Papers by Keyword: Mechanism

Abstract: Surface self-nanocrystallization (SSNC) is a new surface modification technology to develop new materials, which can obtain nanostructured layers with nanograins on the metals surface without changing the chemical composition of the metals. In this study, SSNC was introduced from the aspects of the preparation methods, microstructural mechanism, mechanical properties, surface roughness, corrosion resistance and applications. This paper will provide experience and reference for further comprehensive researches and industrial applications of SSNC.

Abstract: The effects of the contact pressure P_fric and the oxygen concentration c₀ on the ignition resistance of Ti-6Al-4V were studied by friction in oxygen-enriched atmosphere. The relationship of P_fric-c₀ was built to quantitatively describe the ignition resistance, the combustion microstructures were investigated by XRD, SEM and EDS. Further, the principle of improving the ignition resistance was proposed. It indicates that the relationship of P_fric-c₀ obeys parabolic law. The c₀ decreases by 4% when the P_fric increases from 0.1MPa to 0.25MPa, manifesting that the ignition resistance depends on c₀ strongly (or equivalent flow pressure P_eq). The ignition resistance of Ti-6Al-4V is 42.9% of that of TB12. When P_eq varies from 0.1~0.5MPa, the critical ignition temperature Т^* is approximate to 568~461K. Violent sparks form during frictional ignition. The low ignition resistance of Ti-6Al-4V probably results from not only the composite oxides of TiO₂, Al₂O₃ and V₂O₅ generating during ignition which could not prevent the rapid interaction between Ti and O, but also the Al and V elements in the heat-affected zone which could not stop or slow the massive diffusion of O towards the alloy.

Abstract: The oxidation behavior and mechanism of Ti-Cu alloys (0≤w(Cu)≤20%) in the temperature range of 1000°C～1300°C are studied by thermogravimetric analysis(TGA) combined with SEM, EDS and XRD analysis methods. The results show that the oxidation rates of Ti-Cu alloys increase sharply when the temperature rises above 1000°C. The oxidation products have a three-layer structure, from the outside to the inside, which are dense outer oxide layer of TiO₂, porous inner oxide layer of low valence oxide of Ti and Cu-enriched layer. With the increase of the temperature, the thicknesses of oxide layers of Ti-Cu alloy increase and the Cu-enriched phase increases gradually and melts. The melting Cu-enriched phase flows to the oxidation surface along the grain boundaries of the oxide layer. The high temperature oxidation resistance of Ti-Cu alloys declines with the increase of Cu content. The main reason is that more liquid Cu-enriched phase is formed and flows to the oxidation surface along the oxide grain boundaries in the Ti-Cu alloy, and Ti and O ions can diffuse more easily along the liquid Cu-enriched phase, which increases the oxidation rates.

Abstract: Oxidative polymerization of 3-amino,2'-,(3')-nitrodiphenylazomethine was carried out in various ways. A possible mechanism for the polymerization of 3-amino,2'-,(3')- nitrodiphenylazomethine, where chain growth occurs as type N-C, is shown. It has been found that the yield of the polymer product is affected by the polymerization process and time. The chemical structure of the polymers obtained is established. The study of the thermal properties of polymers showed a low thermal stability and the process of destruction proceeds in two stages.

Abstract: The article makes a study of the development of public-private partnerships (PPPs) in Russia in the implementation of investment projects. The article considers the current state of PPPs, the main problems and development trends. Particular attention is paid to potential risks for public and private partners. The paper proposes the recommendations for the main directions of PPPs development.

Abstract: In this study, calcium carbonate was used to coat and link the surface of diatomite for the formation of a novel modified adsorbent (referred to as Ca–diatomite). Various analytical techniques were used to characterize structure and mechanisms of modification and adsorption process, like Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD). Results showed that that Calcium carbonate had been successful grafted onto the surface of diatomite after modification, and Calcium carbonate modification improved the adsorption performance of diatomite for the removal of lead (II) ions from aqueous solution. Ca–diatomite adsorption isotherms and adsorption kinetics were also been studied. The adsorption isotherms and the kinetic data were best fitted with the Langmuir model and pseudo-second-order kinetics, respectively.

Abstract: The article analyses corrosive stock in an oil and gas field, and the protection method for the equipment in boreholes and in oil pipelines is discussed. Subsurface pumping equipment corrosion rate monitoring method has been improved. In an oil and gas field, the inhibitor is pumped into the oil pipeline directly into the oil-gathering line and into the production boreholes with different dosages. Pilot testing was carried out to optimize the corrosion inhibitor dosage.

Abstract: The purpose of this study is to develop computational mathematical models for virtual prototyping of an actuation system from an exoskeleton human knee joint. These models are a part of the virtual and experimental prototype of a mechatronic system for locomotion rehabilitation in case of disabled persons. Experimental tests were performed on a group of persons without locomotion deficiencies. The obtained database was used to develop geometrical kinematic synthesis of the exoskeleton actuation mechanisms for knee’s joint and also ankle.

Abstract: Barrier layer was prepared by Micro-arc oxidation(MAO) technique in silicate solution, and cathodic plasma electrolytic deposition (CPED) technique was used to fabricate Al₂O₃ ceramic coatings on Ti6Al4V alloy in Al(NO₃)₃(30g/L) and ethanol-aqueous solutions. Surface morphology and elemental of the coatings were investigated by scanning electron microscope (SEM) and energy disperse spectroscopy (EDS). Reaction phenomena were recorded and products of reactions were analyzed by infrared absorption spectrum KBr compression method. Furthermore, mechanisms of different electrolytes were evaluated.

Abstract: Titanium dioxide is currently the most important white pigment material used in the world and its surface properties are very important for consumer industries such as paints, papermaking and plastics. If agglomerates are present, the down-stream product properties such as gloss, opacity, and storage stability will be greatly affected. The addition of organic surface treatment agents onto the surface of titanium dioxide particles can change its surface: reduce the inter-particle forces to reduce particle agglomerates; change the hydrophobic or hydrophilic properties of particle surface to enhance the compatibility with the solvent, water, or organic resin; can also improve the particle mobility and industrial processing. Therefore, it is very important to fully understand the interaction mechanism between pigment particles and functional organic surface treatment agents. This paper summarizes the related research results and progress.