In the present work some properties of nanopowders and possible areas of their applications are discussed. Main attention is paid to the use of nanodispersed powders (NDP) in new materials production technologies.
Phase contents and elemental composition of ultradispersed powders obtained by the electrical explosion of tin-leadalloy powders are investigated. It is demonstrated that during the explosion and subsequent cooling, surface layers of powder particles are enriched in lead compared to the initial alloy. The thermal stability of powders oxidizing in air is also investigated.
The feasibility of obtaining highly dispersed aluminum oxide powders by the electrical explosion of aluminum conductors in an inert gas atmosphere and the subsequent oxidation of aluminum particles by water prior to their contact with air is demonstrated. For a specific surface area of the initial aluminum powder of 6.5m2/g, the corresponding specific surface area of the resultant aluminum oxide nanopowder was as large as 300m2/g.
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Electroexplosive Technology of Nanopowders Production: Current Status and Future Prospects Young-Soon Kwon, Jin-Chun Kim, Alexander P. Ilyin, Olga B. Nazarenko, Dmitry V. Tikhonov Journal of Korean Powder Metallurgy Institute.2012; 19(1): 40. CrossRef
The mechanical alloying effect has been studied on the three Cu-based alloy systems with a positive heat of mixing. The extended bcc solid solution has been formed in the Cu-V system and an amorphous phase in the Cu-Ta system. However, it is round that a mixture of nanocrystalline Cu and Mo Is formed in the Cu-Mo system. The neutron diffraction has been employed at a main tool to characterize the detailed amorphization process. The formation of an amorphous phase in Cu-Ta system can be understood by assuming that the smaller Cu atoms preferentially enter into the bcc Ta lattice during ball milling.
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Microstructure and Mechanical Properties of 3vol%CNT Reinforced Cu Matrix Composite Fabricated by a Powder in Sheath Rolling Method Seong-Hee Lee Korean Journal of Materials Research.2020; 30(3): 149. CrossRef
Synthesis of Ultra Fine Titanium-Tungsten Carbide Powder from Titanium Dioxide and Ammonium Metatungstate Gil-Geun Lee, Gook-Hyun Ha MATERIALS TRANSACTIONS.2009; 50(1): 187. CrossRef
Synthesis of WC Nanosized Powder by the Plasma Arc Discharge Process Seoung Soo Lee, Dong Won Joo, Yeon Gil Jung, Chul Jin Choi Key Engineering Materials.2007; 336-338: 2086. CrossRef
Characterization of Ni Nanopowders Produced by Electrical Explosion of Wire Technique Hwan Tae Kim, Won Sik Seo, Dae Hwan Kwon, Pyuck Pa Choi, Ji Soon Kim, Young Soon Kwon Materials Science Forum.2006; 510-511: 710. CrossRef
Interpenetrating phase composites of TiB_2-Cu system were produced via Spark-Plasma Sintering (SPS) oi nanocomposite powders. Under simultaneous action of pressure, temperature and electric current titanium diboride nanoparticles distributed in copper matrix move, agglomerate and form a fine-grained skeleton. Increasing SPS-temperature and he]ding time promote densification due to local melting of copper matrix When copper melting is avoided the compacts contain 17-20% porosity but titanium diboride skeleton is still formed representing the feature of SPS . High degree of densification and formation of titanium diboride network result in increased hardness of high-temperature SPS-compacts.
Mechanically-alloyed NiAl powder was sintered by Spark-Plasma Sintering (SPS) process. Densification and behavior mechanical property were determined from the experimental results and analysis ,such as changes in linear shrinkage, shrinkage rate, microstructure, and phase during sintering process, Victors hardness, and transver.ie-rupture-strength (TRS). Above 97% relative density was obtained after sintering at 1150°C for 5 min. Crystallite size determined by the Scherrer method was approximately 50 nm. From the X-ray diffraction analysis it was confirmed that the sintered bodies were composed mainly of NiAl phase together with Ni_3Al phase. Measured Vickers hardness and TRS value were 555pm10 H_v and 1393pm75 MPa , respectively.
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Densification and Mechanical Property of Nanostructured NiAl Produced by Mechanical-Alloying and Spark-Plasma Sintering Ji Soon Kim, S.-H. Jung, Young Do Kim, Chung Hyo Lee, Young Soon Kwon Materials Science Forum.2004; 449-452: 1101. CrossRef
Pure WC powders which does not include a binder phase were consolidated by spark plasma sintering (SPS) process at 1600~1850°C for 0~30 min under 50 MPa. Microstructure alid mechanical properties of binderless WC prepared by SPS were investigated. With increasing sintering temperature, sintered density and Vickers hardness of binderless WC increased. The fracture toughness of binderless WC was 7~15 MPa m1/2 depending on the sintered density and decreased with increasing the Vickers hardness. It is found that the binderless WC prepared by SPS at 1750°C for 10 min under 50 MPa showed nearly full densification with fine-grained structure and revealed excellent mechanical properties of high hardness (~HV 2400) and considerably high fracture toughness (~7 MPa m1/2).
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Improvement of Surface Properties of Inconel718 by HVOF Coating with WC-Metal Powder and by Laser Heat Treatment of the Coating Hui Gon Chun, Tong Yul Cho, Jae Hong Yoon, Gun Hwan Lee Advances in Materials Science and Engineering.2015; 2015: 1. CrossRef
Improving the Properties of Magnetic Bearing Shaft Material by HVOF Coating of WC-Metal Powder and Laser Heat Treatment T.Y. Cho, Y.K. Joo, J. H. Yoon, H. G. Chun, S.H. Zhang Advanced Materials Research.2012; 560-561: 1052. CrossRef
Surface Modification by HVOF Coating of Micron-Sized WC-Metal Powder and Laser-Heating of the Coating Tong Yul Cho, Jae Hong Yoon, Sung Kang Hur, Hui Gon Chun, Shi Hong Zhang Materials Science Forum.2011; 686: 654. CrossRef
Surface properties and tensile bond strength of HVOF thermal spray coatings of WC-Co powder onto the surface of 420J2 steel and the bond coats of Ni, NiCr, and Ni/NiCr Tong Yul Cho, Jae Hong Yoon, Jae Young Cho, Yun Kon Joo, Jin Ho Kang, Shihong Zhang, Hui Gon Chun, Soon Young Hwang, Sik Chol Kwon Surface and Coatings Technology.2009; 203(20-21): 3250. CrossRef
Rapid sintering process and mechanical properties of binderless ultra fine tungsten carbide Hwan-Cheol Kim, Jin-Kook Yoon, Jung-Mann Doh, In-Yong Ko, In-Jin Shon Materials Science and Engineering: A.2006; 435-436: 717. CrossRef
Consolidation and properties of binderless sub-micron tungsten carbide by field-activated sintering Hwan-Cheol Kim, In-Jin Shon, J.E. Garay, Z.A. Munir International Journal of Refractory Metals and Hard Materials.2004; 22(6): 257. CrossRef
Resistance sintering under ultra-high pressure if developed to fabricate W-Cu composite containing 5 to 80v/o copper. The consolidation was carried out under pressure of 6 to 8 GPa and input power of 18 to 23 kW for 50 seconds. The densification effect and microstructure of these W-Cu composites are investigated. The effect of W particle size on ,sintering density was also studied. The micro hardness was measured to evaluate the sintering effect.
A chemical vapor condensation (CVC) process using the pyrolysis of metal-organic precursors was applied to produce the nanosized WO_3 powders. Morphology and phase changes of the synthesized WO_3 powder as a function of CVC parameters were investigated by XRD, BET and TEM. The agglomerated nanosized monoclinic WO_3 powders with nearly spherical shape and 10-38 nm in mean diameter could be obtained. Conditions to produce the WO_3 nanopowders are presented in this paper.
Thin Ag films deposited onto SiO_2/Si substrates by DC magnetron sputtering and thereafter annealed ,it temperatures 100-500°C are investigated by scanning tunneling and atomic forte microscopy. It is shown that the film surface topography and microstructure are considerably changed as a result of annealing. To provide a quantitative estimation of the surface topography changes of Ag films the surface fractal dimension was calculated. Elasticity and hardness of the films are studied by a nanoindentation technique. The films are found to have value of elastic modulus close to that of bulk silver while their hardness and yield stress are essentially higher.
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Effect of surface roughness on electrical conductivity and hardness of silver plated copper Ameneh Javidjam, Mohammad Hossein Hekmatshoar, Leila Hedayatifar, Sajjad Nasiri Khalil Abad Materials Research Express.2018; 6(3): 036407. CrossRef
Ni coated Al_2O_3 composite was successfully Prepared by the electroless deposition Process. The average size of Ni particles coated on the Al_2O_3 matrix powder was about 20 nm. It was hard to find any reaction compound as an impurity at interface between Al_2O_3 and Ni particles after sintering. The characterization of microstructure crystal structure and fracture behavior of the sintered body were investigated using XRD, TEM and Victors hardness tester, and compared with those of the sintered Al_2O_3 monolithic body. Many dislocations were observed in the Ni phase due to the difference of thermal expansion coefficient between Al_2O_3 and Ni phase, and no observed microcracks at their Al_2O_3 and Ni interface. In the Al_2O_3/Ni composite, the main fracture mode showed a mixed fracture with intergranular and transgranuluar type having some ,surface roughness. The fracture toughness was slightly increased due to the plastic deformation mechanism of Ni phase in the Al_2O_3/Ni composite.
Distributions of diamond particles protruding on the surface of worn diamond segments in circular saw has been investigated. Scanning electron microscope was used to examine the worn ,surface and radial saw blade wear and grinding ratio was measured. The number of protruded diamond particle was approximately 50% of the total number of particles, and that was independent of diamond particle concentration and table speed. It was also noted that the inter-particle distance did not follow a symmetric function like Gaussian distribution function, instead it fitted well with a probability density function based on gamma function. The distribution of inter-particle spacing, therefore, was analyzed using a gamma function model.