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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Desenvolvimento de um sensor amperométrico baseado em ftalocianina de ferro, nanotubo de carbono oxidado e óxido de grafeno para determinação de isoniazida / Development of an amperometric sensor based on iron phthalocyanine, oxidized carbon nanotube and graphene oxide for determination of isoniazid

Spindola, Rolff Ferreira 25 July 2016 (has links)
Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-06-02T19:09:40Z No. of bitstreams: 1 RolffSpindola.pdf: 1912678 bytes, checksum: 00839e9b1b8a2b01a86770dd2561ec07 (MD5) / Made available in DSpace on 2017-06-02T19:09:40Z (GMT). No. of bitstreams: 1 RolffSpindola.pdf: 1912678 bytes, checksum: 00839e9b1b8a2b01a86770dd2561ec07 (MD5) Previous issue date: 2016-07-25 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPQ) / Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA) / A novel platform for electroanalysis of isoniazid based on multi-walled carbon nanotube oxide and graphene oxide composite as support to iron phthalocyanine (MWCNTO-GO/FePc) has been developed. The FePc/MWCNTO-GO modified electrode is sensible for isoniazid, decreasing substantially its oxidation potential to + 200 mV vs. Ag/AgCl. Electrochemical and electroanalytical properties of the FePc/MWCNTO-GO modified electrode were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electrochemical microscopy, and amperometry. The sensor presents better performance in 0,1 mol L-1 phosphate buffer at pH 7,4. Under optimized conditions, a linear response range from 5 μmol L-1 to 476 µmol L-1 was obtained with a sensitivity of 0,0225 μA L μmol-1. The limits of detection and quantification for isoniazid determination were 0,56 μmol L-1 and 1,88 μmol L-1, respectively. The relative standard deviation for 10 determinations of 100 μmol L-1 isoniazid was 2,5%. The sensor was successfully applied for isoniazid determination in artificial body fluids. / No presente trabalho é apresentado o desenvolvimento de uma nova plataforma para eletroanálise de isoniazida baseada em (MWCNTO-GO/FePc). O eletrodo modificado com FePc/MWCNTO-GO diminuiu sensivelmente o potencial de oxidação da isoniazida para +200 mV vs. Ag/AgCl. As propriedades eletroquímicas e eletroanalíticas do eletrodo modificado com FePc/MWCNTO-GO foram investigadas por voltametria cíclica, espectroscopia de impedância eletroquímica, microscopia eletroquímica de varredura, e amperometria. O sensor apresentou melhor desempenho em tampão fosfato 0,1 mol L-1 com pH 7,4. Sob condições otimizadas uma faixa de resposta linear de 5 μmol L-1 a 476 µmol L-1 foi obtida com uma sensibilidade de 0,0225 μA L μmol-1. O limite de detecção e quantificação para a isoniazida foram determinados como sendo 0,56 μmol L-1 e 1,88 μmol L-1, respectivamente. O desvio padrão relativo para 10 determinações de 100 μmol L-1 de isoniazida foi de 2,5%. O sensor foi aplicado com sucesso para determinação de isoniazida em fluidos corporais artificiais.
2

Multiwalled Carbon Nanotube- Poly(2-hydroxyethyl Methacrylate) Composite Conduitfor Peripheral Nerve Repair

Arslantunali, Damla 01 March 2012 (has links) (PDF)
There are different methods used in the surgical treatment of peripheral nerve injury. In this respect, end-to-end surgical reconnection of the damaged nerve ends or autologous nerve grafts are applied as soon as possible after the injury. When autologous tissue transplant is considered, there are some medical devices available generally for relatively short nerve defects. As a solution for this problem, different tissue engineered nerve conduits have been developed. In the current study, a pHEMA hydrogel membranes were designed to mimic the tubular conduits and they were loaded with 1-6% (w/w) multiwalled carbon nanotubes (mwCNTs) to obtain electrical conductivity. The most important reason for the use of CNTs in peripheral nerve injury is their electrical conductivity. Within the context of the study, the degree of swelling, contact angles, electrical conductivity and mechanical properties of the membranes were analyzed. As the amount of mwCNTs were increased, the contact angles, indicating higher hydrophobicity and the electrical conductivity increased. The tensile test of the mwCNT-pHEMA composite membranes showed that the membranes have viscoelastic structure similar to the structure of the soft tissues. The structure of the mwCNT containing pHEMA composite membranes were analyzed with different microscopical techniques such as SEM, CSLM and microCT. MwCNTs on the hydrogels were morphologically similar to the original. SEM micrographs also showed that the mwCNTs were grouped in clumps on hydrogel surfaces. No mwCNT leaching was observed because the mwCNTs were embedded in the hydrogel, therefore, no cytotoxic effect was observed. The pHEMA hydrogels were porous which is suitable for transportation of materials, electrolytes and gas needed for cell nutrition and growth. In the in vitro studies, SHSY5Y neuroblastoma cells were seeded on the membranes to determine the sustainability and effects of the membranes on the cell growth. Electrical potential of 1 and 2 V were used to stimulate the cells. Microscopical examination with SEM and CSLM, and MTT viability assay were used. The SHSY5Y neuroblastoma cells were attached and proliferated on both the composite and the hydrogel membranes. The cells on pHEMA membranes without mwCNTs, however, were not able to survive after application of electrical potential. As a conclusion, use of composite membranes in the treatment of peripheral nerve injury as a nerve conduit is appropriate. Electrical stimulation, however, did not induce the cells to align in contrast to the expected results, indicating potential and current application regime needs to be optimized to obtain the desired results.
3

Characterization and Application of Dynamic in vitro Models of Human Airway

Patel, Hemangkumar J. 01 May 2011 (has links)
In recent years, respiratory diseases have emerged as a leading cause of mortality across the globe. In the United States alone respiratory diseases are the fourth leading cause of deaths annually. Moreover, with the rapid increase of industrialization and urbanization, the occurrences of respiratory diseases are expected to remain high with strong chances of increasing in the future. To ameliorate the epidemic of respiratory disease, it is first important to understand its underlying mechanisms. Respiratory research studies in animals have elucidated the chronological order of the pathological events and systemic responses inside the lung, but understanding the response of individual cell types inside the lung is necessary to outline the initiators and mediators of the pathological events. Many research studies have aimed to understand the behavior of individual cell types, from the lung, under different pathological conditions specific to the respiratory system. However, the cell culture systems used in most of these studies were limited by the absence of the dynamic cell growth environment present in actual lung tissues. The lung exists in a mechanically active environment, where different amounts of circumferential and longitudinal expansion and contraction occur during breathing movements. Thus, simulating the biomechanical environment in in vitro cell culture models may improve the cellular functionality and the outcome of the research studies. Moreover, the stimulation of biomechanical forces in in vitro cell cultures provides the advantage of mimicking the mechanical environment, related to different pathological conditions. In our study we used a dynamic in vitro cell culture system capable of implementing cyclic equibiaxial deformation in cell monolayers to stimulate different biomechanical environments similar to conditions inside the lung. The dynamic cell growth condition was used to determine the effects of ventilator-induced lung injury and nano-material/pollutant exposure in A549 cell cultures. Examples of such pollutants are diesel particulate matter, multi-walled carbon nanotubes, and single-walled carbon nanotubes. Our results indicated that the dynamic cell growth condition specific to ventilator induced lung injury facilitated an increase in inflammatory and tissue remodeling activities in A549 cells. Under the nano-material/pollutant exposure assessment studies, the dynamic cell growth condition induced changes in inflammation and oxidative stress level which closely resembled those in in vivo studies.
4

Synthesis Of Various Carbon Nanostructures And The Transport Properties Of Carbon Nanotubes

Singh, Laishram Tomba 11 1900 (has links) (PDF)
Different carbon nanostructures have different properties and different applications. It is needed to synthesize good quality and also on large scale. From the point of industrial applications, highly productive and low cost synthesis method is very essential. Research has been done extensively on the intrinsic and individual properties of both single walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWC-NTs) in the range of nanometer to micrometer length scale. The important question is how the properties change beyond this length scale and if they are used in group in the form of an array instead of the individual carbon nanotubes (CNTs). Some applications require large current output, large energy production etc. For such kind of applications, it becomes essential to use CNTs in large number in the form of arrays or array, instead of using large numbers of CNTs in individual level. Future nanotechnology scope requires large scale application using the very rich intrinsic properties of the CNTs and nanomaterials. Keeping these problems and challenges in front, this thesis work is devoted to the research of the large scale synthesis of mm long MWCNTs, having different morphology and studies on various physical properties of MWCNTs in the form of arrays. Synthesis of mm long aligned and buckled MWCNTs have been reported for the first time. Generally buckled CNTs were obtained by compressing the straight CNTs. Apart from this, different morphologies like, aligned straight, helical or coiled CNTs are also synthesized. Resistance of the individual CNT increases with the increase in length. Resistance versus length of an array of CNT also shows similar behaviour. The thermal conductivity of CNT array is observed to decrease with the increase of array diameter (diameter �100 µm). There are few reports of the similar behaviour with the experiments done on small diameter CNT arrays (diameter �100 nm). From these observations, it seems that in the arrays of CNT, their intrinsic individual property is preserved though the magnitudes are different. The conductance measurements done on buckled CNT array by compressing it to apply uniaxial strain, shows the conductance oscillation. This conductance oscillation seems to be originating from the band gap change due to strain when the CNTs bend during compression. Recent research focuses on the arrays of CNT as they can carry large current of the order of several milliamperes that make the arrays suitable in nanoscale electronics and in controlling macroscopic devices such as light emitting diodes and electromotors. Regarding this aspect, a part of this thesis work is devoted on the application of CNT array to field effect transistor (FET) and study of thermoelectric power generation using CNT arrays. The entire thesis is based on the works discussed above. It has been organized as follows: Chapter 1 deals with introduction about the different carbon nanostructures and different synthesis methods. A brief introduction about the different current-voltage (IV) characteristics of SWCNTs and MWCNTs, length and diameter dependence and effect of the mode of contacts, are given. Some applications of the array of CNTs like buckling effect on compression, stretching of CNT into the form of rope, and conduction change on compression are discussed. Application of CNT as FET, as a thermometer, and thermoelectric effect of CNT are discussed. The electromechanical effect of CNT is also discussed briefly. Chapter 2 deals with experimental setup for synthesis of different morphologies of carbon nanostructures. The samples are characterized using common characterization techniques like, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. A brief introduction about Raman Spectroscopy of CNT is given. Chapter 3 reports the unusual IV characteristics and breakdown of long CNT arrays. The current carrying ability and the threshold voltage as a function of array diameter are reported. The effect of the ambient like temperature and pressure are discussed. Chapter 4 deals with theoretical models to analyze the IV characteristics reported in Chapter 3. It has been shown that a set of classical equations are applicable to quantum structures and the band gap can be evaluated. Chapter 5 describes with application of CNT arrays as temperature sensors. It has been shown that CNT arrays of suitable diameters are used as temperature sensors after calibration. Chapter 6 reports the high current FET application of CNT arrays. Effects of temperature and ambient pressure are discussed. The type of the majority charge carrier is determined. Chapter 7 deals with application of CNT arrays as thermoelectric power generator to get large thermoelectric current. Effects of different array diameter are discussed. Modulation of thermoemf with gate voltage is discussed. The type of the majority charge carrier is determined. Chapter 8 reports the effect of compressive strain on buckled MWCNT arrays. Conductance is measured during the compression of the array. Quantum electromechanical conductance oscillation is observed. The structural changes are observed with SEM. Raman spectroscopic study supports the explanation of the effect. Chapter 9 provides the conclusion and overall summary of the thesis.
5

Study and Development of Nonwovens made of Electrospun Composite Nanofibers / Etude et développement de non-tissés fait en nanofibres composites obtenues par électrofilage

Almuhamed, Sliman 14 December 2015 (has links)
L’électrofilage est actuellement la méthode la plus utilisée pour la production de nanofibres grâce à sa simplicité, sa reproductibilité et la possibilité d’être industrialisée. Grâce à leurs propriétés particulières telles qu’un grand rapport surface-volume, une porosité inter-fibre élevée et une grande capacité d’adsorption, les nanofibres électrofilées sont de bons candidats pour de nombreuses applications telles que la filtration, les masques respiratoires, les matériaux composites, etc. Cependant, certaines applications particulières, telles que les capteurs, les systèmes d'administration contrôlée de médicaments ou les super condensateurs, exigent que les nanofibres doivent présenter des propriétés complémentaires telles que la conductivité électrique, la porosité de surface de nanofibres, l’hydrophobicité, ou d’autres propriétés particulières. Certains nanomatériaux comme les nanotubes de carbone, la silice mésoporeuse ordonnée, les argiles, ont des propriétés particulières comme la conductivité électriques élevée des nanotubes de carbone, la porosité des matériaux de silice mésoporeuse ordonnée ou de l’argile. Ces propriétés des nanomatériaux peuvent être les fonctions complémentaires cherchées. Dans notre étude, des non-tissés composés de nanofibres de polyacrylonitrile chargées par nanotubes de carbone à multi-parois (MWNT), de la montmorillonite sodique (MMT-Na) ou de la silice mésoporeuse ordonnée (de type SBA-15), sont produits par électrofilage. Les résultats montrent que l’insertion de MWNT rend le non-tissé conducteur en augmentant la conductivité électrique volumique par six ordres de grandeur (de ~ 2×10-12 à ~ 3×10-6 S/m) avec un très faible seuil de percolation de 0.5 % massique. Lorsque le non-tissé est soumis à une compression, la conductivité électrique volumique augmente en augmentant la pression (jusqu’à ~ 2 kPa). Ces non-tissés conducteurs sont très intéressants pour le développement des capteurs à faible amplitude. Les résultats montrent aussi que l’accessibilité des pores des particules inorganiques (c’est-à-dire, les mésopores de SBA-15 et l’espace interfoliaire de MMT-Na) insérées dans la structure nano fibreuse est encore possible. Il a été trouvé que plus de 50% des mésopores de SBA-15 insérées sont encore accessibles quelles que soit les conditions de l’électrofilage et la fraction massique de SBA-15. En outre, l’insertion de ces particules inorganiques apporte plus de stabilité thermique aux nanofibres composites. / Electrospinning is the most common method for the production of nanofibres due to its simplicity, repeatability, and the ability to be scaled up. Owing to their advanced properties like the high surface-to-volume ratio, high interfibrous porosity, high adsorption capacity, etc. electrospun nanofibers are good candidates for many applications such as filtration, respiratory masks, composite materials and others. However, some specific applications including sensors, controlled drug delivery systems, supercapacitors, etc. still require complimentary functions that do not exist in pristine nanofibers in their basic structure like the electrical conductivity, surface porosity of the nanofibers, hydrophobicity, and others.Nanomaterials like carbon nanotubes, ordered mesoporous silica, layered silicate, etc. are characterized by particular properties like the high electrical conductivity of carbon nanotubes, the porosity of ordered mesoporous silica or layered silicate. These particular properties of nanomaterials can fulfill of the targeted functions.In our study, nonwovens made from nanofibers of polyacrylonitrile incorporated with multiwalled carbon nanotubes (MWNT), layered silicate type Na-montmorillonite (Na-MMT) or ordered mesoporous silica type SBA-15 are successfully produced by electrospinning.Results reveal that the incorporation of MWNT altered the electrical state of the nonwoven from insolent to conductor where the volume electrical conductivity increased by six order of magnitude (from ~ 2×10-12 to ~ 3×10-6 S/m) with a very low percolation threshold of about 0.5 wt%. The application of mechanical pressure to the conductive nonwoven causes an increase in the volume electrical conductivity with the increase of the applied pressure (up to ~ 2 kPa). Such conductive nonwoven is very interesting for the development of sensor with low amplitude.Results also show that accessibility of the pores of the inorganic particles (i.e. mesopores of SBA-15 and interlayer space of Na-MMT) incorporated into the nanofibers is still possible. It is found that at least 50% of SBA-15 mesopores are still accessible whatever is the electrospinning conditions and SBA-15 mass fraction. In addition, the incorporation of the studied inorganic particles yields higher thermal stability for the composite nanofibers.
6

Vapour Phase Transport Growth of One-Dimensional Zno Nanostructures and their Applications

Sugavaneshwar, R P January 2013 (has links) (PDF)
One-dimensional (1D) nanostructures have gained tremendous attention over the last decade due to their wide range of potential applications. Particularly, ZnO 1D nanostructures have been investigated with great interest due to their versatility in synthesis with potential applications in electronics, optics, optoelectronics, sensors, photocatalysts and nanogenerators. The thesis deals with the challenges and the answer to grow ZnO 1D nanostructure by vapor phase transport (VPT) continuously without any length limitation. The conventional VPT technique has been modified for the non-catalytic growth of ultralong ZnO 1D nanostructures and branched structures in large area with controllable aspect ratio. It has been shown that the aspect ratio can be controlled both by thermodynamically (temperature) and kinetically (vapour flux). The thesis also deals with the fabrication of carbon nanotube (CNT) -ZnO based multifunctional devices and the field emission performance of ZnO nanowires by employing various strategies. The entire thesis has been organised as follows: Chapter 1 deals with Introduction. In this chapter, importance of ultralong nanowires and significance of ultralong ZnO nanowires has been discussed. Various efforts to grow ultralong ZnO nanowire with their advantages and disadvantages have been summarised. Lastly the significance of forming ZnO nanowires based nano hybrid structures and importance of doping in ZnO nanowires and has also been discussed. Chapter 2 deals with experimental procedure and characterization. In this chapter, a single step VPT method for the growth of ultralong ZnO nanowires that incorporates local oxidation barrier for the source has been described. The synthesized nanowires were characterised by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman & photoluminescence. Chapter 3 deals with growth of ZnO nanowires, controlling the aspect ratio of ZnO nanowires, and role of other experimental aspects. In this chapter, a way to grow nanowires continuously without any apparent length limitation, a way to control the diameter of the nanowires kinetically without catalyst particle or seed layer and obtaining smaller diameter of the nanowires by non-catalytic growth as compared to that set by the thermodynamic limit has been discussed. Furthermore, the significance and importance of local oxidation barrier on source for protecting them from degradation, ensuring the continuous supply of vapour and enabling the thermodynamically and kinetically controlled growth of nanowires has been discussed. Lastly, the scheme for large area deposition and a method to use same source material for several depositions has been presented. Chapter 4 deals with multifunctional device based on CNT -ZnO Nanowire Hybrid Architectures same device can be used as a rectifier, a transistor and a photodetector. In this chapter, the fabrication of CNT arrays-ZnO nanowires based hybrid architectures that exhibit excellent high current Schottky like behavior with p-type conductivity of ZnO has been discussed. CNT-ZnO hybrid structures that can be used as high current p-type field effect transistors (FETs) and deliver currents of the order of milliamperes has been presented. Furthermore, the p-type nature of ZnO and possible mechanism for the rectifying characteristics of CNT-ZnO has been discussed. Lastly, the use of hybrid structures as ultraviolet detectors where the current on-off ratio and the response time can be controlled by the gate voltage has been presented and also an explanation for photoresponse behaviour has been provided. Chapter 5 deals with the substrate-assisted doping of ZnO nanowires grown by this technique. In this chapter, the non-catalytic growth of ZnO nanowires on multiwalled carbon nanotubes (MWCNTs) and soda lime glass (SLG) with controlled aspect ratio has been presented. The elemental mapping to confirm the presence and distribution of carbon and sodium in ZnO nanowires and the transport studies on both carbon and sodium doped ZnO has also been presented. Furthermore the stability of carbon doped ZnO has also been presented. Lastly, the advantage of growing ZnO nanowires on MWCNTs and overall advantage associated with this technique has been discussed. Chapter 6 deals with formation of ZnO nanowire branched structures. In this chapter, a possibility to grow ZnO nanowires on already grown ZnO nanowires has been demonstrated. The formation of branched structure during multiple growth of ZnO nanowire on ZnO nanowire has been presented and evolution of aspect ratio in these branched structures has been discussed. Furthermore, the advantage of using ZnO branched structures and also the ZnO nanoneedles on MWCNT mat for field emission has been presented. Chapter 7 summarizes all the findings of the thesis.
7

Direkter Drucksensor unter Verwendung von Kohlenstoffnanoröhren-Nanokompositen / Direct pressure sensor using carbon nanotubes nanocomposite

Dinh, Nghia Trong 08 July 2016 (has links) (PDF)
Im Gegensatz zu herkömmlichen Dehnungsmessstreifen können Carbon nanotube (CNT)-basierte Komposite zusätzlich eine ausgeprägte Druck-abhängigkeit des Widerstandes aufweisen. Deshalb können Drucksensoren aus CNT-Nanokomposite ohne den Einsatz von Verformungskörpern wie z. B. Biegebalken aufgebaut werden. Die möglichen Anwendungsgebiete für diese direkt messenden Sensoren wurden in der vorliegenden Arbeit bei drei industriellen Anwendungen wie z. B. bei Robotergreifarmen gezeigt. Die Zielstellung dieser Arbeit ist die Entwicklung und Charakterisierung eines neuartigen Sensors aus CNT-Nanokomposite. Unter Verwendung von Multi-walled carbon nanotube (MWCNT)-Epoxidharz und interdigitalen Elektroden soll der Sensor auf wenigen Quadratzentimetern Drücke im Megapascal-Bereich und somit Kräfte im Kilonewton-Bereich messen können. Durch die Auswahl geeigneter Werkstoffe und die Modellierung mit der Finite Element Methode wurde der Sensorentwurf durchgeführt sowie der Messbereich abgeschätzt. Die Herstellung der MWCNT-Epoxidharz-Dispersion erfolgte durch mechanische Mischverfahren. Anschließend wurden aus der Dispersion druckempfindliche Schichten mit der Schablonendrucktechnik hergestellt. Dabei wurden die Herstellungs-parameter und besonders der Füllstoffgehalt der MWCNTs variiert, um deren Einflüsse auf das mechanische, thermische und elektrische Verhalten zu untersuchen. Die Charakterisierung der mechanischen Kenngrößen erfolgte mit Zugversuchen und dynamisch-mechanischer Analyse. In den Untersuchungen zeigen die MWCNT-Komposite eine signifikante Steigerung der Zugfestigkeit und eine Erhöhung der Glasübergangstemperatur gegenüber reinem Epoxidharz. Die Abhängigkeiten der Druckempfindlichkeit und der Temperaturempfindlichkeit vom Füllstoffgehalt wurden untersucht. Eine besonders hohe Druckempfindlichkeit, aber auch Temperaturempfind-lichkeit wurde bei Proben mit geringem Füllstoffgehalt (1 wt% und 1,25 wt%) festgestellt. Es ist also wichtig, die richtige Materialkombination für diese Art Sensor zu finden. Die realisierten Sensoren liefern zuverlässige Antwortsignale bei wiederholten Belastungen bis zu einer Belastung von 20 MPa (entspricht 2 kN). Zusätzlich wurde der Temperatureinfluss in einem Bereich von −20 °C bis 50 °C durch eine Wheatstonesche Brückenschaltung kompensiert. Die vorliegende Arbeit zeigt, dass eine zuverlässige Druckmessung mit einer Temperaturmessabweichung von 0,214 MPa/10 K gewährleistet werden kann. / In contrast to conventional metallic strain gauges, carbon nanotube (CNT) composites have an additional pressure sensitivity. Therefore, deformation elements such as bending beam is not needed by using pressure sensors, which are based on CNT nanocomposite. The possible areas of application for these pressure direct measured sensors were showed in three industrial application such as robot gripper. The focus of this work is the development and characterization of a new sensor manufactured from CNT nanocomposite. By using multi-walled carbon nanotube (MWCNT) epoxy and interdigital electrodes the sensor, which has a dimension of few square centimetre, should measure a pressure in mega Pascal range and hence a force in kilo newton range. By the selection of suitable materials and the modelling using finite element method, the sensor design as well as the measurement range were carried out. The MWCNT epoxy dispersion is manufactured by using a mechanical mixing process. Subsequent, the dispersion is used to fabricate pressure sensitive layers by stencil printing methods. Thereby, the fabrication parameters and especially the filler content of the MWCNTs were varied for the mechanical, thermal and electrical investigation. The characterization of the mechanical characteristic values were carried out by using tensile test and dynamic mechanical analysis. The results show a significant increasing of the tensile strength and glass transition temperature in comparison to neat epoxy. Additionally, the influence of the filler content to the pressure and thermal sensitivity were investigated. A highly pressure sensitivity but also a highly thermal sensitivity are obtained for samples with lower filler contents (1 wt% and 1.25 wt%). Therefore, a suitable material combination has to be chosen. The fabricated sensors show reliable response signals by repeated excitations up to 20 MPa (meets to 2 KN). Moreover, the temperature influence ranged from -20 °C to 50 °C was compensated with a Wheatstone bridge. This work demonstrate a direct pressure sensitive sensor with reliable response signals by a thermal deviation of 0.214 MPa/10K.
8

Direkter Drucksensor unter Verwendung von Kohlenstoffnanoröhren-Nanokompositen

Dinh, Nghia Trong 28 April 2016 (has links)
Im Gegensatz zu herkömmlichen Dehnungsmessstreifen können Carbon nanotube (CNT)-basierte Komposite zusätzlich eine ausgeprägte Druck-abhängigkeit des Widerstandes aufweisen. Deshalb können Drucksensoren aus CNT-Nanokomposite ohne den Einsatz von Verformungskörpern wie z. B. Biegebalken aufgebaut werden. Die möglichen Anwendungsgebiete für diese direkt messenden Sensoren wurden in der vorliegenden Arbeit bei drei industriellen Anwendungen wie z. B. bei Robotergreifarmen gezeigt. Die Zielstellung dieser Arbeit ist die Entwicklung und Charakterisierung eines neuartigen Sensors aus CNT-Nanokomposite. Unter Verwendung von Multi-walled carbon nanotube (MWCNT)-Epoxidharz und interdigitalen Elektroden soll der Sensor auf wenigen Quadratzentimetern Drücke im Megapascal-Bereich und somit Kräfte im Kilonewton-Bereich messen können. Durch die Auswahl geeigneter Werkstoffe und die Modellierung mit der Finite Element Methode wurde der Sensorentwurf durchgeführt sowie der Messbereich abgeschätzt. Die Herstellung der MWCNT-Epoxidharz-Dispersion erfolgte durch mechanische Mischverfahren. Anschließend wurden aus der Dispersion druckempfindliche Schichten mit der Schablonendrucktechnik hergestellt. Dabei wurden die Herstellungs-parameter und besonders der Füllstoffgehalt der MWCNTs variiert, um deren Einflüsse auf das mechanische, thermische und elektrische Verhalten zu untersuchen. Die Charakterisierung der mechanischen Kenngrößen erfolgte mit Zugversuchen und dynamisch-mechanischer Analyse. In den Untersuchungen zeigen die MWCNT-Komposite eine signifikante Steigerung der Zugfestigkeit und eine Erhöhung der Glasübergangstemperatur gegenüber reinem Epoxidharz. Die Abhängigkeiten der Druckempfindlichkeit und der Temperaturempfindlichkeit vom Füllstoffgehalt wurden untersucht. Eine besonders hohe Druckempfindlichkeit, aber auch Temperaturempfind-lichkeit wurde bei Proben mit geringem Füllstoffgehalt (1 wt% und 1,25 wt%) festgestellt. Es ist also wichtig, die richtige Materialkombination für diese Art Sensor zu finden. Die realisierten Sensoren liefern zuverlässige Antwortsignale bei wiederholten Belastungen bis zu einer Belastung von 20 MPa (entspricht 2 kN). Zusätzlich wurde der Temperatureinfluss in einem Bereich von −20 °C bis 50 °C durch eine Wheatstonesche Brückenschaltung kompensiert. Die vorliegende Arbeit zeigt, dass eine zuverlässige Druckmessung mit einer Temperaturmessabweichung von 0,214 MPa/10 K gewährleistet werden kann. / In contrast to conventional metallic strain gauges, carbon nanotube (CNT) composites have an additional pressure sensitivity. Therefore, deformation elements such as bending beam is not needed by using pressure sensors, which are based on CNT nanocomposite. The possible areas of application for these pressure direct measured sensors were showed in three industrial application such as robot gripper. The focus of this work is the development and characterization of a new sensor manufactured from CNT nanocomposite. By using multi-walled carbon nanotube (MWCNT) epoxy and interdigital electrodes the sensor, which has a dimension of few square centimetre, should measure a pressure in mega Pascal range and hence a force in kilo newton range. By the selection of suitable materials and the modelling using finite element method, the sensor design as well as the measurement range were carried out. The MWCNT epoxy dispersion is manufactured by using a mechanical mixing process. Subsequent, the dispersion is used to fabricate pressure sensitive layers by stencil printing methods. Thereby, the fabrication parameters and especially the filler content of the MWCNTs were varied for the mechanical, thermal and electrical investigation. The characterization of the mechanical characteristic values were carried out by using tensile test and dynamic mechanical analysis. The results show a significant increasing of the tensile strength and glass transition temperature in comparison to neat epoxy. Additionally, the influence of the filler content to the pressure and thermal sensitivity were investigated. A highly pressure sensitivity but also a highly thermal sensitivity are obtained for samples with lower filler contents (1 wt% and 1.25 wt%). Therefore, a suitable material combination has to be chosen. The fabricated sensors show reliable response signals by repeated excitations up to 20 MPa (meets to 2 KN). Moreover, the temperature influence ranged from -20 °C to 50 °C was compensated with a Wheatstone bridge. This work demonstrate a direct pressure sensitive sensor with reliable response signals by a thermal deviation of 0.214 MPa/10K.

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