Dissertations / Theses on the topic 'Nano modified composite'

Carbon fibre reinforced plastics (CFRP) have revolutionised industries that demand high specific strength materials. With current advancements in nanotechnology there exists an opportunity to not only improve the mechanical performance of CFRP, but to also impart other functionalities, such as thermal and electrical conductivity, with the aim of reducing the reliance on metals, making CFRP attractive to many other industries. This thesis provides a comprehensive analysis of the nano-phase modification to CFRP by growing carbon nanotubes (CNTs) on carbon fibre (CF) and performing mechanical, electrical and thermal conductivity tests, with comparisons made against standard CFRP. Typical CFs are coated with a polymer sizing that plays a vital role in the mechanical performance of the composite, but as a consequence of CNT growth, it is removed. Therefore, in addition, an ‘intermediate’ composite was fabricated – based on CFs without a polymer sizing – which enabled a greater understanding of how the mechanical properties and processability of the material responds to the CNT modification. A water-cooled chemical vapour deposition system was employed for CNT growth and infused into a composite structure with an industrially relevant vacuum-assisted resin transfer moulding (VARTM) process. High quality CNTs were grown on the CF, resulting in properties not reported to date, such as strong intra-tow binding, leading to the possibility of a polymer sizing-free CFRP. A diverse set of spectroscopic, microscopic and thermal measurements were carried out to aid understanding for this CNT modification. Subsequent electrical conductivity tests performed in three directions showed 300%, 230% and 450% improvements in the ‘surface’, ‘through-thickness’ and ‘through-volume’ directions, for the CNT modified CFRP, respectively. In addition, thermal conductivity measurements performed in the through-thickness direction also gave improvements in excess of 98%, boding well for multifunctional applications of this hybrid material concept. A range of mechanical tests were performed to monitor the effect of the CNT modification, including: single fibre tensile tests, tow pull-out tests (from the polymer matrix), composite tensile tests, in-plane shear tests and interlaminar toughness tests. Single fibre tensile tests demonstrated a performance reduction of only 9.7% after subjecting the fibre to the low temperature CNT growth process, which is significantly smaller than previous reports. A reduction in tensile performance was observed in the composite tensile test however, with a reduction of 33% reduction in the ultimate tensile strength, but a 146% increase in the Young’s modulus suggests that the CNTs may have improved the interfacial interactions between the fibre and the polymer matrix. To support this, improvements of 20% in the in-plane shear stress and 74% and the shear chord modulus, were recorded. Negligible differences were observed using a pull-out test to directly measure the interfacial strength as a consequence of the inherently difficult mechanical test procedure. The fracture toughness was tested under mode-I loading of a double cantilever beam configuration and improvements of 83% for CNT modified composite alluded to CNT pull-out fracture mechanism and crack propagation amongst the microstructures. The changes in the physical properties are correlated to the microstructure modifications ensured by the low temperature CNT growth on the CF substrates used in the CFRP composites. This allows for a new generation of modified multifunctional CFRPs to be produced.

Nella tesi in esame ci si pone come obiettivo principale quello di indagare il comportamento meccanico e dinamico di un materiale composito nano-rinforzato. Il composito posto in esame risulta essere un materiale innovativo in quanto unisce un prepreg in fibra di carbonio con fibre unidirezionali e membrane di nano-fibre in gomma. Negli ultimi anni si è notata una crescente esigenza nel settore industriale volta a diminuire le vibrazione in sistemi meccanici sottoposti a sollecitazioni periodiche, come ad esempio, mandrini per macchine automatiche o rulli per il settore tissue o covering, tutto questo giustifica la ricerca portata avanti in questa tesi che consiste nello sviluppare un materiale composito innovativo in grado di attenuare le vibrazioni senza d’altra parte aumentarne il peso. Sono da tempo riconosciute le alte capacita smorzanti della gomma, ma spesso l’integrazione nei materiali compositi avviene attraverso l’inserimento di una strato spesso di gomma tra due layer rigidi (struttura a sandwich), questo porta ad un aumento considerevole del peso e dello spessore, caratteristiche che possono rendere un materiale composito meno attraente in alcuni campi di applicazione. Lo smorzamento o damping risulta essere un fenomeno impegnativo da studiare nei materiali metallici perché esso è influenzato da innumerevoli fattori. Per quanto riguarda i materiali compositi la sfida diventa ancora più impegnativa data la loro natura intrinsecamente eterogenea. Concludendo, dalle prove sperimentali, è emerso un incremento notevole delle prestazioni smorzanti dei provini nano-modificati, lasciando inalterate le prestazioni meccaniche.

Récemment, les nanostructures de polymères conjuguées π (CPN) ont émergé comme une nouvelle classe de catalyseurs pour diverses applications photocatalytiques comme le fractionnement de (ou photosplitting) de l’eau, la réduction du CO2, le traitement de l’eau (dégradation des polluants organiques et réduction de métaux lourds). Parmi la famille des polymères conjugués, le polypyrrole (PPy) a été le plus étudié en raison de sa stabilité environnementale, de sa synthèse facile, de son excellente stabilité. Dans cette thèse, les nanostructures PPy ont été synthétisées par différentes méthodes : polymérisation chimique dans des matrices souples (mésophases hexagonales ou lamellaires) et polymérisation par radiolyse. Ces nanostructures PPy présentent une activité photocatalytique prometteuse pour la dégradation de polluants organiques (phénol et méthylorgange) sous lumière visible et leurs activités sont supérieures à celle du PPy-bulk (PPy massif). De plus, nous avons modifié TiO2 avec du PPy nanostructuré pour la photodégradation de polluants organiques.Le nanocomposite montre une augmentation importante des performances photocatalytiques sous UV et lumière visible par rapport au TiO2 et PPy seuls pour le traitement de l’eau et de l’air. La production d'hydrogène vert par fractionnement photocatalytique de l'eau offre un moyen prometteur pour résoudre les problèmes d'environnement et d'énergie. Dans cette thèse, nous avons montré que les nanostructures depolypyrrole modifiées avec des nanoparticules mono et bimétalliques (Pt, Ni, Pt-Ni) sont très actives pour la génération d'hydrogène et qu'un effet de synergie est obtenu en alliant Pt avec Ni. Enfin, différentes nanostructures ternaires à base du composite PPy-TiO2 modifié de manière contrôlée avec des nanoparticules de platine ont été développées ((Pt-PPy) -TiO2, (Pt-TiO2)-PPy et Pt-(PPy-TiO2)). L'activité photocatalytique de Pt-(PPy-TiO2) pour la génération d'hydrogène sous UV et lumière visible est très élevée
Recently, π-conjugated polymer nanostructures (CPNs) emerge as a new class of catalysts for various photocatalytic applications such as water splitting, CO2 reduction, water treatment (degradation of organic pollutants and heavy metals reduction). Among the family of CPs, polypyrrole PPy has been the most extensively investigated owing to its environmental stability, facile synthesis, excellent stability. In this thesis, PPy nanostructures were synthesized by different methods: chemical polymerization by soft templates (hexagonal or lamellar mesophases) and polymerization by radiolysis. These PPy nanostructures exhibit promising photocatalytic activity for organic pollutants (phenol and methyl organge) degradation under visible light and their activities are higher than that of PPy- bulk.Besides, we modified TiO2 with nanostructured PPy for photodegradation of organic pollutants (methy orange and phenol as model water pollutants and toluene as air pollutant). The nanocomposite shows an important increase of the photocatalytic performance under UV and visible light compared to bare TiO2 and PPy. This work offers a facile and cheap way to fabricate the heterojunction in organic-inorganic hybrid materials interface and the composite nanomaterials represents a promising photocatalyst for water treatment and indoor application. In another hand, green hydrogen production by photocatalytic water splitting offers a promising way to solve environment and energy issues. In this thesis, we have shown that modified conjugated polymer polypyrrole nanostructures with mono- and bimetallic (Pt, Ni, Pt-Ni) nanoparticles are very active for hydrogen generation, and that a synergistic effect is obtained by alloying Pt with Ni. Lastly, different ternary nanostructures based on PPy-TiO2 composites with controlled active sites modification with Pt nanoparticles were developed ((Pt-PPy)-TiO2, (Pt-TiO2)-PPy and Pt-(PPy-TiO2)). The photocatalytic activity of Pt-(PPy-TiO2) for hydrogen generation under UV and visible light is very high and drastically surpasses those of (Pt-PPy)-TiO2 and (Pt-TiO2)-PPy

碩士
國立高雄應用科技大學
機械與精密工程研究所
101
With the rapid development of nanotechnologies and nano-materials since 1990s, the studies on polymer-based nano-composites have been extensively focused on their properties' enhancement. A novel anticorrosion/antibacterial material, zinc/epoxy and zinc/hybrid resin nanocomposites, was prepared via simple mix technique. In this study, a nano-composite coating was formed by incorporating nano-Zinc particle in epoxy and hybrid resin, respectively, to different loading levels from 500~3000ppm (0.05~0.3% by weight). Corrosion performance of the nano-composite coating was evaluated by applying these nano-composites coatings on carbon steel substrate and exposing them to 5% sodium chloride salt-spray testing chamber. Adhesion test, scanning electron microscopy (SEM), X-ray fluorescence (XRF), energy-dispersive spectrometer (EDS) were employed to character these coated with nano-composite substrates. The results of SEM and XRF showed that the nano-composites were a hybrid of the polymer and the zinc nano-particles, and the zinc nanoparticles were distributed uniformly in general. The results of salt spray test showed that nano-zinc in epoxy and hybrid resin could react with permeated oxygen, leading to the improvement of anticorrosion properties of the zinc nanocomposites with addition of desirable of zinc nanoparticles. The corroded area of Zn/epoxy samples more than 80% (without Zn nanoparticle) to less than 5%(3,000ppm Zn nanoparticle) after 500 hours salt spray test. The corroded area of Zn/hybrid resin samples more than 95% (369ppm Zn nanoparticle) to less than 10%(1,343ppm Zn nanoparticle) after 1,500 hours salt spray test. Adhesion of these films has passed the standard test method for measurement by tape test from 4B~5B. The bactericidal properties evaluation showed that the bactericidal ability of the Zn/Epoxy, Zn/Hybrid resin nanocomposites with at least 360ppm of nano-zinc and increased with nano-Zn content remarkably. Also we have carefully examined the synthesis of zinc nanoparticle concentration by inductively coupled plasma mass spectrometry (ICP-MS). In conclusion, the corrosion resistant and antibacterial properties are enhanced with addition of pure zinc nanoparticle.

碩士
國立高雄應用科技大學
模具工程系
105
Polymer-based composites have been widely used in in mold decoration (IMD) and main structure-related applications due to their outstanding material properties, such as high stiffness and high strength. However, the impact loading resulted in serious damage of the composite laminates, and consequently the structural stiffness, natural frequency and damping property were decreased. In this study, nano-reinforcements of multi-wall carbon nanotube and carbon nanofiber were used to modify the fiber-reinforced polymer composite laminates. The effect of the laminates modified of with nano-reinforcements on the drop-weight impact behaviour was investigated. The drum-winding machine was used to manufacture carbon fiber prepreg in this study. Out of autoclave (OOA) hot-pressure method was used to form the CFRP laminates. The specimens were then cut by using a CNC machine, and were subjected to drop-weight impact loading. The dynamic tests were performed on the damaged laminates in free-free boundary condition, and an impact hammer was used to create a excitation. The non-destructive inspection (NDI) was used to measure the damage area of the laminates after impact tests. According to the experimental results, the addition of nanotube or nanofiber led to an increase in the impact behaviour and a decrease in the damage area. The laminates modified with nanotube have a relatively high value of damping ratio, compared with the laminates modified with nanofiber. The smaller size the nano-reinforcement was used, the higher level of damping performance and impact bheaviour can be obtained.

碩士
南台科技大學
化學工程與材枓工程系
95
In this research, organic/inorganic nanocomposite was prepared from acrylic-polyurethane matrix with direct addition of modified silica. Two type of nano-colloidal silica dispersed in difference solvent are grafted with 2-HEMA, the 2-HEMA-g-silica was the polymerized with acrylic monomer forming acrylic polyol. By cross-linked the polyol with polyisocyante, the resultant nanocomposite was used as coating material and has excellent properties in surface hardness, solvent resistance as well as high Tg. However, the surface of coated film tends to loss its gloss with increasing silica content. The second approach to increase interface strength between the two phases was to pre-react the SiO2 particles with polyisocyanate. In this approach, the functional group of -NCO in polyisocyanate was partially reacted with the functional group of -OH on the surface of silica, the reaction was accelerated by the addition of catalyst. A significant improvement in solvent resistance was observed. In addition, the surface of coated film was smooth and glossy.

碩士
國立臺灣大學
高分子科學與工程學研究所
103
In this research, Epoxy acrylate (EA) was modified with isophorone diisocyanate (IPDI) and 2-Hydroxyethyl methacrylate (HEMA) to synthesize HI-EA, which was used as the resin matrix; whereas nano-aluminum oxide (Nano-Al2O3) and nano-silica (Nano-SiO2 ) was used as the inorganic filler to synthesize dental restorative composite resin. In order to overcome the problem of secondary caries, we have added antibacterial and anticavity elements into composite resin. By using materials that can also be used as inorganic filler: fluoride-releasing kaolinite, Epigallocatechin gallate (EGCG), and Nano-zinc antibacterial agent, we produced a series of antibacterial dental composite resins, and furthermore discussed their mechanical properties and antibacterial ability. In the foliated nano-Al2O3/ fluoride-releasing kaolinite series, as the content of the fluoride-releasing kaolinite increased, the antibacterial ability increased too. Also, under the condition of not influencing the mechanical property of the material, adding EGCG improved the antibacterial ability as well. However, due to the texture of kaolinite being quite soft and with limited inorganic content, the result of mechanical property was under expectation. In order to improve the hardness of the self-synthesized composite resins, we produced another series that contained modified nano-SiO2 mixed along with sphered nano-Al2O3 and fluoride-releasing kaolinite. Due to the content of inorganic filler can reach up to 70 wt%, this series has better hardness performance. Also the material has the same antibacterial trend as the foliated nano-Al2O3/ fluoride-releasing kaolinite series. The last part of the research was to use nano-zinc as the antibacterial element to synthesis composite resin. Due to the higher inorganic filler content, this series has a higher performance in hardness compared to products available in the current market. After adding 1000 ppm of nano-zinc antibacterial agent into the composite resin, the materials would have certain antibacterial ability.

A dissertation submitted in fulfilment of the requirements for the degree of Master of Science in Chemistry, University of the Witwatersrand, 2020
In this work, a hydrothermal method was used to synthesize the radially aligned nano rutile (RANR) TiO2,usingTiCl4as a precursor. The synthesis temperatures, as well as the time involved in the refluxing step of the synthesis were varied to obtain the optimum morphology of the resulting TiO2. The optimum refluxing time for RANR TiO2 synthesis was determined to be 16 hours at 180°C. The synthesized RANR TiO2 with dandelion-like shapes had diameters ranging from 300 nm to 800 nm and an average diameter of 560 nm. The RANR TiO2 had BET surface area of 68 m2/g, which is higher than that of the commercially available Degussa P25 (45 m2/g).The RANR TiO2-nanodiamond composites were all synthesized in situ using the hydrothermal method with detonation nanodiamonds ranging from 0.1 to 1% mass loading. BET surface area analysis showed an increase in the surface area of the RANR TiO2 with an increase in the amount of nanodiamonds used in its modification. Raman spectra confirmed the presence of graphitic carbon and rutileTiO2in all the composite samples. The results obtained from XPS analysis showed that oxygen, carbon and titanium were all present in the sample but there was no evidence showing bond formation between titanium and carbon. RANR TiO2 was the most effective in dye degradation due to their nano rod structure, which increases light harvesting properties due to multiple reflections of light. All the other composites did generally well with respect to dandelions in the first hour, but then the rate of degradation decreased which could be attributed to the reduction in photocatalytic active sites due to blockage by reactants. A good dispersion of the nanodiamonds and RANR TiO2(0.1% loading) helped to create strong electronic interphase interactions. This helps to separate the photogenerated electrons and positive holes, thereby increasing photocatalytic efficiency. Calcination increased photocatalytic efficiency because of the increase in crystallinity of materials which reduces electron/hole recombination, the increase in crystallinity was shown by results from Raman spectroscopy. The photocatalyst recyclability studies showed that the recovery of the catalyst after each cycle and the re-use was not effective as the degradation efficiency decreased from 80% to 60% after 3 cycles
CK2021

碩士
國立臺北科技大學
化學工程研究所
98
Part I：We developed a novel poly (DDS) doped nano TiO2 composite film on indium tin oxide (ITO) electrode through electropolymerization technique. The electrocatalytic and photoelectrocatalytic studies for NADH oxidation was carried out at the composite film using cyclic voltammetry (CV) and amperometric i-t curve studies. CV results show that irradiation of the composite film surface for 5 min produced an enhanced electrocatalytic oxidation current for NADH which is higher than the electrocatalytic current observed at the composite film without irradiation. The composite film detects NADH in the linear concentration range from 5×10-8 to 1.2×10-7 M. We have characterized the prepared composite film through SEM, AFM and XRD studies. The SEM and AFM results confirm that the composite film has been formed on the ITO surface. XRD results show that the TiO2 NPS are crystalline and belongs to anatase phase. EIS and light induced EIS studies corroborates the electrochemical and photoelectrochemical behavior of different films investigated in this study. Part II：Herein we report a novel amperometric ethanol sensor based on alcohol dehydrogenase immobilized onto poly-L-lysine (PLL) coated carminic acid (CA) functionalized multiwalled carbon nanotubes (MWCNTs). In the present study, we prepared a stable dispersion of MWCNTs using CA, anthraquinone dye as a dispersing agent. The prepared CA functionalized MWCNTs (CACNT) are extremely stable for several months without any precipitation. We have characterized the prepared CACNT and the different films through scanning electron microscopy (SEM), atomic force microscopy (AFM), UV–vis absorption spectroscopy and electrochemical impedance spectroscopy (EIS) studies. SEM and AFM results confirm that MWCNTs form a uniform stable suspension in CA aqueous solution. Both CACNT and the composite film containing CACNT exhibit characteristic UV–vis absorption absorption peak at 280 nm for CA which reveals that MWCNTs are functionalized with CA. The prepared stable CACNT dispersion was coated with poly-L-Lysine film on a glassy carbon electrode (GCE) and used for the immobilization of ADH through the electrostatic interactions between the negatively charged ADH (isoelectric point of ADH pI~6.8) and positively charged PLL film. The prepared ADH/PLL/CACNT composite film exhibits excellent electrocatalytic reponse towards 2.5 x 10-2 to 3.01 M ethanol. The proposed ADH/PLL/CACNT composite film was also successfully employed for the determination of ethanol from commercially available wine samples which shows the good practical applicability of this method Part III：We report a novel amperometric H2O2 sensor based on catalase (CAT) immobilized at carminic acid functionalized multiwalled carbon nanotubes (CACNT) modified glassy carbon electrode. We successfully prepared a stable dispersion of MWCNTs in carminic acid aqueous solution which was extremely stable even after one month storage at room temperature. The prepared CACNT suspension was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies. The SEM and AFM results reveal that the prepared CACNT is well dispersed in CA aqueous solution. Further, SEM and AFM images of CANT/CAT composite film shows that CAT has been well immobilized at CACNT. UV–vis absorption spectroscopy results corroborate that the immobilized CAT retains its native structure and remains highly stable at CACNT matrix. Amperometric i-t curve results show that the composite film exhibits excellent electrocatalytic response to H2O2 in the linear concentration range from 1×10-5 M to 5.77×10-3 M. Furthermore, the composite film is highly selective towards H2O2 even in the presence of 0.1 mM of ascorbic acid, dopamine and uric acid. The composite film also successfully detects H2O2 from commercially available wash stain remover solution which shows its good practical applicability.

碩士
國立臺北科技大學
化學工程研究所
98
Part I：In the present study, we have reported the direct electrochemistry of Glucose oxidase (GOx) at gelatin dispersed multiwalled carbon nanotubes (GCNTs) modified glassy carbon electrode. The model enzyme GOx has been covalently immobilized at GCNTs modified glassy carbon electrode surface through the well known glutaraldehyde chemistry. The immobilized GOx exhibits a pair of well defined reversible redox peaks with a formal potential (E°`) of –0.022 V in pH 7 phosphate PBS. The pH studies reveals that the formal potential (E°`) of GOx (FAD/FADH2) redox couple exhibits a linear dependence on pH in the wide pH range (pH 1 to 11). The UV visible absorption spectroscopy study confirms that the immobilized GOx possess its native structure and remains more biocompatible at the GCNTs matrix. The presence of MWCNTs in the immobilization matrix greatly improves the surface coverage concentration of GOx and significantly facilitates the electron transfer process at the modified electrode. The Electrochemical impedance spectroscopy (EIS) results have been successfully used to probe the interfacial properties of the biocomposite electrode upon GOx immobilization. The scanning electron microscopy (SEM) and atomic force microscopy (AFM) results confirm the discriminate surface morphology that exists between the GCNTs/GOx/GAD and the other fabricated films. The amperometric i-t curve studies show that the biocomposite electrode exhibits rapid, steady response towards glucose in the linear concentration range from 0.66 μM to 3.89 μM, respectively. Further studies reveal that GCNTs/GOx/GAD biocomposite electrode displays a good recovery of glucose from human blood samples without any common interferences. The biocomposite electrode also exhibits a reasonable stability for one month when stored in pH 7 PBS, at 4 °C. PartⅡ：We have prepared titanium dioxide (TiO2) nanoparticles modified indium tin oxide (ITO) electrodes using titanium tetrachloride (TiCl4) as the precursor. The prepared nano TiO2 modified ITOs were characterized by SEM and AFM studies. SEM and AFM results reveal that TiO2 nanoparticles are 30 nm in size. The fabricated nano TiO2/ITO films have been successfully employed for H2O2 determination at physiological pH. The detailed studies reveal that thin nafion film coating over the nano TiO2 modified ITO leads to good enhancement in H2O2 determination. The nano TiO2/NF film modified ITO exhibits good selectivity for H2O2 with minimum interferences of ascorbic acid, uric acid, glucose, L-lysine and L-cystine. Further it exhibits good recovery of H2O2 present in clinical contact lens solution which is confirmed by differential pulse voltammetry studies. The potential applicability of the nano TiO2/ITOs for the enzyme based biosensors development has also been investigated in the present study. The nano TiO2 film modified ITOs have been employed for the immobilization of the redox enzyme, catalase (CAT) with NF as the outer coating. The direct electrochemistry of immobilized CAT has been successfully investigated at nano TiO2 films. Cyclic voltammetry results show that immobilized CAT exhibits reversible redox couple with facile electron transfer process at the nano TiO2 films and the Fe(III/II) redox couple of CAT remains stable in the pH range of 4 to 13. UV-visible spectroscopy, stability, inhibition and temperature effect studies have also been carried out at nano TiO2/CAT modified ITO. These studies ultimately reveal that CAT immobilized at the nano/TiO2 film possesses good stability. Part Ⅲ：GCNT/Nano-ZrO2/TBO film has been directly fabricated on glassy carbon electrode (GCE) by simple electrochemical deposition process. The nano ZrO2 nanoparticles modified ITO electrode surface has been studied in detail using atomic force microscopy (AFM). The electrodeposited nano ZrO2 film particles are found in the average size range of 60 nm. This GCNT/Nano-ZrO2/TBO film modified GCE successfully catalyzes the H2O2 and exhibits the electro reduction signals in pH 7.0 PBS. The proposed film modified GCE successfully detects the propofol in the linear range of 24.93 μM to 0.54 mM, respectively. The proposed GCNT/nano-ZrO2/TBO film modified electrode also retains the advantage of easy fabrication, high sensitivity and good repeatability for the detection of H2O2.

碩士
國立臺灣科技大學
材料科學與工程系
101
In this study we utilized an Electro-Spun Composite Yarn Technology to produce nanofiber composite yarn fabrics(NCF). This technique combined electron-spun nanofibers with traditional yarn, and it utilized traditional yarn to be the core yarn. And then it retained the good characteristics of nanofibers and provided excellent strength on composite yarn. In the experiment, we used Nanofiber composite yarn knitted fabrics as the raw material of activated carbon fabrics at different flow rates of activator. To prepare several different conditions of carbon nano fiber absorbent, and evaluate their performance. The experimental results showed that the diameter and tensile strength are decreased with the increase of the heat-treatment temperature. The limit oxygen index (LOI) value is higher than 40% (vol./vol.) after oxidation process, and the tensile strength was decreased 71%. After carbonization and activation, the yield rate was 17%. Although it lost a lot of strength, the processes had not been affected. In addition, the specific surface area of BET of Carbon Nano Fiber Absorbent was around 1100m2/g, and the diameter of nano fiber was 100-150nm.

碩士
國立中山大學
材料科學研究所
94
In this study, PEEK/SiO2 nanocomposites were fabricated by means of simple compression molding technique. The performances and properties of the resulting PEEK nanocomposites were examined in terms of tensile loading, hardness, dynamic mechanical analysis (DMA), thermal mechanical analysis (TMA), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results indicated that the modified nanosilica was seen to disperse more uniformly than the unmodified counterparty. The XRD patterns of the modified-silica filled PEEK composites reveal a systematic shift toward higher angles, suggesting the smaller d-spacing of the PEEK crystallites. As for the thermal properties of the resulting PEEK nanocomposites, there is no significant difference for the melting and crystallization temperatures, as well as the degree of crystallization between the modified and unmodified silica filled PEEK nanocomposites. The TMA results show that the coefficient of thermal expansion (CTE) becomes lowered when the content of the nanosilica increases. Furthermore, the CTE of the modified-silica filled PEEK nanocomposites shows the higher CTE values, as compared with those of the unmodified counterparts. In addition, the inclusion of the nanosilica could improve the microhardness and the stiffness of the resulting PEEK nanocomposites with the sacrifice of the elongation, as evident from the tension and DMA testing.

碩士
國立高雄應用科技大學
模具系碩士在職專班
102
Polymer resins were widely used as the matrix for manufacturing fiber reinforced composites and the adhesive in structures. However, polymers have high crosslinking when they are cured, which results in low resistant to crack growth. In this study, the effect of using different weight percentage of silica nanoparticles on the mechanical and thermal properties of polymer-based composites was investigated. The mechanical properties discussed include tensile property, single-edge notched bending fracture toughness and impact property. Heat deflection temperature was measured for discussing the thermal property. Fracture surfaces of tested specimens and dispersions of nanosilica were observed using scanning electron microscopy(SEM). According to the experimental results, the addition of 2~4 wt% silica nanoparticles to epoxy polymers results in the increase in the mechanical properties, however, the increasing effect is not efficiently at high contentsof nanosilicadue to the fact that the agglomeration of nanoparticles. A decrease in the impact of nanocomposites was found as the nanosilica content higher than 4 wt%. Keywords:nanosilica、mechanical properties、toughness

碩士
朝陽科技大學
應用化學系
105
Abstract The modified and unmodified pineapple leaf cellulose nano-fibers (CNF) were added into the polylactic acid (PLA) and polymethyl methacrylate (PMMA) substrate, and the performance of the composites was investigated. CNF was prepared by TEMPO radical oxidation method, and subsequently, it was modified by MMA suspension polymerization method to obtain MMA modified nanofibers (code MF). The results showed that the tensile strength of the composites can be improved about 14.6% when adding 1wt% of MF. The impact strength of composites can be increased about 43.1% when adding 1wt% of MF, and the heat distortion temperature was also raised to 99.6 ℃. The results showed that the addition of CNF can increase the crystallization rate of PLA. TGA analysis showed that the CNF will be decomposed first to form a carbon layer to protect the internal substrate molecules. SEM analysis was observed that MMA modified CNF could improve the compatibility between CNF and substrates. Transmittance analysis revealed that the transmittance of MF containing composites was higher than those of un-modified ones. The transmittance of 0.5 wt% MF containing composites was almost the same as that of the substrate. The results showed that the MMA-modified CNF can greatly enhance the mechanical properties, thermal properties, and light transmittance of the substrate, so that the material can be used in a wider range.