Ce3+/Tb3+-coactived NaMgBO3 phosphors toward versatile applications in white LED,FED, and optical anti-counterfeiting

Ce³⁺/Tb³⁺ co-doped NaMgBO₃ phosphors were successfully synthesized by solid-state method. Under 381 nm excitation, the cyan emission owing to the 5d → 4f of Ce³⁺ ions and green emissions arising from the ⁵D₄ → ⁷F_J (J = 6, 5, 4, and 3) transitions of Tb³⁺ ions were seen in all the phosphors. Through theoretical analysis, one knows that the energy transfer from Ce³⁺ to Tb³⁺ ions with high efficiency of 83.74% was contributed by dipole–dipole transition. Furthermore, the internal quantum efficiency of NaMgBO₃:0.01Ce³⁺,0.03Tb³⁺ phosphor was 54.28%. Compared with that of at 303 K, the emission intensity of the developed products at 423 K still kept 73%, revealing the splendid thermal stability of the studied phosphors. Through utilizing the resultant phosphors as cyan-green components, the fabricated white-LED device exhibited an excellent correlated color temperature of 2785 K, high color-rendering index of 85.73, suitable luminance efficiency of 25.00 lm/W, and appropriate color coordinate of (0.4279, 0.3617). Aside from the superior photoluminescence, the synthesized phosphors also exhibited excellent cathode-luminescence properties which were sensitive to the current and accelerating voltage. Furthermore, the NaMgBO₃:0.01Ce³⁺,0.03Tb³⁺ phosphors with multi-mode emissions were promising candidates for optical anti-counterfeiting. All the results indicated that the Ce³⁺/Tb³⁺ co-doped NaMgBO₃ phosphors were potential multi-platforms toward white-LED, field emission displays, and optical anti-counterfeiting applications.     

Fabrication of high-efficiency anatase TiO2 photocatalysts using electrospinning with ultra-violet treatment

In metal oxide nanofiber fabrication using the electrospinning method, heat treatment is performed at temperatures of 500°C or higher for crystallization and polymer desorption. Therefore, it is difficult to fabricate low-temperature phase metal oxides that crystallize at low temperatures. TiO₂, a representative metal oxide often used as photocatalysts, is known to have higher photocatalytic activity in the low-temperature phase (anatase structure) than in the high-temperature phase (rutile structure). Studies on the fabrication of TiO₂ anatase nanofibers using conventional electrospinning have reported disadvantages such as the partial expression of rutile structures and low crystallinity. This study developed an anatase TiO₂ nanofiber as a high-efficiency catalyst based on the electrospinning method and a residual organic matter cleaning method that employs ultra-violet (UV) light. We fabricated nanofibers using the electrospinning method and implemented TiO₂ nanofibers with the anatase structure through heat treatment at 260°C. Residual organics remaining after heat treatment of the fabricated crystalized TiO₂ nanofibers were removed by exposing them to UV light, thereby improving photocatalytic efficiency. The photocatalytic efficiency of the fabricated TiO₂ nanofibers was confirmed through a methylene blue (MB) decomposition experiment under visible light irradiation. The photocatalytic efficiency (time taken for the concentration of the MB solution to reach 50%) of the UV-treated TiO₂ nanofibers was approximately six times higher than of P25 and the heat-treated nanofibers.     

The effect of washing process on the cracking of ZrO2 microspheres by internal gelation

ZrO₂ microspheres are widely used as a simulant of UO₂ in the development of nuclear fuel. However, the cracking of ZrO₂ microspheres prepared by internal gelation is still a challenge during drying and sintering processes. To address this issue, we designed and optimized the washing process for obtaining crack-free ZrO₂ microspheres. Through thermogravimetric, infrared, Raman, BET, and SEM analysis, it is shown that the cracking of the microspheres is mainly related to the pores in microspheres. The washing solvent with low surface tension is used to reduce the effect of capillary force on pore shrinkage. Therefore, the optimal washing process was designed as trichloroethylene (TCE)—0.5 M NH₃.H₂O—Propylene glycol methyl ether (PM) and gel microspheres with a high specific surface area of 315.3 m²/g and pore volume of 0.4125 cm³/g were obtained. The characterizations also further showed that when the microspheres were dried and sintered, the water vapor and the decomposition gas of organic matter were completely released from the pores in the microspheres. Our new washing process could be directly extended for preparing crack-free ceramic microspheres by internal gelation.     

Highly-modified polylactide transparent blends with better heat-resistance,melt strength,toughness and stiffness balance due to the compatibilization and chain extender effects of methacrylate-co-glycidyl methacrylate copolymer

A core-shell modifier with the cross-linked acrylate and silicone copolymer as the core and polymethyl methacrylate (PMMA) as the shell (PASi-g-PMMA) was used to toughen the brittle polylactide (PLA). In addition, the copolymer of methyl methacrylate (MMA) and glycidyl methacrylate (GMA) (MG) was utilized to further enhance the modification efficiency of the PASi-g-PMMA. The MG copolymer played the double roles of compatibilizer and chain extender, which not only improved the interfacial adhesion between the PLA and PASi-g-PMMA particles, but also increased the molecular weight and chain entanglement of the PLA. Compared with the PASi-g-PMMA toughened PLA blend, the PLA/PASi-g-PMMA/MG blends showed much higher heat-resistance, melt strength, transparency, toughness and stiffness balance. When the PASi-g-PMMA content was 20 wt%, 20 wt% MG increased the glass transition temperature (T_g), complex viscosity (η*), transparency, impact and tensile strength of PLA/PASi-g-PMMA blend from 60.1°C, 1.9 × 10³ Pa·s, 76.1%, 748 J/m and 37 MPa to 71.5°C, 0.5 × 10⁴ Pa·s, 78.4%, 860 J/m and 45 MPa for the PLA/PASi-g-PMMA/MG blend. This research provided a facile and practical method to overcome the shortcomings of the PLA and promoted its application in broader fields.     

Printability,shape-memory,and mechanical properties of PHB/PCL/CNFs composites

Shape-memory polymers have attracted attention as smart implant materials in recent years because they are lightweight, low-cost, easily processable, and because they undergo large deformation. Here, cellulose nanofibers (CNFs) were used as a reinforcement for polyhydroxybutyrate (PHB)/polycaprolactone (PCL) composites to improve mechanical properties. The composites were investigated by rheological tests, differential scanning calorimetry, dynamic mechanical analysis, mechanical property tests, and shape-memory tests. The printability of PHB/PCL/CNFs composites was demonstrated by using them to print interconnected porous structures with a gyroid surface. The results showed that the PHB/PCL (80:20) composites with 1 wt% CNF displayed the best comprehensive mechanical and shape-memory properties. As a functional verification, a model of the self-opening hand was fabricated by 3D printing, and its deformation and recovery capabilities were evaluated.     

Antibacterial self-healing anticorrosion coatings from single capsule system

It is highly desirable to develop self-healing anticorrosion coatings with enhanced antibacterial function to prevent the scratched area to be fouled or corroded in harsh environments. Herein, we report antibacterial self-healing anticorrosion coatings via the simple incorporation of the easily synthesized single polymer microcapsule system. Well-defined polymer microcapsules containing isophorone diisocyanate (IPDI) as a healing agent and 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) as antibacterial molecules were synthesized by one-pot polymerization. The diameter and core fraction were around 30 μm and 90%, respectively. The active DCOIT content in the core material could be precisely controlled by adjusting the DCOIT/IPDI feeding ratio. The DCOIT/IPDI microcapsules-embedded protective coating exhibits an adaptive self-healing anticorrosion property, as shown by electrochemical test under the condition of the salt-water immersion. Furthermore, the self-healing coating showed efficient antibacterial function against Escherichia coli and Pseudomonas aeruginosa, which is due to the released active biocide molecules on the damaged surfaces. In contrast to other systems, this single capsule system without any catalyst is perspective for extending the service time of the antibacterial self-healing materials in harsh environment.     

A high Cr (VI) absorption efficiency and easy recovery adsorbent: Electrospun polyethersulfone/polydopamine nanofibers

Cr (VI) is a highly toxic pollutant to humans, to achieve high adsorption capacity, easy recovery, and good reusability, polyethersulfone/polydopamine (PES/PDA) ultrafine fibers were prepared successfully. A series of preparing effect factors were investigated systematically and the optimum one is 8.5 pH value at room temperature and 2 g/L dopamine concentration. And then they were used as an adsorbent for the removal of Cr (VI) ions from wastewater. The effect factors pH, the adsorbent dosage, and time were discussed on Cr (VI) adsorption process and the Cr (VI) adsorption behavior was investigated. It is found that the maximum Cr (VI) adsorption capacity is 115.2 ± 4.8 mg/g at pH = 3 using 0.06 g PES/PDA with 80 mins. The Cr (VI) adsorption process followed the pseudo-second-order model (r² ≥ 0.99) and adsorption isotherms were fitted to the Langmuir model (R² ≥ 0.999). Furthermore, the Cr (VI) adsorption mechanism was supposed according to the X-ray photoelectron spectroscopic results. Finally, PES/PDA ultrafine fibers were considered to be a promising adsorbent with good stability (decomposing temperature, 356°C), high adsorption efficiency (112.1 ± 2.5 mg/g), and good reusability (three times) on the coexistence of anions and the actual industry wastewater environment.     

基于控制载波自由度的级联H桥逆变器改进型PWM技术

随着级联H桥(CHB)多电平逆变器输出电压与功率等级的增加,提高载波移相脉宽调制(CPS-PWM)策略下直流侧电压利用率以及改善低调制度时谐波性能比较差的问题具有重要的意义.通过对正弦波脉宽调制(SPWM)以及梯形波脉宽调制(TPWM)原理及输出电压特性的分析,该文提出一种基于控制载波自由度的改进型CPS-PWM策略,该策略基于移相载波自由度,通过周期性的循环改变三角载波的排列方式,利用改进的多载波代替原CPS-SPWM中的三角形载波进行调制,从而可以显著地提高输出电压的直流电压利用率;又能在实现各级联单元功率均衡的条件下,降低输出电压总畸变率,有效地改善低调制度时的谐波性能,且各单元开关频率和损耗相同,同时各开关管工作应力也相同,因此提高了系统的可靠性.该文给出改进型CPS-PWM策略输出电压基波幅值和功率均衡分析,同时列举三种策略并进行比较,并对该文所提策略进行仿真与实验的验证.     

基于PSO-Powell混合算法的软磁复合材料二维矢量磁滞特性模拟

针对经典矢量Preisach模型仅能模拟各向同性磁滞特性的缺陷,提出改进的矢量磁滞模型.通过引入幅值与方向角的关联参数改善磁场强度的曲线形态,使模型能够考虑软磁材料的各向异性特征.利用矢量磁特性实验平台对软磁复合材料(SMC)在二维旋转磁化激励下的磁特性进行测量,根据测量的极限磁滞回线,分别构造标量和矢量Everett函数.提出基于粒子群(PSO)和Powell方向加速的组合优化策略,显著改善PSO的局部寻优能力,提高计算效率和精度,进而实现矢量Preisach磁滞模型的高效参数辨识.矢量磁滞特性的仿真结果与测量结果相吻合,验证了该文所提改进矢量磁滞模型及其参数辨识方法的有效性.     

改进互联通信荷电状态下垂控制及功率均衡优化

作为直流微电网中不可或缺的组成部分,分布式直流储能系统起着平抑系统能量波动、维持系统功率平衡的重要作用.为了提高储能系统工作的可靠性,该文对互联通信荷电状态(SOC)下垂控制策略进行深入研究.首先,对传统互联通信SOC下垂控制的系统性能及存在的问题进行分析,为之后控制策略的改进奠定基础;其次,提出改进互联通信SOC下垂控制策略,即在传统互联通信SOC下垂控制基础上引入变化系数;再次,通过对改进互联通信SOC下垂控制系统性能的分析,得到变化系数参数设计方法,在提高系统功率收敛速度的同时,限制功率输出最大值,从而提高系统可靠性;最后,对由两台储能模块构成的储能系统进行仿真和实验,实验结果验证了改进策略的快速性及对输出功率的限制.