Papers by Keyword: Nano-Al₂O₃

Abstract: 80Ni20Cr coatings produced by high-velocity oxygen fuel (HVOF) thermal spray technique are novel and widely used to improve the corrosion and wear resistance of metal and steel components in many applications, especially in coal-fired power plants. The present study investigated the effects of nano-Al₂O₃ at 0.5 wt.% on the microstructure of HVOF-sprayed 80Ni20Cr coating deposited on AISI 304L steels corresponding to its coating hardness. The coating was successfully sprayed with a thickness of 150 – 180 µm. The microstructure and phase formed by the coating were analyzed by a field emission electron microscope (FE-SEM) and an X-ray diffractometer (XRD). Synchrotron X-ray fluorescence spectroscopy (SRXRF) was used to confirm the Cr solid solution in the Ni-based coating. The presence of the nano-Al₂O₃ phase in the 80Ni20Cr coating was characterized by electron backscattered diffraction (EBSD). The nano-Al₂O₃ particles were homogenously distributed in the coating layers. The incorporation of nano-Al₂O₃ into 80Ni20Cr enhanced coating characteristics by decreasing surface roughness by 23% and increasing coating hardness by around 4%.

Abstract: Surface modification of nanoAl₂O₃ with stearic acid by dry method was researched. The structures of nanoAl₂O₃ before and after modified were characterized by IR. The modification effect on nanoAl₂O₃ was measured with the activation index. In addition, the influence factors of modifier dosage, modification time and modification temperature were also discussed. The results showed that nanoAl₂O₃ had been successfully modified with stearic acid. The hydrophily and lipophilicity experiments indicated that modified nanoAl₂O₃ possessed lipophilicity property and could disperse in xylene. The optimal conditions of modification were as follows: the stearic acid was 7.5 wt%, based on the quality of nanoAl₂O₃, modification time was 50 min and temperature was 150 ^○C.

Abstract: Under the bad environment, high polymer wear-resistant material has more superior erosion wear resistant performance than metal. It can replace wear-resistant metal material partly. In this paper, high polymer wear-resistant coat has been prepared with the epoxy resin, low molecular polyamide, nanoAl₂O₃ coupling agent. The shear strength and wear resistant test has been carried out under different elements content, and the test curve of coat is given. The results are analyzed. By the experiment result, the optimum coat formula is: low molecular polyamide content is 60% relative to E – 51; and the content of MoS₂ is 12%. The result shows that the coat erosion wear resistance is 9 times of 45# steel under the best recipe. The coat is used to repair a worn mortar pump impeller, and the effect is obvious.

Abstract: Cylinder Liner design innovation goal is energy conservation. As the main friction parts engine cylinder liner, reducing friction energy is energy saving basic requirements. Materials research cylinder sleeve is one of the main cylinder liner saving research. Through the piston ring and cylinder liner surface friction dual material hard phase, self-lubricating phase, toughening phase analysis, select compatibility, high strength, heat resistance, good high temperature performance, ease of manufacture, price rational matrix material and an appropriate proportion of nanoscale hard material, self-lubricating materials, ductile materials, using appropriate methods cladding and processing, design developed high-temperature self-lubricating cylinder sets of advanced materials. The latest international high temperature, wear-resistant, self-lubricating materials research: modern nanoα-Al₂O₃+Ni-base alloy composite materials, Ti₂B/Fe metal-ceramic composites, metals and ceramics NiCr-Cr₃C₂ particles CaF₂ self-lubricating composite alloy powder material, NiCr/Cr₃C₂-WS₂ self-lubricating wear-resistant materials were studied and found to TiC, Al₂O₃ is hard reinforcing phase, CaF self-lubricating phase, NiCr/TiC eutectic toughening phase, high-temperature self-lubricating wear-resistant nanocomposite, and Cr₁₈Ni₉ class alloy as base material, by laser cladding method enables conventional cylinder liners manufacturing technological breakthroughs, has practical value.

Abstract: Al₂O₃(x)/ZrO₂ composite ceramics were successfully prepared by microwave sintering. The influence of variety content of nanoAl₂O₃ on mechanical properties and microstructure of ZrO₂ dental materials were studied, and analysied the mutual relations of chemical composition, mechanical properties and microstructure to investigate the reason of strengthening and toughening. Results indicated that The relative density of the Al₂O₃(x)/ZrO₂ composite ceramics reached more than 96.8%.The HV hardness ,bending strength and fracture toughness presented excellent mechanical properties as 12.5GPa, 753.8MPa and 11.8MPa·m^1/2 with the content of nanoAl₂O₃ was 7.5%. Compared with that of pure ZrO₂ ceramics, the bending strength and the fracture toughness were improved 19% and 96%, respectively. The main crystal phases in this composite ceramics were t-ZrO₂ and α-Al₂O₃.The nanoAl₂O₃ have a obvious effect on the strength and toughness of ZrO₂ based ceramics. The reason of strengthening and toughening mainly the additions reduced the ZrO₂ grains growth and promoted grains size uniformity, and changed the fracture mode from transgranular fracture to intergranular fracture characteristics.

Abstract: A new nanomicro composite self-lubricating ceramic tool material was prepared with vacuum hot pressing technique. The effect of nanoAl₂O₃ powders on the microstructure and mechanical properties of nanomicro composite self-lubricating ceramic tool material was investigated. With the increase of nanoAl₂O₃ content, the hardness and fracture toughness first up then down. When the nanoAl₂O₃ content is 4 vol.%, the flexural strength, hardness and fracture toughness reaches 562 MPa, 8.46 MPa·m^1/2 and 18.95 GPa, respectively. The microstructure and mechanical property of nanomicro composite self-lubricating ceramic tool material can be improved by the grain refinement strengthening of nanoAl₂O₃.

Abstract: This paper focuses on the influence of nano-Al2O3 surface state and composite process on the dispersion of nano-Al2O3 filler. Toughening was performed to epoxy resin by nano-Al2O3, and the effect of impact property of epoxy resin/nano-Al2O3 composites was studied. The results showed that coupling agent treatment and high-speed shear dispersion can improve many properties of the composites. With nano-Al2O3 content increasing, the impact strength of the composites increased at first and then decreased. The maximum appears when the nano-Al2O3 content reached 3wt. %, no matter with or without the coupling agent treatment, which is 87.4% and 78.6% higher than that of monolithic epoxy resin respectively. The coupling agent treatment of nano-Al2O3 helped to improve the impact strength of the composites.

Abstract: The metal and nano-ceramic nanocomposite coatings were prepared on gray cast iron surface by electrodepositon. The nickel and cobalt were used as metal matrix of coating, and the nano-Al2O3 was chosen as second-phase particulates, which had good chemical stability, high microhardness and good wear resistance. The morphology of composite coatings was flatter and microstructure was denser than pure nickel and cobalt coatings. The composite coatings were fabricated by different dispersion methods such as high speed mechanical stir, ultrasonic vibration and ultrasonic vibration together with mechanical stir. The result indicated the nano-Al2O3/Ni+Co composite coating with fine and compact microstructure are obtained compared with pure Ni-Co coating. The nanoparticles were dispersion evenly when dispersion style was ultrasonic vibration together with mechanical stir according to composite coatings SEM images of different dispersion style. The concentration of nanoparticulates reached a maximum value when the dispersion style was ultrasonic vibration together with mechanical stir, at the same time the mechanical property such as microhardness reached a maximum value also. The reason was that nano-Al2O3 caused dispersive strengthening and grain refining.

Abstract: Study the affect of nano-Al2O3 additive on the MAO film of titanium ally, the affect of nano-Al2O3 additive on the surface morphology and the thickness is not remarkable, but the nano-Al2O3 additive is good to improve corrosion resistant of the film. The mechanism of nano-Al2O3 additive improving corrosion resistant of the film is that: on the one hand is improving the content of α- Al2O3 in the film, on the other hand is decreasing the size of the pore area of the film and improving the dense of the loose and compact layer.

Abstract: ZL114 aluminum alloy samples were treated by micro-arc oxidation using alkaline solution added different amount of nano-Al₂O₃ to improve the surface properties. Effects of the additives were investigated by thickness, hardness, morphologies and corrosion performance. The results indicated that proper amount of nano-Al₂O₃ had certain contribution with higher corrosion performance. And adding too much nano-Al₂O₃ decreased the property of ceramic coatings.