Two/three-dimensional reduced graphene oxide coating for porous flow distributor in polymer electrolyte membrane fuel cell

There are drawbacks to use stainless-steel plates as a flow distributor plate in fuel cell, due to some of their properties being inferior to graphite flow distributor plates in terms of electrical conductivity and corrosion resistance. To overcome these problems, many researches have been conducted to improve the properties of stainless-steel flow distributor plates through coating of carbon materials. Herein, two-dimensional Web-like graphene (WG) and self-assembled three-dimensional graphene (STG) are coated through superheat vaporization of micro-droplet method. WG is coated in porous Ni–Cr foam and STG is constructed on the flat flow distributor plate, and they exhibit the feasibility to be applied in flow distributors. Compared to uncoated Ni–Cr foam, the performance of the PEMFC system with the graphene coated foam is enhanced remarkably. Furthermore, the flow distributor plate with the STG exhibits potential to be used directly to flow distributor.     

电压降法在水平定向钻穿越管道外涂层评价中的应用研究

介绍了电流-电位法、电流密度法在水平定向钻穿越管道外涂层评价中的应用,联合电压降法计算管内电流值,并结合实际案例对穿越管道两端连头之后外涂层性能进行评价。     

石油储罐防腐涂料施工策略

在经济不断发展的背景下,石油已经成为不可或缺的能源,其从开采至加工整个过程均需使用储油罐,所以储油罐的防腐质量十分重要,需要使用相应的涂料进行防腐。本文对石油储罐防腐涂料施工策略进行分析,以供参考。     

Investigation of surface-modified anhydrous borax utilisation in raw glazes

This study aims to determine the feasibility of preparing ceramic glaze using a surface-modified borate, which contributes boron to the composition without the need of a fritting process. In this context, surface modification of anhydrous borax powders (ABP) with magnesium stearate (MgSt) via dry powder coating is investigated. The surface modification of ABP with MgSt is optimised by employing modifier dosage of 0.5, 1, and 2?wt% and coating periods of 30, 60, and 120?min. The resulting powders are comparatively characterised via wettability, solubility, and dispersibility tests. The structural changes in surface-treated ABP are investigated using X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR) analyses. The results indicate that ABP surface could be switched from hydrophilic (17°) to hydrophobic (115°), its water solubility decreased from 40% to 10%, and a coating yield of approximately 74% was achieved with MgSt dosage of 1?wt% at a processing period of 2?h. Furthermore, FT-IR and XPS results indicated that MgSt is mainly coated over the surface of ABP via physical adsorption rather than chemical bonding. The glaze containing surface-treated ABP that was fired at 1050?°C, demonstrated complete melting and surface coverage without defects. Thus, effective dry coating as a single-step approach could be applied to obtain surface-modified ABP, which offers controlled solubility in glaze suspensions with improved dispersibility and excellent glaze coverage of the surfaces.     

Interface reactions between rutile coatings and molten aluminium or AlSi7Mg0.6 alloy

Rutile coatings deposited on corundum substrates are considered as promising functional elements improving the efficiency of the filtration of oxide inclusions out of aluminium melts. This contribution describes the reactions between rutile and two kinds of the aluminium melts and discusses the consequences of these reactions for the filtration process. It was found that the contact of rutile coatings with molten aluminium leads to the formation of a corundum layer at the solid/liquid interface. The exposure of the rutile coatings to molten AlSi7Mg0.6 alloy produces an interface layer of MgTiO₃. The interface layers possess defined orientation relationship to rutile which is characteristic for locally heteroepitaxial growth. The density functional theory calculations revealed that the TiO₂/α-Al₂O₃ and TiO₂/MgTiO₃ interfaces with the orientation relationships observed experimentally have low interface energies. The mechanisms of the interface layer formation and the impact of these layers on the degradation of the rutile coatings are discussed.     

Improved thermal shock resistance of SiCnw/PyC core-shell structure-toughened CVD-SiC coating

In-situ SiC nanowire (SiCnw)/pyrolytic carbon (PyC) core-shell structures were introduced to mainly improve the thermal shock performance of chemical vapor deposition (CVD)-SiC coating on carbon/carbon (C/C) composites. The microstructure, phase composition, and mechanical properties of the CVD-SiC coating toughened by SiCnw/PyC core-shell structures were studied as well. The results show that the introduction of SiCnw/PyC core-shell structures can effectively alleviate the mismatch of coefficient of thermal expansion (CTE) between SiC coating and C/C substrate, thus enhancing the thermal shock resistance of the coating. Furthermore, the increased numbers of interfaces in the SiC coating owing to the addition of core-shell structures are beneficial to the mechanical properties of the coating after thermal shock test.     

Phase stability and thermo-physical properties of ZrO2-CeO2-TiO2 ceramics for thermal barrier coatings

The properties of ZrO₂ co-stabilized by CeO₂ and TiO₂ ceramic bulks were investigated for potential thermal barrier coating (TBC) applications. Results showed that the (Ce_0.15Ti_x)Zr_0.85-xO7 (x?=?0.05, 0.10, 0.15) compositions with single tetragonal phase were more stable than the traditional 8YSZ at 1573?K. These compositions also showed a large thermal expansion coefficient (TEC) and a high fracture toughness, which were comparable to those of YSZ. However, the phase stability, fracture toughness and sintering resistance of the CeO₂-TiO₂-ZrO₂ system showed a decline tendency with the increase of TiO₂ content. The TEC of the ceramic bulks decreased with increase of TiO₂ content as well because the crystal energy was enhanced with increasing substitution of Zr⁴⁺ by smaller Ti⁴⁺. The (Ce_0.15Ti_0.05)Zr_0.8O₂ had the best comprehensive properties among the (Ce_0.15Ti_x)Zr_0.85-xO₂ compositions as well as a low thermal conductivity. Therefore, it can be explored as a TBC candidate material for high-temperature applications.     

Environmental-barrier coating ceramics for resistance against attack by molten calcia-magnesia-aluminosilicate (CMAS) glass: Part I,YAlO3 and γ-Y2Si2O7

The high-temperature (1500?°C) interactions of two promising dense, polycrystalline EBC ceramics, YAlO₃ (YAP) and γ-Y₂Si₂O₇, with a calcia-magnesia-aluminosilicate (CMAS) glass have been explored as part of a model study. Despite the fact that the optical basicities of both the EBC ceramics and the CMAS are similar, they both react with the CMAS. In the case of the Si-free YAlO₃, the reaction zone is small and it comprises three regions of reaction-crystallization products, including Y-Ca-Si apatite solid-solution (ss) and Y₃Al₅O₁₂ (YAG)(ss). In contrast, only Y-Ca-Si apatite(ss) forms in the case of Si-containing γ-Y₂Si₂O₇, and the reaction zone is an order-of-magnitude thicker. These CMAS interactions are analyzed in detail, and are found to be strikingly different than those observed in Y-free EBC ceramics (β-Yb₂Si₂O₇ and β-Sc₂Si₂O₇) in the accompanying Part II paper. This is attributed to the presence of the Y in the YAlO₃ and γ-Y₂Si₂O₇ EBC ceramics.     

A method for testing the interface toughness of ceramic environmental barrier coatings (EBCs) on ceramic matrix composites (CMCs)

A simple interface fracture test for ceramic environmental barrier coatings (EBCs) on ceramic matrix composites (CMCs) was developed. A variation on the asymmetric double cantilever beam (ADCB) test was proposed so that the interface toughness could be measured in a small specimen of simple shape without applying interlaminar loading to the CMC substrate. The proposed test was applied to an EBC consisting of a mullite layer and Si bond coat on a monolithic SiC substrate. A pre-crack was introduced by pop-in cracking, and then a notch overlapping the pre-crack was machined. The pre-crack was opened by inserting a wedge into the notch. From the critical notch opening displacement the crack starts to propagate, interface toughness is calculated. The measured interface toughness was 4.1?J/m2. Finally, the application range of the test was discussed and suggestions were made for introduction of the notch and pre-crack.