• Issue front cover thumbnail

      Volume 39, Issue 1

      February 2016,   pages  1-336b

    • Biogenic ZnO nanoparticles synthesized using L. aculeata leaf extract and their antifungal activity against plant fungal pathogens

      S Narendhran Rajeshwari Sivaraj

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      In this study, Zinc oxide (ZnO) nanoparticles were synthesized using aqueous extract of Lantana aculeata Linn. leaf and assessed their effects on antifungal activity against the plant fungal pathogens. Synthesized nanoparticles were confirmed by ultraviolet–visible spectroscopy, Fourier transform infrared spectrometer, energy-dispersive X-ray spectrometer, X-ray diffractometer, Field-emission scanning electron microscopy, high-resolution transmission electron microscopy. The antifungal activity of ZnO nanoparticles were determined using the well diffusion method. All the characterization analyses revealed that nanoparticles were highly stable and crystalline in nature. L. aculeata-mediated ZnO nanoparticles were spherical in shape with an average particle size of 12 ± 3 nm. Antifungal studies concluded that the maximum zone of inhibition was observed in Aspergillus flavus (21 ± 1.0 mm) and Fusarium oxysporum (19 ± 1.0 mm) at 100 𝜇g ml-1 concentration. These results clearly indicated the benefits of using ZnO nanoparticles synthesized using biological methods and shown to have antifungal activities and also that it can be effectively used as antifungal agent in environmental aspect of agricultural development.

    • Synthesis, structural and optical properties of nanoparticles (Al, V) co-doped zinc oxide

      J El Ghoul

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      The synthesis by the sol–gel method, structural and optical properties of ZnO, Zn0.99Al0.01O (AlZ), Zn0.9V0.1O (VZ) and Zn0.89Al0.01V0.1O (AlVZ) nanoparticles was reported. The approach was slow release of water for hydrolysis by esterification reaction followed by a supercritical drying in ethyl alcohol. After thermal treatment at 500°C in air, the obtained nanopowders were characterized by various techniques such as transmission electron microscopy, X-ray diffraction and photoluminescence (PL) spectroscopy. The structural properties showed that the ZnO nanoparticles with an average particle size of 25 nm exhibit hexagonal wurtzite structure. From the optical studies, it was found that the optical band gap was located between 2.97 and 3.17 eV. The obtained electrical properties showed the potential application of the samples in optoelectronic devices. The powder of AlVZ presented a strong luminescence band in the visible range. The PL band energy position presented a small blue shift with the increase of measurement temperature. Different possible attributions of this emission band will be discussed.

    • Ti/TiO2 nanotube array electrode as a new sensor to photoelectrocatalytic determination of ethylene glycol

      Reza Ojani Akbar Khanmohammadi Jahan-Bakhsh Raoof

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      The photoelectrocatalytic oxidation behaviour of ethylene glycol (EG) was studied in the present work using the TiO2-modified Ti foil (Ti/TiO2) electrode. The Ti/TiO2 nanotube array (Ti-NTA) electrode was prepared by anodizing of the Ti foil in the HF aqueous solution (0.2% v/v). The anodization was conducted in the constant 30 Vfor 2 h, and then the as-prepared Ti-NTA electrode was calcinated at 50°C for 2 h. The surface morphology of Ti-NTA electrode was studied using scanning electron microscopy images. For EG determination, the photocurrent of EG (EG oxidation current in the UV irradiation) was assessed using the hydrodynamic photoamperometric method in the phosphate buffers. Ultimately, the optimum conditions of EG determination were studied in various pH values andapplied bias potentials, and the pH=3.0 and 𝐸 =1.0 V (vs. reference electrode) were determined as the optimum conditions. It was found that the photocurrent of EG was linearly dependent on the concentration of EG in the range of 3.0 × 10−5 to 0.88 mol l−1, and the detection limit of EG determination was found to be 7.2 × 10−6 mol l−1 (3𝜎).

    • Hydrothermal growth of ZnO nanoflowers and their photocatalyst application

      Jincheng Fan Tengfei Li Hang Heng

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      ZnO nanoflowers were prepared by the hydrothermal method and studied by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy and photoluminescence. ZnO nanoflowers with star-like morphology were of pure wurtzite phase. The edges of the petals were composed of assemblies of smaller nanocrystallites. Green and orange emissions in photoluminescence were attributed to O vacancies and O interstitials, respectively. Furthermore, ZnO nanoflowers demonstrated the effective photocatalytic activities, and O vacancies and O interstitials were considered to be the active sites of the ZnO photocatalyst.

    • Band gap narrowing and photocatalytic studies of Nd3+ ion-doped SnO2 nanoparticles using solar energy

      Dhanya Chandran Lakshmi S Nair S Balachandran K Rajendra Babu M Deepa

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      Pure and Nd3+-doped tin oxide (SnO2) nanoparticles have been prepared by the sol–gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM, energydispersive spectroscopy and UV–visible spectroscopy. The XRD patterns of all the samples are identified as tetragonal rutile-type SnO2 phase which is further confirmed by TEM analysis. Neodymium doping introduces band gap narrowing in the prepared samples and enhances their absorption towards the visible-light region. The photocatalytic activity of all the samples was evaluated by monitoring the degradation of methylene blue solution under day light illumination and it was found that the photocatalytic activity significantly increases for the samples calcined at 600 than 400°C, which is due to the effective charge separation of photogenerated electron–hole pairs. The efficiency of photocatalysts was found to be related to neodymium doping percentage and calcination temperature.

    • Effects of surfactants on size and structure of amylose nanoparticles prepared by precipitation

      Yan Dong Yanjiao Chang Qian Wang Jin Tong Jiang Zhou

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      The present work investigated the influence of surfactants on size and structure of amylose nanoparticles (ANPs) prepared through precipitation. ANPs were fabricated using absolute ethanol containing surfactants (Tween80, Span80 and mixtures of Tween80 and Span80 with ratios of 25/75, 50/50 and 75/25, respectively) as non-solvents. The obtained ANPs were characterized using dynamic light scattering (DLS), scanning electron microscopy and X-ray diffraction. The results showed that surfactant type, concentration and hydrophilic–lipophilic balance (HLB) value had great impact on size of precipitated ANPs. The smallest ANPs with mean size of 155 nm determined by DLS were obtained by using 0.5% (in proportion of the amylose solution volume) of Tween80/Span80 mixture (HLB = 12.33). The precipitated ANPs possessed the V-type crystalline structure no matter whether using the surfactants or not.

    • Effect of high-temperature heat treatment duration on the purity and microstructure of MWCNTs

      I Srikanth N Padmavathi P S R Prasad P Ghosal R K Jain Ch Subrahmanyam

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      The effect of high-temperature heat treatment on purity and structural changes of multiwalled carbon nanotubes (MWCNTs) were studied by subjecting the raw MWCNTs (pristine MWCNTs) to 2600°C for 60 and 120 min. Thermogravimetric analysis (TGA), X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were used to study the effect of heat-treatment duration on the purity and structural changes of MWCNTs. Results show that high-temperature heat treatment can be used to purify MWCNTs with proper optimization of treatment time. It was observed that 60 min heat treatment of raw MWCNTs imparts high purity and structural perfection to MWCNTs, while 120 min heat treatment imparts structural degradation to MWCNTs with collapse of the innermost shells. The present study indicates that metal impurities act as moderators in controlling the degradation of MWCNTs up to certain duration, and once the metal impurities escape completely, further heat treatment degrades the structure of MWCNTs.

    • Carbon nanotubes dispersed polymer nanocomposites: mechanical, electrical, thermal properties and surface morphology

      Nitin Sankar Mamilla Nagarjun Reddy R Krishna Prasad

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      The various properties and surface morphology of the carbon nanotubes (CNTs) dispersed polydimethyl siloxane (PDMS) matrix were studied to determine their usefulness in various applications. The tensile strength, Young's modulus and electrical breakdown strength of CNT/polymer composites were 0.35MPa, 1.2MPa and 8.1 kV, respectively. The thermal conductivity and dielectric constant for the material having 4.28 wt% CNT were 0.225 W m−1 K−1 and 2.329, respectively. The CNT/polymer composites are promising functional composites with improved mechanical and electrical properties. The scanning electron microscope analysis of surface morphology of PDMS/CNT composite showed that the rough surface texture on nanocomposite has large surface area with circular pores. The Fourier transform infrared spectroscopy showed the functional groups present in polymer nanocomposite.

    • Mechanisms of antibacterial activity and stability of silver nanoparticles grown on magnetron sputtered TiO2 coatings

      K Zawadzka A Kisielewska I Piwoński K Kądzioła A Felczak S Różalska N Wrońska K Lisowska

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      Nanomaterials with high stability and efficient antibacterial activity are of considerable interest. The preparation of silver nanoparticles (AgNPs) on titania coatings and their effective antibacterial activity against Staphylococcus aureus ATCC 6538 were reported. Titanium dioxide (TiO2) coatings with AgNPs were prepared on Si wafers using the reactive magnetron sputtering method. The surface topography of AgNPs/TiO2 coatings imaged using scanning electron microscopy revealed that the size and surface density of AgNPs grown by the photoreduction of silver ions were dependent on the concentration of AgNO3 in the primary solution and the time of TiO2 exposure to UV illumination. Evaluation of the antimicrobial properties and surface analysis before and after the biological test of AgNPs/TiO2 coatings indicates their high antimicrobial stability and durability. Furthermore, the interdependence between the concentration of released silver and bacterial growth inhibition was demonstrated. In addition, direct contact killing and released silver-mediated killing have been proposed as a bactericidal mechanism of action of tested coatings with AgNPs.

    • Size-controlled synthesis of biodegradable nanocarriers for targeted and controlled cancer drug delivery using salting out cation

      Madasamy Hari Balakrishanan Mariappan Rajan

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      Research for synthesis of size-controlled carriers is currently challenging one. In this research paper, a method for size-controlled synthesis of biodegradable nanocarriers is proposed and described. Salting out method is suitable for both hydrophilic and hydrophobic drugs for the encapsulation on carriers. This synthetic method is based on polylactic acid (PLA) and non-ionic carboxymethyl cellulose (CMC) composed by CaCl2 as salting out agent. This method permits size-controlled synthesis of particles between 50 and 400 nm simply by varying the concentration of salting out agents. We have prepared cisplatin (CDDP)-loaded PLA-CMC nanocarriers by salting out method, with varying salting out agent (CaCl2) concentrations as 0.05, 0.2, 0.35 and 0.5 M. The nanocarriers were characterized for their size, surface charge and morphology by atomic force microscope, zeta potential analyser and transmission electron microscope, respectively. The encapsulation efficiency and in-vitro drug-releasing behaviour of the nanocarriers were investigated. The cytotoxicity effect of nanocarriers and drug-loaded nanocarriers was tested against MCF-7 breast cancer cell line.

    • Investigation of TaC–TaB2 ceramic composites

      Behzad Mehdikhani Gholam Hossein Borhani Saeed Reza Bakhshi Hamid Reza Baharvandi

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      The TaC–TaB2 composition was sintered by spark plasma (SPS) at 1900–2100°C and applied pressure of 30 MPa. TaC and 2–3 wt% B4C were used as starting powders. Densification process, phase evolution, microstructure and the mechanical properties of the composites were investigated. The results indicated that the TaC–TaB2 composition could be SPS to 97% of theoretical density in 10 min at 2100°C. Addition of B4C leads to an increase in the density sample from 76 to 97%. B4C nano-powder resists grain growth even at high temperature 2100°C. The formation of TaB2/carbon at TaC grain boundaries helps in pinning the grain boundary and inhibiting grain growth. The phase formation was associated with carbon and boron diffusion from the starting particles B4C to form TaB2 phases. TaC grain sizes decreased with increase in B4C concentration. Samples with 2.0 wt% B4C composition had highest flexure strength up to 520 MPa. The effect of B4C addition on hardness measured by microhardness has been studied. Hardness of samples containing 3.0 wt% B4C was 16.99 GPa.

    • Effect of cerium additive and secondary phase analysis on Ag0.5Bi0.5TiO3 ceramics

      S Supriya Antonio J Dos Santos-García F Fernández-Martinez

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      Cerium-doped silver bismuth titanate—Ag0.5Bi0.5TiO3 (ABT) ceramics have been synthesized by the high-temperature solid-state reaction method. The structure and elemental examination of the prepared ceramic was analysed by X-ray diffraction (XRD), Fourier transform infrared, scanning electron microscopy and energydispersive spectroscopy. XRD analysis showed the presence of pyrochlore structure and secondary phase when more than 5 mol% cerium was added. The impact of temperature on cerium-doped silver bismuth titanate samples was analysed by differential thermal analysis and differential scanning calorimetry. Cerium doping caused the flaky morphology comparing with undoped sample. The homogeneity of all the samples was discussed in detail by diffuse reflectance spectrum. This is the first time the reflection process is analysed for the cerium-doped ABT system to the best of our knowledge.

    • The enhanced interface effect induced by thermal pressure in Nd0.7Sr0.3MnOy ceramics

      Shunsheng Chen Dawei Shi Shaozhen Li Changping Yang Yali Zhang

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      Polycrystalline ceramics Nd0.7Sr0.3MnOy prepared by solid-state reaction were treated under high pressure of 9 GPa and temperature of 1000 K. The electrical transport behaviour of samples were investigated by a variable temperature system and a peculiar transport character was found at low temperature of 120 K, the I–V showed an obvious step-shape behaviour with the increase in the measurement voltages; at much lower temperature of 12.3 K, the I–V curves exhibited a notable symmetric hysteresis at a critical voltage of 4.5 V, although a linear I–V behaviour at 293 K. On the other hand, the R–T measurement revealed that the resistivity peak (resistivity at 𝑇MI) disappeared gradually and is replaced by a resistivity platform with the increase in the load currents, surprisingly, the resistivity platform broadened with continuous increase in the load currents but weakened when an external magnetic field was applied. All of these phenomena were not observed for the un-treated sample. The particle attenuated and the enhanced interface effect which resulted from the violent thermal-pressure treatment was responsible for the unique electromagnetic transport.

    • Spray pyrolytically grown NiAlOx cermets for solar thermal selective absorbers: spectral properties and thermal stability

      A Bagheri Khatibani S M Rozati

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      After deposition of NiAlOx thin films on stainless-steel substrates by the spray pyrolysis technique, various properties of the films were investigated using Fourier transform infrared spectroscopy, UV–visible reflectance spectrophotometry, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Optical quantities were determined using reflectance spectra in the relevant spectrum region. At first the optimal substrate temperature was selected and then different nickel to aluminium ratios were examined to find the efficient solar absorber. The SEM revealed changes in morphology due to different molar ratios. The XRD of the selected sample showed a mixture of nickel and nickel oxide phases with the strong presence of substrate peaks and without the presence of alumina phase while in the EDX test the peaks corresponding to O, Al and Ni appeared. Long-term thermal stability study was performed by means of performance criterion concept.

    • Regenerated thermosetting styrene-co-acrylonitrile sandwich composite panels reinforced by jute fibre: structures and properties

      Jinglong Li Qin Peng Anrong Zeng Junlin Li Xiaole Wu Xiaofei Liu

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      Jute fibres-reinforced sandwich regenerated composite panels were fabricated using industrial waste thermosetting styrene-co-acrylonitrile (SAN) foam scraps via compression moulding for the purpose of recycling waste SAN foam and obtaining high physical performance. The jute fibres were, respectively, treated by heat, sodium hydroxide (NaOH) solution (5.0 wt%), and N,N-dimethylacetamide (DMAc) in order to improve the mechanical properties of the composites. The structures and mechanical properties of the composites were studied. The SAN matrix got compact and some crystalline region formed in SAN matrix via compression moulding. The composite reinforced by DMAc-treated jute fibres performed optimum mechanical properties among the regenerated panels whose impact strength, flexural strength, and compressive strength were 19.9 kJ m−2, 41.7 MPa, and 61.0 MPa, respectively. Good interfacial bonding between DMAc-treated fibres and SAN matrix was verified by peel test and exhibited in SEM photographs. Besides, the water absorption of DMAc-treated fibres composite was lower than other SAN/jute fibre-reinforced sandwich composite panels.

    • Structural and magnetic properties of Sr1−xLaxFe12−x(Cu0.5Co0.5)xO19 hexaferrites prepared by the solid-state reaction method

      Yujie Yang Fanhou Wang Juxiang Shao Duohui Huang Xiansong Liu Shuangjiu Feng Mingjie Wan Qilong Cao

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      Hexaferrite Sr1−xLaxFe12−x(Cu0.5Co0.5)xO19 (0 ≤ 𝑥 ≤ 0.50) magnetic powders and magnets were synthesized by the solid-state reaction method. The phase compositions of magnetic powders were investigated by X-ray diffraction. The single magnetoplumbite phase is obtained in magnetic powders with 𝑥 from 0 to 0.40. At 𝑥 = 0.50, CoFe2O4, and 𝛼-Fe2O3 were observed. The morphology of the materials was characterized by a field-emission scanning electron microscopy. The particles were hexagonal platelets. Magnetic properties of the materials were measured by a permanent magnetic measure equipment. The remanence of the materials increases with 𝑥 from 0 to 0.50. However, the intrinsic coercivity and magnetic induction coercivity of the materials increase with 𝑥 from 0 to 0.15, and decreases when 𝑥 varies from 0.15 to 0.50. Accordingly, the maximum energy product of the materials first increases with 𝑥 from 0 to 0.35, and then decreases when 𝑥 exceeds 0.35.

    • Effect of Bi and Sr doping on morphological and magnetic properties of LaCo0.6Fe0.4O3 nanosized perovskites

      U Megha George Varghese K Shijina

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      Nanopowders of La1−xBixCo0.6Fe0.4O3 (𝑥 = 0, 0.1, 0.2) and La1−2xBi𝑥Sr𝑥Co0.6Fe0.4O3 (𝑥 = 0.1) multinary perovskites were synthesized by citrate sol–gel autocombustion method. Crystalline phase and the lattice parameters were obtained from X-ray diffraction pattern. The XRD result shows that all compounds have rhombhohedral crystal structure with $\bar{\rm R3}$c space group and Bi (𝑥 = 0.2) have the presence of secondary peaks. Crystallite size, dislocation density, specific area and strain were calculated from XRD. The elemental composition and micrographs of grain were obtained from EDAX (energy dispersive X-ray analysis) and SEM (scanning electron microscopy), with an average grain size below 400 nm. Surface morphological studies using XPS (X-ray photoelectron spectroscopy) were used to find out the chemical states and surface proportion of oxygen present in samples. Finally, using the vibrating sample magnetometer the room temperature magnetic behaviour of compounds was studied and it was observed that the ferromagnetic behaviour of LaCo0.6Fe0.4O3 was reduced by Bi and Sr doping.

    • Nanohydroxyapatite synthesis using optimized process parameters for load-bearing implant

      Feven Mattews Michael M Khalid C T Ratnam W Rashmi M E Hoque Mohammad Reza Ketabchi

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      In this study, nanohydroxyapatite (NHA) was synthesized using calcium nitrate tetrahydrate and diammonium hydrogen phosphate via the precipitation method assisted with ultrasonication. Three independent process parameters: temperature (𝑇) (70, 80 and 90°C), ultrasonication time (𝑡) (20, 25 and 30 min), and amplitude (𝐴) (60, 65 and 70%) were studied and optimized using response surface methodology based on 3 factors and 5 level central composite design. The responses of the model were analysed with the help of the particle size measured from field-emission scanning electron microscopy and Brunauer–Emmett–Teller (BET). The surface area of particle was measured with BET and the thermal stability of the powder was measured using thermogravimetric analysis. Finally, with the optimized process parameters obtained from the model, the NHA powder was synthesised and validated against the predicted value. The results show a good agreement with an average error 8% between the actual and predicted values. Moreover, the thermal stability and porosity of synthesized NHA was further improved after calcination. This improvement could be due to the removal of impurities from the NHA powder after calcination as indicated by the Fourier transform infrared spectroscopy and energy-dispersive X-ray spectroscopy.

    • Mechanical property analysis of kenaf–glass fibre reinforced polymer composites using finite element analysis

      M Ramesh S Nijanthan

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      Nowadays, natural fibres are used as a reinforcing material in polymer composites, owing to severe environmental concerns. Among many different types of natural resources, kenaf plants have been extensively exploited over the past few years. In this experimental study, partially eco-friendly hybrid composites were fabricated by using kenaf and glass fibres with two different fibre orientations of 0° and 90°. The mechanical properties such as tensile, flexural and impact strengths of these composites have been evaluated. From the experiment, it was observed that the composites with the 0° fibre orientation can withstand the maximum tensile strength of 49.27 MPa, flexural strength of 164.35 MPa, and impact strength of 6 J. Whereas, the composites with the 90° fibre orientation hold the maximum tensile strength of 69.86 MPa, flexural strength of 162.566 MPa and impact strength of 6.66 J. The finite element analysis was carried out to analyse the elastic behaviour of the composites and to predict the mechanical properties by using NX Nastran 9.0 software. The experimental results were compared with the predicted values and a high correlation between the results was observed. The morphology of the fractured surfaces of the composites was analysed using a scanning electron microscopy analysis. The results indicated that the properties were in the increasing trend and comparable with pure synthetic fibre reinforced composites, which shows the potential for hybridization of kenaf fibre with glass fibre.

    • Synthesis and characterization of stable aqueous dispersions of graphene

      Ujjal Kumar Sur Abhijit Saha Aparna Datta Balaprasad Ankamwar Farah Surti Sannak Dutta Roy Debasish Roy

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      A stable aqueous dispersion (5 mg ml$^{−1}$) of graphene was synthesized by a simple protocol based on three-step reduction of graphene oxide (GO) dispersion synthesized using the modified version of Hummers and Offeman method. Reduction of GO was carried out using sodium borohydride, hydrazine hydrate and dimethyl hydrazine as reducing agents. The chemically synthesized graphene was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–visible absorption spectroscopy, Fourier transform infrared (FTIR) and Raman spectroscopy, thermogravimetric analysis (TGA), optical microscopy. The stability of aqueous dispersions of graphene was confirmed through zeta potential measurements and the negative zeta potentials of 55–60 mV were obtained indicating the high stability of aqueous graphene dispersions.

    • Processing and characterization of extruded PET and its r-PET and MWCNT nanocomposite thin films by spin coating

      Arvind R Singh Vineeta D Deshpande

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      The objective of the present study was basic understanding of the formation of thin film morphology by spin coating using reorganized polyethylene terephthalate (r-PET) and multiwalled carbon nanotubes (MWCNTs) as fillers in PET. A study of the correlation between physical properties of the PET films and its surface morphology was carried out using atomic force microscopy-based power spectral density (PSD) analysis. No significant work of surface analysis, using PSD of thin films of PET has been reported till date. Dilute solution of PET, PET with 3 wt% (r-PET) and PET with 3 wt% (2 wt% r-PET + 1 wt% MWCNT) filler were prepared using trifluoroacetic acid (TFA) as a solvent and thin films were fabricated on glass substrate by the optimized spin coating technique. Preparation of r-PET and r-PET+ MWCNT fillers was obtained by the precipitation method using TFA as a solvent and acetone as an antisolvent. The samples before spin coating were extruded and for comparison, a film of non-extruded PET was also prepared. Structural studies by Fourier transform infrared and X-ray diffraction show higher degree of crystallinity in r-PET and decrease in chain entanglements. Owing to the crystallizing behaviour of r-PET, it allows better dispersion of MWCNT in the polymer matrix as compared with PET. The samples with fillers of MWCNT show more compact and unique mesh-like globular structure, indicating application for electromagnetic shielding foams and fibres.

    • Structural, morphological, optical and opto-thermal properties of Ni-doped ZnO thin films using spray pyrolysis chemical technique

      S Rajeh A Barhoumi A Mhamdi G Leroy B Duponchel M Amlouk S Guermazi

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      Nickel-doped zinc oxide thin films (ZnO : Ni) at different percentages were deposited on glass substrates using a chemical spray technique. The effect of Ni concentration on the structural, morphological, optical and photoluminescence (PL) properties of the ZnO : Ni thin films were investigated. X-ray diffraction analysis revealed that all films consist of single phase ZnO and was well crystallized in würtzite phase with the crystallites preferentially oriented towards the (002) direction parallel to the c-axis. The optical transmittance measurement was found to be higher than 90%, the optical band gap values of ZnO thin films decreased after doping from 3.29 to 3.21 eV. A noticeable change in optical constants was observed between undoped and Ni-doped ZnO. Room-temperature PL is observed for ZnO, and Ni-doped ZnO thin films.

    • Enhanced emission of CaNb$_2$O$_6$ : Sm$^{3+}$ phosphor by codoping Na$^+$/B$^{3+}$ and the emission properties

      Renping Cao Zhengdong Qin Shenhua Jiang Aihui Liang Zhiyang Luo Xiaoguang Yu

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      A series of CaNb$_2$O$_6$:$x$Sm$^{3+}$ ($0 \le x \le 10$ mol%) and CaNb$_2$O$_6$:Sm$^{3+}$, Na$^+$/B$^{3+}$ phosphors were synthesized by the solid-state reaction method in air. Their crystal structures and luminescence properties were investigated and analysed, respectively. Host CaNb$_2$O$_6$ emitted blue light with excitation 270 nm. CaNb$_2$O$_6$:$x$Sm$^{3+}$ phosphors showed a systematically varied hue from blue to white by changing Sm3+ ion concentration from 0 to 10 mol% with excitation of 270 nm and their chromaticity coordinates were the regions from (0.1665, 0.1767) to (0.2484, 0.2260). Luminescence properties of CaNb$_2$O$_6$:$x$Sm$^{3+}$ phosphor were tuned and improved significantly by codoping B$^{3+}$ or Na$^+$ ions. Energy transfer between Nb$_2$O$^{2-}_6$ group and Sm$^{3+}$ ion was observed and analysed via luminescence properties. The luminous mechanism was explained by energy level scheme and energy transfer process in CaNb$_2$O$_6$:$x$Sm$^{3+}$ phosphor. The strong excitation band peaking at ∼407 nm indicated that the CaNb$_2$O$_6$:$x$Sm$^{3+}$, Na$^+$/B$^{3+}$ phosphor has a potential application in white light-emitting diodes based on near-UV LED chip.

    • Structural and electronic properties of non-magnetic intermetallic YAuX (X = Ge and Si) in hexagonal and cubic phases

      A Lekhal F Z Benkhelifa S Méçabih B Abbar B Bouhafs

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      The structural and electronic properties of non-magnetic intermetallic YAuX (X = Ge and Si) crystallized in hexagonal phase have been investigated using the full potential linearized augmented-plane wave (FPLAPW) method based on the density functional theory (DFT), within the generalized gradient approximation (GGA). The calculated lattice parameters were in good agreement with experiment. Also, the structural and electronic properties of the non-magnetic half-Heusler YAuPb compound including the artificial YAuX (X = Ge and Si) calculated in cubic phase were determined. It was found that the half-Heusler YAuPb compound presented metallic character. The results showed that YAuGe in cubic phase is a semiconductor whereas the cubic YAuSi is an isolator.

    • Synthesis, characterization and drug-delivery activity of rifampin anchored poly(vinyl alcohol)

      Palanichamy Jeyaraman Balakrishnan Meenarathi Ramasamy Anbarasan

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      Poly(vinyl alcohol) (PVA) has wide applications in film industries owing to the hydrophilicity and biocompatibility. In recent times the application of PVA is extended to drug-delivery field. Unfortunately, the thermal stability of PVA is very poor. In order to increase the thermal stability, the drugs were chemically conjugated with PVA. In the present investigation rifampin (Rif.) a bactericidal antibiotic drug was chemically conjugated with PVA backbone. The resultant Rif.-conjugated PVA was characterized by Fourier transform infrared spectroscopy, UV–visible spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry, and thermogravimetric analysis (TGA). Finally, the Rif.-conjugated PVA was tested for the drug-release activity. The scanning electron microscope morphology declared the presence of microvoids on the surface of PVA and the same was effectively used for the drug-loading purpose. Mechanical properties of PVA before and after the structural modification process were also tested. The aromatic carbon signal around 120–150 ppm in the 13C NMR confirmed the chemical grafting of Rif. on to the PVA backbone. The TGA confirmed the four-step degradation process for the structurally modified PVA.

    • Synthesis, spectral, thermal, optical dispersion and dielectric properties of nanocrystalline dimer complex (PEPyr–diCd) thin films as novel organic semiconductor

      Ahmed Farouk Al-Hossainy

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      Dimer complex PEPyr–diCd (5a) has been prepared by reacting CdCl$_2$·2.5H$_2$O with 1,1$'$-bis(diphenylphosphino)ethyl-6-methyl-3-(pyridin-2-yl)-1,4-dihydro-pyridazine tungsten tetracarbonyl PEPyr (4a) as bipyridine ligand. The structural properties of PEPyr–diCd complex were characterized on the basis of elemental analysis (EA), Fourier transform infrared spectra, fast atom bombardment-mass spectrometry, thermogravimetric/ differential thermal analysis, and 1H nuclear magnetic resonance spectroscopy. The crystal is orthorhombic, space group Pbca. Cd(II) metal in PEPyr–diCd organic semiconductor complex coordinated with two N of the PEPyr and three Cl$^−$ (one terminal and two bridging). The micro-structural properties of the films were studied via X-ray diffraction, and scanning electron microscopy. The as-deposited films were annealed in air for 1 h at 150, 200, and 250°C. An average transmittance >70% for PEPyr–diCd complex at higher wavelength >800 nm was observed.In UV spectrum, the transmittance increases followed by a sharp decrease at wavelength 700–750 nm within visible range. The results of the absorption coefficient were determined to find the binding energy (EB) of PEPyr–diCd organic semiconductor complex as 0.242 and 0.47 eV, respectively. Refractive index (𝑛) and absorption index (𝐾) of PEPyr–diCd complex were calculated. Moreover, the dispersion parameters such as dispersion energy, oscillator energy, dielectric constant, and dissipation factor were determined. The oxidation of the imino-phosphine derivatives were examined using cyclic voltammetry in methylene chloride solvent. The cyclic voltammogram of PEPyr–diCd (5a) organic semiconductor appears to have two quasi-reversible oxidations at 543 and 441 mV. The obtained results indicate that the PEPyr–diCd organic semiconductor thin film is a good candidate in optoelectronic devices based on its band gap and dispersion parameters.

    • Glycine functionalized alumina nanoparticles stabilize collagen in ethanol medium

      S Prabhu K Cheirmadurai J Raghava Rao P Thanikaivelan

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      The synthesis of glycine functionalized Al$_2$O$_3$ nanoparticles (Gly@Al$_2$O$_3$) by a simple two-step process employing sucrose as a template was reported. The functionalization of Al$_2$O$_3$ nanoparticles with glycine was confirmed by Fourier transformed infrared (FT-IR) spectroscopy, X-ray diffraction, high-resolution scanning electron microscopy (HRSEM) and energy-dispersive X-ray (EDX) analysis. The interaction of Gly@Al$_2$O$_3$ nanoparticles with collagen fibres was demonstrated using HRSEM, EDX, differential scanning calorimetry and FT-IR analysis. The thermal stability of collagen is enhanced to 74°C upon interaction with Gly@Al$_2$O$_3$ nanoparticles thereby suggesting applications in leather making, biomedicine and cosmetic fields.

    • Radical coupling of maleic anhydride onto graphite to fabricate oxidized graphene nanolayers

      Fatemeh Samadaei Mehdi Salami-Kalajahi Hossein Roghani-Mamaqani

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      Radical coupling was used to modify graphite with maleic anhydride (MAH). Azobisisobutyronitrile (AIBN) as radical generator activated MAH radically and it was reacted with defects at the surface of nanolayers. A set of batches with different reaction times (24, 48 and 72 h) were performed to obtain fully-modified nanolayers (GMA1, GMA2 and GMA3, respectively). Fourier transform infrared results approved the synthesis of MAHgrafted graphite. Thermogravimetric analysis showed that 5.9, 11.1 and 13.2 wt% of MAH was grafted onto the surface of GMA1, GMA2 and GMA3, respectively, and that was approved by X-ray photoelectron spectroscopy results. Also, X-ray diffraction patterns showed that $d$-spacing increased from 0.34 nm for graphite to 1.00 nm for all modified samples. However, GMA1 showed a weak peak related to graphite structure that disappeared when reaction time was increased. After modification with MAH, lamella flake structure of graphite was retained whereas the edges of sheets became distinguishable as depicted by scanning electron microscopy images. According to Raman spectra, modification progression resulted in more disorder structure of nanolayers due to grafting of MAH. Also, transmission electron microscopy images showed graphite as transparent layers while after modification, surface of nanolayers became folded due to the opposite effects of $\pi$-conjugated domains and electrostatic repulsion of oxygen-containing groups.

    • Synthesis of graphene through direct decomposition of CO$_2$ with the aid of Ni–Ce–Fe trimetallic catalyst

      Ghazaleh Allaedini Siti Masrinda Tasirin Payam Aminayi

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      In this study, few-layered graphene (FLG) has been synthesized using the chemical vapour deposition (CVD) method with the aid of a novel Ni–Ce–Fe trimetallic catalyst. Carbon dioxide was used as the carbon source in the present work. The obtained graphene was characterized by Raman spectroscopy, and the results proved that high-quality graphene sheets were obtained. Scanning electron microscopy, atomic force microscopy and transmission electron microscopy pictures were used to investigate the morphology of the prepared FLG. The energydispersive X-ray spectroscopy results confirmed a high yield ($\sim$48%) of the obtained graphene through this method. Ni–Ce–Fe has been shown to be an active catalyst in the production of high-quality graphene via carbon dioxide decomposition. The X-ray photoelectron spectroscopy spectrum was also obtained to confirm the formation of graphene.

    • Electrochemical supercapacitor behaviour of functionalized candle flame carbon soot

      C Justin Raj Byung Chul Kim Bo-Bae Cho Won-Je Cho Sung-Jin Kim Sang Yeup Park Kook Hyun Yu

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      The electrochemical supercapacitor behaviour of bare, washed and nitric acid functionalized candle flame carbon soots were reported. Crystallinity and the morphology of the candle soots were recorded using X-ray diffraction analysis, scanning and transmission electron microscopy, respectively. The nitric acid functionalized candle soot showed an improved Brunauer–Emmett–Teller surface area of 137.93 from 87.495 m$^2$ g$^{−1}$ of washed candle soot. The presence of various functional groups in candle soots and the development of oxygen functionalities in the functionalized candle soot were examined through Fourier transform infrared spectroscopy and energy-dispersive X-ray analysis. Raman spectra showed the characteristic peaks corresponding to the D (diamond) and G (graphite) phase of carbon present in the candle soots. The electrochemical characterization was performed by cyclic voltammetry, galvanostatic charge/discharge test and impedance spectroscopy in 1MH2SO4 electrolyte. The functionalized candle soot electrode showed an enhanced specific capacitance value of 187 F g$^{−1}$ at 0.15 A g$^{−1}$ discharge current density, which is much higher than that of bare and washed candle soot electrodes.

    • Low dielectric loss in nano-Li-ferrite spinels prepared by sol–gel auto-combustion technique

      Mamata Maisnam Nandeibam Nilima Maisnam Victory Sumitra Phanjoubam

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      Pure and doped nano-Li-ferrite spinels were prepared by the sol–gel auto-combustion technique. The prepared ferrites were pelleted and heat treated at different temperatures. Structural characterization was carried out on the as-prepared samples and also on the heat-treated samples using X-ray diffraction (XRD). The studies confirmed the formation of single phase with spinel structures in all the samples. The crystallite size of the samples evaluated from XRD data was found to be 17–24 nm. Scanning electron microscopic photomicrographs revealed the microstructures and the grain size of these nanoferrites. The room-temperature dielectric constant and dielectric loss tangent, tan δ were measured as a function of frequency in the range 100 Hz–1 MHz. These nanoferrites showed the normal dielectric dispersion behaviour. The observed dielectric constant and dielectric loss tangent were found to be much lower than those measured on substituted Li-ferrites prepared by the conventional ceramic method. The results obtained were discussed in the paper.

    • Electrical conduction mechanism in GeSeSb chalcogenide glasses

      Vandana Kumari Anusaiya Kaswan D Patidar Kananbala Sharma N S Saxena

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      Electrical conductivity of chalcogenide glassy system Ge$_{30−x}$Se$_{70}$Sb$_{x}$ (𝑥 = 10, 15, 20 and 25) prepared by melt quenching has been determined at different temperatures in bulk through the $I$–$V$ characteristic curves. It is quite evident from results that Poole–Frenkel conduction mechanisms hold good for conduction in these glasses in a given temperature range. The variation in electrical conductivity with composition was attributed to the Se–Sb bond concentration in the Se–Ge–Sb system. Results indicated that Ge$_5$Se$_{70}$Sb$_{25}$ showed the minimum resistance. In view of this the composition Ge$_5$Se$_{70}$Sb$_{25}$ may be coined as ‘critical composition’ in the proposed series. Also the activation energies of conduction of these glassy alloys have been calculated in higher and lower temperature range using the Arrhenius equation.

    • Characterization of titanium–hydroxyapatite biocomposites processed by dip coating

      R Baptista D Gadelha M Bandeira D Arteiro M I Delgado A C Ferro M Guedes

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      Ti orthopaedic implants are commonly coated with hydroxyapatite (HA) to achieve increased biocompatibility and osseointegration with natural bone. In this work the dip-coating technique was used to apply HA films on Ti foil. A gel was used as the support vehicle for commercial HA particles. The experimental parameters like surface roughness of the metallic substrate and immersion time were studied. All coated substrates were heat treated and sintered under vacuum atmosphere. The produced coatings were characterized by field-emission gun scanning electron microscopy coupled with energy-dispersive spectroscopy, X-ray diffraction, Raman spectroscopy, microhardness, scratch test and profilometry. Additionally, the apatite-forming ability of the produced material was tested by exposure to a simulated body fluid. Higher substrate surface roughness and longer immersion time produce thicker, denser films, with higher surface roughness. Lower film porosity is accompanied by higher hardness values. However, thicker coating promotes differential shrinkage and crack formation during sintering. Both coating thickness and coating roughness increase with coating time. HA films $\sim$30–40 $\mu$m thick with 45–50% HA theoretical density produced on Ti substrates with surface roughness of $R_z\sim 1.0–1.7$ $\mu$m, display an attractive combination of high hardness and resistance to spallation. Attained results are encouraging regarding the possibility of straightforward production of biocompatible and bioactive prosthetic coatings for orthopaedic applications using commercial HA.

    • The impact of anode design on fuel crossover of direct ethanol fuel cell

      Sethu Sundar Pethaiah Jayakumar Arunkumar Maximiano Ramos Ahmed Al-Jumaily Natarajan Manivannan

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      Direct-ethanol fuel cells (DEFCs) hold a promising future owing to its simple balance of plant operation and potential high-energy density. The significant challenges associated with it is the fuel crossover, which limits its performance and durability. In the present work, Pt–Pd nanocomposites were fused so as to find its impact on the anode design of DEFC. The current paper aimed to address these issues optimally and it also investigated the ethanol crossover by various electrochemical characterization techniques.

    • Development of hybrid composite radar wave absorbing structure for stealth applications

      T Annil Kumar J Inayathullah V A Nagarajan S Hari Kumar

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      The ideally invisible stealth radomes are usually sandwiched constructions composed of E-glass/epoxy composite, polyvinyl chloride foam and frequency selective surfaces (FSS). Nylon 6/6 and balsa wood are well known for their low dielectric properties. In this work the electromagnetic (EM) wave transmission characteristics of the existing stealth radomes were improved by employing nylon 6/6 fibre and balsa wood, along with E-glass/epoxy composite without compromising the mechanical properties. The free space measurement technique was performed to measure the EM wave transmission characteristics in the X-band frequency range (8.2–12.4 GHz) for a specific FSS. The flexural strength of the sandwiched constructions were investigated with three-point bending test.

    • Surface modification of TiO2 coatings by Zn ion implantation for improving antibacterial activities

      Xiaobing Zhao Jiashen Yang Jing You

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      TiO$_2$ coating has been widely applied in orthopaedic and dental implants owing to its excellent mechanical and biological properties. However, one of the biggest complications of TiO$_2$ coating is implant-associated infections. The aim of this work is to improve the antibacterial activity of plasma-sprayed TiO$_2$ coatings by plasma immersion ion implantation (PIII) using zinc (Zn) ions. Results indicate that the as-sprayed TiO$_2$ coating is mainly composed of rutile phase. Zn-PIII modification does not change the phase compositions and the surface morphologies of TiO$_2$ coatings, while change their hydrophilicity. Zn-implanted TiO$_2$ coatings can inhibit the growth of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), and the ability to inhibit S. aureus is greater than that to E. coli. Zn ion release and reactive oxygen species may be attributed to improving the antibacterial activity of TiO$_2$ coating. Therefore, Zn-PIII TiO$_2$ coatings on titanium suggest promising candidates for orthopaedic and dental implants.

    • Low-temperature localization in the transport properties of self-doped La$_{0.9}$Mn$_{0.98}$Zn$_{0.02}$O$_3$

      K De S Das

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      Low-temperature transport properties are investigated in the self-doped compound, La$_{0.9}$Mn$_{0.98}$Zn$_{0.02}$O$_3$. The analysis of the low-temperature resistivity is performed considering various scattering mechanisms. The parameters involved with different scattering processes such as electron–electron, Kondo, electron–phonon and electron–magnon are found to be strongly influenced by the applied magnetic field. The results suggest that interplay between electron–electron and Kondo-like scatterings lead to the localization in the temperature dependence of resistivity at low temperature.

    • A low cost, light weight cenosphere–aluminium composite for brake disc application

      V Saravanan P R Thyla S R Balakrishnan

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      The commonly used composite material for brake rotor consists of silicon carbide (SiC) or aluminium oxide (Al$_2$O$_3$) particles which are more expensive. The weight of conventionally used composite is more compared to base alloy. The aim of this paper is to develop a light weight material for brake disc applications thereby substituting base alloy and conventional composite. This analysis led to 10 vol% cenosphere reinforced aluminium alloy (AA) 6063 composite as the most appropriate material for brake disc. To ensure the manufacturability of composite, composite brake rotor was casted using the sand casting technique and was machined to achieve the final component. Thermal capability of brake disc was ensured by studying temperature variation through vehicle testing procedure of disc brake. Cost reduction is one of the important benefit acquired using cenosphere reinforced composite. This was ensured by cost estimation and analysis. The cost estimated to manufacture the AA6063 brake disc was compared with composite cost.

    • Bias-dependent photo-detection of dual-ion beam sputtered MgZnO thin films

      Saurabh Kumar Pandey Shaibal Mukherjee

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      The structural, morphological, elemental and electrical properties of MgZnO thin films, grown on p-Si (001) substrates by dual-ion beam sputtering deposition (DIBSD) system at different substrate temperatures were thoroughly investigated. X-ray diffraction (XRD) pattern of MgZnO film exhibited crystalline hexagonal wurtzite structure with the preferred (002) crystal orientation. The full-width at half-maximum of the (002) plane was the narrowest with a value of 0.226° from MgZnO film grown at 400°C. X-ray photoelectron spectroscopy analysis confirmed the substitution of Zn$^{2+}$ by Mg$^{2+}$ in MgZnO thin films and the absence of MgO phase. Correlation between calculated crystallite size, as evaluated from XRD measurements, and room-temperature carrier mobility, as obtained from Hall measurements, was established. Current–voltage characteristics of MgZnO thin films were carried out under the influence of dark and light illumination conditions and corresponding values of photosensitivity were calculated. MgZnO film grown at 100°C exhibited the highest photosensitivity of 1.62. Compared with one of the best-reported values of photosensitivity factor from ZnO-material-based films available in the literature, briefly, $\sim$3.085-fold improved photosensitivity factor at the same bias voltage (2 V) was obtained.

    • Explanation of ferromagnetism origin in N-doped ZnO by first-principle calculations

      A El Amiri H Lassri E K Hlil M Abid

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      By $ab-initio$ calculations, the possible source of ferromagnetism in N-doped ZnO compound was systematically studied. The electronic structure and magnetic properties of N-doped ZnO with/without ZnO host and N defects were investigated using the Korringa–Kohn–Rostoker method combined with coherent potential approximation. It was shown that Zn vacancy and the presence of N defects (substitutional, interstitial or combination of both) induce the ferromagnetism in N-doped ZnO. From density of state analysis, it was shown that p–p interaction between 2p-elements (N,O) is the mechanism of ferromagnetic coupling in N-doped ZnO.

    • High-temperature stability of yttria-stabilized zirconia thermal barrier coating on niobium alloy—C-103

      S S Panwar T Umasankar Patro K Balasubramanian B Venkataraman

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      Thermal barrier coatings (TBCs) of yttria-stabilized zirconia (YSZ) of different thicknesses with an intermediate bond coat were deposited on C-103 Nb alloy using the air plasma spraying technique. The coatings were subjected to rapid infra-red (IR) heating ($\sim$25°C s$^{−1}$) up to $\sim$1250°C and exposed up to 100 s at this temperature with heat flux varying from 55 to 61 Wcm$^{−2}$. The TBCs were found to be stable and intact after the heat treatment. In contrast, at the same conditions, the uncoated C-103 alloy specimen showed extensive oxidation followed by weight loss due to spallation. A maximum temperature drop of $\sim$200°C was observed on the opposite side of the coated alloy with 600 $\mu$m YSZ coat; as against negligible temperature drop in case of bare alloy specimen. The temperature drop was found to increase with the coating thickness of YSZ. The coatings before and after IR heating were investigated by scanning electron microscopy, X-ray diffraction, electron probe microanalysis, microhardness and residual stress measurements in order to understand the effect of thermal shock on the properties of the TBC. On account of these high-temperature properties, YSZ coating along with the bond coat is expected to find potential thermal barrier coating system on niobium alloys for supersonic vehicles.

    • Preparation of new thermoluminescent material ($100−x$)B$_2$O$_3$–xLi$_2$O: Cu$^{2+}$ for sensing and detection of radiation

      Zeid A Alothman Tansir Ahamad Mu Naushad Saad M Alshehri

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      The copper-doped lithium borate glass as a thermoluminescent (TL) material ($100−x$)B$_2$O$_3$–$x$Li$_2$O: Cu$^{2+}$ ($x = 20$, 50 and 80 mol%) was prepared by the combustion method. The formation of ($100−x$)B$_2$O$_3$–$x$Li$_2$O: Cu$^{2+}$ after doping 2, 3 and 5 ppm Cu$^{2+}$, was characterized by Fourier transform infrared spectroscopy, X-ray diffraction and transmission electron microscopy. The TL characteristics of the synthesized material were studied at different parameters. The synthesized glass 50B$_2$O$_3$–50i$_2$O: Cu$^{2+}$ with 3 ppm of doped Cu$^{2+}$, exhibited the superior TL properties than other glasses prepared in the current study. The spin-Hamiltonian parameters were assessed using the electron spin resonance spectra of 50B$_2$O$_3$–50Li$_2$O: Cu$^{2+}$ doped with 3 ppm Cu$^{2+}$. The spin-Hamiltonian parameter values in the case of Cu$^{2+}$ revealed that the ground state of Cu$^{2+}$ was $dx^2–y^2$ orbital (${}^2$B$_{1g}$) and the site symmetry around Cu$^{2+}$ ion was distorted octahedral. TL glow curves were recorded with different heating rates (1, 2, 5, 10, 15, and 20°C s$^{−1}$) at the fixed dose $10\times 10^3$ Gy. The results revealed that the glow peak position shifted to higher temperature with heating rate and the heating rate of 10°C s$^{−1}$ showed the superior TL response with highest glow peak which is very good for dosimetry purposes.

    • Contents - February 2016

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