Average Aspect Ratio Research Articles

Well-designed Ag/ZnO/3D graphene structure for dye removal: Adsorption, photocatalysis and physical separation capabilities

In this research, adsorption and photocatalytic degradation process were utilized to remove organic dye from wastewater. To accomplish that, a newly-designed ternary nanostructure based on Ag nanoparticles/ZnO nanorods/three-dimensional graphene network (Ag NPs/ZnO NRs/3DG) was prepared using a combined hydrothermal-photodeposition method. The three-dimensional structure of graphene hydrogel as a support for growth of ZnO nanorods was characterized using field emission scanning electron microscopy (FESEM). In addition, diameter of silver nanoparticles grown on the ZnO nanorods with the average aspect ratio of 5 was determined in the range of 30–80 nm by using transmission electron microscopy (TEM). The X-ray diffraction (XRD) pattern was revealed hexagonal Wurtzite structure of ZnO nanorods and the (1 1 1) lattice plane of the face-centered cubic (FCC) of the silver nanoparticles. The dye adsorption capacity of the synthesized 3DG was evaluated at about 300 mg/g using kinetic study. The photocatalytic dye degradation under both UV and visible light irradiation exhibited an enhanced activity of the prepared ternary Ag/ZnO/3DG sample in comparison to ZnO/3DG and 3DG structures. Different charge-carrier scavengers were utilized to elucidate the synergistic effect of adsorption and visible-light photocatalytic degradation mechanism for dye removal. The facile photocatalyst recovery as well as the high elimination rate of dye is promising for future applications such as efficient removal of organic contaminants from industrial wastewater under solar irradiation.

Nitrate ion effect on gold nanorods plasmon resonance behavior: A potential chemical sensor

High sensitivity of surface plasmon resonances (SPR) in noble metals to the surrounding refractive index variations in the environment is a powerful bio-sensing technique. Here, we report the development of a simple colorimetric detection method for nitrate ion in water using gold nanorods (Au-NRs). Au-NRs suspension with the average aspect ratio of 3.5 was prepared by a modified seed growth method. According to the safety limit standard of nitrate amount in drinking water, different volumes of 10 mg/l nitrate solution were added to the Au-NRs suspension. Adding the nitrate group to the suspension resulted in turning to the nanorods with lower aspect ratios and finally spherical nanoparticles. The concentration of nitrate in water can be determined by monitoring with the naked eye and a UV–Vis spectrometer. It was shown that lower volumes of nitrate additive (25 μl) was a better identifier than those with higher volumes (50–150 μl). The color of Au-NRs suspension turned somehow from faint pink to purple after two days of adding 25 μl of nitrate solution. In addition, the UV–Vis absorption peak corresponding to longitudinal SPR (LSPR) blue-shifted from 814 nm to 712 nm after two days while the peak corresponding to transverse SPR (TSPR) showed a slight shift from 519 nm to 521 nm. Much more effect of nitrate group on LSPR than TSPR showed that nanorods are better identifier and biosensors than spherical nanoparticles. Decomposing and converting the Au NRs to sphere particles and lowering the initial aspect ratio of NDs in presence of nitrate ion is reported for the first time, but more works needed for talking about its mechanism.

The Effects of Reaction Conditions on Growth Process of FGD Gypsum Whisker

Taking FGD gypsum as raw materials, gypsum whisker was prepared by using hydrothermal method. The effects of reaction temperature, reaction time, desulfurization gypsum slurry concentration and pH value on the growth of gypsum whisker were deeply researched. The optimum conditions for the preparation were that the reaction temperature was 140 ℃ ~ 145 ℃, reaction time was 200 ~ 240min, the slurry concentration was 13% ~ 15% and the slurry pH value was between 4.5 and 5. In this paper, an aspect ratio model formula of calcium sulfate whisker can be expressed as Average aspect ratio = 15.89x - 0.13y + 14.74z - 63.26m - 0.06x2 - 0.14z2 - 0.81m2 - 0.08xz + 0.38xm - 0.01yz + 0.01ym + 0.67zm - 1043.89, the sign x denotes reaction temperature,℃; y denotes reaction time, min; z denotes slurry concentration, %; m denotes pH value of the slurry.

Effect of temperature on microstructure and mechanical properties of ECAPed (TiB + La2O3)/Ti-6Al-4V composites

TiB short fibers and La2O3 particles reinforced titanium matrix composites (TMCs) were successfully equal-channel angular pressed (ECAPed) at 600 °C–900 °C. The effect of ECAP temperature on the microstructure and mechanical properties of the TMCs was investigated. The results indicated that dislocation tangling formed cell structures in matrix at lower ECAP temperature. In contrast, continuous dynamic recrystallization occurred at higher ECAP temperature, and promoted the formation of numerous new ultrafine grains. The average aspect ratio of TiB short fibers decreased with increasing ECAP temperature, which induced interfacial debonding. The tensile strength of TMCs ECAPed at 800 °C was up to 1128 MPa, which was 18% higher than the as-received composites. Interfacial debonding led TiB short fibers in low aspect ratios disabled to bear load, while the formation of ultrafine grains increased the strength of TMCs. The coupling of these two factors resulted in little effect of ECAP temperature on the tensile strength. However, the elongation of ECAPed TMCs generally decreased due to the loss of strain hardening capacity. Stress concentration tended to occur around the tips of TiB short fibers due to the interfacial debonding and cause crack propagation. It led to the premature fracture and low ductility.

Synthesis of one-dimensional RuO2 nanorod for hydrogen and oxygen evolution reaction: An efficient and stable electrocatalyst

RuO2 nanorod (NR), an efficient and stable catalyst for hydrogen and oxygen evolution reaction is developed via wet-chemical route. Initially, a carbon slurry has been prepared using glucose and urea via heating at 140 °C for 6 h. During the preparation of carbon slurry Ru3+ salt has been added to disperse homogeneously. Finally, calcination at 500 °C for 10 h has been performed using homogeneously distributed Ru3+ ion in carbon slurry to get RuO2 NR. The synthesized RuO2 NR has been well characterized using FESEM, TEM, PXRD, and XPS analysis. The average aspect ratio of a single RuO2 rod is ∼4.37. The synthesized RuO2 NR has been used extensively as an electrocatalyst for hydrogen and oxygen evolution reaction. RuO2 NR shows cathodic potential of −130 mV vs. RHE to achieve current density of 10 mA/cm2 during hydrogen evolution reaction. Whereas, for oxygen evolution 1.508 V vs. RHE is required to generate 10 mA/cm2 current density. Electrochemically active surface area and Tafel slope have been calculated to exhibit better activity of RuO2 NR as compared to commercial RuO2. The overall electrocatalysis mechanism has also been discussed in detail.

Wire electrochemical micromachining of high-aspect ratio microstructures on stainless steel 304 with 270-μm thickness

High-aspect ratio microstructures made of stainless steel 304 have found its extensive applications in the microsystem industry. Using a nanosecond pulse generator, high-aspect ratio components can be obtained by wire electrochemical micromachining (WEMM). Mass transport is substantially vital in WEMM to achieve high aspect ratio. Combining traveling and vibrating anode can effectively improve mass transport and consequently enhances machining result. When workpieces become thicker, mass transport would get worse. Many researchers have investigated the fabrication of microstructures on 304SS plate with thickness of 100 μm using WEMM. However, not enough attention has been paid to the machining of microstructures on 304SS plates with thickness of more than 100 μm which is an alternative to obtain high aspect ratio. Moreover, the parameters used for 100-μm-thick 304SS are not suitable for thicker 304SS. Therefore, it is necessary to investigate the fabrication of high-aspect ratio microstructures on 304SS plates with thickness of more than 100 μm. In this work, the machining of micro slits on 270-μm-thick 304SS plates by WEMM was investigated. A combination of traveling wire and vibrating anode was also employed to enhance mass transfer. The effects of traveling wire parameters and vibrating anode parameters on the slit width and slit profile were researched. Experimental results show that the stroke and traveling speed of the traveling wire together with frequency and amplitude of the vibrating anode for 270-μm-thick 304SS plates are higher than those for 100-μm-thick 304SS plates. The average slit width machined with optimized parameters using WEMM is 26 μm and the standard deviation is about 1.3. In the meantime, the slit profile is smooth, and the average aspect ratio is about 10.

Cellulose nanocrystals from Miscanthus fibers: insights into rheological, physico-chemical properties and polymer reinforcing ability

Cellulose nanocrystals (CNC) were extracted from Miscanthus (MST) fibers using a sulfuric acid hydrolysis process. The results showed that the obtained CNC exhibit a needle-like shape with an average aspect ratio of 37. The surface charge density was measured at 1.99 sulfate groups per 100 anhydroglucose units while the zeta potential value was found to be -38 mV. The crystallinity of the extracted CNC was 76%, and the cellulose I type crystal structure was predominant. Due to its high importance for potential application of CNC in aqueous systems, the rheological behavior of CNC aqueous suspensions at various CNC concentrations was determined. The CNC suspensions showed gel-like behavior at very low CNC concentrations ranging from 0.1 wt% up to 0.6 wt%, as confirmed by the steady shear viscosity measurements and the oscillatory dynamic tests. The dynamic rheological parameters of CNC suspensions were slightly affected by the temperature profile. At high temperature up to 80 °C a stronger CNC network is formed by increasing the relative motion resistance of CNC macromolecules and the entanglement. In order to identify the reinforcing ability of the newly extracted CNC, starch-based nanocomposite films were produced with various CNC contents (1, 3, 5 and 8 wt%) and their tensile properties were investigated. It was found that the addition 8 wt% CNC within starch matrix increased the Young’s modulus by 150% and the tensile strength by 118%, resulting in mechanically strong and eco-friendly nanocomposite materials.

Development of Cell Analysis Software to Evaluate Fibroblastic Changes in Cultivated Corneal Endothelial Cells for Quality Control.

To develop software to evaluate the fibroblastic morphological changes in cultured human corneal endothelial cells (HCECs) as a quality control measure for use in tissue engineering therapy. Software was designed to recognize cell borders, to approximate cell shape as an ellipse, and to calculate the aspect ratio of the ellipse as an indicator of severity of the fibroblastic morphological change. Using the designed software, 60 phase contrast images of polygonal HCECs and 60 phase contrast images of fibroblastic HCECs were analyzed. The correlations of the aspect ratio and other parameters (cell density, percentage of cells surrounded by 6 cells, and coefficient of variation) were evaluated. Cell shapes were recognized based on phase contrast images and were approximated as ellipses by software. The average aspect ratio was significantly higher (34.9% ± 6.1%) in fibroblastic HCECs than in polygonal HCECs (24.4% ± 2.3%) (P < 0.01). The aspect ratio showed a correlation with cell density, with the percentage of cells surrounded by 6 neighboring cells, and with the coefficient of variation (Pearson correlation coefficients, -0.84, -0.38, and 0.66, respectively). We propose that fibroblastic alteration of HCECs can be evaluated by the cell morphology based on the aspect ratio. Software developed in this study, which can analyze the frequency and severity of fibroblastic alteration, will be useful for nondestructive assessment of cells destined for use in cell-based therapy for corneal endothelial decompensation.

The Main Belt Asteroid Shape Distribution from Gaia Data Release 2

Abstract Gaia Data Release 2 includes observational data for 14099 pre-selected asteroids. From the sparsely sampled G-band photometry, we derive lower-limit light curve amplitudes for 11665 main belt asteroids (MBA) in order to provide constraints on the distribution of shapes in the asteroid main belt. Assuming a triaxial shape model for each asteroid, defined through the axial aspect ratios a &gt; b and b = c, we find an average b/a = 0.80 ± 0.04 for the ensemble, which is in agreement with previous results. By combining the Gaia data with asteroid properties from the literature, we investigate possible correlations of the aspect ratio with size, semimajor axis, geometric albedo, and intrinsic color. Based on our model simulations, we find that MBAs greater than 50 km in diameter on average have higher b/a aspect ratios (are rounder) than smaller asteroids. We furthermore find significant differences in the shape distribution of MBAs as a function of the other properties that do not affect the average aspect ratios. We conclude that a more detailed investigation of shape distribution correlations requires a larger data sample than is provided in Gaia Data Release 2.

Isolation and characterization of cellulose nanocrystals from pueraria root residue.

Cellulose nanocrystals (CNCs) were successfully fabricated from waste pueraria root residue after starch extraction via the phosphoric acid hydrolysis method by a series of chemical treatment processes including ultrasonic washing, pectin elimination, bleaching, alkali boiling, and phosphoric acid hydrolysis. The high aspect ratio of CNCs with a crystallinity index of 60 ± 4.10% was observed by X-ray diffraction (XRD) and transmission electronic microscopy (TEM). The TEM results showed that CNCs were rod-like particles with 100-330 nm in length and 2 to 6 nm in width. The average aspect ratio of the CNCs was 40 ± 10. The XRD results also indicated that the crystalline structure of CNC was cellulose I, compared to that of MCC with the crystallinity index declining from 60 ± 4.10% to 48 ± 0.37%. The FTIR spectra showed the resulting samples were the cellulose species. Interestingly, stable colloidal suspensions were determined by the zeta potential measurement. The thermal properties of CNCs were investigated by thermogravimetric analysis, revealing that CNCs exhibited lower thermal stability compared to those of MCC and the raw pueraria root residue. This study provides a cost effective method and mild process conditions for preparing CNCs from waste pueraria root residue.

Effect of Coherent Lattice Mismatch on the Morphology and Kinetics of Ordered Precipitates

The morphological evolution and precipitation kinetics of ordered precipitates under the influence of lattice mismatch were studied by using the phase field model. The variation of the average aspect ratio of the precipitates and their distributions was investigated quantitatively, and the relationship of particles shape and particles fraction with the variation of the aspect ratio was determined. As the lattice mismatch increases, the coarsening rate constants and the particles number density decrease, the particles size distribution (PSD) becomes narrower, and the peak value of the PSD becomes lower than the value obtained by the Lifshitz–Slyozov–Wagner theory, while it is close to the value obtained by the Brailsford–Wynblatt theory. The change rate of the particles number density shows four-stage characteristics and decreases as the lattice mismatch and time increase, indicating that the precipitation and coarsening are retarded for a large lattice mismatch and that a large lattice mismatch results in fewer particles being dispersed in the matrix phase. The morphology and the particles number density show that a suitable lattice mismatch can enhance the mechanical properties of the alloys.

Development of sustainable biodegradable lignocellulosic hemp fiber/polycaprolactone biocomposites for light weight applications

Biocomposites with poly(ε-caprolactone) (PCL) as matrix and lignocellulosic hemp fiber with varying average aspect ratios (19, 26, 30 and 38) as reinforcement were prepared using twin extrusion process. The influence of fiber aspect ratio on the water absorption behavior and mechanical properties are investigated. The percentage of moisture uptake increased with the aspect ratio, following Fickian behavior. The hemp fiber/PCL biocomposites showed enhanced properties (tensile, flexural and low-velocity impact). The biocomposite with 26 aspect ratio showed the optimal properties, with flexural strength and modulus of 169% and 285% respectively, higher than those of neat PCL. However, a clear reduction on the mechanical properties was observed for water-immersed samples, with reduction in tensile and flexural moduli for the aspect ratio of 26 by 90% and 62%, respectively than those of dry samples. Summarily, the optimal sample provides an eco-friendly alternative to conventional, petroleum-based and non-renewable composites for various applications.

Precipitation location of secondary phase and microstructural evolution during static recrystallization of as-cast Ti-25V-15Cr-0.3Si titanium alloy

Abstract The microstructural evolution and precipitation location of the secondary phase of an as-cast Ti-25V-15Cr-0.3Si titanium alloy were investigated via isothermal compression experiments and heat treatment. The average aspect (length-to-width) ratio, average area and size of the grains at different heat treatment temperatures and holding time were analyzed and the effects of deformation and annealing time on the grain area and size were considered. It was found that the grain size was strongly influenced by the height reduction and holding time. Grain growth was significant when annealing time increased from 10 min to 2 h at 950 °C and height reduction of 30%; however, grain growth was minimal at annealing time between 2 and 4 h. Many dispersion particles were observed to form in continuous chains; the precipitation location was confirmed to be along initial grain boundaries, and the dispersion particles were identified to be Ti5Si3 phase by TEM.

Aspect ratio control and photocatalytic properties analysis of anatase TiO2 nanoparticles

Anatase TiO2 nanoparticles with tuning size and aspect ratio were successfully prepared by a simple solvothermal method, using ethanol as a solvent, titanium butoxide as a precursor, and oleic acid and oleylamine as anionic and cationic capping agents, respectively. The average size and aspect ratio of these nanoparticles can be greatly regulated by varying the oleic acid/oleylamine molar ratio while keeping their total molar content constant and finely adjusted by increasing the total capping agents molar concentration in solvent at constant molar ratio (oleic acid/oleylamine molar ratio = 1:1). The variation of molar ratio or molar concentration enables a manipulation of the growth rate along different facets of TiO2 nanoparticles and, consequently, a control of the aspect ratio of these nanoparticles. Moreover, the photocatalytic degradation rate of methyl blue for sample prepared with molar ratio of oleic acid to oleylamine at 6:24 is over 11% higher than that for the other samples.

In situ synthesis of hydrophobic calcium sulfate hemihydrate whiskers

A simple hydrothermal method was developed in this study to synthesize hydrophobic calcium sulfate hemihydrate whiskers in the presence of stearic acid. The morphology of the whiskers synthesized under different conditions was characterized by scanning electron microscopy, and their average aspect ratio was also estimated. The optimum synthesis conditions are determined as follows: the concentrations of Na2SO4 and CaCl2 solution for preparing the precursor are 1.1 mol L−1; the precursor content in the autoclave is 10 wt%; the hydrothermal reaction temperature is 150 °C; and the hydrothermal reaction time is 4 h, respectively. Glycol was used to promote the dispersion of stearic acid in the seriflux. The results show that the hydrophobic calcium sulfate hemihydrate whiskers can be obtained with stearic acid as surfactant, and their average aspect ratio can reach about 91.

Study on the Size Reduction Characteristics of Miscanthus sacchariflorus via Image Processing

Size reduction is an important pre-processing operation for utilizing biomass as a sustainable resource in industrial-scale energy production and as a raw material for other industries. This work investigates the size reduction characteristics of air-dried Miscanthus sacchariflorus Goedae-Uksae 1 (Amur silver grass) via image processing and identifies the morphological characteristics of comminuted and screened M. sacchariflorus. At chopping lengths of 18, 40, 80, and 160 mm, 81%, 77%, 78%, and 76% of the particles, respectively, passed through a 4-mm sieve. Even a knife mill with a very small screen aperture (&gt;1 mm) admitted over 10% of the particles. The average circularity and aspect ratio of the particles were &lt;0.30 and &gt;10, respectively. These results confirm that in all preparation modes, most M. sacchariflorus particles were needle-like in shape, irrespective of the type of preparation.

Heteromorphic Polymer Nanoparticles in Response to Rotational Magnetic Fields for Stirring inside Living Cells

Heteromorphic polymer nanoparticles containing iron oxide particles were prepared to obtain a nanometer-sized magnetic stir bar that remotely responds to external magnetic fields. The polymer nanoparticles were prepared by the mini-emulsion polymerization of styrene with small amounts of a cross-linker, and the spherical nanoparticles obtained were incorporated into a poly (vinyl alcohol) (PVA) film. The PVA film was stretched and deformed at 160°C to make the nanoparticles heterogeneous. The dimensions of the polymer nanoparticles with a heterogeneous morphology and rugby ball-like shape were about 210 nm ×100 nm with an average aspect ratio greater than 2.0. The dispersion ability of the nanoparticles was sufficient to use in aqueous circumstances. When an external magnetic field was applied to an aqueous suspension of the nanoparticles, the particles aggregated quickly. Also, on the application of a rotational magnetic field, the polymer nanoparticles began rotating with a velocity proportional to the rate of the external magnetic field rotation. Therefore, it was concluded that the heteromorphic polymer nanoparticles have the potential to stir a micrometer-scale reaction vessel, such as living cells.

Preparation of α-CaSO4·½H2O with tunable morphology from flue gas desulphurization gypsum using malic acid as modifier: A theoretical and experimental study

Huge amount of flue gas desulphurization (FGD) gypsum not only occupies the farmland but also causes severe pollution to the surrounding environment. The most effective way to achieve a high-value utilization of FGD gypsum is to prepare short columnar α-calcium sulfate hemihydrate (α-HH) since short columnar crystals show better mechanical strength than needle-like ones. Here, malic acid, a prolific, inexpensive and environment-friendly modifier was explored for the first time to effectively tune the crystal morphology of α-HH prepared from FGD gypsum in glycerol-water-NaCl solutions. When the concentration of malic acid reached 18.54 × 10−4 mol/kg, α-HH crystals with an average aspect (length-to-diameter) ratio of 1.9 (compared to 29.4 in the absence of malic acid) were prepared. The selective complexation of malic acid with Ca active sites on different α-HH crystal planes played a dominant role in the α-HH crystal morphology transformation, which was then explained by the surface broken bonds theory for the first time. The broken bond number per active Ca atom (Nbper Ca) and broken bond density of Ca atoms (DbCa) on the (2 0 4) end plane were larger than those on the (0 2 0) or (2 0 0) side planes. Therefore, the (2 0 4) end plane was more reactive with organics, resulting in the preferential adsorption of malic acid on the end planes, which reduced the specific surface energy of (2 0 4) and led to an increased exposure of this plane and a decreased exposure of (0 2 0) or (2 0 0) side planes in the final α-HH crystals. Consequently, using malic acid as modifier, the α-HH crystal gradually transformed from a needle-like shape to a short columnar one. This work provided important insights into and perspectives for the selection of crystal modifiers and explanation of the mechanism during the preparation of calcium-containing crystals with controllable morphology.

Verteporfin-Loaded Poly(ethylene glycol)-Poly(beta-amino ester)-Poly(ethylene glycol) Triblock Micelles for Cancer Therapy.

Amphiphilic polymers can be used to form micelles to deliver water-insoluble drugs. A biodegradable poly(ethylene glycol) (PEG)-poly(beta-amino ester) (PBAE)-PEG triblock copolymer was developed that is useful for drug delivery. It was shown to successfully encapsulate and pH-dependently release a water-insoluble, small molecule anticancer drug, verteporfin. PEG-PBAE-PEG micelle morphology was also controlled through variations to the hydrophobicity of the central PBAE block of the copolymer in order to evade macrophage uptake. Spherical micelles were 50 nm in diameter, while filamentous micelles were 31 nm in width with an average aspect ratio of 20. When delivered to RAW 264.7 mouse macrophages, filamentous micelles exhibited a 89% drop in cellular uptake percentage and a 5.6-fold drop in normalized geometric mean cellular uptake compared to spherical micelles. This demonstrates the potential of high-aspect-ratio, anisotropically shaped PEG-PBAE-PEG micelles to evade macrophage-mediated clearance. Both spherical and filamentous micelles also showed therapeutic efficacy in human triple-negative breast cancer and small cell lung cancer cells without requiring photodynamic therapy to achieve an anticancer effect. Both spherical and filamentous micelles were more effective in killing lung cancer cells than breast cancer cells at equivalent verteporfin concentrations, while spherical micelles were shown to be more effective than filamentous micelles against both cancer cells. Spherical and filamentous micelles at 5 and 10 μM respective verteporfin concentration resulted in 100% cell killing of lung cancer cells, but both micelles required a higher verteporfin concentration of 20 μM to kill breast cancer cells at the levels of 80% and 50% respectively. This work demonstrates the potential of PEG-PBAE-PEG as a biodegradable, anisotropic drug delivery system as well as the in vitro use of verteporfin-loaded micelles for cancer therapy.

Effects of Cr content on the microstructure and mechanical properties of Mo2FeB2-based cermets prepared via vacuum sintering

Six series of cermet samples with Cr contents between 0 and 12.5 wt.% in 2.5 wt.% increments were prepared by vacuum sintering. The transverse rupture strength (TRS), hardness (HRA) and fracture toughness (K1C) were also measured. It was discovered that the grain size was affected by the Cr content. As the Cr addition increased, the average grain size and aspect ratio of the Mo2FeB2 hard phase decreased, while the lattice constant ratio c/a increased. Consequently, the particle morphology gradually transformed from elongated to nearly equiaxed. The transverse rupture strength and hardness of the cermets firstly increased and following decreased slightly as the Cr content increased, while the fracture toughness gradually decreased. The cermets with 10 wt.% of Cr addition exhibited the lowest grain size. The cermets with 10 wt.% of Cr addition demonstrated the TRS, hardness and fracture toughness values of 2124.1 MPa, 89.0HRA and 23.8 MPa m1/2, respectively.