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Surface and bulk crystallization of Ba1-xSrxZn2Si2O7 from glasses in the system BaO/SrO/ZnO/SiO2 doped with Nb2O5 or Ta2O5
摘要： Stoichiometric 0.5 BaO·0.5 SrO·2 ZnO·2 SiO2 glass was doped with 5 mol% Nb2O5 or Ta2O5. The effect of these additives on the crystallization behavior was studied using thermal analyses, X-ray diffraction, as well as scanning electron microscopy including elemental analyses. The addition of Nb2O5 or Ta2O5 significantly increases the glass stability enabling the preparation of crystal-free BaO·SrO·ZnO·SiO2 glasses with almost stoichiometric composition. Besides the desired main crystal phase Ba1-xSrxZn2Si2O7, also alkaline earth tantalates and niobates as well as Zn2SiO4 are observed. The Nb-containing glass shows solely surface crystallization, whereas in the Ta-containing glass, additionally numerous Ba0.44TaO2.94 crystals precipitate in the bulk acting as seeds for the nucleation of Ba1-xSrxZn2Si2O7. If the surface crystallized layer of Ba1-xSrxZn2Si2O7 approaches such a Ba0.44TaO2.94 crystal or gets close to it, then the crystallization of Ba1-xSrxZn2Si2O7 is initiated. It is supposed that these nucleation processes are notably facilitated by the stresses present in these glass-ceramics.
关键词： barium strontium zinc silicate,heterogeneous nucleation,Glass crystallization
更新于2025-09-23 15:23:52
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Shock wave induced enhancement of optical properties of benzil crystal
摘要： In this article, we present the results of the experimental work on the impact of shock waves on optical properties of benzyl crystalline material. Test material of benzil crystal is grown along [100] plane by Sankaranarayana - Ramasamy method. In the present work, the functional shock waves of Mach number 1.7 are generated from pressure driven shock tube. The optical properties of test material are investigated by UV-Visible spectrometer over the range between 200 and 800nm. The observed results show that the intensity of the absorption spectrum is inversely proportional to the number of exposed shock waves. The direct and indirect optical band gap energy (Eg) and Urbach tail energy (Ug) are determined from the optical absorption spectrum for pre and post shock wave loaded condition and found that shock wave loaded test crystal has high band gap energy. The optical constants namely extinction coefficient, real and imaginary parts of the dielectric constant, skin depth, optical density, optical conductivity and electrical conductivity are investigated and the obtained results are compared with post shock wave loaded benzil crystal with the incident light possessing wavelength at 700 nm. The results are found to be very impressive for the shock wave recovery experiments that are to be clearly discussed.
关键词： Transmission,Shock Waves,Re-crystallization,Benzil crystal,Optical properties
更新于2025-09-23 15:23:52
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EFFECT OF VOLTAGE ON TIO2 NANOTUBES FORMATION IN ETHYLENE GLYCOL SOLUTION
摘要： Anodization of Ti foils in ethylene glycol (EG) containing ammonium fluoride (NH4F), and hydrogen peroxide (H2O2) was carried out to study the effect of voltage on the formation of TiO2 nanotubes. The crystalline phase of the TiO2 nanotubes without further heat treatment were studied. The TiO2 nanotube arrays were produced by anodization of Ti foil at three different voltage; 10, 40, and 60 V in a bath with electrolytes composed of ethylene glycol (EG), ammonium fluoride (NH4F), and hydrogen peroxide (H2O2). The H2O2 is a strong oxidizing agent which was used as oxygen provider to increase the oxidation rate for synthesizing highly ordered and smooth TiO2 nanotubes. Anodization at voltage greater than 10 V leads to the formation of tubular structure where higher anodization voltage (~ 60 V) yield to larger tube diameter (~ 180 nm). Crystallinity of the nanotubes is improved as the voltage was increased. The transformation of amorphous to anatase can be obtained for as anodized TiO2 without any heat treatment. The Raman spectra results show the anodization at 40 V and 60 V gives anatase peak in which confirms the crystalline phase. The stabilization of the crystalline phase is due to the oxygen vacancies and ionic mobilities during the anodization at high voltage.
关键词： anatase,TiO2 nanotubes,crystallization,anodization
更新于2025-09-23 15:23:52
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AIP Conference Proceedings [Author(s) 1ST INTERNATIONAL CONGRESS ON SOLAR ENERGY RESEARCH, TECHNOLOGY AND APPLICATIONS (ICSERTA 2018) - Ouarzazate, Morocco (8–10 May 2018)] - Synthesis and MID-IR characterization of strontium hexaferrite nanoparticles using gel to crystallization technique
摘要： Synthesis and MID-IR characterization of strontium hexaferrite nanoparticles using gel to crystallization technique. Strontium hexaferrite (SrFe12O19) nanoparticles have been synthesized using gel to crystallization technique. Citric acid, iron nitrate and strontium nitrate were used as starting materials to prepare the gel. The prepared gel was heated at 100°C for 4 hrs in muffle furnace and sample was annealed at 800°C for 4 hrs. The prepared sample was characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The XRD pattern confirms the formation of single phase SrFe12O19 nanoparticles. The FTIR spectrum shows the absorption bands in the range 400-600 cm-1 which are assigned to metal-oxygen vibrations. The prepared nanoparticles show the formation of single phase and can be used for various applications such as magnetic recording media, microwave devices and permanent magnets.
关键词： XRD,FTIR,gel to crystallization,Strontium hexaferrite,nanoparticles
更新于2025-09-23 15:23:52
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Crystallization kinetics and thermal stability of ZrO <sub/>2</sub> monolithic aerogel improved by SiO <sub/>2</sub> layer
摘要： ZrO2 aerogel modified by SiO2 (ZSA) was synthesized by aging ZrO2 gel in tetraethoxysilane (TEOS) solution using ZrOCl2·8H2O as precursor, and 1,2-propylene oxide (PO) as gelation agent followed by ethanol supercritical fluid drying. Crystallization kinetics and thermal stability of ZSA while calcined at elevated temperature were studied comparing with pure ZrO2 aerogel. The prepared samples were characterized using TG-DSC, N2 adsorption/desorption, SEM and TEM. The results show that thermal stability of ZSA are highly improved due to the SiO2 layer hindering the proliferation, nucleation and growth process of ZrO2.
关键词： ZrO2,thermal stability,aerogel,SiO2,crystallization kinetics
更新于2025-09-23 15:23:52
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Diversity of TiO <sub/>2</sub> : Controlling the Molecular and Electronic Structure of Atomic-Layer-Deposited Black TiO <sub/>2</sub>
摘要： Visually black, electrically leaky, amorphous titania (am-TiO2) thin films were grown by atomic layer deposition (ALD) for photocatalytic applications. Broad spectral absorbance in the visible range and exceptional conductivity are attributed to trapped Ti3+ in the film. Oxidation of Ti3+ upon heat treatment leads to a drop in conductivity, a color change from black to white and crystallization of am-TiO2. ALD grown black TiO2, without any heat treatment, is subject to dissolution in alkaline photoelectrochemical conditions. The best photocatalytic activity for solar water splitting is obtained for completely crystalline white TiO2.
关键词： atomic layer deposition,photocatalysis,titanium dioxide,protecting overlayers,crystallization,oxide defects,water splitting
更新于2025-09-23 15:23:52
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Ultra-Rapid Crystallization of L-Alanine Using Monomode Microwaves, Indium Tin Oxide and Metal-Assisted and Microwave-Accelerated Evaporative Crystallization
摘要： The use of indium tin oxide (ITO) and focused monomode microwave heating for the ultra-rapid crystallization of L-alanine (a model amino acid) is reported. Commercially available ITO dots (< 5 mm) attached to blank poly(methyl)methacrylate (PMMA, 5 cm in diameter with 21-well silicon isolators: referred to as the iCrystal plates) were found to withstand prolonged microwave heating during crystallization experiments. Crystallization of L-alanine was performed at room temperature (a control experiment), with the use of two microwave sources: a 2.45 GHz conventional microwave (900 W, power level 1, a control experiment) and 8 GHz (20 W) solid state, monomode microwave source with an applicator tip that focuses the microwave field to a 5-mm cavity. Initial appearance of L-alanine crystals and on iCrystal plates with ITO dots took 47 ± 2.9 min, 12 ± 7.6 min and 1.5 ± 0.5 min at room temperature, using a conventional microwave and focused monomode microwave heating, respectively. Complete evaporation of the solvent using the focused microwaves was achieved in 3.2 ± 0.5 min, which is ~52-fold and ~172-fold faster than that observed at room temperature and using conventional microwave heating, respectively. The size and number of L-alanine crystals was dependent on the type of the 21-well iCrystal plates and the microwave heating method: 33 crystals of 585 ± 137 μm in size at room temperature > 37 crystals of 542 ± 100 μm in size with conventional microwave heating > 331 crystals of 311 ± 190 μm in size with focused monomode microwave. FTIR, optical microscopy and powder X-ray diffraction analysis showed that the chemical composition and crystallinity of the L-alanine crystals did not change when exposed to microwave heating and ITO surfaces. In addition, theoretical simulations for the binding of L-alanine molecules to ITO and other metals showed the predicted nature of hydrogen bonds formed between L-alanine and these surfaces.
关键词： ITO,Microwave heating,Silver island films,Evaporative crystallization
更新于2025-09-23 15:22:29
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Stress and Microstructure Study of W/Si X-ray Multilayers with Different Structural Parameters
摘要： X-ray Timing and Polarimetry (XTP) telescope is proposed by using nested focusing optics with a large effective area for studies in the field of high energy physics (energy region of 1–30 keV). High-reflectance and low-stress W/Si multilayers are required for this telescope to improve the spectral response and maintain the figure quality of the mirrors simultaneously. In this paper, we focused on the study of stress and layer structure of W/Si periodic multilayers at different d-spacings (thickness of period), thickness ratios, and bilayer numbers. The results show that the stress of the multilayer increased from ?73.3 to ?465.5 MPa with increase in the d-spacing from 2.7 to 5.5 nm, while the change in the average interface width was negligible, from 0.31 to 0.36 nm. For the multilayers prepared with different thickness ratios of W, from 0.3 to 0.67 (d = 3.7 nm), the lowest stress appeared at the ratio of ～0.46, and the average interface width was unchanged. The number of bilayers (N = 80–160) had negligible effects on both the layer structure and the stress, and the multilayers exhibited a very smooth surface morphology with a root-mean-square roughness of 0.19 nm. To further study the microstructural changes of the multilayer, X-ray diffraction measurements of the samples with different d-spacings and thickness ratios were performed. An increased crystallization along with phase changes were observed in the samples prepared with thicker W layers, which can increase the compressive stress of the multilayer.
关键词： W/Si Multilayer,Stress,X-ray,Crystallization,Interface Width
更新于2025-09-23 15:22:29
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Ferroelectric β-crystalline phase formation and property enhancement in polydopamine modified BaTiO3/poly (vinylidene fluoride-trifluoroethylene) nanocomposite films
摘要： Piezopolymer poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) films doped with BaTiO3 (BT) and polydopamine coated BT (BT-Pdop) nanoparticles were prepared by spin-coating method. Polydopamine modifies the interfaces of inorganic BT nanoparticles and PVDF-TrFE matrix with its polar hydroxyl groups, enhancing the piezoelectric β-phase. BT-Pdop nanoparticles were obtained in pH 8.5 buffer solution. For ferroelectric PVDF-TrFE, the favorable piezoelectric property comes from its ferroelectricity. Therefore, we studied the ferroelectric property of the nanocomposite films. The nanocomposite thin films possess better ferroelectric property than the pure PVDF-TrFE thin films, as demonstrated by the ferroelectric hysteresis curves. The remanent polarizations are 13.59 and 13.94 μC/cm2 after the doping of 1.0 wt% BT and 1.0 wt% BT-Pdop, respectively, which are about twice that of neat PVDF-TrFE. The piezoelectric β-ferroelectric phase increases with doping, according to X-Ray Diffraction analysis. In addition, the images of polarized optical microscopy and atomic force microscopy also reveal significant enhancement in crystallinity. The neat PVDF-TrFE is a semicrystalline polymer and the size of crystalline spherulites increases with the addition of BT and BT-Pdop nanoparticles. However, even the crystallinity of PVDF-TrFE considerably improved with polydopamine interfacial modification of BT, the increase of remanent polarization due to Pdop is only marginal. We infer that there are other defects at interfaces of BT-Pdop doped PVDF-TrFE nanocomposites which counteract the beneficial effect of the polar OH of polydopamine. Considerable enhancement on ferroelectric property of BT-Pdop doped PVDF-TrFE nanocomposites is expected after these issues are addressed.
关键词： nanoparticles,modification,crystallization,thin films,ferroelectricity
更新于2025-09-23 15:21:21
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Preparing Semiconducting Nanoribbons with Tunable Length and Width via Crystallization-Driven Self-Assembly of a Simple Conjugated Homopolymer
摘要： Precise control of width and length of one-dimensional (1D) semiconducting nanostructures has attracted much attention owing to its potential for optoelectronic applications. However, regulating both their length and width using conjugated polymers or even block copolymers is a huge challenge. To solve this problem, we synthesized a unique conjugated polyacetylene homopolymer by living cyclopolymerization, which spontaneously formed 1D nanoribbons via in situ nanoparticlization. Interestingly, their widths could be controlled from 8 to 41 nm, which were directly proportional to their degree of polymerization. Furthermore, a self-seeding technique via crystallization-driven self-assembly (CDSA) was used to control the length of the nanoribbons up to 5.2 μm with narrow distributions less than 1.1. Interestingly, adding a block copolymer unimer to these nanoribbons produced triblock comicelles by the living CDSA mechanism. Finally, these nanoribbons were visualized directly by super-resolution optical fluorescence microscopy. Now, one can modulate both length and width of 1D nanoribbons simultaneously.
关键词： semiconducting nanostructures,crystallization-driven self-assembly,nanoribbons,optoelectronic applications,conjugated polymers
更新于2025-09-23 15:21:21