Fabrication,Structure and Properties of Epoxy/Metal Nanocomposites

Gd₂O₃ nanoparticles surface‐modified with IPDI were compounded with epoxy. IPDI provided an anchor into the porous Gd₂O₃ surface and a bridge into the matrix, thus creating strong bonds between matrix and Gd₂O₃. 1.7 vol.‐% Gd₂O₃ increased the Young's modulus of epoxy by 16–19%; the surface‐modified Gd₂O₃ nanoparticles improved the critical strain energy release rate by 64.3% as compared to 26.4% produced by the unmodified nanoparticles. The X‐ray shielding efficiency of neat epoxy was enhanced by 300–360%, independent of the interface modification. Interface debonding consumes energy and leads to crack pinning and matrix shear banding; most fracture energy is consumed by matrix shear banding as shown by the large number of ridges on the fracture surface.

     

Performance evaluation of combined adsorption refrigeration cycles

This paper presents the results of an investigation on the performance of combined adsorption refrigeration cycles. The novel combined cycle amalgamates the activated carbon (AC)-R507A as the bottoming cycle and AC-R134a cycle as the topping cycle and deliver refrigeration load at as low as −10 °C at the bottoming cycle. The cycle simulation is based on the experimentally confirmed adsorption isotherms, kinetics and isosteric heat of adsorption data for R134a and R507A on highly porous based activated carbon of type Maxsorb III. The optimum cooling capacity, coefficient of performance (COP) and chiller efficiency are calculated in terms of cycle time, switching time, regeneration and brine inlet temperatures. Results show that the combined adsorption cycles are feasible even when low-temperature heat source is available.     

Effects of THF as cosolvent in the preparation of polydimethylsiloxane/polyethersulfone membrane for gas separation

Polydimethylsiloxane/polyethersulfone (PDMS/PES) asymmetric membranes are widely applied in gas separation. However, the effects of common cosolvent on these membranes remain unknown. In order to study the changes in membrane morphology and gas separation properties, asymmetric PDMS/PES membranes were prepared. The studied parameters were types of cosolvents, tetrahydrofuran (THF) concentration, evaporation time, and PDMS concentration. Membrane morphology was examined using scanning electron microscopy and gas separation was conducted using pure CO₂, N₂, CH₄, and Hat 25°C. The addition of cosolvent into the polymer solution decreased the dope viscosity and delayed liquid–liquid demixing during phase inversion. Macrovoids formation was observed in substructure layer after adding THF and these macrovoids elongated with the reduction in THF content. There were microvoids formed on top of macrovoids and microvoids layer became thicker due to the increasing evaporation time of solvents before coagulation in nonsolvent. The PDMS coating on the PES membrane formed a dense skin layer and exhibited higher selectivity compared to the uncoated membrane. Membrane contained THF cosolvent with 60 s evaporation time and 3 wt% coated PDMS is the optimum membrane among other membranes in this work. The CO₂/N₂ selectivity was enhanced by 73.3% with CO₂ permeance of 44.86 GPU. POLYM. ENG. SCI., 54:2177–2186, 2014. © 2013 Society of Plastics Engineers     

The kinetics of interactions between fecapentaene-12 and DNA

Fecapentaene-12 (Fp-12) is a potent colon cancer mutagen, which interacts with DNA. In this study, the kinetics of its interactions with DNA is investigated. Various pHs are used. Three first-order rates are observed at each pH. This suggests that interaction between Fp-12 and DNA occurs through three different mechanisms.     

A Facile Approach to Chemically Modified Graphene and its Polymer Nanocomposites

A scalable approach for the mass production of chemically modified graphene has yet to be developed, which holds the key to the large‐scale production of stable graphene colloids for optical electronics, energy conversion, and storage materials, catalysis, sensors, composites, etc. Here, a facile approach to fabricating covalently modified graphene and its polymer nanocomposites is presented. The method involves: i) employing a common furnace, rather than a furnace installed with a quartz tube and operated in inert gas as required in previous studies, to treat a commercial graphite intercalation compound with thermal shocking and ultrasonication and fabricate graphene platelets (GnPs) with a thickness of 2.51 ± 0.39 nm that contain only 7 at% oxygen; ii) grafting these GnPs with a commercial, long‐chain surfactant, which is able to create molecular entanglement with polymer matrixes by taking advantage of the reactions between the epoxide groups of the platelets and the end amine groups of the surfactant, to produce chemically modified graphene platelets (m‐ GnPs); and iii) solution‐mixing m‐GnPs with a commonly used polymer to fabricate nanocomposites. These m‐GnPs are well dispersed in a polymer with highly improved mechanical properties and a low percolation threshold of electrical conductivity at 0.25 vol%. This novel approach could lead to the future scalable production of graphene and its nanocomposites.     

The effects of ruminally degraded protein on rumen fermentation and ammonia losses from manure in dairy cows

This experiment investigated the effect of dietary crude protein (CP) and ruminally degraded protein (RDP) levels on rumen fermentation, digestibility, ammonia emission from manure, and performance of lactating dairy cows. The experiment was a replicated 3 × 3 Latin square design with 6 cows. Three diets varying in CP concentration were tested (CP, % of dry matter): 15.4 (high CP, control), 13.4 (medium CP), and 12.9% (low CP). These diets provided metabolizable protein balances of 323, −44, and 40 g/d and RDP balances of 162, −326, and −636 g/d (high, medium, and low, respectively). Both the medium and low CP diets decreased ruminal pH compared with high CP, most likely because of the higher nonfiber carbohydrate concentration in the former diets. Ruminal ammonia pool size (rumen ammonia N was labeled with ¹⁵N) and the concentration of total free amino acids were greater for the high CP diet than for the RDP-deficient diets. Apparent total-tract nutrient digestibilities were not affected by treatment. Both the medium and low CP diets resulted in lower absolute and relative excretion of urinary N compared with the high CP diet, as a proportion of N intake. Excretion of fecal N and milk yield and composition were not affected by diet. Milk N efficiency (milk N ÷ N intake) and the cumulative secretion of ammonia-¹⁵N in milk protein were greater for the RDP-deficient diets, and milk urea N concentration was greater for the high CP diet. Both medium and low CP diets decreased the irreversible loss of ruminal ammonia N compared with the high CP diet. The rate and cumulative ammonia emissions from manure were lower for the medium and low CP diets compared with the high CP diet. Overall, this study demonstrated that dairy diets with reduced CP and RDP concentrations will produce manure with lower ammonia-emitting potential without affecting cow performance, if metabolizable protein requirements are met.     

Interactive instabilities of thin‐walled laminated composite pultrusion box columns

The problem of interactive buckling and post‐buckling of intermediate length thin‐walled columns built of laminated plate elements subjected to compressive load has been proposed and solved analytically. Pultrusion columns have wide‐range applications in high‐rise building due to their low weight and high load carrying capacity. Classic stability theory and laminate theory were implemented to prove the existence of mixed‐mode buckling in thin‐walled pultrusion columns. Interactive stability modes can result in lower loading capacity of most compressive members and affects their post‐buckling behaviour in major proportions. Interactive buckling load analysis has been performed by means of a simplified theoretical model and verified by means of numerical analysis. The calculations were carried out for commonly used square section thin‐walled composite columns dimensions. The post‐buckling performance of selected sections has been investigated and an optimum layup configuration criterion for each section has been extracted according to pre‐ and post‐critical behaviour. Copyright © 2010 John Wiley & Sons, Ltd.     

High performance of bulk Mo2N and Co3Mo3N catalysts for hydrogen production from ammonia: Role of citric acid to Mo molar ratio in preparation of high surface area nitride catalysts

Hydrogen production from ammonia decomposition was studied using a series of unsupported high surface area molybdenum nitride (Mo₂N) and cobalt promoted molybdenum nitride (3%Co-Mo₂N) catalysts prepared with citric acid (CA) as a chelating agent. To elucidate the influence of citric acid amount in preparation conditions on the structure and catalytic activity, we prepared catalysts with different citric acid to Mo molar ratios i.e. CA/Mo = 1, 2, 3 and 4. The catalytic activity was evaluated in the temperature range of 300–600 °C at atmospheric pressure. The catalytic activity of the tested samples has changed in the following order of CA/Mo atomic ratio of 1 < 2 < 3 > 4. Therefore, the catalyst prepared by using CA/Mo ratio = 3 showed the highest catalytic activity. BET, XRD, XPS, SEM and TEM-EDS techniques were been used to characterize the catalysts. The increased activity of Mo₂N-3:1 and 3%Co-Mo₂N-3:1 catalysts was due to increased surface area, decreased particle size and increased relative proportions of Mo₂N and Co₃Mo₃N phases. The ammonia conversion for 3%Co-Mo₂N catalyst was increased from 75 to 97% at 550 °C with the increase of CA/Mo ratio from 1 to 3. This enrichment of activity in 3%Co-Mo₂N-3:1 catalyst is due to increased dispersion of Co₃Mo₃N microstructure on γ-Mo₂N platelets confirmed by SEM and TEM results. No deactivation was observed for any catalysts investigated in this study for ammonia decomposition.     

Liquid natural rubber (LNR) as a compatibilizer in NR/LLDPE blends

The effects of molecular weight of LNR, as a compatibilizer in NR/LLDPE blends, were studied. Rheological studies and mechanical properties of the blends showed that the molecular weight of LNR played a very important role in determining their performance. The blends that contained 15–25% LNR with an M_w of 4.8 × 10⁵ and an M_n of 1.66 × 10⁵ showed the highest mechanical properties. Outside this range of molecular weight, the compatibilizing property of LNR is no longer effective due to inhomogeneous blends. Improvements in the mechanical properties were in consonance with the increase in gel contents of the blends. The additions of LNR in the blends were able to reduce the interfacial tension; therefore, they improved the interaction between the phases of the blends. The studies also confirmed that, within the concentration range investigated, the LNR solvent did not influence the blend properties. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1776–1782, 2000