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This study evaluates the removal of several dyes with different charge properties, i.e., anionic (Acid Red 88), cationic (Basic Red 13), and neutral (Basic Red 5) using transition metal-doped TiO2 supported on a high-surface-area activated carbon. Experimental results confirm the successful deposition of TiO2 and the derivatives (Zr-, Cu-, and Ce-doped samples) on the surface of the activated carbon material and the development of extended heterojunctions with improved electronic properties. Incorporating a small percentage of dopants significantly improves the adsorption properties of the composites towards the three dyes evaluated, preferentially for sample AC/TiO2_Zr. Similarly, the photodegradation efficiency highly depends on the nature of the composite evaluated and the characteristics of the dye. Sample AC/TiO2_Zr demonstrates the best overall removal efficiency for Acid Red 88 and Basic Red 5—83% and 63%, respectively. This promising performance must simultaneously be attributed to a dual mechanism, i.e., adsorption and photodegradation. Notably, the AC/TiO2_Ce outperformed the other catalysts in eliminating Basic Red 13 (74%/6 h). A possible Acid Red 88 degradation mechanism using AC/TiO2_Zr was proposed. This study shows that the removal efficiency of AC/TiO2 composites strongly depends on both the material and pollutant.

Producción Científica, Metal-doped carbonaceous materials have garnered significant attention in recent years due to their versatile applications in various fields, including catalysis, energy storage, environmental remediation, electronics, and sensors, as well as reinforcement. This study investigates the synthesis and characterization of a composite material featuring a carbonaceous matrix doped with copper, focusing on the thermolysis of glycine as a precursor. The synthesis methodology involved utilizing glycine and copper acetate monohydrate in varying ratios, with the mixture subjected to heating in ceramic crucibles at temperatures ranging from 450 to 550 °C, with pyrolysis yields over the 5 to 39% interval. The pristine and Cu-doped samples obtained at 500 °C underwent characterization using a diverse array of techniques, including scanning and transmission electron microscopies, multi-elemental analysis by energy dispersive X-ray spectroscopy, CHNS elemental analysis, X-ray photoelectron spectroscopy, X-ray powder diffraction, infrared and Raman spectroscopies, ultraviolet-visible spectroscopy, and terahertz time-domain spectroscopy, along with conductivity measurements. Under optimized conditions, copper (at 6.5%) was present primarily in the free metallic form, accompanied by traces of tenorite (CuO) and cuprite (Cu2O). The carbonaceous matrix exhibited a 6:1 ratio of graphitic carbon to a carbon-nitrogen compound with the formula C2H2N2O2, such as isomers of diazetidinedione, according to multi-elemental analysis results. Conductivity measurements disclosed a significant increase in conductivity compared to the product of glycine thermolysis, showcasing the enhanced electrical properties of the new composite. Additionally, terahertz measurements showed the potential of the material as a broadband absorber for the fabrication of terahertz devices and provided compelling evidence of a significant improvement in radiation absorption upon copper doping. In conclusion, this resear, Ministerio de Ciencia e Innovación - (project PID2020-119418GB-I00)

Producción Científica, Graphitic carbon nitride (g-C3N4) is a metal-free heterogeneous catalyst that has attracted attention because of its good chemical stability, cost-effectiveness, and environmental friendliness. In the work presented herein, F,O,S-codoped carbon nitride was synthesized by heating a mixture of melamine cyanurate and trifluoromethanesulfonic acid at 550 °C for 50 min. The obtained product was characterized by transmission electron microscopy, infrared spectroscopy, X-ray powder diffraction, CHNS elemental analysis, total combustion-ion chromatography, X-ray photoelectron spectroscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and UV-Vis spectroscopy. Results point to an F,O,S-codoped g-C3N4. The material was applied as a photocatalyst for the formation of benzoxazoles and benzimidazoles by condensation–aromatization of 2-aminophenol or 1,2-phenylenediamine with suitable aldehydes (viz. benzaldehyde, 4-chlorobenzaldehyde, 2-naphthaldehyde, 2-hydroxybenzaldehyde, and 2-methoxybenzaldehyde), obtaining yields of up to 90% in 15 min under visible light irradiation, with good selectivity and reusability. Thus, the reported findings suggest that this F,O,S-codoped g-C3N4 may hold promise as a metal-free photocatalyst for the rapid synthesis of 2-arylbenzoxazoles and 2-arylbenzimidazoles., Esta investigación ha sido financiada en parte por la Junta de Castilla y León a través de las ayudas de apoyo al grupo de investigación GIR-TADRUS

Electrochemical removal of organic pollutants represents an attractive methodology in water depollution. The key challenges for researchers comprise finding simple, affordable electrode materials with satisfactory efficiency in all ranges of pollutant concentration. Electrochemical oxidation of a mixture of phenol-based dyes: bromocresol green (BCG), cresol red (CR), and thymol blue (TB), in sulphate medium, at total concentration not exceeding 15 ppm, has been performed using simply prepared, low-cost composite electrodes, based on graphene nanoplatelets (GNP) and metallic oxides (TiO2 and SnO2) loaded on stainless steel substrate: GNP@SS, SnO2/GNP@SS, and TiO2/GNP@SS. Electrodes were characterised by XRD, FTIR, and electrochemical techniques. The degradation kinetics of initial dyes was tracked with UPLC and GC-MS chromatography for 6 h, at a current density of 10 mA/cm2. GC-MS analysis of the degradation products revealed oxidised aromatic compounds as the main products, while TOC analysis confirmed a total mineralisation extent in the range of 30–35%. The proposed degradation mechanism involves the attack of OH-radical, as the main oxidising agent, to the hydroxyl oxygens of dye phenolic rings. Obtained results provide useful information for the further development of affordable laboratory-scale and industrial systems for the complete removal of phenol-based compounds.

This paper presents results related to the development of a carbon composite intended for water purification. The aim was to develop an adsorbent that could be regenerated using light leading to complete degradation of pollutants and avoiding the secondary pollution caused by regeneration. The composites were prepared by hydrothermal carbonization of palm kernel shells, TiO₂, and W followed by activation at 400 °C under N₂ flow. To evaluate the regeneration using light, photocatalytic experiments were carried out under UV-A, UV-B, and visible lights. The materials were thoroughly characterized, and their performance was evaluated for diclofenac removal. A maximum of 74% removal was observed with the composite containing TiO₂, carbon, and W (HCP25W) under UV-B irradiation and non-adjusted pH (~5). Almost similar results were observed for the material that did not contain tungsten. The best results using visible light were achieved with HCP25W providing 24% removal of diclofenac, demonstrating the effect of W in the composite. Both the composites had significant amounts of oxygen-containing functional groups. The specific surface area of HCP25W was about 3 m²g⁻¹, while for HCP25, it was 160 m²g⁻¹. Increasing the specific surface area using a higher activation temperature (600 °C) adversely affected diclofenac removal due to the loss of the surface functional groups. Regeneration of the composite under UV-B light led to a complete recovery of the adsorption capacity. These results show that TiO₂- and W-containing carbon composites are interesting materials for water treatment and they could be regenerated using photocatalysis.

This review paper presents the most recent research progress on carbon-based composite electrocatalysts for the oxygen evolution reaction (OER), which are of interest for application in low temperature water electrolyzers for hydrogen production. The reviewed materials are primarily investigated as active and stable replacements aimed at lowering the cost of the metal electrocatalysts in liquid alkaline electrolyzers as well as potential electrocatalysts for an emerging technology like alkaline exchange membrane (AEM) electrolyzers. Low temperature electrolyzer technologies are first briefly introduced and the challenges thereof are presented. The non-carbon electrocatalysts are briefly overviewed, with an emphasis on the modes of action of different active phases. The main part of the review focuses on the role of carbon–metal compound active phase interfaces with an emphasis on the synergistic and additive effects. The procedures of carbon oxidative pretreatment and an overview of metal-free carbon catalysts for OER are presented. Then, the successful synthesis protocols of composite materials are presented with a discussion on the specific catalytic activity of carbon composites with metal hydroxides/oxyhydroxides/oxides, chalcogenides, nitrides and phosphides. Finally, a summary and outlook on carbon-based composites for low temperature water electrolysis are presented.

Over the last decade, perovskite solar cells (PSCs) have emerged as one of the most promising new photovoltaic technologies in terms of the rapidly rising efficiency and low-cost fabrication processes. The new record of certified power conversion efficiency (PCE) has reached 24.2% in 2019. However, the high-performance PSCs are seriously questioned on the stability issues. The use of vacuum deposition process of noble metal electrodes and employment of the expensive hole transport material (HTM) are high-cost and high energy consuming methods, also limiting their practical applications. In this respect, the HTM-free carbon-based PSCs (C-PSCs) are believed to be the front runner towards commercialization among all types of PSCs because of the long-term stability and low-cost advantages. However, the efficiency of C-PSCs is much lower and increases slower than conventional PSCs, steadily detracting their competitiveness among various kinds of PSCs. The issues in C-PSCs include the poor perovskite/carbon contact, weak hole selectivity, large VOC loss and trap-induced charge recombination, etc. They are undermining the photovoltaic performance of C-PSCs and are urgent to be solved. In my thesis research, I focused on the understanding and designing of C-PSCs, and developed several effective strategies to improve the performance and push the development of C-PSCs. Firstly, to improve the quality of perovskite/carbon contact, I developed a new deposition method named the ultrasound-spray deposition for carbon electrode (CNTs) with the embedded structured C-PSCs. This method employs pure CNT ink as carbon source, the naturally aligned CNT bundles by weak Van der Waals forces can collapse into individual nanotubes with the help of ultrasonic sound power and high surface tension of solvent, which ensures the smoothness and compactness of the CNT electrode. This deposition method achieved a high-quality carbon electrode and seamless contact at perovskite/carbon int

Direct methanol fuel cells (DMFCs) are a kind of electrochemical energy-conversion device which converts the chemical energy of methanol directly into electric energy. Due to methanol’s high energy density, abundant source, low price, safety of storage and transportation, DMFCs have a great application potential in national defense, communication, electric appliances and sensing devices. Although appealing, the commercialization process of DMFCs is significantly hindered by their high cost, resulting from the employment of large amounts of Pt-based catalysts. Thus, to develop new catalysts to replace Pt-based catalyst is one of the most important research on DMFCs. For anode of DMFCs, the complexity and sluggish kinetics of methanol oxidization reaction (MOR) makes it difficult to develop non-Pt catalysts with comparable performance. The focus of developing alternative catalysts is on cathode catalyst for oxygen reduction reaction (ORR). Among the reported catalysts, heteroatom-doped carbons are one of the most promising catalysts for ORR for their low cost and excellent durability. However, the mechanism for ORR is still undecided. In this thesis, heteroatom-doped carbons are prepared and the mechanism for ORR are investigated by a combination of experimental and DFT calculation. Firstly, the impact of carbon precursors on P-doped carbons for ORR is investigated by using PF-resin and glucose as carbon precursors. Ratios of P-O bonds and P-C bonds are influenced because of different carbon precursors used, leading to their discrepancy performance on ORR, implying the different effect of P-O bonds and P-C bonds on ORR. Secondly, the role of P on N, P dual-doped carbons for ORR is studied by modifying the doping order of N and P. Experimental proves the first doped P has an orientation effect on the doped N by increasing the ratio of graphitic-N, leading to the improved ORR performance, which is also confirmed by DFT calculation. Thirdly, a ternary-doped porous carbon

With the increasing use of carbon/glass fibre reinforced polymer composites for large components like wing skins, fuselages and fuel tanks in aircrafts and next generation of spacecraft, utilization of advanced automated manufacturing is critical for mass production. In-situ consolidation in automated fibre placement (AFP) technology through merging several manufacturing stages like cutting, curing and consolidation has opened up a wider range of applications as well as new markets for composite materials in several sectors including aerospace and automobile in large scale. Nevertheless, the quality and integrity of AFP manufactured composites is heavily dependent on large number of variables and parameters like lay-up speed, curing/melting temperature and consolidation force. In order to establish and understand a correlation between the key parameters in AFP and the mechanical properties, several parametric experiments were performed. This is done through manufacturing uni-directional carbon fibre reinforced polymer laminates and identifying some of their main mechanical properties at different location along the length of samples. It was found that, the strength of laminates at different locations is critically dependent on the effect of those parameters.

Direct methanol fuel cells (DMFCs) are a kind of electrochemical energy-conversion device which converts the chemical energy of methanol directly into electric energy. Due to methanol’s high energy density, abundant source, low price, safety of storage and transportation, DMFCs have a great application potential in national defense, communication, electric appliances and sensing devices. Although appealing, the commercialization process of DMFCs is significantly hindered by their high cost, resulting from the employment of large amounts of Pt-based catalysts. Thus, to develop new catalysts to replace Pt-based catalyst is one of the most important research on DMFCs. For anode of DMFCs, the complexity and sluggish kinetics of methanol oxidization reaction (MOR) makes it difficult to develop non-Pt catalysts with comparable performance. The focus of developing alternative catalysts is on cathode catalyst for oxygen reduction reaction (ORR). Among the reported catalysts, heteroatom-doped carbons are one of the most promising catalysts for ORR for their low cost and excellent durability. However, the mechanism for ORR is still undecided. In this thesis, heteroatom-doped carbons are prepared and the mechanism for ORR are investigated by a combination of experimental and DFT calculation. Firstly, the impact of carbon precursors on P-doped carbons for ORR is investigated by using PF-resin and glucose as carbon precursors. Ratios of P-O bonds and P-C bonds are influenced because of different carbon precursors used, leading to their discrepancy performance on ORR, implying the different effect of P-O bonds and P-C bonds on ORR. Secondly, the role of P on N, P dual-doped carbons for ORR is studied by modifying the doping order of N and P. Experimental proves the first doped P has an orientation effect on the doped N by increasing the ratio of graphitic-N, leading to the improved ORR performance, which is also confirmed by DFT calculation. Thirdly, a ternary-doped porous carbon

The superconductivity of the 4-Å single-walled carbon nanotubes (SWCNTs) was discovered more than a decade ago, and marked the breakthrough of finding superconductivity in pure elemental undoped carbon compounds. The van Hove singularities in the electronic density of states at the Fermi level in combination with a large Debye temperature of the SWCNTs are expected to cause an impressively large superconducting gap. We have developed an innovative computational algorithm specially tailored for the investigation of superconductivity in ultrathin SWCNTs. We predict the superconducting transition temperature of various thin carbon nanotubes resulting from electron-phonon coupling by an ab-initio method, taking into account the effect of radial pressure, symmetry, chirality (N,M) and bond lengths. By optimizing the geometry of the carbon nanotubes, a maximum Tc of 60 K is found. We also use our method to calculate the Tc of a linear carbon chain embedded in the center of (5,0) SWCNTs. The strong curvature in the (5,0) carbon nanotubes in the presence of the inner carbon chain provides an alternative path to increase the Tc of this carbon composite by a factor of 2.2 with respect to the empty (5,0) SWCNTs. © 2017 Elsevier Ltd

Direct methanol fuel cells (DMFCs) are a kind of electrochemical energy-conversion device which converts the chemical energy of methanol directly into electric energy. Due to methanol’s high energy density, abundant source, low price, safety of storage and transportation, DMFCs have a great application potential in national defense, communication, electric appliances and sensing devices. Although appealing, the commercialization process of DMFCs is significantly hindered by their high cost, resulting from the employment of large amounts of Pt-based catalysts. Thus, to develop new catalysts to replace Pt-based catalyst is one of the most important research on DMFCs. For anode of DMFCs, the complexity and sluggish kinetics of methanol oxidization reaction (MOR) makes it difficult to develop non-Pt catalysts with comparable performance. The focus of developing alternative catalysts is on cathode catalyst for oxygen reduction reaction (ORR). Among the reported catalysts, heteroatom-doped carbons are one of the most promising catalysts for ORR for their low cost and excellent durability. However, the mechanism for ORR is still undecided. In this thesis, heteroatom-doped carbons are prepared and the mechanism for ORR are investigated by a combination of experimental and DFT calculation. Firstly, the impact of carbon precursors on P-doped carbons for ORR is investigated by using PF-resin and glucose as carbon precursors. Ratios of P-O bonds and P-C bonds are influenced because of different carbon precursors used, leading to their discrepancy performance on ORR, implying the different effect of P-O bonds and P-C bonds on ORR. Secondly, the role of P on N, P dual-doped carbons for ORR is studied by modifying the doping order of N and P. Experimental proves the first doped P has an orientation effect on the doped N by increasing the ratio of graphitic-N, leading to the improved ORR performance, which is also confirmed by DFT calculation. Thirdly, a ternary-doped porous carbon

Graphite has dominated the market for anode materials of lithium ion batteries (LIBs) for more than two decades owing to its low working potential, excellent cyclic stability, low cost and environmental friendliness. Nevertheless, the capacity delivered by graphite with a theoretical specific capacity of 372 mAh g-1 is far from sufficient to satisfy today’s demanding and emerging applications like electric vehicles (EVs) and smart grids, which require much higher energy/power densities, longer cyclic life and lower costs than current LIBs can offer. Exploring and developing alternative electrodes to meet the above requirements become exigent and imperative. Si has long been identified as one of the most promising alternatives to graphite owing to its high theoretical capacity of ~4200 mAh g-1, a low working potential of ~370 mV and abundance in nature. Despite these intriguing benefits, Si electrodes suffer from important drawbacks, like fast capacity degradation, potential pulverization and the formation of unstable solid electrolyte interface (SEI) along with huge volume expansion of ~300 % during discharge. This thesis is dedicated to mitigating the above challenges and developing advanced Si/C composites with excellent electrochemical property. The research objectives include not only designing novel nanostructures but also understanding the lithiation mechanisms by special techniques like in-situ microscopy. Carbon nanofibers (CNFs) containing uniformly dispersed Si nanoparticles (NPs) are synthesized via one-pot electrospinning and carbonization as free-standing electrodes for LIBs. As a prerequisite, monodispersion of Si NPs in aqueous solution is obtained via amino-silane functionalization followed by F ion mediation. The graphene oxide sheets and graphene-covered Ni particles are further introduced to improve the ionic/electronic conductivities of Si/CNF composites, the resultant Si/CNF/G, Si/CNF/Ni electrodes deliver remarkable electr

Graphite has dominated the market for anode materials of lithium ion batteries (LIBs) for more than two decades owing to its low working potential, excellent cyclic stability, low cost and environmental friendliness. Nevertheless, the capacity delivered by graphite with a theoretical specific capacity of 372 mAh g-1 is far from sufficient to satisfy today’s demanding and emerging applications like electric vehicles (EVs) and smart grids, which require much higher energy/power densities, longer cyclic life and lower costs than current LIBs can offer. Exploring and developing alternative electrodes to meet the above requirements become exigent and imperative. Si has long been identified as one of the most promising alternatives to graphite owing to its high theoretical capacity of ~4200 mAh g-1, a low working potential of ~370 mV and abundance in nature. Despite these intriguing benefits, Si electrodes suffer from important drawbacks, like fast capacity degradation, potential pulverization and the formation of unstable solid electrolyte interface (SEI) along with huge volume expansion of ~300 % during discharge. This thesis is dedicated to mitigating the above challenges and developing advanced Si/C composites with excellent electrochemical property. The research objectives include not only designing novel nanostructures but also understanding the lithiation mechanisms by special techniques like in-situ microscopy. Carbon nanofibers (CNFs) containing uniformly dispersed Si nanoparticles (NPs) are synthesized via one-pot electrospinning and carbonization as free-standing electrodes for LIBs. As a prerequisite, monodispersion of Si NPs in aqueous solution is obtained via amino-silane functionalization followed by F ion mediation. The graphene oxide sheets and graphene-covered Ni particles are further introduced to improve the ionic/electronic conductivities of Si/CNF composites, the resultant Si/CNF/G, Si/CNF/Ni electrodes deliver remarkable electr

The key parameters related to cathode materials for commercial use are a high specific capacity, good cycling stability, capacity retention at high current rates, as well as the simplicity of the synthesis process. This study presents a facile synthesis of a composite cathode material, Li2FeSiO4 with carbon, under extreme conditions: rapid heating, short dwell at 750 A degrees C and subsequent quenching. The water-soluble polymer methylcellulose was used both as an excellent dispersing agent and a carbon source that pyrolytically degrades to carbon, thereby enabling the homogeneous deployment of the precursor compounds and the control of the Li2FeSiO4 particle growth from the earliest stage of processing. X-ray powder diffraction reveals the formation of Li2FeSiO4 nanocrystallites with a monoclinic structure in the P2(1)/n space group (#14). The composites electrochemical performance as a cathode material in Li-ion batteries was examined. The influence of the amount of methylcellulose on the microstructural, morphological, conductive, and electrochemical properties of the obtained powders has been discussed. It has been shown that the overall electrochemical performance is improved with an increase of carbon content, through both the decrease of the mean particle diameter and the increase of electrical conductivity.

Epoxy is among the most extensively used thermoset polymer in the composite industry, particularly for high performance and advanced applications. However, most cured epoxy systems are extremely brittle, poor resistance to crack initiation, possess lower impact strength and characteristics poor flame retardancy during fire threats, which limits its extensive applications. These weaknesses are more acute when used with natural fibers. To minimize these shortcomings flame retardant (FR) nano filler are incorporated as additive to improve its strength besides its flame retardancy. This study used oil palm empty fruit bunch (OPEFB) fibers obtained from palm oil processing mill for producing FR nano OPEFB. The FR nano sized OPEFB filler was produced through chemical (bromine water and tin chloride) treatment and cryogenic crushing followed by high energy ball milling process. Evaluation under SEM depicts that the surface morphology of the FR nano OPEFB possess amorphous and irregular shape. Thermal analysis revealed that the treated FR nano OPEFB is thermally stable compared to untreated OPEFB fibers. Residual char obtained is 29% for nano OPEFB, 10.85% for untreated (R-OPEFB) and 14.17% for B-OPEFB fibers. Epoxy nanocomposites were fabricated using different nano OPEFB filler loading (1, 3, 5 % by weight) through hand lay-up technique. A marked increase in mechanical properties and flame retardancy were observed for all filler filled epoxy nanocomposites, in particular at 3% loading. Tensile strength of 1% is 21.43MPa, 3% is 29.01 MPa and 5% is 22.61 MPa, while impact strength of 1% is 68.13% J/m, 3% is 98.71 J/m and 5% is 70.62 J/m are observed. LOI value for pure epoxy is 23%, 1% is 25 %, 3% is 29% and for 5% is 28% while, UL-94V ratings for pure epoxy is V-2, 1% is V-1, 3% and 5% is V-0. Mechanical in terms of tensile, impact and elongation at break, morphological, physical, structural, thermal in terms of decomposition temperature and char yield, dynamic mechanical

The key parameters related to cathode materials for commercial use are a high specific capacity, good cycling stability, capacity retention at high current rates, as well as the simplicity of the synthesis process. This study presents a facile synthesis of a composite cathode material, Li2FeSiO4 with carbon, under extreme conditions: rapid heating, short dwell at 750 A degrees C and subsequent quenching. The water-soluble polymer methylcellulose was used both as an excellent dispersing agent and a carbon source that pyrolytically degrades to carbon, thereby enabling the homogeneous deployment of the precursor compounds and the control of the Li2FeSiO4 particle growth from the earliest stage of processing. X-ray powder diffraction reveals the formation of Li2FeSiO4 nanocrystallites with a monoclinic structure in the P2(1)/n space group (#14). The composites electrochemical performance as a cathode material in Li-ion batteries was examined. The influence of the amount of methylcellulose on the microstructural, morphological, conductive, and electrochemical properties of the obtained powders has been discussed. It has been shown that the overall electrochemical performance is improved with an increase of carbon content, through both the decrease of the mean particle diameter and the increase of electrical conductivity.

Graphite has dominated the market for anode materials of lithium ion batteries (LIBs) for more than two decades owing to its low working potential, excellent cyclic stability, low cost and environmental friendliness. Nevertheless, the capacity delivered by graphite with a theoretical specific capacity of 372 mAh g-1 is far from sufficient to satisfy today’s demanding and emerging applications like electric vehicles (EVs) and smart grids, which require much higher energy/power densities, longer cyclic life and lower costs than current LIBs can offer. Exploring and developing alternative electrodes to meet the above requirements become exigent and imperative. Si has long been identified as one of the most promising alternatives to graphite owing to its high theoretical capacity of ~4200 mAh g-1, a low working potential of ~370 mV and abundance in nature. Despite these intriguing benefits, Si electrodes suffer from important drawbacks, like fast capacity degradation, potential pulverization and the formation of unstable solid electrolyte interface (SEI) along with huge volume expansion of ~300 % during discharge. This thesis is dedicated to mitigating the above challenges and developing advanced Si/C composites with excellent electrochemical property. The research objectives include not only designing novel nanostructures but also understanding the lithiation mechanisms by special techniques like in-situ microscopy. Carbon nanofibers (CNFs) containing uniformly dispersed Si nanoparticles (NPs) are synthesized via one-pot electrospinning and carbonization as free-standing electrodes for LIBs. As a prerequisite, monodispersion of Si NPs in aqueous solution is obtained via amino-silane functionalization followed by F ion mediation. The graphene oxide sheets and graphene-covered Ni particles are further introduced to improve the ionic/electronic conductivities of Si/CNF composites, the resultant Si/CNF/G, Si/CNF/Ni electrodes deliver remarkable electr

Epoxy is among the most extensively used thermoset polymer in the composite industry, particularly for high performance and advanced applications. However, most cured epoxy systems are extremely brittle, poor resistance to crack initiation, possess lower impact strength and characteristics poor flame retardancy during fire threats, which limits its extensive applications. These weaknesses are more acute when used with natural fibers. To minimize these shortcomings flame retardant (FR) nano filler are incorporated as additive to improve its strength besides its flame retardancy. This study used oil palm empty fruit bunch (OPEFB) fibers obtained from palm oil processing mill for producing FR nano OPEFB. The FR nano sized OPEFB filler was produced through chemical (bromine water and tin chloride) treatment and cryogenic crushing followed by high energy ball milling process. Evaluation under SEM depicts that the surface morphology of the FR nano OPEFB possess amorphous and irregular shape. Thermal analysis revealed that the treated FR nano OPEFB is thermally stable compared to untreated OPEFB fibers. Residual char obtained is 29% for nano OPEFB, 10.85% for untreated (R-OPEFB) and 14.17% for B-OPEFB fibers. Epoxy nanocomposites were fabricated using different nano OPEFB filler loading (1, 3, 5 % by weight) through hand lay-up technique. A marked increase in mechanical properties and flame retardancy were observed for all filler filled epoxy nanocomposites, in particular at 3% loading. Tensile strength of 1% is 21.43MPa, 3% is 29.01 MPa and 5% is 22.61 MPa, while impact strength of 1% is 68.13% J/m, 3% is 98.71 J/m and 5% is 70.62 J/m are observed. LOI value for pure epoxy is 23%, 1% is 25 %, 3% is 29% and for 5% is 28% while, UL-94V ratings for pure epoxy is V-2, 1% is V-1, 3% and 5% is V-0. Mechanical in terms of tensile, impact and elongation at break, morphological, physical, structural, thermal in terms of decomposition temperature and char yield, dynamic mechanical

This study developed new methodologies to enhance the performance of carbon fiber in epoxy-based composites. A unique interdisciplinary approach of organic chemistry and engineering resulting in excellent real world outcomes.

Thesis (M. Tech.) -- Central University of Technology, Free State, 2010, The aim of this study is to produce more cost effective carbon fibre (CF) parts. To achieve this there must be a saving on materials, labour and time. Thus, a production process to produce cost effective CF moulds while saving time and money is required. This procedure must be suited for the incorporation in the small to medium production ranges. The composite industry is one of the fastest growing industries in the world. Therefore, the faster a mould can be produced, the faster the end product will reach the market. This research project investigates the possibility to sinter CF moulds on the Electro Optical Systems (EOS) Laser Sintering (LS) machine cheaper and faster than the conventional method using computer numerically controlled (CNC) machining. The surface finish produced on the LS machine is not of the same quality as a CNC machined mould, but there are ways to enhance the surface quality of a LS part to the point that it is compatible to the surface quality of a CNC machined mould. The CF moulding process uses many different types of moulding processes. However, it is not possible to use LS parts for all of the available processes to produce CF parts. In this study only one CF moulding process will be investigated, namely compression moulding. The moulds will be designed to be manufactured as cheaply and as quickly as possible. Different methods of mould adapting have been studied to find the cheapest most suitable method of mould design for the LS process.

Research on carbon materials is, nowadays, the most developed field within the nanotechnology. Graphene and carbon nanotubes (CNTs) are the materials studied the most in this domain due to their astonishing mechanical, thermal, structural and electrical properties. They are expected to be the materials used mostly in the future thanks to their appealing properties. A lot of research for the synthesis of new advanced composite materials in a wide range of applications is developed. Nevertheless, the research and study of these materials has started only 15 years ago, so there is still a long path to go through. Before starting to think about direct applications of CNTs, basic research needs to be done in order to understand the fundamental properties. A very good tool to study CNTs is the Raman Spectroscopy, which has been used in order to characterise them. It has been observed that the laser used in Raman Spectroscopy can damage the CNTs. In this project, by using laser during Raman measurements, thermal properties of CNTs has been studied at low power density (LPD) and high power density (HPD). These studies will help for a better understanding of thermal properties of CNTs as well as future methods of purification and functionalization., Outgoing

The effect of fluid force on the natural frequencies and damping ratios of vibrating structures in contact with fluid is known as the Fluid Structure Interaction (FSI) problem. It can be interpreted as an added mass to the vibrating structure in the analysis of the dynamic response. Because the density of water is much greater than air, the added mass effect becomes even more critical in understanding the dynamic response of composites in water surroundings. In this study, experimental testing was carried out to investigate FSI of composite laminates immersed in fluid and subjected to low-velocity impact. Square composite laminates of carbon fiber weave and vinyl ester resin of size 305 mm and 2.38 mm nominal thickness were subjected to low velocity impact loading, using a specially developed vertical drop-weight testing machine. The composite samples were fitted with gages to provide real-time information on strain levels generated during impact. Impact tests were performed on four side clamped laminates in air-backed, water-backed, and dry surroundings, and at various impact energies for investigation. The findings of this study will provide a better understanding for the use of composite materials in underwater structural applications where impact loading is expected., http://archive.org/details/anexperimentalst109454361, US Navy (USN) author., Approved for public release; distribution is unlimited.

Composite materials are seeing increased use in structural applications because of their various benefits. When composite structures are employed in a water environment, their dynamic responses are greatly affected by the fluid medium. Water density is comparable to many composite materials and the effects of fluid-structure interaction on dynamic behaviors of composite structures are significant. The effects of fluid-structure interaction include changes of frequency, magnitude, energy dissipation, etc., of structural characteristics. Hence, it is critical to understand the fluid-structure interaction of composite structures subjected to dynamic loading in water environments. This work focuses on finding parameters affecting the transient dynamic responses of composite structures. Coupled fluidstructure interaction analyses of composite plates are conducted numerically, using finite element models, including various parametric studies. The results are compared to those of dry structures to identify the role of each parameter., http://archive.org/details/numericalstudyof109454550, Outstanding Thesis, US Navy (USN) author., Approved for public release; distribution is unlimited.

The focus of this thesis is the study of superconducting resistive transition in 4-Å carbon nanotube arrays embedded in the aligned, linear pores of AFI zeolite crystals. While superconductivity was discovered in this material system one decade ago, resistive transition was not observed at that time owing to inadequate sample quality. The present study remedies this situation with samples fabricated from a new approach. Two types of superconducting resistive behaviors were observed in different selective samples. The first is the quasi one dimensional (1D) fluctuation superconductivity, which exhibits a smooth resistance drop with decreasing temperature, initiating at 15 K. At low temperatures, the differential resistance also shows a smooth increase with increasing bias current. Both are not affected by a magnetic field up to 11 Tesla. Such manifestations are consistent with the 1D superconducting characteristics as qualitatively interpreted by the mechanism of thermally activated phase slips, within the framework of the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory. A competing mechanism with the 1D superconductivity, the Peierls distortion, is shown to manifest itself as a differential resistance peak (as a function of the driving current), appearing above a certain temperature. Theoretical calculations suggest the quasi-1D superconducting behavior to arise from thin arrays of (5,0) 4-Å carbon nanotubes, each comprising a central member surrounded by at least six others, with a wall-to-wall separation of ~1 nm as dictated by the molecular structure of the AFI zeolite crystal. These thin (5,0) nanotube arrays plausibly act as the critical electrical links bridging the measuring electrodes. The second type of observed superconducting behavior is the one dimensional (1D) to three dimensional (3D) superconducting crossover transition. In four samples, the transition was observed to initiate at 15 K with a slow resistance decrease switching to a sharp, order of ma

The focus of this thesis is the study of superconducting resistive transition in 4-Å carbon nanotube arrays embedded in the aligned, linear pores of AFI zeolite crystals. While superconductivity was discovered in this material system one decade ago, resistive transition was not observed at that time owing to inadequate sample quality. The present study remedies this situation with samples fabricated from a new approach. Two types of superconducting resistive behaviors were observed in different selective samples. The first is the quasi one dimensional (1D) fluctuation superconductivity, which exhibits a smooth resistance drop with decreasing temperature, initiating at 15 K. At low temperatures, the differential resistance also shows a smooth increase with increasing bias current. Both are not affected by a magnetic field up to 11 Tesla. Such manifestations are consistent with the 1D superconducting characteristics as qualitatively interpreted by the mechanism of thermally activated phase slips, within the framework of the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory. A competing mechanism with the 1D superconductivity, the Peierls distortion, is shown to manifest itself as a differential resistance peak (as a function of the driving current), appearing above a certain temperature. Theoretical calculations suggest the quasi-1D superconducting behavior to arise from thin arrays of (5,0) 4-Å carbon nanotubes, each comprising a central member surrounded by at least six others, with a wall-to-wall separation of ~1 nm as dictated by the molecular structure of the AFI zeolite crystal. These thin (5,0) nanotube arrays plausibly act as the critical electrical links bridging the measuring electrodes. The second type of observed superconducting behavior is the one dimensional (1D) to three dimensional (3D) superconducting crossover transition. In four samples, the transition was observed to initiate at 15 K with a slow resistance decrease switching to a sharp, order of ma

In this thesis, the crash properties of carbon fibre composites were studied in detail. Also, novel materials were developed and characterized so that they could potentially be used for automotive crash applications.

The focus of this thesis is the study of superconducting resistive transition in 4-Å carbon nanotube arrays embedded in the aligned, linear pores of AFI zeolite crystals. While superconductivity was discovered in this material system one decade ago, resistive transition was not observed at that time owing to inadequate sample quality. The present study remedies this situation with samples fabricated from a new approach. Two types of superconducting resistive behaviors were observed in different selective samples. The first is the quasi one dimensional (1D) fluctuation superconductivity, which exhibits a smooth resistance drop with decreasing temperature, initiating at 15 K. At low temperatures, the differential resistance also shows a smooth increase with increasing bias current. Both are not affected by a magnetic field up to 11 Tesla. Such manifestations are consistent with the 1D superconducting characteristics as qualitatively interpreted by the mechanism of thermally activated phase slips, within the framework of the Langer-Ambegaokar-McCumber-Halperin (LAMH) theory. A competing mechanism with the 1D superconductivity, the Peierls distortion, is shown to manifest itself as a differential resistance peak (as a function of the driving current), appearing above a certain temperature. Theoretical calculations suggest the quasi-1D superconducting behavior to arise from thin arrays of (5,0) 4-Å carbon nanotubes, each comprising a central member surrounded by at least six others, with a wall-to-wall separation of ~1 nm as dictated by the molecular structure of the AFI zeolite crystal. These thin (5,0) nanotube arrays plausibly act as the critical electrical links bridging the measuring electrodes. The second type of observed superconducting behavior is the one dimensional (1D) to three dimensional (3D) superconducting crossover transition. In four samples, the transition was observed to initiate at 15 K with a slow resistance decrease switching to a sharp, order of ma

Hybrid inorganic/organic adsorbents were synthesized using mixtures of diatomite and carbon charcoal as precursors, and explored for the removal of p-cresol from aqueous solution. The carbon/diatomite composites displayed a bimodal and interconnected porous structure which was partially inherited from both precursors. They display moderate surface areas (between 100 and 400 m2 g−1) due to their large inorganic content (between 70 and 90 wt.%), since the diatomite is a non-porous material. Compared to activated carbons with a more developed porosity, p-cresol adsorption on the prepared carbon/diatomite composites was much faster, showing adsorption capacities similar to those of conventional adsorbents over a wide pH range. These results show a good affinity of p-cresol molecules towards the hybrid inorganic/organic composites, and demonstrate the suitability of these novel materials for the removal of aromatic (polar) molecules, despite their dominant inorganic character.

Among the three configurations of field-effect transistors that incorporating carbon nanotubes (CNT) as current pathways, aligned CNT array transistors outperform single tube structures due to the capability of good reproducibility and the possibility of cost-effective mass production, and overshadow random networks because of the absence of massive inter-tube junctions in current transport channels. In this thesis, we report the fabrication and characterization of horizontally aligned CNT array transistors. A commonly used method to fabricate CNT is CVD, either thermal CVD or PECVD, with the assistance of catalyst. Catalyst is one significant factor that affects CNT growth results, such as uniformity of CNT diameters, wall numbers, and density. Therefore, the impact of catalyst thickness and catalyst areal fraction on CNT growth were investigated. The as-grown CNT using CVD are vertically aligned due to crowding effect. We introduced a leveling process leveraging capillary effect to convert the vertical CNT into horizontal CNT. By combining with electron-shading effect to confine the initial inclination of CNT, we could achieve horizontal CNT with arbitrary orientations on Si substrate. With the readily available horizontal CNT arrays, we introduced four fabrication processes of CNT array transistors on Si substrates. Preliminary electrical measurements results indicate that the on-chip grown CNT are dense and more suitable for interconnect applications while the transferred CNT with low site density of 2~3 tubes/μm were better choice for transistor structures. We then carried out systematic electrical characterization of CNT array transistors fabricated with transfer process, with the widths varying from 1 μm to 50 μm, and lengths from 1 μm to 10 μm. Our bottom-gated transistors with Ti/Au as source/drain electrodes perform as p-type transistors. Scaling property investigation illustrated a good reproducibility and controllability of our devices. The on-state curr

Gold and iodine contrast enhancements were applied to tows prior to weaving of multi-layer carbon fabrics in order to facilitate microCT scanning. Glass-fiber tows were also placed into multi-layer carbon fabrics in order to provide density difference, resulting in contrast with the untreated carbon. These methods allow visualization of the tows within the weave. Following CT scanning, the resultant images were processed using AMIRA, then converted into finite element models using two different procedures. The first was using CATIA to further process and smooth the volume, followed by paver meshing in ANSYS Workbench, resulting in an irregular mesh which conformed to all tow boundaries within the fabric. The second was automated voxel modeling using a Python script written as part of this research program, resulting in an approximate yet regular mesh.

Probes made of carbon fibre composite NB41 were exposed to deuterium plasmas in the TEXTOR tokamak and in a simulator of plasma-wall interactions, PISCES. The aim was to assess the deuterium retention and its lateral and depth distribution. The analysis was performed by means of D(He-3, p)4He and C-12(He-3, p)14N nuclear reactions analysis using a standard (1 mm spot) and micro-beam (20 mu m resolution). The measurements have revealed non uniform distribution of deuterium atoms in micro-regions: differences by a factor of 3 between the maximum and minimum deuterium concentrations. The differences were associated with the orientation and type of fibres for samples exposed in PICSES. For surface structure in the erosion zone of samples exposed to a tokamak plasma the micro-regions were more complex. Depth profiling has indicated migration of fuel into the bulk of materials.

Probes made of carbon fibre composite NB41 were exposed to deuterium plasmas in the TEXTOR tokamak and in a simulator of plasma-wall interactions, PISCES. The aim was to assess the deuterium retention and its lateral and depth distribution. The analysis was performed by means of D(He-3, p)4He and C-12(He-3, p)14N nuclear reactions analysis using a standard (1 mm spot) and micro-beam (20 mu m resolution). The measurements have revealed non uniform distribution of deuterium atoms in micro-regions: differences by a factor of 3 between the maximum and minimum deuterium concentrations. The differences were associated with the orientation and type of fibres for samples exposed in PICSES. For surface structure in the erosion zone of samples exposed to a tokamak plasma the micro-regions were more complex. Depth profiling has indicated migration of fuel into the bulk of materials., QC 20110214

Composites produced from untreated carbon fibres result in poor mechanical properties. To increase the bonding between the carbon fibres and the matrix, the surface of the carbon fibres has been coated by carbon nanotubes (CNTs) through CNT-coated carbon fibre treatment process using a floating catalyst chemical vapour deposition (FCCVD) technique. This treatment was carried out with the presence of ferrocene and benzene as the catalyst and carbon precursor. By varying the technique of floating catalyst used to introduce ferrocene into the CVD furnace, it will influence the growth of CNT on the carbon fibre surface and hence influence the strength of the resulting carbon fibre composite. In the present investigation, two types of floating catalyst techniques were explored with different approaches in the way in which the ferrocene was introduced inside the furnace. Each technique was applied by varying two selected parameters which were the reaction temperature and the amount of ferrocene concentration. The reaction temperature was fixed at 700 and 800oC meanwhile the amount of ferrocene was varied between 0.2, 0.5 and 1.0g. Technique 1 was to introduce the vapourized ferrocene and benzene into the furnace by the hydrogen as the carrier gas. Through this, only less CNTs were grown with the presence of carbonaceous products. Meanwhile, in technique 2, the ferrocene was dissolved in liquid benzene before the mist of solution being introduced from outside of the furnace using hydrogen gas. The densely packed pure CNT grown by technique 2 was totally covered the structures of the carbon fibres. This directly affected the increase in surface area of the carbon fibre itself which gave an indication of good adhesion between the carbon fibre and the polypropylene (PP) matrix during the fabrication of composite. The morphology of the carbon fibres after the treatment was analysed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) before being in

Composites produced from untreated carbon fibres result in poor mechanical properties. To increase the bonding between the carbon fibres and the matrix, the surface of the carbon fibres has been coated by carbon nanotubes (CNTs) through CNT-coated carbon fibre treatment process using a floating catalyst chemical vapour deposition (FCCVD) technique. This treatment was carried out with the presence of ferrocene and benzene as the catalyst and carbon precursor. By varying the technique of floating catalyst used to introduce ferrocene into the CVD furnace, it will influence the growth of CNT on the carbon fibre surface and hence influence the strength of the resulting carbon fibre composite. In the present investigation, two types of floating catalyst techniques were explored with different approaches in the way in which the ferrocene was introduced inside the furnace. Each technique was applied by varying two selected parameters which were the reaction temperature and the amount of ferrocene concentration. The reaction temperature was fixed at 700 and 800oC meanwhile the amount of ferrocene was varied between 0.2, 0.5 and 1.0g. Technique 1 was to introduce the vapourized ferrocene and benzene into the furnace by the hydrogen as the carrier gas. Through this, only less CNTs were grown with the presence of carbonaceous products. Meanwhile, in technique 2, the ferrocene was dissolved in liquid benzene before the mist of solution being introduced from outside of the furnace using hydrogen gas. The densely packed pure CNT grown by technique 2 was totally covered the structures of the carbon fibres. This directly affected the increase in surface area of the carbon fibre itself which gave an indication of good adhesion between the carbon fibre and the polypropylene (PP) matrix during the fabrication of composite. The morphology of the carbon fibres after the treatment was analysed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) before being in

Modernization in space systems requires employment of new light-weight, high performance composite materials that reduce bulk weight and increase structural integrity. This thesis explored the behavior of one such material prior to and following a 35-year simulated space radiation life-cycle. Select electrical properties of nickel nanostrand(TradeMark)-carbon composites in seven configurations were characterized prior to electron irradiation via surface and bulk resistivity measurements and contact electrostatic discharge (ESD) measurements. Following irradiation at a fluence of 10(exp 16) electrons/sq cm at an average energy of 500 keV, measurements were repeated and compared against pre-irradiation data. Configuration D is the best configuration tested for use as a satellite external surface material. All composite configurations tested in this research showed degradation in critical electrical properties when examined in the aggregate. The data showed no common trend between the electrical performance of the various composites based on location or density of the nickel nanostrands? in the material. Surface resistivity increased for all configurations while bulk resistivity change correlated to the type of epoxy resin used in the composite. The mechanism responsible for these changes is electron induced displacement damage within both the epoxy and carbon which reduce permittivity and, or conductivity within the bulk. ESD current waveform properties of peak current and decay time decreased in a manner sufficient to conclude that every configuration tested is subject to increased ESD frequency and intensity over a lifetime of space radiation. These materials require further engineering to better resist the changes noted in these electrical properties before used as satellite surfaces., The original document contains color images.

This thesis presents the results of a study focussed on the elucidation of the mechanisms responsible for determining the structural integrity of carbon coatings on ductile substrates. Through elucidation of these mechanisms, two different coating systems are designed; a multilayered coating and a functionally graded coating. While concentrating upon carbon coatings, the findings of this study are applicable to a broad range of hard coatings on ductile substrates. The thesis concludes with a chapter outlining a brief study of the effects of gold coatings on silicon under contact load at moderate temperatures to complement the major part of the thesis.Carbon coatings with differing mechanical properties were deposited using plasma enhanced chemical vapour deposition (PECVD), filtered assisted deposition (FAD) and magnetron sputtering deposition methods. Combinations of these techniques plus variation of deposition parameters enabled composite multilayered and functionally-graded coatings to also be deposited. Substrates were ductile metals; stainless steel and aluminium. Characterisation of the coating mechanical properties was undertaken using nanoindentation and nano-scratch tests. The same techniques were used to induce fracture within the coatings to allow subsequent analysis of the fracture mechanism. These were ascertained with the assistance of cross-sectional imaging of indents prepared using a focussed ion beam (FIB) mill and transmission electron microscopy (TEM) using specimen preparation techniques also utilising the focussed ion beam mill. A two dimensional axisymmetric finite element model (FEM) was built of the coating systems using the commercial software package, ANSYS. Substrate elastic-plastic properties were ascertained by calibrating load-displacement curves on substrate materials with the finite element model results. Utilising the simulation of spherical indentation, the distribution of stresses and the locations for fracture initiation were as

Sebelum ini, asbestos dan logam telah digunakan dalam pembuatan pad brek. Namun pengunaan asbestos telah diharamkan kerana boleh menyebabkan kanser. Malah, penggunaan logam juga telah dihadkan kerana habuk dari pad brek semasa pembrekan boleh menyebabkan pencemaran air. Sejak itu, banyak kerja penyelidikan telah dilakukan untuk menghasilkan pad brek tanpa penggunaan asbestos. Dalam kajian ini, formula gentian karbon yang diperkuatkan dengan karbon untuk penggunaan pad brek telah dihasilkan dan kekuatan mekanikal komposit ini telah dikaji. Komposit ini dihasilkan kerana mempunyai kekuatan yang tinggi, ringan dan berkeupayaan untuk mengekalkan sifat mekanikalnya pada suhu lebih daripada 2000 oC dalam atmosfera yang tidak mempunyai oksida. Kaedah yang digunakan dalam penghasilan komposit karbon-karbon untuk penggunaan dalam brek automotif adalah dengan gentian karbon dan phenolic resin ditekan panas oleh alat penempaan tekanan panas. Kemudiannya, komposit berkenaan dikarbonkan pada suhu 1000oC dan akhirnya dibakar pada suhu 1700oC. Empat langkah rendaman dilakukan semasa proses pengkarbonan pada suhu 1000oC. Dalam kajian ini, kesan penambahan gentian karbon dan pengeras dan kesan pengkarbonan dan penggrafitan pada sifat komposit karbon dan pad brek komersil telah dikaji dengan menggunakan ujian mekanikal, haba dan geseran. Komposit dengan pengunaan 40 peratus gentian karbon dan 15 peratus pengeras menunujukkan sifat mekanikal dan terma yang bagus selepas diawet. Kekuatan ketegangan dan lenturan bagi komposit yang telah diawet adalah masing-masing, 411.9 MPa dan 51.7 MPa sebelum diturunkan pada suhu 523oC. Kekuatan lenturan dan ketegangan bagi komposit yang telah melalui proses pengrafitan pada suhu 1700oC adalah masing-masing, 10.7 MPa dan 10.8 MPa. Ketumpatan komposit yang telah diawet adalah 1.21 g/cm3 dan meningkat kepada 1.45 g/cm3 setelah digrafitkan pada 1700oC. Kekuatan lentur dan ketumpatan meningkat dengan proses rendaman semasa proses pengkarbonan. Analisis t

Sebelum ini, asbestos dan logam telah digunakan dalam pembuatan pad brek. Namun pengunaan asbestos telah diharamkan kerana boleh menyebabkan kanser. Malah, penggunaan logam juga telah dihadkan kerana habuk dari pad brek semasa pembrekan boleh menyebabkan pencemaran air. Sejak itu, banyak kerja penyelidikan telah dilakukan untuk menghasilkan pad brek tanpa penggunaan asbestos. Dalam kajian ini, formula gentian karbon yang diperkuatkan dengan karbon untuk penggunaan pad brek telah dihasilkan dan kekuatan mekanikal komposit ini telah dikaji. Komposit ini dihasilkan kerana mempunyai kekuatan yang tinggi, ringan dan berkeupayaan untuk mengekalkan sifat mekanikalnya pada suhu lebih daripada 2000 oC dalam atmosfera yang tidak mempunyai oksida. Kaedah yang digunakan dalam penghasilan komposit karbon-karbon untuk penggunaan dalam brek automotif adalah dengan gentian karbon dan phenolic resin ditekan panas oleh alat penempaan tekanan panas. Kemudiannya, komposit berkenaan dikarbonkan pada suhu 1000oC dan akhirnya dibakar pada suhu 1700oC. Empat langkah rendaman dilakukan semasa proses pengkarbonan pada suhu 1000oC. Dalam kajian ini, kesan penambahan gentian karbon dan pengeras dan kesan pengkarbonan dan penggrafitan pada sifat komposit karbon dan pad brek komersil telah dikaji dengan menggunakan ujian mekanikal, haba dan geseran. Komposit dengan pengunaan 40 peratus gentian karbon dan 15 peratus pengeras menunujukkan sifat mekanikal dan terma yang bagus selepas diawet. Kekuatan ketegangan dan lenturan bagi komposit yang telah diawet adalah masing-masing, 411.9 MPa dan 51.7 MPa sebelum diturunkan pada suhu 523oC. Kekuatan lenturan dan ketegangan bagi komposit yang telah melalui proses pengrafitan pada suhu 1700oC adalah masing-masing, 10.7 MPa dan 10.8 MPa. Ketumpatan komposit yang telah diawet adalah 1.21 g/cm3 dan meningkat kepada 1.45 g/cm3 setelah digrafitkan pada 1700oC. Kekuatan lentur dan ketumpatan meningkat dengan proses rendaman semasa proses pengkarbonan. Analisis t

A novel method for the modification of carbon membranes was developed by zeolite growth on the surface of porous carbon tubes using a hydrothermal synthesis method and carbon zeolite composite membranes were successfully obtained. Zeolite seeds for the zeolite growth were introduced to the inner surface of the tubes by using a slip-casting technique in 1 wt.\% seed ethanol solution and continuous and highly intergrown zeolite layers on the seeded tubes were formed by subsequent hydrothermal synthesis. Different types of zeolite layers can be grown on porous carbon tubes by using different types of zeolite seeds. Without zeolite seeds, a zeolite layer could not be formed on the carbon surface. SEM, XRD and pure gas permeation characterization indicates that the carbon-zeolite membranes are continuous and defect-free. (C) 2005 Elsevier Ltd. All rights reserved.

A novel method for the modification of carbon membranes was developed by zeolite growth on the surface of porous carbon tubes using a hydrothermal synthesis method and carbon zeolite composite membranes were successfully obtained. Zeolite seeds for the zeolite growth were introduced to the inner surface of the tubes by using a slip-casting technique in 1 wt.\% seed ethanol solution and continuous and highly intergrown zeolite layers on the seeded tubes were formed by subsequent hydrothermal synthesis. Different types of zeolite layers can be grown on porous carbon tubes by using different types of zeolite seeds. Without zeolite seeds, a zeolite layer could not be formed on the carbon surface. SEM, XRD and pure gas permeation characterization indicates that the carbon-zeolite membranes are continuous and defect-free. (C) 2005 Elsevier Ltd. All rights reserved.

A novel method for the modification of carbon membranes was developed by zeolite growth on the surface of porous carbon tubes using a hydrothermal synthesis method and carbon zeolite composite membranes were successfully obtained. Zeolite seeds for the zeolite growth were introduced to the inner surface of the tubes by using a slip-casting technique in 1 wt.\% seed ethanol solution and continuous and highly intergrown zeolite layers on the seeded tubes were formed by subsequent hydrothermal synthesis. Different types of zeolite layers can be grown on porous carbon tubes by using different types of zeolite seeds. Without zeolite seeds, a zeolite layer could not be formed on the carbon surface. SEM, XRD and pure gas permeation characterization indicates that the carbon-zeolite membranes are continuous and defect-free. (C) 2005 Elsevier Ltd. All rights reserved.

Carbon–ceramic composites have been prepared and characterised by different techniques (electron microscopy, X-ray microanalysis, X-ray diffraction and cyclic voltammetry). The effect on the conductivity of the thermal treatment temperature of the composites and the structure of the starting ceramic has been analysed. The results demonstrate that the layered structure of the clay determines their conductivity. The composites prepared are conductors and the conductivity goes through a maximum with increasing thermal treatment. Platinum has been successfully deposited on the carbon–ceramic composite by chemical and electrochemical methods. A better distribution of platinum and smaller particle sizes are obtained by the electrochemical method. The direct electrooxidation of methanol in acid medium has been studied on platinum-modified carbon–ceramic electrodes.

Carbon–ceramic composites have been prepared and characterised by different techniques (electron microscopy, X-ray microanalysis, X-ray diffraction and cyclic voltammetry). The effect on the conductivity of the thermal treatment temperature of the composites and the structure of the starting ceramic has been analysed. The results demonstrate that the layered structure of the clay determines their conductivity. The composites prepared are conductors and the conductivity goes through a maximum with increasing thermal treatment. Platinum has been successfully deposited on the carbon–ceramic composite by chemical and electrochemical methods. A better distribution of platinum and smaller particle sizes are obtained by the electrochemical method. The direct electrooxidation of methanol in acid medium has been studied on platinum-modified carbon–ceramic electrodes.

Summary: This study presents the experimental and theoretical studies on debond of carbon fiber laminates bonded to concrete, which aids in understanding the mechanics of the repaired damaged prestressed concrete girders with externally bonded carbon plates. The bond strength of carbon plate specimens bonded to concrete is determined experimentally by the debond test. The initial crack is introduced in the specimens at one location, namely the plate/adhesive interface. The fracture toughness for debonding is evaluated and expressed as the critical strain energy release rate. A finite element analysis was performed to evaluate the compliance and stress distribution in the debond test specimens., College of Engineering and Computer Science, Collection: FAU Electronic Theses and Dissertations Collection, Thesis (M.S.)--Florida Atlantic University, 2000.

In a previous report DR Technologies described the fabrication and testing of the first carbon fiber end plate for the subscale compulsator. The first end plate demonstrated the producibility of the carbon/epoxy composite concept using RTM technology and, following an unintentional overload during structural testing, provided coupon-level material properties. A second identical plate was fabricated in this reporting period, nondestructive structural stiffness measurements were made, and the plate was delivered to UT-CEM for further evaluation. This report summarizes the fabrication, testing, and analysis of the second end plate.

Conductive carbon-ceramic composites have been prepared from coal tar pitch and a ceramic already molded as a monolith having a honeycomb structure. The material has been obtained by subjecting both components to a heat treatment in N2 to a maximum temperature of either 1073 K or 1273 K. The starting ceramic and the composites have been characterized by scanning electron microscopy, EDX, thermogravimetry and X-ray diffraction. Conductivity measurements and electrochemical behavior have been also carried out. The results obtained reveal that the highest conductivities are obtained in those samples heated to the maximum temperature studied. Stability towards oxygen increases with treatment temperature, reaching the samples treated to 1273 K for 2 hours, a gasification temperature similar to the graphite material studied. Additionally, the composites exhibit a high electrochemical stability that makes these materials very promising to be used as electrodes and/or as electrocatalysts support.