Milling Atmosphere Research Articles

Atmosphere matters: The protection of wet ball milling instead of dry ball milling accelerates the electron transfer effect of sulfurized micron iron/biochar to Cr (VI)

Obstacles such as aggregation and low activity of micron zero-valent iron in pollutant treatment could be overcome by sulfidation and biochar support. Ball milling is a promising method for the preparation of iron-based composites but the milling atmosphere is critical. To maximize the reactivity and identify the effects of ball mill atmosphere, ball milling technology under wet and dry atmosphere was applied to prepare composites from mZVI, Na2S2O4, and pine wood biochar (BC) for Cr(VI) removal. The results showed that S-mZVI/BC-wet was highly dispersible with more FeS2 coverage and thus more efficient on Cr (VI) removal than S-mZVI/BC-dry (99.9 % removal in 80 min vs. 87.9 % removal in 24 h) at the optimum Fe: C mass ratio (1:1), S: Fe molar ratio (1:10), and reaction conditions. Cr(VI) was adsorbed by a spontaneous, endothermic mechanism that combined physisorption and chemisorption. The reduction process was vulcanization efficiency and iron cycle dependent. Reduction outperformed adsorption on the Cr(VI) removal and high reduction rateswere electron-selectively related (59.15 % for S-mZVI/BC-wet and 46.72 % for S-mZVI/BC-dry), implying S-mZVI/BC-wet was more capable. S-mZVI/BC-wet presented excellent anti-ageing property and slightly inferior regeneration performance. In conclusion, the composite prepared by wet ball milling have excellent performance in rapid and complete removal of Cr(VI), and S-mZVI/BC-wet has superior potential in acidic wastewater treatment.

The effect of process control agents and milling atmosphere on the structural changes of Ti50Cu27,5Ni10Zr10Co2,5 master alloy during short time milling

Properties of powders made from Ti50Cu27,5Ni10Zr10Co2,5 alloy, milled under different conditions for only 3600 s in total were investigated. For this purpose two different milling atmospheres and two different Process Control Agents (PCA) were tested: argon without PCA, air without PCA, argon combined with stearic acid, argon combined with petroleum spirit. Results showed that the size and shape of particles, and the microstrucutre and hardness of partcicles were highly depended on the milling conditions. According to XRD analysis, the maximal amorphous fraction has been achieved in the air atmosphere withouth PCA milled sample (57 wt. %) powder. However the extent of Fe contamination and weight loss during milling powder resulted bigger values. As a result, the optimal combination of morphology, contamination amount and weight lost level has been observed in the case of powder milled in argon atmosphere using stearic acid.

Synthesis and characterization of in situ-reinforced Al–AlN composites produced by mechanical alloying

This research focuses on the production of Al matrix composites (AMCs) reinforced with various percentages of AlN. For this purpose, Al powder was milled at room temperature for a total time of 5 h. The percentage of the reinforcement phase was varied by milling under different periods of vacuum and ammonia (NH3) gas flow. X-ray diffraction analysis showed the benefits of the combined milling atmosphere in forming higher amounts of AlN after powder heat-treatment. Results showed that the period milled in vacuum determined the capacity of the powder to adsorb N during the NH3 gas period. Even under shorter vacuum milling periods, the amount of AlN formed after sintering can be increased.

Gas Protection of Two-Dimensional Nanomaterials from High-Energy Impacts.

Two-dimensional (2D) materials can be produced using ball milling with the help of liquid surfactants or solid exfoliation agents, as ball milling of bulk precursor materials usually produces nanosized particles because of high-energy impacts. Post-milling treatment is thus needed to purify the nanosheets. We show here that nanosheets of graphene, BN, and MoS2 can be produced by ball milling of their bulk crystals in the presence of ammonia or a hydrocarbon ethylene gas and the obtained nanosheets remain flat and maintain their single-crystalline structure with low defects density even after a long period of time; post-milling treatment is not needed. This study does not just demonstrate production of nanosheets using ball milling, but reveals surprising indestructible behaviour of 2D nanomaterials in ammonia or hydrocarbon gas under the high-energy impacts; in other milling atmospheres such as air, nitrogen or argon the same milling treatment produces nanosized particles. A systematic study reveals chemisorption of ammonia and hydrocarbon gases and chemical reactions occurring at defect sites, which heal the defects by saturating the dangling bonds. Density functional theory was used to understand the mechanism of mechanochemical reactions. Ball milling in ammonia or hydrocarbon is promising for mass-production of pure nanosheets.

Mechanochemically improved surface properties of activated carbon cloth for the removal of As(V) from aqueous solutions

Modified activated carbon cloth is prepared by mechanochemical modification of viscose rayon carbon cloth. The effects of different milling atmospheres, in the air and inert conditions, were investigated. Changes in kind and number of acidic and basic surface groups on the surface of activated carbon cloth, upon modification, as well as before and after the sorption of arsenic were determined. Higher number of basic groups responsible for the removal of arsenic ions was achieved by modification under inert conditions. Breakage and collapse of cylindrical fibers, decrease of particle sizes, change in the shape and consistency of the particles, as well as increase of microstructural disorder i.e. the loss of turbostratic structure occurred upon milling. pHPZC values increased from 4.46 to 5.04 and 5.77 after the air and inert milling, respectively. Adsorption followed pseudo second order kinetics with chemisorption as rate-controlling step. Langmuir isotherm best fit the equilibrium data and maximum adsorption capacity is 5.5mgg−1 at a pH value close to 7.0, typical for groundwater. The mechanism of arsenic adsorption onto activated carbon cloth milled in inert atmosphere involved electrostatic and dispersive interactions between arsenic ions and carbon particles in wide pH range (from 2 to 10).

Effect of the milling atmosphere on the microstructure and mechanical properties of a ODS Fe-14Cr model alloy

A systematic study has been undertaken to assess how the milling atmosphere, in the processing of an ODS steel with nominal composition Fe-14Cr-0.3Y2O3 (wt%), will affect the microstructure and mechanical properties of the resultant alloys. Batches of the steel were manufactured by a powder metallurgy route incorporating mechanical alloying, hot isostatic pressing, forging and heat treatment. Hydrogen or helium atmospheres were used in the mechanical alloying, with all other processing parameters remaining identical. Transmission electron microscopy (TEM) and Atom Probe Tomography (APT) show that both milling atmospheres promote a homogeneous dispersion of Y-rich nanoparticles in the final alloys, being smaller when milling in H. Previously reported mechanical characterisation of these alloys shows better mechanical response at high temperature for the alloy milled in a H. This can be justified by the presence of smaller Y-rich nanoparticles together with the absence of bubbles, observed in the alloy milled in He.

A comparative study on the effects of different milling atmospheres and sintering temperatures on the synthesis and magnetic behavior of spinel single phase Ni0.64Zn0.36Fe2O4 nanocrystals

Synthesis of Ni0.64Zn0.36Fe2O4 ferrite nanoparticles via mechanical alloying and subsequent heat treatment was investigated. The pure metal powder of Zn, Fe2O3 and NiO were ball milled in three different atmospheres including argon, oxygen and air. The X-ray diffraction results showed that after a long time of 30 h milling a desired ferrite was not produced, but heating the 30 h-activated powders in as low a temperature as 400 °C for 2 h led to the formation of Ni–Zn ferrite nanocrystals with some residual Fe2O3 phase. The particle size and lattice parameter of the Ni–Zn ferrite samples were strongly affected by the milling atmospheres. TEM results indicated that the average particle size of the milled samples in the argon atmosphere was the smallest and in the range of 5–67 nm. FT-IR spectra for the Ni–Zn ferrite samples showed two absorption bands associated with tetrahedral and octahedral sites around 600 and 400 cm−1, which depend on the milling atmosphere; their wave-number positions were different. The VSM results indicated that the magnetic properties i.g. Ms were not only affected by the milling atmosphere but also by the sintering temperature. Although increasing sintering temperature caused an increase of the Ms value in all the three atmosphere-milled samples, the milled-sintered samples in the argon atmosphere had the biggest Ms value about 96 emu/g after sintering at 1000 °C.

Prevalence of Aero-Allergenic Micro Fungi in Extra & Intramural Environments of a Saw Mill in Pondicherry City, India

Prevalence of airborne fungal spores with their seasonal periodicity in the extra and intramural environments of a saw mill of Pondicherry region was carried out by gravitation method from January 2011 to December 2011. Composition and concentration of fungal spores considerably varied from indoors to outdoors as well as from season to season. Indoor air harbored maximum fungal spores (61%) in comparison to outdoor air (39%). Occurrence of fungal species was predominated with more number of propagules during mid winter (December) and early rainy (July) periods in comparison to other months. Quantitatively, Cladosporium was found with the highest frequency and had four members i.e., C. cladosporioides, C. herbarum, C. resinae, C. sphaerospermum but qualitatively, Penicilli and aspegilii were isolated highest in its contribution to total CFUs. Out of the 32 isolated fungal taxa, Aspergillus fumigatus, A. niger, Rhizopus stolonifer and Alternaria alternata were the predominant aeroallergens which cause different types of respiratory/lung diseases in atopic human beings were isolated. In seasonal periodicity, winter contributed the maximum spore load (41%) followed by rainy (33%), summer was found with the least (26%) in harboring the spore mass in the indoors and outdoors. Alternaria alternata, which is accounted as a human allergen for sporosis inducer and an agent for hay fever and other pathologies, was also intermittently recorded. A few plant pathogenic fungi like Helmithosporium sp. & Fusarium spp, saprophytic, field and storage fungi were also recorded during the study period. Effect of meteorological parameters on the fungal spores in the saw mill atmosphere was significantly assessed by Pearsons correlation coefficient analysis.

Effect of milling parameters on the formation of nanocrystalline hydroxyapatite using different raw materials

Abstract The influence of milling parameters (time and atmosphere) on the mechanochemical synthesis of nanocrystalline hydroxyapatite (n-HAp) using different raw materials was studied. Two distinct chemical reactions were activated for various milling times under air or in a high purity argon (99.998 vol%) atmosphere. Then, the mechanically activated powder was heat treated at 800 °C for 1 h to produce n-HAp with high degree of crystallinity. Results revealed that the phase purity of products under both milling atmospheres was strongly influenced by the chemical composition of raw materials. The synthesized powders exhibited average sizes about 32 and 27 nm under air atmosphere, and about 32 and 34 nm under argon atmosphere. The fraction of crystalline phase drastically decreased after 80 h of milling under both atmospheres. In addition, the fraction of crystalline phase for the annealed sample at 800 °C was higher than the mechanosynthesized specimens. The results of morphological evaluation confirmed the formation of n-HAp with different morphologies each of which can be used for particular purpose.

The high impact of a milling atmosphere on steel contamination

High-energy ball-milling in an oxidative atmosphere caused gradual transition of pure zincite into zinc ferrite due to the oxidation of steel contamination. The rate of contamination increased dramatically (>3×) in an inert atmosphere due to the abrasion of milling tools by the steel chips coming from it.

Influence of mechanical alloying conditions on amorphous phase formation in Fe67B33

Abstract Mechanical alloying of Fe 67 B 33 mixture was carried out in a planetary ball mill. Variable milling parameters were a balls size, a milling atmosphere (Ar, He) and a filling ratio. Powders were characterized by X-ray diffraction analysis, electron scanning microscopy (SEM) and differential scanning calorimetry (DSC). It was found that balls temperature strongly affects the amorphous phase quantity: the use of atmosphere with higher thermal conductivity (He) and small balls noticeably increases the amorphous phase output. It was revealed by SEM that considerable part of boron particles survives in the course of the milling and their presence can be responsible for a broad exothermic effect on the DSC curves. The maximal volume fraction of amorphous phase was about 77% and its composition was evaluated as 20/22 at.% B.

Effect of the Mechanical Milling Process Condition on Hardness of Pure Titanium

Effect of mechanical milling conditions on hardness and constituent phase of pure titanium was investigated. The mechanical milling atmosphere and amounts of stearic acid, added as a process control agent (PCA), were varied. The hardness of mechanically milled (MMed) pure titanium powders in the air atmosphere was approximately 15 % higher than that in the argon atmosphere. The mean particle size of the MMed powders in the air atmosphere was smaller compared to that in the argon atmosphere. The MMed pure titanium powders produced by two different atmospheres had almost the same constituent phase. The MMed powders were consolidated into bulk materials by spark plasma sintering (SPS). The hardness of the SPS materials produced from the MMed powder in the air atmosphere was 13 % higher than that in the argon atmosphere. The oxygen content in the SPS materials significantly increased by the MM processing in the air atmosphere. Formation of β-Ti or ω-Ti was observed in the all SPSed materials. The products formed by phase transformation were not influenced by the heating rate and the hold time in SPS process. Vickers hardness of 881 HV was obtained for the SPSed material fabricated from 4 h of MM with 0.50 g of PCA in Ar atmosphere at 1073 K for 180 s with the heating rate of 2.33 K/s.

Effect of mechanical milling atmosphere on hardness and constituent phases of pure titanium

Effect of the mechanical milling conditions on hardness and constituent phase of pure titanium was investigated. The mechanical milling atmosphere and amounts of stearic acid, added as a process control agent (PCA), were varied. The hardness of mechanically milled (MMed) pure titanium powders in the air atmosphere was approximately 15% higher than that in the argon atmosphere. The mean particle size of the MMed powders in the air atmosphere was smaller compared to that in the argon atmosphere. The MMed pure titanium powders produced by two different atmospheres had almost the same constituent phase. The MMed powders were consolidated into bulk materials by spark plasma sintering (SPS). The hardness of the SPS materials produced from the MMed powder in the air atmosphere was 13% higher than that in the argon atmosphere. The amount of oxygen in the SPS materials significantly increased by the MM processing in the air atmosphere. The mean grain size of the SPS materials showed approximately 1 μm. The SPS materials were mainly strengthened by both solution hardening of oxygen and grain refinements.

Influencia de la atmósfera de control y tiempo de molienda sobre la morfología y microestructura de polvos de cobre puro y cobre- 2,5 % litio producidos por aleado mecánico

In the present work was investigated the effect of two milling parameters, atmosphere and milling time, on the morphology and microstructure of pure copper powder and a mixture of copper-2,5 wt. % lithium. The mechanical alloying was performed in a SPEX 8000D mill, using steel containers and balls. The two control atmospheres were argon and nitrogen and the milling time was varied from 3 up to 30 hours. The microstructural changes and the phases after milling were analyzed using scanning microscopy and X ray diffraction, whereas the amount of iron was measured by atomic absorption spectroscopy and the amount of oxygen by infrared spectroscopy. The results show the effect of the milling parameters studied on the microstructure as well as on the chemical composition of the samples.

On selection of milling atmosphere for production of Al–10%Ti powders

A mixture of aluminium and 10 wt-% titanium powders was attrition milled for 10 h under air, nitrogen and vacuum atmospheres; pure aluminium powders were also prepared in a like manner. Particle size distribution, morphology and microstructure of the powders were studied by laser diffraction, scanning electron microscopy (SEM) and X-ray diffraction (XRD); special attention was paid to the influence of the milling atmosphere. There were differences in powder particle size obtained from pure Al powders that were not observed for Ti containing powders, however the same homogeneous morphology and microstructure was attained for the different milling atmospheres. The effect of milled powder annealing on microstructure was studied by differential scanning calorimetry (DSC) and XRD. New phases and their crystallite size were characterised as a function of annealing temperature, milling atmosphere, and powder microhardness. In short, the studied milling atmospheres for the production of Al–10%Ti powders do not affect the properties of the obtained powders, and in general, low cost atmospheres could be used.

Mechanism of synthesizing nanocrystalline TiC in different milling atmospheres

The nanocrystalline TiC powders were synthesized by mechanical alloying (MA) from the mixture of pure titanium and graphite in vacuum, argon and hydrogen milling atmospheres, respectively. The phase transformation and powder morphology characteristics were studied by using XRD and TEM. The results showed that synthesizing mechanism and reaction velocity changed when Ti and C mixture were milled in different atmospheres. It was found that nanocrystalline TiC powders were fabricated by mechanical alloying for 1 h at a ball-to-powder weight ratio of 40:1 and rotational speed of 450 rpm in planetary ball-mill in argon atmosphere and vacuum. The formation mechanism was mechanically induced self-propagating reactive synthesis (MSR). However, the formation of intermediate phase TiH 2 changed the mole ratio of Ti and C, brittle phase proportion and energy aggregation in the powder, consequently resulted in reaction controlled by gradual diffusion when the milling atmosphere was hydrogen gas. So the synthesis time extended to 6 h under hydrogen atmosphere on the same milling process.

Magnetism of Fe-doped TiO 2 milled in different milling atmospheres

The Fe-doped TiO 2 powders were prepared by mechanical alloying in argon, air and oxygen atmospheres and characterized using X-ray diffraction, vibrating sample magnetometer (VSM) and Mössbauer spectroscopy. The Fe concentration was found to be 4.468, 4.227 and 4.473 at% for the powders milled in argon, air and oxygen, respectively. The Fe-doped TiO 2 powders presented pure rutile structure. The Fe ions in the powders were found to take Fe 2+/Fe 3+ ionic valences. VSM measurements revealed that all the samples were ferromagnetic at room temperature, and the magnetic moment per Fe atom enhanced with decreasing of the oxygen partial pressures of the milling atmosphere. The enhanced magnetism is related with the increasing concentration of oxygen vacancies.

Modification to the composition of nanocrystalline RuO 2 through reactive milling under O 2

Crystalline ruthenium dioxide (RuO 2) has been ball-milled in an O 2 atmosphere and the changes in the physico-chemical properties induced by different milling atmospheres (Ar and O 2) or milling sequences have been established. Cyclic voltammetry and BET measurements were used to evaluate the electrochemically active surface charge ( q T * , expressed in C g −1) and the specific surface area (expressed in m 2 g −1), respectively. The extent of oxygen uptake in the processed samples was determined by X-ray photoelectron spectroscopy (XPS). The q T * value of RuO 2 milled under O 2 for 30 h (sample S4) is 120.7 C g −1, a factor of two higher than the q T * value of RuO 2 milled under Ar for the same period of time (sample S1, 60.3 C g −1). A still higher q T * value is obtained when the O 2 atmosphere of the crucible is frequently replenished (sample S5, 138.7 C g −1) or when the milling operation is prolonged up to 81 h (sample S6, 160.5 C g −1). These changes are paralleled by a variation of the BET surface area, which increases from 24 m 2 g −1 for sample S1 to 51.5 m 2 g −1 for sample S5. The concentration ratio [O bound to Ru]/[Ru] determined by XPS increases steadily from sample S1 to sample S6, indicating that the amount [O bound to Ru] increases with the exposure of RuO 2 to oxygen during the milling process. All these changes are explained by the fact that freshly exposed RuO 2 surfaces created during the milling process react with O 2 molecules, thereby lowering the surface energies and the tendency of the milled material to cluster into larger aggregates.

Phase transformations in nanocrystalline TiO 2 milled in different milling atmospheres

The structural evolution of nanocrystalline TiO 2 milled in different milling atmospheres was studied by X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy. Rietveld refinements of the XRD data showed that high-energy ball milling induced the transformations from anatase to srilankite and rutile at room temperature and ambient pressure. The milling atmospheres with different oxygen partial pressures had an influence on the transformation kinetics of anatase. When the nanocrystalline TiO 2 powders were, respectively, milled in oxygen, air and nitrogen atmospheres, the transformation rates of anatases in turn increased with a decrease in oxygen partial pressure of the milling atmosphere, due to the reducing concentration of oxygen vacancies in the milled TiO 2 lattice.

ＭＡミリング雰囲気によるガス不純物およびその衝撃強さに及ぼす影響

This study seeks to clarify the effects of gas contamination from milling atmospheres of mechanical alloying (MA) on mechanical properties. An iron-based dispersion alloy of Fe-13Cr-3W-0.5Ti-0.5Y2O3 (mass%) was selected as the experimental material. We prepared MA powders with the same composition as the dispersion alloy by milling mixed powders in various atmospheres such as argon, helium, hydrogen, nitrogen and vacuum, and then made bulk alloys by grooved rolling the MA powders. For the MA powders, we examined included atmospheric elements and their releasing processes with heat treatments under vacuum. For the bulk alloys, we also examined high-temperature behaviors of residual atmospheric elements and their effect on impact strength as a function of heat treatment time at 923 K.Experimental results showed that MA powder included some amount of atmospheric element that was unexpectedly difficult to remove with heat treatment. The contents of widely used argon and helium in MA powders, for example, were 130 and 5.3 mass ppm, and they were hard to remove even with treatments at 1323 K, which is considered the maximum allowable temperature. Therefore, most of these elements were introduced into bulk alloys as gas contamination. In contrast, nitrogen was effectively reduced with the treatment at 1323 K, while hydrogen could not be sufficiently removed. Residual argon and helium in bulk alloys formed bubbles at high temperatures and caused density decrease (swelling). On the other hand, hydrogen and nitrogen caused neither the formation of bubbles nor the swelling. Impact strength decreased with increased treatment time, and more remarkable decreases were observed in the alloys containing argon and hydrogen. We concluded that a proper milling atmosphere in MA for producing iron-based dispersion alloys applied to high-temperature materials was nitrogen.