Defect-Enhanced Polarization Switching in the Improper Ferroelectric LuFeO3

Results of switching behavior of the improper ferroelectric LuFeO₃ are presented. Using a model set of films prepared under controlled chemical and growth-rate conditions, it is shown that defects can reduce the quasi-static switching voltage by up to 40% in qualitative agreement with first-principles calculations. Switching studies show that the coercive field has a stronger frequency dispersion for the improper ferroelectrics compared to a proper ferroelectric such as PbTiO₃. It is concluded that the primary structural order parameter controls the switching dynamics of such improper ferroelectrics.     

Investigation on multiferroic properties of BiFeO3 ceramics

BiFeO₃ polycrystalline ceramics was prepared by solid-state reaction method and its structural, optical and magnetic properties were investigated. BiFeO₃ was synthesized in a wide range of temperature (825–880 °C) and a well crystalline phase was obtained at a sintering temperature of 870 °C. X-ray diffraction patterns of the samples were recorded and analyzed for the confirmation of crystal structure and the determination of the lattice parameters. The average grain size of the samples was found to be between 1–2 μm. The determined value of direct bandgap of BiFeO₃ ceramics was found to be 2.72 eV. The linear behavior of M-H curve at room temperature confirmed antiferromagetic properties of the BiFeO₃ (BFO). S shaped M-H curve was obtained at a temperature of 5 K. In the whole temperature measurement range (5–300 K) of M-T, no anomalies were observed due to high Curie temperature and Neel temperature of the BiFeO₃.     

Evolution to similarity solutions for polymerization and depolymerization with microwave radiation

The kinetics of polymerization and depolymerization are critical in understanding the stability and characterization of polymers. The kinetics of simultaneous polymerization and degradation of poly(methyl methacrylate) have been investigated by varying the initiator concentration and monomer concentration under the influence of microwave energy. Microwave radiation initially polymerizes the monomer, then degrades the resulting polymer and the polymer attains an equilibrium molecular weight distribution with a polydispersity of two. To understand more fully the kinetics, the molecular weight distribution (MWD) is represented as a gamma distribution; the random degradation rate coefficient is assumed to vary linearly with molecular weight and the polymerization rate coefficient is assumed to be independent of molecular weight. The change of the MWD with time is studied by continuous distribution kinetics; the solutions obtained depict the change of the average molecular weight, polydispersity and the gamma distribution parameters with time. Experimental data indicate that reaction rates are enhanced by microwave radiation and the MWD approaches a similarity solution within 10 min for all the investigated cases. The model satisfactorily predicts the change of the MWD with time. © 2001 Society of Chemical Industry     

On-line density and crystallinity of polyethylene terephthalate during melt spinning

The density and crystallinity of polyester fiber were measured on the moving threadline during the melt spinning process. The density was calculated by applying the continuity equation at points along the length of the threadline. Experimental inputs to the equation included paralle, on-line measurements of fiber diameter, fiber velocity, polymer mass flowrate, fiber temperature, and fiber birefringence. When spinning speeds exceeded 4500 m/min, a distinct rise in density occurred along the threadline. This rise corresponded with the rise in birefringence.     

Pd/Fe3O4 supported on bio-waste derived cellulosic-carbon as a nanocatalyst for C–C coupling and electrocatalytic application

The current work describes the synthesis of a new bio-waste derived cellulosic-carbon supported-palladium nanoparticles enriched magnetic nanocatalyst (Pd/Fe₃O₄@C) using a simple multi-step process under aerobic conditions. Under mild reaction conditions, the Pd/Fe₃O₄@C magnetic nanocatalyst demonstrated excellent catalytic activity in the Hiyama cross-coupling reaction for a variety of substrates. Also, the Pd/Fe₃O₄@C magnetic nanocatalyst exhibited excellent catalytic activity up to five recycles without significant catalytic activity loss in the Hiyama cross-coupling reaction. Also, we explored the use of Pd/Fe₃O₄@C magnetic nanocatalyst as an electrocatalyst for hydrogen evolution reaction. Interestingly, the Pd/Fe₃O₄@C magnetic nanocatalyst exhibited better electrochemical activity compared to bare carbon and magnetite (Fe₃O₄ nanoparticles) with an overpotential of 293 mV at a current density of 10 mA·cm^–2.     

A Rapid,Micro FAME Preparation Method for Vegetable Oil Fatty Acid Analysis by Gas Chromatography

A 30-min, micro-base-catalyzed method for vegetable oil fatty acid methyl ester (FAME) preparation was developed using only 1 mg of oil sample by limiting the solvent volumes used. This method was primarily developed to quickly analyze fatty acid composition of CLA-rich soy oil but can be further applicable to pure vegetable oils. Existing base-catalyzed FAME preparation methods are not appropriate to use because they are either rapid but not micro, or micro but not rapid, or are rapid and micro but use acidification in the final step of FAME preparation, which would isomerize oils containing conjugated fatty acids. Serial dilutions of a mixed commercial FAME reference standard were prepared and analyzed by GC with a flame ionization detector (FID) with maximum instrument sensitivity. The novel method was also used to prepare soy oil FAMEs for GC-FID analysis. There were no statistically significant differences (P < 0.05) in fatty acid data from the FAME reference standard dilutions. Similarly, there was no statistical significant difference (P < 0.05) between results obtained for all the soy oil dilutions and the control method. This technique is a rapid method for preparing small pure oil samples as FAMEs for GC-FID analysis.     

Silicon nanoelectronics and beyond: An overview and recent developments

This year marks the 40th anniversary of the invention of the first beam-lead device by Lepselter et al. Lepselter and coworkers proposed a method of fabricating a new semiconductor device structure and its application to high-frequency silicon switching transistors and ultra-high-speed integrated circuits. Beam-lead technology, also known as air-bridge technology, has established itself for its unsurpassed reliability in high-frequency silicon switching transistors and ultra-high-speed integrated circuits for telecommunications and missile systems. The beam-lead device became the first example of a commercial microelectromechanical structure (MEMS). Since its inception, MEMS has taken advantage of the evolving silicon technology, resulting in today’s nano-electromechanical structure and nano-optomechanical structure. In this paper, an overview of recent developments of silicon nanoelectronics is presented. For more information, contact N.M. Ravindra, New Jersey Institute of Technology, Interdisciplinary Program in Materials Science and Engineering, Department of Physics, Newark, New Jersey 07102; (973) 596-3278; fax (973) 642-4978; e-mail nmravindra@comcast.net.     

Thermal performance evaluation of a four pan jaggery processing furnace for improvement in energy utilization

The jaggery making from sugarcane is one of the traditional process industries contributing to the local employment and entrepreneurship opportunities to the rural population. Jaggery is a condensed form of sugarcane juice produced by evaporation of moisture. Bagasse which is internally generated during juice extraction from sugarcane is used as the fuel for evaporation in a jaggery furnace. Any efficiency improvement in the thermal performance of a jaggery furnace leads to bagasse saving which provides additional revenue for the jaggery manufacturer.     

Investigation of potential ionic interactions between anionic and cationic polymethacrylates of multiple coatings of novel colonic delivery system

The objective of this work was to investigate potential interactions between anionic (Eudragit FS) and cationic (Eudragit RL) polymethacrylates of multiple coatings of a novel colonic drug delivery system. Aqueous films of pure polymers Eudragit FS (FS) and Eudragit RL (RL) and their superimposedfilm (FS-RL) were cast on glass slabs. The potential ionic interactions were studied by analysing the dried films using differential scanning calorimetry (DSC), Fourier transform-infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR). The glass transition temperatures (Tg) of pure RL and FS were 60 degrees C and 22 degrees C, respectively; FS-RL showed two distinct glass transitions at 59 degrees C and 24 degrees C in the second heating cycle. In the 13C-MAS spectra of the samples in the solid state, no shifts of the resonance could be detected in the superimposed film compared with the pure polymers. The FT-IR spectra of the superimposed film did not show any significant shift of the bands of the -NMe3+ group of RL and the -COO- function of FS compared with the spectra of the pure polymers. No ionic interactions between anionic and cationic polymethacrylates were revealed by DSC, FT-IR, and NMR.     

Genetically evolved radial basis function network based prediction of drill flank wear

The most important factor that governs the performance of a radial basis function network (RBFN) is the optimization of the network architecture, i.e. determining the exact number of radial basis functions (RBFs) in the hidden layer that can best minimize the error between the actual and network outputs. This work presents a genetic algorithm (GA) based evolution of optimal RBFN architecture and compares its performance with the conventional RBFN training procedure employing a two stage methodology, i.e. utilizing the k-means clustering algorithm for the unsupervised training in the first stage, and using linear supervised techniques for subsequent error minimization in the second stage. The validation of the proposed methodology is carried out for the prediction of flank wear in the drilling process following a series of experiments involving high speed steel (HSS) drills for drilling holes on mild-steel workpieces. The genetically grown RBFN not only provides an improved network performance, it is also computationally efficient as it eliminates the need for the error minimization routine in the second stage training of RBFN.