1. Optimization of Graphene Conductivity Under Pressure Variations Robert W. Raines Introduction The purpose of this experiment was to see if the conductive characteristics of graphene were significantly affected by varying pressures. The rationale of this experiment centers around the idea that this research could open up many opportunities and yield applications for construction. By maximizing effectiveness and understanding optimum conditions for exceptional performance, there may be a large number of applications in the modern world. Engineers may be able to more effectively incorporate conductive inks into large scale construction works and different environments. Background Pressure was the independent variable in the experiment, with conductive performance (resistance) acting as the dependent variable. Graphene has a crystalline structure, but what is very surprising is that it is 2 Dimensional meaning that it’s flat. In fact, it is the thinnest material ever obtained. Graphene is also extremely light in weight. It is the lightest material ever obtained as well. Another fascinating property of graphene is that it is the strongest material ever obtained. Graphene is harder than diamonds and 300 times stronger than steel. The conductive properties of graphene have made it an interesting field of study. Graphene is more conductive than copper, creating uses in electronics or even nanoelectronics if needed (Kshirsagar, 2010) (Raza, 2012). In addition, graphene is also flexible, transparent, and can take on any shape needed. The creation of graphene led to studies of other materials. The results of this work had been applied various fields today (Graphene: World-leading research, 2012). It should also be of note that the graphene nanoplatelets are actually multiple layers of graphene. The atom-thick graphene is stacked repeatedly to obtain flakes or crystalline structuresthat have interatomic spacing in between each layer, which allows electron flow. Pressure is proven to reduce interatomic distances (ESRF, 2013), and in doing so, may increase the band gaps of a solid. Diamonds, for example, have very small interatomic distances and that’s why diamonds are not conductive (Jones, 2001), while similar carbon products like graphite are conductive due to increased molecular distances, and therefore smaller band gaps. This project was formulated based off of research conducted on pressure and temperature as main factors in conductive performance and their interesting applications regarding air compression chemical ionization. Hypotheses The research hypothesis of this experiment stated that there would be significant differences in conductivity (resistance values) between the pressure levels, and that lower pressure levels would yield the greatest conductivity. The null hypothesis of this experiment said that there would not be significant differences in conductivity between the pressure levels, and that the lower pressure levels would not yield the greatest conductivity. These idea were based on the behavior of graphene, and the fact that pressures reduce interatomic distances (ESRF, 2013). Procedures and Materials Experimental Design Diagram Pressure (Psi) Resistance (Ohms) 5psi Trial 1 … Trial 6 10psi Trial 1 … Trial 6 … Trial 1 … Trial 6 50psi Trial 1 … Trial 6 Data Analysis Regression testing was used for inferential statistics. This test was chosen to observe any trends in data and to visibly display them. These tests were performed at a confidence level of.01, making any data with a P value below.01 significant. The regression testing resulted with the following values: F=133.86, P=0.000, DF=1, and R 2 =69.8%. From this it can be inferred that the data is statistically significant under a confidence level of.01 as the P value calculated was less than.01. The null hypothesis is therefore rejected and the research hypothesis is supported. The research hypothesis states, “There will be significant differences in conductivity (resistance values) between the pressure levels, and that the lower pressure levels will yield the greatest conductivity.” It can be deduced that considering the pressure chamber and most of the experimentation process was not a closed system, the data received was subject to error. This would explain the outliers in the data and any indefinite trends. Figure 1:This image is a top view of the pressure chamber constructed. The sample was placed inside. Figure 6: The graph above displays a relationship between the level of pressure and the resistance of the ink sample. There is a strong positive correlation of the data. Shown by the clear trend, the graph states that with increasing pressure levels resistance increases as well. Figure 7: The graph displays a relationship similar to that of Figure 6. However, the graph also shows variation in the resistances obtained for the sample at each pressure level. This defines that the procedures did not involve a closed system and had heavy variation during some IV levels. The graph shows relationships between points more so than the overall data. Conclusion It was concluded from data analysis that the research hypothesis was supported, stating “There will be significant differences in conductivity (resistance values) between the pressure levels, and that the lower pressure levels will yield the greatest conductivity.” Potential sources of error lie in the fact that the testing process was not a closed system, as seals became damaged through repeated testing. This could explain any potential outliers in data reception and any unexpected trends. However, trends were as predicted with strong correlations and outliers were almost insignificant in data analysis. Future Research What effects on conductive performance would be present in a vacuum? Research on a more effective way to construct a pressure chamber would be beneficial. Pressure specific samples (inks/wires) Figure 2: The image is a view inside of the pressure chamber. Inside the chamber is a graphene film sample with connected voltmeter wiring for measurements. Image retrieved from: prlog.org Figure 5: The picture is an up-close view of graphene nanoplatelets, the material of interest in the experiment. Figure 3: Creation of the pressure chamber with graphene nanoplatelets Experimental Testing 1. 100g graphene nanoplatelets were combined with water and black dye to make a visible black ink 2. Samples of the ink were spread on slides with voltmeter probes clamped on each end, touching the ink 3. The slide with the ink was inserted into the chamber with the voltmeter connected from the outside 4. Chamber was resealed and air compressor was attached to the valve 5. Desired pressure level (psi) was set and the chamber exposed the ink sample to the pressure 6. Changes in conductivity measured in Ohms (resistance) were recorded 7. Different levels were tested and the results compared 8. Trials were repeated for each pressure level (psi) Materials (2) 2" cap 1 foot of 2" pipe 1” valve stem 1 pressure gauge (100 g) graphene nanoplatelets Black dye (nonspecific amount) Water Voltmeter Air compressor Figure 4: Experimental testing and the equipment in action