What Is Highly Oriented Pyrolytic Graphite Or HOPG Graphite ?
High oriented pyrolytic graphite, abbreviated HOPG, is a new type of graphite with properties close to single crystal graphite after high temperature treatment. The heat treatment temperature is 3200°C-3600°C. HOPG is over 2.25g/cm3 and Δδ is 2°.
Union Carbide started producing HOPG by pressure heat treatment in 1963, and by 1970 a bulk HOPG with Δδ=0.40°±0.10° was obtained. (Δδ is how the grain (002) surface alignment is distributed along the deposition surface in pyrolytic graphite polycrystals; the smaller it is, the closer it is to a crystal.) HOPG was developed in China in the late 1970s, and it was successfully used as a monochromator for neutron diffractometers and x-ray diffractometers by the mid-1980s.
How HOPG Graphite Is Manufactured?
Liquid or gaseous hydrocarbons. Carbon can be deposited using raw materials like methane, acetylene, propane, natural gas, benzene, toluene, etc. Inert gases like nitrogen and argon are carrier gases. Refractory metals and their compounds, artificial graphite are usually used as substrates.
Parameters For Pyrolytic Graphite:
There’s 1750 degrees and 2250 degrees Celsius in the deposition furnace, 0.67 hPa in the chamber, and gas flows out according to the size of the furnace. The deposition temperature, chamber pressure, and gas flow rate have a huge impact on the quality of the product, and they must stay within these ranges: pressure of 0.6 bars, flow rate of 5%, and temperature of 20 degrees.
Deposition rate depends on process parameters. A high temperature, a high furnace pressure, an increased flow rate, a fast deposition speed, and a selection of specific parameters will depend on the size of the deposition furnace based on the parameters determined by experiment.
Pyrolytic Graphite Heating Method:
There’s direct heating and indirect heating. (1) Direct heating: The substrate is energized to make it hot. It’s good for parts with thin deposition bodies, simple shapes, and small volumes. It’s perfect for research. 2) indirect heating, where the substrate is put inside or outside the heater, and it’s heated by the radiation. Resistance heating and induction heating are both options. It is more suitable for parts of large sizes, thicknesses, and complex shapes. Large deposition furnaces have a 2500mm hot zone diameter and a 3000mm height.
HOPG Standard Graphite Physical Features & Potential Applications?
Features:
Crystal structure and microstructure
HOPG cleaves easily along the deposition surface direction, and the cleaved surface looks mirror-like. Pyrolytic graphite loses its conical microstructure. A network of fine etch grooves and hexagonal etch pits appears after oxidation at 700-900°C. After heat treatment at >3000°C, 45 mMPa pressure for 25 minutes, and then again at 2800°C.
Mechanical properties
With room temperature shear strengths ranging from 0.9 to 2.5 MPa in the parallel plane, HOPG bulk elastic properties are similar to natural graphite.
Applications
X-ray monochromator
For X-ray, HOPG has a really high reflectivity, so white light, fluorescence, and stray light in the X-ray tube can’t add as much background intensity. It’s easy to tell that the diffraction lines annihilated by the background intensity are visible with the HOPG monochromator (the background intensity gets down to (1~2)×103). X-ray diffractometers already require the HOPG monochromator.
Neutron filter and monochromator
The neutron stream coming out of a nuclear reactor is more effectively filtered by HOPG than by polycrystalline beryllium and quartz crystals. In addition to neutron diffraction, HOPG with a mosaic of 3.5° is also used as a neutron monochromator and analyzer, because its reflection intensity is better than that of beryllium monochromators.
Study of graphite basic properties
Natural single-crystal graphite is usually used to study some basic properties of graphite. However, natural single-crystal graphite has a small size, whereas HOPG has a large size and high purity.
A study of graphite interlayers with large sizes.
To do basic research on large graphite interlayer compounds.
Get Started with FS Graphite
At FS Graphite, we understand that no two clients are the same, which is why we provide customized solutions that are tailored to each individual client. Our manufacturing services are designed to be flexible and adaptable, ensuring that we can provide the right solution for each client’s unique needs. Whether you need high-performance pyrolytic graphite for research, industrial or commercial purposes, we have the expertise and resources to provide you with the best solution.
Our pyrolytic graphite is available in a variety of grades, ensuring that you get the right material for your specific application. With a focus on quality and reliability, we ensure that our pyrolytic graphite meets the highest standards of performance, providing you with the confidence you need to take your project to the next level.
If you’re looking for a high-performance pyrolytic graphite manufacturing service that provides customized solutions, look no further than FS Graphite. With a focus on quality, reliability, and customer service, we are the perfect choice for all your pyrolytic graphite needs. Contact us today to learn more about our manufacturing services and how we can help you achieve your goals.