Papers by Keyword: High Energy Milling (HEM)

Abstract: Fully dense and single-phase Ti3AlC2 bulk ceramic was successfully fabricated by a high energy milling and hot-pressing with Ti, C and Al as starting materials. The details of reaction and phase evolution in high energy milling and hot pressing sintering were investigated. The results show that most of the starting materials transform to Ti-Al intermetallics and TiC in high-energy milling. The as milled powders react into Ti2AlC firstly in hot pressing sintering. When the temperature raise high enough, the Ti2AlC transform to Ti3AlC2. The content of aluminum is higher than that in the theoretical composition, which is attributing to the volatilization of Al at high temperature.

Abstract: A kind of new Production flowchart of zinc-flake had investigated by use of the high energy milling(HEM) under the protection of inert gas, researched the properties of effects of zinc-flake of the starting powder, surfactants ,milling Production flowchart by high energy milling .

Abstract: The electrochemical properties of LiFePO4 as a cathode of lithium ion batteries considerably depend on a particle size of LiFePO4 and a condition of carbon coating. In this study, LiFePO4 powders were prepared using ultrasonic spray pyrolysis method, and then LiFePO4/C composites were made by infiltrating sucrose solution into LiFePO4 powders, drying, high-energy milling and annealing. The effects of high-energy milling were analyzed by comparing with electrochemical properties of powders synthesized without high-energy milling. It was found that the milling process drastically reduced the particle size of synthesized powders and electrical conductivity, and improved discharge capacity, cycle stability and rate performance.

Abstract: Many laboratories have researched membrane for gasification of coal technique, separating hydrogen from fossil fuel. In general, Pd membrane of separating hydrogen is very good a property of hydrogen selectivity on high temperature, but it has some problems, hydrogen embrittlement and costly material. So, we need some materials of good properties about hydrogen selectivity instead of Pd. In this research, we fabricate membrane for hydrogen permeation, that is great in resistance to acids and chemically steady TiN. Our laboratory investigated about hydrogen selectivity. TiN powder is milled 30, 60 and 240 minutes by vibration mill, respectively. After than the samples put in operate spark plasma sintering. We analyze XRD, SEM, BET and TG/DSC. Also, in this research take an inspect hydrogen selectivity by ourselves manufactured Sievert’s type hydrogen permeation membrane equipment.

Abstract: The structure and microwave magnetic performance of Fe, Fe-Si-C, and Fe-Co-Si-C powders fabricated by mechanical milling has been studied. The study was aimed at revealing of the effect of shape, composition, and structure of the powder particles on the microwave frequency dispersion of permeability of the powder-filled composites in the frequency range of 0.1−3 GHz. At low frequencies, below 1 GHz, the main reason causing the differences in the microwave magnetic properties of the powders is the shape of powder particles. At higher frequencies, the magnetic performance is mainly due to the effect of eddy currents and is determined by the size of powder particles. The difference in the composition of the powders under study and, therefore, corresponding differences in intrinsic permeability of these have a minor effect on the microwave magnetic performance as compared to the effects of particle size and shape.

Abstract: Single-component, self-setting and injectable calcium phosphate cement (CPC) based on amorphization process of dicalcium phosphate dehydrate (DCPD) is proposed. After preparation of DCPD by wet chemistry, the material was dry milled in an Attritor high energy process (at 400 RPM) during 20 minutes. Experiments were also conducted using a regular ball milling process at 15 and 30h residence time. Amorphization of DCPD confirmed using FTIR, XRD and 31 P solid-states NMR (cross-polarization and decoupling). Upon hydration of amorphized DCPD powder with saline (0.55 ml/g), putty-like consistency produced. The paste hardened in 30 minutes at 37°C and reached a compressive strength of about 20 MPa. The final product was a low crystalline calcium deficient apatite, similar to the composition and structure of bone mineral.

Abstract: In this work a 50Ni50Ti at % powder mixture, commercially pure, prepared by mechanical alloying in an attritor with the following conditions: the milling speed and the ball charge were 1500 rpm and 15:1 respectively. The milling time was 1h under a nitrogen atmosphere at room temperature. After milling it was determined the particles size distribution, the phases by Xray diffractions (XRD) and the powder morphology by scanning electron microscopy (SEM). The powders after milling were compacted and hot extruded at 600 °C with an extrusion ratio of 3 to 1 and characterized by evaluation the density and microstructural determination by optical microscopy. The obtained results are discussed to show that this route could be an alternative route to prepare the shape memory alloy.

Abstract: The addition of nanometric particles of a second phase into ceramics matrix is one of the most recent alternatives in the development of materials with high mechanical properties and wear resistance. These nanostructured materials can be defined as systems that have at least one microstructural characteristic of nanometric dimensions (less 100nm). In this work aluminadiamond nanocomposites were produced using diamond nanometric powders obtained by high energy milling. Diamond powder was produced in the SPEX shaker/mill during 6h, with a ball-tomass ratio of 4:1. The crystallite size was 30nm. After the elimination of the Fe deriving of the contamination during the milling, and desaglomeration, this nanometric powder was added in the alumina matrix in the ratio of 5wt%. The powder densification was performed by hot pressing sintering. The obtained nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and microhardness, and they have promising characteristics regarding abrasion and wear resistance.

Abstract: A new method for SOFC fuel cell anode preparation is proposed where the main difference lies over cermet powder processing by high energy milling. Yttria stabilized zirconia powder and metallic nickel undergo co-milling in a vibratory device employing zirconia bead media. Dispersed and homogeneous powders are therefore obtained. The material is pressed uniaxialy and sintered at 1350°C for 0,5 h in air and under argon and hydrogen. In the former case, partial nickel oxidation occurs before sintering leading to small shrinkage down to 2% and porosity about 38%. Linear shrinkages from 5 to 7% after sintering in both inert and reduced atmospheres were observed not demanding pore-former additives. Conventional YSZ, Ni and NiO powder mixtures were prepared for comparison purpose. The high energy milling process is able to reduce the starting sintering temperature by 130° C besides a higher densification compared to the simple mixtures YSZ+Ni. The excessive sintering and particle coalescence is absent in high energy milled material, where the metal is well dispersed and the microstructure is highly homogenous. The high energy milling process is a promising route to prepare with excellent performance anode materials for SOFC cells.

Abstract: Cr3C2-NiCr coatings have been used for corrosion and wear resistant applications. In the last decade, thermal sprayed coatings using nanostructured feed stock of other materials has exhibited higher hardness, strength and corrosion resistance. Hence, it is anticipated that nanostructured Cr3C2-NiCr coatings will also exhibit these properties and therefore posses improved performance characteristics. Preparation of nanostructured feed stock powders is the first step in the synthesis of nanostructured coatings and mechanical milling is an effective process to obtain the powders. Preliminary studies in which commercial Cr3C2-NiCr powders were milled in hexane and gaseous nitrogen revealed that particle and crystallite size were significantly smaller in powders milled in nitrogen. This paper presents the effect of hexane content and milling parameters on Cr3C2-Ni20Cr powder characteristics. Use of just sufficient hexane as the milling media reduced significantly the particle and crystallite sizes.