Local inhomogeneity and surface degradation of Fe1.15Te and Fe1.03Te0.62Se0.38 single crystals

We have investigated the structural and magnetic properties of Fe_1.15Te and Fe_1.03Te_0.62Se_0.38 single crystals grown by slow cooling method using a specially designed double-walled quartz ampoule. X-ray diffraction reveals significant local inhomogeneity as a result of fractional substitution of Te site by Se in single crystal Fe_1.03Te_0.62Se_0.38. The existence of superconductivity is confirmed for Se substitution to the Te site of Fe_1.03Te_0.62Se_0.38 but with persistent Fe₇Se₈ impurity phase. Raman spectroscopy confirmed the surface structural instability when the samples were exposed to moderate laser irradiation in the atmospheric environment. With high intensity laser irradiation, Fe(Se,Te) compounds can be decomposed into Fe₂O₃ hematite phase.     

Facile heterogenisation of molecular Ti(OSiPh3)4 to form a highly active epoxidation catalyst

The simple grafting procedure of Ti(OSiPh₃)₄ onto the internal surface of MCM-41 to produce an epoxidation catalyst of high activity and selectivity is described. The presence of the phenyl groups on each titanium centre increases the longevity of their catalytic activity towards attack from atmospheric moisture. The conversion of the catalytically inactive titanium centre of the precursor compound to an active centre is followed using XANES.     

Skin permeation of buflomedil form adhesive matrix patches

The main objective of this research work was to fabricate and evaluate adhesive matrix-type transdermal patches of buflomedil hydrochloride, employing different ratios of pressure sensitive adhesives (PSAs) by solvent casting technique. The adhesive matrix-type transdermal patches were evaluated by their in vitro physicochemical properties such as thickness, moisture content, weight variation, drug content uniformity, etc. The effects of PSAs ratio, drug loading, and concentration of permeation enhancer were evaluated thoroughly. Ex vivo skin permeation studies with kinetic modeling of adhesive matrix patches were systematically evaluated. Based on the above observations, the best optimized buflomedil hydrochloride-loaded adhesive matrix-type transdermal patch was further characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction study, and differential scanning calorimetry analyses. Drug containing adhesive matrix patches showed sustained release property without showing any incompatibility in adhesive matrix system. Hence, adhesive matrix-type transdermal patches of buflomedil hydrochloride can be used as a potential carrier for sustained transdermal delivery of hydrophilic drugs like buflomedil hydrochloride.     

Subspace Identification of Transfer Function Models for an Unstable Bioreactor

This work deals with the identification of transfer function model of an unstable bioreactor by a subspace-based identification method. The data set is generated from the simulated closed loop system by giving a random signal at the reference signal. The linear system matrices are estimated through the Multivariable Output Numerical algorithms for Subspace State Space System Identification (MON4SID) algorithm. The delay is estimated directly from the input–output data by the impulse response method. The identified First Order Plus Time Delay (FOPTD) model is compared with the locally linearized transfer function model derived around the unstable operating point. A Proportional Integral Derivative (PID) controller is designed for the identified model using the equating coefficient method. The closed loop servo and regulatory responses show that the model identified by MON4SID is similar to the linearized model and the optimization method.     

On the Nature and Location of Organic Template Molecules and Their Effect on the Stability and Redox Properties of Microporous CoAlPO-34 Catalyst

Small-pore CoAlPO-34 materials were synthesized with a variety of organic template molecules and were characterized in detail, employing microcrystal diffraction, powder diffraction and in situ combined XRD/XAS techniques. We found that, when two template molecules or two nitrogen atoms of a single template molecule are present inside the chabazitic cage, the concentration of cobalt present in the system is ca. 25?at%, which introduces instability in the framework structure during the removal of the organic template. In contrast, when only one template molecule is present, it is possible to control the concentration of Co(II) ions in the framework to ca. 10?at%; these systems show good structural integrity and redox chemistry that was exploited for the regio-selective conversion of linear alkane molecules.     

Performance evaluation of TiAlCrYN nanocomposite coatings deposited using four-cathode reactive unbalanced pulsed direct current magnetron sputtering system

Approximately 1.5-2.5 μm thick nanocomposite coatings of TiAlCrYN were deposited using a four-cathode reactive unbalanced pulsed direct current magnetron sputtering system from the sputtering of Ti, Al, Cr, and Y targets in Ar + N₂ plasma. The TiAlCrYN nanocomposite coatings were deposited on various substrates such as high speed steel (HSS) drill bits, mild steel and silicon. TiAlCrYN coatings with almost similar mechanical properties but with different Ti, Al, Cr and Y contents were prepared to study their thermal stability and machining performance. The structural and mechanical properties of the coatings were characterized using X-ray diffraction and nanoindentation technique, respectively. The elemental composition, bonding structure, surface morphology and cross-sectional data were studied using energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy and field-emission scanning electron microscopy, respectively. Nanoscratch tests were performed to determine the adhesive strength of the coatings. The corrosion behavior of TiAlCrYN nanocomposite coatings on mild steel substrate was studied using potentiodynamic polarization in a 3.5% NaCl solution. Micro-Raman spectroscopy was used to characterize the structural changes as a result of heating of the nanocomposite coatings in air (600-1000 °C). TiAlCrYN coatings prepared at 17 at.% Ti, 13 at.% Al, 21 at.% Cr and 1 at.% Y exhibited thermal stability as high as 900 °C in air (denoted as Sample 3). For the performance evaluation, the TiAlCrYN coated HSS drill bits were tested under accelerated machining conditions. With a drill speed of 800 rpm and a feed rate of 0.08 mm/rev the TiAlCrYN coated HSS drill bits (Sample 3) averaged 657 holes, while drilling a 12 mm thick 304 stainless steel plate under dry conditions, before failure. Whereas, the uncoated drill bits failed after drilling 50 holes under the same machining conditions. Results indicated that for the HSS drill bits coated with TiAlCrYN, the tool life increased by a factor of more than 12.     

Liquid sloshing in rectangular road containers

A study of liquid behaviour in rectangular road containers undergoing a turning or braking manoeuvre is presented and discussed. The steady-state solution in terms of liquid heights, forces and overturning moments is derived analytically from the hydrostatic equations. The transient response of the liquid is obtained via numerical solution of the continuity, Navier-Stokes and free-surface equations. The governing equations are discretized in a Eulerian mesh and solved with respect to the nondimensional primitive variables together with the boundary conditions at rigid walls and the free surface using a modified marker-and-cell technique. Such an approach allows one to take into account all basic nonlinearities proper to the sloshing problem and to obtain the damped frequencies and magnitudes of the sloshing parameters. The present study is a contribution to the overall dynamics of coupled “vehicle-liquid” systems performing some road manoeuvres.