Search results for "Silicon"
showing 10 items of 1391 documents
Comparative evaluation of the effect of impression materials and trays on the accuracy of angulated implants impressions
2018
Background Vinyl Polyether Siloxane is a newly introduced impression material and studies on that is scarce. Implant insertion in posterior mandible might be angulated due to anatomical considerations. The purpose of this study was to compare the dimensional and angular accuracy of impressions using full-arch versus sectional tray and Vinyl Polysiloxane versus Vinyl Polyether Siloxane in angulated implants. Material and Methods Four implants were placed in dental areas #19, #21, #28 and #30 of a Kennedy class I mandibular acrylic model with 30° lingual angulation. Twenty sectional and 20 full-arch open trays were made on the primary cast. Impressions were taken using Vinyl Polysiloxane and …
Ozone-Based Atomic Layer Deposition of Al2O3 from Dimethylaluminum Chloride and Its Impact on Silicon Surface Passivation
2017
Dimethylaluminum chloride (DMACl) as an aluminum source has shown promising potential to replace more expensive and commonly used trimethylaluminum in the semiconductor industry for atomic layer deposited (ALD) thin films. Here, the Al2O3 DMACl-process is modified by replacing the common ALD oxidant, water, by ozone that offers several benefits including shorter purge time, layer-by-layer growth, and improved film adhesion. It is shown that the introduction of the ozone instead of water increases carbon and chlorine content in the Al2O3, while long ozone pulses increase the amount of interfacial hydrogen at silicon surface. These are found to be beneficial effects regarding the surface pass…
Effect of ozone concentration on silicon surface passivation by atomic layer deposited Al2O3
2015
Abstract We study the impact of ozone-based Al2O3 Atomic Layer Deposition (ALD) on the surface passivation quality of crystalline silicon. We show that the passivation quality strongly depends on the ozone concentration: the higher ozone concentration results in lower interface defect density and thereby improved passivation. In contrast to previous studies, our results reveal that too high interface hydrogen content can be detrimental to the passivation. The interface hydrogen concentration can be optimized by the ozone-based process; however, the use of pure ozone increases the harmful carbon concentration in the film. Here we demonstrate that low carbon and optimal hydrogen concentration…
Experimental quantification of useful and parasitic absorption of light in plasmon-enhanced thin silicon films for solar cells application
2016
AbstractA combination of photocurrent and photothermal spectroscopic techniques is applied to experimentally quantify the useful and parasitic absorption of light in thin hydrogenated microcrystalline silicon (μc-Si:H) films incorporating optimized metal nanoparticle arrays, located at the rear surface, for improved light trapping via resonant plasmonic scattering. The photothermal technique accounts for the total absorptance and the photocurrent signal accounts only for the photons absorbed in the μc-Si:H layer (useful absorptance); therefore, the method allows for independent quantification of the useful and parasitic absorptance of the plasmonic (or any other) light trapping structure. W…
Full inhibition of enzymatic browning in the presence of thiol-functionalised silica nanomaterial
2018
[EN] Darkening processed fruits and vegetables is caused mainly by enzymatic browning through polyphenol oxidase (PPO) action. Accordingly, we explored the potential of four silica-based materials (MCM-41 nanometric size, MCM-41 micrometric size, UVM-7 and aerosil), non-functionalised and functionalised with thiol groups, to inhibit PPO activity in the model system and apple juice. All materials showed relevant performance when immobilising and inhibiting PPO in model systems, and support topology is a main factor for enzyme immobilisation and inhibition. Thiol-containing silica UVM7-SH showed the greatest inactivation, and similar browning values to those obtained by acidification. The enz…
Influence of the functionalisation of mesoporous silica material UVM-7 on polyphenol oxidase enzyme capture and enzymatic browning
2020
Polyphenol oxidase (PPO), also known as tyrosinase and catechol oxidase, is the enzyme responsible for enzymatic browning in foods. It causes undesirable organoleptic, nutritional and colour changes. Here, we report the preparation of five nanomaterials and a study of their ability to modulate PPO enzyme activity. The materials consist of UVM-7 supports (a mesoporous silica material) modified with diverse functional groups (i.e. amine, carboxylic acid, isocyanate, alkane and pyridine). We also studied the PPO immobilisation capability of the materials. All the materials, except the carboxylic acid functionalised one, offer high PPO loading capabilities and the immobilisation speed increases…
Towards the column bed stabilization of columns in capillary electroendosmotic chromatography
2000
This article discusses a novel method generating a continuous bed inside the CEC column. The column bed composed of microparticulate reversed-phase silica is completely immobilized by a hydrothermal treatment using water for the immobilization process. This process eliminates the manufacture of frits of both ends of the column and all problems associated with their preparation. Fundamental studies on operational parameters will be presented such as the dependence of the immobilization on the column temperature, the type of stationary phase and the column back pressure. The immobilized CEC columns show the same high column efficiency as packed columns with frits.
Particle packed columns and monolithic columns in high-performance liquid chromatography-comparison and critical appraisal
2007
The review highlights the fundamentals and the most prominent achievements in the field of high-performance liquid chromatography (HPLC) column development over a period of nearly 50 years. After a short introduction on the structure and function of HPLC columns, the first part treats the major steps and processes in the manufacture of a particle packed column: synthesis and control of particle morphology, sizing and size analysis, packing procedures and performance characterization. The next section is devoted to three subjects, which reflect the recent development and the main future directions of packed columns: minimum particle size of packing, totally porous vs. core/shell particles an…
Towards the ultimate minimum particle diameter of silica packings in capillary electrochromatography.
2000
Porous silica beads with an average particle diameter between 0.2 and 3 microm have been applied as packing material in capillary electrochromatography (CEC). The experiments were directed to investigate whether it is really feasible and as promising as expected to use such small particles. In CEC, plate heights of H approximately/= 1-2 d(p) can be achieved which is smaller than the plate heights usually attained in high-performance liquid chromatography. Using a capillary packed with 0.5 microm silica beads we achieved a plate height of H = 3 d(p) indicating the presence of dispersive effects like Joule heating. Calculations demonstrate that at a field strength of about 800 V cm(-1) one th…
Insights into the Maya Blue technology: greenish pellets from the ancient city of La Blanca.
2011
Financial support is gratefully acknowledged from the MEC Projects CTQ2011-28079-CO3-01 and 02 which are also supported with ERDF funds. Research was conducted within the "Grupo de anlisis cientifico de bienes culturales y patrimoniales y estudios de ciencia de la conservacion" Microcluster of the University of Valencia Excellence Campus. The authors would like to thank Dr. Isabel Solana (SCSIE, UV), Dr. Jose Luis Moya Lopez, and Manuel Planes Insausti (Microscopy Service UPV) for their technical support.