Thesis (M.S. in mechanical engineering)--Washington State University, December 2006. / Includes bibliographical references (p. 52-53).

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy Johannesburg, 2016 / Technologies for the separation of CO2 from flue gas require a feat of engineering for efficient achievement. Various CO2 capture technologies, including absorption, adsorption, cryogenics and membranes, have been investigated globally. The absorption technology uses mainly alkanolamine aqueous solutions, the most common being monoethanolamine (MEA); however, further investigation is required to circumvent its weakness due to degradation through oxidation, material corrosion and high energy costs required for regeneration. Attractive advantages in adsorption technology, including the ability to separate the more diluted component in the mixture with a low energy penalty, have been a motivation for many researchers to contribute to the advancement of adsorption technology in CO2 capture. The challenge in CO2 adsorption technology is to design a hydrophobic and biodegradable adsorbent with large CO2 uptake, high selectivity for CO2, adequate adsorption kinetics, water tolerance, and to require low levels of energy for regeneration processes. The existing adsorbent such as activated carbon, silica gel, zeolites, metal organic frameworks and others, have been ineffective where moisture occurs in flue gas. This work provides an advanced adsorption technology through a novel adsorbent, MWNT-PAA, designed from the noncovalent functionalization of multi-walled carbon nanotubes (MWNTs) by polyaspartamide (PAA) as product of amine grafted to polysuccinimide (PSI). Three types of PAA were prepared using ethylenediamine (EDA), 1, 3 propanediamine (PDA) and monoethanolamine (MEA) drafted to PSI to give PSI-EDA, PSI-PDA and PSI-MEA respectively. The CO2 adsorption capacity was 13.5 mg-CO2/g for PSI-PDA and 9.0 mg-CO2/g for PSI-MEA, which decreased significantly from PSI where the CO2 adsorption capacity was 25 mg-CO2/g. PSIEDA was selected as PAA, because the CO2 adsorption capacity was 52 mg-CO2/g which doubled from PSI. The polymer polyethylenimine (PEI), the most commonly polymer used in CO2 capture, was found to be non-biodegradable, while the polymer PAA showed the presence of CONH as a biodegradable bond functionality, occurring in the MWNT-PAA, as confirmed through Fourier Transform Infrared (FTIR) analysis. The adsorbent MWNT-PAA was demonstrated to have a water tolerance in the temperature range 25-55 ℃, where CO2 adsorption capacity increased with the increase of water in the adsorbent. The highest CO2 adsorption capacity recorded was 71 mg-CO2/g for the moist MWNT-PAA using 100% CO2 and 65 mg-CO2/g for the mixture of 14% CO2 with air. Under the same conditions, the dry MWNT-PAA adsorbed 70 and 46 mg-CO2/g respectively (100%, 14% CO2). The 2 regenerability efficiency of the MWNT-PAA absorbent was demonstrated at 100 ᵒC; after 10 cycles of adsorption-desorption 99% of adsorbed gas was recovered in the desorption process. The heat flow for the thermal swing adsorption system resulted in the net release of heat over the complete cycle; a cycle includes adsorption (heat release) and desorption (heat absorbance). Thus, this MWNT-PAA adsorbent demonstrates an advantage in terms of overall energy efficiency, and could be a competitive adsorbent in CO2 capture technology.

Block copolymers containing pendant pyrene, terpyridine and poly(3- hexylthiophene) moieties with different block ratios and chain lengths were synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. The block copolymers obtained had narrow molecular weight distribution. The applications of these polymers for non-covalent functionalization of carbon nanotubes and in photovoltaic devices were studied. The molecular weight distribution and block sizes of the block copolymers could be controlled quite well. The polydispersities measured were below 1.25. The block copolymers could be functionalized on the surface of CNTs. The functionalized CNTs had an improved dispersing ability and a maximum dispersing ability of 0.30 mgmL-1 in DMF was achieved. The photosensitizing properties of an individual functionalized CNT were studied by conductive atomic force microscopy. In the presence of the photosensitizing unit, the photocurrent was measured to be 6.4 nAμW-1 at 580 nm. This suggests the role of metal complexes in the photosensitizing process in the block copolymer. Poly(3-hexylthiophene)-block-pendant pyrene copolymers were synthesized by Grignard metathesis and RAFT polymerization. Different loadings of the block copolymers functionalized CNT were employed as the electron accepting materials in bulk heterojunction photovoltaic devices. A maximum power conversion efficiency of 0.77 × 10-3 % was achieved for the poly(3- hexylthiophene): 0.5% polymer functionalized CNT devices. The poor efficiency was attributed to the low CNT loadings that limited the electron transport in the devices. The poly(3-hexylthiophene)-block-pendant pyrene copolymer were employed as compatibilizer for poly(3-hexylthiophene): [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction photovoltaic devices. With the addition of 20 % of the block copolymer, a maximum power conversion efficiency of 1.62 % could be achieved. The long term stability of the encapsulated photovoltaic devices was studied. There was more than 30 % reduction in the degradation of performance after 30 days when the block copolymer was added as compatibilizer. These results suggested the role of the block copolymer compatibilizers in improving both the photovoltaic performances and stability of the devices. Differential scanning calorimetry results suggested that the improved photovoltaic performances may be attributed to the enhanced compatibility between poly(3- hexylthiophene) and PCBM. / published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--Washington State University, December 2007. / Includes bibliographical references (p. 124-129).

Dissertation (Ph.D.)--Worcester Polytechnic Institute. / Keywords: supported catalyst; spin coating; atomic layer deposition; carbon nanotubes; model catalyst; ferrocene; thin film coating. Includes bibliographical references. (p.256-258)

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (leaves 67-71). Also available in print.

Thesis (Ph.D. in Materials Engineering) -- University of Dayton. / Title from PDF t.p. (viewed 06/23/10). Advisor: Liming Dai. Includes bibliographical references (p. 136-162). Available online via the OhioLINK ETD Center.

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

Thesis (Ph.D.)--University of Delaware, 2005. / Principal faculty advisor: Baidurya Bhattacharya, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

Application of carbon nanomaterials like fullerene, carbon nanotubes, and graphene in solar cells using solution processable methods presents a great potential to reduce the cost of producing electricity from solar energy. However, carbon nanotubes and graphene materials are predominantly metallic and this limits their function in organic photovoltaic devices (OPVs) where semiconducting behavior is required. Doping of carbon nanomaterials is a well-known method for making them semiconducting. Doping of carbon nanomaterials with nitrogen and boron can tune their properties to suit the requirements for use in photovoltaic applications as n-type and p-type semiconducting materials, respectively. Indeed, the use of nitrogen doped and boron doped carbon nanotubes in organic solar cells together with fullerene acceptors can improve the current density of the OPV devices. Nitrogen doping of carbon nanotubes can be achieved by using nitrogen-containing precursor materials during chemical vapor deposition. However the doping of carbon nanotubes with nitrogen does not automatically make them n-type materials; they remain metallic unless a large amount of quaternary type nitrogen is incorporated in the carbon nanotubes. In this work we have developed a method to control the type of nitrogen that is incorporated in CNTs by using an appropriate synthesis temperature and use of oxygen-containing carbon precursors during the chemical deposition of carbon nanotubes. Quaternary N was incorporated in a CVD process when high temperatures and a high concentration of O in the precursor materials were used. We also showed that the type and amount of N can be changed from pyrrolic and pyridinic-N-oxide to pyridinic N and quaternary N by annealing N doped carbon nanotubes at temperatures above 400°C. At temperatures above 800°C most of the nitrogen is converted to quaternary nitrogen. N-CNT thin films were used in OPVs so as to modify the ITO electrode and transform it into a 3D electrode. The resulting effect was an improved short circuit current density in the devices containing an N-CNT thin film that was placed on top of the ITO electrode. A reduction in efficiency losses in OPVs at increasing light intensity was observed in the NCNT ITO modified electrode OPVs. This is a remarkable finding when considering that one of the main problems hindering commercialization of OPVs is the loss of efficiency at high light intensities. We related these effects to the efficient charge collection by the modified ITO electrode. Incorporation of N-CNTs in the bulk heterojunction layer of the OPV device resulted in poor performance when compared to an OPV device made without N-CNTs. This effect is caused by shorting of the OPVs. We used a method of incorporating N-CNTs whilst minimizing shorting and this showed potential for better performance. A study on the attempted doping of graphene with B to make it a p-type material showed that in the presence of a nitrogen carrier gas, BN instead of B was incorporated in graphene. This remarkable finding enabled us to grow a p-type graphene with a possible a band gap opening. This was corroborated by XPS and Raman spectroscopy studies of the material. This BN doped graphene material showed potential as a possible replacement of PEDOT:PSS as a hole transport material in OPVs. The BN doped graphene material can match the performance of PEDOT:PSS when the level of BN doping in graphene is increased.