• Volume 39, Issue 2

April 2016,   pages  337-601

• Cellulose acetate electrospun nanofibrous membrane: fabrication, characterization, drug loading and antibacterial properties

Cellulose-based materials are one of the most commonly used materials for biomedical applications, which normally applied as carriers for pharmaceuticals and drug-releasing scaffolds. In this study, cellulose acetate (CA) was used to fabricate the nanofibrous membrane using the electrospinning technique. CA solutions at different concentrations were prepared by dissolving the polymer in a mixture of acetic acid/acetone solvents with the ratio of 3:1. The field emission scanning electron microscope results showed that electrospinning of 10% (w/v) CA produced nanofibres with many beads. When the CA concentration was increased to 14% (w/v), bead-free nanofibres were produced. The contact angle measurement results confirmed the hydrophilic properties of nanofibres. In order to prevent common bacterial infections, a model drug, Tetracycline · HCL was incorporated into the CA nanofibres. The drug-loaded CA nanofibres showed antibacterial activity against Gram-positive and Gram-negative bacteria.CA nanofibres had high water uptake properties. The CA nanofibrous membrane was non-toxic to human skin fibroblast cells. Thus the CA nanofibres with 14% (w/v) concentration exerted suitable properties for wound healingapplication.

• Efficiency of surface modified Ti coated with copper nanoparticles to control marine bacterial adhesion under laboratory simulated conditions

Titanium (Ti) used as condenser material in nuclear power plants encounter severe biofouling in marine environment which in turn affects the efficiency of the metal. To reduce the biofouling by marine microorganisms, surface modification of the Ti was carried out by anodization process to obtain nanotubes (TiO$_2$-NTs). The electrolyte solution containing 1% of ammonium fluoride resulted in uniform growth of TiO$_2$-NTs. TiO$_2$-NTs were furthercoated with chemically synthesized copper nanoparticles (NT-CuNP) using 3-amino propyl triethoxy silane as a coupling agent. NT-CuNP was characterized by field-emission scanning electron microscopy (FE-SEM), energydispersivespectroscopy and X-ray diffraction. The stability of the coating was determined by the amount of Cu$^+$ ions released into the surrounding using AAS. The microbial adhesion on the surface of Ti, TiO$_2$-NTs and NT-CuNPcoupons were evaluated by sea water exposure studies using total viable count method and also characterized by FE-SEM for any morphological changes. The NT-CuNP coupons show a 60% reduction in microbial adhesion whencompared to control Ti coupons.

• Hydrophobic nano-carrier for lysozyme adsorption

In this work, poly(HEMA–APH) nanoparticles were synthesized by surfactant-free emulsion polymerization technique.Magnetic behaviour was introduced by simple addition of Fe$_3$O$_4$ into the polymerization medium.Characterization of the nanoparticle was carried out by FTIR, ESR, SEM, AFM and EDX analyses. These synthesized magnetic nanoparticles were used for adsorption of lysozyme. For this purpose, adsorption conditions wereoptimized and maximum lysozyme binding capacity was found to be 278.8 mg g$^{−1}$ polymer in pH 7.0 phosphate buffer at 25$^{\circ}$C. Desorption and reusability properties of the nanoparticles were investigated and lysozyme adsorption efficiency did not change significantly at the end of the 10 successive reuses.

• Potentiating effect of ecofriendly synthesis of copper oxide nanoparticles using brown alga: antimicrobial and anticancer activities

This study reports the in vitro antimicrobial and anticancer activities of biologically synthesized copper nanoparticles. The antimicrobial activity of green synthesized copper oxide nanoparticles was assessed by well diffusion method. The anticancer activity of brown algae-mediated copper oxide nanoparticles was determined by MTT assay against the cell line (MCF-7). Maximum activity was observed with Pseudomonas aeruginosa and Aspergillus niger. Effective growth inhibition of cells was observed to be more than 93% in antibacterial activity. Thus, the results of the present study indicates that biologically synthesized copper nanoparticles can be used for several diseases, however, it necessitates clinical studies to ascertain their potential as antimicrobial and anticancer agents.

• Preparation and characterization of Li$_2$O–CaO–Al$_2$O$_3$–P$_2$O$_5$–SiO$_2$ glasses as bioactive material

The aim of the present investigation was to study the role of Al$_2$O$_3$ in the Li$_2$O–CaO–P$_2$O$_5$–SiO$_2$ bioactive glass for improving the bioactivity and other physico-mechanical properties of glass. A comparative studyon structural and physico-mechanical properties and bioactivity of glasses were reported. The structural properties of glasses were investigated by X-ray diffraction, Fourier transform infrared spectrometry, scanning electronmicroscopy and the bioactivity of the glasses was evaluated by in vitro test in simulated body fluid (SBF). Density, compressive strength, Vickers hardness and ultrasonic wave velocity of glass samples were measured to investigatephysical and mechanical properties. Results indicated that partial molar replacement of Li$_2$O by Al$_2$O$_3$ resulted in a significant increase in mechanical properties of glasses. In vitro studies of samples in SBF had shown that the pH of the solution increased after immersion of samples during the initial stage and then after reaching maxima it decreased with the increase in the immersion time. In vitro test in SBF indicated that the addition of Al$_2$O$_3$ up to 1.5 mol% resulted in an increase in bioactivity where as further addition of Al$_2$O$_3$ caused a decrease in bioactivity of the samples. The biocompatibility of these bioactive glass samples was studied using human osteoblast (MG-63) cell lines. The results obtained suggested that Li$_2$O–CaO–Al$_2$O$_3$–P$_2$O$_5$–SiO$_2$-based bioactive glasses containing alumina would be potential materials for biomedical applications.

• Evaluation of biodegradation and biocompatibility of collagen/chitosan/alkaline phosphatase biopolymeric membranes

The aim of this study was to develop a new variant of membranes based on collagen (COL), chitosan (CHI) and alkaline phosphatase (ALP) immobilized and cross-linking with glutaraldehyde (GA) at different concentrations. The biodegradation in the presence of collagenase was investigated. Biocompatibility was evaluated by MTT assay using a mouse fibroblast cell culture type NCTC (clone 929). Non-cross-linked samples were biocompatible and membranes cross-linked with low concentrations of GA (0.04, 0.08%) were also iocompatible. However, high concentrations of GA lead to a decreased biocompatibility. The adsorption behaviour of Ca$^{2+}$ ions to all membraneswere evaluated using the Freundlich isotherms. Haemolytic studies were performed in order to consider their applications in biomineralization process. By the addition of collagen and ALP to chitosan, the haemolytic indexdecreases, the COL–CHI–ALP membrane being in the non-haemolytic domain, while the COL–CHI–ALP–GA membrane has a haemolytic index greater than 2, and is slightly haemolytic.

• Isolation and characterization of biogenic calcium carbonate/phosphate from oral bacteria and their adhesion studies on YSZ-coated titanium substrate for dental implant application

Biogenic calcium carbonate/phosphate were isolated and characterized from oral bacteria (CPOB). The crystalline nature and morphology of calcium carbonate/phosphate were characterized by X-ray diffraction (XRD)and field emission scanning electron microscopy (FESEM), respectively. XRD analysis revealed the cubic phase of YSZ coating as well as biogenic calcium carbonate (rhombohedral) and calcium phosphate oxide (hexagonal) wasobserved from CPOB. FESEM confirmed the extracellular synthesis of calcium compounds. Bacterial adhesion result reveals that YSZ coating drastically reduce bacterial invasion than titanium substrate.

• Development and antibacterial performance of silver nanoparticles incorporated polydopamine–polyester-knitted fabric

Metallization is one of the finishing processes in textile treatment that can produce multifunctional effects. The present study dealt with the development of an antibacterial polyester-knitted fabric via facile and green impregnation of silver nanoparticles (SNPs). This was done by applying a polymeric foundation on the polyesterknitted fabric by simply dip-coating in the aqueous solution of dopamine. Then the SNPs were in situ fabricated and impregnated on the surface of polydopamine-modified polyester-knitted fabric in an aqueous solution of AgNO$_3$ at room temperature. Thus, a multi-functional finishing of polyester-knitted fabric was done. The Fourier transform infrared spectroscopy was done to confirm the polymer attachment. Scanning electron microscopy equipped withenergy dispersive X-ray was done to confirm the presence of SNPs on treated fabric. The crystallography of the treated surface was examined by X-ray diffraction. The antibacterial properties of treated fabrics against broadspectrum bacterial strains were investigated and found significant.

• Screening of metal-resistant coal mine bacteria for biofabrication of elemental silver nanoparticle

Green synthesis approaches for nanoparticle synthesis are considered as nontoxic, eco-friendly and cost-effective approaches than other physical and chemical approaches. Here, we report green synthesis of silver nanoparticle using the bacteria from the habitat of relatively metal-rich coal mine dust. The bacteria showed resistance to significant concentration of anti-microbial Ag(I) ion. The nanoparticle was synthesized at minimum inhibitory concentration (MIC) of Ag(I) using only two isolates. The synthesis of silver nanoparticle was confirmed from the surface plasmon resonance property of the nanoparticle, whereas morphological features were studied using field emission scanning electron microscope. The hydrodynamic size analysis showed the presence ofmicroparticles along with the nanoparticles. Additionally, IR study provided information about the bacterial proteins involved in either reduction of Ag(I) into silver nanoparticle or capping of reduced silver nanocrystal or both.Thus, majority of the bacteria found in the coal mines have the resistance against the antimicrobial metal ion, and the potential to reduce the ion into nano- or micro-particles. Hence, the bacteria can be used as a single cell factoryfor production of silver nanomaterial.

• Chitosan-encapsulated ZnS : M (M: Fe$^{3+}$ or Mn$^{2+}$) quantum dots for fluorescent labelling of sulphate-reducing bacteria

Chitosan-encapsulated Mn$^{2+} and Fe$^{3+}$-doped ZnS colloidal quantum dots (QDs) were synthesized using chemical precipitation method. Though there are many reports on bio-imaging applications of ZnS QDs, thepresent study focussed on the new type ofmicrobial-induced corrosive bacteria known as sulphate-reducing bacteria, Thiobacillus novellus. Sulphate-reducing bacteria can obtain energy by oxidizing organic compounds while reducingsulphates to hydrogen sulphide. This can create a problem in engineering industries. When metals are exposed to sulphate containing water, water and metal interacts and creates a layer of molecular hydrogen on the metal surface.Sulphate-reducing bacteria then oxidize the hydrogen while creating hydrogen sulphide, which contributes to corrosion for instance, in pipelines of oil and gas industries. In this study, detection and labelling of sulphate-reducing bacteria is demonstrated using fluorescent QDs. Chitosan capped ZnS QDs were synthesized using dopants at different doping concentrations. UV–Vis spectroscopy, XRD and FTIR characterizations were done to identify the opticalband gap energy, crystal planes and determine the presence of capping agent, respectively. The morphology and the average particle size of$3.5\pm 0.2$nm were analysed using TEM which substantiated UV–Vis and XRD results. Photoluminescence spectroscopy detected the bacteria attachment to the QDs by showing significant blue shift in bacteria conjugated ZnS QDs. Fluorescence microscopy confirmed the fluorescent labelling of QDs to Thiobacillus novellus bacteria cells making them ideal for bio-labelling applications. • Toxicity of ZnO nanoparticles on germinating Sesamum indicum (Co-1) and their antibacterial activity A comparative study of chemically (ZnO) and biologically synthesized (nano-ZnO) nanoparticles were carried out to determine the effect on seed germination of$Sesamum indicum$(Co-1) by soaking method. Nano-ZnO is synthesized using$Lantana aculeata$aqueous extract. Chemical synthesis of ZnO nanoparticles by precipitate method and was characterized by ultraviolet–Visible spectroscopy (UV–Vis), Fourier transform infrared spectrometer(FT-IR), energy dispersive X-ray spectrometer (EDX), X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). Antibacterial activity against pathogens was determined using well diffusion method. All the characterization analysis revealed that ZnO and nano-ZnO nanoparticles were spherical in shape with an average particle size of$18 \pm 2$and$12\pm 3$nm, respectively.Antibacterial studies conclude that nano-ZnO NPs have maximum zone of inhibition which was observed in$Pseudomonas aeruginosa$($15.60 \pm 1.0$mm) at 100$\mu$g ml$^{−1}$concentration when compared to other ZnO NPs. Phytomediate ZnO have no adverse effects on seed germination, root elongation on$S. indicum$. But chemically synthesized ZnO nanoparticles significantly decreased in germination of$S. indicum$-treated samples and no changes were observed in bulk ZnO. These results clearly indicate the benefits of using bio-fabricate ZnO nanoparticles, i.e., more efficient in germination of$S. indicum$and can also act as antibacterial agent. It can be used as nanofertilizer in environmental aspect of agricultural development. • Biological activities of synthesized silver nanoparticles from Cardiospermum halicacabum L. The present study focuses on the green synthesis of silver nanoparticles using aqueous extract of Cardiospermum halicacabum. AgNPs were confirmed by UV–Visible spectrophotometer analysis showed SPR at424 nm. FT-IR analysis revealed biomolecules capping of the AgNPs. XRD pattern of synthesized AgNPs was found in face-centered-cubic crystal structure and average crystal size was 23 nm. SEM analyses of the synthesized AgNPsdetermine the spherical shape and EDX spectra confirmed the presence of silver ions. DLS studies revealed that the synthesized AgNPs showed the average size as 74 nm and Zeta potential value of AgNPs was −34 mv. The C. halicacabum leaf extract synthesized AgNPs efficiency were tested against different bacterial pathogens MTCC-426 Proteus vulgaris, MTCC-2453 Pseudomonas aeruginosa, MTCC-96 Staphylococcus aureus, MTCC-441 Bacillus subtilis andMTCC-735 Salmonella paratyphi, and fungal pathogens Alternaria solani and Fusarium-oxysporum. The antioxidant ability of the AgNPs was tested and the results showed significant DPPH, hydroxyl and superoxide, radical scavenging activities. • Ternary alloy nanocatalysts for hydrogen evolution reaction Cu–Fe–Ni ternary alloys (size ∼55–80 nm) with varying compositions viz. CuFeNi (A1), CuFe2Ni (A2) and CuFeNi2 (A3) were successfully synthesized using microemulsion. It is to be noted that synthesis of nanocrystallineternary alloys with precise composition is a big challenge which can be overcome by choosing an appropriate microemulsion system. High electrocatalytic activity towards HER in alkaline medium was achieved by the formation of alloys of metals with low and high binding energies. A high value of current density (228 mA cm$^2$) at an overpotential of 545 mV was obtained for CuFeNi (A1), which is significantly high as compared to the previously reported Ni$_{59}$Cu$_{41}$alloy catalyst. • Adsorption isotherms and kinetics for dibenzothiophene on activated carbon and carbon nanotube doped with nickel oxide nanoparticles Activated carbon (AC) and multiwall carbon nanotubes (CNT) doped with 1, 5 and 10% Ni in the form of nickel oxide nanoparticles were prepared using the wetness impregnation method. These percentages were denoted by the endings NI1, NI5 and NI10 in the notations ACNI1, ACNI5, ACNI10 and CNTNI1, CNTNI5, CNTNIL10, respectively. The physicochemical properties for these adsorbents were characterized using N$_2$adsorption–desorption surface area analyzer, thermal gravimetric analysis (TGA), scanning electron microscopy, energy-dispersive X-ray spectroscopy, field-emission transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectrometre. Adsorption isotherms were obtained and desulphurization kinetics were carried out on solutions of dibenzothiophene (DBT) and thiophene in a model fuel. The efficiencies of DBT and thiophene removal were reported. The adsorption isotherms fitted the Langmuir and Freundlich models. The highest adsorption capacity for DBT was$74\pm 5$mg g$^{−1}$on ACNI5; the maximum adsorption capacities of the other adsorbents followed the trend${\rm ACNI1 > ACNI10 > AC > CNTNI5 > CNTNI1 > CNTNI10 > CNT}$. The adsorption rates for DBT and thiophene followed pseudo-second-order kinetics. The selective removal by these adsorbents of DBT relative to thiophene and naphthalene was evaluated. The adsorbents’ reusability and the effect of the percentage of aromaticcompounds on their adsorption capacity were also reported. • Radar absorbing properties of carbon nanotubes/polymer composites in the V-band This research is devoted to the study of radar absorbing properties of the composites, based on the epoxy binder and carbon nanotubes (CNT) in the frequency range of 52–73 GHz. Three species of unmodified multi-walledCNT differing in length and diameter were investigated as fillers. The reflection coefficients (Krefl) at the radar absorbing material (RAM)–air interface and the electro-magnetic radiation (EMR) absorption coefficients (Kabs) in the materials with the different content of nanotubes were measured (Krefl and Kabs were calculated using the highest (the worst) value of the voltage standing-wave ratio (VSWR) in the frequency range of 52–73 GHz). It was established that the increase in nanotubes aspect ratio (a ratio of CNT length to its diameter) leads to Kabs rising for polymer composites. Also, CNT diameter decrease leads to Krefl reduction. CNT of 8–15 nm in diameter and more than 2$\mum in length are the most effective from all investigated fillers. The reflection loss values were calculated and CNT optimal concentrations were obtained at different thickness of RAMs. • Influence of the concentration of carbon nanotubes on electrical conductivity of magnetically aligned MWCNT–polypyrrole composites The goal of this work is to study the effect of high magnetic pulses on electrical property of carbon nanotube–polypyrrole (CNT–PPy) composites with different CNT concentrations. CNT–PPy composites are produced in fractions of 1, 5 and 9 wt%. During the polymerization process, the CNTs are homogeneously dispersed throughout the polymer matrix in an ultrasonic bath. Nanocomposite rods are prepared. After exposure to 30 magnetic pulses, the resistivity of the rods is measured. The surface conductivity of thin tablets of composites is studied by 4-probe technique. The magnitude of the pulsed magnetic field is 10 Tesla with time duration of 1.5 ms. The results show that after applying 30 magnetic pulses, the electrical resistivity of the composites decreases depending on the concentration of CNTs in the composites. The orientation of CNTs is probed by atomic force microscopy (AFM) technique. AFM images approved alignment of CNT–polymer fibres in the magnetic field.We found that the enhancement in the electrical properties of CNT–PPy composites is due to rearrangement and alignment of CNTs in a high magnetic field. The stability of nano-composites is studied by Fourier transform infrared spectroscopy. • A study on the damping capacity of BaTiO3-reinforced Al-matrix composites To study the damping capacity of BaTiO_3$/Al composites, Al composites reinforced with BaTiO$_3$powder (average grain sizes: 100 and 1000 nm) were fabricated by the hot-pressing sintering method. The damping properties of pure Al and BaTiO$_3$/Al composites were investigated and compared based on the dynamic mechanical analysis over a wide range of temperatures (50–285$^{\circ}$C). Compared with pure Al matrix, 1000 nm BaTiO$_3$/Al composites with 5 and 10% mass fractions of BaTiO$_3$exhibited better damping capacity. For 100 nm BaTiO$_3$/Al composite, its damping capacity is slightly higher than that of pure Al below 145$^{\circ}$C, while it becomes lower above this degree. The damping capacity enhancement of BaTiO$_3$/Al composites can be explained by the ferroelastic domain damping. Furthermore, 5 and 10% BaTiO$_3$/Al composites have higher bending strength and hardness than pure Al sample. • Synthesis and characterization of CuO nanoparticles using strong base electrolyte through electrochemical discharge process In the present study, cupric oxide (CuO) nanoparticles were synthesized by electrochemical discharge process using strong base electrolytes. The experiments were carried out separately using NaOH and KOH electrolytes.The mass output rate and the crystal size were obtained with variation of the rotation speed of magnetic stirrer for both types of electrolytes. The mass output rate of CuO nanoparticles increased with the increase in the speed of rotation, and, after an optimum speed, it started decreasing. However, the size of the particles reduced with the increase of the rotation speed. The crystal plane of the obtained CuO nanoparticles was similar for both the electrolytes whereas the yield of nanoparticles was higher in KOH as compared with NaOH under the sameexperiment conditions. In this set of experiments, the maximum output rates obtained were 21.66 mg h$^{−1}$for NaOH and 24.66 mg h$^{−1}$for KOH at 200 rpm for a single discharge arrangement. The average crystal size of CuO particles obtained was in the range of 13–18 nm for KOH electrolyte and 15–20 nm for NaOH electrolyte. Scanning electron microscopy images revealed that flower-like and caddice clew-shaped CuO nanocrystalline particles weresynthesized by the electrochemical discharge process. Fourier transform infrared spectrum showed that the CuO nanoparticles have a pure and monolithic phase. UV–vis–NIR spectroscopy was used to monitor oxidation course of Cu→CuO and the band gap energy was measured as 2 and 2.6 eV for CuO nanoparticle synthesized in NaOH and KOH solutions, respectively. • Synthesis and characterization of nanoboron powders prepared with mechanochemical reaction between B$_2$O$_3$and Mg powders Amorphous boron powders with small particle size, narrow size distribution and high purity are very important in the high-tech fields. Mechanochemical synthesis was used to prepare amorphous boron nanoparticles. Synthesis process stage was carried out using stoichiometric amounts of B$_2$O$_3$and Mg powders (6.7 g). Milling was carried out under argon atmosphere in the high-energy planetary ball mill with a ball-to-powder weight ratio (32:1) for 10 h. The vial rotation speed was about 440 rpm. Milled products were leached by 28% hydrochloric acid (only one) to remove impurities. Boron powders were obtained after centrifuging, decanting, washing and drying operations. Sample was characterized by inductively coupled plasma (ICP), energy-dispersive spectroscopy, X-ray diffraction, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The ICP results showed that boron powders with purity about 91 wt% can be prepared in the planetary ball mill. Also, the leached powders had an amorphous structure. According to the SEM observation, average particle size of boron powders was smaller than 32 nm and the yield of synthesized nanoboron was more than 74%. • Preparation of manganese-based perovskite nanoparticles using a reverse microemulsion method: biomedical applications In this study, La$_{0.7}Sr$_{0.3}Mn$_{0.98}$Ti$_{0.02}$O$_{3}$(LSMTO) nanoparticles with a perovskite structure and an average particle size of 23.5 nm were synthesized using a reverse microemulsion method. In this method, cetyltrimethylammonium bromide (CTAB) was used as a surfactant, 1-butanol as a co-surfactant,$n$-hexane as a continuous oil phase, and an aqueous solution containing metal cations or precipitating agent as a dispersed aqueousphase. The aqueous nanodroplets of microemulsions were used for the formation of perovskite precursor. The obtained precursor was then calcined at 700$^{\circ}$C for 4 h to convert the precursor to the perovskite phase. In addition, the heating ability of the LSMTO nanoparticles was evaluated under a safe alternating magnetic field used in magnetic hyperthermia therapy. The results showed the fast magneto-temperature response of the prepared samplewith sufficient heat loss at the therapeutic temperature range, indicating the LSMTO nanoparticles can be used as a self-regulated heating agent in the magnetic hyperthermia therapy. • Elastic and optical properties of Ge$_x$Se$_2$Sb$_{1−x}$($0.0\le x \le 1.0$) glasses The present study deals with the effect of composition on the elastic and optical properties of Ge$_x$Se$_2$Sb$_{1−x}$($0.0 \le x \le 1.0$) glasses. The various elastic moduli of these glasses such as Young’s modulus ($Y$) andthe bulk modulus ($B$) along with the micro-hardness ($H$), Poisson’s ratio ($\rho$) and Debye temperature ($T_D$) were obtained from the values of the longitudinal ($v_l$) and shear ($v_s$) ultrasonic velocities. On the basis of measurementsof the transmittance and reflectance spectra in the wavelength range of 0.4–2.5$\mu$m the optical constants such as the film thickness ($t$), the refractive index ($n$) and the optical band gap ($E_g$) were investigated with high accuracy. The optically determined bulk modulus of these glasses was in good agreement with that elastically investigated. The obtained results were discussed in terms of the changes in the glass density, electronegativity and electronic polarizability with the variation in antimony content. • A catalyst-free synthesis of germanium nanowires obtained by combined X-ray chemical vapour deposition of GeH$_4$and low-temperature thermal treatment techniques A catalyst-free innovative synthesis, by combined X-ray chemical vapour deposition and lowtemperature thermal treatments, which has not been applied since so far to the growth of germanium nanowires (Ge-NWs), produced high yields of the nanoproducts with theGeH4 reactant gas. Nanowires were grown on both surfaces of a conventional deposition quartz substrate. They were featured with high purity and very large aspect ratios (ranging from 100 to 500). Products were characterized by scanning electron microscopy with energy-dispersiveatomic X-ray fluorescence and transmission electron microscopies, X-ray powder diffraction diffractometry, thermogravimetric analysis with differential scanning calorimetry, vibrational infrared and Raman and ultraviolet–visible–near infrared spectroscopies. A quantitative nanowire bundles formation was observed in the lower surface of the quartz substrate positioned over a heating support, whilst spots of nanoflowers constituted by Ge-NWs emerged from a bulk amorphous germanium film matter, deposited on the upper surface of the substrate. Thenanoproducts were characterized by crystalline core morphology, providing semiconductive features and optical band gap of about 0.67 eV. The possible interpretative base-growth mechanisms of the nanowires, stimulated bythe concomitant application of radiant and thermal conditions with no specific added metal catalyst, are hereafter investigated and presented. • Synthesis and characterization of magnetite/hydroxyapatite tubes using natural template for biomedical applications Inorganic nanotubes have attracted much attention during the last few decades for its potential applications in the field of regenerative medicine and controlled drug delivery. In the present work, we have designed andsynthesized magnetite hydroxyapatite micro and nanotubes. The first step is the formation of magnetite (Fe$_3$O$_4$) tubes on natural template followed by hydroxyapatite (HAp) bioceramic coated on the Fe$_3$O$_4$tubes. HAp improves the biocompatibility and stability of the prepared tubes. Sintering at 900$^{\circ}$C improves the crystalline stability of nanotubes and removes the natural template. X-ray diffraction, N$_2$adsorption–desorption studies (BET), thermogravimetric analysis, differential scanning calorimetry, optical micrographs, field emission scanning electron microscope and transmission electron microscope studies were carried out to confirm the structural and morphological analysis of prepared magnetic tubular structure. • Effect of temperature on structure and corrosion resistance for electroless NiWP coating The effect of plating temperatures between 60 and 90$^{\circ}$C on structure and corrosion resistance for electroless NiWP coatings on AZ91D magnesium alloy substrate was investigated. Results show that temperature has a significant influence on the surface morphology and corrosion resistance of the NiWP alloy coating. An increase in temperature will lead to an increase in coating thickness and form a more uniform and dense NiWP coatings. Moreover, cracks were observed by SEM in coating surface and interface at the plating temperature of 90$^{\circ}$C. Coating corrosion resistance is highly dependent on temperature according to polarization curves. The optimum temperature isfound to be 80$^{\circ}$C and the possible reasons of corrosion resistance for NiWP coating have been discussed. • Physicochemical characterization of zinc-substituted calcium phosphates Biocompatible and bioactive calcium phosphates can make chemical bonds with living bones. Improvement of their biological and physicochemical properties can be achieved by doping with various ions that are presented in natural apatites of bones. These substitutions influence lattice parameters, structure and morphology of apatites. In recent times great attention has been devoted to zinc ions that are the second most abundant trace element present in bones. Zinc embedded into calcium phosphate may enhance the bone formation and in addition exhibits antifungal and antibacterial properties. Therefore, it is rational to form structures incorporated with this ion. In this paper the incorporation of the Zn ions into natural and synthetic calcium phosphates has been reported.Natural hydroxyapatites (HAs) applied in this study were derived mainly from pork bones whereas both brushite and synthetic were formed using wet chemical methods. Ambient temperature synthesis leads to the formation ofbrushite, whereas the process performed at elevated temperature gives HA. Subsequently, attained structures were modified with Zn ions by using in situ or sorption procedures. Phase composition and morphology of obtained materials were determined by means of X-ray diffractometry, Fourier transform infrared spectroscopy and scanning electron microscopy equipped with energy-dispersive spectroscopy. Introduced XRD patterns depict changes of the crystallinity of HA with the increase in the amount of embedded zinc ions. On the contrary, no changes of the crystallinity were observed for the brushite doped with Zn ions. Morphology of attained powders, visualized using scanningelectron microscopy exemplified structural changes between calcium phosphates conjugated with zinc ions. Many authors report that the addition of small amounts of Zn ions leads to loss of crystallinity and decrease of lattice parameters. Interestingly, upon addition of Zn ions to the natural and synthetic HAp by sorption procedures no crystallographic and structural changes were observed. Notably, upon increase of zinc ions also structure of brushite formed by the in situ method remains constant, indicating no influence of added ions. Our outstanding finding promotes sorption procedure as suitable route to form structures incorporated with various ions that can be further employed as potential implants. • Magneto-heat capacity study on Kondo lattice system Ce(Ni$_{1−x}$Cu$_x$)$_2$Al$_3$Heat capacity studies on the Kondo lattice system Ce(Ni$_{1−x}$Cu$_x$)$_2$Al$_3$, in the presence of magnetic fields, were reported for$x = 0.0−0.4$. The physical properties of the intermediate compositions like$x = 0.3$and 0.4 were known for their enhanced thermoelectric power and hence have been analysed with an extra interest. It was also shown from the X-ray diffraction that these systems with$x = 0.3$and 0.4 were in single phase in terms of sample purity and it stabilized the phases easily with the increase in the Cu doping in the system. The low temperature risein$C_p/T$below 10 K under the influence of high magnetic fields was analysed using a multi-level Schottky effect. A gradual decrease of the total angular momentum (J) with the increase of applied magnetic fields indicated ascenario of screening of Ce$^{3+}$magnetic moment while simultaneously the system settled for the Fermi liquid state. The screening thus seen was in line with the expectations of electrical conductivity measurements on these samples. • Physical and electrical characterization of reduced graphene oxide synthesized adopting green route Graphene and its related materials are important areas of research in recent years owing to their unique properties. The wide-range industrial application of graphene-related compounds has led to the development of novel and simple methods for the synthesis of graphene. In this paper, an environmentally friendly green synthesis for the partial reduction of graphene oxide (GO) to reduced GO (RGO) in a cost-effective single-step mechanism was reported. The method completely avoids the use of toxic and environmentally harmful reducing agents commonly used in the chemical reduction of GO to obtain RGO. The reduction of GO was carried out using aqueous leaf extracts of Paederia foetide L. The prepared GO and green RGO were characterized by ultraviolet–visible, Ramanand Fourier transform infra-red spectroscopic analysis which showed a clear indication of the partial removal of oxygen-containing groups from the GO and the formation of RGO. The morphology of the green RGO was characterizedby transmission electron and scanning electron microscopy. Dynamic light scattering was used for zeta potential measurement and correlated with the morphology of the sheets. Electrical conductivity was also measuredto check the extent of reduction of GO to RGO. • Magnetocaloric effect and its implementation in critical behaviour study of La$_{0.67}$Ca$_{0.33}$Mn$_{0.9}$Fe$_{0.1}$O$_3$The magnetocaloric effect (MCE) and the field dependence of the magnetic entropy changes in the perovskite-type a$_{0.67}$Ca$_{0.33}$Mn$_{0.9}$Fe$_{0.1}$O$_3$were studied using the phenomenological model. The model parameters were determined from the magnetization data adjustment and used to give better fits to magnetic transition and to calculate the magnetocaloric properties. The entropy curves have been observed to behave a symmetrical broadning of$\Delta$S$_M$peak with the increase in magnetic field. The values of maximum magnetic entropy change, full-width at half-maximum, relative cooling power (RCP) and the refrigerant capacity (RC), at several magnetic field variations, were calculated. The maximum magnetic entropy change of 1.17 J kg$^{−1}$K$^{−1}$was obtained for 3 T. The theoretical calculations were compared with the available experimental data. The results were found to be in good accordance. The critical exponents associated with ferromagnetic transition have been determined from the MCE methods. By using the field dependence of$\Delta S_{\rm max} \approx a (\mu_0 H)^n$and the${\rm RCP} \approx v(\mu_0H)^w$, the critical behaviour of La$_{0.67}$Ca$_{0.33}$Mn$_{0.9}$Fe$_{0.1}$O$_3$was investigated. From the analysis of the relationship between the local exponent$n$and$w$, other exponents$\beta$,$\gamma$and$\delta$were calculated. Our results indicated that the ferromagnetic coupling in the La$_{0.67}$Ca$_{0.33}$Mn$_{0.9}$Fe$_{0.1}$O$_3$can be well described by the 3D Heisenberg model. This reflects an existence of ferromagnetic short-range order in the sample. • Processing and characterization of screen printing Ba$_{0.5}$Sr$_{0.5}$Co$_{0.8}$Fe$_{0.2}$O$_{3−\delta}$inks Oxygen-selective membranes based on thin layers of barium–strontium–cobalt ferrite Ba$_{0.5}Sr$_{0.5}$Co$_{0.8}$Fe$_{0.2}O$_{3−\delta}$(BSCF) perovskite oxide were manufactured. Five BSCF inks prepared with differentcarriers and milling treatments were rheologically characterized, screen printed on three different porous alumina substrates and sintered at 1050 and 1150$^{\circ}$C. The resulting membranes were characterized. The data collected on the rheological properties of inks (flow curves, thixotropic behaviour, linear viscoelasticity), their processability by screen printing, and the quality of the layers obtained after sintering represents an important starting point to set up the next research activities. • Photocatalytic reactor for organic compound removal using photocatalytic mechanism In this work, a photocatalytic reactor with a working volume of 13 l was fabricated of soda-lime silica glass. Commercial titanium dioxide (TiO$_2$) particles were used as the photocatalyst and trails were conducted on the photodecomposition of methylene blue (MB) solutions (10$^{−5}$M). The activation of the photocatalysts was carried out using 5 UV lamps (378 nm, 36 W), and 13 g of TiO$_2$was added each week to the reactor. The MB solution was fed at a flow rate of 0.87 l h$^{−1}$, while the effluent was removed after 5 h of hydraulic retention time. The performance of the reactor was studied over a period of 45 days. The results showed a sharp decline in the dissolved oxygen (DO) concentration and pH of the solution with the increased addition of TiO$_2$to the reactor owing to the occurrence of the photocatalytic process. The reactor was found to be highly effective in decomposing MB solution. The performance was observed to slightly decrease over the long operating period owing to the TiO$_2$accumulation on the reactor wall, and its non-participation in the reactions. • Severe wear behaviour of alumina balls sliding against diamond ceramic coatings At present alumina is themost widely used bio-ceramic material for implants.However, diamond surface offers very good solid lubricant for different machinery, equipment including biomedical implants (hip implants, knee implants, etc.), since the coefficient of friction (COF) of diamond is lower than alumina. In this tribological study, alumina ball was chosen as the counter body material to show better performance of the polycrystalline diamond (PCD) coatings in biomedical load-bearing applications.Wear and friction data were recorded for microwave plasma chemical vapour deposition (MWCVD) grown PCD coatings of four different types, out of which two sampleswere as-deposited coatings, one was chemo-mechanically polished and the other diamond sample was made free standing by wet-chemical etching of the silicon wafer. The coefficient of friction of the MWCVD grown PCD against Al$_2$O$_3$ball under dry ambient condition was found in the range of 0.29–0.7, but in the presence of simulated body fluid, the COF reduces significantly, in the range of 0.03–0.36. The samples were then characterized by Raman spectroscopy for their quality, by coherence scanning profilometer for surface roughness and by electron microscopy for their microstructural properties. Alumina balls worn out ($14.2 \times 10^{−1}$mm$^3$) very rapidly with zero wear for diamond ceramic coatings. Since the generation of wear particle is the main problem for load-bearing prosthetic joints, it was concluded that the PCD material can potentially replace existing alumina bio-ceramic for their bettertribological properties. • Microwave-assisted brazing of alumina ceramics for electron tube applications Alumina was joined with alumina using microwave-assisted and conventional brazing methods at 960$^{\circ}$C for 15 min using TiCuSil (68.8Ag–26.7Cu–4.5Ti in wt.%) as the brazing alloy. The brazed joints were characterizedby X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, Vickers microhardness evaluation, brazing strength measurement and helium leak test. X-ray diffraction analysis confirmed the formationof Ti-based compounds at the substrate-filler alloy interfaces of the microwave and conventionally brazed joints. The elemental compositions at the joint cross-section were determined by energy dispersive X-ray analysis. Vickers microhardness measurement indicated reliable joint performance for the microwave-assisted brazed joints during actual application in an electron tube. Brazing strength measurement and helium leak test provided the evidence forgood alumina-alumina joint formation. • Magnetic and ferroelectric characteristics of Gd$^{3+}$and Ti$^{4+}$co-doped BiFeO$_3$ceramics Polycrystalline BiFeO3 and Bi$_{0.9}$Gd$_{0.1}$Fe$_{1−x}$Ti$_x$O$_3$($x = 0$, 0.01, 0.05 and 0.1) samples were synthesized by solid-state reaction route. Structural, magnetic and ferroelectric properties of these samples were investigated. X-ray powder diffraction (XRD) results confirmed the presence of a significant amount of Bi$_2$Fe$_4$O$_9$impurity phase in the undoped BiFeO$_3$sample. Mössbauer spectroscopy studies corroborated the XRD studies to confirm the presence of impurity phase.We have observed that gadolinium (Gd$^{3+}$) and titanium (Ti$^{4+}$) doping, respectively, on Bi$^{3+}$and Fe$^{3+}$sites facilitated a significant reduction in the impurity phase formation in BiFeO$_3$. Interestingly, Gd$^{3+}$-doping significantly reduced the impurity phase formation as compared to the undoped BiFeO$_3$sample. This impurity phase formation was further overcome by doping higher ($x \ge 0.05$) amounts of Ti in BiFeO$_3$. The crystallographicsite occupancies of Gd and Ti were confirmed by Rietveld refinement of XRD data,Mössbauer spectroscopy and magnetization measurements. An enhancement in ferromagnetic properties along with moderate ferroelectricproperties have been observed after co-doping. There was an increasing trend in remnant polarization (Pr) with the increase in Ti concentration besides an improvement in the characteristic saturation magnetization. Our resultsdemonstrate that Gd$^{3+}$and Ti$^{4+}\$ doping could be used to enhance multifunctional properties of BiFeO3 ceramics to enable them as potential material for various devices.

• # Bulletin of Materials Science

Current Issue
Volume 42 | Issue 6
December 2019

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019