Fine Spheres Research Articles

Rheological Behavior in the Semisolid State of Al-Si-Cu Alloys Produced by ECAP

It is fundamental in thixoforming to have a refined microstructure that, when heated to the semisolid state, consists of a mixture of small spheres immersed in liquid as this ensures the best rheological properties. The present work therefore aims to analyze the rheological behaviour of aluminum-silicon-copper alloys, namely, Al5Si2.8Cu, Al6Si2.8Cu and Al7Si2.8Cu. The alloys were produced by conventional casting and then deformed by ECAP in one pass in a die containing two channels of the same cross-sectional area forming an angle of 120°. After being processed by ECAP, the alloys were heated to semisolid temperatures, i.e., temperatures corresponding to a solid fraction of 45 %, and kept in the semisolid state for 0, 30 and 90 s, after which they were subjected to hot compression tests. The structures of the three alloys had an excellent response to recovery and recrystallization mechanisms, with refined microstructures that led to the formation of very fine spheres immersed in liquid in the semisolid state. The best rheological behaviour was obtained for the Al5Si2.8Cu alloy, which had an apparent viscosity of the order of 103 Pa.s. The findings suggest that this simple ECAP process is a promising route for the production of semisolid feedstock for use in thixoforming.

Graphene nanospheres and their mechanical and tribological responses

In this simulation study, we have the three main aims as follows: crump the graphene sheets randomly seeded to create the stable nanoparticles of the fine sphere, and investigate the mechanical and tribological responses of the obtained graphene nanospheres. By using this method, we find that such nanospheres can be obtained. These nanospheres can provide the high limitations of the elastic stress and the elastic strain, up to around 263.53 GPa and 73.90 %, at the temperatures up to 3000 K. As used as lubricants, they can provide the ultralow friction for the iron contacts. The obtained results are explained through the observations of density of the nanospheres, the bond among the graphene sheets and their lubrication mechanisms.

Microstructural evolution after heat treatment of high specific strength steel: Fe-13Al-16Mn-5Ni-0.8C and correlation with tensile properties

The present work investigates the microstructure and tensile properties of lightweight steel (Fe-13Al-16Mn-5Ni-0.8C) annealed at two temperatures: 480 °C and 840 °C. A systematic study of the emergence of phases and precipitates using transmission electron microscopy (TEM), scanning electron microscope (SEM) and electron back-scattered diffraction (EBSD) has been carried out. The tensile properties of the samples annealed differently have been studied and correlated with the microstructure. After annealing at 480 °C, κ-carbides were observed inside the austenite grain along with the presence of DO3 adjoining austenite. However, after annealing at 840 °C ordered-particles with two different morphologies (fine spheres and rod-shaped) were formed inside the ferrite grains and needle-shaped particles were formed inside the austenite grains. The high-angle annular dark-field (HAADF) analysis suggested that the Fe-Mn type B2-particles were formed inside the ferrite grains whereas Ni-Al type B2-particles were formed inside the austenite grains. The samples annealed at 840 °C showed higher strength and ductility but the sample annealed at 480 °C showed high strain hardening. The fractography images showed a multi-featured surface carrying a signature of the multi-phase microstructure.

Near‐Net Shape Hot Isostatic Pressing: Microstructural Analysis and Hardness Evolution at a Steel–Nickel Alloy Interface

AbstractFor near‐net shape hot isostatic pressing (HIP) process, the interaction between capsules and consolidating powders at a high pressure and temperature leads to a strong interfacial element diffusion, which is harmful to the surface microstructure and mechanical properties of components. The effects of iron and carbon, in SS400 steel capsules, on the surface microstructure and mechanical properties of the FGH4096M superalloy during HIP are investigated. Results show that the interfacial difussion between the SS400 steel and FGH4096M is divided into three zones: ferrite‐martensite‐austenite mixture zone (≈32.3 µm), Fe‐rich Ni‐Fe‐based superalloy zone (≈27.5 µm), and Ni‐rich Ni‐Fe‐based superalloy zone (≈34.8 µm). The γ′ phase starts to be formed when the mass fraction of iron is below ≈27.2%. The γ′ morphology changes from fine sphere to cuboidal and butterfly‐like shapes as the mass fraction of iron is decreased successively. There is no obvious carbon diffusion around the interface due to a low carbon concentration in the capsule. The Vickers microhardness profile shows an increase, then a decrease, and eventually becomes stable at 425HV. Based on the above conclusions, an understanding of the Fe and C diffusion mechanism at the interface and its extension toward the FGH4096M side is achieved.

Continuous size fractionation of magnetic nanoparticles by using simulated moving bed chromatography

The size fractionation of magnetic nanoparticles is a technical problem, which until today can only be solved with great effort. Nevertheless, there is an important demand for nanoparticles with sharp size distributions, for example for medical technology or sensor technology. Using magnetic chromatography, we show a promising method for fractionation of magnetic nanoparticles with respect to their size and/or magnetic properties. This was achieved by passing magnetic nanoparticles through a packed bed of fine steel spheres with which they interact magnetically because single domain ferro-/ferrimagnetic nanoparticles show a spontaneous magnetization. Since the strength of this interaction is related to particle size, the principle is suitable for size fractionation. This concept was transferred into a continuous process in this work using a so-called simulated moving bed chromatography. Applying a suspension of magnetic nanoparticles within a size range from 20 to 120 nm, the process showed a separation sharpness of up to 0.52 with recovery rates of 100%. The continuous feed stream of magnetic nanoparticles could be fractionated with a space-time-yield of up to 5 mg/(L∙min). Due to the easy scalability of continuous chromatography, the process is a promising approach for the efficient fractionation of industrially relevant amounts of magnetic nanoparticles.

PSVII-10 Evaluation of different biochar sources added at two inclusion levels in a grass hay- based diet on dry matter disappearance and ruminal fermentation parameters in vitro

Abstract This study evaluated the impact of adding biochar to a grass hay-based diet on in vitro dry matter disappearance (DMD), total gas production (GP), methane production (CH4), volatile fatty acid (VFA) and ammonia nitrogen (NH3-N) concentration. Treatments were arranged in a factorial design with 7 biochar products differing in origin (pine or coconut-based) and physical properties (course, fine or loose spheres) at 2 inclusion levels (2.25% and 4.5% of DM) and a grass hay-only control. On each three successive weeks, rumen fluid was collected from 2 ruminally cannulated beef heifers fed a grass hay-based diet, pooled and mixed with a buffer solution (1:2) and treatments incubated in triplicate for 48 h. Gas pressure was recorded at 3, 6, 9, 12, 18, 24, 36 and 48 h of incubation, and gas was collected at each time to measure CH4. At 48 h, pH was measured and the supernatant sampled for determination of VFA and NH3-N, while the residue was used to estimate DMD. Dry matter disappearance decreased (P < 0.05) with increasing addition of biochar. Biochar did not affect GP or CH4, but did reduce (P < 0.05) gas production per g of DM incubated (111.7 vs 107.8 ml/g), but not per g DMD. The lower GP per g DM incubated could be related to the increased proportion of the diet as biochar, without it contributing to GP. Biochar, irrespective of level did not affect the total or molar proportions of VFA. There was a biochar x inclusion level interaction (P < 0.04) in NH3-N concentration. Biochar type and inclusion level in the present study had little or no significant effect on in vitro fermentation and did not mitigate CH4 production from a grass hay-based diet.

In-situ synthesis of Fe2O3/rGO using different hydrothermal methods as anode materials for lithium-ion batteries

Abstract This paper studies in-situ synthesis of Fe2O3/reduced graphene oxide (rGO) anode materials by different hydrothermal process.Scanning Electron Microscopy (SEM) analysis has found that different processes can control the morphology of graphene and Fe2O3. The morphologies of Fe2O3 prepared by the hydrothermal in-situ and oleic acid-assisted hydrothermal in-situ methods are mainly composed of fine spheres, while PVP assists The thermal in-situ law presents porous ellipsoids. Graphene exhibits typical folds and small lumps. X-ray diffraction analysis (XRD) analysis results show that Fe2O3/reduced graphene oxide (rGO) is generated in different ways. Also, the material has good crystallinity, and the crystal form of the iron oxide has not been changed after adding GO. It has been reduced, and a characteristic peak appears around 25°, indicating that a large amount of reduced graphene exists. The results of the electrochemical performance tests have found that the active materials prepared in different processes have different effects on the cycle performance of lithium ion batteries. By comprehensive comparison for these three processes, the electro-chemical performance of the Fe2O3/rGO prepared by the oleic acid-assisted hydrothermal method is best.

Complex Pyrometallurgical Processing of Silicate Raw Material and Technogenic Waste into Market Products

A new approach to solving the problem of complex nonwaste processing of bottom ash waste (BAW) of low-grade metallic and nonmetallic feeds has been set forth. The solution is based on deep recreative melting of various burden materials with dividing the flux into a metallic phase and a silicate part that virtually does not contain any metal oxides. It has been shown that, depending on the method of producing the flux, various materials are generated: a foamed X-ray amorphous material (foamed silicate) with a stable formulation, a fine mineral fiber or spheres depending on technological modes. It follows from this work that the obtained foamed material is a semiproduct used as a fill insulation, a raw material for manufacturing foam ceramics and optically transparent glasses in the visible and near-IR ranges, and a sorbent for collection of oil products. On the basis of the experimental data, an industrial waste processing facility has been developed.

Inter-particle coating variability in a rotary batch seed coater

Coating of particulate solids by a thin film layer is of interest in many industrial applications such as seed and tablet coating. In seed processing, seeds are commonly coated with a protective coating layer consisting of fertilisers and disease control agents, such as pesticides and fungicides. Batch coaters are commonly used for this purpose. A typical coater consists of a vertical axis cylindrical vessel with a rotating base and a spray disc in the centre, onto which the coating liquid is fed to atomise and spray-coat the seeds. The seeds are driven around the vessel by its rotating base, and are mixed by two baffles; one on either side of the vessel. In the present study, Distinct Element Method (DEM) simulations are used to model the seed coating process. Corn seed are used as a model material and their shape is captured using X-Ray Tomography (XRT), which is approximated in the DEM by clumped spheres. The coating uniformity of the seeds is predicted by implementing a coating model in the DEM, whereby the coating droplets are simulated as very fine spheres projecting tangentially from a ring at the edge of the spinning disk. The size and velocity of droplets leaving the spray disk are measured using high speed video imaging and implemented into DEM simulations. The coating mechanism is represented in the DEM by considering that once a droplet contacts a corn seed, it is removed from the simulation and its mass is attributed to the coating of the corn seed. The distribution of mass of sprayed spheres on the corn seeds and their coefficient of variation are evaluated for a range of process conditions, such as the base rotational speed, atomiser disc position relative to the base and baffle arrangement and designs. It is found that the atomiser disc vertical position, baffle angle and clearance to the wall are most influential, whilst the base rotational speed and baffle width and curvature have only minimal effect.

DEM simulation on the packing of fine ellipsoids

In this work, discrete element method (DEM) is used to study the effect of particle size and aspect ratio on packing structure of fine ellipsoids. It shows that porosity and coordination number significantly change with particle size and shape. The porosity-aspect ratio curve has minima at around 0.5 for oblate spheroids and 1.5 for prolate spheroids, but the cusp at 1.0 varies from convex to concave when particle size reduces as a result of the increasing role of the cohesive forces between particles. The coordination number-aspect ratio curves change from a strong to weak “M” shape when particle size reduces. Based on the results, equations are formulated to describe the correlation between bed porosity, aspect ratio, and particle size or force ratio. Microscopically, the radial distribution function is also affected by both particle size and shape. Fine particles have more disordered structure than coarse particles, and the packing of fine spheres is more ordered than fine ellipsoids. For coarse ellipsoids, majority of particles tend to orient horizontally, but the preferred orientation become worse when reducing particle size.

How Does the Gibbs Inequality Condition Affect the Stability and Detachment of Floating Spheres from the Free Surface of Water?

Floating objects on the air-water interfaces are central to a number of everyday activities, from walking on water by insects to flotation separation of valuable minerals using air bubbles. The available theories show that a fine sphere can float if the force of surface tension and buoyancies can support the sphere at the interface with an apical angle subtended by the circle of contact being larger than the contact angle. Here we show that the pinning of the contact line at the sharp edge, known as the Gibbs inequality condition, also plays a significant role in controlling the stability and detachment of floating spheres. Specifically, we truncated the spheres with different angles and used a force sensor device to measure the force of pushing the truncated spheres from the interface into water. We also developed a theoretical modeling to calculate the pushing force that in combination with experimental results shows different effects of the Gibbs inequality condition on the stability and detachment of the spheres from the water surface. For small angles of truncation, the Gibbs inequality condition does not affect the sphere detachment, and hence the classical theories on the floatability of spheres are valid. For large truncated angles, the Gibbs inequality condition determines the tenacity of the particle-meniscus contact and the stability and detachment of floating spheres. In this case, the classical theories on the floatability of spheres are no longer valid. A critical truncated angle for the transition from the classical to the Gibbs inequality regimes of detachment was also established. The outcomes of this research advance our understanding of the behavior of floating objects, in particular, the flotation separation of valuable minerals, which often contain various sharp edges of their crystal faces.

Carbon black supported ultra-high loading silver nanoparticle catalyst and its enhanced electrocatalytic activity towards oxygen reduction reaction in alkaline medium

Carbon black supported ultra-high loading silver nanoparticle catalyst (Ag/C) was prepared by a modified ethylene glycol reduction method. The thermogravimetry analysis showed that the Ag mass loading of this catalyst reached up to 392wt.%. The X-ray diffraction and scanning electron microscopy characterizations showed that the Ag nanoparticles were ca. 10nm diameter of fine spheres with a face-centered cubic crystal structure, and were densely stacked but not aggregated on the carbon black surface in spite of such ultra-high loading and small size. The chronoamperometry and polarization studies utilizing rotating disk electrode (RDE) or rotating ring disk electrode (RRDE) revealed that this ultra-high loading 392wt.% Ag/C catalyst exhibited higher electrocatalytic activity for oxygen reduction reaction (ORR) in alkaline medium. The ORR proceeded a four-electron process when compared with the low loading 40wt.% Ag/C catalyst. Furthermore, the chronopotentiometry test on gas-diffusion electrode containing the 392wt.% Ag/C catalyst implied that this catalyst had a considerably stable ORR activity for application in brine electrolysis.

Influence of Surfactants on the Characteristics of Nickel Matrix Nanocomposite Coatings

Nickel-based nanocomposite coatings were prepared from a Watts-type electrolyte containing reinforcement’s particles (silicon carbide and graphite) to deposit onto the steel St-37 substrate. The electrochemical plating of the coatings in absence and presence of surfactants and reinforcements particles was carried out to optimize high quality coatings with appropriate mechanical and morphological features. The surfactants such as cetyltrimethylammonium bromide (CTAB), sodyumdodecyl sulfate (SDS), and saccharine affected electrodeposition plating and subsequently changed mechanical characteristics. Based on XRD results, the dominant phases in the absence of surfactants were nickel oxide (NiO), nickel, and silicon carbide (SiC), while the main phases in presence of surfactants were nickel (Ni) and SiC. The hardness of the resultant coatings was found to be from 332 to 593 (Hv) depending on the bath parameter and the reinforcements weight percentage (wt%) in the Ni matrix. Microscopic observations illustrated a cluster-like structure which consisted of some fine sphere particulates with average particle size of 65–150 nm. According to elemental mapping spectra, a homogenous distribution of nickel, silicon, and carbon particles appeared into the nickel matrix coating. Finally, the experimental outcomes demonstrated that the surfactants have significant influence on the composition of coatings, surface morphology, and mechanical properties.

Characterization of electrodeposited Ni–SiC–Cg nanocomposite coating

Nickel–silicon carbide–graphite (Ni–SiC–Cg) nanocomposite coating was deposited onto the steel (St-37) substrate by electrochemical plating method. The influence of pH parameter on the mechanical properties and morphological features was studied. The coatings were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), Elemental mapping analysis system, and field emission scanning electron microscopy (FE-SEM) techniques. Besides, the microhardness of specimens was measured by Micro hardness Tester. Based on XRD results, the dominant phases with high crystallinity degree were nickel, silicon carbide and graphite. Microscopic observations illustrated that all the coatings had a cluster like structures which consisted of some fine sphere particles with an average crystallites size of 60nm. Among of all coatings, the specimen at pH equal to 4.8 presented an appropriate morphology as well as lower porosity with high grain boundaries. Moreover, elemental mapping spectra exhibited a homogenous distribution of nickel, silicon and carbon particles. However, the distribution of silicon particles into nickel matrix at pH=4.8 was higher than the other samples. Also, mechanical properties of the attained coatings were improved with increasing of pH values up to 4.8 (593 HV) which is in agreement with microstructural characteristics. Therefore, obtaining of the optimum pH value is the major parameter in electroplating of Ni based nanocomposite which affected microhardness and distribution of reinforcement particles into the matrix.

Preparation and performances of carbon aerogel microspheres for the application of supercapacitor

Carbon aerogel (CA) microspheres were successfully synthesized by an inverse emulsion polymerization routine. Morphology and physical properties of the CA microspheres were characterized by scanning electron microscopy, N2 sorption isotherm, and transmission electron microscopy. The results showed that the CA microspheres were all fine spheres with diameters about 4 μm, and the CA microsphere was a typical mesoporous material with ordered mesoporous nano-network structure. The maximum capacitance of the electrode obtained from cyclic voltammetry was 187.08 F/g and the capacitance of the supercapacitor resulted from galvanostatic charge–discharge tests was up to 45.98 F/g. The supercapacitor using CA microsphere as electrode material presented a long cycle life, high charge–discharge efficiency, and low R s of 0.70 Ω in 6 M KOH electrolyte.

Fabrication and morphological control of three-dimensional cage type mesoporous titanosilicate with extremely high Ti content

TiSBA-1 materials with extremely high Ti content, up to silicon to titanium ratio ( n Si/ n Ti) of 2.4, have been successfully prepared through direct synthesis method by controlling the molar ratio of hydrochloric acid to silicon ( n HCl/ n Si). It has been found that the amount of Ti content and the structure of the TiSBA-1 can easily be controlled by the simple adjustment of n HCl/ n Si ratio. X-ray diffraction pattern (XRD) of the obtained materials revealed that the materials are highly ordered and possess cubic three-dimensional cage type structure with open windows. N 2 adsorption–desorption measurement confirmed the narrow pore size distribution, high specific surface area (1317–1491 m 2 g −1), and large specific pore volume (0.68–0.75 cm 3 g −1) for all the samples. UV–vis DR spectra of the prepared materials confirmed that Ti atoms are exclusively incorporated within silica framework and occupy the tetrahedral position while the presence of isolated bulk titania could be negligible. Morphologies of the TiSBA-1 materials have been also controlled by simply adjusting the n Si/ n Ti ratio. With the appropriate Ti content, TiSBA-1 materials can be obtained as regular fine spheres. Moreover, the detailed mechanism on the morphological and phase transition control, and the incorporation of high amount of Ti in the framework of TiSBA-1 materials has been also discussed in detail.

Manufacture Process of Light Calcium Carbonate from Limestone

This process and parameters of fabricating light calcium carbonate from limestone were discussed in the paper. Raw limestone in experiment comes from Luquan city, Hebei province. The results of chemistry and XRD analysis indicate that ingredient of this limestone is mainly calcium carbonate, dolomite, silicon dioxide, which takes 83.81%, 11.03% and 1.67% separately, and a few of other impurities. The process includes calcinations, assimilation, carbonation, drying and others. It was ascertainable that the time of calcinations exceeded 5 hours at 850~ 950 and loss of calcinations was 42%. The time of assimilation was around 25 minutes at 70~90The time of carbonation was about 30 minutes at 50~90, and the airflow was about 160L/min and PH of latex after carbonation was 7.2~7.4. The light calcium carbonate product was obtained in experiment, whose fine sphere size was about 10 nanometer, with the agglomeration particle size 2~3μm. The degree of white improved from 42 to 76. As a result, the comprehensive properties of the produce were improved consumedly.

Effects of Particle Size and Shear Rate on Melt Flow Properties During Capillary Extrusion of Glass Bead-Filled LDPE Composites

Abstract The melt flow properties of a low-density polyethylene (LDPE) filled with glass brads (GB) were measured at 150°C by means a capillary rheometer to identify the effects of the particle size and extrusion rate on the melt flow behavior in the present paper. The volume fraction of the glass beads was 8.4 %. The surface of the particles had been treated with a silane-coupling agent and the diameter range was from 4 μm to 180 μm. The results showed that the entry pressure drop was a component function of apparent shear rate and the melt shear flow approximately obeyed the power law. The melt shear viscosity decreased roughly linearly with an increase of the wall shear stress, and it varied slightly with an addition of the bead diameter under various shear stress levels. Namely, the influence of the bead size on the melt flow properties of the LDPE/GB composites was insignificant at lower concentration of the fine spheres. This might be attributed to the relatively weak interfacial adhesion between the particles and the matrix due to the smooth spherical surface of the beads.

Manipulation and welding of metal spheres above 10 mm using needle-like probe

A needle-like probe is the simplest tool to manipulate fine spheres. It catches fine spheres by adhesion forces without any holding device. Metallic spheres of 10–100 mm are difficult to manipulate with the needle-like probe, because the gravity rivals the adhesion forces in the dynamics of the spheres. Large and heavy spheres arranged on a substrate areeasily disturbed because of the same reason. Here, a manipulator equipped with a direct power source, which applies voltage to the probe, is fabricated. Large and heavy spheres are adhered by the controllable electrostatic force. Besides the manipulation, the apparatus is designed to weld the spheres by using the probe as electrode for spot/arc welding. Experiments on the manipulation showed that the probe caught gold spheres of 40–80 µm by applying 20–50 V and released by putting them down after cutting the power off. Following to manipulation, welding experiments were carried outat various conditions. Two power sources, a high-voltage and low-current power source and a low-voltage and high-current power source, and two welding methods, arc welding and spot welding, are examined. The experiments showed that the gold spheres of 40–80 mm can be welded by the spot welding using the high-voltage and low-current power source, of which maximum power rating is 10 kV×1 mA. The probe is kept to touch the sphere and 4 kV or more is applied. Electric sparks are generated at the interface of the probe and the substrate, and the sphere is welded to the substrate. In both the manipulation and welding, the contact pressure must be very low. A tower of gold spheres is fabricated as an example of three-dimensional microstructures composed of fine spheres.

Water leaching and magnetic separation for decreasing the chloride level and upgrading the zinc content of EAF steelmaking baghouse dusts

Recycling scrap iron and steel in electric arc furnaces (EAFs) generates very fine metal-containing dusts which can present major environmental problems. This paper describes experimental work on a relatively novel, simple, and inexpensive process for decreasing the chloride content and upgrading the zinc level of dust from an Australian plant, to produce saleable products and environmentally safe waste products for disposal. The dust contained about 2.1% Cl as various chlorides, 23.1% Zn as zincite and franklinite, 27.1% Fe as magnetite, franklinite, and hematite, plus small quantities of lead, cadmium, chromium, and other materials. The dust was very fine ( P 80 about 2 μm). Individual particles were commonly aggregates of fine spheres and other shapes. Simple water washing at ambient temperatures and natural pH (12) for 60 min extracted 99% of the chlorides, giving a residue assaying 200 ppm Cl. This residue was strongly coagulated by lime present in the dust and settled rapidly. The wash solution contained low levels of iron, zinc, lead, cadmium, and chromium, most of which could be removed by sulphide precipitation. Wet magnetic separation with a Davis tube was investigated. At the lowest field strength employed (0.6 A), 95% of the zinc was recovered in a non-magnetic product assaying 28% Zn and 24% Fe. At the highest field strength (1.6 A), 91% of the zinc was recovered in a non-magnetic product assaying 29% Zn and 25% Fe. Wet cycloning at a nominal separation size of 2–5 μm gave a cyclone overflow product assaying 31% Zn and 26% Fe, and containing 85% of the zinc. All these results fit a typical zinc grade–recovery relationship. The proposed process of water washing followed by magnetic separation or cycloning would produce a relatively high-zinc, low-iron, low-chloride product suitable for treatment in a lead–zinc smelter or electrolytic zinc plant, a high-iron, low-zinc product suitable for land fill, and a treated waste water for discharge to a sewer.