Continuous nanofiber yarns were prepared using the electro-blown and hanging yarn process. Unlike typical electrospinning devices, this method uniquely controls the spinning process to induce the hanging phenomenon, and the resulting hanging yarn is twisted to form nanofiber yarns. A polyvinylidene fluoride nanofiber yarn was successfully prepared using the electro-blown and hanging yarn process. Scanning electron microscopy observations confirmed that the nanofibers prepared by this method exhibited good orientation within the yarn. The results indicate that the conductivity of the polymer solution and the applied voltage are crucial for inducing the hanging yarn process, ensuring stable continuous spinning. A possible mechanism is proposed, suggesting that adjusting the solution’s conductivity and controlling the spinning voltage can utilize defects in the yarn-hanging process during spinning to prepare nanofiber yarns.

In this paper, a ball grid array（BGA） solder joint shearing experimental equipment is designed, and a supporting upper computer software to control the movement of the equipment is developed. Based on this equipment, the shear mechanical properties of BGA solder joints of two materials（SAC305 and Sn63Pb37） at fixed heights（60 μm）, different shear rates（0.1, 0.3, 0.5, 0.7 mm/s）, as well as shear mechanical properties at fixed shear rates（0.5 mm/s） and different shear heights（60, 80, 100, 120 μm） are studied. Experiments show that the shear strength of the solder joints of the two materials increases with the increasing of the shear rate under the condition of fixed shear height, and the shear strength of the solder joints of both materials decreases with the increasing of shear height under the condition of fixed shear rate. Experimental teaching through this equipment helps to cultivate students’ scientific thinking and improve students’ practical ability.

纤维直径对纤维的物理性能有着显著影响.在纤维生产过程中,不同工艺参数的组合会直接影响纤维的直径.为探索生产工艺参数与纤维直径之间的潜在影响关系,提出了基于响应面法(RSM)的聚乳酸芯壳纱纤维直径预测模型.通过开发双喷嘴静电纺纱实验装置,实现聚乳酸芯壳纱纤维的生产.利用响应面法对纺丝电压、转杯转速、总体积流量和正负体积流量比展开实验探索,评价各工艺参数对纤维直径的影响.根据实际的工艺参数数值进行计算并校验,获得工艺参数与聚乳酸芯壳纱纤维直径的回归方程和耦合关系.实验结果表明:当纺丝电压为11.42 kV,转杯转速为186.3 r/min,总体积流量为1.04 mL/h,正负体积流量比为127∶100时,聚乳酸芯壳纱纤维直径达到最小值,为0.895 μm,与模型预测结果相符,未来可用于指导纤维纱线的生产.

Electrospinning (ES) of ceramic fibers has mostly remained in the research level, which can be because of the hard process and parameters controlling the low rate of production. The yield of fiber production by solution blow spinning (SBS) is exciting but the production process is unstable due to the reverse flow phenomenon. In this paper, we prepared high-performance ceramic fibers by gas-assisted electrospinning (GES), which combined the advantages of ES and SBS. Also, comprehensive numerical and experimental analysis for nanofibers produced using GES are provided. The gas flow characteristics through different parameters' nozzle were investigated numerically using computational fluid dynamics and experimentally in a custom-built gas-assisted electrospinning setup to produce SiO2 nanofibers.

At present, the situation of air pollution is still serious, and research on air filtration is still crucial. For the nanofiber air filtration membrane, the diameter, porosity, tensile strength, and hydrophilicity of the nanofiber will affect the filtration performance and stability. In this paper, based on the far-field electrospinning process and the performance effect mechanism of the stacked structure fiber membrane, nanofiber membrane was prepared by selecting the environmental protection, degradable and pollution-free natural polysaccharide biopolymer pullulan, and polyvinylidene fluoride polymer with strong hydrophobicity and high impact strength. By combining two kinds of fiber membranes with different fiber diameter and porosity, a three-layer composite nanofiber membrane with better hydrophobicity, higher tensile strength, smaller fiber diameter, and better filtration performance was prepared. Performance characterization showed that this three-layer composite nanofiber membrane had excellent air permeability and filtration efficiency, and the filtration efficiency of particles above PM 2.5 reached 99.9%. This study also provides important reference values for the preparation of high-efficiency composite nanofiber filtration membrane.