Mechanical Activation Method Research Articles

Microstructural and magnetic studies on BaMgxZnxX2xFe12−4xO19 (X=Zr,Ce,Sn) prepared via mechanical activation method to act as a microwave absorber in X-band

In this study, doped barium hexaferrite with the composition of BaMgxZnxX2xFe12−4xO19 (where x= 0.3, 0.5, 0.7, 0.9 and X= Zr, Ce, Sn) was prepared via mechanical activation. X-ray diffractometer (XRD), FTIR spectrophotometer, Field emission scanning electron microscope (FE-SEM), vibrating sample magnetometer (VSM) and vector network analyzer (VNA) were used to analyze its phases, structure, electromagnetic and microwave absorption properties respectively. Based on the results, single phase barium hexaferrite was obtained in all cases after milling the mixed powders for 20h plus calcination at 1000°C for 5h. Morphology of the particles in all of the doped samples was completely hexagonal shape and they had an appropriate distribution. It was found that the sample of BaMg0.9Zn0.9Zr1.8Fe8.4O19 with saturation magnetization and coercive force of 37.3emu/g and 94Oe respectively possessed the maximum reflection loss of −19.3dB at 12.3GHz with 1.7GHz bandwidth.

The Relationship Between the Distribution of Valence Electrons and Electrochemical Properties of Mixtures α-Fe2O3/Al2O3, α-Fe2O3/SiO2 and γ-Fe2O3/SiO2 Before and After Mechanical Activation Synthesis

Using the method of electrochemical analysis the charge capacity of electrochemical cells with cathode material on the bases of simple and mechanically activated mixtures 0,2α-Fe2O3+0,8Al2O3, 0,2α-Fe2O3+0,8SiO2 та 0,2γ-Fe2O30,8SiO2 has been researched. With the help of method of ultra soft X-ray spectroscopy the influence of mechanical activation method on the distribution of valence electrons of these mixtures has been researched. In this research, the relationship between changes in populations of electronic states in the valence band and intercalation properties of studied mixtures has been studied.

Effects of mechanical activation methods on thermo-oxidation behaviors of pyrite

To explore the effects of mechanical activation methods (ball mill, planetary mill and rod mill) on the oxidation and the spontaneous combustion of pyrite, the kinetic curves of non-activated pyrite and mechanically activated pyrite were created by simultaneous thermal analysis. The structural characteristics and changes of mechanically activated pyrite were investigated by X-ray diffraction and SEM, and the relationship between the mean diameter and the grinding time was obtained by using a laser particle size analyzer. The kinetic model of pyrite and the kinetic parameters were deduced using Bagchi method. The relationship between the kinetic parameters indicates that, pyrite activated by ball milling shows the best thermal stability at the same diameter. By comparing and analyzing the X-ray diffraction patterns, results show that different mechanical activation ways played different roles in structural changes of pyrite.

Low temperature synthesis of nano Ti(C,N) by novel mechanical and thermal activation method

This paper presents a novel mechanical and thermal activation assisted carbothermal reduction (CR) method for synthesising Ti(C,N) powder at lower temperatures. Nano Ti(C,N) powder with approximately 30 nm grain size was synthesised by mixing powders of titanium, anatase, and carbon black. The starting powders were first milled for 10 to 40 h under N2/Ar atmosphere, and then vacuum heat treated for 1 h at 800 to 1050°C. Consequently, nano Ti(C,N) powder with approximately 30 nm grain size was synthesised. X-ray diffraction analysis shows that Ti(C,N) is partially formed during mechanical milling, and the remaining reactants react completely below 1050°C. However, when the unmilled starting powders are heat treated at 1050°C under N2 for 1 h, large amounts of reactants remain. Thermogravimetry and differential scanning calorimetry analysis shows that the CR reaction of activated TiO2 occurs at a lower temperature under N2 than under Ar or vacuum.

PREPARATION AND CHARACTERIZATION OF HYDROXYAPATITE REINFORCED WITH HARDYSTONITE AS A NOVEL BIO-NANOCOMPOSITE FOR TISSUE ENGINEERING

Objecttive(s): Despite the poor mechanical properties of hydroxyapatite, its unique biological properties leads we think about study on improving its properties rather than completely replacing it with other biomaterials. Accordingly, in this study we introduced hydroxyapatite reinforced with hardystonite as a novel bio-nanocomposite and evaluate its in-vitro bioactivity with the aim of developing a mechanically strong and highly porous scaffold for bone tissue engineering applications. Materials and Methods: Natural Hydroxyapatite (NHA)-Hardystonite (HT) nanocomposite with different percentage of HT was synthesized by mechanical activation method and subsequent heating annealing process. This study showed that the addition of HT to HA not only increases the mechanical properties of HA but also improves its bioactivity. Dissolution curves presented in this study indicated that the pH value of SBF solution in the vicinity of HA-HT nanocomposite increases during the first week of experiment and decreases to blood pH at the second weekend. Hardystonite was composed of nano-crystalline structure with approximately diameter 40 nm. Specimens were composed of a blend of pure calcite (CaCO3) (98% purity, Merck), silica amorphous (SiO2) (98% purity, Merck) powder and pure zinc oxide (ZnO) with 50 % wt., 30 %wt and 20 %wt., respectively. These powders were milled by high energy ball mill using ball-to- powder ratio 10:1 and rotation speed of 600 rpm for 5 and 10 h. Then, the mixture mechanical activated has been pressed under 20 MPa. The samples pressed have been heated at 1100 oC for 3 h in muffle furnace at air atmosphere. Xray diffraction (XRD), scanning electron microscopy (SEM) and BET performed on the samples to characterize. Results: According to XRD results, the sample milled for 10 h just indicated the hardystonite phase, while the sample milled for 5 h illustrate hardystonite phase along with several phases. Conclusion: In fact, our study indicated that hardystonite powder was composed of nanocrystalline structure, about 40 nm, can be prepared by mechanical activation to use as a new biomaterials for orthopedic applications.

Novel Microstructure Mechanical Activated Nano Composites for Tissue Engineering Applications

Nowadays, tricalcium phosphate TCP (Ca3 (PO4)2) that belongs to the group of calcium phosphate (CaPs) biomaterials as a hot topic of research for bone tissue repair applications. In this investigation, TCP powder was synthesized by mechanical activation (MA) method as a solid state process. The mixture was composed of a blend of pure calcite (CaCO3) and silica amorphous (SiO2) powder with 57% wt. and 43% wt., respectively. Then, the powder mixture milled by high energy ball mill with ball to powder ratio (BPR) 15:1 and rotation speed 600 rpm for 10 h. After then, the materials milled heated at three temperatures 900oC, 1000oC and 1100°C for 2 h in muffle furnace at the air atmosphere. X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET technique performed on heated powders to characterize. According to XRD results, the patterns show that the phase TCP was just appeared in the mixture milled for 10 h. In addition, based on modified Scherer equation the TCP crystalline size was determined 40 nm. In fact, the present investigation indicated that TCP powder was composed of Nano-crystallite structure, 30-40 nm, can be prepared by MA method at 900°C or 1000°C to use as a new biomaterials for tissue engineering application.

Novel electrophoretic deposited nanostructured forsterite coating on 316L stainless steel implants for biocompatibility improvement

In this research, a novel nanostructured forsterite coating was deposited on AISI 316L stainless steel substrates by the electrophoretic deposition (EPD) method. Forsterite nanopowders were synthesized using the mechanical activation method. The as-milled nanoparticles were then immersed in a slurry containing 0.5wt% polyvinyl alcohol (PVA) in order to obtain PVA-coated forsterite nanopowders. The PVA-coated powder particles were electrophoretically deposited on metallic substrates under various conditions (times and voltages). As-deposited coatings were then subjected to a two-step sintering process. The forsterite coatings deposited under different conditions were characterized in terms of microstructural and bioactivity properties. The bioactivity of the prepared specimens was evaluated in simulated body fluid (SBF) at 37°C for up to 28 days. Results showed that the coating which was deposited after 5min under a voltage of 25V was homogeneous and crack-free. The nanostructured forsterite coated samples possessed apatite-formation ability during immersion in SBF.

Novel catalysts for conversion of liquid hydrocarbon

A catalytic system NiO-Al2O3 of conversion of C6+ hydrocarbon fractions obtained after separation of the target natural raw materials was improved by a method of mechanical activation and modification of CeO2. The resulting modified catalyst system of a NiO-BaO-CoO2-Al2O3 structure is characterized by high activity and stability during operation and also it demonstrates an oxidative activity. Structural characteristics and morphology of the modified catalytic system of hydrocarbon conversion were analyzed by adsorption methods, scanning electron microscopy, laser-dispersive and X-ray analysis.

Electrochemical properties of a full cell of lithium iron phosphate cathode using thin amorphous silicon anode

Carbon-coated lithium iron phosphate (LiFePO4/C) with uniform carbon coating was synthesized by a mechanical activation method. Silicon negative electrode material was obtained in the form of thin films of amorphous silicon on a Cu foil substrate by vertical deposition technique. The electrochemical performance of the full cell, LiFePO4/C–Si, was tested with 1M LiPF6 in EC/DMC at 0.5 and 1 C-rates. The cell exhibited an initial discharge capacity of 143.9mAhg−1 at 0.5 C-rate at room temperature. A reasonably good cycling performance under a high current density of 1 C-rate could be obtained with the full cell.

Mechanochemical synthesis of zinc oxides with the use of liquid and gaseous media

X-ray phase analysis, thermogravimetry, and volumometry were used to study the mechanochemical synthesis of zinc oxide. The conversion of metallic zinc was calculated in relation to the time and method of mechanical activation and to the oxidizing medium used. The most optimal conditions of oxidation of metallic zinc were determined.

Effect of W addition on the hydrodeoxygenation of 4-methylphenol over unsupported NiMo sulfide catalysts

Unsupported NiMo sulfide catalysts modified by tungsten were prepared by a mechanical activation method. They were characterized by XRD, XPS, SEM, TEM and BET specific surface area measurements. The effect of tungsten promoter on the structure and catalytic performance was also discussed. The present work suggested that the addition of tungsten could greatly enhance the hydrodeoxygenation (HDO) activity, and promote the direct deoxygenation (DDO) pathway. Moreover, the addition content affects the mount of active NiMo(W)S phase, resulting in various functions.

Distorted MoS2 nanostructures: An efficient catalyst for the electrochemical hydrogen evolution reaction

An effective electrochemical catalyst has been developed through a mechanical activation method for the hydrogen evolution reaction (HER). Catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and BET surface area measurements. It was found that the mechanical activated MoS2 (MA-MoS2) possessed distorted structures with an abundance of exposed edge sites, exhibiting excellent electrochemical activity in the HER with a high current density and a relatively low Tafel slope.

Metal-matrix radiation-protective composite materials based on aluminum

A method of mechanical activation providing a homogeneous distribution of reinforcing boron-bearing components and tungsten nanopowder in the matrix is recommended for making an aluminum-based radiation-protective material. Joint mechanical activation and subsequent extrusion are used to produce aluminum-based composites. The structure and the physical, mechanical and tribological characteristics of the composite materials are studied.

The effect of nickel content on the hydrodeoxygenation of 4-methylphenol over unsupported NiMoW sulfide catalysts

Abstract Unsupported NiMoW sulfide hydrodeoxygenation (HDO) catalysts were prepared by mechanical activation method varying the nickel concentration. Catalysts were characterized by XRD, SEM, TEM and BET surface area measurements. Moreover, catalytic activity and selectivity were evaluated in the HDO of 4-methylphenol (4-MP). The results suggested that the structure and the promoting effects were strongly dependent on the amount of Ni added into the catalysts. Nickel gave a positive effect on HDO of 4-MP and modified the product selectivity slightly. It was also found that nickel played a crucial role in the variation of catalytic performance.

Luminescence and magnetic properties of europium(III) nitrate complex with 1,10-phenanthroline

Luminescent and magnetic properties of the europium nitrate complex with 1,10-phenanthroline synthesized in the traditional way by precipitation from water-ethanol medium and by the method of mechanical activation were investigated. Correlations between luminescent and magnetic properties of the complex compounds were revealed. The higher value of molar magnetic susceptibility χm was shown to be typical for the highly dispersed europium compound obtained by mechanochemistry method due to the presence of the paramagnetic ion Eu2+.

High-rate capability of LiFePO 4 cathode materials containing Fe 2P and trace carbon

Carbon coating and nano-scale particle size are two impactful factors in improving the rate capability of LiFePO 4 cathode materials for lithium-ion batteries. However, both factors decrease the tap density of the materials and are possibly causing unfavorable effect on the volumetric capacity of the cathode materials and thus the batteries, which is undesirable in commercial application. In the present study, LiFePO 4 materials with moderate particle size of sub-micron and trace carbon content (0.5–0.9 wt.%) are synthesized by a mechanical activation method. High-electronic conductivity iron phosphides (Fe 2P/FeP) are in situ introduced into the LiFePO 4 materials and the amount is modified by the calcination temperature. Electrochemical testing shows that Fe 2P/FeP plays an important role in improving the high-rate capability of LiFePO 4 with moderate particle size. The product calcined at 700 °C, which has a high-tap density of 1.37 g cm −3 correlating to a specific surface area approximately of 4 m 2 g −1, possesses discharge capacities of 110 and 100 mAh g −1 at discharge rates of 5 C and 10 C, respectively. The introduction of Fe 2P/FeP in an amount of ca. 5 wt.% rather than carbon coating and the moderate particle size of LiFePO 4 are promising approaches to obtain LiFePO 4 cathode material of high-rate capability without unduly compromising its volumetric capacity.

A carbon-free LiFePO 4 cathode material of high-rate capability prepared by a mechanical activation method

A carbon-free LiFePO 4 cathode material for lithium–ion battery has been synthesized by a mechanical activation method. High electron conductive iron phosphides (Fe 2P/FeP) are in situ introduced into the products during the calcination process in order to improve the high rate capability of the LiFePO 4 materials. The amount of the iron phosphides is adjusted by the calcination time. The study of the structure and electrochemical performance of the LiFePO 4 products shows that the calcination time imposes minor effect on the size and shape of the LiFePO 4 particles, but varies the phase structure, crystallinity and finally the electrochemical performance of the LiFePO 4 products as a consequence. The content of Fe 2P/FeP increases gradually with the calcination time. Suitable amount of Fe 2P/FeP and good crystallinity play effective role in improving the high-rate capability of the carbon-free LiFePO 4 material. Specific discharge capacities over 110 mAh/g at 5 C and 100 mAh/g at 10 C are obtained for the LiFePO 4 material containing 4–5 wt.% Fe 2P/FeP.

Growth of Flower-Like AIN by Combustion Synthesis Assisted with Mechanical Activation

Flower-like AlN microstructure with many cone-like petals was prepared by combustion synthesis assisted with a mechanical activation (MA) method using NH4Cl as a reacting additive. The products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy dispersive spectrum (EDS) and transmission electron microscopy (TEM). A possible mechanism for the growth of AlN microflowers was proposed base on several parallel experiments and discussion. It was found that both the MA time and NH4Cl content play crucial roles for the growth of the flower-like microstructure.

Effects of thermal and mechanical activation methods on compressive strength of ordinary Portland cement–slag mortar

Activation methods and curing regimes have crucial effects on the strength of mortars and concretes. The objective of this investigation is to examine the early and later compressive strength of activated ordinary Portland cement (OPC)–ground granulated blast-furnace slag (GGBFS) mortars and identify the most effective activation technique. The methods of activation used were thermal, mechanical and thermal–mechanical combined. Two curing regimes were adopted and five groups of mortars were prepared. It was observed that OPC–GGBFS mortars have greater sensitivity to OPC mortars against the curing regimes. However, the study revealed that there was no particular activation method which when used gave the best results for both early and later strengths and did not cause strength loss. It also proved that the most effective activation method for early strength is a combination of both the thermal and mechanical, while for later strengths, none of the activation methods was recommended.

Comparison of different methods for activation of ordinary Portland cement-slag mortars

This paper compares three methods for activation of OPC-slag mortars (OSM): (1) prolonged grinding of binders (mechanical method), (2) elevated temperature curing of mortars (thermal method), and (3) use of chemical activators such as NaOH, KOH, and Na 2SiO 3, 9.35H 2O (chemical method). The proper reactivity of OSM was evaluated using a mixture of 50% OPC and 50% slag. Early and ultimate strengths were compared. All three activation methods accelerated both the slag reaction and strength development rates. However, the chemical method did not show a significant effect on the ultimate strength, while thermal activation increased the early strength by 3 days. Mechanical activation increased the early strengths of the mortar significantly, but about 6% strength loss occurred in the ultimate strength. Although, the application of mechanical and thermal activation methods needs extra equipment and energy, due to more significant of strength improvement; based on current test results, it can be said that mechanical activation is the most efficient and feasible method for the activation of OSMs.