The influence of temperature and arsenic molecular form at crystallization stage on the InAs nanostructure growth during droplet epitaxy

In this work, experimental studies of the influence of the arsenic molecular form (di-or tetramers) and substrate temperature on the crystallization of In/GaAs droplet nanostructures during droplet epitaxy have been carried out. We have shown the critical influence of the temperature and arsenic molecular form on the reproducibility of the characteristics of an array of self-organizing InAs nanostructures during crystallization. We also showed that a decrease in the initial In droplet size has a positive effect on the reproducibility of the parameters of the InAs nanostructures arrays. Our work also showed important role of substrate temperature at the crystallization stage.

The Sulfide/Silicate Coefficients of Nd and Sm: Geochemical “Fingerprints” for the Syn- and Epigenetic Cu-Ni-(PGE) Ores in the NE Fennoscandian Shield

One of the current directions of the Sm-Nd isotope systematics development is a dating of the ore process using sulfide minerals. Yet, the issue of the existence of rare earth elements (REE) in sulfides is still a matter for discussion. Sulfides from ore-bearing rocks of Proterozoic (2.53–1.98 Ga) Cu-Ni and platinum group elements (PGE) deposits of the Fennoscandian Shield were studied. It is found that the most probable source of REE in sulfide minerals from Cu-Ni-PGE complexes could be submicronic fluid inclusions, which are trapped at the mineral crystallization stage. In such a case, fluid or melt inclusions are specimens of the syngenetic parental melt, from which the base mineral formed, and these reflect a composition of the parental fluid. The mineral–rock partition coefficients for Nd and Sm can be used as “fingerprints” for individual deposits, and these are isotope-geochemical indicators of the ore-caused fluid that is syngenetic to sulfide. Moreover, the DNd/DSm ratio for various sulfide minerals can be used as a prospective geochemical tool for reconstructing a mineral formation sequence in ore complexes. On the other hand, differences in isotope compositions of sulfide neodymium could be markers of some ore-caused fluids and related to certain generations of sulfide minerals.

Origin of gem-quality barite at Jebel Ouichane district in Nador, Morocco: implications from integrated fluid inclusions, stable isotopes, and geochemistry

Light-blue barite from Jebel Ouichane in Morocco forms blade-like tabular crystals (up to ca. 10 cm) with superb transparency and lustre. It represents one of the most spectacular gem-quality specimens in the world. The barite is hosted by iron-ore-bearing skarns, developed within Jurassic-Cretaceous limestones, and occurs in close spatial association with calcite. Although it exhibits simple chemical composition, some irregular sectorial zoning, maintained by elevated contents of Sr in various crystal domains, were found. Barite from Ouichane is abundant in one phase (liquid or gas) or two-phase (liquid-gas) fluid inclusions of primary, pseudosecondary, and secondary origin. A combination of fluid inclusion microthermometry and stable isotope data suggest that δ18O value of barite-forming solutions, resulting from mixing of meteoric waters with hydrothermal fluids, could be in the range from -3,5‰ to +2,7 ‰ (VSMOW), whereas the main barite crystallization stage falls in the temperatures range of 160-180 °C. The recorded first ice melting temperatures (-35.9 to -41.5 ºC) indicate the presence of divalent cations, i.e. Ca2+and Mg2+ in addition to NaCl ± KCl in the mineralizing fluid composition. The possible source of SO42- and Ba2+, which gave rise to the barite formation was fluid enriched in Ba, Sr, Ca, Mg, S, and other elements derived from the alteration of carbonate and silicate minerals, being components of sedimentary and igneous rocks found in the surroundings of Nador area. Necessary amounts of sulphur could be in turn provided by weathering of pyrite and/or decomposition of organosulphur compounds. The combination of δ34S and δ18O values of barite (+16.39‰ and 6.71‰, respectively) indicate that its formation occurred in a steam-heated (near-surface) environment.

Devitrification of Zr55Cu30Al15Ni5Bulk Metallic Glass under Heating and HPT Deformation

The nanocrystal formation in Zr55Cu30Al15Ni5 bulk metallic glass was studied under heat treatment and deformation. The activation energy of crystallization under heating is 278 kJ/mol. Different crystalline phases were found to be formed during crystallization under heating and deformation. At the first crystallization stage, the metastable phase with a hexagonal structure (lattice of space group P63/mmc with the parameters a = 8.66 Å, c = 14.99 Å) is formed under heat treatment. When the temperature rises, the metastable phase decays with the formation of stable crystalline phases. The crystalline Zr2Cu phase with the lattice of space group Fd3m is formed during crystallization under the action of deformation. It was determined that during deformation nanocrystals are formed primarily in the subsurface regions of the samples.

Allanites in the Sin Quyen IOCG deposit, North Vietnam

Allanite minerals are the principal host of REEs in the Sin Quyen, Iron Oxide Copper Gold (IOCG) type deposit. The geochemical characteristics of these minerals are discussed in this work. The studied allanites have an unstable concentration of all major elements, such as REE (14-27 wt%), Ca (9-16 wt%), Al (8-19 wt%), Si (26-34 wt%) and Fe (12-21 wt%). Two different varieties of these minerals are documented, the older with higher REE concentrations ranging from 20 to 27 wt%, and younger with lower total REE concentration ranging from 14 to 19 wt%, which occur as a rim surrounding the older. Differences between the two groups of allanites are documented by Raman spectra and optical properties. The WDS chemical composition indicate that the allanites belong to the Ce-La-ferriallanite family, with low ƩHREE with an average of 0.21 wt.%. This work also supports the estimated timing of the deposit development focusing on detailed petrological study, and documented chemical composition of allanites confirmed by simplified statistical analysis. Temperature 355ºC which was calculated using value of δ34S isotopes is interpreted as a temperature of the second crystallization stage of allanite group. The pressure of crystallization solution was calculated and is ranging from 0.98 to 5.88 MPa.

Synthesis of Novel Biomaterial for the Treatment of Sepsis in Rats

In this research, glutamine (GLN) and L-Tyrosine were synthesized into AL-GLN synthetic biomaterials to explore their protective effect on the myocardium of sepsis symptoms. In the process of preparation, acyl chloride method was used to generate, which was generated by acylation reaction and ammonolysis reaction. In the ammonolysis reaction, the original ammonia water reaction was replaced by the ammonia water/dimethylformamide (DMF) system. The biomaterial was characterized, and it was confirmed that the product recovery rate could be maximized by adjusting the pH value to 9 during crystallization stage, and the purity could be increased from 94.23% to 98.45% after some technological improvement. During the experiment of myocardial protection in sepsis, 60 SPF rats were selected for the experiment and divided into three groups, namely the unmodified surgery group, the GLN group and the AL-GLN group. Rats with sepsis were obtained by cecum ligation and perforation. The myocardial apoptosis index and the gene expression of Bcl-2/p53mRNA were detected at 6 h, 12 h and 24 h after operation in different groups. The results showed that the expression of Bcl-2mRNA in the surgical group was significantly down-regulated compared with that in the surgical group (P < 0.05), the expression of Bcl-2mRNA in the GLN group was significantly increased compared with that in the surgical group (P < 0.05), and the expression of p53mRNA in the AL-GLN group was first decreased and then slowly increased compared with that in the surgical group (P < 0.05).

Hydration Mechanism and Hardening Property of α-Hemihydrate Phosphogypsum

The hydration and hardening of α-hemihydrate phosphogypsum (HH) prepared in the absence and presence of L-Aspartic acid (L-Asp) were investigated by thermodynamic analysis, measurements of ion concentrations and crystal water content, and morphology observation. In addition, computed tomography (CT) scanning was proposed to analyze the hole characteristic of hardened gypsum in situ. The results show that HH will pass through the unstable region and the stable region of dihydrate gypsum (DH) in turn during the hydration. The hydration of HH follows the dissolution–crystallization principle; the hydration process can be divided into the dissolution stage, dissolution–crystallization stage and equilibrium stage. Compared with the HH prepared without crystal modifier, the hydration process of HH prepared with L-Asp is obviously prolonged, and the morphology of DH changes from needle-like to diamond-shape crystals with an aspect ratio of 1:1. Meanwhile, the defect-specific surface and porosity of hardened gypsum significantly decreases, achieving a more compact, hardened paste with higher compressive strength.

Impurities Accumulation on the Surface of Alumina Hydrate Particles in Bayer Technology

The purity, structural surface, particle dimensions, particle size distribution, and the associated reactivity of chemical and surface properties are the most important and most required properties of alumina hydrate special brands. The purpose of this paper concerns the common metallic impurities accumulation on the surface of alumina hydrate particles, during the sodium aluminates decomposition in liquid phase, during the entire aluminum hydroxide crystallization stage in the Bayer technology.