Vamsi Sanagavarapu-Week 2-Ramachandran's Lab: RTD!!!!!

(WOW CALCULUS IS ACTUALLY IMPORTANT)

I decided not to write about my second week here because we didn't really do much. The majority of our time was spent gathering background knowledge on RTD and preparing for the experiment we are doing this week. RTD stands for residence time distribution and it is used to find out how much time a particle spends in the muller. It is expressed in the form of a graph that looks like a bell curve. It is very important to our experiment because companies would like to know the range of time each particle is spending in the muller so they can maximize production and profits. As you can see, on the x-axis, it tells you the range of time that the particle spent in the muller. When you conduct an RTD experiment, you have to inject a tracer in the muller (a dye or something of that sort) and see how long it takes for a colored particle to come out. Because at different times, different amounts of colored particles will come out,, you can conclude how much time a specific particle spent in the muller by recording the concentration of dyed particles in each sample you take. Thus, this can be expressed using an equation (in the top left corner). This tells you the fraction of molecules that have spent between time t0 and t1. This is a very complicated and hard concept so in a nutshell, residence time distribution is used to find out how many particles were in the muller between any two times or how long each particle spent in the machine. In order to complete the RTD process, we have to build a calibration curve. This curve helps us identify what the concentration of each of our samples that we collect during the RTD experiment is.

So last week, we worked on creating the calibration curve. In order to do so, we had to take a sample of alumina powder (about 400 grams) and dye it. Sounds easy right? Wrong. It was the most time consuming thing I have done so far. It took us 2 full days to do it. Let me explain. When you put a tracer into a powder, the tracer can’t affect the chemical properties of the powder or else that will give a wrong calibration curve and ultimately wrong results. So we had to use a dye. Also, when you mix the powder and the dye, you can’t use a machine because that may change the physical characteristics of the powder particles. So we had to mix it manually using a spoon and some lab equipment. But you still might be thinking that it should be easy right? Wrong again. Because the powder is so fine and the particles are so small, they stick to the dye droplets very easily and form a coat around the droplet. It forms a shell like cover so the dye can’t mix with the powder. So we had to break these droplets and when they did break, it formed even smaller droplets with shells. We couldn’t have so many lumps in the powder because that would screw up the calibration so we had to break every little lump and droplet until the powder was uniform. This took us 2 full days and I couldn’t even sit down because when we were mixing, we had to put in under a vent because we can’t inhale the powder.

We finished the mixing on Friday mid-day and now we had to make our calibration samples. Each of our samples would be 60 grams and would have different concentrations. The concentrations were 0% dyed - 100% dyed with increments of 10 so 0%, 10%, 20%...100%. In order to make this, we took some plain white alumina powder and mixed it with some of the dyed powder we made. For example, if we were to make a 30% dyed sample that was 100 grams, we would take 30 grams of dyed powder and 70 grams of white powder. So we made our samples and that was the end of the week.

I didn’t only work on RTD but I also attended the Catalyst Consortium. This was held on Tuesday and it was basically a meeting with the researchers from Rutgers and some executives from companies that sponsored this research. It was a phone conference because the people were from England and other parts of the eastern side of the world. My lab partner presented the work that she did before I got here which concerned NIR characterization of samples with different variables such as particle size, agglomerate size, water content, and smooth or roughness. I also got to listen to other research that was related to ours but I did not understand anything that they were talking about. I understood the big ideas but it was very hard for me to grasp what they were doing in the experiments and what the results meant. However, I think that with more experience I should be able to understand the research better.

I also worked with 2 guys, Sarang and Ashu, to learn how to use some equipment. Although this didn't really relate to the experiments I was doing now, it was still important because it is likely that we will use them in the future. First, Sarang taught Ashu and I how to use the laser diffraction for primary particle size measurement. Primary particle size is how big one particle takes up. I thought that machine was very cool. To measure the particle size, the machine blows air into the enclosed area containing the particles. This causes them to float around and then the machine shoots a laser towards the particles. A shadow is formed behind the particle and then the machine traces the circle of the shadow and that is how it measures the primary particles size. Cool right?

I learned a bit about density too. Density is a pretty easy concept to catch but I learned that the way we measure density at school is not completely accurate. There are two kinds of density: bulk density and true density. Bulk density is calculated using the regular way of measuring the volume and mass of the sample and dividing mass by volume. However this is inaccurate because the particles consist of millions of tiny pores that are filled with air and not the actual material. So true density is the density of the actual material excluding the volume taken up by the pores. To find out what the volume of the pores is, you have to inject a gas such has helium into the particle and see how much gas goes in. That tells you the volume of the pores and then you can calculate true density.

I guess I did a lot during this week so I'll just put this under week 2. This week was more demanding than the last but I did learn a lot about a bunch of different concepts and machinery. I tended to stay at the lab 30 minutes later than usual because we have a lot of work but I don't mind too much. Overall, this was a solid week and next week we will be running the RTD stuff which will be interesting.

 This is my office desk where I do all my reading and analysis.