Dhafer Abdulameer Shnawah

Bio: Dhafer Abdulameer Shnawah is an academic researcher from University of Malaya. The author has contributed to research in topics: Intermetallic & Soldering. The author has an hindex of 16, co-authored 32 publications receiving 1330 citations.

A review on thermoelectric renewable energy: Principle parameters that affect their performance

Abstract: Developing thermoelectric materials with superior performance means tailoring interrelated thermoelectric physical parameters – electrical conductivities, Seebeck coefficients, and thermal conductivities – for a crystalline system. High electrical conductivity, low thermal conductivity, and a high Seebeck coefficient are desirable for thermoelectric materials. Therefore, knowledge of the relation between electrical conductivity and thermal conductivity is essential to improve thermoelectric properties. In general, research in recent years has focused on developing thermoelectric structures and materials of high efficiency. The importance of this parameter is universally recognized; it is an established, ubiquitous, routinely used tool for material, device, equipment and process characterization both in the thermoelectric industry and in research. In this paper, basic knowledge of thermoelectric materials and an overview of parameters that affect the figure of merit ZT are provided. The prospects for the optimization of thermoelectric materials and their applications are also discussed.

High-Reliability Low-Ag-Content Sn-Ag-Cu Solder Joints for Electronics Applications

Abstract: Sn-Ag-Cu (SAC) alloy is currently recognized as the standard lead-free solder alloy for packaging of interconnects in the electronics industry, and high- Ag-content SAC alloys are the most popular choice. However, this choice has been encumbered by the fragility of the solder joints that has been observed in drop testing as well as the high cost of the Ag itself. Therefore, low-Ag-content SAC alloy was considered as a solution for both issues. However, this approach may compromise the thermal-cycling performance of the solders. Therefore, to enhance the thermal-cycling reliability of low-Ag-content SAC alloys without sacrificing their drop-impact performance, alloying elements such as Mn, Ce, Ti, Bi, In, Sb, Ni, Zn, Al, Fe, and Co were selected as additions to these alloys. However, research reports related to these modified SAC alloys are limited. To address this paucity, the present study reviews the effect of these minor alloying elements on the solder joint reliability of low-Ag-content SAC alloys in terms of thermal cycling and drop impact. Addition of Mn, Ce, Bi, and Ni to low-Ag-content SAC solder effectively improves the thermal-cycling reliability of joints without sacrificing the drop-impact performance. Taking into consideration the improvement in the bulk alloy microstructure and mechanical properties, wetting properties, and growth suppression of the interface intermetallic compound (IMC) layers, addition of Ti, In, Sb, Zn, Al, Fe, and Co to low-Ag-content SAC solder has the potential to improve the thermal-cycling reliability of joints without sacrificing the drop-impact performance. Consequently, further investigations of both thermal-cycling and drop reliability of these modified solder joints must be carried out in future work.

Recent advances on Mg2Si1−xSnx materials for thermoelectric generation

Abstract: Thermoelectric generators (TEGs) have been identified as a viable technology for waste energy harvesting, from heat into electricity Key to successful realization of this technology on a commercial scale lies largely with the thermoelectric material which drives this technology While bismuth telluride based TEGs dominate the current market, liabilities such as toxicity, depletion of raw resources and high production costs have triggered the search for alternative thermoelectric materials One of the contenders as thermoelectric materials in the mid-temperature range is the family of Mg–Mn silicides, given the advantages of abundance of raw resources, relatively high thermoelectric performance, lowered production costs, and environmental compatibility In this paper, the thermoelectric performance of this class of materials is first reviewed through the key thermoelectric parameters: thermal and electrical conductivity, Seebeck coefficient and power factor The development fabrication processes for this class of materials, using nanostructuring and element doping strategies, are then elaborated Finally, comments on the thermoelectric applications and device efficiency are made within the context of this material

Microstructure, mechanical, and thermal properties of the Sn–1Ag–0.5Cu solder alloy bearing Fe for electronics applications

Abstract: This work investigates the effect of Fe addition on the microstructural, mechanical, and thermal properties of the Sn–1Ag–0.5Cu (SAC105) solder alloy. The addition of Fe leads to the formation of large circular FeSn 2 intermetallic compound (IMC) particles, which produce a weak interface with the β-Sn matrix. The addition of Fe also leads to the inclusion of Fe in the Ag 3 Sn and Cu 6 Sn 5 IMC particles. Moreover, Fe-bearing solders have been shown to form large primary β-Sn grains. The weak interface between the large FeSn 2 IMC particles and the β-Sn matrix together with the presence of the large primary β-Sn grains results in a significant reduction on the elastic modulus and yield strength of the Fe-bearing solders. Moreover, the improved plasticity of the large primary β-Sn grains causes the Fe-bearing solders to exhibit large total elongation. The addition of Fe also significantly reduces the effect of aging. After aging at 100 °C and 180 °C, it has been observed that the Fe-bearing solders significantly suppress the coarsening of the Ag 3 Sn IMC particles; consequently, they exhibit stable mechanical properties. This effect can be attributed to the inclusion of Fe in the Ag 3 Sn IMC particles. In addition, fracture surface analysis indicates that the addition of Fe to the SAC105 solder alloy does not affect the mode of fracture, and all tested solders exhibited large ductile-dimples on the fracture surface. Moreover, the addition of Fe did not produce any significant effect on the melting behavior. As a result, the use conditions of the Fe-bearing solders are consistent with the conditions for conventional Sn–Ag–Cu solder alloys.

A review of energy sources and energy management system in electric vehicles

Abstract: The issues of global warming and depletion of fossil fuels have paved opportunities to electric vehicle (EV). Moreover, the rapid development of power electronics technologies has even realized high energy-efficient vehicles. EV could be the alternative to decrease the global green house gases emission as the energy consumption in the world transportation is high. However, EV faces huge challenges in battery cost since one-third of the EV cost lies on battery. This paper reviews state-of-the-art of the energy sources, storage devices, power converters, low-level control energy management strategies and high supervisor control algorithms used in EV. The comparison on advantages and disadvantages of vehicle technology is highlighted. In addition, the standards and patterns of drive cycles for EV are also outlined. The advancement of power electronics and power processors has enabled sophisticated controls (low-level and high supervisory algorithms) to be implemented in EV to achieve optimum performance as well as the realization of fast-charging stations. The rapid growth of EV has led to the integration of alternative resources to the utility grid and hence smart grid control plays an important role in managing the demand. The awareness of environmental issue and fuel crisis has brought up the sales of EV worldwide.

Micropower energy harvesting

Abstract: More than a decade of research in the field of thermal, motion, vibration and electromagnetic radiation energy harvesting has yielded increasing power output and smaller embodiments. Power management circuits for rectification and DC-DC conversion are becoming able to efficiently convert the power from these energy harvesters. This paper summarizes recent energy harvesting results and their power management circuits.

High Performance Thermoelectric Materials: Progress and Their Applications

Abstract: Thermoelectric (TE) materials have the capability of converting heat into electricity, which can improve fuel efficiency, as well as providing robust alternative energy supply in multiple applications by collecting wasted heat, and therefore, assisting in finding new energy solutions. In order to construct high performance TE devices, superior TE materials have to be targeted via various strategies. The development of high performance TE devices can broaden the market of TE application and eventually boost the enthusiasm of TE material research. This review focuses on major novel strategies to achieve high-performance TE materials and their applications. Manipulating the carrier concentration and band structures of materials are effective in optimizing the electrical transport properties, while nanostructure engineering and defect engineering can greatly reduce the thermal conductivity approaching the amorphous limit. Currently, TE devices are utilized to generate power in remote missions, solar-thermal systems, implantable or/wearable devices, the automotive industry, and many other fields; they are also serving as temperature sensors and controllers or even gas sensors. The future tendency is to synergistically optimize and integrate all the effective factors to further improve the TE performance, so that highly efficient TE materials and devices can be more beneficial to daily lives.