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Solidification processing of aluminum graphene composite is an attractive option for synthesis of metal matrix composites. Graphene reinforced aluminum metal matrix composites (GAMMCs) are of interest due to the low density and ultrahigh physical and mechanical properties of Graphene which can improve the properties of Al-Graphene composites. However, solidification processing of aluminum graphene composites has served challenges, including agglomeration of reinforcement and porosity resulting in decrease in properties above 0.five to three wt% graphene. Also, the graphene surface can react with molten aluminum alloys to form aluminum carbide. Challenges with particle distribution and porosity are frequently caused by the poor wetting of reinforcement by melt, requiring additions of selected wetting agents. The other problems include movement of reinforcement within the melt due to density differences and convection leading to nonuniform distribution of reinforcements. The graphene reinforcements can be pushed by solidifying interfaces under certain conditions during solidification leading to segregation of reinforcements in the interdendritic regions. The paper critically analyzes the above problems related to solidification processing of Aluminum-Graphene composites which has not been done in previous publications aluminumgraphene composites. The objective of this paper is to examine the challenges, and suggest possible solutions including addition of elements like silicon and magnesium to aluminum melt, coating graphene with metals like nickel and copper, controlling rate of advancement and nature of advancing solid liquid interface in a manner that they engulf graphene with dendrites or grains. [ABSTRACT FROM AUTHOR]

In this study, the accumulative roll bonding (ARB) method, a severe plastic deformation (SPD) process, was used to fabricate copper-2 wt% silicon carbide composite strips. The ARB process was successfully conducted for up to nine cycles on pure copper strips with silicon carbide particles distributed between them, as well as on monolithic copper. Equiaxed tensile and Vickers hardness tests were conducted to evaluate the mechanical properties of the samples. SEM was utilized to study the fracture surfaces and to determine the fracture mechanism of ARB processed monolithic copper and composite samples after the tensile test. Texture parameters were calculated through X-ray analysis. The Rietveld method using MAUD software were employed to assess the crystallite size of the samples. Results indicated that average amount of porosity decreased and interface bonding between copper strip layers improved with increasing the number of ARB cycles. Moreover, an increased number of cycles led to homogeneous distribution of SiC particles within the copper matrix. The tensile strength of the fabricated composites improved with an increase in the number of cycles, ultimately reaching 483 MPa after nine cycles, compared to 388 MPa for the composite processed with a single cycle of ARB and 194 MPa for annealed copper strips. Initially, the elongation of the composite samples decreased dramatically to about 6% after applying five cycle of ARB process from the 46% observed for annealed pure copper strip. However, it improved as the process continued, reaching 8.9% after the ninth cycle. Investigation of fracture surfaces after the tensile test using SEM revealed that the dominant failure mode was shear ductile fracture. Analysis of sample textures demonstrated that the dominant texture was (100). Crystallite sizes for pure copper and nine cyclesrolled composites, as determined by Reitveld method, reached 111 nm and 89 nm, respectively. [ABSTRACT FROM AUTHOR]

Author(s): Zhihao Bao [1]; Michael R. Weatherspoon [1]; Samuel Shian [1]; Ye Cai [1]; Phillip D. Graham [1]; Shawn M. Allan [1]; Gul Ahmad [1]; Matthew B. Dickerson [1]; Benjamin [...]

Multi-junction architecture is an attractive method to overcome the efficiency limit of single-junction photovoltaic solar cells. Series-connected multi-junction polymer solar cells (PSCs) have attracted much attention during the past decade. In this study, single and double layer polymer solar cells were fabricated incorporating copper oxide and zinc oxide nanoparticles (CuO and ZnO NPs) in the active layers. Thermal annealing treatment was applied to the single and double junction devices at 200°C to optimize the nanoscale morphology. The single layer device produced 2.963% power conversion efficiency and it was reduced to 1.102% in the double junction solar cell. However, the enhanced morphological and optoelectronic properties attained by applying thermal annealing slightly increased the power conversion efficiency. Meanwhile, the external quantum efficiency (EQE) increased from 32.4% to 37%, showing an enhancement of 12.4% with the thermal annealing treatment. [ABSTRACT FROM AUTHOR]

Polymer solar cells were fabricated with varying amounts of electron transporting ZnO NPs in a buffer layer located over an active layer of P3HT/PCBM incorporating a fixed amount of CuO nanoparticles. The enhanced electronic and optical properties attained by adding ZnO nanoparticles proportionally increased the power conversion efficiency by 32.19% compared to a reference cell without ZnO-NPs buffer layer. ZnO-NPs buffer layer improved the exciton dissociation rate, electron mobility, optical absorption and charge collection at the anode, resulting in higher short circuit current and external quantum efficiency. The short circuit current (Jsc) of the optimum device was measured at 7.620 mA/cm2 compared to 6.480 mA/cm2 in the reference cell with 0.6 mg of CuO nanoparticles. Meanwhile, the external quantum efficiency (EQE) increased from 54.6% to 61.8%, showing an enhancement of 13.18% with the incorporation of ZnO nanoparticle layer. [ABSTRACT FROM AUTHOR]

In this study, to enhance the power conversion efficiency (PCE) of the polymer solar cells (PSCs), Gold (Au) and Copper oxide nanoparticles (CuO-NPs) are incorporated into the PEDOT:PSS and P3HT/PCBM active layers respectively. PSCs with a constant CuO-NP content were fabricated with varying amounts of Au NPs. Addition of Au NPs increased the power conversion efficiency by up to 18% compared to a reference cell without Au-NPs. The short circuit current(Jsc) of the cells containing 0.06 mg of Au NPs was measured at 7.491 mA/cm2 compared to 6.484 mA/cm2 in the reference cells with 0.6 mg of CuO nanoparticles; meanwhile, the external quantum efficiency(EQE) increased from 53% to 61%, showing an enhancement of 15.1%. Au-NPs improved the charge collection at the anode, which results in higher short circuit current and fill factor. However, the strong near field surrounding Au-NPs due to localized surface plasmonic resonance (LSPR) effect is not distributed into the active layer. Instead, it is spread horizontally through the PEDOT:PSS layer, thus minimizing the light absorption in the active layer. [ABSTRACT FROM AUTHOR]