Abstract: Chemical synthesis is cheap and easy to be tailored. Reduction of graphite oxide to form graphene nanosheets is a necessary step that determines yield, quality, chemical and surface properties of graphene nanosheets. In this report, the reduction of graphite oxides by chemical and thermal methods has been employed to convert graphite oxide synthesized by the same wet chemical method using KMnO4 and H2O2. The characterization results from the two reduction methods indicate that a combination of wet oxidation of graphite and thermal reduction method is an efficient and environmental friendly way to produce graphene.
Abstract: Coal fly ash is a complex mixture of anthropogenic materials produced during the combustion of pulverised coal in coal fired power plants. They pose environmental concerns that lead to air and water pollution. Effort has been done to reduce the production of coal fly ash or to extract potentially valuable products from coal fly ash, such as cenospheres. Cenospheres are light, low density, thin-walled hollow ceramic microsphere with unique properties. Conventional cenosphere production methods involve the separation of cenospheres from coal fly ash. Due to its small quantities in fly ash (1 % wt.), separation process results in low production of cenospheres. In this work, an attempt by applying a vertical thermal flame (VTF) process is done to produce cenospheres from coal fly ash. Particle size of coal fly ash 63 to 90 μm and 90 to 126 μm are selected to undergo the VTF process. Effect of size of precursor, number of passes through the thermal process, density, morphology and particles size of generated spheres are evaluated. The results show that different sizes of coal fly ash and number of passes through the VTF process affect the morphology of obtained spheres and the overall real density. Further optimization of the VTF process design in terms of heat source and the feeding mechanism are required to increase the transformation of coal fly ash to cenospheres.
Abstract: Composite nanofibers of polyvinylpyrrolidone (PVP) and Garcinia mangostana L. extract (GME) have been synthesized through electrospinning method for application in drug delivery systems. The precursor solution of 10 mL PVP 10% w/w and GME 2% w/w was then electrospun collected at the rotating collector at the following optimum parameters: a voltage of 15 kV, a collector-nozzle distance of 12 cm, and a flow rate of 1 mL/hour. SEM images showed that the average diameters were 476 nm and 690 nm for the PVP and PVP-GME composite nanofibers, respectively. To some degree, the addition of GME into PVP nanofibers increased the average diameter size of nanofibers. Moreover, the release studies, it was shown that 80% of the GME was released within 30 minutes. Therefore, the PVP-GME composite nanofibers can be applied as the drug delivery systems.
Abstract: Ab initio density functional theory employed to study the adsorption of hydrogen and nitrogen gas molecule on the α-Fe2O3 (111) surface for ammonia synthesis. The calculated adsorption energy is-4.70kcal/mol, -4.60kcal/mol,-4.38kcal/mol and-3.77kcal/mol for different orientations of adsorbed gas molecules and shows that system is stable and gas molecules have adsorbed. It can also be seen with adsorption of gas molecules the net spin of hematite enhanced from 0 to 2 hence confirms the activity of hematite surface. Hematite nanowires synthesized by oxidation method. Raman spectrum analyses demonstrates that the nanowires are single-crystalline. Field Emission Scanning Electron Microscopy (FESEM) reveals that the nanowires have lengths of 10-25 μm. The magnetic saturation of the nanowires is 15.6 emu/g investigated by vibrating sample magnetometer (VSM). Ammonia was synthesized by magnetic induction method using the hematite nanowires as catlyst and quantified by Kjeldahl method. It is found that the role of gases adsorption was able to enhance catalytic activity of hematite nanowires for the ammonia synthesis. This green synthesis method could be a contender to the Haber-Bosch process currently used by the industry.
Abstract: In this study, AISI 1020 plate of 6 mm thickness has been welded by autogenous TIG welding process maintaining different root gap (0, 0.5, 0.75 and 1 mm). The weld bead profile and the tensile strength of the welded joint has been analysed. From the experimental results it is revealed that, for increasing the root gap, weld depth penetration increases; whereas weld bead width and heat affected zone (HAZ) is almost uniform. However, at the similar condition, under-filling of the weld joint increases with the increase in root gap. For using 1 mm root gap, weld joint exhibit full depth of penetration and maximum tensile strength, along with higher under-filling.
Abstract: The microstructure of non-combustible magnesium alloy, AMX602, was modified by friction stir processing (FSP) at the tool rotational speed of 800 rpm and traveling speed of 300 mm/min. In the microstructure of the as-extruded material, some intermetallic compounds (IMCs), Al2Ca and Al-Mn, inhomogeneously distributed in the matrix. The inhomogeneity was dependent on the extruding condition. The largest size of IMCs was a few tens microns. By FSP, large IMCs were broken up, and fine IMCs were uniformly dispersed in the matrix. Furthermore, grain refinement occurred due to dynamic recrystallization.
Abstract: The demand for new materials that provide excellent structural performance while reducing weight and being cost-effectively manufactured is increasing. For applications with high strength requirements, ultra-high strength steels (UHSS) have been widely used. However, with such a high strength level, UHSS are very sensitive to the hydrogen that could be ease by the tempering process. In this research, the correlation of hydrogen and tempering process on commercial UHSS 15B30 has been studied. Results show that the tensile strength (TS) of as-quenched 15B30 is about 1900MPa. After tempering treatment of the quenched 15B30, the TS decreases from 1600MPa to 1200MPa with tempering temperature increased from 200°C to 400°C. The 15B30 specimens, being subjected to hydrogen charge, exhibit the dramatic reduction of mechanical strengths.
Abstract: In past few decades, a lot of research has been done in the field of machining to improve the quality of machined surface. Out of these machining operations, drilling is widely used in the areas of marine and aerospace for assembly requirements. Titanium alloy Ti-6Al-4V, owing to its vast applications, is regarded as an important material for these industries. Ti-6Al-4V is categorized as difficult to machine material. Based on above stated facts, an experimental study was conducted on the dry drilling of Ti-6Al-4V. The objective of this study was to establish the correlations between drilling parameters such as feed rate and spindle speed, and quality of machined surface which is evaluated in terms of drill hole diameter deviation, exit burr height and surface roughness.
Abstract: The bimetallic welds (BMWs) between ferritic low alloy steels and austenitic stainless steel are used widely in steam generators of the power plants. The adoption of these welds in wide industrial applications provides feasible solutions for the flexible design of the products by using each material efficiently and economically. The present paper is an effort towards studying the development of austenitic stainless steel buttering filler material for bimetallic weld joint. The work aims at the design and development of buttering layer electrode coatings for shielded metal arc welding process using extreme vertices design methodology suggested by McLean and Anderson to study the effect of electrode coating ingredients on the buttering layer metal composition and delta ferrite content to prevent solidification cracking.