The use of PEO-PPO-PEO block copolymers in the synthesis of ZnO via the hydrothermal method

Zinc oxide particles were produced by aqueous precipitation in hydrothermal conditions (140°C for 6 hours). The influence of surfactant and base to control morphology was investigated. With a change in surfactant, rod-like bundles of different size were obtained, depending on the core and corona size. By changing the base different complexes were formed which interacted differently with the surfactant present (L64). Platelets, rod-like and elliptical particles were obtained

Influence of temperature, ripening time and calcination on the morphology and crystallinity of hydroxyapatite nanoparticles

Nano-sized hydroxyapatite (HA) particles were prepared by chemical precipitation through aqueous solutions of calcium chloride and ammonium hydrogenphosphate. The influence of temperature, ripening time and calcination on the crystallinity and morphology of the HA nanoparticles were investigated. It was found that the crystallinity and crystallite size increased with the increase of synthetic temperature and ripening time. XRD and TEM results showed that the morphology change of HA nanoparticles was related to their crystallinity. High crystallinity of HA led to regular shape and smooth surface of the nanoparticles. The crystallinity of HA powders increased greatly after calcination at 650 C for 6 h but the change of the crystallite size after calcination was dependent on the crystallinity and crystallite size of ‘‘as prepared’’ HA nanoparticles

Mechanical behaviour of advanced composite laminates embedded with carbon nanotubes: review

Embedding carbon nanotubes (CNTs) in load-bearing composite laminate hosts and thereby turning them into nanolaminates is a rapidly emerging field and has tremendous potential in enhancing mechanical performance of host laminates. This state-of-the-art review intends to provide physical insight into the understanding of enhancing mechanisms of processed and controlled CNTs in nano-laminates. It focuses on four aspects: (1) physical characteristics of CNTs including CNT length, diameter and weight percentage; (2) processing and control techniques of CNTs in fabrication of nano-laminates including distribution, dispersion and orientation controls of CNTs; (3) mechanical properties along with their testing methods including tension, in-plane compression, interlaminar shear (ILS), flexure, mode I and mode II fracture toughness as well as compression-after-impact (CAI); and (4) post-mortem microscopic corroborative evidence after mechanical testing. As this review indicates, selective and uniform production of CNTs with specific dimensions and physical properties has yet to be achieved on a consistent basis. There is little control over CNT orientations in most fabrication processes of nano-laminates except for some cases associated with chemical vapour deposition (CVD). There are only two reports on the in-plane compression and there is none on in-plane shear. For reinforcement-dominated mechanical properties such as tension and flexure, there is little enhancement as reported. However, substantial enhancement in in-plane compression strength was reported. For matrix-dominated mechanical properties such as ILS strength and mode-I and mode-II fracture toughness, significant enhancement, albeit with substantially varying degrees, has been reported. In the meanwhile, the lack of consistent characterisation in those properties was also noticeable. Post-mortem microscopic corroborative evidence was very limited

The use of post-electroplating surface modification treatments to mitigate tin whisker growth

The use of post-electroplating surface modification treatments to mitigate tin whisker growt

Study of damage characteristics in composite structures from simulated lightning strikes

This work investigated experimentally the direct effects of simulated lightning strikes in carbon/epoxy and E-glass/epoxy laminates. The direct effects were represented by Joule heating and kinetic shock waves. The experimental set-up was designed to maximize these direct effects by employing a solid electrode, pointed vertically to the surface of the specimens with a small electrode gap. The damage mechanisms were found to be in the form of resin sublimation, delamination and fibre tufting. The damage characteristics depended on type of composite materials, lightning current and action integral. In the carbon/epoxy laminates, resin sublimation and degradation were dominant at relatively low currents and with the further increase in current fibre tufting appeared due to kinetic shock waves. Penetration into the laminates was found to be limited to the only top two plies in the extreme case. The damage characteristics of the E-glass/epoxy laminates with a tiny hole were dominated by extensive delamination due entirely to shock waves with little sign of Joule heating. Analytical work will be desired to aid establishment of relationships between the damage characteristics and the lightning strike parameters via lightning channel radius and raised temperatures

High-temperature polymer electrolyte membranes based on poly(2,5-benzimidazole) (ABPBI) and POSS incorporated ionic liquid

This paper reported a method to modify polyhedral oligomeric silsesquioxane (POSS) particle into POSS ionic liquid (POSS-IL) and its incorporation into ABPBI/H3PO4 system to enhance the proton conductivities and mechanical properties of the membranes simultaneously. It was found that good dispersion of POSS-IL in the polymer matrix increased the tensile strength and Young’s modulus of the membranes. For membranes with the same H3PO4 content, the incorporation of POSS-IL increased the conductivities of the membranes by about two orders of magnitude. The highest conductivity was achieved by ABPBI/10 wt% POSS-IL composite membrane, which was 7.6×10-2 S/cm at 200 °C

The development of a tin whisker mitigating conformal coating

The development of a tin whisker mitigating conformal coatin

New rubber compound

Ethylene-propylene-diene rubber cured with a new single chemical additive and reinforced with mineral kaolin is a suitable compound for possible use in tires

Current understanding and applications of the cold sintering process

In traditional ceramic processing techniques, high sintering temperature is necessary to achieve fully dense microstructures. But it can cause various problems including warpage, overfiring, element evaporation, and polymorphic transformation. To overcome these drawbacks, a novel processing technique called “cold sintering process (CSP)” has been explored by Randall et al. CSP enables densification of ceramics at ultra-low temperature (≤ 300 °C) with the assistance of transient aqueous solution and applied pressure. In CSP, the processing conditions including aqueous solution, pressure, temperature, and sintering duration play critical roles in the densification and properties of ceramics, which will be reviewed. The review will also include the applications of CSP in solid-state rechargeable batteries. Finally, the perspectives about CSP is proposed

The perfect cure

I n the processing of raw rubber, sulfur is added for shape retention. To enhance the efficiency of curing and the vulcanization process, chemical curatives known as accelerators and activators are frequently used. However, excessive use of chemical curatives has raised major concerns about their adverse impact on human and animal health as well as on the environment. In most tire compounds, sulfenamide accelerators and zinc oxide are used in combination with sulfur to achieve efficient vulcanization. Since these chemicals are essential to improve the curing process, it is likely that their use in tire compounds will continue for some time. Therefore, their use must be lowered without compromising the cure properties and adversely affecting the cure cycle of tire compounds. ...