Narrow Results

Antiferroelectrics have recently captured widespread attention for their potential applications in energy storage capacitors, electronic and electrothermal devices. PbZrO₃, being the first antiferroelectric discovered, remains the focus of antiferroelectric studies. Conventionally, the PbZrO₃ ceramics were prepared via a high-temperature solid-state reaction method (higher than 1000^∘C). Here, we report a simple sol–gel route to prepare single-phase PbZrO₃ ceramic at a much lower calcination temperature of 600^∘C. By using the single-phase PbZrO₃ ceramics, thin films with outstanding antiferroelectric property showing well-defined double-hysteresis polarization switching were further obtained by pulsed laser deposition.

Dust and other environmentally suspended particles deposited on the solar panels reduce the sunlight to photovoltaic cells, reducing the total energy outcome. A dust-reflecting coating keeps a cleaner surface, thus enhancing light absorption and improving the overall energy outcome. This study synthesized the sol–gel of SiO₂, MgF₂, and TiO₂ and made the coating on the glass substrate by SiO${}_2+{\mathrm{\text{MgF}}}_2$, SiO${}_2+{\mathrm{\text{TiO}}}_2$, and MgF${}_2+{\mathrm{\text{SiO}}}_2+{\mathrm{\text{TiO}}}_2$ using sol–gel dip coating and spin coating method. Coatings that occurred on the glass sample surfaces were identified by using FTIR analysis. Five of the above six coatings made using different mixtures have increased transmittance than pure glass, while one SiO${}_2+{\mathrm{\text{MgF}}}_2$ spin coating reduced the transmittance. The minimum water contact angle of 37.69^∘ was found on the SiO${}_2+{\mathrm{\text{TiO}}}_2$ spin-coated surface, and the maximum contact angle was 72.10^∘ on the MgF₂ dip-coated surface. This shows that the self-cleaning properties in SiO${}_2+{\mathrm{\text{TiO}}}_2$ spin-coated surfaces are maximum and minimum in MgF₂ dip-coated surfaces. The angle found by the test shows that spin coating is a better technique than dip coating for hydrophilic surface coating. This was due to the more homogenous coating on the spin-coated sample surfaces. There was less accumulation of dust found on the coated surfaces compared to non-coated glass sample surfaces.

An analysis to the characteristics of Co, Mg and Cu ferrites that were prepared using sol–gel method and annealed at $800^{\circ }$C for 1 hour, performed using X-ray diffraction and Raman spectroscopy for structural characteristics, while the Vibrating Sample Magnetometer (VSM), was used for the magnetic characteristics. The X-ray analysis of both cobalt and magnesium ferrites shows a reverse crystal structure of a cubic spinel, while copper ferrite shows a tetragonal crystal structure characteristic at this annealing temperature. The lattice constant (a) was found to be $a=8.186$ for CoFe₂O₄, $a=8.199$ for MgFe₂O₄ and $a=5.969$ for CuFe₂O₄. The Raman spectrum confirms a spinel crystalline form of the prepared ferrites where a likely distribution of cation is indicated at the tetrahedral and octahedral sites. The peaks of the Raman shift appear between 200–800cm${}^{-1}$. These peaks indicate the formation of ferrites. The hysteresis loop of CoFe₂O₄ indicates a hard magnet material. Cu ferrites have relatively lower remnants and magnetocrystalline anisotropy, which indicates soft magnetic characteristics even though it showed higher coercivity. The squareness ratio (Mr/Ms) values varied between 0.52, 0.13 and 0.57 for CoFe₂O₄, MgFe₂O₄ and CuFe₂O₄, respectively. These insights highlight the possibility of tuning the properties of ferrites using a cost-effective sol–gel method.

Single layer (SLAR: TiO₂ and ZnO), and DLAR: TiO₂/ZnO bi-layer were deposited on glass substrates by sol–gel dip and spray pyrolysis for TiO₂ and ZnO thin films respectively. The structural and optical properties have been studied by different characterization techniques: Raman spectroscopy, UV–Visible spectrophotometer and m-lines spectroscopy. The SLAR of TiO₂ and ZnO thin films crystallizes in the Anatase and the wurtzite phase, respectively. The fabrication of the DLAR bi-layer increased the optical gap energies. Also, the DLAR film experienced a decrease in the visible transmittance. However, the present work is principally focused on the influence of the DLAR on the performance of the waveguide characterized by the m-lines measurements. The SLAR samples exhibit a single mode in the TE and TM polarizations. The DLAR sample had two modes in each polarization, one mode in the TE polarization was due to light traveling in the TiO₂ film and the rest three were assigned to ZnO. The results shed light on the effect of the deposition method and the role of refractive index difference in bi-layer waveguide design.

The (Ni/NiO)${}_{CG}$/g-C₃N₄ nanocomposite was green synthesized using Cleome gynandra via sol–gel method. The photocatalytic dye decomposition, antioxidant and antidiabetic activities of the nanocomposite were studied and compared with those of (Ni/NiO)${}_{\mathrm{\text{CG}}}$ and g-C₃N₄. The nanocomposite exhibited enhanced photocatalytic efficiency of 97% compared to (Ni/NiO)${}_{\mathrm{\text{CG}}}$ (63%) and g-C₃N₄ (80%) due to the synergistic effect between both the composite partners. The nanocomposite, (Ni/NiO)${}_{\mathrm{\text{CG}}}$/g-C₃N₄ showed notable antioxidant activity in DPPH (IC${}_{50}$ of $41.76\pm 0.88$$\mu$g/mL with 87.06% of inhibition at 500$\mu$g/mL) and ABTS (IC${}_{50}$ of $47.60\pm 0.81$$\mu$g/mL with 88.40 % of inhibition at 500$\mu$g/mL) radical scavenging assays. The green synthesized nanocomposite also exhibited significant antidiabetic activity in $\alpha$-amylase and $\alpha$-glucosidase enzyme inhibition assays with the IC${}_{50}$ of $33.83\pm 0.53$$\mu$g/mL and $49.94\pm 0.64$$\mu$g/mL, respectively. The XRD and SEM analyses confirmed the nanocomposite formation of (Ni/NiO)${}_{CG}$/g-C₃N₄. The results showed that the green synthesized (Ni/NiO)${}_{\mathrm{\text{CG}}}$/g-C₃N₄ has desirable dye degradation, antidiabetic and antioxidant properties. This paper presents the results of the remarkable photocatalytic dye decomposition, antidiabetic and antioxidant properties of the nanocomposite (Ni/NiO)${}_{\mathrm{\text{CG}}}$/g-C₃N₄ synthesized via an eco-friendly greeny way using Cleome gynandra leaf extract which may be the first report of this kind utilizing this plant.

Nanoferrites of CoGd${}_x$Fe${}_{2-x}$O₄ ($x=0.0,0.03,0.06,0.09,0.12$ and $0.15)$ were synthesized via sol–gel auto combustion. The fashioned samples were examined by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer and UV spectroscopic analysis. A cubic spinel phase with no impurities was confirmed by XRD. Doping with Gd${}^{3+}$ ions raises the crystallite size from 20nm to 25nm and the lattice constant from 8.351Å to 8.413Å. Formations of two significant bands are supported by FTIR spectra between 590cm${}^{-1}$ and 601cm${}^{-1}$, 403cm${}^{-1}$ and 407cm${}^{-1}$, which approve the establishment of ferrite structure. FESEM certified the formation of the nanoparticles and the fact that most of the grains are spherical and agglomerated and the EDX spectrographs certified the existence of the elemental compositions. With an increase in Gd${}^{3+}$ ion, saturation magnetization (M${}_s$) and remanence magnetization (M${}_r$) dropped from 132emu/g to 69emu/g and 93emu/g to 41emu/g, respectively. The coercivity (H${}_c$) increased with gadolinium and at the $x=0.15$ recording the extreme value of $H_c=1715$Oe. UV-spectroscopy studies authorized the samples’ semiconducting nature because band gap values were found from 2.108eV to 1.992eV.

The sol-gel method has been employed in the fabrication of mesoporous composite films consisting of a nonionic surfactant, Pluronic P123, as the organic component, and silica as the inorganic component. The hybrid nature of these films resulted in their having an internal structure consisting of nanometer size self-assembled organic mesostructures surrounded by a silica framework. These films served as the host matrix for the laser dye coumarin 481 (C481) and an energy transfer complex formed between C481 and J-aggregated meso-tetra(4-sulfonatophenyl)porphyrin (TSPP). Upon exposure to methanol vapor, a rapid and reversible decrease in fluorescence intensity occurs for films containing C481 alone as well as containing both C481 and TSPP. Steady-state and time-resolved spectroscopic studies suggest that the decrease in fluorescence intensity is primarily due to an excited state interaction between methanol and C481; while, additionally, morphological changes within the film appear to play a role for films containing both C481 and TSPP.

Transparent sols of crystalline gadolinium doped zirconia particles with the general formula Zr_{1 - x}Gd_xO_{2 - x/2} (where x = 0–0.20), were prepared by a hydrothermal sol-gel method using cheap inorganic precursors. The composition, structure, crystallite size and lattice parameters of the crystalline dried sol particles and heated powders were studied. Thin films were deposited on quartz substrates using a simple dipping process and the structure, composition and crystallite size found to be identical to the powders with respect to the variation in temperature. Spectral transmittance studies showed that the films were transparent in the region between 400 and 1100 nm. The refractive index increased with the increase in annealing temperature, varying between 1.56 and 1.74. Optical band gap calculations gave band of 5.52 to 5.55 eV. Refractive indices and optical band gaps were compared with those of films containing other lanthanide dopants previously reported in the literature.

A solution process was used to grow SrTiO₃ (STO) buffer layers on LaAlO₃ (LAO) and biaxially textured Ni substrates by spin coating technique. The epitaxial STO film obtained has strong cube texture and uniform microstructure. A metal organic decomposition process using trifluoroacetate precursors was applied to deposit YBa₂Cu₃O_7-δ (YBCO) thin films on these buffer layers. The YBCO/STO/LAO was biaxially textured and the T_Conset and ΔT_C is 90.1K and 2.7K, respectively.

A new preparation process of the vanadium catalyst with nano-V₂O₅ particles was introduced in this paper. The inorganic sol-gel method is used to prepare the sols and gels with p nano-V₂O₅ particles. The morphology, size and distribution of the nano-V₂O₅ particles in the sols-gels and vanadium catalyst had been studied by TEM, SEM, XRD and DSC. The results show that with the w/v (the ratio of water and vanadium) declining, the morphology of the nano-V₂O₅ particles varies from needle to near-ball then to sphere; the better process parameter to prepare the sols and gels with nano-V₂O₅ particles is 800~860°C×10~15min; the sols and gels and catalyst with 30~60nm V₂O₅ particles had been obtained by this process.

Ferroelectric barium titanate (BaTiO₃) films have been prepared from barium acetate and titanium (IV) isopropoxide precursors by the sol-gel technique. The structural and optical properties of films annealed at different temperatures have been investigated. The as-fired films were found to be amorphous and crystallized to the tetragonal phase after annealing at 700°C for one hour in air. The lattice constants "a" and "c" were found to be 3.996 Å and 4.040 Å respectively. The X-ray density of the crystalline film was about 6.00g·cm^-3. The amorphous film showed very high transparency (~95%), which decreased slightly after crystallization (~90%). The band gap and the refractive index of the amorphous and crystalline films were estimated. The influences of porosity on the optical properties of films have also been investigated. The optical dispersion data are also analyzed in the light of the single oscillator model, and are discussed.

ZnO thin films were first prepared by the sol–gel process, and then Ge ions were implanted into the ZnO films. The effects of ion implantation on the structural and optical properties of the ZnO films were investigated by X-ray diffraction, photoluminescence (PL), and optical transmittance measurements. Measurement results showed that the intensity of the (002) diffraction peak was decreased and the full width at half maximum was narrowed. PL emission was greatly extinguished after Ge ion implantation. Both the near band edge (NBE) excitonic UV emission at 391 nm and the defect related deep level emission centered at 470 nm in the visible region were decreased after Ge ion implantation. NBE peak and the absorption edge were observed to have a blueshift toward higher energy.

LiTaO₃ thin films were deposited on Pt/Ti/SiO₂/Si substrates by means of a sol-gel spin-coating technology and rapid thermal annealing (RTA). The influence of various annealing treatments on the characteristics of the thin films were studied by varying the single-annealed-layer thickness (50 ~ 200 nm) and heating temperatures (500 ~ 800°C) of the samples. Experimental results reveal that the single-annealed-layer strongly influences grain size, dielectricity and ferroelectricity of LiTaO₃ thin films. The grain size of LiTaO₃ thin film decreases slightly with increasing thickness of the single-annealed-layer, and highly c-axis orientated LiTaO₃ films can be obtained for a single-annealed-layer of 50 nm. When the thickness of the single-annealed-layer was increased from 50 to 200 nm, the relative dielectric constant of LiTaO₃ thin film decreased from 65 to 35, but the dielectric loss factor (tanδ) was increased. The LiTaO₃ films with the single-annealed-layer of 50 nm showed excellent ferroelectric properties in terms of a remanent polarization (P_r) of 12.3 μC/cm² (E_c ∼ 60 kV/cm), and a low current density of 5.2×l0^-8A/cm² at 20 kV/cm.

The effect of nano size Ag addition on the YBa₂Cu₃O_7-δ (Y-123) system has been investigated. 2–15% weight of nano size Ag was added to the Y-123 system prepared by using the sol-gel-solid-state method. The phase purity was investigated by the powder X-ray diffraction method. Energy Dispersive X-ray Analysis (EDAX) was used to determine the distribution of nano Ag in the samples, and the microstructure was observed using a Scanning Electron Microscope (SEM). The transport critical current density was found to increase with increase in nano Ag content.

In this research a sol-gel auto-combustion route has been proposed to synthesize nickel-zinc ferrite nanocrystalline powder, using metal nitrates, citric acid as fuel and ammonia as pH adjusting agent. The influence of pH value of the solution on phase evolution, crystallite size and morphology of as-burnt powders were investigated by XRD, SEM and TEM techniques. The results revealed that with pH=7 the single phase nickel-zinc ferrite nanocrystalline powders with crystallite size of about 27nm were formed directly after auto combustion process.

Nano sized copper oxide-zirconia particles were prepared by using a sol-gel technique. The phase change with the calcinations temperature was also investigated for the sample containing 30 wt% copper. It was found that the calcinations temperature strongly influenced the interaction between the active species and support and hence the structure and catalytic performance. Low calcinations temperature yielded poorly crystallized catalysts and favored the formation of a Cu(OH)₂ and Zr(OH)₄ like structure. The results show that cubic ZrO₂ and copper oxide were present below calcinations at 400°C, and cubic ZrO₂ with some amount of monoclinic ZrO₂ and tetragonal ZrO₂, as well as copper oxide, formed after calcinations at 500°C. However, below heating at 500°C, amorphous compounds were obtained; suggesting that 500°C could be a phase transition point. The incorporation of copper in the ZrO₂ lattice resulted in a loss of order in the ZrO₂ structure when calcined at 500°C, with a further increase in the calcinations temperature leading to the phase change. In this work, the latest results on nano crystalline CuO-ZrO₂ as the catalyst for hydrogen synthesis from methanol is reported. The effect of calcinations temperature on the nanoparticle structure of catalyst is focused.

Ceramic materials based on zirconium titanate prepared by sol-gel method are used extensively in microwave, telecommunications and catalysis. In order to investigate the effects of concentration of TTIP, a series of ZrO₂–TiO₂ mixed oxides was prepared by a modified sol–gel method and varying mole fraction of TTIP from 0.002, to 0.1. The samples were characterized by XRD, TG/DTA, and SEM. The XRD pattern of 370°C calcined samples showed the formation of TiO₂ phase. The optimum concentration of TTIP in the zirconia-titania mixed oxide in the precipitation solution was 0.032 for obtaining complete coating. Each oxide was calcined between 250 and 620°C. The results showed that concentration of TTIP have a pronounced effect on particle size of the calcined zirconium titanate (ZT) powders. The results showed that the surface area of the composite powder increased proper to monolithic ZrO2 powder.

Magnesium is light, biocompatible and has similar mechanical properties to natural bone, so it has the potential to be used as a biodegradable material for orthopedic applications. However, pure magnesium severely corrodes in a physiological environment, which may hinder its use for in vivo applications. Protective coatings are effective method to delay the corrosion of Mg. In this study, sol-gel and hydroxyapatite (HA) coatings were applied onto the surface of pure magnesium substrates using a biomimetic technique. The corrosion rate of surface-treated substrates was tested. It was found that both types of coatings substantially slowed down the corrosion of the substrate, the 60Ca so-gel and HA coating was more effectively than the 100Si so-gel and HA coating in hindering the degradation of the substrate. Thus, the corrosion rate of magnesium implants can be closely tailored by coating sol-gel then coating apatite thereby monitoring the release of magnesium ions into the body.

The effect of post-deposition annealing in forming gas on the structural and electrical properties of sol–gel derived SiO₂ thick film on n-type 4H–SiC has been systematically investigated. Tetraethylorthosilicate-based precursor with H₂SO₄ as catalyst was prepared and prior to film deposition, substrate surface was treated by hexamethyldisilizane. The spin-coated film was annealed at 750–950°C for 30 min with an approximately 185-nm thick film. It was found that oxide annealed at the highest temperature revealed the densest film, lowest oxide defects, and lowest total interface trap density. As a result, this oxide had demonstrated the lowest leakage current density if compared with other oxides.

Thin films of V₂O₅ were deposited on glass substrates by dip-coating technique using sol–gel route. The vanadium pentoxide sol was prepared by dissolving V₂O₅ powder in H₂O₂ solution. The solutions were kept in water bath and heated at five different temperatures for 30 min. The samples were annealed at 150^°C for 60 min. The optical, structural, and morphological measurements were performed for characterization of samples. The effect of viscosity on optical constants (n, k, and E_g) of V₂O₅ were studied. The indirect optical band gap energy of sol–gel V₂O₅ thin films are about 2.33 eV and independent of viscosity within the error limits. The results show that the water-bath temperature strongly influences the viscosity of sol. The viscosity of sol was changed from 12.5 to 75 m Pa s. with increasing water-bath temperature from 50 to 90^°C. The XRD measurements show that the structure of the V₂O₅ films and powders is polycrystalline after annealing at 450^°C. A correlation exists between the viscosity, morphology, and optical characteristics.