Materials Science Forum Vol. 1003

Abstract: Modified graphene (MG) incorporated into a matrix of polyvinyl alcohol (PVA) were prepared by a hydrothermal method and ultrasonic dispersion. The effect of high MG content on the properties of composite films was studied. Due to the chemical reaction between MG and PVA, the water resistance and electrical conductivity were improved. The properties of new film and the possibility of its application as conductivity materials were discussed.

Abstract: PA6 fibers and fabric properties were studied by adding PDMS, and PA6 / PDMS blend fibers were prepared by melt spinning. The experiment found that the addition of PDMS can significantly promote the rheology of the PET / PDMS blend melt. DSC tests show that the addition of PDMS has basically no effect on its crystallization and melting characteristics. With the increase of PDMS content, the contact angle of water on the blended fabric surface increased. KES-FB was used to evaluate fabrics made from PA6 / PDMS blended fibers. It was found that with the increase of PDMS content, the softness and elasticity of the fabrics were improved, and the stain resistance experiments showed that the modified fabrics had good resistance dirty performance.

Abstract: The effect of polymerization on the swelling properties of a sodium bentonite has been investigated experimentally using free swelling index (FSI). Using free radical polymerization method in cationic solution with acrylate acid as the monomer (M) and potassium persulfate as initiator (I), the optimum conditons for higher FSI value in 0.6 M NaCl solution were pH of 5.5 and I/M ratio of 0.005. The polymerized bentonite (PB) had much higher FSI values than that of untreated bentonite (UB) in deionized water and 0.6 M NaCl solution. However, in the 0.6 M CaCl₂ solution, the FSI value of PB was slightly lower than that of UB and the reason is not clear yet. The X-ray diffraction (XRD) test shows that polymer chains did not enter the interlayer of sodium bentonite crystals and it is postulated that the polymers only wrapped around the particles of the bentonite.

Abstract: The work aim to the reaction mechanism of laser engraving polycarbonate (PC)-based films. The calculation of infrared-laser acting on the PC films, was carried out by using one-dimensional heat conduction model. The power density of laser device required for laser engraving polycarbonate-based films was determined to be 4.86~7.73×10⁴ W/cm². Characterized by the FTIR spectra, SEM, DSC and TGA, the reaction mechanism was studied. The results show that the light-sensitive particles in the PC films absorb the laser energy with wavelength of 1064nm. After reaching the temperature of 509°C, the main chain of PC molecule opened due to the breakage of C-O bond in PC molecular terminal group and C-O bond between PC monomers. As the energy continues to be absorbed, the temperature reach to 610°C, the decomposition products decomposed into carbon black, which can form a black carbon spot.

Abstract: In this paper, upcovnerison luminescence in Er³⁺/Yb³⁺ co-doped NaYF₄ nanophosphors was regulated by changing the Er³⁺ concentration. With increasing the Er³⁺ concentration, the green and red emissions increased first and then decreased, but the intensity ratio of red to green emission decreased monotonically. To clarify the role of Er³⁺ doping, the factors including crystal structure, morphology and size of particle, photon absorption, energy transfer, multi-phonon relaxation, population of emissive levels and emission probability of radiative transitions were considered and analyzed. More importantly, we proposed a simple method for discussing radiation transitions based on luminescence temperature sensing.

Abstract: LYSO:Ce single crystal was widely manufactured by Czochralski method. Considering its high cost and the pollution of the crucible, we tried to prepare the crystal by Verneuil method. Unlike Czochralski method, the Verneuil method need the powders with excellent fluidity and high purity. By comparing the powders annealed at 1100°C,1200°C,1300°C,1400°C and 1500°C, we can obtained the needed powders at 1500°C. We also increased the content of silica to satisfy the volatilization in crystal growth process. The single crystal was prepared by changing the growth parameter. We investigated the phase and the microstructure of the powders and observed the microstucture of the crystal fracture. We discussed the improved method of the process of crystal growth.

Abstract: In this work, the optimal sintering temperature and time of commercial copper paste were tested experimentally. The electrical properties of conductive paste including square resistance and resistivity were characterized and analyzed. The influence of diatomite with different purification processes on the electrical properties of commercial copper paste was analyzed. The performance of copper slurry modified by copper-based modified diatomite prepared by two-step reduction method was analyzed. The optimum square resistance and resistivity was obtained with copper paste doped by 0.25wt.% and 1 h-ball milled diatomite and was 0.02Ω/_ϒ and 0.011Ω·mm, respectively.

Abstract: Based on the drying technology principle of lithium-ion battery cathode coating, the variation law of dry base moisture content and drying rate in the process of hot-air drying and infrared drying was studied. The experimental results show that the cathode coating of lithium-ion battery dried under hot-air and infrared conditions can be divided into three stages: increasing-rate, constant-rate, and falling-rate. The constant-rate stage is the main drying stage, accounting for more than 50% of the weight loss, the falling-rate stage is the main energy consumption stage, accounting for more than 50% of the time. Under the condition of hot-air, the change level of airspeed is the main influencing factor of the drying process, and the drying time can be reduced by about 35% for each 0.7 m/s increase in airspeed. Under infrared conditions, the change level of radiation power is the main influencing factor of the drying process, and the drying time can be reduced by about 34.1% for every 100W of power increase. The optimal drying conditions under hot-air conditions are: air temperature 90 °C, airspeed 2.3 m/s; the optimal drying conditions under infrared conditions are: radiation distance 13 cm, radiation power 200 W. By comparing the best conditions of hot-air and infrared, it can be known that the drying efficiency is higher in the infrared condition and the drying duration is 160 s, but the energy utilization rate in the falling-rate stage in the infrared condition is lower than that in the hot-air condition. Therefore, when infrared drying enters the falling-rate stage, it can be supplemented by hot-air drying to further improve the drying efficiency.

Abstract: Well-crystallized and nanosized LiFePO₄/C composite have been successfully synthesized by spray-drying under N₂ atmosphere. The morphology, physical and electrochemical properties of the LiFePO₄/C were tested and analyzed. The charge transfer resistances (Rct) and chemical diffusion coefficients of lithium ions (D_Li+) in LiFePO₄/C was systematically tested by EIS. The results show that the lithium ions diffusion coefficients obtained from EIS is 1.58×10^-14 cm²·s^-1. The assembled soft-packed cell with LiFePO₄/C show better rate capability and cycling stability. The average capacity retention of LiFePO₄/C soft-packed cell decreases to 100%, 98.9%, 96.5%, 92.4%, and 90.3% when current rate increases to 0.3, 0.5, 1, 2, and 3C, respectively. The capacity retention after 80 cycles is retained at more than 99%.

Abstract: In this investigation, ternary Ag-alloy wires were doped with different Pd and Au concentrations, and each wire was encapsulated in an LED package. The static and dynamic reliability were tested, and the lumen maintenance performance was examined. The static reliability tests included the sulfur test, LTSL, HTSL, and WHTSL. According to the sulfur test data, higher Pd and Au contents led to better lumen maintenance. Furthermore, the bonding wire of the LED with better lumen maintenance in the sulfur test had higher electrical resistance. The brightness decay rate of the white light LEDs was low in low-and high-temperature environments, but it was significantly higher after the WHTSL test. The dynamic reliability test after 1,000 hours of HTOL and WHTOL showed that the lumen maintenance improved with higher Pd and Au contents, indicating that doping Ag-alloy wires with sufficient amounts of Pd and Au can retard degradation due to thermal and humidity aging and oxidation reaction. Therefore, ternary Ag-Pd-Au alloy wires produced with specific drawing and annealing processes are suitable for application to mid-power white light LEDs.