AETC has a wealth of experience in the materials science world. We have an expert understanding of various materials and their respective properties and can apply our sophisticated knowledge to improve or even reinvent numerous relevant materials science synthesis operations. We employ both destructive and non-destructive methods of evaluation, which allow us to determine the failure mechanisms of existing materials, and we conduct refined technological processing to alter material properties and render materials more effective.
Our superior particle grinding, sizing, and shaping, and other such alterations in material characteristics, yield superior products for use in assorted critical applications.
Cathode-Active Materials and Expanded Graphite
We are actively engaging in production of various cathode-active materials for batteries. One of our products consists of cathode-active material that has been coated with nanoceramics. Ranging from 20-80 nm in diameter, these standalone particles can be applied in a uniform manner to a range of electrode active material matrices. In particular, when it comes to high-voltage cathode-active materials for lithium ion batteries, we can provide nanoceramic-enhanced particle substrates which are permeable to lithium ions but will protect cathode matrices and electrolytes from oxidation.
Our capabilities also feature the ability to produce a range of expanded graphites. This unique material finds use in advanced batteries as conductivity-enhancement additives, fire retardants, and chemically-resistant foils and gaskets. While the latter two accept low-purity concentrate-grade expanded graphite, the former requires ultra-high-purity products. Fortuitously, we have advanced technologies that can purify industrial graphite from concentrate levels to at least 99.95 wt% carbon. We intercalate purified graphite and delaminate it, producing an ultra-thin sheet-like particle morphology. These particles are the exact opposite of spherical graphite—they are thin, twisted, and display multiple breaks on their surface. BET surface area tests offer an indirect indication of how many breaks are on a material’s particles. Each break serves as a contact point for conductivity enhancement when used in batteries or conductive plastic matrices: the more contact points, the higher the conductivity of the product. With our expanded graphite, we reach anywhere from 18 to almost 150 square meters per gram in surface area, depending on processing conditions. This impressive capability demonstrates the range in applications and advancement of new synthesized materials within the industry.
Conductivity Enhancement Additives
One of the focuses of our industrial synthesis research has been the development of conductivity enhancement additives for positive electrodes of lead acid batteries. When a particular type of graphite is used for conductivity enhancement purposes in aqueous battery systems, it may be subject to oxidation. Therefore, the use of additives in lead electrodes has been impossible up until recently due to the additives’ instability in the presence of oxygen gas. However, AETC has synthesized a new form of carbon—boron-doped graphite—which enabled us to create a material in which the overvoltage of oxygen evolution has been shifted by as much as 250 mV. This means that oxygen evolves on electrodes with this additive at a higher voltage than it would otherwise, and as a result, the graphite survives in this electrochemical system and the battery’s long-term life cycle is improved and lengthened.
Another major accomplishment we’ve realized involves the synthesis of material for electromagnetic attenuation. We have created a range of materials for infrared signal obscuration, which are effective within the wavelength range of operation of infrared seekers and radars. To do this, we either dope or intercalate graphite with heavier atoms, such as iodine or other proprietary chemistries, and we form individual graphite particles into a unique shape that allows the material to linger in the air. To shape the particles, first we peel individual graphene layers of the graphite material’s macro-molecules and create concave blisters on one side of the graphene stack plane, giving the particles a domed shape. When dispersed in the form of ultra-fine aerosol mist, the particles orient themselves with the dome up and float like parachutes, keeping them suspended in air for up to 15 minutes, until the forces of gravity inevitably cause them to settle. We offer this advanced particle-altering technology to interested parties within the United States or US-allied governments.
Partially Graphetized Carbon Black
AETC has successfully employed thermal technological applications to synthesize partially-graphetized carbon black material for improved performance. To manufacture this product, we start off with classic carbon black material, irrespective of whether it is high- or low-structure micromolecule substance, and we apply heat while protecting the particles from oxidation. In temperatures in excess of 2000°C, randomly oriented stacks of graphene layers start aligning themselves parallel to each other—this happens solely as a function of temperature and dwell time in furnaces. Once a partially graphitic structure has been formed, the substance has evolved into a new material—graphetized carbon black. During graphetization synthesis, carbon black can be doped on an atomic level with a variety of performance-enhancing additives. We invite interested parties to explore what can be done to advance your carbon black product to a higher performance level.
Silicon-Enhanced Spherical Graphite
Our silicon-enhanced spherical graphite is usable as an anode-active material within lithium ion batteries. To synthesize this graphite, we use in-house technologies that allow us to trap silicon inside the spherical graphite shell and further encapsulate it into a layer of amorphous carbon. Traditional silicon graphite composites contract and expand by as much as 400% during cycling, but our composite was seen to change in volume by a factor of less than 10%, which in turn resulted in outstanding cycle life at double the expected capacity of extraction from pure spherical graphite.
We authored the first book chapter written in the electrochemical industry specifically dedicated to the role of silicon- and tin-doped graphites for use as emerging lithium ion battery anodes. This chapter was published as NATO Science Series II. Mathematics, Physics and Chemistry vol. 299 in 2006. Please follow these publications to further assess the performance of these materials, or simply reach out to us if you have any inquiries.
A joint focused development effort between AETC, Drexel University and NASA Glenn Research Center featured outstanding industry response: Joint article ”Nano-Silicon Containing Composite Graphitic Anodes with Improved Cycling Stability for Application in High Energy Lithium-Ion Batteries” scored #4 in the list of 50 most frequently read articles in JECS as of Dec. 2013.
Of special interest is our recent work with synthetic diamonds. The diamonds are formed with our high-temperature, high-pressure reactive synthesis technology, which allows us to produce altered structures such as germanium-doped cultured diamonds; these diamonds find a number of uses in high-temperature semiconductor applications where classic silicon wafers do not work. To address the need for massive heat removal from concentrated confined areas, we work with our partners to develop new semiconductor materials. Furthermore, certain forms of natural coal produce better synthetic diamonds than classic precursors such as synthetic graphite or graphetized needle coke, and we are doing extensive research with different coals to identify what products can be yielded from initial materials. You can read more about our work with synthetic diamonds here.