Silicon Carbide: Structure, Uses and History

Silicon Carbide: Structure, Uses and History 2.1 Silicon Carbide 2.1.1 Historic Overview Silicon carbide as a material that precedes our solar system, travelling through interstellar space for billions of years, generated inside the fiery nuclear hearts of carbon rich red giant stars and in the remnants of supernovae (Davis, 2011). As a synthesized material it was first discovered by the Swedish scientist Jà ¶ns Jacob Berzelius in 1824 during his pursuit to synthesize diamonds. Sixty years later, Eugene and Alfred Cowles, invented the electric smelting furnace in 1885 (Cowles and Cowles, 1885). Edward Goodrich Acheson based on Cowles invention, created the first process to produce SiC (silicon carbide) while experimenting to find an alternative suitable mineral to substitute diamond as an abrasive and cutting material. The synthetic mineral created by the process was characterized by great refractability and hardness (Saddow and Agarwal, 2004). During the production of SiC crystals, Acheson found hexagonal crystals inside his patented reactor and sent a sample to Profes sor B.W. Frazier were it was discovered that although the crystals were all made from the same substance their crystalline structure differed (Acheson, 1893, p.287). Later, in 1905 Henri Moissan discovered natural SiC crystal inside a meteorite thus the mineralogist community named the mineral moissanite (Saddow and Agarwal, 2004). In 1907, was the year were the first Light Emitting Diode (LED) was produced by H.J. Round, when by placing contacts on a SiC crystal and applying 10V, yellow, green and orange luminescence was observed at the cathode (Brezeanu, 2005). Decades later, a renewal of interest surrounding SiC emmerged when the seeded sublimation growth invented by Tairov and Tsvetkov (1978) made the creation of SiC wafers a reality, thus giving the material the opportunity to be studied for electronic applications. Three years later, Matsunami, Nishino and Ono (1981) showed that the creation of a single crystal of SiC on a Si substrate was feasible increasing the number and va riety of possible applications even more. A huge milestone occurred in 1987 when through the use of â€Å"step controlled epitaxy†, high quality epitaxy of SiC could be made at low temperature on off-axis substrates (Kuroda et al., 1987). Based on this breakthrough Cree Inc. was founded in 1989, and manufactured the first commercial blue LEDs based on SiC along with the production of SiC wafers. 2.2.2 Crystal structure polytypes and characteristics 4. Examples of applications of CDC (Carbide derived Carbon) The multiple nanostructures that CDC presents, makes it a strong candidate to be implemented in numerous potential applications. In their paper, Presser, Heon and Gogotsi (2011) delineate the major research fields for future applications that CDC is currently attracting. In particular, these fields are: (1) The creation of Graphene based electronic devices (2) CDC as a new electrode material for supercapacitors (3) The use of CDC in fuel cells as a gas storage (e.g. hydrogen, methane) (4) CDC application in tribological coatings (5) Pt catalyst on CDC support (6) Protein sorption using CDC . Apart from the aforementioned fields another application area under research is to use CDC for CDI (capacitive deionization) of water or for desalination. The following chapters will give an extensive view of the research done on these fields although the main focus is the . 4.1 Graphene based electronic devices In 2003, (Dimitrijev and Jamet) published a paper were they stated that â€Å"Although SiC offers substantial advantages over Si, in terms of physical properties and thermal stability, it cannot compete Si devices in the areas of low cost, functional density, and moderate temperature applications. However, SiC has created its own applications niche where its unique material properties high electric breakdown field, high thermal conductivity, and high saturated electron drift velocity give this material significant advantages†. Since then, major manufacturers of SiC wafers such as Cree Inc., broke the 500$ barrier per wafer and made SiC accessible for researchers and the industry for optoelectronic devices (EE-Times, 1999) along with the introduction of 150 mm 4H SiC wafer in 2012 (Cree Inc., 2012). The previous breakthroughs made SiC a cheap precursor for the growth of epitaxial graphene. Grapse gia to pos to ftiaxnoume apo to prohgoumeno kefalaio. The intermediate product o f Si sublimation from SiC is CDC were further process gives monolayer or multilayers of graphene. An application under research and a proposed manufacturing method, is the creation of flexible transparent electrodes for screens due to the flexibility, high electrical conductivity and strength of the material (Bae et al., 2010). Studies have shown that CDC is a powerful selective sorbent for a number of molecules due to the variety of sizes its porosity exhibits (Nikitin and Gogotsi, 2004, p. 533) and is suitable for applications such as the removal of toxins or cytokines from human blood (Yushin et al., 2006). Another field of application is the removal of toxic compounds from water or the capacitive deionization (CDI) of water. Particularly, according to (Zou et al., 2008) the ordered mesoporosity of CDC used as an electrode material for electrosorptive deionization is a more effective way of removing salt from water, when compared with the salt-removing capability of activated carbon. The explanation is that activated carbon materials contain randomly arranged mesopores and micropores were ordered mesoporous carbon contains predominately ordered mesopores that increase the capacity to desalinate water. Another example is the usage of CDC as catalyst supports for fuel cells (Jerome, 2005) References Acheson, E.G. (1893) Carborundum: Its history, manufacture and uses, Journal of the Franklin Institute, 136(4), pp. 279 289. Bae, S., Kim, H., Lee, Y., Xu, X., Park, J.S., Zheng, Y., Balakrishnan, J., Lei, T., Kim, H.R., Song, Y.I., Kim, Y.J., Kim, K.S., Ozyilmaz, B., Ahn, J.H., Hong, B.H. and Iijima, S. (2010) Roll-to-roll production of 30-inch graphene films for transparent electrodes, Nature nanotechnology, 5(8), pp. 574-578. Brezeanu, G. (2005) Silicon carbide (SiC): a short history. an analytical approach for SiC power device design. Available at: http://ieeexplore.ieee.org/xpl/articleDetails.jsp?arnumber=1558796 (Accessed: 7/31/2014 2014). Cowles, A.H. and Cowles, E.H. (1885) Electric Smelting Furnace. U.S. Patent 319945. Cree Inc. (2012) Cree News: Cree Introduces 150-mm 4HN Silicon Carbide Epitaxial Wafers. Available at: http://www.cree.com/News-and-Events/Cree-News/Press-Releases/2012/August/150mm-wafers (Accessed: 7/28/2014 2014). Davis, A.M. (2011) Stardust in meteorites, Proceedings of the National Academy of Sciences of the United States of America, 108(48), pp. 19142-19146. Dimitrijev, S. and Jamet, P. (2003) Advances in SiC power MOSFET technology, Microelectronics Reliability, 43(2), pp. 225 233. EE-Times (1999) Cree Researchs SiC wafers break $500-price barrier for opto applications | EE Times. Available at: http://www.eetimes.com/document.asp?doc_id=1268808 (Accessed: 7/28/2014 2014). Jerome, A. (2005) MIXED REACTANT MOLECULAR SCREEN FUEL CELL. US 2005/0058875 A1. Available at: http://patents.com/us-20050058875.html (Accessed: 21/07/2014). Kuroda, N., Shibahara, K., Yoo, W.S., Nishino, S. and Matsunami, H. (1987) Extended Abstracts of the 19th Conf. on Solid State Devices and Materials, Tokyo, Japan, 1987. , 227. Matsunami, H., Nishino, S. and Ono, H. (1981) Heteroepitaxial growth of cubic silicon carbide on foreign substrates, IEEE Transactions on Electron Devices, 28(10), pp. 1235 1236. Nikitin, A. and Gogotsi, Y. (2004) Encyclopedia of Nanoscience and Nanotechnology, Vol. 7. Valencia, CA: American Scientific Publishers. Presser, V., Heon, M. and Gogotsi, Y. (2011) Carbide-Derived Carbons From Porous Networks to Nanotubes and Graphene, Advanced Functional Materials, 21(5), pp. 810-833. Saddow, S.E. and Agarwal, A. (eds.) (2004) Advances in Silicon Carbide Processing an Applications. Boston: Artech House Inc. Tairov, Y.M. and Tsvetkov, V.F. (1978) Investigation of growth processes of ingots of silicon carbide single crystals, Journal of Crystal Growth, 43(2), pp. 209 212. Yushin, G., Hoffman, E.N., Barsoum, M.W., Gogotsi, Y., Howell, C.A., Sandeman, S.R., Phillips, G.J., Lloyd, A.W. and Mikhalovsky, S.V. (2006) Mesoporous carbide-derived carbon with porosity tuned for efficient adsorption of cytokines, Biomaterials, 27(34), pp. 5755 5762. Zou, L., Li, L., Song, H. and Morris, G. (2008) Using mesoporous carbon electrodes for brackish water desalination, Water research, 42(8-9), pp. 2340-2348.

Political Science Essay

1) Who is Oedipus? Jocasta? Laius? Theseus? Answer: Oedipus is the son of Laius and Jocasta there was prophet that he was going to kill his father and wed his mother. Laius is the king of Thebes and Oedipus’ father who was killed as a fulfillment on an oracle. Theseus is the king of Athens who takes Oedipus in and protects him after he has suffered greatly. 2) In the play Oedipus Rex, what is the relationship between truth, freedom, identity, and responsibility? Answer: Fate is inescapable. Oedipus learning the truth is him learning his identity and with freedom comes responsibility. 3) What is pollution? OR, why must Oedipus assume responsibility for things he did not know? Answer: Pollution is that for which Oedipus is responsible for. There are consequences for his actions and he must accept them. 4) What does it mean to say that freedom is recognition of necessity? Answer: It means we are never absolutely free. There is always a restraint. 5) In the final analysis, what advice about freedom, fate and the gods is Sophocles giving in Oedipus Rex? Answer: Strive for excellence in a world of constraints, rebel and accept the Gods, bravely acceptthe consequences of one’s actions, and do all of this in reverence and humility. 6) What does it mean to defend freedom on the basis of natural rights? Answer: Natural rights are rights that no person can give us. We have them because we arehuman.To say this is defending it. – Normative way of thinking 7) What does it mean to defend freedom on the basis of utility? Answer: Freedom as a utility are rights that defend the right on grounds of the city rather than ofthe Gods. 8) According to Adrienne Rich, what does a woman need to know to be free? Answer: She needs to know her own history, analysis of her own condition, her politicized female body, and creative genius of women in the past. 9) Whose freedom is Sojourner Truth advocating? Answer: Sojourner Truth is advocating the freedom of African Americans, free slaves, and women 10) According to John Stuart Mill, what is the greatest danger to freedom in a democratic society? Answer: The greatest danger to freedom in a democratic society is social tyranny (public opinion) because it penetrates so deeply into one’s soul that there is no alternative. It feathers the development of individuality (the notion of an autonomous and rationality of the individual). 11) According to Mill, what is the domain of consciousness, or those freedoms that are most precious? Answer: Conscious, Thought/Feeling, Opinion/Sentiment, Expression, Tastes & Pursuits, Unite/Assembly 12) According to Mill, what utility does freedom have for the pursuit of truth? Answer: Partial truths may have some truth, but even truth must be combatted, questioned or it isnothing but prejudice or dogma. 13) According to Mill, what utility does freedom have for the development of individuality? Answer: The individual needs freedom for observation, needs freedom of reason and judgment, freedom to gather information, freedom to discriminate/to decide, and freedom and courage to hold firm to our tastes. 14) According to Mill, what utility does freedom have for the development of a progressive society? Answer: Societies that are possessive of innovation sustain truths and tradition and avoid mediocrity. 15) How does Sophocles portray Oedipus and the issue of guilt/innocence in Oedipus at Colonus? Answer: Oedipus is a stranger in need, he declares his innocence, and Thesesus and Athens offer him gifts. 16) What does Theseus offer to Oedipus in Oedipus at Colonus? Why? Answer: Theseus greets Oedipus with respect and empathy. He asks Oedipus what does he need and offers him hospitality and protection from Creon, Creon’s army, and Polynices. He gives him citizenship and grace. Theseus gives him gifts given by Athens because Theseus was once to in exile. 17) What is the function/importance of a language of the good? Answer: It teaches us what human beings need to achieve their potential. 18) What is Abraham Maslow’s hierarchy of needs? How does it compare to Aristotle’s theory of the goods of life? Answer: It is a pyramid showing the balanced goods or â€Å"diet† a human being needs to be happy like self-actualization, belongingness, esteem, safety, and physiological. How it compares idk. 19) Who is Pericles and what are the main principles of his funeral oration? Answer: Pericles is general and orator in Athens. The main principles of his funeral oration are city of freedom, city of empire, and citizenship. 20) What does Pericles have to say about citizenship? Answer: Citizenship requires excellence, public service, reverence for the city (patriotism), respect for authorities and law, military training, beauty, and willingness to die for the city. 21) What is Socrates’ vocation? Answer: He literally disapproves of the oracle which says he is the wisest man. 22) What are the formal charges against Socrates? Answer: The formal charges against Socrates are public opinion. 23) What are the informal charges against Socrates? Answer: He studies things that are above the sky and are below the earth. He makes strong arguments weak and weak arguments strong. He does not believe in the Gods of the city, but one new God. 24) What is Socratic ignorance? Answer: A certain type of wisdom is a certain type of ignorance. You don’t say what you don’t know. 25) What is Socrates’ daimon? Answer: The daimon is the inner God that speaks to him. It is a voice of subjectivity, consciousness, and rational insight. (picture a little angel on one shoulder and a devil on the other trying to tell you what you should do) 26) What is the relationship, in Socrates, of philosophy, death and the heroic tradition? Answer: Socrates does not fear death. He sees it as his characters (an eternal sleep or rejoining with loved one). The soul of one is not at stake. The soul of many is. 27) What does Socrates mean by caring for the soul? Answer: Caring for the soul means avoid injustice, ruthless intellectual honesty, engage in self-examination, and sustain moral energy. 28) What are the characteristics of Socrates’ theory of citizenship? Answer: The characteristics are caring for the soul, moral skepticism/dissent, a strong sense of moral individualism, all of this occurs in socratic ignorance, heroic citizenship (a citizen that does not fear death), and love of the city.

Help on a Research Paper for Dummies

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3D Printing Free Essay Example, 1250 words

ZPrinter 350 developed the latest 3D printing technology in 2009 that defined improved accessibility, speed, usability, efficiency, and affordability (Bogue, 2013). Materials and Processes 3D printing technology uses different types of materials depending on the required product. Some of the materials used in 3D printing include alloys, polymers, glass, metal, and plastic. Notably, 3D printing involves arranging the materials in different layers and designing different shapes to complete the additive process (Lipson & Kurman, 2013). In 3D printing, manufacturers use standard inkjet printing technology to develop layered parts by depositing a liquid binder onto thin layers of powder (Z Corporation, 2005). Consequently, the print heads moves over powder and prints cross-sectional data sent from. stl, .wrl, .ply, and. sfx files through a feed piston and platform (Z Corporation, 2005). Indeed, 3D CAD software export 3D models as standard and printable file formats for 3D printing (Z Corporation, 2009). Evidently, the 3D printing process aims at transforming a digital model or design into a physical product of any geometrical dimensions. Using the standard and printable fi le formats for 3D printing, manufacturers launch ZPrintâ„ ¢ software in a PC that slices the 3D model file into various digital cross-sections, or layers (Z Corporation, 2009). We will write a custom essay sample on 3D Printing or any topic specifically for you Only $17.96 $11.86/pageorder now Consequently, the ZPrinter prints every layer and places the layers on one another to develop a unique product. A short drying cycle culminates the 3D printing process by drying the multi-layered products (Z Corporation, 2009). The joining of cross-sectional layers develops the final shape of the physical product (Lipson & Kurman, 2013). Ideally, the 3D printing technology enhances visualization, automation, and cost-effectiveness of 3D data or digital models. The process enhances the production of highly customized products and designs since manufacturers will only feed the ZPrintâ„ ¢ software with relevant 3D data (DAveni 2013). As such, the manufacturer controls the 3D printing process and can initiate changes and incorporate creativity where necessary. Clearly, 3D printing defines an effective, flexible, and modern manufacturing process that applies in various industries. Examples of 3D Printing Applications Printed Car (Strati) The Strati depicts 3D printing innovation and the world’s first 3-D printed car (Kurczewski, 2014). Local Motors designs and builds the two-passenger car. The 3D printing innovation uses carbon fiber-reinforced thermoplastic material to manufacture the Strati.