Effect of UV Light on the Barrier Performance of Aluminum Powder/Epoxy Coating.

Spherical aluminum powder was added to an epoxy composite coating in order to improve its protection performance for metal materials. The strength of the coating before and after UV (Ultraviolet Light) aging, its yellowing value, and its barrier properties were tested to explore the influence of UV light on the barrier performance of aluminum powder/epoxy coating. The results show that the addition of the aluminum powder enhanced the strength of the epoxy coating and reflected environmental UV light. This improved the resistance of the coating to UV aging and prolonged its service life. The composite prepared with 6 wt.% aluminum power exhibited the highest strength values before and after aging: 64.5 MPa and 58.5 MPa, respectively. After aging, the strength loss rate of this epoxy coating was 9.3%, and its yellowing value was +1.43.

A Stabilized Polyacrylonitrile-Encapsulated Matrix on a Nanolayered Vanadium-Based Cathode Material Facilitating the K-Storage Performance.

Layered vanadium-based metal oxides were regarded as promising cathode materials accounting for suitable K+ transport channels as well as high work potential in K-ion batteries. Nevertheless, because of the large radius of K+ and the rigid structure of inorganic materials, the typical K0.486V2O5 suffers from volume expansion seriously in the repeated charging and discharging processes along with poor ionic and electronic conductivity, consequently determining inevitably poor electrochemical properties. Herein, we proposed a stabilized polymer (PAN) matrix on K0.486V2O5 nanobelts by a liquid-assisted methodology and further electrospinning technology. As a result, a nanocomposite containing a 3D conductive and interconnected mesh structure was thus constructed. By avoiding the full carbonization of polyacrylonitrile (PAN) with appropriate thermal treatment, the elastic properties of the PAN precursor can be retained, effectively inhibiting the volume effect, and the stabilized PAN-encapsulated matrix can also greatly accelerate transport rates of K+ and electrons at a high rate as well as restrict the decomposition of organic electrolytes and side reactions. This work can supply significant basic scientific value of the polymer surface coating methodology for the far-reaching development of inorganic cathode materials in K-ion batteries.

Fabrication and Properties of Superhydrophobic Waterborne Polyurethane Composites with Micro-Rough Surface Structure Using Electrostatic Spraying.

Waterborne polyurethane (WPU) coatings hold advantages of good toughness, low cost and environmental protection. However, the low water contact angle (WCA), poor wear and corrosion resistance make them unsuitable for application in the superhydrophobic coatings such as antipollution flashover coatings for transmission lines, self-cleaning coatings for outdoor equipment and waterproof textiles. A series of superhydrophobic WPU composites (SHWPUCs) with micro-rough surface structure was prepared by electrostatic spraying nano-SiO2 particles on WPU composites with low surface energy. It showed that as the hydrophobic system content rose the WCAs of the composites first increased and then remained stationary; however, the adhesion and corrosion resistance first increased and then decreased. An appropriate addition of the hydrophobic system content would lead to a dense coating structure, but an excessive addition could increase the interfaces in the coating and then reduce the coating performance. When the mass ratio of the WPU dispersion, polytetrafluoroethylene (PTFE) particles and modified polydimethylsiloxane was 8:0.3:0.4, 10 g/m2 nano-SiO2 particles were sprayed on the uncured coating surface to construct the SHWPUC with a WCA of 156°. Compared with pure WPU coating, its adhesion and corrosion resistance increased by 12.5% and one order of magnitude, respectively; its wear rate decreased by 88.8%.

Mechanical Properties of Multi-Walled Carbon Nanotube/Waterborne Polyurethane Conductive Coatings Prepared by Electrostatic Spraying.

Electrostatic spraying (ES) was used to prepare multi-walled carbon nanotube (MWCNT)/waterborne polyurethane (WPU) abrasion-proof, conductive coatings to improve the electrical conductivity and mechanical properties of WPU coatings. The dispersity of MWCNTs and the electrical conductivity, surface hardness, and wear resistance of the coating prepared by ES (ESC) were investigated. The ESC was further compared with coatings prepared by brushing (BrC). The results provide a theoretical basis for the preparation and application of conductive WPU coatings with excellent wear resistance. The dispersity of MWCNTs and the surface hardness and wear resistance of ESC were obviously better than those of BrC. With an increase in the MWCNT content, the surface hardness of both ESC and BrC went up. As the MWCNT content increased, the wear resistance of ESC first increased and then decreased, while the wear resistance of BrC decreased. It was evident that ESC with 0.3 wt% MWCNT was fully capable of conducting electricity, but BrC with 0.3 wt% MWCNT failed to conduct electricity. The best wear resistance was achieved for ESC with 0.3 wt% MWCNT. Its wear rate (1.18 × 10-10 cm3/mm N) and friction coefficient (0.28) were the lowest, which were 50.21% and 20.00% lower, respectively, than those of pure WPU ESC.

Properties of Waterborne Polyurethane Conductive Coating with Low MWCNTs Content by Electrostatic Spraying.

Because flammable organic solvents are emitted during the construction process, oil-based conductive coatings generally result in potential safety problems. A high content of conductive mediums can also weaken the adhesive and protective abilities of existing conductive coatings. Therefore, an anticorrosive and conductive coating was prepared on Q235 steel substrate by spraying the multi-walled carbon nanotubes (MWCNTs)/waterborne polyurethane (WPU) dispersion with a low MWCNT content in this work. The effect of the MWCNT content on the electrical conductivity, corrosion resistance, and adhesive strength of the WPU conductive coating was investigated. It was concluded that a spatial network structure of MWCNTs-WPU was formed to make the coating structure more compact. The electrical conductivity, corrosion resistance, and adhesive strength of the WPU conductive coating first increased and then decreased as the MWCNT content increased. When the MWCNT content was only 0.2 wt % (which was far lower than that of the existing conductive coatings at 1 wt %), the coating began to conduct electricity; its resistivity was 12,675.0 Ω·m. The best combination property was the 0.3 wt % MWCNTs/WPU conductive coating. Its adhesive strength was 19.99% higher than that of pure WPU coating. Its corrosion rate was about one order of magnitude lower than that of pure WPU coating after being immersed in 3.5 wt % NaCl solution for 17 days.

The bactericidal mechanism of action against Staphylococcus aureus for AgO nanoparticles.

To identify the mechanistic effects of AgO nanoparticles on Gram-positive bacteria, S. aureus cells suspended in phosphate buffer solution (PBS) and deionized water were separately treated using AgO nanoparticles at different concentrations. The phase composition changes of the bactericide after killing S. aureus and the cellular responses of S. aureus to AgO were characterized by X-ray diffraction, atomic absorption spectrophotometer, scanning electron microscopy, transmission electron microscopy, and energy dispersive spectroscopy. The results show that AgO nanoparticles could kill S. aureus suspended in PBS and deionized water. The bactericidal effect of AgO bactericide against S. aureus in water was better than that in PBS, due to the formation of Ag3PO4 from the reaction between AgO and PBS. AgO nanoparticles exerted their bactericidal activity by multiple processes. AgO nanoparticles adhered to the surface of S. aureus cells firstly, then induced physical alterations in cell morphology and released silver ions, leading to initial injuries of cell membrane. Once membrane damage occurred, they entered the cells, and damaged the intracellular materials, eventually causing severe morphological and structural injuries to the cells and leakage of cytoplasm.

Characterizations of lanthanum trivalent ions/TiO2 nanopowders catalysis prepared by plasma spray.

Lanthanum trivalent ions (La(3+)) doped titanium dioxide (TiO(2)) nanopowders in the range of 20-60 nm were prepared successfully by plasma spray in the self-developed plasma spray equipment. The photocatalytic activity of samples at different doping concentrations in photocatalytic degradation of methyl orange was discussed. The nanopowders prepared were characterized by transmission electron microscopy, X-ray diffraction, ultraviolet-visible spectra, photoluminescence (PL) and X-ray photoelectron spectroscopy. The results show that La(3+) doping increased the photocatalytic activity of TiO(2) greatly, the optimal doping concentration was 0.5 at%. The La(3+) doping decreases the particle size and the distribution of particle sizes becomes more uniform. The doped powders were the mixture of anatase and rutile phase. The contents of anatase phase decreased firstly and then increased with an increase in the contents of La(3+). The intrinsic absorption band of La(3+) doped TiO(2) nanopowders appears red shift from that of pure TiO(2) nanopowders. The intensity of PL spectra increases and then decreases with increasing the content of La(3+). The PL spectral intensity reaches its peak when the ratio of La(3+)/TiO(2) is 0.2 at%. There are O, Ti, C and La elements in the prepared La(3+) doped TiO(2) nanopowders, La element still exists in trivalent and Ti element always exists in tetravalent.