Phase transition between sphalerite and wurtzite in ZnS optical ceramic materials

The phase transition behavior of zinc sulfide (ZnS) ceramics consolidated via pressureless and hot press sintering has been investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) analyses. Two types of ZnS powders with different particle sizes and morphologies were employed to study the influence of microstructural features of starting powders on the ZnS phase transition behaviors. The present work has revealed that during sintering of ZnS ceramics, the phase transition behavior varies based on the starting powder particle size and magnitude of the applied pressure. It has been demonstrated that smaller particle sizes lead to an increased degree of “early” phase transformation from sphalerite to wurtzite at 1000 °C. Additionally, the application of uniaxial pressure during sintering can lead to a reverse phase transition from wurtzite to sphalerite while simultaneously inducing twinning, resulting in improved optical transmittance and mechanical hardness.     

Transparent and Luminescent ZnS Ceramics Consolidated by Vacuum Hot Pressing Method

In this study, ZnS powders with homogeneous morphology were synthesized using a colloidal processing method. Vacuum hot pressing was subsequently applied to consolidate the ZnS powders into infrared transparent ceramics (77.3% transmittance at wavelengths of 6.74 and 9.29 μm). The phase composition of the sintered ZnS suggests the presence of wurtzite as a minor phase in addition to the primary sphalerite phase, and microstructural analysis indicates that the ceramics are highly densified. It has been found that the VHP‐sintered ZnS ceramics exhibit blue (450 nm) and green (530 nm) luminescence, which is due to the formation of zinc vacancies and sulfur interstitials, respectively, during the sintering process.     

Synthesis of Zinc Sulfide Nanostructures with Different Sulfur Sources via Mild Hydrothermal Route: Investigation of Crystal Phase and Morphology

In this paper, we report a facile hydrothermal route to prepare different morphologies of zinc sulfide nanostructures, using a new inorganic precursor, zinc phthalate [Zn(pht)(H₂O)]_n, and different sulfur sources. This study focuses on the effect of different sulfur sources on the crystal structure and morphology of the products. The structural and morphological studies of the products were performed by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and selected area electron diffraction. The high temperature (over 1020 °C) hexagonal ZnS nanostructured spheres self-assembled from ZnS nanocrystals have been synthesized at a low temperature of 160 °C by using thioglycolic acid as sulfur source.     

Novel simple solvent-less preparation,characterization and degradation of the cationic dye over holmium oxide ceramic nanostructures

Pure holmium oxide ceramic nanostructures were prepared via a new simple approach. Nanostructures were synthesized by heat treatment in air at 600 °C for 5 h, utilizing [Ho L(NO₃)₂]NO₃ (L=bis-(2-hydroxy-1-naphthaldehyde)-butanediamine Schiff base ligand), as precursor, which was prepared via a solvent-free solid–solid reaction from different molar ratios of holmium nitrate and Schiff base ligand. The as-prepared nanostructures were characterized by field emission scanning electron microscopy (FESEM), thermo-gravimetric analysis (TGA), X-ray diffraction (XRD), energy dispersive X-ray microanalysis (EDX), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectroscopy and Fourier transform infrared (FT-IR) spectroscopy. It was found that the calcination temperature and molar ratio of holmium nitrate and Schiff base ligand have significant and key effect on the morphology and particle size of the holmium oxide. To investigate the catalytic properties of as-obtained holmium oxide nanostructures, the photocatalytic degradation of rhodamine B as cationic dye under ultraviolet light irradiation was performed.     

Synthesis of ZnS nanorods by a surfactant-assisted soft chemistry method

ZnS nanorods were synthesized using solvothermal process with ethylenediamine as a bidentate ligand to form Zn²⁺ complexes and dodecylthiol providing an effective control over the crystal growth of ZnS nanorod. The diameter and length of ZnS nanorods obtained are ∼40 nm and 1.0–1.5 μm, respectively. The microstructure and composition of the nanorods were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). And the optical properties of ZnS nanorods were examined by photoluminescence (PL) spectrum.     

Blue light emission from barium doped zinc sulfide nanoparticles

ZnS nanoparticles with Ba²⁺doping have been prepared at room temperature through chemical route, namely the chemical precipitation method. The nanostructures of the prepared nanoparticles have been analyzed using X-ray diffraction (XRD) for phase analysis, Field emission scanning electron microscope (FESEM) for the morphological characterization, UV–Vis–NIR spectrophotometer for determining band gap energy and fluorescence spectroscopy for determining the emission wave length. The sizes of as prepared nanoparticles are found to be in 9–10 nm range. FESEM morphology shows the formation of nanostructure of ZnS samples. The value of optical band gap has been found to be in range 4.10–4.63 eV. Room temperature photoluminescence (PL) spectrum of the undoped sample exhibits emission in the blue region with multiple peaks under UV excitation. On the other hand, the Ba²⁺ doped ZnS samples exhibit visible light emissions under the same UV excitation wavelength of 310 nm.     

XPS and optical studies of different morphologies of ZnO nanostructures prepared by microwave methods

Zinc oxide (ZnO) nanostructures of various morphologies were prepared using a microwave-assisted aqueous solution method. Herein, a comparative study between three different morphologies of ZnO nanostructures, namely nanoparticles (NPs), nanoflowers (NFs) and nanorods (NRs) has been reviewed and presented. The morphologies of the prepared powders have been studied using field effect scanning electron microscopy (FESEM). X-ray diffraction (XRD) results prove that ZnO nanorods have biggest crystallite size compared with nanoflowers and nanoparticles. The texture coefficient (T_c) of three morphologies has been calculated. The T_c changed with varying morphology. A comparative study of surfaces of NPs, NFs and NRs were investigated using X-ray photoelectron spectroscopy (XPS). The possible growth mechanisms of ZnO NPs, NFs and NRs have been described. The optical properties of the ZnO nanostructures of various morphologies have been investigated and showed that the biggest crystallite size of ZnO nanostructures has lowest band gap energy. The obtained results are in agreement with experimental and theoretical data of other researchers.     

Preparation of ZnO nanorod by solvothermal reaction of zinc acetate in various alcohols

Solvothermal reaction of zinc acetate in various alcohols resulted in the formation of zinc oxide (ZnO) nanorods. The effects of reaction conditions on the product morphology as well as crystallization mechanism were investigated by using X-ray diffraction (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) techniques. It was found that average diameter and length of the nanorods increased with an increase in reaction temperature or the initial concentration of zinc acetate. On the contrary, the aspect ratio of the product depended upon type of alcohol used as the reaction medium. The aspect ratio of ZnO nanorods increased from 1.7 to 5.6 when the alcohol was changed from 1-butanol to 1-decanol. An investigation of the reaction mechanism suggested that the formation of ZnO nanorods was initiated from the esterification reaction between zinc acetate precursor and alcohol to form ZnO seeds.     

ZnSe纳米棒的水热法合成及发光性能研究

以氢氧化钠、单质硒粉与4种不同锌盐为起始原料、EDTA为软模板剂,在190℃水热条件下合成了ZnSe半导体材料。采用X-射线粉末衍射(XRD)、扫描电镜(SEM)、X-射线光电子能谱(XPS)、荧光光谱(FS)、紫外可见吸收光谱(UV-Vis)等测试手段对所得样品的物相结构、化学组成、形貌和性能进行了测试。结果表明,所得ZnSe为立方闪锌矿型结构且纯度较高;锌源对产物的形貌具有一定的影响;合成的粉体在紫外区有强的吸收峰,具有良好的光学性能。     

锌基硫化锌纳米棒阵列的溶剂热原位合成及其光学性质

利用金属锌片为锌源,采用溶剂热法在锌片表面生长出垂直于表面的直径约为200nm的硫化锌纳米棒阵列。利用X射线衍射(XRD)和扫描电镜(SEM)对不同反应时间制备的锌基硫化锌纳米结构进行表征发现,延长反应时间有助于得到均匀一致的定向生长的纳米棒阵列。利用漫反射紫外可见吸收光谱(UV/Visdiffuse-reflectance spectra)对锌基硫化锌纳米棒阵列在紫外可见光波段的光学吸收性能进行了研究,结果表明合成的结晶性良好的ZnS纳米棒阵列其带边吸收在347nm,对应的禁带宽度为3.47eV。提出了硫化锌纳米棒阵列在形成过程中的化学反应机理。     

Application of impregnation combustion method for fabrication of nanostructure CuO/ZnO composite oxide: XRD,FESEM, DRS and FTIR study

Nanostructured CuO/ZnO composite oxide was prepared by a novel impregnation combustion method using copper nitrate and zinc oxide tetrapod. The X-ray diffraction patterns revealed that CuO/ZnO composite oxide was formed. The effects of different impregnation combustion parameters on the properties of composite were studied by field-emission scanning electron microscope (FESEM), powder X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR) and UV–vis diffuse reflectance spectrum (DRS). The synthesis of ZnO–CuO nanocomposites through impregnation of a zinc oxide tetrapod with copper nitrate aqueous sodium carbonate solutions is reported. During thermal treatment the samples evolve toward the formation of nanocrystalline ZnO particles (zincite phase) dispersed onto tenorite, CuO annealed at 450 °C. XRD patterns of the precursors calcined at 450 °C showed the formation of the zincite–tenorite phases. Field emission scanning electron microscopy (FESEM) exhibited loosely agglomerated hexagonal particles with uniform morphology having a size around 50 nm.     

Zinc oxide nanostructure decorated amorphous carbon nanotubes: An improved field emitter

Amorphous carbon nanotubes (aCNTs), synthesized through a low-temperature simple method have been decorated with chemically synthesized different zinc oxide (ZnO) nanostructures like nanocones and nanoflowers. The as-prepared samples have been characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM). It has been found that attachment of ZnO nanostructure can effectively enhance the field electron emission properties of the aCNTs. Modification with ZnO nanoflower-like structure can reduce the turn-on field of aCNTs from 8.91 to 3.64 V/μm. The results have been explained in terms of increased roughness which in-turn led to large enhancement of the local electric field and thus facilitated electron emission from this hybrid emitter.     

Effects of Temperature, Pressure, and Metal Promoter on the Recrystallized Structure and Optical Transmission of Chemical Vapor Deposited Zinc Sulfide

Structural changes from processing in polytype-rich zinc sulfide (ZnS) are complex and poorly understood. In this study, recrystallization was induced in chemical vapor deposited ZnS by annealing and hot isostatic pressing (HIPping). Samples were characterized using optical microscopy, SEM, TEM, electron diffraction, polycrystalline and powder X-ray diffraction, and transmission spectroscopy. Recrystallization was found to reduce the hexagonality and increase the {111} texture of as-deposited ZnS. Changes in hexagonality and texture can occur independently of each other. HIPped ZnS with superior transmission exhibits both a change in texture and a reduction in hexagonal content. Reduction in hexagonality, alone, was not sufficient to improve optical transmission from the visible to the infrared. For the first time, the effects of pressure, temperature, and the presence of platinum on recrystallization during commercial ZnS HIPping are separated and identified. Platinum was found to actively promote recrystallization and silver demonstrated a similar effect. Several theories focusing on the unique polytypic nature of ZnS are offered to explain the changes in structure and properties occurring during recrystallization. These findings contribute to a broader understanding of the nature of order–disorder and martensitic phase transformations in ceramic materials.     

ZnS, CdS and HgS Nanoparticles via Alkyl-Phenyl Dithiocarbamate Complexes as Single Source Precursors

The synthesis of II-VI semiconductor nanoparticles obtained by the thermolysis of certain group 12 metal complexes as precursors is reported. Thermogravimetric analysis of the single source precursors showed sharp decomposition leading to their respective metal sulfides. The structural and optical properties of the prepared nanoparticles were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) UV-Vis and photoluminescence spectroscopy. The X-ray diffraction pattern showed that the prepared ZnS nanoparticles have a cubic sphalerite structure; the CdS indicates a hexagonal phase and the HgS show the presence of metacinnabar phase. The TEM image demonstrates that the ZnS nanoparticles are dot-shaped, the CdS and the HgS clearly showed a rice and spherical morphology respectively. The UV-Vis spectra exhibited a blue-shift with respect to that of the bulk samples which is attributed to the quantum size effect. The band gap of the samples have been calculated from absorption spectra and werefound to be about 4.33 eV (286 nm), 2.91 eV (426 nm) and 4.27 eV (290 nm) for the ZnS, CdS and HgS samples respectively.     

Structural and optical properties of ZnS thin films deposited by RF magnetron sputtering

Zinc sulfide [ZnS] thin films were deposited on glass substrates using radio frequency magnetron sputtering. The substrate temperature was varied in the range of 100°C to 400°C. The structural and optical properties of ZnS thin films were characterized with X-ray diffraction [XRD], field emission scanning electron microscopy [FESEM], energy dispersive analysis of X-rays and UV-visible transmission spectra. The XRD analyses indicate that ZnS films have zinc blende structures with (111) preferential orientation, whereas the diffraction patterns sharpen with the increase in substrate temperatures. The FESEM data also reveal that the films have nano-size grains with a grain size of approximately 69 nm. The films grown at 350°C exhibit a relatively high transmittance of 80% in the visible region, with an energy band gap of 3.79 eV. These results show that ZnS films are suitable for use as the buffer layer of the Cu(In, Ga)Se₂ solar cells.     

Aluminum nitride‐single walled carbon nanotube nanocomposite with superior electrical and thermal conductivities

Development of aluminum nitride (AlN)‐single walled carbon nanotube (SWCNT) ceramic‐matrix composite containing 1‐6 vol% SWCNT by hot pressing has been reported in this article. The composites containing 6 vol% SWCNT are dense (~99% relative density) and show high dc electrical conductivity (200 Sm^?1) and thermal conductivity (62 Wm^?1K^?1) at room temperature. SWCNTs contain mostly metallic variety tubes obtained by controlled processing of the pristine tubes before incorporation into the ceramic matrix. Raman spectroscopy and field emission scanning electron microscopy (FESEM) of the fracture surface of the samples show the excellent survivability of the SWCNTs even after high‐temperature hot pressing. The results indicate the possibility of preparation of AlN nanocomposite for use in plasma devices and electromagnetic shielding.     

Preparation of nanostructure CuO/ZnO mixed oxide by sol–gel thermal decomposition of a CuCO3 and ZnCO3: TG,DTG, XRD,FESEM and DRS investigations

Nanostructure CuO/ZnO mixed oxide was systematically prepared via the sol–gel route using zinc and copper carbonates as precursors (molar ratio of 2:1) under thermal decomposition. The zinc and copper carbonates precursors have been synthesized by a simple chemical reaction in high yield and characterized by its melting point, FT-IR and thermal analysis (TG/DTG). The TG/DTG analysis proved that the thermal decomposition of zinc and copper carbonates precursors at 255 °C and 289 °C respectively. Thermo-gravimetric analysis (TG-DTG), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and diffuse reflectance spectroscopy (DRS) studies were undertaken to investigate the thermal properties and electronic structure of the CuO/ZnO mixed oxide catalysts. XRD data of the samples proved the formation of the nano-crystalline CuO/ZnO mixed oxide. Scanning electron microscopy (SEM) showed that the spherical-like particles have a diameter in the range 35–45 nm. Optical spectra of the nanostructure show a band peaked at 1.35 eV which is associated to near band gap transitions of CuO and a band centered at about 3.00 eV related to band gap transitions of ZnO nanostructures.     

Photocatalytic and antibacterial characteristics of decorated polyester textile with ceramic nanoparticles of cobalt ferrite

In this study, a multifunctional textile profiting from photocatalytic activity, magnetic, and antibacterial properties was generated through decorating polyester fabric with cobalt ferrite (CoFe₂O₄) nanoparticles using the co-precipitation technique. The X-ray diffraction (XRD) results supported the successful decoration of fabrics with CoFe₂O₄ magnetic nanoparticles. Field emission electron scanning microscopy (FESEM) images accompanied by energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) analyses demonstrated the morphology, dispersion, and chemical structure of particles on the surface. The mean particle size of cobalt ferrite was measured to be approximately 40 nm. Vibrating sample magnetometer (VSM) results confirmed the ferrimagnetic behavior of the decorated fabrics with saturation magnetization (M_s) and coercivity (H_c) of 1.8 emu/g and 1902 Oe, respectively. The UV–vis diffuse reflectance spectrum (DRS) and photoluminescence (PL) data indicated the appropriate performance under visible light irradiation and postponed electron-hole recombination of the decorated fabric, respectively. The maximum MB degradation efficiency of 97% after 180 min of visible light illumination was obtained. The active species trapping analyses indicated that hydroxyl radicals (^●OH) were the effective species in the photocatalytic degradation mechanism. The decorated sample with the best photocatalytic activity revealed more than 99% reduction in the number of colonies against gram-negative and gram-positive bacteria after 24 h contact time, which validated its excellent potential for antibacterial applications. Outstanding photocatalytic and antibacterial characteristics of the decorated textile with cobalt ferrite nanoparticles turn it into promising composite material for self-cleaning purposes.     

超声辅助均匀沉淀法由前躯体ZnS制备ZnO纳米颗粒及其表征

前躯体ZnS在超声辅助60℃的低温条件下,采用醋酸锌为锌源、硫代乙酰胺为硫源来制备,然后采用在空气中热处理前躯体ZnS的方法制备了直径约为20~40 nm的ZnO纳米颗粒。所得产物分别采用红外光谱(FTIR)、热重-差热分析(TGA-DTA)、X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、透射电镜(TEM)、电子能谱(EDS)和荧光光谱(PL)进行表征。实验结果表明,所得产物ZnO为六方纤锌矿结构,且结晶性很好,并且随着超声时间的延长其粒径有所降低。室温PL光谱表明,样品在400~550 nm内有3个较强的荧光发射峰。     

Investigation of hot pressed ZrB2–SiC–carbon black nanocomposite by scanning and transmission electron microscopy

Hybrid ZrB₂-based composite having 10 vol% nano-sized carbon black and 20 vol% SiC was fabricated by vacuum hot pressing at 1850 °C under 20 MPa for 60 min. The microstructure and sinterability of the as-sintered ceramic was studied by X-ray powder diffraction, scanning electron microscopy, X-ray spectroscopy, scanning transmission electron microscopy and transmission electron microscopy analyses. A fully-dense hybrid composite could be achieved by hot pressing method under the aforementioned conditions. No new in-situ phase formation was detected after sintering process. Although the densification progressed in a non-reactive manner, the addition of carbonaceous material assisted the sinterability acting as the surface oxides cleaner. The precise phase and nanostructural investigations of the prepared ceramic verified the partial graphitization of carbon black and conversion of amorphous nano-additive into crystalline graphite nano-flakes.