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老板给了一篇关于燃料电池的文献要我翻译，，，我自己用金山看了半天能看个大概意思懂，
但是很多地方确实不知道怎么表达出来，谁能帮忙翻译下，
永感大恩。
Dry layer preparation and characterization of polymer electrolyte fuel cell components.
Preparation technique
The aim of the preparation process development at DLR was to achieve a low-cost and effective manufacturing process for PEFC MEAs. Therefore, a novel technique for MEA production was developed at DLR[26a,26b],This process is based on other dry production techniques developed at DLR[2,3,20,27-29].The fundamental idea for this simple process is to spray a dry catalytic layer directly onto the membrane to avoid waiting times for evaporating solvents and at the same time, to accomplish good contact between the catalytic layer and the electrolyte membrane。Therefore, it was necessary to develop a dry coating system that can handle fine powders ( <0.1 um diameter) like carbon-supported catalysts (e. g, Pt on Vulcan XC-72).
The preparation process for MEAs is divided into three main steps:
1. Preparation of the electrode powder
2. Dry spraying the powder onto the membrane
3. Hot rolling or pressing the membrane with the gas diffusion layers Fig。1 shows a scheme of the manufacturing process.
The first main preparation step for MEA production comprises mixing of the reactive layer material(e. g, platinum supported on carbon black with different amounts of PTFE, polymer electrolyte powder and/ or filler materials) in a knife mill[2,30]。In order to obtain homogeneous and thin reactive layers, the material is atomized and sprayed in a nitrogen stream through a slit nozzle directly on a membrane. The adhesion of the catalytic layer material onto the surface is already secure. However, in order to improve the electrical and ionic contact, it is necessary to fix the layer by hot rolling or pressing. Depending on the degree atomization of a completely uniformly covered reactive layer, with thickness down to 5 um, can be prepared using the production technique described. This fact yields to a low noble metal catalyst loading.
In addition to the preparation of the reaction layers, this technique can also be used to form a hydrophobic coverage for the surface of the MEA backing material , especially as this preparation step of the electrode production is also free of solvents.
From the low catalyst loading combined with the simplicity and degree of automation of the procedure , it is clear that the aim of a low-cost production technique can be achieved. By changing the composition of the raw powder and the deposition conditions of subsequent layers , it is possible to establish gradients, for instance , in porosity, catalyst loading or hydrophobicity in electrodes for other applications, for example, for DMFC. Another advantage of this production technique is that environmentally hazardous solvents are totally avoided. In addition this technique can be scaled up to an industrial production process. From all the advantages, it is clear that our procedure has the capability to become an important industrial production technique for fuel cell MEA..
The electrode raw powder for standard MEAs consists of 20 wt% PTFE( Hostaflon TF 2053 from Hoechst ) and 80 wt% carbon-supported Pt (20 wt% Pt on Vulcan XC-72 from E-TEK) and is mixed in a knife mill for 5 s. In the next step, the powder is transferred to a sprayer where it is sprayed on the membrane in thin layers by moving the membrane over a coating nozzle. Thereby , various Pt-loadings up to 4 mg/cm2 and down to 0.05 mg/cm2 are possible, TO fix the catalytic layer and to complete the MEA, gas-diffusion layers are hot-rolled or pressed onto the coated membrane, Fig 2 shows the performance of a standard MEA with Nafion112 membrane and a Pt-loading of 0.07 mg/cm2 on each electrode. |
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发表于 2007-7-23 17:00
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发表于 2007-7-23 17:01
