Internal structure and pigment granules in colored alpaca fibers

Alpaca fibers have some distinct properties such as softness and warmth, which have not been fully understood in combination with the fiber internal structures. In the present investigation, the internal structures of alpaca fibers have been closely examined under the scanning electron microscope (SEM), especially in the longitudinal direction. The results showed that numerous pigment granules reside loosely inside pockets in brown and dark-brown alpaca fibers. These pigment granules were mainly distributed inside the cortical cells, the medullation regions as well as underneath the cuticles. Their size in the brown alpaca fibers was smaller and more uniformly round than in the dark-brown fibers. These granules in colored alpaca fibers loosen the bundle of cortical cells, providing many crannies in the fibers which may contribute to the superior flexibility, warmth and softness of the fibers. Moreover, there are no heavy metal elements found in the granules. The mordant hydrogen peroxide bleaching employed could eliminate the pigment granules and create many nano-volumes for further dyeing of fibers into more attractive colors.

Microscopic nature and elemental composition of brown coal fly ash particles from a large coal fired power station

In this study, Australian brown coal fly ash particles have been collected from power station and analysed by scanning electron microscopy to obtain morphological information and elemental composition of individual particles. The most common particles found to be the irregular shape particle aggregates. Other shapes include ball shape with smooth surface and with some attachments; and crystal shape fine particles. The X-ray spectra of each fly ash particle revealed five groups of elemental composition, they are Si-rich particles; Ca-rich particles; Fe-rich particles; particles with Mg-Ca Matrix and particles with Si-Ca matrix. A particle sire distribution analysis has been conducted using particle size analyser and found to have a mean particle size of 21fim. The sample then was separated into fine and coarse fractions using aerodynamic classifier, and the elemental composition of both fractions were determined by ICP-AES. Borate fusion and acid dissolution method was used for sample preparation. It is found that some environmental sensitive elements such as Zn, Pb, Ni, K and Cu are enriched in fine fly ash particles. Ca has much higher contents in fine particles as well. Si and Mg have higher concentrations in coarse particles.

Thermal and mechanical properties of a dendritic hydroxyl-functional hyperbranched polymer and tetrafunctional epoxy resin blends

Blends of a tetrafunctional epoxy resin, tetraglycidyl- 4,40'-diaminodiphenylmethane (TGDDM), and a hydroxylfunctionalized hyperbranched polymer (HBP), aliphatic hyperbranched polyester Boltorn H40, were prepared using 3,3'-diaminodiphenyl sulfone (DDS) as curing agent. The phase behavior and morphology of the DDS-cured epoxy/HBP blends with HBP content up to 30 phr were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), and scanning electron microscopy (SEM). The phase behavior and morphology of the DDS-cured epoxy/HBP blends were observed to be dependent on the blend composition. Blends with HBP content from 10 to 30 phr, show a particulate morphology where discrete HBP-rich particles are dispersed in the continuous cured epoxy-rich matrix. The cured blends with 15 and 20 phr exhibit a bimodal particle size distribution whereas the cured blend with 30 phr HBP demonstrates a monomodal particle size distribution. Mechanical measurements show that at a concentration range of 0–30 phr addition, the HBP is able to almost double the fracture toughness of the unmodified TGDDM epoxy resin. FTIR displays the formation of hydrogen bonding between the epoxy network and the HBP modifier.

Influence of mechanical mixing rates on sludge characteristics and membrane fouling in MBRs

The influence of shear intensity (G) induced by mechanical mixing on activated sludge characteristics as well as membrane fouling propensity in membrane bioreactors (MBRs) was investigated. Four MBRs were operated at different mechanical mixing conditions. The control reactor (MBR0) was operated with aeration only supplemented by mechanical stirring at 150, 300, and 450 rpm in MBR150, MBR300, and MBR450, respectively. It was found that the MBR300 demonstrated minimum rate of membrane fouling. The fouling potential of the MBR300 mixed liquor was lowest characterized by the specific cake resistance and the normalized capillary suction time (CSTN). Moreover, it was found that the mean particle size reduced with an increase in the shear intensity. These results reveal that membrane fouling can be significantly mitigated by appropriate shear stress on membrane fibers induced by mechanical mixing condition.

Positron annihilation lifetime spectroscopy of mechanically milled protein fibre powders and their free volume aspects

The present study reports the fabrication of ultra-fine powders from animal protein fibres such as cashmere guard hair, merino wool and eri silk along with their free volume aspects. The respectively mechanically cleaned, scoured and degummed cashmere guard hair, wool and silk fibres were converted into dry powders by a process sequence: Chopping, Attritor Milling, and Spray Drying. The fabricated protein fibre powders were characterised by scanning electron microscope, particle size distribution and positron annihilation lifetime spectroscopy (PALS). The PALS results indicated that the average free volume size in protein fibres increased on their wet mechanical milling with a decrease in the corresponding intensities leading to a resultant decrease in their fractional free volumes.

Silk powder for regenerative medicine

Two approaches are used for silk particle production: bottom up and top down. In the bottom up approach, different liquid-solid phase transfer techniques are adapted to fabricate particles from silk solution. In the top down approach, silk fibres are milled by various means to prepare ultrafine silk particles. Many important properties of particles such as size, geometry, porosity, stability and biodegradability are dependent on the specific methods of particle production. These properties influence drug loading and release, delivery modes, biocompatibility and their clearance from the body. Particle properties also determine biomechanical properties of particle reinforced composite scaffolds. Thus correlation between preparation, characterisation and application of silk particles for a specific biomedical application is critical. Progress made in this direction and challenges ahead are discussed in this chapter. © 2014 Woodhead Publishing Limited. All rights reserved.

Study on nanocellulose by high pressure homogenization in homogeneous isolation

Nanocellulose from cotton cellulose was prepared by high pressure homogenization (HPH) in ionic liquids (1-butyl-3-methylimidazolium chloride ([Bmim]Cl). The nanocellulose possessed narrow particle size distribution, with diameter range of 10–20 nm. Weight average molecular weight (Mw) of nanocellulose treated by HPH was lower (173.8 kDa) than the one ILs treated cellulose (344.6 kDa). X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and Solid-state CP/MAS 13C NMR measurements were employed to study the mechanism of structural changes, which suggested that network structure between cellulose chains were destructed by the shearing forces of HPH in combination with ionic liquids. The intermolecular and intra-molecular hydrogen bonds of cellulose were further destroyed, leading to the long cellulose molecular chains being collapsed into short chains. Therefore, the nanocellulose could provide desired properties, such as lower thermal stability and strong water holding capacity. Results indicated that it had great potential in the applications for packaging, medicines, cosmetics and tissue engineering.

Influence of fuel-borne oxygen on European stationary cycle: diesel engine performance and emissions with a special emphasis on particulate and NO emissions

Exploration of sustainable fuels and their influence on reductions in diesel emissions are nowadays a challenge for the engine and fuel researchers. This study investigates the role of fuel-borne oxygen on engine performance and exhaust emissions with a special emphasis on diesel particulate and nitric oxide (NO) emissions. A number of oxygenated-blends were prepared with waste cooking biodiesel as a base oxygenated fuel. Triacetin, a derivative from transesterified biodiesel was chosen for its high oxygen content and superior fuel properties. The experimental campaign was conducted with a 6-cylinder, common rail turbocharged diesel engine equipped with highly precise instruments for nano and other size particles and other emissions. All experiments were performed in accordance with European Stationary Cycle (ESC 13-mode). A commercial diesel was chosen as a reference fuel with 0% oxygen and five other oxygenated blends having a range of 6.02–14.2% oxygen were prepared. The experimental results revealed that the oxygenated blends having higher a percentage of fuel-borne oxygen reduced particulate matter (PM), particle number (PN), unburned hydrocarbon (UBHC) and carbon monoxide (CO) emissions to a significantly low level with a slight penalty of NO emissions. The main target of this study was to effectively utilise triacetin as an additive for waste cooking biodiesel and suppress emissions without deteriorating engine performance. The key finding of this investigation is the significant reductions in both particle mass and number emissions simultaneously without worsening engine performance with triacetin-biodiesel blends. Reductions in both particle mass and number emissions with a cost-effective additive would be a new dimension for the fuel and engine researchers to effectively use triacetin as an emission suppressor in the future.

Equal channel angular pressing of metal matrix composites: effect on particle distribution and fracture toughness

An Al6061-20%Al₂O₃ powder metallurgy (PM) metal matrix composite (MMC) with a strongly clustered particle distribution is subjected to equal channel angular pressing (ECAP) at a temperature of 370 °C. The evolution of the homogeneity of the particle distribution in the material during ECAP is investigated by the quadrat method. The model proposed by Tan and Zhang [Mater Sci Eng 1998;244:80] for estimating the critical particle size which is required for a homogeneous particle distribution in PM MMCs is extended to the case of a combination of extrusion and ECAP. The applicability of the model to predict a homogeneity of the particle distribution after extrusion and ECAP is discussed. It is shown that ECAP leads to an increase of the  uniformity of the particle distribution and the fracture toughness.

Influence of particle size and size distribution in deep bed filtration and dynamic microfiltration

Particle size and size distribution is an important parameter in solid liquid separation process especially in granular bed filtration and in dynamic microfiltration. This paper discusses their effects on the above processes from extensive experimental data obtained. In granular bed filtration, the experimental results showed that the initial efficiency follows the pattern reported by previous experimental and theoretical studies, i.e., lower efficiency for particles which fall in the range of critical size of 1 m. However, the particle removal during the transient stage increased with an increase in particle size for the range of sizes studied. An attempt was made to quantify these effects in granular bed filtration using semi-empirical approach. In dynamic membrane filtration also, the particle size plays a major role in the retention. However, despite the relative thickness of the membrane (compared to particle size) dynamic microfiltration appears more as a sieving process; the retention is mainly related to the largest pore size.

Size distribution and volume fraction of T1 phase precipitates from TEM images: Direct measurements and related correction

Transmission Electron Microscopy (TEM) can be used to measure the size distribution and volume fraction of fine scale precipitates in metallic systems. However, such measurements suffer from a number of artefacts that need to be accounted for, related to the finite thickness of the TEM foil and to the projected observation in two dimensions of the microstructure. We present a correction procedure to describe the 3D distribution of disc-like particles and apply this method to the plate-like T1 precipitates in an Al-Li-Cu alloy in two ageing conditions showing different particle morphologies. The precipitates were imaged in a High-Angular Annular Dark Field Microscope (HAADF-STEM). The corrected size distribution is further used to determine the precipitate volume fraction. Atom probe tomography (APT) is finally utilised as an alternative way to measure the precipitate volume fraction and test the validity of the electron microscopy results.