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Wide Band Gap Nano-Semiconductors for Solar Driven Hydrogen Generation
Published in Ranjusha Rajagopalan, Avinash Balakrishnan, Innovations in Engineered Porous Materials for Energy Generation and Storage Applications, 2018
Nur Azimah Abd Samad, Kung Shiuh Lau, Chin Wei Lai
ZnO is commonly used to couple with the TiO2. High electron mobility of ZnO tends to improve the process of electron transfer between CB and VB. This will significantly reduce the recombination of photogenerated charge carrier as compared to that of the TiO2. It has been reported by Momeni and Ghayeb that the photocurrent density and hydrogen generated by ZnO-TiO2 nanotubes were found to be 1.24 mA/cm2 and 11 gL/cm2h, respectively (Momeni and Ghayeb 2015). Furthermore, the transition metal oxide was also adopted to synthesise the nanocomposite. One of the commonly used transition metal oxide is Chromium III oxide (Cr2O3). Through chemical bath deposition, Cr2O3 was deposited onto the porous TiO2 nanotubes. The photocurrent density of the nanocomposites was > 150 gA/cm2 at 0.2 V (vs. Ag/AgCl) as compared to that of the bare TiO2 with only < 8 gA/cm2. The hydrogen generation performance was found to be 10.67 gL/cm2h, which is 12.8 times higher than that of the bare TiO2 (Momeni and Ghayeb 2016).
Optimization of stirrer parameters by Taguchi method for a better ceramic particle stirring performance in the production of Aluminum Alloy Matrix Composite
Published in Cogent Engineering, 2023
Farooq Muhammad, Shawnam Jalal
Microscopic examination of the composites was carried out by optical and scanning electron microscopy. According to the American Society for Testing Materials (ASTM) standard, the specimens were chemically etched for 50 seconds (Annual Book of ASTM G 67, 2004). The etchant solution consists of 90 ml of water, 4 ml of sulphuric acid (H2S04), 2 ml of chromium (III) oxide (Cr2O3), and 4 ml of Hydrofluoric acid (Hf). Then specimens were placed on the metallurgical microscope, model IMM 901 from Metkon. Images with 100 micron magnification were taken respectively as shown in Figures 15 A, B, and C. It has been shown that when helical stirrer (D5), stirring speed (540 PRM), and longest stirring duration (6 minutes) were used for both ceramic reinforcements, reinforcement particles are well dispersed in the matrix. Pointing out that silicon carbide has higher uniformity than silica. The factors that contributed to the weaker properties of silica when compared to silicon carbide are that it has a lower density, which increases its desire to float and decreases the homogeneous distribution of the particles. Another factor is that the shape and size of the silica particles differ, and it appears in the image that it is similar to the case of mesoporous structure.
Selective laser melting and post-processing stages for enhancing the material behavior of cobalt-chromium alloy in total hip replacement: a review
Published in Materials and Manufacturing Processes, 2023
Uva Narayanan C, Suya Prem Anand P
In biomedical applications, the product needs to be converted into biomaterial by coating the biomineral and forming the oxide layer. Modifying the Co-Cr alloys with the assistance of the oxidation process is inadequately discussed due to the presence of chromium chemical composition. In the oxidation process, the chromium promotes different grades such as chromium II, III, Ⅳ, Ⅴ, and VI. In these, chromium VI causes health risks to the patient by affecting the DNA, and Cells. On the other hand, chromium III helps to enhance the patient because it is one of the trace elements suggested by health organizations. Therefore, modifying the SLM printed Co-Cr alloys with the assistance of a chromium III oxide layer enhances the biocompatibility of the stems. Furthermore, performing the heat treatment refine the surface hardness and increases the tribological resistance of the chromium III/SLM printed Co-Cr alloys for the hip joints, knee joints, stem, and dental applications.
Cr–Ag coatings: synthesis, microstructure and antimicrobial properties
Published in Surface Engineering, 2019
Afshin Karami, Hu Zhang, Victoria G. Pederick, Christopher A. McDevitt, Mohammad Sharear Kabir, Song Xu, Paul Munroe, Zhifeng Zhou, Zonghan Xie
The X-ray photoelectron spectroscopy (XPS) is a tool to define and study the chemical bonding structure in the coatings. To do so, Al kα radiation (photon energy, hν = 1468.68 eV) was applied as the excitation source. The high resolution (HR) scans were carried out at 100 eV while the spectrometer calibration was performed using binding energy levels of Au4f7 (83.96 eV), Ag3d5 (368.21 eV) and Cu2p3 (932.62 eV). From the XPS graphs in Figure 1, the deconvolution of HR spectra of Cr3p clearly indicates the presence of metallic chromium and chromium (III) oxide [35]. The existence of Cr (III) oxide is further confirmed by the deconvolution of O 1s HR spectra [35] indicating the highly oxidising nature of the Cr–Ag coatings since the enthalpy of formation of Cr (III) oxide is quite high (−1134.70 kJ mol−1 [36]). Furthermore, Cr3p and Ag3d5 spectra clearly show the absence of bonding between Cr and Ag. A study on the Cr–Ag system by Franke and Neuschütz [37] confirms the immiscibility of Cr and Ag in both solid and liquid states indicating the absence of any stable intermediate phases.