Mechanical and Conductive Properties of Cu Matrix Composites Reinforced by Oriented Carbon Nanotubes with Different Coatings

Because of the dilemma that the current industrial Cu enhancement methods lead to a significant decline in conductivity and ductility, Cu matrix composites reinforced by oriented multi-walled carbon nanotubes (MWCNTs) were prepared through sintering, hot extrusion, and cold drawing. Before sintering, Ni, Cu, and Ni&Cu coatings were electroless plated on MWCNTs as the intermediate transition layer, and then they were mixed with Cu powder through a nitrogen bubbling assisted ultrasonic process. By analyzing the composition, microstructure, and formation mechanism of the interface between MWCNTs and the matrix, the influence and mechanism of the interface on the mechanical properties, conductivity, and ductility of the composites were explored. The results indicated that MWCNTs maintained a highly dispersed and highly consistent orientation in the Cu matrix. The coating on Ni@CNT was the densest, continuous, and complete. The Ni@CNTs/Cu composite had the greatest effect, while the Cu composite reinforced by MWCNT without coating had the smallest reduction in elongation and conductivity. The comprehensive performance of the Cu@CNTs/Cu composite was the most balanced, with an ultimate tensile strength that reached 373 MPa, while the ductility and conductivity were not excessively reduced. The axial electrical and thermal conductivity were 79.9 IACS % (International Annealed Copper Standard) and 376 W/mK, respectively.

Ultrasound in Continuous Tubular Crystallizers: Parameters Affecting the Nucleation Rate

Ultrasound has proven to be an important tool for controlling nucleation in continuous tubular crystallizers. However, insufficient information is available about the parameters controlling the nucleation rate in a continuous ultrasonic process. Previous research has studied parameters related to the nucleation rate, but has not measured the nucleation rate directly or continuously. In this work, the nucleation rate is measured continuously and inline to solve this problem and achieve a better process understanding. The results indicate that the ultrasound-assisted nucleation process is presumably dominated by secondary nucleation. Additionally, the supersaturation, residence time and flow rate have a strong influence on the nucleation rate. On the other hand, the influence of the ultrasonic power is crucial but levels off once a certain amount of power is reached. The static pressure in the system determines the effective ultrasonic power and is therefore also important for the nucleation rate. Finally, maintaining an equal power per unit of volume and an equal residence time by increasing the tubing diameter seems to be a good scale-up method. These results will improve understanding of ultrasonic tubular crystallizers and how to control them.

Research on Ultrasonic-Assisted Multi-Point Stretch Bending Process of Aluminum Profile

The tensile and bending process of asymmetric L-shaped aluminum alloy profile is studied by the Abaqus software using the finite element numerical simulation method. The geometric parameters of the ultrasonic-assisted vibration multi-point die (UMPD), and the law of influence on the stress-strain and spring-back of the L-section profile after bending are studied. The results show that the UMPD can reduce the forming stress of the profile during plastic deformation, and the stress-strain distribution of the aluminum profile is more uniform. The changes in the ultrasonic vibration frequency and amplitude of the mold are beneficial to reduce the spring-back of aluminum profiles. The ultrasonic process parameters with a vibration frequency of 20 kHz and an amplitude of 0.02 mm have the best effect on suppressing spring-back, which is reduced by 20.6% compared to the case of no ultrasonic application. Finally, it is verified by experiments that the experimental results are basically consistent with the simulation results, and the changing trend of spring-back deformation is consistent.

The structure and properties of porous copper produced by powder metallurgy using NaCl as space holder agent

In this work, the porous copper samples were produced via the powder metallurgy using NaCl as the space holder. Cu and NaCl powders were mixed by a double-cone mixing machine and then pressed into the cylindrical pellets (12 mm in diameter) at the pressure of 100 MPa. The sintering was done in a tube furnace using hydrogen environment at 900 oC for 1h. After sintering, the samples were subjected to vibration in water for 3h to remove the NaCl particles. The results showed that the porous copper has been produced and NaCl has been completely removed after the ultrasonic process in distilled water. Using NaCl space holder, the porous structure has two types of pores: the macropore induced by the removement of NaCl and the micro-pore induced by the partial sintering of Cu powders. With increase of NaCl content from 0 to 20 wt.%, the porosity and permeability of the samples increased from 24 to 58 % and from 1.53×10-13 to 12.46×10-13 m2, respectively. However, the compressive strength of the samples has a decrease with the increase of porosity resulted from the increase of NaCl content.

Ultrasonic Process Intensification During the Preparation of Dimethyl Carbonate Based on the Alcoholysis of Ethylene Carbonate and the Kinetics Behaviors of Dimethyl Carbonate

The use of ultrasonic process intensification in the preparation of dimethyl carbonate (DMC) by alcoholysis of ethylene carbonate can make up for several disadvantages of heterogeneous catalysis, such as low...