Materials Science Forum Vol. 1074

Abstract: Nowadays, there is an ever-increasing demand for lightweight, robust, and low-cost materials. The desire for increasingly exotic and superior materials has become unavoidable as science progresses. The manufacturing industry is looking for more complex geometries. For example, composite materials are a sort of innovative material that blends the properties of its constituent materials. One of the most extensively used composite materials is metal matrix composites. Aluminium matrix composites are lightweight, high-performance structural and functional materials used in a variety of industries, including defense, aerospace, automotive, heating systems, and sports and entertainment. It is really good for the environment to use by-products from agricultural sectors, such as rice husk, as reinforcement with MMCs. The purpose of this research is to use powder metallurgy technology to build an aluminum-based composite with rice husk ash (RHA) and evaluate how its properties may be enhanced. Whereas metal casting can be used to fabricate composites, powder metallurgy is more cost-effective because it allows for the production of parts that are closer to net shape, and castings cool slowly from the liquid state, causing workability concerns as well as other restrictions such as segregation limitations. Good microstructure in the finished product is possible to obtain as powder particles are small and homogenous, resulting in improved mechanical properties. The experiment was conducted using an L27 orthogonal array with four different input parameters from prior studies: composition (wt.% of RHA), compaction pressure (CP), sintering temperatures (STE), and sintering time (ST). On the aluminium based composite, several mechanical tests, such as density and hardness, as well as tribological testing, such as the wear test, were conducted, with each test yielding noteworthy results. To satisfy the industry's needs, a comparison study was conducted.

Abstract: This work was focused on development of LM26 composites reinforced with Chromium Oxide particles by utilizing the technique of stir casting. Percentage of chromium oxide was varied between 0 to 10wt%. A study of the mechanical properties as well as microstructure of the developed composites had been performed. With the assistance of optical microscope, the microstructural studies of LM26 alloy as well as composites have been conducted. Investigations were carried out on the LM26 alloy as well as composites for properties such as tensile strength as well as hardness. Microstructure confirms that the chromium oxide particles' distribution has been uniform. The hardness of composites was found to higher than unreinforced alloy and increases over time as weight percentage increases of Chromium Oxide particles from 0% to 10%. For LM26/10% Chromium Oxide composite showed highest yield and tensile strength compared to other composites and unreinforced LM26 alloy. Keywords: Aluminium matrix composites, stir casting, Microstructure, Mechanical properties.

Abstract: In this work, the creep analysis of thick-walled rotating cylinder made of Aluminum Silicon Carbide under internal pressure has been investigated taking some assumptions, viz. no change in the volume of the cylinder, cylinder material is anisotropic, principal axes coincides with the axes of anisotropy, effective stress is dependent upon effective strain rate, and there is zero strain in the axial direction (Z direction in polar coordinate). Sherby’s law has been used to calculate the creep rate. After finding the formulas for radial, tangential and axial stresses for anisotropic cylinder, the findings have been validated by checking the values and comparing the graphs for an isotropic cylinder case with one of the already published research for isotropic cylinders with similar conditions. The graphs plotted in cases of anisotropic cylinder, enables us to conclude that despite large stress values in the radial and tangential directions, the creep rates in such cylinders were found to be approximately zero. This led to deduce that anisotropy is very helpful in designing long-lasting cylinders. In corollary, anisotropy helps in minimizing creep behaviour in radial and tangential directions.

Abstract: Among the various nanomaterials, Zinc Oxide (ZnO) has recently attracted the attention of researchers due to its potential application in various fields such as solar cells, bio-sensors, optoelectronic devices, gas sensors, water purification, piezoelectric devices, and liquid crystal displays. The accurate knowledge of the optical and structural properties of ZnO film is important for the fabrication of high-quality devices. In this work, 0.2M ZnO thin film was prepared by the economic spin coating technique. The Swanepoel method was employed to determine the average thickness and refractive index of the film with high accuracy in the spectral region of 200-1000 nm. The transmittance spectra were utilized to determine the absorption coefficient and extinction coefficients. The bandgap (E_g) was determined using Tauc’s formula and was found to be 3.22 eV. The real and imaginary parts of the dielectric decrease sharply with the wavelength. The single oscillator model was employed to discuss the dispersion parameters. The dispersion energy (E_d) and single-oscillator energy (E_o) were found to be 7.862 eV and 6.863 eV respectively with E_o≈ 2E_g proving the validity of the Swanepoel method for ZnO film. Structural analysis revealed that the film was polycrystalline in nature with a hexagonal wurtzite structure and an average crystallite size of ~31 nm with a Zn–O bond length of 1.9435 Å. The gas sensing properties in terms of the response of the ZnO sensor towards ethanol vapour were measured in the temperature range of 100–330 °C using DC electrical resistance. The ZnO film showed the maximum response of ~7 at temperature 260 °C for 800 ppm ethanol vapour exposure which may be due to the higher reaction rate at that temperature. The response of the sensor was increased on the exposure to a higher concentration of ethanol vapour. The sample showed a faster response on exposure to higher concentrations (400-800 ppm) of ethanol with a response time of ~13 s and a good response of 3.75 for 40 ppm of ethanol vapour exposure at 260 ^oC.

Abstract: This research aimed to study the effects of Ni content on melting behaviors and wettability of SnBiAgNi lead-free solder. Sn-58Bi-0.05Ag was used as the base solder, and Ni was then put in by 0.05, 0.10, 0.50 or 1.00 wt%. Solidus and liquidus temperatures of the solder alloys were examined to study melting behaviors. The Ni content changed the solidus and liquidus temperatures, and Sn-58Bi-0.05Ag-0.10Ni possessed the lowest solidus and liquidus temperatures. Sn-58Bi-0.05Ag-0.10Ni also provided the narrowest pasty range. Wettability of the solders on the copper substrate was expressed in terms of spread factor. The addition of Ni improved the wettability of the base solder, and Sn-58Bi-0.05Ag-0.10Ni provided the highest spread factor.

Abstract: This paper introduced an accurate empirical model for the thermal resistance of a single-finger AlGaN-GaN high electron mobility transistor (HEMT) on three different substrates including Sapphire, SiC and Si. The model reckons the constant thermal conductivity of GaN and substrate, thickness of host substrate layers, gate length (Lg) and width (Wg). The model plausibility is verified by comparing it with DC channel temperature measurement method and charge controlled based device modeling which agrees very favorable observation of the model data. Having nimble expression for the channel temperature is of inordinate importance in the field of designers of power device and monolithic microwave integrated circuits. Proposed model gives a variety of inquiries that would be impossible or impractical to do using time-consuming numerical simulations.

Abstract: This study presents a new model to estimate the compressive strength of masonry prisms considering both crashing and splitting failure mechanisms of the masonry prisms. The model is developed considering a probability of events by defining the resulted failure of the masonry prism as the main event. On the other hand, the different modes of failure including crushing of brick units, crushing of mortar under compression stresses and splitting of the brick units and mortar under bilateral stresses have defined as sub-events of the resulted failure. Eventuaaly, the developed model is verified against extensive results of experimental tests of masonry prisms that published by other researchers. A comparison is conducted between the estimated strength and the experimental results as well as those obtained from several available models in term of statistical measures. Comparison results reveal that the new proposed equation exhibits very good agreement with experimental results and shows the best accurate estimations with less deviations compared with the other available equations. The new proposed equation shows a mean value of the experimental to the estimated compressive strength of masonry equals to 1.01 ± 0.35 and a coefficient of variations equals to 35.12 %.

Abstract: This paper presents the test results of experimental study on unconfined compressive strength of natural rubber modified soil cement. In this study, the cement content, defined as ratio of dry cement weight to dry soil weight, ranged from 4 to 12 percent and the rubber-cement ratio, defined as ratio of natural liquid latex rubber weight to dry cement weight, ranged from 0 to 0.08. It can be observed that the unconfined compressive strength increased with increasing value of rubber-cement ratio for the specimens with cement content of 4 and 8 percent. However, a decrease in unconfined compressive strength with increasing rubber-cement ratio was observed in the specimens with cement content of 12 percent. The effect of rubber-cement ratio on strength was found to be significant at low value for both cases. It was also found that the unconfined compressive strength was increased with increasing cement content. A linear relationship was found for specimens without rubber content. It should be noted that a unique relationship was found for the specimens with rubber content.

Abstract: This work is aimed at uncovering the hidden value of waste cow bones towards their use as a sustainable biofiller for hot-mix asphalt (HMA) paving applications. To do so, the effect of various contents of calcined cow bone powder (e.g., 5, 10, and 15 wt. % CBP) on the AP-5 bitumen performance was investigated. Numerous lab techniques were adopted to assess the physicochemical attributes of finished filler-asphalt mastics, namely: elemental analysis, Fourier transform-infrared spectroscopy (FT-IR), thin-layer chromatography-flame ionization detection (TLC-FID), needle penetration, ring and ball softening point, Brookfield viscometer, and ductility. Iatroscan analysis revealed that the CBP treatment did not alter the saturates but induced an increase in the fractions of aromatics/asphaltenes and a decrease in the resins. The FT-IR scan highlighted that the CBP–binder interactions were mainly governed by physical mechanisms rather than chemical ones. The empirical methods showed that the CBP incorporation enhanced the stiffness/hardness, the consistency, as well as the high-temperature performance of bituminous mixtures. Overall, the use of waste cow bones as a green biofiller is viable and profitable, and it has the potential to reduce the environmental pollution caused by the livestock industry while also improving the performance of hot-asphalt mixes and extending the pavement life at a low cost.

Abstract: The present experimental study aims to contribute to the knowledge of the physical-mechanical properties of limestone blocks quarried in the Republic of Moldova. Apparent density, water absorption and compressive strength are examined based on laboratory work. The masonry material - limestone blocks are characterized both in comparison with other types of masonry materials and by comparing the compressive strength with other types of limestones. The analysed limestone samples were taken from 3 limestone quarries located in different areas on the territory of the Republic of Moldova. The results showed that limestone blocks from Moldova have better properties than AAC and some bricks. The materials used in the experimental work were selected to be representative of the mechanical characteristics present in old and existing buildings in Chisinau. This research is significant for the variation of the physical-mechanical properties of Moldovan limestone blocks compared to the same properties of other types of masonry blocks.