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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
421

1.Pyrolytic Studies of Arylimines 2.Synthetic Studies of Natural Products With 2-Phenylbenzofuran framework by the Flash Vacuum Pyrolysis 3.Pyrolytic Studies of Furylmethyl benzoates¡BBenzothienylmethyl benzoates and N-Methylpyrrolylmethyl benzoates

Hsueh, Yu-Tan 07 September 2011 (has links)
The thesis is divided into three chapters Chapter 1¡BFlash vacuum pyrolysis of 2-chloro-N-arenylideneaniline gave quinolines by the intromolecular cyclization. And then, flash vacuum pyrolysis of 2-methoxy-N-arenylideneaniline gave the benzothiazole products by the bond cleavage and the radical reaction. Chapter 2¡BFlash vacuum pyrolysis of 32 gave Stemofuran C. And then, flash vacuum pyrolysis of 33 gave 31 which belonging to the former compound of E6 reported on the paper. We also found that we also could get 2-phenylbenzofuran by flash vacuum pyrolysis of 44. Chapter 3¡BFlash vacuum pyrolysis of furylmethyl benzoates¡Bbenzo- thienylmethyl benzoates and N-methylpyrrolylmethyl benzoates gave the corresponding products by the interconversion between vinylcarbene and cyclopropene.
422

Investigation on Adsorption of Vapor-phase Mercury Chloride on Powdered Activated Carbon Derived from Recycled Waste

Lin, Hsun-Yu 24 March 2005 (has links)
This study investigated the production of powdered activated carbon derived from carbon black of pyrolyzed waste tires, and their adsorptive capacity on vapor-phase mercury chloride (HgCl2) using both adsorption column and thermogravimetric adsorption systems. The adsorption isotherms and kinetic models were further simulated in the study. In addition, an innovative compositive impregnation process was developed to increase the sulfur content of powdered activated carbon derived from waste tires. The activation of carbon black to form powdered activated carbon was performed in a tubular oven. The operating parameters including activation temperatures, activation time, and water feed rates were investigated in this study. Experimental results indicated that the yield of carbon-black derived powdered activated carbon (CBPAC) decreased with the increase of activation temperature, activation time, and water feed rate, while the BET surface area and pore volume decreased. In the comparison of activation time and water feed rate in the activation process, activation time had an important impact on the production of specific surface area than water feed rate. The optimal operating parameters included activation temperature of 900¢J, activation time of 180min, water feed rate of 0.5 mLH2O/gC-sec, and water injection behind activation process of 17.5 min. From the analysis of carbon surface, the carbon contents of powdered carbon black (PCB), CBPAC, commercial powdered activated carbon (CPAC) were 89.5%, 87.6%, and 88%, respectively. The C (1s) peak region of PCB consisted of 49.8% C-C, 38.9% C-O, 10.5% C=O or O-C-O. Similar analysis results showed that the total area of the C (1s) peak region of CBPAC consisted of 57.5% C-C, 26.8% C-O, 8.1% C=O or O-C-O, and 7.6% O-C=O. Similar to CPAC, the C (1s) peak region consisted of 42.6% C-C, 41.8% C-O, and 15.6% O-C=O. Furthermore, the sulfur contents of PCB and CBPAC were both 0.5%. The S (2p) peak region of PCB consisted of 58.9% ZnS (zinc sulfide) and 41.1% S=C=S. For CBPAC, the S (2p) peak region solely contained S=C=S. The comparison of two sulfur impregnation processes revealed that the innovative compositive impregnation process could simultaneously increased the sulfur content and the BET surface area of powdered activated carbon (PAC), however, the direct impregnation process increased the sulfur content while the BET surface area of PAC decreased linearly. Without the disadvantages of time and energy consumption associated with direct impregnation, the compositive impregnation is an efficient and energy-saving process for producing sulfurized PAC with a high BET surface area and high sulfur content. Experimental results obtained from the adsorption column tests indicated that the influence of the adsorption depth on the adsorptive capacity of CBPAC did not vary much, while the adsorptive capacity of CBPAC increased with HgCl2 concentration. Furthermore, the adsorptive capacity of CBPAC on vapor-phase HgCl2 was less than that of CPAC at the adsorption temperatures of 25~150¢J and high humidity of 12.3 wt %. The difference of adsorptive capacity for CBPAC and CPAC correlated closely with BET surface area and sulfur content. Results form the thermogravimetric adsorption analysis indicated that the adsorptive capacity of CBPAC and initial adsorption rate on vapor-phase HgCl2 increased with HgCl2 concentration and decreased with adsorption temperature. In the kinetic modeling, the deviation of experimental and simulated values simulated by the pseudo-first-order model was lower than those of pseudo-second-order models. Furthermore, the r (correlation coefficient) of pseudo-first-order and pseudo-second-order models were 0.9745~0.9977 and 0.9217~0.9780, respectively. It suggested that the pseudo-first-order model could simulate the adsorption of HgCl2 onto CBPAC better than pseudo-second-order model.
423

A study of electrochemical properties of Ni-CGO composite for SOFC anode

Chen, Jing-Chiang 29 June 2006 (has links)
For the past few decades, Ni-YSZ (yttria-stabilized zirconia) has been the dominate anode material of high temperature (>1000¢J) solid oxide fuel cells (SOFCs). However, the conductivity of Ni/YSZ is not enough when the operation temperature is in the intermediate rage of 500~700¢J. Instead, Ni/CGO is a good candidate as the anode material of intermediate temperature SOFCs (IT-SOFC), due to its enhanced conductivity. This work was aimed at the preparation of Ni/CGO composite anodes using the electrostatic assisted ultrasonic spray pyrolysis (EAUSP) method. By properly adjusting the deposition parameters, highly porous composite films with desired phases and microstructure rendering low electrode impedances were obtained. The results indicated that deposition temperature and the applied voltage dictated the evolution of film morphology and hence the interface impedance between the electrode and the electrolyte. Therefore, the optimum deposition parameters for the best microstructure and hence minimum interface impedance were 12 kV for the applied voltage, 6 : 4 for the Ni-CGO mole ratio, 450¢J for the deposition temperature. The microstructure thus obtained possessed a cauliflower-like structure with high porosity. The resultant interface impedance at 550¢J was 0.09 Ωcm2, lower than that obtained from the conventional anode preparation routes of dip-casting (0.14 Ωcm2) or mechanical mixing (0.12 Ωcm2).
424

Nano Structural Metal Composites: Synthesis, Structural And Thermal Characterization

Kaleli, Kadir 01 July 2008 (has links) (PDF)
In this work , metal functional polymers, namely Cr-PS-b-P2VP, Co-PS-b-P2VP, Au-PS-b-P2VP, Fe-PS-b-P2VP and Mo-PS-b-P2VP were prepared by thermal reaction of hexacarbonylchromium, Cr(CO)6, octacarbonyldicobalt,Co2(CO)8, hydrogentetrachloroaurate(III), H(AuCl4).4H2O, trichloroiron(III), FeCl3.6H2O, molybdenum(VI)oxide, MoO3 and PS-b-P2VP. TEM images indicated formation of AuIII, Cr and Co nanoparticles. On the other hand, crystalline structures were detected for Fe-PS-b-P2VP and Mo-PS-b-P2VP. Samples involving nanoparticles were further characterized by FTIR, UV-Vis and direct pyrolysis mass spectroscopy techniques. FTIR analysis indicated dissapearance of characteristic carbonyl peaks of Cr(CO)6 and Co2(CO)8 for Cr-PS-b-P2VP and Co-PS-b-P2VP samples. The appearance of a peak at about 467 cm-1 supported the formation of metal-nitrogen bond. Pyrolysis mass spectrometry analysis showed an increase in the thermal stability of P2VP chains involving coordinated pyridine units. The thermal stability of these chains increased in the order Co&lt / Cr &lt / Au3+ indicating stronger coordination in the same order.
425

Thermal Characterization Of Phenol And Bisphenol-a Based Polybenzoxazines

Bagherifam, Shahla 01 March 2009 (has links) (PDF)
Although, several researches on synthesis and characterization of benzoxazines and polybenzoxazines have appeared in the literature, detailed studies on thermal characterization are still limited. In this study, polymerization and thermal degradation mechanisms of benzoxazines were investigated via direct pyrolysis mass spectrometry. Benzoxazine monomers prepared by reactions of phenol or bisphenol- A with aniline or methyl amine were analyzed to investigate the effects of the structures of phenyl and amine groups on both polymerization and thermal degradation behaviours. It has been proposed in the literature that polymerization of benzoxazines occurs by ring opening polymerization of oxazine ring / cleavage of O-CH2 bond of the oxazine ring and attack of n-CH2 group to phenol or bisphenol-A ring. However, the direct pyrolysis mass spectrometry analyses of polymerization and thermal degradation of benzoxazines pointed out that after the cleavage of O-CH2 bond of the oxazine ring, polymerization proceeded through opposing pathways. Strong evidences confirming coupling of (CH3)NCH2 or (C6H5)NCH2 groups yielding dimers involving diamine linkages were detected. Polymerization of the dimer by the reactions with the corresponding monomers was proposed. In case of benzoxazines based on bisphenol-A, the results indicated polymerization of the dimer ii by coupling of both of the oxazine rings. On the other hand, polymerization of the dimer through the ethylene units (vinyl polymerization) in case of benzoxazine monomer based on phenol and methyl amine was also noted. For polybenzoxazines based on aniline another polymerization pathway involved attack of radicals generated by cleavage of the oxazine ring to aniline ring. Multi-step thermal decomposition was observed for all the polybenzoxazines under investigation confirming the presence of units with different structures and stabilities.
426

Nano Structural Metal Nano Composites: Synthesis, Structural And Thermal Characterization

Orhan, Tugba 01 August 2008 (has links) (PDF)
Recently, the use of block copolymers in preparation of nanocomposites has received great attention as they form well-defined micelles. In this work, the synthesis of different metal functional copolymers, nano structural metal composites and investigation of their reaction mechanism and thermal characteristics by pyrolysis mass spectroscopy have been aimed. Namely, polyisoprene-block-poly2vinylpyridine, (PI-b-P2VP) and poly2vinylpyridine-block-polymetylmethacrylate, (PMMA-b-P2VP) were used as block copolymers and the thermal reaction of these copolymers with two different transition metal complexes Cr(CO)6 and HAuCl4.3H2O were investigated which mostly lead to the coordination of metal through nitrogen atom of the pyridine ring which then degrates to form nano particles. The samples were further characterized by TEM, ATR-FT-IR, UV-Vis and Direct-Pyrolysis Mass Spectroscopy techniques. TEM images proved the formation of nanoparticles and the results showed that synthesized Au nanoparticles have 2 to 3 fold larger size than Cr nanoparticles. ATR-FT-IR spectrum of metal functional copolymers showed that the disappearance of characteristic peaks of pyridine stretching and bending mode when metal coordinates to the pyridine nitrogen. Furthermore, the spectrum indicated the appearance of a new absorption peak at around 740 cm-1 which may be a clue for the coordination of gold(III) ion to the pyridine nitrogen. Different from chromium case, in the spectrum of Au3+-(PMMA-b-P2VP), CO stretching frequency of PMMA which may appear at around 1720&ndash / 1718 cm-1 decreased in intensity while a new absorption peak appeared at around 1600 cm-1. This results reveals that electron deficient gold (III) ion prefers the coordination from both donor atoms namely carbonyl oxygen PMMA and pyridine nitrogen of P2VP in order to compensate its electron deficiency. In the UV-Vis spectrum of copolymers, Cr-functional copolymers showed a sharp absorption peak appeared at around 290 nm is attributed to a MLCT transition from chromium atom to * orbital of pyridine group. Furthermore, Au-functional copolymers showed a completely new absorption band at around 320 nm which can be associated again with a LMCT transition since gold is electron deficient and more willing to accept electrons from the ligand. Pyrolysis mass spectrometry analysis showed that poly2vinylpyridine blocks for each copolymers were affected similarly but polyisoprene block was not affected much from the coordination of metal compared to poly(methyl methacrylate) block in copolymers. For (PI-b-P2VP), Au3+ coordination to copolymer resulted in the higher thermal stability compared to Cr coordination. For (PMMA-b-P2VP), different from Cr, Au3+ coordination to P2VP nitrogen atom was extensive and PMMA based products changed drastically due to the coordination of electron deficient Au3+ to PMMA carbonyl group.
427

Thermal Characterization And Kinetics Of Crude Oils By Tga And Dsc Methods

Gundogar, Sati Asli 01 February 2010 (has links) (PDF)
In recent years, the application of thermal analysis to study the combustion and pyrolysis behavior of fossil fuels has gained a wide acceptance because of its significance for industry and economy. In this thesis, the thermal and kinetic analysis of different origin crude oil samples are performed by two well-known thermal analysis techniques: Differential Scanning Calorimetry (DSC) and Thermogravimetry (TG/DTG). The investigation of combustion and pyrolysis behaviors, kinetic analysis of oil samples and the determination of heating rate effect are the main objectives of this study. Six different crude oils from the Southeastern region of Turkey are analyzed throughout the study. All experiments are performed at different heating rates (5, 10 and 15&ordm / C/min) and air is used for combustion and nitrogen for pyrolysis experiments. In combustion experiments, TGA and DSC techniques indicate that the combustion process of crude oils studied is composed of two main reaction regions. These are low-temperature (LTO) and high-temperature oxidation (HTO) regions. In LTO, huge mass loss occurs (from 69 to 87 %) due to high amount of free moisture and volatile hydrocarbons contained in oil samples. Combustion reactions continue up to 900 K. On DSC curves, two exothermic regions of oxidation regimes are detected. Comparing TG/DTG and DSC curves, it can be understood that the mass loss under combustion is accompanied by exothermic peaks because of the oxidative degradation of crude oil components. As in combustion, two distinct reaction regions are revealed under pyrolysis for all samples. The first region indicates distillation and the second one is due to thermal cracking reactions occur at high temperatures and completed up to 840 K. As expected, lighter crude oils have relatively higher amounts of mass loss in distillation region as compared to heavier ones. Besides, residue amount and burn-out temperatures are higher for heavier oils with higher asphaltene content in cracking region. DSC curves for both reactions show endothermic effects. In combustion and pyrolysis experiments, it is noticed that higher heating rates are resulted in higher reaction regions. Distinguishing peaks of samples shift to higher temperatures with an increase in heating rate. Heat of reaction amount under DSC curves is related to asphaltene content and &amp / #730 / API gravity of crude oils. It is deduced that, when &amp / #730 / API gravity of crude oils decreases, the heat value of this reaction increases. The kinetic parameters are evaluated by different kinetic models and mean activation energies (Em) of samples are obtained. At the end, a correlation is established between Em and &amp / #730 / API gravity of oil samples. It is concluded that heavier oils have higher activation energy and Arrhenius constant values for each reaction region. Besides, it is proved that the activation energy is mostly insensitive to the heating rate.
428

A Study on the Measurement and Analysis of Mercury in Flue Gas Emitted from Municipal Waste Incinerator and the Adsorption of Gaseous Mercury Chloride by Powder Activated Carbon Derived from the Pyrolysis of Waste Tires

Wu, Chun-Hsin 01 August 2000 (has links)
The objective of this study was to remove mercury vapor from municipal waste incinerator (MWI) by the adsorption of powder activated carbon (PAC) prepared from the pyrolysis of waste tire. The study focused on the measurement of mercury concentration in flue gas emitted from municipal waste incinerator, the preparation of PAC from the pyrolysis of the waste tire and impregnated with sulfur, and the adsorption capacity of mercury by the self-made PAC. The measurement of heavy metals in flue gas emitted from four typical MWIs was conducted in this study. Experimental results obtained from the measurement of mercury from flue gas indicated that the removal efficiency of mercury ranged from 83.71%~96.22%for the tested MWIs. This study revealed that the injection of PAC in flue gas would enhance the removal efficiency of mercury. Besides, oxided mercury (Hg2+) can be removed much more easily than elemental mercury (Hg0). Experimental results obtained from the pyrolysis of waste tires indicated that the pyrolysis temperature of waste tire was approximately 400~500¢J, and the percentage of carbon residue is 35~37%. With higher temperature and water feed rate and longer activation time, the specific surface area and total pore volume of PAC increased while the average pore radius decreased. The highest specific surface area of PAC obtained in this study was 996 m2/g. In addition, experimental results obtained from sulfur impregnation process indicated that the specific surface area of PAC decreased dramatically as sulfur was added to PAC. Experiment results obtained from the adsorption capacity of HgCl2 on PAC by column test indicated that PAC with higher specific surface area could adsorb more HgCl2 at room temperature (25¢J). The adsorption capacity of sulfur impregnated PAC decreased at 25¢J was due to the decrease of specific surface area of PAC. However, results from the comparison of two PAC with similar specific surface area indicated that the PAC with higher sulfur content had higher adsorption capacity. It suggested that the addition of sulfur to PAC could enhance the adsorption of HgCl2 at 25¢J. Experimental results obtained from column tests at 150¢J showed that the adsorption capacity of PAC increased as sulfur content of PAC increased. These results suggested that the adsorption mechanism of HgCl2 by PAC was mainly physical adsorption at lower temperature and it was chemisorption at higher temperature. Besides, the self-made PAC demonstrated the similar adsorption capacity of HgCl2 with commercial PAC used in MWIs.
429

Electro-optical properties of Sb and Ta doped SnO2 thin films derived from an ultrasonic atomization process

Li, Shang-Chien 10 July 2002 (has links)
The thin film deposition system using ultrasonic nebulization was adopted in this study. SnCl4.5H2O, SbCl3, and TaCl5 were used as solutes. Ethanol was used as the solvent. Solutions of different Sn4+ concentration, Sb concentration (Sb/Sn atomic ratio) in Sn, and Ta concentration (Ta/Sn atomic ratio) in Sn were mixed. The mist was generated from a solution by the agitation of an ultrasonic device operating at about 1.65MHz. The mist was carried to the heated substrate (corning 7059 glass) by the flow of nitrogen gas so that it was decomposed by heat. SnO2-x films were deposited on the substrate due to the pyrolysis reaction. The experiment included six series: Sn4+ concentration series, Sb-doping series, temperature series, Ta-doping series, aging time series and nebulization rate series. SnO2-x films were analyzed by XRD, UV-Visible, SEM, and Hall-measurement. The optimum deposition conditions were obtained through analyses of these six series. The film deposition rate of nonaged solution was faster than aged solution. When the nebulization rate of solution was 1.6 ml/min, the resistivity of undoped SnO2 film obtained with the substrate kept at 450 oC is 2.364¡Ñ10-2£[-cm and the maximum transmittance of the visible light is 78.7%. When Sb/Sn atomic ratio in the solution was 2%, the resistivity of Sb doped SnO2 film obtained with the substrate kept at 525 oC is 2.77¡Ñ10-3£[-cm and the maximum transmittance of the visible light is 71% . When Ta/Sn atomic ratio in the solution was 0.1%, the resistivity of Ta doped SnO2 film obtained with the substrate kept at 450 oC is 3.917¡Ñ10-2£[-cm and the maximum transmittance of the visible light is 85% In this study, the electro-optical properties of Sb and Ta doped SnO2 thin films derived from an ultrasonic nebulization process were reported and discussed carefully through film characterizations.
430

Removal of Ash from Waste-Tire Pyrolytic Char by the Principle of Electrostatic Separation

Lin, Chih-Feng 06 July 2008 (has links)
Pyrolysis has been a useful procedure to treat waste-tire, which decomposes waste-tire at high temperature in the absence of oxygen. This thermal decomposition process generates pyrolysis oil, combustible gas, and char, which distribute in liquid phase, gas phase, and solid phase, respectively. Pyrolysis oil and combustible gas are fuels, while char is composed of carbon black and ash. Thus, char would be economically worth while to be treated before reuse. In this study, based on the resistivity difference between carbon black and ash, ash can be removed from char in the principle of electrostatic separation and thus increase the value of char. In this study, the objective was to separate ash from char by electrostatic separation process, different char including waste-tire pyrolytic char (raw char), low pressure re-pyrolytic char, ZnO-added char (12% ZnO mixed with 600 oC re-pyrolytic cahr) and man-made char (N600 carbon black mixed with 14.5% metallic oxide) were tested. The Electro-Static Separator (ESS) was designed and constructed with two types of discharge electrodes including a needle-plate electrode (NPE) and a needle-bar electrode (NBE) and two kinds of dust feeders to generate either fine or coarse particles. The results indicated that raw char had higher collection efficiency using the NBE system than the NPE system in the operating voltages of -7 kV to -15 kV because the surface area of the NBE system was less than the NPE system, thus led higher surface charge density for the NBE system than the NPE system, resulting in higher discharge current of the NBE system. In order to lower resistivity and reduce deposited pyrolysis oil on char, low pressure repyrolysis process was used. Because the removal efficiency of pyrolysis oil is proportional to repyrolysis temperature, more pyrolysis oil can be removed from the surface of char, resulting in more carbon blacks exposed on the char surface as conductive material. Thus, the collection efficiency of 600 oC repyrolytic char was less than that of 400 oC repyrolytic char. Furthermore, because particle charging quantity was proportional to particle size, fine char particles had less collection efficiency than coarse char particles. However, both raw char and repyrolytic char, the collection efficiency of carbon and ash had similar trends, suggesting that similar percentage of carbon and ash were collected on the plate and penetrated the ESS system. Therefore, the separation efficiency of carbon and ash were similar, same situation was observed for the ZnO-added char. In order to verify the feasibility of carbon and ash separation by electrostatic separation process, N660 carbon black mixing with 14.5% man-made ash (Al2O3, ZnO and CaO composed) to simulate man-made char, which was further used to proceed the electrostatic separation experiments in this study. The results indicated that the collection efficiency of man-made char increased with operating voltage, and the ash content seems to increase with voltage. Carbon black is a low resistivity material, which causing sparkover during the experiments, thus operating voltage cannot be regulated more than -8.25 kV. In order to verify the feasibility of carbon black and ash separation by the principle of electrostatic separation, this study applied non-linear regression to model the collection efficiency of man-made char, carbon black and ash, and further simulate the collection efficiency at higher electrical field strength. The simulated results indicated that the maximum collection efficiency of carbon and ash was approached around -10 kV/cm of carbon black and ash and their collection efficiencies were similar. The collection efficiency of ash was close to the ash content of man-made char (the collection efficiency of ash equal to the collected ash per mass of injected char), suggesting that most injected ash was collected by the ESS system. In addition, the ash content of penetration char was also simulated, the modeling results showed that the ash content of penetrated char were lower than 2%, while was relatively lower than the raw man-made char, and more than 75% injected char could penetrate the ESS system during the operation procedure. According to the modeling results, solid-solid separation technology could be more efficient if carbon and ash are independently separate particles, and lower resistivity materials would penetrate the ESS system and higher resistivity materials would be collected by the electrostatic separation process.

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