Numerical study of shock waves propagating through right angled multiple elbows

Introduction The elbow is one of the important elements used in pipe lines, and it is very important to clarify the propagating phenomena of shock waves through the elbow for engineering applications. Although some investigations of the propagating shock in the single and double elbows have been carried out[1?The working gas is air. The numbers of the grid in the computational domain are 251·(a) Type 4-1 (b) Type 4-2 Fig.3 Pressure distributions on each wall the merging with the 2nd shock…     

Combustion Behavior of Fluorocarbon/Boron/AP Propellant at high pressure

Thermal decomposition and the burning properties of fluorocarbon/boron/AP propellant granule have been investigated. The fluoro-carbon binder (FBDR) was oxidized by the decomposition products of admixed ammonium perchlorate (AP) and its decomposition region was 150°C lowered in the slow thermolysis. The boron particles, however reacted with neither FBDR nor AP at 550°C. In the micro-motor tests, the boron particles completely burnt at a pressure range of from 30 MPa to 80 MPa in a short period of time (one millisecond) even at a low characteristic exhaust velocity. Minimum free volume, however, was needed to complete the combustion reaction in the chamber case. The characteristic exhaust velocity significantly decreased at below the characteristic chamber length of 11 cm. The boronized propellant showed low temperature sensitivity between −30°C and 60°C.     

Easy formation process of anatase-TiO2 coating layer strongly bonded to titanium metal surface

Because of the formation of a surface passive film (rutile TiO₂) on its surface layer, titanium metal shows adequate corrosion resistance. As the surface layer (passive film) of titanium metal is very stable, any functionalization of the titanium metal has been generally performed using relatively complicated methods. This is because any direct oxidation of titanium metal only leads to the formation of rutile TiO₂ over the entire temperature range. Chemical reactions using titanium chemicals can easily produce anatase TiO₂ at temperatures of ≤600°C. Using precursors is one of the ways of producing an anatase TiO₂ coating on titanium metal. However, in previous studies, anatase TiO₂ layers easily peeled off when they were used in flowing water. Herein, we describe a simple process for obtaining an anatase TiO₂ coating layer strongly bonded to the titanium metal surface. In our process, titanium metal was pretreated with a reducing agent to create a surface TiH₂ layer, whose condensation reaction easily proceeds with a precursor (composed of oxalic acid and tetra-butoxy titanium). Subsequently, the treated titanium metal was calcinated at 550°C in air to achieve strong bonding between the anatase TiO₂ coating layer and titanium metal surface. The treated titanium metal exhibited excellent photocatalytic activity.     

Hydrophilic property of titanium oxide aiming for bio-applications

Surface functionalization of titanium metal is very attractive for bio- and environmental applications. This is because titanium metal is very stable and has a good biocompatibility. In this case, surface roughness and crystalline structure are important factors for obtaining effective characteristics. Titanium metal is usually covered with a surface passive film of thermodynamically stable rutile-TiO₂ that grows as the heat treatment temperature in air increases. On the other hand, to obtain an anatase-TiO₂ surface layer on titanium metal, we must employ specific treatments such as our previous method, which uses a silica-coexisting heat-treatment process. In this paper, the relationship between the fine structure formed on the titanium metal and the surface hydrophilic property was clarified, and the potential for the bio-application was discussed. The formed anatase-TiO₂ coexisting with silica exhibited improved biocompatibility with good apatite formation.     

Easy control of surface morphology through a natural phenomenon

This paper provides an innovative controlling process of surface morphology. The contact area between a liquid and a solid is strongly affected by the critical surface tension (cft) of both materials. Using this phenomenon, a wide range of morphologies, from flat surface layers to sea-grape-like surface structures, were created. Due to the bleed-out phenomenon, low-molecular-mass additive (liquid) oozed out of a precursor polymer (solid), leading to different surface morphologies depending on the cft values of the liquid (Mcft) and solid (Pcft). When Mcft < < Pcft, a flat surface layer was obtained; however, in the case of Pcft < < Mcft, the formation of a sea-grape-like surface layer was created. Tetra-butoxy-titanium and polydimethylsiloxane were used as low-molecular-mass additive and precursor polymer, respectively. After coating on titanium metal and calcination, sea-grape-like materials composed of titanium oxide and silicon oxide were obtained. Furthermore, unique characteristics (bioactivity, photocatalytic activity, and prevention of atomic diffusion) were observed. A remarkable increase in the wettability, bioactivity, and catalytic activity of materials was achieved using our simple process to create unique surface morphologies. Our proposed process is applicable to a wide range of materials and morphologies, and can be used in catalysts, biomaterials, and environmental barrier coatings.