Revista de Ciências e Engenharia de Materiais

The article is devoted to the issue of increasing of efficiency of using of local cucurbits crops. The statistical data of cultivation of cucurbits crops in South Kazakhstan region are analyzed in the article. According to the given data there is growth of cultivation areas and productivity of cucurbits crops observed. Since 1994 the cultivated area for cucurbits crops has increased 5.9 times, the whole yield–19.08 times, the productivity – 3.2 times. In 2014 year in South Kazakhstan region the whole yield of cucurbits crops composed 64% from total volume. Useful properties of cucurbits crops are described. The problem of absence of industrial processing of cucurbits crops is pointed out. Recommendations to process cucurbits crop into plant honey which is possible to use for obtaining wide assortment of food products are described. The problem of processing of cucurbits crops is offered by creation of concentrated jelly-like melon product technology and using this product in confectionery industry. Flash-free melon concentrate and melon and fruit-melon concentrates with flash are developed. The formulations of melon-fruit concentrates are developed. Their sensory characteristics, physical-chemical indicators are determined, energetic value and specific heat capacity is calculated. The review of scientific researches on melon is given; the review includes investigation of chemical composition of melon, development of methods and devices for storage and treatment melon and creation of new melon products. Investigation object of scientists in the field of melon employment is not only its flesh but seeds rich by proteins and fats as well.

Different coating systems were characterized using a commercial API 5CT steel grade L80 type 1, which is commonly used in the oil and gas industry. Two Ni-based alloys and one Co-based alloy were deposited by laser cladding. Two coatings were deposited (Ni-based alloy and a composite W-C/Co-base) by means of thermal spray process. It has been shown the presence of a hard heat affected zone (HAZ) in the substrate for the as-laser deposited coating. The main explanation for this HAZ is devoted to the heat gradient causing a gradient on the prior austenite grain size and consequently different martensite hardness along the HAZ. For the thermal sprayed coatings, no HAZ was formed due to low heat input process. All the studied coating systems seem to be very interesting for different technically demanding applications, such as, stress sulfide corrosion and wear resistance.

The MAX phase Ti2SnC was successfully welded to Ti6Al4V (TC4) through Cu interlayer in Ar atmosphere at low temperature 750ºC, during 1h under an applied mechanical pressure 10 MPa. The results indicated that the outward diffusion of Sn from Ti2SnC played a critical role in the chemical composition of joints. After 60 mins, the reaction layers consist of five zones: interleaved β-Cu(Sn) and α-Cu(Sn) zone zone (V), enriched Sn and CuTi0.5Sn0.5 intermetallic phase (IV), poor Sn, Ti and rich Cu zone (III), Ti3Cu4 intermetallic (II) and β-Ti (Cu) phase (I). Shear test results showed that the average shear strength reached 85.7 ±10 MPa. Corresponding fractographs indicated that the crack mainly propagated along Ti2SnC substrate adjacent to the bonding zone, accompanied with an intergranular fracture mode.

In this study, highly crystalline BaTiO3 and SrTiO3 nanoparticles were synthesized by bi-modal distribution solution process followed by annealing at different temperatures. The impact of annealing temperatures on the nanoparticles was investigated by their various chemical, structural and surface properties. The particle sizes of both BaTiO3 and SrTiO3 increased from 30-80 nm with increase in annealing temperature due to the agglomeration of the nanoparticles. It was found that the optical band gap of BaTiO3 and SrTiO3 was considerably decreased with the increase of annealing temperatures from 500 - 900°C. With the observed results, we can say that annealing BaTiO3 and SrTiO3 nanoparticles significantly enhance their optical, structural, morphological and crystalline properties.

Large-scale BEC of cesium at T=353 K was first observed. Until now, scientists have applied magnetic fields and lasers, but never applied electric fields, and atoms are oriented at random, so observation of BEC is very difficult. Our innovation lies in the application of electric fields. We theoretically proved that alkali atom (include Cs) may be polar atom doesn't conflict with quantum mechanics. Variation of the capacitance with temperature offers a means of separating the polar and non-polar atom. Cs vapor was filled in cylindrical capacitor. Our experiment shows that Cs is polar atom because its capacitance is related to temperature. In the past, to realize the phase transition, ultralow temperature is necessary. But now we don’t require ultralow temperature, because we use the critical voltage Vc to achieve the phase transition. From the entropy S=Nk ln 2πe /a=0, a=dV/kTH =2πe, Vc ≈ 63volts. When V < Vc, S > 0; when V >Vc, S < 0, phase transition occurred. When V=350 volts, the capacitance decreased from C=1.97C0 to C ≈ C0 (C0 is the vacuum capacitance), this result implies that almost all Cs atoms (more than 98.9%), like as dipoles, are aligned with the field. We create BEC with 1.928×1017 atoms, these atoms have the same momentum. Cs material with purity 99.95% was supplied by Strem Chemicals Co., USA. Both BEC and superconductivity are condensed in the momentum space, therefore these two kinds of condensation can’t be observed with the naked eye. When superconductivity occurs, the resistance R≈0, a simple and direct method to observe superconductivity is to measure the resistance by voltammetry. Similarly, when BEC occurs, the electric susceptibility χe=C/C0 –1 ≈ 0, a simple and direct method to observe BEC is to measure the capacitance by cylindrical capacitor. BEC is also a quasi-superconducting state.

Bioelectrochemical systems based on polymer-bacteria thin film modified electrode were explored. The prepared polymer-bacteria modified copper electrode was characterized with voltametric methods, as cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The proposed electrode indicated a definite redox response, high conductivity and electrochemical stability. The experimental results revealed that the prepared electrode could be a feasible for degradation of hazardous phenol pollutants

For achieving additional benefits and improving the material characteristics two or more materials are often combined together in the form of composites. Composites are important because of their light weight, high strength and flexibility of design. Composite materials provide various advantages based on their particulate or fibrous nature and on the basis of individual qualities of the constituting elements of the composites. Besides the multiplied benefits achieved with the composite materials, they being composed of two different materials exhibit greater challenges and biocompatibility threats which need to be addressed while developing a composite material. A structural composite of bioabsorbable nature is developed using a polymeric material and metal particles. The composite material so developed would provide altered strength and flexibility, better than the individual constituting materials for use in various biomedical devices and would eventually degrade on subject to exposure to the physiological environment. The two different varieties of the composite have been developed using metal particles and metal salt and they have been tested for their tensile, degradation and drug release properties, which have been found satisfactory for use of the composite in various biomedical devices and drug release applications.

The results of a comprehensive experimental and theoretical study is reported to empathize the optical properties of binary GaAs, ZnTe, CdTe and ternary Cd1-xZnxTe (CZT) alloys in the two energy regions: (i) far-infrared (FIR), and (ii) near-infrared (NIR) to ultraviolet (UV). A high resolution Fourier transform infrared spectrometer is used to assess the FIR response of GaAs, ZnTe, CdTe and CZT alloys in the entire composition 1.0 ≥ x ≥ 0 range. Accurate model dielectric functions are established appositely to extort the optical constants of the binary materials. The simulated dielectric functions ε(ω) and refractive indices n~(ω) are meticulously appraised in the FIR → NIR → UV energy range by comparing them against the existing spectroscopic FTIR and ellipsometry data. These outcomes are expended eloquently for evaluating the polarization dependent reflectivity R(λ) and transmission T(λ) spectra of ultrathin CZT/GaAs (001) epifilms. A reasonably accurate assessment of the CZT film thickness by reflectivity study has offered a credible testimony for characterizing any semiconducting epitaxially grown nanostructured materials of technological importance.

Natural fiber Composites typically have a fiber or particle phase that is stiffer and stronger than the continuous matrix phase and serve as the principal load carrying members. The matrix acts as a load transfer medium between fibers, and in less ideal cases where the loads are complex, the matrix may even have to bear loads transverse to the fiber axis. In this research the comparative synthesis and analysis of Kenaf fiber (FRPMC1) and Polmera fibers (FRPMC2) are treated with NaOH solution and the fibers are properly reinforced with polypropylene resin and epoxy resin respectively in a matrix form to prepare hybrid composite laminates of 6 mm fiber length thereafter to with suitable specimens with ASTM D-638 and D-790 standards. The analysis was carried out by using FEA software for various loads and result factors. The surface is analyzed by SEM test with various resolutions. The matrix also serves to protect the fibers from environmental damage before, during and after composite processing. The surface is analyzed using when designed properly, the new combined material exhibits better strength than each individual material. Composites are used not only for their structural properties, but also for electrical, thermal, and eco-friendly environmental applications.

Short arecanut leaf sheath (ALS) fiber (2-3 mm) reinforced polypropylene (PP) composites were prepared by compression molding technique. Heat and cold press were used. Chemical composition of the fiber was analyzed and the percents of lignin, α-cellulose and hemicellulose were determined. Fiber content in the composites was optimized with the extent of mechanical properties and composites with 10% arecanut leaf sheath fiber showed higher mechanical properties. Tensile strength (TS), Bending strength (BS), elongation at break (EB%), water absorption capacity, scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC) and biodegradation properties of arecanut leaf sheath/PP composites were investigated. ATR spectra of the polypropylene and composites were also analyzed.

Developed a silicon-based photodetector with high sensitivity integrated in the short range. The influence of gamma radiation on the mechanism of current flow in the structure type Schottky barrier, and the p-n junctions. It is shown that the double-barrier structure can improve the photoelectric parameters of conventional detectors.

In this article is considered the data of species composition of pathogens of skin and visceral leishmaniasis in the South of Kazakhstan. The research results are shown that the studies within the stationary conditions landscapes differ by all indications, determining the intensity of epizootic: contamination of great gerbils, the nature of mosquito species complexes and their abundance on promastigots infected mosquitoes. Considering the above, there is basis to assume existence on the studied by us territory of the independent natural centers or well shown morphological shares of the natural centers of zoonotic skin leishmaniasis which, most likely are dated for the certain studied landscape.

Iron aluminum alloy with composition of 30, 35 and 40 at % Al were prepared via powder metallurgy route: mechanical milling, consolidating, sintering. Solid solution Fe (Al) formed after several hours milling, and completely at around 10h from elemental powders. During sintering, phase transformation take place from solid solution Fe(Al) into intermetallic FeAl and carbon impurities from elemental powder lead to an in situ precipitation of κ-AlFe3C0.5 simultaneously. Mechanical properties were improving with higher Fe contents and higher sintering temperature with maximum hardness of 5.5 GPa and maximum yield stress of compression test of 700 MPa in the sample of 30 at %Al, 1 h sintering of 1300°C after 10 h milling. The mechanical properties of sintered samples will be discussed in term of microstructure, precipitate and phase formed after sintering.