PARAMETERIZATION OF REAXFF POTENTIAL OF MG/AL/SI/O INTERACTION AND INVESTIGATION OF MECHANICAL PROPERTIES FOR S-GLASS

New ReaxFF parameters are developed for the description of Mg/Al/Si/O interaction for the Magnesium Aluminosilicate (MAS) glass structure. The training set contains energy curves from equation of state for various Mg/Al/Si/O crystals, valence angle and bond distance scan, and heat of formation for the Mg/Al/Si/O interactions. A semi-automated Genetic Algorithm assisted by Artificial Neural Network is applied for this parametrization. Validation efforts showed the current ReaxFF parameter set can describe the atomistic structure and property of tectosilicate MAS glass including S-glass. Estimated quasi-static modulus of S-glass structure matches well with experimental value. Analysis shows the key of high modulus of S-glass is numerous Mg-BO (Bridge Oxygen) interactions across the Mg-O-AlSi structure. In addition, atomistic origin of high ductility and progressive failure of S-glass is derived from the reconstruction of the atomic structure, forming Mg-BO-Si interactions that delays fracture formation.

Nano-design of Zeolites Biomass Wastes Valorization: Dehydration of Lactic Acid into Acrylic Acid

The valorization of waste from biomass currently arouses great interest. In the present study we concentrate on the design of innovative BEA zeolite catalysts with applied metal nanoparticles - copper, vanadium and manganese for the dehydration of lactic acid to acrylic acid. Th e ab initio method based on density functional theory (DFT) was used to calculate the electron structure of the analyzed molecules. The non-local generalized gradient corrected functionals GGA-RPBE was used to in order to account for electron exchange and correlation. The cluster model was represented by a hierarchical zeolite M2Al2Si12O40H22 (M = Cu, V, Mn). Th e stabilization of the M-Ob-M dimer complex in the hierarchical structure of BEA, mechanism of adsorption of lactic acid on BEA zeolite with applied metal dimers and formation of acrylic acid on these zeolites were investigated. Th e examined metals form stable dimers interconnected by a bridge oxygen (Ob). Adsorption of lactic acid takes place in the vicinity of a dimer of M-Ob-M.The dehydration of lactic acid to acrylic acid in all cases consists in the separation of the hydroxyl group and creating a connection with a metal center of dimer and disconnection of a single hydrogen atom from the methyl group and its interaction with bridge oxygen of dimer.

Hydraulic Activity and Microstructure Analysis of High-Titanium Slag

To explain the relationship between the hydration activity of high-titanium slag and its microstructure, the hydration activity of high-titanium slag was determined, then the mineral phase and microstructure characteristics of high-titanium slag glass phase and blast furnace slag were investigated using a series of analytical methods, which contain X-Ray Diffraction (XRD), Scanning Electronic Microscope (SEM), Fourier Transform Infrared spectroscopy (FTIR), Raman spectroscopy, and Nuclear Magnetic Resonance spectroscopy (NMR). The results showed that in slow-cooled high-titanium slag, the hydration inert mineral content was about 98%, and the glass phase content was less than 2%, hence, the hydration activity of slow-cooled high titanium slag accounted for less than 25% of that of the blast furnace slag. The content of the glass phase in water-quenched high-titanium slag was 98%, but the microstructure of the glass phase was very different from that of the blast furnace slag. The glass phase of high-titanium slag has stable forms, which are TiO44− monomers, chain or sheet units O–Ti–O, and a small amount of 6-coordination Ti4+. The Ti makes the SiO4 tetrahedron in a glass phase network not only a monosilicate, but more stable forms of disilicates and chain middle groups also appeared. The relative bridge oxygen number increased to 0.2, hence, the hydration activity of water-quenched high-titanium slag took up less than 37% of that of the blast furnace slag.

Formation of oxygen bubbles in K-208 glass under electron irradiation

The formation of gas-filled bubbles, which is one of the indicators and quantitative criteria for radiation degradation of the surface layer of K-208 glass irradiated by 20-keV electrons, and the effect of ITO (Indium tin oxide) film deposited on the glass, are investigated. Using atomic force microscopy, the nucleation of oxygen bubbles in the surface layer of glass irradiated with a fluence (Φ) of the order of 1015 cm–2 at a particle flux density (φ) of 2·1010 cm–2·s–1 was detected. Gas-filled bubbles appear on the surface of samples with an ITO film at Φ ≥ 4·1015 cm–2 in smaller amounts but larger sizes than on glass without a film. The formation of oxygen bubbles is explained by the formation of a negative charge region in the surface layer of the irradiated glass, in the field of which sodium ions migrate, which plays a key role in the release of non-bridge oxygen atoms. Migration and aggregation of liberated oxygen atoms in defective places in the glass grid leads to the formation of gas-filled bubbles.

Study on desulfurization capacity of high alumina blast furnace slag at 1773 K using slag-metal equilibrium technique

In the current paper, we have determined the desulfurization ability of a CaO–MgO–SiO2–Al2O3 slag system using slag-metal equilibrium technique. The chemical composition of slag samples consists of Al2O3 in the range of 25–30 wt%, CaO/SiO2 ratio (0.8–1.6) and MgO (8–16 wt%). All the experiments are conducted at a temperature of 1773 K. The sulphur content in the slag as well as in metal after desulfurization reaction is analyzed using XRF (X-ray Fluorescence Spectroscopy) for calculating sulphur partition ratio (LS) of the slags. The influence of Al2O3, CaO/SiO2 ratio and MgO content on LS have been studied. It is observed that LS increase with an increase in CaO/SiO2 ratio and MgO content, but it reduces as the Al2O3 content increase in slag. Also, the amount of bridge oxygen ([BO]) represented by (O0) decreases with increase in basicity and MgO content. However, O0 increases with increase in Al2O3. It is witnessed that the experimental values closely fit with the values obtained from corrected optical basicity model.

Transformation Mechanism of Fluormica to Fluoramphibole in Fluoramphibole Glass Ceramics

During isothermal sintering at 820°C, the transformation mechanism of fluormica to fluoramphibole in powder compacts of fluormica and soda-lime glass was investigated using differential thermal analysis, infrared reflection spectrometry, X-ray diffraction, scanning electron microscopy, and so forth. Results show that an interaction between fluormica and glass occurred during isothermal heating; O2−, Na+, and Ca2+ions were diffused from glass to fluormica. This diffusion facilitates the transformation of the sheet structures of fluormica crystals to double-chain structures by the breakage of bridge oxygen bonds in the sheet. Subsequently, the broken two parallel double chains were rearranged by relative displacement along thec-axis direction of the fluormica crystal and were linked by Na+and Ca2+ions to form fluoramphibole. A crystallography model of fluormica-fluoramphibole transformation was established in this study.

Adsorption Mechanism of Cu-Doped SnO2 (110) Surface toward H2 Dissolved in Power Transformer

The content of hydrogen is a key quantity in condition assessment and fault diagnosis of power transformer. Based on the density functional theory (DFT), the adsorption mechanism of Cu-doped SnO2 surface toward H2 has been systematically studied in this work. Firstly, the relaxation, the bond length, and overlap population of both the pure and Cu-doped SnO2 are computed. To determine the optimal doping position, the formation energies of four potential sites (i.e., Sn5c, Sn6c, Sn5c-s, and Sn6c-s) are then compared with each other. The adsorption energy and the electronic structure of SnO2 surface are analysed and discussed in detail. Furthermore, to estimate the partial atomic charges and the electrical conductance, the Mulliken population analysis is also performed. It has been found that the bridge oxygen is the most favourable position. The partial density of states of H2 after adsorption is broadened and shifted close to the Fermi level. A large amount of charges would be transferred and then released back into its conduction band, leading to the reduction of resistance and the enhancement of sensitivity toward H2. The results of this work provide references for SnO2-based sensor design.

Synthesis of a Novel Lanthanide Oxide Nitrate Compound with 3D Structure

One lanthanide nitrate (Ln = Tb) with a novel three dimensional structure have been prepared through hydrothermal method. Single crystal X-ray diffraction structures were obtained. The compound crystallizes in the orthorhombic,Pnmaspace group. The lanthanide ions are eight-coordinate with six oxygen atoms coming from nitrate ions and two from bridge oxygen atoms. If the bridge oxygen atoms could be ignored, the compound can be described as a rare microporous 3D Lanthanide nitride with the open framework.

A new Rubidium - Bismuth polyphosphate RbBi(PO3)4: Growth, X-ray single crystal and vibrational study

Solid-solution studies in the ternary Rb2O – Bi2O3 – P2O5 system, carried out in a search for inorganic materials have a considerable interest mainly for their optical properties, specifically in laser technology, yielded the new compound RbBi(PO3)4. Single-crystal X-ray measurement revealed that RbBi(PO3)4 crystallizes in space group P21/c with a structural type IV and has lattice parameters a = 10.430, b = 8.984, c = 12.967 Å,  = 126.1°, Z = 4 and V = 981.6 Å3. The all eighteen atoms were located in the asymmetric unit. Refinement using anisotropic temperature factors for all atoms yielded weighted residuals based on F and F2 values, respectively, of R1 = 0.0131 and WR2 = 0.0252 for all observed reflections. The atomic arrangement can be described as a long chain polyphosphate organization, helical ribbons (PO3)n. Two types of infinite chains, with a period of eight PO4 tetrahedra run along the longest unit-cell directions. Infrared and Raman spectra at room temperature, were investigated, show clearly some characteristics bands of infinite chains structure of PO4 tetrahedra linked by a bridge oxygen.

Properties Investigation of Yb3+-Doped Phosphate Glasses for Fiber Laser

The physical and optical properties of P2O5-Al2O3-ZnO glasses doped with different concentration of Yb3+ions were investigated. The experimental results indicated that density, chemical durability, glass transition temperature (Tg) and glass softening temperature (Td) of glasses increase with increasing the Yb2O3content of glasses. However, the coefficient of thermal expansion (α) for glasses decrease with increasing the Yb2O3content. From the results of Fourier transform infrared spectroscopy, the numbers of (-P-O-P-) bonds decrease and (-P-O-M+-) bonds increase with increasing the Yb2O3content. Increase of non-bridge oxygen (-P-O-M+-) raise the refractive index of glasses. Moreover, the results of absorption spectra indicate that the absorption peak of glasses are observed at both wavelengths of 916nm and 977nm. As increasing the concentration of Yb2O3, the absorption efficiencies become stronger. In accordance with the results of fluorescence spectra, the fluorescence emission of glasses are detected at wavelengths of 970nm, 995nm, 1020nm and 1048nm, respectively. The intensity of the fluorescence emission peaks significantly decrease at wavelengths of 970nm and 995nm as the concentration of Yb2O3increases. However, the intensity of the fluorescence emission peaks significantly increase at wavelength of 1048nm under the same condition.