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Capacity degradation and voltage fade of Li2MnO3 during cycling are the limiting factors for its practical use as a high-capacity lithium-ion battery cathode. Here, the simulated amorphisation and recrystallisation (A + R) technique is used, for generating nanoporous Li2MnO3 models of different lattice sizes (73 Å and 75 Å), under molecular dynamics (MD) simulations. Charging was carried out by removing oxygen and lithium ions, with oxygen charge compensated for, to restrain the release of oxygen, resulting in Li2−xMnO3−x composites. Detailed analysis of these composites reveals that the models crystallised into multiple grains, with grain boundaries increasing with decreasing Li/O content, and the complex internal microstructures depicted a wealth of defects, leading to the evolution of distorted cubic spinel LiMn2O4, Li2MnO3, and LiMnO2 polymorphs. The X-ray diffraction (XRD) patterns for the simulated systems revealed peak broadening in comparison with calculated XRD, also, the emergence of peak 2Θ ~ 18–25° and peak 2Θ ~ 29° were associated with the spinel phase. Lithium ions diffuse better on the nanoporous 73 Å structures than on the nanoporous 75 Å structures. Particularly, the Li1.00MnO2.00 shows a high diffusion coefficient value, compared to all concentrations. This study shed insights on the structural behaviour of Li2MnO3 cathodes during the charging mechanism, involving the concurrent removal of lithium and oxygen. [ABSTRACT FROM AUTHOR]

The elastic-plastic deformation mechanism of single crystal diamond under spherical nanoindentation was emphasised using molecular dynamics (MD). The benchmark tests to determine the empirical potential that accurately describe the interactions between diamond atoms were completed. Tensile strength of diamond at different temperatures was studied under the empirical potential preferentially selected by benchmark tests. The nanoindentation process of the diamond is subsequently carried out on the surface (001). Plastic deformation behaviour of brittle diamond was found, such as amorphisation, phase transformation, graphitisation and dislocation evolution were analysed and discussed using combined methods. The simulation results show that the plastic deformation behaviour of the diamond material is also evident, even though diamond is a brittle material with high strength and hardness. 'Pop-in' event of the P-h curve is the turning point from elastic to plastic deformation. The elastic stage can be divided into the pure elastic and the quasi-elastic deformation stages. The plastic deformation behaviour of diamond is dominated by a combination of phase transformation, graphitisation and dislocation nucleation. It is also found that the primary dislocation type is 1/2<110> perfect dislocation, which was distributed in the area of large stress concentration below the indenter. [ABSTRACT FROM AUTHOR]

Developing efficient, stable, and cost-effective electrocatalysts is crucial for large-scale industrial water electrolysis hydrogen production. In this study, a-Cu 2 Se@Cu 3 P/CF heterostructure electrode was constructed by form amorphous Cu 2 Se on Cu 3 P nanowire array, which proved the electrode efficient contact with electrolyte, enhanced electron transfer in the electrode with abundant pathway and active sites. Ultimately, these enhancements significantly improved the HER performance of the a-Cu 2 Se@Cu 3 P/CF electrode. In alkaline electrolyte, the a-Cu 2 Se@Cu 3 P/CF electrode exhibits overpotential as 99 mV@10 mA cm−2 and Tafel slope as 79 mV/dec. The a-Cu 2 Se@Cu 3 P/CF electrode is capable of maintaining a stable potential (− 1.17 V, − 1.21 V, − 1.30 V, − 1.37 V, − 1.50 V) for a long duration (10 h) at different current densities (10 mA cm−2, 20 mA cm−2, 50 mA cm−2, 100 mA cm−2, 200 mA cm−2). Additionally, at a current density of 100 mA cm−2 and 200 mA cm−2, the catalytic performance has been slightly enhanced approximately 1.5 % and 1.8 % at the end of 10 h duration test. This demonstrated the excellent stability of the a-Cu 2 Se@Cu 3 P/CF electrocatalyst, showcasing its potential for practical applications in hydrogen production. • We fit the values of hydrogen adsorption free energy and overpotential from recent heterostructure reports into a function. • The a-Cu 2 Se@Cu 3 P/CF electrode with a-Cu 2 Se@Cu 3 P heterostructure exhibits a lower overpotential than Cu 2 Se-Cu 3 P/CF electrode. • The strong interaction between a-Cu 2 Se and Cu 3 P improved the electronic structure near the heterojunction interface. • The a-Cu 2 Se@Cu 3 P/CF electrode exhibits excellent stability and slightly improved in performance at high current density. [ABSTRACT FROM AUTHOR]

Capacity degradation and voltage fade of Li2MnO3 during cycling are the limiting factors for its practical use as a high-capacity lithium-ion battery cathode. Here, the simulated amorphisation and recrystallisation (A + R) technique is used, for generating nanoporous Li2MnO3 models of different lattice sizes (73 Å and 75 Å), under molecular dynamics (MD) simulations. Charging was carried out by removing oxygen and lithium ions, with oxygen charge compensated for, to restrain the release of oxygen, resulting in Li2−xMnO3−x composites. Detailed analysis of these composites reveals that the models crystallised into multiple grains, with grain boundaries increasing with decreasing Li/O content, and the complex internal microstructures depicted a wealth of defects, leading to the evolution of distorted cubic spinel LiMn2O4, Li2MnO3, and LiMnO2 polymorphs. The X-ray diffraction (XRD) patterns for the simulated systems revealed peak broadening in comparison with calculated XRD, also, the emergence of peak 2Θ ~ 18–25° and peak 2Θ ~ 29° were associated with the spinel phase. Lithium ions diffuse better on the nanoporous 73 Å structures than on the nanoporous 75 Å structures. Particularly, the Li1.00MnO2.00 shows a high diffusion coefficient value, compared to all concentrations. This study shed insights on the structural behaviour of Li2MnO3 cathodes during the charging mechanism, involving the concurrent removal of lithium and oxygen.

In the current study, Ti-Ni-Cu alloy powders were prepared by mechanical alloying using high-energy planetary ball mill under argon atmosphere. The effects of milling time on the evolution of structure, microstructure, and magnetic properties were analysed. Morphological observations indicated a narrow particle size distribution and homogeneous shape. According to the Rietveld analysis, during early milling stage (1–6 h), the milled powder consists of Ti-based solid solution [HCP-Ti(Ni,Cu)], Ni-based solid solution [FCC-Ni(Ti,Cu)], Cu-based solid solution [FCC-Cu(Ti,Ni)], and amorphous phase (28.52 wt%). For prolonged milling time, the NiTiCu (β19) was achieved from the pre-formed phases. Moreover, microstructural parameters varied considerably with milling time; the crystallite size was found to decrease to the nanoscale range, Ti (41), Ni (21 nm), Cu (16 nm), and β19 (29 nm), while the microstrain <σ2>1/2 increased due to the deformations and defects induced during the milling process. Magnetic measurements indicated that all powders exhibited a ferromagnetic behaviour irrespective of milling time whereas the corresponding magnetic parameters were found very sensitive to the milling time. This was associated with particle size refinement in addition to the phase composition and the amount of the amorphous phase; the higher the percentage of the amorphous phase was, the lower the values of Ms and Mr. [ABSTRACT FROM AUTHOR]

• Y 2 O 3 amorphisation upon mechanical milling, without chemical decomposition. • Addition of Ti in the alloy has no effect on amorphisation of Y 2 O 3. • FeYO 3 oxide formed upon annealing of mechanically milled Fe-15Y2O3-xTi model alloy with Ti ≤ 2 wt%. • Y 1.6 Ti 1.8 Fe 0.4 O 6.6 evolved upon annealing of mechanically milled model ODS alloys with Ti ≥ 10 wt%. • Y 2 O 3 : Ti ratio of 1:1 is favorable for formation of fine dispersoid of Y 1.6 Ti 1.8 Fe 0.4 O 6.6. A model Oxide Dispersion Strengthened (ODS) alloy powder of composition Fe – 15 wt. % Y 2 O 3 – x wt. % Ti (x = 0, 2, 5, 10 and 15) were synthesized by high energy mechanical milling in Ar atmosphere for a prolonged duration of 60 h. Synchrotron X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations suggested the amorphisation of Y 2 O 3 nano-crystallites, irrespective of Ti content, which is further studied by Raman spectroscopy. The Raman spectroscopy analysis confirms the presence of Y O bonding in the milled powder and ruled out the possibility of elemental dissociation of Y 2 O 3 and dissolution into the Fe matrix. Annealing of the milled powders containing different amounts of Ti led to formation of different types of oxide complexes which were also studied using synchrotron XRD and TEM studies. The role of Ti in refining the dispersoids through formation of Y 1.6 Ti 1.8 Fe 0.4 O 6.6 is established through these studies. [ABSTRACT FROM AUTHOR]

Boron carbide ( B 4 C ) has been widely used in nuclear reactors and nuclear applications. In this work, the high-purity (99.9%) B 4 C samples were irradiated using a gamma source ( 60 Co ) with a dose rate (D) of 0.27 Gy/s at different gamma irradiation doses at room temperature. Phase and microstructural characterisation of B 4 C samples were carried out using X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results displayed some degradation of the diffraction peaks. The calculations reveal that 62% of B 4 C has changed into the amorphous phase when the irradiation dose is 194.4 kGy. Fourier transform infrared spectroscopy (FTIR) was used to explain chemical bonds and functional groups of B 4 C samples before and after gamma irradiation. The results showed that C–C chemical bonds are weaker than B–C chemical bonds and tend to break under gamma irradiation. Element mapping analysis for each gamma irradiation dose of B 4 C samples was performed using SEM patterns. The dynamics of the elements on the surface and chemical formula of all B 4 C samples were also determined after gamma irradiation. [ABSTRACT FROM AUTHOR]

Synthesis of the bulk Li 1+x Mn 2 O 4 (0 ≤ x ≤ 1) was simulated by using molecular dynamics approach, from amorphous precursors where crystallisation was confirmed by the sharpness of the radial distribution functions. The resulting structures in the range Li 1+x Mn 2 O 4 (0 ≤ x ≤ 0.5) and Li 2·00 Mn 2 O 4 appear to be highly crystalline. On the contrary Li 1·75 Mn 2 O 4 is predicted as an intermediate multi-grained phase. Furthermore, the simulated XRDs of the latter have extensive peak broadening, whereas at lower and highest Li concentration the XRD peaks are narrow. The results are explained in terms of a transition from cubic to tetragonal spinel phases with enhanced Li content. Lastly, the XRDs suggest the evolution of composite or heterostructured bulk Li 1+x Mn 2 O 4 during simulated synthesis which is modified by the discharge process. • Molecular dynamics methods using the DL_POLY code was used to amorphise and recrystallise bulk structures of different lithium concentrations, Li 1·00 Mn 2 O 4 to Li 2·00 Mn 2 O 4 at elevated temperatures. • Amorphous structures depict broad peaks, whilst recrystallised depict sharp peaks (RDFs). • The Li 1·75 Mn 2 O 4 bulk crystallise into a multi-grained structure, whilst the other structures crystallise into single crystals. • Shifts, splits and broadening of peaks are observed on the XRDs. • The co-existence of layered-spinel components is also observed on the XRDs. [ABSTRACT FROM AUTHOR]

Highlights • Crystalline surface of SnTe and GeTe was sputtered by low energy (160 eV) argon ions. • Significant morphological and structural changes occurred. • Amorphisation was evoked by the low energy argon ion bombardment. Abstract Amorphisation effect on the surface of SnTe and GeTe samples under low Ar+ ion energy sputtering (160 eV) has been firstly observed. Scanning electron microscopy and Raman spectroscopy methods were used for the investigation. Microscope images show that ion bombardment changes significantly the morphology of SnTe and GeTe sample surfaces. Comparative Raman spectroscopy studies of the as-prepared and sputtered surfaces revealed that sputtering changes not only the surface morphology, but also the crystal structure of samples. Due to sputtering, the initial crystalline GeTe sample surface completely changed to amorphous, while the SnTe sample surface changed to a mixed amorphous-crystalline structure. This means that on the surface of IVB group binary tellurides an amorphisation can be evoked by low energy Ar+ ion bombardment, up to a few hundred electron volts energy. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Comparison of the largest set of APIs, solvents and loading concentrations reported to date. • TGA method for accurate determination of API content in the presence of moisture. • High API concentration in solvent does not guarantee high loading. • Dielectric constant of solvent found to be more important than logP of the API. • Drug loading to silica particles enhances dissolution rate. Abstract Increasing the dissolution rate of poorly water-soluble active pharmaceutical ingredients (APIs) is a key strategy used for improving their oral bioavailability. One of the formulation approaches is API loading to mesoporous carrier particles, which can increase the dissolution rate through the combination of improved powder wettability and dispersion, higher surface area, and API conversion from crystalline to the amorphous state. From the formulation process point of view, the maximum achievable drug loading is a crucial parameter, which depends on the loading method. Drug loading by sorption from a solution is a technologically attractive approach, since it involves familiar unit operations (mixing, filtration, drying). However, the success of the equilibrium sorption approach depends on the choice of the solvent. In this work we present an experimental study of loading efficiency to mesoporous silica particles, based on a set of 10 APIs combined with 6 different solvents at a range of concentrations. We show that due to the competitive nature of the adsorption process, the solvent with the highest API solubility is not necessarily the best candidate for maximising the API loading. Based on the investigated drug-solvent combinations, we show that the dielectric constant of the solvent is a good predictor of loading efficiency and can be used as a general guideline for solvent selection. On the other hand, we did not find any systematic correlation between commonly measured API properties such as logP and their loading efficiency. [ABSTRACT FROM AUTHOR]

To improve thermal stability and reduce power dissipation of phase‐change memory (PCM), the oxygen‐doped Sn15 Sb85 (SS) thin film is proposed by magnetron sputtering in this study. Comparing to undoped Sn15Sb85(SS), the oxygen‐doped‐SS thin film has superior thermal stability and better data retention. Meanwhile, the electrical conductivity of crystallisation oxygen‐doped‐SS thin film is also lower than that of SS, which means its less power consuming in PCM. The electrical conductivity ratio between amorphous and crystalline states for oxygen‐doped SS reaches up to two orders of magnitude. After oxygen doping, the root‐mean‐square surface roughness from amorphous (0.29 nm) to crystalline (0.46 nm) state for oxygen‐doped‐SS thin films becomes smaller. The switching time of amorphisation process for the oxygen‐doped‐SS thin film (∼2.07 ns) is shorter than Ge2 Sb2 Te5 (GST) (∼3.05 ns). X‐ray diffractometer is recorded to investigate the change of crystalline structure. Thus, the authors infer that oxygen‐doped SS is a promising phase‐change thin film for PCM. [ABSTRACT FROM AUTHOR]

Abstract The underlying micromechanism remains to be clarified for the bulk inelastic behaviour of specific ceramics under impact loads. In this study, the silicon carbide materials were subjected to the split-Hopkinson pressure bar compression in which the strain rate was not constant but increased to the dynamic level at high stresses. The inelastic deformation occurs in the high strain rate stage in compression, followed by the final transgranular fracture. The post-test fragments were examined in both the SEM and high resolution TEM. It was found that macroscopic inelastic behaviour is dominated by the dislocation motion and the localised amorphisation that arise at high strain rates. The damage and thus the degraded modulus in the dynamic inelastic deformation were incorporated to modify a dynamic fragmentation model to evaluate the fragment size as a function of strain rates. The modified model more accurately predicts the size of fragments produced at high strain rates. Graphical abstract Unlabelled Image Highlights • Inelastic deformation followed by transgranular fracture occurs at dynamic strain rates. • Dislocation motion and localised amorphisation determine the bulk inelastic behaviour. • Dynamic fragmentation model modified with damage accurately predicts the fragment size. [ABSTRACT FROM AUTHOR]

Abstract In the present investigation the poorly crystalline hydroxyapatite was rapidly fabricated by the gel auto-ignition route using calcium nitrate tetra-hydrate and di-ammonium hydrogen orthophosphate as a starting materials and urea as a fuel. The produced powders were employed as adsorbents for uptake of disperse blue 60 from aqueous solution and the adsorption performance was spectrophotometrically studied to determine the appropriate condition for fabrication of amorphous hydroxyapatite. The effects of synthesis parameters such as fuel ratio, gel preparation pH, calcination temperature and the influence of processing factors like dye solution pH and material dosage on dye adsorption have been investigated, comparatively. The properties of products were characterized by X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), dynamic light scattering (DLS) and scanning electron microscopy (SEM). The synthesized hydroxyapatite can supply a large quantity of active sites to enhance the uptake of dye. Although, the change in pH of synthesis condition shows a negligible variation in the adsorption efficiency, the acidic condition leads to formation of β-tricalcium phosphate. The stronger adsorption as well as the higher activity with disperse blue 60 was observed in pH of 2.0. In addition, the adsorption was found to be controlled by the calcination temperature. Furthermore, it was indicated that the dye adsorption on poorly crystalline hydroxyapatite prepared in the appropriate condition, fuel ratio of 0.50 and pH of 7.0, is well adjusted with Langmuir isotherm in which the maximum adsorption capacity was determined to be 4600 mg g−1, approximately. Graphical abstract Image 1 Highlights • The non-crystalline hydroxyapatite was rapidly fabricated by gel auto-ignition route. • The produced powders were employed as adsorbents for uptake of disperse blue 60. • The dye removal is controlled by fuel ratio and calcination temperature. • The stronger adsorption of dye was observed in pH of 2.0. • The maximum adsorption capacity was determined to be 4600 mg g−1. [ABSTRACT FROM AUTHOR]

Preprocessing of pharmaceutical powders is a common procedure to condition the materials for a better manufacturing performance. However, such operations may induce undesired material properties modifications when conditioning particle size through milling, for example. Modification of both surface and bulk material structure will change the material properties, thus affecting the processability of the powder. Hence it is essential to control the material transformations that occur during milling. Topographical and mechanical changes in surface properties can be a preliminary indication of further material transformations. Therefore a surface evaluation of the α-lactose monohydrate after short and prolonged milling times has been performed. Unprocessed α-lactose monohydrate and spray dried lactose were evaluated in parallel to the milled samples as reference examples of the crystalline and amorphous lactose structure. Morphological differences between unprocessed α-lactose, 1 h and 20 h milled lactose and spray dried lactose were detected from SEM and AFM images. Additionally, AFM was used to simultaneously characterize particle surface amorphicity by measuring energy dissipation. Extensive surface amorphicity was detected after 1 h of milling while prolonged milling times showed only a moderate particle surface amorphisation. Bulk material characterization performed with DSC indicated a partial amorphicity for the 1 h milled lactose and a fully amorphous thermal profile for the 20 h milled lactose. The temperature profiles however, were shifted somewhat in the comparison to the amorphous reference, particularly after extended milling, suggesting a different amorphous state compared to the spray-dried material. Water loss during milling was measured with TGA, showing lower water content for the lactose amorphized through milling compared to spray dried amorphous lactose. The combined results suggest a surface-bulk propagation of the amorphicity during milling in combination with a different amorphous structural conformation to that of the amorphous spray dried lactose. The hardened surface may be due to either surface crystallization of lactose or to formation of a low-water glass transition. [ABSTRACT FROM AUTHOR]

Non-equilibrium molecular-dynamics (NEMD) simulations of bulk methane clathrate hydrates have been conducted in a range of externally-applied static electric fields of up to 2.0 V·nm −1 in intensity, at 250 K and 60 atm. Studies into frequencies of system-mass-density fluctuations showed that these clathrates have two major modes: the dominant one is attributable to water molecules’ librations and occurs at 720 cm −1 , regardless of applied fields. A more minor global density fluctuation arises at 10–12 cm −1 , due to the propagation of local-density fluctuations; again, this is independent of applied fields. A threshold intensity of 1.2 V·nm −1 was necessary to overcome the strong clathrate hydrogen-bonding network to produce any appreciable structural changes. Aside from variations in hydrate system density per se , a key interest in this study was (electro-) dissociation; a number of analysis methods were used to gauge this, including system-density and configurational-energy studies (and their respective autocorrelation functions and corresponding Fourier transforms), as well as radial distribution functions (RDFs) and density of states (DOS). In terms of electro-dissociation itself, a ‘plateau’ intensity of 1.6 V·nm −1 led to outright dissociation over the 0.5 ns timescales probed in the current study, where any field intensity above this level produced essentially identical dissociation outcomes: a marked loss of hydrate structure and increase in system configurational energy. RDF analysis of electro-dissociation indicates the collapse of the host lattice towards an amorphous structure and concomitant release of methane molecules from their now-collapsed cages to form a ‘nano-bubble’. Upon post-dissociation field removal, it was found that this process was irreversible: the system transitions to an entirely new, less dense structure, featuring a phase-segregated methane nano-bubble within a liquid-like aqueous phase. [ABSTRACT FROM AUTHOR]

Characterisation of mechanochemically activated Tsagaan-tsav zeolite has been performed. Tsagaan-tsav zeolite has been activated with a vibration mill for 2, 3, 5, 10 and 20 minutes. Ball to powder ratios were varied 1:10, 1:20, 1:50 and 1:100. Efficiency of milling determined based on amorphisation rate and cation exchange capacity changes. The highest efficiency was obtained for zeolite milled with ball to powder ratio of 100. Structural characterisation was performed with XRD, SEM, BET and particle size analyzer. Mechanochemical activation improves cation exchange capacity of natural zeolite.DOI: http://dx.doi.org/10.5564/mjc.v12i0.181 Mongolian Journal of Chemistry Vol.12 2011: 98-101

A novel processing method for amorphous Al50Ti50 alloy, obtained by mechanical alloying and subsequently consolidated by electrical resistance sintering, has been investigated. The characterisation of the powders and the confirmation of the presence of amorphous phase have been carried out by laser diffraction, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The amorphous Al50Ti50 powders, milled for 75 h, have a high hardness and small plastic deformation capacity, not being possible to achieve green compacts for conventional sintering. Moreover, conventional sintering takes a long time, being not possible to avoid crystallisation. Amorphous powders have been consolidated by electrical resistance sintering. Electrically sintered compacts with different current intensities (7−8 kA) and processing times (0.8−1.6 s) show a porosity between 16.5 and 20%. The highest Vickers hardness of 662 HV is reached in the centre of an electrically sintered compact with 8 kA and 1.2 s from amorphous Al50Ti50 powder. The hardness results are compared with the values found in the literature.

Among the many methods available for solubility enhancement, mesoporous carriers are generating significant industrial interest. Owing to the spatial confinement of drug molecules within the mesopore network, low solubility crystalline drugs can be converted into their amorphous counterparts, which exhibit higher solubility. This work aims to understand the impact of drug overloading, i.e., above theoretical monolayer surface coverage, within mesoporous silica on the release behaviour and the thermal properties of loaded drugs. The study also looks at the inclusion of hypromellose acetate succinate (HPMCAS) to improve amorphisation. Various techniques including DSC, TGA, SEM, assay and dissolution were employed to investigate critical formulation factors of drug-loaded mesoporous silica prepared at drug loads of 100−300% of monolayer surface coverage, i.e., monolayer, double layer and triple layer coverage. A significant improvement in the dissolution of both Felodipine and Furosemide was obtained (96.4% and 96.2%, respectively). However, incomplete drug release was also observed at low drug load in both drugs, possibly due to a reversible adsorption to mesoporous silica. The addition of a polymeric precipitation inhibitor HPMCAS to mesoporous silica did not promote amorphisation. In fact, a partial coating of HPMCAS was observed on the exterior surface of mesoporous silica particles, which resulted in slower release for both drugs.

In order to improve the understanding of the microscopic phenomena occurring during irradiation in zirconium alloys, ion beam irradiations are performed at 350 °C (dose-rate of 2 × 10 −5 dpa/s) on recrystallized Zy-4 and M5 ® alloys, with 2 MeV protons. The aim of this study is to determine in which way proton irradiations can be representative of neutron irradiations, considering the second phase particle changes and the influence of these changes on the microstructural evolution of the material during irradiation. The 2 MeV proton irradiation at 350 °C, performed here, seems to reproduces well what happened in Zy-4 in PWR conditions with a progressive amorphisation of the Zr(Fe,Cr) 2 Laves phases, but with a lower growth rate and a higher Fe/Cr ratio of the amorphous rim. The Zr(Fe,Nb) 2 s phase particles in M5 ® undergo a uniform amorphisation, while the native βNb precipitates remain fully crystalline as evidenced in neutron irradiation at very low irradiation temperature. No radiation-enhanced precipitation of nanometric βNb particles was observed. Thus, for M5 ® alloy, the present irradiation seems to be representative of neutron irradiations at a very low irradiation temperature. Nevertheless it does not reproduce what happens in PWR conditions, where no amorphisation and a drastic loss of iron is reported for the Zr(Fe,Nb) 2 Laves phase SPPs. Despite the lower iron rejection from the particles into the matrix during proton irradiation than during neutron irradiation, -component loop distribution is found to be similar after both types of irradiations. These results underline the influence of both dose-rate and temperature on second phase particles behavior under irradiation and point out the complexity of iron rejection influence on the basal -component loops. Indeed, although the -component loop nucleation and growth seem locally correlated to iron dissolution into the matrix, they do not seem to be directly correlated to the global amount of iron rejected. [ABSTRACT FROM AUTHOR]

The purpose of the study was to investigate the relationship between comminution and amorphisation of α-lactose monohydrate particles during ball milling under different milling conditions, including ball-to-powder mass ratio, milling time and ball diameter. The results revealed that at a constant ball filling ratio, ball-to-powder mass ratio of 25:1 resulted in the lowest minimum particle diameter of ∼5 μm and the highest degree of apparent amorphous content of 82%. The rate of comminution was high during early stage of milling whereas the degree of apparent amorphous content increased gradually at a slow rate. An increased ball-to-powder mass ratio during milling increased both the rate of comminution and the rate of amorphisation. Using a given ball-to-powder mass ratio, the ball diameter affected the degree of apparent amorphous content of the particles while the particle diameter remained unchanged. The relationship between comminution and amorphisation could be described as consisting of two stages, i.e. comminution dominated and amorphisation dominated stage. It was proposed that the rate constant of comminution and amorphisation are controlled by stress energy distribution in the milling jar and the stress energy distribution is regulated by the ball motion pattern that can be affected by the process parameter used. [ABSTRACT FROM AUTHOR]

Pulsed electrical discharge (PED) treatment was applied as a novel method to synthesize amorphous or amorphous/crystalline composite layers on the surfaces of Zr-, Fe-, Ti- and Al-based crystalline alloys. The formation of amorphous or amorphous/crystalline composite layers was investigated in terms of the significant disparity in glass-forming ability of the alloys. The influences of PED processing parameters on the surface glass formation of Zr 55 Al 10 Ni 5 Cu 30 alloy were further discussed and the PED-treated alloy exhibited a gradient structure: amorphous surface, amorphous/crystalline composite region and crystalline substrate from surface to inside. Besides, effects of processing parameters on the microhardness and corrosion behavior of the treated Zr 55 Al 10 Ni 5 Cu 30 alloy were investigated and the results revealed that the PED treatment could improve the microhardness and corrosion resistance of the crystalline substrate alloy. This PED treatment is a promising method to synthesize amorphous or amorphous/crystalline composite layers for novel mechanical, physical or chemical applications. [ABSTRACT FROM AUTHOR]

Physicochemical changes in a siliceous bauxite ore during attrition milling, and corresponding changes in reactivity are described in this paper. Atrition milling of bauxite has been found to have high milling efficiency. BET Specific surface area has sharply increased in the initial stages, but flattened eventually. Decrease in the enthalpy and temperature of transformation (gibbsite to boehmite) with increase in milling time is a consequence of mechanically induced reactivity. The surface charge, as measured by zeta potential, altered as the milling time is increased; such changes in the surface, surface activation, are also a manifestation of reactivity enhancement with milling. The increase in surface reactivity has been explained in terms of generation of more proton active species (≡ AlOH) at the surface. Analysis of X-ray diffraction patterns of bauxite milled for different duration shows progressive breakdown of gibbsite structure to an amorphous state – high energy state - with milling. Reactivity enhancement ensuing attrition milling leads to near complete digestion of bauxite (alumina) in Bayer (caustic soda) solution even at ambient pressure. Alumina recovery correlates well with specific surface area and degree of amorphisation; however, amorphisation (mechanical activation) is more relevant than specific surface area for multiphase systems like that of bauxite used in this study. [ABSTRACT FROM AUTHOR]

This study investigates crystallographic orientations to exhibit fractures in silicon, such as those on the (100) plane cracks which travel along the [011] direction. Molecular dynamics simulations are performed to investigate the competing processes of cleavage bond-breaking and amorphisation under a uniaxial tensile load (mode I load) in the (100) [011] Si system. Notably, we observe two types of crack propagation behaviour: (1) downward step mechanism followed by small fracture steps on the alternating {111} plane and (2) zigzag propagation mechanism. Our simulations also show that local structural amorphisations of the lattice which act as the self-protecting mechanism of crack propagation contribute to the preservation of the crack on the {100} plane. [ABSTRACT FROM AUTHOR]

Boron carbide B 4 C is widely used as a neutron absorber in nuclear plants. Most of the post-irradiation examinations have shown that the structure of the material remains crystalline, in spite of very high atomic displacement rates. Here, we have irradiated B 4 C samples with 4 MeV Au ions with different fluences at room temperature. Transmission electron microscopy (TEM) and Raman spectroscopy have been performed. The Raman analyses show a high structural disorder at low fluence, around 10 −2 displacements per atoms (dpa). However, the TEM observations show that the material remains crystalline up to a few dpa. At high fluence, small amorphous areas a few nanometers large appear in the damaged zone but the long range order is preserved. Moreover, the size and density of the amorphous zones do not significantly grow when the damage increases. On the other hand, full amorphisation is observed in the implanted zone at a Au concentration of about 0.0005. It can be inferred from those results that short range and long range damages arise at highly different fluences, that heavy ions implantation has drastic effects on the structure stability and that in this material self-healing mechanisms are active in the damaged zone. [ABSTRACT FROM AUTHOR]

Detailed transmission electron microscopy analysis on a severely deformed Al-Si composite material has revealed that partial dislocation slips and deformation twinning are the major plastic deformation carriers in ultrafine silicon grains. This resembles the deformation twinning activities and mechanisms observed in nano-crystalline face-centred-cubic metallic materials. While deformation twinning and amorphisation in Si were thought unlikely to co-exist, it is observed for the first time that excessive twinning and partial dislocation interactions can lead to localised solid state amorphisation inside ultrafine silicon grains. [ABSTRACT FROM AUTHOR]

Transmission electron microscopy with in situ ion irradiation has been used to examine the ion-beam-induced amorphisation of crystalline silicon under irradiation with light (He) and heavy (Xe) ions at room temperature. Analysis of the electron diffraction data reveal the heterogeneous amorphisation mechanism to be dominant in both cases. The differences in the amorphisation curves are discussed in terms of intra-cascade dynamic recovery, and the role of electronic and nuclear loss mechanisms. [ABSTRACT FROM AUTHOR]

Objectives This study aimed to prepare Coenzyme Q10 (CoQ10) microparticles using electrospraying technology, and evaluate the in-vitro properties and in-vivo oral bioavailability. Key findings Electrospraying was successfully used to prepare CoQ10 to enhance its solubility and dissolution properties. In-vitro evaluation of the electrosprayed microparticles showed bioavailability-enhancing properties such as reduced crystallinity and particle size. The formulation was evaluated using dissolution study and in-vivo oral bioavailability using rat model. The dissolution study revealed enhanced dissolution properties of electrosprayed microparticles compared with physical mixture and raw material. The absorption profiles showed increasing mean plasma levels CoQ10 in the following order: raw material < physical mixture < electrosprayed microparticles. Conclusion Based on the findings in this study, electrospraying is a highly prospective technology to produce functional nano- and micro-structures as delivery vehicles for drugs with poor oral bioavailability due to rate-limiting solubility. [ABSTRACT FROM AUTHOR]

A simple method to grow single crystals of α-V 2 O 5 is presented and discussed. Crystal structures of two Wadsley phases, α-V 2 O 5 (Pmmn, Z = 2) and α-V 6 O 13 (C 2/ m , Z = 2), are studied with single-crystal X-ray diffraction in diamond anvil cells up to 12.8 GPa and 9.4 GPa, respectively, at room temperature. α-V 2 O 5 irreversibly amorphizes above about 7.3 GPa. No phase transition is observed at lower pressures. The polymorph that crystallizes from the amorphous material at high pressures and high temperatures is δ-V 2 O 5 (C 2/ c , Z = 4) as evidenced by in-situ angle-dispersive synchrotron powder diffraction using large-volume multi-anvil press. No phase transitions were observed during high temperature decompression of the as synthesized δ-V 2 O 5. The crystal structure of α-V 6 O 13 is stable up to at least 9.4 GPa. Present data could be used to achieve better understanding of the high-pressure behavior of related Wadsley phases. • Simple synthesis of high-quality single crystals of α-V2O5 • Single-crystal X-ray diffraction at high pressures resolving discrepancies in previous studies on powdered samples of α-V2O5 • The very first structural study on a Wadsley phase at high pressures • Systematics and comparative study of the high-pressure behavior of Wadsley phases [ABSTRACT FROM AUTHOR]

Complex oxides with the spinel structure often called spinels belong to the group of strategic materials which are used in the wide area of modern technologies. They exhibit excellent magnetic, refractory, semiconducting, catalytic and sorption properties. Spinels based on magnesium aluminate (MA spinels) are used for the preparation of refractory ceramic materials and bricks. Due to its good properties MA spinel is predestinated for special applications in electronics.Several methods and precursors for the synthesis of MA spinel have been studied experimentally. The conventional process of MA spinel preparation based on the high temperature solid state reaction of precursors is connected with the difficulty to obtain the high spinel phase purity required for its special applications. From the viewpoint of final material properties and of intensification of solid state reactions, the non-standard mechanochemical techniques are suitable.In the paper, results of the mechanochemical modification of the mixture of crystalline hydroxide precursors caused by the high-energy milling and subsequent heating in the temperature range 300-1500 °C are presented.Mixtures of brucite and gibbsite in the molar ratio 1:2 were submitted to grinding in a planetary mill using the corundum chamber for various milling times (0.5-12 hours). The specific surface area of the milled samples was determined by the BET method. Changes in the structure of mechanosynthesized products and the evolution of the spinel phase during the subsequent calcination of both mechanosynthesized samples and reference homogenised mixtures were monitored by the X-ray diffraction analysis and IR spectroscopy. The degree of conversion of hydroxide mixture to the MA spinel was determined by chelatometry.During the early stage of grinding (up to 1 hour), a considerable refinement of hydroxide mixture occurs. With the increasing grinding time, amorphisation of structure as well as a gradual mechanochemical dehydration and formation of aggregates take place. A structural metastability of high reactive products of dehydration and a large area of particle contacts lead to the solid state mechanochemical reaction with the formation of nucleation centres of amorphous magnesium aluminate. By the combination of mechanosynthesis with the subsequent thermal treatment, crystalline magnesium aluminate with the spinel structure is prepared at temperatures which are by 300 K lower than those at which the spinel is synthesized by conventional ceramic method.

Molecular dynamics simulations using empirical potentials reveal HOPG graphite’s response to irradiations. Two different methodologies: displacement cascades and Frenkel pair accumulations, probe the primary damage and dose effect, respectively. This work reveals that in HOPG graphite primary knock-on atoms with initial energies less than 40 keV do not induce amorphisation by direct impact. Rather, defects stabilise and persist after a single irradiation event. However, amorphisation occurs via the accumulation of defects mimicking multiple events. Before amorphisation the graphite structure undergoes three stages of evolution characterised by (i) an increase in point defects; (ii) a wrinkling of graphene layers pinned by small amorphous pockets; and (iii) a full amorphisation of the structure via percolation of the small amorphous pockets. This structural evolution gives way to an irradiation induced volume change of the HOPG graphite. In the first stage, interstitials contribute, as expected, to c -axis swelling, while vacancies contribute to basal plane shrinkage. Subsequently, rippling of the graphene layers induces the overall volume to change. A power law relation illustrates the relation between the c -axis swelling and the basal-plane shrinkage as a function of the irradiation dose. [ABSTRACT FROM AUTHOR]

Ni 52 Pd 26 P 20 B 2 glassy alloy rods up to 5 mm in diameter were prepared by a copper mold casting technique. The obtained Ni 52 Pd 26 P 20 B 2 BMG exhibited rather good glass forming ability and mechanical properties: high strength and reasonable room-temperature plasticity. Two regions of deformation were observed in shear steps on the lateral surface. Propagation of the shear bands was analyzed using video recording and correlated with the stress–strain curve. [ABSTRACT FROM AUTHOR]

While the electrical conductivity of semiconductors can be easily changed over order of magnitudes (8 in silicon) by playing on the doping, the thermal conductivity (TC) control is a challenging issue. Nevertheless, numerous applications require TC control in Si down to 1 W m −1 K −1 . Among them, there are thermal insulation requirements in MEMS, thermal management issues in 3D packaging or TC reduction for thermoelectric applications. Towards this end, the formation of nanoporous Si by electrochemical anodisation is efficient. Nevertheless, in this case the material is too fragile for MEMS application or even to withstand CMOS technological processes. In this work, we show that ion irradiation in the electronic regime is efficient for reducing TC in meso-porous Si (PSi), which is more mechanically robust than the nanoporous PSi. We have studied three different mass to energy ratios ( 238 U at 110 MeV and 130 Xe at 91 MeV and 29 MeV) with fluences ranging from 10 12 cm −2 to 7 × 10 13 cm −2 . The sample properties, after irradiation, have been measured by infrared spectroscopy, Raman spectroscopy and scanning electron microscopy. The TC has been measured using scanning thermal microscopy. Although, bulk Si is insensitive to ion interaction in the electronic regime, we have observed the amorphisation of the PSi resulting in a TC reduction even for the low dose and energy. For the highest irradiation dose a very important reduction factor of four was obtained. [ABSTRACT FROM AUTHOR]

• Effects of 200 keV H+ ions on poly(vinylidene fluoride) films. • Investigation on surface modifications and loss of crystallinity. • Probing the effect of amorphisation on the phases have been probed. Free-standing, flexible films of poly(vinylidene fluoride) were synthesized using sol-gel method. Effects of implantation of 200 keV H+ ions on these samples were studied. An apparent change in colour of the films, with ion implantation, was observed. Morphological studies revealed breaking up of larger spherulites into smaller ones with irradiation. Microstructural analysis revealed an increase in amorphous content with irradiation. Microscopic and vibrational spectroscopy (Raman and Fourier transform infrared spectroscopy) also point out to the loss of crystalline nature upon irradiation. Effect of ion implantation on the fraction of electroactive phases and the non-polar α phase has been discussed. [ABSTRACT FROM AUTHOR]

Size reduction of Diaqua-bis(Omeprazolate)-Magnesium Dihydrate (DABOMD) crystals, an active pharmaceutical ingredient (API) which inhibits gastric acid secretion and its related disorder in mammals, has been investigated using a planetary ball mill and a single ball mill. The outcome of milling shows that DABOMD undergoes prominent comminution and amorphisation processes that occur parallel to each other, with planetary ball mill causing higher amorphisation rate compared to the single ball mill. To establish a relationship between the degree of comminution and amorphisation, the energies of the planetary ball mill and the single ball mill were quantified using a collision model derived from the literature, and through tracking the milling jar with high speed-camera, respectively. In addition, energies were calculated using the Discrete Element Method (DEM) simulations of both mills. The energy obtained from the DEM simulation of the planetary ball mill is lower than the calculated energies from the literature collision model. This could be due to the fact that the collision model does not consider additional factors affecting the motion of balls, such as friction between the balls and balls and the wall. However, the energy calculated from the DEM simulation is higher than that generated from high speed video tracking of the milling jar for the single ball, since as shown by the DEM the movement pattern and the velocity magnitude of the ball is different to those of the jar, resulting in higher relative collision velocities than the jar velocity itself. Nevertheless, it was found that the planetary ball mill produces higher energy than the single ball mill which explains the difference in the amorphisation obtained in the two mills. This methodology enables quantification of the changes that arise with the milling of a solid (i.e. comminution and amorphisation) with respect to the energy level involved. [Display omitted] • The input energy in planetary ball mill and single ball mill was calculated using DEM. • The relationship between the mill input energy and comminution and amorphisation is analyzed for both types of mills. • The rate of amorphization was found to be directly correlated to the level of mill input power. [ABSTRACT FROM AUTHOR]

Mechanically induced reactivity of gibbsite in an attrition mill is focused in this paper. Reactivity of milled gibbsite, assessed in terms of its dehydroxylation and dissolution in alkali solution, is found to increase with the increase in milling time. Besides analysing the increased reactivity in terms of the changes in physicochemical characteristics, an attempt has also been made to correlate the reactivity with physicochemical changes. Changes in the physicochemical characteristics of gibbsite during milling in an attrition mill and corresponding change in reactivity are compared with that observed for gibbsite milled in a planetary mill, described in Part 1; thus a comparison of two different types of mills in terms of their efficiency in bringing out structural/reactivity changes is illustrated using the same feed stock, gibbsite. [ABSTRACT FROM AUTHOR]

Gibbsite [γ-Al(OH)3] precipitated from Bayer leach liquor is mechanically activated in a planetary mill at ambient conditions. Mechanical activated (MA) gibbsite is characterized in terms of particulate characteristics, structural characteristics and reactivity. Physicochemical changes during MA involved (1) size reduction in the initial stages followed by particle aggregation in the later stages and changes in particle size distribution, and (2) progressive decrease in crystallite size, and increase in microstrain leading to eventual amorphisation. Reactivity of milled gibbsite (measured in terms of (1) decrease in its dehydroxylation temperature, and (2) increase in alkali dissolution) is found to increase with mechanical activation. Increased reactivity of milled gibbsite is correlated with various physicochemical characteristics. [ABSTRACT FROM AUTHOR]

Abstract: The recrystallization and subsequent crystal growth during annealing of amorphous surface layers on 6H-SiC produced by ion implantation is investigated. Amorphous surface layers were produced by ion implantation of 360keV ions of iodine, silver, xenon, cesium and strontium into single crystalline 6H-silicon carbide samples. The ion fluence for all the implantations were in the order of 1016 cm−2. Vacuum annealing of the damaged silicon carbide samples was then performed. The microstructure of SiC surfaces before and after annealing was investigated using a high resolution field emission scanning electron microscope (SEM). SEM analysis was complimented by Atomic Force Microscopy (AFM). SEM images acquired by an in-lens detector using an accelerating voltage of 2kV show nano-crystallites developed for all implanted samples after annealing. Larger and more faceted crystallites along with elongated thin crystallites were observed for iodine and xenon implanted 6H-SiC. Crystallites formed on surfaces implanted with strontium and cesium were smaller and less faceted. Strontium, silver and cesium implanted samples also exhibited more cavities on the surface. AFM was used to evaluate the effect of annealing on the surface roughness. For all the amorphous surfaces which were essentially featureless, the root mean square (rms) roughness was approximately 1nm. The roughness increased to approximately 17nm for the iodine implanted sample after annealing with the surface roughness below this value for all the other samples. AFM also showed that the largest crystals grew to heights of about 17, 20, 45, 50 and 65nm for Sr, Cs, Ag, Xe and I implanted samples after annealing at 1200°C for 5h respectively. SEM images and AFM analysis suggest that iodine is more effective in promoting crystal growth during the annealing of bombardment-induced amorphous SiC layers than the rest of the ions we implanted. In samples of silicon carbide co-implanted with iodine and silver, few cavities were visible on the surface indicating that iodine influenced the recrystallization. Surface crystallites that grew on the iodine implanted surfaces were more resistant to thermal etching and decomposition than those that grew on the silver implanted samples at temperatures of up to 1400°C for 30h. [Copyright &y& Elsevier]

Highlights: [•] Laser microstructural refinement eliminatd large and brittle Al8Co2Ce particles. [•] Refined microstructure made LAEB homogenisation and amorphisation easier. [•] Laser microstructural refinement successfully decreased the extent of LAEB cracking. [Copyright &y& Elsevier]

Highlights: [•] Ti2Ni second phase particles forms in different sizes and shapes in cast ingot. [•] TEM evidences showed shearing/fragmentation of Ti2Ni during processing. [•] Matrix close to Ti2Ni experienced severe plastic deformation lead to amorphisation. [•] Ti2Ni interfaces were mostly faceted and assist in nucleation of martensite. [•] Heterogeneity of microstructure observed near to and away from Ti2Ni. [ABSTRACT FROM AUTHOR]

The purpose of the research was to investigate the degree of solid-state amorphisation during powder flow and to propose a mechanism for this transformation. Micro-particles of griseofulvin (about 2 μm in diameter) were mixed in a shear mixer under different conditions to influence the inter-particulate collisions during flow, and the degree of amorphisation was determined by micro-calorimeter. The amorphisation of griseofulvin particles ( GPs) during repeated compaction was also determined. The GPs generally became disordered during mixing in a range from about 6% to about 86%. The degree of amorphisation increased with increased mixing time and increased batch size of the mixer, whereas the addition of a lubricant to the blend reduced the degree of amorphisation. Repeated compaction using the press with ejection mode gave limited amorphisation, whereas repeated compaction without an ejection process gave minute amorphisation. It is concluded that during powder flow, the most important inter-particulate contact process that cause the transformation of a crystalline solid into an amorphous state is sliding. On the molecular scale, this amorphisation is proposed to be caused by vitrification, that is the melting of a solid because of the generation of heat during sliding followed by solidification into an amorphous phase. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:4036-4045, 2013 [ABSTRACT FROM AUTHOR]

A substantial number of new chemical entities and marketed drugs show poor solubility characteristics and amorphisation is one of the favorable approaches to enhance solubility characteristics of such poorly soluble drugs. Formulation efforts in the present study were devoted to investigate amorphisation of a model poorly soluble drug, atorvastatin calcium by molecular complexation with anion exchange resin, Duolite(r)AP 143/1093 and hence enhancement in its solubility characteristics. Drug resinates in 1:1, 1:2, and 1:4 weight ratios were prepared by simple batch operation and subsequently studied for drug content, residual solvent content, molecular interactions, solid state characterisation and solubility characteristics. During initial characterisation, all the proportions of drug resinates, except 1:1 proportion showed partial amorphisation of the drug, whereas 1:1 proportion showed complete amorphisation of the drug. This proportion reported distinctly enhanced solubility characteristics over pure drug and other proportions. Such amorphisation and solubility enhancement could be attributed to the binding of individual drug molecules to the functional sites of the resin molecules, either partially or completely, resulting in reduction of crystal lattice energy, a main barrier to dissolution. Hydrophilic nature of ion exchange resin matrices also assisted in enhancing dissolution of the drug from the resinates. During accelerated stability study, there was an insignificant decrease in solubility characteristics of the drug and its amorphous form was also found to be stable in 1:1 proportion. Atorvastatin resinates formed in 1:1 weight ratio were in stoichiometric proportion and such drug resinates in stoichiometric proportion showed to have tremendous potential in conversion of crystalline form of drug substances to its amorphous form and subsequent stabilisation. It hence proved to be a very effective, yet simple approach for improving solubility characteristics of poorly soluble actives. [ABSTRACT FROM AUTHOR]

The potential of rupture-oxide mushroom phase-change memory cells is assessed through 2-D finite element analysis using electro-thermal models with temperature-dependent material parameters, coupled with a circuit model for access transistors. The mushroom cell structure used for the simulations consists of a 100-nm thick Ge2Sb2Te5 layer separated from a 20-nm wide TiN bottom heater by a 3-nm thick SiO2 rupture-oxide layer. The ruptured oxide is modeled as a conductive filament through the oxide layer at the center of the heater. The effects of supply voltage, gate voltage, access transistor width, filament diameter and resistivity are studied using a read/reset/read sequence enabled by a dynamic amorphization model. The simulation results show that rupture-oxide cells can be operated with smaller voltages, currents and transistor widths compared to their conventional counterparts for the same resistance contrast. Moreover, it is shown that the cell performance is further improved for narrower and more resistive filaments. [ABSTRACT FROM AUTHOR]

Abstract: The Mn valency and the crystallinity of Li2MnSiO4 cathodes (Pmnb form) were examined with electron energy-loss spectroscopy (EELS) and selected area electron diffraction (SAED) both before and after electrochemical lithium extraction. A decrease in the crystallinity of the delithiated charged cathode particles compared to the as-prepared material was observed. The decrease in crystallinity varied from particle to particle. EELS analysis showed that the non-uniform decrease in crystallinity was due to a non-uniform extraction of lithium from the particles. The observed decrease in discharge capacity of the Pmnb polymorph of Li2MnSiO4 with cycling was attributed to the progressive loss of crystallinity and the structural collapse of Li diffusion pathways. [Copyright &y& Elsevier]