Papers by Keyword: Powder Jet Deposition

Abstract: This study aimed to create a thick hydroxyapatite (HAp) film on the surface of a human tooth by using a newly developed powder jet deposition (PJD) device for dental handpieces, and sought to examine the microstructural and mechanical properties of the resulting HAp film. The film was evaluated on three-dimensional view, surface roughness, Vickers hardness, and bonding strength before and after artificial aging through thermal cycling (555°C) for 500 cycles (30 sec for each cycle, 20 sec of dwell time).The HAp particles in the deposited film were densely packed, and the HAp films three-dimensional microstructure and its rough surface were maintained after thermal cycling. There was no significant difference in either the HAp films Vickers hardness or the bonding strength between the film and the enamel substrate before and after thermal cycling. The HAp films created in this study demonstrated excellent microstructural and mechanical properties even after the application of thermal stress. We demonstrated the possibility of using a new type of powder jet deposition (PJD) method we developed to form a new type of interface between the tooth and biomaterials. Consequently, we propose the use of this method in new dental treatments.

Abstract: Powder jet deposition (PJD) method is one of the blasting methods to generate surface coatings. The optimization of PJD conditions has been reported in our previous research. However, the deposition mechanism in PJD is still under investigation. Impact phenomena between an alumina particle with the mean particle size of 2 μm and a glass substrate has been successfully simulated by smoothed particle hydrodynamics (SPH) method. From the simulation result, we have deduced that a cubic particle is fractured by an impact, and it is adhered on to the substrate. It has been also deduced that substrate is removed by a spherical particle impact. Furthermore, PJD experiments of alumina particles blasted onto a glass substrate were also conducted. The particle size distribution of rectangular particles before and after impact was measured. It was found that the particle sizes after impact averagely became smaller than those before impact. The substrate was partly removed when spherical particles impact. From the results of the simulation and the experiment, we believe that the rectangular particles are fractured due to the impacts at the moment blasting onto the substrate, and then, firmly deposited on the substrate.

Abstract: Amorphous NiP plate is used as a mold of precision optical parts owing to the superior machinability. In the amorphous NiP plate, some pores, whose diameter is about 100m, are generated occasionally. At present, the amorphous NiP plates with pore are rejected. However, because size of the mold becomes large in recent years, the possibility of pores becomes high. In addition, the cost of the amorphous NiP plate also becomes high. Therefore, reparation method of the pore in the amorphous NiP plate should be developed. In this paper, laser assist powder jet deposition is proposed as a reparation method of the amorphous NiP plate. And fundamental experiments are carried out.

Abstract: Thick films are needed in micro-electro-mechanical systems (MEMS) as insulation, piezoelectric and ferroelectric materials. To form the thick film, powder jet deposition (PJD) method has been proposed. In the PJD process, microparticles are sprayed out from nozzle under the conditions of room temperature and atmospheric pressure, and make a film on the substrate. We have developed a new jet mechanism of double-nozzle type, and reported its results previously [1]. In this study, we optimized the shape of the nozzle through investigating the influence of different dimensions and shape of the nozzle on the particles blasting velocity. As a result, it is found that nozzle diameter has a large affect on particles velocity.