As a core functional material in the metal sintering and electrolyzer industries, nickel felt is widely used in high-end fields such as hydrogen energy water electrolysis for hydrogen production, fuel cells, high-temperature filtration, and electrochemical catalysis. Its quality directly determines the operational efficiency, stability, and service life of equipment. Inferior nickel felt is prone to problems such as oxidation and shedding, uneven conductivity, and pore blockage, which not only increase replacement costs but also may lead to significant losses such as reduced electrolyzer efficiency and potential safety hazards.
As a lead company with more than ten years of experience in the metal sintering fields, TOPTITECH will break down the 6 core dimensions to "judge the quality of nickel felt" for you today. From basic appearance to core performance, from practical testing to standard comparison, even beginners can quickly get started, avoid procurement pitfalls, and choose cost-effective nickel felt.
First Look at the Appearance: Details Hide the Most Intuitive Quality Signals
The appearance of nickel felt is the "first face" of its quality. No professional equipment is needed; preliminary judgment can be made with the naked eye and simple touch. Focus on 3 points to avoid obviously inferior products:
1. Surface Color and Cleanliness (Core Foundation)
High-quality nickel felt has a uniform silver-gray metallic luster on the surface, without obvious color difference, blackening, yellowing, rust spots, or oxidation spots. The overall color is consistent, with no local dullness or uneven brightness-this is a direct reflection of qualified nickel content, no impurities, and low oxidation level. According to the "T/CSTM00689-2023 General Technical Specification for Metal Nickel Felt" issued by CSTM, qualified nickel felt should have a clean surface without stains or obvious oxidative attachments.
Inferior nickel felt, mostly due to insufficient raw material purity (doped with iron, copper, and other impurities) or improper oxidation control during the production process, will have a dull surface, spots, rust, and even residual oil, dust, etc. Such nickel felt is extremely prone to rapid oxidation and failure in corrosive environments such as electrolyzers.
2. Structural Uniformity (Affects Conductivity and Permeability)
High-quality nickel felt is made of continuous nickel fibers through wet laying and vacuum sintering. The fibers are evenly interwoven, with no obvious agglomeration, broken wires, skipped wires, or locally sparse areas. When gently pulled by hand, the felt body has no delamination or fiber shedding, and the overall thickness is uniform.
Inferior nickel felt has messy fiber distribution, local fiber agglomeration, and some areas are sparse and light-transmitting. It is prone to wire shedding and delamination when pulled, and even obvious holes or damage-such nickel felt has uneven pore distribution, which will lead to poor current conduction and uneven distribution of reaction gas during electrolysis, greatly reducing electrolysis efficiency.
3. Edge and Flatness (Reflects Production Process Precision)
High-quality nickel felt has a neat cut edge, no burrs, no curling, no warping, and can fully fit the plane when laid flat, without wavy deformation or local depression and protrusion; inferior nickel felt has a rough and irregular cut edge, which is easy to curl and deform, and even has loose and falling edge fibers. It is difficult to accurately fit with electrolyzers, filtration equipment, etc. during subsequent installation, affecting the sealing and use effect.
Test Core Performance: These 3 Points Determine the Practical Value of Nickel Felt
Qualified appearance is only the foundation. The core value of nickel felt lies in its physical, chemical, and electrochemical properties, which is also the key to distinguishing "high-quality nickel felt" from "qualified nickel felt". Focus on testing 3 core indicators, which are suitable for practical application scenarios such as electrolyzers and fuel cells:
1. Material Purity: Nickel Content ≥99.0% is the Bottom Line (Top Priority)
The material purity of nickel felt directly determines its corrosion resistance, conductivity, and service life. High-quality nickel felt must meet the requirements of the "T/CSTM00689-2023 General Technical Specification for Metal Nickel Felt", with a minimum nickel content of not less than 99.0%. For nickel felt used in high-end electrolyzers, it is recommended to choose products with nickel content ≥99.6%. The content of impurities (iron, copper, carbon, oxygen, etc.) must be strictly controlled.
How to test? When purchasing, you can ask the supplier to provide a material test report (such as an X-ray fluorescence spectroscopy test report) clearly indicating the nickel content and impurity content; if conditions permit, you can observe the microstructure through a metallographic microscope. High-quality nickel felt has no obvious impurity particles and uniform fiber crystallization.
Inferior nickel felt mostly uses low-purity nickel raw materials, doped with a large number of impurities. It not only has poor conductivity and corrosion resistance but also is prone to oxidative dissolution in alkaline electrolyzer environments, and may contaminate the electrolyte, affecting product purity (such as the purity of hydrogen in hydrogen energy production).
2. Pore Characteristics: Porosity and Pore Size Distribution Determine Application Scenario Adaptability
The core advantage of nickel felt is its three-dimensional porous structure. Porosity and pore size distribution directly affect fluid permeability, specific surface area, and catalytic efficiency. Different application scenarios have different requirements for pore indicators (for example, nickel felt used in water electrolysis for hydrogen production requires high porosity to ensure gas diffusion, while nickel felt used in filtration requires precise pore size distribution to improve interception efficiency). High-quality nickel felt must meet the following requirements:
- Porosity: For nickel felt used in electrolyzers and fuel cells, it is recommended to choose a porosity of 60%-80%. Too low porosity will affect gas/liquid circulation, while too high porosity will reduce the mechanical strength of the felt;
- Pore size distribution: The pore size is uniform, without excessively large or small abnormal pores. The pore size of nickel felt used in water electrolysis for hydrogen production is recommended to be controlled between 10-20μm;
- Air permeability: Uniform air permeability without obvious blockage, to ensure that gas/liquid can pass smoothly and the reaction can be fully carried out.
Inferior nickel felt has large fluctuations in porosity, messy pore size distribution, and some pores are blocked or too large, which will lead to uneven gas diffusion and excessive pressure drop in the electrolyzer, or insufficient interception efficiency during filtration, shortening the service life of the equipment.
3. Mechanical and Electrochemical Properties: Key to Adapting to Extreme Working Conditions
Nickel felt is mostly used in working conditions with high temperature, high pressure, and strong corrosion. Therefore, mechanical strength and electrochemical properties are crucial. High-quality nickel felt must meet:
- Mechanical properties: The tensile strength can reach 5-25MPa, with good compression resilience. After repeated compression to 50% strain, it can still recover more than 85% of its original thickness. It has no breakage or obvious deformation when pulled by hand. The tensile strength and elongation can be tested by a universal testing machine;
- Electrochemical properties: Low contact resistance, strong stability in alkaline electrolyte, no obvious oxygen evolution or hydrogen evolution abnormalities, which can be verified by resistivity testing;
- Corrosion resistance and high-temperature resistance: It can operate stably for a long time in an oxidizing or reducing atmosphere above 600℃, with no obvious corrosion in salt spray tests, suitable for harsh working conditions such as electrolyzers and high-temperature filtration.
Inferior nickel felt has poor mechanical strength, is easy to break and deform, and has high contact resistance, which will increase the energy consumption of the electrolyzer. It is prone to oxidation, corrosion, and shedding after long-term use, leading to equipment failure.
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