AETC and its operating labs are very proud of adherence to high standards of quality when it comes to advanced analytics. For the measurements we do, we operate high precision, five-decimal-place balances, some of the most accurate in the analytical research field. Yet, even that precision is not enough when it comes to the analysis of impurities in ultra-high carbon materials for certain value-added markets which we proudly serve. This is exemplified by the platinum crucible Loss on Ignition test for ultra-high purity graphites and carbons, used for advanced battery, synthetic diamond, nuclear and semiconductor applications. These materials feature six to nine purity of carbon, and determining their weight using some of the world’s most accurate 5-place balances introduces measurement error. We have developed ways to counter errors and provide our customers with superb analytical capabilities of determining the true purity of material.
The advanced analytical capabilities of our lab are represented by a recently-commissioned solid-ICP (Inductively Coupled Plasma on Solids). At AETC, we are able to test dry mineral samples without having to subject them to acid leaching. In the presence of activating chemicals, mineral impurities contained in a sample that undergoes testing are disintegrated in a high-temperature furnace. All impurities are transferred into a torch to generate the intensity signal tied to their concentration, which determines the ultimate purity. Through this method, we have observed more accurate concentrations of poisons previously undetected by the most advanced traditional method of glow mass discharge spectrometry (GDMS). We invite industry representatives to contact us and discover the benefits of solid-ICP for your system.
The AETC Scanning Electron Microscope Hitachi S-3200N (SEM) forms images from signals generated by a beam of electrons. Thus, we are able to see particle appearance and judge characteristics such as particle shape and size at magnifications of near 20,000X. An electron beam in the range of 1-10 keV is used for imaging. The Secondary Electron Imaging mode (SE) is most often employed for samples of pure materials. However, when we need to see how impurities are distributed in an impure mineral, back-scattering imaging (BSE) mode is turned on. Certain samples are additionally analyzed by an EDS (energy dispersive scan function). The SEM technology works for electrically conductive materials. If the material is poorly conductive, it is sputtered with gold prior to imaging to ensure a clear analysis.
AETC is proud to have an ISI 200 kV Transmission Electron Microscope (TEM), as it holds one of the largest magnifications in the industry. By the time an X-Ray beam reaches the CCV camera, the image has been magnified by up to 3 million times. The high magnification value allows for atomic-level resolution, particularly in graphites and nanosized silicon. Our use of TEM makes our analytical imaging capabilities one of the strongest in the nation.
Atomic Absorption Spectrometry (AAS) allows our analytical chemists to identify the compositions of sample with impurities. We are able to determine which elements are in the sample by analyzing the wavelengths of the light they absorb to enter an excited state. The instrument we use has a lamp for each element which produces light at a certain wavelength. This lamp is calibrated with standards of at 2.5, 5, 10, and 20 ppm of the element being tested, which creates a linear relationship between absorbance and concentration. Finally, the instrument measures the absorbance of the 1 gram samples diluted by a factor of 100 and consequently calculated the concentration of individual elements.
Particle Size Analysis
AETC employs a Microtrac S3500 to measure particle sizes. This machine uses lasers and detectors placed at fixed angles to capture scattered light from moving particles of samples, which are dispersed in a mixture of deionized water and surfactant. The analyzer measures the particles’ light scattering and send data through a sequence of automated parallel channels to measure the diffraction pattern. This, in turn, provides for a measurement capability of 0.009-1,020 ?m. The machine displays results in a form of a bell-shaped curve to show the particle size distribution of the sample.
AETC utilizes the Quantachrome Nova 2200e to measure porosity. This instrument also allows us to determine multiple point BET surface areas, generating more accurate measurements than the single point surface area analyzer. We also have a single point surface area analyzer, MonoSorb, which we use for quality control purposes and to affirm the quality of our findings in Nova. When it comes to research on particle compaction, porosity of particles plays a very important role, as pores can be open or closed. Open pores can range anywhere from a few nanometers to several millimeters in diameter. This instrument allows us to determine pore size distribution in particles down to two nanometers, which is the same as the diameter of a strand of DNA. Knowledge of the precise distribution of pores has helped a number of our customers in development of shapes for structural composites and specialty ceramics, such as ceramic armor used for bulletproof vests and for protection of vehicles.
Horiba LA 910
When it comes to the particle size analysis of materials which are finer than 1 micron, AETC employs a Horiba LA-910 laser scattering analyzer. This instrument allows us to determine true particle sizes by laser diffraction down to 70 nanometers, which is very rare. This allows us to work with nanoceramics and to determine true primary size of battery grade nano-silicon and de-aggregated carbon blacks.
AETC routinely deals with graphitized, non-graphitized, and partially graphitized carbon materials. Often times, the performance of materials is tied to the degree of graphiticity of a particular carbon. This can be controlled through the processing temperature and dwell time of material in reactors. We use helium pycnometery as an instrument for determination of true density of fine powders.
Kerosene Absorption Test
Kerosene absorption measures the ability of expanded graphite to absorb electrolyte, relative to the absorption ability of kerosene. Kerosene absorption measurements are created by wetting a fixed amount of expanded graphite with a solution composed of kerosene and quaternary ammonium chlorides and titrating.
We use the QUV Weatherometer when it comes to performing accelerated aging of paints and coatings as well as for the exposure to elements. This instrument allows us to test the effect of UV light, humidity, direct rain, and elevated temperature on 48 panels of metal. We typically put our coatings onto AISI steel 1010, and aluminum, grade 1024. An unprotected metal shows severe signs of corrosion, but if you protect it with AETC coating, corrosion could be dramatically slowed down. We follow guidelines and ASTM standards for performing these tests.
We have several statisticians on our team of scientists who create analytical models based on published weather patterns in project sites where our customers want us to run their projects and do installations. AETC then uses this data to create a mathematical algorithm which mimics the weather in the particular part of the world.
In operation, specific analytical data is programmed into the Weatherometer and the cycle is run. A 500 hour test typically produces enough data to mimic 1 year’s worth of real-life performance at that site. We use this statistical data to predict how our coatings are going to behave after 5 or 10 years of exposure to elements.
Salt spray is another method for statistical determination for how coated panels will behave in installations near a sea site. We load the salt spray chamber with forty-eight panels and feed 5% saline solution into chamber and at temperature of 43°C. The saline solution is then sprayed onto panels in the form of an ultra-fine mist aerosol. Finally, we make note of the degradation of panels after the test is run for 35 hours. This technique has allowed us to develop critical performance data for several of our projects.
AETC operates a number of analytical processes in inert atmosphere. We use gloveboxes to make batteries, prepare nano-silicon composites with graphite, and perform reactive synthesis to create new materials.
It is very important to insure that the purity of gas in gloveboxes is as high as possible. For instance, the presence of only 15 ppm of moisture in the ambient environment during the assembly of lithium-ion batteries may result in deficient performance of this battery. Therefore, we operate glove box chambers that essentially exclude retro diffusion of air, moisture, and oxygen into the environmental chamber, and are constantly monitoring the condition of the glovebox to include the purity of the argon atmosphere. We consistently operate at less than 0.1 ppm of moisture in our glove boxes, ultimately ensuring that we are able to make long-lasting, high-performance batteries.