Tuesday, June 28, 2005

VIEWING IMAGE UNDER SEM

Using the Scanning Electron Microscope (SEM), we were able to observe the results of the aluminum membrane synthesis. The images clearly show that the pores formed and that the anodizations went smoothly. However, we were unable to conclude whether our "radial" experiment worked. Since the sample is so large on a nanoscale, we could not find a specific area of the sample to examine whether the current density and pore size decreased radially as predicted. With more time with the microscope and careful planning prior to that, I think we will be able to later determine more accurate results of our experiment. We did notice that there were smaller pores within the larger ones, similar to the results often seen by applying different voltages to each separate anodization. However, again, our main objective to determine whether current density and pore size decreased radially was not determined conclusively. I think there is an important lesson to be learned here. Time with the SEM is limited and costly. I think careful preparation of the sample prior to microscope use is very important. I think that we should have developed a means of marking the area of the membrane where we targeted the 508 micron stainless steel wire. That way, we would not need to spend relative any time in trying to determine the area perpendicular to the anodization, which could be timely on a nanoscale. Below are two of the images taken from the SEM of the membrane:




Monday, June 27, 2005

REANODIZATION

For the reanodization, the same procedure will be used. The purpose for reanodization, again is to get a uniform arrangement of the pores. Setting up the panels and gasket with respect to the membrane will be unchanged. The procedure will go in similar fashion to the first anodization. The voltage will remain the same as well as the duration of anodization.


Sunday, June 26, 2005

PREPARING FOR REANODIZATION

Re-anodization of the aluminum metal is important so that the pores arrange uniformly and meet the desired configuration. Therefore, the alumina membrane must be removed, restoring the aluminum metal (This would make it possible to re-anodize). We immersed the membrane in 50 mL of chromic acid solution. A regular flask was used to hold the solution and the membrane. The flask was then placed under a condenser, where it would be heated. The reaction with the chromic acid would remove the membrane, preparing us for a second anodization.

Saturday, June 25, 2005

THE ANODIZATION OF THE ALUMINUM METAL

Before anodizing the aluminum metal, a 100 mL .3 M oxalic acid solution was prepared. Since I was using a .5 M bottle of oxalic acid, I used simple mathematics to calculate that 60 mL of the .5 M bottle and 40 mL of water will give me my desired solution. The solution was mixed vigorously and then poured into a 50 mL beaker. The beaker was placed on a magnetic stirring device, where it would remain for the whole anodization. The reason the solution would have the constant need of stirring is because the anodization process is a diffusion-limited process. Without proper stirring, the pores will not uniformly form across the metal.
Anyways, once the solution's temperature reached the desired temperature of 10 degrees Celsius, we were ready for the anodization. The aluminum metal-stainless steel "device" was immersed in the oxalic acid solution. At the same time, a magnetic stirrer was stirring the solution. It became very important to make sure the device and the stirrer did not interfere in each other's space. Once a good position for the device was established, a clamp was used to keep it in place. We then attached the appropriate wires to the copper on which the aluminum metal (anode) rested and the stainless steel plate (cathode). Once in solution, we raised the voltage to 80 volts. The anodization time was set for 12 hours.


Friday, June 24, 2005

SECURING THE ALUMINUM METAL

Using an electropolished piece of aluminum metal, I prepared the metal in a device we would use for its anodization. With the use of two plastic frames, a rubber gasket, and screws, I was able to secure the aluminum metal in place. The rubber gasket was used to make sure that the liquid does not get between the two plastic frames and onto the meta during anodization. The screws have to be tightened to ensure the efficiency of the gasket. I found that this first time around, it was time consuming to align the two plastic frames and the gasket so that the screws would go down right through. However, I think with more repetition and experience, this problem will surely be resolved. Anyways, after I had secured the metal, it was time to attach the aluminum metal piece (anode) with the stainless steel plate (cathode). I again used screws to keep the surface of the aluminum metal in close range of the stainless steel plate. The use of spacers helped to ensure that the two would not touch, as such an occurence would ruin the process. Once I had attached the stainless steel plate to the secured aluminum membrane, the "device" was ready for anodization.


Thursday, June 23, 2005

ELECTROPOLISHING

Electropolishing is a procedure that is used to level out the surface of the aluminum template. By smoothening the surface, it will ensure that the pores form in the desired ordered, uniform array. The electropolishing of the aluminum metal involves two basic steps. The first is to prepare a solution of perchloric acid and ethanol (Pure perchloric acid would ruin the metal). I poured the solution into a 50 mL beaker, and then placed it in the center of a copper bowl. The second step is to place the dry ice around the beaker. Once I had put the dry ice around the beaker, I added acetone, which reacts with the dry ice to lower the temperature. Once the temperature drops to around -50 degrees Celsius, we can begin the procedure. The beaker should be pre-prepared with a stainless steel plate attached to save time. Otherwise, make sure it is set up before pouring the acid in the beaker. The stainless steel plate will be the cathode so I attached it to the appropriate wire on the voltmeter. The aluminum piece that is set to be electropolished will then be the anode, and should be lowered into the perchloric acid-ethanol solution once it is attached to the appropriate wire. The picture below provides a good visual of this setup. After setting the voltage to 20 volts, we just wait for 10 minutes to take out the polished, flattened aluminum piece now ready for anodization.

Wednesday, June 22, 2005

INTRODUCTION

My name is Rikesh Parikh. I am an undergraduate freshman student at Drexel University. This summer of 2005, I was fortunate enough to be given the opportunity to pursue research through an internship from the Maryanoff Program. The topic of study I wanted to work with is nanotechnology. Once mere science fiction, this science of manufacturing on a molecular level is now more real than ever. Fundamentally routed in chemistry, though it has both chemical and biological applications, it has grown exponentially over the years. My specific area of study will be dealing with the synthesis of alumina membranes. These membranes are vital in creating nanowires, structures whose unique electrical and optical properties have already shown to have tremendous applications in industry. The scientific fundamentals and procedure involved in this growing field is what I ultimately hope to understand and take with me from this experience. I would like to give special thanks to Dr. Wade, Dr. Bradley, and Dr. Babu for making this opportunity possible.