Significant Reduction In Particle Size Research Articles

Extraction of oxidized nanocellulose from date palm (Phoenix Dactylifera L.) sheath fibers: Influence of CI and CII polymorphs on the properties of chitosan/bionanocomposite films

Packaging has increasingly become a dominant factor in the global market competitiveness. This implies we should obtain new raw materials with improved packaging properties. In particular, oxidized nanocelluloses, obtained from locally cultivated date palm sheath fibers, were extracted by ammonium persulfate treatment of unbleached pulp and mercerized date palm sheath fibers. The influence of reaction parameters (e.g. ammonium persulfate concentration 0.5–1.5 M, duration 8–20 h and temperature 50–80 °C) were studied. A significant particle size reduction, surface charge density diminishing and thermal stability enhancement resulted as a consequence of the ammonium persulfate hydrolysis. The extracted oxidized nanocelluloses, at the optimum conditions, were used as a packaging additive in chitosan films. The physicochemical and mechanical analyses of the resulting bionanocomposite films show potential improvements in water vapor barrier and strength properties.

Cataclasis and silt smear on normal faults in weakly lithified turbidites

Fault-seal analysis in sand-shale multilayers emphasises the role of shale smear without explicitly accounting for cataclasis. These processes produce low-permeability fault rock and are examined here for small displacement (0.001–70 m) normal faults displacing weakly lithified turbidites comprising ∼55–80% lithic grains. Late Miocene Mount Messenger Formation (MMF) turbidites from the North Island of New Zealand provide fault rock data over a range of scales from individual grains (∼0.1–350 μm) to the height of coastal cliffs (∼10–20 m). Fault rock and unfaulted source beds has been analysed using thin sections, SEM images, particle-size distribution (PSD) measurements and outcrops of faults mainly in cross section. Cataclasis associated with particle size and macroscopic porosity reduction of protolith sandstones commences at low fault shear strains (<1) and continues as fault displacement accrues. The relationship between particle-size reduction and displacement is non-linear with initial rapid cataclasis facilitated by disaggregation of weak lithic and altered feldspar grains along pre-existing grain defects (e.g., grain boundaries, fractures and altered cleavage planes). Silt smear, by contrast, is not accompanied by significant particle-size reduction and appears to have been achieved by intergrain slip and micro-faulting. Despite the occurrence of silt smear, cataclasis can produce a significant proportion (>50%) of the total fault-rock in sand-silt multilayers. The resulting fault-rock thickness varies by up to three orders of magnitude for a given fault displacement and at short distances (2–10 m) along individual faults. Variations in fault-rock thickness and associated cataclasis have the potential to modify the hydraulic properties of faults and may need to be accounted for in fault-seal analysis.

Particle Size Analysis of Nano-sized Talc Prepared by Mechanical Milling Using High-energy Ball Mill

Talc, hydrous magnesium phyllosilicate, is one of the most popular industrial minerals due to their chemical stability and adsorptivity. While micro-sized talc has long been used as a filler and coating, nano-sized talc recently is attracting attention as additives for improving the stability of nanocomposites. In this study, we produced the nano-sized talc powder by mechanical method using high energy ball mill and investigated the changes in particle size and crystallinity with increasing milling time up to 720 minutes. X-ray diffraction results show that the peak width of talc gradually as the milling proceeded, and after 720 minutes of pulverization, the talc showed an amorphous-like X-ray diffraction pattern. Lase diffraction particle size analysis presents that particle size of talc which was ~12 μm decreased to ~0.45 μm as the milling progressed, but no significant reduction of particle size was observed even after grinding for 120 minutes or more. BET specific surface area, however, steadily increases up to the milling time of 720 minutes, indicating that the particle size and morphology change steadily as the milling progressed. Scanning electron microscope and transmission electron microscope images shows that layered particles of about 100 to 300 nm was aggregated as micro-sized particles after pulverization for 720 minutes. As the grinding time increases, the particle size and morphology of talc continuously change, but the nano-sized talc particles form micro sized agglomerates. These results suggest that there is a critical size along the a, b axes in which the size of plates is reduced even though the grinding proceeds, and the reduction of plate thickness along the c axis leads the increase in specific surface area with further grinding. This study could enhance the understanding of the mechanism of the formation of nano-sized talc by mechanical grinding.

Graphene‐Tailored Thermodynamics and Kinetics to Fabricate Metal Borohydride Nanoparticles with High Purity and Enhanced Reversibility

AbstractDue to their ultrahigh theoretical capacity, metal borohydrides are considered to be one of the most promising candidate hydrogen storage materials. Their application still suffers, however, from high operating temperature, sluggish kinetics, and poor reversibility. Designing nanostructures is an effective way of addressing these issues, but seeking suitable approaches remains a big challenge. Here, a space‐confined solid‐gas reaction to synthesize Mg(BH4)2 nanoparticles supported on grapheme is reported, which serves as the structural support for the dispersed Mg(BH4)2 nanoparticles. More notably, density functional theory calculations reveal that graphene could weaken both the MgH bonds of MgH2 and BB bonds of B2H6, which could thermodynamically and kinetically facilitate the chemical transformation to synthesize Mg(BH4)2 with high purity. Because of the synergistic effects of both the significant reduction in particle size and the catalytic effect of graphene, an onset dehydrogenation temperature of ≈154 °C is observed for Mg(BH4)2 nanoparticles, and a complete dehydrogenation could be achieved at a temperature as low as 225 °C, with the formation of MgB2 as the by‐product. This work provides a new perspective to tailoring the thermodynamics and kinetics of chemical reactions toward the favorable synthesis of functional inorganic materials.

Comparison of different sintering methods of Pb1−xCrxTe thermoelectric nanocomposites doped with iodine

N-type PbTe polycrystals were fabricated by the Bridgman method. Subsequently, the materials were pulverized in a planetary ball mill for 15h, pressed and sintered. In this paper we compare two sintering techniques: cold pressing followed by the sintering in a furnace (CPS) and the spark plasma sintering (SPS). The electrical and thermoelectric measurements were conducted for both materials (CPS and SPS) and the results are presented and discussed in the paper. Maximal ZT values of 0.2 and 0.45 were obtained for the CPS and SPS materials, respectively. Additionally, SEM and EDX analyses were performed. To determine the obtained crystallites size, the X-ray diffraction measurements were carried out. The obtained results show that the significant reduction in particle size may be obtained by the milling procedure - from a few milimeters in the polycrystalline material to a few tens of nanometers for the powdered one.

Effect of high pressure homogenization (HPH) on microstructure and rheological properties of hazelnut milk

Abstract The effect of high pressure homogenization (HPH) on microstructure and rheological properties of hazelnut milks was investigated. Hazelnut milk samples were produced from cold pressed hazelnut cake and homogenized up to 150 MPa pressure. Microstructural and rheological properties of products, except temperature sweep, were greatly affected by HPH treatments. Homogenized samples showed significant reduction in particle size, which turned from bimodal and poly-disperse to monodisperse distributions. HPH decreased the consistency of products from 91.82 to 0.51 Pa.sn and increased flow behavior index from 0.15 to 0.36. All samples showed higher values G′ than G″, which indicates that samples could be classified as soft-gel network, and hazelnut milk samples did not obey the Cox-Merz rule without multiplying angular frequency with shift factor. In conclusion, HPH can be used to reduce the consistency of samples and the friction loss, thus minimizing the amount of energy required to flow during processing and distribution. Industrial relevance. Vegetable based beverages are available at any supermarket as an alternative to dairy products with an increasing consumer acceptance. Between these beverages hazelnut milk samples are the most noteworthy products due to important role in human nutrition and health, and moreover due to well accepted and widely consumed product. Due to its composition, hazelnut milks have very high consistency, and therefore, the energy consumption for processing and handling is too high. In this research, the high pressure homogenization (HPH) technology was successfully proposed to be used for improving microstructural properties, and hence reducing its consistency. The energy consumption during processing and distribution can be minimized by reducing the consistency and friction losses of product.

An experimental study of the local electronic structure of B-site gallium doped bismuth ferrite powders

The un-doped and gallium (Ga) doped multiferroic bismuth ferrite (BiFeO3) compounds were successfully synthesized by the hydrothermal technique. This is then followed by a series of detailed investigations into the influence of Ga doping on the structural, morphological, optical and magnetic properties of BiFe1−xGaxO3(0≤x≤0.15). X-ray diffraction (XRD) analyses reveal that B-site doping of Ga may lead to the transformation of its crystal structure from a rhombohedral with a space group of R3c to an orthorhombic with a space group of Pbnm phase. The scanning electron microscope (SEM) images show that doping with Ga causes a significant reduction in particle size, when compared to un-doped BiFeO3. X-ray absorption near-edge structure (XANES) spectra have also shown that as the substitution of Ga increases, the Fe K and Bi LIII-edge absorption spectra shift towards higher energy site. It also implies that doping of Ga affects the local structures of both Bi and Fe atoms. Distinct transmission band fluctuations, as shown by Fourier transform infrared (FT-IR) spectra, can provide significant evidence for a transformation in crystal structure, following the increase of Ga concentration. The magnetization hysteresis measurements show that the magnetization decreases when Ga content is x≥0.05. Such a phenomenon mainly stems from the substitution of Fe for an excessive amount of Ga, resulting in reduction of both valence fluctuations and the magnetization in the BiFe1−xGaxO3 system.

Ultrasonic degradation kinetics and rheological profiles of a food polysaccharide (konjac glucomannan) in water

This study was carried out to evaluate the effects of power ultrasound (US) on the molecular weight and rheological properties of a food polysaccharide, konjac glucomannan (KGM). Upon the exposure of KGM solution (1% w/v in water) to US at a relatively high power intensity (50 W/cm2), the apparent viscosity decreased rapidly from about 50 Pa s to a negligible level within 10–20 min. The intrinsic viscosity ([η]) of KGM solution decreased gradually during the US exposure with a time course closely fitted to the first-order polymer degradation kinetics (random chain scission). The US treatment also caused a significant reduction of particle size (Zavg) of KGM aggregates and changes in the rheological properties including the decrease of storage modulus (G′) and loss modulus (G″), and the increase in phase angle (tan δ = G″/G′). Nevertheless, no change in primary structure was detected by Fourier transformation infrared (FT-IR) analysis. The results suggested that high intensity US was an effective means for KGM degradation without significant structural destruction.

Effects of flaxseed gum concentrations and pH values on the stability of oil-in-water emulsions

This study investigated the effects of flaxseed gum (FG) concentrations (0.1–0.5%, w/w) and pH values (5.0, 6.0 and 7.0) on the stability of 10% (w/w) liquid lard emulsions. The emulsions were analyzed for particle size, rheological properties, creaming stability, optical microscopy and nuclear magnetic resonance (NMR) measurement. With the increase of FG concentration, there was an improved packing of polysaccharide onto the droplet surface, which caused a significant reduction in particle size, with the smallest oil droplets being formed in 0.5% (w/w) FG emulsions. Rheological and creaming stability measurements showed that FG solutions had thickening and gelling properties. When FG concentration increased to greater than 0.3% (w/w), the samples no longer exhibited creaming behavior, and pH values no longer had significant effect on the emulsion stability. Shorter spin-spin relaxation time (T2, by low-field 1H NMR) were observed for emulsions containing 0.1% (w/w) and 0.2% (w/w) FG, suggesting more restriction of mobility of oil droplets. The increased line-width in high-field 1H, 13C NMR spectra with increasing FG concentration indicated an increased interaction between FG and oil molecules. These results showed that FG had the potential to substitute for protein emulsifiers which is sensitive to pH to stabilize the emulsion-type products.

Low-Temperature Synthesis and Surface Modification of High Surface Area Calcium Hydroxyapatite Nanorods Incorporating Organofunctionalized Surfaces

A new low-temperature continuous approach for the surface modification of hydroxyapatite (HA) is described. In this method, the HA particle surfaces were modified using methacrylic acid, vinylphosphonic acid, adipic acid, citric acid, or polyvinyalcohol, respectively, using a continuous plastic flow synthesis (CPFS) system at a reaction temperature of 70 °C for 5 min. The materials were investigated using a range of analytical techniques, including TEM (transmission electron microscopy), zeta potential, XRD (X-ray diffraction), BET (Brunauer–Emmett–Teller) surface area analysis, FTIR (Fourier transform infrared) spectroscopy, and XPS (X-ray photoelectron spectroscopy). The presence of organic agents in the reagents, resulted in a significant reduction in particle size of the nano-HA rods; TEM studies confirmed the formation of highly dispersed nanorods of HA with average lengths and diameters in the ranges 20–60 nm and 4–10 nm, respectively. XPS analyses suggested that the Ca:P molar ratio decreased from ...

Effect of Cr3+ substitution on electric and magnetic properties of cobalt ferrite nanoparticles

This work describes the effect of incorporation of Cr3+ into CoFe2O4 nanoparticles on its magnetic and electric properties, prepared by auto combustion method. The samples of CoFe2-xCrxO4 (x = 0, 0.15, 0.3) series were characterized by x-ray diffraction and field emission scanning electron microscopy to find out the average particle size. The substitution of Cr3+ caused a significant reduction in particle size of the modified systems. Room temperature Mossbauer spectroscopy and magnetic characterization were performed. Analysis of extracted parameters concluded that Cr3+ replaced the Fe3+ at B-site (octahedral). The decrease in magnetization at B-site was found responsible for the observed reduced saturation magnetization and coercivity. Impedance spectroscopic analysis has revealed the suppression of electrode-sample surface conduction effect and enhancement of material resistivity. The latter was confirmed by dc resistivity measurement. All these results were explained on the basis of occupancy of Cr3+ at B-site, surface anisotropy potential and reduced particle size.

Preparation of Nickel Oxide-Samarium-Doped Ceria Carbonate Composite Anode Powders by Using High-Energy Ball Milling for Low-Temperature Solid Oxide Fuel Cells

The characteristics of the starting powder in powder preparation method are important for enhancement of cell performance. In this study, the composite anode powders of NiO–samarium-doped ceria carbonates (SDCC) were prepared by using different NiO loadings (50–70 wt.%) via high-energy ball milling. The composite anode powders were ball-milled in ethanol at a milling speed of 550 rpm. The obtained NiO–SDCC composite anode powders were characterized by XRD, FTIR, FESEM, and EDS. Results indicate that the composite anode powders demonstrated good chemical compatibility between NiO and SDCC, given that no new phases were detected in the XRD analysis. FTIR spectra confirmed that the composite anode powders contain carbonates in amorphous state after high-energy ball milling. FESEM investigation revealed well-distributed fine particles and significant reduction of particle size at nanoscale compared with the powder prepared using NiO particles as the starting material. EDS mapping verified the homogeneity of the composite powder with good elemental distribution. Thus, high-energy ball milling is an effective method to prepare NiO–SDCC composite anode powders within a relatively short processing time.

Particle Size, Morphology and Color Characteristics of C.I. Pigment Red 57:1 : 2. Effect of Salt Milling Process

The effect of salt milling process on the crystal size, morphology, and color characteristics of C.I. Pigment Red 57:1 was studied. The primitive morphology and color properties of the pigment after synthesis were studied in the former series work. The size and morphology of primary particles and the second aggregation features should be considered because they are very important to determine pigment quality. We compared the primary morphology of pigment particles before drying with the secondary aggregated morphology of pigment particles after drying and salt milling process. Morphological properties were investigated by particle size analysis, X-ray diffraction, and scanning electron microscopy and color measurement was carried out. Significant reduction in particle size as well as enhanced crystallite size after salt milling process was observed. This result might give a difference in color of the pigment, turning into brighter and more blue-toned red color. It was revealed that synthesis condition affect the morphology and color of the pigment even after milling. Increase in HCl concentration in the synthesis process enhanced crystal size and quality forming bluer-red pigments but an increase in concentration resulted in more amorphous crystals forming darker-red pigments after salt milling.

Influence of the polymorphism of cellulose on the formation of nanocrystals and their application in chitosan/nanocellulose composites

ABSTRACTIn this study, we evaluated the physicochemical properties of the chitosan/nanocellulose composites. Wide‐angle X‐ray scattering was applied to define the supermolecular structure of the materials, the laser diffracting technique was used to characterize the particle sizes, and scanning electron microscopy was used to evaluate the morphologies of the samples. The tensile properties of the composite films were also determined. Cellulose pulp was mercerized with 16% sodium hydroxide to give only cellulose II. Cellulose I and cellulose II were subsequently hydrolyzed with 64% sulfuric acid. As a result, nanocellulose I (NCC I) from cellulose I and nanocellulose II (NCC II) from cellulose II were produced. The mercerization of cellulose pulp contributed to a significant particle size reduction; more than 50% of the particles of the NCC II sample and only 36% of the particles of the NCC I sample were smaller than 100 nm. Chitosan composite films containing 5, 10, and 20% w/w of nanocelluloses were prepared by a solvent casting method. This was the first study investigating the influence of the crystallographic forms of cellulose on the formation of nanocrystals. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 42864.

Power Ultrasound Assisted Design of Egg Albumin Nanoparticles

The objective of this work was to develop egg white (EW) nanoparticles by application of high intensity ultrasound (HIUS) at different solution pHs and treatment temperatures. At pH 7 HIUS without heating decreased the particle size. In contrast, the use of thermosonication (TS) increased the particle size. At pH 3, the application of both HIUS and TS induced a significant reduction of particle size. at pH 7 zeta potential did not vary significantly when native solutions were sonicated without heating; however a great decrease was observed when TS or heating were applied. At pH 3, sonication decreased the zeta potential of particles but TS or heating increased the charge. By applying TS (85 °C, 20 min and pH 3) a bimodal distribution was obtained, including particles of 295 and 70 nm of diameter. At the same pH, without heating, a monomodal population of 220 nm of diameter was obtained.

Controlling the size and morphology of griseofulvin nanoparticles using polymeric stabilizers by evaporation-assisted solvent–antisolvent interaction method

Griseofulvin (GF) is a potential drug for cancer therapy. However, its application is limited by its poor water solubility. Ultrafine GF nanoparticles were prepared through evaporation-assisted solvent–antisolvent interaction method for improving its solubility. Acetone was used as the solvent and water was used as the antisolvent. It was observed that particle size could be controlled by varying the concentration of GF in acetone. Average particle size was very low, 16 ± 4 and 28 ± 8 nm, when the concentration of GF was 5 and 25 mM, respectively, in acetone. However, the particle size increased drastically to more than 3 µm, when the concentration was increased to 50 mM. Interestingly, the presence of optimized concentration of polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) as stabilizers in the antisolvent resulted in significant reduction of particle size. Particle size decreased to less than 40 nm in the presence of the polymeric stabilizers, even when the concentration was 50 mM. Field emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy imaging revealed that the polymeric stabilizers encapsulated very small GF particles and thus stabilized them. The solubility of GF-HPMC, GF-PVP, and the bare GF particles that were prepared from 50 mM solution (micro-GF) was nearly 24, 19, and 11 times, respectively, higher than that of raw-GF. In vitro dissolution studies revealed that almost 100 % of the drug was released in 60 min from GF-PVP and GF-HPMC. Fourier transform infrared spectroscopy did not detect any strong interaction between GF and the stabilizers. X-ray diffraction showed that the prepared GF nanoparticles and the micro-GF were in polymorphic form I. Differential scanning calorimetric studies showed that the crystallinity of the nanoformulated GF was only slightly lower than that of raw-GF. Thus, particle size reduction and the presence of stabilizers led to significant enhancement in solubility and dissolution rate.

Liquid antisolvent crystallization of griseofulvin from organic solutions

Griseofulvin was recrystallized from organic solutions using a liquid antisolvent crystallization technique. Griseofulvin was dissolved in organic solvents and the solutions were mixed with an aqueous antisolvent leading to a particle precipitation. Process variables such as temperature, concentration of solution, and solution injection rate were manipulated during the crystallization experiments. In particular, an ultrasonic wave was applied to the mixture of the solution and antisolvent in order to investigate the effect of ultrasound on the properties of the precipitated crystals. The intensity of the ultrasonic waves, the sonication time and the moment when the ultrasonic waves were applied were all regulated during the crystallization experiments. The size of the crystalline particles decreased when the concentrations of griseofulvin in the organic solutions increased. Smaller particles were produced when the griseofulvin solution was rapidly injected into the antisolvent. A higher heat of fusion for the crystalline particles was observed when the crystals were precipitated at lower temperatures. A significant reduction in particle size was achieved as the intensity of the ultrasonic waves and the duration of sonication increased during the crystallization experiments.

Effect of Particle Size of Additives on the Flammability and Mechanical Properties of Intumescent Flame Retarded Polypropylene Compounds

The effect of particle size reduction of the components of a common intumescent flame retardant system, consisting of pentaerythritol (PER) and ammonium polyphosphate (APP) in a weight ratio of 1 to 2, was investigated on the flammability and mechanical performance of flame retarded polypropylene (PP) compounds. Additives of reduced particle size were obtained by ball milling. In the case of PER, the significant reduction of particle size resulted in inferior flame retardant and mechanical performance, while the systems containing milled APP noticeably outperformed the reference intumescent system containing as-received additives. The beneficial effect of the particle size reduction of APP is explained by the better distribution of the particles in the polymer matrix and by the modified degradation mechanism which results in the formation of an effectively protecting carbonaceous foam accompanied with improved mechanical resistance. Nevertheless, 10% higher tensile strength was measured for the flame retarded PP compound when as-received APP was substituted by milled APP.

Characterization of Physicochemical and Thermal Properties of Chitosan and Sodium Alginate after Biofield Treatment

Chitosan (CS) and sodium alginate (SA) are two widely popular biopolymers which are used for biomedical and pharmaceutical applications from many years. The objective of present study was to study the effect of biofield treatment on physical, chemical and thermal properties of CS and SA. The study was performed in two groups (control and treated). The control group remained as untreated, and biofield treatment was given to treated group. The control and treated polymers were characterized by Fourier transform infrared (FT-IR) spectroscopy, CHNSO analysis, X-ray diffraction (XRD), particle size analysis, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). FT-IR of treated chitosan showed increase in frequency of –CH stretching (2925→2979 cm- 1) vibrations with respect to control. However, the treated SA showed increase in frequency of –OH stretching (3182→3284 cm-1) which may be correlated to increase in force constant or bond strength with respect to control. CHNSO results showed significant increase in percentage of oxygen and hydrogen of treated polymers (CS and SA) with respect to control. XRD studies revealed that crystallinity was improved in treated CS as compared to control. The percentage crystallite size was increased significantly by 69.59% in treated CS with respect to control. However, treated SA showed decrease in crystallite size by 41.04% as compared to control sample. The treated SA showed significant reduction in particle size (d50 and d99) with respect to control SA. DSC study showed changes in decomposition temperature in treated CS with respect to control. A significant change in enthalpy was observed in treated polymers (CS and CA) with respect to control. TGA results of treated CS showed decrease in Tmax with respect to control. Likewise, the treated SA also showed decrease in Tmax which could be correlated to reduction in thermal stability after biofield treatment. Overall, the results showed that biofield treatment has significantly changed the physical, chemical and thermal properties of CS and SA.

Effect of size reduction by freeze-milling on processing properties of beta-glucan oat bran

An effect of freeze-milling on processing properties of beta-glucan oat bran has been evaluated. A comparison with existing, patented methods of high molecular weight oat beta-glucan has been carried out. The new method employs raw material pre-treatment with freezing and milling in a hammer mill, resulting in significant reduction of particle size – 89% was between 80 and 50 μm in comparison with initial material when 79% were between 250 and 200 μm. Reduction of particle size also improved some process parameters of extraction technology – 30% improvement in fat removal during first stage of beta-glucan recovery was observed. The achieved pilot plant yield of product containing beta-glucan extraction was 64,03%, purity (ie. beta-glucan content), of achieved product was 84,4% and average molecular weight was about 69,500 g/mol.