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The properties of high-energy milled pre-alloyed copper powders containing 1 wt. % Al
Journal of the Serbian Chemical Society , 2007,
Abstract: The microstructural and morphological changes of inert gas atomized pre-alloyed Cu-1 wt. % Al powders subjected to hith-energy milling were studied. The microhardness of hot-pressed compacts was measured as a function of milling time. The thermal stability during exposure at 800 °C and the electrical conductivity of compacts were also examined. During the high-energy milling, severe deformation led to refinement of the powder particle grain size (from 550 nm to about 55 nm) and a decrease in the lattice parameter (0.10 %), indicating precipitation of aluminium from the copper matrix. The microhardness of compacts obtained from 5 h-milled powders was 2160 MPa. After exposure at 800 °C for 5 h, these compacts still exhibited a high microhardness value (1325 MPa), indicating good thermal stability. The increase of microhardness and good thermal stability is attributed to the small grain size (270 and 390 nm before and after high temperature exposure, respectively). The room temperature electrical conductivity of compacts processed from 5 h-milled powder was 79 % IACS.
Preparation, Sintering Behavior and Microstructure of Al2O3-Coated Ni Powders

LU Jin-Shan,GAO Lian,GUI Lin-Hua,Guo Jing-Kun,

无机材料学报 , 2001,
Abstract: Alumina precursor-coated nanosized Ni powders were prepared by the heterogeneous precipitation method in the aluminium salt solution. The chemical composition of the as-prepared coated powder was characterized by energy dispersive spectra and Auger electron spectra. It revealed that nanosized Ni particles were homogeneously coated with layers of alumina hydrate. The calcined powders that were performed in argon were hot pressed in a protective atmosphere of argon. The experimental results indicate that the calcined powders can be sintered to nearly fully dense at a lower temperature as compared with that from sol-gel prepared powder mixtures. The microstructures of these sintered specimens are different from that of ball-milled and hot-pressed counterparts. Irrespective of the location of Ni particles in alumina matrix, there exist holes at the interfaces between alumina grains and Ni particles, which is attributed to thermal expansion mismatch between alumina and nickel. The fracture mode of these composites is mainly an intergranular-type.
Synthesis and Characterization of Alumina-Zirconia Powders Obtained by Sol-Gel Method: Effect of Solvent and Water Addition Rate  [PDF]
Julio Del Angel, Alberto F. Aguilera, Ignacio R. Galindo, Merced Martínez, Tomas Viveros
Materials Sciences and Applications (MSA) , 2012, DOI: 10.4236/msa.2012.39095
Abstract: The influence of solvent and the rate of addition of water on the characteristics of alumina-zirconia powders obtained by sol-gel method were investigated. The Al2O3-ZrO2 powders (1:1 molar ratio) were prepared using aluminum tri-sec-butoxide and zirconium n-propoxide as precursors. Ethanol (EtOH), isopropanol (iPrOH) and isobutanol (iBuOH) were used as solvents. The Al2O3-ZrO2 powders were characterized by nitrogen physisorption (SBET), Fourier transformed infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Prepared oxides calcined at 700℃ showed high specific surface area (200 - 240 m2/g). Obtained results suggest that the homogeneity of the mixed oxides is favored by using a water addition rate of 0.06 and 0.10 mL/min with ethanol as solvent.
Surface area, crystal morphology and characterization of transition alumina powders from a new gibbsite precursor
Vieira Coelho, Antonio Carlos;Souza Santos, Helena de;Kiyohara, Pedro Kuniiko;Marcos, Kelly Nanci Pinto;Souza Santos, Pérsio de;
Materials Research , 2007, DOI: 10.1590/S1516-14392007000200015
Abstract: a new procedure was used to prepare a microcrystalline powder constituted by thin euhedral hexagonal gibbsite plates, 0.2 to 0.6 μm in diameter and 32 nm thick. the powder, fired between 200 and 1000 °c, produced chi and kappa transition aluminas. alpha-alumina is formed from 1000 °c and recrystallized up to 1500 °c. at 1000 °c, kappa- and alpha-alumina coexisted, but kappa-alumina could only be characterized by saed. the details of the internal organization of the transition alumina pseudomorphs were clearly observable in tem due to the great thinness of the i-gibbsite plates. the specific surface area varied from pristine i-gibbsite (24.9 m2.g-1) to chi- and kappa transition aluminas (25.4 m2.g-1) at 1000 °c to alpha-alumina (4.0 m2.g-1) at 1500 °c. the maximum value of specific surface area is 347 m2.g-1 in chi-alumina powder at 300 °c, a difference from bayer gibbsite, in which the chi-alumina highest surface area is 370 m2.g-1 at 400 °c.
Microstructure studies of ball milled and vacuum hot pressed NiZrTiAl powders  [PDF]
J. Dutkiewicz,W. Maziarz,L. Litynska,M. Molnarova
Archives of Materials Science and Engineering , 2007,
Abstract: To determine microstructure and hardness of hot pressed mechanically alloyed MA NiZrTiAl powderwell known as a good glass formers.Design/methodology/approach: Powders has been ball milled r 40 hours starting from pure elementsChanges of particle’s size and crystallographic structure of nanocrystals embedded in the amorphous matrix durinmilling has been determined using High Resolution Transmission Electron Microscopy HRTEM.Findings: The MA particles first grow, then decrease after 40 hours of milling, when powders possess amorphoustructure. HRTEM studies of powders allowed to reveal small nanocrystals of NiTi2 within milled powders whicwere not detected using X-Ray diffraction. The powders show crystallization peak at temperature Tx near 553°CConsolidation of powders was performed under vacuum using uniaxial hot pressing method at temperature slightlbelow Tx. Mean microhardness was determined near 430 HV and the mean Young′s modulus as 81 GPa.Practical implications: It was shown a possibility of hot densification in vacuum of amorphous Ni base alloyallowing to obtain bulk amorphous compacts with embedded nanocrystals.Originality/value: The size and structure of nanmocrystals within the amorphous matrix after MA and aftehot vacuum densification has been determined. The microhardness and Young’s modulus of compacts showperspectives of application of such materials.
Effect of Nano-Al3Mg2 Addition on the Microstructure of PEEK Nanocomposite Bulk Samples Consolidated from Mechanically Milled Powders  [cached]
Zolriasatein A.,Shokuhfar A.,Alzamani M.
Proceedings of the International Conference Nanomaterials : Applications and Properties , 2012,
Abstract: In this investigation, the effect of the novel nano-Al3Mg2 particles addition on the microstructure of polyetheretherketone (PEEK) polymer matrix nanocomposite was studied. Bulk nanocomposite samples were fabricated by consolidation of ball milled composite powders through hot pressing method. The structural evolutions of mechanically milled powders as well as consolidated nanocomposites were examined by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with an energy dispersive X-ray analyzer (EDX). The results showed that, although increasing the amount of β-Al3Mg2 nanoparticles up to 5 vol. % results in no chemical interaction, a low degree of PEEK crystallization, reduction in powder particle size, homogeneous distribution and well bonding of nanoparticles in the PEEK matrix but the tendency for agglomeration and porosity formation increases in comparison with 3 vol% of β-Al3Mg2.

金属学报(英文版) , 2004,
Abstract: Based on the characteristic of high energy milling and the micromechanics of composite material, a plastic constitutive equation is implemented for milled composite powders. To check the equation, the extrusion of Ti/Al composite powders prepared by high energy milling was simulated. It was from the numerical analysis that the predicted extrusion pressure mounted up with milling time and extrusion ratio increasing, which was perfect agreement with experimental results.
Challenges and Strategies in the Synthesis of Mesoporous Alumina Powders and Hierarchical Alumina Monoliths  [PDF]
Sarah Hartmann,Alexander Sachse,Anne Galarneau
Materials , 2012, DOI: 10.3390/ma5020336
Abstract: A new rapid, very simple and one-step sol-gel strategy for the large-scale preparation of highly porous γ-Al 2O 3 is presented. The resulting mesoporous alumina materials feature high surface areas (400 m 2 g ?1), large pore volumes (0.8 mL g ?1) and the γ-Al 2O 3 phase is obtained at low temperature (500 °C). The main advantages and drawbacks of different preparations of mesoporous alumina materials exhibiting high specific surface areas and large pore volumes such as surfactant-nanostructured alumina, sol-gel methods and hierarchically macro-/mesoporous alumina monoliths have been analyzed and compared. The most reproducible synthesis of mesoporous alumina are given. Evaporation-Induced Self-Assembly (EISA) is the sole method to lead to nanostructured mesoporous alumina by direct templating, but it is a difficult method to scale-up. Alumina featuring macro- and mesoporosity in monolithic shape is a very promising material for in flow applications; an optimized synthesis is described.
Particle Size Distribution, Powder Agglomerates and Their Effects on Sinterability of Ultrafine Alumina Powders
Particle Size Distribution,Powder Agglomerates and Their Effects on Sinterability of Ultrafine Alumina Powders

Renjie ZENG,BRand,

材料科学技术学报 , 2000,
Abstract: An intensive study of the particle size distribution of four commercial ultrafine alumina powders to obtain information about the powder agglomeration and relate them to the compactibility and the sinterability has been made.
Nanocarbon-coated α-Al2O3 Composite Powders Synthesized by High-energy Ball Milling
WU Xiao-Xian, LI Hong-Xia, LIU Guo-Qi, NIU Chong-Chong, WANG Gang, SUN Jia-Lin
无机材料学报 , 2013, DOI: 10.3724/sp.j.1077.2013.12233
Abstract: Nanocarbon-coated α-Al2O3 composite powders were synthesized by high-energy ball milling using expanded graphite and α-Al2O3 as raw materials. The effects of milling time and speed on phase composition and microstructure of the composite powders were investigated. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) were employed to characterize the phase composition, morphology and microstructure of the composite powders. The results show that nanocarbon with a size of 20–50 nm coated on the α-Al2O3 particles when the expanded graphite and α-Al2O3 with a weight ratio of 1:2 were milled for 5 h at a speed of 600 r/min. By increasing the milling time, the (002) diffraction peak of graphite gradually disappeared, and nano-graphite sheets desquamated from expanded graphite and then chaped to nanocarbon particles. Milling for the same time, higher milling speed was beneficial to synthesize nanocarbon particles, but when milling speed reached certain value, the size of nanocarbon cannot become smaller again. Nanocarbon-coated α-Al2O3 composite powders cannot be synthesized using a milling speed of 480 r/min even milled for 5 h. The morphology and microstructure of the composite powders were basically the same when the composite powders were milled at 600 and 700 r/min for 5 h.
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