乳浊液和均匀沉淀结合法制备球形纳米ZrO2(Y2O3)粉末

采用二甲苯为油相,span-80为表面活性剂,Zr(NO3)4(3Y)的水溶液为水相的W/O乳浊液和草酸二甲酯均匀沉淀结合法制备四方相ZrO2(3Y)纳米粉。用热重差热法、X射线衍射仪、透射电镜、比表面积分析等手段对粉末及其前驱体进行分析和表征。结果表明:采用乳浊液与均匀沉淀结合法所制得的ZrO2纳米粉具有产率高、球形和分散性好等特点。在制备过程中,锆盐溶液的浓度、水浴反应温度和草酸二甲酯的含量对产物的平均粒径具有规律性的影响。     

Synthesis and crystallization behavior of 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) nanosized powders prepared using a simple co-precipitation process

The synthesis and crystallization behavior of 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) nanopowders prepared using a simple co-precipitation process at 348 K and pH = 7 were investigated using differential scanning calorimetry/thermogravimetry (DSC/TG), an X-ray diffractometer (XRD), the Raman spectra, transmission electron microscopy (TEM), selected area electron diffraction (SAED), and an energy dispersive spectrometer (EDS). The activation energy of tetragonal ZrO₂ crystallization from 3Y-TZP freeze-dried precursor powders using a non-isothermal method, namely, 169.2 ± 21.9 kJ mol⁻¹, was obtained. The growth morphology parameter n was approximated as 2.0, which indicated that it had a plate-like morphology. The XRD, Raman spectra, and SAED patterns showed that the phase of the tetragonal ZrO₂ was maintained at 1273 K. The crystallite size of 3Y-TZP freeze-dried precursor powders calcined at 1273 K for 5 min was 21.3 nm.     

CVD deposition and characterization of coloured Al2O3/ZrO2 multilayers

Coloured Al₂O₃/ZrO₂ multilayers have been deposited onto WC-Co based inserts by a CVD process. Through physical as well as optical analysis of such multilayers, colour is believed to originate from interference. The coatings are obtained with good process reproducibility. It was found that the ZrO₂ process used in the multilayer, with ZrCl₄ as the only metal chloride precursor, results in a mixture of tetragonal and monoclinic ZrO₂ phases. However by adding a relatively small amount of AlCl₃ during such a process results in ZrO₂ layers being composed of predominantly tetragonal ZrO₂ phase. Corresponding multilayers seem to have a more fine grained and smoother morphology whereas multilayers containing monoclinic ZrO₂ phase seem to be less perfect with existence of larger grains of ZrO₂ which are believed to scatter light and alter the reflectance of such a multilayer. In addition to this, such multilayers were found to be free of or with greatly reduced amount of thermal cracks, normally present in pure CVD grown Al₂O₃ layers.It is believed that, in the studied Al₂O₃/ZrO₂ multilayers, the observed tetragonal ZrO₂ phase is the result of a size effect, where small enough ZrO₂ crystallites energetically favor the tetragonal phase. However as the ZrO₂ crystallite size distribution is shifted to larger sizes it is believed that a mixture of crystallites with both stable and metastable tetragonal phases as well as a stable monoclinic phase is obtained. The proposed metastable tetragonal ZrO₂ phase may in fact explain the absence of thermal cracks in such multilayers through a transformation toughening mechanism, well known in ZrO₂ based ceramics.     

Nanocrystalline ZrO<Subscript>2</Subscript> preparation and kinetics research of phase transition

The precursor of nanocrystalline ZrO2 was synthesized by solid-state reaction at low heat using ZrOCl2·8H2O,and Na2CO3·10H2O as raw materials.The nanocrystalline ZrO2 was obtained by calcining the precursor.The precursor and its calcined products were characterized using TG/DTA,FT-IR,XRD,and SEM.The results showed that the precursor dried at 353 K was a zirconyl carbonate compound.When the precursor was calcined at 673 K for 150 min,highly crystallization ZrO2 with tetragonal structure (space group P42/nmc (137)) was obtained with a crystallite size of 24 nm.However,when the precursor was calcined at 1023 K for 150 min,highly crystallization ZrO2 with monoclinic structure (space group P21/c (14)) was obtained with a crystallite size of 20 nm.The mechanism and kinetics of the thermal process of the precursor were studied using DTA and XRD techniques.Based on the Kissinger and Arrhenius equation,the values of the activation energies associated with the thermal process of the precursor were determined to be 26.80 and 566.73 kJ·mol-1 for the first and third steps,respectively.The mechanism of ZrO2 phase transition from tetragonal to monoclinic structure is the random nucleation and growth of nuclei reaction.     

Electrophoretic enhanced micro arc oxidation of ZrO2-HAp-TiO2 nanostructured porous layers

Micro arc oxidation (MAO) and electrophoretic deposition (EPD) processes were simultaneously employed to grow ZrO₂-HAp-TiO₂ porous layers on titanium substrates under different conditions. Influence of the electrolyte composition and the growth time on surface morphology, topography, phase structure, and stoichiometry of the layers was investigated. The utilized electrolytes consisted of β-glycerophosphate, calcium acetate, sodium phosphate, and micron sized yttria-stabilized zirconia with different concentrations. AFM and SEM evaluations revealed a rough surface with a porous structure with a pores size of 50-750 nm. The pores size increased with the time and the electrolyte concentration. Based on the XRD and XPS results, the layers consisted of anatase, hydroxyapatite, monoclinic ZrO₂, tetragonal ZrO₂, ZrO, CaTiO₃, and α-TCP phases whose fractions were observed to change depending on the synthesis conditions. The average crystalline size of the HAp phase was determined as ∼54 nm. The nano-sized zirconia particles (d = 20-60 nm) were dispersed not only on surface, but also in depth of the layers. Utilizing thicker electrolytes and prolonging the growth time resulted in decomposition of hydroxyapatite as well as tetragonal ZrO₂ to monoclinic ZrO₂. EDX results also showed that the zirconium wt% in the layers increased with the time. EPD-enhanced MAO (EEMAO) technique was expressed as an efficient route to fabricate ZrO₂-HAp-TiO₂ multiphase systems within short times and only in one step.     

Effect of acidity on the citrate-nitrate combustion synthesis of alumina-zirconia composite powder

Alumina-zirconia composite powders were produced by sol-gel autocombustion. 20 wt.% ZrO₂-Al₂O₃ mixture precursor solutions were chelated by citric acid ions at different pH. DTA analysis shows sluggish decomposition at low pH, whereas there was rapid decomposition at high pH = 9. XRD patterns of the calcined powders showed that well crystallized powder with 100 % tetragonal phase and α-alumina phase is produced when pH = 0.58 (without ammonia addition). TEM characterization of composite powders revealed homogenous distribution of nanosized zirconia particles in the alumina matrix. FTIR analysis shows peaks at 590 cm^?1 and 454 cm^?1, which are identified as the characteristic absorption bands of Zr-O and Al-O.     

Synthesis, vacuum sintering and dielectric characterization of zirconia (t-ZrO2) nanopowder

Phase pure zirconium oxide powders have been synthesized using the single step auto-ignition combustion method, the particles were nanometer sized (20 nm) and the size distribution was very narrow (3.4 nm). Systematic structural characterization revealed the t-ZrO₂ and indexed for its tetragonal structure (a = 3.5975 Å and c = 5.1649 Å). Calculated microstrain in most of the plane indicated the presence of compressive stress (65-288 MPa) along various planes of the particles. Observed space group (P4₂/nmc) revealed the presence of cations in the 8e positions (0.75, 0.25, 0.75) and the anions in the 16 h positions (0.25, 0.25, 0.4534). The metal-oxide (Zr-O) band observed at the low wavenumber region further confirmed the phase purity of the as-prepared ZrO₂ nanopowders. Peaks at the binding energy positions 2.042 and 0.525 keV in the energy dispersive X-ray spectrum revealed oxygen deficient zirconia. The particle size estimated by TEM was in good agreement with the results obtained through X-ray line broadening (20.81 nm) measurements. The nanopowders were sintered to above 98% of the theoretical density by using vacuum sintering technique at a relatively low temperature of 1300 °C. Stable tetragonal ZrO₂ experimentally yield the permittivity value of about 28 at 10 MHz.     

Size effects on the crystal structure of nanoscale BaTiO<Subscript>3</Subscript> powders prepared by hydro-thermal synthesis

The size effect on crystal structure has been investigated for nanoscale BaTiO₃ powders prepared by hydrothermal methods. The powders were composed of both the cubic and tetragonal phases at room temperature. The relative volume fraction of the tetragonal phase was found to be approximately 30% by X-ray diffraction and Raman spectroscopy. High resolution transmission electron microscopy (HRTEM) revealed that the surface region of the powders was of the tetragonal phase, while the core was of the cubic phase.     

Carbothermal synthesis of ZrC powders using a combustion synthesis precursor

ZrC powders were synthesized by carbothermal reduction of a combustion synthesized precursor derived from zirconium nitrate, urea, and glucose mixed solution. The results showed that the obtained precursor was comprised of polyporous blocky particles. The precursor powders were subsequently calcined under argon at 1200–1600 °C for 3 h. The transformation of ZrO₂ to ZrC, by adopting this route, occurred at 1300 °C. The preparation of ZrC experienced an intermediate phase of ZrOxCy. ZrC powders synthesized at 1500 °C are characterized by the spherical shape, small particle size (120–180 nm in diameter), low oxygen content (1.4 wt.%) and non-aggregated particles.     

锂离子电池用LiVPO4F/C基正极材料的制备和性能（英文）

将H2C2O4·2H2O,NH4H2PO4,NH4VO3和LiF通过球磨反应、烧结,合成了LiVPO4F/C基正极材料。在这个过程中,草酸起还原剂和碳源的作用,利用热重、X射线衍射、扫描电镜、透射电镜和碳-硫分析等手段对合成的前驱体和材料进行检测和分析。XRD分析表明,球磨反应后所得到的前驱体为无定形态,而烧结后的材料中除了LiVPO4F的衍射峰外,还存在Li3V2(PO4)3和V2O3衍射峰。材料颗粒均匀,尺寸约2μm。透射电镜分析表明,合成的材料颗粒表面包裹着一层约2nm厚的无定形碳。在截止电压3.0～4.4V时,合成的材料在0.1C和10C倍率下的放电比容量分别为151.3和102.5mA·h/g。在10C倍率下循环50次后容量保持率为90.4%。在LiVPO4F和Li3V2(PO4)3的循环伏安曲线中可以明显看到V3+/V4+的氧化还原峰。     

Effects of additives on synthesis of vanadium carbide (V8C7) nanopowders by thermal processing of the precursor

Vanadium carbide (V₈C₇) nanopowders can be synthesized by thermal processing of the precursor of ammonium vanadate (NH₄VO₃) and nanometer carbon black. Effects of additives (CaF₂, CeCl₃·7H₂O and LaCl₃·7H₂O) on the phase composition and microstructure of the synthesized powders were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that additives (CaF₂, CeCl₃·7H₂O and LaCl₃·7H₂O) can accelerate the solid state reaction during synthesis of V₈C₇, and these additives play a vital role in determining the phase composition and microstructure. V₈C₇ powders with basically single phase can be synthesized at 1100 °C for 0.5 h with the addition of additives (CaF₂, CeCl₃·7H₂O and LaCl₃·7H₂O), and the powders show good dispersion and are mainly composed of uniformly-sized spherical particles with a mean diameter of 50 nm. Further experiment shows that V₈C₇ powders can be prepared at 950 °C for 1 h with 1.0 wt% CaF₂ as additive.     

In situ synthesis of V8C7 nanopowders from a new precursor

Vanadium carbide (V₈C₇) nanopowders were prepared through simultaneous thermal decomposition and carbothermal reduction of the precursor VOC₂O₄/sucrose in vacuum. The products were characterized by X-ray diffractometer (XRD) and transmission electron microscopy (TEM) techniques. The thermolysis process of the precursor has been investigated by themogravimetric analysis and differential thermal analysis (TG-DSC). The results showed that the pure V₈C₇ powders can be obtained at 950 °C for 30 min and the particle size is in the range from 30 to 50 nm with good dispersion. The effects of experimental parameters and reaction mechanism have been explored. The lower synthesis temperature and shorter reaction time were attributed to take the quadrivalence vanadium as a reactant, as well as carbon source and vanadium source intimate contact in the precursor. This facile and quickly synthetic strategy may open a new route to the preparation of other carbide nanomaterials.     

Characteristics of BaO-B2O3-SiO2 nano glass powders prepared by flame spray pyrolysis as the sintering agent of BaTiO3 ceramics

Nanosized BaO-B₂O₃-SiO₂ glass powders are directly prepared by flame spray pyrolysis. The mean size of the BaO-B₂O₃-SiO₂ glass powders with amorphous phase and spherical shape is 30 nm. The effects of glass powders on the sintering characteristics of the BaTiO₃ pellet formed from the nanosized BaTiO₃ powders are investigated. The mean size and BET surface area of the BaTiO₃ powders prepared by spray pyrolysis are 110 nm and 9.1 m²/g. The BaTiO₃ pellet with glass additive has large grain size with several microns, dense structure and pure tetragonal crystal structure at a sintering temperature of 1000 °C. The XRD pattern of the pellet has distinct split of (2 0 0) and (0 0 2) peaks at 2θ ≈ 44.95°. The dielectric constant of the pellet without glass additive is 2180. However, the dielectric constants of the pellets with 1, 3, 5 and 7 wt% glass additive with respect to BaTiO₃ are 2496, 2514, 2700 and 2225, respectively.     

CaCuO2颗粒尺寸对双粉法制备Bi系高温超导带材性能的影响

本文通过基于共沉淀工艺的双粉法制备了Bi_1.76Pb_0.34Sr_1.93Ca_2.0Cu_3.06O_8+d (Bi-2223)前驱体粉末。在这一过程中,首先单独制备了Bi_1.76Pb_0.34Sr_1.93CaCu_2.06O_8+d (Bi-2212)和CaCuO₂(实际相组成为Ca₂CuO₃和CuO)粉末,并分别进行了烧结。通过调节共沉淀工艺过程中的pH值,获得了颗粒尺寸不同的CaCuO₂粉末,然后将Bi-2212与其按照相组成相组成为1:1进行混合,并装入Ag包套中,通过一系列的旋锻、拉拔和轧制工艺,获得设计尺寸的Bi-2223带材。比表面积测试表明随着pH值从3.0增加到5.0和6.5,获得CaCuO₂粉末的平均颗粒尺寸从1.1减小到0.75和0.60 mm。通过扫描电镜对不同尺寸CaCuO₂颗粒制备的Bi-2223生带、第一次热处理和后处理之后带材的相组成和分布进行了表征。结果表明,适当尺寸的CaCuO₂颗粒可以避免团聚现象的出现,因此有利于高载流性能带材的获得。最终通过进一步调节带材的尺寸,1#带材的性能最高,达到了12200 Acm^_-2。     

Preparation,microstructure, and properties of tungsten alloys reinforced by ZrO2 particles

Tungsten alloys reinforced by in-situ tetragonal zirconia (W–ZrO₂) were developed via the azeotropic distillation method combined with the powder metallurgy method. The microstructure and abrasive wear properties were studied. The in-situ ZrO₂ particles in the tungsten matrix were obtained by the decomposition of zirconium nitrate after liquid–liquid incorporation of (NH₄)₆H₂W₁₂O₄₀ and Zr(NO₃)₄ aqueous solution. The ZrO₂ particles were distributed evenly in the tungsten matrix, which refined tungsten powders and the grains of tungsten alloys significantly. The density and Vickers hardness of the tungsten alloys decreased with increasing ZrO₂ mass fraction. However, the wear resistance increased firstly and then decreased with increasing ZrO₂ mass fraction. The optimal amount of ZrO₂ for improving wear property is 3%, with the wear resistance of W–3% ZrO₂ improving by approximately 20%–40% compared with that of pure tungsten. The proper amount of ZrO₂ particles can efficiently prevent microcutting to protect the tungsten matrix, thereby enhancing the wear resistance of tungsten alloys.     

Synthesis and characterization of the Mg-based amorphous/nano ZrO2 composite alloy

Mg-based composites are fabricated through mechanical alloying (MA) in the planetary mill, using amorphous Mg₆₅Cu_25−xY₁₀Ag_x (x=0, 5, 10) matrix alloy prepared by melt spun and 1–5 vol.% spherical nano-sized ZrO₂ particles. The melt spun amorphous matrix ribbons are ground into powders and mixed with the ZrO₂ nano particles in the planetary mill, after then formed by hot pressing in Ar atmosphere under different pressures at the temperature 5 K above the glass transition temperature (T_g). The microstructure characterizations of the resulting specimens are conducted by means of XRD, FEG-SEM, and TEM techniques. It is found that the nano-sized ZrO₂ dispersed Mg-based composite alloy powders can reach to a homogeneous size distribution (about 80 nm) after 50 h mechanical alloying. After hot pressing of these composite alloy powders under the pressure of 1100 MPa at 409 K, a 96% dense bulk specimen can be formed. Throughout the MA and hot pressing, the amorphous nature of the Mg₆₅Cu_25−xY₁₀Ag_x matrix is maintained. The hardness of the formed bulk Mg-based composites (with 5 vol% nano-sized ZrO₂ particles) can reach to 360 in H_v scale. In addition, the microstructure near the interface between the matrix and nano particles presents a well-bonded condition.     

液料等离子热喷法制备Fe3+/TiO2纳米粉末

通过对液料等离子热喷前驱物添加掺杂成分实现了液料等离子热喷TiO2纳米粉末的掺杂改性,并利用TEM,XRD及XPS对其进行表征.结果表明,采用液料等离子热喷法可以制备Fe3 掺杂TiO2纳米粉末,所制备粉末形貌基本呈球形或近球形,粒径分布为10～35 nm,掺杂量小于2.0%时粉末为锐钛矿及金红石相混晶,Fd3 掺杂促进锐钛矿向金红石相的转变,掺杂量为10.0%时析出了Fe2Ti3O9相.Fe3 掺杂不会引起TiO2粒径的大范围波动.粉末中含有O,Ti,Fe和C等元素,Fe元素在TiO2中仍为 3价.     

The influence of experimental conditions on the morphology and phase composition of Nb-doped ZrO2 films prepared by spark anodization

This paper reports the morphological and microstructural characterization of Nb-doped ZrO₂ films obtained by anodic doping in conditions of spark electrolytic breakdown. The oxide films were prepared by galvanostatic anodization of metallic Zr in oxalic acid solution containing ammonium oxaloniobate, NH₄H₂[NbO(C₂O₄)₃]⋅3H₂O using Nb(V) ions as the precursor dopant. The characterization was performed by SEM and XRD. A factorial design was used to optimize the experiments and study the influence of experimental variables on morphology and phase composition. The results demonstrated that the dopant concentration is the most important factor that affected the analyzed responses. A significant influence of this variable was observed on the pore average diameter and on the percentage of the stabilized tetragonal phase. The temperature also affected the phase composition, however no effect was observed on the morphological response.     

Photocatalytic activity of anatase thin films coated cotton fibers prepared via a microwave assisted liquid phase deposition process

Nanocrystalline titanium dioxide thin films in the anatase phase was successfully coated on cotton fibers via a simple microwave (MW) assisted liquid phase deposition (MW-LPD) process with hexafluorotitanate ammonium (NH₄)₂TiF₆ as precursor. Compared with the conventional LPD processes, the MW-LPD technique could provide quickly high yield and crystallinity in a diluted precursor solution at a low temperature. Microwave irradiation penetrated and simultaneously heated the bulk of the material and led to higher heating efficiency with faster processing. The X-ray diffraction (XRD) and selected-area electron diffraction (SAED) studies on these powders indicated that the powders obtained with MW irradiation have much higher crystallinity with a single phase anatase. Scanning electron microscopy (SEM) images showed the information of continuous layers of titania on cotton fibers. UV-vis analyses revealed the coated titania produced an excellent UV protection of the coated fiber. The fibers with anatase coatings showed high photocatalytic property and better repetition on the photodegradation of methylene blue (MB).     

Pressure consolidation of amorphous ZrO2–Al2O3 by plastic deformation of powder particles

Amorphous ZrO₂–Al₂O₃ powders undergo densification at low temperatures (<650°C) and moderate uniaxial pressures (~750 MPa). It is established that large pressure dependent densification and little time dependent densification occur. Viscous sintering is not the dominant densification mechanism. Study of the particle size effect in densification of amorphous ZrO₂–40% Al₂O₃, and comparison with hot pressing of borosilicate glass powder at 500 and 550°C and cold compaction of silver powder, clearly indicate the possibility of compaction of amorphous ZrO₂–Al₂O₃ by plastic deformation. Good agreement was seen between a model for the compaction of ductile metal powders and the observed hot pressing behaviour.