Οι βιοαντιδραστήρες μεμβρανών αποτελούν μια καινοτόμο τεχνολογία, ιδανική για την αποκατάσταση προηγμένων αστικών και βιομηχανικών λυμάτων, τα οποία περιέχουν υψηλά ποσοστά βιοαποικοδομήσιμων οργανικών ενώσεων. Η παρούσα εργασία αποτελεί ένα μέρος μιας ευρύτερης προσπάθειας ανάπτυξης μιας νέας κατηγορίας λειτουργικών μεμβρανών τεχνολογίας “Βιοαντιδραστήρα Μεμβρανών” (Membrane Bioreactors, MBRs) ή/και βελτίωσης των ήδη χρησιμοποιούμενων μεμβρανών τεχνολογίας MBR με την ενσωμάτωση στο ενεργό πορώδες τους νανοσωλήνες άνθρακα. Οι νανοσωλήνες άνθρακα δυνητικά θα προσέφεραν ταυτόχρονα υψηλότερες ταχύτητες ροής νερού, υψηλότερο ποσοστό απόρριψης οργανικών ενώσεων και ανόργανων αλάτων χαμηλού μοριακού βάρους, καθώς και υψηλότερη αντοχή της μεμβράνης στην εναπόθεση διαφόρων μικροοργανισμών. Η πρόκληση στην περίπτωση αυτή είναι η αποτελεσματική ενθυλάκωση τους στην ενεργή εκλεκτική στοιβάδα των μεμβρανών αυτών. Οι νανοσωλήνες άνθρακα από την πρώτη στιγμή της ανακάλυψης τους, έχουν προσελκύσει το ενδιαφέρον της επιστημονικής κοινότητας, λόγω της ευρείας εφαρμογής τους σε πολλά επιστημονικά και τεχνολογικά πεδία, ως συνέπεια των μοναδικών ιδιοτήτων τους. Οι χημικές, οπτικές, ηλεκτρικές και μηχανικές ιδιότητές τους, τους καθιστούν δυνητικά χρήσιμους σε πάρα πολλές εφαρμογές. Στη συγκεκριμένη περίπτωση, τα τελευταία 5-7 έτη, οι νανοσωλήνες άνθρακα έχουν ταυτοποιηθεί ως μια καινούργια γενιά νανο-πορωδών υλικών με τρομερό δυναμικό για εφαρμογές ως φίλτρα σε υλικά μεμβρανών που θα μπορούσε να φέρει πραγματική επανάσταση στο σχετικό χώρο. H δυνατότητα ελέγχου της διαμέτρου τους και κατά συνέπεια του μεγέθους των πόρων τους μέσω των οποίων λαμβάνει χώρα το φαινόμενο της διάχυσης ή ροής (από τα 4 Angstroms έως τα 15 nm), σε συνδυασμό με τα σχεδόν άτριβου χαρακτήρα γραφιτικά τους τοιχώματα, εξασφαλίζει εξαιρετικά ταχεία ροή μικρών μορίων με ταυτόχρονη καταπληκτική εκλεκτικότητα στη διαπερατότητα μορίων με βάση το μέγεθός τους. Η ροή υγρών μέσα από αυτές των νανοσωλήνων άνθρακα προβλέπεται να είναι 3-5 τάξεις μεγέθους πάνω απ’ ότι αναμένεται με βάση υπολογισμούς βασισμένους σε απλές αρχές της υδροδυναμικής. Στο πλαίσιο αυτό, μελετήθηκε ο εμβολισμός νανοπορωδών εμπορικών μεμβρανών με διάφορα είδη νανοσωλήνων άνθρακα (CNTs): μονοφλοιϊκών (με ένα τοίχωμα) (Single Wall CNT: SWCNT), διπλοφλοιϊκών (με δύο τοιχώματα) (Double Wall CNT: DWCNT), πολυφλοιϊκών (με πολλαπλά (~15) τοιχώματα) (Multi Wall CNT: MWCNT), λεπτών “πολλαπλού” τοιχώματος (με λίγα (~6-7 ) τοιχώματα) (thin MWCNT), αλλά και τροποποιημένων νανοσωλήνων άνθρακα πολλαπλού τοιχώματος με υδρόξυ-ομάδες (-OH) και καρβόξυ-ομάδες (-COOH) καθώς επίσης και νανοσωλήνων άνθρακα τροποποιημένων με διάφορα πολυμερή όπως πολυβινυλοπυρολιδόνη (PVP), πολυμεθακρυλικό γλυκιδιλεστέρα (PGMA), (PSSPC16). Οι νανοσωλήνες άνθρακα, αρχικά, χαρακτηρίσθηκαν με τη βοήθεια της φασματοσκοπίας Raman και της Ηλεκτρονικής Μικροσκοπίας Σάρωσης και μελετήθηκε η διασπορά τους σε νερό (H2O) και αιθανόλη (EtOH). Κατόπιν, εμβολίσθηκαν σε διαφόρων τύπων πορώδεις ανισοτροπικές μεμβράνες (πόρων κωνικού τύπου), αλλά και σε μεμβράνες καθορισμένου μεγέθους πόρων κυλινδρικού τύπου (track etched), στην προσπάθεια ανάδειξης μιας βέλτιστης ενθυλάκωσής τους στο ενεργό/εκλεκτικό τμήμα των μεμβρανών αυτών, κάτι που δεν είναι καθόλου προφανές. Αναπτύχθηκε μια πειραματική διάταξη εμβολισμού νανοσωλήνων άνθρακα, βασιζόμενη στην αρχή της διήθησης/φιλτραρίσματος, η οποία επέτρεψε ένα βαθμό εμβολισμού τους στις μεμβράνες και μια τάση βελτίωσης του χρόνου/των ρυθμών διέλευσης του νερού από αυτές. Στην προσπάθεια αυτή αρωγός σ’ ένα μεγάλο βαθμό αποδείχθηκε η Ηλεκτρονική Μικροσκοπία Σάρωσης. / Membrane Bioreactors are an innovative technology, ideal for the treatment and rehabilitation of advanced municipal and industrial wastewater which contain high biodegradable organic compounds. A new category of functional membranes for technology MBR, which offer higher water flow, higher rejection rate of organic compounds and inorganic salts of low molecular weight, and greater resistance to the deposition of the membrane of microorganisms may be ensured by the inclusion of various types of carbon nanotubes (CNT’s) into porous polymeric membranes and its basic principle is the efficient binding of modified carbon nanotubes in these membranes. Carbon nanotubes, from the first moment of their discovery, have attracted the interest of the scientific community, due to their wide application in many scientific and technological fields, as a result of their unique properties. More specifically, the chemical, optical, electrical and mechanical properties make them potentially useful in many applications. Important is the use of carbon nanotubes for the development of an innovative high performance membrane for use in Membrane Bioreactors Technology (Membrane Bioreactors, MBR’s). In the present study different types of carbon nanotubes were examined, such as single-wall carbon nanotubes (SWCNT’s), double-wall carbon nanotubes (DWCNT’s), multi-wall carbon nanotubes (MWCNT’s), thin multi-wall carbon nanotubes (thin MWCNT’s), and modified carbon nanotubes with hydroxy groups (-OH), carboxyl groups (-COOH) as well as carbon nanotubes modified with various polymers such as polyvinylpyrrolidone (PVP), phosphonium salt of polystyrene sulfonate (PSSPC16) and polyglycidyl methacrylate (PGMA). Initially, the different types of carbon nanotubes were characterized, using Raman Spectroscopy and Scanning Electron Microscopy. Their dispersion in H2O and ethanol was also examined. Then, they were infiltrated into various types of porous anisotropic membranes with conical porous and into defined pore size membranes (track etched), to find the most suitable combination, which would result to the best water flow through the infiltrated membrane. For this purpose, an experimental device was developed, based on the principle of filtration, which allowed both the filtration of the nanotubes in the films, and the measuring of the water flow through them. Furthermore, the optimal conditions of the system were studied that could both bring about the greater coverage of the membrane pores from nanotube suspensions, (probed by SEM), and result to the optimum water flow rate.

Nanomaterials such as carbon nanotubes, gold nanorods, magnetic nanocrystals, and binary nanocrystal superlattices have exciting potential applications. However, before these ideas can be applied, it is imperative to fully understand the materials synthesis. Multiwall carbon nanotubes were synthesized in supercritical toluene using cobaltocene, nickelocene, ferrocene, or metal nanocrystals as catalysts. Toluene served as both the solvent and carbon source for nanotube growth. The reaction was optimized by introducing supplemental carbon sources; either hexane or ethanol increased the yield relative to pure toluene and catalytic amounts of water minimized carbon filament and amorphous carbon formation. Gold nanorods were synthesized by the colloidal seed-mediated, surfactantassisted approach using cetyltrimethylammonium bromide (CTAB) obtained from ten different suppliers. The gold nanorod yield depended strongly on the CTAB used: with the same recipe, three of the CTABs produced only spherical particles, whereas the other CTABs produced nanorods with nearly 100% yield. Inductively coupled plasma mass spectrometry revealed a trace iodide impurity in the CTABs that did not yield nanorods. Further experiments introducing potassium iodide to the nanorod synthesis verified the detrimental effect of iodide on nanorod formation. Multifunctional colloidal core-shell nanoparticles of magnetic nanocrystals or gold nanorods coated with a fluorescent dye (Tris(2,2 -bipyridyl)dichlororuthenium(II) hexahydrate) doped silica shells were also synthesized. The as-prepared magnetic nanocrystals were initially hydrophobic and silica coated using a microemulsion approach, while the gold nanorods were hydrophilic and silica coated using a Stöber process. These colloidal heterostructures have the potential to be used as dual-purpose tags, exhibiting a fluorescent signal that could be combined with either dark-field optical contrast or enhanced contrast in magnetic resonance imaging. Binary superlattices (BSLs) of large iron oxide and small gold nanocrystals were assembled by slow evaporation of colloidal dispersions on tilted substrates. SEM and grazing incidence small angle X-ray scattering (GISAXS) confirmed the BSLs were simple hexagonal AB2 superlattices with long range order. GISAXS also revealed that the superlattice was slightly contracted perpendicular to the substrate as a result of solvent drying during the deposition process. Additionally, in some BSLs nearly periodic superlattice dislocations consisting of inserted half-planes of gold nanocrystals were observed. / text

Acrylic bone cement is widely used as a structural material in orthopaedics, dentistry, and orofacial surgery. Although bone cement celebrates four decades of success, it remains susceptible to fatigue fracture. This type of failure can directly lead to implant loosening, revision surgery, and increased healthcare expenditures. The mechanism of fatigue failure is divided into three stages: 1) fatigue crack initiation, 2) fatigue crack propagation, and 3) fast, brittle fracture. Adding reinforcing fibers and particles to bone cement is a proposed solution for improving fatigue performance. The mechanical performance of these reinforced bone cements is limited by fiber ductility, fibermatrix de-bonding, elevated viscosity, and mismatch of fiber size and scale of fatigue induced damage. In this dissertation, I report that adding small amounts (0% - 10% by weight) of multiwall carbon nanotubes (MWNTs) enhances the strength and fatigue performance of single phase bone cement. MWNTs (diameters of 10-9 10-8 m; lengths of 10-6 10-3 m) are a recently discovered nanomaterial with high surface area to volume ratios (conferring MWNT bone cement composites with large interfaces for stress transfer) that are capable of directly addressing sub-microscale, fatigue induced damage. MWNTs (2wt%) significantly increased the flexural strength of single phase bone cement by a modest 12%; whereas, similar additions of MWNTs dramatically enhanced fatigue performance by 340% and 592% in ambient and physiologically relevant conditions, respectively. Comparing the fatigue crack propagation behaviors of reinforced and unreinforced single phase bone cements revealed that the reinforcing mechanisms of MWNTs are strongly dependent on stress intensity factor, K, a numerical parameter that accounts for the combinatorial effect of the applied load and the crack size. As the crack grows the apparent stress at the crack tip intensified and the MWNTs lost their reinforcing capabilities. For that reason, it is likely that the predominant role of the MWNTs is to reinforce the bone cement matrix prior to crack initiation and during the early stages of crack propagation. Therefore, MWNTs are an excellent candidate for improving the clinical performance of bone cement, thereby improving implant longevity and reducing patient risk and healthcare costs.

A promising approach investigated here is to utilize thin film multilayer structures where the thickness of a catalyst layer at an exposed edge of photolithographically defined pattern determines the diameter of the nanotubes/nanowires grown from it. This can in turn be incorporated into photolithographically defined post structures resulting in an array of suspended nanowires for line-of-site shadow lithography. Success of the diameter control approach has been shown by selectively growing carbon nanotubes (CNTs) from narrow lines (12-60 nm) of SiO2, Fe, Ni, Co on micron-scale patterned substrates in a ferrocene or nonferrocene catalyzed CVD process. In addition, the concept has been extended to VS growth of CuO nanowires and VLS growth of ZnO nanowires from an exposed edge in a Al2O3/Cu(40-100 nm)/Al2O3 and Al2O3/Au(10 nm)/Al2O3 thin film multilayer structures. The exposed middle layer of patterned thin-film multilayer acts as a nm-scale wide selective growth area. The resultant CNT/nanowire diameter is directly related to the catalyst/catalyst support size. Growth kinetic studies of CuO nanowires from a thin film multilayer structure indicate diffusion controlled process. Dispersion of CNTs between lithographically defined trenches of width of 200 nm and depth of 500 nm when coupled with line-of-site deposition resulted in nm-scale line underneath the suspended CNT. The width of the resulting shadow is nearly a simple function of CNT/nanowire diameter, incident evaporation angle, and height of CNT above the substrate in a line-of-site evaporation geometry. Another promising approach to control the placement of nanotubes/nanowires is the selective functionalization of only their tips followed by selfassembly onto chemically patterned substrates. Towards this goal, arrays of aligned CNTs were impregnated with polystyrene to form aligned CNT membranes. These CNT membranes were also studied for gas and ionic transport studies. Different functionalization chemistry was performed on each side of the membrane. After dissolution of polymer matrix, a suspension of CNTs with different functionality at each tip was formed, allowing for sophisticated selfassembled architectures.

Nitrogen oxides (NOx) are atmospheric pollutants that pose a serious threat to both the environment and human health. Although catalytic deNOx technologies for engines working under stoichiometric air-to-fuel ratios (i.e., most gasoline engines) are already available, their performance is unsatisfactory under excess air conditions like those under which diesel engines operate. The selective catalytic reduction of NOx with hydrocarbon reductants (HC-SCR) is a potential deNOxsolution for diesel engines, whose operating temperatures are 150-500 ºC. Given that is unlikely for a single catalyst to show acceptable activity throughout this entire temperature span, the use of two catalysts is proposed in this dissertation. Whereas several catalysts active at high temperatures (>300 ºC) are already available, a catalyst showing an acceptable performance at low temperatures (<300 ºC) is yet to be found. Platinum group metals (PGMs) supported on activated carbon have been identified as promising low temperature HC-SCR catalysts. However, these materials show three main drawbacks: 1) the propensity of the carbon support to undergo combustion in an oxidizing environment, 2) a narrow temperature window of operation; and 3) a high selectivity towards N2O (as opposed to N2). To address the first limitation, the use of multi-walled carbon nanotubes (MWCNTs) as the support has been investigated and found to yield catalysts displaying a higher resistance to oxidation. Further, the acid activation of MWCNTs prior to their use as catalyst support has been explored, following reports than link carrier acidity with improved catalyst performance. In turn, the use of PGM alloys as the active phase has been examined as a means to improve catalyst activity and selectivity. Additionally, kinetic, spectroscopic and mechanistic studies have been performed in an attempt to probe structure-activity relationships in the MWCNTs-based formulations showing the best deNOx performance. The fundamental insights gained through these studies may inform further improvements to HC-SCR catalysts. Finally, the synthesis of the most promising formulations has been scaled-up using commercial metal monoliths as the catalyst substrate and the resulting monolithic catalysts have been tested in a diesel engine for activity in the HC-SCR reaction.

Non-oxidative dehydrogenation of hydrocarbons is an attractive alternative route for the production of CO- and CO2-free hydrogen. It will satisfy a major requirement for successful utilization of polymer electrolyte membrane (PEM) fuel cells (< 10 ppm CO) and sequestering carbon as a potentially valuable by-product, carbon nanotubes (CNTs). Due to the deposition of carbon on the surface of catalyst particles during the reaction, catalyst performance, life-time, and purification of the generated carbon product, are significant issues to solve in order to make the process practically feasible. The scope of this thesis includes: the development of novel Fe, Ni, and Fe-Ni catalysts supported on a Mg(Al)O support to achieve improved catalytic performance with easily-purified CNTs; evaluation of catalysts for ethane/methane dehydrogenation at moderate reaction temperatures; and study of activation and deactivation mechanisms by a variety of characterization techniques including TEM, HRTEM, XRD, Mössbauer spectroscopy, and x-ray absorption fine structure (XAFS) spectroscopy. The Mg(Al)O support was prepared by calcination of synthetic MgAl-hydrotalcite with a Mg to Al ratio of 5. The catalysts were prepared either by conventional incipient wetness method or by a novel nanoparticle impregnation method, where the monodisperse catalyst nanoparticles were prepared in advance by thermal decomposition of a metal-organic complex in an organic-phase solution and then dispersed onto the Mg(Al)O support. Dehydrogenation of undiluted methane was conducted in a fix-bed plug-flow reactor. Before reaction, the catalysts were activated by reduction in hydrogen. Fe-based catalysts exhibit a higher hydrogen yield at temperature above 600ºC compared with monometallic Ni catalyst. FeNi-9 nm/Mg(Al)O, Fe-10 nm/Mg(Al)O and Fe-5 nm/ Mg(Al)O nanoparticle catalysts show much improved performance and longer life-times compared with the corresponding FeNi IW/Mg(Al)O and Fe IW/Mg(Al)O catalysts prepared by incipient wetness. 10 nm is the optimum particle size for methane dehydrogenation. Addition of Ni to Fe forming a bimetallic FeNi alloy catalyst enhances the catalytic performance at the temperatures below 650ºC. Metallic Fe, Ni, FeNi alloy and Fe-Ni-C alloy, unstable iron carbide are all catalytically active components. Catalysts deactivation is due to the carbon encapsulation. The carbon products are in the form of stack-cone CNTs (SCNTs) and multi-walled CNTs (MWNTs), depending on the reaction temperature and catalyst composition. The growth of CNTs follows a tip growth mechanism and the purity of cleaned CNTs is more than 99.5%.

The discovery of carbon nanotubes by Iijima in 1991 has created a torrent of new research activities. Research on carbon nanotubes ranges from studying their fundamental properties, such as their electron band structure and plasma frequencies, to developing new applications, such as self-assembled nano-circuits and field emission displays. Robust models are now needed to enable a better understanding of the electronic response of carbon nanotubes. We use time-dependent density functional theory to derive a two-fluid two-dimensional (2D) hydrodynamic model describing the collective response of a multiwalled carbon nanotube with dielectric media embedded inside or surrounding the nanotube. We study plasmon hybridization of the nanotube system in the UV range, the stopping force for ion channelling, the dynamical image potential for fast ions, channelled diclusters and point dipoles, and the energy loss for ions with oblique trajectories. Comparisons are made of results obtained from the 2D hydrodynamic model with those obtained from an extension of the 3D Kitagawa model to cylindrical geometries.

Graphene has recently become the focus of enormous attention for experimentalists and theorists alike mainly due to its unique electronic properties. However, the limited way in which one can control these properties is a major obstacle for device applications. The unifying theme of this thesis is to propose and thoroughly justify ways to control the electronic properties of graphene and carbon nanotubes by light or static electric and magnetic fields and to harness these properties for optoelectronic applications. A linearly polarized excitation is shown to create a strongly anisotropic distribution of photoexcited carriers in graphene, where the momenta of photoexcited carriers are aligned preferentially normal to the polarization plane. This effect offers an experimental tool to generate highly directional photoexcited carriers which could assist in the investigation of "direction-dependent phenomena" in graphene-based nanostructures. The depolarization of hot photoluminescence is used to study relaxation processes in graphene, both free standing and grown on silicon carbide. This analysis is extended to include the effect of a magnetic field, thereby allowing one to obtain the momentum relaxation times of hot electrons. The analysis of momentum alignment in the high frequency regime shows that a linearly polarized excitation allows the spatial separation of carriers belonging to different valleys. Quasi-metallic carbon nanotubes are considered for terahertz applications. They are shown to emit terahertz radiation when a potential difference is applied across their ends and their spontaneous emission spectra have a universal frequency and bias voltage dependence. It is shown that the same intrinsic curvature which opens the gap in the quasi-metallic carbon nanotube energy spectrum also allows optical transitions in the terahertz range. The exciton binding energy in narrow-gap carbon nanotubes is calculated and found to scale with the band gap and vanishes as the gap decreases, even in the case of strong electron-hole attraction. Therefore, excitonic effects should not dominate in narrow-gap nanotubes. Contrary to widespread belief, it is shown that full confinement is possible for zero-energy states in pristine graphene. The exact analytical solutions for the zero-energy modes confined within a smooth one-dimensional potential V = α/ cosh (βx) are presented. This potential provides a good fit for the potential profiles of top-gated graphene structures. It is shown that there is a threshold value of the characteristic potential strength α/β for which the first mode appears, in striking contrast to the non-relativistic case. A relationship between the characteristic strength and the number of modes within the potential is found. An experimental setup is proposed for the observation of these modes. The proposed geometry could be utilized in future graphene-based devices with high on/off current ratios.

A resonant cavity operating in TE011 mode was used to study the adsorption response of single walled carbon nanotubes (SWCNTs) and other nanomaterials for different types of gas molecules. The range of the frequency signal as a probe was chosen as geometry dependent range between 9.1 -9.8 GHz. A highly specific range can be studied for further experiments dependent on the type of molecule being investigated. It was found that for different pressures of gases and for different types of nanomaterials, there was a different response in the shifts of the probe signal for each cycle of gassing and degassing of the cavity. This dissertation suggests that microwave spectroscopy of a complex medium of gases and carbon nanotubes can be used as a highly sensitive technique to determine the complex dielectric response of different polar as well as non-polar gases when subjected to intense electromagnetic fields within the cavity. Also, as part of the experimental work, a range of other micro-porous materials was tested using the residual gas analysis (RGA) technique to determine their intrinsic absorption/adsorption characteristics when under an ultra-high vacuum environment. The scientific results obtained from this investigation, led to the development of a chemical biological sensor prototype. The method proposed is to develop operational sensors to detect toxin gases for homeland security applications and also develop sniffers to detect toxin drugs for law enforcement agency personnel.

<p>Carbon nanotubes (CNTs) have recently emerged as promising candidates for electron field emission (FE) cathodes in integrated FE devices. These nanostructured carbon materials possess exceptional properties and their synthesis can be thoroughly controlled. Their integration into advanced electronic devices, including not only FE cathodes, but sensors, energy storage devices, and circuit components, has seen rapid growth in recent years. The results of the studies presented here demonstrate that the CNT field emitter is an excellent candidate for next generation vacuum microelectronics and related electron emission devices in several advanced applications.</p><p> The work presented in this study addresses determining factors that currently confine the performance and application of CNT-FE devices. Characterization studies and improvements to the FE properties of CNTs, along with Micro-Electro-Mechanical Systems (MEMS) design and fabrication, were utilized in achieving these goals. Important performance limiting parameters, including emitter lifetime and failure from poor substrate adhesion, are examined. The compatibility and integration of CNT emitters with the governing MEMS substrate (i.e., polycrystalline silicon), and its impact on these performance limiting parameters, are reported. CNT growth mechanisms and kinetics were investigated and compared to silicon (100) to improve the design of CNT emitter integrated MEMS based electronic devices, specifically in vacuum microelectronic device (VMD) applications.</p><p> Improved growth allowed for design and development of novel cold-cathode FE devices utilizing CNT field emitters. A chemical ionization (CI) source based on a CNT-FE electron source was developed and evaluated in a commercial desktop mass spectrometer for explosives trace detection. This work demonstrated the first reported use of a CNT-based ion source capable of collecting CI mass spectra. The CNT-FE source demonstrated low power requirements, pulsing capabilities, and average lifetimes of over 320 hours when operated in constant emission mode under elevated pressures, without sacrificing performance. Additionally, a novel packaged ion source for miniature mass spectrometer applications using CNT emitters, a MEMS based Nier-type geometry, and a Low Temperature Cofired Ceramic (LTCC) 3D scaffold with integrated ion optics were developed and characterized. While previous research has shown other devices capable of collecting ion currents on chip, this LTCC packaged MEMS micro-ion source demonstrated improvements in energy and angular dispersion as well as the ability to direct the ions out of the packaged source and towards a mass analyzer. Simulations and experimental design, fabrication, and characterization were used to make these improvements.</p><p> Finally, novel CNT-FE devices were developed to investigate their potential to perform as active circuit elements in VMD circuits. Difficulty integrating devices at micron-scales has hindered the use of vacuum electronic devices in integrated circuits, despite the unique advantages they offer in select applications. Using a combination of particle trajectory simulation and experimental characterization, device performance in an integrated platform was investigated. Solutions to the difficulties in operating multiple devices in close proximity and enhancing electron transmission (i.e., reducing grid loss) are explored in detail. A systematic and iterative process was used to develop isolation structures that reduced crosstalk between neighboring devices from 15% on average, to nearly zero. Innovative geometries and a new operational mode reduced grid loss by nearly threefold, thereby improving transmission of the emitted cathode current to the anode from 25% in initial designs to 70% on average. These performance enhancements are important enablers for larger scale integration and for the realization of complex vacuum microelectronic circuits.</p> / Dissertation