Abstract: The Al/Ni multilayer composite with highly exothermic reactions and good plasticity was fabricated by electrodeposition and hot press bonding process. The Al/Ni multilayer composite consisted of the microscale Al and Ni layers. The Ni layers were electroplated on Al foils for a certain time and DC current, and then a mounts of deposited foils were stacked and combined as a whole bulk Al/Ni multilayer composite. In this study, the microstructure evolution, phase transformation, exothermic heat and bending property of the Al/Ni multilayer composite during various hot press bonding were studied by SEM, XRD, DSC and bending test. Under the hot press bonding condition of 400°C and 1h, the exothermic heat, the bending strength and the bending displacement reached 916J/g, 614.5MPa and 4mm, respectively. The results showed that by the increasing time of hot press bonding, the bending displacement of the Al/Ni multilayer composite improved firstly and then declined sharply. It was also found that when the time of hot press bonding increased, the bending strength and the exothermic heat decreased simultaneously, owing to the nucleation and growth of the Al3Ni phases in the interfaces between Al and Ni layers.
Abstract: Composite materials are widely used in the industry for their physical and mechanical properties. The objective of this work is the characterization of some composite materials with natural fibers, in order to determine the suitability in a later use in automotive components. For this purpose, we intend to obtain a model of tensile tests using finite element software, in order to be able to dimension real components.
Abstract: To investigate grain rotation caused by twinning-detwinning during plastic deformation, experiments using synchrotron high energy X-ray Diffraction (XRD) and Electron Backscatter Diffraction (EBSD) are carried out under in situ compression-tension loading. Comparison between the XRD and EBSD data confirms that the intensity change of diffraction rings in XRD experiment is caused by twining and detwinning. A good agreement of twin fraction values obtained from XRD and EBSD is achieved. This demonstrates that the grains and texture are homogeneously distributed along the normal direction of the sample. In the meantime, it is observed that detwinning can only be activated in a large quantity when the loading reverses into tension from compression in the first loading stage.
Abstract: Nitinol consists of nickel and titanium. Nitinol is one of the shape memory alloys, which changes the crystal structure at a certain temperature and is restored to a memorized form. Because of these unique features, it is used in medical devices, high precision sensors, and aerospace industries. However, Nitinol is a traditional method of processing, resulting in thermal deformation and residual stress after processing. Therefore, the electrochemical machining (ECM), which does not produce residual stress and thermal deformation, has emerged as an alternative processing technique. This study used artificial neural network (ANN), which are the basis of AI, to replace conventional design of experiments (DOE). This method was shown to be more useful than conventional method of design of experiments (RSM, Taguchi) by applying artificial neural network to electrochamical machining (ECM) and comparing root mean square errors (RMSE).
Abstract: Nonpolar ZnO films are deposited on (100) Si substrate using LaNiO3 conducting buffer layer by radio frequency sputtering. X-ray diffraction results show that ZnO films are (110) and (002) orientation with and without LaNiO3 buffer layer. The current behavior of ZnO/LaNiO3 heterojunction exhibits ohmic conduction which is different from the diode-like rectification current behavior of ZnO film using insulated buffer layers. The photoluminescence properties indicate that the (110)-oriented nonpolar ZnO film has better band-edge emission than that of (002)-oriented polar ZnO film. It is suggested that LaNiO3 buffer layer can be used to deposit silicon-based ZnO film with well ohmic contact electrode in optoelectronic devices.
Abstract: To reveal the effects of annealing condition on CZTSSe thin film solar cells, co-sputtering and subsequent selenization were used to prepare CZTSSe thin films. Structural, morphological and optical properties of CZTSSe thin films were investigated. CZTSSe thin films with various Se/(S+Se) ratio ranging from 0.69-0.78 were obtained. Representative peaks corresponding to CZTSSe in XRD and Raman results showed a slight shift to lower diffraction angle and wavenumbers. Selenization time significantly influenced the morphologies of CZTSSe films and the gradual grown up grain size was observed. VOC deficit values down to 839 mV was achieved for the best cell. CZTSSe solar cell with the selenization time of 10 min showed a best conversion efficiency of 5.32%, which presented a 50% enhancement comparing to the solar cells with insufficient and over-selenized absorbers.
Abstract: AZ91, as one the most popular magnesium alloys is widely employed for various engineering applications in the automotive industry. They are primarily made from high pressure die cast processes (HPDC) with different wall stocks, which affect their engineering performance. Understanding the effect of thick wall stocks on mechanical behaviors of HPDC AZ91 is crucial for proper design of lightweight components to meet desired engineering requirement. In this research, a conventional high pressure die casting process was utilized to prepare rectangular specimen of AZ91 with wall thicknesses of 10 mm, 6 mm and 2 mm. Tensile testing, porosity measurement and microstructure analyses were carried out on prepared specimens at room temperature. The mechanical testing evaluation reveals that, as the wall stocks of AZ91 deceases, their tensile properties including yield strength (YS), ultimate tensile strength (UTS) and elongation (ef) increase. The porosity content caused by air entrapment and the dendritic structure due cooling mechanisms should be responsible for the resultant mechanical properties.
Abstract: In this paper, we propose preparation of PEGylated AuNPs by direct sputtering of Au into pure PEG with subsequent addition of amine terminated PEG. Effect of post-deposition amine addition on properties, aging and thermal stability will be discussed. Transmission electron microscopy and dynamic light scattering measurements showed that we have prepared non-agglomerated spherical NPs with size ranging from 2.9 to 5.9 nm depending on parameters of the preparation. Aging and thermal stability results revealed significant changes in the spectra after addition of PEG–NH2. Differences in the optical absorption spectra can be assigned to change of refractive index (concentration of amine groups on NPsʼ surface) on the metal core and solvent interface with time and temperature.
Abstract: The Mechanical parameters of elastic modulus about the preparation technology of BaTiO3/IPMC (Ionic Polymer Metal Composite) were studied. In order to get the relationship between the elastic modulus and the different content of BaTiO3/IPMC the Mori-Tanaka method based on Eshelby equivalent inclusion theory was used. In order to verify the correctness of the model, Solution casting method was used to prepare different content of BaTiO3/IPMC (100:1,100:3,100:5,100:7). The elastic modulus of IPMC was texted by tensile testing and the bending test of cantilever. The result shows that: The elastic modulus of IPMC film increased by 6.3% ~ 84.7% with addition of BaTiO3. It was proved that the reinforced fillers could greatly improve the elasticity modulus of IPMC.