Vacuum Ball Milling Research Articles

Effect of the TiB2 content on the mechanical and tribological properties of TiB2/AZ91 composites fabricated by vacuum hot-press sintering process incorporating vacuum ball milling

Magnesium alloys have poor strength and wear resistance, restricting their application greatly, while Mg matrix composites can improve these deficiencies. TiB2/AZ91 composites with high TiB2 content were prepared by vacuum hot-press sintering process incorporating vacuum ball milling. The effects of TiB2 content on the microstructure, mechanical properties and tribological properties of the composites were investigated in detail. The results suggested that the TiB2 particle exhibited good bonding with the Mg matrix. With the increasing TiB2 content, the ultimate tensile strength, yield strength and elongation of TiB2/AZ91 composites firstly increased and then decreased, while the wear rate and wear surface roughness presented an opposite trend, and the hardness and coefficient of friction gradually increased. The composites with 5 wt% TiB2 obtained the maximum tensile properties (UTS: 234 MPa YS: 91 MPa EL: 7.3 %). This improvement in mechanical properties was attributed to the uniform distribution of TiB2 particles and the well bonding at the interface. The strengthening mechanisms were found to be the load transfer strengthening and the thermal mismatch strengthening. Furthermore, the composites with 15 wt% TiB2 demonstrated the lowest wear rate of 1.06×10−6 mm3/Nm and lowest wear surface roughness of 2.971 μm. This wear resistance was enhanced because of the significant increasing in hardness. The dominant wear mechanisms observed in TiB2/AZ91 composites were abrasive wear and oxidation wear.

Synthesis of Integrated Material with Activation and Oxidation Functions by Mechanical Milling of Activated Carbon and Persulfate for Enhanced Tetracycline Degradation over Non-Radical Mechanism

As an alternative to the traditional advanced oxidation process of adding potassium persulfate (PS) and its activator to the solution separately, in this study, M(AC-PS), an integrated activator and catalyst, was synthesized by vacuum ball milling of PS and activated carbon (AC) to improve the PS’s utilization efficiency. The joint mechanical milling caused a change in the preferentially exposed crystal surface of the PS and the generation of more π-π* structures on the AC, leading to successful and stable connection of the PS onto the surface of the AC. Within 40 min, the M(AC-PS) achieved a degradation rate of 97.3% for tetracycline (TC, 20 mg/L), while the mixed system where AC and PS were separately ball milled achieved only a 53.1% removal of TC. Reactive oxygen species and electrochemical tests showed that M(AC-PS) mainly oxidized TC through non-free radical mechanisms. In M(AC-PS), AC provided oxygen-containing functional groups (e.g., C=O) to activate the PS and electron holes as an electron transfer medium, generating 1O2 and promoting electron donation from the TC to enhance the oxidation of the TC. Almost no catalytic components were detected in the solution, indicating that the obtained solid composite material avoids the limitations of solid–liquid interface contact and mass transfer, and then improves the efficiency of activation and catalysis. This study presents a simple and feasible method for obtaining efficient and convenient material for the advanced oxidation treatment of wastewater.

Sulfur-doped g-C3N4/V2C MXene Schottky junctions for superior photocatalytic H2 evolution

An advanced sulfur-doped g-C3N4/V2C MXene (SCN/V2C) Schottky junction HER photocatalyst was prepared via vacuum ball milling and subsequent annealing.

Effects of Reinforcement Volume Fraction on Mechanical Properties and Microstructures of 7075Al Matrix Composites Reinforced by FeCoCrNiAl High-Entropy Alloy Particles

High-entropy alloy particles reinforcements improve the mechanical properties of aluminum matrix composites while increasing its density. Investigating the effects of the reinforcement content is conducive to the fabrication of lightweight and high strength composites. FeCoCrNiAl high-entropy alloy particles (HEAp) reinforced 7075Al matrix composites (HEAp/Al) with different HEAp volume fractions of 5, 10, 15, and 20 vol% were fabricated via a vacuum ball milling and vacuum hot pressing sintering, and then the microstructures, interface, density, and mechanical properties of the HEAp/Al composites were characterized. The results indicated that composites with high relative density can be obtained with a holding time of 10 min at 580 °C, 30 MPa; the HEAp distribution was homogeneous as the increase of reinforcement volume fraction decreases and forms agglomeration, especially when the volume fraction is up to 15 vol% and 20 vol%; the density and hardness of HEAp/Al composites improved with the increase of reinforcements’ volume fraction, whereas the flexural strength and fracture toughness of HEAp/Al composites increased at first and then decreased; the HEAp/Al composites reinforced by 10 vol% HEAp showed the maximum flexural strength and fracture toughness, which were increased by 124.6% and 107% compared with 7075Al, respectively; the improvement of mechanical properties was attributed to the dislocation strengthening behavior and load transfer effect of the HEAp reinforcement.

Mechanism and kinetic analysis of vacuum aluminothermic reduction for preparing TiAl intermetallics powder

This work investigates the mechanism and kinetics of an aluminothermic reduction process using Na2TiF6 as the raw material for preparing TiAl alloy powder. The experiment was carried out at 1100 °C with a 3:7 M ratio of Na2TiF6 to Al. Quasispherical TiAl alloy powder with an oxygen content of 0.32% could be achieved after vacuum ball milling of the reduction product. The thermal analysis results demonstrated that the aluminothermic reduction reaction was an exothermic process. Moreover, the kinetic parameters and the equation for the exothermic reaction rate of the reduction process were calculated by a thermoanalytical technique. According to XRD, SEM, and EDS analyses, the reduction mechanism and the evolution process of the products were discussed. Experimental evidence indicated that TiAl3 and TiF3 could be generated as intermediate products during reduction. TiAl could be produced through further reduction reactions between TiAl3 and TiF3.

Novel method of the surface modification of the microcrystalline cellulose powder with poly(isobutyl vinyl ether) using mechanochemical polymerization

The surface modification of microcrystalline cellulose (MCC) powder with poly(isobutyl vinyl ether) (PIBVE) chains of block copolymers of MCC and PIVBE (MCC-block-PIBVE) was produced by ball milling of MCC with isobutyl vinyl ether (IBVE) in vacuum at 77K. The polymerization of IBVE was initiated by mechano-cations of MCC (MCC+) on the MCC powder surface in vacuum at 77K. MCC+s located on the surface of MCC powder were produced by heterogeneous scissions of the β-1,4 glycosidic linkages comprising MCC main chain by ball milling in vacuum at 77K, and existed on the powder surface of MCC in vacuum at 77K as cations isolated from counter mechano-anions. The counterion-free MCC+s on the powder surface of MCC interacted with IBVE during milling, covalently bonded to IBVE, and simultaneously formed counterion-free cations (MCC-IBVE+) on the MCC powder surface. The counterion-free MCC-IBVE+s initiated a novel cationic polymerization of IBVE on the surface of MCC powder under vacuum, produced MCC-block-PIBVE, and gave rise to a surface chemical modification of MCC powder with MCC-block-PIBVE. This scheme is supported by 1H NMR, FT-IR, ESR, GPC, and MO calculations.

Dose-dependent effects of lanthanum chloride on wear particle-induced aseptic inflammation in a murine air-pouch model

To investigate the effects of local injection of different doses of lanthanum chloride (LaCl3) on aseptic inflammation in mice stimulated by wear particles from artificial joints, the particles were prepared by vacuum ball mill in vitro and air-pouch models were performed with 45 male BALB/c mice that were randomly divided into blank control group, wear particle group and wear particle + LaCl3 (0.1, 0.9 and 8.1 μmol) group. All animals were sacrificed and tissue specimens were harvested 7 days after treatment. Hematoxylin and eosin (H&E) staining, enzyme-linked immunosorbent assay (ELISA), reverse transcription-polymerase chain reaction (RT-PCR) and western blot were applied to observe inflammatory reaction and detect the expression of pro-inflammatory cytokines (TNF-α, IL-1β) and nuclear factor-κB (NF-κB) in mRNA and protein levels in air-pouch membrances. The results showed that wear particles could stimulate aseptic inflammation in vivo effectively; 0.9 μmol LaCl3 could significantly inhibit wear particle-induced gene and protein expression of pro-inflammatory cytokines and NF-κB (P>0.05); 0.1 and 8.1 μmol LaCl3 did not exert an inflammation-inhibiting effect and even caused adverse effects at 8.1 μmol. In conclusion, LaCl3 played a protective role against wear particle-induced aseptic inflammation dose-dependently, which was involved in NF-κB related signaling pathways.

Preparation of Metallic Wear Particles Around Joint Prosthesis by Vacuum Ball Mill <i>In Vitro</i>

To study a method of in vitro preparation and seperation for metallic wear particles around joint prosthesis, and evaluate its feasibility in medical experiments of prosthetic loosening.Preparation of Metallic Wear Particles Around Joint Prosthesis by Vacuum Ball Mill in Vitro .Particle size,size distribution,chemical composition,and shape were characterized by element trace analysis, laser countersizer,scanning electron microscopy. Metal particles co-culture with RAW264.7,then detect cytotoxicity.Our metal particles that prepare by vacuum ball mill that closely resembled particles found around solid and loose human prostheses(＜5μm in diameter).The addition of metal particles（＜1.0 mg/ ml in concentration) to RAW264.7 co-culture did not cause cell cytotoxicity，and we can use it in relative research of Cytology.This method is good enough to produce metallic wear particles that closely resembled particles in vivo, which has convenient ,reproducibility. and can be used in vitro studies of Cytology.

Ball-milling in vacuum of α and σ phases of near-equiatomic FeCr alloys

The structural changes induced by ball-milling of near-equiatomic σ-FeCr and α-FeCr in vacuum were followed. Besides the α-phase, an amorphous phase appears when milling the σ-phase for times longer than 20 h. An amorphous phase forms too, but at a slower rate than the latter, when milling the α-phase. The partial amorphisation of σ-FeCr and α-FeCr ball-milled in vacuum is concluded to be a phenomenon of intrinsic origin. The amorphous phase crystallizes into a bcc Cr-rich phase and a bcc Fe-rich phase during short annealing steps.

Synthesis of Fe3N by mechano-chemical reactions between iron and organic Hx(CN)6 ring compounds

Novel mechanically activated solid state synthesis reactions between elemental αFe powder and amine compounds-piperazine (Hi10C4N2) and pyrazine (H4C4N2) — have been studied. Powder samples prepared after 144 and 228 h of ball milling in vacuum were examined by X-ray diffraction, scanning electron microscopy and thermal analysis methods. After ball milling for a time brief compared to that required for most solid state-gas reactions formation of a crystalline iron nitride (Fe3N) a predominant phase with nitrogen concentration up to ca. 9.0 wt% was observed. Thermal analysis experiments showed structural stability of the Fe3N phase up to ca. 720 K. In the final product a small residual fraction was formed from αFe and carbon dispersed during mechanical processing. The concentration of carbon in this fraction, estimated from thermogravimetric analysis was up to 2.5 wt%, dependent on milling conditions and the organic compound used. Mechanochemical synthesis, reaction effectiveness, product composition and particle morphology depends on the milling time and chemical characteristics of the organic compound used. Fine Fe3N particles at a submicrometre size range were obtained only by milling with pyrazine. Further, the higher chemical reactivity of pyrazine than piperazine was confirmed through the higher level of nitridation achieved in the same preparation time.

Precise determination of hydrogen and oxygen isotope ratios of water in fluid inclusions of quartz and halite.

A vacuum ball mill was devised to extract volatiles from fluid inclusions in minerals. A special feature of the crushing mode is the horizontal oscillation of the mill, which enhances crushing efficiency and overcomes the fragility of the mill, which is made of Pyrex glass. This ball mill is equipped with a cold finger trap cooled with liquid nitrogen to reduce the influence of adsorption of once extracted volatiles on to mineral powder during the crushing process. Amounts and isotope ratios were determined for water extracted from the fluid inclusins of quartz and halite. The determinations were made for CO2 as well in fluid inclusions of quartz. The influence of adsorption on amounts and isotopic ratios of volatiles was evaluated by comparing the results of repeated extractions with and without the liquid nitrogen trap during the crushing process. In a single run of extraction, two kinds of water were obtained: one was water trapped in the cold finger trap during the crushing, the other was desorbed water given by heating of the sample after crushing. A simple summation of the isotope ratios of the desorbd and the trapped waters gives an erratic result in comparison with the original isotope ratio. As for the fluid inclusions in hydrothermal quartz, the original δ18O and δD values for water in the inclusions can be estimated by applying Rayleigh's equation to the adsorption process. In the case of halite samples, however, the estimation of the original δ18O and δD values is much more difficult because of the formation of hydrate salts. However, in the special case where the brine in inclusions is a pure NaCl solution, the original inclusion water is simply the sum of the desorbed and trapped waters. For CO2 analysis of inclusion fluids, the adsorption during the crushing process is negligibly small, not affecting appreciably the results on δ13C and δ18O values.

Extraction and isotopic analysis of fluid inclusions in halites.

Basic technique for the extraction and isotopic analysis of fluid inclusions in halite was investigated using synthetic single crystals of halite and three natural halite samples from China. Vacuum ball-mill, vacuum decrepitation and vacuum melting methods were examined for the extraction of fluid inclusions. Results of analyses on δD and δ18O of the water in fluid inclusions extracted by the ball-mill method from synthetic single crystals agreed with those of the mother solution from which the single crystals were formed. Although the δ18O value of the water extracted by the melting method agrees well with that of the mother solution, the δD value was about 7‰ more negative than that of the mother solution. There was a great difference in both δD and δ18O of the water extracted by the two methods applied to the identical natural halite samples; the melting method gave consistently more negative values for both δD and δ18O compared with those by the ball-mill method. The difference was interpreted as a result of the hydrolysis of NaCI with H2O combined with the formation of oxides of alkaline-earth elements in brine inclusions in natural halite samples in the process of the melting method. Although the melting method has an advantage of complete recovery of volatiles in halite samples, the chemical and isotopic compositions of volatiles can not be retained owing to a variety of thermal reactions which occur at high temperatures. It was concluded that the ball-mill method is much superior to the melting method in order to obtain isotopic and chemical information on fluid inclusions in halite, though the recovery of fluid inclusions by the ball-mill method is not 100%, and high concentrations of Mg2+ and Ca2+ in fluid inclusions require correction for the δD and δ18O values of the water.

A study on gas inclusions in minerals. Analysis of the gases from micro-inclusions in allanite

In order to determine the chemical composition of the gases from micro-inclusions in allanite a comparative study, using the methods of heating to decrepitation and grinding in vacuum was undertaken. The dependence of gas composition on the grain size was studied, too. The analysis of gases was carried out in a vacuum apparatus for micro-analysis; the measurement was volumetric. The experiments using the decrepitation method were made in the temperature interval 200–1100°C. CO 2, H 2, CO, CH 4, N 2, He, and water were identified and determined. However, a considerable part of these gases is probably due to chemical reactions. By grinding in a vacuum ball mill, only small amounts of H 2, N 2, and He were evolved. Some experiments showed that CO 2 and H 2O are strongly adsorbed on the ground material, thus being lost for the analysis. The results obtained from these two methods were supplemented with data obtained from a new method for studying the composition of gas inclusions, by tracing the gas composition as a function of the sample grain size. Using an approximate model it was shown that this dependence should be non-linear (hyperbolic). The amount of gases, due to inclusions, decreases parallel to the decrease in size of the mineral grains down to a certain limiting size. This dependence could not be observed if the grains are smaller than this limiting value. The method offers a possibility for taking into account the amounts of gases having another origin (desorption, chemical interactions, etc.), using the experimental plots. The results from the three series of experiments showed that the gas phase of inclusions in examined allanite consists mainly of CO 2. The other gases which were found by the decrepitation method could not be unambiguously ascribed to inclusions.

Excess radiogenic argon in fluid inclusions

Most minerals, with the possible exception of micas, commonly contain fluid inclusions, Argon contained in such inclusions may be considered a possible source of error in dating very young or low potassium minerals by the K-Ar method. Wahler [1956] first demonstrated spectrographically the presence of Ar in fluid inclusions in quartz. Elinson and Polykovskii [1961, 1963] used a vacuum ball mill to extract the gases present in fluid inclusions in various pegmatite minerals. They obtained Ar from quartz in quantities up to 8.9×10−3 cc/g. Preisinger and Huber [1964] state that they determined the Ar content of the gas emitted by heating very small samples (10−6 g) of feldspar crystals from a granite in a cycloidal mass spectrometer. The total gas emitted (water-free basis) varied from 0.8 to 3.3×10−3 cc/g. Nesmelova [1959] found up to 1.7% (Ar + Kr + Xe) in the gas from gas inclusions in sylvites from the Bereznikovsk mine in the USSR. Hoy et al. [1962] found 0.4 volume % Ar in the gases of highpressure gas inclusions in ‘popping-salt’ from the Winnfield salt dome in Louisiana. Sample weight and total gas volume were not specified. Damon and Kulp [1958] extracted excess radiogenic Ar from beryl, cordierite, and tourmaline in quantities ranging from 10−5 cc/g to 10−2 cc/g, some of which was assumed to come from fluid inclusions (p. 449). Lippolt and Gentner [1963] reported the finding of excess radiogenic Ar of the order of 10−7 cc/g in several fluorite samples and indicated that much of the excess was probably contained in fluid inclusions.