Mechanical and thermal behavior of poly(acrylonitrile-butadiene-styrene)/polycarbonate blends reinforced with potassium titanate whiskers

Poly(acrylonitrile-butadiene-styrene) (ABS)/polycarbonate (PC) blends reinforced with potassium titanate (K₂Ti₆O₁₃) whiskers were prepared in a twin screw extruder followed by injection molding. The whiskers were pretreated with tetrabutyl orthotitanate prior to compounding. The tensile, dynamic mechanical, impact, morphology and thermal properties of the blends were studied. Tensile tests showed that the modulus of ABS/PC/K₂Ti₆O₁₃ blend increased markedly with increasing whisker content. However, the variation of the modulus of ABS/PC/K₂Ti₆O₁₃ blend with PC content followed a sigmoidal relation. In addition, the tensile strength of the blends containing 20 wt% PC tended to increase markedly with increasing whisker content. But the impact strength of the blends containing 20 wt% PC decreased rapidly with increasing whisker content. Dynamic mechanical analyses (DMA) results indicated that the storage modulus of the blends increased markedly with increasing K₂Ti₆O₁₃ whisker content. Differential thermal analysis and thermogravimetric measurements showed that potassium titanate whiskers tend to induce chemical decomposition of PC during blending of the PC/whisker blends. However, the incorporation of ABS into PC was beneficial to reduce the PC decomposition during compounding with the whiskers.     

Mechanical and thermal properties of poly(acrylonitrile–butadiene–styrene) copolymer reinforced with potassium titanate whiskers

Potassium titanate (K₂Ti₆O₁₃) whisker treated with tetrabutyl orthotitanate was used to improve the mechanical and thermal properties of the poly(acrylonitrile–butadiene–styrene) (ABS) copolymer. The composites were prepared in a twin‐screw extruder followed by injection molding. Static tensile measurements showed that both the modulus and breaking stress of ABS/K₂Ti₆O₁₃ composites increase considerably with increasing whisker content; the strain at break of ABS was almost unaffected by the incorporation of a whisker content up to 15 wt %. Izod impact tests indicated that the composites showed a decrease in the impact strength with increasing whiskers content. Thermogravimetric analysis showed that the K₂Ti₆O₁₃ whisker additions have little effect on the thermooxidative stability of ABS. Scanning electron microscopic observations revealed that the whiskers were aligned along the melt‐flow direction in the thin surface layer, whereas the whiskers were oriented randomly as well as perpendicular to the injection direction in the thick core region of the composites. The Tsai–Halpin equation was used to evaluate the moduli of the ABS/K₂Ti₆O₁₃ composites. The theoretical calculations generally correlated well with the experiment data by assuming K₂Ti₆O₁₃ whiskers to have an aspect ratio of 12. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2985–2991, 1999     

Mechanical and thermal properties of polycarbonate composites reinforced with potassium titanate whiskers

Polycarbonate (PC) composites reinforced with potassium titanate (K₂Ti₆O₁₃) whiskers were blended in a twin‐screw extruder followed by injection molding. The surface of whiskers was treated with tetrabutyl orthotitanate prior to blending. The effects of potassium titanate whisker additions on the tensile, impact, and thermal properties of PC were investigated. Tensile tests showed that the stiffness of composites markedly improved with increasing whisker content. However, potassium titanate whiskers were ineffective to reinforce PC because these whiskers promoted chemical decomposition of PC matrix during compounding. Consequently, the torque values of PC/K₂Ti₆O₁₃ composites were much lower than that of PC. Moreover, torque measurements revealed that titanate coupling agent also facilitated decomposition of PC during blending. The mechanisms responsible for the degradation of PC matrix of the surface‐treated PC/K₂Ti₆O₁₃ composites are discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 501–508, 1999     

Influence of stoichiometry and alkalinity on barium hexaferrite formation via the supercritical water crystallization method

Fine particles of barium hexaferrite were prepared from aqueous solutions of iron nitrate, barium nitrate and potassium hydroxide by utilizing a continuous flow type supercritical water crystallization method. The influence of stoichiometry (Fe/Ba mole ratio) and alkalinity (R) on the product composition and morphology was studied under fixed temperature, pressure and residence time. Experiments were performed with varying Fe/Ba mole ratios and alkali mole ratio (R). Within mole ratio ranges of 0.5< Fe/Ba< 5, BaO-6Fe₂O₃ single phase was produced; and as the Fe/Ba mole ratio increased, α-Fe₂O₃ was also formed and its quantity increased with increasing mole ratio. At an Fe/Ba ratio of 12, stoichiometric mole ratio of BaO-6Fe₂O₃, the only product formed was α-Fe₂O₃ fine particles. In the case of the influence of alkalinity, single phase α-Fe₂O₃ was detected at R of 0.5 and if R exceeded 2, a single phase BaO-6Fe₂O₃ was detected. According to the results of the experiment and the study of reaction mechanisms, the formation of BaO-6Fe₂O₃ proceeds via a non-stoichiometric reaction and the product composition and morphology can be controlled by adjusting the reaction parameters to obtain optimum conditions for Ba(OH)₂ precipitate formation.     

A study of tribological and mechanical properties of PTFE composites filled with surface treated K2Ti6O13 whisker

K₂Ti₆O₁₃ whisker was modified with n‐octadecyltrichlorosilane (OTS), fluorosurfactant (FSK), and silane coupling agent (KH‐550), respectively. The surface energy of K₂Ti₆O₁₃ whisker was calculated based on Van Oss‐Chaudhury‐Good function. Then the influence of surface modification on the tribological and mechanical properties of K₂Ti₆O₁₃ whisker filled polytetrafluoroethylene (PTFE) composites was studied. Surface energy calculation shows that the surface energy of OTS‐treated K₂Ti₆O₁₃ whisker is only 29.0 mJ/m², which is the closest to the value of pure PTFE. Among all samples, the PTFE composite filled with OTS‐treated K₂Ti₆O₁₃ whisker shows the best antiwear property, tensile strength, and impact strength, which is about 19 to 33%, 15 and 55% higher than that of untreated K₂Ti₆O₁₃ whisker filled PTFE, respectively. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Study on thermolysis process of a new hydrated and protonated perovskite-like oxides H2K0.5Bi2.5Ti4O13·yH2O

A protonated form of the n?=?4 layered bismuth containing perovskite-like titanate K_2.5Bi_2.5Ti₄O₁₃ belonging to Ruddlesden-Popper phases was prepared via ion exchange reaction of interlayer K⁺ with protons. Its composition was investigated by TG ICP and EDX analysis was found to be H₂K_0.5Bi_2.5Ti₄O₁₃·H₂O. The thermal behavior of the obtained phase was investigated by STA coupled with mass-spectrometry, the structural changes, happening with the sample during heating, were examined by XRD. It was shown that the as-prepared hydrated phase undergoes two-stage dehydration at low temperatures (up to 160?°C). The further heating leads to the gradual decomposition and crystallization of new phases, notably Bi₂Ti₂O₇, Bi₄Ti₃O₁₂ and Bi₂Ti₄O₁₁. The morphology of the as-prepared sample and samples after heat treatment was examined using SEM.     

Electrochemical studies of titanium in fluoride-chloride molten salts

The interaction between titanium and Ti⁴⁺ ions (K₂TiF₆), the electroreduction reaction of Ti⁴⁺ ions and the anodic reaction of Ti in KCl–NaCl–KF melts with K₂TiF₆ at 973 K were studied by means of electrochemical and physical measurements. It was found that the fluoride ions played a very important role in these reactionsIn KCl–NaCl-3 wt % K₂TiF₆ molten salts with less than 3 wt % KF, the interaction reaction was considered to proceed as Ti⁴⁺+Ti=2Ti²⁺. If the bath contained more than 10 wt% KF, the reaction 3Ti⁴⁺+Ti=4Ti³⁺ occurred.The electrochemical reduction of Ti⁴⁺ (K₂TiF₆) ions in the molten salts with less fluoride ions was observed to proceed according to three reaction steps, i.e. Ti⁴⁺+e=Ti³⁺, Ti³⁺+e=Ti²⁺, Ti²⁺+2e=Ti. In the case of the fluoride ion concentration being higher, two reduction steps, i.e. Ti⁴⁺+e=Ti³⁺, Ti³⁺+3e=Ti were suggested.     

Catalytic Ammonia Decomposition Over Ruthenium Nanoparticles Supported on Nano-Titanates

Nanosized Na₂Ti₃O₇, K₂Ti₆O₁₃ and Cs₂Ti₆O₁₃ materials were prepared and used as supports of ruthenium nanoparticles for catalytic ammonia decomposition. It is shown that these catalysts exhibit higher catalytic activity than ruthenium supported on TiO₂ nanoparticles promoted with cesium. The difference is attributed to the use of nanostructured materials with incorporated alkali metals in the crystal lattice, which apparently gives a higher effect of the promoter. All samples were characterized by X-ray powder diffraction, transmission electron microscopy and N₂ physisorption measurements. Furthermore, the effect of ruthenium loading on the catalytic decomposition of ammonia was investigated.     

Pore structure of reactively synthesized nanolaminate Ti3SiC2 alloyed with Al

Ti₃SiC₂ has the unique properties integrating the advantages of metals and ceramics, and good open pore structure when alloyed with Al. In this work, porous Ti₃SiC₂ compounds with different Al/Si atom ratios were prepared through the reactive synthesis of elemental powders at 1300 °C. The results indicate that the phase compositions are determined by Al element mole number, and that the pore structure can be controlled through varying Ti particle size. The MAX phase transits from Ti₃SiC₂ with Al element mole number no more than 0.6 to Ti₃AlC₂ with Al element mole number in the range of 0.8–1.2. When Al element mole number is 0.6, the porous compound has a single MAX phase of Ti₃SiC₂ with uniform microporous structure and high bending strength. Porous Ti₃SiC₂ alloyed with 0.6Al has a slow linear increase rate of 0.0083%/μm in open porosity with increasing Ti particle size, and a strict linear relationship between the maximum aperture and Ti particle size with the increase rate of 0.0342 μm/μm. The pore structure formed by the phase transition mechanism for porous MAX phase has the smallest tortuosity factor compared with that formed by the clearance mechanism and the Kirkendall effect.     

The thermal decomposition of K0.5Bi0.5TiO3 ceramics

The high-temperature behaviour of K_0.5Bi_0.5TiO₃, prepared using a conventional solid-state reaction method, was investigated using X-ray powder diffraction, scanning electron microscopy, wavelength-dispersive X-ray spectroscopy and Knudsen effusion combined with mass spectrometry. The results revealed the formation of an off-stoichiometric matrix phase with an excess of bismuth and a deficit of potassium compared to the stoichiometric K_0.5Bi_0.5TiO₃ during the solid-state reaction. During the thermal treatment potassium and bismuth vapours were detected over the solid sample and related to the thermal decomposition of the matrix phase. The losses of the potassium and bismuth components shifted the nominal composition to a three-phase region, and as a result, K₂Ti₆O₁₃ and a new Bi-rich ternary phase were formed in the system, the latter being formed after prolonged sintering. Differential thermal analyses and heating-microscope analyses showed a narrow sintering-temperature range limited by the melting of the sample above 1040 °C.     

Preparation and gaseous photocatalytic activity of smooth potassium dititanate film

A new smooth potassium dititanate film was prepared by sol-gel method and characterized by thermogravimetry (TG) and differential scanning calorimetry (DSC), X-ray diffraction (XRD), atomic force microscopy (AFM), UV-Visible diffuse reflectance and Raman spectroscopy. The gaseous photocatalytic activity of smooth K₂Ti₂O₅ films was studied using contact angle analysis from the photocatalytic decomposition of octadecyltrichlorosilane (OTS) based self-assembled monolayers (SAMs) formed on K₂Ti₂O₅ films. The photocurrent response of the film was determined by an electrochemical method. It was shown that the films were smooth, compact, and transparent when formed on glass. Compared with TiO₂ film, the K₂Ti₂O₅ film showed wide absorption in the ultraviolet and visible region. It was found that the monolayers on K₂Ti₂O₅ decomposed much faster than those on TiO₂ under UV irradiation of 254 nm in air. The film also exhibited a stronger photoresponse and a more stable anodic photocurrent. The K₂Ti₂O₅ film efficiently decomposes the alkylsiloxane monolayers under UVirradiation in air and it was found to be a good photocatalyst for gaseous organic pollutant treatment. __________ Translated from Journal of functional materials, 2007, 38(7): 1067–1070, 1073 [译自: 功能材料]     

Molten salt synthesis and characterization of lead-free (1-x)Na0.5Bi0.5TiO3-xSrTiO3 (x = 0, 0.10, 0.26) whiskers

In this study, Na_0.5Bi_0.5TiO₃-xSrTiO₃ (NBT-xST, x?=?0, 0.10, 0.26) whiskers were synthesized by a two step molten salt method using Na₂Ti₆O₁₃ whiskers as templates. The crystalline phase, morphology, microstructure, composition and ferroelectric characteristic of the whiskers were investigated in details. The topochemical transformation from Na₂Ti₆O₁₃ structure to NBT-xST perovskite structure was found to occur by structural rearrangement of the edge sharing octahedra into vertex sharing octahedra. The prepared polycrystalline NBT-xST whiskers possessed high aspect ratio with diameter of 500–800?nm and length of 5–10?µm. The PFM investigations confirmed the favorable piezoelectricity of NBT whiskers while the NBT-0.26ST whiskers displayed relaxor-ferroelectric characteristics at room temperature, exhibiting the potential of NBT-xST whiskers for fabricating high performance micro/nano-devices.     

BaO–TiO2 microwave ceramics

In this paper, the structure and dielectric properties of BaO–TiO₂ system ceramics were studied. By adding ZnO and Nb₂O₅ as sintering agents to the raw materials, the BaO–TiO₂ system ceramics were sintered at a temperature of 1260 °C for 2 h and have superior dielectric properties at 1 GHz: quality factor Q=12,500, relative dielectric constant ε_r≈37, temperature coefficient of dielectric constant α_ε=0±30 ppm/°C. XRD pattern shows that the main crystal phase of the ceramics is Ba₂Ti₉O₂₀, accompanied by a small number of additional phases: BaTi₄O₉, Ba₄Ti₁₃Zn₇O₃₄, Ba₄Ti₁₃O₃₀ and Ti₂Nb₁₀O₂₉, etc. The initial Ba/Ti ratio has a great effect on the dielectric properties of the ceramics, which can be explained by the variance in the formation of phases due to different Ba/Ti ratios.     

Effect of Heat-Treatment on the Mechanism and Kinetics of the Hydrogen Evolution Reaction on Ni—P + TiO2 + Ti Electrodes

Composite Ni—P + TiO₂ + Ti layers were prepared by codeposition of Ni—P alloy with TiO₂ and Ti powders from a solution containing suspension of TiO₂ and Ti particles. The electrodeposition was carried out under galvanostatic conditions at room temperature. The layers exhibited an amorphous Ni—P matrix in which crystalline TiO₂ and Ti were embedded. On the deposit surface, the nonstoichiometric Ti oxide, Ti₁₀O₁₉, and intermetallic compounds, NiTi, formed during the electrodeposition, were also present. The heat treatment of these layers in argon leads to the crystallization of Ni—P matrix and formation of nonstoichiometric Ti oxides, detected by XRD. Electrolytic activity towards the hydrogen evolution reaction (HER) was studied on these electrode materials before and after heat treatment. The mechanism of the HER was also studied, and the kinetic parameters were determined using steady-state polarization and electrochemical impedance spectroscopy (EIS). An increase in activity occurring after heating of Ni—P + TiO₂ + Ti layers is related to TiO₂ reduction and formation of nonstoichiometric Ti oxides: Ti₁₀O₁₉(400 °C), Ti₇O₁₃(500 °C) and Ti₄O₇(800 °C). It is postulated that the increase in electrochemical activity is related to the properties of these oxides and a facility for H reduction/adsorption on their surface, as well as to the presence of NiTi intermetallics as compared with the Ni—P + TiO₂ + Ti electrode.     

Fabrication of nanostructured non-stoichiometric TiO2-x by spark plasma sintering for enhancing its thermoelectric properties

In this study, nanostructured non-stoichiometric TiO_2-x compacts were prepared by the in-situ reduction of rutile titanium oxide (TiO₂) powder with urea powder via spark plasma sintering (SPS). The crystal structure and particle size of the prepared compacts were examined. The XRD patterns revealed that TiO₂ could be reduced easily by the urea powder to obtain non-stoichiometric TiO_2-x, and the compacts still possessed rutile crystal structures. The average particle sizes of the compacts were less than 250 nm, successfully obtaining the non-stoichiometric TiO_2-x with uniform nanostructures at the sintering temperature of 1073 K. In addition, nanostructured TiO_2-x compacts with Magnéli phase Ti_nO_2n-1 (n = 2, 4, 8) were fabricated by varying the volume fraction of Ti powder in a urea environment via SPS. The results suggested that addition of Ti powder contributed to the formation of Magnéli phases Ti_nO_2n-1, and the value of n decreased with an increase in the volume fraction of the Ti powder. Furthermore, the thermoelectric properties of the compacts sintered with and without Ti powder were both investigated. The TiO₂–U13.3-Ti10 compact displayed the highest power factor of 5.04 μWcm⁻¹K⁻² at 973 K. A lower thermal conductivity was achieved by TiO₂–U13.3-Ti10 compact in the temperature range of 373–973 K, approximately 3 Wm⁻¹K⁻¹, due to the nanostructures and Magnéli phases. The highest ZT value of 0.146 was obtained for the TiO₂–U13.3-Ti10 compact at 973 K, achieving a reasonable enhancement of thermoelectric properties.     

Thickness Dependence of Dielectric,Leakage, and Ferroelectric Properties of Bi6Fe2Ti3O18 Thin Films Derived by Chemical Solution Deposition

We prepared Bi₆Fe₂Ti₃O₁₈ thin films on Pt/Ti/SiO₂/Si substrates with thickness ranging from ～300 to ～900 nm by using a chemical solution deposition route and investigated the thickness effects on the microstructure, dielectric, leakage, and ferroelectric properties of Bi₆Fe₂Ti₃O₁₈ thin films. Increasing thickness improves the surface morphology, dielectric, and leakage properties of Bi₆Fe₂Ti₃O₁₈ thin films and a well‐defined ferroelectric hysteresis loops can form for the thin films with the thickness above 400 nm. Moreover, the thickness dependence of saturation polarization is insignificant, whereas the remnant polarization decreases slightly with increasing thickness and it possesses a maximal value of ～20 μC/cm² for the 500 nm‐thick thin films. The mechanisms of the thickness dependence of microstructure, dielectric, and ferroelectric properties are discussed in detail. The results will provide a guidance to optimize the ferroelectric properties in Bi₆Fe₂Ti₃O₁₈ thin films by chemical solution deposition, which is important to further explore single‐phase multiferroics in the n = 5 Aurivillius thin films.     

Synthesis and crystal structure of the dimeric,Ti–O–Ti bridged hydrid form polyoxoanion [α-1,2-PW10Ti2O39]210−

The reaction of trivacant precursor Na₉[A–PW₉O₃₄]·19H₂O with Ti(SO₄)₂ affords the novel dimeric, di-Ti^IV-substituted tungstophosphate K₄Na₆[α-1,2-PW₁₀Ti₂O₃₉]₂·14H₂O. The X-ray structural determination shows the dimeric, anhydride structure was formed by two Ti–O–Ti bonds linking two di-titanium-substituted Keggin anion [α-1,2-PW₁₀Ti₂O₄₀]. It was also characterized by elemental analysis, TGA, FT-IR and UV–vis spectroscopies.     

Photocatalysts using hexa- and octa-titanates with different tunnel space for water decomposition

Photocatalytic activities for water decomposition were examined for photocatalysts using hexa- and octa-titanates and TiO2(B) with different tunnel space in the structure. Using RuO2 as promoter, M2Ti6O13 (M = Li, Na, K, Rb) showed the stoichiometric production of Hz and O₂ except for Li, whereas H₂Ti₈O₁₇ and TiO₂(B) had very low activity producing only hydrogen as a product. The effects of promoters on Na₂Ti₆O₁₃ showed that the activity increased in the order of RuO₂ > RuO₂ + IrO₂ > IrO₂ > RuO₂ + Pt > MnO₂. These effects along with other related ones are discussed: it emerges that the presence of the tunnels is important for the achievement of high photocatalytic activity.     

The effect of second phase La0.67TiO2.87 on the phase structure and impedance spectroscopy of La2Ti2(1 + x)O7 piezoelectric ceramics

The Ti excess La₂Ti_{2 (1+x)} O₇ (x = 0, 0.005, 0.01, 0.02, 0.05, 0.1) piezoelectric ceramics have been prepared by sol-gel technology and solid state synthesis method. Through refinement analysis, the phase structure of the ceramics varies with Ti content. Most monoclinic phase (∼93%) and a handful of orthogonal phase (∼7%) coexist in La₂Ti_{2 (1+0)} O₇ ceramics. Pure monoclinic phase La₂Ti₂O₇ with space group P2₁ appears in La₂Ti_{2 (1+0.005)} O₇ and La₂Ti_{2 (1+0.01)} O₇ ceramics. Monoclinic phase La₂Ti₂ O₇ and a certain proportion of tetragonal phase La_0.67TiO_2.87 coexist in La₂Ti_{2 (1+0.02)} O₇, La₂Ti_{2 (1+0.05)} O₇ and Ti_{2 (1+0.1)} O₇ ceramics. With the excess of Ti content, the monoclinic phase ratio and distortion angles in a-b projection plane of the ceramics increase first and then decrease, which is consistent with the variation tendency of piezoelectric constant d₃₃. The excellent piezoelectric constant for Ti_{2 (1+0.01)} O₇ ceramics is 2.8 pC/N.Impedance analysis shows that the conductive mechanisms of all samples include both grain and grain boundary conductivity at temperature range T ≥ 500 °C. The formation of tetragonal phase La_0.67TiO_2.87 derives from Ti excess in pure monoclinic phase La₂Ti₂O₇. The existence of tetragonal phase La_0.67TiO_2.87 can obviously increase the capacitance of ceramics at x ≥ 0.05. All prepared piezoelectric La₂Ti_{2 (1+x)} O₇ ceramics have highly frequency stability and are candidates for ultrahigh temperature piezoelectric application.     

Enhanced intrinsic permittivity and bulk response in Y2/3Cu3Ti4+xO12 ceramics

Considering the contribution of the mixed valence structure of Ti³⁺ and Ti⁴⁺ to the semiconductivity of grain, compositions with the formula of Y_2/3Cu₃Ti_4+xO₁₂ were designed and prepared. The dielectric bulk responses of Y_2/3Cu₃Ti_4+xO₁₂ ceramics were explored in detail. Changing Ti stoichiometry gives rise to an increase of the intrinsic permittivity. Y_2/3Cu₃Ti_3.925O₁₂ ceramic exhibits a higher intrinsic permittivity of ~120 at 60 MHz than that of pure Y_2/3Cu₃Ti₄O₁₂ ceramics (87 at 60 MHz). Additionally, the activation energies of bulk responses are significantly enhanced by changing Ti stoichiometry, which is closely linked with the increase of Ti³⁺/Ti⁴⁺.