Modern Physics Letters B

Taking the high volume fraction SiCp/6061Al-based composite material prepared by the powder metallurgy method under different sintering temperatures and holding times as the research object, the microstructure and interface actions are investigated by X-ray diffractometer, scanning electron microscope, transmission electron microscope, etc. The results show that as the sintering temperature increases, the interface reaction between SiC and Al intensifies, producing brittle phase Al₄C₃ and MgAl₂O₄ and MgO interface products. The nucleation and growth of Al₄C₃ are controlled by the sintering temperature and time. When preparing large-size workpieces with high volume fraction SiCp/6061Al-based composite materials, the sintering temperature should be controlled below $670^{\circ }$C, and the holding time should not exceed 24 h.

In this study, in order to improve the iron removal rate of iron remover, the effects of magnetic flux density, number of magnetic poles and powder fluidity on the removal rate of filed SUS304 particles mixed with high-purity spherical silica powders of different particle sizes were investigated. The iron removal tests were performed using an iron removal testing device equipped with a single bar magnet. The silica powders mixed with filed SUS304 particles were sifted, and the weight of the filed SUS304 particles captured by the bar magnet was measured. Three types of bar magnets were prepared in order to investigate the effect of the maximum magnetic flux density and the number of magnetic poles. As a result, the number of magnetic poles was more effective in improving iron removal performance than the maximum magnetic flux density. In addition, the iron removal rate decreased with decreasing the nominal particle size of the silica powder. As a result of the constant load direct shear test, the shear cohesion of silica powders increased with decreasing the average particle size ${\square }_{50}$. Therefore, it was found that the iron removal performance deteriorates when the powder cohesion increases.

The chemical bonding of substrate and adhesive occurs in thermoplastic adhesive bonding, and the molecular deformation caused by the difference in chemical bonding affects the adhesive properties. Therefore, it is essential to investigate the correlation between the molecular deformation of interphase and the strength change behavior. As adhesive bonding involves the combination of two materials with different coefficients of thermal expansion, it is important to analyze the behavior at high temperatures. Therefore, to determine the effects of the molecular deformation of the interphase caused by differences in the adhesive type on the high-temperature performance when adhesive bonding is applied to thermoplastic composites, fusion and adhesive bonding were applied to carbon fiber/polyetherketoneketone thermoplastic composites. The lap shear strength test was conducted at three different temperatures to evaluate the adhesive performances. Scanning electron microscopy was used to determine the fracture mode and the molecular deformation of the interphase was analyzed by Fourier transform infrared spectroscopy. Temperature does not affect the strength of fusion bonded composites. When polyetheretherketone is used as an adhesive, the strength decreases as the temperature increases. When polyetherimide is used as an adhesive, the strength first increases at $100^{\circ }$C and then decreases at $160^{\circ }$C. The amount of C–O–C and C=C bond formation, diphenyl ketone group, and imide carbonyl group in the interphase followed the same trend as the strength.

Zinc silicate was successfully synthesized by solid-state sintering at the temperature no less than $1100^{\circ }$C. Co-existing ZnO phase was observed as adopting the stoichiometry reactant ratio 2:1 of ZnO:SiO₂. Single-phase $\alpha$-Zn₂SiO₄ (willemite structure) was obtained by adjusting the ZnO:SiO₂ ratio to 1:1. Prolonging sintering time has helped to increase the fluorescence efficiency and what is more, repeated solid-state sintering process is found to have further improved fluorescence of Zn₂SiO₄:Mn.

This study was conducted for the purpose of deriving the optimal process conditions for the pultrusion of carbon fiber–polyester composite materials. For this purpose, the mechanical characteristics were evaluated according to fiber content, curing time, and curing temperature. Tensile strength characteristics are improved as the fiber content, curing temperature, and curing time increased. But, in a fiber content of 70% over, it does not improve due to internal defects such as delamination and voids. The effect of curing temperature and curing time was analyzed through the fracture mode. Fracture characteristics due to un-curing were observed in tensile specimens. In addition, the curing reaction of the polyester as the heating rate was confirmed through differential scanning calorimetry. Finally, the optimal process conditions for the pultrusion of carbon fiber–polyester composite materials were derived.

In this paper, the Ba${}_{(1-x)}$Sr${}_x$TiO₃ (BST) fiber arrays in an orderly manner were successfully fabricated by electrospinning. The arrangement of the fiber arrays and their dielectric properties at different rotation speeds were investigated. The microstructure, phase composition and dielectric properties of the fabricated fiber arrays were detected via field-emission scanning electron microscope, X-ray diffraction and automatic component analyzer. The results indicated that the orientation of the BST fiber arrays could be affected by the drum rotational speed variation of the roller receiver. The orientation degree of the BST fiber arrays increased and the diameter of the BST fiber arrays decreased with the increasing of the drum rotational speed. With the content of polyvinylpyrrolidone at 8% and the speed of 1000 r/min, the orientation degree of the BST fiber arrays gets a better state and the best dielectric constant of 104. Moreover, the ferroelectric performance of BST fiber arrays in ambient and cryogenic environments has a maxima Curie temperature of $-5^{\circ }$C.

In the automobile industry, improving the properties of the mold improves productivity and reduces the defect rate of the product. In this study, a laser heat source was used to improve the properties of the mold. To improve the surface strength of the mold steel, laser cladding was applied to form a surface alloy layer. In addition, an experiment was performed to improve the tensile residual stress of the cladding layer by applying laser shock peening. A continuous wave high-power fiber laser was used for laser cladding, and a high-peak Nd:YAG pulsed laser system was used for laser peening. As a result, an alloy layer harder by more than 1.5 times than the base material was formed on the surface of the mold steel through laser cladding, and the tensile residual stress of the laser cladding layer with peening applied was improved by about 50%.

A radio-frequency magnetron sputter was used to deposit a 60 nm TiO${}_x$ film on a W-coated Si substrate at room temperature. Subsequently, a 100 nm Ni film was deposited using a thermal evaporator to form a Ni/TiO${}_x$/W structure. Numerous oxygen vacancies and defects were present in the TiO${}_x$ film. The current–voltage characteristics indicate that Schottky emission dominated the conduction mechanism of the Ni/TiO${}_x$/W structure. Because of Schottky barrier modulation, analog resistive switching of the Ni/TiO${}_x$/W structure can be performed using consecutive voltage sweepings or voltage pulses. Various pulse waveforms were used to demonstrate synaptic potentiation and depression.

There are numerous methods for reinforcing laminate composites using nanoadditives. However, the random dispersion of nanoparticles in polymer resins leads to critical defects owing to excessive dispersion. This study investigated a method of depositing halloysite nanotubes (HNTs) on a carbon fabric surface via electrophoresis deposition (EPD) for reinforcing the through-thickness strength of carbon fiber-reinforced plastic (CFRP) composites. The voltage during the EPD process was set as 6–12 V, which is the working range for nanoparticles during EPD. In addition, CFRPs were fabricated from modified carbon fabrics using vacuum-assisted resin transfer molding. The optimum voltage was determined as 6 V. At higher voltages, the mechanical properties deteriorated owing to the distribution of HNTs and damage to the fibers. The performance of the EPD-modified CFRPs was better than that of neat CFRPs. The highest strength was observed at 0.7 wt.% HNTs and 6 V, which indicated the feasibility of the EPD process and a well-dispersed morphology. The strong interaction of HNTs with carbon fabric influences the through-thickness mechanical properties of CFRP composites.

The effect of spraying power and immersion time on the microstructure and electrochemical corrosion behavior of plasma-sprayed Ni-5wt.%Al alloy coatings were studied. The spraying powers have a great influence on the electrochemical corrosion behavior of the coatings by affecting their surface roughness and porosity. The self-corrosion current density of the coatings was much lower when the surface roughness and porosity of the coatings were both lower. In addition, with the increase of immersion time, the self-corrosion current density of the coatings was decreased first, then increased, and finally decreased, which may be related to the formation and disappearance of Al₂O₃ in the coatings.

In order to improve the anti-corrosion performance of thin stainless steel bipolar plates of proton exchange membrane fuel cell (PEMFC), the carbon film (of about 0.82-$\mu$m thickness) was fabricated on the thin stainless steel by laser direct writing technology irradiating the formed dense polydopamine (PDA) film. The results indicated that the PDA film has partially transformed into nanocrystalline graphite. Laser power and scanning speed had great effect on the anti-corrosion performance of the final obtained film in simulated PEMFC environment. When the laser power is 3.5 W and the scanning speed is 10 mm/s, the film obtained on the thin stainless steel has the best electrochemical performance in simulated PEMFC environment. Its corrosion current densities were $8.64\mu$A $\cdot$ cm${}^{-2}$@ −0.1 V (versus SCE) and $1.33\mu$A $\cdot$ cm ${}^{-2}$@ 0.6 V (versus SCE) in simulated anode and cathode environments, respectively. Compared with the bare thin stainless steel, the corresponding corrosion current densities decreased by 45% and 62%. The results obtained in this text provide a novel strategy for modifyingPEMFC thin metal bipolar plates.

We synthesized rock-salt-type Li–Ti oxynitride (LiTi${}_n$O${}_x$N${}_y$, $n=1$, 1.25, 1.5, 1.75, and 2) using solid-phase reaction. The best charge/discharge characteristics were obtained with a Ti/Li ratio of 1.25, and the maximum discharge capacity was 140 mAh/g.

To investigate the model of fatigue crack growth rate da/dN based on crack tip opening displacement (CTOD) as the driving parameter, the variation ranges $\mathrm{\Delta }{\delta }_M$ by linear elastic fracture mechanics and $\mathrm{\Delta }{\delta }_G$ by geometric principle of CTOD were deduced. The fitting relationships of $\mathrm{\Delta }{\delta }_M-da/dN$ and $\mathrm{\Delta }{\delta }_G-da/dN$ were attained through da/dN experiment by taking 17Cr16Ni2 stainless steel, and their discrepancies were compared. The results showed that at the early and middle periods, the relationships of $\mathrm{\Delta }{\delta }_M-da/dN$ and $\mathrm{\Delta }{\delta }_G-da/dN$ could be expressed by Paris law, and da/dN driven by $\mathrm{\Delta }{\delta }_M$ was faster than that by $\mathrm{\Delta }{\delta }_G$ notably; at the later period, the experimental data of $\mathrm{\Delta }{\delta }_M-da/dN$ and $\mathrm{\Delta }{\delta }_G-da/dN$ deviated from the fitted Paris curves and were above them with being crossed with each other; in the total variation range of CTOD, it was better to fit the relationships of $\mathrm{\Delta }{\delta }_M-da/dN$ and $\mathrm{\Delta }{\delta }_G-da/dN$ by polynomial method rather than Paris law.

H₂S is a gas that can cause poisoning with a composition starting from 2.5 ppm. This study investigated the ability of gas sensors to detect H₂S gas at below 1 ppm. The primary material used for the gas sensor was ZnO. To increase sensor response, Au was used as a decorated metal. These materials were dissolved using deionized water with ultrasonication and were deposited by solution deposition method onto the Pt electrode. Powder and film characterizations were made using XRD, SEM, and TEM. The characterization results show high crystallinity of the annealed ZnO. The coating material shows a highly porous interconnected structure that can absorb gas quickly. There are Au spots attached to the ZnO particles, which are spherical and homogeneous. Based on these results, the device sensor can detect H₂S gas with a high sensing response even at low gas concentration.

In this study, the hydrothermal method was used to synthesize Na${}^{+}$-doped ZnO nanowires with different concentrations of Na${}^{+}$ ions under different synthesis temperatures. First, ZnO films with a thickness of about 300 nm were deposited on glass substrates as a seed layer, and C₆H${}_{12}$N₄, Na(NO${}_3)\cdot 6$H₂O, and Zn(NO${}_3{)}_2\cdot 6$H₂O were used as source materials to grow the Na${}^{+}$-doped ZnO nanowires using different Na${}^{+}$ concentrations and under different synthesis temperatures. After the Na${}^{+}$-doped ZnO nanowires were synthesized, their XRD patterns were obtained to analyze their crystal phases. FESEM observations were used to observe the synthesized morphologies, and a fluorescence spectrophotometer was used to show the photoluminescence excitation (PLE) and photoluminescence (PL) emission properties of the Na${}^{+}$-doped ZnO nanowires. We showed that Na${}^{+}$ precursor concentrations and synthesis temperatures had considerable effects on the crystal phase, surface morphologies, and PL emission and PLE properties of the Na${}^{+}$-doped ZnO nanowires.