Influence of the physico-chemical properties of Selangor soil series on the distribution coefficient (<Emphasis Type="Italic">K</Emphasis><Subscript>d</Subscript>-value) of <Superscript>226</Superscript>Ra

²²⁶Ra is a member of the ²³⁸U natural decay series and is one of the most important isotope to be determined among the naturally occurring nuclides in environmental samples. In order to evaluate the radiation dose from ²²⁶Ra, it is important to know its mobility in different types of soils. The aim of the present study is to quantify the influence of physico-chemical soil properties on ²²⁶Ra adsorption. The distribution coefficients (K _d-value) of ²²⁶Ra in Selangor soil series samples were measured in one core, at three depth levels to evaluate the adsorbability of ²²⁶Ra. The soil samples were spiked with ²²⁶Ra tracer and the activities of ²²⁶Ra in the separated phase from batch sorption test were measured by a low background but high efficiency well-type HPGe detector. Several physico-chemical soil properties were also characterised for each soil samples. Pearson’s correlation and stepwise multiple regression test were applied at the 0.05 level of significance throughout all analysis to determine the relationships and influences between distribution coefficients (K _d-value) of ²²⁶Ra with physicochemical soil properties for the Selangor soil series. The observed K _d value was in the range of 50.55–172.28 mL g⁻¹ (mean: 93.20 ± 46.99 mL g⁻¹). The regression showed that the highest positive correlations were observed for organic matter (OM) and cation exchange capacity (CEC) (r = 0.96**, 0.81**, respectively) with K _d-values. The results indicate that the stepwise multiple regression model incorporating the soil’s OM and CEC accounts for 98% of the variability in distribution coefficients of ²²⁶Ra.     

Preparation of cellulose nanofibers with hydrophobic surface characteristics

The aim of this study was to develop cellulose nanofibers with hydrophobic surface characteristics using chemical modification. Kenaf fibers were modified using acetic anhydride and cellulose nanofibers were isolated from the acetylated kenaf using mechanical isolation methods. Fourier transform infrared spectroscopy (FTIR) indicated acetylation of the hydroxyl groups of cellulose. The study of the dispersion demonstrated that acetylated cellulose nanofibers formed stable, well-dispersed suspensions in both acetone and ethanol. The contact angle measurements showed that the surface characteristics of nanofibers were changed from hydrophilic to more hydrophobic when acetylated. The microscopy study showed that the acetylation caused a swelling of the kenaf fiber cell wall and that the diameters of isolated nanofibers were between 5 and 50 nm. X-ray analysis showed that the acetylation process reduced the crystallinity of the fibers, whereas mechanical isolation increased it. The method used provides a novel processing route for producing cellulose nanofibers with hydrophobic surfaces.     

Metal-Assisted and Microwave-Accelerated Evaporative Crystallization

We describe a platform technology, called metal-assisted and microwave-assisted evaporative crystallization (MA-MAEC), based on the combined use of silver nanoparticles and microwave heating for selective and rapid crystallization of small molecules. In this regard, the crystallization of a model small molecule (glycine) was achieved in several seconds. Glycine crystals grown on silver nanostructures with and without microwave heating were found to be larger than those grown on blank glass slides. The MA-MAEC technique has the potential to selectively grow the desired polymorphs of small molecules "on-demand" in a fraction of the time as compared to the conventional evaporative crystallization.     

Analysis of coir fiber acoustical characteristics

Coir fiber from coconut husk is an important agricultural waste in Malaysia. Acoustic absorption coefficient of the fiber as a porous material is studied in this paper. Two types of fiber are investigated, fresh from wet market and industrial prepared mixed with binder. Moreover two analytical models, namely; Delany–Bazley and Biot–Allard are used for analysis. Experimental measurements in impedance tube are conducted to validate the analytical outcomes. Results show that fresh coir fiber has an average absorption coefficient of 0.8 at f > 1360 Hz and 20 mm thickness. Increasing the thickness is improved the sound absorption in lower frequencies, having the same average at f > 578 Hz and 45 mm thickness. Delany–Bazley technique can be used for both types of fiber while Biot–Allard method is compensated for the industrial prepared fiber considering the binder additive. This form generally shows poor acoustical absorption in low frequencies. Inevitably, fiber has to be mixed with additives in commercial use to enhance its characteristics such as stiffness, unti-fungus and flammability. Hence other approaches such as adding air gap or perforated plate should be used to improve the acoustical properties of industrial treated coir fiber.     

Experimental investigation of long-wavelength optical lattice vibrations in quaternary AlxInyGa1−x−yN alloys and comparison with results from the pseudo-unit cell model

Raman and Fourier transform infrared (FTIR) spectroscopies have been utilized to measure long-wavelength optical lattice vibrations of high-quality quaternary Al_xIn_yGa_1−x−yN thin films at room temperature. The Al_xIn_yGa_1−x−yN films were grown on c-plane (0 0 0 1) sapphire substrates with AlN as buffer layers using plasma assisted molecular beam epitaxy (PA-MBE) technique with aluminum (Al) mole fraction x ranging from 0.0 to 0.2 and constant indium (In) mole fraction y=0.1. Pseudo unit cell (PUC) model was applied to investigate the phonons frequency, mode number, static dielectric constant, and high frequency dielectric constant of the Al_xIn_yGa_1−x−yN mixed crystals. The theoretical results were compared with the experimental results obtained from the quaternary samples by using Raman and FTIR spectroscopies. The experimental results indicated that the Al_xIn_yGa_1−x−yN alloy had two-mode behavior, which includes A₁(LO), E₁(TO), and E₂(H). Thus, these results are in agreement with the theoretical results of PUC model, which also revealed a two-mode behavior for the quaternary nitride. We also obtained new values of E₁(TO) and E₂(H) for the quaternary nitride samples that have not yet been reported in the literature.     

Effects of MnO<Subscript>2</Subscript> nano-particles on the conductivity of PMMA-PEO-LiClO<Subscript>4</Subscript>-EC polymer electrolytes

Li-ion rechargeable batteries based on polymer electrolytes are of great interest for solid state electrochemical devices nowadays. Many studies have been carried out to improve the ionic conductivity of polymer electrolytes, which include polymer blending, incorporating plasticizers and filler additives in the electrolyte systems. This paper describes the effects of incorporating nano-sized MnO₂ filler on the ionic conductivity enhancement of a plasticized polymer blend PMMA–PEO–LiClO₄–EC electrolyte system. The maximum conductivity achieved is within the range of 10⁻³ S cm⁻¹ by optimizing the composition of the polymers, salts, plasticizer, and filler. The temperature dependence of the polymer conductivity obeys the VTF relationship. DSC and XRD studies are carried out to clarify the complex formation between the polymers, salts, and plasticizer.     

Gas by-products of CF3I under AC partial discharge

This paper presents the decomposition by-products of trifluro-iodo-methane and their relative proportions in the gas phase under the occurrence of partial discharge. The experiment was performed in the presence of water vapor from 250 to 400 ppm under a non-uniform electric field configuration. The experimental results reveal that the by-products of C₂F₆, C₂F₄, C₂F₅I with the amount of 1300, 200, and 55 (CH₃I) ppm, respectively, were produced for a cumulative charge of 161 mC. Other by-products, such as C₃F₈, CHF₃, C₃F₆ CH₃I were obtained at less than 30 ppm C₂F₆ was the dominant gas by-product of trifluro-iodo-methane suffering partial discharge.     

Modelling and measuring the thermal conductivity of multi-metallic Zn/Cu nanofluid

A metallic nanofluid is a suspension of metallic nanoparticles in a base fluid. Multi-metallic nanoparticles are a combination of two or more types of metallic particles. Such multi-metallic nanoparticles were suspended in water using an ultrasonic vibrator for different total volume fractions and different ratios of metallic/metallic nanoparticles. A transient hot wire setup was built to measure the thermal conductivity of the nanofluid at different temperatures. The experimental results were in good agreement with the results in the literature. Then, the experimental results were used as input data for an adaptive neural fuzzy inference system (ANFIS) to predict the thermal conductivity of the multi-metallic nanofluid. The maximum deviation between the ANFIS results and experimental measurements was 1 %. The predicted results and the experimental data were compared with other models. The ANFIS model was found to have good ability to predict the thermal conductivity of the multi-metallic nanofluid over the range of the experimental results.     

Phosphorus ligands for iron(III)‐mediated ATRP of styrene via generation of activators by monomer addition

Styrene polymerization via generation of activators by monomer addition (GAMA) for atom transfer radical polymerization (ATRP) has been examined extensively with bulk FeX₃ and FeX₂ at 110 °C in conjunction with various phosphorus‐bearing ligands. It was found that GAMA possesses advantages over normal ATRP. Most importantly, narrower polydispersity index (PDI) values were observed from the styrene polymerizations with Fe(III) over those with Fe(II). Every instance of 2‐(diphenylphosphino)‐N,N′‐dimethyl‐[1,1′‐biphenyl]‐2‐amine and 2‐(diphenylphosphino) pyridine with the Fe(III) system were controlled excellently without addition of any radical initiator or reducing agent additives. Initiator type was found to exert a significant factor to influence on the controllability of polymerization. The initiation of 1‐phenylethyl chloride and methyl‐2‐chloropropionate gave rise to formation of polymers with narrow PDI (1.05–1.20), whereas those from 1‐phenylethyl bromide increased to 1.35. The GAMA of bulk styrene exhibited the best performance in terms of both rate and controllability compared with toluene and anisole. Both formation of block copolymer from the macroinitiator and efficient perturbation of polymerization with 2,2,6,6‐tetramethylpiperidine 1‐oxyl provided firm evidence to support the living and radical characteristics for the GAMA of styrene. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 144–151, 2010