High purity hematite (Fe2O3) from beach sands for soft ferrite magnetic materials application

Actually, the potential and deposites are rich and spread in many place, but the process from raw material to industrial product is not optimal yet. In this work, the manufacture of iron sand was done using direct reduction technique by compact coals as reductor. The carbon compound of coals were using for releasing oxide in magnetite compounds (Fe3O4) of iron sand, so it could be transformed to Fe phase. The iron sand was firstly milled using high energy ball mill (HEBM) for 0, 10, 20, and 40 hours. Then the iron sands samples were mixed with coals, bentonite and compacted using hydraulic press. Then, loaded into furnace and sintered at 700 °C, 800 °C, and 900 °C. As the results, it was identified (using XRF) that the major phase was Fe2O3 (75.40 %). Consistent with XRF results, the phase composition observation by using XRD was shown that the major phase of sample was Fe2O3 (hematite). It was also shown that the crystallite size of the sample was around 8 nm, as calcultaed using Scherrer formula. The magnetic behavior investigation was showed that the decreasing in magnetic saturation value (Ms) and remanent (Br) and followed by increasing the coercivity value (Hc).

A Study To Evaluate The Bioactivity Behavior And Electrical Properties of Hydroxyapatite/Ag2O-Borosilicate Glass Nanocomposites For Biomedical Applications

The aim of this work is to prepare nanocomposites with excellent bioactivity and appropriate mechanical properties. In this regard, the nanocomposites, with different contents of borosilicate glass (BG) and carbonated hydroxyapatite (CHA), were mixed and milled using a high-energy ball mill. Then, these milled powders were subjected to sintering at 750 ºC. In order to examine their phase composition, molecular structure and microstructure, X-ray diffraction (XRD) technique, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM), respectively were used. Moreover, the DC electrical conductivity, and physical and mechanical properties of the prepared nanocomposites were also measured. In addition, the in vitro bioactivity of the sintered samples was evaluated using XRD and SEM. Unexpectedly; the results indicated that the successive increase in BG contents promoted the partial decomposition of CHA molecules at this lower sintering temperature. Also, it was responsible for the enhanced bioactivity behavior along with giving CHA better mechanical properties. However, the electrical conductivity of the examined samples exhibited an opposite trend where it decreased significantly with increasing BG content. According to the results obtained, the prepared samples are suitable for use in various biomedical applications.

The Effect of Ball Milling on Properties and Sintering of Nanostructured TiB2

TiB2 powder was milled in a high-energy ball mill (Pulverisette-5 planetary mill) at 250 rpm for various time periods (0, 1, 4, and 10 h) and consolidated by the high frequency induction heated sintering (HFIHS). The effect of milling on the sintering behavior and crystallite size of TiB2 powders were investigated. A nanostructured dense TiB2 specimen with a relative density of up to 98% was readily achieved within very short time (two min). The ball milling effectively refined the crystallite structure of TiB2 powders and facilitated the subsequent consolidation. The sinter-onset temperature was reduced remarkably by the prior milling for 10 h. Accordingly, the relative density and mechanical properties of TiB2 compact increased as the milling time increased.

Seismic fault weakening via CO2 pressurization enhanced by mechanical deformation of dolomite fault gouges

Carbon dioxide emissions from dolomite decarbonation play an essential role in the weakening of carbonate faults by lowering the effective normal stress, which is thermally activated at temperatures above 600–700 °C. However, the mechanochemical effect of low-crystalline ultrafine fault gouge on the decarbonation and slip behavior of dolomite-bearing faults remains unclear. In this study, we obtained a series of artificial dolomite fault gouges with systematically varying particle sizes and dolomite crystallinities using a high-energy ball mill. The laboratory-scale pulverization of dolomite yielded MgO at temperatures below 50 °C, indicating that mechanical decarbonation without significant heating occurred due to the collapse of the crystalline structure, as revealed by X-ray diffraction and solid-state nuclear magnetic resonance results. Furthermore, the onset temperature of thermal decarbonation decreased to ~400 °C. Numerical modeling reproduced this two-stage decarbonation, where the pore pressure increased due to low-temperature thermal decarbonation, leading to slip weakening on the fault plane even at 400–500 °C; i.e., 200–300 °C lower than previously reported temperatures. Thus, the presence of small amounts of low-crystalline dolomite in a fault plane may lead to a severely reduced shear strength due to thermal decomposition at ~400 °C with a small slip weakening distance.

Defect-induced B4C electrodes for high energy density supercapacitor devices

Boron carbide powders were synthesized by mechanically activated annealing process using anhydrous boron oxide (B2O3) and varying carbon (C) sources such as graphite and activated carbon: The precursors were mechanically activated for different times in a high energy ball mill and reacted in an induction furnace. According to the Raman analyses of the carbon sources, the I(D)/I(G) ratio increased from ~ 0.25 to ~ 0.99, as the carbon material changed from graphite to active carbon, indicating the highly defected and disordered structure of active carbon. Complementary advanced EPR analysis of defect centers in B4C revealed that the intrinsic defects play a major role in the electrochemical performance of the supercapacitor device once they have an electrode component made of bare B4C. Depending on the starting material and synthesis conditions the conductivity, energy, and power density, as well as capacity, can be controlled hence high-performance supercapacitor devices can be produced.

Synthesis, structural and biomedical characterization of hydroxyapatite/borosilicate bioactive glass nanocomposites

In this work, a borosilicate glass sample (5SiO2-45B2O3-20Na2O-25CaO-5Ag2O) was added to nano-sized carbonated hydroxyapatite (CHA) powders with different contents up to 20 wt.% to improve the bioactivity, antibacterial effect, physical and mechanical properties of the resulting nanocomposites. Then, these samples were mixed, milled with a high-energy ball mill, sintered at 700°C and subjected to X-ray diffraction (XRD) technique, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) to examine their structure, chemical composition and microstructure, respectively. Furthermore, the physical and mechanical properties of the sintered nanocomposites were also measured. Moreover, the in vitro bioactivity of the prepared nanocomposites was examined with XRD and SEM. Additionally, the antibacterial behavior of these samples was tested against E. coli and S. aureus by the disc-diffusion method. The results obtained pointed out that the sample with the highest content of BG possessed the best bioactivity, antibacterial effect, physical and mechanical properties.

Thermoelectric and Transport Properties of Permingeatite Cu3SbSe4 Prepared Using Mechanical Alloying and Hot Pressing

Permingeatite (Cu3SbSe4) is a promising thermoelectric material because it has a narrow band gap, large carrier effective mass, and abundant and nontoxic components. Mechanical alloying (MA), which is a high-energy ball mill process, has various advantages, e.g., segregation/evaporation is not required and homogeneous powders can be prepared in a short time. In this study, the effects of MA and hot-pressing (HP) conditions on the synthesis of the Cu3SbSe4 phase and its thermoelectric properties were evaluated. The electrical conductivity decreased with increasing HP temperature, while the Seebeck coefficient increased. The power factor (PF) was 0.38–0.50 mW m−1 K−2 and the thermal conductivity was 0.76–0.78 W m−1 K−1 at 623 K. The dimensionless figure of merit, ZT, increased with increasing temperature, and a reliable and maximum ZT value of 0.39 was obtained at 623 K for Cu3SbSe4 prepared using MA at 350 rpm for 12 h and HP at 573 K for 2 h.

Defect-induced B4C Electrodes for High Energy Density Supercapacitor Devices

Boron carbide powders were synthesized by mechanically activated annealing process using anhydrous boron oxide (B2O3) and varying carbon (C) sources such as graphite and activated carbon: The precursors were mechanically activated for different times in a high energy ball mill and reacted in an induction furnace. According to the Raman analyses of the carbon sources, the I(D)/I(G) ratio increased from ~0.25 to ~0.99, as the carbon material changed from graphite to active carbon, indicating the highly defected and disordered structure of active carbon. Complementary advanced EPR analysis of defect centers in B4C revealed that the intrinsic defects play a major role in the electrochemical performance of the supercapacitor device once they have an electrode component made of bare B4C. Depending on the starting material and synthesis conditions the conductivity, energy, and power density, as well as capacity, can be controlled hence high-performance supercapacitor devices can be produced.