Chemical, morphological characterizations of Ririwai biotite and determination of yield point of its weighting agent application in drilling mud

Chemical, morphological characterizations and drilling mud yield point impact of Ririwai biotite have been investigated and reported in this work. Local Ririwai biotite mined in Doguwa Local Government Area of Kano State was used as a weighting agent in drilling mud formulation. Scanning Electron Microscopy (SEM) characterization, X-ray Diffraction (XRD) and Electron Dispersion X-ray (EDX) analysis of the Ririwai biotite were carried out. Water-based drilling mud was prepared using commercial bentonite according to the API 13A Standard. Effect of gradual addition of Ririwai weighting agent; 0 – 100 wt%, on the yield point of the formulated drilling mud was studied. XRD analysis showed that the dominant mineral phase in the material was biotite. Morphological analysis carried out showed that the Ririwai biotite had a sheet-like morphology while the commercial bentonite had clumpy morphology. The estimated average particle sizes were 60 and 25 μm for the Ririwai biotite and commercial bentonite, respectively. EDX analysis showed that silica-alumina ratio of the Ririwai biotite was 9.3 while that of the commercial bentonite was 1.58. The optimum yield point of the formulated drilling mud was 2.0 lb/100 ft2 corresponding to formulation having 0 – 30 wt% weighting agent composition. The specific gravity of Ririwai biotite was determined as 2.4.

In Vitro Corrosion of Quaternery Magnesium Alloy Foam by Addition of Zinc

Magnesium alloys have been intensively studied as possible resorbable material with adequate mechanical properties similar to natural bones but very poor corrosion properties. In this analysis, the addition of Zn element to quaternary Mg-Ca-Zn alloy foam was evaluated with TiH2 as a foaming agent and manufactured with high-purity raw materials the powder metallurgy process. In Hank's solution, the rate of corrosion of specimens by direct observations with Scanning Electron Microscopy ( SEM), Electron Dispersion Spectrometry (EDS), static immersion studies, potentiodynamic evaluations, and X-Ray Diffraction (XRD). The specimens post-immersion characteristics and the corresponding Hank's solutions were examined at 2, 4, 6, 24, 48, and 72 hours of immersion. The findings show that the microstructure of alloy morphology, such as pores, pitting corrosion, needle shapes, and galvanic corrosion has the main corrosion products Mg(OH)2 and Ca10(PO4)6(OH)2. The addition of less than 6 percent wt Zn will minimize the corrosion rate but increase with 10 percent wt Zn. From this study, Mg-Zn-Ca alloy at 6 percent wt Zn has the lowest corrosion rate with slow pH changes in the process.

Extraction and Characterization of Chitosan from Crab Shells: Kinetic and Thermodynamic Studies of Arsenic and Copper Adsorption from Electroplating Wastewater

Crab shells were used to produce chitosan via the three stages of deproteinization, demineralization and deacetylation using sodium hydroxide and hydrochloric acid under different treatment conditions of temperature and time. The produced chitosan was characterized using Fourier transform infrared spectroscopy (FTIRS), X-ray diffraction (XRD), high – resolution scanning electron microscopy (HRSEM), electron dispersion spectroscopy (EDS), dynamic light scattering (DLS), Brunauer Emmett Teller (BET) and Thermogravimetric analysis (TGA). The adsorption behavior of chitosan to remove arsenic (As) and copper (Cu) from electroplating wastewater was examined by batch adsorption process as a function of adsorbent dose, contact time and temperature. The FTIR, XRD, HRSEM and EDS analyses confirmed, respectively, the presence of –NH2 and –OH functional groups, with amorphous/crystalline phases, crystallinity index of 69.54%, needle-like morphology and Carbon (C), Oxygen (O) and Nitrogen N) in the produced chitosan. While DLS, BET and TGA showed, respectively, that the produced chitosan has an average particle size of 729nm, is moderately polydisperse, has12.67 m2/g surface area, mesoporous in nature, and with thermal stability of up to 1430C. The optimum adsorbent dose, contact time and temperature values to remove As and Cu by chitosan were 15mg, 45 minutes, 333K and25mg, 60 minutes, 349K,respectively. Under the employed conditions, chitosan though has a low surface area, displaying high adsorption capacity for both metal ions. The adsorption isotherm data were better fitted to the Jovanovic isotherm model while the kinetic data fitted best to the pseudo-second order model. The thermodynamic studies established that the adsorption was feasible but endothermic in nature. This study shows that chitosan adsorbents purify electroplating wastewater.

Doping dependence of thermopower in cuprate superconductors

The doping dependence of the thermopower of cuprate superconductors in the normal-state is studied within the [Formula: see text]–[Formula: see text] model. It is shown that with a proper modification of the bare electron dispersion in the [Formula: see text]–[Formula: see text] model, the experimental results of the doping dependence of the normal-state thermopower are qualitatively reproduced. In particular, the theory shows that a pseudogap-generated split of the van Hove peak in the density of states appears in the underdoped and optimally doped regimes, however, this split is absent from the overdoped regime. Concomitantly, the strong asymmetry of the spectral conductivity near the electron Fermi surface emerges, where the peak in the spectral conductivity appears always below the electron Fermi surface in the underdoped and optimally doped regimes, while it appears above the electron Fermi surface in the overdoped regime. This strong asymmetry of the spectral conductivity leads to the unusual behaviors of the normal-state thermopower from the underdoped regime to the overdoped regime.

Low Temperature Growth of the Nanotextured Island and Solid 3C-SiC Layers on Si from Hydric Si, Ge and C Compounds

Different growth stages and surface morphology of the epitaxial 3C-SiC/Si(100) structures were studied. Heterocompositions were grown in vacuum from hydric compounds at a lower temperature. The composition, surface morphology and crystal structure of the 3C-SiC films were tested using X-ray diffraction, second ion mass spectrometry, scanning ion and electron microscopy, photo- and cathode luminescence. It was demonstrated that the fine crystal structure of the 3C-SiC islands was formed by the close-packed nanometer-size grains and precipitated on the underlying solid carbonized Si layer. Luminescence spectral lines of the solid carbonized Si layer, separated island and solid textured 3C-SiC layer were shifted toward the high ultraviolet range. The spectra measured by different methods were compared and the nature of the revealed lines was considered. This article discusses a quantum confinement effect observation in the 3C-SiC nanostructures and a perspective for the use of nanotextured island 3C-SiC layers as a two-dimensional surface quantum superlattice for high-frequency applications. The conductivity anisotropy and current-voltage characteristics of the two-dimensional superlattices with a non-additive electron dispersion law in the presence of a strong electric field were studied theoretically. Main efforts were focused on a search of the mechanisms allowing realization of the high-frequency negative dynamical conductivity for the structures having a positive static differential conductivity.

Obtaining salts of resin acids from Cuban pine by metathesis reactions

The resin acids obtained from the Cuban pine rosin are the starting material for the development and application of metathesis reactions. These reactions allow the obtaining of salts with high added value which could be used in the development of biomaterials for dental use. The objective of this work was to obtain calcium, magnesium and zinc resinates from the resin acid obtained from the Cuban pine resin by metathesis reaction for possible use in the development of biomaterials. The products obtained were evaluated by elemental analysis, X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy associated with electron dispersion spectroscopy, nuclear magnetic resonance and biological tests (antibacterial activity). The results showed the formation of the different resinates, observing the presence of cations in the salts obtained. The disappearance of the signal corresponding to the hydrogen of the carboxyl group was verified by nuclear magnetic resonance analysis due to the reaction between the resinic acid and the different metals studied. The biological analyzes showed that the best results are achieved with zinc resinate.

The Evolution of Electron Dispersion in the Series of Rare-Earth Tritelluride Compounds Obtained from Their Charge-Density-Wave Properties and Susceptibility Calculations

We calculated the electron susceptibility of rare-earth tritelluride compounds RTe3 as a function of temperature, wave vector, and electron-dispersion parameters. Comparison of the results obtained with the available experimental data on the transition temperature and on the wave vector of a charge-density wave in these compounds allowed us to predict the values and evolution of electron-dispersion parameters with the variation of the atomic number of rare-earth elements (R).