Search

Adding the compound solution included hydrochloric acid and hydrofluoric acid into coal seam, the pore structure of coal can be destroyed by acidizing treatment, and the permeability of coal seam can be improved. In order to increase the acidification damage effect, in this paper, the effects of anion surfactant named Sodium Dodecyl Sulfate (SDS) on the pressure relief and enlarge permeability effect of compound solution acidified coal were studied from four aspects: mechanical characteristics, porosity and pore distribution of coal samples, retention effect of fracturing fluid and microscopic morphology of coal sample surface. The results show that the SDS promotes the pressure relief effect of acidified coal body and reduces the strength of the treated coal sample. At the same time, the SDS increases the reaction area of acid fracturing fluid and impurity minerals in the fractures of coal sample, enhancing the acidification effect of HCL and HF on coal sample and increasing the porosity of coal. In the aspect of pore distribution, through the acidification synergism of SDS, the macropores and fractures of coal samples increase obviously. With the addition of SDS, the reversible work required for HCL and HF compound solution to break away from coal molecules is reduced by 18.45 J, which can significantly reduce the water blocking effect caused by the fracturing fluid retention, and improve the efficiency of coalbed methane extraction. After the compound solution erodes the coal sample, the microscopic morphology of coal sample surface has changed greatly, and the destruction degree of acidizing erosion is the highest after SDS synergism. The results of this paper are great significance for studying the mechanism of pressure relief and enlarge permeability effect of acidified coal.

Spark discharge is widely applied in the fabrication process of the particles with very small sizes. The ultrasound-aided spark discharge process is based on the electrical discharge in the liquid media of the electrical discharge machining (EDM). In this paper, the morphology, element composition, and crystal structure of the Nickle particles produced by the ultrasound-aided spark discharge were observed and analyzed by SEM, EDS and XRD respectively. The EDS and XRD indicated that the purity of the nickel particles generated in pure water is higher than that in kerosene. Meanwhile the effects of dielectric media on the size distribution were also investigated. It was found that the size distribution of the particles in pure water is narrower than that in kerosene, but when the ultrasound was introduced into the generating process, the size distributions of the particles in both media have remarkable improvements (both became narrower). Based on the attaching and entrapping processes, the formation mechanism of different structural particles was also presented. Following the study on the changes of the effective densities and the ratios of the closed hollow particles in different experiments (with and without ultrasound), we found that, with the aid of ultrasound, the ratio of the closed hollow particles increased about 10–15%. In overall, the results in this paper provide a foundation for the some future research, such as the study on the control of the particle properties (in size and morphology) by improving the experimental conditions.

In order to confirm reliable particle size measurement technique and to prepare standard reference particles for calibrating particle size measurement devices, experimental and theoretical studies have been conducted about particle size measurement of 0.1–1 μm silica particles. The microscopic method with sample size greater than 90,000 particles was conducted for the size measurement. Theoretical equation of uncertainty region over all particle diameter range is newly proposed and compared with computer simulation. Previous paper [H. Masuda, K. Iinoya, Theoretical study of the scatter of experimental data due to particle size distribution, J. Chem. Eng. 4(1) (1971) 60–67] reported the uncertainty region only for mass median diameter, but this paper presents the uncertainty region for all particle size range. The uncertainty region increases with the increase in particle diameter and also increases as the sample size decreases. Theoretical uncertainty region agreed with the results of computer simulation.

Modelling the high-pressure grinding rolls mass flow rate from the continuity principle represents a difficult task, partly because the ore may slip against the rolls. In effort to increase the understanding of this phenomenon, this paper introduces a state observer to estimate the slip profile in the HPGR working gap from the force balance equations and Coulomb friction criterion. The observer is used off-line and a posteriori, i.e. it requires a series of HPGR tests conducted at different levels of specific force and roll speed. It allows observing the slip profile on a gold ore at the pilot scale. As the material enters the compression zone, it descends at a slower rate than the vertical component of the roll peripheral speed. As it progresses downward, its velocity increases. It exceeds the roll peripheral speed at the working gap level and peaks below. The pressure peaking above the working gap makes slipping possible. It leads to the material above the working gap to push onto the one below and thus accelerating it.

Until now, influences of different grinding mechanisms on specific energy consumption have been subject of many researches. In this regard, the technologies of impact and attrition milling have been compared by several studies. Although energy consumption is of major concern, the product properties or the behaviour of the components within the mixture may vary depending on the mechanism chosen. Such investigation is still missing for the dry stirred media milling. Moreover, its comparison with the conventional techniques regarding to this phenomenon is also lacking within the literature. This paper initially aims to provide an insight on components' interaction within ball milling and stirred milling and then comparison of the two outcomes. Within the scope, the first phase of grinding tests consisted of ball milling and stirred milling of calcite within a single and multi-component environment. For the mixtures, each component was separated via chemical analyses hence comparisons were made regarding to size reduction of the individuals. Further tests were performed with a copper ore to investigate the behaviours of the minerals by benefitting from MLA analyses. As a result, the two technologies were compared on the basis of energy consumption, components' interaction and their contributions to the liberation characteristics of the minerals. (c) 2021 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

In this paper the influence of the inlet and outlet configurations of a pseudo-2D fluidized riser on the hydrodynamics (i.e. flow pattern and cluster characteristics) are studied. A detailed comparison between experimental data and full 3D CFD-DEM simulation results is performed. Solids volume fraction and mass flux are characterized and particle clusters are detected in our CFD-DEM simulations and compared to experimental data. It is shown that a correct representation of the outlet is very important for a correct simulation of the solids holdup in the top section of the riser. The core-annulus flow behavior is generally well predicted by the model and cluster characteristics such as cluster occurance and velocity are also in good agreement with experimental data. Finally, an outlook is given for the future use of CFD-DEM simulation approaches to study riser flows.

A novel device has been developed for continuous shearing and repeated impact of granules in order to simulate granule attrition and dust formation under realistic plant conditions of mechanical stresses, shear strains and strain rates. The device subjects the granules to multiple impacts at a range of velocities prevailing in typical process plants, and to shear deformations using two rollers with an adjustable gap to simulate the level of shear stresses and strains experienced during bulk motion, e.g. discharge from silos onto conveyor belts, etc. In this paper, the device operation and tests carried out to determine the settings required for attaining a desired impact velocity and shear strain rate are described. Subsequently, the extent of breakage of the granules is determined for the specified settings and the results are compared with data obtained by more established methods, e.g. annular shear cell and single particle impact tests.

In various fields ranging from manufacturing or pharmaceutical industry to agriculture or automotive industry air filters and -dryers filled with porous desiccant media are used for industrial air preparation. It is necessary to increase the mass of particulate material filled into the dryer for improving its efficiency. Practically this means decreasing porosity of the filler media. In order to achieve this, mechanical excitation (ensured by a vibration platform) is commonly used. However, applying outer excitation decreases the efficiency of filling procedure because of the high energy consumption of the vibratory device. To avoid unnecessary energy consumption it is recommended to examine the possibility of filling more particles into the canister without outer excitation. According to this in our present paper the gravitational deposition of particulate materials was investigated from viewpoint of porosity. Main idea of this research was the usage of the so called “snowstorm” filling technique. A conical hopper and under this multiple cylindrical rods were used to reach uniform deposition and high value of particle packing density. Thus efficiency of air preparation units may be increased as it is possible to fill more material into the container without additional energy usage compared to normal gravitational deposition.

Some organic additive manufacturing feedstocks can be cohesive and tend to agglomerate in suspensions, which can lead to significant challenges in formulating solids-loaded fluids, like those used in many additive manufacturing processes. By depositing an ultra-thin, layer of a second material conformally with the surface of the feedstock powder, Atomic Layer Deposition (ALD) can be used to uniquely modify the surface and, thereby, cohesion of the powder material without changing the properties of the bulk material. This paper demonstrates low temperature (

Using water vapor to improve the efficiency of dust removal in gas cyclones was recently proposed. However, some dust particles are not hydrophilic which can reduce the effectiveness of the vapor. This paper investigates using surfactants to overcome such a difficulty. In particular, surfactants are added to the water solution which is atomized into vapor and added in a cyclone dust collector. The effects of surfactant type and quantity on the removal efficiency of the cyclone are studied by a series of experiments. Three surfactants are used to change the wettability of the two types of fine particles to be collected: molecular sieve dust and white carbon black. The particles in the cyclone are found to form agglomerates, which are measured by using a laser particle size analyzer and scanning electron microscopy. The results show that the addition of surfactants can greatly enhance the agglomeration and thus improve the collection efficiency, especially for particles approximately two microns in size. This indicates that using the atomized vapor with containing surfactants is an effective way to enhance the collection of fine particles in a cyclone separator.

Zeolite-supported metal catalysts have been proven effective in many important catalytic reactions, such as hydrogenation, Fisher-Tropsch synthesis, automobile exhaust catalysis, selective catalytic reduction and many others. Despite the successful preparation of the catalyst through widely adopted methods, including ion exchange and impregnation, the metal dispersion over the zeolite is lack of control with high randomness. This renders the so-called “catalytic performance” an overall contribution from the metal sites located inside the zeolite micropores and those located on the external surface. This is exceptionally true for small to medium pore zeolites with typical free apertures of 0.3–0.6 nm (such as LTA and MFI). A more rational design of zeolite-supported metal catalysts is by encapsulating the metal nanoparticles or clusters within zeolite pores prior to the zeolite formation. Encapsulation of metals in zeolite prevents them from sintering and sulphur poisoning by cage confinement and molecular exclusion (via well-defined pore size and shape), respectively. This paper gives a new perspective on using metal clusters and nanoparticles as catalysts and the design of an effective zeolite-supported catalytic system.

This paper is a review of the progress and perspective of an approach for morphology controlled synthesis of particles by tuning chemical diffusion and reaction. Rational synthesis of materials with designed structures is a long term dream of scientists and engineers. The challenges of this dream lie in the poor understanding on the formation mechanism of diverse structures and the insufficient ability to program structure evolutions. From a view of chemical engineering, a shape-controlled synthesis of particles by regulating chemical diffusion and reaction was developed, which was experimentally confirmed by synthesizing diverse morphologies of silver particles at different diffusion and reaction and synthesizing similar dendritic structures of various materials at diffusion limitation. Diffusion and reaction determines the chemical distribution in the growth front of particles, which drives the anisotropic growth of particles, forming diverse morphologies. Ongoing study focuses on the dynamic stability of structure evolution, to establish a general model for structure design and rational synthesis by considering both the local environment and the nature of materials under the concept of mesoscience.

In this paper, the preparation of rutile TiO2 powder from titanium slag by microwave-assisted activation roasting followed by hydrochloric acid leaching was investigated. The effects of the additive Na2CO3 on the crystal form, cell, crystallinity, phase transformation, surface functional groups and micro-surface structure of the calcined product were systematically studied using X-ray powder diffraction, Raman spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy. The results confirmed that the strongest characteristic Raman bands of rutile TiO2 and the weakest FT-IR bands of (CO3)−2 were found when the Na2CO3 mass ratio was 0.4. Accordingly, the crystallinity for the product, namely short rod structure rutile TiO2 powder, reached its peak value of 99.21% with a corresponding average grain size of 43.5 nm. The excessive Na2CO3 was found to be disadvantageous for the crystallinity of the product, since it formed a coverage on the surface of titanium slag which prevented the oxidation reaction for the decomposition of anosovite.

Developing strategies for the production of porous particles with controllable structures using a spray-drying method has attracted attention of researchers for decades. Although many papers have reported their successful production of porous particles using this method, information on how to create and control the porous structures as well as what parameters involving and what formation mechanism occurring during the synthesis process are still not clear. To meet these demands, the present review covers strategies in the spray-drying developments for the fabrication of porous particles with controllable structure. This information is important for optimizing the production of porous particles with desirable properties. Regulation of process conditions and precursor formulations are also explained, including composition, type, and physicochemical properties of droplet and raw components used (i.e., host component, template, and solvent). The electrostatic interactions between the individual components and the droplets are also presented, while this information tends to be neglected in the conventional spray-drying process. To clarify how the porous particles are designed, current experimental results completed with illustrations for the proposal particle formation mechanism are presented. The review also completed with the opportunities and potential roles of the changing porous structures in practical uses. This review would provide information on how to produce porous particles that can be used for advanced functional materials, such as catalysts, adsorbents, and sensors.

Measurement and prediction of cohesive powder behaviour related to flowability, flooding or arching in silos is found to be very challenging. Previous round robin [52] attempts with ring shear testers did not furnish reliable data and have shown considerable degrees of scatter and uncertainty in key measurements. Thus studies to build a reliable experimental database using reference materials are needed in order to evaluate the repeatability and effectiveness of shear testers and the adopted procedures. In this paper, we study the effect of particle size on the yield locus for different grades of limestone (calcium carbonate). We use the nonlinear Warren Spring equation to obtain the values of cohesion C, tensile strength T, and the shear index n. We recover linear (n = 1) yield loci for d50>70 μm with respectively small C and T, with consistent, finite macroscopic friction C/T = 0.7. With particle size decreasing below 70 μm the response becomes more and more cohesive and non-linear (1

In the analysis of particle size distribution (PSD), evaluation of the uncertainty of the percentile values is often required. Both theoretical and data processing methods are applicable to estimate standard deviations of percentile values. In this paper, a theory, applicable both in paramedic and non-parametric ways, is introduced. As a practical example, theoretical results based on a lognormal distribution are compared to those obtained by bootstrap method. Excellent agreement is demonstrated between the theory and the direct data processing method.

This paper deals with the physics of high-pressure gas atomization in metal powder production. To gain understanding of the effect of gas pressure on droplet size distribution, a numerical two-phase flow study is performed using Eulerian-Eulerian Volume of Fluid (VOF) interface tracking method. Annular-slit, close-coupled gas atomizer is considered to atomize molten aluminum using nitrogen as the atomizing gas. Four cases with different gas pressures are considered, while geometry and other operational parameters are fixed. Characteristics of several interfacial instabilities have been identified at different stages of the atomization process. Despite the increment in the rate of the atomization with the increasing gas pressure, deformation characteristics and the breakup mechanisms remain unchanged. Droplet size and the cumulative volume distributions indicate that the effectiveness of the atomization process increases with the elevating gas pressure. Cumulative volume obtained from the numerical simulations at low gas pressures display similar trends to the experimental results.

In order to control dust in a tunnel boring machine (TBM) construction tunnels, this paper, in combination with field measurements, applies CFD computer simulation technology to study the dust control effect of TBM construction tunnels under different dust extraction flow rates. Firstly, the dust extraction system is closed, and the result of the simulation show that the dust diffuses to the entire TBM working area within 181 s, indicating the necessity of having a dust extraction system in the tunnel. Secondly, the dust extraction system is open and under the original dust extraction flow rate of Qe = 8 m3/s, the overall dust diffuses to the entire working area Lo = 130 m, and the full-face dust diffusion distance is Lf = 47.54 m. Then the study was carried out with the setting of 2 m3/s ≤ Qe ≤ 14 m3/s. The results show that: when Qe ≤ 8 m3/s, the full-face dust diffuses to 47.54–71.84 m; when Qe > 8 m3/s, the full-face dust can be controlled at 42.81–46.34 m; and when Qe = 8 m3/s, the full-face dust control effect is better, and the average dust concentration in the tunnel is as low as 12.25 mg/m3, indicating that the original dust extraction system has a better design. The field measurement results verify that the CFD computer simulation results are accurate.

The determination of the wall liner properties and more importantly the flow properties of a bulk material is critical for the design of any bulk materials handling system. The design of such materials handling systems will be most effective when handling bulk materials at the physical properties they were designed to handle. Due to the fast-paced nature of expansion in the mining industry and demand of mineral resources, it is quite common for materials handling systems to handle bulk materials that were not intended for the system. Wet and Sticky Materials (WSM) within the materials handling stream can cause significant downtime, due to events such as blockages of bins, hoppers and transfer chutes, remains left in train wagons and dump trucks as well as conveyor belt carry back (Roberts, 2005; Connelly, 2011 [2] ). WSM are problematic within the materials handling stream due to the inter-particle and boundary cohesion and adhesion forces. The current measurement techniques for WSM have limitations and new methods must be considered. The development of new testers that can measure the wall adhesion and inter-particle adhesion of a bulk material can give a quantitative value for the adhesion present in a bulk material sample. The following paper will present a revised methodology for the estimation of the adhesion of bulk materials determined from the extrapolation of the Instantaneous Yield Locus (IYL). The predicted adhesion values from this methodology will be compared to experimental measurements using an inter-particle adhesion tester.

The coal spontaneous combustion is an urgent issue to be solved for the mine safety production. In the present paper, a new flame retardant of the calcification foam is proposed to improve the prevention effectiveness on the high temperature coal. The molecular dynamics simulation shows that the calcification foam exhibits a superior water retention performance at the thermal environment than the original foam. Ca2+ enters the hydration layer of the calcification foam and expands the head groups distance by 22.27%. Ca2+ focuses on the second hydrated water shell around the head groups and restricts the water molecule drainage. The drainage rate decreases with the temperature rise according to the diffusion coefficient. The oil bath experiment explains that the drainage rate of the calcification foam is slower and the growth rate is only half of the original foam at 100–150 °C. The calcification foam successfully restrains the coal spontaneous combustion. The coal heating rate treated by the calcification foam decreases obviously and the maximum reduction of CO release achieves 60%. The calcification foam has a good plugging and water retention properties for coal with the average inhibition rate up to 75.36%. The calcification foam has a superior effectiveness on suppressing the flame development.

Blending a mixture of powders to a homogeneous system is a crucial step in many manufacturing processes. To achieve a high quality of the end product, powder mixtures should be made with high content uniformity. For instance, producing uniform tablets depends on the homogeneous dispersion of active pharmaceutical ingredient (API), often in low level quantities, into excipients. To control the uniformity of a powder mixture, the first required step is to estimate the powder content information during blending. There are several powder homogeneity evaluation techniques which differ in accuracy, fundamental basis, cost and operating conditions. In this article, emerging techniques for the analysis of powder content and powder blend uniformity, are explained and compared. The advantages and drawbacks of all the techniques are reviewed to help the readers to select the appropriate equipment for the powder mixing evaluation. In addition, the paper highlights the recent innovative on-line measurement techniques used for the non-invasive evaluation of the mixing performance.

The inherent moisture in a coal cargo constantly migrates under the dynamic ship motion during maritime transport. The moisture often builds up at the bottom of the cargo. The accumulated water, if not removed sufficiently by the bilge well, can cause safety concerns during a voyage and difficulties during cargo unloading. The study presented in this paper aims to develop a program to investigate the moisture migration within coal cargoes in order to assess and eliminate shipping risks. The moisture migration phenomenon is initially modelled by adopting the classic infiltration theory, and considering the ship motions experienced by bulk carriers. An experimental method is developed to empirically characterise the moisture migration of a coal sample under simulated shipping dynamics. A predictive model is also developed to estimate the total moisture migration in a full size cargo by properly scaling up the experimental results. The model was validated by bilge well log collected from actual coal shipping voyages from Australia to international destinations.

Nanoparticle powders added into a liquid medium form structures which are much larger than the primary particle size (aggregates and agglomerates)-typically of the order of 10’s of microns. An important process step is therefore the deagglomeration of these clusters to achieve as fine a dispersion as possible. This paper reports the findings of a study on the dispersion of hydrophilic fumed silica nanoparticle clusters, Aerosil 200 V, in water using two batch rotor-stators: MICCRA D-9 and VMI. The MICCRA D-9 head consists of a set of teeth for the stator and another for the rotor, whereas the VMI has a stator with slots and a rotor which consists of a 4-bladed impeller attached to an outer set of teeth. The dispersion process, studied at different power input values and over a range of concentrations (1, 5, 10 wt.%), was monitored through the evolution of PSD. Erosion was found to be the dominant breakage mechanism irrespective of operating conditions or rotor-stator type. The smallest attainable size was also found to be independent of the power input or the design of the rotor-stator. Break up kinetics increased upon the increase of power input, and this also depended on the rotor-stator design. With MICCRA D-9 which has smaller openings on both the stator and rotor, the break up rate was faster. Increasing the particle concentration decreased break up kinetics. It could also be shown that operating at high concentrations can still be beneficial as the break up rate is higher when assessed on the basis of specific power input per mass of solids.

This study presents the numerical modeling of a hollow cylinder test (HCT) on granular soils by modifying the TRUBAL code. The discrete element method (DEM) was employed for this purpose. Owing to the significant expenditure of the HCT, a verified numerical modeling for this test was developed. The introduced numerical model (HCTBALL) defines plane and cylindrical walls for the boundary conditions to be applied. In addition, the article presents an efficient method to apply the torque. The displacements of the inner and outer walls are interdependent while torsion was applied to control the intermediate principal stress parameter ( b ). To verify the model, the paper employs results from experimental HCTs on Firoozkooh sand under both monotonic loading and drained conditions. A comparison of the presented model and the experimental results shows that both are closely concordant. It was shown that the deviatoric stress decreases as the principal stress angle ( α ) increases. In addition, it was observed that by increasing the confining pressure, the internal friction angle (φ′) decreases; however, at higher confining pressures, this reduction is insignificant. Furthermore, this study investigates the coordination number and its relationship to volumetric strain variations.

In this paper we present an experimental technique and a novel colourimetric image analysis algorithm to economically evaluate particle residence times within regions of batch granulators for use in compartmental population balance models. Residence times are extracted using a simple mixing model in conjunction with colourimetric data. The technique is applied to the mixing of wet coloured granules (binary and ternary systems) in a laboratory scale mixer. The resulting particle concentration evolutions were in qualitative agreement with those from the mixing model. It was seen that the algorithm was most stable in the case of the binary colour experiments. Lastly, simulations using the Discrete Element Method (DEM) were also performed to further validate the assumptions made in the analysis of the experimental results. Particle concentrations from the simulations showed the same trends as the experiment and highlighted the importance of particle size distributions on the DEM residence times.

In this paper, we report a new and convenient synthetic method based on a reaction in an aqueous system, which can produce a new nanocomposite superionic system (CdHgI4/HgI2) at 70 °C for 20 min. It is the first time that these nanocomposites are synthesized. In this work, we have chosen lithium iodide, cadmium and mercury acetate as starting reagents. First, an aqueous solution of cadmium acetate, surfactant and lithium iodide is obtained. Second, an aqueous solution of mercury acetate and lithium iodide is prepared. Then obtained solution is added to the first solution. The effects of the surfactant and mole ratio of Cd:Hg have been optimized to achieve the best products on morphology and purity. When the molar ratio of Cd:Hg is 1:1, in the absence of surfactant also in the presence of CTAB and Triplex, pure aggregated nanostructures are formed. The nanocomposites are characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and cyclic voltammetry (CV). The electrical conductivity measurement carries out at frequencies of 100 Hz, 1000 Hz, 10 kHz and 100 kHz in the temperature range 70–140 °C. Results show that the best morphology and purity have been achieved in the absence of surfactant, in 1:1 ratio of precursors.

This paper presents an analytical study of magnetohydrodynamics and convective heat transfer of nanofluids synthesized by three different shaped (brick, platelet and cylinder) silver (Ag) nanoparticles in water. A two-phase nanoscale formulation is adopted which is more appropriate for biophysical systems. The flow is induced by metachronal beating of cilia and the flow geometry is considered as a cylindrical tube. The analysis is carried out under the low Reynolds number and long wavelength approximations and the fluid and cilia dynamics is of the creeping type. A Lorentzian magnetic body force model is employed and magnetic induction effects are neglected. Solutions to the transformed boundary value problem are obtained via numerical integration. The influence of cilia length parameter, Hartmann (magnetic) number, heat absorption parameter, Grashof number (free convection), solid nanoparticle volume fraction, and cilia eccentricity parameter on the flow and heat transfer characteristics (including effective thermal conductivity of the nanofluid) are examined in detail. Furthermore a comparative study for different nanoparticle geometries (i.e. bricks, platelets and cylinders) is conducted. The computations show that pressure increases with enhancing the heat absorption, buoyancy force (i.e. Grashof number) and nanoparticle fraction however it reduces with increasing the magnetic field. The computations also reveal that pressure enhancement is a maximum for the platelet nano-particle case compared with the brick and cylinder nanoparticle cases. Furthermore the quantity of trapped streamlines for cylinder type nanoparticles exceeds substantially that computed for brick and platelet nanoparticles, whereas the bolus magnitude (trapped zone) for brick nanoparticles is demonstrably greater than that obtained for cylinder and platelet nanoparticles.The present model is applicable in biological and biomimetic transport phenomena exploiting magnetic nanofluids and ciliated inner tube surfaces.

This paper evaluated the potential of counter current spray drying to produce engineered crystalline particles in-situ. One main feature of the counter current spray dryer is in inducing droplet drying history with a progressively increasing drying rate; in contrast to a co-current spray dryer in which the particle is immediately confronted with high driving force of evaporation. In addition, counter current dryer provides higher residence time for particles within the drying chamber. This work explored the manipulation of these unique features of counter current spray drying to control the crystallinity of the particles formed. Sucrose, lactose and mannitol were spray dried as model materials exhibit contrasting crystallization. Counter current spray drying was suitable in producing well defined crystalline lactose particles mainly due to the higher residence time. The produced lactose particles were composed of agglomeration of fine thin lactose crystals. Surprisingly, the counter current spray drying with relatively lower initial evaporation rate resulted in amorphous mannitol particles. Fully crystalline mannitol was produced when the feed spray temperature was elevated leading to rapid supersaturation. This may be an important strategy to control the crystallinity of mannitol particles particularly for pharmaceutical application. Similar feed pre-heating strategy in conjunction with counter current spray drying was used for sucrose drying. Crystalline sucrose was achieved with relatively lower drying temperature. This will be a valuable strategy for producing free flowing sucrose particles specifically for the food industry.

The properties of ZnO nanoparticles were modified by doping them with cobalt ions (Co2+) in various compositions through a sol-gel route. The Co2+-doped ZnO nanoparticles were characterised using X-ray diffraction (XRD), UV/Vis spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and zeta potential measurements. A hexagonal wurtzite-phase structure of Co2+-doped ZnO was observed, with a slight decrease in particle size as the Co2+ doping concentration increased. Absorption by Co2+-doped ZnO was found to shift to longer wavelengths, towards the visible region, which was also confirmed by photoluminescence analysis. The band gap of the Co2+-doped ZnO samples decreased from 3.19 to 2.66 eV as the content of dopant Co2+ increased from 0.0 to 1.0 wt.%. The zeta potential results showed slight effects of Co2+ doping compared with undoped ZnO, indicating that Co2+ doping influences the optical properties and morphology of pure ZnO nanoparticles. The photocatalytic activity of the Co2+-doped ZnO samples was evaluated for the removal of Congo red dye from aqueous solution under solar radiation. The Co2+-doped ZnO samples showed higher effective removal of the dye using the optimal doping of 0.50 wt.%, which produced higher efficiency (about 96%, compared with 80% for pure ZnO). This paper was made possible by a NPRP Grant # [ 5-1425-2-607 ] from the Qatar National Research Fund ? Qatar (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors. Also, one of the authors (Muneer M. Ba-abbad) is grateful to the Hadhramout University of Science & Technology , Yemen for financial support for his PhD study. Scopus

In the alkali fusion process for the production of zirconium oxychloride, the formation of the water insoluble by-product, Na2ZrSiO5, largely affects NaOH recovery and results in the formation of silicon slags. Thus, controlling Na2ZrSiO5 formation is necessary. In this paper, we studied the effects of roasting temperature, NaOH/zircon mole ratio, and particle size of zircon sand on Na2ZrSiO5 formation. The optimum reaction parameters, when the roasting time was 1 h, were as follows: >= 95 mu m average particle size of zircon sand, 6:1 NaOH/zircon mole ratio, and 750 degrees C roasting temperature. To avoid an uneven roasting temperature during alkali fusion, the use of a rotary kiln reactor is recommended. The amount of Na2ZrSiO5 was significantly decreased under these optimum conditions, and the content of Na2O was reduced from 7.049% to only 2.21% after three water-leaching cycles. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

This paper presents a microscopic analysis of the saltation of particles on an obliquely oscillating plate driven by sine waves with an amplitude on the order of tens of micrometers and a frequency on the order of hundreds of hertz. To examine the effect of the diameter of a particle on its motion, the trajectories and velocities of different-sized particles, from 0.5 to 500 μm in mass median diameter, are analyzed using images captured by a high-speed microscope camera. The results show that larger particles bounce higher, whereas smaller particles easily agglomerate and bounce only slightly, owing to the low restitution caused by their loosely packed structure. In addition, larger particles bounce forward and backward repeatedly, while the agglomerated particles always bounce forward, and consequently have the highest transport velocity among these particles. The particle motion and the transport velocity can be explained by a theoretical probability model.

This paper performs further study on the micro–macro homogenization approach of granular materials (Li et al., 2010) based on the advancement of Hill’s lemma for Cosserat continuum (Liu, 2013). Firstly, the average couple stress tensor, expressed as the volume integration of quantities over the representative volume element (RVE) in the average-field theory of Cosserat continuum, is further deduced and expressed in terms of discrete quantities on the discrete particle assembly RVE of granular materials. The expression is also discussed and compared with other typical definitions of the effective couple stress tensor for granular materials in the literature. Then, rate forms of micromechanically based constitutive models consistent with different types of RVE boundary conditions are derived and discussed. Since the presented micro–macro homogenization approach is used, not only the micro–macro energy equivalence is satisfied, but also the microstructure and its evolution can be taken into account in the constitutive formulation with no need of specifying macroscopic phenomenological constitutive model.

Bottom-up self-organization approaches are promising for fabricating higher-order patterned surfaces composed of colloidal particles. The first example among the patterns that have been extensively studied would be stripes; however, the formation of stripe patterns has so far been confined to partially or fully hydrophobic surfaces. By contrast, we have succeeded in preparing well-defined stripe patterns even on strongly hydrophilic substrates via a convective self-assembly technique. By using this technique, a stripe pattern was produced simply by suspending a substrate in a dilute suspension, without any complicated procedure; the stripes spontaneously aligned parallel to the contact line. Driven by this finding, we further investigate this self-assembly process, and find out that the convective self-assembly is quite promising as a template-free pattern formation technique. In the present paper, we first overview the convective self-assembly technique which is originally developed for uniform film formation, and then present our recent results on the pattern formation of colloidal particles through the convective self-assembly. This technique can produce various patterns including stripes, cluster arrays, and grids in response to macroscopic experimental parameters such as particle concentration and temperature.

In this paper, fuel cell catalyst layer was developed using the optimized sphere packing algorithm. An optimization technique named adaptive random search technique (ARSET) was employed in this packing algorithm. The ARSET algorithm will generate the initial location of spheres and allow them to move in the random direction with the variable moving distance, randomly selected from the sampling range (α), based on the Lennard–Jones potential and Morse potential of the current and new configuration. The solid fraction values obtained from this developed algorithm are in the range of 0.610–0.624 while the actual processing time can significantly be reduced by 5.58–34% based on the number of spheres. The initial random number sampling range (α) was investigated and the appropriate α value is equal to 0.5.

Cataloged from PDF version of article. The harmful effect of nickel ions released from conventional stainless steel implants has provided a high level of motivation for the further development of nickel-free stainless steels. In this paper, the microstructure of medical-grade nickel-free stainless steel powders, with the chemical composition of ASTM F2581, is studied during mechanical alloying and subsequent annealing. Rietveld X-ray diffraction and transmission electron microscopy evaluations reflect nanocrystallization, austenitization and amorphization of the powders due to mechanical activation. It is also realized that annealing of the as-milled powder can develop a single austenitic structure with nanometric crystallite sizes, implying a considerable inherent resistance to grain growth. This study demonstrates the merit of mechanical alloying and subsequent annealing in the development of nanostructured medical-grade stainless steels. (C) 2012 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved

The present paper gives an overview of two methodologies for the computer simulation of wetting and capillary forces as well as particle-stabilized emulsions, which usually appear in a two-phase fluid system including solid bodies. One method is the molecular simulation with a coarse-grained model. The other is the computational fluid dynamics with a phase-field model. The main emphasis of this review is concerning our idea how to model the solid surfaces with wettability for the different simulation methods in the same spirit of “a simple modeling with focusing on hydrophilicity and hydrophobicity”.

This paper reports additive-free, reproducible, low-temperature solution-based process for the preparation of crystalline ZnO nanorods by homogeneous precipitation from zinc acetate. Also, ZnO nanorod structured dye sensitized solar cells using ruthenium dye (Z907) have been fabricated and characterized. The formation and growth of zinc oxide nanorods are successfully achieved. We analyzed three different synthesis method using solution phase, autoclave and microwave. The calcination effects on the morphology of ZnO nanorods are also investigated. Analysis of ZnO nanorods shows that calcination at lower temperature is resulted in a nanorod growth. Additive-free, well-aligned ZnO nanorods are obtained with the length of 330-558 nm and diameters of 14-36 nm. The XRD, SEM, and PL spectra have been provided for the characterization of ZnO nanorods. Microwave-assisted ZnO nanostructured dye sensitized solar cell devices yielded a short-circuit photocurrent density of 6.60 mA/cm(2), an open-circuit voltage of 600 mV. and a fill factor of 0.59, corresponding to an overall conversion efficiency of 2.35% under standard AM 1.5 sun light. (C) 2011 The Society of Powder Technology Japan. Published by Elsevier BA/. and The Society of Powder Technology Japan. All rights reserved.

In dry powder process, particles collide against each other and onto wall, and normally, electrostatic charge is generated. Such a process is called trioelectrification or tribo-/contact-/impact-charging of particles. In this paper, the amount of maximum (or saturated or equilibrium) charge on a particle in a powder flow of a pneumatic conveyer with a metal pipe was discussed. A theoretical discussion involving the space charge effect with the basis of ‘charge relaxation model,’ in which the maximum charge is limited to cause gas break down, is shown. The result showed two regions in which the space charge does not affect on, and dominates the amount of the charge. The charge was proportional to the particle size raised to the power 1.5 in the region of no space charge effect, whilst power 3 in the other region of the space charge dominant. Empirically a well approximated analytical formula was found, for all over the range including these two regions. The maximum charge as a function of particle size, pipe size, and volume fraction of the powder, was given as: q / C = 1.10 × 10 - 4 ( d p / m ) 3 { ϕ ( D / m ) } 2 + { 17.1 ( d p / m ) 1.5 } . A comparison showed that the theory gives a certain overestimation to the data cited from literatures. Additional discussions were given in details.

Ions of inorganic salts are known to affect bubble coalescence via ion size, charge density and polarizability. In this paper, a systematic study of the effect of monovalent anions (F-, Cl-, Br- and I-) and cations (Li+, Na+ and K+) on the lifetime of liquid films between two bubble surfaces is carried out by applying the thin film interferometry method. To mimic realistic conditions of bubble coalescence in a bubble column, drainage and stability of saline water films driven by different interface approach speeds (10-300 mu m/s) using a nano-pump was investigated. The results show significant effects of interface approach speed on transient film thickness and radius, film stability and rupture, and lifetime of saline water films. The experiments also indicate that there is a critical approach speed of 35 mu m/s for pure deionised water above which the water films instantly coalesce, i.e., no water film can be obtained. High interface approach speed creates corrugation on saline water film surfaces, which rapidly increases the rates of film radial expansion and drainage, and shortens the film lifetime. There is a critical salt concentration above which the saline water film lifetime abruptly increases. This critical concentration is independent of the interface approach speeds of 10-300 mu m/s. Our experimental results show a decreasing trend of film lifetime with increasing the size of either the cation or anion (NaF > LiCl > NaCl > NaBr > NaI). The order of the critical concentrations is the opposite of the order of lifetimes. The experimental results highlight the ion-specific effect of salt ions on the water structure and hence the behavior of saline liquid films. These results are relevant to a number of chemical engineering processes taking place in saline water, including mineral separation by flotation using air bubbles in saline water. (c) 2014 The Society of Powder Technology Japan. Published by Elsevier B. V. and The Society of Powder Technology Japan.