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Herein, a palladium-coated copper wire was prepared using a halogen-free direct coating process, and the effects of the coating temperature on the morphology of the palladium coating and the mechanical properties of the wire were studied. The structural characteristics of the coating and copper matrix as well as the diffusion, reaction, and bonding characteristics of the elements at the copper–palladium interface were investigated. Results show that the deposition rate of palladium and the aggregation of palladium grains were accelerated with increasing coating temperature, promoting the formation of large palladium particles on the surface of the palladium-coated copper wire. The strength of the coated wire decreases and the elongation increases with increasing coating temperature. At 400 °C, the thickness of the coating was approximately 51 nm coating, consisting of approximately 4 nm nanocrystals. The improvement in plasticity was attributed to the distortionless recrystallized subgrain nucleus formed by the cell structure comprising dislocation tangles in the copper matrix, which reduces the matrix dislocation density. Positive and negative edge dislocations were present in the coating, and the two dislocation lines of the edge dislocation dipole offset each other. Numerous crystal defects were found in the copper–palladium bonding interface zone. Moreover, copper unidirectionally diffuses into the palladium coating, forming the intermetallic-compound CuPd in the interface bonding zone. Furthermore, the formation of twins was caused by the change in the stacking order of atoms due to the stacking fault occurring on the crystal surface, and the thickness of the diffusion zone was approximately 9 nm. [Display omitted] • A uniform Pd coating with a thickness of 51 nm was obtained. • Diffusion and reaction behavior of Pd coating on Cu wire were explored. • Formation mechanism of Pd coating morphology was proposed. • Effect of temperature on the mechanical properties of the wire was discussed. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract This study describes the effect of coating temperature on the performance of mechanical particle coating using ethylcellulose, which was done to produce controlled-release particles (diameters less than 100 μm) with different release rates. First, theophylline crystals were spheronized using a mechanical powder processor, yielding theophylline spheres (used as core particles). Second, ethylcellulose aqueous dispersion was powdered by spray-freeze drying to prepare colloidal agglomerates (used as coating powder). Finally, the spheres and agglomerates were mechanically mixed at various temperatures using the processor to produce composite particles. The ethylcellulose agglomerates were pulverized during processing to coat the theophylline spheres effectively. When the coating temperature was higher than the glass transition temperature (T g) of ethylcellulose, the amount of coated polymer increased significantly due to plastics deformation, causing thickening of the coated layer. The porosity of the coated layer decreased upon coalescence of coated polymer particles due to plastic deformation, which prevented the appearance of cracks in the film during curing. Therefore, controlled-release fine particles with various release rates can be produced effectively by mechanical particle coating at temperatures higher than the T g of the polymer. [ABSTRACT FROM AUTHOR]

Abstract: Coating temperature is important for the coating reliability and reproducibility during the process of atmospheric plasma spray. A novel measurement and control approach for substrate and coating temperatures is presented. It is based on infrared (IR) pyrometry combined to specific robot spray trajectories in order to avoid harsh environment of spray workshops. The temperature evolution is continuously detected and recorded during preheating, spraying and cooling stages. The two specific factors, periodic average temperature and standard deviation were adopted to evaluate the temperature variation and the fluctuation of the thermal cycle relevant to one robot spray cycle based on the statistical method. These two factors are successful in describing the temperature variation during experimental processing sets. Finally, based on the monitoring system, the influence of Z-type robot spray trajectory parameters, including spray distance, scanning velocity and scanning step on coating temperature characterized by the two factors, is systemically investigated. Experimental results show that average temperature has no evident difference as a function of scanning velocity and no fixed relationship with scanning step, but just is dominated by the heating time of plasma jet and particle flux. Therefore, the selection of optimal scanning velocity just needs to take the temperature fluctuation into consideration. The temperature fluctuation decreases when scanning step increases, but both average temperature and fluctuation decrease with the increasing of spray distance and vice versa. Finally, on the basis of experimental results, a control experiment of sprayed coating temperature is presented to obtain constant temperature cycles by means of adjusting robot trajectories, cooling, among other considered operating parameters. Excellent control performance is observed. [Copyright &y& Elsevier]