Preparation of silica-decorated graphene oxide nanohybrid system as a highly efficient reinforcement for woven jute fabric reinforced epoxy composites

In the current work, silica-decorated graphene oxide (SiO₂@GONPs) nanohybrids were used to reinforce the jute fiber/epoxy (JF/EP) composite. Tetraethylorthosilicate (TEOS) was utilized to prepare the SiO₂@GONPs using a facial route. The results of Fourier-transform infrared spectroscopy (FTIR), atomic force microscopy, and elemental X-ray mapping confirmed the successful synthesis of SiO₂@GONPs nanohybrids. Herein, the effects of SiO₂@GONPs loading (0, 0.1, 0.3, and 0.5 wt%) on the mechanical behavior of the JF/EP composite were investigated with emphasis on the flexural and high-velocity impact properties. The results revealed that reinforcement of matrix with 0.3 wt% SiO₂@GONPs enhanced the flexural strength of the JF/EP composite by about 40%. The energy absorption capability and impact limit velocity of the 0.3 wt% SiO₂@GONPs-filled JF/EP composite were 61 and 28%, respectively, higher than those of the neat specimen. Compared to the untreated-GONPs, the SiO₂@GONPs nanohybrid demonstrated an evident superiority in improving the mechanical properties of the JF/EP composite at the same loading. Evaluation of the fracture surfaces of the multiscale composites revealed that the improved fiber-matrix interfacial bonding was the basic mechanism of fracture in these specimens.     

Effect of processing conditions on porosity formation in cold gas dynamic spraying of copper

The cold gas dynamics process is a promising low-temperature spray process in which particles are accelerated in a supersonic flow before impacting with substrate to be coated. In this study the effect of spray temperature, spray pressure, and particle size on porosity formation in cold spray coatings are investigated. Results show that an increase in spray temperature and a decrease in particle size lead to a decline in volume fraction of porosity. Furthermore, particle velocity and particle temperature are determined to be the significant parameters for elimination of porosity. A model is proposed for estimation of the volume fraction of porosity for alloy of this study.     

Zero‐Trans Cake Shortening: Formulation and Characterization of Physicochemical,Rheological, and Textural Properties

Cake shortening is an important ingredient that imparts taste and texture in the cake as the final product. Hydrogenated shortenings contain high amounts of trans fatty acids, which is considered a risk factor for obesity, cancers, and cardiovascular diseases. In this research, chemically interesterified blends of canola oil (CO) and palm stearin (PS) were recruited in order to formulate zero‐trans shortening, specifically for cake application. The optimization of shortening formulation was performed by Design‐Expert software, considering melting, congelation, textural, and rheological properties of cake shortening as responses. The formulated shortening in the weight ratio of 66.41:33.58 (PS:CO) (%, w/w) was analyzed and compared with two commercial cake shortenings in terms of fatty acid and triacylglycerol composition, slip melting point (SMP), solid fat content (SFC), and rheological and textural properties. The results showed that the formulated zero‐trans cake shortening with 0.2% trans, 47.2% saturated fatty acids, SMP of 40.9 °C, SFC of 10.51% at 37 °C, firmness of 1522.5 g, and linear viscoelastic range of 0.035% had the most acceptable criteria among cake‐shortening samples. The findings of this study offer insights into the relationship between shortening functionality and physicochemical properties and serve as a base for future studies on zero‐trans shortenings formulation.     

Pervaporation study of ethylene glycol dehydration through synthesized (PVA–4A)/polypropylene mixed matrix composite membranes

Poly(vinyl alcohol) (PVA)/zeolite 4A mixed matrix composite membranes supported on polypropylene microfiltration membranes were prepared by solution casting method and crosslinked with glutaraldehyde to investigate their pervaporation (PV) separation properties of water–ethylene glycol mixtures. Scanning electron microscopy images showed homogeneous distribution of zeolite nanoparticles within the polymer matrix without any visible macroscopic voids at the zeolite–polymer interface. The PV experiments were accomplished to investigate the effects of water concentration (10–40 wt%) and temperature (60–80°C) on separation performance of the membranes. It was found out that 5 wt% loading of the 4A nanoparticles into the PVA matrix is optimal to obtain the best separation performance. The experimental results revealed that loading of zeolite 4A enhanced the membrane performance [both permeation flux (5%) and separation factor (32%) at 5 wt% zeolite loading]. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Rare Earth/Metal Composite Formation by Cold Spray

Nd₂Fe₁₄B permanent magnet/aluminum composite coatings were produced by cold spray deposition. Isotropic Nd₂Fe₁₄B powder was blended with aluminum powder to make mixtures of 20-80 vol.% Nd₂Fe₁₄B, and these mixtures were sprayed at temperatures of 200-480 °C. The hard Nd₂Fe₁₄B particles tended to fracture and fragment upon impact, while aluminum underwent severe plastic deformation, eliminating pores, and trapping Nd₂Fe₁₄B within the coating. It was found that higher spray temperatures and finer Nd₂Fe₁₄B particle sizes improved the retention rate of Nd₂Fe₁₄B within the composite structure. This was explained from a contact mechanics viewpoint by calculating the effect of process parameters on the rebound momentum of Nd₂Fe₁₄B particles. The magnetic properties of Nd₂Fe₁₄B remained unaffected by the cold spray process.     

Physical,optical, and electrical properties of a new conducting polymer

This work studies the electrical and optical properties of the conducting polymer composite films of polypyrrole–chitosan (PPy–CHI). The surface plasmon resonance (SPR) technique was used to study the optical properties of PPy and PPy–CHI composite films. Then, the values of the real and imaginary parts of the refractive indexes of PPy and PPy–CHI films were obtained by nonlinear least square fitting using Fresnel equations for a three-layer system of SPR system. The electrical conductivity measurements showed that the conductivity of the electrochemical prepared films improved in the presence of CHI and can be controlled by varying the CHI amount in the composite. The thermal diffusivity of the PPy–CHI composite films was measured by open photoacoustic spectroscopy and it has been shown that the thermal diffusivity is related to the electron migration in the conjugation chain length. The increase in electromagnetic interference shielding effectiveness (EMI SE) with the increase in electrical conductivity of the films is mostly from shielding by reflection rather than absorption.     

T-Stress Effects on Isochromatic Fringe Patterns in Mode II

The theory of photoelasticity is used to study analytically the effects of T-stress on the fringe patterns around the crack tip in mode II crack specimens. The locus of an isochromatic fringe determined by taking into account the T-stress is compared with the locus of a fringe with no T-stress. It is shown for mode II cracks that in the presence of T-stress, the fringe loops are neither symmetric nor continuous. Asymmetric and discontinuous fringe patterns predicted in this paper are consistent with the experimental results observed previously in photoelasticity tests.     

Hydrogen gas sensing properties of microwave-assisted 2D Hybrid Pd/rGO: Effect of temperature,humidity and UV illumination

A novel microwave assisted two-dimensional (2D) hybrid material based on nanostructured reduced graphene oxide (rGO) doped with Pd nanoparticles (Pd/rGO) has been synthesised to investigate its hydrogen sensing performance at different operational conditions. The sensing performance has been evaluated at various operating temperatures (room temperature up to 120 °C), hydrogen concentrations (up to 1%), and relative humidity (up to ~44%). The material characterization of the hybrid Pd/rGO analysed by different techniques which confirms homogeneous distribution of Pd NPs (<35 nm) on the multi-layered porous structure of the rGO nanosheets (NSs) and forming the hybrid Pd/rGO NSs. Moreover, the fundamental hydrogen sensing mechanism as well as recovery enhancement by ultraviolet (UV) light are investigated. This work offers an environmentally friendly and energy-saving synthesis approach for hydrogen sensing with excellent control over experimental parameters which can lead to fabrication of a highly selective and sensitive hydrogen sensor.     

Elimination of porosity in directly fabricated titanium via cold gas dynamic spraying

Cold gas dynamic spray (cold spray) is a deposition technology in which particles achieve supersonic velocities. Commercial purity titanium (CP Ti) is directly fabricated to exploit the potential for cold spray to be utilised as a new fabrication technology. Deposition parameters for elimination of porosity were identified. Results show that using helium as the deposition gas has a significant influence on the elimination of pores. The volume fraction of porosity decreased with a decrease in the distance between the nozzle and the substrate. Furthermore, a decrease in average particle size led to a reduction in porosity of the deposited material. The results show that the directly fabricated CP Ti exhibits a higher hardness compared with wrought CP Ti. Optimisation of cold spray parameters led to a significant reduction of pores in directly fabricated parts.     

Hemodialysis cost in Tehran,Iran

The purpose of this study was to assess the health service cost of hemodialysis (HD) delivered at hospitals in Iran as a developing country with a well‐defined program of renal replacement therapy. A cost analysis was performed from the viewpoint of the 2 hospitals, with 3 shifts and full chairs, on current practice for dialysis maintenance. Cost and patient data were collected in 2006 and from April 1 to May 31, 2007, respectively. A total of 22,464 HD sessions were performed and 247 patients were studied during the study period. The reference year for the value of USD for different mentioned costs was 2006. Health care sector costs associated with each HD session were estimated at US$78.87. Most of the total maintenance expenditure was made up of medical supplies (36.19%), with dialyzers as the major cost driver. Staff salaries represented 17% of the cost and fixed direct capital costs accounted for 21.4%. Of the family members, 32.4% accompanied their patients. The mean cost for transportation of patients and accompanied person was US$3.15 ± 2.83 and US$1.5 ± 0.29, respectively. These findings are important in the light of limited available resources coupled with the increasing prevalence of kidney failure. A major attempt should also be made to increase peritoneal dialysis coverage as in some centers we cannot keep all chairs full, especially in some vast areas. It is highly recommended to place initial focus on strategies and treatments that slow disease progression, to postpone renal replacement therapy to save resources.