Carbon Aerogels - Literature review Example

Carbon Aerogels Student’s Name Institution Abstract Aerogels have been in use for a long period of time due to their undisputed advantages resulting from their properties. However, in 1980 carbon aerogels were created and have become the most preferred aerogel. This is attributed to the fact that carbon aerogel have numerous applications in the industrial world. These applications are dependent on the various properties of carbon aerogels. However, in order to understand these applications it is equally important to understand how carbon aerogels come to existence. As the name suggest carbon aerogels consist of carbon as the main component. Therefore, in order to come up with carbon aerogels, organic carbon is heated in inert atmosphere such as nitrogen. In doing so, oxidation is avoided thus resulting to carbon aerogels. As earlier stated carbon aerogels have numerous application such as in water treatment. The use of carbon aerogels in water treatment is attributed to the high adsorption ability of carbon aerogels. This property makes carbon aerogel the most preferred materials for elimination of contaminants. In addition to this, carbon aerogels are also used in the production of capacitors. This is attributed to the fact that carbon aerogels are good conductors of electricity. Additionally, carbon aerogels have been used as a solution to oil spillage which has become quite rampant. This is attributed to the fact that carbon aerogels are adsorbing agents, thus making it possible to eliminate crude oil molecules. Therefore, this paper tries to understand carbon aerogels by looking at their history and chemical composition. In doing so, the paper also looks at the various ways in which aerogels have been put into use. Introduction Over the years use of carbon has gained a lot of popularity, which has seen carbon being integrated in almost every type of industry. This can be attributed to the numerous favorable characteristics of carbon. These characteristics make carbon stand out from other materials, thus making it suitable for use in almost every industry in the world. One of the newest use of carbon is in relation carbon aerogel. Aerogels are nanostructured solid material which are generally porous and are made using the sol-gel technology (Antonietti, et al 2014). By looking at the name it is clear that aerogels are in themselves gels only that liquid has been replaced with gas. Carbon aerogel is one of the classification of aerogel, whose main component is carbon. Carbon aerogels are formed by heating organic aerogels in an inert atmosphere most preferably nitrogen (Du et al 2013). Since the discovery of carbon aerogel, it has become an important material in the industrial world. This is attributed to the fact that carbon aerogels are used for various activities such as protection of the environment. The ability of carbon aerogel to be used for environmental protection is attributed to carbon activation. Through carbon activation carbon aerogels adsorb contaminants thus making it desirable in environment protection (Wu et al 2014). Theoretical and background As earlier stated physical and chemical properties of carbon have made carbon to regarded as one of the most important components in the world when it comes to undertaking industrial activities. In an effort to illustrate this, one could look at the automobile industry where carbon is used in the form of carbon fiber. Therefore, carbon aerogels are no different from other forms of carbon in relation to their significance in the industrial world. Carbon aerogels as earlier indicated are created through heating of Resorcinol-formaldehyde aerogel in an inert atmosphere such as nitrogen (Fang et al 2005). Carbon aerogel first came to existence 1980 and it is accredited to the Livermore scientists. However, since the first creation of carbon aerogel, there have been creation of other forms of carbon aerogel. Each type of carbon aerogel differs from each other from chemical; composition of carbon to the physical their physical appearance (Biener, et al 2011). However, what is common among the various forms of carbon aerogels is that they all share common characteristics of carbon. This is attributed to the fact that all forms of carbon aerogel are composed of carbon which is the main component thus almost similar characteristics in all the forms of carbon aerogel. Due to their favorable characteristics carbon are the most preferred materials in purification of oil and are mostly used in the manufacture of capacitors (Pierre & Pajonk 2002). Porosity of carbon and carbon aerogel Porosity refers to the ability of liquid and gases to pass through a material. Porosity is determined by the manner in which molecular particles of a given material are arranged. This is because molecular particles that are closely held together tend to make a material non-porous. However, molecular particles that are not closely held together tend to make a material quite porous. This is attributed to the space that exist between the molecular particles. Therefore, the spaces between molecular particles greatly determine the porosity of a material (Serp & Figueiredo 2009). This is to say that that materials whose molecular arrangements are characterized by large spaces tend to be more porous when compared to materials whose molecular arrangements are characterized by small spaces. In addition to molecular arrangement the surface area of any material greatly determines their porosity. This is due to the fact that surface area greatly determines the amount of liquid or gas can pass through a material at a given time. Therefore, by understanding the factors that determine the porosity of materials it becomes quite easy to investigate and determine the porosity of carbon and carbon aerogels (Xu, et al 2014) Carbon and carbon aerogels are highly porous which can be attributed to both their molecular structure and their surface are. This can be demonstrated by looking at figure 1 which shows the molecular structure of carbon. By looking at figure 1 one factor that comes out quite clearly is the manner in which molecular particles of carbon are arranged. From the diagram it is also quite clear that carbon molecule particles are not closely held together. This in return makes carbon to be quite a porous material compared to other materials. Additionally, the fact that the molecule particles are held together by strong bonds means that carbon molecular does not easily disintegrate. This factor is of great significance as it ensures that liquid and gases are able to pass through without affecting the molecular structure of carbon (Xu, et al 2014). Therefore, as a result of the manner in which molecular particles of carbon are arranged, carbon aerogels are equally porous. This is attributed to the fact that carbon aerogel adopt the porous characteristic of carbon. In addition to molecular arrangement of particles, carbon and carbon aerogels have a large surface area. Surface area refers to the total area of an object and therefore, by looking at the total area of a material it becomes quite easy to determine its porosity. This is attributed to the fact that materials with large surface are capable of allowing more liquid and gases to pass through them at a given time. However, the surface area of any material is determined by molecular arrangement of particles. The molecular arrangement of particles for both carbon and carbon aerogel is accredited for the large surface area exhibited by carbon and carbon aerogels. Therefore, due to the large surface area carbon aerogels are quite porous, an attribute that has made them the most preferred material for water treatment when separating crude oil and water (Li, et al 2006). Figure 1. Carbon molecule structure. Adsorption and desorption of carbon and carbon aerogels Adsorption refers to the ability of particles of one substance to attach themselves on other substances. This process should not be confused with absorption as they are quite different chemical processes. In absorption particles of a given substance usually diffuse in liquids resulting to a solution. Therefore, in relation to adsorption carbon is regarded as one of the most preferred adsorbing agent. This is attributed to the fact that carbon will in most adsorb gases thus making it easy to eliminate unwanted gases and other organic dissolved substances as demonstrated by figure 2 (Manocha 2003). Figure 2. Carbon adsorption (Manocha 2003) Adsorption by carbon and carbon aerogels is achieved through activated carbon. Activated carbon is carbon that has been subjected to treatment using oxygen. As a result activated carbon is characterized with a larger internal surface area. This is in return ensures that there is a large room for adsorption to take place. This characteristics of carbon has seen carbon aerogels being the preferred material in water treatment. This is also attributed to the fact that carbon aerogels do not in any way contaminate water thus making them suitable for water treatment. However, the rate of adsorption is dependent on various factors such as the pH of water treated. The rate of adsorption will in most cases increase with a decrease in pH. This is to say that adsorption is greater at lower pH than when the pH is high. Additionally, adsorption is greatly affected by size of molecules this is due to the fact that large molecules tend to be absorbed more than small molecules (Marsh & Reinoso 2006). Desorption on the other hand refers to the detachment of particles from the surface of another substance. Desorption is the basically the opposite of adsorption and in most cases they go hand in hand. Desorption normally takes place when activated carbon and adsorbed substances are subjected to high temperature. Therefore, through desorption it becomes quite easy to conduct the process of water treatment over a period of time. This is attributed to the fact that carbon is not affected by high temperature, as only detachment of particles on its surface takes place during desorption (Marsh & Reinoso 2006). Preparation of carbon aerogel Carbon aerogels are created through various chemical processes depending on the intended purpose of the carbon aerogel. However, the most common method is the sol-gel and pyrolysis method. The sol-gel method has been in use for such a long time such that it has become the most preferred method. This is attributed to the fact that, sol-gel method is not complicated when compared to other methods. Additionally, sol-gel method is inexpensive thus making it economical in preparation of carbon aerogels. Upon the completion of sol-gel process the resultant substance is an organic aerogel. However, to get carbon aerogel the resultant subject is subjected to pyrolysis. Therefore, by combining this is two process one is capable of developing a carbon aerogel (Dimitriev, et al 2008). Sol-gel process and pyrolysis As earlier stated the sol-gel method is the most used method for preparation of aerogels. Preparation of aerogels using sol-gel method usually comprise of various steps, which when adhered to result in the creation of aerogels. The first step involves the formation of a sol, which is achieved using Brownian motions. Brownian motions result to dispersion of desired colloidal particles which are collected to form a sol. The colloidal particles are then made to link with each other through the process of gelation. This process results into transformation of sol to gel and the resultant substance is referred to as a colloidal gel. Once the gel has been formed, it is then dried up through heating. The purpose of heating is to replace the liquid components found in the gel by gas. Once this process is completed the resulting product is an aerogel. However, it should be noted that the product is not a carbon aerogel as it composition is not made up of carbon (Dimitriev, et al 2008). Therefore, to come up with carbon aerogel, the aerogel is subjected to another process referred to as pyrolysis. Pyrolysis refers to the transformation of a molecular compound to a simpler compound using high temperature. However, pyrolysis should not be confused to combustion. This is attributed to the fact that unlike combustion pyrolysis is conducted in the absence of oxygen. Therefore, this means that during pyrolysis process oxidation does not take place, as is common with combustion. Therefore, by subjecting the aerogel prepared through sol-gel to pyrolysis, the resultant product is a carbon aerogel. This is attributed to the fact that heating of product in the absence of oxygen tend to become carbonated. However, to ensure the success of pyrolysis, the process is usually conducted in an inert gas such as nitrogen. Application of carbon aerogel As earlier stated the carbon properties have made carbon aerogels the most suitable material for various industrial applications. One such industrial application is in the industrial treatment of water. Carbon aerogels have for years been used in removal of contaminants found in water due to the fact that carbon aerogels have proven to be quite effective when compared to other materials. However, the main attribute of carbon aerogel that makes them preferable when compared to other materials is the adsorption ability. Through carbon activation which increases the internal surface are of carbon, carbon aerogels are capable of treating industrial water. Adsorption refers to the process by which particles of one substance attach on the surface of another substance (Hsu, et al 2013). Therefore, by incorporating carbon aerogels in water treatment it becomes quite easy to treat the water, based on the fact that carbon is capable of adsorbing molecules that cannot be eliminated using other material. However, the effectiveness of carbon aerogel is subject to various factors such as pH value of water. This is attributed to the fact that adsorption using carbon aerogels is more successful with low pH values. Therefore, an increase in pH value undermines the ability of carbon aerogels to adsorb molecular particles (Serp & Figueiredo 2009). In addition to industrial water treatment carbon aerogels are also used for electrical purpose. This is attributed to the electrical properties of carbon. Carbon is a good conductor of electricity which makes carbon aerogels suitable for certain electrical components such as capacitors. Capacitors are essential in performing various activities such as production of flash lights when using cameras. However, the amount of flash produced depend on the ability of the capacitors to store enough energy to produce the flash. Carbon aerogels have been found to be quote efficient in performing this action. This has led to capacitor manufactures incorporating the use of carbon aerogels in production of capacitors. This is attributed to the fact that carbon aerogels have demonstrated the ability to store enough energy required to produce the most desired flash. In addition to this, there have been discussions relating the use of carbon aerogels in the place of car batteries. This is attributed to the fact that carbon aerogels have demonstrated their ability to store more energy when compared to car batteries, therefore, as a result carbon aerogels experiments have shown that cars would perform much better with carbon aerogels compared to when using traditional car batteries (Lee, et al 2010). In addition to these two applications, carbon aerogels have also stood out as the most preferable materials in dealing oil spillage. Oil spillage has become a common event in the modern world something that can be attributed to the growth of the automobile industry. Almost every automobile relies on oil to run efficiently, which, in return, leads to increased incidences of oil spillage. Additionally, explorations in major water bodies for crude oil have resulted to spillage of oil in the water bodies. Oil spillage has great consequences to the environment thus concerns have been raised on how to deal with oil spillages. In line with these concerns, carbon aerogels have stood out as the most preferred solution to oil spillage. This is achieved through adsorption by carbon aerogels. Through adsorption carbon aerogels filter out crude oil molecules leaving out water molecules (Sun, et al 2013) Conclusion In conclusion, the discovery of aerogels has had a great impact in the modern world, which can be attributed to the various benefits associated with the use of aerogels. However, the most significant development is the discovery of carbon aerogels. Carbon aerogels as the name suggest are aerogels woes main component is carbon. The presence of carbon greatly influences the chemical and physical properties of carbon aerogels. The combination of these properties have made carbon aerogels to be accorded vast applications in the modern world. Carbon aerogels form the basic component for water treatment plants. This is attributed to their adsorption abilities. Additionally, due to their adsorption ability, carbon aerogels are used in controlling oil spillage, thus ensuring that the environment is protected. In addition to these, carbon aerogels have made significant contribution in electricity especially in production of capacitors. Their electrical properties have led to improvement of capacitors by increasing their energy storage capacities. Therefore, these applications demonstrate the importance of carbon aerogels in the modern world. References Al-Muhtaseb, S.A & Ritter, J.A (2003). Preparation and Properties of Resorcinol-formaldehyde Organic and Carbon Gels. Advanced Materials, 15(2), 101-114. Antonietti, M., Fechler, N & Fellinger, T (2014). Carbon Aerogels and Monoliths: Control of Porosity and Nanoarchitecture via Sol−Gel routes. Chemistry Materials, 26,196-210. Biener, J., Stadermann, M., Suss, M., … Baumann, T.F (2011). Advanced carbon aerogels for energy applications. Energy Environ. Sci., 4, 656-667. Dimitriev, Y., Ivanova, Y & Iordanova, R (2008). HISTORY OF SOL-GEL SCIENCE AND TECHNOLOGY (REVIEW). Journal of the University of Chemical Technology and Metallurgy, 43(2), 181-192. Du, A., Zhou, A., Zhang, Z & Shen, J (2013). A Special Material or a New State of Matter: A Review and Reconsideration of the Aerogel. Materials, 6, 941-968 FANG, B., WEI, Y.Z., MARUYAMA, K & KUMAGAI, M (2005). High capacity supercapacitors based on modified activated carbon aerogel. Journal of Applied Electrochemistry, 35, 229–233. Hsu, S., Lin, Y., Chung, T., … Liu, k (2013). Mesoporous carbon aerogel membrane for phospholipid removal from Jatropha curcas oil. Separation and Purification Technology, 109, 129–134. Lee, Y.J., Jung, J.C., Park, S., Seo, J.G., Baeck, S.H., Yoon, J.R. & Yi, I.K. (2010). Song, Preparation and characterization of metal-doped carbon aerogel for supercapacitor. Curr. Appl. Phys., 10, 947–951. Li, J., Wang, X., Huang, Q., Gamboa, S & Sebastian, P.J (2006). Studies on preparation and performances of carbon aerogel electrodes for the application of supercapacitor. Journal of Power Sources, 158, 784–788. MANOCHA, S (2003). Porous carbons, Sadhana, 28, 335–348. Marsh, H & Reinoso, F.R (2006). Activated Carbon. Amsterdam: Elsevier. Pierre, A.C & Pajonk, G.M (2002). Chemistry of Aerogels and Their Applications. Chemical Reviews, 102(11), 4243−4265. Serp, P & Figueiredo, J.S (2009). Carbon Materials for Catalysis. New Jersey: John Wiley & Sons. Shariff, A.M., Beshir, D.M., Bustam, M.A & Maitra, S (2010). Some Studies on the Synthesis and Characterization of Carbon Aerogel. Trans. Ind. Ceram. Soc., 69 (2), 1-4. Sun, H., Xu, Z & Gao, C (2013). Multifunctional, Ultra-Flyweight, Synergistically Assembled Carbon Aerogels. Advanced Materials, 25(18), 2554-2560. Wu, Z., Li, C., Liang, H., Zhang, Y., … Yu, S (2014). Carbon nanofiber aerogels for emergence cleanup of oil spillage and chemical leakage under harsh conditions. Scientific Report, 1-6. Xu, Z., Cai, D., Hu, Z & Gan, L (2014). A combination of porous and crystalline characters in carbon aerogels by a synergistic graphitization. Microporous and Mesoporous Materials, 195, 36–42. Zafra, M.C., Lavela, P., Macías, C., Rasines, G & Tirado, T.L (2013). Electrosorption of environmental concerning anions on a highly porous carbon aerogel. Journal of Electroanalytical Chemistry, 708, 80–86. Read More

Porosity of carbon and carbon aerogel Porosity refers to the ability of liquid and gases to pass through a material. Porosity is determined by the manner in which molecular particles of a given material are arranged. This is because molecular particles that are closely held together tend to make a material non-porous. However, molecular particles that are not closely held together tend to make a material quite porous. This is attributed to the space that exist between the molecular particles.

Therefore, the spaces between molecular particles greatly determine the porosity of a material (Serp & Figueiredo 2009). This is to say that that materials whose molecular arrangements are characterized by large spaces tend to be more porous when compared to materials whose molecular arrangements are characterized by small spaces. In addition to molecular arrangement the surface area of any material greatly determines their porosity. This is due to the fact that surface area greatly determines the amount of liquid or gas can pass through a material at a given time.

Therefore, by understanding the factors that determine the porosity of materials it becomes quite easy to investigate and determine the porosity of carbon and carbon aerogels (Xu, et al 2014) Carbon and carbon aerogels are highly porous which can be attributed to both their molecular structure and their surface are. This can be demonstrated by looking at figure 1 which shows the molecular structure of carbon. By looking at figure 1 one factor that comes out quite clearly is the manner in which molecular particles of carbon are arranged.

From the diagram it is also quite clear that carbon molecule particles are not closely held together. This in return makes carbon to be quite a porous material compared to other materials. Additionally, the fact that the molecule particles are held together by strong bonds means that carbon molecular does not easily disintegrate. This factor is of great significance as it ensures that liquid and gases are able to pass through without affecting the molecular structure of carbon (Xu, et al 2014).

Therefore, as a result of the manner in which molecular particles of carbon are arranged, carbon aerogels are equally porous. This is attributed to the fact that carbon aerogel adopt the porous characteristic of carbon. In addition to molecular arrangement of particles, carbon and carbon aerogels have a large surface area. Surface area refers to the total area of an object and therefore, by looking at the total area of a material it becomes quite easy to determine its porosity. This is attributed to the fact that materials with large surface are capable of allowing more liquid and gases to pass through them at a given time.

However, the surface area of any material is determined by molecular arrangement of particles. The molecular arrangement of particles for both carbon and carbon aerogel is accredited for the large surface area exhibited by carbon and carbon aerogels. Therefore, due to the large surface area carbon aerogels are quite porous, an attribute that has made them the most preferred material for water treatment when separating crude oil and water (Li, et al 2006). Figure 1. Carbon molecule structure.

Adsorption and desorption of carbon and carbon aerogels Adsorption refers to the ability of particles of one substance to attach themselves on other substances. This process should not be confused with absorption as they are quite different chemical processes. In absorption particles of a given substance usually diffuse in liquids resulting to a solution. Therefore, in relation to adsorption carbon is regarded as one of the most preferred adsorbing agent. This is attributed to the fact that carbon will in most adsorb gases thus making it easy to eliminate unwanted gases and other organic dissolved substances as demonstrated by figure 2 (Manocha 2003).

Figure 2. Carbon adsorption (Manocha 2003) Adsorption by carbon and carbon aerogels is achieved through activated carbon.

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