Influence of sintering temperature on ion dynamics of Na0.5Bi0.5TiO3-δ: Suitability as an electrolyte material for SOFC

Sodium bismuth titanate samples with different morphology were synthesized via varying the sintering temperature from 1000 to 1150 °C. The conductivity was significantly affected with the morphology of the system. The dynamics of ions was understood from the conductivity spectra. The dc conductivity, hopping frequency and exponent values were extracted from the conductivity spectra analysis. The impedance and modulus spectroscopy along with exponent behaviour suggested short range hopping for the sample sintered at 1000 °C and followed Ghosh scaling instead of Summerfield scaling. While long-range hopping was observed for the samples sintered at 1150 °C and it followed both the Summerfield scaling and Ghosh scaling. Moreover, the stability of the sample is checked in reducing atmosphere.     

蛋白质分配系数的实验测定和热力学模型计算

本文实验测定了６种蛋白质在电解质／高聚物双水相体系中的４组分配系数。在Ｅａｓｋｉｒ的蛋白质球形晶格模型基础上计算了蛋白质和水、高聚物链段的短程作用，用Ｐｉｔｚｅｒ－Ｌｉ长程静电项计算它们的长程作用。由１组分配系数回归多数预测另外３组分配系数，其预测值和实验值的平均相对误差低于６％。并讨论了蛋白质在双水相体系中分配系数的影响因素。     

涡轮叶片气膜冷却孔电解加工气液两相流场特性分析

以高温镍基合金Inconel718为基材进行气膜冷却孔电解加工基础试验,在电解加工过程中,阴极反应界面析出氢气,导致电解液的电导率不再是一个常数,从而影响冷却孔的加工成型精度。结合前期基础试验,建立冷却孔电解加工流道二维模型,基于COMSOL Multiphysics软件对冷却孔端面间隙内气液两相流场进行仿真,研究加工电压、电解液入口压力及管电极进给速度对氢气析出量的影响,并定性地分析电解加工过程中气泡率与电导率之间的关系。由仿真结果可知:氢气的体积分数随加工电压和电极进给速度的增大而增大,随电解液入口压力的增大而减小,且氢气体积分数越大,电解液的电导率越小。     

等离子喷涂-物理气相沉积制备7YSZ纳米结构固体氧化物燃料电池电解质层

氧化钇稳定的氧化锆（YSZ）因其高热稳定性和良好的氧离子电导率被广泛地作为电解质材料应用于固体氧化物燃料电池（SOFC）。常规的平面SOFC电解质制备技术,如带式流延或丝网印刷,需要在1300℃以上的温度下进行烧结,因此采用传统制备技术获得纳米结构电解质层是一个挑战。等离子喷涂-物理气相沉积（PS-PVD）作为一种新技术由于可以实现气相沉积可以提供快速、低成本的方法来制备纳米致密结构电解质层,可避免传统技术在长时间高温烧结引起的材料晶体结构变化以及相邻电极材料间的化学反应。PS-PVD技术具有与传统大气等离子喷涂（APS）完全不同的沉积机制。本研究采用该技术成功地制备了致密的纳米结构7YSZ薄电解质层。当电解质层厚度为8.7～12.3 μm时,其泄露率为2.24～2.29 10-8 cm4gf-1s-1.     

Development of electrolyte filtration system for ECM taking into account removal of chromium (VI) ions

During the ECM process, the metal workpiece is dissolved and turns into sludge which contaminates the electrolyte. To realize precise ECM with high cost-effectiveness, an electrolyte treatment system which can realize reuse of the electrolyte and maintain the electrolyte quality constant is significantly important and essential. Especially, in the ECM of alloys containing a certain level of chromium, it is very likely chromium dissolves to the toxic carcinogen Cr(VI). Therefore, an electrolyte filtration system is required for removing not only the sludge but also residual toxic ions in the electrolyte for health and environment conservation reasons. In this study, activated carbon and scrap iron, which are low cost and easily available materials, were newly utilized to reduce and remove toxic Cr(VI) ions. Experiments clarified that use of activated carbon has no influence on the machining ability of NaNO₃ aqueous solution serving as the electrolyte. By adjusting the pH of the electrolyte to acidic, activated carbon can remove Cr(VI) from the NaNO₃ aqueous solution electrolyte to a concentration of less than 0.1 mg/L. On the other hand, scrap iron generated from metal cutting processes can be used to reduce Cr(VI) to non-toxic Cr(III). By mixing HNO₃ into the electrolyte solution, the reduction efficiency of scrap iron on Cr(VI) improves significantly.     

Study on grinding of LiTaO3 wafer using effective cooling and electrolyte solution

As a typical multi-functional single crystal material, lithium tantalate (LiTaO₃ or LT) exhibits its excellent electro-optical, piezoelectric properties and has now been widely applied into many applications, such as electro-optical modulators, pyroelectric detectors, optical waveguide, piezoelectric transducers and SAW (surface acoustic wave) substrates. LT is known as a very important functional material, however the details of its machinability are not readily available yet. The content in this study is firstly focuses on the physical properties of LT like piezoelectric and pyroelectric effects and their influence on grinding performance. The obtained results are analyzed and discussed to understand its physical properties which have significant influences on their machinability in the grinding process. The crack initiation is possible to be dominated by internal stress which originated from self-polarization of the material itself. Hence, in order to suppress the physical effects induced by polarization during grinding of LT, control the temperature of coolant and increase the electrical conductivity of coolant are purposely tried in this study. The grinding results suggest that control of coolant temperature and use of electrolyte solution can effectively suppress the increasing rate of grinding torque and surface roughness, which in turn enhance the performance of LT wafer grinding. The LT wafers are eventually able to be thinned less than 100 μm.     

Supercritical carbon dioxide extraction of lithium-ion battery electrolytes

Two different separator materials (polyethylene fleece – Freudenberg 2190 and porous glass fiber – Whatman^® GF/D) and two different lithium-ion battery electrolytes have been investigated regarding their behavior in an autoclave extraction with supercritical helium head pressure carbon dioxide (sc HHPCO₂). Mixtures of dimethyl carbonate (DMC)/ethylene carbonate (EC) and ethylmethyl carbonate (EMC)/EC, each with 1 mol/L LiPF₆ were used.In addition to these proof of principle experiments, the developed extraction method was further applied to real battery samples. Commercial 18650 cells (after formation and aging) were opened and the jelly roll was extracted with sc HHPCO₂. Extracts were analyzed with gas and ion chromatography (GC, IC). Recovery rates and extract compositions strongly depend on the material of which the electrolyte is extracted. Further structure determination of electrolyte aging products was performed with different ionization modes in GC–mass spectrometry (GC–MS) experiments. Diethyl carbonate (DEC), dimethyl-2,5-dioxahexane dicarboxylate (DMDOHC), ethylmethyl-2,5-dioxahexane dicarboxylate (EMDOHC) and diethyl-2,5-dioxahexane dicarboxylate (DEDOHC) are aging products of electrolyte degradation which were successfully extracted and identified. Their concentrations correlate with solid electrolyte interphase (SEI) growth on the negative electrode which was investigated with scanning electron microscopy (SEM).     

Enhancing oxygen surface exchange coefficients of strontium-doped lanthanum manganates with electrolytes

Electrolyte effects on the oxygen surface exchange coefficients of strontium-doped lanthanum manganates (LSM) are investigated using electrical conductivity relaxation technique. Introducing electrolytes can significantly reduce the re-equilibration time, demonstrating the substantial promotion in the surface exchange kinetics. The coefficient at 1000 °C increases from 9.00 × 10⁻⁵ cm s⁻¹ for pure LSM to 2.45 × 10⁻⁴ cm s⁻¹ for LSM coated with yttria-stabilized zirconia, and further increases to 7.92 × 10⁻⁴ cm s⁻¹ for LSM with samaria-doped ceria. The nearly one order of magnitude increase in the coefficient demonstrates that introducing electrolytes can effectively increase the electrochemical performance of solid-oxide-fuel-cell cathodes by enhancing the surface exchange reaction in addition to extending the reaction sites.     

Development of an experimentally validated semi-empirical fully-coupled performance model of a PEM electrolysis cell with a 3-D structured porous transport layer

A semi-empirical non-isothermal model incorporating coupled momentum, heat and mass transport phenomena for predicting the performance of a proton exchange membrane (PEM) water electrolysis cell operating without flow channels is presented. Model input parameters such as electro-kinetics properties and mean pore size of the porous transport layer (PTL) were determined by rotating disc electrode and capillary flow porometry, respectively. This is the first report of a semi-empirical fully coupled model which allows one to quantify and investigate the effect of the gas phase and bubble coverage on PEM cell performance up to very high current densities of about 5 A/cm². The mass transport effects are discussed in terms of the operating conditions, design parameters and the microstructure of the PTL. The results show that, the operating temperature and pressure, and the inlet water flowrate and thickness of the PTL are the critical parameters for mitigating mass transport limitation at high current densities. The model presented here can serve as a tool for further development and scale-up effort in the area of PEM water electrolysis, and provide insight during the design stage.     

电解液浓度对纯钛微弧氧化陶瓷膜结构的影响

为了得到具有生物活性的陶瓷膜,通过研究微弧氧化的工艺条件,得到了适宜于制备多孔生物活性膜的电解液配方,其中Na2HPO4质量浓度为20g/L、KOH质量浓度为2g/L。结果表明,随电解液浓度的增加,起弧电压降低,陶瓷层厚度增加,最大达到13.6μm,表面粗糙度增大,最大达到3.2μm。采用该电解液在适当的微弧氧化工艺条件下,在纯钛表面制备的陶瓷膜具有分布均匀的多孔结构。