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Chandrasekaran, Shankar. « Surface micromachined hollow metallic microneedles ». Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/15505.
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Abboud, Jaafar Hadi. « Laser surface alloying of titanium by metallic and non-metallic additions ». Thesis, Imperial College London, 1990. http://hdl.handle.net/10044/1/47732.
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Wong, Hoi-man, et 黃凱文. « Surface modification of biodegradable metallic material ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41290689.
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Wong, Hoi-man. « Surface modification of biodegradable metallic material ». Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B41290689.
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Chen, Zhuo. « Grating coupled surface plasmons in metallic structures ». Thesis, University of Exeter, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441770.
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Iyer, Srinivasan. « Effects of surface plasmons in subwavelength metallic structures ». Doctoral thesis, KTH, Optik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103613.
Texte intégralRésumé :
The study of optical phenomena related to the strong electromagnetic response of noble metals (silver (Ag) and gold (Au) being most popular) over the last couple of decades has led to the emergence of a fast growing research area called plasmonics named after 'surface plasmons' which are electron density waves that propagate along the interface of a metal and a dielectric medium. Surface plasmons are formed by the coupling of light to the electrons on the metal surface subject to the fulfillment of certain physical conditions and they are bound to the metal surface. Depending on whether the metallic medium is a continuous film or a structure having dimensions less than or comparable to the wavelength of the exciting light, propagating or localized surface plasmons can be excited. The structure can be either a hole or an arbitrary pattern in a metal film, or a metallic particle. An array of subwavelength structures can behave as an effective homogeneous medium to incident light and this is the basis of a new class of media known as metamaterials. Metallic metamaterials enable one to engineer the electromagnetic response to incident light and provide unconventional optical properties like negative refractive index as one prominent example. Metamaterials exhibiting negative index (also called negative index materials (NIMs)) open the door for super resolution imaging and development of invisibility cloaks. However, the only problem affecting the utilization of plasmonic media to their fullest potential is the intrinsic loss of the metal, and it becomes a major issue especially at visible-near infrared (NIR) frequencies. The frequency of the surface plasmon is the same as that of the exciting light but its wavelength could be as short as that of X-rays. This property allows light of a given optical frequency to be conned into very small volumes via subwave lengthmetallic structures, that can be used to develop ecient sensors, solar cells, antennas and ultrasensitive molecular detectors to name a few applications. Also, interaction of surface plasmons excited in two or more metallic subwavelength structures in close proximity inuences the far-eld optical properties of the overall coupled system. Some eects of plasmonic interaction in certain coupled particles include polarization conversion, optical activity and transmission spectra mimicking electromagnetically-induced transparency (EIT) as observed in gas based atomicsy stems. In this thesis, we mainly focus on the optical properties of square arrays of certain plasmonic structures popularly researched in the last decade. The structures considered are as follows: (1) subwavelength holes of a composite hole-shape providing superior near-eld enhancement such as two intersecting circles (called' double hole') in an optically thick Au/Ag lm, (2) double layer shnets, (3) subwavelength U-shaped particles and (4) rectangular bars. The entire work is based on electromagnetic simulations using time and frequency domain methods. Au/Ag lms with periodic subwavelength holes provide extraordinarily high transmission of light at certain wavelengths much larger than the dimension of the perforations or holes. The spectral positions of the maxima depend on the shape of the hole and the intra-hole medium, thereby making such lms function as a refractive index sensor in the transmission mode. The sensing performance of the double-hole geometry is analyzed in detail and compared to rectangular holes. Fishnet metamaterials are highly preferred when it comes to constructing a NIM at optical frequencies. A shnet design that theoretically oers a negative refractive index with least losses at telecommunication wavelengths (1.4 1.5 microns) is presented. U-shaped subwavelength metallic particles, in particular single-slit split-ring resonators (SSRRs), provide a large negative response to the magnetic eld of light at a specic resonance frequency. The spectral positions of the structural resonances of the U-shaped particle can be found from its array far field transmission spectrum at normal incidence. An effort is made to clarify our understanding of these resonances with the help of localized surface plasmon modes excited in the overall particle. From an application point of view, it is found that a planar square array of SSRRs eectively functions as an optical half-wave waveplate at the main resonance frequency by creating a polarization in transmission that is orthogonal to that of incident light. A similar waveplate eect can be obtained purely by exploiting the near-eld interaction of dierently oriented neighbouring SSRRs. The physical reasons behind polarization conversion in dierent SSRR-array systems are discussed. A rectangular metallic bar having its dipolar resonance in the visible-NIR is called a nanoantenna, owing to its physical length in the order of nanometers. The excitation of localized surface plasmons, metal dispersion and the geometry of the rectangular nanoantenna make an analytical estimation of the physical length of the antenna from the desired dipolar resonance dicult. A practical map of simulated resonance values corresponding to a variation in geometrical parameters of Au bar is presented. A square array of a coupled plasmonic system comprising of three nanoantennas provides a net transmission response that mimicks the EIT effect. The high transmission spectral window possesses a peculiar dispersion profile that enables light with frequencies in that region to be slowed down. Two popular designs of such plasmonic EIT systems are numerically characterized and compared.QC 20121017
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Dorcéna, Cassandre Jenny. « Effects of Metallic Nanoalloys on Dye Fluorescence ». Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/35057.
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Metallic nanoparticles (NPs) are exploited for their ability to interact with organic
compounds and to increase significantly the fluorescence intensity and the photostability
of many fluorescent dye molecules. Metal enhanced fluorescence (MEF) is therefore
widely investigated for biosensing applications. When used in immunoassays, silver
island films (SIFs) could augment the fluorescence intensity of fluorescein by a factor of
seventeen; SIFs were also able to double or triple the emission intensity of cyanine dyes
which are commonly used in (deoxyribonucleic acid) DNA microarrays. The emission
intensity of indocyanine green â widely used as a contrast agent in medical imaging â
was about twenty times higher in the proximity of SIFs.
This enhancement phenomenon - due to the surface plasmon polaritons associated
with the metallic NPs â can be explained by energy transfer from the metal NPs to the
fluorescent dye molecules or by a modified local electromagnetic field experienced by
the fluorophores in the vicinity of metal surfaces.
Our research focused on the optical characterization of colloidal gold-silver alloy
NPs containing different ratios of gold and silver (Au1.00-Ag0.00, Au0.75-Ag0.25, Au0.50-
Ag0.50, and Au0.25-Ag0.75), as well as their interaction with three fluorophores: rose
bengal, rhodamine B, and fluorescein sodium. Depending upon the dye quantum yield
and its concentration in solution, enhancement or quenching of fluorescence was
obtained. Thus, a three to five times increase in fluorescence intensity was observed in a
2.0 mM solution of rose bengal with all nanoalloys, a slight enhancement of fluorescence
(1.2 â 1.6 times) was noticed in a 0.13 mM solution of rhodamine B with all four types of
NPs, and fluorescence quenching occurred in all the fluorescein-NP solutions regardless
of the dye concentration.Master of Science
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Samuel, Sonia Banerjee Rajarshi. « Surface engineering and characterization of laser deposited metallic biomaterials ». [Denton, Tex.] : University of North Texas, 2007. http://digital.library.unt.edu/permalink/meta-dc-3618.
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Leung, Kit-ying, et 梁潔瑩. « Anti-bacteria plasma-treated metallic surface for orthopaedics use ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41633994.
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Samuel, Sonia. « Surface Engineering and Characterization of Laser Deposited Metallic Biomaterials ». Thesis, University of North Texas, 2007. https://digital.library.unt.edu/ark:/67531/metadc3618/.
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Novel net shaping technique Laser Engineered Net shaping (LENS) laser based manufacturing solution (Sandia Corp., Albuquerque, NM); Laser can be used to deposit orthopedic implant alloys. Ti-35Nb-7Zr-5Ta (TNZT) alloy system was deposited using LENS. The corrosion resistance being an important prerequisite was tested electrochemically and was found that the LENS deposited TNZT was better than conventionally used Ti-6Al-4V in 0.1N HCl and a simulated body solution. A detailed analysis of the corrosion product exhibited the presence of complex oxides which are responsible for the excellent corrosion resistance. In addition, the in vitro tests done on LENS deposited TNZT showed that they have excellent biocompatibility. In order to improve the wear resistance of the TNZT system boride reinforcements were carried out in the matrix using LENS processing. The tribological response of the metal matrix composites was studied under different conditions and compared with Ti-6Al-4V. Usage of Si3N4 balls as a counterpart in the wear studies showed that there is boride pullout resulting in third body abrasive wear with higher coefficient of friction (COF). Using 440C stainless steel balls drastically improved the COF of as deposited TNZT+2B and seemed to eliminate the effect of “three body abrasive wear,” and also exhibited superior wear resistance than Ti-6Al-4V.
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Leung, Kit-ying. « Anti-bacteria plasma-treated metallic surface for orthopaedics use ». Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B41633994.
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Mousselli, Jad. « On surface electropolishing for the development of metallic stents ». Master's thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/36574.
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Les maladies cardiovasculaires sont responsables d'environ le tiers de tous les cas de décès au Canada. L'une des solutions utilisées pour résoudre ce problème consiste à utiliser un dispositif métallique constitué d'un maillage ayant une forme d’un filet et appelé stent. Les stents sont de petits dispositifs implantés dans des vaisseaux sanguins rétrécis pour rétablir la circulation sanguine et éviter une crise cardiaque ou un accident vasculaire cérébral et pour traiter les anévrismes du cerveau. Un contrôle précis de la surface de ces stents est nécessaire pour assurer la compatibilité de l'alliage choisi avec le milieu biologique dont il va être en contact avec. Les stents métalliques doivent satisfaire à des conditions précises définies en fonction de leur application finale. Ils doivent respecter des exigences strictes en termes de propriétés mécaniques, d'interaction électrochimique (corrosion) et de cytocompatibilité. Les alliages suivants sont traditionnellement utilisés dans les applications biomédicales et plus précisément pour les applications cardiovasculaires: l'alliage AISI316L est considéré comme une référence dans ce domaine, mais l'alliage L605, un alliage à base de Cobalt, prend de plus en plus d'importance grâce à ses propriétés mécaniques élevées (haute ductilité et haute résistance à la traction) et résistance élevée à la corrosion. L'utilisation d'alliages de titane est la nouvelle frontière pour les biomatériaux dans les applications cardiovasculaires, il est considéré comme un nouveau candidat potentiel pour les stents cardiovasculaires. Les alliages de titane présentent une combinaison unique de haute résistance et de grande ductilité (résistance à la traction et déformation uniforme supérieures à 1000 MPa et 30% respectivement). L’électropolissage est une étape de prétraitement appliquée à ces alliages métalliques pour obtenir des surfaces chimiquement homogènes, recouvertes d'une couche d'oxyde uniforme et amorphe, généralement de rugosité très lisse. Ce processus permet non seulement de contrôler les propriétés physiques de la surface, mais également celles chimiques. Le processus d'électropolissage comporte certaines variables, telles que le courant, la tension, la solution électrolytique et la température de l'électrolyte. En les contrôlant, il est possible de comprendre et d'améliorer les propriétés de la surface. Le but de ce projet est d’étudier les effets des différents variables d’électropolissage (courant, tension, solution électrolytique) sur les caractéristiques / propriétés de surface (morphologie, composition chimique et mouillabilité) des alliages utilisés pour la fabrication de stents.Cardiovascular diseases (CVD) are responsible for about one-third of all death cases in Canada. One of the solutions used to solve this problem is using a metallic device made of a mesh and called a stent. Stents are small devices that are implanted in narrowed blood vessels to restore blood flow and to avoid a heart attack or stroke and to treat brain aneurysms. An accurate surface control is needed to assure the cytocompatibility of the chosen alloy with its biologic environment. Metallic stents must satisfy precise conditions defined according to their final application. They need to respect strict requirements, in terms of mechanical properties, electrochemical interaction (corrosion) and cytocompatibility. The following alloys are traditionally used in biomedical applications and more precisely for cardiovascular applications: the alloy AISI316L is considered a reference in this field, but the alloy L605, a Co-based material, is gaining more and more importance, due to its high mechanical properties (high ductility and high ultimate tensile strength) and high corrosion resistance. The use of Titanium alloys is the new frontier for biomaterials in cardiovascular applications, it is considered as a new potential candidate for cardiovascular stents. Titanium alloys, shows a unique combination of high strength and high ductility (ultimate tensile strength and uniform deformation higher than 1000 MPa and 30%, respectively). Electropolishing is a pre-treatment step applied to these alloys to obtain chemically homogeneous surfaces, covered with a uniform and amorphous oxide layer, generally with a very smooth roughness. This process not only makes it possible to control the physical properties of the surface, but also the chemical ones. The electropolishing process has some changeable variables, such as current, voltage, electrolytic solution and temperature of electrolyte. By controlling them, it is possible to understand and improve the surface properties. This work is aimed at studying the effects of electropolishing changeable variables (current, voltage, electrolytic solution) on surface characteristics/properties (morphology, chemical composition and wettability) of those alloys used for the manufacture of stents.
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Watts, Richard Adrian. « The optical response of metallic diffraction gratings ». Thesis, University of Exeter, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361343.
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Craib, Glenn R. G. « Thin film structural determination and surface analysis ». Thesis, University of Aberdeen, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320771.
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A combined approach to the use of surface analysis techniques and X-ray diffraction has been introduced. In particular the development of the microstructure of UHV evaporated thin metallic films has been investigated with a view to clarifying influences on microstructure (particularly texture). This study has shown the wide range of experimental parameters which affect the final film structure, such as temperature, oblique incidence and substrate roughness. An automated energy dispersive X-ray diffractometer has been developed for the study of thin film texture. The required corrections for loss of intensity due to sample positioning have been developed and verified. Pole figures have been collected for erbium and nickel thin films (thickness 200-1200 nm) grown on molybdenum or glass substrates. Results for the erbium films show a substantial effect on the texture of the film, contributed by the temperature of the substrate during deposition. The texture varies from mixed fiber at low temperature, to a strong single fiber orientation at around 663 K, to mixed fiber at higher temperatures. The strong orientation at 663 K has been shown to vary from either (002) to (101) depending on as yet unknown experimental conditions. The effect of substrate roughness appears to be only in the degree of orientation and it does not affect the overall nature of the texture of the film. The texture of the nickel films shows a form of "granular epitaxy" at substrate temperatures above 300 K. The presence of tensile stress within one of these nickel thin film samples has been determined and is interpreted to give support to a proposed mode of granular epitaxy.
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Pike-Wilson, Emily Alexandra. « Flow boiling of R245fa in vertical small metallic tubes ». Thesis, Brunel University, 2014. http://bura.brunel.ac.uk/handle/2438/10625.
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The research presented is part of a larger study, dedicated to investigating flow boiling in small to microchannels. The test facility, originally designed by Huo (2005) and since used by Chen (2006) and Mahmoud (2011), has been used to investigate flow boiling of R134a across a range of channel diameters and both seamless cold drawn and welded channels. These previous studies concluded that one of the reasons for discrepancies in reported data is the result of surface characteristics. The objective of this current study is to further investigate the effect of channel characteristics and changing the refrigerant to R245fa. Surface characteristics are investigated with stainless steel, copper and brass channels, all seamless cold drawn and 1.1 mm internal diameter. Experiments using R245fa were initially conducted in the same stainless steel channel used with R134a by Mahmoud (2011). This allowed for the surface characteristics to be negated and the comparison to be based purely on the changes in the thermophysical properties between R134a and R245fa. Experiments were conducted at inlet pressures of 1.85 and 2.45 bar, mass fluxes of 100 – 400 kg/m2s, heat fluxes from 1 – 60 kW/m2 and vapour qualities from 0 – 0.95. The test section surfaces were evaluated based on scanning electron microscopy (SEM) and confocal laser microscopy (CFLSM). SEM allowed for a visual inspection of the channel surface, with clear differences in the surface stricter evident. The surfaces were then compared based on two CFLSM profilers. The values of the surface parameters differed between the two profilers but the same trend was seen, brass being the roughest surface and copper the smoothest. Changes in the surface parameter values were found to be a function of the scan area, scan resolution and cut-off value. A borosilicate glass tube, at the test section exit, allowed for flow visualisation. Mahmoud (2011) reported bubbly, slug, churn and annular flow for R134a, with no effect of hysteresis. Churn and annular flow were present for R245fa with an increasing heat flux. This was a result of a higher surface tension for R245fa which facilitates annular flow. Hysteresis was evident for R245fa, with bubbly, slug, churn and annular flow seen with a decreasing heat flux. The hysteresis effect is a result of nucleation sites activating during the increase in heat flux and remaining activated as the heat flux is decreased. The activation of nucleation sites depends on the size, which was constant due to the same channel being used, and the wall superheat. The wall superheat is lower for R245fa which does not allow for the nucleation sites to be initially activated with an increasing heat flux. The same effect of hysteresis was evident for copper and brass. Differences in the exit vapour quality and heat flux at which flow patterns occurred were seen between the three materials. The heat transfer coefficient varied in both magnitude and trend between R134a and R245fa. Mahmoud (2011) reported an almost constant heat transfer coefficient with vapour quality at a higher magnitude than seen for R245fa. R245fa showed an increasing trend with vapour quality. Peaks in the heat transfer coefficient were seen to be a result of surface flaw, evident when plotting as a function of the axial location. The test section was reversed in orientation, moving the location of the peak from near the entry of the test section to near the exit. A similar heat transfer coefficient peak was seen at the same axial location, near the exit of the test section, confirming that the peak was a result of a surface flaw and a result of the flow developing. The heat transfer coefficient changed in magnitude and trend for copper and brass. The magnitude of the recorded heat transfer coefficient did not follow the same trend as the surface parameters. The heat transfer correlations in literature did not predict the increase in the heat transfer with vapour quality, performing poorly compared with R134a. The best correlation for the prediction of both refrigerants was that of Mahmoud and Karayiannis I (2012). The pressure drop for R245fa was over 300 % higher than that of R134a, with a steeper increase with heat flux. This is attributed to a higher liquid viscosity and lower vapour density for R245fa. The pressure drop was highest for the roughest channel, brass, but lowest for stainless steel which had the intermediate roughness. The smoothest channel, copper, showed the largest difference in the effect of inlet pressure on the measured pressure drop and the roughest surface, brass, the smallest difference. The effect of surface characteristics on pressure drop is greater than the effect of changes in the fluid properties with inlet pressure. Pressure drop correlations performed poorly for R245fa in comparison with R134a, with the majority under predicting the pressure drop. Only one pressure drop correlation included a function of the surface parameters, Del Col et al. (2013), but this correlation under predicted the effect of the surface parameters on pressure drop. There was no one correlation which gave satisfactory results for all three materials.
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Garnier, Jérôme. « Polymer electrochromism and surface plasmons combined on metallic diffraction gratings ». Thesis, Linköping University, Department of Science and Technology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11522.
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All conducting polymers are potentially electrochromic, owing to the injection of charge carriers that changes their electronic structure and results in a shift of their optical absorption towards higher wavelengths. PEDOT-PSS and PEDOT-S are very promising materials in terms of electrochromic properties, due to the good contrast existing between their doped and undoped forms. However this contrast has to be enhanced in order to design more efficient electrochromic devices, and new solutions should thus be found in order to solve this issue.
Surface plasmons are described as electromagnetic waves propagating along the surface between a dielectric and a metal. Coupled to an incident radiation, they create an energy loss in the light transmitted and reflected by the interface. When the metallic surface is periodically corrugated, this absorption phenomenon due to plasmonic resonance occurs at a specific wavelength that depends on several parameters, such as the incidence angle, the dielectric constants of the two media and the grating period. By coating metallic gratings with electrochromic polymers, we may thus be able to trigger a plasmonic absorption at a given wavelength and shift it upon reduction or oxidation of the material.
Electrochromic devices consisting of PEDOT-PSS or PEDOT-S spin-deposited on gold and silver gratings were investigated by UV-visible reflectance measurements. The periodically corrugated structures were reproduced from commercial gratings by soft nanolithography and were analyzed by AFM. Some electrochromic cells exhibited new colors or a high shift of the plasmonic resonance upon redox switching of the polymer film. Depending on the step and the nature of the grating employed, this shift could reach 20 nm in the case of PEDOT-PSS and more than 100 nm for PEDOT-S. A theoretical model was found to predict the wavelength of plasmonic excitation and the orientation of the shift.
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Walker, Andrew Meredith. « Laser surface alloying of metallic substrates with carbon and silicon ». Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38178.
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Went, Hazel Elizabeth. « Surface plasmon resonances in deep metallic gratings at microwave frequencies ». Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248177.
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Abtahi, Seyyed Mohammad Hossein. « Synthesis and characterization of metallic nanoparticles with photoactivated surface chemistries ». Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/78081.
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During recent decades metallic nanoparticles have been found very interesting due to their unique characteristics which make them suitable for different applications. In this research, for the very first time, we tried to perform selective surface photo activation chemistry on the targeted facets of nanoparticles while they are in suspension. This technique enabled us to form desired assemblies of nanoparticles. We focused on elongated shaped gold nanorod due to its unique surface plasmon resonance and probable biomedical applications. In this research we formed a dumbbell shape assembly of nanoparticles in suspension. A probable application for these assemblies can be in vivo imaging. Initially, we reproduced gold nanorods using existing techniques in prior papers and optimized them according to our research needs. A low rpm centrifugal separation technique was developed to efficiently separate synthesized gold nanorods from other shapes. Several characterization techniques were utilized to characterize nanoparticles at each step including UV-absorbance, zeta potential, and dynamic light scattering. Different generations of oligomers were synthesized to be used as gold nanorods coating, and each coating was tested and characterized using appropriate techniques. Our two-step coating replacement method using one of these photocleavable oligomers enabled us to achieve, for the very first time, selective UV photo activation of gold nanorod tips. The photo activated tips were then exposed to oppositely charged gold nanospheres to form dumbbell shape assemblies of gold nanorods and nanospheres. Furthermore, dumbbell shape assembly of nanoparticles was investigated and characterized.Master of Science
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Hou, Xiaoning. « Surface Topographies and Mechanical Properties of Metallic Biomaterials Processed by Ultrasonic Nanocrystal Surface Modification (UNSM) ». University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555602578757154.
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Kitchens, Christopher Lawrence Roberts Christopher B. « Metallic nanoparticle synthesis within reverse micellar micromulsion systems ». Auburn, Ala., 2004. http://repo.lib.auburn.edu/EtdRoot/2004/FALL/Chemical_Engineering/Dissertation/kitchcl_13_Dissertation(abbrv).pdf.
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Edmunds, James David. « Microwave transmissivity of sub-wavelength metallic structures ». Thesis, University of Exeter, 2011. http://hdl.handle.net/10036/3214.
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The use of patterned metallic surfaces for the control of the transmission of microwave radiation has been reinvigorated in recent years due to the success and interest in metamaterial research. These metallic periodic structures, commonly referred to as frequency selective screens (FSSs), allow responses to be tailored according to the geometry of the metallic structure as opposed to the material composition. A consequence of the presence of a metallic corrugation is the possible excitation of surfaces waves (commonly referred to as surface plasmon polaritons at visible frequencies). Surface waves can be utilised to achieve further control of the transmission properties of a structure. In this thesis several highly original metallic structures are investigated which use FSS and surface wave concepts. These structures exhibit interesting and previously unexplained transmission behaviour. The experimental chapters within this thesis are divided into two areas. The first three experimental chapters (4-6) present original investigations into the excitation of diffractively coupled surface waves on metallic hole/patch arrays and their role in the enhanced transmission/reflection of microwave radiation. The importance of metallic connectivity within arrays is highlighted through measurements of the metallic filling fraction dependence on the transmission properties of regular periodic and random arrays. The last two experimental chapters (7-8) contain investigations into the transmission properties of two novel resonant cavities. The structure studied in chapter 7 provides a mechanism for remarkably enhanced microwave transmission on resonance through an otherwise opaque continuous thin metal film. The second resonant cavity structure in chapter 8 uses a resonant array of metallic crosses to form a ‘resonant mirror’ Fabry-Perot cavity. These resonant FSSs exhibit a frequency dependent transmission/reflection and phase response thus producing an interesting series of modes which have very different properties to those supported by a non-resonant mirror etalon.
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Ayyagari, Venkata A. « Surface Degradation Behavior of Bulk Metallic Glasses and High Entropy Alloys ». Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1062863/.
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In this study, the surface degradation behavior was studied for typical examples from bulk metallic glasses (BMGs), metallic glass composites (MGCs) and high entropy alloys (HEAs) alloy systems that are of scientific and commercial interest. The corrosion and wear behavior of two Zr-based bulk metallic glasses, Zr41.2Cu12.5Ni10Ti13.8Be22.5 and Zr57Cu15.4Ni12.6Al10Nb5, were evaluated in as-cast and thermally relaxed states. Significant improvement in corrosion rate, wear behavior, and friction coefficient was seen for both the alloys after thermal relaxation. Fully amorphous structure was retained with thermal relaxation below the glass transition temperature. This improvement in surface properties was explained by annihilation of free volume, the atomic scale defects in amorphous metals resulting from kinetic freezing. Recently developed MGCs, with in situ crystalline ductile phase, demonstrate a combination of mechanical properties and fracture behavior unseen in known structural metals. The composites showed higher wear rates but lower coefficient of friction compared to monolithic amorphous glasses. No tribolayer formation was seen for the composites in sharp contrast to that of the monolithic metallic glasses. Corrosion was evaluated by open circuit potential (OCP) analysis and potentiodynamic polarization. Site-specific corrosion behavior was studied by scanning vibration electrode technique (SVET) to identify formation of galvanic couples. Scanning kelvin probe microscope was used to map elecropositivity difference between the phases and linked to wear/corrosion behavior. Phases with higher elecropositivity were more susceptible to surface degradation. Wear and corrosion synergy in marine environment was evaluated for two high entropy alloys (HEAs), CoCrFeMnNi and Al0.1CoCrFeNi. Between the two alloys, Al0.1CoCrFeNi showed better wear resistance compared to CoCrFeMnNi in dry and marine conditions due to quicker passivation, a higher magnitude of polarization resistance and significantly larger pitting resistance.
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Williams, Shaun Michael. « Characteristics and applications of the infrared enhanced transmission of metallic subwavelength arrays ». Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1147279544.
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Venkata, Pradeep Kumar Garudadri. « SURFACE WAVE SCATTERING FROM METALLIC NANO PARTICLES : THEORETICAL FRAMEWORK AND NUMERICAL ANALYSIS ». Lexington, Ky. : [University of Kentucky Libraries], 2006. http://lib.uky.edu/ETD/ukymeen2006t00408/Thesis%5FPGV%5FFinal%5Fn.pdf.
Texte intégralRésumé :
Thesis (M.S.)--University of Kentucky, 2006.Title from document title page (viewed on June 1, 2006). Document formatted into pages; contains ix, 94 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 91-93).
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Viik, Rickard. « Surface layer formation on the surfaces of metallic lithium, copper and iron ». Thesis, Uppsala universitet, Molekyl- och kondenserade materiens fysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-257571.
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Ryu, Jae-Joong. « Surface damage of metallic implants due to mechanical loading and chemical reactions ». [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3355528.
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To, Theany. « Fracture toughness and fracture surface energy of inorganic and non-metallic glasses ». Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S013/document.
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La ténacité et l’énergie de surface de fracture de verres, de vitrocéramiques et de composites à matrice en verre ont été étudiées. Tout d'abord, un test de flexion bi-axiale (configuration anneau/anneau) a été réalisé sur des verres de silice et des verre-à-vitres avec différentes conditions de surface afin d’identifier la relation entre le défaut de surface, la résistance et la ténacité du verre. Ensuite, trois méthodes d’expérimentation ont été mises en œuvre, principalement la méthode de poutre de flexion à pré-entaille droit (SEPB), la méthode de la poutre entaillée en chevron (CNB) et la méthode de la poutre avec indentations Vickers (VIF), afin de déterminer la ténacité de quatre verres produits industriellement et de déterminer les avantages et les inconvénients des différents méthodes sélectionnées. La méthode qui est apparue la plus fiable et auto-cohérente, la méthode SEPB (Single Edge Precrack Beam), a été appliquée à la détermination de la ténacité de nombreux verres et vitrocéramiques, afin d’étudier l’influence de la composition et de la microstructure sur les caractéristiques de fissuration (KIC et énergie de fissuration, γ). Enfin, l’influence de la température et de l'environnement sur la ténacité a été étudiée à l'aide de la méthode SEPB. Deux verres d'oxyde ont été testés à des températures élevées et avec une vitesse de charge de 10 MPa∙√m/s, une température de transition de 1,11Tg a été trouvée. Quatre autres verres d'oxyde ont été testés en environnement inerte et les mêmes valeurs de ténacité ont été obtenues à partir de deux vitesses de charge (100 fois) différentesFracture toughness and fracture surface energy of commercial and laboratory glasses, glass-ceramics and glass matrix composites have been studied. First, bi-axial bending test (RoR configuration) was performed on fused silica and window float glasses with different surface conditions to identify the relationship between the surface flaw, the strength and fracture toughness. After, three experiment methods, mainly single-edge precracked beam (SEPB), chevron-notched beam (CNB) and Vickers indentation fracture (VIF) were performed to determine the fracture toughness of four commercial known glasses and to determine the advantages and inconveniences of the different selected methods. The method that is appeared as the most reliable and self-consistent, the SEPB (Single Edge Precrack Beam) method, was applied to determine the toughness of the large amount of glasses and glass-ceramics, to study the influence of the composition and the microstructure on the characteristics of cracking (KIC and fracture energy, γ). Last but not least, the influence of the temperature and environment on the fracture toughness was studied by means of the SEPB method. Two oxide glasses were tested in elevated temperatures and with the loading rate of 10 MPa∙√m/s, a transition temperature of 1.11Tg was found. Four other oxide glasses were tested in the inert environment and the same fracture toughness values were obtained from (100 times) two different cross-head speeds
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Ropers, Claus. « Femtosecond excitations in metallic nanostructures ». Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15664.
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Diese Arbeit leistet einen Beitrag zum Verständnis optischer Anregungen in metallischen Nanostrukturen. Am Beispiel ausgewählter Strukturen werden experimentell die Dynamik dieser Anregungen mit Femtosekunden-Zeitauflösung und ihre elektromagnetischen Moden auf der Nanometer-Längenskala untersucht. Anhand winkel- und zeitaufgelöster Transmissionsexperimente an metallischen Dünnfilmgittern wird gezeigt, dass resonante Oberflächenplasmon-Polaritonen (OPPen) wesentlich die optischen Eigenschaften dieser Strukturen beeinflussen. Die Lebensdauer solcher Anregungen wird ermittelt und damit nachgewiesen, dass Kopplungen zwischen OPP-Resonanzen drastische Lebensdauer-Modifikationen zur Folge haben. In einem eigens konstruierten, spektral auflösenden optischen Nahfeldmikroskop werden die elektromagnetischen Feldverteilungen der OPPen direkt abgebildet. Derartige Experimente erlauben erstmals eine Zuordnung der räumlichen Moden zur zeitlichen Dynamik verschiedener OPP-Resonanzen. Diese Erkenntnisse ermöglichen zudem eine Interpretation des nahfeldmikroskopischen Bildkontrasts bezüglich der Beiträge verschiedener vektorieller Komponenten des optischen Nahfeldes. Die selektive Abbildung unterschiedlicher elektrischer und magnetischer Feldkomponenten in Abhängigkeit vom Sondentyp wird demonstriert. Darüberhinaus wird die OPP-Erzeugung in einem Gitter auf dem Schaft einer Nahfeldspitze ausgenutzt, um propagierende OPPen im Apex zu konzentrieren. Ein weiterer Teil der Arbeit nutzt elektrische Feldüberhöhungen an scharfen Metallspitzen für die lokalisierte Erzeugung nichtlinearer optischer Signale. Die Beobachtung intensiver Multiphoton-Elektronenemission nach Femtosekundenanregung stellt ein zentrales Ergebnis dar. Dieser Prozess wird umfangreich charakterisiert und findet seine erste Anwendung in einer neuartigen Rastersondentechnik, in der die örtlich variierende Elektronenemission der Bildgebung dient.This thesis contributes to the understanding of optical excitations in metallic nanostructures. In experiments on selected model structures, the dynamics of these excitations and their electromagnetic spatial modes are investigated with femtosecond temporal and nanometer spatial resolution, respectively. Angle- and time-resolved transmission experiments on metallic thin film gratings demonstrate the dominant role resonant surface plasmon polaritons (SPPs) play in the optical properties of such structures. The lifetimes of these excitations are determined, and it is shown that coherent couplings among SPP-resonances result in drastic lifetime modifications. The spatial SPP mode profiles are imaged using a custom-built near-field optical microscope. The experiments reveal a direct correlation between the spatial mode structure and the dynamics of different SPP resonances. These findings allow for an interpretation of the near-field optical image contrast in terms of the contributions of different vectorial components of the electromagnetic near-field. A selective imaging of different electric and magnetic field components is demonstrated for various types of near-field probes. Furthermore, the excitation of SPPs in periodic structures is employed in a novel type of near-field tip. The resonant excitation of SPPs in a nanofabricated grating on the shaft of a sharp metallic tip results in their concentration at the tip apex. The final part of the thesis highlights the importance of optical field enhancements for the local generation of nonlinear optical signals at the apex of sharp metallic tips. Specifically, the observation of intense multiphoton electron emission after femtosecond excitation is a major result. This process is thoroughly characterized, and a novel scanning microscopy application based on this effect is presented. In this technique, an image contrast with nanometer resolution arises from spatially varying electron emission rates.
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Starr, David E. « Microcalorimetric heats of adsorption, surface residence times and sticking probabilities of metals on metal-oxide, and silicon substrates / ». Thesis, Connect to this title online ; UW restricted, 2001. http://hdl.handle.net/1773/8492.
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Yin, Liang. « Reactive wetting and spreading in binary metallic systems ». Diss., Online access via UMI:, 2005.
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Comite, Valeria. « Studio dei processi di degrado naturale e simulato in rocce carbonatiche ». Doctoral thesis, Università di Catania, 2014. http://hdl.handle.net/10761/1568.
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Il presente lavoro di tesi è volto allo studio dei prodotti di degrado che si sviluppano su materiali lapidei di natura carbonatica a causa di diversi fattori ambientali. Il lavoro è stato sviluppato su due distinti filoni di ricerca: a) un primo filone incentrato sulla caratterizzazione mineralogico-petrografica e geochimica di croste nere prelevate dalle superfici di monumenti; b) un secondo filone riguardante, invece, lo studio sperimentale di alcuni provini di marmo e calcareniti esposti in ambiente outdoor.
La prima linea di ricerca ha riguardato la caratterizzazione di 23 campioni di crosta nera prelevati da 8 rilevanti monumenti Europei, mediante l utilizzo di un approccio multianalitico utile a valutare l interazione tra il substrato e l ambiente. Tale approccio ha riguardato lo studio dei caratteri composizionali e microtessiturali delle croste e lo stato di conservazione dei substrati lapidei, nonché l interazione di questi ultimi con le soprastanti croste. In generale, i risultati acquisiti da questo primo filone di ricerca hanno dimostrato come la variabilità osservata dai dati ottenuti su ciascun campione di crosta possa essere giustificata dal processo stesso che porta alla formazione delle croste nere, un fenomeno complesso e dinamico che è certamente influenzato nel tempo dalle diverse fonti d inquinamento (fisse o mobili) oltre che da numerosi fattori quali: altezza di campionamento, tipologia di substrato, morfologia delle superfici di deposito del particolato, esposizione agli agenti atmosferici, alle fonti di inquinamento, al wash-out e alla deposizione di aerosol atmosferico. Inoltre, la possibilità di poter analizzare la composizione geochimica, in termini di elementi in tracce, delle croste nere e dei substrati alterati, può fornire risposte utili per comprendere l influenza degli inquinanti nella genesi di queste forme di degrado.
La seconda linea di ricerca ha riguardato uno studio sperimentale finalizzato al monitoraggio del processo di degrado cui sono sottoposti nel tempo i materiali lapidei di natura carbonatica posti in opera. La sperimentazione condotta ha previsto l esposizione di provini di marmo di Carrara, pietra di Noto e pietra di Comiso (sia tal quali che trattati con un materiale nano-strutturato) in due diversi ambienti outdoor, ubicati in due importanti città siciliane, Catania e Palermo. Il tempo di permanenza dei provini in ambiente outdoor e di relativo monitoraggio è stato di due anni. Sia nella fase pre-espositiva che in quella post-espositiva, la caratterizzazione è avvenuta mediante l utilizzo di diverse metodologie analitiche, al fine di ottenere informazioni circa le eventuali modificazioni fisiche, chimiche e mineralogiche subite dai provini dopo esposizione prolungata.
I dati ottenuti hanno permesso di identificare le principali cause di annerimento e soiling di materiali a composizione carbonatica nei due centri di Catania e Palermo. Inoltre, le prove condotte sui provini trattati con biossido di titanio hanno evidenziato che l applicazione dei formulati deve essere testata prima del suo utilizzo sulle superfici dei monumenti d interesse storico-artistico, allo scopo di evitare interventi di restauro errati e/o privi di efficacia. Il lavoro sviluppato in questi due anni di monitoraggio contribuisce indubbiamente alla messa a punto di una metodologia finalizzata alla valutazione della durabilità di diversi litotipi nei confronti dell inquinamento (sorgenti di combustione mobili e fisse) e dell efficacia del prodotto autopulente preso in considerazione.
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Khullar, Piyush. « Development and Implementation of Novel Bristle Tool for Surface Treatment of Metallic Components ». [Milwaukee, Wis.] : e-Publications@Marquette, 2009. http://epublications.marquette.edu/theses_open/10.
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Darugar, Qusai A. « Surface effects on the ultrafast electronic relaxation of some semiconductor and metallic nanoparticles ». Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-06272006-160645/.
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Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007.Zhang, John, Committee Member ; Wang, Zhong, Committee Member ; El-Sayed, Mostafa, Committee Chair ; Orlando, Thomas, Committee Member ; Lyon, Andrew, Committee Member.
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Egbujor, Grace. « Surface Microstructure Evolution of Metallic Specimens Using the Large Chamber Scanning Electron Microscope ». TopSCHOLAR®, 2015. http://digitalcommons.wku.edu/theses/1473.
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An initial study into the use of the large chamber scanning electron microscope (LCSEM) to interrogate the surface microstructure evolution of metallic specimens has been carried out. The LC-SEM located at Western Kentucky University is the largest instrument of its type at any university in the world. As such, unique measurements can be performed due to the size of its chamber and extended view of its optic system. Strain was varied for each individual specimen, and imaged using Secondary Electrons within the gauge length as well as near the grip position. Results will show progression of surface microstructures and nickel content of metallic specimens. Additionally, results will demonstrate the capability of the LC-SEM to carry out these types of measurements. Future measurements will include the incorporation of an in-situ uniaxial load frame for dynamic studies.
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Taylor, John Abner. « Effects of a Surface Engineered Metallic Coating on Elastomeric Valve Stem Seal Leakage ». Thesis, University of North Texas, 2000. https://digital.library.unt.edu/ark:/67531/metadc2690/.
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Valve stem seal leakage is a major source of fugitive emissions, and controlling these emissions can result in added expense in leak detection and repair programs. Elastomeric O-rings can be used as valve stem seals, and O-ring manufacturers recommend lubrication of elastomeric seals to prevent damage and to assure proper sealing. In this research, a metallic coating was applied as a lubricant using a vacuum vapor deposition process to the surface of elastomeric valve stem seals. Valve stem leak measurements were taken to determine if the coated O-rings, alone or with the recommended lubrication, reduced valve stem seal leakage. This research determined that the metallic coating did not reduce valve stem leakage.
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Samarjy, Ramiz Saeed Matti. « Interaction mechanisms for a laser-induced metallic boiling front ». Doctoral thesis, Luleå tekniska universitet, Produkt- och produktionsutveckling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-65281.
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This thesis is about fundamental interaction mechanisms of laser remote fusion cutting, RFC, which is based on the formation of a quasi-stationary laser-induced boiling front that causes drop ejection, preferably downwards. Laser cutting of metals, invented in 1967, has developed from a niche to a well established high quality cutting technique in the manufacturing industry. Usually a gas jet is employed concentric to the laser beam, to eject the molten metal. One technique option, interesting though hardly applied yet because of usually low quality and speed, is remote laser cutting. Two techniques are distinguished, remote ablation cutting, grooving down through a sheet, layer-by-layer, and the here addressed remote fusion cutting, by a single pass through the sheet. For the latter, the ablation pressure from laser-induced boiling at the cutting front continuously accelerates and ejects the melt downwards. Advantages of remote laser cutting, facilitated by high brilliance lasers during the last decade, are the possibility of a larger working distance along with the avoidance of cutting gas and of a gas jet nozzle. The review paper of the thesis surveys different laser remote cutting techniques, including their modelling, as well as the transition to keyhole welding, owing to similarities particularly from the boiling front and from root spatter ejection. The six Papers I-VI that compose the thesis address fundamental mechanisms of laser remote fusion cutting, theoretically and experimentally. In Paper I a simplified mathematical model of the RFC cutting front enables to estimate the geometrical and energetic conditions of the process. By evidence and post-modelling from high speed imaging, HSI, the simplified smooth cutting front model is developed further to a wavy topology in Paper III, for more sophisticated absorption analysis. As a systematic support, Paper II categorizes and analyses for the first time the different wavy topologies observed at the front, from HSI. The melt dynamics induced by a pulsed laser beam was studied in Paper IV, again from HSI. Apart from other interesting transient melt phenomena it was demonstrated that the ablation pressure can push the melt to a certain pending position during the laser pulse while the melt retreats by surface tension during the pulse break. To engage remote fusion cutting with additive manufacturing, Paper V introduces a novel technique where the drops ejected from RFC are transferred to a substrate, about a centimetre underneath, on which a continuous track forms. This technique can even be applied as an efficient recycling approach. In Paper VI a variant of the technique is presented, to develop a boiling front along the edge of a metal sheet from which the drop transfer takes place, in a different manner. This enables to systematically machine-off the entire sheet, which can be converted to a new shape and product. Summarizing, the thesis provides a variety of analysis of fundamental mechanisms of a laser-induced boiling front that bear a certain simplicity and in turn controllability, of interest for established as well as for new applications, in manufacturing and in other sectors, including remote fusion cutting.
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Tang, Feng. « Micro SERS sensors based on photonic-plasmonic circuits and metallic nanoparticles ». Thesis, Troyes, 2017. http://www.theses.fr/2017TROY0020/document.
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La spectroscopie Raman exaltée de surface (SERS) est largement utilisée comme un outil non-intrusif et sans marquage pour identifier les empreintes spectrales moléculaires dans des applications comme la pharmacologie, la salubrité des aliments, etc. Cette thèse présente un micro-capteur SERS basé sur un guide d'ondes hybride constitué de fentes métalliques (Au/Al) et de rubans diélectriques (Si3N4) et sur une méthode pour promouvoir la capacité de détection SERS en plaçant des nanoparticules métalliques dans la fente du capteur. L'étude théorique du capteur est principalement menée par la méthode des différences finies dans le domaine temps en trois dimensions (3D-FDTD) qui fournit la réponse électromagnétique à large bande des nanostructures métalliques. Les facteurs d'exaltation du capteur sont estimés par l’approximation |E|4. Les expériences sont basées principalement sur la fabrication de fentes métalliques, qui est réalisée par la lithographie à faisceau d'électrons (EBL), et sur la caractérisation de la capacité de détection SERS des capteurs. Les résultats montrent que les signaux Raman donnés par les capteurs SERS sont détectables. Les nanoparticules métalliques, qui sont situées dans le capteur, peuvent améliorer considérablement la capacité de détection SERS. En combinant le capteur SERS avec les éléments photoniques et électroniques, un système de détection SERS entièrement intégré sur une puce peut être développé dans un proche avenir pour des détections SERS portables et stablesSurface-enhanced Raman spectroscopy (SERS) is widely used as a non-intrusive and label-free tool to identify the molecular spectral fingerprints in pharmacology, biology, etc. This thesis presents a SERS sensor based on the hybrid waveguide made of metallic (Au/Al) slots and dielectric (Si3N4) strips and a method to improve the SERS-detection capacity by placing metallic nanoparticles into the sensor’s slot. The theoretical investigation of the sensor is mainly conducted by the 3D finite-difference time-domain method (3D-FDTD) which provides the broadband electromagnetic response of metallic nanostructures. The enhancement factors in the sensor’s slot are estimated based on the |E|4-approximation. The experiments are mainly the fabrication of metallic slots, which is conducted by the electron beam lithography (EBL), and the characterization of the SERS-detection capacity of the sensors. The results show that the Raman signals given out by the SERS sensors are detectable. Metallic nanoparticles, which are located in the sensor’s slot, can improve dramatically the SERS-detection capacity. By combining the SERS sensor with the extended photonic and electronic elements, a fully integrated-on-chip SERS detection system on a chip can be developed in the near future for portable and stable SERS detections
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Steinsiek, Christoph. « Molecular Beam Scattering from Ultrathin Metallic Films ». Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://hdl.handle.net/11858/00-1735-0000-0023-3EB8-2.
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Chalastaras, Athanasios. « Giant magnetoresistance in magnetic multilayers using a new embossed surface ». ScholarWorks@UNO, 2004. http://louisdl.louislibraries.org/u?/NOD,137.
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Thesis (M.S.)--University of New Orleans, 2004.Title from electronic submission form. "A thesis ... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Physics."--Thesis t.p. Vita. Includes bibliographical references.
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Hervier, Paul. « Fonctionnalisation de surface de verres métalliques base Zirconium ». Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAI088/document.
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Les verres métalliques sont des matériaux récents. Développés depuis les années 60, ils sont connus pour leur haute résistance mécanique et leur capacité à devenir visqueux à relativement basse température. La fonctionnalisation de leur surface est un moyen prometteur d’amélioration et d’optimisation de leurs propriétés. Cependant, la structure amorphe de ces matériaux est métastable et un maintien à une température trop élevée conduit systématiquement à la cristallisation du matériau et donc à une perte de ces propriétés uniques. La plupart des techniques de traitement de surface étant réalisées à hautes températures, elles ne sont pas adaptées à ce type de matériaux. Dans ce travail, deux techniques innovantes que sont le thermoformage et le traitement laser à impulsion ultra-courtes sont utilisées, permettant une texturation de la surface des verres métalliques tout en évitant la cristallisation. Cette thèse porte donc sur l’effet de ces deux traitements de surfaces sur les propriétés physico-chimiques de verres métalliques base zirconium et donc sur la modification de leur propriétés de surface telles que la mouillabilité ou la résistance à la corrosion. Nous verrons que ces deux techniques présentent chacune leur avantages et peuvent être particulièrement adaptées dans le cadre d’applications biomédicalesMetallic glasses are recent materials. First developed in the 60s, they are well-known for their high mechanical resistance and their ability to become viscous at relatively low temperatures. Functionalization of their surfaces is a promising way to further increase their properties. However, their amorphous structure is in a metastable state and maintaining them at too high temperatures leads systematically to their crystallization, and thus the loss of their unique properties. Most of surface treatment techniques are performed at high temperatures and thus are not adapted to these materials. In this work, two innovative techniques which are thermoforming and ultra-short pulse duration laser treatment have been used and allow to texture the surfaces of the alloys by avoiding their crystallization. This thesis is focused on the effect of these two processing techniques on physical and chemical properties of Zr-based bulk metallic glasses and thus on the modification of their surface properties such as wettability or corrosion resistance. We will see that both techniques present their advantages and can be particularly adapted for biomedical applications
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Altzar, Oskar. « Surface Characteristics and Their Impact on Press Joint Strength ». Thesis, KTH, Mekanisk metallografi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-205919.
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Press fitting is a commonly used method in the assembly of shafts and gearwheels in gearboxes andare using the friction created between them to hold them together. To increase productivity Scania CVAB in Södertälje, Sweden, are going to replace the current hard machining method for layshafts. Whiletesting the new methods in rig it occurred that the gearwheel slipped in tangential direction towardsthe layshaft at a lower torque then with the current method even through all requirements on thelayshafts surface was meet. The purpose and aim with this study is to investigate differences betweenthe methods and to find new requirements for the layshaft. The torque of slip, (Ms) established in atorque test rig and analysis of surface roughness, hardness and microstructure conducted of both thelayshafts and gearwheels. The characteristics of the layshaft surface was also analysed and comparedbetween the different hard machining methods. The study concludes that no correlation between thesurface parameters and the Ms occurred and no major differences in the material between themethods. The study also concluded that the Ms between the layshaft and gearwheel is lower if thelayshaft surface is harder and smoother than the gearwheel surface.
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Humphrey, Alastair Dalziell. « Exploration of how light interacts with arrays of plasmonic, metallic nanoparticles ». Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/19365.
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The content of this thesis is based upon the interaction of light with metallic nanoparticles arranged in different array geometries. An incident electric field (light) can force the conduction electrons of a metallic nanoparticle to oscillate. At particular frequencies, in the optical regime for gold and silver particles, absorption and scattering of the light by the particle is enhanced, corresponding to the particle plasmon resonance. The spectral position and width of the particle plasmon resonance of an isolated single particle may be tuned by adjusting its size and shape, thus changing the surface charge distribution. Periodic arrays of particles offer additional control over the frequency and width of the resonance attributed to the re-radiating (scattering) property of plasmonic particles. By fabricating arrays with a pitch comparable to the wavelength of an isolated single particle plasmon resonance, a coherent interaction between particles may be produced, known as surface lattice resonances (SLRs). The electromagnetic coupling between in-plane particle plasmon modes for different particle array geometries is explored through experiment and theory. Firstly, SLRs in square, hexagonal and honeycomb arrays are investigated by normal-incidence extinction measurements and compared to a simple-coupled dipole model. Secondly, to verify the nature of the coupling between the scattered electric field associated with particle resonances, the incident electric field polarization-dependence of the extinction of rectangular arrays and chains is studied. Thirdly, the optical response of square arrays with a symmetric two-particle basis is investigated, particularly the retardation of the scattered electric field between particles in a pair. Fourthly, square arrays with an asymmetric two-particle basis are fabricated to explore the symmetric (dipole moments of both particles are parallel) and anti-symmetric (dipole moment of both particles anti-parallel) SLRs, excited by normal-incidence light.
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Smith, Randall William. « Investigations of the Air-Water Interface : A Structural Analysis of Metallic Surface Films and Aquatic Surface Films by Comparative Microscopy ». PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2306.
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The air-water interface is an important natural boundary layer that has been neglected as an area of environmental field research. This study establishes that comparative microscopy can be an effective environmental method, and establishes that the term metallic surface films, is a more accurate descriptor than iron oxide surface films. This research shows that surface films are complex, often with layered structure, serve as habitat for significant biota, and act as a point of mineralization to several transition metal elements including manganese, iron, copper, nickel and zinc. This study demonstrates that surface films form under several conditions and can have diverse morphology. Activity of biota, microbes, particularly diatoms, suggests that bacteria and cyanobacteria integrate into the film often in patches, represented by forms and casts. Analytical imaging is used to document and compare film morphology and structures, using scanning electron microscopy, photoemission electron microscopy and transmission electron microscopy with elemental analysis by energy dispersive spectroscopy to confirm the hypothesis. Instrument parameters and strengths are reviewed. Component layers of a copper/zinc film were used to confirm metallic layers and elemental distribution. Bacterial casts were used to confirm film interaction, and to show entrainment and enrichment of the film to incorporate autochthonous and allochthonous materials into the films themselves. Most samples were from Oregon selected sites, with some samples from Maryland and Barbados.
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Drisko, Glenna L. « Template synthesis and surface modification of metal oxides / ». Connect to thesis, 2010. http://repository.unimelb.edu.au/10187/7090.
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Bergström, David. « The absorptance of metallic alloys to Nd:YAG and Nd:YLF laser light ». Licentiate thesis, Luleå tekniska universitet, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18217.
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In Laser Material Processing of metals, an understanding of the fundamental absorption mechanisms plays a vital role in determining the optimum processing parameters and conditions. The absorptance, which is the fraction of the incident laser light which is absorbed, depends on a number of different parameters. These include laser parameters such as intensity, wavelength, polarisation and angle of incidence and material properties such as composition, temperature, surface roughness, oxide layers and contamination. The vast theoretical and experimental knowledge of the absorptance of pure elements with smooth, contamination-free surfaces contrasts with the relatively sparse information on the engineering materials found in real processing applications. In this thesis a thorough investigation of the absorption mechanisms in engineering grade materials has been started. The Licentiate thesis consists of 5 papers. Paper 1 is a short review of some of the most important mathematical models used in describing the interaction between laser light and a metal. Paper 2 is a review of a few experimental methods of measuring the absorptance of an opaque solid such as a metal. Papers 3 and 4 are experimental investigations of the absorptance of some of the most frequently found metallic alloys used in Laser Material Processing today. Paper 5 is a co-authored paper on the cleaning of copper artefacts with the use of second harmonic generated Nd:YAG laser light.Godkänd; 2005; 20061213 (haneit)
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Fostner, Shawn. « Ultra high vacuum fabrication of metallic contacts for molecular devices on an insulating surface ». Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=95011.
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The preparation and characterization of metallic wires on insulating substrates by a variety of mechanisms has been explored. A multi-scale approach utilizing microfabricated silicon stencil masks, feedback controlled electromigration, and field induced metal cluster deposition in a novel geometry has been explored on potassium bromide (KBr), indium phosphide (InP), and silicon oxide substrates in an ultra-high vacuum environment (UHV). The initial deposition of gold, and tantalum wires between one hundred nanometers and micrometers in size was performed using reinforced silicon nanostencils. The stencil fabrication was discussed, and an examination of the deformation of the integrated structures under the deposition of highly stressed tantalum films was shown to be significantly smaller than typical structures. Metallic wires deposited using these stencils as well as electron beam lithography were electrically stressed and the breaking characteristics analyzed. Typical nanometer scale gaps were observed, as well as larger features more commonly found in the breaking of bamboo-like structures in gold wires 100 nm in size or less, particularly with a significant series resistance. These larger gaps are expected to be more applicable for the deposition of subsequent metallic clusters and preparation of molecular devices. As a step towards connecting the initially deposited wires as well as localized molecules in an a fashion allowing atomic scale imaging by AFM, modelling and experiments of field induced deposition of gold clusters on KBr and InP substrates was carried out. Deposition on InP substrates with a backside 2D electron gas as a counter-electrode demonstrated the feability of this deposition technique in UHV. Subsequent depositions on or adjacent to metallic pads on the bulk insulating KBr provided a proof of principle of the technique, though some experimental limitations such as large current pulses with the tip in close proximity to the surface are dLa préparation et la caractérisation de fils métalliques sur des substrats isolants par une variété de mécanismes a été explorée. Une approche multi-échelle utilisant des masques-stencils microfabriqués de silicium, l'électromigration contrôlée par rétroaction, et le dépôt induit par champ en nouvelle géométrie d'agrégats métalliques, a été explorée sur des substrats de bromure de potassium (KBr), de phosphure d'indium (InP) et d'oxyde de silicium sous Ultra Haut Vide (UHV). Le dépôt initial de fils d'or et de tantale entre cent nanomètres et quelques micromètres a été réalisé en utilisant des nanostencils au silicium renforcé. La fabrication des stencils a été discutée, et un examen de la déformation des structures intégrées dans le cas du dépôt de couches de tantale sous hautes contraintes a montré qu'elle était significativement plus petite que pour les structures typiques. Les fils métalliques déposés à l'aide de ces stencils, ainsi que la lithographie par faisceau électronique ont été mis sous contrainte électriquement et les caractéristiques de rupture analysées. Des vides typiques à l'échelle du nanomètre ont été observés, ainsi que des structures communément retrouvées dans la rupture de structure de type bambou dans les fils d'or de 100nm et moins, en particulier avec une résistance en série importante. Ces vides plus grands devraient être plus applicables pour le dépôt par la suite d'agrégats métalliques et la préparation de dispositifs moléculaires. Une étape a été franchie vers la connexion des fils déposés initialement ainsi que de molécules localisées de façon imageable, en réalisant un modèle et des expériences de dépôt induit par champ d'agrégats d'or sur KBr et InP. Le dépôt sur des substrats InP avec derrière un gaz d'électrons 2D comme contre-électrode a démontré la faisabilité de cette technique de dépôt sous UHV. Des dépôts ultérieurs sur ou
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MATARRESE, CATERINA. « Co-solvents and chelating agents confined in complex fluids for the cleaning of surfaces of works of art ». Doctoral thesis, 2015. http://hdl.handle.net/2158/984618.
Texte intégralRésumé :
In a modern society that is always more and more sensitive to the respect and the preservation of the environment and its living beings, and where the research of sustainable resources and ecological solutions is continuous, also in the field of the Cultural Heritage conservation, in the last decades, the developing of innovative technologies has been inspired by those principles.
It’s in this context that in the laboratories of the chemistry department of the University of Florence and CSGI Consortium, a new family of Highly Viscous Polymeric Dispersions (HVPDs) for the cleaning of artistic, fragile surfaces was formulated and studied. They are 95% aqueous systems obtained from poly(vinyl alcohol) (PVA) or poly(vinyl acetate)s (PVAc) via complexation and crosslinking between the side-chain hydroxyl groups of the polymer and borate ions.
Due to the low toxicity of the formulations these HVPDs are very attractive eco-friendly cleaning tools for the conservation of painted surfaces. They can incorporate a wide range of organic liquids, with particular reference to the less toxic ones, and thank to their high viscosity and thickness, the significant retention of the solvent reduces the potential damages to the original materials of the work of art but also the intoxication risk for the operators and the environmental impact. Their cleaning action is effective, confined to the desired area, controllable and gradual, parameters that are greatly appreciated by restorers.
Their viscoelastic properties ensure a good adhesion onto the surface (even the molded, irregular or vertical ones) and easiness of removal in one piece through lifting with tweezers; thereby, the potential for residues is minimized and the clearance step with neat solvents often is not necessary.
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WEI, HAN-DONG, et 魏漢東. « Surface second-harmonic generation for studying properties of metallic surface ». Thesis, 1989. http://ndltd.ncl.edu.tw/handle/75242261483238514562.
Texte intégral
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Lin, Shih-Ya, et 林詩雅. « Surface Plasmon Polariton on Metallic Micro-ring ». Thesis, 2016. http://ndltd.ncl.edu.tw/handle/31341315288188832327.
Texte intégralRésumé :
碩士國立中央大學
照明與顯示科技研究所
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In this thesis, we study the surface plasmon polariton effect on a metallic micro-ring to generate a nano-magnetic field. The structure consists of a metallic micro-ring and InGaAs pulley-type waveguide on GaAs substrate. COMSOL Multiphysics is used to analyze the device. Positive charges are positioned on the metallic micro-ring. The surface plasmon polariton is induced on the surface of metallic micro-ring by launching the light into the InGaAs waveguide. The propagation of the surface plasmon polariton along the direction of the incident light drives the charge flow to form an electric current on the metallic micro-ring. According to Biot-Savart law, it can form a nano-magnetic field in the center region of the metallic micro-ring.