Fine Powder Mixtures Research Articles

Investigation of Depressant Activity of an Ayurvedic Churna in Mice: A Preliminary Study

The history of herbal medicines is as old as human civilization. Ayurved-Ancient science of life is believed to be prevalent for last 5000 years in India. It is one of the most noted systems of medicine in the world. One medicinal formulation churna subdues excitement and calms the subject without inducing sleep, though drowsiness may be produced. It gives sedation, with decreased responsiveness to any level of stimulation and associated decrease in motor activity and ideation. This churna of the roots of vatjata (Ficus bingalensis), sariva (Hemidasmus indicus), manjistha (Rubia cardifolia) and jatamansi (Nordostachys jatamansi) have been used by Ayurvedic practitioner in rural Chhattisgarh to calm down the patient. It is a mixture of fine powder of the above components. However no phytochemical investigations of these roots have been conducted so far to substantiate practice of Ayurved. The current study is aimed to explore the neuropharmacological potential of Churna. The central inhibitory effects of the Churna (from Ayurvedic Formulary) were investigated in mice to provide scientific evidence. Churna is a mixture of fine powder of Manjistha, Sariva, Vatjata and Jatamansi and decoction of drugs (watery extract). T

Electronic properties of BZT nano-ceramic grades at low frequency region

BZT ceramics was prepared by using fine powder mixture of BaCO3, TiO2 and ZrO2 in the respective molar ratio to form Ba(Zr0.10Ti0.90)O3 via solid state reaction at elevated temperature. The prepared BZT was milled in the planetary ball mill from 0-120 min to achieve different powder grades from micron to nano-sized particles. After the powder characterization by XRD and SEM the samples were pressed in disc shape and sintered at different temperatures from 1100-1350?C in the air. The sintered samples were characterized by SEM and their density and average grain size was determined and presented vs. sintering temperature and powder grades (milling time). After that the silver epoxy electrodes were deposited on sintered disc samples. The disc samples capacity and resistivity were measured at low frequency region from 1 Hz to 200 kHz using low frequency impedance analyzer. The sintering temperatures and powder grades were used as parameters. Finally the specific resistance ?, dielectric constant (?' + j?") and tg? where determined from the impedance measurements. The behavior of electronic properties where analyzed e.g. the relaxation effect of the space charge (inter-granular electric charges) vs. sintering temperature and ceramic grades. The results obtained were compared with best literature data for the losses in BZT ceramics at low frequencies.

Alloying of Al2Au intermetallic compound with Cu by the ball milling technique

A mixture of fine powder of the Al2Au intermetallic compound and coarse Cu-powder was processed by the ball milling (BM) technique. The phase composition of the obtained powder product and the microstructure of separate particles were studied by TEM, SEM and XRD methods. It was found that BM for 4 h leads to the formation of Cu-clusters that are evenly distributed among the Al2Au-particles. There was discovered a decrease in the lattice parameter of the Al2Au-phase, which is associated with the formation of a solid solution of copper in Al2Au. The crystallite size in the resulting powder is near 20 nm. The mechanical properties of the (Al2Au + Cu)-powder were evaluated using nanoindentation tests.

PCM assisted reverse electro discharge machining process for pattern generation

ABSTRACT This research work reports about pattern generation using the photochemical machining (PCM) assisted reverse electro discharge machining (EDM) process on an aluminum 6061 workpiece. A mixture of fine powder of copper and tungsten is used to fabricate a green compact tool. A complex shape is generated onto the tool surface and is further implemented to migrate the shaped tool particle onto the work surface. The output parameters are the material deposition rate (MDR), tool wear rate (TWR), edge deviation (ED), and surface roughness (Ra). The pattern is characterized by Field Emission Scanning Electron Microscopy (FESEM) and Energy Disperse Spectroscopy (EDS) analyses. The presence of tungsten particles increases the microhardness of the substrate material. The surface microhardness of the pattern is found to be 362Hv.

Optimization of Coating Process from Cermet Powders by Plasma Spraying in Air

The paper presents studies on the optimization of the process of applying coatings from cermet powders with different solid phase contents by plasma spraying in air to restore and harden parts of machines and mechanisms operating under adverse conditions. Such conditions are usually created in heavily loaded tribojoints when the mechanisms operate at a low speed of relative movement of surfaces during friction. At the same time, the destruction of the working surfaces is mainly due to the process of microcontact setting and subsequent detachment of the formed particles at their contact points. The application of special protective coatings with the required properties is possible with the manufacture of high-quality starting powder materials and optimization of the technology for their application. Such powders and powder compositions can be obtained by the method of agglomeration of a fine powder mixture with its subsequent high-temperature sintering. To identify the hardening mechanism of composite coatings made of cermet by gas-thermal spraying, important stages are the optimization of the deposition process parameters and the study of the properties of plasma coatings obtained in this case. When optimizing the technological parameters of plasma spraying of coatings, the utilization rate of the sprayed powder material has been taken into account as the main indicator of the process efficiency, the structure of the obtained layers, and the morphology of individual particles deposited on the polished surface. The paper provides data on the structural elements of sprayed materials for wear-resistant coatings obtained by plasma spraying at optimal conditions. Taking into account the processes that occur during the wear of tribological conjugations, the data indicate the existing prerequisites for the wear resistance of the studied composite coatings made of metal ceramics. Special wear-resistant coatings made of materials with a soft matrix hardened by solid inclusions Al2O3–TiO2–Ni–Cr–Al–Y are widely used in various industries. Based on the detailed analysis of the features of cermet plasma coatings, it can be stated that such powder compositions (complex oxides-metal component) are often used as wear-resistant plasma coatings. The research results can be taken into account in cases of application of wear-resistant plasma coatings made of metal-ceramics and compositions based on them, containing solid phases in the form of oxides, as well as the manufacture of a whole range of parts operating under conditions of intense wear.

X-ray analysis and Rietveld refinement of ball milled Fe50Al35Ni15 powder

In this work, nanocrystalline Fe50Al35Ni15 powder was synthesized by mechanical alloying (MA) in a high-energy ball mill. The phase transformations and structural changes occurring in the studied material during MA, were investigated by X-ray diffraction. The end product of milling is a fine powder mixture consisting of a nanosized B2-FeAl(Ni) intermetallic phase and a disordered BCC α-Fe(Al,Ni) solid solution. The crystal size refinement was observed in all cases, while the lattice strain increases due to the severe plastic deformations and the structural defects. Transformation in the lattice parameters is principally dependent on the milling process and conditions. The diffusion of the Ni atoms was also investigated, and significant results were attained in the BCC phases. Indeed, the experimental results showed that an addition of 5% Ni retarded the formation of the intermetallic phase by 3 hours, with respect to our earlier studies.

On the Use of Photometric Separation for the Processing of Techno-Genic Raw Materials

This work presents studies on the material composition and physico-mechanical characteristics of an alumina-containing estimate formed during the production of aluminum on electrolyzers with self-baking anodes during technological operations. The material is a mixture of fine powder 2.5 mm in size (62.78% on average mass) with the presence of pieces of material ranging in size from 0.5 to 6 cm (average 20.26% by weight). The samples contain pieces of hardened aluminum with sizes from 5 to 20 mm (16.96%). The largest content in the sample has the fineness classes-0.315 + 0.16 mm in the volume of 29.85% and the largest class +2.5 mm-37.22%. B It was established that aluminum is concentrated in the fractions-0.315 + 0.16 mm (45.7%) and 0.16 + 0 mm (48.8%), silicon in the fraction-0.63 + 0.315 mm (1.91%), iron at-1.25 + 0.63 mm (0.601%) and-0.63 + 0.315 mm (0.62%). The material consists of cryolite (Na3AlF6), chiolite (Al3F14Na5), quartz, feldspar, carbonaceous matter and the technogenic phase of the composition (NaF) 1.5CaF2 AlF3. The material is characterized as non-abrasive (working index Ai - 0.0184) and very soft in relation to impact crushing (working index CWi - 3.64), the working index of ball grinding Bond (BWi - 6.47) characterizes a very low resistance to ball grinding. The implementation of the crushing operation of an alumina-containing estimate will allow the use of dry cascade-gravity and centrifugal classification to separate impurities in the form of SiO2, and Fe2O3 for the use of alumina-containing material in primary aluminum technology. On the basis of laboratory tests, it is established that alumina-containing raw materials can be separated and photometric and gravitational separation methods can be used. A mathematical model of the motion of particles of primary and prepared alumina-containing raw materials in a cascade-gravity classifier was developed. The criteria and factors characterizing the alumina-containing material, as well as influencing and determining the maximum material enrichment, are established.

Triboelectric Charging and Separation of Fine Powder Mixtures

AbstractFor increasingly finer powders, the material‐specific separation at high loadings is a challenging task, for instance in recycling processes. Here, a combination of triboelectric charging and electrostatic separation was investigated for powder mixtures of talcum and calcite. The dependencies of the triboelectric charge on the mass loading, the gas velocity, and the mixture ratio were investigated. While higher charge levels were achieved with increasing gas velocity, the mass loading had an opposite effect on the net charge. Although bipolar charge distributions were observed within pure materials and mixtures, electrical neutralization did not occur in the mixtures. Therefore, already in a non‐optimized setup, a decent degree of material enrichment (of up to 53 %) was found on the separating electrodes.

Naoxintong Capsule Inhibits the Development of Cardiovascular Pathological Changes in Bama Minipig Through Improving Gut Microbiota.

Naoxintong capsule (NXT), a Chinese medicine, has performed excellent effects on the prevention and treatment against cardiovascular diseases. NXT is a fine powder mixture without any herb extraction, and there must be lots of ingredients hard to be absorbed. However, little is known about the correlation between the NXT’s cardioprotective effects and gut microbiota. Herein, we report the effect of NXT on the development of cardiovascular diseases and clarify the correlation between NXT’s cardioprotective effects and gut microbiota. In the current study, minipigs were selected and fed with high-fat diet and NXT daily for successive 8 months. During the process, up to 18 biomedical parameters were monthly determined to observe the dynamic changes after NXT treatment. At the end of experimental process, pathological examinations of heart, coronary artery, carotid artery, thoracic aorta, and abdominal aorta were conducted by HE staining and 16SrDNA sequencing, and analyzing of gut microbiota were conducted. Our results showed that NXT’s effects against cardiovascular diseases were through regulating blood lipid profiles, inhibiting vascular inflammation, enhancing antioxidant capacity, and alleviating myocardial injury, without damages on liver and kidney particularly. Concurrently, we also found that long-term administration of NXT increased the diversity of gut microbiota, influenced the microbiome structure and composition stably, and revered the increase of the ratio of the Firmicutes to Bacteroidetes (F/B ratio) in relative abundance. Specifically, our results revealed some key bacterium of Caproiciproducens (enhanced), Sutterella (enhanced), Erysipelotrichaceae (enhanced), and Romboutsia (decreased) that were closely involved in NXT’s effects. Taken together, our study demonstrates that NXT can inhibit the development of cardiovascular diseases by ameliorating high-fat diet–induced metabolic disorders and partly through improving gut microbiota.

High Energy Milling of WС-FeСr Cemented Carbide

During production of cemented carbides hard and brittle tungsten carbide (WC) and ductile metal powders (mainly from Fe-group) are milled together. Complete milling results in a Gaussian distribution and narrow particle size range of the milled powder which promote the homogeneity and improve the properties of sintered composites. Cobalt, conventional metal employed in cemented carbides, possesses good comminution characteristics with WC powder. However, its toxicity and fluctuating price pushes researchers to find suitable alternatives and Fe-based alloys have shown most promising results. Cemented carbides with the Fe-Cr system as metal binder phase have potential to perform better than regular WC-Co composites in corrosive and oxidative environments. The goal of this paper was to prepare uniform cemented carbides powders with relatively high fraction of stainless Fe-Cr steel. To achieve a uniform powder mixture is a challenge at high ductile steel fraction. High energy milling (HEM) is a powerful technique for achieving (ultra) fine powder mixtures with narrow powder size range. HEM was carried out in a novel high energy ball mill RETSCH Emax. Milling in tumbling ball mill, which is the most widely used method, was employed for reference. Prepared powder mixtures were characterised in terms of particle size, size distribution and shape. In addition, powder mixtures were consolidated via spark plasma sintering to evaluate the effect of the milling method and the duration on the microstructure of final cemented carbide.

Novel colloidal approach for the microstructural improvement in Ti(C,N)/FeNi cermets

In this work, the combination of colloidal and powder metallurgy techniques was proposed as an alternative route to produce Ti(C,N)-based cermets with a 15–20 vol% of Fe/Ni alloy (85/15 wt%) as metal matrix. The novelty of this processing route is based in the mixture of fine powders (1–3 μm) in suspension which promotes the uniformity of the phase distribution and consequently its reactivity, leading to 99.9% dense cermets with 1300 Vickers Hardness (HV30). The preparation of colloidal and chemically stable slurries of non-oxide and metal powders in aqueous media is a key step of the process. Highly concentrated aqueous slurries of Ti(C,N), Fe, Ni and C powders were prepared and mixed. Then bulk pieces were shaped by Slip casting (SC), Slip Casting + Cold Isostatic Pressing (SC-CIP) and Spray-Dry + Uniaxial Pressing of the obtained spherical granules (SDP). The composite formulation and the thermal treatment were optimized to prevent Ni sublimation during sintering as well as to improve liquid phase sintering in terms of wetting and reactivity among well packed particles. The effective dispersion of the slurry and the synergistic effect of combined techniques yielded the preparation of reliable materials by the SDP process with 15 wt% of FeNi with the addition of 0.5 wt% of C. The optimization of the composite formulation and the processing parameters improves both density and hardness of a finer microstructure of the composite after a short sintering treatment (120 min) at 1450 °C in vacuum.

The effect of colemanite addition on the properties of mullite-zirconia composites prepared by slip casting

Purpose: This study deals with the effects of colemanite (Ca2B6O115H2O) on properties ofslip-cast mullite–zirconia composites prepared via reaction–sintering of kaolinite, aluminaand zircon powders.Design/methodology/approach: Colloidal processing (slip casting) is the routetowards preparing these materials using 45 vol.% aqueous suspensions of a mixture offine powders stabilized with polyacrylate solution as a dispersant.Findings: The influence of powder composition on physical, mineralogical properties, andmicrostructure of these composites after firing at 1450, 1500 and 1550°C are observed.The results show that the density of composites tends to increase with the addition of7 wt.% colemanite. XRD analyses reveal that using colemanite during the synthesis ofmullite-zirconia composites lowers the reaction temperature. All of the composites consistof irregularly shaped mullite and round-shaped zirconia grains, which are distributedhomogenously.Practical implications: Mullite–zirconia composites, owing to their chemical inertnessand good resistance against chemical attack-corrosion by siliceous and metallic melts, theyare employed in the glass industry.Originality/value: Reaction sintering process is considered as a promising technology forpreparing mullite-zirconia composites, because it has some advantages such as low costof traditional raw materials, straightforward production technology and low manufacturingcost.

Pyrolytic Reactions of Lignin within Naturally Occurring Plant Matrices: Challenges in Biomass Pyrolysis Modeling Due to Synergistic Effects

Systematically larger char yields were observed from the pyrolysis of chemically isolated lignins, compared to expected yields from the pyrolysis of lignins embedded in plant material. Naturally occurring lignins are known to be intermeshed with other plant constituents within the composite matrices of lignocellulosic biomass. An attempt was made to simulate their behavior by pyrolyzing pellets prepared from mixtures of lignin and cellulose powders. However, the results gave char yield trends that did not conform to trends observed when pyrolyzing plant derived biomass. These findings are interpreted in terms of entirely different reaction pathways operating when lignins are pyrolyzed within naturally occurring biomass, compared to “pure” lignins or composite particles made from mixtures of fine powders. It appears that char yield trends from the pyrolysis of lignocellulosic biomass are closely linked to the detailed morphology, as well as the chemical makeup, of the highly oxygenated plant derived materi...

A Quantitative Study on Packing Density and Pozzolanic Activity of Cementitious Materials Based on the Compaction Packing Model

A brief introduction to the theoretical basis of compaction packing model (CPM) and an over-view of the principle of the specific strength method provided the starting point of this study. Then, research on quantitative relations was carried out to find the correlation between the contribution rate of the pozzolanic activity and the contribution value of packing density when CPM was applied to fine powder mixture systems. The concept of the contribution value of the packing density being in direct correspondence with the contribution rate was proved by the compressive strength results and SEM images. The results indicated that the variation rule of the contribution rate of the pozzolanic activity is similar to that of the contribution value of packing density as calculated by CPM. This means the contribution value of the packing density could approximately simulate the change tendency of the contribution rate of the pozzolanic activity, which is of significant value for the future of mix designs for high and ultra-high performance concrete.

Hydrogen sorption properties of mechanically alloyed Mg1−2xFexTix powder mixtures

We report an investigation on the hydrogen sorption properties of mechanically alloyed systems of nominal composition Mg1−2xFexTix (x=0.10, 0.15 and 0.20). The starting metallic powder mixtures were milled in H2 ambient, till a steady state with no further H2 absorption was attained. The resulting samples were then characterized and submitted to several H2 discharge–charge cycles in order to determine their hydrogen sorption properties. With the aim to investigate the dependence of these properties on the sample microstructure we also studied samples of nominal composition Mg80Fe10Ti10 obtained through different processing routes. In those samples the Fe and Ti additives were added as a fine powder mixture or as the intermetallic compound FeTi while their mechanical alloying with Mg was conducted under H2 or Ar atmosphere. All the samples were characterized by X-ray diffraction and Mössbauer spectroscopy on 57Fe, before and after their cycling in H2. The results are analyzed in the framework of possible mechanisms for the transition metals catalytic action on the H2 sorption processes and the influence of the sample microstructure.

Explosive Initiation of Various Forms of Ti/2B Reactive Materials

AbstractThe reactivity of titanium and boron mixtures under detonation initiation in air is examined experimentally in a constant volume blast chamber. Fine powder mixtures and mechanical alloys are pressed into compacts and are ignited using an HMX‐based explosive initiated with both single point and triple point detonator configurations. Transient pressure measurements, optical imaging, pyrometry, and spectroscopy are performed to analyse the reaction. All mixtures show no significant enhancement in the primary blast wave strength, indicating a relatively slow reaction. However, measurable increases in overpressure are generated due to Ti and/or B reaction. It is found that Ti/2B mechanical alloys significantly outperform blended powder mixtures in generating larger overpressures, yielding energy releases of 45 % and 20 %, respectively. Triple point initiation of the mechanical alloys further enhances the overpressure generation when compared to single point initiation of the alloys, increasing the energy yield. The overpressure of blended powders is also exceeded by a TiB2 compound, suggesting that the intermetallic reaction may be less critical than previously thought. Detonation merging at the plane of interaction between explosive and Ti/2B material is shown to significantly enhance conversion. Spectroscopic measurements show the appearance of BO2 emission relatively late after detonation in the most reactive Ti/2B reactive mechanical alloys, and it appears strongest in system that show greatest reactivity.

Dissolution properties of different compositions of biphasic calcium phosphate bimodal porous ceramics following immersion in simulated body fluid solution

Biphasic calcium phosphate (BCP) bimodal porous ceramics were prepared from a mixture of fine powders of hydroxyapatite (HAp) and beta-tricalcium phosphate (β-TCP) with varying HAp/β-TCP ratios. Two types of HAp powders and one type of β-TCP powder were used to produce porous BCP bioceramics with HAp/β-TCP weight ratios of 20/80, 40/60, and 80/20. Dissolution tests were performed to compare the dissolution properties of BCP-based bioceramics with different structural properties. Porous ceramic samples of approximately 0.5 g were individually soaked in 30 ml of simulated body fluid (SBF) solution at 36.5 °C for 1, 3, 7 and 10 days, respectively. The calcium content of the SBF solution was analyzed by ICP. The porous bodies were filtered, dried, and characterized using SEM, XRD, and FT-IR. The results indicate that the sample structural properties seem to have a greater effect than the storage environment on the dissolution properties.

Incipient flow properties of two-component fine powder systems and their relationships with bulk density and particle contacts

The effect of incipient flow properties, such as cohesion and internal angle of friction, on the flowability of two-component fine powder systems is of great importance for controlling the process efficiency and quality of industrial products such as developers for electrophotographic (EP) printing devices. In this paper, we have studied the flow properties of model fine powders composed of glass ballotini (d50=69.4μm) and resin toners (d50=6–8μm), using different mixing ratios of the components under a low normal consolidation stress (2kPa) using a ring shear tester (RST). We have found that the dependence of the cohesion of the two-component mixtures on the mixing ratio can be reproduced by a linear superposition of the cohesions of each component weighted by the number of the three different types of interparticle contacts, which suggests that the bulk cohesive properties of fine powder mixtures are dominated by cohesion between particles and the number of each type of particle contacts in the system. Also, the frictional properties of the two-component mixtures are strongly related to the packing density of the mixture, and its dependence on the mixing ratio can be related to the densities of each type of particle contacts. Our results suggest that the dependence of the incipient flow properties of two-component fine powders on the ratio of the components can be predicted by measuring only the flow properties of each component and estimating the ease with which the mixture can be compacted.

EFFECT OF PARTICLE DENSITY AND COMPOSITION ON MIXTURES DURING NONELECTROSTATIC AND ELECTROSTATIC POWDER COATING

ABSTRACTNonelectrostatic and electrostatic coating processes cause the proportion of each powder in a mixture to be different on the target than in the initial mixture. First, some loss of powder occurs during the targeting step; thus, not all of the powder lands on the target. This targeting loss is caused by the individual powder characteristics and interactions that occur between powders in the mixture. Also, an uneven distribution is produced on the target because of the way the powder is dispersed. Finally, adhesion loss occurs on the target, also because of individual and mixture characteristics. During nonelectrostatic coating, a mixture of fine NaCl and starch particles changed in proportion due to the differences between individual targeting, and mixture adhesion, losses. Little change in proportion occurred in the coarse NaCl and starch mixture. During electrostatic coating of both mixtures, proportions changed because of differences between individual adhesion losses.PRACTICAL APPLICATIONSFood coatings usually consist of mixtures of powders with different densities and compositions, which cause separation of the powders. For maximum consumer acceptance, the powder should be evenly coated on the surface, with the same proportion of ingredients as in the original powder. In fine powder mixtures, during nonelectrostatic coating, targeting loss is the biggest cause of separation. Therefore, when mixtures of different density and composition are used, the coating systems need to be designed to minimize the targeting loss difference between the powders. Electrostatic coating reduced targeting loss of the fine powders by a large amount; therefore, it is one way to decrease separation. Electrostatic coating of both mixtures had high adhesion loss; therefore, the electrostatic coating system needs to be designed to minimize adhesion loss, such as by addition of oil or other tack agents, when powder mixtures are coated.

Matrix-assisted laser desorption mass spectrometry of gas-phase peptide–metal complexes

Cation attachment to a model peptide has been investigated in matrix-assisted laser desorption experiments. Angiotensin I (Asp–Arg–Val–Tyr–Ile–His–Pro–Phe–His–Leu) is chosen as a system for study, and Cu2+ and K+ salts are used as cationizing agents. Three fundamentally different types of samples are investigated: (1) a crystalline sample of Ang I, metal salt and MALDI matrix, prepared with the conventional dried droplet method; (2) a solvent-free fine powder mixture of the same three compounds, and (3) a solution of the angiotensin and the metal salt in an ionic liquid matrix (a molten organic salt that acts as a MALDI active solvent). Effective protonation and cationization of the peptide are achieved with the three methods. The transition metal systematically provides more efficient cationization than the alkali metal. At sufficiently high concentration of the salt, the attachment of up to four copper cations to the angiotensin is observed in the MALDI spectrum. In contrast, only one K+ cation is efficiently bound to the peptide. For a given salt concentration, the highest degree of cationization is obtained in the laser desorption from the ionic liquid matrix. This is attributed to the efficient transfer of free metal cations to the desorption plume, where the complexation takes place.