Relevant bibliographies by topics / Amorphous Silica Surface

Academic literature on the topic 'Amorphous Silica Surface'

Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles

Select a source type:

Contents

Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Amorphous Silica Surface.'

Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.

You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.

Journal articles on the topic "Amorphous Silica Surface"

1

Zhuravlev, L. T. "Characterization of amorphous silica surface." Reaction Kinetics & Catalysis Letters 50, no. 1-2 (September 1993): 15–25. http://dx.doi.org/10.1007/bf02062184.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Stievano, Lorenzo, Ling Yu Piao, Irène Lopes, Ming Meng, Dominique Costa, and Jean-François Lambert. "Glycine and lysine adsorption and reactivity on the surface of amorphous silica." European Journal of Mineralogy 19, no. 3 (July 2, 2007): 321–31. http://dx.doi.org/10.1127/0935-1221/2007/0019-1731.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Taj, S., A. Rosu-Finsen, and M. R. S. McCoustra. "Impact of surface heterogeneity on IR line profiles of adsorbed carbon monoxide on models of interstellar grain surfaces." Monthly Notices of the Royal Astronomical Society 504, no. 4 (May 22, 2021): 5806–12. http://dx.doi.org/10.1093/mnras/stab1174.

Full text
Abstract:
ABSTRACT Surface heterogeneity of model amorphous silica films used as a model for interstellar grain surfaces is revealed through the application of the pre-exponential optimized inversion method to previously reported sub-monolayer thermal desorption studies of carbon monoxide (CO) desorption. The impact of that surface heterogeneity, as represented by the coverage dependence of the CO activation energy for desorption from the amorphous silica surface, on the IR spectroscopy of the CO stretching vibration is explored through vibrational line profile synthesis. Comparison is then made to previous investigations of CO line profiles on this surface and on amorphous solid water as reported in Taj et al. (2017, 2019a). A tentative conclusion is drawn that CO vibrationally promoted desorption from, and diffusion on, the amorphous silica surface may be responsible for the correspondingly short vibrational excited state lifetime of CO on that surface. The contrast with CO on amorphous solid water, where direct and rapid vibrational relaxation into the solid water phonon bath occurs, is highlighted. The consequences of this from the standpoint of CO deposition on grain surfaces are discussed.
APA, Harvard, Vancouver, ISO, and other styles
4

Liu, Quan Xiao, and Wen Cai Xu. "Study on Amorphous Silica Powder Properties." Advanced Materials Research 512-515 (May 2012): 2428–33. http://dx.doi.org/10.4028/www.scientific.net/amr.512-515.2428.

Full text
Abstract:
In this paper amorphous silica powder properties are analyzed and studied. It shows that precipitated silica has larger specific surface area, higher absorption value, higher whiteness and lower bulk density. Different usage of amorphous silica has different properties and different particle size. The order of particle size is that precipitation silica for rubber is bigger than precipitated silica for filler, and the smallest is precipitated silica for coating. XRD, FTIR, SEM and TEM show that precipitated silica is amorphous silica which has wealthy hydroxyl and porous properties and chain branched structure.
APA, Harvard, Vancouver, ISO, and other styles
5

Tosheva, Lubomira, Valentin Valtchev, and Johan Sterte. "Amorphous very high surface area silica macrostructures." Journal of Materials Chemistry 10, no. 10 (2000): 2330–37. http://dx.doi.org/10.1039/b001096k.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Wang, Bai Kun, Hao Ding, Yun Xing Zheng, and Ning Liang. "Preparation and Characterisation of Amorphous Silica from Alkali Wastewater Produced in Manufacturing Process of ZrOCl2." Advanced Materials Research 194-196 (February 2011): 2164–68. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.2164.

Full text
Abstract:
The amorphous silica was prepared from the alkali wastewater rich in Na2O•nSiO2 produced in manufacturing process of zirconium oxychloride (ZrOCl2). The composition and microstructure of amorphous silica were studied by X-ray diffraction, X-ray fluorescence and scanning electron microscope, respectively. The results showed that the amorphous silica was mainly composed of uncrystallized substance, and the silica content was 96.4%. Its whiteness was 97.5% and the particle size was between 100nm and 200nm without agglomeration. The specific surface area of the amorphous silica was 531.9 m2/g, and its pore volume and diameter were 0.945 cm3/g and 4.94 nm, respectively.
APA, Harvard, Vancouver, ISO, and other styles
7

Hefland, R. B., P. E. Schwarzel, B. V. Johansen, T. Myran, N. Uthus, and M. Refsnes. "Silica-induced cytokine release from A549 cells: importance of surface area versus size." Human & Experimental Toxicology 20, no. 1 (January 2001): 46–55. http://dx.doi.org/10.1191/096032701676225130.

Full text
Abstract:
Physical and chemical properties such as structure, composition and surface reactivity determine the biological activity of mineral particles. Long-term exposureto crystalline silica is known to cause persistent pulmonary inflammation leading to adverse health effects. There is less information about the potential health effects of amorphous (noncrystal-line) silica. In this study, the inflammatory and cytotoxic potency of crystalline and amorphous silica in relation to particle size and surface area was assessed. Human epithelial lung cells (A549) were exposed to different size fractions of quartz (aerodynamic diameter 0.5,2 and 10 sm) and amorphous silica (diameter 0.3 pm). All particles induced increased release ofthe proinflammatory cytokines interleukin (IL)-6 and IL-8. When cells were exposed to equal masses of quartz, the smallest size fraction was the most potent. These differences, however, disappeared when cytokine release was related to equal surface areas. When amorphous silica and quartz were compared, the amorphoussilicawas mostpotentto induce IL-6 regardless of how exposure was expressed, whereas the smallest size fraction of quartz was the most potent inducer of IL-8. Thus, the surface area seems to be the critical determinant when potency of different sizes of quartz is compared.
APA, Harvard, Vancouver, ISO, and other styles
8

Yong, R. N., A. M. O. Mohamed, and B. W. Wang. "Influence of amorphous silica and iron hydroxide on interparticle action and soil surface properties." Canadian Geotechnical Journal 29, no. 5 (October 1, 1992): 803–18. http://dx.doi.org/10.1139/t92-088.

Full text
Abstract:
The study of the physicochemical properties of pure amorphous materials (complexes) consisting of Fe2O3 and SiO2 in various proportions indicates that the amorphous complexes will exhibit different properties and characteristics depending on the proportions of Fe2O3 and SiO2. Addition of the amorphous complexes with illitic clay studied shows that the properties of the clay admixture will also vary according to the properties of the amorphous complex, albeit to a lesser degree. The properties and behaviour observed for the amorphous complexes and the clay admixtures can be linked directly to the large specific surface area and high surface charge of the amorphous complexes. The contribution of amorphous complexes to the clay – amorphous complex mixtures (clay admixtures) is twofold: firstly, by the amount of amorphous complex in the clay admixture, and secondly by the composition of the amorphous complex used. The contribution from the amorphous complex is in two forms: water-holding capacity and bonding action. The presence of pH-dependent surface charges associated with the amorphous complexes makes the physicochemical properties and behaviour of the clay admixtures (e.g., liquid limits and zeta potential) sensitive to the pH environment. Coating of amorphous colloids onto clay particle surfaces, shown by scanning electron microscopy, appears to, be enhanced by a decrease in pH of the system, indicating that the enhancement is likely due to the increased electrostatic attraction resulting from the increased amounts of positive charges on the amorphous colloids. Key words : amorphous materials, mass ratio, zeta potential, Bingham yield stress, clay admixtures, hydrogen bonding, specific surface area, cation exchange capacity, anion exchange capacity, fabric and soil structure.
APA, Harvard, Vancouver, ISO, and other styles
9

Schrader, Alex M., Jacob I. Monroe, Ryan Sheil, Howard A. Dobbs, Timothy J. Keller, Yuanxin Li, Sheetal Jain, M. Scott Shell, Jacob N. Israelachvili, and Songi Han. "Surface chemical heterogeneity modulates silica surface hydration." Proceedings of the National Academy of Sciences 115, no. 12 (March 5, 2018): 2890–95. http://dx.doi.org/10.1073/pnas.1722263115.

Full text
Abstract:
An in-depth knowledge of the interaction of water with amorphous silica is critical to fundamental studies of interfacial hydration water, as well as to industrial processes such as catalysis, nanofabrication, and chromatography. Silica has a tunable surface comprising hydrophilic silanol groups and moderately hydrophobic siloxane groups that can be interchanged through thermal and chemical treatments. Despite extensive studies of silica surfaces, the influence of surface hydrophilicity and chemical topology on the molecular properties of interfacial water is not well understood. In this work, we controllably altered the surface silanol density, and measured surface water diffusivity using Overhauser dynamic nuclear polarization (ODNP) and complementary silica–silica interaction forces across water using a surface forces apparatus (SFA). The results show that increased silanol density generally leads to slower water diffusivity and stronger silica–silica repulsion at short aqueous separations (less than ∼4 nm). Both techniques show sharp changes in hydration properties at intermediate silanol densities (2.0–2.9 nm−2). Molecular dynamics simulations of model silica–water interfaces corroborate the increase in water diffusivity with silanol density, and furthermore show that even on a smooth and crystalline surface at a fixed silanol density, adjusting the spatial distribution of silanols results in a range of surface water diffusivities spanning ∼10%. We speculate that a critical silanol cluster size or connectivity parameter could explain the sharp transition in our results, and can modulate wettability, colloidal interactions, and surface reactions, and thus is a phenomenon worth further investigation on silica and chemically heterogeneous surfaces.
APA, Harvard, Vancouver, ISO, and other styles
10

Zhang, Xiao Jing, Hao Ding, and Bai Kun Wang. "Recycling and Characterisation of Amorphous Silica from Zr-Containing Silica Residue." Advanced Materials Research 194-196 (February 2011): 2109–14. http://dx.doi.org/10.4028/www.scientific.net/amr.194-196.2109.

Full text
Abstract:
Preparation of amorphous silica using Zr-containing silica residue and the properties of the product have been studied. The results show that the separation of amorphous silica from Zr component can be realized using a process flow that pulping, grinding, washing and solid-liquid separation. The main constituent of the product is amorphous state, the content of SiO2 in the product comes up to 94.3%, the content of ZrO2 comes up to 7.48%, the grain size is 2-3 μm, the surface area is 494.3 m2/g. The quality of the recovery can meet the requirement of white carbon black standards ISO 5794-1 and HG/T 3061.
APA, Harvard, Vancouver, ISO, and other styles
More sources

Dissertations / Theses on the topic "Amorphous Silica Surface"

1

Chen, Si-Han. "Molecular Dynamics Investigation of Surface Potential andElectrokinetic Phenomena at the Amorphous Silica/WaterInterface." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1534510054324125.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Wilmsmeyer, Amanda Rose. "Ultrahigh Vacuum Studies of the Fundamental Interactions of Chemical Warfare Agents and Their Simulants with Amorphous Silica." Diss., Virginia Polytechnic Institute and State University, 2012. http://hdl.handle.net/10919/54366.

Full text
Abstract:
Developing a fundamental understanding of the interactions of chemical warfare agents (CWAs) with surfaces is essential for the rational design of new sorbents, sensors, and decontamination strategies. The interactions of chemical warfare agent simulants, molecules which retain many of the same chemical or physical properties of the agent without the toxic effects, with amorphous silica were conducted to investigate how small changes in chemical structure affect the overall chemistry. Experiments investigating the surface chemistry of two classes of CWAs, nerve and blister agents, were performed in ultrahigh vacuum to provide a well-characterized system in the absence of background gases. Transmission infrared spectroscopy and temperature-programmed desorption techniques were used to learn about the adsorption mechanism and to measure the activation energy for desorption for each of the simulant studied. In the organophosphate series, the simulants diisopropyl methylphosphonate (DIMP), dimethyl methylphosphonate (DMMP), trimethyl phosphate (TMP), dimethyl chlorophosphate (DMCP), and methyl dichlorophosphate (MDCP) were all observed to interact with the silica surface through the formation of a hydrogen bond between the phosphoryl oxygen of the simulant and an isolated hydroxyl group on the surface. In the limit of zero coverage, and after defect effects were excluded, the activation energies for desorption were measured to be 57.9 ± 1, 54.5 ± 0.3, 52.4 ± 0.6, 48.4 ± 1, and 43.0 ± 0.8 kJ/mol for DIMP. DMMP, TMP, DMCP, and MDCP respectively. The adsorption strength was linearly correlated to the magnitude of the frequency shift of the ν(SiO-H) mode upon simulant adsorption. The interaction strength was also linearly correlated to the calculated negative charge on the phosphoryl oxygen, which is affected by the combined inductive effects of the simulants’ different substituents. From the structure-function relationship provided by the simulant studies, the CWA, Sarin is predicted to adsorb to isolated hydroxyl groups of the silica surface via the phosphoryl oxygen with a strength of 53 kJ/mol. The interactions of two common mustard simulants, 2-chloroethyl ethyl sulfide (2-CEES) and methyl salicylate (MeS), with amorphous silica were also studied. 2-CEES was observed to adsorb to form two different types of hydrogen bonds with isolated hydroxyl groups, one via the S moiety and another via the Cl moiety. The desorption energy depends strongly on the simulant coverage, suggesting that each 2-CEES adsorbate forms two hydrogen bonds. MeS interacts with the surface via a single hydrogen bond through either its hydroxyl or carbonyl functionality. While the simulant work has allowed us to make predictions agent-surface interactions, actual experiments with the live agents need to be conducted to fully understand this chemistry. To this end, a new surface science instrument specifically designed for agent-surface experiments has been developed, constructed, and tested. The instrument, located at Edgewood Chemical Biological Center, now makes it possible to make direct comparisons between simulants and agents that will aid in choosing which simulants best model live agent chemistry for a given system. These fundamental studies will also contribute to the development of new agent detection and decontamination strategies.
Ph. D.
APA, Harvard, Vancouver, ISO, and other styles
3

Arancon, Rick Arneil. "Exploration of Transition Metal Sulfide Catalysts Prepared by Controlled Surface Chemistry." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEN063.

Full text
Abstract:
L'hydrotraitement est un procédé catalytique important dans le raffinage du pétrole qui utilise des catalyseurs bimétalliques sulfurés NiWS ou NiMoS (ou CoMoS) supportés sur alumine. Leur mode conventionnel de préparation implique l’imprégnation d'une solution aqueuse de sels de Mo/W et de Ni/Co, puis l’activation par un agent sulfo-réducteur (H2S/H2). Pour répondre aux exigences environnementales et améliorer l'efficacité de l'hydrotraitement, des améliorations permanentes de la performance de ces systèmes catalytiques sont attendues. Ce travail se concentre sur la préparation de catalyseurs d'hydrotraitement hautement actifs par une approche de chimie de surface contrôlée (CSC) qui implique l'imprégnation successive de précurseurs moléculaires de MoV et NiII en solvant organique sur un support silice-alumine traité thermiquement. Dans la première partie de cette thèse, la genèse de la phase active du catalyseur CSC et conventionnel Mo et NiMo est étudiée par quick-XAS combinée à d’autres techniques (chimiométrie, XPS, RPE, STEM-HAADF, modélisation moléculaire). Nous proposons ainsi des structures moléculaires depuis les précurseurs oxydes de Mo et Ni supportés jusqu’aux nombreuses espèces intermédiaires (oxysulfure et sulfures) en fonction de la température. Cette analyse multi-technique permet d'abord de révéler les spécificités de la genèse des catalyseurs CSC et conventionnels qui peuvent expliquer leurs différentes activités catalytiques. Ensuite, elle révèle également de nouvelles connaissances sur les mécanismes d’insertion du Ni dans la phase NiMoS en fonction de la préparation. Dans la seconde partie, la possibilité de remplacer Co et Ni comme promoteurs est explorée. Ceci est entrepris en synthétisant des catalyseurs alternatifs de type XYMoS, où X et Y sont des métaux de transition 3d. Comme suggéré par des études de modélisation quantiques antérieures, certaines formulations XYMoS peuvent présenter un effet de synergie analogue à ceux des phases actives CoMoS et NiMoS. L’étude des formulations les plus prometteuses méritent d'être approfondies afin de mieux comprendre leur fonctionnement
Hydrotreating is an important catalytic process in petroleum refining which uses sulfided bimetallic catalysts NiWS or NiMoS (or CoMoS) supported on alumina. Their conventional preparation involves an incipient wetness impregnation of an aqueous solution of Mo/W and Ni/Co salts, and then activation by a sulfo-reductive agent (such as H2S/H2). To meet environmental regulations and improve the energy efficiency of hydrotreatment, permanent improvements on the performance of these catalytic systems are expected. This work is thus focused on the preparation of highly active hydrotreating catalysts through a controlled surface chemistry (CSC) approach; which involves the successive impregnation of Mo5+ and Ni2+ molecular precursors in an organic solvent on a thermally treated silica-alumina support. In the first part of this thesis, the active phase genesis of CSC and conventional Mo and NiMo catalysts is studied by in situ quick-XAS combined with various other techniques (chemometrics, XPS, EPR, STEM-HAADF, molecular modeling). We thus propose molecular structures from the oxide of supported Mo and Ni precursors up to the numerous intermediate sulfided species as a function of temperature. This multi-technique analysis enables first to reveal the specific features of the genesis of CSC and conventional catalysts which may explain their different catalytic activities. Then, it also reveals new insights into the mechanisms of Ni promoter incorporation into the NiMoS phase as a function of the preparation. In the second part, the feasibility of replacing Co and Ni as promoters is explored. Using the CSC method, we attempted to synthesize alternative catalysts of the form XYMoS ternary sulfides, where X and Y are 3d transition metals. As suggested by previous quantum simulations, certain XY formulations possibly reveal a synergy effect as observed in CoMoS and NiMoS active phases. The most promising formulations merit further investigations
APA, Harvard, Vancouver, ISO, and other styles
4

Lund, Christopher Paul. "Surface spectroscopy and Auger lineshape analysis studies of amorphous silicon surfaces." Thesis, Lund, Christopher Paul (1993) Surface spectroscopy and Auger lineshape analysis studies of amorphous silicon surfaces. PhD thesis, Murdoch University, 1993. https://researchrepository.murdoch.edu.au/id/eprint/42221/.

Full text
Abstract:
This work deals with the experimental investigation of the surface of one of the most interesting and important new semiconductor materials, hydrogenated amorphous silicon (a-Si:H). Ultra-high vacuum surface spectroscopy methods, especially Auger lineshape analysis and X-ray photoelectron spectroscopy (XPS), have been used with a view to studying the effect on the local densities of states at the surface of various preparation methods and subsequent treatments. X-ray excited Si L2,3VV and Si L1L2,3V Auger lines as well as XPS valence band (XPS VB) spectra have been measured for a number of silicon materials and surfaces prepared in different ways. These materials included crystalline silicon (c-Si), amorphous silicon (a-Si) and hydrogenated amorphous silicon (a-Si:H). Preparation techniques used included atmospheric pressure chemical vapour deposition (APCVD), glow discharge (GD) or plasma enhanced CVD and radio frequency (RF) sputtering. Surface treatments included disordering of c-Si by argon ion bombardment, hydrogenation by hydrogen ion bombardment, annealing and rehydrogenation from the bulk. Methods have been developed and thoroughly tested to enable X-ray excited silicon Auger spectra to be treated routinely using numerical debroadening and deconvolution to obtain an indication of the valence band transition densities of states (VBTDOS). These show good agreement with previously published results for electron initiated Auger spectra and theoretical results. In particular a method has been developed for treating the experimentally difficult Si L1L2,3V Auger line. Techniques have been developed to remove the sloping background and Coster-Kronig broadening to enable an indication of the transition densities of states. The L1L2,3V derived VBTDOS approximates closely to the theoretical DOS and the experimental results obtained from UPS and XPS. It is shown that because of this the Si L1L2,3V line is a more effective method of monitoring changes in the surface VBTDOS of a-Si:H due to various treatments than the more commonly used but harder to interpret Si L2,3VV line. A method based on the simplex algorithm has been applied to enable the Si L2,3VV and Si L1L2,3V spectra to be decomposed (decoupled) into their component (p-, sp- and s/L2H like) peaks. Changes in the relative contributions of these components have been compared with changes induced by disordering and hydrogenation. It is shown that both the Si L2,3VV and Si L1L2,3V lines give a semiquantitative method for monitoring hydrogen incorporation and changes in the localised states near the valence band edge. Results are presented for varying amounts of disorder (or amorphousness) produced by argon ion bombardment of the surface. A number of results are ·presented· for artificial and naturally hydrogenated surfaces as well as for different deposition techniques. AES and XPS are shown to be very sensitive to changes in disorder (amorphousness) and hydrogen bonding in a-Si:H. The L1L2,3V Auger spectrum is found to be particularly sensitive. Both the AES and XPS VB spectra for a disordered c-Si sample give new information on the affect of disorder on the DOS. The L1L2,3V Auger line is also shown to be sensitive to varying degrees of disorder. Si L2,3VV and L1L2,3V spectra are successfully used to study the effect of several rehydrogenation methods on a-Si. These methods are shown to lead to different amounts of hydrogen in the surface as well as differences in the type of hydrogen bonding. A-Si:H prepared using different techniques is shown to have differences in the amount of order and hydrogen present in the films produced. The deposition technique is also seen to effect the type of hydrogen bonding present in the surface. A novel transfer vessel has been constructed to enable samples prepared in one system to be analysed in another UHV system without exposure to air and the subsequent contamination of the surface. Results are presented for a pure, 'as deposited' surface of a-Si:H prepared by GD. The 'as deposited' surface is shown to be significantly different to one that has been argon ion cleaned and then rehydrogenated. Also using the transfer method changes in the Si L1L2,3V, Si L2,3VV and XPS VB spectra were studied for an a-Si:H surface after heating above the first desorption threshold for hydrogen. This enables the effect of different Si-H bonding configurations on the VBDOS to be studied.
APA, Harvard, Vancouver, ISO, and other styles
5

Ferré, Tomàs Rafel. "Surface passivation of crystalline silicon by amorphous silicon carbide films for photovoltaic applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2008. http://hdl.handle.net/10803/6350.

Full text
Abstract:
En aquesta tesi s'estudia la passivació del silici cristal·lí per a la producció de cèl·lules solars d'alta eficiència (> 20%) a baix preu.
Actualment la indústria fotovoltaica empra capes de nitrur de silici crescut mitjançant la tècnica PECVD. Com a alternativa, es presenta el carbur de silici amorf (a-SiC), també crescut mitjançant PECVD. Resultats anteriors mostren que la passivacio del silici a partir de carbur de silici amorf son excel·lents quan el material és ric en silici i dopat amb fòsfor. L'alt contingut en silici provoca absorció de la llum a la capa, que no es tradueix en corrent elèctric, fent d'aquesta manera que el material sigui només útil quan s'aplica a la cara no il·luminada de la cèl·lula.
L'objectiu d'aquesta tesi és millorar les propietats de passivació del carbur de silici afegint els requisits indispensables en cèl·lules solars: uniformitat, transparència i propietats antireflectants, estabilitat a llarg termini i enfront altes temperatures. A part de les aplicacions tecnològiques també es pretèn entendre millor les propietats fonamentals de passivació.
Els principals resultats són:
- La passivació millora a mesura que s'incrementa el gruix de la capa de a-SiC, fins arribar a una saturació a partir de 50 nm. El mecanisme responsable es una millor saturació dels defectes de la interficie amb hidrogen. Al contrari del que es pensava a priori, la càrrega el·lèctrica emmagatzemada a la capa es manté constant amb el gruix.
- Experiments amb "corona charge" indiquen que l'origen de la càrrega el·lèctrica que produeix la passivació per efecte de camp es troba en la densitat d'estats a la interfície.
- No ha estat possible trobar una capa tranparent (rica en carboni) amb bona passivació. La millor aproximació per combinar passivació més transparència és emprar dues capes, una molt prima rica en silici per passivar i l'altra rica en carboni per aconseguir les propietats antireflectants adequades. S'ha optimitzat el gruix de la capa rica en silici per aconseguir un compromís entre la pèrdua de corrent degut a l'absorció de la llum a la capa i les propietats de passivació. Aquesta combinació de doble capa s'ha fet servir per passivar bases tipus p i emissors tipus n amb resultats excel·lents. Finalment, amb la doble capa es va poder fabricar la primera cèl·lula passivada amb carbur de silici amb una eficiencia > 20%.
- S'ha desenvolupat un material nou: l'al·leació de silici, carboni i nitrogen dopada amb fòsfor. Aquest material ha donat els millors resultats de passició fins ara obtingut dins el nostre grup en bases tipus p i tipus n i en emissors tipus n. La composició òptima és rica en silici i la combinació de capes dobles amb diferents composicions, com en el cas anterior, torna a donar bons resultats de passivació i transparència.
- S'han desenvolupat experiments d'estrès tèrmic a alta temperatura. Les propietats de passivació es veuen fortament afectades desprès de l'estrès si les capes són riques en silici. D'altra banda, les dobles capes mostren una estabilitat molt més alta a l'estrès tèrmic.
The thesis focuses on the study of surface passivation of crystalline silicon to produce high efficiency solar cells (with conversion efficiencies > 20%) at reduced prices. The state of the art in surface passivation is done by thin films of amorphous silicon nitride grown by Plasma Enhanced Chemical Vapour Deposition (PECVD) and it is a very well established material in the photovoltaic field.
In this thesis we offer an alternative that is based on amorphous silicon carbide (a-SiC), also grown by PECVD. The passivation properties of silicon carbide have been already studied in our group finding that excellent results can be obtained when the films are rich in silicon, especially for those doped with phosphorus to make a n-type material. Because this feature leads to undesirable absorption of solar light within the films that does not contribute to the photocurrent, silicon carbide would then be relegated to passivate only the rear side of the solar cell.
The aim of this work is to improve surface passivation properties developed previously and add compulsory requisites for the application of crystalline solar cells. These requisites are: uniformity, transparency and antireflective properties, stability under long term operation and stability under high temperature steps (allowing screen printing processes). Also it is the willing to provide a better understanding of the fundamental properties.
The main results achieved are enumerated hereafter:
- Surface passivation improves with the film thickness and then saturates for films thicker than 50 nm. The mechanism responsible for this improvement is not an increase of the electric charge in the film, as in principle could be thought, but a better saturation of defects by the presence of hydrogen. The amount of charge density seems to be independent of the film.
- Experiments of corona charge reveal some treats about the nature of the charge density to provide the field effect passivation. The origin of the charge seems to be a continuous density of states at the interface, rather a fixed charge allocated in the film.
- None of the attempts using carbon rich films, which are transparent and with antireflective properties, resulted in excellent surface passivation. Such attempts included variation of the deposition parameters, use of remote plasma PECVD with high incorporation of hydrogen, and introduction of nitrogen of in the phosphorus doped a-SiC films. Therefore, up to now it becomes apparent that it is a fundamental property of silicon carbide films the necessity to be rich in silicon to perform surface passivation.
- The way to combine surface passivation and antireflective properties was applying stacks of different a-SiC layers: one silicon rich and one carbon rich. The thickness of the silicon rich layer was optimized to reach a trade-off between level of passivation and lost of photocurrent due to the absorption in the film. The stacks were used to passivate p-type bases, with reasonably good results, and n+- type emitters, with very good results. The stacks provided the the first silicon solar a-SiC rear side passivated with efficiency above 20%.
- A new material was tested: a ternary alloy of silicon, carbon and nitrogen doped with phosphorus. This material was applied to n- and p-type bases and n+-type emitters, presenting the best results in surface passivation achieved by our group, and comparable to surface passivation record achieved by amorphous silicon carbide. Best composition was rich in silicon, and again stacks of silicon rich and carbon rich films was combined successfully.
- Stability against thermal processes was tested on different passivation schemes. After the treatment, the passivation is strongly reduced for single silicon rich films, which were offering good initial results. On the other hand, the stacks with a second carbon rich film maintain reasonably well the surface passivation properties.
APA, Harvard, Vancouver, ISO, and other styles
6

Almeida, Serrita Avril. "Modification of amorphous silicon nitride surfaces by ion implantation of gallium." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/843307/.

Full text
Abstract:
This study was undertaken to investigate the possibility of synthesis of nitride based semiconductors. To this end hydrogenated amorphous silicon nitride (a-SiNx:Hy) has been deposited as the starting material using PECVD (plasma enhanced chemical vapour deposition). Then the effects of implanting gallium into the a-SiNx:H target material have been studied with the aim of forming GaN compounds. Should this technique work, it opens the possibility of carrying out similar synthesis of Al, hi and other nitride based compounds. PECVD hydrogenated amorphous silicon nitride thin films are studied as a function of the ammonia/silane gas ratio. The power coupled to the plasma, pressure and the substrate temperature were held constant, while the gas flow ratio of NH3/SiH4 was varied. IV measurements on the metal- nitride-metal structures indicated that the conduction mechanism might be explained by Poole-Frenkel conduction. The composition of the a-SiNx:Hy films were analysed using Rutherford backscattering spectroscopy (RBS) and Elastic recoil detection analysis (ERDA). The Si content decreased in a logarithmic manner for 0 < NH3/SiH4 < 4 and saturated for higher NH3/SiH4, ratios at 27 at.%. The N content mirrored this trend and saturated to a maximum asymptotic value of 49 at.% for NH3/SiH4 > 4. Stress, refractive index and optical absorption studies were also conducted. A turning point for most of the properties was observed at a NH3/SiH4 ratio of 4. This corresponds to a N/Si ratio of about 1.4 with a hydrogen content of 22 at.% for the deposited films. Below this ratio, a-SiNx:H films have high growth rates, a refractive index between 1.9 and 2.7, a N/Si ratio between 0.5 and 1.5 and moderate values of compressive stress (~ 0.7 GPa). While, above this pivotal ratio, growth rates become significantly lower, the refractive index minimises to 1.8, N and Si concentrations in the films saturate and the compressive stress rapidly increases. Evidence has been found for Ga-N bonds by implanting gallium into amorphous silicon nitride films. The a-SiNx:H films grown at high gas ratios (R > 70) are highly stressed and the nitrogen content is saturated. They are, therefore, ideally suited to forming GaN bonds under the high energy conditions of Ga ion implantation, a phase that is not thermodynamically favourable. X-ray photoelectron spectroscopy (XPS), FTIR and RBS have been used to examine the bond structure, composition and the depth profile of the synthesised material. It has been found that the implanted Ga bonds with the N from the NH2, NH and SiN bonds and the released Si and H from these bonds combine to form additional SiH. From the RBS and XPS data, annealing at 200°C was shown to increase the thickness of the a-GaN and transform more of the target. The Ga profile moves deeper into the material and the stoichiometric phase of SiN that is thermodynamically stable, recovers. Annealing at a higher temperature (500°C) shows a significant reduction in the amount of H from the amorphous network (ERD), mainly from the NH bonds (FTIR), thus leaving the free N available to bond with the unbonded Ga in the material. Up to ~ 22 at.% Ga is present in the material and can be converted to GaN on annealing. Electron diffraction through the material shows no evidence of any crystallites in the synthesised material.
APA, Harvard, Vancouver, ISO, and other styles
7

Suwito, Dominik [Verfasser]. "Intrinsic and doped amorphous silicon carbide films for the surface passivation of silicon solar cells / Dominik Suwito." München : Verlag Dr. Hut, 2011. http://d-nb.info/1011441772/34.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Labrune, Martin. "Silicon surface passivation and epitaxial growth on c-Si by low temperature plasma processes for high efficiency solar cells." Phd thesis, Ecole Polytechnique X, 2011. http://pastel.archives-ouvertes.fr/pastel-00611652.

Full text
Abstract:
This thesis presents a work which has been devoted to the growth of silicon thin films on crystalline silicon for photovoltaic applications by means of RF PECVD. The primary goal of this work was to obtain an amorphous growth on any c-Si surface in order to provide an efficient passivation, as required in heterojunction solar cells. Indeed, we demonstrated that epitaxial or mixed phase growths, easy to obtain on (100) Si, would lead to poor surface passivation. We proved that growing a few nm thin a-Si1-xCx:H alloy film was an efficient, stable and reproducible way to hinder epitaxy while keeping an excellent surface passivation by the subsequent deposition of a-Si:H films. Process optimization mainly based on Spectroscopic Ellipsometry, Effective lifetime measurements (Sinton lifetime tester) and current-voltage characterization led us to demonstrate that it was possible to obtain a-Si:H/c-Si heterojunction solar cells with stable VOC of 710 mV and FF of 76 % on flat (n) c-Si wafers, with solar cells of 25 cm2 whose metallization was realized by screen-printing technology. This work has also demonstrated the viability of a completely dry process where the native oxide is removed by SiF4 plasma etching instead of the wet HF removal. Last but not least, the epitaxial growth of silicon thin films, undoped and n or p-type doped, on (100)-oriented surfaces has been studied by Spectroscopic Ellipsometry and Hall effect measurements. We have been able to fabricate homojunction solar cells with a p-type emitter as well as p-i-n structures with an undoped epitaxial absorber on a heavily-doped (p) c-Si wafers.
APA, Harvard, Vancouver, ISO, and other styles
9

Carteret, Cédric. "Etude, par spectroscopie dans le proche infrarouge, et modélisation des structures de surface et de l'hydratation de silices amorphes." Nancy 1, 1999. http://www.theses.fr/1999NAN10238.

Full text
Abstract:
Ce travail contribue à l'étude des propriétés de surface des silices amorphes. La principale technique d'analyse mise en oeuvre pour caractériser les hydroxyles présents à la surface du matériau (silanol et eau physisorbée) est la spectrométrie proche infrarouge (PIR). Les types de silanols à la surface d'une silice, leurs interactions, leur condensation par traitement thermique sont décrits à partir des absorptions IR. Le coefficient molaire d'absorption intégrée pour les transitions vOH, (v+[delta])SiOH et 2vOH est obtenu en corrélant PIR et thermogravimétrie. Ce demier ne dépend pas de l'environnement des hydroxyles pour des transitions de combinaison ou harmonique d'ordre 2 alors qu'il augmente fortement par formation de liaison hydrogène pour la transition fondamentale vOH. Une méthode de mesure spectrométrique de la quantité totale de silanols d'une silice est proposée. A 700°C, la surface d'une silice présente majoritairement des silanols isolés (0,7 OH/nm2). Une attribution détaillée des absorptions IR du groupement SiOH de 100 à 11000 cm-1 est déduite des spectres PIR. Un site de surface est simulé à partir de calculs ab initio sur une série de molécules modèles comportant les groupements SiOH et Si(OH)2. Le PIR présente une région spectrale propre à l'absorption de H2O qui permet de suivre l'hydratation du solide. L'étude quantitative est réalisée en combinant spectres PIR et isothermes d'adsorption par gravimétrie. Les silanols sont les centres d'adsorption et nous les avons classés en fonction de leur affinité pour la molécule d'eau. Lors de l'hydratation, les molécules d'eau occupent en premier les sites préférentiels puis forment des agrégats autour des premiers sites. Le verre poreux Vycor contient du bore en impureté. Sa migration vers la surface par traitement thermique est mise en évidence. Elle s'accompagne de la formation de groupements boranol. Les propriétés du bore de surface (hydratation et dissolution) et les vibrations de BOH sont examinées.
APA, Harvard, Vancouver, ISO, and other styles
10

Pepenene, Refuoe Donald. "Macroscopic and Microscopic surface features of Hydrogenated silicon thin films." University of the Western Cape, 2018. http://hdl.handle.net/11394/6414.

Full text
Abstract:
Magister Scientiae - MSc (Physics)
An increasing energy demand and growing environmental concerns regarding the use of fossil fuels in South Africa has led to the challenge to explore cheap, alternative sources of energy. The generation of electricity from Photovoltaic (PV) devices such as solar cells is currently seen as a viable alternative source of clean energy. As such, crystalline, amorphous and nanocrystalline silicon thin films are expected to play increasingly important roles as economically viable materials for PV development. Despite the growing interest shown in these materials, challenges such as the partial understanding of standardized measurement protocols, and the relationship between the structure and optoelectronic properties still need to be overcome.
APA, Harvard, Vancouver, ISO, and other styles
More sources

Books on the topic "Amorphous Silica Surface"

1

Devine, Roderick A. B. The Physics and Technology of Amorphous SiO2. Boston, MA: Springer US, 1988.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
2

B, Devine Roderick A., ed. The physics and technology of amorphous SiO₂. New York: Plenum Press, 1988.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
3

Hydrogenated amorphous silicon. Cambridge: Cambridge University Press, 1991.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
4

1940-, Tanaka K., ed. Glow-discharge hydrogenated amorphous silicon. Tokyo: KTK Scientific Publishers, 1989.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
5

Wilfried G. J. H. M. Sark. Physics and Technology of Amorphous-Crystalline Heterostructure Silicon Solar Cells. Berlin, Heidelberg: Springer-Verlag Berlin Heidelberg, 2011.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
6

Rahman, Mahmud M. Amorphous and Crystalline Silicon Carbide II: Recent Developments Proceedings of the 2nd International Conference, Santa Clara, CA, December 15-16, 1988. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
7

Senoussaoui, Nadia. Einfluss der Oberflächenstrukturierung auf die optischen Eigenschaften der Dünnschichtsolarzellen auf der Basis von a-Si : H und [mu]c-Si: H. Jülich: Forschungszentrum Jülich, Zentralbibliothek, 2004.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
8

Street, R. A. Hydrogenated Amorphous Silicon. Cambridge University Press, 2005.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
9

Street, R. A. Hydrogenated Amorphous Silicon. Cambridge University Press, 2010.

Find full text
APA, Harvard, Vancouver, ISO, and other styles
10

Street, R. A. Hydrogenated Amorphous Silicon. Cambridge University Press, 2011.

Find full text
APA, Harvard, Vancouver, ISO, and other styles

Book chapters on the topic "Amorphous Silica Surface"

1

Bernasconi, M. "AB-INITIO MOLECULAR DYNAMICS SIMULATION OF AMORPHOUS SILICA SURFACE." In Defects in SiO2 and Related Dielectrics: Science and Technology, 371–90. Dordrecht: Springer Netherlands, 2000. http://dx.doi.org/10.1007/978-94-010-0944-7_13.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Bacca, E., L. F. Castro, M. Gómez, and P. Prieto. "Photoconductivity in Posthydrogenated Amorphous Silicon Thin Films." In Lectures on Surface Science, 78–81. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-71723-9_12.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Horbach, J., T. Stühn, C. Mischler, W. Kob, and K. Binder. "Amorphous Silica at Surfaces and Interfaces: Simulation Studies." In High Performance Computing in Science and Engineering ’03, 167–79. Berlin, Heidelberg: Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-642-55876-4_13.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Unger, K. K. "Surface Structure of Amorphous and Crystalline Porous Silicas." In Advances in Chemistry, 165–81. Washington DC: American Chemical Society, 1994. http://dx.doi.org/10.1021/ba-1994-0234.ch008.

Full text
APA, Harvard, Vancouver, ISO, and other styles
5

Wagner, H. "Similarities Between Crystalline Silicon Surfaces and Amorphous Silicon Films." In Springer Proceedings in Physics, 155–60. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-84933-6_13.

Full text
APA, Harvard, Vancouver, ISO, and other styles
6

Zeller, M. V., and J. J. Bellina. "Effect of Surface Modifications of Cubic SiC on Metallization Interactions." In Amorphous and Crystalline Silicon Carbide and Related Materials, 133. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-93406-3_19.

Full text
APA, Harvard, Vancouver, ISO, and other styles
7

Kaplan, R. "Surface Structures of β-SiC, 6H-SiC and Pseudomorphic Si Adlayers." In Amorphous and Crystalline Silicon Carbide and Related Materials, 100–106. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-93406-3_14.

Full text
APA, Harvard, Vancouver, ISO, and other styles
8

Rappich, Jörg. "Electrochemical Passivation and Modification of c-Si surfaces." In Physics and Technology of Amorphous-Crystalline Heterostructure Silicon Solar Cells, 95–130. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-22275-7_4.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Das, Sonali, Avra Kundu, Chandan Banerjee, Prasenjit Dey, Swapan K. Datta, and Hiranmay Saha. "Front Surface Glass Texturization for Improved Performance of Amorphous Silicon Solar Cell." In Physics of Semiconductor Devices, 375–78. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-03002-9_94.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Germain, Aurèle, Marta Corno, and Piero Ugliengo. "Computing Binding Energies of Interstellar Molecules by Semiempirical Quantum Methods: Comparison Between DFT and GFN2 on Crystalline Ice." In Computational Science and Its Applications – ICCSA 2021, 632–45. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-86976-2_43.

Full text
Abstract:
AbstractInterstellar Grains (IGs) spread in the Interstellar Medium (ISM) host a multitude of chemical reactions that could lead to the production of interstellar Complex Organic Molecules (iCOMs), relevant in the context of prebiotic chemistry. These IGs are composed of a silicate-based core covered by several layers of amorphous water ice, known as a grain mantle. Molecules from the ISM gas-phase can be adsorbed at the grain surfaces, diffuse and react to give iCOMs and ultimately desorbed back to the gas phase. Thus, the study of the Binding Energy (BE) of these molecules at the water ice grain surface is important to understand the molecular composition of the ISM and its evolution in time. In this paper, we propose to use a recently developed semiempirical quantum approach, named GFN-xTB, and more precisely the GFN2 method, to compute the BE of several molecular species at the crystalline water ice slab model. This method is very cheap in term of computing power and time and was already showed in a previous work to be very accurate with small water clusters. To support our proposition, we decided to use, as a benchmark, the recent work published by some of us in which a crystalline model of proton-ordered water ice (P-ice) was adopted to predict the BEs of 21 molecules relevant in the ISM. The relatively good results obtained confirm GFN2 as the method of choice to model adsorption processes occurring at the icy grains in the ISM. The only notable exception was for the CO molecule, in which both structure and BE are badly predicted by GFN2, a real pity due to the relevance of CO in astrochemistry.
APA, Harvard, Vancouver, ISO, and other styles

Conference papers on the topic "Amorphous Silica Surface"

1

Zhang, Ziyang, Matteo Dainese, Lech Wosinski, Marcin Swillo, Sanshui Xiao, and Min Qiu. "Experimental demonstration of 2D photonic crystal surface cavity in amorphous silicon on silica structure." In OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference. IEEE, 2007. http://dx.doi.org/10.1109/ofc.2007.4348573.

Full text
APA, Harvard, Vancouver, ISO, and other styles
2

Copeland, Grant, Andrew Jacobson, John Kaszuba, Janet Dewey, and Subhash Risbud. "Dependence of Amorphous Silica Surface Speciation on Electric Double Layer (EDL) Overlap in Confinement." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.477.

Full text
APA, Harvard, Vancouver, ISO, and other styles
3

Agnello, S., A. Alessi, G. Iovino, M. Cannas, F. M. Gelardi, and R. Boscaino. "Diffusion and outgassing of O2 in amorphous SiO2 silica nanoparticles with specific surface properties." In 2014 IEEE 9th Nanotechnology Materials and Devices Conference (NMDC). IEEE, 2014. http://dx.doi.org/10.1109/nmdc.2014.6997425.

Full text
APA, Harvard, Vancouver, ISO, and other styles
4

Vukelic, S., B. Gao, S. Ryu, and Y. L. Yao. "Structural Modification of Amorphous Fused Silica Under Femtosecond Laser Irradiation." In ASME 2008 International Manufacturing Science and Engineering Conference collocated with the 3rd JSME/ASME International Conference on Materials and Processing. ASMEDC, 2008. http://dx.doi.org/10.1115/msec_icmp2008-72210.

Full text
Abstract:
Non-linear absorption of femtosecond laser pulses enables the induction of structural changes in the interior of bulk transparent materials without affecting their surface. This property can be exploited for the transmission welding of transparent dielectrics, three dimensional optical data storages and waveguides. In the present study, femtosecond laser pulses were tightly focused within the interior of bulk fused silica specimen. Localized plasma was formed, initiating rearrangement of the network structure. The change in material properties were studied through employment of spatially resolved Raman spectroscopy, atomic force microscopy and optical microscopy. The nature of the physical mechanisms responsible for the alteration of material properties as a function of process parameters is discussed.
APA, Harvard, Vancouver, ISO, and other styles
5

Meng, Fanhe, Jin Liu, and Robert F. Richards. "Molecular Dynamics Study on Thermal Resistance Between Amorphous Silica Nanoparticles." In ASME 2017 Heat Transfer Summer Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ht2017-4894.

Full text
Abstract:
Nanoparticle-based materials have demonstrated extremely low thermal conductivities, a property that has made them attractive candidates in a variety of macroscale and microscale applications. Understanding the thermal transport between nanoparticles is necessary for the further development of these materials. Molecular dynamics simulation is an effective method to investigate thermal transport on these scales because no assumption about phonon transmission at the nanoparticle interface, nor prior knowledge of thermal transport of the system is necessary. In this work, the total thermal resistance between adjacent amorphous silica nanoparticles is calculated using non-equilibrium molecular dynamics simulations (NEMD). Numerical results show that interparticle resistance depends strongly on the forces between particles, in particular the presence or absence of chemical bonds between nanoparticles. In addition, the effect of interfacial force strength on thermal resistance increases as nanoparticle diameter decreases. Numerical results are compared to interparticle resistances determined from the predictions of the analytical constriction resistance model. The simulation results are shown to be in good agreement the constriction resistance theory depending on the choice of surface energy.
APA, Harvard, Vancouver, ISO, and other styles
6

McQueen, Mark T. "Energy and High Surface Area Siliceous Ash From the Combustion of Rice Hulls." In 17th International Conference on Fluidized Bed Combustion. ASMEDC, 2003. http://dx.doi.org/10.1115/fbc2003-018.

Full text
Abstract:
Biomass combustion is an attractive energy production method since it is a zero net emitter of carbon dioxide. Rice hulls are a significant source of biomass fuel: approximately 100Mt of rice hulls are produced yearly from the processing and milling of paddy rice. Previous studies have shown that the ash produced from the combustion of rice hulls possesses pozzolanic properties. When used as a concrete additive, the ash can behave similar to silica fume and improve the strength and porosity of the finished concrete. In such cases, the surface area attributed to the pozzolan is related to the residual carbon content of the ash, which is often well in excess of 5%. The excessive carbon level stems from the awkward geometry of the hulls combined with the low melting point and heat sensitive nature of the ash minerals: these create problems for commercial combustion devices. As a result, the ash produced at these facilities contains either high residual carbon or a high proportion of crystalline silica, both of which renders the ash unattractive for use as a concrete additive. However, if the ash is of sufficient quality to be sold as a concrete additive, the economics of energy generation from the rice hulls can be improved. Test work conducted in Mississauga, Canada has produced an ash with less than 3% residual carbon, and greater than 90% silica, nearly all of which is amorphous. This work was done at temperatures higher than those in conventional operations without significant conversion of the siliceous component from the amorphous state to crystalline forms such as crystobalite or quartz. The key to this unexpected result is an enhanced combustion environment in which the solids residence time at elevated temperatures, and therefore the opportunity for silica phase changes, is minimized. In this instance, the total measured surface area of this ash is lower than that of the other ashes due to the reduced residual carbon content, but the siliceous surface area is equal or greater due to the high amorphous content. Consistent with this fact, the rice hull ash performed well in a number of standard concrete tests, in which the ash replaced 7.5% to 12.5% of the Portland cement for similar water to cement mixture ratios. With proper application of a TORBED process reactor as a combustor, a high value and high surface area siliceous ash can be produced as energy is simultaneously recovered from the system.
APA, Harvard, Vancouver, ISO, and other styles
7

Neralla, Sudheer, Sergey Yarmolenko, Dhananjay Kumar, Devdas Pai, and Jag Sankar. "Cross-Sectional Nanoindentation of Alumina Thin Films Deposited by Pulsed Laser Deposition Process." In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-14924.

Full text
Abstract:
Alumina is a widely used ceramic material due to its high hardness, wear resistance and dielectric properties. The study of phase transformation and its correlation to the mechanical properties of alumina is essential. In this study, interfacial adhesion properties of alumina thin films are studied using cross-sectional nanoindentation (CSN) technique. Alumina thin films are deposited at 200 and 700 °C, on Si (100) substrates with a weak Silica interface, using pulsed laser deposition (PLD) process. Effect of annealing on the surface morphology of the thin films is studied using atomic force microscopy. Xray diffraction studies revealed that alumina thin films are amorphous in nature at 200 °C and polycrystalline with predominant gamma alumina phase at 700 °C.
APA, Harvard, Vancouver, ISO, and other styles
8

Weisz, S. Z., J. Avalos, M. Gomez, A. Many, Y. Goldstein, and E. Savir. "Bulk and surface states on hydrogenated amorphous silicon." In The 8th Latin American congress on surface science: Surfaces , vacuum, and their applications. AIP, 1996. http://dx.doi.org/10.1063/1.51116.

Full text
APA, Harvard, Vancouver, ISO, and other styles
9

Matsumoto, Yasuhiro, René Asomoza, Gustavo Hirata, and Leonel Cota-Araiza. "Boron-carbide p-type layer for amorphous silicon solar cells." In The 8th Latin American congress on surface science: Surfaces , vacuum, and their applications. AIP, 1996. http://dx.doi.org/10.1063/1.51130.

Full text
APA, Harvard, Vancouver, ISO, and other styles
10

Armandi, Marco, Barbara Bonelli, and Edoardo Garrone. "Synthesis and Characterization of Mesoporous and Microporous Carbons With Potential Applications as Hydrogen Storage Media." In ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95740.

Full text
Abstract:
The preparation and physico-chemical characterization of mesoporous and microporous carbons, obtained via a casting procedure, from a SBA-15 silica and a commercial Na-Y zeolite, is reported. XRD spectra showed that ordered carbon replicas occur in all cases. Micro-Raman spectra showed that rather homogeneous powders are obtained, exhibiting the presence of a graphitized carbon phase of small imperfect graphene sheets, typical of sp2 C, along with an amorphous one, notwithstanding the relatively low temperature adopted during the carbonization processes (1173 K). N2 adsorption isotherms at 77 K allowed the determination of BET surface areas and pore volumes: on account of the high porosity and the low specific weight, with respect to zeolites, for example, these carbon materials could be promising media for hydrogen storage. They could be used as such, or after convenient functionalization or metal doping.
APA, Harvard, Vancouver, ISO, and other styles
You might also be interested in the extended bibliographies on the topic 'Amorphous Silica Surface' for particular source types:
Journal articles Dissertations / Theses
We offer discounts on all premium plans for authors whose works are included in thematic literature selections. Contact us to get a unique promo code!

To the bibliography