The four-point probe method is the four-terminal measurement using four-point array probes and with RCF calculation.
It can be used to calculate volume resistivity and surface resistivity (sheet resistance).

Four point probe is used to measure resistive properties of semiconductor wafers and thin films. If the thickness of a thin film is known, the sheet resistance measured by four point probe can be used to calculate the resistivity of the material; conversely, if the material’s resistivity is known, the thickness of the thin film can be calculated.

Carbon paper is commonly used as the gas diffusion layer in hydrogen fuel cells. The purpose of the gas diffusion layer is to allow the gases to diffuse uniformly over the surface of the electrode while also acting as an electrical conductor. Carbon paper is a good material for this purpose because it has a high porosity, high electrical conductivity, and is chemically inert. However, the high cost of carbon paper limits its widespread use in fuel cells.

Bipolar plates are used to connect multiple cells in a fuel cell stack and to distribute reactants and products. Bipolar plates must be electrically conductive, corrosion-resistant, and have a low electrical resistance. Several materials have been evaluated for use as bipolar plates, including graphite, metals, and composites. Composite bipolar plates made from a mixture of graphite and thermoplastic polymers offer a good balance of mechanical strength, electrical conductivity, and corrosion resistance.

In summary, hydrogen fuel cells offer a promising energy source for the future, with carbon paper playing a key role as the gas diffusion layer and composite bipolar plates offering a cost-effective solution for connecting multiple cells in a fuel cell stack. Ongoing research is focused on developing more efficient and durable fuel cells with improved materials and designs.

The basic idea of a tensile test is to place a sample of a material between two fixtures called “grips” which clamp the material. The material has known dimensions, like length and cross-sectional area. We then begin to apply weight to the material gripped at one end while the other end is fixed. We keep increasing the weight (often called the load or force) while at the same time measuring the change in length of the sample.

The result of this test is a graph of load (amount of weight) versus displacement (amount it stretched). Since the amount of weight needed to stretch the material depends on the size of the material (and of course the properties of the material), comparison between materials can be very challenging. The ability to make a proper comparison can be very important to someone designing for structural applications where the material must withstand certain forces.

The co-effiffifficient defifines the sliding resistance of two surfaces, such as a ski on snow (A), or feet on grass (B). In the absence of friction, the effffort needed to slide an object would be signifificantly reduced, as would the effffort needed to stop or change direction.

Newton’s fifirst law of motion states that a body remains at rest or in uniform motion unless acted upon by a force. Gravity causes a mass to press down with a force equal to its mass multiplied by acceleration. It follows that friction is the force needed to start sliding an object (Static Friction), or the force needed to keep it sliding (Kinetic Friction), expressed as a ratio by dividing into the downward force of the mass.

In industrial applications it can be important to understand how two surfaces interact with one another, e.g. flflexible plastic fifilm sliding over pouch formers in a highspeed packaging machine, or paperboard cartons being drawn into an erector then later stacked on top of one another. Things can go wrong when the interaction is not constant. In automated processing, adjustments made to dynamic machinery only work when the material reacts the same way each time. When replenishing a roll of flflexible plastic fifilm on a high-speed packaging line, fifilm that exhibits difffferent friction may not run smoothly, potentially causing alignment, snagging and running problems.