even higher scale of the porous material, high interfacial rigidities or low interfacial friction angles may result in closed elastic domains, indicating material failure even under hydrostatic pressure. This micromechanics model can satisfactorily reproduce the experimental strength data of different (brittle) hydroxyapatite biomaterials, across largely variable porosities. Thereby, the brittle failure criteria can be well approximated by micromechanically derived criteria referring to ductile solid matrices, both criteria being even identical if the solid matrix is incompressible. [ABSTRACT FROM AUTHOR]

Both the approach used and the progress made in the assignment of structure types to the crystal structures contained in the ICSD database are reported. Extending earlier work, an hierarchical set of criteria for the separation of isopointal structures into isoconfigurational structure types is used. It is shown how these criteria, which include the space group (number), Wyckoff sequence and Pearson symbol, c/ a ratio, β ranges, ANX formulae and, in certain cases, the necessary elements and forbidden elements, may be used to uniquely identify the representative structure types of the compounds contained in the ICSD database. [ABSTRACT FROM AUTHOR]

The structural reorganization of polyoxymethylene powders during sintering has been investigated through a detailed analysis of the SAXS data in order to determine the origin of the mechanical property improvement with regard to the compression-moulded counterpart. Two approaches afford a quantitative evaluation of the structural parameter evolutions. On one hand, the correlation and interface distribution functions were calculated for the samples submitted to various thermo-mechanical treatments. On the other hand, the Hosemann's paracrystalline model modified with Reinhold distributions of the crystal and amorphous phase thicknesses was used to evaluate the disorder in the lamella stacking. Both approaches suggest that a more perfect and regular crystalline structure with thicker and wider crystals develops in the sintered samples as compared with the parent powders and the material crystallized from the melt. Theses morphological modifications are discussed in relation to the very high stiffness and brittleness of the sintered materials. Two possible mechanisms of coalescence of the powder grains via the crystalline phase are proposed to account for these specific mechanical properties of the sintered materials. [ABSTRACT FROM AUTHOR]

The synthesis of single crystalline and polycrystalline material is reported in the system ZnO1 – x S x . Substitution of oxygen by sulphur yields hexagonal wurtzite-type mixed crystals in the range 0 ≤ x ≤ 0.05. The cubic zincblende structure is observed for oxygen incorporation into ZnS for 0.96 ≤ x ≤ 1. At intermediate compositions, the system is two-phase. For both types of anion substitution, the band gap energies, as determined from optical transmission and remission experiments, are found to decrease from the pure end members. Quantum chemical calculations at density functional level identify local structural changes as the main factor responsible for the reduction of band gap energies. [ABSTRACT FROM AUTHOR]

The effect of defect ion concentration on conductivity in the CaNd2S4 system has been investigated by varying the CaS:Nd2S3 ratio. Samples with the formula xCaS:Nd2S3 x = 0.7–1.0 have been prepared using solid state methods by high temperature synthesis in evacuated quartz tubes followed by annealing in hydrogen sulfide. The structures of the materials were determined using the Rietveld refinement of powder neutron diffraction data. The phases crystallise with a defect version of the cubic Th3P4 structure in the space group I-43d with cell parameter a ≈ 8.53 Å. Temperature programmed oxidation (TPO) in a 5 Vol.% O2/Ar atmosphere show that the materials resist oxidation up to a temperature of approximately 680 °C. TPO also indicates that there is only one type of sulfide ion present in the system, based on the presence of only one peak in the TPO trace. In-situ impedance spectroscopy was carried out in an Ar and H2S/Ar atmosphere between 300 °C and 500 °C. Bulk conductivities, activation energies and time constants for ion hopping processes were determined. The sample, 0.9CaS:Nd2S3, was found to exhibit three impedance arcs in the Nyquist plot suggesting ionic conduction. The independence of the material’s bulk conductivity when exposed to an H2S/Ar atmosphere supports this statement. The xCaS:Nd2S3 sample with x ≤ 0.8 show strong electronic contributions to the overall conductivity. The total ionic conductivity for 0.9CaS:Nd2S3 of 1.09 × 10−6 S cm−1 measured at 500 °C, matches conductivity values reported using galvanic cells. [ABSTRACT FROM AUTHOR]

The present article is an overview of some mathematical results, which provide elements of rigorous basis for some multiscale computations in materials science. The emphasis is laid upon atomistic to continuum limits for crystalline materials. Various mathematical approaches are addressed. The setting is stationary. The relation to existing techniques used in the engineering literature is investigated. [ABSTRACT FROM AUTHOR]

Abstract: Molecular dynamics (MD) simulations are used to model dislocation nucleation at or near symmetric tilt bicrystal copper interfaces with 〈100〉 or 〈110〉 misorientation axes. MD simulations indicate that orientation of the opposing lattice regions and the presence of certain structural units are two critical attributes of the interface structure that affect the stress required for dislocation nucleation. Boundaries that contain the E structural unit are found to emit dislocations at comparatively low tensile stress magnitudes. A simple model is proposed to illustrate the impact of interfacial porosity and stresses acting on the slip-plane in non-glide directions on tensile interface strength. Accounting for interfacial porosity through an average measure is found to be sufficient to model the tensile strength of boundaries with a 〈100〉 misorientation axis and many boundaries with a 〈110〉 misorientation axis. [Copyright &y& Elsevier]

Abstract: The chemical potential of a curved interface contains a term that is proportional to the product of the interface curvature and the interface stiffness. In crystalline materials, the interface stiffness is a tensor. This paper examines several basic issues related to the properties of the interface stiffness, especially the determination of the interface stiffness in particular directions (i.e. the commonly used scalar form of the interface stiffness). Of the five parameters that describe an arbitrary grain boundary, only those describing the inclination are crucial for the scalar stiffness. We also examine the influence of crystal symmetry on the stiffness tensor for both free surfaces and grain boundaries. This results in substantial simplifications for cases in which interfaces possess mirror or rotational symmetries. An efficient method for determining the interface stiffness tensor using atomistic simulations is proposed. [Copyright &y& Elsevier]

The interfaces between liquid or solid Pb islands and single- or poly-crystalline Cu substrates are investigated. EBSD (Electron backscattered diffraction) analyses show that when Pb is solidified from droplets, a cube-on-cube orientation relationship prevails between the Pb crystals and each Cu grain surface, whatever its surface orientation, even though the lattice parameter of Pb is 1.37 times larger than that of Cu. Scanning electron microscope (SEM) and atomic force microscope (AFM) analyses show that during annealing of Pb droplets, ridges develop at the droplet-substrate triple lines, indicating that the interfaces evolve towards equilibrium by diffusional processes. These features are discussed in comparison with experiments and calculations performed on Pb nanocrystals embedded in Al, another fcc solid with a lattice parameter smaller than that of Pb. It is proposed that the cube-on-cube orientation relationship results from the solidification of Pb along the {111} planes of the solid Cu/liquid Pb interface which have developed by diffusion during the process of equilibration of the interface shape. [ABSTRACT FROM AUTHOR]

The problem of computing the index of a coincidence isometry of the hypercubic lattice is considered. The normal form of a rational orthogonal matrix is analyzed in detail and explicit formulas for the indices of certain coincidence isometries of are obtained. These formulas generalize the known results for n ≤ 4. [ABSTRACT FROM AUTHOR]

Resorbable, porous glass scaffolds for tissue engineering were prepared by sintering borate glass with salt (sodium chloride). Subsequently, the sodium chloride was dissolved in water resulting in a highly porous material. By modifying the process parameters including salt particle size, salt volume percentage, sintering temperature and sintering time, sintered matrix structures were optimized. Analysis of the structure data indicates that the 50 vol% glass—50 vol% salt with particle sizes from 250–315 μm sintered at a temperature of 520°C for 10 min resulted in an optimum structure with 76.5% porosity and 29.3 N/cm2 compressive strength. The process of HAP formation on the scaffolds in 0.25 M K2HPO4 solutions with pH 9.0 at 37°C was evaluated. The structural changes were analyzed by X-ray diffraction and scanning electron microscopy. An amorphous phosphate was formed on the surface of the scaffolds within 1d and crystalline hydroxyapatite (HA) within 10d. [ABSTRACT FROM AUTHOR]

Thin PVA/magnesium acetate composite fibres were prepared by using sol-gel processing and electrospinning technique. After calcinations of the above precursor fibres, MgO nanofibres with a diameter of 50–150 nm could be successfully obtained. The fibres were characterized by SEM, FT-IR, XRD, respectively. The results showed that the crystalline phase and morphology of MgO fibres were largely influenced by the calcination temperature. [ABSTRACT FROM AUTHOR]

Abstract: Degree of crosslinking in silane-water crosslinked ethylene–octene copolymer and its blends with low-density polyethylene was investigated, using three different techniques: the conventional gel content determination, solvent uptake factor method and infrared analysis. The results from those techniques show a similar trend in which the degree of crosslinking increases with increase of crosslinking time, and decreases with increase of crystalline portion in the materials. The measurement of gel content, although it is a direct way to yield results on degree of crosslinking, is time consuming and uses a large amount of solvent for extraction. Also, good care must be taken when analysing the gel content of samples with low degree of crosslinking. Analysis of FTIR data has shown potential for the determination of crosslink variations in the silane crosslinked materials and gives meaningful information on the progress of the silane-water crosslinking reaction. [Copyright &y& Elsevier]

Abstract: Unit cell volumes of intermetallic compounds have been calculated using reported volume size factors. An equation to calculate unit cell volume for intermetallics of any crystalline structure was derived from previously reported expressions for L12 and B2 compounds. Average error for 122 analyzed compounds was 3.16%. Errors ranged from 0.00 to 14.01%. Factors that could influence the error value, such as order, structure type, solid solubility, and type of elements forming the compound were evaluated. A combination of solid solubility and type of elements forming the compounds seem to be the most relevant factors influencing the error value. [Copyright &y& Elsevier]

Abstract: Charge distribution at the YSZ/Si interface and in the bulk of ZrO2 + x.Y2O3 (x =1.22, 2.39, 3.73 and 6.49mol% Y2O3) thin films were studied by the charge transient methods and the impedance spectroscopy. The smallest amount of mobile ionic charge for the film with 6.49mol% Y2O3 was found, while the positive charge fixed at the YSZ/Si interface is almost the same for each of the investigated films. The currents flowing across the films were influenced by their phase compositions, mainly in the film with 6.49mol Y2O3. The observed diode behaviour with the characteristic leakage current was present probably due to the absence of interface traps, capable to capture the mobile positive charge. The electrical conductivity as the function of yttria amount and phase composition indicates the presence of isolated oxygen vacancies as well as the associated point defects. The behaviour of electrical conductivity is in a relatively good agreement with that observed for the crystalline YSZ samples used as the targets at the deposition of investigated films by e-beam evaporation on the Si substrate. [Copyright &y& Elsevier]

Abstract: A rectifying nanocrystalline diamond (NCD) pn-structure has been grown by Hot-Filament CVD onto a large-area silicon substrate. N-type as well as p-type doping has been realized with this HFCVD process. IV-measurements at different temperatures show a diode behavior with an ideality factor of approximately n =10 and a barrier height for current injection of approximately 0.76 eV. CV-plots show a dielectric barrier of 4.2 eV. This points towards a complex interface behavior, which is analysed on the basis of highly disordered materials. [Copyright &y& Elsevier]

The quantum solid para-hydrogen (p-H[sub 2]) has recently proven useful in matrix isolation spectroscopy. Spectral lines of compounds embedded in this host are unusually narrow, and several species have been reported to rotate in p-H[sub 2]. We found that a p-H[sub 2] matrix inhibits rotation of isolated methanol (CH[sub 3]OH) but still allows internal rotation about the C-O bond, with splittings of the E/A torsional doublet in internal rotation — coupled vibrational modes that are qualitatively consistent with those for CH[sub 3]OH in the gaseous phase. This simplified high-resolution spectrum further revealed the slow conversion of nuclear spin symmetry from species E to species A in the host matrix, offering potential insight into nuclear spin conversion in astrophysical sources. [ABSTRACT FROM AUTHOR]

Abstract: The crystal structure of the new ternary compound TmCu4−x Sb2 (x =1.065) was determined by direct methods from X-ray powder data (diffractometer DRON-3M, Cu Kα-radiation). It crystallizes with the orthorhombic structure type ErFe4Ge2 (low-temperature modification) and is the first representative of this structure type among known antimonides: space group Pnnm, Pearson code oP14-2.13, a =7.00565(6)Å, b =7.83582(6)Å, c =4.25051(3)Å, Z =2. Investigated structure is an orthorhombically deformed derivative of the ZrFe4Si2 structure type. [Copyright &y& Elsevier]

Extensive theoretical analysis and experimental observations show surface roughening transitions of crystals. The surface roughening is characterized by step free energy, which gradually decreases to 0 at the roughening transition temperature. For a crystal of finite size, the surface roughening transition is manifested by gradual increase of the curved edge and corner areas. In alloys, the interfaces between the solid and the liquid phases can be either singular, partially rough, or completely rough at different temperatures. Their thermally induced roughening transitions are similar to those of the solid-vapor interfaces. The interface roughening and the reverse transition to singular structures can also be induced by additives. The grain boundaries of any misorientation angles in oxides and metals also show roughening transitions. The singular grain boundaries have either flat, hill-and-valley, or kinked shapes, and with temperature increase or composition changes, they become defaceted to curved shapes. These defaceted grain boundaries are rough. It is thus possible to produce either singular or rough grain boundaries by heat-treatment or additives to vary their properties. [ABSTRACT FROM AUTHOR]

Abstract: . A crystalline interface is often covered by a dense network of linear defects with a (pseudo) biperiodic geometry. The elastic field of this network is calculated by thinking the interface as paved by adjacent Somigliana dislocations. The analysis of a portion of an erratic zigzag line of a (001)Si low angle twist boundary, observed in two-beam transmission electron microscopy, is given as an example. To cite this article: A. Boussaid et al., C. R. Physique 6 (2005). [Copyright &y& Elsevier]

The nature and the extent of reactive crystalline surfaces for colloidal particles is an essential factor for understanding of reactions at the solid-liquid interfaces. The measurement of this specific surface area for colloidal mineral particles is usually obtained from gas-adsorption isotherms. This measurement, based on adsorbate-adsorbent interactions, yields overall weight-averaged values that fail to display the distribution of geometrical specific surface areas of individual particles. The present work proposes to use three dimensional atomic force microscopy (AFM) images to characterize the distribution of geometrical features of hexagonal plate-like gibbsite [Al(OH)3] particles without microporosity. This sub-micrometer approach, which requires minute quantities of solids (picograms), demonstrates the broad distribution of specific surface areas (lateral, basal, and total) determined for each individual particle in our sample. The resulting weight-averaged specific surface area values of basal and lateral surfaces, calculated from this distribution, agree with values measured by Kr-adsorption isotherms. The lateral specific surface area values thus obtained confirm the estimates given by and are correlated with the infrared spectrum analysis proposed in our previous papers. Moreover, these results reveal the importance of the smallest particles in the overall distribution, whereas the weight-averaged value is monitored by high-mass particles that are few in number. This kind of specific surface area heterogeneity must be taken into account in describing the reactivity of anisotropic shaped mineral particles. [ABSTRACT FROM AUTHOR]