Rough Particle Research Articles

Effect of comminution on particle shape and surface roughness and their relation to flotation process

The essential physical characteristics of the distinction of particles are size, shape and surface roughness. Particle shape and surface roughness are considered important parameters in the prediction of the behavior of particles individually or collectively. These parameters are of great importance to industries employing various materials in a powder form. These parameters have not been currently reviewed satisfactory in the mineral processing field. Therefore, this research is concerned with the different methods used to estimate the particle shape and surface roughness and also to relate these parameters with the behavior of some mineral processing operations, especially comminution and flotation processes.The surface roughness of mineral particle influences the fundamental processes of particle–bubble attachment and the other sub-processes in froth flotation. The contact angle is dependent on the surface roughness. The modification of the wettability due to surface roughness can be greatly enhanced in the fractal surface; that is the fractal surface will be superrepellent (superwettable) to a liquid when the contact angle is greater (less) than 90°. Correlations were found between the shape properties, surface roughness values and wettability.The dry grinding produces relatively rough particle surfaces with a high concentration of microstructural defects while the wet grinding produces smoother cleaner surfaces. The dry ground samples exhibited more stable, higher loaded froths and faster flotation kinetics.

TAILORING DRY POWDER INHALER PERFORMANCE BY MODIFYINGCARRIER SURFACE TOPOGRAPHY BY SPRAY DRYING

In order to provide adequate performance of dry powder inhalates with respect to dosing and fine particle fraction, interparticle adhesion between drug and carrier has to be well balanced. It has to be large enough to ensure attachment of the active ingredient during powder handling and dosing, but small enough to ensure detachment of the drug from the carrier on inhalation. In this study, interparticle interactions have been modified by targeting the surface topography of the carrier or rather the contact area between drug and carrier using spray drying. Because lactose is susceptible to spray drying, resulting in partial or full amorphicity, mannitol was used here. The spray drying outlet temperature turned out to be an appropriate parameter to affect surface topography, spray drying at low temperature leading to smooth particles, and spray drying at high temperature leading to rough particle surfaces. Dosing of the inhalate was found not to be affected by surface roughness of the carrier. However, the fine particle fraction decreases with increasing surface roughness. Consequently, the use of mannitol carrier particles exhibiting different surface topographies allows for modifying interparticle interactions, thereby providing an effective tool for tailoring the performance of an inhalate.

Synthesis of palladium nanoshell using a layer-by-layer technique

Complete palladium nanoshells were prepared by reducing palladium ions in a one-step reaction onto preformed silica cores of ca. 90 nm, which had been coated with successive layers of poly(diallyldimethyl ammonium chloride), poly(sodium styrenesulfonate) and finally poly(diallyldimethyl ammonium chloride) to reverse the zeta potential of the silica cores. This constitutes the first reported method for complete palladium nanoshell formation without the use of other metals as nucleation sites. The morphology of the nanoshell is of the rough discrete particle type rather than the smooth continuous type.

Superhydrophobic surfaces: a model approach to predict contact angle and surface energy of soil particles

SummaryWettability of soil affects a wide variety of processes including infiltration, preferential flow and surface runoff. The problem of determining contact angles and surface energy of powders, such as soil particles, remains unsolved. So far, several theories and approaches have been proposed, but formulation of surface and interfacial free energy, as regards its components, is still a very debatable issue. In the present study, the general problem of the interpretation of contact angles and surface free energy on chemically heterogeneous and rough soil particle surfaces is evaluated by a reformulation of the Cassie‐Baxter equation, assuming that the particles are attached on to a plane and rigid surface. Compared with common approaches, our model considers a roughness factor that depends on the Young’s Law contact angle determined by the surface chemistry. Results of the model are discussed and compared with independent contact angle measurements using the Sessile Drop and the Wilhelmy Plate methods. Based on contact angle data, the critical surface tension of the grains were determined by the method proposed by Zisman. Experiments were made with glass beads and three soil materials ranging from sand to clay. Soil particles were coated with different loadings of dichlorodimethylsilane (DCDMS) to vary the wettability. Varying the solid surface tension using DCDMS treatments provided pure water‐wetting behaviours ranging from wettable to extremely hydrophobic, with contact angles > 150°. Results showed that the critical surface energy measured on grains with the highest DCDMS loadings was similar to the surface energy measured independently on ideal DCDMS‐coated smooth glass plates, except for the clay soil. Contact angles measured on plane surfaces were related to contact angles measured on rough grain surfaces using the new model based on the combined Cassie‐Baxter Wenzel equation, which takes into account the particle packing density on the sample surface.

Temporal Variability on Lowland River Sediment Properties and Yield

Problem statement: A sediment analysis study was conducted at the Chini River on 16 and 31 August 2008. This study was conducted to review the formation of suspended sediment load in the Lake Chini catchment area, which flows into the Pahang River via the Chini River. Approach: Three sampling stations were chosen, the first one at upstream Chini River (S1), mid-stream Chini River (S2) and downstream Chini River (S3). Three parameters were quantified for this study, namely: distribution of sediment grain size (g), concentration of suspended sediment (mg L-1) and river discharge values (in m3 sec-1). Results: The findings of the study show that the sizes of sediment fall between phi O-2.00 with very rough particle sizes falling between phi-1.00 and phi 0.00. At the study area, the daily discharge value is estimated at 722, 304, 00 L day-1. The average suspended sediment concentration recorded for each station shows varying values for both timelines. The values were 27.33 mg L-1 on 16/08/08 and 2.233 mg L-1 on 31/08/08. Conclusion: The average value for all stations calculated based on the formation of suspended sediment load per day falls between 16,480.4627 kg day-1 on 16/08/08 and 1,540.43 kg day-1 on 31/08/08. Overall, when this number was extrapolated to every square kilometre, the result showed that the estimated average sediment that flows out of Lake Chini is 73.22 tonnes km-2 year-1.

Changes in the Mucoadhesion of Powder Formulations after Drug Application Investigated with a Simplified Method

The residence time in the nasal cavity can be prolonged by dry particles that absorb water and subsequently increase the viscosity of the mucus layer. A novel nasal drug delivery system based on interactive mixtures has previously been developed, where fine particles of the active component are adhered to the surface of mucoadhesive carrier particles by dry mixing. The surface coverage may alter the original mucoadhesiveness of the carrier particles and to investigate this, a simplified tensile strength method was developed and evaluated. Reliable results were obtained with a plastic coated absorbent paper covered by a mucin solution as a substitution for porcine nasal mucosa and should also be applicable to other dry particle systems. The method showed that the swelling of sodium starch glycolate particles was slightly delayed, corresponding to the degree of hydrophobic surface coverage. Carrier particles of partly pregelatinized maize starch were not influenced by the addition of a hydrophobic substance, probably because of the rough particle shape that inhibited a complete surface coverage. It was concluded that the surface coverage of carrier particles in interactive mixtures only could cause a short delay in water absorption that should not affect their mucoadhesive characteristics in vivo.

Rough particle swarm optimization and its applications in data mining

This paper proposes a novel particle swarm optimization algorithm, rough particle swarm optimization algorithm (RPSOA), based on the notion of rough patterns that use rough values defined with upper and lower intervals that represent a range or set of values. In this paper, various operators and evaluation measures that can be used in RPSOA have been described and efficiently utilized in data mining applications, especially in automatic mining of numeric association rules which is a hard problem.

Preparation, characterization and chlorine stability of aromatic–cycloaliphatic polyamide thin film composite membranes

Novel composite nanofiltration membranes containing aromatic–cycloaliphatic polyamide skin layer on a reinforced polyethersulfone ultrafiltration membrane were prepared by in situ interfacial polymerization of 1,3-cyclohexanebis(methylamine) (CHMA) in water with trimesoyl chloride in hexane under different conditions. The composite membranes were exposed to 1, 3 or 5 ppm NaOCl solution containing 2000 ppm NaCl for a period of 1–10 days. The membranes were characterized by infrared spectroscopy (FT–ATIR), scanning electron microscopy (SEM), contact angle measurements, and separation performance by permeation tests using 2000 ppm NaCl solution. The IR spectra of virgin TFC membrane has shown strong amide-I (C O stretch) and amide-II (C N H) bands at 1644 and 1543 cm −1, respectively. The IR spectra of chlorine exposed membranes have shown a split in both the bands with peaks around 1655 and 1640 cm −1 for amide-I band, and around 1580, 1560, 1545, and 1512 cm −1 for amide-II band. SEM analysis has sown a change in the surface morphology from smooth granular structure of the virgin membrane to rough particle structure in chlorinated membranes. The contact angles of the membrane surface have been increased from 57° for the virgin membrane to 60–65° for the membranes treated with NaOCl solution within 24 h. NaCl rejection of the membranes has been decreased from the initial 78 to 63–65%, and water flux was decreased from the initial 73 to 32–38 l m −2 h −1, depending upon the chlorine concentration, within 24 h of exposure. The higher the chlorine concentration the higher was the reduction in flux and rejection. Further decrease in the performance has occurred at a considerably slower rate. The faster initial decrease in both salt rejection and water flux may be attributed to the faster conversion of the hydrogen bonding amide N H group to the non-hydrogen bonding N Cl group and thus resulting a change in the polyamide skin layer chemistry and morphology. The results clearly indicate that N-chlorination itself adversely affects the membrane performance in the absence of Orton rearrangement and cleavage of the polyamide chain.

The Method of the Least Reduction in Oil Reservoir Based on Rough Set Particle Swarm

The Method of the Least Reduction in Oil Reservoir Based on Rough Set Particle Swarm

Evaluation of flow properties of toner powder using conical rotor

In order to accurately evaluate the dynamic flow properties of toner powder, a new rotary shearing tester with a conical rotor was developed. This instrument was equipped with an automatic pressing system to compress toner powder. The tester could simultaneously measure torque and compression load during the intrusion and rotation of the conical rotor into the same packed toner powder. The optimum rotational speed and intrusion rate of the conical rotor for the characterization of the flow properties of toner powder were discussed based on test results; their values were calculated as 0.017 s − 1 and 0.083 mm/s, respectively. The torque of toner powder changed in proportion to the cube of the depth of intrusion in the toner powder bed. The surfaces of toner powder samples prepared from polymer resin and carbon pigment particles were coated with fine particles (SiO 2, TiO 2) under a different condition. The flow characteristics of toner powder with a different particle surface were evaluated based on the relationship between the shearing torque and the void fraction of packed toner. In the present case, the Rumpf model was applied to estimate the shearing force H at the contact point between two particles of toner powder. The value of H for toner powder with a rough particle surface, which was covered with fine particles (SiO 2, TiO 2), was 41 nN, while that for toner powder with a smooth particle surface, which was not covered with fine particles, was 357 nN. Further the effects of the particle shape of the toner on the torque of toner powder after compression under the same conditions were investigated. The torque of toner powder decreased with an increase in circularity.

Interlocking hexagons model for auxetic behaviour

A 2D ‘Rough Particle’ model consisting of interlocking hexagons is reported. Analytical expressions for the in-plane Poisson’s ratios and Young’s moduli due to particle translation along the geometrically matched male and female interlocks are derived for the model. The dependency of the mechanical properties on each of the model (geometrical and stiffness) parameters is provided, and it is shown that the assembly of interlocking hexagons deforming by particle translation along the interlocks displays auxetic (negative Poisson’s ratio) behaviour. The model predictions are compared with experimental mechanical properties for auxetic polypropylene (PP) films and fibres. The model predicts the experimental Poisson’s ratio values very well (model: νxy = −1.30, νyx = −0.77; experiment (PP films): ν|| = −1.12, \(\nu_{\bot} = -0.77\)). The model generally overestimates the Young’s moduli of the films, but is in reasonable agreement with the axial Young’s modulus of the fibres.

Feature selection based on rough sets and particle swarm optimization

We propose a new feature selection strategy based on rough sets and particle swarm optimization (PSO). Rough sets have been used as a feature selection method with much success, but current hill-climbing rough set approaches to feature selection are inadequate at finding optimal reductions as no perfect heuristic can guarantee optimality. On the other hand, complete searches are not feasible for even medium-sized datasets. So, stochastic approaches provide a promising feature selection mechanism. Like Genetic Algorithms, PSO is a new evolutionary computation technique, in which each potential solution is seen as a particle with a certain velocity flying through the problem space. The Particle Swarms find optimal regions of the complex search space through the interaction of individuals in the population. PSO is attractive for feature selection in that particle swarms will discover best feature combinations as they fly within the subset space. Compared with GAs, PSO does not need complex operators such as crossover and mutation, it requires only primitive and simple mathematical operators, and is computationally inexpensive in terms of both memory and runtime. Experimentation is carried out, using UCI data, which compares the proposed algorithm with a GA-based approach and other deterministic rough set reduction algorithms. The results show that PSO is efficient for rough set-based feature selection.

Hierarchical surface rough ordered Au particle arrays and their surface enhanced Raman scattering

A simple, effective, and low-cost method is presented to fabricate an ordered Au particle array with hierarchical surface roughness on an indium tin oxide substrate based on an ordered alumina through-pore template, induced by solution dipping on colloidal monolayer, using an electrochemical deposition strategy. The array consists of periodically arranged and isolated Au microparticles, which show nanoscaled surface roughness. Importantly, this hierarchically rough particle array exhibits strong surface-enhanced Raman scattering effect using rhodamine 6G as probe molecules, associated with its surface geometry. Such structure could be useful, e.g., in sensors, biotechnology, and nanodevices.

The constitutive relation for the granular flow of rough particles, and its application to the flow down an inclined plane

A perturbation expansion of the Boltzmann equation is used to derive constitutive relations for the granular flow of rough spheres in the limit where the energy dissipation in a collision is small compared to the energy of a particle. In the collision model, the post-collisional relative normal velocity at the point of contact is in the present calculation), and is close to 1 if the angle between the relative velocity vector and the line joining the centres is less than the roughness angle. The conserved variables in this case are mass and momentum; energy is not a conserved variable in the ‘adiabatic limit’ considered here, when the length scale is large compared to the ‘conduction length’. The results for the constitutive relations show that in the Navier–Stokes approximation, the form of the constitutive relation is identical to that for smooth particles, but the coefficient of shear viscosity for rough particles is 10%–50% higher than that for smooth particles. The coefficient of bulk viscosity, which is zero in the dilute limit for smooth particles, is found to be non-zero for rough and partially rough particles, owing to the transport of energy between the translational and rotational modes. In the Burnett approximation, there is an antisymmetric component in the stress tensor for rough and partially rough particles, which is not present for smooth particles.The constitutive relations are used to analyse the ‘core region’ of a steady granular flow down an inclined plane, where there is a local balance between the production of energy due to the mean shear and the dissipation due to inelastic collisions. It is found that realistic results, such as the decrease in density upon increase in the angle of inclination near close packing, are obtained for the rough and partially rough particle models when the Burnett coefficients are included in the stress tensor, but realistic results are not obtained using the constitutive relations for smooth particles. This shows that the flow dynamics is sensitive to the numerical values of the viscometric coefficients, and provides an indication of the minimal model required to capture the flow dynamics.

The motion of a rough particle in a Stokes flow adjacent to a boundary

Results are presented of experimental investigations into the motion of a heavy sphere in a rotating cylinder which is completely fllled with highly viscous ∞uid. For a given cylinder rotation rate, the sphere adopts a flxed position and rotates adjacent to the cylinder wall. For the case of a smooth sphere the motion is consistent with that predicted by a Stokes ∞ow model. Artiflcially roughened spheres exhibit particle-boundary contact caused by impacts of surface asperities with the boundary for low cylinder speeds. For higher cylinder speeds the behaviour of the roughened spheres crosses smoothly from the particle-boundary contact regime to motion with hydrodynamically lubricated ∞ow.

The characterisation of rough particle contacts by atomic force microscopy

An Atomic Force Microscopy (AFM) reverse imaging technique has been used to determine the contact zone topography of glass and UO 3 particles in contact with flat mica substrates. A method is proposed that uses this topography to determine an effective asperity radius of curvature for the contacting particle. Application of the method has been found to be consistent with established contact mechanics models, for both glass and UO 3 particle probes that present significantly different surface roughness. The method proposed is straightforward to apply and offers a greater insight into the influence of particle micro- and nano-roughness on adhesion. This is important for applications that rely on the control of granular flow such as pellet or tablet manufacture.

Structure of bioactive mixed polymer/colloid aerogels

The structure of polymer/colloid mixed silica sono-aerogels has been studied by SAXS, N2 adsorption–desorption and Hg porosimetry. The system is described as a composite in which the polymeric phase (sonogel) is the matrix. The structure of this phase prepared with ultrasounds is very fine consisting in aggregates of ∼5nm radius formed by elementary particles of 1nm radius. Including Ca(II) into the silica atomic network causes enlarging the average size of the particle more than three times with respect to its size in its pure silica counterpart. The stiffness increases as well by 50%. The size of the particles and pores is also affected by the ultrasound dose applied; the higher for the larger the particles. On the other hand, a low dose produces a rough particle surface.

In vitro and in vivo studies of ibuprofen-loaded biodegradable alginate beads

The irritation effects of ibuprofen, a widely used non-steroidal anti-inflammatory drug (NSAID), were evaluated on mouse gastric and duodenal mucosa when suspended in 0.5% (w/v) sodiumcarboxymethylcellulose (NaCMC) solution and loaded in alginate beads. The ionotropic gelation method was used to prepare controlled release alginate beads of ibuprofen. The influence of various formulation factors on the encapsulation efficiency, as in vitro drug release and micromeritic properties, was investigated. Other variables included the alginate concentration, percentage drug loading and stirring speed during the microencapsulation process. Scanning electron micrographs of alginate beads loaded with ibuprofen showed rough surface morphology and particle sizes in the range of 1.15 ± 0.4–3.15 ± 0.6 mm. The yield of microspheres, as collected after drying, was generally 80–90%. Formulation code H showing t50% value of 3.5 h was chosen for in vivo trials because of the appropriate drug release properties. For in vivo trials, free ibuprofen (100 mg kg−1), blank and ibuprofen (100 mg kg−1) loaded alginate beads (formulation code H) were suspended in 0.5% (w/v) NaCMC solution and each group was given to six mice orally by gavage. NaCMC solution was used as a control in experimental studies. In vivo data showed that the administration of ibuprofen in alginate beads prevented the gastric lesions.

Expanding the range of auxetic polymeric products using a novel melt‐spinning route

AbstractThe first auxetic fibre was successfully produced in polypropylene using a novel melt‐spinning route. These fibres were extruded at 159 °C with a screw speed 10 rpm (1.05 rad s–1) and 2 mpm (0.03 m s–1) take‐up speed. Characterisation of these fibres involved optical techniques (videoextensometry) to measure the strains along both the length and the width simultaneously during deformation. The unique processing route has now been developed to expand the range of auxetic extruded polymeric products. We report here that auxetic polypropylene films have been developed, and auxetic polyester and polyamide fibres have now been produced. We also report the development of a simple rough particle model to predict auxetic behaviour that may be applicable to the developed fibres and films. Finally, a review of some potential applications for auxetic fibres and films will be presented. These include as reinforcements in composites, anchoring devices, smart bandages for health‐care, breathable packaging and tear resistant films. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Lithium ion conductivity of the B-site substitution in Li3xLa0.67−xRE y III Ti1−2yPyO3 system (REIII=Sc3+, Y3+, Nd3+, Sm3+, Eu3+, Yb3+)

The B-site substituted perovskite solid solution systems Li3xLa0.67−xREyTi1−2yPyO3 (RE=Sc, Y, Nd, Sm, Eu, Yb) have been investigated. Perovskite solid solutions formed in the range of x=0.10, y<0.10 for RE=Sc3+, Y3+, Yb3+, x=0.10, y≤0.05 for RE=Nd3+, Sm3+, Eu3+. Li0.3La0.57Nd0.05Ti0.9P0.05O3 has the highest bulk conductivity of 4.31×10−4 S·cm−1 and the highest total conductivity of 2.52×10−4 S·cm−1 at room temperature in all prepared compositions. The compositions have low activation energies of about 24–30 kJ/mol in the temperature ranges of 298–523 K. SEM studies showed that the sample made by solid-state reaction has a sphere-like morphology and a rough particle with particle size of about 50 µm. The research results also indicated that the reaction temperature decreases and the electrochemical stabilities of the titanate-based perovskite-type solid solutions are improved by using RE3+ and P5+ replaced Ti4+ on B-site in the Li3xLa0.67−xTiO3 parent.