Densification behavior of yttria-stabilized zirconia powders for solid oxide fuel cell electrolytes

Yttria-stabilized zirconia(YSZ) is the most common electrolyte material for solid oxide fuel cells. Herein, we conducted a comparative study on the densification behavior of three different kinds of commercial 8 mol% YSZ powders:(i) TZ-8Y(Tosoh, Japan),(ii) MELox 8Y(MEL Chemicals, UK), and(iii) YSZ-HT(Huatsing Power, China). The comparison was made on both the selfsupporting pellets and thin-film electrolytes coated onto a NiO–YSZ anode support. For the pellets, MELox 8Y showed the highest densification at lower sintering temperatures with 93% and 96% of the theoretical density at 1250 and 1300 ℃, respectively. Although YSZ-HT showed a higher sintering rate than TZ-8Y, a sintering temperature of 1350 ℃ was required for both the powders to reach 95% of the theoretical density. For the thin-film electrolytes, on the other hand, YSZ-HT showed the highest sintering rate with a dense microstructure at a co-sintering temperature of 1250 ℃. Our results indicate that besides the average particle size, other factors such as particle size distribution and post-processing play a significant role in determining the sintering rate and densification behavior of the YSZ powders. Additionally, a close match in the sintering shrinkage of the electrolyte and anode support is important for facilitating the densification of the thin-film electrolytes.

Hot corrosion mechanism of yttria-stabilized zirconia powder in the presence of molten Na_(2)SO_(4)+V_(2)O_(5) salts

The hot corrosion behavior of yttria-stabilized zirconia(YSZ)powder specimens exposed to Na_(2)SO_(4)/V_(2)O_(5) salts mixtures at high temperature was evaluated.Initial tests were carried out at 1000℃ for 10 h,the salt concentrations varied from 0.1 wt%to 1.00 wt%,and the Na_(2)SO_(4)/V_(2)O_(5) mass ratios were between 0.20 and 0.44 following a factorial design 22.X-ray diffraction(XRD)analyses of the tested samples showed with a confidence of95%that the mixture composed of 32 wt%Na_(2)SO_(4)+68 wt%V_(2)O_(5),and 1.00 wt% salt concentration led to high destabilization of the t’-YSZ phase and formation of YVO_(4) products.A second set of experiments were conducted to assess the influence of temperature on the hot corrosion response of the YSZ in the range between 490 and 1100℃.Thermogravimetric analysis(TGA)experiments and Rietveld adjustments of XRD patterns showed that the mass loss of the samples varied with testing temperature and also that the major destabilization of tetragonal phase occurred at 900℃.

Industrial growth of yttria-stabilized cubic zirconia crystals by skull melting process

We reported the development of a Ф100 cm growth apparatus for skull melting growth of yttria-stabilized cubic zirconia(YSZ) crystals and more than 1000 kg crystals have been grown in the furnace each time.The growth conditions were optimized and the structure of the as-grown crystals was characterized by X-ray diffraction.The transmittance of 15 mol.% yttria-stabilized cubic zirconia crystal was nearly 80% in the range of 400–1600 nm.The refractive indices were measured and fitted the Sellmeier equation whi...

Crystal growth,structure and optical properties of Pr^(3+)-doped yttria-stabilized zirconia single crystals

The development of blue semiconductor light-emitting diodes(LEDs)has produced potential applications for Prdoped materials that can absorb blue light,especially crystals,and we now report structure and optical properties for high-quality Pr-doped single crystals of yttria-stabilized zirconia(YSZ)grown by the optical floating zone(FZ)method.X-ray diffraction(XRD)and Raman spectroscopy showed that all of the single crystal samples were in the cubic phase,whereas the corresponding ceramic samples contained a mixture of monoclinic and cubic phases.X-ray photoelectron spectroscopy(XPS)and electron paramagnetic resonance(EPR)spectroscopy showed that Pr was present as the Pr^(3+)ion in ceramic rods and single crystals after heating to high temperatures.The absorption and photoluminescence excitation(PLE)spectra of the Pr-doped YSZ crystals measured at room temperature showed strong absorption of blue light,while their photoluminescence(PL)spectra showed five emission peaks at 565 nm,588 nm,614 nm,638 nm,and 716 nm under450 nm excitation.The optimum luminescence properties were obtained with the crystal prepared using 0.15 mol%Pr_(6)O_(11),and those with higher concentrations showed evidence of quenching of the luminescence properties.In addition,the color purity of Pr-doped YSZ single crystal reached 98.9%in the orange–red region.

Thermophysical and Mechanical Properties of ZrO_2 (CaO) Powder and Colloidal Zirconia Sol Dip-Coat Layer Used for Titanium Investment Casting

Both green and residual bending strength of the dip-coat layer composed of ZrO2 (CaO) powder and colloi-dal zirconiz sol binder are sutdied and the effects of process factrs on the strength of dip-coat layer are interpreted,using the results of TG-DTA ,TMA and SEM analyses of the fracture morphology of the coating layer and following the strength theory for porous body.

Preparation and characterization of monodisperse zirconia spherical nanometer powder via lamellar liquid crystal template method

Cubic phase spherical zirconia nano-powder was prepared by a direct template route in the lamellar liquid crystal formed by polyoxyethylene tert-octylphenyl ether(Triton X-100)/sodium dodecyl sulfate(SDS)/H_2O.The precursor powder and zirconia powder were characterized by XRD,FT-IR,TG/DSC,TEM,and SEM methods.Results show that the stability of the lamellar liquid crystal is controlled by NH_3·H_2O concentration.The size of nanoparticles is greatly affected by NH_3·H_2O and ZrOCl_2·8H_2O concentrations.The zirconia nanoparticles show narrow particle size distribution of 10-30 nm.

Preparation of zirconia-alumina powder by co-precipitation

A zirconia alumina powder with a near spherical shape and an average size of 0.1～0.2 μm was prepared by co precipitation. XRD analysis shows that α Al 2O 3 phase may be directly transformed from amorphous in calcining the hydroxide composite. The ZrO 2 Al 2O 3 composite ceramics manufactured from this powder has the maximum fracture toughness of 9 MPa·m -1/2 at 15% ZrO 2 and 740 MPa fracture strength at 5% ZrO 2. Zirconia grains about 1 μm in diameter are dispersed uniformly in the alumina ceramic matrix.

Preparation and Mechanical Properties of Zirconia Ceramics Doped with Different Y_(2)O_(3)Contents

The sintering behavior and mechanical properties of zirconia doped with 2.0mol%-3.0mol%Y_(2)O_(3)were studied by pressure-less sintering.The experimental results show that the densification temperature of zirconia ceramics increases gradually with the decrease of Y_(2)O_(3)doping content by which decreases the sintering driving force due to the lower oxygen vacancy concentration of the systems.Furthermore,the bending strength and fracture toughness of the prepared zirconia ceramics increase with the decrease of Y_(2)O_(3)doping content.It can be attributed to the fact that the phase stability of tetragonal zirconia decreases with the decrease of Y_(2)O_(3)doping content,which is easier to induce"phase transformation toughening"and dissipate impact energy.The relative density,bending strength and fracture toughness of 2.0 mol%Y_(2)O_(3)doped zirconia ceramics(2.0Y-ZrO_(2))sintered at 1525℃are 99.00%,1256.65±20.82 MPa and 9.85±0.13 MPa·m^(1/2),respectively.

新微乳液体系下超细ZrO_(2)纳米粉体的可控合成及形成机理探究

ZrO_(2)纳米粉体由于其优异的性能被广泛应用于热障涂层、功能陶瓷、燃料电池、催化剂载体等多个领域。本文开发了一种新的微乳液体系(油酸/2-氨基-2-甲基-1-丙醇(AMP)/正辛醇/煤油/水溶液),经过热脱乳处理和煅烧成功制备出了超细ZrO_(2)纳米粉体。XRD、Raman和SAED分析证实,粉体在550~750℃范围内焙烧,物相结构保持为四方相ZrO_(2),说明该超细纳米粉体具有良好的稳定性。HRTEM结果表明,晶面间距为0.291 nm左右,与四方相ZrO_(2)的(101)面相对应。通过控制不同条件,如溶液用量、正辛醇用量、表面活性剂油酸用量,实现了ZrO_(2)纳米粉体尺寸在10~20 nm的区间内可以精确调控,基于微结构的演变并讨论了上述参数对形成机理的影响。

钇掺杂氧化锆粉体的制备方法及性能分析

通过不同制备技术(固相合成法、共沉淀法、水解法、自蔓延燃烧法)合成了摩尔分数为8%的钇掺杂氧化锆陶瓷粉体(8YSZ)。研究了不同制备技术对粉体粒度、比表面积和相结构的影响。探讨了pH、焙烧温度、研磨方式与研磨时间等条件因素对共沉淀法制备的8YSZ粉体相结构和粒度的影响。同时对其密度、抗弯强度和离子电导率进行了测试表征。结果表明:共沉淀法制备的8YSZ粉体,控制pH=8~10均可以合成出单一相的样品;焙烧温度对8YSZ粉体结晶度有较大影响,1000℃以上焙烧可生成结晶度较好的粉体;球磨和砂磨方式分别能控制粉体粒度在10μm和1μm以下。此外,共沉淀法制备的8YSZ粉体密度和抗弯强度分别达到了5.78 g·cm^(-3)和207.7 MPa,其在500~750℃具有良好的Arrhenius电导线性关系(相关系数为0.9927)和最低的电导活化能(0.70 eV·K^(-1))。

A review of C_1 chemistry synthesis using yttrium-stabilized zirconia catalyst

C1 chemistry based on synthesis gas, methane, and carbon dioxide offers many routes to industrial chemicals. The reactions related to the synthesis of gas can be classified into direct and indirect approach for making such products, such as acetic acid, dimethyl ether, and alcohol. Catalytic syngas processing is currently done at high temperatures and pressures, conditions that could be unfavorable for the life of the catalyst. Another issue of C1 chemistry is related to the methane-initiated process. It has been known that direct methane conversions are still suffering from low yields and selectivity of products resulting in unprofitable ways to produce products, such as higher hydrocarbons, methanol, and so on. However, many experts and researchers are still trying to find the best method to overcome these barriers, for example, by finding the best catalyst to reduce the high-energy barrier of the reactions and conduct only selective catalyst-surface reactions. The appli- cation of Yttria-Stabilized Zirconia （YSZ） and its combination with other metals for catalyzing purposes are increasing. The existence of an interesting site that acts as oxygen store could be the main reason for it. Moreover, formation of intermediate species on the surface of YSZ also contributes significantly in increasing the production of some specific products. Understanding the phenomena happening inside could be necessary. In this article, the use of YSZ for some C1 chemistry reactions was discussed and reviewed.

Review on Enhancement of Nitridation of Si Powder

This paper reviewed the effect of powder characteristics and additives including metals,rare earth oxides,and ZrO2 on nitridation of Si powder.The decrease of particle size of Si powder increased nitridation.Most of metal additives inhibited nitridation,while some metal additives such as Fe,Cu,Cr,and Ca increased nitrida—tion.Otherwise,the addition of metals might lead to the degradation of physical and mechanical properties of Si3N4.All the rare earth oxides,especially CeO2 and Eu2O3,showed nitridation enhancing effect.In addition,ZrO2 with small particle size showed a stronger enhancing effect.

Effect of ZrO_2-nitrides Composite Powder Addition on Oxidation Resistance of Al_2O_3-C Refractories

Oxidation of carbon is the main problem or Al2O3 - C refractories. ZrO2 - nitrides composite powder was synthesized through carbothermal reduction and nitridation （CRN） of zircon. The effect of ZrO2 - nitrides composite powder addition on oxidation resistance of the Al2O3 - C refractories was investigated by measuring the thickness of oxidation layer. Phase compositions of the Al2O3 - C refractories before and after oxidation were investigated by X-ray diffraction （ XRD ）. Results show that the oxidation resistance of the Al2O3 - C refractories can be obviously improved by adding the synthesized ZrO2 - nitrides composite powder. The formation of mullite and zircon in the oxidation layer results in the densification of oxidation layer, which prevents oxygen diffusion and bnproves the oxidation resistance of the Al2O3 - C refractories.

Influences of ZrO_2-SiC Composite Powder and Commercial SiC on Properties of Al_2O_3-C Refractories

In order to improve oxidation resistance and ther- mal shock resistance of Al2O3-C refractories, two groups of specimens were prepared with phenolic resin as binder, adding 0, 2 wt% , 4 wt% and 6 wt% commercial SiC or ZrO2-SiC composite powder synthesized from zircon respectively to Al2O3- C refractories, pressing at 200 MPa, drying fully at 250℃, and then carbon embedded firing at 1400℃ for 2 h. Oxidation resistance and thermal shock resistance were researched, phase composition was analyzed by XRD. The results showed that the oxidation of SiC in additives could protect carbon in specimens effectively and thus decreased the mass loss ratio and oxidation area, and improved the oxidation resistance of the specimen. Thermal shock resistance was improved owing to the micro crack toughening of ZrO2 and grain toughening of SiC. In this experiment, the specimens with 6 wt% ZrO2 -SiC composite powder or 6 wt% SiC powder had the best oxidation resistance and thermal shock resistance.

Mechanical Properties of a new Dental all-ceramic Material-zirconia Toughened Nanometer-ceramic Composite

目的 :口腔全瓷修复体以其独特优越性受到医患青睐 ,但脆性问题一直限制其应用范围及使用可靠性。本研究旨在研制用于玻璃渗透全瓷修复的纳米氧化锆增韧陶瓷并全面检测评价其力学性能。方法 :采用化学共沉淀与球磨相结合的方法合成纳米氧化锆增韧陶瓷 (α -Al2 O3 /nZrO2 ceramicspowder ,W) ,扫描电镜评价陶瓷材料的粉体形态特征及粒度分布。预制氧化锆含量不同的陶瓷粉体 (5wt% ,10wt% ,15wt%and 2 0wt% ) ,采用粉浆涂塑技术将材料制成标准试件 ,并在不同温度下 (12 0 0～ 16 0 0℃ )烧结成型 ,用三点弯曲法及单边刀口梁法检测材料试件的抗弯强度和断裂韧性。结果 :1)α -Al2 O3 /nZrO2 材料粉体粒度分布范围大致为 0 .0 2～ 3.0 μm ,其中超细粉体 (低于 0 .1μm)占 2 0 % ;2 )不同烧结温度组试件的力学强度有显著差异 (P <0 .0 5 ) ,14 5 0℃和 16 0 0℃组高于12 0 0℃组 ;3)相同烧结温度下不同氧化锆含量组材料强度有显著差异 ,一定范围内氧化锆含量增高有助于材料的增韧增强。结论 :本研究所研制的纳米氧化锆增韧陶瓷材料组分配比及微观特征能增韧增强材料 。

DEPENDENCE OF SINTERABILITY ON STATE OF AGGLOMERATION OF ULTRAFINE ZrO_2，（Y_2O_3） POWDERS

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Influence of characteristics of stabilized zirconia electrolyte on performance of cermet supported tubular SOFCs

Ni-Al_(2)O_(3)cermet supported tubular SOFC was fabricated by thermal spraying.Flame-sprayed Al_(2)O_(3)-Ni cermet coating plays dual roles of a support tube and an anode current collector.4.5mol.%yttria-stabilized zirconia(YSZ)and 10mol.%scandia-stabilized zirconia(ScSZ)coatings were deposited by atmospheric plasma spraying(APS)as the electrolyte in present study.The electrical conductivity of electrolyte was measured using DC method.The post treatment was employed using nitrate solution infiltration to densify APS electrolyte layer for improvement of gas permeability.The electrical conductivity of electrolyte and the performance of single cell were investigated to optimize SOFC performance.The electrical conductivity of the as-sprayed YSZ and ScSZ coating is about 0.03 and 0.07 S·cm^(-1)at 1000℃,respectively.The ohmic polarization significantly influences the performance of SOFC.The maximum output power density at 1000℃increases from 0.47 to 0.76 W·cm^(-2)as the YSZ electrolyte thickness reduces from 100μm to 40μm.Using APS ScSZ coating of about 40μm as the electrolyte,the test cell presents a maximum power output density of over 0.89 W·cm^(-2)at 1000℃.

Effect of Al_2O_3-ZrO_2 Composite Powder on Thermal Shock Resistance of ZrO_2 Sizing Nozzles

ZrO2 sizing nozzles with a basic Jormulation were prepared using 45% （by mass, the same hereinafter ） （ Mg, Y） - PSZ aggregate, 55% （ Mg, Y） - PSZ fines and 5% PVA binder. Al2O3 - ZrO2 composite powders （ 3%, 6%, 9% and 12% ） prepared by sol - gel method were added to replace the equal amount of （ Mg, Y） - PSZfines. Effects of Al2O3 - ZrO2 composite powders on physical properties, phase composition and microstructure of the ZrO2 sizing nozzles were studied. The results show that： the performances of the modified sizing nozzles with 3% Al2O3 - ZrO2 composite powder are better than those of the nobles without composite powder used in current production process, and the thermal shock resistance of the ,former nozzles is six times of that of the latter one.

氧化锆粉体的制备及其在热障涂层中的应用

分别描述了纳米氧化锆粉体与空心球氧化锆粉体的制备工艺,分析了不同工艺影响氧化锆产物形态、结构、粒度等方面的因素,并将2种粉末制备的涂层分别与传统微结构涂层进行性能对比。在分析由不同氧化锆粉末制备而成的涂层性能时,除了工艺参数外,更多的是考虑初始氧化锆粉末对涂层性能所带来的影响。期待在未来的研究中,能够优化现有或者探索出更优异的制粉工艺,研究出性能更加优良的新型粉末,以期能够提高热障涂层的性能,满足高精尖领域在未来的使用需求。最后,针对不同制粉工艺及不同粉末制备涂层的发展方向进行了展望。

氧化锆陶瓷增韧机制及其粉体制备的研究进展

氧化锆陶瓷优异的韧性、高硬度、高抗弯强度及良好的生物相容性,在结构陶瓷、功能陶瓷和电子陶瓷方面得到广泛应用。本文综述了氧化锆的增韧机制,氧化锆增韧机制可分为相变增韧、应力微裂纹增韧、铁弹性增韧及耦合反应增韧。氧化锆粉体特性对陶瓷品质有直接影响,制备高品质氧化锆粉体是获得性能优异氧化锆陶瓷的前提,制备氧化锆粉体的方法有液相法、气相法以及固相法等,本文介绍氧化锆粉体的主要制备方法,并总结各种方法的优缺点。