Hardness, tribological properties and electron work function (EWF) of AZ31 alloy pre-deformed at high and low strain rates were investigated. It was observed that the pre-deformation lowered hardness of the magnesium alloy, ascribed to the formation of micro-cracks/voids in addition to dislocations. The deformation at the higher strain rate resulted in larger decrease in hardness and consequently more material loss during wear tests. XRD diffraction analysis did not provide clear clues in regard to residual strain that is related to the dislocation density. However, the observed influences of the strain rate-dependent pre-deformation on the properties of the alloy are explainable based on corresponding changes in work function. It was observed that the lower strain rate led to a larger decrease in EWF, corresponding to a higher fraction ratio of dislocations to micro-cracks/voids, which affected the performance of the alloy. First-principle calculations were conducted to investigate changes in EWF caused by dislocation and vacancy cluster, respectively, which support the explanation. This study demonstrates that the work function can provide supplementary information towards clarification of underlying mechanisms for the observed phenomena.

This article reports a study on production of mirror-shining surface of electrogalvanized steel with significantly elevated scratch resistance, achieved by combined nano-electrodeposition and passivation treatment. Roughness, indentation deformation, elastic modulus and micro-scratch resistance of the treated electrogalvanized steel surface were investigated. Through in situ property mapping using a multi-mode atomic force microscope, surface properties of passivation films on coarse-grained and nanocrystalline zinc coatings were evaluated. It was demonstrated that the combination of nano-electrodeposition and passivation treatment greatly improved the passive film on the zinc coating with mirror brightness and significantly raised resistance to scratch, which is about two orders of magnitude higher than that of oxide film on conventional electrogalvanized steel.

This study investigates the performance of impact ionization (II) enhanced thin film c-Si solar cells using Technology Computer Aided Design simulation. 2-D numerical simulation is carried out to study the effect of II concerning the electrical and optical properties of the c-Si solar cell. We have introduced \(\hbox {P}^{+}\) pocket with a high doping density of magnitude \(>\) \(10^{18}\hbox { cm}^{-3}\) in an intrinsic absorber layer which increases the electric field near the junction up to 1 MV/m. The effects of II on various solar cell parameters like short circuit current density, open circuit voltage and quantum efficiency are investigated. The simulation results show that high concentration of \(\hbox {P}^{+}\) pocket enhances the short circuit current density \((\hbox {J}_{\mathrm{sc}})\) of c-Si solar cell without affecting its open circuit voltage \((\hbox {V}_{\mathrm{oc}})\). In addition, the modelling results depict that by varying the doping concentration of \(\hbox {P}^{+}\) pocket from \(10^{18}\) to \(9\times 10^{18} \hbox { cm}^{-3}\), the current density increases from 18 to \(32\hbox { mA/cm}^{2}\). Furthermore, an internal quantum efficiency of 189 % is achieved at \(\hbox {P}^{+}\) pocket doping concentration of \(9\times 10^{18}\) \(\hbox {cm}^{-3}\).

10 A concentrated solar power beam-down tower focuses its energy directly into a single-tank molten salt volumetric receiver that also 11 acts as a thermal energy storage unit. The system is being developed in connection with the CSPonD Demo (Concentrated Solar 12 Power on Demand Demonstration) at the Masdar Institute of Science and Technology in partnership with MIT.. The relatively small 13 angle subtended by rays emanating from the central reflector of a beam down optical system, together with the nature of solar energy 14 absorption within the volumetric receiver, make use of a compound parabolic concentrator (CPC) or CPC-like final optical element 15 (FOE) attractive. An effective concentration of about 4-5 can be achieved to increase solar flux at the tank aperture from 150 to 600 16 suns. This paper describes preliminary designs of the CPC and tank/receiver. Optical simulations reveal that, for a given solar incident 17 power at the tank aperture, a conical final concentrator design produces a more uniform flux distribution with better axial alignment 18 (lower average horizontal component) of rays at its outlet, compared to a conventional CPC of revolution. However, the cone may 19 require a larger outlet radius, leading to higher thermal losses through the tank aperture. With the current design of the tank, the losses 20 through the walls, as well as the convective losses through the aperture during day time, correspond to 4.5 % of the thermal capacity. 21 22 © 2015 The Authors. Published by Elsevier Ltd. 23 Selection and/or peer-review under responsibility of ICAE. 24 25

In the framework of the CSPonD Demo project, the optical characterization of the Beam Down Optical Experiment (BDOE) heliostats field is an important step to certify the required power is provided. To achieve this goal, an experiment involving a single heliostat is carried out. The results of the experiment and the comparison with simulated results are presented in this paper. Only the reflection on the heliostat is observed in order to have a better assessment of its optical performance. The heliostat reflectance is modified and the experimental and simulated concentration distribution are confronted. Results indicate that the shapes of the concentration distributions are quite similar, hence validating the optical model respects the geometry of the BDOE. Moreover these results lead to an increase of the optimized heliostat reflectance when the incident angle on the heliostat decreases. Further investigation is required to validate this method with all the individual heliostats of the BDOE solar field.

An innovative concept in which a single-tank molten salt thermal energy storage arrangement also acts as a volumetric receiver is being developed in connection with the CSPonD 2 (Concentrated Solar Power on Demand Demonstration) project. The tank is located at the focal point of a beam-down tower to act as both solar energy receiver and thermal energy storage. The relatively small angle subtended by rays emanating from the central reflector of a beam down optical system, together with the nature of solar energy absorption within the volumetric receiver, make use of a compound parabolic concentrator (CPC) or CPC-like final optical element attractive. An effective concentration of about 4 can be achieved to increase solar flux at the tank aperture from 150 to 600 suns. This paper describes preliminary designs of the CPC and tank/receiver. Optical simulations reveal that, for a given solar incident power at the tank aperture, a conical final concentrator design produces a more uniform flux distribution with better axial alignment (lower average horizontal component) of rays at its outlet compared to a conventional CPC of revolution. However the cone may require a larger outlet radius, leading to higher thermal losses through the tank aperture. With the current design of the tank, the losses through the walls correspond to 5.5% of the thermal capacity. To maximize the tank thermal efficiency, a thorough investigation will be carried out, starting with measurements of the molten salt emissivity, to determine the cone outlet radius/tank aperture and cone height that achieve maximum system efficiency with a 250-550 °C molten salt working temperature range.

The effect of carbon diffusion on the performance of c-Si HIT cells with aSi1-xCx:H passivation layer is studied. Two HIT cells are fabricated, one with a-Si passivation layer and one with a-SiC layer. SIMS is used to quantify the carbon diffusion into cSi. The results show a significant amount of carbon at the interface and in the c-Si layer. With the carbon diffusion, the Voc, Jsc and fill factor drop from 0.523V to 0.331V, 24 mA/cm2 to 21 mA/cm2 and from 56% to 21% respectively. In addition, the peak EQE drops by 4%. The dark current increases from 6.24×10-4 mA/cm2 to 3.50×10-3 mA/cm2 at V=-0.5V. Moreover, the results indicate that the carbon diffusion reduces the overall c-Si lifetime in addition to increasing the amount of Dit at the interface.

This study investigates the performance of impact ionization (ii) enhanced thin film c-si solar cells using technology computer aided design (tcad) simulations. The effect of ii concerning the electrical and optical properties of the c-si solar cell is carried out. We introduce p + pocket with a high doping density of the magnitude > 10 18 cm -3 to increase the electric field near the junction to values near 1 mv/cm. Using this structure the effect of ii on key solar cell parameters like J sc , V oc , efficiency and quantum efficiency are investigated. The simulation results show that high doping density of p + pocket enhances the current density without affecting the voltage. In addition, by varying the doping concentration of the p + pocket from 10 18 cm -3 to 9×10 18 cm -3 the current density increases from 18 mA/cm 2 to 32 mA/cm 2 . In addition simulation results also show that internal quantum efficiency (iqe) can reach up to 1.89 with very highly doped p+ pocket (9×10 18 cm -3 ).

The effect of Impact Ionization (II) on thin film c-Si solar cells is modeled and investigated by TCAD simulation. The doping concentration of absorber layer is varied to see the effect of Impact Ionization (II) on c-Si solar cell by increasing the electric field. The results show that, II can increase the short circuit current (Jsc). Namely we show a 2mA/cm2 increase in Jsc by increasing the doping of the c-Si layer from 1×1018 cm-3 to 1×1019 cm-3. In addition the Internal Quantum Efficiency (IQE) increases from 98% to 116% with impact ionization.