Rectangular Particles Research Articles

OPTICAL AND CONFOCAL MICROSCOPIC STUDIES ON DISSOLUTION OF RICE STRAW PARTICLES IN 1-ETHYL-3- METHYLIMIDAZOLIUM ACETATE

Abundant agriculture residue such as rice straw needs an effective pretreatment method in order to efficiently and economically process it into biofuels and chemicals. In order to develop an economical liquefaction process for pretreatment of rice straw, a 3D particle based-dissolution process model needs to be investigated. As a result, this study was undertaken to develop a dissolution model of ball milled rice straw (RS) particles in 1-Ethyl-3-Methylimidazolium Acetate [Emim][OAc], at 120°, 140° and 160°C using optical and confocal microscopes. These results showed the rectangular particle swelled in-plane during the heat treatment in [Emim][OAc] but the thickness and volume decreased with heating time. As the particle swelling progressed, the particle light intensity ratio increased which was confirmed by confocal and optical microscopy. Both the particle light intensity ratio and volume ratio measurement were used to estimate the particle dissolution end point. Heating at 160oC accelerated particle dissolution and swelling significantly. Decreasing the temperature from 160oC to 120oC extended the dissolving time changing from 10 min to 1 h. This new imaging analysis process model utilizing particle light intensity and volume ratios allows significant improvement in dissolution process modeling for endpoint determination and prediction. The dissolution process also has applications to other types of biomass.

In-situ modification of cellulose nanofibrils by organosilanes during spray drying

Cellulose nanofibrils (CNFs) have shown their potential as the sustainable choice for reinforcements in thermoplastic composites. Studies on surface properties are important because they directly relate to the compatibility between CNFs and polymer matrices. In this study, CNF suspensions were treated with two different organosilane functionalities before being spray-dried (SD). Three concentration levels of organosilane solution were applied based on the mass of the CNFs in suspension: 1wt. %, 3wt. % and 5wt. %. Morphological and surface properties of the CNFs were measured to understand changes induced by the organosilane modification. Scanning electron microscopy analysis shows some aggregation of larger particles as well as many small twisted rectangular particles. Particle size distribution analysis (PSD) indicates certain differences among treated and untreated CNFs. Inverse gas chromatography (IGC) reveals that the organosilane treatment reduces the dispersion component of surface energy of dried CNFs and changed the acid-base characteristic of CNFs by the attachment of different functional end-groups.

A generalized particle-to-wall collision model for non-spherical rigid particles

An extended theoretical particle-to-wall collision model for the rigid particles of general shape is presented. It is based on an improved definition of the restitution coefficient, which is consistent with the previous definition of the restitution coefficient for spherical particles, but modified to meet the conditions of arbitrary non-spherical shapes. Moreover, it follows the fundamental conservation laws of momenta, as well as the Coulomb’s law of friction. In addition, this model is validated by comparing the simulation results to experimental measurements of the collision between rectangular particles and walls, which shows the correctness of the model. Finally, the applications of present model for multiple-impacts and the walls with roughness are demonstrated, which shows its potential feasibility for complex granular system simulations.

Creation of lithographic masks using a scanning probe microscope

The experimental results on scanning probe lithography (SPL)—the formation of lithographic masks using scanning probe microscope—are presented. Polymethylmethacrylate (PMMA)-based masks prepared by the SPL method are used to form metal nanoparticles of the specified sizes and shape, as well as the metallic nanowires connecting the contact areas. The analysis of various SPL modes showed that the procedure of point indentation with the switched-on microscope feedback is optimal for the formation of round nanoparticles. When forming the rectangular particles, the procedure of multiple scanning of one region in the contact mode is optimal. The quality of lithographic masks can be substantially increased by the additional use of chemical etching to remove excess PMMA after the mask is formed. The topography and magnetization structure of the formed structures were monitored by atomic force microscopy and magnetic force microscopy.

Highly sensitive biochemical sensor comprising rectangular nanometal arrays

This paper proposes a novel design for a highly sensitive high-resolution localized surface plasmon resonance (LSPR) biochemical sensor. The geometrical structure of the sensor consists of three segments. The first segment comprises single-mode fibers located in the output and input ends of the sensor. The second and third segments comprise rectangular nanometal arrays and serve as the analyte regions of the sensor; the amount of displacement between these two segments is one rectangular nonmetal particle. We integrated two breakthrough methods, the object meshing method and the boundary meshing method, with the finite element method to effectively improve the accuracy of simulation outcomes and reduce the amount of time and memory required for performing calculations. Subsequently, we constructed the proposed LSPR biochemical sensor, and the results indicated that the proposed sensor exhibited excellent geometric structure and spectral characteristics. Specifically, the sensor is short (approximately 250μm) and features high resolution (approximately −130dB) and high sensitivity (approximately 126,849.1333nm/RIU).

A Novel Seed-Assisted Route for Fabricating Potassium Titanoniobate Photocatalytic Nanomaterials.

A novel, facile and mild preparation route was proposed to synthesize well-crystallined potassium titanoniobate (KTiNbO5) powders with pure phase and mono-dispersed particle morphology. The preparation process mainly included a hydrothermal reaction under temperature of 200 degrees C, then following with a short time calcining at 500 degrees C. The utility of crystal seed during the hydrothermal process was essential and pivotal. Most importantly, only the crystal seed was prepared through a particular sol-gel process, was the desired KTiNbO5 particles successfully achieved. The unique effect of such crystal seed was discussed in detail. We demonstrated that particle quantity and morphology of the crystal seed was a key point for the successful preparation. The KTiNbO5 particles synthesized in this work exhibited thin and rectangular particle shape with the average size around one micron. Moreover, the photocatalytic behavior of such KTiNbO5 powders was investigated. It was proved that such KTiNbO5 powders had potential applications as photocatalytic materials.

Finite element analysis of compressive behavior of hybrid short fiber/particle/mg metal matrix composites using RVE model

The compressive behavior of hybrid short fiber/particle composites was examined by using finite element analysis and representative volume element models for two different particle shapes. The realistic, random and complex distributions of the short fibers and particles were reconstructed to produce a representative volume element of the hybrid composites using a random sequential adsorption algorithm. The predicted mechanical properties and overall compressive stress-strain by finite element analysis corresponded well to the experimental results at the elastic region and near the yield surface, but the model slightly overestimated the strength of the composites at higher stress. This deviation possibly occurs from micro-mechanical factors, which were not considered in the RVE models. In contrast to FE analysis, fracture of the short fiber and fiber-matrix debonding occurred because of large localized stress. In the case of a high applied load, non-linear behavior of reinforcements and interfacial strength should be considered to obtain accurate results. Meanwhile, mechanical properties of rectangular particles are more effective on the hybrid composites the spherical ones for the hybrid composites.

Fabrication of nanocomposites composed of silver cyanamide and titania for improved photocatalytic hydrogen generation.

Highly efficient composite photocatalysts composed of silver cyanamide (Ag2NCN) and anatase titania (TiO2) were fabricated through a chemical precipitation process of silver nitrate and cyanamide in TiO2 suspensions. The TiO2 nanoparticles around 15 nm were immobilized on the surface of rectangular Ag2NCN particles to form a hetero-structure, and the contents of TiO2 were varied to tune the structure and the photocatalytic performances. In comparison with single TiO2 or Ag2NCN, the TiO2/Ag2NCN nanocomposites exhibited a prominent improved photocatalytic activity in the hydrogen generation, and the hydrogen evolution rate (1494.0 μmol (g h)(-1)) was higher than most of the reported TiO2-composite photocatalysts. Based on the structure investigation, the photocatalytic mechanism of these TiO2/Ag2NCN nanocomposites was proposed. The enhanced photocatalytic activity was attributed to three points: the matched energy level between TiO2 and Ag2NCN promoted the electron-hole transfer and thus inhibited the recombination of photogenerated electrons and holes; the great electron storage capacity of metallic silver produced in the photocatalytic process also facilitated the charge separation; in addition, the expanded absorption spectrum because of the composite structure enhanced the UV and visible light response ability. These TiO2/Ag2NCN nanocomposites also presented good photocatalytic stability in the typical cycle tests. This work provided new insights into fabricating highly efficient composite photocatalysts containing silver and TiO2 for hydrogen generation.

Optical response of noble metal alloy nanostructures

Abstract The optical response, stability, and cost-effectiveness of individual noble metals can be improved by combining them to form alloy nanostructures. The present work reveals the influence of shape, size, and metal type on the optical response of alloy nanoparticles using discrete dipole approximation (DDA) simulations. It is found that sharp corner nanostructures show enhanced plasmonic properties in comparison to rounded counterpart. For all the three shapes, viz., nanocubes, rectangular, and nanobar particles, the increase in length resulted in redshifts of the longitudinal plasmon resonance alongwith enhancement in the scattering yield as well as relative efficiency parameters except for nanocubes of edge length 120 nm. The effect of size on full width at half maxima (FWHM) has also been studied and found to be maximal for nanocubes in comparison to other nanostructures.

A novel synaptic vesicle fusion path in the rat cerebral cortex: the "saddle" point hypothesis.

We improved freeze-fracture electron microscopy to study synapses in the neuropil of the rat cerebral cortex at ∼2 nm resolution and in three-dimensions. In the pre-synaptic axon, we found that “rods” assembled from short filaments protruding from the vesicle and the plasma membrane connects synaptic vesicles to the membrane of the active zone. We equated these “connector rods” to protein complexes involved in “docking” and “priming” vesicles to the active zone. Depending on their orientation, the “rods” define two synaptic vesicle-fusion paths: When parallel to the plasma membrane, the vesicles hemi-fuse anywhere (“randomly”) in the active zone following the conventional path anticipated by the SNARE hypothesis. When perpendicular to the plasma membrane, the vesicles hemi-fuse at the base of sharp crooks, called “indentations,” that are spaced 75–85 nm center-to-center, arranged in files and contained within gutters. They result from primary and secondary membrane curvatures that intersect at stationary inflection (“saddle”) points. Computer simulations indicate that this novel vesicle-fusion path evokes neurotransmitter concentration domains on the post-synaptic spine that are wider, shallower, and that reach higher average concentrations than the more conventional vesicle fusion path. In the post-synaptic spine, large (∼9× ∼15 nm) rectangular particles at densities of 72±10/ µm2 (170–240/spine) match the envelopes of the homotetrameric GluR2 AMPA-sensitive receptor. While these putative receptors join clusters, called the “post-synaptic domains,” the overwhelming majority of the rectangular particles formed bands in the “non-synaptic” plasma membrane of the spine. In conclusion, in the neuropil of the rat cerebral cortex, curvatures of the plasma membrane define a novel vesicle-fusion path that preconditions specific regions of the active zone for neurotransmitter release. We hypothesize that a change in the hybridization of the R-SNARE synaptobrevin from parallel to antiparallel swings the synapse into this novel vesicle-fusion path.

Research and Empoldering of High Strength Weathering Steel S450EW

According to the characteristics of high strength weathering steel, this paper designs to develop anexperimental steel S450EW with yield strength higher than 450MPa.Through the study,it has been found that with decreasing cooling rate, the organizational changed largely, while ferrite and pearlite gradually transformed to martensite and a small amount of ferrite, then finally tomartensite organization.It has also been found that the crystal size decreased, and the experimentalsteel also precipitated a rectangular second phase particles of (NbTi) CN phase and TiC, which were sparsely distributed with the size of 100 ~ 300nm and below 30nm, while some phases were distributedasa number of strips in the grain boundary which mainly are C, Fe, Cr.

Terahertz imaging of sub-wavelength particles with Zenneck surface waves

Impact of sub-wavelength-size dielectric particles on Zenneck surface waves on planar metallic antennas is investigated at terahertz (THz) frequencies with THz near-field probe microscopy. Perturbations of the surface waves show the particle presence, despite its sub-wavelength size. The experimental configuration, which utilizes excitation of surface waves at metallic edges, is suitable for THz imaging of dielectric sub-wavelength size objects. As a proof of concept, the effects of a small strontium titanate rectangular particle and a titanium dioxide sphere on the surface field of a bow-tie antenna are experimentally detected and verified using full-wave simulations.

Modeling Study of the Valid Apparent Interface Thickness in Particulate Materials with Ellipsoidal Particles

When interfacial layers are viewed as a separate phase, the interface thickness plays an essential role in assessing physicomechanical properties of particulate materials. However, the actual interface thickness is difficult to determine because of the opacity of particulate materials. The apparent interface thickness obtained from sectional analysis is often overestimated, due to the irregularity of surface texture of grain that gives rise to the normal of a cross-sectional plane nonperpendicular to the grain surface. Hence, the determination of the overestimation degree between the apparent value and preconfigured value is very critical to quantify precisely the valid apparent interface thickness. The majority of previous works focused on the overestimation degree for three-dimensional (3D) spherical, two-dimensional (2D) elliptical and rectangular particles, whereas little is known about 3D ellipsoidal particles. In this work, a numerical scheme is proposed to obtain the overestimation degree of the interface thickness around ellipsoidal grains. On the basis of the quantitative stereology and geometrical probability, the valid statistical mean apparent interface thickness and overestimation degree are analyzed theoretically. The deduced results show that the two values primarily subject to an unknown coefficient. A sectional analysis numerical algorithm is then implemented to derive the coefficient for an ellipsoidal grain. To test the proposed numerical model, valid theoretical data for spherical and ellipsoidal particles is selected for comparisons. Finally, by the developed numerical model, the effects of geometrical characteristics of ellipsoidal grains and the preconfigured thickness on the overestimation degree and valid apparent interface thickness are investigated in a quantitative manner.

Application of convex streamline theory to circular-crested weir

Circular-crested weirs are overflow structures that can be used for flow measurement, water level control in open channels and flood control in reservoirs. Combining Newton's second law for a rectangular fluid particle on a convex streamline with Bernoulli's equation, the differential equation of velocity profile at crest section of circular-crested weir is obtained. This equation was used to derive the discharge coefficient, crest velocity profile and crest pressure profile of the weir. A wide range (0.44 ≤ H/R ≤ 7.56) of existing experimental data of circular-crested weir is used to evaluate the obtained equations. Results of the study indicated that obtained equations have good agreement with experimental data. Also, in comparison with Dressler and potential flow theories, proposed theory predicts the crest velocity profile with the better precision.

Physicochemical Characterization, Solubilization, and Stabilization of 9-Nitrocamptothecin Using Pluronic Block Copolymers

Solid-state properties and physicochemical characteristics of 9-nitrocamptothecin (9NC) were investigated with a view of molecular and bulk level understanding of its poor aqueous solubility and hydrolytic instability that prevent efficient drug delivery and pharmacological activity. 9NC bulk drug substance was found to be a nonhygroscopic, yellowish crystalline solid with long rectangular prism-shaped particle morphology and a sharp melting point at 264°C. Hydrolysis of 9NC-lactone occurs above pH 4, whereas complete conversion of lactone to carboxylate was recorded above pH 8. At saturated conditions, appreciable concentrations of 9NC-lactone were detected at pH as high as 11. 9NC undergoes oxidation in the presence of dimethyl sulfoxide with formation of 9NC-N-oxide. The total solubility of lactone and carboxylate forms of 9NC in deionized water was found to be less than 5 μg/mL, whereas the solubility of 9NC-lactone in aqueous acidic media was determined to be approximately 2.5 μg/mL. Incorporation of 10% pluronic copolymers P123, F127, and F68 in 10 mM HCl increased 9NC solubility by 13-fold, eightfold, and fivefold, respectively. The thermodynamic stability of drug-loaded pluronic micelles was evaluated under isothermal variable volume conditions and found F127, among all poloxamers, to offer the best hydrolytic protection efficacy for 9NC.

Liquid-crystal patterns of rectangular particles in a square nanocavity

Using density-functional theory in the restricted-orientation approximation, we analyze the liquid-crystal patterns and phase behavior of a fluid of hard rectangular particles confined in a two-dimensional square nanocavity of side length H composed of hard inner walls. Patterning in the cavity is governed by surface-induced order as well as capillary and frustration effects and depends on the relative values of the particle aspect ratio κ≡L/σ, with L the length and σ the width of the rectangles (L≥σ), and cavity size H. Ordering may be very different from bulk (H→∞) behavior when H is a few times the particle length L (nanocavity). Bulk and confinement properties are obtained for the cases κ=1, 3, and 6. In bulk the isotropic phase is always stable at low packing fractions η=Lσρ_{0} (with ρ_{0} the average density) and nematic, smectic, columnar, and crystal phases can be stabilized at higher η depending on κ: For increasing η the sequence of isotropic to columnar is obtained for κ=1 and 3, whereas for κ=6 we obtain isotropic to nematic to smectic (the crystal being unstable in all three cases for the density range explored). In the confined fluid surface-induced frustration leads to fourfold symmetry breaking in all phases (which become twofold symmetric). Since no director distortion can arise in our model by construction, frustration in the director orientation is relaxed by the creation of domain walls (where the director changes by 90^{∘}); this configuration is necessary to stabilize periodic phases. For κ=1 the crystal becomes stable with commensurate transitions taking place as H is varied. These transitions involve structures with different number of peaks in the local density. In the case κ=3 the commensurate transitions involve columnar phases with different number of columns. In the case κ=6 the high-density region of the phase diagram is dominated by commensurate transitions between smectic structures; at lower densities there is a symmetry-breaking isotropic to nematic transition exhibiting nonmonotonic behavior with cavity size. Apart from the present application in a confinement setup, our model could be used to explore the bulk region near close packing in order to elucidate the possible existence of disordered phases at close packing.

3D insights into nickel converter matte phases: Direct observations via TEM and FIB SEM tomography

A prior application of mineralogy to the analysis of nickel converter matte was based on two dimensional in-plane projections of three dimensional phase structures. Recent developments in electron microscopy have established suitable techniques to base further analysis on actual three dimensional projections. Focused ion beam scanning electron microscopy tomography in arrangement with transmission electron microscopy was considered suitable in acquiring three dimensional projections of nickel converter matte phase structures at the mesoscale with subsequent reconstruction for 3D visualization and analysis.Transmission electron microscopic section analysis was particularly useful in signifying that phase structures were geometrically arranged within an underlying nickel-sulfide microtexture. Tomography reconstruction and rendering of a rectangular particle volume allowed for color and grayscale based 3D visualization of the nickel-sulfide microtexture, copper-sulfide and NiCu-alloy phase structures. Color based 3D visualization was specifically effective in assigning a cubic morphology to smaller alloy phase structures. Grayscale based 3D visualization of alloy phase structures illustrated compositional zones correlating to the presence of bright Pt-dominant cores and darker Ni-dominant rims. High-fidelity reconstruction of developed Pt-dominant lobes was produced illustrating insightful morphological detail. It would be important to consider the three dimensional insights gained to the downstream metallurgy of nickel converter matte.

Synthesis and characterization of CaTiO3 particles with controlled shape and size

CaTiO3 particles with different morphologies and sizes are synthesized by mixing calcium nitrate and tetrabutyl titanate (Ti(OC4H9)4, TNB) into PEG [poly(ethylene glycol)] with varying water content. Electron microscopy observations reveal that the experimental conditions, such as the temperature of the suspension, NaOH concentration, reaction time and water content, can influence the shape and size of the CaTiO3 particles. The photocatalytic results show that the CaTiO3 rectangular particles have the highest photocatalytic activity.

Synthesis of non-spherical CdSe nanocrystals

Non-spherical CdSe quantum dots were synthesized through high temperature reduction of cadmium and selenium in the presence of TOP (tri-n-octylphosphine) and TOPO (tri-n-octylphosphine oxide). The high affinity of phosphine oxide to the surface of CdSe nanocrystals typically leads to the formation of spherical particles with diameters between 1.5 and 10 nm. However, with lower temperatures and longer reaction times relative to conventional synthesis techniques, the formation of non-spherical nanocrystals dominated. The three reaction temperatures that were studied were 230, 250, and 270 °C. Results verify the need to quench CdSe nanocrystals immediately following the injection of selenium dissolved in TOP (TOPSe) if spherical particles are the desired shape. Nanocrystal shape evolves from sphere to rectangle to hexagon or triangle as the reaction time is extended regardless of temperature. The highest yield of rectangular particles (~89 %) was achieved while maintaining a temperature of 250 °C for 20 min.

Investigation of Particle Impact Phenomena in Powder Jet Deposition Process

Powder jet deposition (PJD) method is one of the blasting methods to generate surface coatings. The optimization of PJD conditions has been reported in our previous research. However, the deposition mechanism in PJD is still under investigation. Impact phenomena between an alumina particle with the mean particle size of 2 μm and a glass substrate has been successfully simulated by smoothed particle hydrodynamics (SPH) method. From the simulation result, we have deduced that a cubic particle is fractured by an impact, and it is adhered on to the substrate. It has been also deduced that substrate is removed by a spherical particle impact. Furthermore, PJD experiments of alumina particles blasted onto a glass substrate were also conducted. The particle size distribution of rectangular particles before and after impact was measured. It was found that the particle sizes after impact averagely became smaller than those before impact. The substrate was partly removed when spherical particles impact. From the results of the simulation and the experiment, we believe that the rectangular particles are fractured due to the impacts at the moment blasting onto the substrate, and then, firmly deposited on the substrate.