Potassium Hexatitanate Whiskers Research Articles

Microstructure, Mechanical and Thermal Insulation Properties of Potassium Hexatitanate Whiskers Thermal Insulation Materials

Potassium hexatitanate whiskers (PTW) materials have attracted much attention in thermal insulation fields. Nevertheless, the low mechanical properties limited the development and application of PTW thermal insulation materials. In this work, low density, high mechanical properties and high thermal insulation capacity of PTW thermal insulation materials can be obtained through mesocarbon microbeads (MCMB) adopted as pore-forming agent. The pyrolysis and oxidation of MCMB promoted the development of whiskers during the calcination process, rendering the increased materials porosity. The as-prepared PTW materials heat treated at 1000°C possessed low thermal conductivity of 0.043-0.035 W.m−1.K−1 from room temperature to 900°C and a low bulk density of 0.52 g.cm−3. Owing to the point of contact between whiskers with developed diameter and aspect ratio, comperssive strength of PTW materials heat treated at 900° and 1000°C was 1.92 and 2.51 MPa, respectively, maintaining high resilience rates of above 70% at 5% compressive strain. The elevated heat-treatment temperature (above 1100°C) led to the sintering between whiskers and the resultant enhanced compressive strength of higher than 4.23 MPa. The researched low density, high mechanical properties and thermal insulation PTW materials exhibit huge prospects as insulation linings in thermal insulation fields.

One-step synthesis and its mechanism of potassium hexatitanate whiskers from potassium dititanate and metatitanic acid

The high price of potassium hexatitanate (K2Ti6O13) whiskers restricts its broad applications. The current production method is composed of complex processes and generates a large amount of wastewater. In this work, we propose a new one-step synthesis approach for producing potassium hexatitanate whiskers. Potassium dititanate and metatitanic acid are mixed at the ratio of TiO2/K2O = 4 and then calcined at 1000 °C to synthesize potassium hexatitanate whiskers. We used XRD, SEM, TG-DSC, and other characterization techniques combined with thermodynamic calculations to study the synthesis mechanism of such one-step process. The thermodynamic calculations show that the reaction free energy of K2Ti6O13 whiskers synthesized by this process is negative even at room temperature, confirming that this process has a higher reactivity than the conventional synthesis approach by K2CO3 and TiO2. Moreover, the melting of K2Ti2O5 at 916 °C provides a necessary environment for the crystal growth of K2Ti6O13 nanoparticles, which is the key to the preparation of K2Ti6O13 whiskers. This new synthesis approach will significantly reduce the producing cost of K2Ti6O13 whiskers, thereby expanding its applications.

Preparation and properties of anti-infrared transparent thermal-insulating film based on polymethyl methacrylate

A series of thermal-insulating films are prepared by adding the corresponding new thermal insulating materials to polymethyl methacrylate (PMMA) by dissolution-condensation method. On the basis, the microstructure of the thermal barrier film, the corresponding infrared, ultraviolet blocking rate and visible light transmittance are tested by the infrared spectroscopy analyzer and solar film tester (LS183). The thermal-insulating properties of the film are tested by a self-built semi-closed hot box model. The results show that: When the molar ratio of Al to Si is 1:9, the composite material with 5 wt% modified potassium hexatitanate whiskers shows the best infrared radiation blocking performance and the lowest thermal conductivity reaches 0.06036 (W/(m·K)). Based on this, the heat-insulating film prepared with 12 wt% such new composite materials based PMMA exhibits the best heat-radiating resistance：The infrared blocking rate reaches 62.1%, and the ultraviolet blocking rate reaches 73.9%. And the maximum temperature difference can reach 5 °C at an ambient temperature of 40 °C.

Facile synthesis of potassium hexatitanate whiskers by calcination at low temperature

Traditional calcination method is very popular for large-scale production of potassium hexatitanate (K2Ti6O13) whiskers. While the required high resultant temperature (always over 1000 °C) will consume more energy and increase the costs. Therefore, it is of great practical interest to explore efficient synthesis methods for K2Ti6O13 whiskers. In the present work, K2Ti6O13 whiskers were directly synthesized from TiO2, K2CO3, and carbon black by a facile calcination method. The well-crystallized K2Ti6O13 whiskers with 3–5 μm in length and 0.1–0.3 μm in diameter can be obtained when the molar ratio of K2CO3 to TiO2 was 1:6 at the calcining temperature as low as 800 °C. The generated CO2 from oxidation of carbon black slowed down the violence of the synthesis reaction rate for potassium titanates, and the lower synthesizing temperature decreased the volatilization loss of molten K2CO3, resulting in the promoted development of whiskers. The facile and low-cost synthesis method presented in this work indicated promising application in the large-scale production of K2Ti6O13 whiskers.

Microstructure and tribological properties of epoxy composites modified by methyl silicone oil-loaded microcapsules and/or reinforced with potassium hexatitanate whiskers

Self-lubricating functional microcapsules using melamine-formaldehyde resin encapsulating methyl silicone oil as core materials were synthesized by in situ polymerization method. And they are further adopted as antifriction additive to improve the tribological properties of binary and ternary epoxy (EP) composites, which were fabricated by incorporating microcapsules and the potassium hexatitanate whiskers (PTWs) into the EP matrix. The tribological behaviors of the as-synthesized EP composites have been evaluated by means of a block-on-ring high-speed wear tester. The results demonstrated that the friction coefficient and wear rate of EP /microcapsules binary composites decreased with the increase of microcapsule concentration due to the self-lubricating effect of the core material. For the EP /microcapsules/PTWs ternary composites, not only the mechanical properties and thermal stability PTWs were improved, but also the friction reduction and antiwear effect of the ternary composite are further enhanced due to the synergistic effect of PTWs and microcapsules.

Morphology control and characteristic parameter R of molten-salt-synthesized K2Ti6O13 whiskers

The influence of reaction conditions including reaction temperature, reaction duration, and molar ratio of reactants on the morphology of products was systematically investigated, in order to prepare potassium hexatitanate (K2Ti6O13) whiskers with uniform morphology and high crystallinity by molten salt synthesis toward industrial applications. Three typical types of K2Ti6O13 whiskers including short, long, and thick K2Ti6O13 whiskers with the length and diameter ranges falling in 0–20 and 0.5–2 μm, 10–50 and 0.5–1 μm, and 10–50 and 2–10 μm, respectively, are presented in particular. After surface modification with silane coupling agent A-172, all the three K2Ti6O13 whisker samples can evenly disperse in butyl acetate forming parallel arrays along the preferential growth direction [010] and exhibit predominated peaks of crystallographic planes of (200) and (20 $$ \bar{1} $$ ) in X-ray diffraction patterns. A characteristic parameter R which is sensitive to the reaction conditions and directly relates to the size and crystallinity of K2Ti6O13 whiskers was developed from the intensity ratio of (200)/(20 $$ \bar{1} $$ ) in order to quickly evaluate the feature of K2Ti6O13 whiskers.

Improving anti-infrared radiation and heat insulation by potassium hexatitanate whisker-doped Al 2 O 3 –SiO 2 composite xerogel

Taking potassium hexatitanate whisker (PTW) modified by silane coupling agent KH550, aluminium nitrate inorganic salt and tetraethyl orthosilicate and deionized water, respectively, as infrared sunscreen, aluminium source and raw materials forming the network structure of a composite xerogel, a series of structurally intact PTW-doped Al2O3–SiO2 composite xerogel thermal-insulating materials were prepared by the sol–gel method and dried under atmospheric pressure. The infrared spectral characteristics, infrared radiation transmittance, microstructures, morphology and thermal conductivity of different composite materials prepared have been determined by a Fourier transform infrared spectrometer, UV–visible–near-infrared spectrophotometer, X-ray diffractometer, scanning electron microscope and thermal conductivity tester. The results exhibit that when the Al to Si molar ratio is 1 : 9, the composite material with 5 wt% modified PTW shows the best infrared radiation blocking performance and the lowest thermal conductivity (0.0604 W m−1 K−1).

Self-propagating high-temperature synthesis of potassium hexatitanate whiskers

Abstract Potassium hexatitanate (K 2 Ti 6 O 13 ) whiskers with high thermal insulating capacity, good mechanical properties, and excellent chemical stability are promising functional materials. In this study, K 2 Ti 6 O 13 whiskers were successfully prepared by one-step self-propagating high-temperature synthesis (SHS) method for the first time. Titanium dioxide (TiO 2 ), potassium carbonate (K 2 CO 3 ) and combustion accelerant with different molar ratios were mixed, and the combustion synthesis was performed using the oxygen bomb calorimeter. The effects of molar ratio TiO 2 to K 2 CO 3 , the type and the amount of combustion accelerant on the purity and morphology of products were investigated by SEM and XRD. The results showed that uniformly distributed K 2 Ti 6 O 13 whiskers with high purity, good crystallinity, and morphology were obtained when the molar ratio of TiO 2 to K 2 CO 3 and the mass ratio of benzoic acid to (TiO 2 +K 2 CO 3 ) were 4 and 2, respectively. K 2 Ti 6 O 13 whiskers of length 10 µm and 1 µm in diameter were obtained within 15 min. In addition, the benzoic acid was a better combustion accelerant than the starch and acetylene black.

Efficient removal of Co(II) from aqueous solution by titanate sodium nanotubes

In this paper, a novel material for Co(II) adsorption, titanate sodium nanotubes (Na2Ti2O5-NTs) were synthesized and characterized, and then they were used to remove Co(II) from aqueous solution and compared with titanic acid nanotubes (H2Ti2O5-NTs) and potassium hexatitanate whiskers (K2Ti6O13). The results showed that the adsorption of Co(II) on the materials was dependent on pH values and was a spontaneous, endothermic process. Specifically, Na2Ti2O5-NTs exhibited much more efficient ability to adsorb Co(II) from aqueous solution, with the maximum adsorption capacity of 85.25 mg/g. Furthermore, Na2Ti2O5-NTs could selectively adsorb Co(II) from aqueous solution containing coexisting ions (Na+, K+, Mg2+, and Ca2+). The results suggested that Na2Ti2O5-NTs were potential effective adsorbents for removal of Co(II) or cobalt-60 from wastewater.

Study on the Friction Factor and High-Temperature Friction Resistance of Semi-Metal Frictional Materials

The orthogonal experimental study is carried out to study the Incorporation of different proportion of functional components and the effect on tribological performance among semi-metallic friction materials. A test is conducted for each sample on XXD-MSM constant speed tester in accordance with Brake Linings for Automobiles (GB5763-2008). The friction factor and high-temperature abrasion resistance properties are evaluated along with the obtaining of optimal formula, and the mechanism of affecting the tribological properties is analyzed on the worn surfaces by using a scanning electron microscope (SEM). The study results indicate that the high-temperature friction stability could be deeply affected by the adequate content of steel fiber, Kevlar pulp, potassium hexatitanate whisker and cashew nut shell. The mechanism of High-temperature tribological behaviors are the thermal decompositions. The thermal decomposition of organic matter might greatly weakened the bonding effect. The thermal decomposition of tribo-film fall off as lamellar chip under the effect of friction stress. The addition level of nanoparticles is 3%, the sample’s tensile strength, tensile strength, hardness index and noise level are better. If the modified resin is further applied, this formula can be close to the index of excellent Chinese industrial product JF04-20.

Synthesis of potassium hexatitanate whiskers with high thermal stability from Ti-bearing electric arc furnace molten slag

Potassium hexatitanate (K2Ti6O13) whiskers with excellent dispersity were synthesized from titanium-bearing electric arc furnace molten slag (Ti-bearing EAF slag) by calcination method in this paper. The effects of TiO2 to KOH molar ratios (RTiO2KOH), calcination temperature and duration on the micromorphology and crystallinity of as-prepared K2Ti6O13 whiskers were systematically investigated. The results indicated that well disperse and relatively pure K2Ti6O13 whiskers were synthesized when the calcination temperature was 900°C and calcination time was 300min with RTiO2KOH value at 1.75. The diameter of prepared whiskers was larger with the increase of calcination temperature from 850 to 1100°C and time from 10 to 300min. At the same time, the morphology of prepared K2Ti6O13 whiskers transformed from fibrous structure to rod-like structure. In addition, the thermal stability of K2Ti6O13 whiskers was also discussed under optimum conditions by using TG-DSC analysis. It is shown that the product exhibited excellent thermal stability and K2Ti6O13 whiskers would not decompose up to about 1430°C.

Preparation and application of sulfadiazine surface molecularly imprinted polymers with temperature‐responsive properties

ABSTRACTNovel, temperature‐responsive molecularly imprinted polymers (TMIPs) based on potassium hexatitanate whiskers for selectively adsorbing sulfadiazine (SDZ) from aqueous media were prepared with methacrylic acid (MAA) and 4‐vinylpyridine (4‐VP) as cofunctional monomers and N‐isopropyl acrylamide (NIPAM) as a temperature‐responsive monomer. The template–monomer interactions were studied by molecular simulation. In particular, the effects of different kinds of crosslinkers on the selective recognition ability of the TMIPs in water media were investigated. The temperature–responsive adsorption performance and phase behavior of the molecularly imprinted polymers were studied by batch‐mode binding experiments, swelling experiments, and contact angle testing. The results demonstrate that the combination of MAA, 4‐VP, and NIPAM was a favorable temperature‐responsive imprinted system for SDZ in water, and the cocrosslinking agent of ethylene glycol dimethacrylate (EGDMA) and N,N′‐methylene bisacrylamide (MBA) was more suitable compared with either pure EGDMA or MBA. The adsorption kinetics and adsorption isotherms were analyzed by the fitting of different adsorption models. Also, the effect of the temperature on the recovery was investigated by the determination of the spiked SDZ in real‐water samples with solid‐phase extraction and high‐performance liquid chromatography. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41769.

Synthesis and Characterization of a Surface Molecular Imprinted Polymer as a New Adsorbent for the Removal of Dibenzothiophene

A surface molecular imprinted polymer (SMIP) was synthesized by using dibenzothiophene (DBT) as the template, 4-vinylpyridine as the functional monomer, and modified potassium hexatitanate whisker as the carrier. The structural and textural properties of the product were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption. Different factors affecting the adsorption such as contact time, initial concentration, and temperature were investigated. Kinetic analyses were performed using pseudo-first-order and pseudo-second-order models; the equilibrium data were fitted with Langmuir and Freundlich models, and thermodynamic parameters were also evaluated. It was determined that the SMIP exhibited high recognition selectivity and binding affinity to template DBT over the structure analogues. Moreover, the SMIP could be reused eight times without significant loss in performance; then the SMIP was successfully applied for the desulfurization of the gasoline sample.

Structural, electronic and elastic properties of potassium hexatitanate crystal from first-principles calculations

The structural, electronic and elastic properties of potassium hexatitanate (K2Ti6O13) whisker were investigated using first-principles calculations. The calculated cell parameters of K2Ti6O13 including lattice constants and atomic positions are in good agreement with the experimental data. The obtained formation enthalpy (−61.1535eV/atom) and cohesive energy (−137.4502eV/atom) are both negative, showing its high structural stability. Further analysis of the electronic structures shows that the potassium hexatitanate is a wide-band semiconductor. Within K2Ti6O13 crystal, the TiO bonding interactions are stronger than that of KO, while no apparent KTi bonding interactions can be observed. The structural stability of K2Ti6O13 was closely associated with the covalent bond interactions between Ti (d) and O (p) orbits. Further calculations on elastic properties show that K2Ti6O13 is a high stiffness and brittle material with small anisotropy in shear and compression.

Comparative study of potassium hexatitanate (K2Ti6O13) whiskers prepared by sol–gel and solid state reaction routes

Polycrystalline phases of the potassium hexatitanate (K2Ti6O13) were synthesized by conventional solid state reaction and sol–gel methods with a view to compare structural, electrical, optical and photocatalytic properties. Single phase K2Ti6O13 prepared by sol–gel method (PSG) revealed higher value of dielectric constant than same obtained by the solid state reaction method (PSS), attributed to smaller particle size in sol–gel method. Band gap (3.48eV) of K2Ti6O13 prepared by sol–gel method was found higher than (3.06eV), obtained in solid state reaction method. Additionally, K2Ti6O13 was tested as photocatalyst on the degradation of methyl orange (MO) under UV light and found better activity for sample PSG. Morphological characteristic exhibited formation of nanorods in sol–gel route and formation of microrods in solid state reaction method.

Preparation and evaluation of a novel surface-imprinted polymer for selective adsorption of dibenzothiophene

We have prepared a novel surface molecular imprinted polymer (S-MIP) using dibenzothiophene (DBT) as the template molecule, 4-vinylpyridine as the functional monomer, and potassium hexatitanate whisker as the carrier. The S-MIP was characterized by Fourier transform infrared spectroscopy and and scanning electron microscopy. The kinetics and isotherms for the adsorption of DBT on the S-MIP followed pseudo-second-order and Freundlich models, respectively. Thermodynamic parameters were determined. The overall adsorption process was endothermic and spontaneous. Selectivity studies showed that the S-MIP selectively adsorbs DBT over its structural analogs and can be regenerated. Its adsorption capacity was still at 84.8% at the sixth cycle.

Selective Synthesis of Potassium Titanate Whiskers Starting from Metatitanic Acid and Potassium Carbonate

Selective synthesis of potassium titanate whiskers starting from metatitanic acid and potassium carbonate was successfully carried out by a facile calcination method. The mole ratio of potassium carbonate to metatitanic acid and the calcination temperature and time were crucial to the formation of different-structured potassium titanate whiskers. Well-crystallized potassium tetratitanate whiskers were prepared at a calcination temperature of 1000 °C when the mole ratio of potassium carbonate to metatitanic acid was 1:2.5. Potassium hexatitanate whiskers were dominantly formed at 1150 °C when the mole ratios of potassium carbonate to metatitanic acid were in a range of 1:3.5−1:4.5. Well-crystallized potassium octatitanate whiskers were prepared when potassium tetratitanate whiskers were boiled in water and then dried at a high temperature of 400 °C. The growth directions of all the potassium titanate whiskers are along their [010] crystal directions.

Preparation, Characterization and Performance of a Novel Surface-Imprinting Polymer for the Adsorption of Dibenzothiophene

A novel surface-imprinting polymer (MIP/K2Ti6O13) was prepared using potassium hexatitanate whiskers (K2Ti6O13) as the carrier employing electrostatic interaction and π-π interaction between the template molecule [dibenzothiophene (DBT)] and the functional monomer [4-vinylpyridine (4VP)]. The synthetic polymer was characterized via Fourier-transform infrared (FT-IR) spectroscopy, surface area and porosity analysis, and X-ray diffraction (XRD). Static adsorption experiments were conducted to evaluate the adsorption kinetics, adsorption isotherms and adsorption selectivity of MIP/K2Ti6O13. Adsorption kinetic studies revealed that a contact time of 300 min was necessary to attain equilibrium. Adsorption isotherm studies indicated that the capacity of MIP/K2Ti6O13 towards the adsorption of DBT at 298 K, 308 K and 318 K was 16.18 mg/g, 22.74 mg/g and 29.89 mg/g, respectively. Selectivity experiments showed that the adsorption capacity of DBT on MIP/K2Ti6O13 was greater than for the other three analogues, while...

Synthesis of potassium hexatitanate whiskers using hydrothermal method

High quality potassium hexatitanate whiskers were hydrothermally synthesized in one step under moderate temperature and pressure conditions. Effects of the titanium source and reaction conditions on the hydrothermal reaction rate, product phase component, and morphology of whiskers were investigated. The results show that the reactivity of hydrated titania, anatase TiO2, and rutile TiO2 with KOH decreases in turn, and with hydrated titania as titanium source, it is difficult to obtain potassium hexatitanate whiskers with good morphology. In contrast, uniform potassium hexatitanate whiskers with a length of 10–20 μm and a diameter of 200–700 nm were obtained using anatase TiO2 as titanium source. The investigation demonstrates that the initial KOH concentration, annealing temperature and time, molar ratio of K2O/TiO2, etc. significantly affect the morphology of the as-synthesized whiskers. The optimized synthesis condition is as follows: anatase as a titanium source; 10 wt.% KOH solution; annealing temperature and time of 300°C and 5 h, respectively; K2O/TiO2 molar ratio of 5, etc. A rhombic potassium hexatitanate was prepared under the optimum condition and the whisker grew along the [110] direction. The reaction mechanism was discussed.

Synthesis of potassium hexatitanate whiskers starting from metatitanic acid and potassium carbonate and sulfate by calcination method

Potassium hexatitanate whiskers were synthesized starting from metatitanic acid (H 2TiO 3), potassium carbonate and sulfate by calcination method. The effects of mole ratios of K 2CO 3 to metatitanic acid (H 2TiO 3), content of potassium sulfate, and calcination temperature on the crystallinity and morphology of the resultant potassium titanate whiskers were investigated by X-ray diffraction and scanning electron microscopy. Well crystallized potassium hexatitanate whiskers with an average length of 7.3 μm and an average diameter of 0.62 μm were synthesized when the molar ratio of K 2CO 3 to metatitanic acid was kept at 1:3.5 and the calcination temperature was up to 1150 °C. The presence of K 2SO 4 favored the formation of thin potassium hexatitanate whiskers as compared to the absence of K 2SO 4. The whiteness and brightness of the synthesized potassium hexatitanate whiskers were comparable to that of rutile TiO 2 pigment.