Advanced Materials Research Vol. 795

Abstract: Leaching plays an important role in the recovery of rare earth elements. A study on optimizing the relevant parameters such agitation, leaching time and temperature in the dissolution of these elements in HCl, H₂SO₄ and HNO₃ acids were carried out. The recovery of the rare earths is much depended upon the type of acid used in the leaching system. The H₂SO₄ system shows the highest leached with a rate of 82% while the leaching rate recorded for HCl and HNO₃ system were lower at 67% and 59% respectively. Comparative rate of leaching study was also done on the light and heavy rare earths for the three different acid leaching systems and the result shows that the light group has a better rate of leaching than the heavy group.

Abstract: Ceramic foam is a class of highly porous materials that are used for wide range of technological applications, specifically as absorbents and membrane for wastewater treatment process. Among the potential materials include silicon carbide (SiC), alumina (Al₂O₃), zirconia (ZrO₂), titania (TiO₂), and silica (SiO₂). The review clarifies on the broad types of ceramic foam, and the common techniques of foam fabrication, such as polymeric sponge method, starch consolidation, direct foaming, and gel-casting of foam. The parameters of each fabrication techniques will be discussed crucial based on the new research findings in the field of ceramic foam.

Abstract: The impact of nanofiller surface modifications and hydrophobicity on the morphology and mechanical properties of the biomedical TPU nanocomposites was studied. We show that incorporating nanofillers with higher hydrophobicity promotes better dispersion of nanofiller in TPU matrix due to greater interaction between the nanofiller and the hydrophobic PDMS soft segment in this ElastEon TPU system. The nanocomposite with the most hydrophobic surface modification demonstrates the best nanofiller dispersion and intercalation and hence resulted in an overall best mechanical and thermomechanical properties when incorporated in 2 wt%. These findings show that the polarity matching between the TPU and the nanofiller determines the nanofiller-TPU interactions and thus the mechanical properties of the produced nanocomposites.

Abstract: The aim of this study is to determine the influence of rice husk ash (RHA) on the engineering properties of fired-clay brick with the present of 10% sand. Temperature 1200°C is selected as the optimum temperature based on the preliminaries study. X-ray Diffraction (XRD) and X-Ray Fluorescence (XRF), were carried out to determine the characteristic of raw materials used. Mechanical properties of rice husk ash-clay bricks are determined in terms of compressive strength, porosity and water absorption. The results shows that increase in RHA replacement percentage reduce the compressive strength and linear shrinkage of fired-clay bricks while the porosity and water absorption value increase. From the investigation, we can conclude that the optimum mixing ratio for fired-clay brick containing RHA is 15% because it complied with the minimum requirement for building material in term of strength and water absorption.

Abstract: We investigated the structural, optoelectronic and antibacterial properties of two commercial ZnO powder namely White (rubber grade) and Pharma (pharmaceutical grade) in order to study the correlation between the structural-optical property and the antibacterial efficacy. Transmission electron microscopy (TEM) micrographs showed rod-like morphology for the Pharma specimen and grainular shape for the White sample. X-ray diffractometry (XRD) results confirmed the superior crystallinity of the Pharma powder and photoluminescence (PL) data also showed higher UV photocatalysis of the Pharma powder if compared to that of White powder. Using the broth macrodilution method to determine the antibacterial activity of ZnO specimens, we discovered the Pharma grade exhibited stronger inhibition (80-98%) on the growth of Escherichia Coli (E. coli) especially for the ZnO suspension concentration of 10-20 mM. We believe that the superior crystallinity and stronger photocatalysis of the rod-like Pharma powder could have generated much more reactive oxygen species (OH^-, H₂O₂ and O₂^2-) than that of White sample resulting in the higher growth inhibition of E.coli. This work also highlights the impact of rod-like primary particles of Pharma powder in exhibiting good antibacterial efficacy if compared to the grainular particles of White powder and this observation justifies the usage of ZnO Pharma powder in pharmaceutical and healthcare products.

Abstract: Thermal barrier coating has proven to be effective in improving the thermal efficiency and initiation of an effective cooling system of the engine. In the present work the engine piston crown was plasma coated with 150μm thicknss of catalytic ceramic material Alumina-Titanium oxide (Al₂O₃-TiO₂) over a 60μm thickness of NiCrAl bond coat. Available literature on this topic suggest that the particular effect of TiO₂ on the over all thermal barrier characteristics have not been established clearly. It was therefore felt that the effect of weight percentage of TiO₂ in the Al₂O₃-TiO₂, might influence the performance and emission characteristics of the engine. The TiO₂ weight % has been tested at 10% and 15% levels. The engine used was four strokes, single cylinder direct injected diesel engine. The engine was tested with diesel & at 30% Honge bio-diesel with diesel and the results obtained clearly indicate that the specific fuel consumption, CO & HC emissions have come down by increasing the weight % of TiO₂.

Abstract: High chemical corrosion, low manufacturing cost and light of total mass of bipolar plate in Proton Exchange Membrane Fuel Cell (PEMFC) lead most of the PEMFCs researchers over the world attracted their interest to replace pure graphite or metal based bipolar plate with conductive polymer composites (CPCs) bipolar plate. CPCs is fabricate from the mixed of conductive fillers such as and Graphite (G) andCarbon Black (CB) had been incorporated in Polypropylene (PP) matrix for fabrication of electrical conductive polymer composite plate. Most researchers reported only at high loading of fillers (more than 90 wt.%), are gave electrical conductivity above 100 S/cm, which is target from Department of Energy (USA). Higher loading of fillers cause change in rheological properties and increase the difficulties in polymer processing. Thus will decreasing the electrical and mechanical properties of CPCs as bipolar plate. Therefore, in this study carbon nanotubes (CNTs) which have 1000 time electrical conductivity than copper wire are introduced into G/CB/PP composite to compensate above problems. But the main problems of CNTs, at high loading it tend to agglomerate and thus will affect the properties of CPCs. So that, small amount of CNTs which is 0.2, 0.4, 0.6 and 0.8 wt.% will be added into G/CB/PP composite. But weight percentage of CB and PP has been fixed which is 25 wt.% and 20 wt.% respectively and the weight percentage of G will various from 55 wt.% to 54.2 wt.% according to CNTs loading. The result shows that the G/CB/CNTs/PP composite with 0.2 wt% CNTs has the higher electrical conductivity 295.78 S/cm.

Abstract: The stress and lattice constants in zinc oxide (ZnO) nanoparticles play a major role in determining the distortions that occur in the crystal during the preparation of the sample as a result of exposure to several factors, such as external strain, temperature, pressing, and structural defects (oxygen vacancies and zinc/oxygen interstitials). 20 nm zinc oxide nanoparticles were used to make high-density ZnO discs doped with Bi₂O₃ and Mn₂O₃ via uniaxial pressing at 4 ton/cm² and sintering at 1200 °C for 1 h. Structural, elemental, and optical characterizations were then performed on the samples using various techniques. High-oxygen thermal annealing significantly affected the varistor, particularly in enhancing the growth of the grain even at a low annealing temperature (400 °C). The strong solid-state reaction during annealing may be attributed to the high surface area of the 20 nm ZnO nanoparticles that exhibited a strong surface reaction even at low annealing temperatures. The annealing treatment also improved the grain crystallinity, as shown by the transition of the intrinsic compressive stress to tensile stress based on the XRD lattice constant and full-width at half-maximum data. Therefore, high-oxygen thermal annealing can be used as a new technique in controlling the stress in ZnO nanoparticle-Bi₂O₃-Mn₂O₃ based varistors with improved structural and optical properties.

Abstract: The main source for lubricant oils is mineral oils, but the source of mineral oils are depleting from day to day and it is also a major cause for environmental pollution in the world. This aim of research is to introduce vegetable oil as an alternative source of lubricant oil in industrial applications. In this study, we measured the physical properties of Jatropha, palm fatty acid distillate (PFAD) and empty fruit bunches. All experiment were done according to the American Society for Testing and Materials (ASTM) condition, method B and with the use of four-ball tribotester, CCD camera, microscope and viscometer to obtain results. The test oils were measured of their coefficient of friction, wear, viscosity and flash temperature parameter. To evaluate the results, the same conditions were applied for all experiments with the use of engine and hydraulic mineral oil. The results showed that the anti-friction ability of Jatropha oil and PFAD was higher than the engine and hydraulic mineral oils.