Papers by Keyword: Mechanism

Abstract: Stearic acid was applied to modify the VO₂ nanopowders, and the influence of modified medium, dosage of modifier, amount of activator, time of modification on the surface modification effect were studied. The modification parameters such as modifying agent and the conditions were optimized. The changes of Surface groups, particle size and the lipophilic degree of the dispersion system of VO₂ nanopowders before and after modified by the stearic acid were researched. The modification mechanism is chemical bonding, which is not physical adsorption. And then the stearic acid modified mechanism was established and applied to explain the the process of modification parameters optimization. The modification of VO₂ nanopowders could be used in color nanometer energy-saving coating.

Abstract: Leakage is a persistent problem in buildings and some other structures, such as dam, bridge and water tower. For a long time, kinds of plugging agents have been developed successfully by modifying organic or inorganic materials. In this paper, the definition, classification and mechanism of plugging agent were introduced and explored in detail. Besides, some application principles and noteworthy matters in engineering were analyzed at well. Furthermore, based on the development of the construction industry in China, some viewpoints of the development prospects of plugging agent were proposed at last.

Abstract: Electromagnetic field (EMF) can promote the reaction between the Fe/Mn ion in slag and MgO-C refractories to form Mn-doped MgFe₂O₄ spinel. In order to further study the morphology and characteristics of Mn-doped MgFe₂O₄ spinel, the experiments were respectively carried out in medium-frequency induction furnace and resistance furnace. MgO-C refractories containing 6 wt.% carbon and iron-rich slag containing 53.62 wt.% Fe₂O₃ were used. The results show that the penetration layer in the slag line under EMF is obvious and the reduced Fe from FexO is distributed homogeneously in this layer. However in the resistance furnace having no EMF, there is not MgFe₂O₄ spinel but MgAl₂O₄ spinel formed. The iron content in Mn-doped MgFe₂O₄ spinels decrease dramatically from the erosion layer to penetration layer, while the manganese content in the spinel remains unchangeable.

Abstract: In this study, the modification effects and mechanism of manganese (Mn) and ultrasonic vibration (USV) on the needle-like Fe-containing intermetallic compounds of Al-20Si-xFe-2.0Cu-0.4Mg-1.0Ni (x=1, 2 wt.%) alloy have been studied respectively. The effect of Fe-containing phases on volume fraction of hard phases is also investigated. The results show that the mechanism and effect of Fe-containing intermetallic compounds improved by Mn are in close relationship with Fe content. Mn can promote to form less harmful α-Al₁₅(Fe,Mn)₃Si₂ phase, or replace some Fe atoms of β-Al₅FeSi and δ-Al₄FeSi₂ according to different Fe content. When USV was applied to this alloy containing 2%Fe near liquidus temperature, most of the acicular β phases formed in traditional process are substituted by fine plate δ phases. With the combined effects of 0.5%Mn and USV, the acicular β phases are almost repressed and the Fe-containing phases exist in form of fine Al₄(Fe,Mn)Si₂ and Al₅(Fe,Mn)Si particles about 20~30μm. Consequently, the total volume fraction of hard phases which are composed of primary silicon particles and Fe-containing phases increases significantly.

Abstract: This paper has designed the pendulum type in high speed of single grit cutting equipment, discussed the material process of deformation and failure mechanism. During the investigation, compared with the abrasive cutting export and cutting entry based on the MP tool coating, which is badly broken when the cutting depth increases gradually at the entrance, and is broken less when the cutting depth gradually decreases at the export. Researched the MP tool coating of Surface and subsurface damages by indentation and scratching, it has demonstrated that on one side of the groove has appeared the crack and with severe plastic flow phenomena by scratching, and by indentation the cracks of the groove is not produce on both sides and bottom, but at the bottom of the trench existing extrusion phenomenon.

Abstract: This paper is regarding the reduction in the cost of electricity generation. This is achieved by using the proposed new mechanics/mechanism/machines as an intermediate, in the process of converting the source energy (Both Conventional Sources of Energy and Non-Conventional Sources of Energy, mainly solar energy and thermal energy from waste or the electricity itself) to electrical energy at truncated charge.

Abstract: For the limitation of single-component superplasticizer, condensate-type and copolymer-type combined superplasticizers were prepared. The adsorption of compound superplasticizers on cement paste was tested by Total Organic Carbon (TOC) measurement. Influences of superplasticizers on early hydration process of cement and Organo-mineral phase formation were studied by X-Ray Diffraction Analysis (XRD), Scanning Electron Microscope analysis (SEM) and so on. The results show that owing to the electrostatic repulsion and steric effect cooperative mechanism, condensate-type and copolymer-type combined superplasticizers reduce the superplasticizers adsorption in cement minerals and its hydration products surface, delay the process of hydration of C₃A, form Organic-Layered double hydroxides (LDH), increase the early chemical shrinkage and promote the growth of cement early hydration and Ettringite

Abstract: Abstract. The forsterite thermal insulation materials were synthesized by molten salt method with forsterite and NaCl-Na₂CO₃ salt, sintered at 1000°C, 1050 °C, 1100°C and 1150°C respectively. Studying complex pore structures is the key to understand the mechanism of pore-forming. The mechanism of the variation in the heterogeneous pore structure was analyzed based on differential thermal analysis, thermogravimetry, high-pressure mercury intrusion porosimetry and scanning electron microscope. The results show that the NaCl-Na₂CO₃ salt play the role of promoting sintering in liquid environment at high temperature as well as forming pore as placeholder. The mechanism of pore-forming contains three parts: the pores < 6.6 μm are mainly formed by sodium carbonate decomposition under high temperature and vapor pressure; the forming way of 6.6~66μm derives from carbonate decomposition and salt evaporate jointly; The salt stay in the slender and curved space shaped by the rearrangement of forsterite particles, forms the pore diameter of > 66 μm after salt dissolves in water.

Abstract: A nanostructured surface layer is formed on 2219 Al alloy plate by means of supersonic fine particles bombarding (SFPB). The surface microstructure formation mechanism of morphology change is systematically characterized by using scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The average grain size of 30nanostructured layer is about 30 nm when the surface of sample is induced by severe plastic deformation. Based on the experimental observations, nanoscale dislocation cells exist in strain layer about 200 from the surface, and we put forward a new formation mechanism of Al alloy surface nanocrystalline layer through theoretical analysis. The original grain is segmented fast into nanoscale dislocation cell or lamellar cell. As the Burgers vector of cell walls continue to accumulate, grain orientation difference constantly increases to form the nanoscale subboundary. Eventually, equiaxed nanocrystallites with random crystallographic orientations are formed by grain rotating or grain boundary sliding.

Abstract: Dental ceramics has become dominant materials used in dental restorations. Dental ceramics have several advantages, such as stable performance, good bio-compatibility, little possibility to attach plaque, and similarity to the color of permanent tooth. However complex surface characteristics and hard and brittle properties of dental ceramic materials caused difficulties in the processing and subsequent grinding. The complicated craft and high failure rate of dental ceramics greatly limit its wide application in clinical. Thus, fully understanding the special cutting tools grinding performance and researching the material damage process caused by grinding temperature and grinding force are of great significance. Research on dental ceramic grinding was reviewed in this paper. The removal mechanism of dental ceramic materials and the influence of parameters settings on the grinding force, grinding temperature, and the surface quality have been studied. Besides the existing problems in dental ceramic grinding technology were pointed out.