Synthesis of platy potassium magnesium titanate and its application in removal of copper ions from aqueous solution

Platy potassium magnesium titanate (K0.8Mg0.4Ti1.6O4, KMTO) was synthesized by a flux method. The potential application of KMTO in removing copper ions from water pollutants was investigated. The crystal phases of specimens were identified by XRD. The morphology and structural information were characterized by SEM and TEM. The adsorption behavior under different conditions was investigated, including different pH values and different initial copper ion concentrations. The results show that the maximum adsorption capacity of Cu(II) ions is 290.697 mg/g, and almost 99.9% of Cu(II) ions can be removed, which is much higher than that of other sorbents reported. The kinetics of KMTO for the adsorption of Cu(II)ions was studied and the best fit can be obtained by the pseudo-second-order model. Adsorption isothermal data can be well interpreted by the Freundlich equation (R2=0.991). In conclusion, this study highlights that KMTO is a potential material for the efficient removal of heavy metal ions in polluted water. It also opens up a new opportunity for the applications of platy KMTO.

Mussel-inspired PTW@PDA composites for developing high-energy gun propellants with reduced erosion and enhanced mechanical strength

The severe erosion and inadequate mechanical strength are prominent challenges for high-energy gun propellants.To address it,novel PTW@PDA composites was prepared by polydopamine(PDA)-modifying onto potassium titanate whisker(PTW,K_(2)Ti_(6)O_(13)),and after was incorporated into gun propellant as erosion-reducing and mechanical-reinforcing fillers.The interfacial characterizations results indicated that as-prepared PTW@PDA composites exhibits an enhanced surface compatible with propellant matrix,thereby facilitating their dispersion into propellants more effectively than raw PTW materials.Compared to original propellants,PTW@PDA-modified propellants exhibited significant less erosion,with a Ti-Kbased protective coating being detected on the eroded steel.And 0.5 wt%and 1.0 wt%addition of PTW@PDA significantly improved impact,compressive and tensile strength of propellants.Despite the inevitably reduction in relative force,PTW@PDA slightly increase propellant burning rate while exerting little adverse impact on propellant dynamic activity.This strategy can provide a promising alternative to develop high-energy gun propellant with less erosion and more mechanical strength.

Selective Oxidation of PM over Li Doped Potassium Titanate Catalysts

K2Ti2O5 and LixK2-xTi2O5 samples with varying K contents （x=0.125, 0.15, 0.3）, targeted on removal of two main environmental pollutants： PM and NOx, were synthesized by the solid state method using TiO2, KNO3 and LiOH-H2O as starting materials and were characterized by X-ray diffractometry, scanning electron microscopy, and BET. The catalytic activity of titanate catalysts on PM oxidation was evaluated using the temperature programmed oxidation （TPO） method. The test results showed that the perovskite structure of K2Ti205 was still retained after doping a small amount of Li, and the catalytic performance of LixK2-xTi2O5 had been improved significantly compared with that of K2Ti2O5. Li0.15K1.85Ti205 catalyst had the highest catalytic activity with an ignition temperature of 210℃ and a peak temperature of 290℃. The catalytic activity of both K2Ti2O5 and LixK2-xTi2O5 under intimate contact was higher than that under loose contact. When the exhaust gas flow rate was around 100 mL/min, the catalyst samples showed a highest activity. The Li doped K2Ti2O5 could be an excellent candidate for PM oxidation due to its high oxidation activity, water stability, resistance to sulfur poisoning and economical advantages.

Wear properties of potassium titanate whiskers-reinforced Al-12Si alloy composites

Potassium titanate （K2O·6TIO2） whiskers-reinforced Al-12Si alloy composites were prepared by the squeeze casting technique. Wear properties of the composites were investigated by pin-on-disc tests under dry conditions. The experimental results showed that K20 ·6TiO2 whiskers can effectively reinforce the matrix alloy and improve the wear resistance of the composite when the volume fraction of whiskers is low at 10 vol%. However, the composites with a high volume fraction of whiskers showed lower wear resistance than the Al-12Si alloy. The main wear mechanism of the composites is clarified as de-lamination and abrasive wear.

Preparation and Tribological Properties of Ni-P Electroless Composite Coating Containing Potassium Titanate Whisker

Nickel-phosphorus （Ni-P） composite coatings containing potassium titanate （K2Ti6O13） whiskers （PTWs） were prepared by electroless plating. The surface morphology and component of coatings were investigated by scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDX）, respectively before and after wear test. The tribological performance was evaluated using a pin-on-disk wear tester under dry conditions. It is found that the Ni-P-PTWs composite coatings exhibit higher wear resistance than Ni-P and Ni-P-SiC electroless coatings. The favorable effects of PTWs on the tribological properties of the composite coatings are attributed to the super-strong mechanical properties and the specific tunneling structures of PTWs. The PTWs greatly reinforce the structure of the Ni-P-based composite coatings and thereby greatly reduce the adhesive and plough wear of Ni-P-PTWs composite coatings.

Preparation and Characterization of Alkaline Resistant Porous Ceramics from Potassium Titanate Whiskers

The preparation and characterization of alkaline resistant porous ceramics from potassium titanate whiskers are studied. K2Ti4O9 whiskers in the whisker preforms （mixtures of K2Ti6O13 and K2Ti4O9） were completely converted to K2Ti6O13 at 960℃. The alkaline resistance as well as the change in bending strength, porosity and permeability of the ceramics was investigated by altering the composition of the preforms in which the content of K2Ti6O13 whiskers was higher than 50% （molar fraction）. The alkaline resistance of the porous K2Ti6O13 ceramics is found much higher than that of Al2O3 in caustic NaOH solutions, and further study indicates that the K2Ti6O13 ceramics can be stably used in solutions of pH〉2.0. The bending strength increases initially with the content of the raw K2Ti6O13 in the preforms up to 66% （molar fraction） and then decreases, contrary to the behaviors of porosity and permeability. The values of bending strength, porosity and permeability of the ceramics prepared from the preform of 80% （molar fraction） raw K2Ti6O13 whiskers are respectively 56MPa, 29.4% and 330L·m^-2〈h^-1 , which are comparable to those of the porous Al2O3 ceramics.

Effect of atmosphere on the synthesis of potassium titanate

Potassium titanate （K4Ti3O8） was synthesized by the reaction between ilmenite and concentrated KOH solution in the atmosphere of nitrogen,still air,and oxygen,respectively.The obtained samples were systematically investigated by X-ray diffraction （XRD）,inductively coupled plasma optical emission spectrometer （ICP-OES）,and scanning electron microscopy （SEM）.XRD results indicate that K4Ti3O8 have been synthesized in different atmospheres.The oxidizing atmosphere could enhance the conversion rate of Ti from ilmenite to K4Ti3O8,and Fe（II） is easily oxidized to trivalent iron Fe（III） during the reaction.Furthermore,SEM images show that the different atmospheres have significant effect on K4Ti3O8 crystal morphology and particle size.Well shaped K4Ti3O8 crystals are obtained in nonoxidizing atmosphere.

Performance of Potassium Titanate Whisker Reinforced PPESK Composites

A group of poly (phthalazinone ether sulfone ketone)/potassium-titanate-whisker (PPSEK/whisker) composites was prepared by coprecipitation from solution. The whisker surface was modified using titanate coupling agent prior to blending. The tensile, impact, morphology and thermal properties of the moulded composites were investigated. The measurements showed that the tensile strength and impact strength of the composites increased with increasing whiskers content up to 10 to 20 phr, thereafter they showed a decrease in the whiskers content reached 40 phr. At the same time, the modulus of the composites increased with increasing whiskers content. Scanning electron microscopy studies revealed that the whiskers within the composites were dispersed uniformly by treated with coupling agent. Finally, thermogravimetric analysis showed that the heat resistance of the composites tended to increase with increasing whisker content. The results were analysed and discussed in terms of established models of the behaviour of short-fiber reinforced composites.

Preparation of Layered Potassium Titanate Whiskers with Large Length-diameter Ratio by KDC Method

Pure K2Ti4O9 whiskers were prepared by KDC（Kneading-Drying-Calcination） method with TiO2 and K2CO3 as raw materials. The influences of TiO2/K2CO3 molar ratio（RT/K）, calcination temperature（TC） and cooling process on phase composition and morphology of the whiskers were investigated by TG-DSC（thermo gravimetric-differential scanning calorimeter）, XRD（X-ray diffraction）, and SEM（scanning electron microscope）. Pure K2Ti4O9 potassium titanate whiskers with large length-diameter ratio（r）（over 250） can be obtained at RT/K = 2.9 and TC = 950 ℃.

A Novel Method to Prepare Potassium Sodium Titanate Nanotubes

A novel method, i.e. molten salt method, was adopted to prepare potassium sodium titanate nanotubes. EDX results indicated that the ion-exchange reaction reached an equilibrium state at around 9 h. The 24 h ion-exchanged product maintained nano-tubular and its crystalline structure was consistent with that of Na2Ti2O4（OH）2 nanotubes. The nanotubes have a high specific surface area, possibly making this material a good candidate as controlled release materials, catalyst, electrode materials, etc..

Preparation and Catalytic Performance of Potassium Titanate Used as Soot Oxidation Catalyst

To prepare potassium titanate catalyst, a novel citrate acid complex-combustion method using CH3COOK and Ti（OC4H9）4 as raw materials was developed. The crystalline phase and surface morphology of K2Ti205 were investigated by X-ray diffraction （XRD）, field emission scanning electron microscope （FE-SEM） and transmission electron microscope （TEM）. The impact of some factors, such as the type of contact between K2Ti205 and soot, the content of water vapor and SO2 in exhaust, and the repeated use on catalytic activity of K2Ti205 were studied by temperature programmed reaction （TPR）. A comparison between the new method and the reported ones on catalytic activity of potassium titanate was investigated. The results showed that K2Ti205 had high catalytic activity and good stability.

STUDY ON APPLICATION OF POTASSIUM TITANATE WHISKER MATERIALS IN PREPARATION OF PHOTOCATALYST

The K2Ti4O9 whiskers were chosen for the catalyst carrier, TiO2/potassium titanate photocatalyst was prepared by Sol-gel method. The product was characterated by X-ray diffraction and SEM. EDS shows that, the main peck included Ti, O, and K in potassium titanate whisker. The main peak of K disappeared and the peaks of Ti, O stayed after whisker was covered. It directed that the surface of sample was covered by TiO2. XRD shows that diffraction peak appeared, which was corresponded to the peak of anatase TiO2. In the reaction device of photochemistry, using middle-pressure mercury lamp as illumination, rhodamine B as simulant pollutant, the photocatalytic performance of TiO2/potassium titanate was studied. Under the same conditions, the lower pH, the larger illuminance, the higher temperature, the greater aeration quantum and the lower initial concentration of rhodamine B, the higher decoloration rate was got. Under our experiment conditions: pH 6, the illuminance of 250W, the temperature of 313K, and the aeration quantum of 2.0L/min. When the concentration of rhodamine B was 8mg/L The photocatalyst of TiO2/potassium titanate was 0.01g/L. The decoloration rate of TiO2/potassium titanate dealt with the rhodamine B reach over 95% in 160min, and compare with TiO2, the decoloration rate of rhodamine B was improved 0.50~1.91 multiple. TiO2/potassium titanate can be used to treatment of dye wastewater.

Adsorption and photo-catalytic properties of layered lepidocrocite-like quasi-amorphous compounds based on modified potassium polytitanates

TiO2 compounds possess relatively high adsorption abilities and exhibit high photocatalytic activities that exhibit potential for the destruction of organic pollutants in natural and waste waters.Nanostructured potassium polytitanates modified using transition metals and their oxides/hydroxides generate new nanomaterials that operate in the visible spectral range.This study presents the synthesis and investigation of the structure,composition and photocatalytic activity of powdered nanoscale quasi-amorphous potassium polytitanates particles modified with iron,zinc,copper,cobalt and nickel sulfate in aqueous solutions.All of the powders investigated in this work exhibit a high adsorption capacity for methylene blue dye（15-20mg/g） related to the welldeveloped surface of the layered potassium polytitanate particles.Introducing transition metals and their oxides/hydroxides influences the electronic structure of the obtained systems.A high photocatalytic activity was observed for systems containing iron,zinc,nickel and their oxides/hydroxides in the ultraviolet and visible ranges.

STUDY OF K_2O·6TiO_2 WHISKER REINFORCED AI COMPOSITES FOR THEIR MECHANICAL PROPERTIES AND INTERFACIAL STRUCTURES

A newly developed whisker K_(2)O 6TiO_(2) reinforced 6061 Al composite was prepared by squeeze casting process. The flexural strength of the composite is 518MPa, and decreases to 490 M Pa after T6 treatment.The hardness of the composite also shows the similar change while T6 treating. The results of HRTEMobservation may explaine this property change. It was considered that there is a continuous TiO layer at the whisker-matrix interface, which is easily to react with the segregated Mg and to form MgTi_(2)O_(4), MgAl_(2)O_(4). The thickening of TiO layer after T6 treatment is the main reason resulting in strength degradation of composite.

Effects of Processing Conditions on Hydrothermal Synthesis of K_(0.5)Bi_(0.5)TiO_3 Nano-Powders

Potassium bismuth titanate nanosized powders were prepared by the hydrothermal method using Ti(C_4H_9O)_4 and Bi(NO_3)_3·5H_2O as raw materials in alkaline solution.The phase composition,particle size and morphology of the powders were studied by XRD and TEM analysis.The results showed that the powders were well crystallized and dispersed.The crystal phase of the powders was K_(0.5)Bi_(0.5)TiO_3 with the grain size of about 50 nm～100 nm.Hydrothermal temperature and alkaline concentrations had great effects on the phase composition and morphology of the resultant powders.Pure K_(0.5)Bi_(0.5)TiO_3 powders could be synthesized at 170℃～180℃with KOH concentration of 8 mol/L～12 mol/L.

STABILITY OF WHISKERS AND INTERFACIAL MICROSTRUCTURE IN ALUMINUM MATRIX COMPOSITES REINFORCED BY K_2O·8TiO_2 WHISKERS

The stability of K_2O·8TiO_2 whiskers and the microstructures of the interfaces in K_2O·8TiO_2 whisker reinforced ZL109 aluminum composites under different heat treatment conditions were investigated by means of transmission electron microscopy(TEM) , mostly by high resolution TEM( HRTEM). It was found that K_2O·8TiO_2 whiskers were not very stable.The edge of the whiskers decomposed and a TiO interfacial layer formed during the process of fabricating K_2O·8TiO_2/ ZL109Al composite,and so the interior with increasing temperature and time of heatreatment. Two kinds of interfacial microstructures between the whiskers and the matrix were characterized; one was the TiO layer and the other was a nano scale amorphous transition layer. A few MgAl_2O_4 particles were also observed at the whisker/ matrix interfaces.

Synthesis and characterisation of potassium polytitanate for photocatalytic degradation of crystal violet

Potassium titanate nanostructures were synthesised by hydrothermal treatment of TiO2 （P25） in KOH and H2O2. As-produced powders were characterised by scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray diffraction, and nitrogen adsorption-desorption methods. Longitudinally-oriented-wire-like structures with a length up to several micrometres and diameters ranging from 10 to 30 nm were obtained. Larger size fibrous nanowires resulting from the hydrotherrnal treatment showed high affinity in adsorbing crystal violet （CV）, which was mainly due to their high surface area. The photocatalytic bleaching of CV solution revealed that the wires are photoactive under ultraviolet light irradiation. Macroporous nanowires are considered as effective adsorbents of CV, capable of photocatalvtic degradation, and they can be easily separated from the solution by settling.

ENHANCED PIEZOELECTRIC PROPERTIES IN(Bi_(0.5)K_(0.5))TiO_(3)-(Bi_(0.5)Na_(0.5))TiO_(3)FERROELECTRIC SINGLE CRYSTALS

Single crystals of x(Bi,K)TiO_(3)-(1-x)(Bi,Na)TiO_(3)(0.11≤x≤0.47) were grown by a flux method and their polarization and piezoelectric properties were investigated along h100i cubic at 25℃.Rietveld analysis of powder X-ray diffraction data provides a tentative phase diagram in this system.rhombohedral R3c for x≤0.22,pseudocubic for 0.22<x<0.3 and tetragonal P4mm for 0.3≤x.Piezoelectric strain properties show that the crystals(x=0.38)exhibited an extremely large piezoelectric strain constant of 637 pm/V.

Correlations between structure,microstructure,density and dielectric properties of the lead-free ferroelectrics Bi_(0.5)(Na,K)_(0.5)TiO_(3)

Solid solutions of the lead-free ferroelectric oxides Bi_(0.5)Na_(0.5)TiO_(3)(BNT)and Bi_(0.5)Na_(0.5)TiO_(3)(BKT),represented as(1-x)BNT-xBKT,are studied for very close compositions in the range0≤x≤0.36 to understand the correlation between the structure and the properties.Compositions are varied in steps of △x=0.02 in the range0≤x≤0.1 and0.2≤x≤0.36 and△x=0.01 in the range 0.1≤x≤0.2,to precisely locate the structural transition as well as the morphotropic phase boundary(MPB)region and the compositional region of best performance.Rietveld refinement analysis of the powder X-ray diffraction patterns showed monoclinic phase up to x=0.17 and a mixture of monoclinic and tetragonal phases for x>0.17.Similarly,the density and the dielectric constant showed linear variation up to x=0.17 and a large increase above this composition,showing maximum values in the compositional range 0.22≤x≤0.26,corresponding to the MPB region.Microstructural features also showed corresponding changes,indicating close relationship between the structure,microstructure and properties of the different compositions.