Environmentally friendly growth of single-crystalline K2Ti6O13 nanoribbons from KCl flux

Single-crystalline K₂Ti₆O₁₃ nanoribbons with typical width ranging from one hundred nanometers to a few hundred nanometers and length up to tens of microns were prepared from KCl flux. The nanoribbons were characterized by a range of methods including X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, selected area electron diffraction and high-resolution transmission electron microscopy. Ultraviolet–visible experiments showed that the K₂Ti₆O₁₃ nanoribbons were wide-band semiconductors with a band width E_g = 3.4 eV. The mechanism of one-dimensional growth of the nanoribbons was attributed to the oriented attachment mechanism.     

Molten salt synthesis of single-phase BaNd2Ti4O12 powder

The single-phase BaNd2Ti4O12 powder was successfully prepared at 1000 to 1200°C by the KCI molten salt method, and the sinterability of the powder was briefly studied. Longitudinal single-phase powders could be fully densified at 1450°C. Measurements showed that the dielectric constant and Q-value of the densified ceramics were high, and the Q-value in particular was markedly affected by the preparatory conditions. These results indicate that single-phase BaNd2Ti4O12 powder can easily be prepared by the KCI molten salt method and that the ceramics made from the powder show optimal properties for microwave dielectrics.     

K2Ti6O13-TiO2／Ti生物陶瓷材料的微弧氧化法制备

通过微弧氧化成功的在两种含钾的电解质中制备了K2Ti6O13-TiO2/Ti复合生物陶瓷材料.XRD检测表明制备得到的陶瓷膜的主要成分是K2Ti6O13和金红石型TiO2,还有少量的锐钛矿型TiO2和K2Ti4O9.EDX线扫描检测结果说明陶瓷膜中的各相是相互交织的结合在一起的,能提高陶瓷膜与钛基体的结合强度.表面SEM形貌检测显示表面呈现多微孔的陶瓷结构.两种体系中制备的陶瓷膜经仿生溶液浸泡6d后能检测到明显的片状结构的HAp涂层,表明K2Ti6O13-TiO2/Ti生物陶瓷材料具有很强诱导HAp沉积的能力,生物活性很好.分析结果表明K2Ti6O13和金红石型TiO2成分的存在是陶瓷膜具有良好生物活性的关键所在.     

K2Ti6O13 Nanoparticle-Loaded Porous rGO Crumples for Supercapacitors

One-dimensional alkali metal titanates containing potassium,sodium,and lithium are of great concern owing to their high ion mobility and high specific surface area.When those titanates are combined with conductive materials such as graphene,carbon nanotube,and carbon nanofiber,they are able to be employed as efficient electrode materials for supercapacitors.Potassium hexa-titanate(K2Ti6O13,KTO),in particular,has shown superior electrochemical properties compared to other alkali metal titanates because of their large lattice parameters induced by the large radius of potassium ions.Here,we present porous rGO crumples(PGC)decorated with KTO nanoparticles(NPs)for application to supercapacitors.The KTO NP/PGC composites were synthesized by aerosol spray pyrolysis and post-heat treatment.KTO NPs less than 10 nm in diameter were loaded onto PGCs ranging from 3 to 5μm.Enhanced porous structure of the composites was obtained by the activation of rGO by adding an excessive amount of KOH to the composites.The KTO NP/PGC composite electrodes fabricated at the GO/KOH/TiO2 ratio of 1:3:0.25 showed the highest performance(275 F g−1)in capacitance with different KOH concentrations and cycling stability(83%)after 2000 cycles at a current density of 1 A g−1.     

钛合金表面K2Ti6O13w涂层的制备及其生物活性

K2Ti6O13晶须不仅具有优越的力学性能和良好的生物学特性,而且具有与常规Ti合金相近的膨胀系数。本研究尝试选用K2Ti6O13晶须（K2Fi6O13w）作为生物活性涂层材料,利用BCC方法（混合-包埋-煅烧）在Ti合金基体上成功制备了K2Ti6O13w涂层,并对涂层的表面形态、结合强度和生物活性进行了研究。结果表明,涂层由K2Ti6O13晶须和少量的TiO2和K2Ti6O9组成,其表面粗糙多孔。由于膨胀系数的良好匹配,涂层与基体之间具有较高的结合强度,达24MPa。模拟体液培养后,涂层表面沉积了一层多孔的骨状羟基磷灰石,它由平均直径20nm,长200nm的羟基磷灰石纳米线组成,这表明钛酸钾涂层具有良好的生物活性。涂层较高的生物活性与其独特的生化特性和组分密切相关。     

K2Ti6O13晶须改性硅酸盐无机胶粘剂的研究

以K2Ti6O13晶须为改性剂制备了一种改性硅酸盐胶粘剂.采用AG-250KNI电子精密材料试验机和DTG60H差热-热重分析仪对胶粘剂的力学性能和耐热性能进行了表征,采用常温水浸实验对胶粘剂的耐水性能进行了评价.结果表明,K2Ti6O13晶须有效的改善了胶粘剂的粘接强度、耐水性能和耐热性能.运用GBC10e紫外-可见分光光谱仪研究了K2Ti6O13对胶粘剂的改性机理.     

Interfacial reactions in K2Ti6O13(w)/Al2O3/Al composite

Abstract

A pure Al matrix composite, reinforced by potassium titanate whiskers coated with sol–gel alumina, was fabricated by squeeze casting. Good interface bonding was achieved in the coated composite. Interfacial reactions in the composite were found to be less severe than those in an uncoated composite, owing to the barrier effect of sol–gel -Al₂O₃ coating. After the composite was thermally exposed at 530°C for 30 h, the alumina coating still restrained the decomposition of the whisker structure, and thus prevented a decrease in the strength of the composite. However, after a thermal exposure at 700°C for 10 h, the coating was no longer held on whisker surfaces. Mechanical testing showed that tensile fracturing of the coated composite tended to occur at the coating/matrix interface where the interfacial bonding is weaker than at the coating/whisker interface.     

Molten salt synthesis of anisotropic BaFe12O19 powders

The formation mechanism, morphology, and magnetic properties of anisotropic BaFe₁₂O₁₉ powders prepared by the 0.8 Na₂SO₄-0.2 K₂SO₄ molten salt synthesis have been investigated. The reaction can be completed at temperatures lower than 845 °C which is the melting point of the 0.8 Na₂SO₄-0.2 K₂SO₄ salt mixture, due to the presence of the low melting phase related to the formation of BaSO₄ and Na₆CO₃(SO₄)₂. Even at temperatures lower than 845 °C, with the aid of the low melting phase, the morphology of ferrites was thin platelets. Magnetic properties such as coercivity, saturation magnetization, and remanent force are comparable to those found in other processing techniques. The orientation degree of the sintered body was very high due to anisotropic morphology; thus powders from molten salt synthesis are suitable for grain oriented ceramics.     

Molten salt synthesis of SnS2 microplate particles

A molten salt method to synthesize SnS₂ nanoplates, in a melt of tin dichloride and thiourea in air at 250–280 °C for 0–5 h, coupled with a subsequent washing treatment using distilled water, is demonstrated. The X-ray diffraction, Raman spectra, and field emission scanning electron microscope images disclosed that all the obtained products were phase pure hexagonal SnS₂ nanoplates, of 20–70 nm thickness.     

Molten salt synthesis of ZnNb2O6 powder

Pure ZnNb₂O₆ powder was successfully prepared by the molten salt synthesis method using Nb₂O₅ and ZnO as raw materials and a mixture of NaCl and KCl as the solvent. The phase form and morphology of the prepared powder were characterized by X-ray diffraction and scanning electron microscopy. The effect of reacting temperature on phase formation was investigated. The results indicated that the single phase ZnNb₂O₆ powder can be obtained by the molten salt synthesis method at 600 °C, and the SEM photographs show that the grains of the powder are rod-like particles.     

Crystalline characterization and photodecomposition properties of rod-shaped Na2Ti6O13 powder prepared by molten salt process

To prepare one-dimensional nanostructured Na2Ti6O13 powder, the starting materials of TiO2, NaCl and Na2CO3 were mixed and then heat-treated at 1000 degrees C for 2 hrs in air under molten state of NaCl. Changes in shape and phase, photo absorbance and photocatalytic ability of TiO2 particle were observed controlling added amount of Na2CO3 under constant weight ratio of TiO2 to NaCl using SEM, X-ray diffractometer, Raman spectroscopy, and UV-Vis spectroscopy. The TiO2 particle was changed into rod-shape Na2Ti6O13 with the addition of Na2CO3, showing increase in optical energy band-gap of the powder as well as gradual decrease of the photo-decomposition ability.     

Dielectric and spectroscopic analysis of cobalt doped potassium hexatitanate (K2Ti6O13) ceramics

Pure and cobalt doped (x = 0.05, 0.10, 0.15 mol %) polycrystalline potassium hexatitanate (K₂Ti₆O₁₃) ceramics were synthesized using conventional solid state reaction route. XRD result confirmed the successful doping of Co in the K₂Ti₆O₁₃ matrix, as no additional peak was observed in the pattern. Dielectric permittivity was found to decrease with the increase in frequency while it increased with the increase in doping. The dielectric loss decreased with small doping whereas excessive doping caused its augmentation. Ac conductivity (σ _ac ) has also been studied as a function of frequency at room temperature for all the samples. Scanning Electron Microscope (SEM) inspection of the synthesized samples showed the formation of rod like shapes. FTIR analysis was carried out to identify the chemical bonds present in the system.     

纳米K2Ti6O13W合成中的形态演化和生长机理

以纳米TiO2为原料,通过煅烧反应制备了纳米K2Ti6O13晶须,对晶须合成中温度和时间诱导的相变、形态演化和生长机理等进行了原位研究.结果表明:纳米TiO2作原料可显著降低晶须合成温度,适宜的煅烧温度为900～1100℃.形态演化观察和高温XRD分析表明:K2Ti6O13晶须的相变及生长对温度极为敏感,形态演化是基于初期爆发式的相变和随后串并联式的长大.K2Ti6O13晶须的生长遵守本研究提出的串并联机制,晶须轴向的生长台阶是串并联生长的直接结果.     

Molten salt synthesis of potassium hexatitanate

Potassium hexatitanate fibrous crystals have been synthesized by a conventional solid-state reaction and via molten salt process. The molten salt process has been shown to be effective in preparing fine and non-agglomerated K₂Ti₆O₁₃ whiskers. The type of molten salt (KCl, NaCl-KCl) has a significant effect on the chemical composition of the whiskers. By using a eutectic mixture of NaCl and KCl, the replacement of potassium ions in solid potassium hexatitanate by smaller sodium ions from the chloride flux can be achieved. The characterization of the samples was carried out by means of XRD, SEM, EDX and WDX.     

Molten salt synthesis of lead-based relaxors

The molten salt synthesis (MSS) of lead-based relaxors which have a perovskite structure, A(BIBII)O3 where BI is Mg2+, Fe3+, Zn2+, Ni2+ or Co2+, and BII is Nb5+, has been reviewed with regard to the formation of the perovskites, phase stability and morphology characteristics. Two relaxor materials, Pb(Mg1/3Nb2/3)O3 and Pb(Fe1/2Nb1/2)O3 were found to be successfully synthesized at a low temperature in a very short time by the MSS method. Using the example of Pb(Mg1/3Nb2/3)O3, the phase stability has been discussed on the basis of thermal and chemical analyses. The influences of the processing parameters, such as temperature, time, type and amount of salt, and non-stoichiometry, on the formation and the powder characteristics of the perovskite phase were investigated with possible explanations for the observed differences which were induced by changing the parameters. Finally, densification behaviour and dielectric properties resulting from the MSS powder were examined and compared to those of powders obtained by using the conventional mixed oxides (CMO) method. © 1998 Kluwer Academic Publishers     

FTIR and dielectric studies of nickel doped potassium hexa-titanate (K2Ti6O13) fine ceramics

The dielectric and electrical properties such as relative permittivity $(\varepsilon^{\prime } )$ , loss tangent (tanδ), and ac conductivity (σ_ac) have been studied in the temperature range 373–773 K at three different frequencies 100, 200, 400 kHz for doped potassium hexa-titanate (K₂Ti₆O₁₃) samples. It was observed that dielectric constant and loss tangent decreases while ac conductivity increases with the increase in frequency. The temperature dependent relative permittivity showed a phase transition for all samples. Dielectric loss mechanism was observed to include space charge polarization and dipole orientation. Moreover, electron-hopping conduction was observed to be dominant in the low temperature region, whereas intratunnel ionic conduction prevailed at higher temperatures. Fourier transform infrared spectroscopy analysis was also carried out to identify the chemical bonds present in the specimens.     

熔盐合成技术制备片状Sr3Ti2O7粉体的研究

采用熔盐合成技术制备片状Sr3Ti2O7粉体，研究了Sr3Ti2O7在KCl熔盐中的合成过程，以及升/降温速率等工艺参数对Sr3Ti2O7粉体形貌的影响。在熔盐合成过程中，Sr^2＋离子扩散迁移至TiO2颗粒表面，经反应后首先得到SrTiO3。随着Sr2^2＋离子的不断扩散，SrTiO3与Sr^2＋进一步反应生成Sr3Ti2O7。过快的升温速率引起产物在熔盐中形核率的增加，导致产物最终尺寸的减小；而过快的降温速率使得降温过程中熔盐内的产物不能根据Sr3Ti2O7的晶体结构特征选择性地析出到粉体的表面，导致片状粉体的厚度增加，从而降低其各向异性程度。因此缓慢的升温和降温过程更有利于获得高度各向异性的大尺寸片状Sr3n2O7粉体。以0.5℃/min的升/降温速率在1200℃下保温4h可制备出宽度约15～30um、厚度约2～5μm的片状Sr3Ti2O7粉体。