SiO2含量对YSZ陶瓷在高温时效中烧结性的影响

研究了SiO2含量对YSZ陶瓷在不同温度下时效后的烧结速率影响,同时研究了其对YSZ时效过程中的结构形貌和性能变化的影响。实验中以正硅酸乙酯(TEOS)为硅源,制备了SiO2含量不同且有约10%气孔的YSZ陶瓷块体,并在不同温度下热处理180 h。通过扫描电镜(SEM)表征了样品的微观形貌,并使用阿基米德法测试得到样品气孔率,同时表征了样品高温时效后的相组成、力学及热学性能的变化。通过交流阻抗谱法初步判断了SiO2在YSZ陶瓷晶界上的分布。研究发现,0.3%(质量分数,下同)SiO2的引入将会使YSZ晶粒尺寸变大且气孔率显著降低,同时其硬度、杨氏模量及热导率的变化率明显较未添加SiO2的要快。     

Structural and Electrical Analysis of Microwave Processed YSZ Electrolytes for SOFC Prepared by Co-precipitation Method

The aim of the present study is to investigate the effect of microwave energy on the structural and electrical properties of yttria-stabilized zirconia (YSZ) electrolyte for solid oxide fuel cells (SOFC). Five different compositions of Zr_1?x Y _x O_2?x/2 (x = 0.06–0.14) were prepared by a co-precipitation method and were then sintered by microwave as well as conventional heating at 1400°C for 20 min and 240 min, respectively. The structural and electrical properties of the samples sintered by both the methods were compared. The x-ray diffraction (XRD) results revealed that YSZ samples sintered by both methods had either a tetragonal crystal structure or a cubic structure depending on its composition. Almost the same degree of densification as well as conductivity of same order was found from impedance analysis for both microwave- and conventionally sintered YSZ products, which showed that microwave sintering is the better alternative for material processing in terms of saving energy and time without compromising the product quality.     

SOEC电解质与氢电极的流延制备、共烧结及性能

采用流延成型技术同时制备致密固体电解质与多孔阳极半电池坯体,然后采用共烧结技术烧结出半电池.系统地研究了8YSZ陶瓷浆料与氢电极NiO/YSZ浆料的流变学特性.通过DTA和TG曲线确定了半电池的排胶工艺.用扫描电镜观察了半电池的显微结构.在800、850和900 ℃下测试了电池电解性能曲线,且在850、900和950 ℃电解模式下测试了电解质的欧姆阻抗.     

A facile and environment-friendly method to fabricate thin electrolyte films for solid oxide fuel cells

A facile and environment-friendly method, the so-called vertical deposition (abbreviated as VD) method, is used to prepare thin yttria-stabilized zirconia (YSZ) films (≤5 μm) for solid oxide fuel cells (SOFCs). The YSZ films are self-assembled by VD process based on capillary force. The influence of experimental conditions (e.g. concentration of YSZ dispersion, deposition times, and sintering procedure) on the morphology of the films produced and thereby on the performance of SOFC devices is investigated. The single cell utilizing a 5 μm dense YSZ film as solid electrolyte achieves a high open circuit voltage of 1.05 V which remains stable at 700 °C for 4 h. The peak power density is 0.4 W cm⁻² at 800 °C for the phase inversion anode-supported fuel cell composed of an YSZ electrolyte film of 5 μm thick. The VD method developed herein is promising for preparing ultra-thin electrolyte films for SOFCs.     

Influence of t-ZrO2 addition on mechanical property and electrical conductivity of YSZ electrolyte

8YSZ material that has high electrical conductivity is widely used as electrolytes for solid oxide fuel cells (SOFCs). But its low strength and low fracture toughness hampered the development of SOFCs. In order to find a best method to improve the capability of YSZ electrolyte, the effects of 3Y-TZP additive on the density, strength, conductivity and microstructure were studied by means of X-ray diffraction and Vicker's hardness apparatus. The strength and conductivity of YSZ electrolyte doped with different amounts of 3Y-TZP were determined. It is shown that the samples sintered at 1450 ℃ for 2 h are the best in properties. When 3Y-TZP powders are added to the YSZ system, the results demonstrate that strength of the electrolyte increases remarkably, and the fracture toughness is improved. The electrical conductivity is lowered only slightly. The results display that the flexural strength and the fracture toughness of ceramics with 30wt.% TZP reach 300 MPa and 3.7 MPa·m1/2 , respectively, and the conductivity at 1000 ℃ reaches 0.11 S·cm-1 .     

Phase Transformation and Lattice Parameter Changes of Trivalent Rare Earth Doped YSZ as a Function of Temperature

Yttria-stabilized zirconia (YSZ) co-doped with trivalent oxide Sc₂O₃ and Yb₂O₃ is prepared using mechanical alloying and high-temperature sintering. High-temperature XRD analysis was performed to study the phase transformation and lattice parameter changes of various phases in the baseline YSZ and co-doped samples. The results show that the structure for the co-doped samples tends to be more thermally stable at test temperature above critical value. The lattice parameters for all samples increase with temperature at which XRD is carried out, and the lattice parameters for the two trivalent rare earth oxides co-doped YSZ are smaller than that for 7YSZ under the same temperature.     

Research on sintering process of YSZ electrolyte

Yttria stabilized zirconia (YSZ) has widely been used as electrolyte in solid oxide fuel cell (SOFC).The microstructure of YSZ related to the fabrication process was discussed in the paper.With YSZ nano-powders about 40-100 nm as raw material, the YSZ adobe was manufactured by tape calendering process.The named three-step sintering process was performed at 1000 ℃ for 2 h, then raised the temperature with normal rate and as soon as up to 1400 ℃, the furnace was controlled at 1250-1300 ℃ for 10-20 h.The high dense YSZs with the relative density of 96%-99% were obtained; the grain size of YSZ could be reduced to 0.5-3 μm.The above result is benefited to co-fired in the electrode-supported SOFCs.     

Predicting model on ultimate compressive strength of Al2O3-ZrO2ceramic foam filter based on BP neural network

In present study, BP neural network model was proposed for the prediction of ultimate compressive strength of Al2O3-ZrO2 ceramic foam filter prepared by centrifugal slip casting. The inputs of the BP neural network model were the applied load on the epispastic polystyrene template (F), centrifugal acceleration (v) and sintering temperature (T), while the only output was the ultimate compressive strength (σ). According to the registered BP model, the effects of F, v, T on σ were analyzed. The predicted resul...     

高阻相对La2／3Ca1／3MnO3低场磁电阻效应的影响

实验研究了La2／3Ca1/3MnO3系统晶界上掺杂(YSZ)对其输运性能和磁电阻效应(MR)的影响。样品是由溶胶．凝胶法制成的。通过对样品的电输运特性的测量表明,在掺杂量(x)低于2％时,掺杂引起电阻的增大并降低了金属．绝缘体转变温度;当掺杂量高于2％时电阻逐渐减小,且转变温度增加。而低场磁电阻效应随掺杂量增加,在x=1％时达到最大。     

Pressureless sintered high-strength mullite from commercial powder

High-strength monolithic mullite ceramics were prepared from commercial-grade power by carefully controlled processing of the powder followed by pressureless sintering at 1700 °C. Mullite powder was mechanically and chemically dispersed, ball milled, and screened prior to slip casting. Specimens were sintered to 97% of theoretical density under pressureless conditions. The furnace ramp and soak schedule was an important variable. Four-point flexural strengths of 250 MPa were achieved, exceeding literature values for pressureless sintering of Baikowski mullite powder.[a] Pore sizes were small and were not strength limiting. Griffith calculations suggest a critical flaw size of 20 μm, in good agreement with the maximum observed crystal size in the microstructure.     

Toward Highly Sintering-Resistant Nanostructured ZrO2-7wt.%Y2O3 Coatings for TBC Applications by Employing Differential Sintering

There are still concerns in the scientific community about the stability of nanostructured YSZ coatings at high temperatures. Questions have been raised about the possibility of accelerated sintering of these ultrafine materials and the associated changes in properties that could accompany this sintering. In this work, nanostructured YSZ coatings were engineered to counteract sintering effects by tailoring the coatings to exhibit a bimodal microstructure formed by (i) a matrix of dense YSZ zones (produced from molten YSZ particles) and (ii) large porous nanostructured YSZ zones (produced from semimolten nanostructured YSZ particles) that were embedded in the coating microstructure during thermal spraying. These coatings were subjected to heat treatment in air at 1400 °C for 1, 5, and 20 h. The superior driving force for sintering exhibited by the porous nanozones, when compared to that of the dense zones, caused the nanozones to shrink at much faster rates than those exhibited by the denser matrix zones (i.e., differential sintering), thereby creating a significant network of voids in the coating microstructure. Due to these effects, after 20 h exposure at 1400 °C, the thermal conductivity and elastic modulus values of the conventional coatings were approximately two times higher than those of the nanostructured ones.     

陶土对铸钢消失模涂料烧结性的影响

采用阿基米德法测试烧结试样密度,研究了陶土对铸钢消失模涂料烧结性的影响。结果表明,随着陶土含量和烧结温度的增加,试样体积密度都有增大趋势。陶土含量为5%时,试样在1550℃时密度显著增大,符合铸钢消失模涂料要求。另外,进行现场浇注试验,对涂片层断面进行扫描电镜分析,涂片层断面与钢水接触部分烧结良好,耐火骨料连成整片,阻止钢水进一步渗透,使涂料烧结壳从铸件表面自动剥离。     

三层共烧制备LaCrO3基连接体/复合阳极/YsZ电解质的研究

将La_0.7Ca_0.3Cr_0.97O_3-δ（LCC）连接材料引入到NiO/YSZ阳极中,制备NiO/YSZ/LCC三相复合阳极,并进行烧结特性、微观结构、电导率、热嘭胀系数等性能对比测试.结果表明,NiO/YSZ/LCC新型复合阳极具有优良的综合性能.采用浆料浸渍法在NiO/YSZ/LCC阳极戈撑体两个表面上分别制备LCC和YSZ湿膜,1400℃空气条件下三层共烧4 h后,获得致密LCC连接体和YSZ电解质薄膜.     

Microstructure characterization and electrical conductivity of electroless nano Ni coated 8YSZ cermets

Using a common electroless bath, Ni-8YSZ (Ni-8 mol% yttria stabilized zirconia) composite nano powder have been synthesized without use of any expensive sensitizing agent. HRTEM micrographs indicated that the coating morphology of Ni nano particles on the 8YSZ showed a spotty, discontinuous distribution and the Ni nano particles appeared as a crystalline phase. The amount of Ni in the composite powders was varied from 36-51 wt.% by changing the substrate powder loading in the electroless bath. Bar type samples were prepared by uniaxial pressing and sintering at 1300 °C for 2 h with these coated powders. The cubic (c)-zirconia was found to partially dissociate into monoclinic (m)-zirconia on sintering with Ni content 41% or higher and also increases with the increase of Ni content. The microstructure of each Ni-YSZ cermet after reduction in a H₂ + Ar gas atmosphere showed dual scale porosity (micro and submicron porosity). The Ni-8YSZ cermet samples showed metallic electrical conduction behavior, proving the percolation capability of the synthesized nano composite.     

稀土掺杂Gd2 O3对YSZ/（Ni，Al）热障涂层组织与性能的影响

目的提高YSZ/(Ni,Al)复合涂层与基体的结合强度和抗高温氧化性。方法采用电泳沉积的方法,在Inconel 600高温合金表面上沉积YSZ/(Ni,Al)复合涂层和掺杂稀土Gd2O3-YSZ/(Ni,Al)(简称G-YSZ/(Al,Ni))复合涂层,后进行真空烧结,然后对制备好的热障复合涂层进行划痕实验和等温循环氧化实验。通过对样品进行等温循环氧化实验,获取不同氧化时间段的复合涂层样品,并采用SEM和XRD对复合涂层组织和形貌进行分析。结果在1100℃等温氧化过程中,未掺杂稀土元素的氧化增重速率为0.0057 mg/mm2,而掺杂钆元素的氧化速率为0.0049 mg/mm2,氧化增重速率比未掺杂稀土YSZ/(Ni,Al)复合涂层的低。G-YSZ/(Ni,Al)热障复合涂层在等温氧化过程中颗粒长大较小、裂纹少、表面更加致密。真空烧结后的YSZ/(Al,Ni)复合涂层和G-YSZ/(Al,Ni)复合涂层与基体的结合强度约为4.0 N,氧化100 h后,掺杂稀土的G-YSZ/(Al,Ni)复合涂层结合强度为3.5 N,未掺杂稀土的YSZ/(Al,Ni)复合涂层与基体的结合强度为2.6 N。G-YSZ/(Ni,Al)热障复合涂层中存在Gd2Zr2O7相和稳定的Ni Al2O4相,Gd2Zr2O7相具有良好的稳定性以及耐高温氧化。结论掺杂稀土氧化钆的G-YSZ/(Al,Ni)涂层的抗高温氧化性能显著提高。在等温氧化过程中,掺杂稀土元素的G-YSZ/(Al,Ni)复合涂层,其颗粒趋向于均匀化,裂纹明显变少,使得涂层更加致密,表面更加平整。等温氧化100 h后,掺杂了稀土氧化钆的G-YSZ/(Al,Ni)复合涂层基体之间具有更好的结合力,抗剥落性和服役寿命较好。     

Microstructural and Mechanical Property Evolutions of Plasma-Sprayed YSZ Coating During High-Temperature Exposure: Comparison Study Between 8YSZ and 20YSZ

Plasma-sprayed YSZ coatings, serving as the thermal insulating top coating for thermal barrier coatings, involve thermally activated microstructural evolution, which may change the physical and mechanical properties and thereby influence the thermal barrier performance and service lifetime. In this study, 8YSZ and 20YSZ coatings annealed at 1300 °C were comparatively investigated to understand the effects of phase structure on the sintering behavior. Results show that, compared with the 20YSZ coating consisting of mainly thermodynamically stable cubic phase, the as-sprayed 8YSZ coating presented a multiphase structure mainly composed of thermodynamically metastable tetragonal phase, and significant phase transformation occurred during high-temperature exposure. The lamellar bonding had significantly improved because of the healing of intersplat pores. Fracture toughness, microhardness, and elastic modulus increased with sintering duration. The 8YSZ coating exhibiting the thermodynamically metastable tetragonal phase structure experienced a slower sintering kinetics than the 20YSZ coatings consisting mainly of thermodynamically stable cubic phase.     

Erosion Performance of Gadolinium Zirconate-Based Thermal Barrier Coatings Processed by Suspension Plasma Spray

7-8 wt.% Yttria-stabilized zirconia (YSZ) is the standard thermal barrier coating (TBC) material used by the gas turbines industry due to its excellent thermal and thermo-mechanical properties up to 1200 °C. The need for improvement in gas turbine efficiency has led to an increase in the turbine inlet gas temperature. However, above 1200 °C, YSZ has issues such as poor sintering resistance, poor phase stability and susceptibility to calcium magnesium alumino silicates (CMAS) degradation. Gadolinium zirconate (GZ) is considered as one of the promising top coat candidates for TBC applications at high temperatures (>1200 °C) due to its low thermal conductivity, good sintering resistance and CMAS attack resistance. Single-layer 8YSZ, double-layer GZ/YSZ and triple-layer GZdense/GZ/YSZ TBCs were deposited by suspension plasma spray (SPS) process. Microstructural analysis was carried out by scanning electron microscopy (SEM). A columnar microstructure was observed in the single-, double- and triple-layer TBCs. Phase analysis of the as-sprayed TBCs was carried out using XRD (x-ray diffraction) where a tetragonal prime phase of zirconia in the single-layer YSZ TBC and a cubic defect fluorite phase of GZ in the double and triple-layer TBCs was observed. Porosity measurements of the as-sprayed TBCs were made by water intrusion method and image analysis method. The as-sprayed GZ-based multi-layered TBCs were subjected to erosion test at room temperature, and their erosion resistance was compared with single-layer 8YSZ. It was shown that the erosion resistance of 8YSZ single-layer TBC was higher than GZ-based multi-layered TBCs. Among the multi-layered TBCs, triple-layer TBC was slightly better than double layer in terms of erosion resistance. The eroded TBCs were cold-mounted and analyzed by SEM.     

Mechanical wet-milling and subsequent consolidation of ultra-fine Al2O3-（ZrO2＋3%Y2O3） bioceramics by using high-frequency induction heat sintering

Alumina/zirconia composites were synthesized by wet-milling technique and rapid consolidation with high frequency induction heat sintering(HFIHS). The starting materials were a mixture of alumina micro-powder (80%, volume fraction) and 3YSZ nano-powders (20%). The mixtures were optimized for good sintering behaviors and mechanical properties. Nano-crystalline grains are obtained after 24 h milling. The nano-structured powder compacts are then processed to full density at different temperatures by HFIHS. Effects of temperature on the mechanical and microstructure properties were studied. Al2O3-3YSZ composites with higher mechanical properties and small grain size are successfully developed at relatively low temperatures through this technique.     

Mo基体上锆酸镧热障涂层的研究

利用自行研制的La1.4Nd0.6Zr2O7(LNZ)喷涂粉末,采用大气等离子喷涂在Mo基体上制备LNZ热障涂层.测试粉末的各项热物理性能,考核涂层的抗热震性能和高温隔热性能,并与常规氧化钇稳定氧化锆(YSZ)涂层进行比较.结果表明,与YSZ相比,LNZ由于具有热膨胀系数小、导热系数低、烧结速率低等特点而更适合在Mo基体作为热障涂层使用.     

应力-应变法检测保护渣烧结特性

保护渣的烧结特性直接影响连铸过程的稳定性,因此保护渣烧结倾向是评价保护渣性能的重要指标。针对保护渣烧结特性检测误差大,方法不统一的现状,介绍了一种检测评价保护渣烧结温度和液相生成量的方法。应力-应变法在惰性气氛下,对升温过程中的保护渣施加压应力,通过实时检测渣样的应变情况,得到保护渣微区液相生成信息。由于微区液相的生成行为直接影响保护渣烧结特性,因此,应力-应变法可通过渣样的应变数据得到保护渣烧结特性。试验验证表明,应力-应变法检测保护渣烧结温度及烧结速率准确可行,重复性好。