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.     

Mechanism of Ruthenium (III) Catalysis of Periodate Oxidation of Aldoses in Aqueous Alkaline Medium

The NO/H₂ reaction has been studied over a Ni loaded carbon film catalysts using in situ FTIR spectroscopy at the temperature range 25–350°C. On these catalysts, the differences in activity and selectivity were found depending on the nature of the surface functional groups. These differences were correlated with transient infrared spectral features which appeared during the reaction. It has been proved experimentally that the chemical character of the support is of vital importance during the process. The rise in NO conversion and N₂ selectivity was observed when the surface of the catalysts was changed by the NH₃ chemisorption. Amide and/or imide species formed due to the reduction of ammonium salts of carboxylic acids can play a significant role as active centers during the NO reduction.     

Rheological behaviour of emulsions of avocado and watermelon oils during storage

Rheological properties of emulsions made out of avocado pulp and watermelon seed oils with whey protein concentrate were determined during different storage periods. The oils, as well as the emulsions behaved like non-Newtonian liquids, having shear-thinning characteristics. Both oils showed moderate shear-thinning characteristics as the flow behaviour indices were between 0.86 and 0.88. The shear-rate/shear-stress data could be adequately fitted (r = 0.997–0.999) to a common rheological equation, e.g. the power-law model. Avocado pulp oil was markedly more viscous than was watermelon seed oil which was also evident from the higher apparent viscosity and consistency index values.     

Crack stability in edge-notched clamped beam specimens: modeling and experiments

Stability of a fracture toughness testing geometry is important to determine the crack trajectory and R-curve behavior of the specimen. Few configurations provide for inherent geometric stability, especially when the specimen being tested is brittle. We propose a new geometrical construction called the single edge notched clamped bend specimen (SENCB), a modified form of three point bending, yielding stable cracking under load control. It is shown to be particularly suitable for small-scale structures which cannot be made free-standing, (e.g., thin films, coatings). The SENCB is elastically clamped at the two ends to its parent material. A notch is inserted at the bottom center and loaded in bending, to fracture. Numerical simulations are carried out through extended finite element method to derive the geometrical factor f(a/W) and \(\hbox {K}_{\mathrm{I}}\) for different beam dimensions. Experimental corroborations of the FEM results are carried out on both micro-scale and macro-scale brittle specimens. A plot of \(\hbox {K}_{\mathrm{I}}\) vs a/W, is shown to rise initially and fall off, beyond a critical a/W ratio. The difference between conventional SENB and SENCB is highlighted in terms of \(\hbox {K}_{\mathrm{I}}\) and FEM simulated stress contours across the beam cross-section. The \(\hbox {K}_{\mathrm{IC}}\) ’s of bulk NiAl and Si determined experimentally are shown to match closely with literature values. Crack stability and R-curve effect is demonstrated in a PtNiAl bond coat sample and compared with predicted crack trajectories from the simulations. The stability of SENCB is shown for a critical range of a/W ratios, proving that it can be used to get controlled crack growth even in brittle samples under load control.     

Synthesis,structural and optical characterization of ZrO2 core–ZnO@SiO2 shell nanoparticles prepared using co-precipitation method for opto-electronic applications

Nanocrystalline Zirconia (ZrO₂) and Zinc oxide (ZnO) as well as Silica (SiO₂) coated ZrO₂ core–shell structures were synthesized by both Co-precipitation and seeded polymerization technique. The phase analysis and the core–shell structure formation were confirmed by X-ray diffraction (XRD), FESEM and high resolution transmission electron microscopy (HRTEM) analysis. The existence of SiO₂ on ZrO₂@ZnO was characterized by FT-IR measurement. UV–Vis study reveals coating of ZnO over Zirconia shows red shift in the absorption spectra. Photoluminescence studies show the non-monotonous variation in luminescence behavior of these core–shell nanoparticles. This investigation explains that the interfacial effect between the core (ZrO₂) and the shell materials (ZnO and SiO₂) can be exploited to tune the optical properties of the material. This implies that we can envisage the core–shell materials as potential candidates for optical–electronic devices.     

Basis arrays and successive packing for M-D interleaving

In this paper, we first present a novel concept of 2-D basis interleaving array (also referred to as basis array for short). That is, an m × m interleaved array is said to be a basis array if the shortest distance among all pairs of elements in each of the so-called m-equivalent sets within the m × m array reaches the maximum. It is shown that this maximum is given by ${\lfloor \sqrt{2m} \rfloor}$ and an m × m basis array can be constructed by using a simple cyclic translation method. The previously developed concept of successive packing is then generalized in the sense that it can be applied to any basis array to generate an interleaved array with a larger size. Except that optimality cannot be guaranteed, the concept of basis arrays and successive packing are extended to M-D cases. It is shown that for any M ?? 2, the proposed technique can spread any error burst of block size ${m_{1}^{k} \times m_{2}^{k} \times \cdots \times m_{M}^{k}}$ within an ${ m_{1}^{n} \times m_{2}^{n} \times \cdots \times m_{M}^{n}}$ array (1 ?? k ?? n?1) so effectively that the error burst can be corrected with some simple random error-correcting code (provided the error-correcting code is available). It is shown that important prior results in M-D interleaving such as the t-interleaved array based approach by Blaum et al. and the successive packing approach by Shi and Zhang now become special cases of the framework based on basis arrays and successive packing, proposed in this paper.