Titanium and its alloys have a series of advantages, such as low density, high strength and anticorrosion, and they are widely used in the field of aerospace, national defence and military, light industry, and so on. However, the production and utilization of titanium and its alloys are limited for their high chemical activity at molten state. For example, titanium and its alloys can react with all conventional refractories.It is known that yttria is an ideal materials for the melting of titanium and its alloys because of its high melting point, anticorrosion and high-temperature stability. But the application of yttria is retarded for its high sintering temperature and poor thermal shock resistance. On the consideration that calcia, zirconia and their compounds with yttria have relatively good chemical stability between molten titanium, in present work, nanosized Y2O3 powder was firstly prepared, and then the effect of the addition of CaO and ZrO2 on the sintering properties of yttria was investigated. Based on the work, the main results are listed in the following.（1） The higher heating temperature results in higher density and lower porosity.Moreover, the decrease of the size of powder can improve the density of yttria.（2） Addition of calcia can promote the sintering at lower temperature. With theincrease of temperature, the sintering ability of yttira can be remarkably improved by the addition of merely 1mol% calcia, whereas the sintering could not be better by adding more calcia and extending sintering time. After sintering the calcia aggregates on the grain boundary of yttria, forming solid solution or compound. Once the temperature is overtop, samples will suffer oversintering. Thus 1600°C is a suitable temperature as a small quantity of calcia addition.（3） A ZrO2 addition less than 1mol% has no obvious effect on the sintering ability ofyttria. However, the density of yttria decreased with increasing ZrO2 content. With a more addition to 7mol% of zirconia, a certain increment of density is obtained.
Post about "Zirconia"
Since the discovery of carbon nanotubes（CNT） in the early 90s,much attention has been paid to them.The one-dimensional tubular structure of CNT has greatly stimulated studies of this novel material in the field of physics,chemistry and material science.Depending on their atomic structure,CNT behave electronic properties suggest that CNT have the ability to promote electron-transfer reactions.In a recent review,Attention has been paid that the CNT composite material has electronic,adsorption,mechanical and thermal properties.With the further development of CNT and nanotechnology,studies on preparation,properties and application of CNT composite materials have still been a hot topic attracting lots of researches in the world.PartⅠThe systemtic aspects,the concept of biosensor,the classification of biosensor, the classification of electrobiosensor,the preparation of CNT,the structure of CNT, the modification of CNT and its application were described in detail.PartⅡIn part two,a novel amperometric sensor for glucose was constructed by entrapping glucose oxdise（GOD） in a new chitosan composite doped with ferrocene monocarboxylic acid-modified 3-（aminopropyl） triethoxysilane enwrapping multiwalled carbon nanotubes（FMC-AMWNTs）.The approach was very simple, timesaving and effectively prevented the leakage of the ferrocene monocarboxylic acid mediator during measurements.The entrapped FMC-AMWNTs composite performed excellent redox electrochemistry and acted as an electron transfer mediator. This matrix showed a biocompatible microenvironment for retaining the native activity of the entrapped GOD and a very low mass transport barrier to the substrate. Under optimal conditions,this biosensor was able to detect glucose in the linear range of 0.01～4.2 mM with a detection limit of 3.4μM（S/N=3）,the value of KMapp was 6.3 mM.This immobilization approach effectively improved the stability of the electron transfer mediator and is promising for construction of biosensor and bioelectronic devices.PartⅢIn part three,a novel Single-walled carbon nanotubes wrapped by polyvinyl/ ferrocene（Fc/SWNTs） composite was synthesized by in-situ polymerization of vinylferrocene initiated by free radical.The approach was very simple,timesaving and effectively prevented the leakage of the vinyl/ferrocene mediator during measurements.FT-IR and electrochemical measurements were employed to characterize the composite.The Fc/SWNTs modified glassy carbon electrode（GC） presented a good electrocatalytic activity to ascorbic acid（AA） and the modified electrode was used for amperometric detection of AA,the linear range is from 6.0μM to 0.53 mM（R=0.998） with a detection limit of 0.22μM at 3σ.When the applied potential was controlled at 0.43V,uric acid（UA） caused no interference in the detection of AA.PartⅣIn part four,Zirconia/multiwalled carbon nanotube（ZrO2/MWNTs） nanocomposites were successfully prepared by hydrothermal treatment of MWNTs in ZrOCl2·8H2O aqueous solution.The composites were characterized by TEM and XRD analysis.It was found that ZrO2 nanoparticles homogeneously distributed on the sidewall of MWNTs.Myoglobin（Mb）,as a model protein to investigate the nanocomposites,was immobilized on ZrO2/MWNTs nanocomposites.UV-vis and electrochemical measurements showed that the nanocomposites were well biocompatible and could retain the bioactivity of immobilized Mb to a large extent. The Mb immobilized in the composite showed excellent direct electrochemistry（DET） with an electron transfer rate constant of 1.52 s-1,and electrocatalytic activity to the reduction of hydrogen peroxide（H2O2）.The linear response range of the biosensor to H2O2 concentration was from 1.0 to 116.0μM with the limit of detection of 0.53μM （S/N=3）.The biosensor exhibited high sensitivity,acceptable stability and reproducibility.The ZrO2/MWNTs nanocomposites provided a good matrix for protein immobilization and biosensors. PartⅤIn part five,manganese dioxides（MnO2） was costed on multiwalled carbon nanotubes（MWNTs） surface by simple immersion of MWNTs into a KMnO4 aqueous solution.The manganese dioxides/multiwalled carbon nanotubes（MnO2 /MWNTs） were characterized by TEM and and electrochemical measurements.The MnO2/MWNTs composite modified carbon electrode was prepared by immobilizing MnO2/MWNTs composite onto glassy electrode surface,and its electrocatalytic property was investigated.With the introduction of MWNTs,the electrocatalytical activity of MnO2 was improved due to the excellent electron-transfer ability of MWNTs.A sensitive biosensor for the determination of hydrogen peroxide（H2O2） was fabricated with complex substance.The performance of H2O2 biosensor was investigated by cyclic voltammetry and chronoamperometry.The factors in the fabrication and manipulation of the sensor are initially studied.Under optimal conditions,this biosensor was able to detect H2O2 in the linear range of of 6.7μM～5.22 mM with a detection limit of 0.86μM（S/N=3）.The biosensor exhibited high sensitivity,acceptable stability and reproducibility.
Recently,the solid superacid catalysts,SO42-/MxOy,have attracted much more attention to the researchers’due to their strong acidity,thermal stability,environmentally amity and excellent catalytic activity. The catalysts are very attractive for petrochemical industryIt studied SO42-/ZrO2 which has the strongest acidity among the SO42-/MxOy solid superacid catalysts,mainly about the preparation and application of solid superacid catalyst SO42-/ZrO2 for n-pentane isomerization. The solid superacid catalyst Pd-SO42-/ZrO2-WO3 was prepared by adding noble metal Pd and using WO3 as an secondary oxide. The catalyst was evaluated with n-pentane as feed on high pressure microreactor of 10mL continuous flow fixed-bed which was connected with online chromatogram unit. In order to study the effects of preparation methods,such as quantity of WO3,calcination temperature,kind of impregnated solutions,concentration of H2SO4,way of adding H2SO4,concentration of H2SO4,quantity of Pd,activating temperature and activating time,on the performance of catalyst were investigated respectively,and the best preparing conditions were defined. Also,the reaction tempreture,reaction pressure,airspeed and the molar ratio of H2 and nC5 were studied to define the best technological conditions. Because of adding Pd,the catalyst possessed both abilities of the isomerization and hydrodesulfurization. The catlyst still showed steady isomerization activity even in the presence of sulfur-containing pentane.The results showed that the sample,whose mass ratio of WO3 and ZrO2 being 0.10,quantity of Pd being 0.05%,impregnating in the H2SO4 solution of 0.8mol/L,calcinating at 600℃and activated at 300℃for 3h in H2,is best for the reaction of alkyl isomerization. The n-pentane conversion is 65.29%,isopentane selectivity is 93.52%,isopentane yield is 61.06% and liquid product yield is 95.77% ,when the catalyst was reacted at the conditions of reaction temperature of 260℃,space velocity of 1.0h-1,H2/ n-pentane molar ration of 4.0 and reaction pressure of 2.0MPa.
Nano-ZrO2 has widespread potential applicability in the fields of inorganic materials with many unique properties.Various novel properties of ZrO2 nanostructures stem from the chemical component,equally important,that these properties change with respect to specific structure,size and morphology.The strategy of using organic templates or modifiers with complex functionalization patterns to control the nucleation,growth,and alignment of crystals has been widely adapted for the biomimetic synthesis of a variety of inorganic materials with complex forms.This dissertation focuses on the shape-controlled synthesis of ZrO2 modulated by organic templates,We primarily investigated the formation mechanism and optical properties of the as-prepared ZrO2 with different morphologies.The main contents are shown as below:1.Controlled synthesis of floriated and peanut-like ZrO2 was studied in a systems of acetone and aether,and the results showed that the acetone and aether system were very effective crystal growth modifiers to direct the growth of ZrO2 crystals to various morphologies.2.ZrO2 crystal with morphology of dendritic was prepared in the presence of PEG200. The results showed that PEG200 obviously influenced the formation of precipitates and the morphology of final products.PEG200 have dual roles.On the one hand,the PEG200 provided nucleation sites with Zr4+ through the role of charge matching.On the other hand, the PEG200 has played the role of steric and that avoid the hard reunion.3.spindle-shaped ZrO2 was synthesized using saccharide compounds such as glucose, sucrose,dextrin and starch as templates.At acidic conditions,the sucrose,dextrin and starch hydrolysis to generate glucose.Therefore,the mechanism of interaction between ZrOCl2 and sucrose,dextrin and starch similar to the interaction between ZrOCl2 and glucose.4.Rod-like and.cube-shaped ZrO2 were synthesized successfully by a biomimetic method with the existence of tryptophan and p-hydroxyphenylglycine by biomimetic method. In the synthesis process,the functional group of the amino acid molecular played a crucial role.Preparation of pit-shaped ZrO2 nanoparticles using microzyme as template. 5.PL spectrum obtained from Shape-controlled ZrO2 nanostructures.Compared with the conventional ZrO2 material,the fluorescence intensity of nano-ZrO2 with special morphology is far stronger than conventional materials zirconia.The emission peak of nano-ZrO2 with different morphologies has different intensity.The PL relative intensity is apparently intensifying with increasing temperature.
The ZrO2 matrix nano-ceramic composites were fabricated by hot press sintering using nano- ZrO2 powders. The microstructures were analyzed by means of XRD, SEM, EDS and so on. The effect of the second phases Al2O3 and SiC particles on the mechanical properties and microstructure of ZrO2 nano-ceramics were investigated, and the reinforced and toughening mechanism were discussed.First of all, based on the introduction of microstructure, development of ZrO2 based ceramics, fabrication methods and sintering methods, the content and significance of this thesis were indicated. Second, fabrication techniques, testing methods of mechanical properties and observing methods of microstructure of nano-ZrO2 matrix ceramic composites were introduced.The research results showed that composite powders of Al2O3/ZrO2 can be well dispersed after being ultrasonically dispersed with dispersant agent of PHAA-NH4 and wet ball milled. The second phase Al2O3 dispersed homogeneously in the matrix grains. The second phase Al2O3 inhibited matrix grains growth, i.e. the ratio of grains is inverse proportion to the amount of Al2O3, but excessive amount of Al2O3 causes grains agglomeration decreasing the density. When the amount of doped-Al2O3 was 9mol%, the relative density, hardness and flexure strength of composite ceramics reached the maximum; but fracture toughness arrived crest value when doped-Al2O3 was 12mol%. The matrix ZrO2 grains were refined after adding Al2O3 and SiC, which induced fracture model to change from intergranular fracture to transgranular fracture.It was analyzed from SEM photos that many toughening mechanisms played roles in composite ceramics material. Firstly, the second phase Al2O3 which located at grain boundary refined matrix grains as a result of pinning effect. Secondly, the second phases Al2O3 induced crack deflection and bridging crack obviously, which Al2O3 grains shape played a very important role in performance improvement. Thirdly, transgranular microstructure formed when Al2O3 entered matrix grains. The formation of this microstructure has direct relationship with sintering temperature and second phase’s grain diameter. Transgranular fracture became the chief fracture model because that difference of thermal expansion coefficient between Al2O3, SiC and matrix ZrO2 exerted compression stress on matrix and reinforced grain boundary. Those mechanics increased fracture toughness of composite ceramics.
The ceramics of zirconia is one of the engineering ceramics with outstanding performance, it has attracted much attention of material scientists to research deeply for a long time. It can be show that the hotspots of the forming technique research of zirconia go through for recent 20 years like other engineering ceramics. The gelcasting forming process of zirconia was investigated in this paper against the background of research for water pump impeller of zirconia ceramics with high corrosion-resistant.Preparation of suspensions with low viscosity and high solid volume fraction is a key technology for the gelcasting process of ceramics, namely. In the work, the suspensions in the water system were prepared by the acrylamide[CH3CONH2] （AM）, N,N’-methylene bisacrylamide[C7H10N2O2] （MBAM） and E80 as a monomer, a coupling agent and a dispersant, respectively. Influences of the solid volume, dispersant amount, pH and monomer concentration on the rheological properties were investigated. The result indicated that E80 can disperse zirconia powders in the monomer solution adequately; the suspension with 50vol.% high solid volume and 300mPa·s low-viscosity was achieved in the premix with the the ratio of AM to MBAM was 17:1, （AM+MBAM） to water was 18:85, respectively, the E80 in 0.3% out of the suspension weight and pH in 10.5.Gelation behavior of the suspensions with 50vol.% zirconia were studied by the traditional gelling conditions and microwave treatment in the condition that APS is used as initiator and TEMED as catalyst. The influences of initiator, catalyst and gelling temperature on the gelling time were investigated in the traditional gelling conditions. It shows that high stable and low-viscosity zirconia suspensions was achieved at ambient temperature when initiator addition is less than 1 %, volume content of catalyst is between 0.4% and 0.5% gelling temperature is 60℃, the gelling time can be controlled in 20-30mintues in the case of gelling temperature is 60℃. The zirconia ceramics body of water pump impeller was prepared successfully with the 50vol.% zirconia suspensions.The effects of microwave treatment time and microwave power on the solidification time of slurry were discussed using the isopyknic suspension irradiated by microwave with different power in the case of the amount of initiator and catalyst keeping the same ratio as the traditional solidification and the mechanical property of the green body were also analyzed. The experimental results show that microwave power greatly affected the gelation time and the intensity of the green body. The green body of ceramics with high density and strength were achieved in the proper delivered power. The solidified technics with microwave treatment can reduce the gelation time effectively compared to traditional gelling conditions. The microvave treatment was double action （heating and initiating radical） in the process of gelation and was propitious to polymerization of the organic monomer quickly and equably.
Carbon nanotubes have demonstrated a wealth of exceptional structure, mechanical and electronic properties.In recent years, the investigations on the synthesis and properties of CNTs nanocomposites are one of the research hot spots in CNTs science and research area.In the presented paper, different oxides were respectively combined with carbon nanotubes to form novel nano-composites,The obtained composites were characterized using X-ray powder diffraction (XRD),X-ray energy dispersion spectrum(EDS),Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM);Nano-sized hole had been made on the surface of carbon nanotubes by air oxidation.Main research contents as followed:1.The purified carbon nanotubes were prepared with acid-treatment in nitric acid solution. The results show that purified carbon nanotubes were clean, many catalysts and unformed carbon had been removed; meanwhile,chemical functional groups had been attached the surface of carbon nanotubes,which was in favor of preparing carbon nanotubes nano-composites;the purified carbon nanotubes had good solubility in solvent.2.Two different ceria nano-particles/multi-wall carbon nanotubes (CeO2/CNTs) had been prepared by solvent-thermal method.Sizes, morphology, and conformation of CeO2 nanoparticles with CNTs were investigated by X-ray diffraction (XRD), Scanning electron microscope (SEM) and High Resolution transmission electron microscopy (HRTEM).Results indicate that the sizes, morphology,and conformation of CeO2 nanoparticles with CNTs can be controlled via H2O quantity.Spherical ceria nanoparticles along CNTs necklace-like supper-stable nanocomposites with size about 100 nm were synthesized at 7% H2O,otherwise, ceria nanoparticles coating on MCNTs with size about 20 nm were founded without H2O.Finally,the influence of H2O in methanol to the size of ceria nano-particles was discussed. 3.Two different gadolinium oxides/multi-wall carbon nanotubes (Gd2O3/CNTs) had been prepared by solvent-thermal method.The gadolinium oxide layer with thin coating sheath about 3-8 nm can be acquired at pH=3,while gadolinium oxide nanparticles with different shapes are got at pH=10.The structure,morphology of nanocomposites was characterized by X-ray powder diffraction (XRD),X-ray energy dispersion spectrum(EDS),Scanning electron microscopy (SEM), Transmission electron microscopy(TEM)respectively.The structure of gadolinium oxide can be established body-centered cubic phase finally.4.Anatase and Rutile had been deposited on the defects of the carbon nanotubes,the result of X-ray powder diffraction indicated Titania was tetragonal structure,single crystal;tetragonal structure zirconia single crystal nano-particles had been prepared by solvent-thermal method.The result of transmission electron microscopy(TEM) showed the size of zirconia was 6nm, based on Scherrer formula,5.4nm.5.Nano-sized hole had been made by air-oxidation controlling calefactive velocity、keeping time.As high energy dangling bonds exist on the defects of carbon nanotubes,air oxide carbon nanotubes by layer, finally forming nano-sized hole.
In this paper, Zirconia composite materials were prepared by semi-dry forming and sintering at high temperature. The main raw materials were Zircon, baddeleyite, mullite and alumina. The influences of sintering temperature, zirconia content and mullite content on the linear change rate, bulk density, apparent porosity, flexural strength and compressive strength were researchd. The phase compositions of samples were analyzed by the means of analysis of X-ray diffraction. The microstructures of samples were studied by SEM and EDX. The following conclusions have been approached from this study:1. The phase compositions of the zirconia-mullite composite materials were zirconia and mullite. The phase compositions of the zirconia composite materials which were prepared by in-situ synthesis were zirconia, mullite and corundum.2. Mosaic structure of granular zirconia and acicular mullite was found in the microstructures of the zirconia-mullite composite materials. The grain size increases gradually while the sintering temperature is increased. Mosaic structure of granular zirconia, corundum and acicular mullite was found in the microstructures of the zirconia composite materials which were prepared by in-situ synthesis. The grain size and mullite increases gradually with the rising of sintering temperature.3. General performance of zirconia-mullite composite materials was better when the content of mullite is 30%. When the sintering temperature of Z sample is 1550℃, the apparent porosity is 1.86%, and the flexural strength is 73MPa.4. Flexural strength of the zirconia composite materials which are prepared by in-situ synthesis appeared to have an increased trend after an initial decreased with the increase of zirconia content. General performance was better when the content of zirconia is 35%. When the sintering temperature of A sample is 1550℃, the apparent porosity is 2.73%, and the flexural strength is 128.25MPa.5. The conclusion will be summarized: General performance of the zirconia composite materials which are prepared by in-situ synthesis was better. When the sintering temperature is 1550℃, zirconia composite materials who has the better performance will be prepared according to the A sample. The bulk density is 3.56g/cm~3, the apparent porosity is 2.73% and the flexural strength is 128.25MPa.
This paper presents the characteristics of zirconia ceramic materials,as well as the research and development of metering nozzle refractory at home and abroad.To baddeleyite,zircon andα-Al2O3 powder as main raw material,adding a certain amount of binders and additives,according to ZrSiO4/Al2O3 and ZrO2/CaO different ingredients, prepared zirconia metering nozzle materials.The linear change rate,bulk density, apparent porosity,flexural strength and compressive strength of the samples were tested. The phase composition and microstructure of the samples were analyzed by XRD and SEM.And the influence of sintering temperature and additives added to the material composition,structure and performance is also discussed.The results show that:（1） The system of ZrO2-Al2O3-SiO2,the main phase of Z1 sample is zircon, zirconia and mullite.The main phase of Z2 and Z3 sample is zirconia,mullite and corundum.The system of ZrO2-CaO,the main phase of 3# and 6# sample is zirconia solid solution and calcium zirconate.The main phase composition of 4# and 5# sample is zirconia solid solution.（2） The system of ZrO2-Al23-SiO2,grain size is increased with increasing sintering temperature.Grain size is increased with the content increased ofα-Al2O3 The system of ZrO2-CaO,grain size is increased with the content increased of CaCO3.（3） The effects of preparation parameters on the performance of ZrO2-Al2O3-SiO2 sample were studied.The suitable sintering temperature was 1550℃,and the suitable addition ofα-Al2O3 was 45%～54%.（4） The effects of the addition of additives on the performance of ZrO2-CaO.The sample by adding CaCO3 had a higher flexural strength,the largest for 37.2 MPa,its adding the appropriate is 9.31%～16.89%;The sample by adding CaCO3+CaO had a higher compressive strength,the largest for 186 MPa,for its adding the CaCO3:5.2%～ 9.65%,CaO:2.29%～4.3%.（5） The performance of ZrO2-Al2O3-SiO2 sample was bettter than ZrO2-CaO samples.Add the amount of zircon was 55%,α-Al2O3 was 45%and an appropriate amount of stabilizer,sintering sample under 1550℃,can be prepared with excellent performance zirconia metering nozzle material.The bulk density was 3.46 g/cm3, apparent porosity was 1.5%,flexural strength was 112.2 MPa,and compressive strength was 435 MPa.
In this paper,monodisperse polystyrene microspheres in the size range of nano to sub-micron were prepared by emulsion polymerization method using styrene as monomer , potassium persulfate as initiator and sodium dodecyl sulfate as emulsifier.Then uniform coating ZrO2/PS core-shell microspheres were prepared using polystyrene microspheres as template and combining homogeneous precipitation method.The ZrO2 hollow spheres sample were obtained by calcining the ZrO2/PS core-shell microspheres.The main process conditions on the size of polystyrene microspheres and the situation of polystyrene microspheres coated with hydrated zirconia nanoparticles were studied,then reliable process parameters were obtained.Then the dispersion stability of polystyrene microspheres latex and formation mechanism of ZrO2/PS core-shell microspheres were analysised.The appearance,size,structure and component of the polystyrene microspheres, ZrO2/PS core-shell microspheres and ZrO2 hollow spheres sample were studied with SEM, laser particle size analysis,TG,FT-IR,XRD and XPS.The effects of the monomer consumption and initiator and emulsifier concentration on the size of polystyrene microspheres were studied. The results show that the size of polystyrene microspheres decreases with increase in concentration of initiator and emulsifier,and an increase in the monomer consumption will increase the particle size.The ZrO2/PS core-shell microspheres were prepared in water system using polystyrene microspheres about 350nm that have uniform particle size distribution prepared by ourselves as template,zirconium oxynitrate as zirconium source and urea as precipitant and regulator of PH,then the ZrO2 hollow spheres sample were obtained by calcining the ZrO2/PS core-shell microspheres at 600℃. The effects of the reactant concentration and dispersant on the situation of polystyrene microspheres coated with hydrated zirconia nanoparticles were studied.The results show that there haven’t hydrolyzate on the surface of the polystyrene microspheres with low zirconium oxynitrate and urea concentration,when increasing urea concentration the hydrolyzate will formate part-coating.The appropriate increase of concentration of urea and zirconium oxynitrate will be good for the formation of ZrO2/PS core-shell microspheres.When the concentration of zirconium oxynitrate is greater than 5.6×10-3mol/l and the concentration of urea is greater than 0.8mol/l,the polystyrene microspheres can be coated uniform by hydrated zirconia nanoparticles.However, too high concentration of urea will lead to hydrolysis of zirconium oxynitrate too fast and some small zirconia particles adsorped by the surface of polystyrene microspheres very slowly will grow up into big aggregates. The addition of dispersant is good for the dispersion of the zirconia nanoparticles and polystyrene microspheres latex and the formation of ZrO2/PS core-shell microspheres.The formation of characteristics of core-shell structure were confirmed by FT-IR,XPS and TG..The change in reaction process of PH value of the reaction system was investigated,and then we thought that PH value of the reaction system was the result of the combined effect of urea and zirconium oxynitrate and the control of PH value was very important for the formation ZrO2/PS core-shell microspheres.For the system of successful coating, generally the PH value of system goes through a process from strong acid to weak alkaline.