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1.
The chemical reactivity of the ligand initially coordinated on the TiO2 precursor plays a decisive role in the morphology of TiO2:poly(N-vinylcarbazole) (PVK) thin film elaborated by in situ generation of the inorganic phase in the polymer matrix. The final aim of this study is to prepare a new nanocomposite TiO2:poly(N-vinylcarbazole) (PVK) thin film from hydrolysis-condensation of titanium alkoxide in polymer thin film. In this context, we synthesized a new TiO2 precursor, the tetrakis (9H-carbazole-9-yl-ethyl-oxy) [Ti(OeCarb)4], bearing ligands close to the repetitive unit structure of the PVK to improve the interaction between both materials. In this study, the synthesis and reactivity to hydrolysis of Ti(OeCarb)4 is presented. Ti(OeCarb)4 was elaborated from alcoholysis reaction between titanium isopropoxide [Ti(iOPr)4] and 9H-carbazole-9-ethanol (ECOH) and identified by 1H and 13C NMR spectroscopy. The reactivity to hydrolysis-oxolation of Ti(OeCarb)4 was evaluated first in aqueous media by in situ 1H NMR spectroscopy analysis. Moreover, reactivity of Ti(OeCarb)4 to surrounding humidity was evaluated in thin film by X-ray photoelectron spectroscopy (XPS). Results show that steric hindrance of 9H-carbazole-9-yl-ethyl-oxide ligands do not influence the hydrolysis-condensation process in aqueous media in our experimental conditions when compared to [Ti(iOPr)4] but decrease the reactivity when the precursor is simply exposed to air humidity. 相似文献
2.
The distribution of gas inclusions in single-crystal sapphire ribbons with different crystallographic orientations, grown by the Stepanov method, is analyzed. In all ribbons gas inclusions are observed only in thin surface layers located at a depth of about 100 μm. One characteristic feature is the presence of several zones with different distributions and morphologies of inclusions. We observed inclusions of the two types: cylindrical pores and microbubbles. The differences in the morphology and zonality of the gas-inclusion distribution are consistent with the α-Al2O3 crystallography. 相似文献
3.
This paper is to investigate the growth of Nd:YVO4 (yttrium vanadate) crystal by the modified Czochralski technique with a submerged plate. Numerical studies are performed to examine melt convection and heat transfer during Nd:YVO4 growth. The attention is paid to study the effects of initial elevation of the submerged plate, crystal diameter, and melt level on melt inclusions. It is found that the increase in crystal rotation rate and crystal diameter, and the decrease in melt level will increase the axial temperature gradient at the edge and in the center of the crystal, and change the interface shape from convex to flat. The experiments are also carried out to confirm the feasibility of the proposed new technique for controlling melt inclusions in Nd:YVO4 crystal growth. 相似文献
4.
N. V. Zubkova D. Yu. Pushcharovsky G. Giester I. V. Pekov A. G. Turchkova E. Tillmanns N. V. Chukanov 《Crystallography Reports》2006,51(3):379-382
The crystal structure of a Pb-exchanged form of zorite is studied by X-ray diffraction: Pb3.95(Ca0.1Sr0.05)[Ti(Ti0.80Nb0.20)4Si12O38(OH)] · 9.52H2O (sp. gr. Cmmm, R = 0.0530 for 680 independent reflections). The structure retains the mixed polyhedral framework of zorite, Na6[Ti(Ti,Nb)4(Si6O17)2(O,OH)5] · 11H2O. This framework is composed of xonotlite-like [Si6O17] ribbons linked to each other by columns of vertex-sharing (Ti,Nb)O6 octahedra and isolated TiO5 half-octahedra. Lead atoms in the Pb-exchanged form occupy one site, unlike Cs cations in the Cs-exchanged form of zorite, which are strongly disordered and partially occupy eight positions. The position of Pb2+ cations corresponds to the Na(2) position in the zorite structure, the Sr position in the Sr-exchanged form of ETS-4, and the K position in the K-exchanged form and is similar to the position of the water molecule W(3) in the structure of the Cs-exchanged form of zorite. 相似文献
5.
G. H. Cao Y. N. Zhou N. Liu X. Li A. M. Russell D. Gerthsen 《Crystal Research and Technology》2014,49(5):338-344
Bulk Ti65Fe35 and (Ti65Fe35)96.15‐xSn3.85Nbx (x = 0, 3, 5 and 7 at.%) alloys were prepared by cold crucible levitation melting, and tested in compression at room temperature. The Sn and Nb modified hypereutectic Ti‐Fe alloys exhibited improved mechanical properties under compression. (Ti65Fe35)93.15Sn3.85Nb3 alloy displayed an ultimate compressive strength of 2.7 GPa and a compressive plastic strain of 15%. Electron microscope observations revealed Ti‐Fe(Sn,Nb) alloys having a bimodal microstructure with micrometer‐scale primary TiFe dendrites distributed in an ultrafine eutectic (β‐Ti+TiFe) matrix. The orientation relationship of β‐Ti with TiFe phases is TiFe (011)[100] ∥ β‐Ti (011)[100]. The improved mechanical properties are attributed to the morphology of the phase constituents and the larger lattice mismatches between β‐Ti and TiFe phases due to the additions of Sn and Nb. 相似文献
6.
V. S. Sergienko 《Crystallography Reports》2004,49(6):907-929
Structural characteristics of peroxo complexes of transition metals of Groups IV and V (Ti, V, Nb, and Ta) with the ratios M: O2 = 1: 1, 1: 2, 1: 3, and 1: 4 and alkyl peroxo complexes of Ti, Hf, and V have been considered. The structural manifestation of the trans effect of η2-coordinated peroxo ligand in pseudooctahedral Ti, Nb, and V monoperoxo complexes is characterized. The structural manifestations of the trans effect of multiply bonded peroxo and oxo ligands in monooxomonoperoxo complexes of vanadium(V) are compared. 相似文献
7.
Cerium‐doped lutetium oxyorthosilicate crystals (Lu2SiO5:Ce) with dimension of ∅︁50 × 60 mm were grown by Czochralski method from an inductively heated iridium crucible. The vaporized substance during growth was examined with XRD and proved to be SiO2. The vertical and the screw strips existing on the surface of the boule were observed with optical microscope and tested with electron microprobe. They are confirmed to be iridium from the crucible and harmful to the crystal growth. The cleavage orientation of LSO was proved to be (110) and it is one of factors to cause crystal cracking. The scattering particles in LSO crystals are analyzed to be mainly composed of Lu2O3 inclusions. Two possible origins on these inclusions are proposed. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
8.
Using electron microscopy methods it has been determined that there are numerous crystalline inclusions in evaporated layers of amorphous selenium. The density, dimensions, modification and distribution in the cross section of a layer are essentially dependent upon the method of layer preparation. The maximum micro-inclusion density is observed in layers evaporated at a substrate temperature (ts) between 8 to 30°C. These layers also possess crystallites of monoclinic modification. In layers evaporated at ts ? 50°C inclusions of trigonal modification prevail.The parameters of the deep trapping levels for holes and electrons have been determined from photodischarge kinetics. The origin of these levels is found to be related to the phase transition. The hole traps are caused by the crystalline formation of trigonal modification, and the electron traps by crystallites of monoclinic modification. 相似文献
9.
N. V. Zubkova D. Yu. Pushcharovsky G. Giester I. V. Pekov A. G. Turchkova N. V. Chukanov E. Tillmanns 《Crystallography Reports》2005,50(3):367-373
The crystal structures of K-and Cs-exchanged forms of zorite were studied by X-ray diffraction and IR spectroscopy: K4.75Na1.82[Ti(Ti0.79Nb0.20)4Si12O34(O,OH)5.2] × 10.62 H2O (sp. gr. Cmmm, R= 0.0481 for 516 independent reflections) and Cs4.34Na1.90[Ti(Ti0.80Nb0.18)4Si12O34(O,OH)5] × 5.37 H2O (sp. gr. Cmmm, R = 0.0285 for 621 independent reflections). Both structures retain the mixed polyhedral framework of zorite: Na6Ti(Ti,Nb)4(Si6O17)2(O,OH)5 × nH2O, where n ~ 11. It is shown that the positions of the atoms located in the cavities of the frameworks of these compounds differ from those in the structures of zorite and its synthetic analogs. 相似文献
10.
We report a method for synthesizing TiO2 nanostructures by applying microwave irradiation (1200 W, 2.45 GHz, single-mode) to a Ti substrate under an atmosphere comprising of O2 and Ar. After 1200 W microwave irradiation, one-dimensional (1D) nanostructure arrays were synthesized on the surface of the substrate. The average dimensions of the 1D structures were 200 nm in length and 30 nm in diameter. The structures were single crystalline. The EDX elemental maps of the areas examined using HAADF-STEM demonstrated that Ti and O were distributed homogeneously throughout the nanostructure. Quantitative analysis of the mean atomic ratios in the nanostructures disclosed a Ti:O ratio of 0.331:0.669. XPS analysis demonstrated that the predominant oxidation state of Ti in the samples was +4. On the basis of these results, we propose a possible mechanism for the formation of the TiO2 nanostructures via microwave irradiation. 相似文献
11.
Z. Wokulski 《Crystal Research and Technology》1991,26(8):1025-1037
Thin layers of TiN and Ti(N, C) solid solution were obtained by the CVD process, making use of the following gas mixtures: TiCl4–N2–H2 for TiN and TiCl4–CCl4–N2–H2 for Ti(N, C). The thin layers deposition processes were carried out in the temperature range from 900–1450 °C. As growth substrates were used polycrystalline Al2O3, graphite, W, Mo and Cu plates and also single crystal Al2O3 (leucosapphire), (111) Cu and (111) Si plates. The influence of certain technological factors on the morphology of the layers obtained was studied. TEM examinations were also made of the microstructure of the thin TiN layers and the Ti(N, C) solid solution layers deposited on polycrystalline and single crystal Cu plates. Factors responsible for the presence of a high density of dislocations in the tested films were ascertained. 相似文献
12.
Titanium exposed to dry air at varying temperatures are studied by X-ray photoelectron spectroscopy (XPS) in combination with low energy Ar ion sputtering. The 2 nm deposit formed at room temperature in 30d is an oxide mixture with chiefly Ti2O3. This result is indicated by the Ti(2p) level binding energy, FWHM and asymmetry. The dry air exposures at high temperatures resulted in oxide species of nonstoichiometric TiO2–x. As proposed from sputtering effects to XP-spectra the oxygen deficient TiO2–x surface region includes Ti3+-interstitials. These interstitials act as donors (emission to (3d)-states) and hinder the oxygen diffusion via interstitials (temperature: ≦ 550 °C). It is to be noted that electron emission from donor states is favoured in deeper lying (2p)-states by decreasing concentration of oxygen vacancies. 相似文献
13.
The process of one‐ and two‐dimensional Ti in‐diffusion in lithium niobate, LiNbO3 (LN), single crystals of 〈x〉 and 〈z〉 orientations at 950‐1060°C in oxygen/water vapor medium had been studied. In the case of one‐dimensional diffusion, a flat diffusion front consisting of Ti solid solution in LN is formed. The process kinetics is described by Fick's equation for the case of a permanent source. In the case of two‐dimensional Ti diffusion, the diffusion zone contour acquires the shape close to elliptical. The diffusion rate in the tangential direction is about an order of magnitude higher than in the normal direction. A model qualitatively describing such nontrivial character of the diffusion process is suggested. The model is based on: a) incongruent lithium evaporation out of LN at high temperatures; b) low thermodynamic activity of Li in LiTiO3 – product of Ti interaction with LN. These factors produce a significant nonlinearity of the process, since a strong chemical bond between Li and Ti in this phase leads to a mutual increase in their diffusive mobility. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
14.
Effects of the single or simultaneous addition of trace Ti and B (?1 at.%) on the glass-forming ability (GFA) and crystallization behaviors of Al88Ni6La6 and Al89Ni6La5 amorphous alloys were investigated by X-ray diffraction and differential scanning calorimetry. The addition of trace Ti and B deteriorates the GFA, but improves the thermal stability especially if Ti is added singly. The crystallization onset temperature Tx1 of the first exothermic peak increases by 29.5 and 18.0 K when 1% of the Al atoms in Al88Ni6La6 and Al89Ni6La5 are replaced by Ti, respectively. However, the primary phase during annealing remains unchanged. 相似文献
15.
A complement of experimental characterization techniques - positron annihilation spectroscopy (PAS), transmission electron microscopy, synchrotron X-ray diffraction and elevated temperature ac and dc magnetic measurements - were applied to the study of melt-quenched stoichiometric Nd2Fe14B ribbons modified by various amounts of the alloying additions Ti and C. These alloying additions are known to enhance the glass-forming ability in Nd2Fe14B melts, allowing for a wider processing window to produce homogeneous nanoscale materials with tailored magnetic properties. The experimental techniques used in this study reveal the complex multi-phase and multi-scale nature of the ribbons, a result that had escaped detection by lower-resolution techniques. The as-quenched ribbons were found to consist of at least three phases: α-Fe nanocrystals, poorly crystalline Nd2Fe14B and glass. The measured weight fraction of glass does not show a direct correspondence with quenching wheel speed, a result attributed to the complexity of the melt-spinning heat-transfer process. The Curie temperature of the glassy component of the ribbons varies in a non-systematic way with both Ti and C alloying addition content and wheel speed. PAS provides quantitative measurements of the S (or ‘shape’)-parameter which represents the size of a void or open volume in the material volume probed. The experimental results indicate that an excess of free volume in the glass is associated with increased glass stability, a counterintuitive conclusion. However, the results are consistent with the model of Sietsma and Thijsse [Phys. Rev. B 52 (5) (1995) 3248] who propose that thermal relaxation in glass causes the larger free volume regions in the amorphous structure to break up into smaller voids, which necessarily increases the total number of voids, but decreases the volume per void. This void breakup fosters the processes of cooperative diffusion and subsequent devitrification. It is concluded that the free volume concentration in the amorphous component of melt-spun Nd2Fe14B alloys produced by the highest quenching wheel speeds and Ti/C alloying addition content is thus not sufficient to allow cooperative diffusion to take place, resulting in an increased stability against devitrification. 相似文献
16.
W. Z. Zhong H. C. Hong Z. P. Lu T. D. Zhao S. K. Hua D. Y. Tang Q. L. Zhao W. R. Zeng X. Lin 《Crystal Research and Technology》1993,28(6):867-870
This paper reports on the morphology and inclusions in the low temperature phase barium metaborate BaB2O4(BBO) crystal grown by an improved flux pulling method. The morphology of ideal BBO crystals and the relationship between the faces and the growth rate are given. The result that BBO has the symmetry L33P and belongs to the space group C3v−3m can therefore be concluded. It is found that the polarity of the BBO crystal along the Z (or c) axis has a visible influence on the morphology. The investigation of the inclusions in BBO crystals shows that these have a six-fold symmetry which corresponds to the extension of flute-like facets. It is also found that most of the inclusions have a regular geometric figure and can be regarded as the negative-crystal structure which is due to the internal growth mechanism. 相似文献
17.
《Journal of Non》2007,353(18-21):1802-1807
The structure of binary (TiO2)x(P2O5)1−x glasses with x = 0.60, 0.65 and a ternary K2O–TiO2–P2O5 (KTP) glass were studied by X-ray and neutron diffraction. The experiments were performed at the high-energy beamline BW5 of the synchrotron DORIS (Hamburg/Germany) and at the GEM instrument of the neutron source ISIS (Chilton/UK). Gaussian fitting of well-resolved first-neighbor peaks in the correlation functions of the binary glasses with TiO2 contents of 0.65 and 0.60 result in Ti–O coordination numbers of 5.65 ± 0.2 and 5.9 ± 0.2, respectively. Distorted TiO6 octahedra and isolated PO4 units form the glassy networks, with a small number of lower coordinated Ti sites for the 0.65 TiO2 glass. For comparison, only TiO6 octahedra are found for a ternary K2O–TiO2–P2O5 glass. The Ti–O coordination numbers are compared with a structural model where all oxygen atoms occupy sites in Ti–O–Ti, Ti–O–P or P–O–P bridges. The presence of three-coordinated oxygens must be assumed for the binary glasses, whereas a structure with nearly all oxygen atoms forming network bridges exists for the ternary KTP glass. 相似文献
18.
V. I. Voronkova I. N. Leont’eva N. I. Sorokina T. I. Ovsetsina I. A. Verin 《Crystallography Reports》2006,51(6):977-981
A series of iron-doped KTiOPO4 (KTP: Fe) single crystals in which iron substitutes for 0.1–0.3% titanium was grown. The structure of the KTP: Fe crystals was determined, and their dielectric and conducting properties were studied. An X-ray diffraction analysis failed to reveal such asmall amount of Fe+3 ions in titanium octahedral positions of the structure. It was found that an increase in the iron concentration results in a lowering of the symmetry of Ti(1)O6 and Ti(2)O6 octahedra. The splitting of the dielectric anomaly due to the ferroelectric phase transition was explained by the mechanism of incorporation of an impurity into different growth pyramids of the crystals. It was established that the aging of the KTP: Fe crystals leads to changes in the permittivity and electrical conductivity during long storage. 相似文献
19.
Forsterite monocrystals doped with Ti and Ni were grown by the flux growth technique. A suitable mixture of flux (MoO3, V2O5, Li2CO3) and nutrient was slowly cooled down to 750 °C from 1250 °C or 1350 °C. The crystals were then characterized by powder and single‐crystal X‐ray diffraction, scanning electron microscopy and differential scanning calorimetry (DSC). Variations observed in crystal size were attributed by both the varying experimental conditions in which they had been obtained, and to the amount of Ni substituted for Mg in the structure. High abundances of doped forsterite required a cooling rate of 1.8 K h‐1. These synthetic, well‐characterized Ti and Ni doped forsterite crystals may have potential for exploitation in industrial fields. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
20.
《Journal of Non》2006,352(23-25):2367-2370
Epitaxial layers of up to 50% Yb-doped monoclinic KLu(WO4)2 could be successfully grown on passive KLu(WO4)2 substrates. These composite samples were characterized and continuous-wave and mode-locked laser operation was achieved with Ti:sapphire and diode-laser pumping. A 10% Yb-doped epitaxy provided an output power exceeding 500 mW at 1030 nm and a maximum slope efficiency of 66% with Ti:sapphire laser pumping. A 50% Yb-doped epitaxy exhibited serious thermal problems without special cooling and rather limited cw performance. Quasi-cw operation provided in this case an average output power of 43 mW at 1032 nm for a 10% duty cycle. More than 100 mW cw could be generated at 1030 nm also with diode-pumping of the 10% Yb-doped KLu(WO4)2 epitaxy. Pulses as short as 114 fs were generated at 1030 nm with this same sample under Ti:sapphire laser pumping in a laser mode-locked by a saturable absorber mirror. 相似文献