Procedia Materials Science最新文献

In order to improve adsorptive properties and provide a viable alternative to humidity control techniques, the desiccants can be modified with chemical aggregates such as calcium chloride (CaCl₂), the latter often used as dehydrating due to its hygroscopicity and low cost. Its use as a drying agent has disadvantages because of its particles form a liquid film. However, the CaCl₂ may be mixed with other materials for preparing desiccant products. In this work we studied, at 298 K and different relative humidities (RH), the adsorption processes of desiccants mixtures composed of a bentonite clay Argentinian and CaCl₂. The results showed a better performance of the desiccant mixture with respect to natural clay in the whole HR working range. It was also observed that addition of CaCl₂ favors adsorptive properties with respect to a purification treatment.

In recent years, addition of rare earth elements such as Zr, Y and Hf to pack diffused aluminide coatings has been studied and practiced aiming to improve high temperature oxidation resistance of the coatings. In this work cementation packs containing ZrOCl₂.8H₂O as the activator and source of zirconium as well as mechanically alloyed 30% Al -Cr compound as the source of aluminum plus alumina as filler material were used to produce zirconium doped aluminide coatings. The cyclic oxidation of the coatings was measured at 1100 °C and each cycle was consisted of one hour heating in furnace and 10 minutes cooling in the air.

The results showed that the Zr modified aluminide coatings provide a better resistance against high temperature oxidation and the highest resistance belonged to the coating that was achieved by 5 hours diffusion process in a pack that contained 2% activator.

The purpose of this paper is to use software package ATK-SE package, in combination with virtual Nano-Lab (VNL), can be used to investigate a Nano-scale transistor. For the transistor structure we will use a graphene junction device, where ATK is used to investigate the properties of a similar system. The effect of various parameters on the structure of graphene Nano-ribbon checked. It consists of 3 regions and forms a metal-semiconductor-metal junction. By applying a gate potential to the central region, the system can function as a field effect transistor, which is able to calculate properties, Transmission spectrum, Temperature dependent conductance, Conductance and Current as function of gate potential and temperature. So in this paper, the device design and simulation parameters are associated with improved performance.

The antimicrobial activity of silver nanoparticles makes this chemical element attractive for their incorporation in different materials. Additionally, heteropolyacids (HPAs) have advantages as catalysts which make them environmentally very interesting. The objective of this work is to incorporate in a silica matrix obtained by sol-gel an HPA together with Ag, for their use as fillers in paints or adhesives. Six samples were synthesized, using tetraethoxysilane, methyltrimethoxysilane, acetic acid, molybdophosphoric acid and silver acetate. The silicas were characterized by potentiometric titration, XRD, SEM, TEM, S_BET and FT-IR. When HPA is used instead of acetic acid, a variation on the final acidity is produced. The specific surface area decreases when HPA is incorporated into the silica synthesized using tetraethoxysilane as precursor, noticing a slight increase when Ag is added because a different distribution of HPA in the matrix. By SEM, it was observed that the particle size is bigger when the silicas are synthesized with TEOS-HPA, but it still shows the characteristic morphology of bulk silica. Additionally, preliminary test to evaluate the antimicrobial properties of the solids were carried out with fungi as Chaetomium globosum and Alternaria alternate, isolated from contaminated paints, and the first results are encouraging to continue with the development of these materials.

In the last 50 years in the worldwide market for power transmission cables, there has been a tendency to replace aluminium cables electrical grade (EC) with steel cables by fully aluminium alloy (AAAC). The advantage in using cable AAAC is mainly economic (least amount of support structures and maintenance), addition to the elimination of the problems of galvanic corrosion and improved abrasion resistance. In order to obtain better mechanical properties, respect to the pure aluminium, aluminium alloyed with magnesium and silicon (AA6XXX series) is used, which by a combination of cold working and heat treatment allows obtaining greater mechanical strength without affecting too much the electrical conductivity. In this development it has worked with AA6101/6101 M alloy. The manufacturing of aluminium alloy wire rods for such applications, using the conventional process Properzi, requires heat treatment of solubilized, continuous or discontinuous (batch). During the waiting time of two months or more, the wire coils are exposed to natural aging at room temperature, entering into the wiredrawing machines with different mechanical properties. The wires obtained by the traditional method of manufacture in Argentina, through the wiredrawing, result in significantly higher mechanical properties, not complying with the standards. Furthermore many breaks occur mainly when a high tensile strength wire is processed for wire 2 mm in diameter or less. In the proposed method, a part of the initial wiredrawing is replaced by cold rolling and a subsequent partial aging. The results obtained in this study allow us to conclude that in the proposed process better properties and mechanical integrity are achieved than the traditional process, maintaining the electrical conductivity.

Synthesis of nanoparticles and ultrafine particles of zinc oxide with controlled morphology using microwave irradiation is carried out by various methods. The effect of type of precursor as well as the time and the microwave irradiation power on the structure and size of ZnO nanoparticles have been studied. Particles Studied by SEM, TEM images and XRD analyze. By increasing the time of synthesis from 10 to 15 minutes needle-shaped particles with a diameter of 50-150 nm can be achieved. While increasing the microwave power from 540 to 680 watts, flower-shaped particles are obtained. By replacing zinc nitrate with zinc acetate, at different power and time of irradiation, needle-shaped particles are obtained and diameter of needles is decreased.

In this paper, details on the techniques used towards analyzing the acoustic signals generated by Red Palm Weevil RPW are presented. Besides, the acoustic signals generated by RPW in the palm and in the laboratory have been taken for this analysis. This paper describes in detail the great significance pertaining to the analysis of acoustic signals of red palm weevil recorded. The spectrum obtained for RPW is stored for analysis. The frequency in Hz and sound level in dB for both signals are determined. The frequencies are also of low range. Adequate number of spectrum has been displayed for easy understanding. Movement of RPW signal could not be compared with that of the eating and biting signature since no evenness existed for evaluation.

In the present work, we carried out a systematic study of structure, UV-Vis Spectra and surface conductivity of pure Bi₂Te₃, pure Polyaniline (PANI) and Bi₂Te₃ (5%)-PANI (95%) composite. Bi₂Te₃ was synthesized by a method similar to solvothermal method, whereas, pure PANI and Bi₂Te₃-PANI composite were synthesized by a chemical oxidative method. The materials were structurally characterized and the electrical properties were investigated in the temperature range from room temperature to 100 °C. The electrical conductivity of the Bi₂Te₃-PANI composite is found to be higher than that of its pure constituents at all the temperatures. The enhancement in the surface conductivity may be due to the PANI generated ordered molecular arrangement of Bi₂Te₃ in the Bi₂Te₃-PANI composite, as confirmed from powder x-ray diffraction, UV–vis spectral analysis.

A new photoluminescence material cadmium [(1,10-phenanthroline)(8-hydroxyquinoline)] Cd(Phen)q has been synthesized and characterized. The prepared material Cd(Phen)q was characterized by Fourier-infrared spectroscopy(FTIR),Nuclear magnetic resonance spectroscopy (NMR),Thermo gravimetric analysis (TGA), UV-visible spectroscopy and photoluminescence (PL). Solution of this material Cd(Phen)q in toluene showed absorption maxima at 256 nm and 295 nm which may be attributed to the moderate energy (π – π*) transitions of the aromatic rings while absorption maxima at 335 nm and 387 nm observed were due to the coordination of cadmium and organic ligands (Phen and q). The photoluminescence spectrum of Cd(Phen)q in toluene solution showed peak at 510 nm. This material is thermally stable up to 400⁰C. The time resolved photoluminescence spectra of this material Cd(Phen)q showed two life time components, 3.8 ns and 15 ns respectively.

In this paper the fault diagnosis of multiple faults in linear circuits is studied for distortion analysis for 2nd and 3rd harmonic components by considering a state variable filter circuit. To study the testability of the circuit the distortion analysis is plotted for various fault conditions. The sensitivity of the output signal with respect to the faults along with pole-zero analysis is obtained. The transfer function of the state variable filter considered for the analysis is given by: