Applied Mechanics and Materials Vols. 548-549

Abstract: Pereskia Bleo is commonly used among the local traditional medicine practitioners to prevent or treat cancer by consuming the leaves either raw or taken as a concoction brewed from fresh leaves. However, more research, regulation and standardization are required before herbal medicines can be recommended as effective and safe therapies. The objectives of this study are to obtain the optimum drying parameter and to identify the concentrations of phenolic content expressed as gallic acid equivalents (GAEs) in Pereskia bleo leaves. Pareto ANOVA method was used to study the optimum condition and the total phenolic content via F-Test using three samples for variance and three-factor with replication. Taguchi ANOVA was performed using SN ratio with L9 orthogonal array to accommodate the three factor level. The drying time were tested for 3 hours, 4 hours and 5 hours. The result shows that drying time is the significant factor in drying process and followed by drying temperature and solvent volume used. The drying experiments were conducted at operating temperature of 35 °C, 40 °C and 45 °C. While the extraction were conducted at different volume using methanol of 150 ml, 180 ml and 200 ml. The standard curve of total phenolic content was based on the gallic acid compound. The total phenolic content in C2 was at the most suitable for being used as antioxidant for consumption in human body with drying time of 5 hours at 45 °C by using 180 ml of methanol for extraction of P.bleo leaves.

Abstract: Cement strength must be carefully maintained so that the cement is able to sustain formation stresses without failing. Such a mechanical failure in a cement sheath can cause a loss of annular isolation. A synthetic polymer cement retarder has been designed to provide extended pumping times for cement slurries, while having minimal effect on compressive strength development. However, it is difficult to select a retarder that can suit a wide range of field conditions. Fluid loss control can also be affected by the addition of a retarder, especially at high temperatures. Addition of retarder sometimes may increase the viscosity and pumping pressure of the slurry and may result in fracturing of the hydrocarbon bearing zone and costly job failure. The main idea for this study is to determine whether Agarwood waste from distillation process (AGW) can be used as a retarder in oil well cement with excellent compressive strength development. The compressive strength developments were evaluated at different curing time and particle sizes of AGW which are 90 μm, 150μm and 250μm. The performance of AGW slurries were compared with commercial retarder slurry. Apart from that, chemical analysis on AGW was conducted by using X-ray Fluorescent (XRF) to determine the presence of cementations component in this material. All cement testing procedures should follow API recommended specification 10B standard. From the results obtained, the performance of 250 μm of AGW is better than commercial retarder by 10% increment in the development of cement strength.

Abstract: Reliable quantification techniques for graphene oxide (GO) and graphene nanosheets (GNs) in ESD rubber product are limited. We demonstrated an effective ultrasonically−assisted latex mixing (ULM) technique for dispersion of GO and GNs at low concentration (0.5, 1.0 and 1.5 part per hundred of rubber; phr) in natural rubber latex (NRL) to produce NR/GO and NR/GNs conductive thin film. The filled−NR composites were prepared by ULM, followed by latex dipping coagulation. The morphologies from transmittance electron microscopy (TEM) of stabilized GO and GNs dispersion showed successfully dispersion and exfoliation in NR matrix. Compared to pure NR, the tensile strengths of NR/GO and NR/GNs (1.5 phr) increased by ~58% and ~32%, respectively, while there were decreased in the %elongation at break and were no significant change in the force at break. In case of studying the electrical properties, sheet resistances of filled−NR composites declined with the incorporation of GO and GNs. However, the NR composite with 1.5 phr of GNs showed the best conductivity.

Abstract: Pulverized fuel ash (PFA) can be classified as hazardous Coal Combustion by-Product (CCP), which can contributes to the environmental pollution. According to (ACAA 2009), USA itself has produced approximately 125.5 million tons per annual of CCP which merely 56 million tons of these waste by-products has been successfully employed in applications and others still remain untreated. Disposal of these materials in landfills can deduce ecological. Thus, finding the solutions and methods of recycling these waste materials are needed, as it can be used as one of the materials in construction projects, engineering purpose or stabilizing process. Therefore, a study on direct shear test have been conducted and the data collected from this study were compared and analyzed through various methods to find out how does PFA works on improving geotechnical properties.

Abstract: This study investigates the synergistic effect of combining multi-walled carbon nanotubes (MWNTs) and Fe₂O₃ nanoparticles on thermal conductivity of nanofluid. Results show that low percentage hybrid fillers loading improve thermal conductivity of water based nanofluid, due to the good dispersion and interfacial adhesion, which is confirmed by scanning electron microscope. Furthermore, the hybrid fillers provide synergistic effect on heat conductive networks. The thermal conductivity enhancement of water based nanofluid containing 0.05 wt % MWNTs and 0.02 wt % Fe₂O₃ nanoparticles is 27.75%, which is higher than that of nanofluid containing 0.2 wt % single MWNTs or Fe₂O₃ nanoparticles.

Abstract: In this work, properties of Nd³⁺ in Gd₂O₃-CaO-SiO₂-B₂O₃ glass systems with composition 25Gd₂O₃-10CaO-10SiO₂-(55-x)B₂O₃-xNd₂O₃ where x = 0.0, 0.5, 1.0, 1.5, 2.0 and 2.5 mol% were investigated. The optical absorption spectra show peaks at ⁴F_3/2 (877 nm) , ⁴F_5/2+²H_9/2 (802 nm), ⁴F_7/2+⁴S_3/2 (743 nm), ⁴F_9/2 (682 nm), ²H_11/2 (627 nm), ²G_7/2 +⁴G_5/2 (582 nm), ⁴G_7/2 +²K_13/2 (527 nm), ⁴G_11/2 (481 nm), ²P_1/2 (427 nm) and ²L_15/2 + ⁴D_1/2 + ¹I_11/2+ ⁴D_5/2+ ⁴D_3/2 (355 nm) reflecting the Nd³⁺ ions in glass matrices. The densities were increased with increasing of Nd₂O₃ concentration. This indicates the increase of the molecular weight by the replacement of B₂O₃ with a heavier Nd₂O₃ oxide in the glass. The upconversion luminescence spectra show bands at 393 nm for all Nd₂O₃ concentration and the strongest intensity from 2.5 % mol of Nd₂O₃ was obtained. For NIR luminescence, the intensity of Nd³⁺ emission spectra increases with increasing concentrations of Nd³⁺ up to 1.5 mol% and beyond 1.5 mol% the concentration quenching is observed.

Abstract: Lignin was obtained from black liquor of papermaking by the acid to separation, and carbonized after loading various amounts of nickel and calcium or nickel alone. The influences of the temperature, amount of nickel and amount of calcium on the crystallized size (Lc) and the electromagnetic shielding (EMS) capacities in the range of 50~800 MHz for the chars from lignin were investigated. The results showed that Lc and EMS capacities in the entire of frequency of the chars with 6wt% calcium increased with increasing amount of the nickel loaded and also increased with increasing carbonization temperature from 700 to 900°C. Some amounts of calcium significantly enhanced the formation of crystallized carbon. Lc and EMS capacities of the chars with loaded 8wt% nickel increased with increasing amount of calcium and then decreased. It was founded that chars of lignin with co-loading of 8wt% nickel and 6wt% calcium were suitable as EMS materials with exceeding a practical standard of EMS capacity (30dB) in the range of 50~800 MHz.

Abstract: Selective Laser Sintering (SLS) or Laser Sintering (LS) allows functional parts to be produced in a wide range of powdered materials using a dedicated machine, and is thus gaining popularity within the field of Rapid Prototyping (RP). One of the advantages of employing LS is that the loose powder of the building chamber can be recycled. The properties of polymer powder significantly influence the melt viscosity and sintering mechanism during Laser Sintering (LS) processes which results in a good surface finish. The objective of this research is to investigate the chemical composition of fresh polymer materials used in Laser Sintering. There are seven virgin SLS materials which are PA2200, GF3200, Alumide, PrimeCast, PrimePart, Duraflex and CastForm. Fourier Transform Infrared Spectroscopy (FTIR) was used to analyze the chemical composition of the materials by using infrared radiation and absorbed frequency. The spectra show that similar functional groups were found in the materials apart from PrimePart and Duraflex. Obtained data from this analysis could be used to investigate on how the fresh and recycled powder materials with different chemical properties would affect the part surface finish.

Abstract: Micromagnetic simulation enabled us to fully characterize the nucleation and growth of buried domain walls in a layered hard/soft/hard ferromagnetic thin film. Simulation results show that the exchange spring trilayer exhibits a spiral spin magnetic structure and reveals detailed features of field-dependent domain walls evolution.

Abstract: Powder metallurgy method was used to prepare copper alloy nanocomposites (CuCrZr/AlN) with high strength and conductivity. The morphologies and structures of the CuCrZr/AlN nanocomposites were analyzed using scanning electronic microscope (SEM) and transmission electronic microscope (TEM). The impact of aging treatment on mechanical properties of CuCrZr/AlN nanocomposites was studied. The result showed that dislocation density of the sample decreased and the solid solution atoms precipitated after aging treatment. The micro-hardness of the sample decreased and Brinell hardness increased after aging treatment.