Effect of gamma irradiation on structural,morphological and optical properties of thermal spray pyrolysis deposited CuO thin film

This study reports the influences of gamma irradiation (GI) in the range of 20–100 kGy on CuO thin films via thermal spray pyrolysis technique on the glass substrates. The results demonstrate significant influences of GI on the crystallographic, microstructural and optical characteristics of CuO thin films. The obtained XRD results showed that the crystallinity of the films deteriorates by gradually decreasing crystallite size (from 59.13 to 46 nm) as applied gamma doses increases. However, the basic monoclinic crystal structure remains same. The dislocation density and lattice strain increased with the rise of GI absorbed dose due to the creation of defects. The values of number of crystallites per unit surface area increased as dose increased indicating the abundance of crystallization of nano CuO thin films. A UV–Vis–NIR spectrophotometer was utilized to determine the optical properties and obtained results indicated that the optical energy band gap (OBG) energies reduced from 2.00 to 1.72 eV as the doses increased from 0 to 100 kGy. No distinctions of the monoclinic phase of virgin CuO thin film have been perceived under applied absorbed doses, notwithstanding the slight deterioration of the crystallinity and narrowing the OBG.     

Engineering of morphological,optical, structural,photocatalytic and catalytic properties of nanostructured CuO thin films fabricated by reactive DC magnetron sputtering

Nanostructured thin films of CuO were deposited on silica glass substrates using reactive DC magnetron sputtering technique. Microstructural, morphological, optical, catalytic and photocatalytic properties of the prepared CuO thin films were examined using FESEM, AFM, Rutherford backscattering spectrometry, XRD, XPS, UV–Vis absorption and PL spectroscopy. FESEM showed nanostructures in the thin films, which were confirmed to be of monoclinic CuO by XRD analysis. Substrate temperature variation (40 °C, 100 °C and 300 °C) was found to significantly alter the optical, morphological, photocatalytic and structural properties of the CuO nanostructured thin film coatings. FESEM and AFM analyses showed decrease in size of nanostructures and surface roughness increase with increase in substrate temperature. Increase in UV–Vis absorbance and PL intensity of CuO thin films with decrease in crystallite size were noticed as the substrate temperature was increased. The prepared nanostructured CuO thin films exhibited highly enhanced photocatalytic activities and degraded dyes (MB and MO) in water in just 40 min under solar exposure and catalytic transformation of 4-nitrophenol (4-NP) took place in just 15 min. The developed CuO nanostructured thin film coatings are very promising for large scale, practical and advanced catalytic reduction of toxic 4-NP and photocatalytic applications in solar driven water purification.     

Natural citric acid assisted synthesis of CuO nanoparticles: Evaluation of structural,optical, morphological properties and colloidal stability for gas sensor applications

In the present research, natural ingredient lemon juice was selected as a fuel to prepare nanoparticles under combustion method. The structural properties of nanophase copper oxide nanoparticles (CuO NPs) synthesized by a natural citric acid aided combustion process were studied using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). According to the SEM and TEM images, the manufactured product is made up of spherical nanoparticles with a limited size distribution. According to the XRD pattern, the average crystallite size of monoclinic structured CuO nanoparticles was 10.4 nm for as-prepared samples and 20.5 nm for annealed samples. The zeta potential value confirms the negative surface charge of the samples and the values show the excellent stability (-58.1 mV) for as-prepared sample and the good particles stability (-38.3 mV) was exhibited for heat treated sample. The optical band gap of CuO nanoparticles is 2.01 eV and it decreases to 1.28 eV under heat treatment. The sensitivity and selectivity of the samples were tested under different operating temperatures (OT) and different gas concentrations (GC). Recovery-response time plots confirm that the CuO nanoparticles are promising materials for gas sensor fabrications.     

Synthesis,structural, magnetic and NO2 gas sensing property of CuO nanoparticles

Cupric oxide (CuO) nanoparticles are synthesized by the oxidation of Cu/Cu₂O, which is obtained by the chemical reduction of Cu²⁺ ions with ascorbic acid. XRD pattern confirmed the formation of CuO, and FE-SEM image shows the clusters consisting of 25–30 nm sized particles. The band gap energy (3.7 eV) from optical absorption spectra is blue shifted to that of bulk values. The Néel temperature, T_N ≈ 230 K for paramagnetic to antiferromagnetic transition was clearly seen. The magnetic hysteresis loops at 5 K showed weak ferromagnetic behavior. Based on the dc electrical conductivity (300–500 K), the apparent activation energy was 0.36 eV. The NO₂ gas sensing property of CuO was reasonably good in the temperature range of 200–300 °C, and the sensitivity increased with an increase in gas concentration but the effect of temperature is marginal.     

Review on design,preparation and performance characterization of gelled fuels for advanced propulsion

With the increasing demand for high-performance and safe fuels in aerospace propulsion systems, gelled fuels have attracted increasing attention. Because of their unique structure, gelled fuels exhibit the advantages of both solid and liquid fuels, such as high energy density, controllable thrust and storage safety. This review provides an overview on design, preparation and performance characterization of gelled fuels. The composition, preparation process and gelation mechanism of gelled high-energy-density fuels are described. Considering these aspects, the rheology and flow behavior of gelled fuels is summarized in terms of the shear thinning property, dynamic viscoelasticity and thixotropy. Moreover, the progress of atomization of gelled fuels is reviewed with a focus on the effect of atomizing nozzles. In addition, the experiments and theoretical models of single droplet combustion and combustor combustion are described. Finally, research directions for the development and application of gelled fuels are suggested.     

Investigation of structural,optical and magnetic properties of thermal plasma synthesized Ni-Co spinel ferrite nanoparticles

Magnetic nanoparticles of nickel substituted cobalt ferrites, Ni_xCo_1−xFe₂O₄, (x=0 to 1 in the step of 0.2) were successfully synthesized by gas phase nucleation and growth process. For the first time, we report feasibility of synthesizing such mixed ferrite system using thermal plasma route. Further, effect of change in molar ratio of Co:Ni on the structural, optical and magnetic properties has been investigated in detail. The structural and phase formation analysis of the samples under investigation have been carried out using powder X-ray diffraction and Raman spectroscopy. The surface morphology of these particles has been studied using scanning electron microscopy and the micrographs so obtained were used to find out average gain size and size distribution. The optical and magnetic properties of the as synthesized samples were finally correlated with the magnetic moment of substituted species such as Ni for Co and cation distribution, analyzed using Mössbauer spectroscopy. Special modification in Thermo Gravimetric Analyzer was used to determine magnetic transition temperature.     

Phase stability,thermo-physical properties and thermal cycling behavior of plasma-sprayed CTZ,CTZ/YSZ thermal barrier coatings

ZrO₂ co-stabilized by CeO₂ and TiO₂ with stable, nontransformable tetragonal phase has attracted much attention as a potential material for thermal barrier coatings (TBCs) applied at temperatures >?1200?°C. In this study, ZrO₂ co-stabilized by 15?mol% CeO₂ and 5?mol% TiO₂ (CTZ) and CTZ/YSZ (zirconia stabilized by 7.4?wt% Y₂O₃) double-ceramic-layer TBCs were respectively deposited by atmospheric plasma spraying. The microstructures, phase stability and thermo-physical properties of the CTZ coating were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric-differential scanning calorimeter (TG-DSC), laser pulses and dilatometry. Results showed that the CTZ coating with single tetragonal phase was more stable than the YSZ coating during isothermal heat-treatment at 1300?°C. The CTZ coating had a lower thermal conductivity than that of YSZ coating, decreasing from 0.89?W?m^?1 K^?1 to 0.76?W?m^?1 K^?1 with increasing temperature from room temperature to 1000?°C. The thermal expansion coefficients were in the range of 8.98?×?10^?6 K^?1 – 9.88 ×10^?6 K^?1. Samples were also thermally cycled at 1000?°C and 1100?°C. Failure of the TBCs was mainly a result of the thermal expansion mismatch between CTZ coating and superallloy substrate, the severe coating sintering and the reduction-oxidation of cerium oxide. The thermal durability of the TBCs at 1000?°C can be effectively enhanced by using a YSZ buffer layer, while the thermal cycling life of CTZ/YSZ double-ceramic-layer TBCs at 1100?°C was still unsatisfying. The thermal shock resistance of the CTZ coating should be improved; otherwise the promising properties of CTZ could not be transferred to a well-functioning coating.     

Gadolinium ferrite nanoparticles: Synthesis and morphological,structural and magnetic properties

In this study we report on the successful synthesis of Gd_xFe_3−xO₄ nanoparticles with nominal Gd-content (x) in the range 0.00≤x≤0.50. The effect of the nominal Gd-content on morphological, structural and magnetic properties was investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy and Mössbauer spectroscopy. We found the actual inclusion of Gd³⁺ ions into cubic ferrite structure lower than the nominal values, though no extra phase was observed in the whole range of our investigation. Moreover, from Mössbauer data we found evidences of Gd³⁺ ions replacing both Fe³⁺ and Fe²⁺ ions, the latter leading to iron vacancies in the cubic ferrite crystal structure. As the nominal Gd-content, the lattice parameter and the average crystallite size increases monotonically. We found that in the same range of nominal Gd-content the lattice parameter decreases with the increase of iron vacancy content.     

Mechanical,thermal, morphological,and curing properties of geopolymer filled natural rubber composites

The main objective of this work was to investigate influence of natural rubber (NR) types on mechanical, thermal, morphological, and curing properties together with relaxation behavior of geopolymer filled NR composites with and without bis(triethoxysilylpropyl) tetrasulfide (TESPT) silane coupling agent. Three alternative types of NR: unmodified NR, and epoxidized NR with 25 (ENR-25) or 50 mol % epoxide (ENR-50) were exploited. Rubber compounds filled with GP particles were prepared in an internal mixer at 60 °C and 130–150 °C for the ones with and without TESPT, respectively. It was found that incorporation of GP significantly affected cure characteristics and mechanical properties of the rubber composites. That is, decreasing cure time was observed from 11.6, 3.2, and 7.0 min in gum NR, ENR-25, and ENR-50 to 6.9, 2.1, and 5.0 min in NR/GP, ENR-25/GP, and ENR-50/GP compounds, respectively. Furthermore, the ENR-25/GP and ENR-50/GP composites showed finely dispersed GP particles which indicate high filler–rubber interactions. The in situ silanization with TESPT in rubber composites enhanced the mechanical properties of NR/GP and ENR-25/GP composites but no such enhancement was found in the ENR-50/GP composite. This matched the observations of Payne effect, maximum tan δ, and stress relaxation properties of the composites. We found that the ENR-25/GP composites exhibited the best overall properties. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47346.     

Synthesis of novel copper nanoparticles/ternary polymer blend nanocomposites and their structural,thermal and rheological properties and AC impedance

Copper nanoparticles (Cu NPs)/ternary polymer blend nanocomposites were synthesized via a solution‐casting technique. The nanocomposites were studied for their structural, thermal, rheological and electric properties. Scanning electron micrographs and atomic force micrographs showed no phase separation between the polymers, a narrow size distribution of Cu NPs (in the range 25–43 nm) and good dispersion of Cu NPs in the polymer matrix. Energy‐dispersive X‐ray analysis confirmed the presences of Cu in the matrix. X‐ray diffraction data showed a characteristic face‐centred cubic architecture for Cu unit cell and interaction of the Cu NPs with oxygen‐carrying polymers. Thermogravimetric analysis showed an increase in the degradation temperature (from 254 to 268 °C) and three‐step degradation of the nanocomposites. Rheological analysis showed an increase in the complex viscosities and storage modulus for the nanocomposites. AC impedance studies showed increased ionic conductivities and decreased bulk resistance for the nanocomposites. All these studies suggested interactions between Cu NPs and polymer matrix and the formation of a network structure. © 2017 Society of Chemical Industry     

Effects of zirconium carbide content on thermal stability and ablation properties of carbon/phenolic composites

Ceramic particles were utilized to improve thermal stability and ablation properties of carbon/phenolic (C/Ph) composites. In this study, zirconium carbide (ZrC) modified C/Ph composites were fabricated by vacuum impregnation method, and effects of ZrC content on thermal stability and ablation properties were investigated by thermogravimetry analysis and plasma wind tunnel test. Moreover, morphological characterization was carried out using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. Experimental results showed that increasing ZrC content could lead to an evident increase in char yield, but an observable reduction in linear ablation rates and back-face temperatures because of the formation of ZrO₂ layer on the ablation surface. The work provided an effective way to improve thermal stability and ablation properties of C/Ph composites.     

Improvements of the structural,thermal, and mechanical properties of structural adhesive with functionalized boron nitride nanoparticles

Investigations on the production and development of nanoparticle-reinforced polymer materials have been attracted attention by researchers. Various nanoparticles have been used to improve the mechanical, chemical, thermal, and physical properties of polymer matrix composites. Boron compounds come to the fore to improve the mechanical and thermal properties of polymers. In this study, mechanical, thermal, and structural properties of structural adhesive have been examined by adding nano hexagonal boron nitride (h-BN) to epoxy matrix at different percentages (0.5, 1, 2, 3, 4, and 5%). For this purpose, nano h-BN particles were functionalized with 3-aminopropyltriethoxysilane (APTES) to disperse the h-BN nanoparticles homogeneously in epoxy matrix and to form a strong bond at the matrix interface. Two-component structural epoxy adhesive was modified by using functionalized h-BN nanoparticles. The structural and thermal properties of the modified adhesives were investigated by scanning electron microscopy and energy dispersion X-ray spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis techniques. Tensile test and dynamic mechanical analysis were performed to determine the mechanical properties of the adhesives. When the results obtained from analysis were examined, it was seen that the nano h-BN particles functionalized with APTES were homogeneously dispersed in the epoxy matrix and formed a strong bond. In addition that, it was concluded from the experimental results that the thermal and mechanical properties of adhesives were improved by adding functionalized nano h-BN particles into epoxy at different ratios.     

Physical,thermal, optical,structural and nuclear radiation shielding properties of Sm2O3 reinforced borotellurite glasses

To observe direct effect of samarium (III) oxide reinforcement on physical, thermal, optical, structural and nuclear radiation attenuation properties, a broad-range experimental and numerical investigations were performed with a group of novel borotellurite glasses. FTIR spectra of powdered samples were taken at 250-4000 cm^-1. The transmittance and absorption characteristics, optical band gaps, and Urbach energies were measured. The glass transition temperatures, crystallization temperatures and melting temperature values of the samples were determined. Nuclear radiation shielding properties have been determined for gamma-ray, neutrons and heavy charged particles. The lowest transmittance and highest absorbance were reported for the TBVS1.5 sample with highest Sm₂O₃ additive. In addition, obtained results from the nuclear radiation shielding calculations have showed that TBVS1.5 sample has superior nuclear radiation shielding properties against gamma-ray, neutron and heavy charged particles. The increasing Sm2O3 additive has visibly improved the nuclear radiation attenuation properties by keeping other material properties within usable limits.     

Enhancing the thermoelectric performance of CoSb3-based skutterudite by decoupling the electrical and thermal properties by embedding Cu nanoparticles

Co_0.91Ni_0.09Sb₃ embedded with Cu nanoparticles (NPs) was synthesized by applying a hydrothermal process followed by spark plasma sintering. The effects of Cu NPs on the electrical and thermal transport properties of the Co_0.91Ni_0.09Sb₃ matrix were investigated in the temperature range of 303–773 K. Cu NPs introduced into the Co_0.91Ni_0.09Sb₃ matrix slightly decreased the electrical conductivity and significantly enhanced the Seebeck coefficient by the energy filtering effect, leading to an improved power factor at 773 K. Furthermore, a significant decrease in the thermal conductivity was realized by increasing the number of grain boundaries. These favorable effects contributed to the improvement in ZT to a value ~57% higher than that of pristine Co_0.91Ni_0.09Sb₃. The highest ZT value of 1.02 was achieved by incorporating 4.5 wt% of Cu NPs in Co_0.91Ni_0.09Sb₃ at 773 K. Thus, decoupling the electrical and thermal transport properties of thermoelectric materials is a viable strategy for optimizing the ZT value.     

Effect of Ba concentration on phase stability and mechanical and thermal properties of La2Mo2O9

Ba-substituted La₂Mo₂O₉ ((La_1−xBa_x)₂Mo₂O_9−δ, x = 0–0.12) was prepared and the thermal and mechanical properties were evaluated. The thermal expansion coefficients (TECs) were determined from high-temperature X-ray diffraction (XRD) analysis. Phase transition in La₂Mo₂O₉ was suppressed via substitution of Ba for La, as demonstrated by differential scanning calorimetry (DSC) analysis. The mechanical properties, such as the bulk modulus, shear modulus, Young’s modulus, compressibility, and Debye temperature were evaluated from the measured sound velocities. The thermal conductivity was evaluated from the thermal diffusivity, heat capacity, and density in the temperature range from room temperature to 1073 K. The thermal conductivity decreased with increasing Ba content. Theoretical calculations based on the Klemens–Callaway model were performed to analyze the thermal conductivity, and the results suggest that the reduction of the thermal conductivity was mainly attributed to oxygen defects in the anion sublattice of La₂Mo₂O₉.     

Solid-state synthesis and effect of temperature on optical properties of Cu-ZnO, Cu-CdO and CuO nanoparticles

Controlling novel morphologies and developing effective doping strategies are two important tasks for advancing ZnO and CdO based nanomaterials. Modulation of band energies through size control offers new ways to control photoresponse and photoconversion efficiencies of the solar cell. The P-type semiconductors of copper oxide and zinc oxide are an important functional material used for photovoltaic cells. CuO is attractive as a selective solar absorber since it has high solar absorbance and a low thermal emittance. This work describes the synthesis and characterization of semiconducting nanoparticles (ZnO, CuO, CdO, Cu-ZnO, Cu-CdO) via one-step, solid-state reaction in the presence of polyethylene glycol 400.Solid-state mechanochemical processing—which is not only a physical size reduction process in conventional grinding but also a chemical reaction that is mechanically activated at the nanoscale during grinding. The present method is a simple and efficient method for the preparation of nanoparticles with high yield at low cost. The structural and chemical composition of the nanoparticles were analyzed by X-ray diffraction, field emission scanning electron microscopy and energy-dispersive spectrometer (FESEM/EDAX). Optical properties and band gap were studied by UV-vis absorption spectra. XRD data has been concluded that the Cu doping induced the lattice constants to change to some extent. These results have showed that the band gap energy decreases with increase in annealing temperature, which can be attributed to the improvement in crystallinity of the samples. The band gap of the Cu-ZnO and Cu-CdO crystals can be tuned in the range of 3.34-3.28 eV and 2.80-2.21 eV respectively, by the use of dopants.     

Comparative investigation on the structural,morphological, optical,and magnetic properties of CoFe2O4 nanoparticles

Herein, we report a sustainable production of magnetic cobalt ferrite nanoparticles by conventional (CHM) and microwave heating (MHM) method. Hibiscus rosa-sinensis extract was used as both reducing and stabilizing agent. Using plant extracts to synthesize nanoparticles has been considered as an eco-friendly method, since it avoids noxious chemicals. The plethora of plant extract mediated nanoparticles were compared by techniques, such as XRD, Rietveld, FT-IR, SEM, EDX, UV-Visible DRS, PL and VSM were carried out to analyze and understand their crystallite size, functional groups, morphology, optical and magnetic properties. The crystalline structure of cobalt ferrite nanoparticles revealed the cubic structure and the microwave heating of nanoparticles showed smaller crystallite size compared to the conventional heating, which was then confirmed by XRD analysis. To analyze the presence of functional groups and the phytochemical involvement of the plant extract was confirmed by FT-IR studies. Spherical morphology with less than 100 nm sized particles was confirmed by SEM and EDX analysis confirm the existence of Co, O, and Fe elements present in the samples. UV-Visible DRS studies were carried out to calculate the band gap of the as-synthesized nanoparticles, estimated from the Kubelka-Munk function, as 2.06, and 1.87 eV for CHM and MHM, respectively. Photoluminescence emission spectrum of the nanoparticles showed two different bands at 494 and 620 nm, which explores the optical properties of the nanoparticles, due to the quantum confinement effect. VSM analysis showed better ferromagnetic behavior, which can be used for magnetic applications.     

Evaluation of the phase stability,and mechanical and thermal properties of Ba(Sr1/3Ta2/3)O3 as a potential ceramic material for thermal barrier coatings

Ba(Sr_1/3Ta_2/3)O₃ (BST) ceramic was synthesized by a solid-state reaction method. The phase stability, microstructural evolution, and mechanical and thermal properties of the BST ceramic were investigated and characterized to evaluate the potential application of BST as a top coating material for thermal barrier coatings (TBCs). The results show that BST can maintain a stable hexagonal perovskite structure up to 1600 °C. Anisotropic growth of the grains above 1400 °C was observed. Its low elastic modulus and high fracture toughness suggest a high damage tolerance for the BST ceramic. In addition, the moderate coefficient of thermal expansion and superior heat insulation capability of the BST ceramic provide this ceramic the potential to serve as a top coating material of TBCs at higher temperature.     

Main-chain azo polyaramides with high thermal stability and liquid crystal properties

Two novel main-chain aromatic polyamides containing azobenzene were synthesized by polycondensation of trans-azobenzene-4,4′-dicarbonyl chloride with various aromatic diamines under low temperature. Their molecular structures were identified to be symmetric and regular by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and elemental analysis. Polymers exhibited not only high thermal stability, but also lyotropic liquid crystal (LC) phases in N,N-dimethylacetamide solution which is due to hydrogen bonding and an ordered rigid structure. The crystal behaviours of the polymers were studied with X-ray diffraction analysis, and the photochromism was investigated with an ultraviolet–visible spectrophotometer with 365 nm ultraviolet irradiation. An abnormal change of the crystal behavior and thermal stability of polymer was found to be related with molecular structure containing ether linkage. The azo polyaramides can be applied in fields of optical techniques and potential photochromics fibres spinning in wide temperature ranges     

Fabrication,structural and vibrational properties,and physical and optical properties tailoring of nanocrystalline MoS2 films

The modification and tuning features of nanostructured films are of great interest because of controllable and distinctive inherent properties in these materials. Here, nanocrystalline MoS₂ films were fabricated on the stainless steels by a radio frequency magnetron sputtering at ambient temperature. X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and Raman scattering spectroscopy were used to study the chemical state, chemical composition, crystal structure and vibrational properties of the fabricated MoS₂ films. The bias voltage dependent structural evolution and its influence on the optical properties of MoS₂ nanocrystalline films were systematically investigated. Besides, the residual stresses of MoS₂ nanocrystalline films were explored by employing sin²ψ approach. X-ray diffraction demonstrates that the nanocrystalline MoS₂ films have single-phase hexagonal crystal structure. All MoS₂ films are polycrystalline in nature. The bandgap values are found to be intensively dependent on bias voltage. Our findings show that the nanocrystalline MoS₂ films with different physical properties and intense quantum confinement effect can be realized through adjusting bias voltages. This work may provide deep insight for realizing transitional metal dichalcogenide-based nanostructured film optoelectronic devices with tunable physical properties through a traditional, very cost-effective, and large-scale fabrication method.