Zincite Phase Research Articles

The Reduction Reaction Behavior of Steelmaking Dusts with Lignin under Different Atmospheres.

This study investigated lignin as a reducing agent instead of fossil carbon for the reduction of zinc oxide and zinc ferrite contained in steelmaking dusts. Three types of dusts from different steelmaking processes were considered: ferrochrome converter (CRC), electric arc furnace stainless steel (EAFSS) and electric arc furnace carbon steel (EAFCS). Zinc is primarily found in zincite phases within CRC dust, while EAFSS and EAFCS dusts contain franklinite and zincite phases as Zn-bearing minerals. The proximate analysis of lignin showed that the fixed carbon content is 28.9%. Thermogravimetric (TG) analysis coupled with differential scanning calorimetry (DSC) and mass spectrometry (MS) was used to study the reduction behavior of different mixtures of lignin and steel dusts under inert and air atmospheres. Simultaneously, the minimum ratio of lignin out of three different proportions required to achieve a complete reduction of franklinite and zincite phases into metallic zinc was identified. The results indicated that a 1.1 stoichiometric amount of lignin is sufficient for the complete reduction of zinc-bearing minerals into metallic zinc. In conclusion, lignin can be used efficiently for processing steelmaking dusts.

Synthesis and characterization of Fe3O4 core nanoparticles coated with TiO2 and ZnO

The room temperature synthesis of the core-shell-shell (CSS) nanoparticles was demonstrated to be green, low-cost, and reproducible. The magnetic core of Fe3O4 nanoparticles was coated with TiO2 and ZnO in two steps. The obtained CSS nanoparticles were extensively characterized by XPS, TEM, XRD, DRS-UV–vis, N2 Physisorption, Electromagnetic, and Raman spectroscopy. XPS analysis revealed that the magnetic core was successfully functionalized with the citric acid. The ratio between the ferric cations (Fe3+) and ferrous (Fe2+) is typically reported to be around two due to the presence of FeO and Fe2O3 to balance the charge in the structure. Nevertheless, XPS results demonstrated that the ratio resulted in higher stability than that of the crystal nominal structure, suggesting that the surface of the CSS is slightly enriched with Fe3+ cations. TEM results indicated an average core diameter of approximately 9±1 nm for Fe3O4 (M-US); the first shell exhibited an average thickness of 3±1 nm, while the ZnO second shell thickness resulted in around 2±1 nm. X-ray diffraction analysis identified inverse spinel, hematite, anatase, and zincite phases in M-US, MT, and MTZ, respectively. Notably, the MTZ sample also contained hematite in addition to inverse spinel. Diffuse Reflectance UV-Vis Spectroscopy results demonstrated a reduction in the band gap as the shell coverage varied. N2 adsorption-desorption isotherms indicated an increase in the surface area as the core nanoparticles were coated with the subsequent shells. Additionally, the coated samples presented a mesoporous structure with a maximum surface area of 110 m2g−1 for the MT material. Raman spectroscopy confirmed the presence of vibrational modes related to TiO2 and ZnO. The core-shell-shell nanoparticles presented suitable electronic properties to potentially be applied in the photodegradation of harmful compounds and azo dyes.

Controlled evolution of surface microstructure and phase boundary of ZnO nanoparticles for the multiple sensitization effects on triethylamine detection.

In ZnO gas sensors, donor defects (such as zinc interstitials and oxygen vacancies) are considered active sites for the chemical adsorption and ionization of oxygen on the surface of ZnO, which can significantly enhance the sensor's response. However, the influence of the surface microstructure and phase boundaries of ZnO nanoparticles on the chemical adsorption and ionization of surface oxygen has rarely been explored. In this study, we developed a mixed-phase ZnO nanoparticle gas sensor with a rich phase boundary showing 198-50 ppm improvement in response to triethylamine at 340 °C. This is attributed to the generation of defects originating from lattice mismatch at the ZnO - zincite phase boundaries, which providing more active sites for adsorption of oxygen and triethylamine molecules. This work demonstrates a feasible method of combining surface microstructure regulation with pyrolysis strategies to develop ZnO sensors with significantly enhanced gas response performance.

Green Synthesis, Characterization, and Photocatalytic Activity of Zinc Oxide Nanoparticles on Photodegradation of Naphthol Blue Black Dye

Zinc oxide (ZnO) nanoparticles have been successfully synthesized using water extract of red dragon fruit (Hylocereus polyrhizus) stem with zinc acetate dihydrate as a precursor of ZnO. Chemical compounds contained in the red dragon fruit stem extract, such as phenolics, terpenoids, and steroids, acted as reducing agents, stabilizers, and capping agents. The phase structure, crystallite size, functional groups, shape, and morphology of ZnO nanoparticles were determined by X-ray diffraction (XRD), Fourier Transform infrared (FT-IR) Spectroscopy, and Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX). The XRD pattern confirmed the crystallinity of synthesized zinc oxide was in the zincite (ZnO) phase with an average crystallite size of 79.09 nm. Spectroscopy FTIR analysis showed that the synthesized ZnO nanoparticles had characteristics similar to the ZnO standard/commercial. SEM-EDX analysis revealed that the synthesized ZnO nanoparticles were spherical, evenly distributed, and homogeneous particle size. The photocatalytic activity of synthesized ZnO nanoparticles was evaluated on the photodegradation of naphthol blue black (NBB) dye. The results showed that the synthesized ZnO nanoparticles have high photocatalytic activity that can degrade NBB dye up to 98.82%. This high photocatalytic activity was obtained at operating parameter conditions with the initial pH of NBB at 2, the dosage of ZnO nanoparticles at 250 mg, and the initial dye concentration at 10 ppm.

Effect of synthesis conditions on the photocatalytic behavior of ZnS-ZnO heterojunctions for the H2 generation

In the present work, the synthesis and photocatalytic performance for H2 production of ZnS-ZnO composites at different compositions of cubic sphalerite (ZnS-c), hexagonal wurtzite (ZnS-h) and zincite (ZnO) phases are shown. The synthesis was carried out by the solvothermal method using mono ethylene glycol and thiourea as solvent and sulfur source, respectively, for the partial sulfidation of ZnO at different temperatures (150 °C, 200 °C, and 250 °C). When the temperature is increased in the solvothermal process, the hexagonal phase grows at the expense of the cubic phase. The materials as powders were characterized by X-ray diffraction, scanning and transmission electron microscopy, UV–visible spectroscopy, X-ray photoelectron microscopy, N2 adsorption-desorption isotherms, and photoelectrochemical techniques. These materials were applied in H2 production as an alternative source of clean and sustainable energy generation. It was found that the most photoactive material was the one synthesized at 200 °C, this photocatalyst presented an H2 production rate of 580 µmol h−1 g−1. The enhancement of the photocatalytic activity is due to the optimization of the interfacial properties between ZnS-c/ZnS-h and ZnO as a model system for coupled photocatalysts.

Influence of the filling ratio of vial in chemical surface and physicochemical properties of ZnO nanoparticles obtained by planetary ball milling process

The production of nanoparticles (Np) is an important sector in current technological development. Processes such as high‐energy grinding are among the most promising because of their high efficiency and low energy cost. In this sense, the filling ratio of vial (FRV) is one of the most interesting and poorly studied process variables that can optimize the production of Np on a large scale. In the present work, dry ZnO Np are produced, with different FRV values (40%, 38%, 23%, and 10%), as well as wet samples. The results show that the variation of the FRV allows to generate an energetic increase of the grinding, modifying the morphology, the particle size, and the surface area of the ZnO powders, without generating structural or chemical changes. The X‐ray diffraction (XRD) results show the presence of the zincite phase (hexagonal) with a variation in crystallinity depending on the FRV, which is due to the deformation of the Np during the process. The XPS results showed a slight chemical shift (variation in binding energy) as a function of grinding because of the activation shown by deformation. UV–VIS analyses showed a marked increase in the magnitude of absorbed intensity for all analyzed samples compared with the commercial powder. These results confirm that FRV is a sensitive parameter in the process of obtaining ZnO Np by the planetary mill technique, which allows efficient control of its characteristics for a given application.

Impact of the B/C-doping ratio on the microstructure, mechanical properties, and cutting performance of AlTiN-based coatings

Certain element doping is a facile and powerful vehicle for tailoring the organization and properties of hard coatings. This research fabricated AlTiBCN coatings with various B/C doping ratios (the boron-carbon incorporation totaled 10 at.%) and explored the effect law of varying B/C ratios on the coatings' microstructure, mechanical properties, tribological, and cutting performances. All coatings exhibited a mixed structure of cubic and fibrous zincite phases, with the major phase being w- Al(Ti)N and the minor phases being c-Al(Ti)N and c-Ti(C, N). Besides, along with the increase in C-doping proportion, the coating organization shifted from a featureless glassy pattern to a fine-grained columnar crystal morphology. Boron was mainly found as -BN in the coatings, while carbon was mostly found as c-Ti(C, N) replacement solid solution (B/C ratio≤2.5:1, 0:10) and amorphous C (B/C ratio≤1:2.5, 0:10). According to the properties results, (1) AlTiBCN coating with a B/C ratio of 1:1 had the optimal mechanical, tribological, and cutting performance; (2) AlTiBCN coating with a B/C ratio≥ 2.5:1 and 10:0 had higher hardness but poorer coating brittleness and tribological properties due to excessive α-BN; (3) At B/C ratios≤ 1:2.5 and 0:10, the mechanical properties of its coatings dropped sharply, which means the coating's hardness, toughness, and wear resistance are aggravated by the strong softening effect of α-C.

Novel application of sub-Antarctic macroalgae as zinc oxide nanoparticles biosynthesizers

The search for novel starting materials in the biological synthesis of zinc oxide nanoparticles (ZnO NPs) is crucial to develop synthetic procedures using environment-friendly approaches. In this sense, the aim of this study was to synthesize and evaluate ZnO NPs using green approaches produced from three sub-Antarctic macroalgae. It is worth noting that this was the first time that sub-Antarctic macroalgae were used for this purpose. Results showed that band intensity of polar bands that included hydroxyl (3779–3002 cm−1) and carbonyl groups (1770–1639 cm−1) decreased with the formation of ZnO NPs while the band associated to the zinc-oxygen bond appeared at 450 cm−1 in the synthesized nanomaterials. Further analysis confirmed the formation of ZnO NPs as the product was mostly composed of zinc (≥97.27%) in the form of nanoparticles. Finally, X-Ray Diffraction indicated the zincite phase present in the hexagonal structures of ZnO NPs while SEM analysis confirmed that the nanomaterials were homogeneous and well-compacted. Therefore, sub-Antarctic could be promising sources of phytochemicals to produce nanomaterials under environment-friendly approaches.

Design and characterization of biphasic ferric hydroxyapatite-zincite nanoassembly for bone tissue engineering

Hydroxyapatite (HAp) is one of the most studied biomaterials for orthopaedic applications, yet its commercialization holds in a few of the lags, such as non-antibacterial activity and target deficiency. In this context, we aimed to design a biphasic nanoassembly of Ferric-HAp-Zincite (ZFHAp) via a one-step co-precipitation method. Ferric-HAp obtained Ca9·333Fe1·167(PO4)7 phase in all the samples, and the secondary phases such as Ca9Fe(PO4)7 and Ca28·8Fe3·2(PO4)21O0.5 were governed by the Fe dopant concentration. Along with ferric-HAp, zincite phases were present in all the samples depending on the concentration of Zn precursor. The synthesized ZFHAp samples were hexagonal in structure with size <100 nm, and a dual morphology, i.e., rod-shaped (77.8 ± 10 nm; major corresponding to HAp) and particulate shaped (30.9 ± 5 nm; minor due to Zincite). Doping of iron imparted paramagnetism resulting in the magnetic target efficiency. ZFHAp samples showed excellent self-antibacterial activity against clinically significant two Gram-positive (E. hirae, S. aureus) and two Gram-negative (E. coli, S. paratyphi) bacteria with lower MIC values (60–80 μg/ml). The antibacterial mechanism was found to be ROS independent and due to the linear release of Zn2+ and Fe3+ ions. The designed ZFHAp samples showed no cytotoxicity up to 5 mg/mL and exhibited 3 times higher bone cell proliferation along with the significant Alkaline Phosphatase (ALP) activity. The prepared nanomaterials also did not show any inflammatory response to bone cells. These findings entitle ZFHAp as a potential candidate for orthopaedic as well as other biomedical applications subject to further clinical trials.

Comparative study of crystallite size using Williamson-Hall and Debye-Scherrer plots for ZnO nanoparticles

ZnO nanoparticles at different pH were synthesised by a sol-gel technique from zinc acetate dihydrate at a calcination temperature of 450 °C. The synthesized ZnO nanoparticles were characterised by x-ray diffraction (XDR) peak profile analysis, high-resolution scanning electron microscopy and Fourier transform infrared spectroscopy. The effects of solution pH on the crystallite size using Williamson-Hall and Debye–Scherrer were determined. The XRD analysis of the zincite phase structure of ZnO nanoparticles was obtained in the form of spheres for all the samples. The average crystallite sizes of ZnO nanoparticles decrease with increasing pH. The crystallite sizes of ZnO nanoparticles were investigated using Williamson-Hall analysis and Scherrer’s formula. The parameters such as dislocation density and lattice strain were computed for the diffraction peaks of XRD in the range of 2θ = 10–90°. The results showed that the crystallite sizes calculated from Scherrer’s equation and Williamson-Hall analysis from XRD are not inter-correlated. Both methods give a wide deviation of crystallite size. Also, it was found that the crystallite sizes using both methods decrease with an increase in pH. Smaller crystallite sizes were estimated using the Scherrer’s formula. Thus, it is deduced that the equation fitted well for the synthesised ZnO nanoparticles.

Influence of Al and Al-Cu dual doping on structural, optical, wetting and anti-fungal properties of ZnO nanoparticles

ABSTRACT Sol-gel (SG) and direct precipitation (DP) routes were employed to synthesize zinc oxide (ZnO) nanoparticles. Al doping and Al-Cu dual doping in ZnO nanoparticles were performed. The structural, morphological, optical, wetting properties and antifungal activity of the undoped and doped nanoparticles were studied. The Al doping transformed the ZnO to zinc aluminate nanostructure, while Al-Cu dual doping produced zincite and tenorite phases of ZnO. FESEM revealed the morphology of undoped and doped nanoparticles. The doping of ZnO increased the band gap compared to the band gap of the ZnO nanoparticles. Photoluminescence (PL) spectroscopy endorsed the formation of zinc aluminate, zincite and tenorite phases. The hydrophilic SG-derived ZnO nanoparticles transformed to the hydrophobic due to Al doping which is attributed to the variation in the roughness of the doped nanostructures. The doped ZnO nanostructures revealed better resistance to the growth of the ‘Rhizopus Stolonifer’ fungus compared to the undoped ZnO nanoparticles.

Effect of ZnO/PbO and FeOX/SiO2 ratio on the viscosity of lead smelting slags

The effect of ZnO/PbO and FeOX/SiO2 on the viscosity of the PbO-ZnO-Fe3O4-SiO2-CaO slag was measured using the rotating spindle method. The slag viscosity decreased with decreasing ZnO/PbO mass ratio because of the depolymerization of the silicate structures. The viscosity decreased with increasing FeOX/SiO2 mass ratio as the experimental temperature was above 1623 K, while the viscosity increased significantly with the increase of FeOX/SiO2 as the experimental temperature below 1623 K because of the phase transition and the change of slag melting point. According to XRD analysis of as-quenched slag, the spinel and the zincite phase increased with increasing FeOX/SiO2. Increasing ZnO/PbO and FeOX/SiO2 could enhance the crystallization capacity of the slag. FTIR analysis revealed that the degree of polymerization of the as-quenched slags decreased with decreasing ZnO/PbO and increasing FeOX/SiO2. The temperature dependencies of the viscosity on ZnO/PbO and FeOX/SiO2 were investigated, and the apparent activation energies of each system were found to be between 169.5 to 227.4 KJ/mol, and 151.1 to 676.4 KJ/mol, respectively.

Optical and Piezoelectric Properties of Mn-Doped ZnO Films Deposited by Sol-Gel and Hydrothermal Methods

Nowadays, multifunctional materials are of high interest due to their ability to be used in different applications by controlling one or two parameters (e.g., morphology and/or dopant). Zinc oxide is an intensive-studied material because of its large usability. Recently, we have shown that the conduction, transparency, and charge carrier concentration of ZnO can be controlled by changing the dopants, leading to promising materials as transparent conductive oxide films. In this work, sol-gel (SG) and hydrothermal (HT) methods were used separately or in combination in order to obtain ZnO films doped with Mn (1, 2, and 5%) for possible application in transparent optoelectronics or as piezoelectric materials. The manganese (Mn) dopant in the form of anhydrous manganese acetate was used to obtain Mn-doped ZnO films. ZnO hydrothermal (HT) growth was made on a previously ZnO seed layer, formed by sol-gel method. The Mn-doped ZnO films were deposited on microscope glass and on Pt/Ti/SiO2/Si substrates. A comparative characterization of the films for their structure, morphology, and optical and piezoelectric properties was achieved. SG films exhibit equiaxed nanoparticles, with diameters around 50 nm, while the films prepared by HT show a homogeneous morphology consisting of uniform 1D nanorods, sized about 30 nm diameter and 200–300 nm length. XRD diffractograms evidenced the presence of zincite phase (wurtzite structure hexagonally close packed), with an improvement in crystallinity of the HT films (compared with SG ones), which present a stronger tendency to be oriented along (002) plane (c-axis) at 2% at Mn. Spectroscopic ellipsometry shows that the films obtained by SG are much thinner than the ones obtained by HT and that the refractive index is increasing with the percent of dopant. The band gap energy was found to decrease with the Mn doping level from 3.28 eV (undoped ZnO) to 3.10 eV (ZnO doped with 5 at% Mn) for the samples deposited on Pt/Ti/SiO2/Si. The maximum transmission is found for the undoped ZnO film and decreases with Mn concentration but remains over 78% in the visible range. From the piezoelectric tests, it was found that the d33 coefficient is much larger for the HT samples in comparison with the SG samples, especially for 2 and 5 at% Mn. The optical and piezoelectric results could be of interest for applications in optoelectronic or piezoelectric devices.

Viscosities in PbO − ZnO − “FexO” − SiO2–CaO system for lead and zinc smelting slags

With the increase of Zn content in lead raw materials, it is essential to understand the viscous behavior of high lead-zinc smelting slags in improving the process efficiency and inhibiting the formation of foaming slag. In this article, the viscosities in lead and zinc smelting slag in the multicomponent system PbO-ZnO-“FexO”-SiO2-CaO were measured using the rotating cylinder method at a fixed ZnO/PbO mass ratio. The results indicated that the apparent viscosity increased with the increasing Fe/SiO2 mass ratio because of the formation of spinel (ZnxFe3-xO4+y) and zincite (ZnO) phase. The viscosity decreased with the increase of CaO/SiO2 mass ratio above 1573 K, and apparent viscosity increased significantly as the Ca3Fe15O25 and zincite phase emerged. The influences of Fe3O4, sulfur and CuO content of slag on apparent viscosities at lower temperatures were also due to the presence of crystals.

The Effect of ZnO Nanorods Morphology on Electrical Properties of Perovskite Solar Cells

Perovskite solar cells have attracted the researchers’ attention because they are one of the most promising candidates that are cheap, easy to fabricate and high-efficiency solar cell. ZnO nanorods (ZnO NRs) can be used as an electron and hole recombination barrier to improve the perovskite solar cell performance. This research aimed to investigate the effect of growing time on the characteristics of ZnO NRs and its application for perovskite solar cell device. The ZnO NRs was synthesized on ITO substrate by hydrothermal method at the different growing times of 4, 6, and 8 hours. The CH3NH3PbI3 perovskite solar cells were deposited on the top of ZnO NRs/ITO thin films by a two-stage spin coating method. The solar cell devices were characterized by using XRD, SEM-EDX, FTIR, UV-vis, and LCR meter. The results showed that ZnO NRs/ITO thin films were formed homogeneously and vertically oriented on all ITO substrates with hexagonal structures of zincite phases. When the growing time of ZnO NRs increased, the degree of homogeneity, density, and length of the rods enhanced as well. All the samples have the bandgap around 3.05 eV. The FTIR results showed the absorbent functional forces at 870 cm−1 and 1250 cm−1 related with H-C-N wavelengths, and ZnO wavelength ranges from 400 to 515 cm−1. The CH3NH3PbI3 perovskite solar cell device still contained PbI2 as impurities phase. The longer the growing time, the rods resulted by ZnO NRs had the wider diameter and the longer length and they were more homogenous. Meanwhile, the effect of the number of PbI2 impurities resulted in the higher dielectric and smaller current.

The Effect of Strength of Bases and Temperature on the Synthesis of Zn‐Al Layered Double Hydroxides by a Non‐Aqueous ‘Soft Chemical’ Sol‐Gel Method and Formation of High Surface Area Mesoporous ZnAl2O4 Spinel

AbstractLayered double hydroxides are the 2D layered material also known as the anionic clays having the general formula [M1‐x2+Mx3+(OH)2]x+[Ax/n]n−.m H2O where different M2+ ions such as Zn2+, Ni2+, Mg2+, Co2+ and M3+ ions such as Al3+, Cr3+, Ga3+, In3+, Mn3+, Fe3+ are uniformly distributed and orderly prearranged in the brucite‐like sheets and various charge‐compensating anions (An−=CO32−, NO3−, Cl−, OH− ) are present in their interlayer spaces along with the water molecules. During the synthesis of Zn−Al layered double hydroxides by non aqueous soft chemical method the strength of bases as well as the temperature influences immensely the hydrolysis of Zinc acetylacetonate (Zn(acac)2) and Aluminium acetylacetonate (Al(acac)3). Different bases such as sodium hydroxide (NaOH), piperidine, diethylamine and ammonia (NH3) was used and it was found that Zinc acetylacetonate (Zn(acac)2) directly forms Zincite (ZnO) phase without reacting with Aluminium acetylacetonate (Al(acac)3) at temperature of around 80oC. When the temperature was decreased to 0oC from room temperature as well as side by side the strength of bases were increased the formation of Zincite (ZnO) phases reduced. Thus, Zn−Al layered double hydroxide could only be synthesized at 0oC and in presence of stronger bases like sodium hydroxide (NaOH) and piperidine. The X‐ray diffraction analysis showed the presence of low intensity Zincite (ZnO) phases in Zn−Al layered double hydroxide synthesized in presence of sodium hydroxide (NaOH) which was absent in presence of piperidine. Zn−Al layered double hydroxide synthesized were further characterized by thermal analysis (TGA‐DTA), Infrared spectroscopy (FTIR), Scanning electron microscopic and energy dispersive X‐ray spectroscopic (SEM‐EDS) analysis, Brunauer–Emmett–Teller (BET) surface area and pore diameter analysis which showed their different characteristics as the base is changed. Zn−Al layered double hydroxide synthesized in presence of piperidine after thermal treatment at 800oC formed high surface area mesoporous flower platelet like Zinc‐Aluminium Oxide (ZnAl2O4) spinel which have surface area of 124.8 m2g−1 and mesopores of dimensions about 5–20 nm respectively.

ZnO and Cu-based adsorbents for biogas desulfurization at room temperature

Synthesis and structural characterization of ZnO and Cu based materials were done in order to compare chemical, morphological and microstructural effects in sorbent materials for gas-phase desulfurization reaction at room temperatures as a potential application in biogas cleaning. The materials were synthesized through two wet chemical routes, firstly using zinc nitrate, hexamethylenetetramine and NaOH reagents at 70 and 90 °C for ZnO flower-like and rod-like structures, respectively; and secondly a typical calcination of metallic copper to obtain CuO. Powder X-ray diffraction, X-ray fluorescent spectroscopy analysis were realized. Results showed a unique zincite phase for ZnO and three phases in copper samples: Cu0, Cu2O and CuO (76.3, 18.3 and 5.4 wt%). The size of crystal domains varied from 180 to 1600 nm, while the particle size varied from 660 to 1020 nm. These materials were tested in desulfurization reactions at room temperature using a fixed-bed glass reactor. In order to avoid poisoning and asphyxiation risks a non-desulfurized biogas influent was simulated by a gas mixture of N2 and H2S (100 ppm). The reactor was fed with the gas mixture at rate of 450 ml/min (GHSV 9120 h−1). The composition of effluent gas was determined using a biogas detector, coupled with an electrochemical H2S sensor. Results show that CuO and ZnO could be feasible adsorbents for the removal of hydrogen sulfide; however, they became saturated after 300 s while high surface area materials, evidenced by SEM, showed higher saturation capacity. Characterization of wasted adsorbents using electron microscopy techniques and fluorescence X-ray spectroscopy evidenced the presence of metallic sulfides at amounts less than 0.05 wt%, although no crystalline phases were detected in further analysis.

Impact of titanium ions in the hexagonal nanostructured ZnO thin films

ZnO thin films containing different ratios of Ti metal were prepared by the DC/RF sputtering technique. XPS analysis showed the presence of Ti content in the range from 0.9 to 1.5 at.%, and Ti was existed as Ti4+ states. Zincite phase has been detected by XRD technique through all samples and the crystallite size, the strain, and the dislocation density were estimated. Surface morphology and roughness were examined by atomic force microscopy. Optical absorbance and optical band gap were measured and determined. The optical band gap is proposed to be direct and varied from 3.25 to 3.282 eV as the Ti content increase. Photoluminescence properties show a highly intense peak at 412 nm related to the transition from shallow donor level to valence band comes from the interface traps through the grain boundaries.

Low temperature synthesis of ZnO nanowires on GAZO thin films annealed at different temperatures for solar cell application

ZnO nanowires were hydrothermally grown on sputtered gallium and aluminium co-doped ZnO (GAZO) thin films as seed layers and the effect of seed layer annealing temperature on their microstructural and optoelectronic properties was investigated. Atomic force microscopy revealed an increase in the GAZO films' mean particle size and surface roughness with annealing temperature. The GAZO films exhibited a zincite phase with a preferred orientation along the (002) plane and their crystallinity improved with annealing temperature, resulting in low electrical resistivity. The nanowires' alignment improved with seed layer annealing temperature up to 150°C and then deteriorated at 250−350°C. This was attributed to the improvement in nanowire crystallinity up to 150°C and its deterioration at 250–350°C. Energy dispersive spectroscopy confirmed that the nanowires were closer to stoichiometric ZnO (1:1). Raman spectroscopy revealed the presence of few defects and slight residual tensile stress in the nanowires, in corroboration with XRD analysis. The films and nanowires exhibited average visible transmittances around 75–85% and 50–80%, respectively. The least electrical resistivity (7.0×10−3Ωcm) and highest figure of merit (1.02×10−2Ω−1) were obtained for the well-aligned nanowires grown on 150°C annealed films, demonstrating their suitability for solar cell transparent electrode fabrication.

Phase Diagram Study for the PbO-ZnO-CaO-SiO2-"Fe2O3" System in Air with CaO/SiO2 in 1.1 and PbO/(CaO+SiO2) in 2.4 Weight Ratios

An experimental study on the phase equilibrium and the liquidus isotherms for the PbO-ZnO-CaO-SiO2-Fe2O3 system with CaO/SiO2 in 1.1 and PbO/(CaO+SiO2) in 2.4 weight ratios, respectively, was carried out in the temperature range 1100-1300oC (1373-1573 K). High temperature phases were determined by the equilibrium-quenching method. Results are presented in the form of pseudo-ternary sections Fe2O3-ZnO-(PbO+CaO+SiO2). X-Ray diffraction (XRD) and SEM-EDS results showed that the phase equilibria in this system are dominated by the high melting temperature spinel and zincite phases. It was observed that if the system is at a temperature below 1300oC and the total (Fe2O3 + ZnO) is greater than 20 wt%, spinel and/or zincite will be present in the slag system. As an application of the phase diagram, the liquid phase compositions below the liquidus surface were estimated, then their viscosities were calculated using FACTSage software.