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Search Results: 1 - 10 of 32560 matches for " Baiyun HUANG "
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Injection Molding of W-Ni-Fe Nanocomposite Powder Prepared by Mechanical Alloying

Xuanhui Qu,Jinglian FAN,Baiyun HUANG,

材料科学技术学报 , 2001,
Abstract: Nanocrystalline 90W-7Ni-3Fe (wt pct) composite powder was prepared by mechanical alloying and mixed with binder to form a feedstock. Its rheological and sintering behaviors were compared with those of the feedstock from the original powder. It is found that milling can increase the maximum powder loading of feedstock and enhance the sintering densification process.
Development of Novel Binder for Hardmetal Powder Extrusion Molding
Jicheng ZHOU,Baiyun HUANG,
JichengZHOU
,BaiyunHUANG

材料科学技术学报 , 2002,
Abstract: A novel binder system for hardmetal powder extrusion moulding (PEM) process has been developed. The binder system comprises a major fraction of a mixture of low molecular weight components (LMWCs) and a minor fraction of very finely dispersed polymer. The feedstocks are mixed as a thick slurry at a suitable temperature and are rapidly homogenized by stirring at an adequate shear force. The binders are removed by thermal debinding. The thermal debinding mechanism has been investigated by thermogravimetry (TG) and differential thermogravimetry (DTG). At the first stage of debinding, the LMWCs are removed. These open up pore channels which allows much faster removal of the remaining polymer component during the subsequent stage. The microstructures of the moulded green parts were observed by scanning electron microscopy (SEM). The debound samples were sintered at different temperatures, and the sintered samples properties were measured.
Structure of Unsupported Small Palladium Nanoparticles
Qi Weihong,Huang Baiyun,Wang Mingpu
Nanoscale Research Letters , 2009,
Abstract: A tight binding molecular dynamics calculation has been conducted to study the size and coordination dependence of bond length and bond energy of Pd atomic clusters of 1.2–5.4 nm in diameter. It has been found that the bond contraction associated with bond energy increases in the outermost layer about 0.24 nm in a radial way, yet in the core interior the bond length and the bond energy remain their corresponding bulk values. This surface bond contraction is independent of the particle size.
Size Effect on Order-Disorder Transition Kinetics of FePt Nanoparticles
Shuaidi Zhang,Weihong Qi,Baiyun Huang
Physics , 2013, DOI: 10.1063/1.4863350
Abstract: The kinetics of order-disorder transition of FePt nanoparticles during high temperature annealing is theoretically investigated. A model is developed to address the influence of large surface to volume ratio of nanoparticles on both the thermodynamic and kinetic aspect of the ordering process; specifically, the nucleation and growth of L10 ordered domain within disordered nanoparticles. The size- and shape-dependence of transition kinetics are quantitatively addressed by a revised Johnson-Mehl-Avrami equation that included corrections for deviations caused by the domination of surface nucleation in nanoscale systems and the non-negligible size of the ordered nuclei. Calculation results based on the model suggested that smaller nanoparticles are kinetically more active but thermodynamically less transformable. The major obstacle in obtaining completely ordered nanoparticles is the elimination of antiphase boundaries. The results also quantitatively confirmed the existence of a size-limit in ordering, beyond which, inducing order-disorder transitions through annealing is impossible. A good agreement is observed between theory, experiment and computer simulation results.
Effect of Rare Earth Y on Properties of Nanosized 90W-7Ni-3Fe Composite Powder Fabricated by Spray Drying-Hydrogen Reduction
Y.-Z. Ma,Liu Wensheng,Huang Baiyun,Fan Jinglian
Journal of Nanomaterials , 2008, DOI: 10.1155/2008/459093
Abstract: (W,Ni,Fe) composite oxide powder synthesized by spray drying was reduced at 700°C for 90 minutes in H2 atmosphere. The effect of rare earth Y on H2 reduction of (W,Ni,Fe) composite oxide powder was studied. Phase composition, crystalline size, and particle morphology of the reduced powder have been measured by X-ray diffraction and scanning electron microscope (SEM). Fsss particle size and special surface area of the reduced powder were also measured and analyzed. The result showed that new phase Y(Ni0.75W0.25)O3 appeared in the reduced powder and particle morphology was nearly spherical or polyhedron by Y additions. The higher the rare earth element content was, the bigger the influencing on particle morphology was. When the rare earth Y content was under 0.8%, with the increase of the rare earth element content, BET, Fsss, and crystal sizes of the reduced powder decreased greatly.
Carbide Formation Process in Directionally Solidified MAR-M247 LC Superalloy
Jian CHEN,Baiyun HUANG,JHLee,SJChoe,YTLee,

材料科学技术学报 , 1999,
Abstract: 1.IntroductionSeveralphasesforminthesolidificationandcool-.ingprocessofcastsuperalloys'].MCcarbidesand7'precipitatesarethemainphasestoprovidehightemperaturestrengthinthesuperalloys.TheMCcarbidesstrengthengrainboundariesandsub-grainboundariesatelevatedtemperature.Theirvolumefraction,sizeandmorphologyhaveaveryimpor-tanteffectonthemechanicalpropertiesofNi-basesuperalloys'l.Considerable..,..,.h.s3~14]havebeencarriedoutfromslowtorapidsolidificationconditionstocharacterizethesequenceofformation…
Investigation on the Microstructure Homogenization in a TiAl Based Alloy Prepared by Elemental Powder Metallurgy
Yong LIU,Baiyun HUANG,Yuehui HE,Jiannong WANG,

材料科学技术学报 , 1999,
Abstract: 1.IntroductionTiAlbasedalloyhasdrawnintensiveattentioninhightemperaturestructuralmaterialarea,be-causeofitslowdensity,excellellthightemperaturepropertiesf1~2].However,itspoorworkabilityisanobstacleforitsapplication.Inordertoovercomethisdifficulty,extensiveworkhasbeenconductedtoim-proveitsworkabi1ityandnearnetshaping.Elementalpowdermetallurgy(EPM)hasbeenusedforfabricatingTiAl-basedalloys,becauseofitstwoapparentadvantages'lowcostandconvenientad-ditionofalloyelemellts3].Thistechniqueincludesr…
Behaviour of Composite Ca/P Bioceramics in Simulated Body Fluid
Yong LIU,Baiyun HUANG,Jianmin RUAN,Yuehui HE,

材料科学技术学报 , 1998,
Abstract: Behavior of Ca/P ceramics enhanced by MgAl2O4 in simulated body fluid(SBF) was studied.Results show that, biological apatite can precipitate on the sudece of Ca/P composite ceramics,however, dissolution of the surface of Ca/P composite ceramics also occurs due to a kind of amorphous material which is produced through reaction of MgAl2O4 with Ca/P ceramics at elevated temperature, therefore, the behavior of Ca/P composite ceramics in SBF mainly depends on those two processes. Analyses of joint influence of those two processes show that low content of MgAl2O4 favors the formation of biological apatite, therefore, brings about higher bioactivity
Comparison between the Requirements of Flowability and Moldability and the Shape Retention of PIM Compacts during Debinding Process

KAKhaliI,Baiyun HUANG,Yimin LI,MMEl-Sayed Seleman,

材料科学技术学报 , 2001,
Abstract: To successfully employ powder injection molding (PIM) as a manufacturing technique, the function of the component, design of the part, material and process should be optimized for overall processing ability of the PIM process. A comparison between the requirements of flowability and moldability and the compacts shape retention has been made in this work. There is often a contradiction between the requirements of flowability and the compacts shape retention. Many works have been done to attain good molding conditions. However, they fail to take into account the effect of some factors that satisfies good molding conditions on the compacts shape retention during debinding. This paper studies the effect of the powder-binder mixture characteristics and the molding conditions on the flowability and moldability and the shape retention of PIM compacts during debinding process so as to attain the benefits of each.
Phase Structure Change of Mo-Si System during Mechanical Alloying
Phase Structure Change of Mo-Si System duringMechanical Alloying

Shaojun LIU,Xuanhui QU,Zhijiang LIU,Baiyun HUANG,

材料科学技术学报 , 1999,
Abstract: The structure of Mo-15.16 Si, Mo-30 Si and Mo-36.3 Si (wt pct) elemental powder mixture during mechanical alloying was studied using electron microscopy and X-ray diffraction. It had been found that, in all the systems under study, silicon disappeared initially during mechanical alloying (MA). In the Mo-Si systems all products were in form of amorphous state after long time milling, but there were different intermediate products. MoSi2 and Mo5Si3 intermetallic compounds in the Mo-30Si and Mo-36.3Si (wt pct) were directly synthesized from elements through inter-diffussion process. The high density of defects and interface of nano-crystallines induced by ball milling would promote the reaction process. Only in the Mo-15.16Si (wt pct) system was Mo(Si) supersaturated solid solution formed as an intermediate product. Schematic free-energy diagram of Mo-Si system based on the thermodynamics was used to analyze the difference among the intermediate state products.
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