Solid State Phenomena Vol. 317

Abstract: In the present work, Cr-Al₂O₃ nanocomposite coatings were electrodeposited onto a copper substrate using a modified trivalent chromium electroplating bath with the addition of 80nm Al₂O₃ powder. The effects of mechanical agitation of electrodeposition bath on Al₂O₃ particles dispersion and particles embedment were studied. The Cr-Al₂O₃ nanocomposite samples were subjected to different tests to characterize their surface morphology, crystalline structure, and mechanical properties. The crystalline structure, composition and surface morphology of the deposits were studied by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and field emission scanning electron microscopy (FESEM). The corrosion resistance test was carried out by electrochemical polarization method. The microhardness was studied via Vickers Microhardness Test. The variation in the microhardness as a main property to achieve enhancement of Al₂O₃ incorporations with Cr matrix. From the EDX analysis, Cr-Al₂O₃ nanocomposite deposited at 200 rpm stirring speed showed the highest weight percentage (wt%) of alumina. The hardness results showed the Cr-Al₂O₃ composite coating has the best performance at 200 rpm stirring speed which the hardness increased 32.3 % compared to that of Cr coating. The corrosion current density (i_corr) of Cr-Al₂O₃ coating achieved highest value at 200 rpm. This result revealed that the corrosion resistance of Cr-Al₂O₃ coating decreases with increasing Al₂O₃ particles content.

Abstract: Tempcore process considers the widest process that is being used in the production of reinforced steel rebar. The normal tempcore process is fundamentally dependent on the amount of latent heat in the core of the steel rebar, and the cooling rate of the rebar cross-section. Cooled water box and the cooling bed have a powerful effect on the cooling rate of the steel rebar. This research has been designed to monitor the continuous cooling transformation CCT diagram of steel rebar with different two contents of residual elements. Moreover, the effect of the cooling bed’s conditions has been simulated to identify the effect of cooling rate at the cooling bed step on the microstructure, as well as the hardness value of the produced steel rebar. It was found that the cooling rate at the cooling bed step has a great powerful effect on the produced steel rebar in term of bainite phase increment, and the hardness value as well.

Abstract: This study discussed the effect of blast exposure distance of lead-free solder on micromechanical properties. Sn-Ag-Cu solder samples were exposed to 1000 g of Plastic Explosive. The soldered samples were placed at a distance of 1 m, 2 m and 4 m distance from the blast source. In order to study micromechanical properties in localized and more details, the nanoindentation approach was used. The indentation was performed at the center of the solder to examine the hardness and reduced modulus properties. The load-depth curve of indentation for 1 m distance from the blast source has apparent the discontinuity during loading as compared to the control sample. The hardness value increased as the distance from the blast source increased. The shortest distance from the blast source gives a high impact on the degradation of hardness properties as compared to others. This result is important in assessing the effect of exposure distance from the blast source.

Abstract: Peat is commonly described as a soil that is possess to high rate of compressibility due to present of high organic substance derived from plant origins. Peat soil naturally associated with settlement and consolidation characterized by its high initial void ratio, organic content and water holding capacity. This paper presents the performance of peat soil treated with powdered melamine urea formaldehyde resin (MUF-P) in term of compression and consolidation behaviour under standard compressibility test. In this study, series of one-dimensional oedometer test were carried out with the load increment method from 12.5 to 400 kPa after 24 hours of each loading. Peat soils under high moisture condition were mixed with MUF-P within 3 days of stipulated periods of curing times. The results indicate that increasing the MUF-P proportion has improved the compressibility characteristics of peat soil. The result shows the values of compression index (C_c) decreased from 4.12 to 0.9, and secondary compression index (C_α) were also decreased from the range of 0.026 to 0.320 to the range of 0.080 to 0.161 with the increase of peat MUF-P proportions up to maximum 350 kg/m³.

Abstract: Electronic packaging is the technology concerning to the establishment of electrical interconnections and it is a major discipline within the field of electronics engineering. Packaging of an electronics system should considered the protection from mechanical damage, cooling, radio frequency noise emission and protection from electrostatic charge. Solder alloys have been extensively used as interconnection materials for microelectronic package. Solder joint in radiation environment requires higher reliability and resistance to any damage caused by ionizing radiation. The electrical failure during radiation has proved that the reliability of solder joint is importance and sensitive to the service condition. In this study, a lead-free solder alloy, SAC305 (96.5Sn3.0Ag0.5Cu wt.%) were prepared into two batches, which are unirradiated and irradiated batches with the various doses 5, 50, 500 Gy of gamma radiation. Nanoindentation was used in order to investigate the effect of the radiation to micromechanical properties such as hardness, H and reduced modulus, E of the solder. The results showed that the SAC solder changed when exposed to gamma rays. The hardness of the specimens calculated from the nanoindentation were decreased to 195.4 from 279.6 MPa with the increasing of radiation dose. These values of hardness are also lower than the hardness of non-irradiated sample indicating possible radiation damage and needs further related atomic dislocation study. The reduced modulus for irradiated specimens significantly increased as well, with values from 25.6 to 123.9 GPa after exposure. The increment of the reduced modulus occurred as a result of strain hardening or softening of the solder.

Abstract: The search for clean energy conversion technologies promotes the study of thermoelectric materials. In this paper, the electronic structure and thermoelectric properties of CaMnO₃ doped with 17% V using first principles calculations and semi-classic Boltzmann theory on Ca site as well as Mn sites. The G-type AFM magnetic ordering is most stable among four types of magnetic ordering for CaMnO₃ and V doped CaMnO₃ a Mn site while FM ordering was found for V doped CaMnO₃ at Ca site. The calculated partial density of states plot shows half metallic and metallic behavior for V doped at A site and B site respectively. Thermoelectric property calculations show that the magnitude of Seebeck coefficient decreased with V doping at both sites with V doping at Mn sites has the lowest magnitude of Seebeck coefficient. All samples show the negative Seebeck coefficient indicating n type behavior. The magnitude of conductivity increases with V doping with the highest magnitude belong to V doped at Mn site. The magnitude of thermal conductivity also increased with V doping at Mn site, but shows a reduction for V doping at Ca site. The figure of merit (ZT) for V doping at Ca site shows a significant improvement over intrinsic CaMnO₃ at 0.14 at 1000 K. However, V doping at Mn site sample shows a reduction of ZT at 0.0028 for CaMnO₃ at 1000 K which is much lower than CaMnO₃ at 0.08.

Abstract: This study reports on the First Principle Study via Density Functional Theory (DFT) used to determine the structural and electronic properties of Ag-dopant in Ba-site of YBa_2-xAg_xCu₃O_δ superconductor. The computational method adopting CASTEP computational code was used to calculate the structural and electronic properties for Ag-dopant in range of x=0.150 to x=0.250 in Ba-site of YBa_2-xAg_xCu₃O_δ to enhance the performance finding of experimental work shown at dopant x=0.20 ceramic superconductor. The structural changes in terms of lattice parameters were compared as the percentage of dopant increases to seek both CuO chain and CuO₂ plane bond length and the spontaneous strain variance on the structure orthorhombicity. The crystal structure constructed and calculated using Visual Crystal Approximation (VCA) applying the local density approximation (LDA) and ultrasoft pseuodopotential. Geometry optimization shown energy converged at 400 eV with k-point sampling of 4x4x1. The structural properties of YBa_2-xAg_xCu₃O_δ are observed to be approximately close to the experimental data obtained by other researches. The electronic properties were determined via energy band gap, density of states and electron energy differences visualisation a to further enhance the experimental findings.

Abstract: In this paper, a 3D laser plasma interaction system is presented, analysed, and implemented. The system has two unstable equilibria, and two types of coexisting attractors in which the coexistence of two periodic orbits and the coexistence of two chaotic attractors can be clearly observed. The multistability behaviours are determined by the bifurcation diagrams, largest Lyapunov exponents, and phase spaces. Moreover, the complexity performance of the laser plasma interaction system is investigated by the contour plot of the Sample Entropy.