First step of anodization influences the final nanopore arrangement in anodized alumina

Anodic porous alumina is a well-known template material for nanofabrication. To obtain highly ordered nanoporous array, sophisticated and expensive methods are applied. On the other hand there is two-step self organized anodization, which is much cheaper, but obtained alumina arrangement is not ideal. In our paper, influence of the first step of anodization on the final AAO structure arrangement is studied in details. Anodizations were carried out in 0.3 M oxalic acid at 35 °C at various potentials and durations of the first step of anodization. Second step of the anodization was constant for all the experiments and was 15 min long. Oxide layer thickness formed during the first step of the anodization was 50, 100, 150 and 200 μm and after oxide removal, remaining concaves were serving as a mask for further growth during second step of the anodization. The longer first step of anodization, the higher regularity ratio and circularity, and lower percentage of defects in the nanoporous array. Anodic porous alumina was formed at four various potentials: 30, 40, 50, 60 V. The best arrangement of nanopores was found for samples anodized at 40 V. Maximum of regularity ratio was corresponding to the minimum of defect content in the AAO array. Long enough first step of two-step self-organized anodization in 0.3 M oxalic acid can provide high-ordered nanoporous template for fabrication of various nanomaterials with new, unique properties.     

Sorption Properties of Vacuum-Dried Strawberries

This work demonstrates the influence of changes in parameters of vacuum drying (temperature and pressure) on the sorption properties of dried strawberries. Fruits were dried at 50 and 70°C under pressures of 4 and 16 kPa. Vacuum drying was also conducted during the first 4 h at 70°C and then the temperature was decreased to 50°C at a pressure of 4 kPa. The other combination included increasing the pressure after the first 4 h from 4 to 16 kPa at a drying temperature of 70°C. Sorption isotherms were determined in the dried strawberries. It was shown that with increasing drying temperatures, there was a notable deterioration in the capacity for absorbing water vapor by the vacuum-dried fruit. On the other hand, the pressure at which vacuum drying proceeded did not significantly affect water vapor absorption. Changing the parameters of vacuum drying—that is, temperature in the range of 50–70°C and pressure in the range of 4–16 kPa—affected the shape and structure of the resultant dried strawberries. The combination of vacuum drying with convective drying also influenced the shape and structure of the dried fruit.     

Functionality of graphene as a result of its heterogenic growth on SiC nanoparticles on the basis of reversible hydrogen storage

This article presents the results from research related to graphene functionality based on the production of spatial structures provided for the reversible storage of hydrogen. The functionality process was conducted during graphene synthesis onto a liquid metallic support, on a single level, using SiC nanoparticles. Within the scope of research it was proved that heterogenic growth of the domains of polycrystalline graphene onto the SiC nanoparticles is possible. These nanoparticles are in-built into the graphene structure constituting the pillars of the spatial structure. Material produced in such a way constitutes the foundation for creating a spatial 3D structure (through the rolling operation), called GraphRoll, for the reversible storage of hydrogen in order to conduct its sorption and de-sorption. So, independently of the theoretical configuration, deviations or a possible exception from the 2D configuration on the silicon carbide/graphene were discussed. These differences resulted from the difference between the crystallographic structures of the analyzed forms as well as the structure determined to decrease tensions within the structure.     

Can We Predict the Isosymmetric Phase Transition? Application of DFT Calculations to Study the Pressure Induced Transformation of Chlorothiazide

Isosymmetric structural phase transition (IPT, type 0), in which there are no changes in the occupation of Wyckoff positions, the number of atoms in the unit cell, and the space group symmetry, is relatively uncommon. Chlorothiazide, a diuretic agent with a secondary function as an antihypertensive, has been proven to undergo pressure-induced IPT of Form I to Form II at 4.2 GPa. For that reason, it has been chosen as a model compound in this study to determine if IPT can be predicted in silico using periodic DFT calculations. The transformation of Form II into Form I, occurring under decompression, was observed in geometry optimization calculations. However, the reverse transition was not detected, although the calculated differences in the DFT energies and thermodynamic parameters indicated that Form II should be more stable at increased pressure. Finally, the IPT was successfully simulated using ab initio molecular dynamics calculations.     

A multifactor study of catalyzed hydrolysis of solid NaBH4 on cobalt nanoparticles: Thermodynamics and kinetics

In the present work, hydrogen generation through hydrolysis of a NaBH_4(s)/catalyst_(s) solid mixture was realized for the first time as a solid/liquid compact hydrogen storage system using Co nanoparticles as a model catalyst. The performance of the system was analysed from both the thermodynamic and kinetic points of view and compared with the classical catalyzed hydrolysis of a NaBH₄ solution. The kinetic analysis of the NaBH_4(s)/catalyst_(s)/H₂O_(l) system shows that the reaction is first order with respect to the catalyst concentration, and the activation energy equal to 35 kJ mol_NaBH4⁻¹. Additionally, calorimetric measurements of the heat evolved during the hydrolysis of NaBH₄ solutions evidence the global process energy (−217 kJ mol_NaBH4⁻¹). Characterization of the cobalt nanoparticles before and after the hydrolysis associated with the calorimetric measurements suggests the “in situ” formation of a catalytically active Co_xB phase through “reduction” of an outer protective oxide layer that is regenerated at the end of reaction.     

Constitution, structural chemistry and magnetism in the ternary system Ce–Ag–Si

Phase relations were established for the Ce–Ag–Si system at 850°C by means of X-ray diffraction, light optical microscopy and quantitative electron probe microanalysis. Phase equilibria are characterised by the existence of extended solid solutions starting from the binaries: Ce(Ag_xSi_1−x)_2−y (ThSi₂-type), Ce(Ag_1−xSi_x)_1−y (unknown structure type) and Ce(Ag_1−xSi_x)_2−y (unknown structure type). Three ternary phases were found to exist, CeAg₂Si₂ (ThCr₂Si₂-type), Ce(Ag_xSi_1−x)_2−y (AlB₂-type) and the new ternary compound CeAgSi₂ with unknown structure type. Magnetic behaviour was studied from magnetic susceptibility and magnetisation measurements down to 1.7 K and employing magnetic fields up to 5 T. Soft ferromagnetism is observed for CeAg_xSi_2−x (AlB₂-type) below 5 K. Alloys Ce(Ag_xSi_1−x)_2−y with 0.08<x_Ag<0.30 (ThSi₂-type) encounter ferromagnetic order below 7 K. For x_Ag=0.31 the ferromagnetic interaction changes to antiferromagnetism with T_N=5.7 K. For CeAgSi₂ ferrimagnetic or canted antiferromagnetic order is indicated below 7 K.     

Formation Mechanism of AlN–SiC Solid Solution by Combustion Nitridation in Si3N4–Si-Al-C System

The synthesis of solid solutions of AlN–SiC was investigated through the combustion reaction between Si₃N₄, aluminum, and carbon powders and nitrogen gas at pressures ranging from 0.1 to 6.0 MPa. The combustion reaction was initiated locally and then the wave front propagated spontaneously, passing through the cylindrical bed containing the loose powder. In the presence of Si₃N₄ as a reactant, it was feasible to synthesize solid solutions at an ambient pressure (0.1 MPa). The relationship between nitrogen pressure and full-width at half-maximum of the (110) peak of the product showed that lower pressures produced more-homogeneous solid solutions. Some aspects of formation of the AlN–SiC solid solutions were discussed with special emphasis on the influence of nitrogen pressure and reactant stoichiometry.     

Polyphenol-Enriched Composite Bone Regeneration Materials: A Systematic Review of In Vitro Studies

One of the possible alternatives for creating materials for the regeneration of bone tissue supporting comprehensive reconstruction is the incorporation of active substances whose controlled release will improve this process. This systematic review aimed to identify and synthesize in vitro studies that assess the suitability of polyphenolics as additives to polymer-ceramic composite bone regeneration materials. Data on experimental studies in terms of the difference in mechanical, wettability, cytocompatibility, antioxidant and anti-inflammatory properties of materials were synthesized. The obtained numerical data were compiled and analyzed in search of percentage changes of these parameters. The results of the systematic review were based on data from forty-six studies presented in nineteen articles. The addition of polyphenolic compounds to composite materials for bone regeneration improved the cytocompatibility and increased the activity of early markers of osteoblast differentiation, indicating a high osteoinductive potential of the materials. Polyphenolic compounds incorporated into the materials presumably give them high antioxidant properties and reduce the production of reactive oxygen species in macrophage cells, implying anti-inflammatory activity. The evidence was limited by the number of missing data and the heterogeneity of the data.