Surface Purity Effect on Irregularities of Changes in Deformation Texture of Zr-2.5% Nb Alloy

This work is a continuation of a series of works on the study of regularities and structural mechanisms of changes in characteristics of crystallographic texture during cold deformation of plates made of Zr2.5%Nb alloy. Effects of influence of surface cleanliness of the plates on the textural regularities during their rolling were investigated. For this, longitudinal fragments of the tube Æ15.0´1.5 mm² were used, flattened, annealed at 580°C in a vacuum of 1.5...3.0 Pa and rolled along the axis of the original tube with various degrees deformation up to 56%, which is likened to longitudinal rolling of plates. Techniques of maximally uniform straightening of tube fragments were used. An analysis of the results of studies of textural changes during cross rolling of plates, straightened from rings of the same tube and pretreated under similar conditions, is also carried out. To analyze the results, the method of inverse pole figures was used, which, in these studies, is distinguished by the possibility of achieving satisfactory accuracy in calculating the integral characteristics of texture. On this basis, the Kearns textural coefficient was calculated along the normal to the plates’ plane. Corrections were introduced for texture dissimilarity along the thickness of the plates, which is caused by the unbending of the preliminary blanks. Additionally, the analysis of texture distributions was carried out using original techniques. According to the results obtained – as a result of X-ray measuring from the plates’ surface – oscillations of the course of changes in the texture coefficient were revealed. This is associated with an alternating process of relaxation of residual stresses during deformation. It has been established that this effect is initiated from the near-surface regions, is associated with a near-surface impurity, and in some cases can penetrate to a considerable depth of the plates. The twinning nature of such regularities is confirmed and active systems of twins are noted.

Энергия связи пластин кремния и сапфира при повышенных температурах соединения

The hydrophilicity of surfaces and the bonding energy of silicon and sapphire wafers at the temperature of joining 50°C are studied. It is established that heating of the Si and Al_2O_3 wafers to 50°C is accompanied by an increase in the degree of hydrophilicity of the wafer surfaces. The effect is attributed to improvement in the surface purity due to the desorption of impurity atoms into vacuum and to an increase in the density of dangling bonds. It is found that the bonding energy of silicon and sapphire wafers joined at a temperature of 50°C and upon further heating in the range 100–250°C is higher compared to the bonding energy of wafers joined at room temperature. The activation energy of the growth of the bonding energy is determined. It is found that this activation energy is 0.57 eV.

Влияние химической подготовки поверхности кремния на качество и структуру эпитаксиальных пленок карбида кремния, синтезированных методом замещения атомов

The fundamentals of a new technique for the cleaning and passivation of (111), (110), and (100) silicon wafer surfaces by hydride groups, which ensure a high surface purity and smoothness at the nanoscale upon long-term storage of the wafers at room temperature in air, are discussed. A new composition of the passivation solution for the long-term antioxidation protection of silicon surfaces is developed. The proposed solution is suitable for the long-term storage and repeated passivation of silicon wafers. The composition of the passivation solution and the conditions of passivation of the silicon wafers in it are described. Silicon wafers treated using the proposed technique can be used for growing epitaxial semiconductor films and different nanostructures. It is shown that only silicon surfaces prepared in this way allow SiC epitaxial films on silicon to be grown by atom substitution. The experimental dependences of the SiC and GaN film structures grown on silicon on the silicon-surface etching conditions are presented. The developed technique for silicon cleaning and passivation can both be used under laboratory conditions and easily adapted for the industrial production of silicon wafers with an oxidation-resistant surface coating.

Bioethanol Production from Ball-Milled and Regenerated Rice Husk

This research focused on the bioethanol production from rice husk via enzymatic hydrolysis and fermentation of glucose product. Rice husks were ball-milled, alkali pretreated with 2 %(w/v) NaOH for 3 hours and regenerated by N-methylmorpholine N-oxide (NMMO)/H2O solution into Cellulose II structure. These processes were aimed to enhance the surface purity area and accessibility of enzyme, respectively. Rice husks were hydrolyzed with cellulase from Trichodermareesei ATCC 26921 at various concentrations ranging from 10 to 40 FPU/g of rice husk. The maximum yields of glucose from alkali pretreated rice husk, ball-milled rice husk of sieve size 45-75 μm and regenerated rice husk were 7.13, 9.52 and 10.36 mg/mL, respectively. This was conducted at the enzyme concentration of 20 FPU/g of rice husk for 48 hours. The glucose product was fermented by using Saccharomyces cerevisiae Safale US-05 at various concentrations ranging from 10 to 70 %(v/v). The maximum yields of ethanol products at 50 %(v/v) of yeast and 48 hours of fermentation from the alkali pretreated rice husk, ball-milled rice husk of sieve size 45-75 μm and regenerated rice husk were 44.36%, 68.79% and 89.11% of glucose respectively. The greater yield may be arise from an increase in surface area and the swollen cellulose structure of rice husk.

Simple Thermal Decompose Method for Synthesis of Nickel Disulfide Nanostructures

In this work, a simple thermal decompose method was served to synthesize NiS2 nanostructures via a nickel complex. Also polyethylene glycol (PEG) was used as surfactant to increase the steric effect around nanostructure surfaces and decrease the particles size. The product was characterized with different analysis methods. The crystal structure of the product was studied by X-ray diffraction (XRD) pattern. The particle size and morphology were investigated by scanning electron microscopy (SEM). To study the nanostructures surface purity, Fourier transform infrared spectroscopy (FT-IR) was used. And finally to study the optical properties of the product photoluminescence (PL) spectroscopy was served.

Synthesis and Characterization of Cadmium Sulfide Nanoparticles via a Simple Thermal Decompose Method

In this work, cadmium sulfide (CdS) nanoparticles were synthesized from a new Cd-octanoate complex via a simple thermal decompose method. The crystallinity of the product was obtained from X-ray diffraction (XRD) pattern. The morphology and product size were analyzed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Also Fourier transform infrared (FT-IR) spectroscopy was used to investigate the CdS surface purity. Finally, the optical properties of the product were obtained from photoluminescence (PL) spectroscopy.