Surface hardening in N<Superscript>+</Superscript> implanted polycarbonate

The influence of low energy nitrogen ions on the surface hardness of polycarbonate has been studied by implanting some of these specimens with 100 keV N⁺ ions at a beam current of 1 μA/cm² in the dose range of 1 × 10¹⁵ to 1 × 10¹⁷ ions cm^?2. Knoop microhardness has been found to be increased nearly 24 times at a load of 9.8 mN, for the dose of 1 × 10¹⁷ ions cm^?2. The structural changes occurred in implanted specimens were studied by Raman analysis, UV–Visible spectroscopy, and X-ray diffraction techniques. Raman studies point toward the formation of a structure resembling hydrogenated amorphous carbon. Disordering in the surface structure (I _D/I _G ratio) has also been found to increase with ion fluence using Raman technique. UV–Visible spectroscopic analysis shows a clear enhancement in Urbach energy (disorder parameter) from a value of 0.61 eV (virgin sample) to 1.72 eV (at a fluence of 1 × 10¹⁷ N⁺ cm^?2) with increasing ion dose. The increase in Urbach energy has been found to be correlated linearly with the increase in Knoop microhardness number. Results of X-ray diffraction analysis also indicate disordering in implanted layers as a result of implantation. In the present work, the possible mechanism behind the formation of harder surfaces due to implantation has been discussed in detail.     

Reaction Kinetics of C60 Fullerene Ozonation

Abstract

It has been verified that the reaction between O₃ and C₆₀ follows the general second order reaction rate which is valid for all the reactions between ozone and unsaturated olefinic bonds: v = k[C?C][O₃]. The reaction rate constant k has been measured ≈(1.5 ± 0.3) × 10⁴ L mol^?1 s^?1. The value of this rate constant has the same order of magnitude of the rate constant measured for instance in the ozonation of 1,4‐diphenylbutadiene.     

Hot workability analysis with processing map and texture characteristics of as-cast TX32 magnesium alloy

Hot deformation behavior of as-cast TX32 (Mg–3Sn–2Ca) alloy has been studied in uniaxial compression in the temperature and strain rate ranges of 300–500 °C and 0.0003–10 s^?1 with a view to characterize the evolution of microstructure and texture. On the basis of the temperature and strain rate dependence of flow stress, a processing map has been developed and the crystallographic orientation information on the deformed specimens has been obtained from electron back scatter diffraction micro-texture analysis. The processing map revealed two domains of dynamic recrystallization in the temperature and strain rate ranges of (1) 300–350 °C and 0.0003–0.001 s^?1 and (2) 390–500 °C and 0.005–0.6 s^?1. Specimens deformed at peak in Domain 1 exhibited maximum intensity of basal poles located at about 35–45° to the compression axis while those deformed at peak in Domain 2 showed near-random texture. Schmid factor analysis of different slip systems operating in the two domains suggests that basal + prismatic slip causes the basal texture in Domain 1 while second-order pyramidal slip randomizes the texture in Domain 2.     

Effect of aluminum on microstructural evolution during hot deformation of TX32 magnesium alloy

The effect of Al (0.4 and 1 wt%) addition on the hot deformation behavior of the Mg–3Sn–2Ca (TX32) alloy has been studied with the help of processing maps generated in the temperature and strain rate ranges of 300–500 °C and 0.0003–10 s^?1. The deformed specimens have been examined as regards changes in texture and microstructure using electron back scatter diffraction and transmission electron microscopy, respectively. The map for the TX32 base alloy exhibited two dynamic recrystallization (DRX) domains in the temperature and strain rate ranges: (1) 300–350 °C and 0.0003–0.001 s^?1, and (2) 390–500 °C and 0.005–0.6 s^?1. While 0.4 wt% Al addition to TX32 did not result in any significant change in the processing map, the map for the alloy with 1 wt% Al (TX32-1Al) exhibited four domains in the ranges: (1) 300–325 °C and 0.0003–0.001 s^?1, (2) 325–430 °C and 0.001–0.04 s^?1, (3) 430–500 °C and 0.01–0.5 s^?1, and (4) 430–500 °C and 0.0003–0.002 s^?1. In the first three domains, DRX has occurred, whereas in the fourth domain, grain boundary sliding takes place causing intercrystalline cracking in tension. In Domain 1 for all the alloys, DRX has occurred predominantly by basal slip and recovery by climb as confirmed by the resulting basal texture and tilt type sub-boundary structure. In Domain 2 of the base alloy and Domain 3 of the alloy with 1 wt% Al, second-order pyramidal slip dominates associated with cross-slip which randomizes the texture, and forms tangled dislocations and twist type sub-boundaries in the microstructure. The addition of 1 wt% Al causes solid solution strengthening and results in Domain 2 of the map of TX32-1Al alloy and in this domain basal+prismatic slip dominate.     

Lithium ion conducting solid polymer blend electrolyte based on bio-degradable polymers

Lithium ion conducting polymer blend electrolyte films based on poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) with different Mwt% of lithium nitrate (LiNO₃) salt, using a solution cast technique, have been prepared. The polymer blend electrolyte has been characterized by XRD, FTIR, DSC and impedance analyses. The XRD study reveals the amorphous nature of the polymer electrolyte. The FTIR study confirms the complex formation between the polymer and salt. The shifts in T _g values of 70 PVA–30 PVP blend and 70 PVA–30 PVP with different Mwt% of LiNO₃ electrolytes shown by DSC thermograms indicate an interaction between the polymer and the salt. The dependence of T _g and conductivity upon salt concentration has been discussed. The ion conductivity of the prepared polymer electrolyte has been found by a.c. impedance spectroscopic analysis. The PVA–PVP blend system with a composition of 70 wt% PVA: 30 wt% PVP exhibits the highest conductivity of 1·58 × 10^???6 Scm^???1 at room temperature. Polymer samples of 70 wt% PVA–30 wt% PVP blend with different molecular weight percentage of lithium nitrate with DMSO as solvent have been prepared and studied. High conductivity of 6·828 × 10^???4 Scm^???1 has been observed for the composition of 70 PVA:30 PVP:25 Mwt% of LiNO₃ with low activation energy 0·2673 eV. The conductivity is found to increase with increase in temperature. The temperature dependent conductivity of the polymer electrolyte follows the Arrhenius relationship which shows hopping of ions in the polymer matrix. The relaxation parameters (ω) and (τ) of the complexes have been calculated by using loss tangent spectra. The mechanical properties of polymer blend electrolyte such as tensile strength, elongation and degree of swelling have been measured and the results are presented.     

AFM analysis of the surface of nanoporous membranes: application to the nanofiltration of potassium clavulanate

This study presents the structural characterization of the surface of four commercial nanofiltration membranes: NF90 (polyamide) and NF (polypiperazine amide) from Filmtec^TM and NP010 and NP030 (polysulfone) from Microdyn Nadir^®, by Atomic Force Microscopy (AFM). These membranes have been studied before and after undergoing a filtration process with potassium clavulanate. The fast Fourier filtering of AFM images with very high magnification (40 × 40 nm) has allowed identifying the pore size distribution and geometry of the pores on the surface of the membrane before their use. Images between 0.5 × 0.5 and 10 × 10 μm² have allowed the study of the surface roughness of the samples before and after being used to filtrate potassium clavulanate solutions. The results of roughness and power spectral fractal dimension along with the skewness and kurtosis of the height distribution have been analyzed in terms of pore size, hydraulic permeability, and the adsorption of clavulanate for the different samples.     

Synthesis,growth and characterization of (tri) glycine barium chloride single crystal for applications in the domain of optoelectronics and photonics

The single crystal of (tri) glycine barium chloride, a semiorganic crystal has been grown from an aqueous solution by slow evaporation technique at room temperature. Glycine and barium chloride were used in molar ratio of 3:1 for synthesis. Good optical quality single crystal of size 18 × 10 × 5 mm³ was harvested in a period of 5 weeks (35 days) at pH value 5. The lattice parameters have been measured by single crystal XRD study. The crystalline nature has been confirmed by powder XRD study. Fourier transform infrared spectroscopy study confirmed the presence of functional groups in grown crystal. Transmission spectrum has been recorded and the cut-off wavelength has been determined as 234 nm. Also optical constants like band gap, refractive index, reflectance, extinction coefficient and electric susceptibility were determined from UV–Vis-NIR spectrum. The thermal behavior of the crystal was investigated by TG–DTA analysis, which reveals that crystal has thermally stable up to 169 °C. Non-linear optical property of the grown crystal has been confirmed using the Kurtz and Perry powder technique and result was compared with KDP. The dielectric behavior of the sample was analyzed with various frequencies at different temperatures. The photoconducting nature of the crystal was analyzed by photoconductivity study.     

Effect of very low to high Sb-doping on the structural,electrical, photo-conductive and thermoelectric properties of fluorine-doped SnO<Subscript>2</Subscript> (FTO) thin films prepared by spray pyrolysis technique

Transparent conducting fluorine and Sb-doped [SnO₂: (F, Sb)] thin films have been deposited onto preheated glass substrates using the spray pyrolysis technique by the various dopant quantity of spray solution. The effect of antimony impurities on the structural, morphological, electrical, Thermo-electrical, optical and photoconductive properties of films has been investigated. The [F/Sn] atomic concentration ratio (x) in the spray solution is kept at value of 0.7 and the [Sb/Sn] atomic ratio (y) varied at values of 0, 0.0005, 0.001, 0.002, 0.01, 0.03, 0.05, 0.07 and 0.10. It is found that the films are polycrystalline in nature with a tetragonal crystal structure corresponding to SnO₂ phase having orientation along the (110) and (200) planes. SEM images indicated that nanostructure of the films has a particle type growth. The average grain size increases with increasing spraying quantity of Sb-dopant. The compositional analysis of SnO₂: (F, Sb) thin films were studied using EDAX. SEM and AFM study reveals the surface of SnO₂: (F, Sb) to be made of nanocrystalline particles. The Hall Effect measurements have shown n-type conductivity in all deposited films. The lowest sheet resistance and highest the carrier concentration about 7.7 Ω/□ and 6.6 × 10²², respectively, were obtained for the film deposited with y = [Sb/Sn] = 0.001 and x = [F/Sn] = 0.7. The maximum of the Seebeck coefficient equal to 12.8 μV K^?1 was obtained at 400 K for the film deposited with y = [Sb/Sn] = 0.10. The average transmittance of films varied over the range 10–80 % with change of Sb-concentration. The band gap values of samples were obtained in the range of 3.19–3.8 eV. From the photoconductive studies, the Sb-doped films exhibited sensitivity to incident light especially in y = 0.001. The electrical resistivity and carrier concentration vary in range 5.44 × 10^?4 to 1.02 × 10^?2Ω cm and 2.6 × 10²²–6.6 × 10²² cm^?3, respectively.     

Naphthalene diimide self-assembled ribbons with high electrical conductivity and mobility without doping

The thermally activated electrical conductivity and charge transfer properties of self-assembled naphthalene diimide molecule have been studied with N,N’di(hexadecyl)naphthalene tetracarboxylic diimide (HD-NDI) derivative. The self-assembly of HD-NDI has been resulted in one-dimensional large micron-size ribbons. The aggregate formation and self-assembling property have been extensively studied by absorption, fluorescence and X-ray diffraction analysis. Absorption and fluorescence measurements were taken in variety of solvents in fresh and aged samples, and the study suggested J-type aggregation for self-assembly formation. The electrical conductivity of self-assembled HD-NDI material was measured as a function of temperature where the conductivity increased with temperature and the highest conductivity (1 × 10^?5 S/cm) was obtained at 250 °C. SEM images clearly show the formation of ribbons of micron size. Further the electron transport property of HD-NDI was also evaluated by SCLC method at room temperature by fabricating electron-only devices with annealing the film at ~ 200 °C. HD-NDI shows excellent electron mobility (1.8 × 10^?3 cm² V^?1 s^?1) because of effective channel formation due to self-assembly of HD-NDI molecules, and this material may find potential application in variety of electronic devices.     

Influence of Bias Parameters and Plasma Density on Vacuum Arc Macroparticle Accumulation

Several regularities of the accumulation of vacuum arc metal macroparticles (MP) on the sample on repetitively pulsed biasing (10⁵ Hz, 7 µs, ?0.5 kV to ?3.5 kV) have been investigated. It has been shown that the substrate temperature plays a very important role in controlling the MP amounts on the sample. A possibility to change the metal particle number density on the substrate in the range from 10⁵/cm² to 10⁷/cm², depending on bias pulse parameters, sample temperature, and ion plasma saturation current density, has been demonstrated. The shape of MPs and their adhesion to the substrate surface depends strongly on the MP energy balance in a high-voltage space charge sheath.     

Studies on electrical double layer capacitor with a low-viscosity ionic liquid 1-ethyl-3-methylimidazolium tetracyanoborate as electrolyte

The performance of an electrical double layer capacitor (EDLC) composed of high surface area activated carbon electrodes and a new ionic liquid, 1-ethyl-3-methylimidazolium tetracyanoborate, [EMIm]TCB, as the electrolyte has been investigated by impedance spectroscopy, cyclic voltammetry and galvanostatic charge–discharge studies. The high ionic conductivity (~1·3 × 10^???2 S cm^???1 at 20 °C) and low viscosity (~22 cP) of the ionic liquid, [EMIm]TCB, make it attractive as electrolyte for its use in EDLCs. The optimum capacitance value of 195·5 F g^???1 of activated carbon has been achieved with stable cyclic performance.     

Novelties of low energy microwave-irradiated tri-liquid phase transfer catalysis (MILLL-PTC): halo-exchange of benzyl chloride with sodium bromide

In situ halogen exchange is witnessed in many organic reactions before the actual species participates in the main reaction. The aim of this work is to analyse the synergistic effect of microwave irradiation on tri-liquid phase transfer catalysed halo-exchange reaction between sodium bromide and benzyl chloride (BnCl) with tetra-butyl ammonium bromide as a catalyst. There is a process intensification leading to savings on reactor volume and processing costs. There is also waste minimisation since the catalyst phase is reused. The effects of various parameters such as mass transfer resistance, catalyst loading, mole ratio, temperature and reusability of third catalyst phase have been studied to provide an insight into the mechanism and kinetics of the reaction. A kinetic model has been developed and validated against the experimental data. The overall order of reaction is first order in BnCl. The values of apparent energy of activation and frequency factor were 23.0 kcal/mol and 1.03 × 10¹² kmol/(m³ s), respectively, for microwave irradiation and 20.19 kcal/mol and 1.27 × 10¹⁰ kmol/(m³ s), respectively, for conventional heating.     

Electrohydrodynamic atomization approach to graphene/zinc oxide film fabrication for application in electronic devices

Graphene-based composites represent a new class of materials with potential for many applications. Metal, semiconductor, or any polymer properties can be tuned by attaching it to graphene. Here, a new route for fabrication of graphene based composites thin films has been explored. Graphene flakes (<4 layers) and a well-known semiconductor zinc oxide (ZnO) (<50 nm particle size) have been dispersed in N-methylpyrrolidone and ethanol, respectively. Thin film of graphene flakes is deposited and decorated with ZnO nanoparticles to fabricate graphene/ZnO composite thin film on silicon substrate by electro hydrodynamic atomization technique. Graphene/ZnO composite thin film has been characterized morphologically, structurally and chemically. To investigate electronic behavior of the composite thin film, it is deployed as cathode in a diode device i.e. indium tin oxide/poly (3,4-ethylenedioxythiophene) poly (styrenesulfonate)/polydioctylfluorene-benzothiadiazole/(graphene/ZnO). The J–V analysis of diode device has shown that at voltage of 1 V, the current density in organic structure is at low value of 4.69 × 10^?3 A/cm² and when voltage applied voltage is further increased; the device current density has increased by the order of 200 that is 1.034 A/cm² at voltage of 12 V.     

Pressure infiltration of boron nitride preforms with molten aluminum for low density heat sink materials

Cubic boron nitride (cBN) has outstanding mechanical and thermal properties. The previous research focused on mechanical properties, to data, the thermal property of cBN has rarely been reported. In this work, a wide range of aluminum/cubic boron nitride (Al/cBN) composites were fabricated by pressure infiltration at 5.0 GPa and 960–1600 °C. The microstructure, phase composition, thermal conductivity and coefficient of thermal expansion of the Al/cBN composites were investigated. The results showed that a maximum thermal conductivity of 266 W/mK and the coefficient of thermal expansion of 4–6 × 10^?6 K^?1 which matches well to semiconductors, indicating that the Al/cBN composites are promised heat sink materials of high efficiency for the wide band gap semiconductors.     

The preparation of novel hollow tetragonal starlike polyaniline and its electrochemical performance

Novel hollow tetragonal starlike polyaniline (HTS-PANI) doped with citric acid has been successfully synthesized by hydrothermal method for the first time. Scanning electron microscopy, transmission electron microscopy, UV–visible spectroscopy, Fourier transmission infrared spectroscopy, and X-ray diffraction were employed to analysis the morphology and structure of the obtained PANI. The results show that the HTS-PANI is in semi redox state and highly crystallized, accompanied with good thermal stability. According to the galvanostatic charge–discharge analysis, the specific capacitance of the sample is up to 460 F g^?1 at a current density of 0.2 A g^?1 in 1 M KCl electrolyte, and retains about 58 % after 1,000 charge–discharge processes at a current density of 5 A g^?1.     

Surface morphology and thermal figure of merit of a new compound thin film

The third nonlinear optical properties of a new compound 4,4′-bis(3-methoxy benzylidene amino) biphenyl doped poly-methyl methacrylate (PMMA) have been studied using Z-scan technique. Experiments are performed using a continuous waveguide (cw) diode laser at 532 nm wavelength and 0.68 kW/cm² laser intensity. The optical power limiting behavior of sample doped PMMA was also investigated. It also shows a very good optical limiting behavior with a limiting threshold of 4.7 mW. We attribute the nonlinear absorption and optical limiting property of the sample film to two photon absorption effect at 532 nm. The experimental evidences of observing diffraction pattern in compound 4,4′-bis(3-methoxybenzylideneamino) biphenyl doped PMMA has been present. The refractive index change, Δn, and nonlinear refractive index, n ₂ determined from the number of observed ring. We obtained good values of Δn = 105.154 × 10^?4and n ₂ = 154.154 × 10^?7 cm²/W. Variation of refractive index with temperature, dn/dT, and figure of merit, H, are found to be 8.858 × 10^?6 1/°C and 5.316 × 10^?6, respectively. This large nonlinearity is attributed to a thermal effect resulting from linear absorption. Theoretical diffraction pattern that agree well with experimental one are generated using a wave theory.     

P-type reduced graphene oxide membranes induced by iodine doping

Reduced graphene oxide membranes with electrical conductivity of 201 S/cm were successfully fabricated by a simple hydriodic acid reducing method. It has been shown that the obtained graphene oxide membranes exhibit a p-type conductive property with a hole carrier concentration of 3.66 × 10¹⁷ cm^?2 and a mobility of 13.7 cm²/Vs. The p-type conductive property was mainly attributed to iodine atom adsorption on C atom layer, supported by the energy dispersive X-ray spectrometry and the first-principles calculations based on the density functional theory. The Bader method was used to analyze charge density of each atom. It has been shown that 0.38 electrons per unit cell are transferred to I atom from the C atom layer which leaves a lot of holes.     

Ferroelectric properties of pulsed laser deposited PZT (92/8) thin films

The effect of pulse amplitude on the ferroelectric and switching properties of pulsed laser deposited PZT (92/8) thin films has been studied. The structural analysis revealed that the films had a well crystallized perovskite phase without secondary phases. The atomic force microscopy has been employed to estimate the grain size and surface roughness of the film. A well-saturated P–E hysteresis loop was observed with average values of remnant polarization (P_r) ≈ 16.0 μC/cm², saturation polarization (P_s) ≈ 21.7 μC/cm² and coercive field ≈138 kV/cm. The P–E loops were very stable with frequency, confirming that the contribution of the leakage current and/or mobile free charges to the polarization is minimum. The polarization current exhibits the exponential dependence on the pulse amplitude and the leakage current seems to be governed by the hopping mechanism which is generally associated to structural defects.     

The conversion technology of fly ash into zeolites

This paper presents a sub-pilot scale process of synthesis of Na-P1 zeolite from the coal fly ash. After establishing the appropriate synthesis conditions (20 kg of fly ash, 12 kg of NaOH, 90 dm³ of water, the reaction temperature: 80 °C and reaction time: 36 h), the high-purity (81 wt%) Na-P1 zeolite product was obtained. Its chemical, mineralogical, and textural properties were determined (by means of XRD, XRF, SEM–EDS and ASAP 2020). The synthesized material has a specific BET surface area (88 m²/g) c.a. six times higher than the fly ash from which it has been derived (15 m²/g). The pore-size distribution indicates a mesoporous character of the obtained zeolite, with the following pores size contents: micropores (2.76 %), mesopores (61.81 %), and macropores (35.43 %). The presented technological/production line is fully automated and allows to regulate the conditions of the synthesis process, therefore different types of zeolite materials (including: Na-X, Linde-A, and Na-P1) can be obtained using the same equipment.     

Energy Transfer Modes in Pulsed Laser Seam Welding

A systematic parametric study has been made in pulsed Nd:YAG laser welding to understand the energy transfer modes. Four different energy transfer zones, namely conduction, transition, penetration, and keyhole, have been identified. The traditional classification of energy transfer modes based on the power density value of 10⁶ W/cm² is not strictly applicable as the transfer mode varies with pulse duration. The threshold power density to form keyhole is not constant, but the threshold energy density has been found to be invariant around 2.4 kJ/cm². The pulse duration has been optimized to be of about 8 ms to achieve welds of higher aspect ratio.