Synthesis and Electrochemical Characterization of Niobium Pentoxide/Carbon Nanotubes Composites

Synthesis and Electrochemical Characterization of Niobium Pentoxide/Carbon Nanotubes Composites Introduction In the last few years, a range of energy-storage device applications has expanded from portable electronics to large-scale energy storage systems, including renewable energy storage and electric transportation [1,2]. To fulfill the energy and power density requirements for energy applications, many researchers have given attention to the synthesis of nanomaterials based on oxides due to their chemical, physical, optical, and electronic properties [1–4]. In this way, niobium pentoxide (Nb2O5) is a promising candidate because of its semiconductor properties with a band gap of ~3.4 eV, n-type, low toxicity, surface acidity, and good chemical and thermal stabilities [3,5–8]. It has been demonstrated that Nb2O5 can deliver high power through a mainly pseudocapacitive reaction of Li-ion (Li+), which could occur not only at the surface but also in the bulk of the Nb2O5 nanocrystals in non-aqueous Li+ electrolyte [2,9]. Moreover, the intercalation pseudo-capacitive behavior was highly dependent upon the presence of a crystalline structure, where amorphous and pseudo-hexagonal (TT-Nb2O5) exhibited lower specific capacitance values than the orthorhombic (T-Nb2O5) phase, however, nanoparticles aggregation is inevitable due to the high calcination temperature (>600  °C) for the orthorhombic phase formation of Nb2O5 [10–17]. Nonetheless, the application of Nb2O5 has been hampered by low bulk electrical conductivity (~3.4Ãâ€"10-6 S.cm-1 at 300 K) and by the difficult control of the ideal crystal structure [3,10,11]. Therefore, when T-Nb2O5 nanocrystals were fabricated into a relatively thick electrode, the power performance would be limited due to the impaired mobility of electrons. A possible effective method to improve these adversities in Nb2O5 is through of surface modifications (e.g., carbon coating), which could expose more redox active nanoparticles to the electrolyte as well as greatly i mprove the electronic conductivity [1,3,11–13]. It must be noted that the introduction of multiwalled carbon nanotubes (MWCNTs) networks can enhance electron transport of the Nb2O5 and further improve the rate capability. Physical mixing of MWCNTs and Nb2O5 nanoparticles can fabricate composite with improved conductivity, but this type of mixing fails to fulfill a good interfacial interaction between the MWCNTs and Nb2O5 [3]. Wherefore, soft-chemistry methods like oxidant-peroxo method matched with hydrothermal treatment and heating by microwaves could be a promising alternative for niobium synthesis, mainly because it is performed at low temperatures which avoids the elimination of the hydroxyl groups in as-formed surfaces resulting in a material with high surface area and greater number of acid sites [6,18,19]. In addition, carbon materials have a good microwave radiation absorption, which facilitates the interaction with other particles [20]. The use of niobium oxides for energy storage devices is already well known and exploited [21] but its performance is only obtained by a hybrid supercapacitor based on lithium intercalation processes [21] where high values of energy and power density are obtained. These intercalation processes require the application of potentials between 1 to 3 V vs. Li/Li+, a careful and humidity-free assembly scheme and non-aqueous electrolytes [16]. In this work, niobium pentoxide with different structures and morphologies were grown onto the surface of carbon nanotubes were synthesized by MHS. Moreover, we evaluated some electrochemical properties of electrodes with high mass loading on Ni foam current collectors (Fig. 1) using aqueous electrolyte, which brings the material closer to real and practical applications. Methods The acid functionalization on the MWCNTs was performed to create functional groups through a controlled functionalization of the nanotube walls, which allowed the anchoring an d growth of the Nb2O5 nanoparticles. This functionalization is accomplished by exposing the MWCNTs in a concentrated HNO3/H2SO4 (1:3) as described by Goyanes, et al. 2007 [22]. Nb2O5 nanoparticles were synthesized by the microwave-assisted hydrothermal method followed by a heat treatment. The sample preparation started with the dispersion of the 50 mg of functionalized MWCNTs and 100 mg of SDS (1:2) in 100 mL of distilled H2O in an ultrasonic bath. After dispersing, 2 g of (NH4[NbO(C2O4)2(H2O)2] ·nH2O) and 1.6 mL of H2O2 were added under ultrasound frequency. The solution was ultrasonicated continuously for 30 min and then poured into a Teflon vessel reaching about 50% of its volume, the autoclave was sealed and heated in the microwave equipment (Electrolux, MEF41, Brazil). The synthesis was performed with amendments according to Marins, et al., 2017 [23], where the temperature was set at 160  °C during 30 min, under a constant pressure of approximately 6 kgf cm-2 using 2.45 GHz microwave radiation with a maximum output power of 1500 W. Temperature and pressure during synthesis were monitored and controlled with the aid of a shielded thermocouple inserted directly into the vessel and with a pressure transducer sensor connected to the vessel [5]. After cooling at r oom temperature, the obtained powders were washed and centrifuged at 5000 rpm six times with distilled H2O to remove unreacted reagents and surfactant. The washed powder was over dried with no air circulation at 50  °C for 48 h. This sample was identified as CNT+TT-Nb2O5. To obtain the samples under heat treatment, part of the powder was heated in a furnace (FT-1200 1Z, Fortelab, Brazil) at 400  °C for 120 min and 650  °C for 180 min with a heating rate of 10  °C/min under nitrogen atmosphere aiming to get the orthorhombic phase [12,22]. After cooling at room temperature, the powders were stored in an oven with no air circulation at 50  °C and identified as CNT+T-Nb2O5. PVB solution in ethanol was added to the mixture in the electrode preparation. The PVB content in the slurry was 3% of the total mass of Nb2O5 and MWCNTs to each sample. The obtained slurry was used for the impregnation of Ni foam current collectors with area of 1 cm2. The active mass loading was 32 mg cm-2.

Use book content to explain 5 video Essay Example | Topics and Well Written Essays - 500 words

Use book content to explain 5 video - Essay Example These organizations adopt different strategies to manage respective production operations. Notably, quality control and technology are the most common things among the five videos (Russell and Taylor 54). In the video on how to make Jeans, quality control is very prominent. The making of jeans includes choosing the fabric, designing patterns, and tailoring. Manufactures enhance the quality of denim jeans by choosing unique textiles and high quality fabric for denim and pocketing since denims are seemingly too thin. As such, they chose â€Å"jeans-grade" denim that guarantee high quality denim jeans. Cotton is a high quality material for denim jeans. The fabric distinguishes denim jeans from other off-the-rack jeans. The manufactures washes and dries the fabric to make it easier to work with. The process also ensures that finished denim jeans are fitting. The process also entails roughening up which adds quality to the jeans. The manufactures use modern technologies to trim and design patterns for the denim jeans. In the video on how to make skateboards, quality control is supreme. The manufactures use high quality materials that include veneer, tie bond glue, router of rasp, and molded press. Notably, veneer defines a hard rock maple that prevents the skateboards from vibrating. Moreover, the hard maple made from oak wood prevents the skateboard from breaking since it is strong. On the other hand, the tie bond glue guarantees a strong bond thus creating a durable skateboard. To add on quality, manufactures adopt a specific arrangement of venners. The venners follow one another in layers that include the Face, Core layer, Cross band, Core layer, Cross Band, Core layer, and a final Face. The molded press enhances compatibility of the skateboards. In the video on how to make cosmetics, it is clear that quality is supreme. The process of making cosmetics includes ingredients that must have the approval of the FDA. It involves color additives that

Research Review for teaching strategies for reading using evidence Paper

Review for teaching strategies for reading using evidence based practices for special education students - Research Paper Example However, many educators have failed to recognize the importance of EBP in learning institutions. There are numerous students with varied disabilities; hence there is a need for experienced professionals to implement effective reading strategies for teaching. They can also engage parents in this intervention program in order to increase the performance level. This is because parents are the first primary caregivers and educators of the child; thus engaging them in the program will contribute to positive change. Therefore, the EBP should be matched with the unique needs of students and their skills; thus developing effective Individualized Education Program (IEP) for producing better learning outcomes. The themes in the research articles focus on reading instructions, developing fluency and vocabulary instructions for students with learning disabilities. Therefore, the study seeks to offer an insight on the research issues as to whether teaching strategies for reading using EBP is an e ffective approach for individual education students. It seeks to reveal the way educators can teach students to read, but  how well do  students with disabilities understand what they are reading? Educators can also help students with LD (learning disabilities) to think critically. However,  do they actually comprehend what the vocabulary words mean and talk fluent? Therefore, what can educators do in order to help these students to think critically, understand vocabularies and read fluent? The research employs varied methods such as questionnaires, surveys of the perception of students and standardized tests in order to determine how students can develop effective reading or improve performance learning skills. The results varied across students with learning disabilities, but the majority of the students showed improved reading comprehensive skills when employing EBP approach. Summary of Studies Article 1 Participants Stetter, M. E., & Hughes, M. T. (January 01, 2011). Compu ter Assisted Instruction to Promote Comprehension in Students with Learning Disabilities. International Journal of Special Education, 26, 1, 88-100 reveals the way reading comprehension is significant. The article reveals the way students with LD strive to improve reading skills and many of them face numerous challenges in learning environment. Therefore, the article attempts to analyze whether the computer assisted instructions can help in promoting reading comprehension for students with LD (Stetter and Hughes, 2011). The authors carried out research through employing a single-subject and diverse baseline designed for achieving the desired outcomes. They employed varied methodologies such as surveys, standardized tests and daily questions in order to determine the way reading comprehension is valuable for achieving academic success. The study results revealed that computer assisted instructions could have influenced the reading comprehension of students with LD. The participants w ho participated in the research study were students from varied schools in the United States. Of these students, 90 % of them were from lower socio-economic background and the remaining percentage from high socio-economic class. The students with LD also participated in

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Electrical Principles - Assignment Example In this way, each series circuit will have a series protection resistor. We will calculate the amount of current in each parallel circuit by adding the individual currents taken by the each series circuit. Lest suppose we have 2 series circuits in parallel connection then the current will be +. Use a combination of truth tables and Karnaugh maps to design a logic circuit to control the compressor Credit will be given for creating an efficient circuit using the smallest possible number of logic gates. There is no need for the microprocessor in this process, as the microprocessor will have more losses as compared to that of the logic gate ICs. Moreover, if microprocessor is used for the process it will require excessive cooling. Microprocessors are fast and rapid in processing various type of information. It is only the fact and advantage of the microprocessor in this application. Calculate the required rotational speed in Hz for the generator to produce a voltage whose average magnitude is 12V. You may assume that the flux witnessed by the coil drops to zero momentarily each time it leaves the field. Calculate the maximum amount of energy which can be harvested when a vehicle slows from 40km/h to a standstill. Assume the vehicle mass is given by 1XX0 kg where XX are the last two numbers of your student number. A bank of 100 supercapacitors is to be used to store the energy. Each supercapacitor has a capacitance of 1.5F. Assuming 80 percent of the available energy is captured, and assuming that the capacitors have an initial voltage of 12V, determine the voltage to which they must be charged to store the captured energy. You should specify how the capacitors are connected and justify your

Exam answer3 Essay Example | Topics and Well Written Essays - 750 words

Exam answer3 - Essay Example e the following: local resource munificence, current and future competition for scarce resources, sectoral trends, social, legal and political conditions. Government regulation and taxation, interest rates and exchange rates are also examples of external forces that influence the growth of the firm. The stage models of development provide the best theories explaining the growth of the business and perhaps that’s why it is preferred by most practitioners. However, the stage models have a number of limitations which at times make discourage its use. Firstly, the model is too general, making its applicability a challenge to firm owners. For instance, it is difficult to determine what, how and why states change from one to another. Further, it is difficult to determine how the answers to the above questions are modified by a range of contextual variables. Research on external factors like demand and competition is done during the first stage of development, which is the existence stage. It does not provide answers as to what can be done if for example consumers change taste. For this reason, I can recommend the industrial organization model, which uses the game theory extensively. In this case, the industrial organization model focuses on competition in the market and variou s ways of countering firms that pause completion. The other setback for developmental model is that it depicts a linear pathway and it doesn’t consider branching away from this pathway. This means that the firm may not make changes to the model in the process of its growth should there be changes both in the internal and external environment. The company may as well become extinct at a given stage of development. This is unlike the organizational ecology theory, which emphasizes on understanding the conditions under which a company emerges, grows and dies (Tushman and Romanelli 2008, p.174). The theory focuses on various factors that may lead to organizational mortality, and thus the

Plagiarism Article Example | Topics and Well Written Essays - 500 words

Plagiarism - Article Example Unlike a few years ago, lecturers are today implementing more stringent measures to discourage students from indulging in plagiarism. They making efforts to sensitize students on the dangers associated with plagiarism and the repercussions one risks facing if found plagiarizing. As a result of this, many students in my other classes are vigilant and abide by the rules of plagiarism (Gilmore 73). There are a number of indicators that confirm this assertion. For instance, most lectures insist that students turn in their assignments through Turnitin. The Turnitin system detects any form of plagiarism in a paper and rejects papers that have high percentages of plagiarism. The fact that most students do well in class assignment is an implication that they avoid plagiarism because it is only those assignments forwarded through Turnitin that are marked (Gilmore 73). Despite the fact that stern measures are being implemented to discourage plagiarism amongst students, there are some students who still engage in this act. Such students ought to be punished accordingly because they are undermining the quality of education that has gone down considerably in the past few years. First of all, students who still plagiarize their work in spite of the widespread campaign against the malice should not be awarded marks for their plagiarized assignments. This is because they do not deserve the marks. Culprits should not be left at that. Their cases should be forwarded to the school’s disciplinary committee for further disciplinary actions. They should perhaps be suspended from school for some time (Gilmore 97). The punishment should be universal for students who plagiarize content above fifty percent of the entire assignment. However, percentages below 50% can be treated fairly and perhaps be awarded zero marks but their perpetrators should be exempted from suspension. There have been concerns of whether

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Lean in Nissan UK - Assignment Example The organizational hierarchy determines the shape of the organization that is, how many employees and positions there are after the CEO or MD. The degree of centralization is concerned with how power is distributed. Formalization, on the other hand, deals with the organization of work in the organization. It could be either explicit or rigid. Finally, complexity is concerned with the subunits in the organization and their differences (Wernham, 2012, p56) An operations manager for the Nissan should considers four main variables in managing operations namely; volume, variation, variety and variability. All are unique in their own respective ways and could make or break a company (Cooke, 2010, p22). There are, however, three main operations of a business such as the Nissan Motor assembling companies. They are; materials, customers and information. Materials refer to everything tangible to the business and which is used as an input in the business. Customers refer to the current and potential consumers of business products. Information is any information that contributes positively or negatively to the success or failure of the business. (Highsmith, 2002, 55) Materials, customers and information are different from each other in some respect. Materials are powerless until they are handled but behave in different ways based on their chemical and physical natures. Customers are people who are mobile and can move from one place to another. Information is the communication of data in ways often not visible to the human eye. Information and customers are similar in the sense that both of them can move from one point to another. Information is, however, intangible while customers are tangible. Materials are also tangible (Goodpasture,2010, p34) In managing any projects, the company must, therefore, consider the above factors as they all