Zhou De-rui

Study of double layer rare earth metal conversion coating on aluminum alloy LY12

The process of the double layer rare earth metal (REM) conversion coating on aluminum alloy LY12 (2024) was introduced in this paper. The corrosion resistance of REM conversion coating was examined by electrochemical impedance spectroscopy. The results showed that the coating increased the corrosion resistance (Rp) of the alloy surface, thus reducing the driving force of corrosion. The morphologies of the coating were studied by scanning electron microscope. The results revealed that the coating consisted of layers of spherical particles with different size, which grew gradually to cover the surface of aluminum alloy. The X-ray diffraction analysis revealed that the film was amorphous. The results of X-ray photoelectron spectroscopy indicated that the film consisted of cerium(III and IV) oxide and cerium(III and IV) hydroxide.

Corrosion behavior of rare earth metal (REM) conversion coatings on aluminum alloy LY12

The processes of the double layer rare earth metal (REM) conversion coating on aluminum alloy LY12 (2024) were introduced. The results of polarization tests showed that the corrosion resistance of the double layer REM conversion coating was superior to that of chromate conversion coating. The corrosion behavior of REM conversion coatings on LY12 alloy was studied with optical microscopy and energy dispersive spectroscopy (EDS). The results showed that in NaCl solution, pits initiated on the coatings formed on Cu-rich intermetalics. According to the equivalent circuit of pitting, a new method for analyzing the pit growth of REM conversion coatings was put forward by employing electrochemical impedance spectroscopy (EIS). Transmission line W in equivalent circuit could be neglected in short term exposure of REM conversion coatings to NaCl solution. This led to a formula for calculating the area fraction of pitting (F) on the surface of REM conversion coatings by simplifying the equivalent circuit

Study on Properties of LSGM Electrolyte Made by Tape Casting Method and Applications in SOFC

Abstract Solid oxide fuel cell is attracting more attention in recent years for its lower pollution emission and high energy convert efficiency. La0.9Sr0.1Ga0.8Mg0.2O3-δ is a new kind of electrolyte for intermediate temperature SOFC. In this paper, La0.9Sr0.1Ga0.8Mg0.8O3-δ (LSGM) was prepared by solid state reaction method and formed by tape casting process to make a planar electrolyte. The appropriate amount of the dispersive was obtained by viscosity test. The densities of sintered samples increase with the increasing sintering temperature. It was found that the relative density of electrolyte can approach the value of 95% by the isostatic pressing treatment of the green tape. The average thermal expansion coefficient of the LSGM is 11.4 × 10−6/°C at temperature range (200 ∼ 1200 °C). Measurements of the current-voltage and power-current characteristics of the H2-Air cell show that the open-circuit voltage is 1.067 V at 800 °C, peak current density is 0.56 A · cm−2 and the maximum power output is 0.147 W · cm−2.

Preparation and Characterization of La0.8Sr0.2MnO3-δ Cathode for SOFCs Fabricated Using Azeotropic Distillation Method

Abstract Strontium doped lanthanum manganite (LSM) powders were synthesized by three different routes: azeotropic distillation, sol-gel and solid state reaction respectively. The LSM samples, made by azeotropic distillation and sol-gel methods were prepared by firing at 1000 °C for 6 h, and the LSM sample, made by solid state reaction method was produced by sintering at 1400 °C for 18 h. The samples were characterized by XRD, TEC, SEM, EIS and polarization performance analysis. The results show that all the samples made by different methods have pure orthorhombic LSM phase, however exhibit different micro structure and electrochemical characterization, which relates to the different synthesis methods. The solid state reaction method produces the samples with larger particle size compared with azeotropic distillation and sol-gel methods. The powders made by azeotropic distillation method have less agglomerated particles compared with that made by sol-gel method because the precursor in the former is dispersed in n-butanol before sintering. The polarization current density of powder made by azeotropic distillation method was twice of that made by sol-gel method and four times of that made by solid state reaction method. The values of polarization resistance ( R p ) are 0.35 Ω · cm 2 for the cathode synthesized by azeotropic distillation route, which is much lower than sol-gel (1.5 Ω · cm 2 ) and solid state reaction (2.3 Ω · cm 2 ) at 800 °C.

Anode-Supported IT-SOFC anode Prepared by Tape Casting Technique

This paper used composite multi-layer tape casting technique successfully in fabricating Ni-YSZ/YSZ anode/ electrolyte composite ceramic of planar intermediate-temperature solid oxide fuel cell (IT-SOFC). The anode was designed as a double-layer structure, which consisted of an anode substrate and an anode functional layer. This design optimized anode microstructure and improved its performances. This design made anode match electrolyte well during the co-sintering process. The anode conductivity was higher than 1000 S-cm-1 at 800degC. The TEC of the composite ceramic was 12.1times10-6 K-1, which matched those of inter connector and sealant. When NiO content of functional layer was 50 mass%, the current density was about 80 mA-cm-2 at an overpotential of 0.1 V. EIS measurement showed that anodic catalytic activity and interfacial resistances were main factors affecting electrode performance. Unit cells were assembled and tested after above performances were measured.