The overall goal of this experimental characterization method is to predict a nanomaterial's particle emission behavior during it's product life. This method can help answer key questions in the nanosafety field, such as predicting a nanoproduct's safe lifetime. This aims to provide use before date for nanomaterials.
The main advantage of this technique is that the experimental lifetime is accelerated when it doesn't have to wait decades. Demonstrating the procedure will be Morgan Dahl, a technician from our laboratory. Assemble all the units and instruments shown in the experimental setup, and make the necessary connections as described in the text protocol.
Switch on the circulation of the particle-free air inside the nanosecured work post by pressing the flux on button. Direct this particle-free air to pass through the emission test chamber by opening the chamber and keeping it open inside the nanosecured work post. To set up the experiment, connect the particle counter directly to the emission test chamber the measure the instantaneous number concentration of the particles inside the chamber.
Observe the concentration value directly on the display counter. While the particle-free air is passing through the chamber, continue to monitor this instantaneous number concentration value until it drops to zero, which ensures that the chamber is free of any background particles. In the meantime, camphor the edges of the standard cylindrically-shaped abradant by gently turning its one end in a to and fro motion inside the slot of the tool provided with the abrasian apparatus.
Using a digital balance with a measurement precision of at least 0.1 grams, weigh the abradant and the sample to be abraded. Once done, fix the camphored abradant to the vertical shaft of the abrasion apparatus through a chuck present at its bottom. Place the nanostructured product to be abraded gently beneath the fixed abradant and firmly fix its position on the mounting system.
Open the aerosol sampler, and by using a tweezer, place a copper mesh grid inside the slot with it's brighter side upwards. Put a circular ring over the grid to fix it. Close the sampler and connect it to a pump via a filter on one end and to the particle source on the other end.
Mount the required normal load on the vertical shaft using the dead weights. Through the particle counter, check if the background particle concentration inside the open chamber has dropped to zero. If it has, close the door of the emission test chamber.
Via the digital consoles on the instruments, manually set the flow rates of the particle counter and the sizers. Set the total sampling duration at 20 minutes for all three of these instruments. Set the abrasion duration equal to 10 minutes and the speed equal to 60 cycles per minute in the abrasion apparatus.
After two minutes, switch on the pump connected to the miniaturized particle sampler, or MPS. Keep the pump running for two to four minutes, depending upon the quantity of the emission of the aerosol particles. The number of aerosol particles sampled using MPS should be optimal in number, neither too scarce, nor too surplus, which might prevent a thorough microscopic analysis.
After the counter and sizers stop acquiring data, open the emission test chamber and weigh the abradant and the abraded nanostructured product. Continue the entire process for every abrasion test. Following the abrasion test, verify that the three-particle aerosol characterizing instruments are on the calibration bench of the S-nano platform.
Prepare a one percent volume diluted aqueous solution of the liquid suspension by adding one part of the coating suspension in 99 parts of the filtered and deionized water. Next, open the cover of the glow discharge machine, and proceed to set the operating conditions. In order to make a TEM copper mesh grid hydrophilic by its plasma treatment, put it on the metal stand.
Close the cover, and start the motor. After three minutes, it stops automatically. Take out the hydrophilic turned mesh grid using a tweezer.
Place it gently with its brighter side up. Deposit a drop of the diluted solution onto the hydrophilic mesh grid using a syringe. Dry the mesh grid in ambient atmosphere so that the water content gets evaporated and the constituent particles rest deposited on the grid.
Make sure that the mesh grid doesn't get charged with the stray particles. If the grid appears too laden with particles to analyze, lower the dilution percentage and volume of the deposited droplet. The maximum volume an operator can deposit is approximately equal to 12 micro liters.
Shown here is the TEM analyses of the morphology of the nanoparticles present in two nanocoatings. Apart from the different constituent nanoparticle sizes of the two nanocoatings, their individual morphologies are also different. As characterized by a cloud-like structure for the PMMA dispersant, and a stranded structure for the alcoholic-based dispersant.
Shown here is the particle size distribution of the emitted aerosol particles as a function of normal load. Several orders of magnitude are present. The modal size of the particle size distribution curves of the emitted aerosol particles increases with normal load.
The microscopic analysis of the progressively deteriorating nanocoating shows how flakes are forming and leaving the substrate. The deterioration is via the appearance of cracks on the surface which deepens with time. After watching this video, you should have a good understanding of how to investigate particle aerosolization of a product under abrasion.
Once mastered, this technique can be done in one working day, once artificially aged samples are available, and if it is performed properly. Following this procedure, other methods like the predictional verdibrous release can be performed in order to answer additional questions like how to reduce health risks of breaks.
