Wear and Corrosion Resistance of Al0.5CoCrCuFeNi High-Entropy Alloy Coating Deposited on AZ91D Magnesium Alloy by Laser Cladding.

In order to improve the wear and corrosion resistance of an AZ91D magnesium alloy substrate, an Al0.5CoCrCuFeNi high-entropy alloy coating was successfully prepared on an AZ91D magnesium alloy surface by laser cladding using mixed elemental powders. Optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction were used to characterize the microstructure of the coating. The wear resistance and corrosion resistance of the coating were evaluated by dry sliding wear and potentiodynamic polarization curve test methods, respectively. The results show that the coating was composed of a simple FCC solid solution phase with a microhardness about 3.7 times higher than that of the AZ91D matrix and even higher than that of the same high-entropy alloy prepared by an arc melting method. The coating had better wear resistance than the AZ91D matrix, and the wear rate was about 2.5 times lower than that of the AZ91D matrix. Moreover, the main wear mechanisms of the coating and the AZ91D matrix were different. The former was abrasive wear and the latter was adhesive wear. The corrosion resistance of the coating was also better than that of the AZ91D matrix because the corrosion potential of the former was more positive and the corrosion current was smaller.

Nanoscale SnO2 flat-type coplanar hexanal gas sensor arrays at ppb level.

Hexanal is one of the most important aroma compounds which play a crucial role in the odor of cereal, meat, fruit, plant oils and wood. The detection technique of hexanal has attracted more attention. In this paper, the nano-SnO2 flat-type coplanar hexanal gas-sensor arrays were fabricated by screen-printing technique based on nano-SnO2 powders prepared by hydrothermal method. The test results show that the nano-SnO2 flat-type coplanar gas sensor arrays have good hexanal gas-sensing characteristics, such as low detection limit and high sensitivity. Especially, the gas sensitivity of the nano-SnO2 gas sensor arrays to 100 ppb hexanal can reach 2.8 at 350 degrees C. The nanometer size effect of nano-SnO2 and nature property of hexanal caused the ppb-level hexanal gas sensing characteristics.

Strong interface scattering induced low thermal conductivity in Bi-based GeTe/Bi2Te3 superlattice-like materials.

The thermal conductivities of GeTe/Bi2Te3 superlattice-like materials are calculated based on density functional perturbation theory (DFPT) and measured using a 3ω method. The calculated results show that the lattice thermal conductivity or thermal diffusivity of GeTe/Bi2Te3 superlattice-like materials significantly decrease due to the effects of interfaces and Bi atoms in Bi2Te3. Our measured results are in line with the theoretical calculations, and reach an extremely low thermal conductivity at 0.162 W mK-1 compared with published work on Ge-Sb(Bi)-Te, indicating the effectiveness of modulating the thermal properties of phase change materials by using Bi-based GeTe/Bi2Te3 superlattice-like materials. Our findings give a calculation method to modify the thermal characteristics of superlattice-like materials and confirm Bi-based GeTe/Bi2Te3 superlattice-like materials as promising candidates for phase change materials with lower thermal conductivity.

Synthesis of Histidine-Containing Oligopeptides via Histidine-Promoted Peptide Ligation.

Histidine-containing peptides are valuable therapeutic agents for a treatment of neurodegenerative diseases. However, the synthesis of histidine-containing peptides is not trivial due to the potential of imidazole sidechain of histidine to act as a nucleophile if unprotected. A peptide ligation method utilizing the imidazole sidechain of histidine has been developed. The key imidazolate intermediate that acts as an internal acyl transfer catalyst during ligation is generated by deprotonation. Transesterification with amino acids or peptides tethered with C-terminal thioester followed by N→N acyl shifts led to the final ligated products. A range of histidine-containing dipeptides could be synthesized in moderate to good yields via this method without protecting the imidazole sidechain. The protocol was further extended to tripeptide synthesis via a long-range N→N acyl transfer, and tetrapeptide synthesis.

The production and characteristics of solid lipid nanoparticles (SLNs).

Modified high shear homogenization and ultrasound techniques were employed to produce solid lipid nanoparticles (SLNs). Model drug mifepristone had been incorporated in SLNs. The mean particle size measured by laser diffractometry (LD) was found to be 106 nm with a narrow particle distribution of polydispersity index, 0.278. Differential scanning calorimetry and X-ray diffraction measurements suggested that the majority of the SLNs were less ordered arrangement of crystals, and this was favorable for increasing the drug loading capacity. The drug entrapment efficiency (EE%) of SLNs was more than 87 percent and showed relatively long-term physical stability as the leakage was very small after being stored for one month. Therefore, seemed this modified method could prepare high quality SLNs loading lipophilic drugs. It is a simple, available and effective method to produce SLNs.

In situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) study of formaldehyde adsorption and reactions on Pd-doped nano-γ-Fe2O3 films.

Palladium-doped nano-γ-Fe2O3 films were printed on Al2O3 substrates by screen printing-injecting hybrid technology. X-ray diffraction and scanning electron microscopy techniques were used to characterize the phase structures and morphologies of the films, respectively. The sensitivity of the films to 100 ppm formaldehyde in air was investigated. The surface adsorption and reaction process between Pd-doped nano-γ-Fe2O3 films and formaldehyde was studied by in situ diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS) at different temperatures. Dioxymethylene, formate ions, polyoxymethylene, and adsorbed formaldehyde were detected when the Pd-doped nano-γ-Fe2O3 films were exposed to 100 ppm formaldehyde at different temperatures. A possible mechanism of the reaction process is discussed.