Cleaning the basis metal of surface films in the spray-deposition of powders

Conclusions In gasothermic spray-deposition the surface of the basis material experiences self-cleaning as a result of the disintegration of surface films by frictional forces set up by the spreading layer of particles and their subsequent removal to the periphery of the contact zone. The intensity of self-cleaning of the surface of a basis material grows with increasing velocity of the particles being deposited. The self-cleaning phenomenon occurring on the basis material in the zone of collision with particles being deposited facilitates the formation of physical contact with the powder particles subsequently interacting with this zone on the surface of the basis material.Translated from Poroshkovaya Metallurgiya, No. 11(251), pp. 41–47, November, 1983.     

Effect of surface oxide films on the properties of pulse electric-current sintered metal powders

Metallic powders with various thermodynamic stability oxide films (Ag, Cu, and Al powders) were sintered using a pulse electric-current sintering (PECS) process. Behavior of oxide films at powder surfaces and their effect on the sintering properties were investigated. The results showed that the sintering properties of metallic powders in the PECS process were subject to the thermodynamic stability of oxide films at particles surfaces. The oxide films at Ag powder surfaces are decomposed during sintering with the contact region between the particles being metal/metal bond. The oxide films at Cu powder surfaces are mainly broken via loading pressure at a low sintering temperature. At a high sintering temperature, they are mainly dissolved in the parent metal, and the contact regions turn into the direct metal/metal bonding. Excellent sintering properties can be received. The oxide films at Al powder surfaces are very stable, and cannot be decomposed and dissolved, but broken by plastic deformation of particles under loading pressure at experimental temperatures. The interface between particles is partially bonded via the direct metal/metal bonding making it difficult to achieve good sintered properties.     

原子荧光光谱法测定微量镉的增感效应

研究了4种过渡金属阳离子、30多种有机化合物和7种表面活性剂对原子荧光光谱法测定镉的荧光强度的影响。结果发现,Co(,Ni(以及一些含氮氧键、含氮键和含氮硫键的有机化合物对镉荧光强度有较好的增感效应;部分含氧键的有机化合物有较小增感作用;表面活性剂对镉的荧光信号有较强的抑制作用。对金属离子及有机试剂的增感机理进行了探讨。