Papers by Keyword: High-Energy Ball Milling (HEM)

Abstract: High energy milling (HEM) was used to the preparation of multi-walled carbon nanotubes reinforced copper matrix (MWCNTs/Cu) composite powders in this paper. And the MWCNTs/Cu composite material was prepared by the cold-press sintering method. The influence law of balls/powder weight ratio to the MWCNTs/Cu composite powders was discussed. Particle size distribution and fracture micrograph were analyzed by XRD and SEM. The results show that particle size distribution of CNTs/Cu composite powders reached a minimum, when the balls/powder weight ratio was 10: 1. The particle size distribution (D50) of CNTs/Cu composite powders was 22.33μm. The CNTs distributes homogeneously , which is in favor of the mechanical combination of the CNTs and Cu substrate. The tensile strength of CNTs/Cu composite reached 189 MPa.

Abstract: The Ti-48at%Al composite powder was synthesized by high energy ball milling. The properties of the composite particles, such as medium diameter,Phase ,microstructure and components, were respectively investigated . Results show that, the phase evolution process can be described by: Ti+ Al fcc Ti (Al),TiAl,TiAl₃,Ti₃AlTiAl₃,Ti₃Alamorphous phase. After milling 3 hours, Fcc Ti (Al) solid solution, TiAl, TiAl₃, Ti₃Al were found. After milling 9 hours, the amorphous phase of Ti - 48 at % Al were produced. The element distribution of the mechanically alloyed Ti-48at%Al powder was close to the initial design composition after 5 h milling, but this distribution was inhomogeneous. Medium diameter (D₅₀) of Ti-48at%Al composite powder achieved the minimal size 9.56 μm after milling for 5hours.

Abstract: Ti/Al(Ti-50at.%Al) composite powders were prepared by high-energy ball milling followed by reaction sintering heat treatment at 550°C ~ 650°C for 2 hours. Mechanical alloying of TiAl had been performed in a high energy plant ball after different milling times and pre-sintered at different temperatures. The particle sizes of Ti/Al powders were analyzed by scanning electron microscopy (SEM). X-ray diffraction (XRD) analysis was performed for microstructural characterization. The results show that microstructural and morphological changes of high energy milled powder are studied as a function of milling time. Over 600°C TiAl powders are completely alloyed by being sintered at different temperatures. The powders are mainly composed of γ-TiAl as well as a small amount of AlTi3. The TiAl alloy powders of high energy ball mill/2h and sintered at 650°C/2h get plasma spheroidization. Spheroidizing powders with fine texture, γ-TiAl and AlTi₃ phase, particle size of 10~40μm are obtained.

Abstract: The relevance of sensor response to NO₂ with the nanostructure of the sensing body was investigated for thick-film devices using ZnO(WO₃) nanocomposites. When the nanocomposites was prepared from constituent oxides by milling in a high energy ball mill for various spans of time (1–21 h), the sensor response to 100 ppm NO₂, defined as the ratio of the electrical resistance in air to that in the sample gas, was found to reach a maximum as large as about 80 at 21 h of high energy ball-milling (HEBM). XRD and SEM observations of the granular state and pore size distribution analyses indicated that increasing HEBM time gave rise especially to an increase in the volume of pores in the pore size range of 20–35 nm. It is suggested that such a change in nanostructure is responsible for the marked promotion of the response to NO₂. For comparison, the response to NO₂ of ZnO or WO₃ nanoparticles prepared by an HEBM method was also presented. In this case, the response to NO₂ can be 10 times larger at HEBM for 21 h.

Abstract: The NdFe magnetic absorbing materials were prepared by rapid solidification and high-energy ball milling method. The effect of high-energy ball milling on particle morphology, organizational structure and microwave absorbing properties of NdFe magnetic absorbing materials were analyzed with the aid of X-ray diffractometer, scanning electron microscope and vector network analysis. The results show that the Nd2Fe17 and α-Fe phase are refined, the particles become smaller and thinner; the span-ratio of the particles increases along with time during the process of high-energy ball milling; and meanwhile, the frequency of absorbing peak reduces. The absorbing bandwidth broadens as the increase of the time of ball milling, except that of 48h.The minimum reflectance of the powder decreases from -22dB to - 44dB under the circumstances that the time of high energy ball milling reaches 48h and the thickness of the microwave absorbing coating is 1.5mm. But it rebounds to about - 6dB when the time of ball milling reaches 72h.

Abstract: This paper using high energy ball milling(HEM), researched the technology of preparation of Al compound material reinforced by CNT. Researched the different milling time, rotary speed, amount of CNT and sinter technology on properties of hardness and density. Preparation the Al-CNT at milling time about 30 to 100 min, rotational speed is about 300-600/rpm.the wt% of CNT is 0-5%, Analyzed the XRD patterns、SEM and STM micrograph, the results showed the Al material could be reinforced by CNT using HEM. the hardness of Al-CNT is 75 HB and the density is 2.65 g/cm3 when milling 90 min and CNT 3%.

Abstract: Bulk nanostructured Al-4Cu alloy was synthesized by high energy ball milling followed by vacuum hot pressing. Its thermal stability was investigated up to 450°C using differential scanning calorimetry, X-ray diffraction, and transmission electron microscopy. The results showed that grain growth in this Al-4Cu alloy was very limited and grain sizes in the range of 100 nm were still present in the alloys after exposure to 450 °C corresponding to a temperature as high as 0.77 T/Tm. The TEM investigations reveal that such a high thermal stability against grain growth observed in this alloy is attributed to the presence of ultrafine dispersoids.

Abstract: In this paper, TiH₂-47Al-5Nb (at.%) and TiH₂-47Al-7Nb(at.%) alloys were mixed and synthesized using TiH₂, Al and Nb powders. The composition and morphology evolution of the mixed powder were systematically investigated during high energy ball milling. The results show obvious that structure change of the particle during milling, and amorphous, TiAl, Ti₃Al and Ti₂Al phases at nanoscale are formed. The addition of Nb shows an active influence on the decomposition of TiH₂ and formation of TiAl-intermetallics. Compare with Ti-Al system alloy, the forming process of TiAl-intermetallics for TiH₂-Al-Nb system alloy is different and slower. Ti₂Al metastable phase formed after ball milling for 15 h in our experiments.

Abstract: In this paper, carbon nanotubes (CNT)-reinforced aluminum (Al) matrix composites were fabricated by High-Energy Ball Milling, the objective was to investigate the evolvement of particle size, density and hardness of CNT-Al composites with increasing wt% CNT, and analyzed the micrographs of mixture powders at different milling time. The results showed that the addition of CNT can play a role of grinding aid to refine grain, improve the hardness and decrease the density, and CNT can be homogeneous dispersed in the matrix with increasing ball-milling time, it also showed that too much CNT was no help on hardness, this attributed to clustering of CNT, the proper addition of CNT was 2wt%, and the mixture powders could reached a state of equilibrium between fracturing and cold-welding at 75min.

Abstract: Thermo-sensitive copper/paraffin nanocomposites were prepared by high energy ball milling. Fourier transform infrared spectrometer (FTIR), x-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to analyze the composition, phase and microstructure of the composites. Furthermore, their thermal sensitivity was investigated. Results reveal that the phase of composites is mainly composed of copper, paraffin and a small amount of cuprous oxide copper. Nanoparticles homogeneously covered by paraffin form the similar core-shell structure. The mass ratio of copper to paraffin has an obvious influence on the thermal sensitivity.