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Weaver, Cameron L. "Lead silicate solubility and the control of lead contamination in drinking water". Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-07112009-040433/.
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Ozisik, Gulsevim. "Genetical Investigation Of Balya-balikesir Lead-zinc Mineralizations". Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611319/index.pdf.
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This thesis study is concerned with genetical investigation of Balikesir Balya Pb-Zn mineralization through the mineralogic-petrographic and geochemical examination of the core samples obtained from a total of 9 holes drilled by EczacibaSi ESAN Madencilik.
The Pb-Zn mineralization in Balya is mainly of vein-type. Wall rocks hosting mineralizations are dacite, dacite porphyry and microdiorite. Major types of alteration are silicification, carbonatization and calc-silicate alteration, each of which is further subdivided into early and late stages and overprinted by argillic alteration of probable supergene origin. The ore minerals are mainly Zn- and Pb-sulphides and are hosted by the rocks with late calc-silicate alteration that underwent pervasive late silicification and late carbonatization. Sulfide mineralization is spatially and temporally associated with the late silicification and carbonatization stages. Lateral-vertical correlation of drill logs suggest that thickness of the ore zone tends to decrease towards north.
The volcanic rocks hosting the mineralization have calc-alkaline nature. Major, trace and rare earth element (REE) geochemistry suggests either crustal contamination or subduction signature in the mantle source of the volcanics. Multi element patterns and discrimination diagrams collectively point to a post-collisional setting for their generation. Alteration geochemistry reveals that Fe2O3 and CaO are enriched during calc-silicate alteration in contrast to depletion of SiO2. Al2O3 and TiO2 are almost constant during late calc-silicate alteration. Enrichment of Fe2O3 and Na2O, and depletion of K2O characterize the silicified zones. Carbonatization is accompanied by strong enrichment of CaO and depletion of SiO2, Al2O3 and K2O.
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Leong, Julie Yeen Yeen. "Fabrication and applications of lead-silicate glass holey fibre for 1-1.5 microns : nonlinearity and dispersion trade offs". Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/50197/.
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This thesis describes the development of novel microstructured optical fibres (MOFs), namely holey optical fibres (HFs), based on a commercial highly nonlinear non-silica glass: By taking the advantages of the zero dispersion of the HFs at 1 μm and 1.55 μm, the SC studies are carried out using these HFs (WW HFs and SEST HFs). Both of the fibre SC studies combined experimental and numerical results, and the simulations and experiments were in qualitative agreement. We observed a spectrum spanning over 1000nm by using just ~98 pJ energy pulses in a 60cm piece of the WW HF. This demonstrated the advantage of SG-HFs in terms of compact devices and low power requirements.
4
Lintereur, Phillip. "EFFECTS OF SOURCE WATER BLENDING FOLLOWING TREATMENT WITH SODIUM SILICATE AS A CORROSION INHIBITOR ON METAL RELEASE WITHIN A WAT". Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2967.
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A study was conducted to investigate and quantify the effects of corrosion inhibitors on metal release within a pilot distribution system while varying the source water. The pilot distribution system consisted of pre-existing facilities from Taylor et al (2005). Iron, copper, and lead release data were collected during four separate phases of operation. Each phase was characterized by the particular blend ratios used during the study. A blended source water represented a water that had been derived from a consistent proportion of three different source waters. These source waters included (1) surface water treated through enhanced coagulation/sedimentation/filtration, (2) conventionally treated groundwater, and (3) finished surface water treated using reverse osmosis membranes. The corrosion inhibitors used during the study were blended orthophosphate (BOP), orthophosphate (OP), zinc orthophosphate (ZOP), and sodium silicate (Si). This document was intended to cite the findings from the study associated with corrosion treatment using various doses of sodium silicate. The doses were maintained to 3, 6, and 12 mg/L as SiO2 above the blend-dependent background silica concentration. Sources of iron release within the pilot distribution system consisted of, in the following order of entry, (1) lined cast iron, (2) un-lined cast iron, and (3) galvanized steel. Iron release data from these materials was not collected for each individual iron source. Instead, iron release data represented the measurement of iron upon exposure to the pilot distribution system in general. There was little evidence to suggest that iron release was affected by sodium silicate. Statistical modeling of iron release suggested that iron release could be described by the water quality parameters of alkalinity, chlorides, and pH. The R2 statistic implied that the model could account for only 36% of the total variation within the iron release data set (i.e. R2 = 0.36). The model implies that increases in alkalinity and pH would be expected to decrease iron release on average, while an increase in chlorides would increase iron release. The surface composition of cast iron and galvanized steel coupons were analyzed using X-ray photoelectron spectroscopy (XPS). The surface analysis located binding energies consistent with Fe2O3, Fe3O4, and FeOOH for both cast iron and galvanized steel. Elemental scans detected the presence of silicon as amorphous silica; however, there was no significant difference between scans of coupons treated with sodium silicate and coupons simply exposed to the blended source water. The predominant form of zinc found on the galvanized steel coupons was ZnO. Thermodynamic modeling of the galvanized steel system suggested that zinc release was more appropriately described by Zn5(CO3)2(OH)6. The analysis of the copper release data set suggested that treatment with sodium silicate decreased copper release during the study. On average the low, medium, and high doses decreased copper release, when compared to the original blend source water prior to sodium silicate addition, by approximately 20%, 30%, and 50%, respectively. Statistical modeling found that alkalinity, chlorides, pH, and sodium silicate dose were significant variables (R2 = 0.68). The coefficients of the model implied that increases in pH and sodium silicate dose decreased copper release, while increases in alkalinity and chlorides increased copper release. XPS for copper coupons suggested that the scale composition consisted of Cu2O, CuO, and Cu(OH)2 for both the coupons treated with sodium silicate and those exposed to the blended source water. Analysis of the silicon elemental scan detected amorphous silica on 3/5 copper coupons exposed to sodium silicate. Silicon was not detected on any of the 8 control coupons. This suggested that sodium silicate inhibitor varied the surface composition of the copper scale. The XPS results seemed to be validated by the visual differences of the copper coupons exposed to sodium silicate. Copper coupons treated with sodium silicate developed a blue-green scale, while control coupons were reddish-brown. Thermodynamic modeling was unsuccessful in identifying a controlling solid that consisted of a silicate-based cupric solid. Lead release was generally decreased when treated with sodium silicate. Many of the observations were recorded below the detection limit (1 ppb as Pb) of the instrument used to measure the lead concentration of the samples during the study. The frequency of observations below the detection limit tended to increase as the dose of sodium silicate increased. An accurate quantification of the effect of sodium silicate was complicated by the observations recorded below detection limit. If the lead concentration of a sample was below detection limit, then the observation was recorded as 1 ppb. Statistical modeling suggested that temperature, alkalinity, chlorides, pH, and sodium silicate dose were important variables associated with lead release (R2 = 0.60). The exponents of the non-linear model implied that an increase in temperature, alkalinity, and chlorides increased lead release, while an increase in pH and sodium silicate dose were associated with a decrease in lead release. XPS surface characterization of lead coupons indicated the presence of PbO, PbO2, PbCO3, and Pb3(OH)2(CO3)2. XPS also found evidence of silicate scale formation. Thermodynamic modeling did not support the possibility of a silicate-based lead controlling solid. A solubility model assuming Pb3(OH)2(CO3)2 as the controlling solid was used to evaluate lead release data from samples in which lead coupons were incubated for long stagnation times. This thermodynamic model seemed to similarly describe the lead release of samples treated with sodium silicate and samples exposed to the blended source water. The pH of each sample was similar, thus sodium silicate, rather than the corresponding increase in pH, would appear to be responsible if a difference had been observed. During the overall study, the effects of BOP, OP, ZOP, and Si corrosion inhibitors were described by empirical models. Statistically, the model represented the expected value, or mean average, function. If these models are to be used to predict a dose for copper release, then the relationship between the expected value function and the 90th percentile must be approximated. The USEPA Lead and Copper Rule (LCR) regulates total copper release at an action level of 1.3 mg/L. This action level represents a 90th percentile rather than a mean average. Evaluation of the complete copper release data set suggested that the standard deviation was proportional to the mean average of a particular treatment. This relationship was estimated using a linear model. It was found that most of the copper data sub-sets (represented by a given phase, inhibitor, and dose) could be described by a normal distribution. The information obtained from the standard deviation analysis and the normality assumption validated the use of a z-score to relate the empirical models to the estimated 90th percentile observations. Since an analysis of the normality and variance (essentially contains the same information as the standard deviation) are required to assess the assumptions associated with an ANOVA, an ANOVA was performed to directly compare the effects of the inhibitors and corresponding doses. The findings suggested that phosphate-based inhibitors were consistently more effective than sodium silicate when comparing the same treatment levels (i.e. doses). Among the phosphate-based inhibitors, the effectiveness of each respective treatment level was inconsistent (i.e. there was no clear indication that any one phosphate-based inhibitor was more effective than the other). As the doses increased for each inhibitor, the results generally suggested that there was a corresponding tendency for copper release to decrease.Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Electrical Engineering PhD
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Roisine, Gauthier. "Céramiques glaçurées de Bernard Palissy : À la recherche des secrets d'un maître de la Renaissance". Electronic Thesis or Diss., Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEC010.
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Les céramiques glaçurées plombifères transparentes ou opalescentes de Bernard Palissy à la Renaissance constituent aujourd’hui encore des oeuvres techniquement inimitables, tant leurs procédés chimiques et thermiques restent énigmatiques. Ce projet porte sur l’étude de compositions de verres du ternaire SiO2-Al2O3-PbO auxquels Bernard Palissy a ajouté différents agents colorants ou opacifiants. Après une analyse multi-échelle fine de glaçures superficielles d’échantillons archéologiques (composition, propriétés thermomécaniques, micro-inclusions à l’interface glaçures/substrat céramique), on cherchera à les reproduire le plus précisément possible en laboratoire en jouant sur les matières premières, les conditions de traitement thermique et le support céramique. L’impact de la concentration en certains oxydes tels que Al2O3 sur la structure des verres (approche multi-spectroscopique), leur microstructure (nature, distribution des cristaux), leurs caractéristiques physiques (viscosité, coefficient de dilatation, couleur…) et l’interaction avec le substrat seront particulièrement étudiés. L’approche allie l’analyse approfondie d’un corpus archéologique et la reproduction des systèmes chimiques et des procédés thermiques. Elle permettra de connaître les indicateurs pertinents liés aux procédés innovants et aux matières premières qui permirent à Palissy d’obtenir des composites alliant la perfection mécanique (absence de fissuration, cohésion interfaciale remarquable) à celle de l’illusion réaliste. Ils permettront enfin de définir des critères d’authentification de ses oeuvresThe high-lead glazes transparent or opalescent made by Bernard Palissy during the Renaissance still constitute technically inimitable works, so their chemical and thermal processes remain enigmatic. This project involves the study of glass compositions of the ternary SiO2-Al2O3-PbO to which Bernard Palissy added various coloring agents or opacifiers. After a fine multi-scale analysis of superficial glazes of archaeological samples (composition, thermomechanical properties, the interface glazes / ceramic substrate), we will try to reproduce them as accurately as possible in the laboratory by playing on raw materials, heat treatment conditions and ceramic support. The impact of the concentration of certain oxides such as Al2O3 on the glass structure (multi-spectroscopic approach), their microstructure (nature, distribution of crystals), their physical characteristics (viscosity, coefficient of expansion, color ...) and interaction with the substrate will be particularly studied. The approach combines in-depth analysis of an archaeological corpus and the reproduction of chemical systems and thermal processes. It will enable us to know the relevant indicators linked to the innovative processes and raw materials that allowed Palissy to obtain composites combining mechanical perfection (absence of cracking, remarkable interfacial cohesion) with that of realistic illusion. Finally, they will enable us to define criteria for the authentication of his works
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MacNevin, David. "THE EFFECTS OF PHOSPHATE AND SILICATE INHIBITORS ON SURFACE ROUGHNESS AND COPPER RELEASE IN WATER DISTRIBUTION SYSTEMS". Doctoral diss., University of Central Florida, 2008. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3713.
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The effects of corrosion inhibitors on water quality and the distribution system were studied. This dissertation investigates the effect of inhibitors on iron surface roughness, copper surface roughness, and copper release. Corrosion inhibitors included blended poly/ortho phosphate, sodium orthophosphate, zinc orthophosphate, and sodium silicate. These inhibitors were added to a blend of surface water, groundwater, and desalinated brackish water. Surface roughness of galvanized iron, unlined cast iron, lined cast iron, and polyvinyl chloride was measured using pipe coupons exposed for three months. Roughness of each pipe coupon was measured with an optical surface profiler before and after exposure to inhibitors. For most materials, inhibitor did not have a significant effect on surface roughness; instead, the most significant factor determining the final surface roughness was the initial surface roughness. Coupons with low initial surface roughness tended to have an increase in surface roughness during exposure, and vice versa, implying that surface roughness tended to regress towards an average or equilibrium value. For unlined cast iron, increased alkalinity and increased temperature tended to correspond with increases in surface roughness. Unlined cast iron coupons receiving phosphate inhibitors were more likely to have a significant change in surface roughness, suggesting that phosphate inhibitors affect stability of iron pipe scales. Similar roughness data collected with new copper coupons showed that elevated orthophosphate, alkalinity, and temperature were all factors associated with increased copper surface roughness. The greatest increases in surface roughness were observed with copper coupons receiving phosphate inhibitors. Smaller increases were observed with copper coupons receiving silicate inhibitor or no inhibitor. With phosphate inhibitors, elevated temperature and alkalinity were associated with larger increases in surface roughness and blue-green copper (II) scales.. Otherwise a compact, dull red copper (I) scale was observed. These data suggest that phosphate inhibitor addition corresponds with changes in surface morphology, and surface composition, including the oxidation state of copper solids. The effects of corrosion inhibitors on copper surface chemistry and cuprosolvency were investigated. Most copper scales had X-ray photoelectron spectroscopy binding energies consistent with a mixture of Cu2O, CuO, Cu(OH)2, and other copper (II) salts. Orthophosphate and silica were detected on copper surfaces exposed to each inhibitor. All phosphate and silicate inhibitors reduced copper release relative to the no inhibitor treatments, keeping total copper below the 1.3 mg/L MCLG for all water quality blends. All three kinds of phosphate inhibitors, when added at 1 mg/L as P, corresponded with a 60% reduction in copper release relative to the no inhibitor control. On average, this percent reduction was consistent across varying water quality conditions in all four phases. Similarly when silicate inhibitor was added at 6 mg/L as SiO2, this corresponded with a 25-40% reduction in copper release relative to the no inhibitor control. Hence, on average, for the given inhibitors and doses, phosphate inhibitors provided more predictable control of copper release across changing water quality conditions. A plot of cupric ion concentration versus orthophosphate concentration showed a decrease in copper release consistent with mechanistic control by either cupric phosphate solubility or a diffusion limiting phosphate film. Thermodynamic models were developed to identify feasible controlling solids. For the no inhibitor treatment, Cu(OH)2 provided the closest prediction of copper release. With phosphate inhibitors both Cu(OH)2 and Cu(PO4)·2H2O models provided plausible predictions. Similarly, with silicate inhibitor, the Cu(OH)2 and CuSiO3·H2O models provided plausible predictions.Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Environmental Engineering PhD
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Lepe, Jose J. "FINITE ELEMENT MODELING OF ICD LEAD SILICONE SOFT-TIPS". DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/286.
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Although highly underutilized by the medical device industry, Finite Element Analysis (FEA) in the development of new technologies is gaining popularity as regulatory bodies such as the Food and Drug Administration (FDA) begin to require additional proof of safety through scientific methods. Non-linear FEA allows engineers to realistically simulate the mechanical behavior of implants as seen in the in-vitro, or in some cases, the in-vivo configurations. The work presented in this report investigates how computational methods can be used to simulate the interaction of a St. Jude Medical silicone soft-tip as it passes through a Peel-Away Sheath (i.e. introducer). In this analysis the soft-tips were modeled as axisymmetric with hyperelastic material properties assigned to the soft-tips. An Ogden, second order hyperelastic material model was used to describe the non-linear stress-strain behavior of silicone soft-tips. The finite element program, ABAQUS/Standard was used to simulate the soft-tip/introducer interactions. The reaction forces obtained through these simulations represent the force required to push a lead through an introducer, and were then compared to experimental data.
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McNeish, Darlene Ivey. "Electrorheological Properties of Lead Titanate and Zeolite Silicone Oil Suspensions". NCSU, 2004. http://www.lib.ncsu.edu/theses/available/etd-04272004-151239/.
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The purpose of this research has been to prepare and accurately evaluate the dielectric and rheological properties of lead titanate/silicone oil and zeolite/silicone oil suspensions. The dielectric characteristics and rheological changes occurring with the application of electric fields to the suspensions were compared and the lead titanate suspensions were examined for potential use as electrorheological (ER) fluids. A dielectric spectrometer was utilized to quantify the particle/fluid dielectric mismatch of the lead titanate suspensions and the particle/fluid conductivity mismatch of the zeolite suspensions. The rheological properties were examined by conducting a series of systematic analyses without an electric field and then subsequently with the application of dc and ac fields of various frequencies. Optical microscopy of the suspensions without and with an applied electric field has been employed to determine the particle movement and structure within the suspensions. Observations of the lead titanate particles in suspension under an applied electric field elicited the electrophoretic nature of the particles, which moved towards the electrodes instead of forming chains of particles bridging the electrodes. The lead titanate suspensions exhibited either a very small positive ER effect or in some cases a slight negative ER effect, which involves a reduction in the yield stress with applied electric field. This leads us to conclude that the lead titanate/silicone oil suspensions examined in this study are ineffective ER fluid materials. The zeolite/silicone oil suspensions exhibited a positive ER effect.
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Guedes, Victor Hugo de Farias Guedes. "Pulverização foliar de zinco com silício é viável agronomicamente para plantas de sorgo /". Jaboticabal, 2019. http://hdl.handle.net/11449/183157.
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Orientador: Renato de Mello PradoResumo: A pulverização foliar de silício (Si) pode diminuir os efeitos da deficiência de zinco (Zn) nas plantas, pois a adição de Si e de Zn na calda pode aumentar a eficiência da adubação foliar, porém os efeitos em plantas de sorgo ainda não são conhecidos. Assim, objetivou-se avaliar a aplicação foliar de Si na ausência de Zn e com a adição na calda em plantas de sorgo e seus efeitos na nutrição e no desenvolvimento das plantas. O delineamento foi em esquema fatorial 4 x 2, com cinco repetições, tendo quatro concentrações de Zn, na forma de Zn-EDTA: 0; 0,60; 1,20 e 1,80 g L-1 e na ausência e na presença de Si (0,50 g L-1) na calda. Avaliou-se o acúmulo de Zn e Si, eficiência de uso de Zn, extravasamento de eletrólitos celular, teores de clorofila, carotenoides, proteína e a massa seca de parte aérea e de raiz. Nas plantas deficientes em Zn, a pulverização foliar de Si ao aumentar o acúmulo deste elemento na planta diminuiu o extravasamento de eletrólitos celular, aumentou o conteúdo dos pigmentos fotossintéticos e incrementou a produção de massa seca da parte aérea e de raiz. A pulverização foliar de Zn na forma de quelato com adição de Si na calda, em relação a sua ausência, aumentou o acúmulo de Zn na planta, o teor dos pigmentos fotossintetizantes, o teor de proteína e a produção de massa seca de raiz. Conclui-se que a pulverização foliar de Si alivia a deficiência de Zn, e a adição de Si na calda com o Zn é viável agronomicamente para plantas de sorgo.
Abstract: Foliar spraying of silicon (Si) can decrease the effects of zinco (Zn) deficiency on plants. While the addition of Si and Zn in the solution may increase the efficiency of foliar fertilization with this micronutrient, however the effects on sorghum plants are not yet known. The objective of this study was to evaluate the foliar application of Si in the absence of Zn and with the addition of different concentrations of Zn in sorghum plants and their effects on plant nutrition and development. The experiment was carried out in a 4x2 factorial scheme with five replicates having four concentrations of Zn as Zn-EDTA: 0.60, 1.20 and 1.80 g L-1 and in the absence and presence of Si (0.50 g L-1) in solution. Zn and Si accumulation, Zn use efficiency, cellular electrolyte leakage, chlorophyll content, carotenoids, protein content and shoot and root dry mass were evaluated. In the plants deficient in Zn, a foliar spraying of Si increasing the accumulation of this element in the plant, decreased the cellular extravasation and increased the photosynthetic pigments and the dry mass production of shoot and root. Foliar spraying of Zn in the chelate form with addition of Si in relation to its absence increased the accumulation of Zn in the plant, the content of photosynthetic pigments, protein content and root dry mass production. It is concluded that foliar spraying of Si alleviates Zn deficiency and the addition of Si in the solution with Zn is agronomically viable for sorghum plants.
Mestre
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Tchalala, Mohamed Rachid. "Croissance et réactivité du silicène". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112287/document.
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L’objet de cette thèse est l’étude de la croissance de silicène sur des substrats d’argent,ainsi que l’étude de sa réactivité vis-à-vis de l’oxygène. La croissance a été réalisée sous ultra-vide et contrôlée par spectroscopie d’électrons Auger (AES) et par diffraction d’électrons lents (LEED). Les structures obtenues et leurs réactivités à l’oxygène ont été étudiées par microscopie à champ proche (STM et nc-AFM) et par spectroscopie de photoémission résolue en angle (ARPES). Nous avons étudié la structure interne des nano-rubans de silicène auto-assemblés sur un substrat d’Ag(110). Sur Ag(111) nous obtenons un feuillet de silicène qui présente différentes structures en fonction de la température du substrat. L’étude de la réactivité des rubans et des feuillets a montré que le silicène formé sur substrat d’argent est relativement stable vis-à-vis de l’oxygène ce qui ouvre des perspectives de fonctionnalisation du silicène. La dernière partie de cette thèse concerne la synthèse de feuillets de silicium par voie chimique. Nous avons mis au point une nouvelle méthode prometteuse de synthèse chimique qui nous a permis de synthétiser des feuillets de silicium de structure graphitiqueThe objective of this thesis is the study of the growth of silicene on silver substrates as well as its reactivity towards the oxygen. The growth was performed under ultra-high vacuum and controlled by Auger electrons spectroscopy (AES) and low energy electrons diffraction (LEED). The obtained structures and their relativities towards the oxygen were studied by near field microscopy (STM and nc-AFM) and by angle resolved electrons photoemission spectroscopy (ARPES). We have studied the internal structure of the selfassembled silicene nanoribbons on Ag(110) substrate. On Ag(111), we have obtained a silicene sheet presenting different structures versus the temperature of the substrate. The reactivity of silicene nanoribbons and sheets grown on silver show that silicene is relatively stable towards the oxygen which opens a new perspectives of functionalization of the silicene. The last part of this thesis concerns the synthesis of silicone sheets by chemical process. We have develpped a new promising process of chemical synthesis which allowed us to synthesize silicon sheets with graphitic structure
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Allenstein, Frank. "LEED- und AES-Untersuchungen an Silicidschichten". [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10607562.
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Allenstein, Frank. "LEED- und AES-Untersuchungen an Silicidschichten". Master's thesis, Universitätsbibliothek Chemnitz, 2003. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200300575.
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Die Arbeit befasst sich mit dem Wachstum dünner CrSi2-Schichten auf Si(001). Die Schichtherstellung wurde mittels eines template-Verfahrens in einer MBE-Anlage realisiert. Die Charakterisierung der Schichten erfolgte mittels RBS,AES,LEED,REM,TEM,XRD sowie Widerstandsmessungen.
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Zhao, Xueying. "STRETCHABLE AND TRANSPARENT SILICONE/ZINC OXIDE NANOCOMPOSITE FOR ADVANCED LED PACKAGING". Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/52120.
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At present, one of the key challenges in the light-emitting diode (LED) packaging technology is light extraction due to the difference in index of refraction between LED chip and air. Silicone nanocomposites have been extensively researched for applications in LED encapsulant to reduce such difference in refractive index. It is well-known that silicone is desirable for LED encapsulant because of its optical transparency and photothermal resistance. However, not much has been accomplished to leverage the elastic properties of silicone for enabling a stretchable LED encapsulant. In this work, I aim to investigate the stretch ability of silicone/zinc oxide (ZnO) nanocomposites for LED packaging. Wurtzite ZnO nanoparticles were prepared in colloids and subjected to silane treatment. Effects of both ex situ and in situ silane treatment on the final mechanical and optical properties of the silicone/ZnO nanocomposites were examined. Silicone/ZnO nanocomposites exhibit significantly more compliant stress-strain behavior than silicone control. In particular, silicone/silane-treated ZnO nanocomposites show more serrated stress-strain curves. They also embrace higher transmittance than silicone/unmodified ZnO nanocomposites, indicating an improvement in the dispersion of the nanoparticles. It was found that the silicone/5% silane-treated ZnO nanocomposite prepared by an in situ method was able to deform over a range of up to 160%. The film made of this unique silicone/ZnO nanocomposite (~40 microns thick) exhibits transmittance >70% throughout the visible range.
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Bowe, Craig Alcindor Ivan. "Use of silica-supported adsorbents, modified silica gel, modified montmorillonite ksf and magnetite in the remediation of selected heavy metals from aqueous media". [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000625.
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Kvech, Steven Joseph. "Formation of Aluminum Containing Solids in Drinking Water: Influence on Pb/Cu Corrosion, Al Solubility and Enhanced Softening". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33810.
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Aluminum salts are used as the primary coagulants in the majority of United States drinking
water treatment plants. Despite decades of practical experience, there are important knowledge
gaps regarding the effects of residual Al on distribution system materials as well as specific types
of solids formed. The first phase of this work examined the formation of aluminosilicate
deposits in copper and lead pipes using water from Denver, Colorado. It was anticipated was
that these deposits could form barrier films on the pipe, protecting it from corrosion. However,
the deposits had slightly detrimental effects on leaching of metal to water, and higher levels of
aluminosilicates could further worsen corrosion by-product release.
The second phase of work attempted to extend understanding of aluminum solubility controls by
accounting for effects of sulfate and formation of solids other than Al(OH)3 during water
treatment. Sulfate was found to destabilize small Al(OH)3 colloids resulting in agglomeration
into larger flocs from pH 5.0-6.2 . At pH 9.0 and above, Al-Mg, Al-Mg-Si and Al-Si solids were
discovered to control Al solubility, while also having significant impacts on the precipitation of
calcite in the presence of silica and overall softening effectiveness. This could be of
considerable importance to water treatment practice. These solids also had some potential for
removal of arsenic, TOC and boron.Master of Science
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Hedenström, Hanna. "The Set-Up of a Foundation Colorant File for the Purpose of Color-Matching Foundations, With a View to Improving the Current Foundation Color-Matching Process in the Future". Thesis, KTH, Skolan för kemivetenskap (CHE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-40908.
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The process of color-matching any color product is a process that can be quite complicated and requires great skill from a color analyst. As the name suggests color-matching is the process in which the color of a standard is obtained from a sample through careful inspection and precision in order for the colors to match up. It is a process that can vary in length dependent of the amount of pigments used. Foundations are a type of liquid emulsion cosmetic and consist of five main pigments; white (titanium dioxide), red, brown, yellow and black iron oxides. These five pigments can when mixed together result in hundreds of shades. One of the greatest challenges for cosmetics companies is to successfully manufacture these shades often from a benchmark, a desired shade, as well as maintaining this same shade when the batch is scaled up from lab production to factory. Oriflame is a direct-selling cosmetics company in which the Marketing department and Color Cosmetic department work closely in order to produce new products and shades for each catalogue. Liquid foundation shades are decided by the Marketing department and given to the Color Cosmetic department to color-match. Currently the process of color-matching is carried out through the visual assessment by the color analyst. In order to improve the efficiency and lead - time of the current method, Oriflame has drawn inspiration from other sectors dealing with color and taken the decision to color-match with the use of a spectrophotometer coupled with color-appropriate software. The method was divided into four separate processes; confirming a sample method presentation to the spectrophotometer, colorant file set-up & process, color-matching process with the color-appropriate software and color match comparison. The results showed that with an adequate sized colorant file a method for color-matching with a spectrophotometer was established. The lead-time could be decreased by, as much as 66.6 % and providing strong evidence that this is a valuable tool for color analysts working at Oriflame.
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Ferreira, Nuno Miguel Freitas. "Materials and concepts for CO2 lean ironmaking by pyroelectrolysis". Doctoral thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14004.
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Doutoramento em Engenharia FísicaThe main purpose of this PhD thesis was to provide convincing demonstration for a breakthrough concept of pyroelectrolysis at laboratory scale. One attempted to identify fundamental objections and/or the most critical constraints, to propose workable concepts for the overall process and for feasible electrodes, and to establish the main requirements on a clearer basis. The main effort was dedicated to studying suitable anode materials to be developed for large scale industrial units with molten silicate electrolyte. This concept relies on consumable anodes based on iron oxides, and a liquid Fe cathode, separated from the refractory materials by a freeze lining (solid) layer. In addition, one assessed an alternative concept of pyroelectrolysis with electron blocking membranes, and developed a prototype at small laboratory scale. The main composition of the molten electrolyte was based on a magnesium aluminosilicate composition, with minimum liquidus temperature, and with different additions of iron oxide. One studied the dynamics of devitrification of these melts, crystallization of iron oxides or other phases, and Fe2+/Fe3+ redox changes under laser zone melting, at different pulling rates. These studies were intended to provide guidelines for dissolution of raw materials (iron oxides) in the molten electrolyte, to assess compatibility with magnetite based consumable anodes, and to account for thermal gradients or insufficient thermal management in large scale cells. Several laboratory scale prototype cells were used to demonstrate the concept of pyroelectrolysis with electron blocking, and to identify the most critical issues and challenges. Operation with and without electron blocking provided useful information on transport properties of the molten electrolyte (i.e., ionic and electronic conductivities), their expected dependence on anodic and cathodic overpotentials, limitations in faradaic efficiency, and onset of side electrochemical reactions. The concept of consumable anodes was based on magnetite and derived spinel compositions, for their expected redox stability at high temperatures, even under oxidising conditions. Spinel compositions were designed for prospective gains in refractoriness and redox stability in wider ranges of conditions (T, pO2 and anodic overpotentials), without excessive penalty for electrical conductivity, thermomechanical stability or other requirements. Composition changes were also mainly based on components of the molten aluminosilicate melt, to avoid undue contamination and to minimize the dissolution rate of consumable anodes. Additional changes in composition were intended for prospective pyroelectrolysis of Fe alloys, with additions of different elements (Cr, Mn, Ni, Ti).
Esta tese de doutoramento pretendeu demonstrar o conceito de piroeletrólise de ferro à escala laboratorial. Visou-se a deteção de objeções fundamentais e/ou restrições críticas, de modo a propor conceitos exequíveis para o método global e para elétrodos adequados, e identificar mais claramente os principais requisitos. O principal esforço foi dedicado ao estudo de materiais de ânodo adequados para o desenvolvimento de unidades industriais de larga escala, com eletrólito fundido à base de silicatos. O conceito compreende ânodos consumíveis à base de óxidos de ferro e um elétrodo de Fe fundido, com uma camada intermédia de Fe sólido entre o metal fundido e os refratários. Adicionalmente, foi testado um conceito alternativo de piroeletrólise com membrana bloqueadora eletrónica, e foram desenvolvidos protótipos com base neste conceito. O eletrólito fundido baseou-se numa composição de aluminosilicato de magnésio com um mínimo de temperatura liquidus, com diferentes teores de óxido de ferro. Foram realizados estudos de desvitrificação, cristalização de óxidos de ferro ou outras fases e alterações redox da razão Fe2+/Fe3+, recorrendo à fusão de zona por laser, a diferentes velocidades. Estes estudos visaram a obtenção de critérios fundamentais para a dissolução de matériasprimas (óxidos de ferro) no eletrólito fundido, para avaliar a compatibilidade de espinelas à base de magnetite com potenciais ânodos e para prever as implicações de gradientes térmicos e/ou deficiente regulação térmica. Foram preparados e testados diversos protótipos laboratoriais, para demonstrar o conceito de piroeletrólise com bloqueamento eletrónico e para identificar as questões mais críticas e desafios deste conceito. O comportamento destas células em condições de operação com e sem bloqueamento eletrónico originou informações muito pertinentes sobre as propriedades de transporte do eletrólito fundido (i.e., condutividades iónica e eletrónica), a sua variação sob polarização anódica e catódica, as limitações de eficiência faradaica e a ocorrência de reações eletroquímicas parasitas ou secundárias. O conceito de ânodos consumíveis baseou-se em espinelas com composições derivadas da magnetite, em virtude da esperada estabilidade redox a altas temperaturas, mesmo em condições oxidantes. A composição destas espinelas foi ajustada para melhorar a sua refrataridade e a estabilidade em condições redox mais alargadas (T, pO2 e sobretensão anódica), sem excessivo prejuízo para a condutividade elétrica, estabilidade termomecânica e outros requisitos. As alterações de composição dos materiais de ânodo consumíveis também foram determinadas pelos constituintes do eletrólito fundido, de modo a prevenir contaminações inaceitáveis e para minimizar a velocidade de dissolução dos ânodos consumíveis. Outras alterações de composição tiveram o propósito de incluir componentes de aços ou ligas de ferro (Cr, Mn, Ni, Ti).
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Grening, Shawn. "SHEAR STRENGTH AND ARTIFICIAL AGING CHARACTERIZATION FOR SILICONE BONDING OF POLYISOBUTYLENE (PIBS) BLENDS IN RELATION TO THEIR USE AS LEAD INSULATION MATERIAL". DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/169.
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In order to take advantage of the properties of poly(styrene-isobutylene-styrene) PIBS and PIB based blends as lead insulation materials, they must be able to sufficiently bond to the various materials that make up the cardiac device. The bonded PIBS must be able to withstand the mechanical stress and corrosive environment of the human body due to the long term use of these devices. Based on the component requirements of lead insulation, the first objective of this study was to perform an initial screening of multiple PIBS / stainless steel / silicone adhesive combinations. The specific polymers of interest were PIBS, 10%55D polyurethane, 10%75D polyurethane, 10%PP, and a silicone control. Based on the bonding shear strength results of the initial screening, the best performing combinations were artificially aged to simulate their resistance to degradation in vivo. Each combination was subjected to both 3% hydrogen peroxide and Phosphate Buffered Saline solutions for a period of 8 weeks to test for oxidative and hydrolytic stability. Bonding shear strengths for all sample groups were tested at each 2-week period. The 10%55D sample group had the highest mean bonding shear strength at .5602 MPa, but to observe the aging stability of all sample groups, all combinations were used in Phase II. The phosphate buffered saline solution in Phase II caused no significant decrease in bonding shear strength for all sample groups. Alternatively, oxidation caused by the 3% hydrogen peroxide solution did significantly affect the bonding shear strengths of all sample groups (minus the silicone control). Over the 8-week period PIBS degraded 28% and 10%55D and 10%75D decreased 40.0% and 30.8%, respectively. 10%PP degraded 32.0% and the silicone control remained relatively unchanged.
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Hirvonen, Grytzelius Joakim. "Thin Mn silicide and germanide layers studied by photoemission and STM". Doctoral thesis, Karlstads universitet, Avdelningen för fysik och elektroteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-14488.
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The research presented in this thesis concerns experimental studies of thin manganese silicide and germanide layers, grown by solid phase epitaxy on the Si(111)7×7 and the Ge(111)c(2×8) surfaces, respectively. The atomic and electronic structures, as well as growth modes of the epitaxial Mn-Si and Mn-Ge layers, were investigated by low-energy electron diffraction (LEED), angle-resolved photoelectron spectroscopy (ARPES), core-level spectroscopy (CLS), and scanning tunneling microscopy and spectroscopy (STM and STS). The magnetic properties of the Mn-Ge films were investigated by X-ray magnetic circular dichroism (XMCD). The Mn-Si layers, annealed at 400 °C, showed a √3×√3 LEED pattern, consistent with the formation of the stoichiometric monosilicide MnSi. Up to 4 monolayers (ML) of Mn coverage, island formation was observed. For higher Mn coverages, uniform film growth was found. Our results concerning morphology and the atomic and electronic structure of the Mn/Si(111)-√3×√3 surface, are in good agreement with a recent theoretical model for a layered MnSi structure and the √3×√3 surface structure. Similar to the Mn-Si case, the grown Mn-Ge films, annealed at 330 °C and 450 °C, showed a √3×√3 LEED pattern. This indicated the formation of the ordered Mn5Ge3 germanide. A strong tendency to island formation was observed for the Mn5Ge3 films, and a Mn coverage of about 32 ML was needed to obtain a continuous film. Our STM and CLS results are in good agreement with the established model for the bulk Mn5Ge3 germanide, with a surface termination of Mn atoms arranged in a honeycomb pattern. Mn-Ge films grown at a lower annealing temperature, 260 °C, showed a continuous film at lower coverages, with a film structure that is different compared to the structure of the Mn5Ge3 film. XMCD studies showed that the low-temperature films are ferromagnetic for 16 ML Mn coverage and above, with a Curie temperature of ~250 K.
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Vasconcelos, Ana Carolina Pereira de. "Bioestimulantes contendo silício e micronutrientes aplicados via foliar em arroz de sequeiro". Universidade Federal de Uberlândia, 2016. https://repositorio.ufu.br/handle/123456789/17921.
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Conselho Nacional de Desenvolvimento Científico e TecnológicoCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
Fundação de Amparo a Pesquisa do Estado de Minas Gerais
Na agricultura moderna, apesar de serem empregadas as mais modernas tecnologias de cultivo de plantas e apesar dos progressos que têm sido feitos em programas de melhoramento, o máximo potencial das culturas de interesse agronômico está ainda longe de ser plenamente explorado. Assim, os bioestimulantes – uma categoria de produtos relativamente novos de diversas formulações, os quais afetam positivamente processos vitais de uma planta e apresentam grande potencial para uso na agricultura brasileira – podem ser uma alternativa promissora para os orizicultores. O objetivo deste trabalho foi conceituar e discutir o uso de agroquímicos de regulação hormonal e avaliar a influência de duas fontes bioestimulantes de aplicação foliar com Tecnologia AZAL5 (extrato de Ascophyllum nodosum) contendo silicato de potássio e micronutrientes, em aspectos nutricionais e vegetativos, na cultura do arroz de sequeiro. O primeiro capítulo teve a finalidade de, a partir de uma revisão bibliográfica, discutir o uso, os conceitos, os percalços e os benefícios de bioestimulantes, biorreguladores, bioativadores, ácidos húmicos e fúlvicos, bem como extrato de algas na agricultura brasileira. Os capítulos seguintes consistiram de dois experimentos (testes biológicos) em que foram avaliadas as duas fontes bioestimulantes – uma contendo silicato de potássio + molibdênio (Capítulo 2) e outra contendo silicato de potássio + zinco (Capítulo 3) – aplicadas via foliar na cultura do arroz. Os experimentos foram realizados em casa de vegetação, em vasos de 5 kg, com solo classificado como Neossolo Quartzarênico, utilizando-se a cultivar BRS Primavera. O delineamento experimental foi inteiramente casualizado, com quatro repetições, em arranjo 5 x 2. Os tratamentos consistiram de cinco doses (0; 1,50; 3,00; 4,50; 6,00 L ha-1), em dois modos de aplicação (parcelado e não parcelado). Foram avaliados: teores de clorofilas A, B e Total; teores foliares de silício e macro e micronutrientes; massa de matéria seca de raiz e parte aérea. Foram testadas as pressuposições estatísticas dos dados obtidos com os testes de normalidade de Kolmogorov-Smirnov e de homogeneidade das variâncias de Levene, ambos a 0,01 de significância e submetidos à análise de variância pelo teste de Tukey a 0,05 de significância. Os dados significativos para o fator quantitativo (doses) foram submetidos à análise de regressão. A aplicação da fonte bioestimulante contendo silicato de potássio + molibdênio alterou os teores foliares de K, Ca, S, Zn, Cu e a produção de massa de matéria seca de raiz; porém, não houve alteração nos teores foliares de N, P, Mg, Fe, Mn e Si, nos teores das clorofilas A, B e Total aos 55 DAE e na produção de massa de matéria seca da parte aérea em função das diferentes doses da fonte bioestimulante e dos diferentes modos de aplicação. A aplicação da fonte bioestimulante contendo silicato de potássio + zinco alterou os teores foliares de N, Ca, Mg, S, Zn e Cu e a produção de massa de matéria seca de raiz; contudo, não houve alteração nos teores foliares de Si, P, K, Fe e Mn, na produção de massa de matéria seca de parte aérea e nos teores das clorofilas A, B e Total aos 55 DAE em função das diferentes doses da fonte bioestimulante e dos diferentes modos de aplicação.
Despite the use of the most modern technologies of plant cultivation and the progress in breeding programs, the full potential of crops of agronomic interest is still far from being fully exploited. Biostimulants, a relatively new product category of various formulations, positively affect vital processes of plants and have shown great potential for use in the Brazilian agriculture, especially in the rice agriculture. The aim of this study is to discuss the use of hormonal regulation agrochemicals and assess the agronomic and nutritional efficiency of the foliar application of two biostimulants based on AZAL5 Technology (extract of Ascophyllum nodosum) containing potassium silicate and micronutrients. Chapter 1 draws on a review of the literature to discuss uses, concepts, benefits of and obstacles to biostimulants, bioregulators, bio-activators, humic and fulvic acids, as well as seaweed extract in the Brazilian agriculture. The following chapters report on two experiments (biological testing) that assessed both biostimulants – one containing potassium silicate + molybdenum (Chapter 2) and the other containing potassium silicate + zinc (Chapter 3) – applied to upland rice foliage. The experiments were carried out in a greenhouse, using 5-kg vases with Quartzipsamment soil and BRS Primavera cultivar. The experimental design was completely randomized, with four repetitions in a 5 x 2 structure. The treatments consisted of five doses (0; 1.50; 3.00; 4.50; 6.00 L ha-1) used in two modes of application (single application or in portions). The following parameters were evaluated: concentrations of chlorophyll A, B and Total; leaf content of macro and micronutrients and Si; and dry matter of root and aerial part. Statistical assumptions were assessed for the obtained data using Kolmogorov-Smirnov normality test and Levene’s test for homogeneity of variances, both set at 1%. Tukey’s test was used for analysis of variance and set at 5% significance. The significant data for the quantitative factor (doses) were included in a regression analysis. The application of biostimulant containing potassium silicate + molybdenum significantly changed the leaf content of K, Ca, S, Zn and Cu, as well as the production of dry matter of root. However, the leaf content of N, P, Mg, Fe, Mn and Si, the concentrations of chlorophyll A, B and Total, and the production of dry matter of aerial part were not significantly influenced by the different doses of said biostimulant and modes of application. The application of biostimulant containing potassium silicate + zinc significantly impacted on the leaf content of N, Ca, Mg, S, Zn and Cu, and on the production of dry matter of root. However, the leaf content of Si, P, K, Fe, and Mn, the production of dry matter of aerial part and the concentrations of chlorophyll A, B and Total were not significantly influenced by the different doses of said biostimulant applied in different modes.
Dissertação (Mestrado)
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Garcia, Neto Júlio. "Concentrações e fontes de silício foliar na produção e na qualidade do agrião e do almeirão". Universidade Estadual Paulista (UNESP), 2018. http://hdl.handle.net/11449/153861.
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A pulverização foliar de silício (Si) pode beneficiar a produção e a qualidade das hortaliças folhosas, sendo desconhecidos esses efeitos no agrião-da-terra (Barbarea verna) e no almeirão (Cichorium intybus cv. Spadona). Objetivou-se verificar o efeito da pulverização foliar de silício em diferentes fontes e concentrações no teor foliar de Si, nas variáveis de crescimento, no teor foliar de ascorbato e na perda de água durante o armazenamento das hortaliças agrião e almeirão. Foram realizados dois experimentos, com as duas hortaliças cultivadas em vasos (4 dm3) preenchidos com areia, recebendo solução nutritiva. Durante o cultivo, a média da temperatura máxima atingiu 43,1 °C ± 10,6 °C. Utilizou-se delineamento inteiramente casualizado, em esquema fatorial 2 x 4, sendo duas fontes de silício: silicato de potássio e silicato de sódio e potássio estabilizado, e quatro concentrações de Si foliar: 0 (controle); 0,84; 1,68; 2,52 g L-1 de Si, com quatro repetições. As mudas foram transplantadas após 10 dias da emergência para vasos. Foram realizadas três aplicações foliares de Si, a cada dez dias, sendo a primeira realizada aos 28 dias após o transplantio (DAT). A pulverização foliar de silício é viável, para incrementar o acúmulo deste elemento na planta, o crescimento e a biofortificação, e diminui a perda de água da folha pós-colheita do agrião da terra e do almeirão, destacando-se a concentração de 2,52 g L-1 de Si na forma de silicato de potássio.
Silicon (Si) leaf spraying can benefit the production and quality of leafy vegetables. Such knowing is unclear to land cress (Barbarea verna) and root chicory (Cichorium intybus cv. Spadona). This study aimed was verify the effect of silicon leaf spraying under different sources and concentrations in Si leaf content, on growth variables, ascorbate leaf content, and water loss during storage of land cress and root chicory. We carried out two experiments with two vegetables grown in (4 dm3) pots filled with sand, receiving nutrient solution. During growing, the maximum temperature average was 43.1 °C ± 10.6 ºC. A completely randomized design was used in a 2 x 4 factorial scheme, with two sources of silicon: potassium silicate and stabilized sodium and potassium silicate, and four concentrations of leaf spraying Si: 0 (control), 0.84, 1.68, and 2.52 g L-1 of Si, with four replications. The seedlings were transplanted after 10 days of vessel emergence. Three Si leaf sprayings were done every ten days where the first spraying was at 28 days after transplanting (DAT). Silicon leaf spraying is feasible to increase the Si accumulation, plant growth and biofortification and decrease the post-harvest water loss of land cress and root chicory leaves. The Si concentration of 2.52 g L-1 as potassium silicate was highlighted.
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SORDO, FILHO GIOVANNI del. "Estudo da adsorção de íons metálicos em caulinita para água de reuso". reponame:Repositório Institucional do IPEN, 2015. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26394.
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Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Curcella, Alberto. "Looking for silicene: studies of silicon deposition on metallic and semiconductor substrates". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9314/.
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Nel presente lavoro espongo i risultati degli esperimenti svolti durante la mia internship all’Institut des NanoSciences de Paris (INSP), presso l’Università Pierre et Marie Curie (Paris VI), nel team "Phisico-Chimie et Dynamique des Surfaces", sotto la supervisione del Dott. Geoffroy Prévot. L’elaborato è stato redatto e in- tegrato sotto la guida del Dott. Pasquini, del dipartimento di Fisica e Astronomia dell’Università di Bologna. La tesi s’inserisce nel campo di ricerca del silicene, i.e. l’allotropo bidimensionale del silicio. Il cosidetto free-standing silicene è stato predetto teoricamente nel 2009 utilizzando calcoli di Density Functional Theory, e da allora ha stimolato un’intensa ricerca per la sua realizzazione sperimentale. La sua struttura elettronica lo rende particolarmente adatto per eventuali appli- cazioni tecnologiche e sperimentali, mentre lo studio delle sue proprietà è di grande interesse per la scienza di base.
Nel capitolo 1 presento innanzitutto la struttura del silicene e le proprietà previste dagli studi pubblicati nella letteratura scientifica. In seguito espongo alcuni dei risultati sperimentali ottenuti negli ultimi anni, in quanto utili per un paragone con i risultati ottenuti durante l’internship.
Nel capitolo 2 presento le tecniche sperimentali che ho utilizzato per effettuare le misure. Molto tempo è stato investito per ottenere una certa dimistichezza con gli apparati in modo da svolgere gli esperimenti in maniera autonoma.
Il capitolo 3 è dedicato alla discussione e analisi dei risultati delle misure, che sono presentati in relazione ad alcune considerazioni esposte nel primo capitolo.
Infine le conclusioni riassumono brevemente quanto ottenuto dall’analisi dati. A partire da queste considerazioni propongo alcuni esperimenti che potrebbero ulteriormente contribuire alla ricerca del silicene. I risultati ottenuti su Ag(111) sono contenuti in un articolo accettato da Physical Review B.
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Baillot, Raphaël. "Méthodologie d'analyse de défaillance pour l'évaluation de la fiabilité de diodes électroluminescentes GaN". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14364/document.
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Ce mémoire s'inscrit dans la construction d'une méthodologie d'analyse de défaillance pour l'évaluation de la fiabilité de diodes électroluminescentes, par une approche basée sur l'analyse physique de dégradation et l'extraction de signatures de défaillance électriques et optiques pour localiser les zones dégradées. L'ajout d'analyses physico-chimiques réduit le nombre de composants et peut confirmer les mécanismes de dégradation induits par les vieillissements en stockage actif. Un projet, en collaboration avec le CNES, a permis la mise en évidence des zones sensibles de DELs à MPQ InGaN/GaN à faible puissance (30mW) soumises à un vieillissement en conditions opérationnelles (1500h/85°C/Inominal). L'analyse de défaillance de ces DELs a permis d'expliquer une perte de 65% de puissance optique par la polymérisation de l'huile silicone activée photothermiquement induisant une perte de fluorescence de 69% et une très forte diminution de l'absorption de la lumière de la DEL (90%). Nous avons également démontré (projet CEA-LETI éclairage public) que le même mécanisme est présent dans le mélange gel silicone/phosphore YAG:Ce de DELs blanches à MPQ InGaN/GaN soumises à un vieillissement similaire (85°C/550mA/500h). A 450nm, le rendement de fluorescence a augmenté de 1,2% malgré des pertes en absorption (> 94%) et en réémission de fluorescence (> 85%). La polymérisation de l'huile silicone a induit une perte de puissance optique des DELs de 45% et une dérive de la couleur blanche vers le jaune (≈ 3,6%). Cette dérive est due à un décalage spectral de la fluorescence de l'UV (5nm) vers le bleu entraînant un décalage vers le rouge (2nm) de la lumière de la DELGaN-based LEDs are currently used in a wide range of applications as solid-state lighting, backlighting or full-color displays. Up to date, polymer-based packaging degradation mechanisms are not fully understood. The purpose of this thesis is to work out a methodology of failure analysis contributing towards reliability estimation of GaN-based LEDs under active storage ageing tests. The methodology consists in extracting electro-optical failure signatures to locate degraded zones. A second step is based on physico-chemical analyses used to both confirm failure mechanisms and reduce the number of components to study. Environmental ageing tests (1500h/85°C/Inominal) have been performed on low power InGaN/GaN MQW LEDs (30mW) through a project in collaboration with the French Space Agency (CNES). A 65% loss of optical power has been reported after ageing. Through the methodology, we have found out that optical loss is due to the silicone oil (i.e. chip coating) polymerization activated by photothermal mechanism thereby involving both a 69% fluorescence emission loss and a strong decrease of LED light absorption (90%). A similar failure mechanism has been reported on YAG:Ce/silicone oil mixture located in phosphor converted high power white InGaN/GaN MQW LEDs (CEA-LETI collaboration - Solid-State Lighting project). Fluorescence efficiency has increased (1,2% at 450 nm) despite both strong absorption (94%) and fluorescence emission (85%) losses. Actually, silicone oil polymerization has induced a 45% loss of optical power and a 3,6% yellow shift of white light. Such drift has been linked to both a 5nm blue shift of UV fluorescence involving a 2nm red shift of LED light
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Baillot, Raphaël. "METHODOLOGIE D'ANALYSE DE DEFAILLANCE POUR L'EVALUATION DE LA FIABILITE DE DIODES ELECTROLUMINESCENTES GaN". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2011. http://tel.archives-ouvertes.fr/tel-00673985.
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Ce mémoire s'inscrit dans la construction d'une méthodologie d'analyse de défaillance pour l'évaluation de la fiabilité de diodes électroluminescentes, par une approche basée sur l'analyse physique de dégradation et l'extraction de signatures électriques de défaillance et optiques pour localiser les zones dégradées. L'ajout d'analyses physico-chimiques réduit le nombre de composants et peut confirmer les mécanismes de dégradation induits par les vieillissements en stockage actif. Un projet, en collaboration avec le CNES, a permis la mise en évidence des zones sensibles de DELs à MPQ InGaN/GaN à faible puissance (30mW) soumises à un vieillissement en conditions opérationnelles (1500h/85°C/Inominal). L'analyse de défaillance de ces DELs a permis d'expliquer une perte de 65% de puissance optique par la modification de la structure moléculaire de l'huile silicone activée photothermiquement induisant une perte de fluorescence de 69% et une très forte diminution de l'absorption de la lumière de la DEL (90%). Nous avons également démontré (projet CEA-LETI - éclairage public) que le même mécanisme est présent dans le mélange gel silicone/phosphore YAG:Ce de DELs blanches à MPQ InGaN/GaN soumises à un vieillissement similaire (85°C/550mA/500h). A 450nm, le rendement de fluorescence a augmenté de 1,2% malgré des pertes en absorption (> 94%) et en réémission de fluorescence (> 85%). La modification de la structure moléculaire du gel a induit une perte de puissance optique des DELs de 45% et une dérive de la couleur blanche vers le jaune (≈ 3,6%). Cette dérive est due à un décalage spectral de la fluorescence de l'UV (5nm) vers le bleu entraînant un décalage vers le rouge (2nm) de la lumière de la DEL.
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Gunathilake, Chamila Asanka. "SOFT-TEMPLATING SYNTHESIS OF MESOPOROUS SILICA-BASED MATERIALS FOR ENVIRONMENTAL APPLICATIONS". Kent State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=kent1471543020.
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Дячок, Дарія Романівна. "Оптимізація технологічного процесу відтворення художніх виробів у металі". Bachelor's thesis, КПІ ім. Ігоря Сікорського, 2021. https://ela.kpi.ua/handle/123456789/43657.
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Дипломна робота: 86 с., 20 рис., 30 табл., 16 посилань.
Мета роботи – оптимізація технологічних процесів відтворення у
металі копій двох художніх виробів за наявними неметалевими
оригіналами.
Методика дослідження – виготовлення силіконових та гіпсових
прес-форм із різними варіантами ливникової системи; виготовлення гіпсо кремнеземистих ливарних форм, їх прожарювання та заливання при різних
температурах; контроль параметрів якості виливків (шорсткість поверхонь
та наявність ливарних дефектів).
Результати та їх новизна – теоретично і практично установлено
придатність силіконових прес-форм для виготовлення якісних виливків із
легкоплавких (олов’яно-свинцевих) сплавів; досліджено параметри
технологічних процесів відтворення у металі копій художніх виробів;
виготовлено серію якісних художніх виливків із олов’яно-свинцевого і
мідного сплаву.
Основні показники – в результаті виконання роботи визначено
оптимальні параметри технологічних процесів виготовлення художніх
виробів. Відлито статуетку «Вікінг» масою 0,099 кг із олов’яно-свинцевого
сплаву та масою 0,073 к із латуні Л63, а також статуетку «Кельт» масою
0,468 кг із латуні Л63. Вироби не мають ливарних дефектів, шорсткість
поверхонь виливка «Кельт» не перевищує 12,5 мкм, а «Вікінг» - 6,3 мкм.
Область застосування – Художнє та ювелірне литво унікальних
виробів.
Економічна ефективність – 214 137,4 грн.
Прогнозні припущення щодо розвитку об’єкта дослідження – за
аналогією із дослідженими технологічними процесами, розроблення схем
виготовлення схожих за розмірами та складністю литих художніх виробів в
умовах дрібносерійного виробництва.Bachelor’s dissertation: 86 pages, 20 figures, 30 tables, 16 references. The purpose of the work – optimize the technological processes of reproduction in metal copies, two works of art, according to the available non metallic originals. Research methodology – production of silicone and plaster molds with different variants of the foundry system; production of plaster-silica molds, their calcination and pouring at different temperatures; control of quality parameters of castings (surface roughness and the presence of casting defects). Results of the work and their novelty – theoretically and practically established the suitability of silicone molds for the manufacture of high-quality castings from low-melting (tin-lead) alloys; the parameters of technological processes of reproduction in metal copies of art products are investigated; made a series of high-quality art castings from tin-lead and copper alloy. The main indicators – as a result of work the optimum parameters of technological processes of manufacturing of art products are defined. A 0.099 kg Viking figure made of tin-lead alloy and 0.073 kg L63 brass was cast, as well as a 0.468 kg Celt statue made of L63 brass. The products do not have casting defects, the surface roughness does not exceed 12,5 microns and 6,3 microns, Areas of application – art and jewelry casting of unique products. Economic efficiency – UAH 214,137.4. Predictive assumptions about the development of the object of study – by analogy with the studied technological processes, the development of plans for the manufacture of similar size and complexity of cast art products in small scale production.
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Toquet, Fabien. "Study of the combined roles of the Silica/Oil/UHMWPE formulation and process parameters on morphological and electrical properties of battery Separators". Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1014/document.
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Ce travail s'est concentré sur la compréhension de l'influence de la formulation et plus spécifiquement de la silice précipitée sur la résistivité électrique de séparateurs en polyéthylène destinés à des batteries au plomb. Les séparateurs de batteries en polyéthylène sont composés de silice précipitée, de polyéthylène ultra haute masse molaire (UHMWPE) et d'huile organique. La première partie de ce travail a été d'élaborer à l'échelle du laboratoire, des membranes modèles en polyéthylène. La seconde a été de comprendre l'influence de certains facteurs sur les propriétés structurales et physicochimiques des membranes. Ces facteurs sont principalement la quantité d'huile, la quantité et le grade de silice précipitée, les conditions de température lors de la cristallisation de la membrane et le mode de mise en œuvre utilisé. Les influences des quantités d'huile et de silice sur la cristallisation du polyéthylène sont méticuleusement étudiées, montrant que l'huile aide à augmenter la cristallinité finale de l'UHMWPE et que la silice joue un rôle de réservoir d'huile. Il a également été mis en évidence que la quantité ainsi que le grade de silice influencent la quantité de porosité de la membrane mouillable par l'électrolyte. La présence de silice en surface des pores est responsable de la mouillabilité de la membrane. Un paramètre empirique a donc été proposé dans le but de pouvoir quantifier l'efficacité de l'état de dispersion/distribution de la silice précipitée dans la membrane. Pour terminer, pour une formulation et un même mode de mise en œuvre, il est possible de discriminer l'efficacité des grades de silice précipitée pour l'application séparateur de batterieThis work is devoted to understand the effect of the formulation and more specifically of the precipitated silica on the resistivity of the PE-separators. The PE-separators are designed for the lead-acid batteries. PE-separators are composed of precipitated silica, ultrahigh molecular weight polyethylene (UHMW-PE) and organic oil. The first part of this work was to elaborate PE-separator models at a laboratory scale. Then, the factors impacting the structural and physico-chemicals properties of PE-separators were investigated. These factors are mainly the amounts of oil, precipitated silica, the grade of the precipitated silica, the temperature conditions of crystallization and the device used to elaborate the membrane. The influence of the amounts of oil and precipitated silica on the crystallization of the polyethylene wasthoroughly described showing that the oil helps to increase the final crystallinity of UHMWPE and that the silica plays a role of oil reservoir. Moreover, it was shown that the amount and the grade of precipitated silica have an influence on the wettable part of the porosity of the PE-separators. The coating of the pores by the precipitated silica is responsible of the wettability of the membranes by the electrolyte. Thus, an empirical parameter has been proposed in order to quantify the efficiency of the dispersion and distribution of the precipitated silica in the membrane. The more the membranes are wettable by the electrolyte the more the resistivity of the membranes is decreased. To finish, for a same amount of components and a same method of processing, it is possible to discriminate the efficiency of each grade of precipitated silica for the battery separator application
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Garafolo, Nicholas Gordon. "A Compressible Advection Approach in Permeation of Elastomer Space Seals". University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1271086523.
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El, Fouhaili Bandar. "Development of hydrophobic/superhydrophobic anti-fouling photopolymer coatings for PVC reactor". Thesis, Mulhouse, 2014. http://www.theses.fr/2014MULH6191.
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Lors de la polymérisation en suspension du chlorure de vinyle, il se forme sur les parois un dépôt de polychlorure de vinyle (PVC). Ce phénomène, nommé encroûtement, génère des problèmes car il limite la production de PVC et affecte la qualité du produit final. Dans ce contexte, un projet FUI (Fond Unique Interministériel) intitulé «Ecoating», a été financé dans le cadre d’une collaboration entre plusieurs partenaires industriels et universitaires (INEOS ChlorVinyls, Mäder Research, Avenir Group, LPIM, ESPCI-ParisTech). Deux thèses ont vu le jour au LPIM, avec pour but de développer un revêtement (photo)polymère aux propriétés anti-encroûtement durables qui permettrait d’améliorer la qualité du PVC produit, d’augmenter les quantités produites et ainsi d’améliorer la compétitivité des usines de PVC. Cette thèse s’inscrit dans le développement d’un vernis photopolymère répondant au cahier des charges. Pour éviter l’encroûtement des réacteurs, il est nécessaire de stopper une étape du mécanisme d’encroûtement comme l'adsorption sur les parois du réacteur d’un copolymère nommé Acvagen Graft Copolymer (AGC). Ce copolymère est très actif dans le phénomène d’encroûtement (site de nucléation) et se trouve principalement dans la phase aqueuse du milieu réactionnel. La stratégie de recherche élaborée dans ce projet a été basée sur le développement d'un revêtement photopolymère présentant une faible affinité pour l'eau et devant adhérer à la surface des réacteurs pour éviter la formation de croûte. Les polymères à base de fluoroacrylates ont été les premiers candidats choisis dans cette étude du fait que leurs propriétés exceptionnelles (faible énergie de surface, stabilité chimique et haute hydrophobicité...) pouvaient éviter l'adsorption de l'AGC sur les parois du réacteur, et par conséquent le développement de la croûte. Une recherche bibliographique a été réalisée pour comprendre le comportement particulier de ces molécules qui migrent vers la surface du film et s’organisent en surface pour donner des surfaces hydrophobes. Des mélanges de résines fluoroacryliques modèles ont été testés pour évaluer le caractère hydrophobe du revêtement, comprendre la migration des molécules de fluor vers l’interface en fonction de la nature de substrat et aussi déterminer l’influence de l’ajout d’additifs fluorés au mélange sur les propriétés globales du film. Cette étude nous a permis de comprendre l’influence de l’additif fluoré sur les propriétés chimiques et physiques du film. À l’échelle du laboratoire des tests d’immersion de ces revêtements déposés sur l’acier inoxydable ont étés réalisés dans l’eau chaude (80°C) afin de caractériser leur caractère hydrophobe en fonction du vieillissement dans l’eau chaude ainsi que l’adhésion du film au substrat. Nous avons observé une diminution de l'hydrophobicité de la surface du film au cours du temps lors d’une immersion. [...]Our scientific approach has explored different strategies to develop a durable UV-cured coating with antifouling properties to prevent the crust formation. Firstly, the potential of fluoroacrylate photocurable coatings was exhaustively investigated. Indeed, their outstanding properties (low surface energy, chemical stability and high hydrophobicity...) could limit the adsorption of the AGC on the reactor walls and further encrusting. A bibliographic research highlighted the behavior of fluorinated monomers on film surface and the parameters affecting the hydrophobic properties. Different fluorinated monomers were selected. At low concentration, they provide hydrophobic surfaces on 316L stainless steel, the reference substrate. However, a decrease of the films surface hydrophobicity in hot water was observed with time, and was attributed to a disorganization of the fluorinated chains on the coating surface. An optimization of the amount of fluoroacrylate monomer was performed by confocal Raman microscopy (CRM) to promote the fluorinated chains stability on the surface before and after immersion in hot water at 80°C. The beneficial effect was found maximal at a concentration ranging from 1 to 1.8 wt%. However, even after this optimization, a decrease of the film surface hydrophobicity was observed for increased immersion time in hot water. Therefore, optimized fluoroacrylate monomer concentration was combined with alternated thermal/immersion post-treatment and has conducted to more stable photocured films. This result was attributed to a rigidification of the fluorinated chains on the film surface limiting thus, the extent of their disorganization. After this study realized at a laboratory scale, we tested the photocured coating in the VCM pilot reactor. A surface cleaning, an increase of the stainless steel roughness by shot blasting and the use of alkoxysilanes as coupling agents were implemented in order to enhance the adhesion properties of the photopolymer film on stainless steel. In addition, the use of a fluorinated monomer containing a heteroatom improved the rigidification when associated with the alternated thermal/immersion post-treatment. The crust formation was limited during four successive polymerizations in the VCM pilot reactor. A durable anti-fouling UV-coating could be not obtained due to some swelling phenomena resulting from the lack of coating adhesion or some abrasion occurring from small PVC pellets during the PVC polymerization.A second part of this project was dedicated to superhydrophobic coatings. Indeed, reducing interaction with water should lead to a better protection of the substrate. A literature review on the superhydrophobic surfaces has shown that the contact with hot water generally strongly affects their antiwetting properties and induces a large contact angle decrease. [...]
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Woszczynski, Meghan. "Controlling Lead Release from Premise Plumbing: A Pilot Scale Comparison of Sodium Silicates and Phosphate". 2011. http://hdl.handle.net/10222/14071.
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Lead and lead-tin solder were widely used in premise plumbing in North America until the 1980’s. Although this soldering practice has reduced significantly, lead release from older premise plumbing remains a concern. Utilities often use corrosion inhibitors to protect the piping in the distribution system and reduce lead release in premise plumbing. This study compares sodium silicates and phosphates as corrosion inhibitors for lead release in low alkalinity water. The study was carried out at the J.D. Kline Water Treatment Plant in Halifax, Nova Scotia, Canada. The experimental design compared sodium silicates (concentration of 18mg/L) and zinc orthophosphate (concentration of 0.8mg/L) as corrosion inhibitors at a pH of 7.3 for three disinfectant treatment groups (high chloramines (3mg/L), low chloramines (1mg/L), and chlorine (1mg/L)).
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El, Henawy Walid. "The Effect of Selected Coagulants on Chloride-to-Sulfate Mass Ratio for Lead Control and on Organics Removal in Two Source Waters". Thesis, 2009. http://hdl.handle.net/10012/4229.
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Lead is a known toxin, with the ability to accumulate in the human body from as early as fetal development. Lead exposure is known to cause a myriad of health effects which are more prominent among children. Health effects upon exposure can range from renal and heart disease or potentially cancer in adults to neurotoxicity in children.
The continued presence of old lead service lines and plumbing in distribution systems as well as lead-containing solders and brass fixtures in homes may contribute lead to drinking water. Recent studies have highlighted the importance of a predictor known as the chloride-to-sulfate mass ratio (CSMR) in controlling lead release. A ratio above 0.5 – 0.6 theoretically increases the aggressiveness of lead leaching in galvanic settings, while a lower ratio controls lead corrosion. A switch in coagulant type could significantly alter the ratio. However, a coagulant switch could also trigger changes in finished water turbidity and organics, including disinfection by-product (DBP) precursors, as well as impact sludge production.
Anecdotal evidence from an Ontario water treatment utility suggested the potential applicability of a newly formulated polymer, cationic activated silica (CAS), in improving DBP precursor removal when used in concurrence with a primary coagulant. No previous scientific research had been dedicated to testing of the polymer.
The present research had three primary objectives: The first was to investigate the effect of conventional coagulation with six different coagulants on the chloride-to-sulfate mass ratio as it pertains to lead corrosion in two Ontario source waters of differing quality. Additionally, the effect of coagulant choice on pH, turbidity, and organics removal was investigated. The second objective was aimed at testing potential reductions in CSMR and organics that could be brought about by the use of two polymers, cationic and anionic activated silica (CAS and AAS, respectively), as flocculant aids. Finally, the performance of a high-rate sand-ballasted clarification process was simulated at bench-scale to gauge its performance in comparison with conventional coagulation simulation techniques.
The first series of jar-tests investigated the effectiveness of CAS as a primary coagulant on Lake Ontario water. In comparison with the conventional coagulants aluminum sulfate and polyaluminum chloride, CAS did not offer any apparent advantage with respect to turbidity and organics removal.
Testing of CAS and AAS as flocculant aids was also conducted. Results from a full factorial experiment focused on CAS testing on Lake Ontario water showed that coagulant dose is the most significant contributor to CSMR, turbidity, DOC removal, and THM control. Generally, improvements resulting from CAS addition were of small magnitude (<15%). Reductions in CSMR were attributed to the presence of the sulfate-containing chemicals alum and sulfuric acid in the CAS formulation. Testing of sulfuric acid-activated AAS on Grand River water showed that pairing of AAS with polyaluminum chloride provides better results than with alum with respect to DOC removal (39% and 27% respectively at 60 mg/L coagulant dose). Highest turbidity removals (>90%) with both coagulants were achieved at the tested coagulant and AAS doses of 10 mg/L and 4 mg/L respectively. CSMR reductions in the presence of AAS were also attributable to sulfate contribution from sulfuric acid. Bench-scale simulation of a high-rate sand-ballasted clarification process on Grand River water showed comparable removal efficiencies for turbidity (80 – 90% at 10 mg/L), and DOC (30 – 40% at 50 mg/L).
Finally, six different coagulants were tested on the two source waters for potential applicability in CSMR adjustment in the context of lead corrosion. The two chloride-containing coagulants polyaluminum chloride and aluminum chlorohydrate increased CSMR in proportion to the coagulant dose added, as would be expected. Average chloride contribution per 10 mg/L coagulant dose was 2.7 mg/L and 2.0 mg/L for polyaluminum chloride and aluminum chlorohydrate, respectively. Sulfate-contributing coagulants aluminum sulfate, ferric sulfate, pre-hydroxylated aluminum sulfate, and polyaluminum silicate sulfate reduced CSMR as coagulant dose increased, also as would be expected. The highest sulfate contributors per 10 mg/L dose were pre-hydroxylated aluminum sulfate (6.2 mg/L) and ferric sulfate (6.0 mg/L). The lowest CSMR achieved was 0.6 in Lake Ontario water at a 30 mg/L dose and 0.8 in Grand River water at a 60 mg/L dose. Highest DOC removals were achieved with the chloride-containing coagulants in both waters (35 – 50%) with aluminum chlorohydrate showing superiority in that respect. DOC removals with sulfate-containing coagulants were less, generally in the range of 22 – 41%.
Specificity of critical CSMR values to source water needs to be investigated. Additionally, long term effects of sustained high or low CSMR values in distribution systems need to be further looked into. Finally, the effect of interventions to alter CSMR on other water quality parameters influencing lead corrosion such as pH and alkalinity still represent a research deficit.
33
Chen, Ching-Yi, i 陳靜儀. "The study of optical modeling of silicate phosphor for white LED". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/58412756928074354085.
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碩士國立中央大學
光電科學研究所
96
In this thesis, we study the optical model to precisely describe optics and color distribution of the lights emitted by a blue LED covered with silicate phosphors. The optical model starts Mie scattering model and Monte Carlo ray tracing to describe the scattering of the lights when they are propagated in the phosphors, and the ray tracing is performed with blue and yellow rays. Through simulation and experimental measurement, we have successfully built an optical model, which can be applied to decide some package parameters in a white LED and to avoid color dispersion of the light pattern. Besides, we observed some interesting effects such as thermal decay and re-absorption of the phosphors. These effects could limit the validity of the optical model and need more study to make the optical model more correct.
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Hsu, Ming-Hung, i 徐銘鴻. "Study for cooling impact of silicone oil for LED lamps". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/74462724388284238077.
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碩士中原大學
機械工程研究所
103
LED industry is viewed as one of the most potential industry in recent year. The main reason is that everyone expects LED could get into the lighting and become a brand new light engine. High efficiency, fast turn on/off, longer lifetime than other light engines and free-mercury are the advantages of LED。 However, in addition to the big problem -“radiating”, the main defect of LED is uneven brightness and much higher cost than other light engine, especially in lighting. The main purpose of this research is to investigate the feasibility of using silicone oil for helping heat dissipation of a LED fixture, and to compare with the solid and liquid gel. This research used CFD simulation software to analyze the influences of heat on LED fixture parameters, and conducted experiments to verify the analysis results.
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Luo, Shih-Chao, i 羅士超. "Defect Selective Passivation by Silica Nanospheres for GaN LED Application". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/27068041446106093554.
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碩士國立清華大學
電子工程研究所
100
Gallium nitrid semiconductors have been a focus of intense research effort because of their importance in light emitting, lasing, high frequency, and high power devices. In this study, we use a defect selective passivation with filling silica nanospheres in GaN light emitting diodes. Wet etching are used to reveal the termination of defect site and forms hexagonal etched pits. Then the etched pits are filled with silica nanospheres, which could blocking the propagation of threading dislocations in subsequent regrows, and finally improving both the electrical and optical characteristics in GaN light emitting diodes.
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Chen, Yun-Sie, i 陳允協. "A study of LED packages by runnerless liquid silicone rubber injection molding". Thesis, 2010. http://ndltd.ncl.edu.tw/handle/89719608019413829487.
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碩士雲林科技大學
機械工程系碩士班
98
Dispensing, encapsulating, and molding are current methods for LED packaging process. Dispensing reduces waste produced, but the package outline is highly restricted and the finished product may vary. Encapsulating can only be applied on Lamp-LED, high power LED chips is beyond encapsulating practical capabilities. Molding requires more materials on the runner, thus not cost-effective on high cost, high performance LED package resin. In this study, dispenser is used as the source of pressure, cold waterway on the runner is utilized to preserve material in liquid form, and using SMD-LED leadframe as mold inject to perform injection molding. The experiment in this study indicates that in order to achieve the best result (in the range of this experiment parameter), the air output pressure has to be set to 800KPa for 6.80sec, then mold is clamped and vacuumed, next the mold is opened by 20 minutes of 150℃ heating. According to profilometer, the mold with the surface roughness (Ra) of 0.289μm results in finished product with Ra of 0.191μm. This study provides an alternative to LED packaging process. The process in this study results in product that emits light pattern designed without the necessity of further making of optical components. The process enables the final product to be done in the mold. Also, slug well and gates are the only waste produced.
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Huang, Shih-Hua, i 黃詩樺. "Sol-Gel Synthesis and Luminescence of Novel Silicate-Derivative Phosphors and Their Application in White-Light LED Fabrication". Thesis, 2015. http://ndltd.ncl.edu.tw/handle/59362588371227431864.
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碩士國立交通大學
應用化學系碩博士班
103
In this study, we have successfully synthesized several new red-emitting phosphors with compositions of Sr2TiSi2O8:Mn2+, Sr2Ti2Si4O14:Mn2+, BaGe2.5Si1.5O9:Mn4+, and green-emitting phosphors with compositions of BaGe2.5Si1.5O9:Eu2+, Ba2TiSi2O8:Eu2+ and Ba4La6O(SiO4)6:Eu2+ by using PGMS/sol-gel and microwave-assisted synthetic methods, which may shorten the preparation time of tedious sol-gel method. The crystal structure, luminescence, chromaticity properties and thermal luminescence quenching behaviors of the above phosphors were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence (PL) and UV/Vis spectroscopy. The first part of this thesis reports the optimization of synthetic conditions for all novel silicate-derivative phosphors, and analyzing the XRD profiles and SEM images. Secondly, we discuss the optimization of dopant concentration of the activator for various phosphors, luminescence properties, chromaticity coordinates, diffuse reflectance spectroscopy and thermal quenching effect. The last part of this study investigated the use of as-prepared phosphors and complementary commercial phosphors with near UV-LED chips to fabricate white-light LED (WLED) and studied the luminescence characteristics, chromaticity and color temperature performances. The red-emitting Sr2TiSi2O8:Mn2+ and Sr2Ti2Si4O14:Mn2+ phosphors were utilized to fabricate a WLED device with yellow-emitting Ba2SiO4:Eu2+, blue-emitting BAM:Eu2+, and a 380 nm near-UV LED chip. In addition, the green-emitting BaGe2.5Si1.5O9:Eu2+, Ba2TiSi2O8:Eu2+, and Ba4La6O(SiO4)6:Eu2+ phosphors were utilized to fabricate a WLED device with blue-emitting BAM:Eu2+, red-emitting Sr2Si5N8:Eu2+ with corresponding near-UV chips with wavelengths of 365 -385 nm. These results suggest that the new phosphors developed herein are potentially useful for trichromatic WLED application.
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Kuo-ChingCheng i 鄭國清. "The Synthesis of Silicate Phosphors for Near Ultraviolet Excitation and Application of Phosphor Films for Replaceable White LED". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/66674523212508314978.
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碩士國立成功大學
電機工程學系
104
In this study, BaZr1-yHfySi3O9: Eu2+ and Li2SrSi1-yTiyO4: Eu2+ silicate phosphors were synthesized by the solid-state reaction method, which could be well excited by near-ultraviolet (UV) light. Using near-UV light-emitting diode (LED) chip to excite cyan and yellow color phosphors was a feasible way to generate white light. However, due to higher operating temperature for UV-LEDs, phosphors with better thermal stability became crucial. Thus, this work focused on improving the thermal stability and the luminous intensity. The thermal stability of the former was improved with increasing the concentration of Hf4+ ions. T50 value (the temperature at which the emission intensity falls to 50% of that at room temperature) was enhanced from 230 to 281 °C. Besides, the emission intensity of the latter was enhanced 14.15% by doping Ti4+. Because of their broad excitation spectra, these phosphors could be applied on the near-UV LEDs to form the phosphor-converted white LEDs (pc-WLEDs). The thermal stability of BaZr1-yHfySi3O9:Eu2+ phosphors enhanced due to the substitution of Zr4+ by Hf4+ ions, which affected smaller lattice vibrations by phonons from heating. Therefore, the activation energy was increased from 0.374 to 0.3832 eV, reducing the probabilities of non-radiative reaction. However, due to the doping of Hf4+, the emission intensity decreased apparently with the increasing concentration of Hf4+ with impurity phase.Finally, NH4Cl was added to raw material as flux and promoted the crystallization reaction. The optimal concentration of NH4Cl was found to be 6 wt%. Besides, Li2SrSi1-yTiyO4: Eu2+phosphors were doped by Ti4+, which leads to larger crystallite size, from 65.71 to 70.47 nm. The optimal concentration of Ti4+ was 2 mol% and the emission intensity could depend on the crystallite size. For the WLED application, BaZr1-yHfySi3O9:Eu2+ cyan phosphors and commercial (Ba, Sr, Ca)2SiO4:Eu2+ yellow phosphors were combined with near-UV-LEDs (λex=395-400 nm) to generate white light. In the past, the conventional dispensing technology was directly coating on chip. In this study, the reflector cup was combined with phosphor films to form replaceable white LEDs. It takes significant advantages for practical applications such as detachable, low-cost, and one LED with various parameters for characteristics of white LED. By modulating number of different pieces of phosphor films, it is suitable to find the optimal characteristics of the white LEDs. The optimum luminous efficiency, CIE coordinates, and CRI of the final proposed devices were 20.9158 lm/W, (0.325, 0.358), and 80.47, respectively.
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吳宜芳. "Preparation and Characterization of High Performance Modified TiO2/Silicone Resin Nanocomposites for LED Encapsulation". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/41781565655798414155.
Pełny tekst źródła
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Li, YEN-HSIEN, i 李彥賢. "Preparation of Silanes Modified Zirconium Dioxide/Silicone Resin Composite Materials and Its Evaluation on LED Encapsulating Materials". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/86369743118080411169.
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碩士國立臺灣大學
材料科學與工程學研究所
102
In this research, the main purpose is the development of high refractive index and reliable encapsulating material of light emitting diodes (LEDs). Zirconium dioxide (ZrO2) nanoparticles with high refractive index are synthesized by sol-gel reaction of zirconium propoxide in suitable solution. Acetic acid is used as chelating agent to control the particle size of ZrO2 and then the surface of ZrO2 is modified by silane molecule to provide the linkages between the water phase of ZrO2 and the oil phase of silicone resin. The ZrO2-silane particles are subsequently mixed with commercial-grade silicone resin to obtain the ZrO2-silane/silicone hybrid materials (ZrO2-silane/AB). These high-refractive-index ZrO2-silane/AB hybrids are used as encapsulating materials to improve the luminous flux of the LEDs. From the result of the luminous flux measurement, the LED encapsulated with the pure silicone resin only has luminous flux of 4.11 lm. After being encapsulated with the ZrO2-silane/AB hybrid, the luminous flux of the LED raises to 4.52 lm, which reveals that increasing in the refractive index of the encapsulating materials by the incorporation of the ZrO2-silane can improve the luminous flux of the LED. The results of Dynamic Mechanical Analyzer and Thermal Mechanical Analyzer on ZrO2-silane/AB hybrids tell us that the ZrO2-silane/AB hybrids have lower thermal stress than that of ZrO2 /AB hybrids. We believe that encapsulating materials with lower thermal stress have a better mechanical resistance against the thermal shock .The result of thermal shock experiment also shows that LED encapsulated with ZrO2-silane/AB hybrids have better reliability than the ZrO2 /AB hybrids.
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Lai, Dai-Fu, i 賴岱甫. "Preparation of High Refractive Index Zirconium Dioxide / Silicone Resin Composite Materials and Its Application on LED Encapsulating Materials". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/39266866397833608855.
Pełny tekst źródłaStreszczenie:
碩士國立臺灣大學
化學工程學研究所
100
The research was divided into two parts. Zirconium dioxide (ZrO2) nanoparticles with high refractive index were introduced into commercial-grade silicone resin by an in-situ sol gel reaction in the first part. The acetic acid was used as chelating agent to control the particle size of ZrO2 and modified the surface of ZrO2 to provide linkages between the water phase of ZrO2 and the oil phase of silicone resins. Moreover, butanol and methyl ethyl ketone were chosen as the co-solvent system to prevent ZrO2 particles from aggregation during the sol-gel process. Then we synthesized optical films with high refractive index and high transmittance and synthesized composite films with high refractive index thin film on the bottom and encapsulating material on the top of the composite film. Through using the encapsulating materials with decreasing refractive index layer-by-layer, LEDs could achieve higher light extraction efficiency. In order to achieve the requirements of LED encapsulating materials, optical thin films and composite films were synthesized and measured in terms of refractive index, transmittance, water uptake, thermal resistance and UV resistance. The curing degree of the silicone resin after introducing zirconium dioxide nanoparticles was investigated in the second part. The influences of the concentration and the size domain of the zirconium dioxide on the degree of curing degree was studied by DSC measurement, and the curing degree of the composite film was investigated by DSC measurement as well.
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Yu, Cheng-Mao, i 余承懋. "Optical and Thermal Performance Enhancement of InGaN Blue High-Power LED via Graphene Doped Silicone Encapsulant and Silver Paste". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3c6g3n.
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碩士崑山科技大學
光電工程研究所
106
This paper has demonstrated the effects of graphene doped in silicone encapsulate and silver paste respectively for InGaN blue high-power light-emitting diode (LED) package on the optical and thermal properties of the LEDs.The research is divided into two experiments. In Experiment 1, the alignment effects of graphene with different concentrations in silicone encapsulate on the optical and thermal properties of the LEDs were investigated. In Experiment 2, the effects of graphene with different concentrations in silver paste on the optical and thermal properties of the LEDs were investigated. In Experiment 1, the alignment of graphene with different doped concentrations in silicone encapsulate was changed by applied an electric field (37 V/mm) for increasing the light output power (LOP) of LEDs. The dispersion of graphene in silicone encapsulate increases with the increasing duration of ultrasonic vibrations and reaches saturation after the duration exceeds 50 minutes. The LOP of LEDs with graphene doped silicone treated by electric field is larger than that without electric field treatment, except that the graphene doping concentration of 0.10 wt%. The average LOP of LEDs with the doping concentration of aligned graphene 0.01 wt% in the silicone encapsulate is 289.2 mW with the injection current at 0.35 A and it has increased by 4.97% compared with that of unaligned graphene under the same doping concentration. The LOP of LEDs for different variable currents is measured. The doping concentration of aligned graphene 0.01 wt% was aligned or not aligned in the silicone encapsulate of the LED, and the saturation currents of the LED are 3.0 A and 2.7 A, respectively. The graphene in the silicone encapsulate was aligned by applying a uniform electric field then the LOP and heat dissipation properties of the LEDs were efficiently improved. In Experiment 2, the effect of graphene with different concentrations in the silver paste on the optical and thermal properties of LEDs was demonstrated. The doping concentration of the graphene was 0 wt% in the silver paste of the LED. The operating current of the LED was 0.35 A and the corresponding average LOP was 530 mW. The doping concentration of the graphene was 0.01 wt% in the silver paste of the LED, the LOP of the LED decreased by about 1% compared to the doping concentration of 0 wt%. The LOP of LEDs for different variable currents was measured. The doping concentration of the graphene was 0.01 wt% in the silver paste of the LED. The saturation current of the LED was 0.9 A. The doping concentration of the graphene was 0 wt% in the silver paste of the LED. The saturation current of the LED was only 0.8 A. Blue LEDs with metal mirror on the back of the chip, its frontal optical reflectance can theoretically reach over 99%. The doping of the graphene in the silver paste coated to glass and measures its optical absorption rates and optical reflectance. As the doping of the graphene was 0 wt%, 0.01wt%, and 0.10 wt% in silver paste, the difference of silver paste is not significant and it is respectively 4.21%, 4.24%, and 4.22% on optical absorption rates. As the doping of the graphene was 0 wt%, 0.01wt%, and 0.10 wt% in silver paste, and it is respectively 0.75%, 0.68%, and 0.50% on optical reflectance. The effect of graphene with different concentrations in the silver paste on thermal properties of LEDs was compared. Excellent heat dissipation properties when graphene doping concentration is 0.01 wt%. The junction temperature of the LED was 76.7°C and the thermal resistance was 9.9°C/W. The hot/cold ratio of LOP is increased 0.96 for LEDs with the graphene doping concentrations of 0.01 wt% and 0.10 wt% in the silver paste compared to that of LED without the graphene doping in the silver paste at room temperature. The silver paste with the graphene doping concentrations of 0.01 wt% can afford a maximum shear force of 1.07 kgf. Therefore, after doping of graphene, the silver paste still has sufficient bonding strength. However, the chip structure has been damaged under the shear force. Therefore, the adhesive strength of silver paste will be greater. After ultrasonic vibration, the graphene is well dispersed in silicone encapsulate. As the dispersion time is 50 min, the dispersion effect is the best. Graphene absorbs light, although the LOP of LED with graphene doped silicone encapsulate can be improved by aligning graphene, but graphene is still not suitable appearance in the light path. However, graphene doped silicone is suitable to be placed on the heat conduction path and play the role of heat dissipation / thermal conductive adhesive. The high reflectance of the silver in the silver paste, the effect of optical absorption by graphene is not obvious. Mixing graphene into silver paste is a suitable grain adhesive for using in a variety of optoelectronic device die-bonding processes.