DIFFUSION BONDING: UNDERSTANDING THE BASICS

Diffusion bonding is the joining of two surfaces by the action of pressure and temperature. Hence, melting and melting-related errors are avoided in the diffusion bonding process. Since the bonding pressure is considerably below the yield stresses of the material, bulk plastic deformation of the materials is entirely avoided. Stoll vacuum diffusion bonding relies on pressure, temperature, time, and vacuum levels to help atomic exchange over the interface between the materials. The process will work on similar or different materials so long as they are in close contact with one another.

Benefits of Diffusion Bonding  

Using a hydraulic pressing device, the joining sections of the component to be connected are pressed against each other powerfully, bringing them in close contact. A virtually pore-free composite material appears by solid-state diffusion, which meets the highest thermal, mechanical, and corrosion technical requirements. A key characteristic of diffusion bonding is that usually, no filler material is used. The joint does not have any foreign alloy parts and has properties related to base materials when adequately performed. Due to the lack of a molten phase in the joining process, highly exact and accurate contour bonding of precision components can also be guaranteed. Examples of the diffusion bonding's chosen application in this context are micro-coolers and micro-reactors characterized by magnificent channel structures near the joint.

 

Flow channels can be made on either or both sides of a metal, graphite, or composite material plate. A channel flow plate on both sides in a fuel cell stack is called a bipolar plate. The fabrication method of a flow field plate depends on the elements used.Micro channel flow plate lines are well-distributed, no burr, no gap, no size hole, for precision products, can be well assembled supporting operation.

Bipolar plates are a vital component of proton exchange membrane fuel cells. Bipolar Plate Chinese manufacturer is liable for transporting reactant gases, carrying the current from the membrane electrode device to the endplates, providing heat and water management, and departing the individual cells. However, these plates contribute to 80% of the fuel cell's weight, 50% of its volume, and 40% of its cost, posing a barrier to the commercialization of fuel cells. This paper comprehensively reviews the elements and manufacturing processes used in the fabrication of bipolar plates and recent research on improving bipolar plate volume, weight, and cost through material selection and manufacturing methods. A bipolar plate, also called a current collecting plate, is one of the essential components of the fuel cell. 

Optimizing Material Choice for Fuel Cell Metal Bipolar Plates

The function of BPPs is required in fuel cells, as they connect each cell electrically and provide the necessary reactant gases. They also eliminate the reaction by-products from the cell. Fuel cell metal bipolar plates were generally believed to be the better choice for long-term cost targets. This is, in significant part, due to the misperception that carbon plates are only fit for low-volume due to higher production value at large scale.

A Printed Circuit Heat Exchanger (PCHE) is categorized as a plate-fin type heat exchanger. PCHE is based mainly on the two technologies of chemical etching and diffusion bonding. Flow channels are etched chemically on the metal plates. Etched plates are stacked and to produce one block by diffusion bonding.

Some of the benefits of PCHEs are as follows:

• Four to six times smaller than traditional shell and tube heat exchangers for the same duty.

• Excessive pressure capability over 600 bar (9000 psi)

• High thermal effectiveness of over 98% in a single unit.

• Extreme temperature capability ranging from cryogenic to 900°C.

• Suitable for a variety of corrosive and high purity streams.

• Has space and weight benefits, as several process streams can be into a single unit.

In recent years, with the shortage of resources and environmental pollution, the adjustment of industrial structure and the realization of energy-saving and emission reduction of heat exchangers have gradually become the focus of the development of the petrochemical industry. The printed circuit heat exchanger is a fine channel compact plate heat exchanger with many advantages, such as high temperature resistance (50 MPa), high-pressure resistance (700℃), ultra-high efficiency (up to 98%), low-pressure drop, high tightness (1/6/4 of traditional tube-shell heat exchanger), corrosion resistance and long life.