Multi-wall carbon nanotube coating of fluorine-doped tin oxide as an electrode surface modifier for polymer solar cells

A controlled layer of multi-wall carbon nanotubes (MWCNT) was grown directly on top of fluorine-doped tin oxide (FTO) glass electrodes as a surface modifier for improving the performance of polymer solar cells. By using low-temperature chemical vapor deposition with short synthesis times, very short MWCNTs were grown, these uniformly decorating the FTO surface. The chemical vapor deposition parameters were carefully refined to balance the tube size and density, while minimizing the decrease in conductivity and light harvesting of the electrode. As created FTO/CNT electrodes were applied to bulk-heterojunction polymer solar cells, both in direct and inverted architecture. Thanks to the inclusion of MWCNT and the consequent nano-structuring of the electrode surface, we observe an increase in external quantum efficiency in the wavelength range from 550 to 650 nm. Overall, polymer solar cells realized with these FTO/CNT electrodes attain power conversion efficiency higher than 2%, outclassing reference cells based on standard FTO electrodes.

Superior piezoelectric composite films : taking advantage of carbon nanomaterials

Piezoelectric composites comprising an active phase of ferroelectric ceramic and a polymer matrix have recently attracted numerous sensory applications. However, it remains a major challenge to further improve their electromechanical response for advanced applications such as precision control and monitoring systems. We hereby investigated the incorporation of graphene platelets (GnPs) and multi-walled carbon nanotubes (MWNTs), each with various weight fractions, into PZT (lead zirconate titanate)/epoxy composites to produce three-phase nanocomposites. The nanocomposite films show markedly improved piezoelectric coefficients and electromechanical responses (50%) besides an enhancement of ~200% in stiffness. Carbon nanomaterials strengthened the impact of electric field on the PZT particles by appropriately raising the electrical conductivity of epoxy. GnPs have been proved far more promising in improving the poling behavior and dynamic response than MWNTs. The superior dynamic sensitivity of GnP-reinforced composite may be caused by GnPs’ high load transfer efficiency arising from their two-dimensional geometry and good compatibility with the matrix. Reduced acoustic impedance mismatch resulted from the improved thermal conductance may also contribute to the higher sensitivity of GnP-reinforced composite. This research pointed out the potential of employing GnPs to develop highly sensitive piezoelectric composites for sensing applications.

Methodology for measuring the vertical displacements of bridges using fibre bragg grating sensors

In many bridges, vertical displacements are one of the most relevant parameters for structural health monitoring in both the short- and long-terms. Bridge managers around the globe are always looking for a simple way to measure vertical displacements of bridges. However, it is difficult to carry out such measurements. On the other hand, in recent years, with the advancement of fibre-optic technologies, fibre Bragg grating (FBG) sensors are more commonly used in structural health monitoring due to their outstanding advantages including multiplexing capability, immunity of electromagnetic interference as well as high resolution and accuracy. For these reasons, a methodology for measuring the vertical displacements of bridges using FBG sensors is proposed. The methodology includes two approaches. One of which is based on curvature measurements while the other utilises inclination measurements from successfully developed FBG tilt sensors. A series of simulation tests of a full-scale bridge was conducted. It shows that both approaches can be implemented to measure the vertical displacements for bridges with various support conditions, varying stiffness along the spans and without any prior known loading. A static loading beam test with increasing loads at the mid-span and a beam test with different loading locations were conducted to measure vertical displacements using FBG strain sensors and tilt sensors. The results show that the approaches can successfully measure vertical displacements.

Atomistic simulation of interfacial behaviour in graphene-polymer nanocomposites

Graphene–polymer nanocomposites have promising properties as new structural and functional materials. The remarkable mechanical property enhancement in these nanocomposites is generally attributed to exceptional mechanical property of graphene and possible load transfer between graphene and polymer matrix. However, the underlying strengthening and toughening mechanisms have not been well understood. In this work, the interfacial behavior of graphene-polyethylene (PE) was investigated using molecular dynamics (MD) method. The interfacial shear force (ISF) and interfacial shear stress (ISS) between graphene and PE matrix were evaluated, taking into account graphene size, the number of graphene layers and the structural defects in graphene. MD results show that the ISS at graphene-PE interface mainly distributes at each end of the graphene nanofiller within the range of 1 nm, and much larger than that at carbon nanotube (CNT)-PE interface. Moreover, it was found that the ISS at graphene-PE interface is sensitive to the layer number.

Dry powder inhaler formulations-effect of polymer carrier size on the drug dispersion

Background The size of the carrier influences the aerosolization of drug from a dry powder inhaler (DPI) formulation. Currently, lactose monohydrate particles in a variety of sizes are preferably used in carrier based DPI formulations of various drugs; however, contradictory reports exist regarding the effect of the size of the carrier on the dispersion of drug. In this study we examined the influence of the intrinsic particle size of the polymeric carrier on the aerosolization of a model drug salbutamol sulphate (SS). Methods Four different sizes (20–150 lm) of polymer carriers were fabricated using solvent evaporation technique and the dispersion of SS particles from these carriers was measured by a Twin Stage Impinger (TSI). The size and morphological properties of polymer carriers were by laser diffraction and SEM, respectively. Results The FPF from these carriers was found to be increasing from 5.6% to 21.3% with increasing the carrier size. The FPF was found to be greater (21%) with the highest particle size of the carrier (150 lm). Conclusions The aerosolization of drug was dependent on the size of polymer carriers. The smaller size of the carrier resulted in lower FPF which was increased with increasing the carrier size. For a fixed mass of drug particles in a formulation, the mass of drug particles per unit area of carriers is higher in formulations containing the larger carriers, which leads to an increase in the dispersion of drug due to the increased mechanical forces occurred between the carriers and the device walls.

Blast response of reinforced concrete pile using fully coupled computer simulation techniques

Pile foundations transfer loads from superstructures to stronger sub soil. Their strength and stability can hence affect structural safety. This paper treats the response of reinforced concrete pile in saturated sand to a buried explosion. Fully coupled computer simulation techniques are used together with five different material models. Influence of reinforcement on pile response is investigated and important safety parameters of horizontal deformations and tensile stresses in the pile are evaluated. Results indicate that adequate longitudinal reinforcement and proper detailing of transverse reinforcement can reduce pile damage. Present findings can serve as a benchmark reference for future analysis and design.

Standardising corneal nerve fibre length for nerve tortuosity increases its association with measures of diabetic neuropathy

AIMS: Recent studies on corneal markers have advocated corneal nerve fibre length as the most important measure of diabetic peripheral neuropathy. The aim of this study was to determine if standardizing corneal nerve fibre length for tortuosity increases its association with other measures of diabetic peripheral neuropathy. METHODS: Two hundred and thirty-one individuals with diabetes with either predominantly mild or absent neuropathic changes and 61 control subjects underwent evaluation of diabetic neuropathy symptom score, neuropathy disability score, testing with 10-g monofilament, quantitative sensory testing (warm, cold, vibration detection) and nerve conduction studies. Corneal nerve fibre length and corneal nerve fibre tortuosity were measured using corneal confocal microscopy. A tortuosity-standardised corneal nerve fibre length variable was generated by dividing corneal nerve fibre length by corneal nerve fibre tortuosity. Differences in corneal nerve morphology between individuals with and without diabetic peripheral neuropathy and control subjects were determined and associations were estimated between corneal morphology and established tests of, and risk factors for, diabetic peripheral neuropathy. RESULTS: The tortuosity-standardised corneal nerve fibre length variable was better than corneal nerve fibre length in demonstrating differences between individuals with diabetes, with and without neuropathy (tortuosity-standardised corneal nerve fibre length variable: 70.5 ± 27.3 vs. 84.9 ± 28.7, P < 0.001, receiver operating characteristic area under the curve = 0.67; corneal nerve fibre length: 15.9 ± 6.9 vs. 18.4 ± 6.2 mm/mm(2) , P = 0.004, receiver operating characteristic area under the curve = 0.64). Furthermore, the tortuosity-standardised corneal nerve fibre length variable demonstrated a significant difference between the control subjects and individuals with diabetes, without neuropathy, while corneal nerve fibre length did not (tortuosity-standardised corneal nerve fibre length variable: 94.3 ± 27.1 vs. 84.9 ± 28.7, P = 0.028; corneal nerve fibre length: 20.1 ± 6.3 vs. 18.4 ± 6.2 mm/mm(2) , P = 0.084). Correlations between corneal nerve fibre length and established measures of neuropathy and risk factors for neuropathy were higher when a correction was made for the nerve tortuosity. CONCLUSIONS: Standardizing corneal nerve fibre length for tortuosity enhances the ability to differentiate individuals with diabetes, with and without neuropathy.

Vulnerability and damage analysis of reinforced concrete framed buildings subjected to near field blast events

Terrorists usually target high occupancy iconic and public buildings using vehicle borne incendiary devices in order to claim a maximum number of lives and cause extensive damage to public property. While initial casualties are due to direct shock by the explosion, collapse of structural elements may extensively increase the total figure. Most of these buildings have been or are built without consideration of their vulnerability to such events. Therefore, the vulnerability and residual capacity assessment of buildings to deliberately exploded bombs is important to provide mitigation strategies to protect the buildings' occupants and the property. Explosive loads and their effects on a building have therefore attracted significant attention in the recent past. Comprehensive and economical design strategies must be developed for future construction. This research investigates the response and damage of reinforced concrete (RC) framed buildings together with their load bearing key structural components to a near field blast event. Finite element method (FEM) based analysis was used to investigate the structural framing system and components for global stability, followed by a rigorous analysis of key structural components for damage evaluation using the codes SAP2000 and LS DYNA respectively. The research involved four important areas in structural engineering. They are blast load determination, numerical modelling with FEM techniques, material performance under high strain rate and non-linear dynamic structural analysis. The response and damage of a RC framed building for different blast load scenarios were investigated. The blast influence region for a two dimensional RC frame was investigated for different load conditions and identified the critical region for each loading case. Two types of design methods are recommended for RC columns to provide superior residual capacities. They are RC columns detailing with multi-layer steel reinforcement cages and a composite columns including a central structural steel core. These are to provide post blast gravity load resisting capacity compared to typical RC column against a catastrophic collapse. Overall, this research broadens the current knowledge of blast and residual capacity analysis of RC framed structures and recommends methods to evaluate and mitigate blast impact on key elements of multi-storey buildings.

Retinal nerve fibre layer thickness is associated with higher risk of foot ulceration in diabetic peripheral neuropathy

Purpose To evaluate the association between retinal nerve fibre layer (RNFL) thickness and diabetic peripheral neuropathy in people with type 2 diabetes, and specifically those at higher risk of foot ulceration. Methods RNFL thicknesses was measured globally and in four quadrants (temporal, superior, nasal and inferior) at 3.45 mm diameter around the optic nerve head using optical coherence tomography (OCT). Severity of neuropathy was assessed using the Neuropathy Disability Score (NDS). Eighty-two participants with type 2 diabetes were stratified according to NDS scores (0-10) as: none, mild, moderate, and severe neuropathy. A control group was additionally included (n=17). Individuals with NDS≥ 6 (moderate and severe neuropathy) have been shown to be at higher risk of foot ulceration. A linear regression model was used to determine the association between RNFL and severity of neuropathy. Age, disease duration and diabetic retinopathy levels were fitted in the models. Independent t-test was employed for comparison between controls and the group without neuropathy, as well as for comparison between groups with higher and lower risk of foot ulceration. Analysis of variance was used to compare across all NDS groups. Results RNFL thickness was significantly associated with NDS in the inferior quadrant (b= -1.46, p=0.03). RNFL thicknesses globally and in superior, temporal and nasal quadrants did not show significant associations with NDS (all p>0.51). These findings were independent of the effect of age, disease duration and retinopathy. RNFL was thinner for the group with NDS ≥ 6 in all quadrants but was significant only inferiorly (p<0.005). RNFL for control participants was not significantly different from the group with diabetes and no neuropathy (superior p=0.07, global and all other quadrants: p>0.23). Mean RNFL thickness was not significantly different between the four NDS groups globally and in all quadrants (p=0.08 for inferior, P>0.14 for all other comparisons). Conclusions Retinal nerve fibre layer thinning is associated with neuropathy in people with type 2 diabetes. This relationship is strongest in the inferior retina and in individuals at higher risk of foot ulceration.

Paint spray mass spectrometry for the detection of additives from polymers on conducting surfaces

Paint Spray is developed as a direct sampling ionisation method for mass spectrometric analysis of additives in polymer-based surface coatings. The technique simply involves applying an external high voltage (5 kV) to the wetted sample placed in front of the mass spectrometer inlet and represents a much simpler ionisation technique compared to those currently available. The capabilities of Paint Spray are demonstrated herein with the detection of four commercially available hindered amine light stabilisers; TINUVIN® 770, TINUVIN® 292, TINUVIN® 123 and TINUVIN® 152 directly from thermoset polyester-based coil coatings. Paint Spray requires no sample preparation or pre-treatment and combined with its simplicity - requiring no specialised equipment - makes it ideal for use by non-specialists. The application of Paint Spray for industrial use has significant potential as sample collection from a coil coating production line and Paint Spray ionisation could enable fast quality control screening at high sensitivity.

Ambient ionisation mass spectrometry for the characterisation of polymers and polymer additives : A review

The purpose of this review is to showcase the present capabilities of ambient sampling and ionisation technologies for the analysis of polymers and polymer additives by mass spectrometry (MS) while simultaneously highlighting their advantages and limitations in a critical fashion. To qualify as an ambient ionisation technique, the method must be able to probe the surface of solid or liquid samples while operating in an open environment, allowing a variety of sample sizes, shapes, and substrate materials to be analysed. The main sections of this review will be guided by the underlying principle governing the desorption/extraction step of the analysis; liquid extraction, laser ablation, or thermal desorption, and the major component investigated, either the polymer itself or exogenous compounds (additives and contaminants) present within or on the polymer substrate. The review will conclude by summarising some of the challenges these technologies still face and possible directions that would further enhance the utility of ambient ionisation mass spectrometry as a tool for polymer analysis. (C) 2013 Elsevier B. V. All rights reserved.

Measuring the mechanical properties of ground ophthalmic polymer surfaces using nanoindentation

This work is motivated by the need to efficiently machine the edges of ophthalmic polymer lenses for mounting in spectacle or instrument frames. The polymer materials used are required to have suitable optical characteristics such high refractive index and Abbe number, combined with low density and high scratch and impact resistance. Edge surface finish is an important aesthetic consideration; its quality is governed by the material removal operation and the physical properties of the material being processed. The wear behaviour of polymer materials is not as straightforward as for other materials due to their molecular and structural complexity, not to mention their time-dependent properties. Four commercial ophthalmic polymers have been studied in this work using nanoindentation techniques which are evaluated as tools for probing surface mechanical properties in order to better understand the grinding response of polymer materials.

Atomistic simulation of surface functionalization on the interfacial properties of graphene-polymer nanocomposites

Graphene has been increasingly used as nano sized fillers to create a broad range of nanocomposites with exceptional properties. The interfaces between fillers and matrix play a critical role in dictating the overall performance of a composite. However, the load transfer mechanism along graphene-polymer interface has not been well understood. In this study, we conducted molecular dynamics simulations to investigate the influence of surface functionalization and layer length on the interfacial load transfer in graphene polymer nanocomposites. The simulation results show that oxygen-functionalized graphene leads to larger interfacial shear force than hydrogen-functionalized and pristine ones during pull-out process. The increase of oxygen coverage and layer length enhances interfacial shear force. Further increase of oxygen coverage to about 7% leads to a saturated interfacial shear force. A model was also established to demonstrate that the mechanism of interfacial load transfer consists of two contributing parts, including the formation of new surface and relative sliding along the interface. These results are believed to be useful in development of new graphene-based nanocomposites with better interfacial properties.

Factors affecting the extraction of absorbed dose information in a 3D polymer gel dosimeter by X ray computed tomography (IAEA-CN-96/122P)

Two sources of uncertainty in the X ray computed tomography imaging of polymer gel dosimeters are investigated in the paper.The first cause is a change in postirradiation density, which is proportional to the computed tomography signal and is associated with a volume change. The second cause of uncertainty is reconstruction noise.A simple technique that increases the residual signal to noise ratio by almost two orders of magnitude is examined.

Age and curing effect on the bond strength of thin bed concrete masonry with polymer cement mortar

Bond characteristics of masonry are partly affected by the type of mortar used, the techniques of dispersion of mortar and the surface texture of the concrete blocks. Additionally it is understood from the studies on conventional masonry, the bond characteristics are influenced by masonry age and curing methods as well as dryness/dampness at the time of testing. However, all these effects on bond for thin bed masonry containing polymer cement mortar are not well researched. Therefore, the effect of ageing and curing method on bond strength of masonry made with polymer cement mortar was experimentally investigated as part of an ongoing bond strength research program on thin bed concrete masonry at Queensland University of technology. This paper presents the experimental investigation of the flexural and shears bond characteristics of thin bed concrete masonry of varying age/ curing methods. Since, the polymer cement mortar is commonly used in thin bed masonry; bond development through two different curing conditions (dry/wet) was investigated in this research work. The results exhibit that the bond strength increases with the age under the wet and dry curing conditions; dry curing produce stronger bond and is considered as an advantage towards making this form of thin bed masonry better sustainable.