Influence of reduced graphene oxide on structural,optical, thermal and dielectric properties of SnO2 nanoparticles

The present work has been carried out with the aim to synthesize tin oxide decorated reduce graphene oxide nanocomposite (SnO₂/RGO-Nc) via in-situ synthesis process and the influence of RGO loading on structural, optical, thermal and dielectric properties of SnO₂ has been discussed. The XRD, FESEM coupled with EDX elemental mapping, TEM, FTIR, Raman and XPS results reveal that the SnO₂ nanoparticles have been successfully incorporated onto the RGO sheets. The reduction in the energy gap of the composite sample as compared to SnO₂ measured from the Tauc’s relation can be attributed to strong coupling between RGO and SnO₂ NPs. Thermogravimetric analysis (TGA) shows improved thermal stability of the SnO₂/RGO-Nc. From the dielectric measurements, it is observed that the dielectric constant and dielectric loss decreases as frequency of applied field increases. AC conductivity of all samples increases as applied frequency increases which follows Jonscher’s power law. All composite samples show better conductivity as compared to SnO₂. This is due to the formation of continuous conductive pathway between SnO₂ and RGO sheets. Further high dielectric constant, low loss and high ac conductivity have been observed at optimum loading of RGO in SnO₂/RGO2-Nc as compared to other composite samples which is due the percolation effects. The impedance analysis exhibits only one semicircle for SnO₂ and SnO₂/RGO composite which suggests that the involvement of grain boundaries dominated over the grain contribution.     

A comparison of SWAT, HSPF and SHETRAN/GOPC for modelling phosphorus export from three catchments in Ireland

Recent extensive water quality surveys in Ireland revealed that diffuse phosphorus (P) pollution originating from agricultural land and transported by runoff and subsurface flows is the primary cause of the deterioration of surface water quality. P transport from land to water can be described by mathematical models that vary in modelling approach, complexity and scale (plot, field and catchment). Here, three mathematical models (soil water and analysis tools (SWAT), hydrological simulation program-FORTRAN (HSPF) and système hydrologique Européen TRANsport (SHETRAN)/grid oriented phosphorus component (GOPC)) of diffuse P pollution have been tested in three Irish catchments to explore their suitability in Irish conditions for future use in implementing the European Water Framework Directive. After calibrating the models, their daily flows and total phosphorus (TP) exports are compared and assessed. The HSPF model was the best at simulating the mean daily discharge while SWAT gave the best calibration results for daily TP loads. Annual TP exports for the three models and for two empirical models were compared with measured data. No single model is consistently better in estimating the annual TP export for all three catchments.     

Sliding wear evaluation of hot isostatically pressed thermal spray ceramet coatings

The principal aim of this study was to compare the sliding wear performance of as-sprayed and Hot Isostatically Pressed (HIPed) thermal spray cermet (WC-12Co) coatings. Results indicate that HIPing technique can be successfully applied to post-treat thermal spray cermet coatings for improved sliding wear performance, not only in terms of coating wear, but also in terms of the total volume loss for test couples. WC-12Co coatings sprayed by a HVOF system were deposited on SUJ-2 bearing steel substrate and then encapsulated and HIPed at 850 °C for one hour. A high frequency reciprocating ball on plate rig was used to measure the sliding wear resistance of these coatings in dry conditions under steel and ceramic contact configurations at two different loads. Results are discussed in terms of coating microstructure, microhardness, fracture toughness and residual stress evaluations. Microstructural investigations indicate fundamental changes in grain morphology, whereas x-ray diffraction revealed beneficial transformations in phase composition of these coatings during the HIPing post treatment. The effects of these microstructural changes on the physical properties and wear resistance are discussed.     

Natural convection mass transfer inside cylindrical cavities of different orientation

Rates of free convection mass transfer inside cylindrical cavities were studied by measuring the limiting current for the cathodic deposition of copper from acidified copper sulphate solution using a cylindrical anode placed inside the cavity. Variables studied were cavity orientation (vertical with upward facing opening, vertical with downward facing opening and horizontal), physical properties of the solution and cavity dimensions (diameter and depth). For vertical cavities with upward facing openings the data were correlated by the equation Sh = 0.257 (Sc × Gr)^0.33 For horizontal cavities the data were correlated by the equation Sh = 0.139 (Sc × Gr)^0.33 For vertical cavities with downward facing openings the data were correlated by the equation Sh = 0.187 (Sc × Gr)^0.297 A comparison between the present data and the data obtained from other cavity geometries was made to shed light on the role of cavity geometry in thermosyphon design.List of symbols a, b constants - A cavity area - C copper sulphate bulk concentration - C _p specific heat - D diffusivity - d cavity diameter - F Faraday constant - g acceleration due to gravity - h heat transfer coefficient - I _L limiting current - k thermal conductivity - K mass transfer coefficient - L cavity depth - L _c characteristic length calculated from Equation 3 - Z number of electrons involved in the reaction - Gr Grashof number (gL _c ³/²/_i) - Nu Nusselt number (hL _c/k - Pr Prandtl number (C _pµ/k) - Sc Schmidt number (/D) - Sh Sherwood number (KL _c/D) - Ra Rayleigh number (Sc × Gr) or (Pr × Gr) Greek letters µ dynamic viscosity of the electrolyte - kinematic viscosity of the electrolyte - density of the electrolyte - _i interfacial density - density difference between the bulk solution and interfacial solution     

Synthesis and Characterization of Carbon Steel Corrosion Inhibitors Based on 4,5,6,7-tetrahydrobenzo[b]thiophene Scaffold

Protection of Metals and Physical Chemistry of Surfaces - Three novel inhibitors based on 4,5,6,7-tetrahydrobenzo[b]thiophene scaffold were synthesized and characterized. The inhibitive action of...     

Particle-Substrate Collisions, Particle Rebound and Removal

Recent progress in particle capture and rebound and its effect on the adhesion force is reviewed in this paper. Particles rebound when the incident velocity is greater than a characteristic critical velocity. Lower impaction velocity particles experience elastic and plastic deformation. Recent models for particle rebound and capture are discussed and evaluated in terms of their restrictive assumptions and results. Recent experimental data of particle rebound and capture is also discussed, as is the hydrodynamic removal of captured particles. The removal of particles occurs when the applied hydrodynamic removal force overcomes the adhesion force. The effect of adhesion-induced deformation on the removal of particles is introduced and discussed.     

Using PLS-SEM technique to model construction organizations' willingness to participate in e-bidding

The push for the use of e-bidding is on the increase. In many countries, e-bidding has become part of the public procurement reform. However, previous studies have reported the low uptake of e-bidding in the construction industry. This study develops a theoretical structural model representing the impact six latent variables on the willingness of construction organizations to participate in e-bidding. Data from a questionnaire survey of 64 respondents from clients, contractors, consultants, and suppliers organizations was used to analyze the model. The result of the data analysis suggests that perceived barriers, cost, the perceived benefits of e-bidding and security concerns are the factors influencing willingness participate in e-bidding with perceived barriers being the most significant influencing factor. The perception about the adequacy of the existing traditional paper-based tendering and the perception about the non-readiness of business partners are the underlying barriers that need to be addressed when introducing e-biding. This study also discovers that when the respondents concern about the cost of e-bidding is high, their reported willingness to participate in e-bidding is higher when the perceived benefits is high that when the perceived benefits is low. To enhance the participation of the industry in e-bidding, public sector and large private clients would need to take leadership by making bidder's capability for e-bidding and e-project management at all project phases a criteria in bid evaluation. E-bidding developers and promoters need to use test project cases to monitor, measure, and document the benefits of e-bidding. To disseminate the perceived benefits, promoters would need to work closely with industry professional associations to develop promotional programmes linked to continuous professional development (CPD) points. The analytical approach used in this study should assist other researchers who might wish to address a similar research problem under a similar data and model constraints.     

Aging of novel membranes made of PVA and cellulose nanocrystals extracted from Egyptian rice husk manufactured by compression moulding process

Novel membranes consisting of polyvinyl alcohol (PVA), cellulose nanocrystals (CNCs) originated from Rice Husk (RH), Glutaraldehyde (GLA) and Glycerine (G) were manufactured by the compression moulding process. Rice husk is a new source to isolate pure cellulose nanocrystals via mechanical and chemical treatment. The biodegradability of the membranes has been evaluated using UV accelerated weathering as well as a soil burial test. The morphology of membranes (PVA/RH-CNCs) was characterized by using the Scanning Electron Microscope (SEM). The chemical structure of the membranes (PVA/RH-CNCs) was characterised by Fourier-Transformation Infrared (FTIR) spectroscopy as well as wide-angle X-ray diffraction. The mechanical properties of the membranes were evaluated using standard techniques. Swelling and weight loss resulting from biodegradation were also evaluated. The results showed that the developed transient membranes can be used as food packaging bags owing to biodegradability (weight loss) under irradiation and during soil burial.