Gas-phase Synthesis of Silica Nanoparticles: Reaction Kinetics, Synthesis and Characterization PDF Download

Author: Ali Abdali
Publisher:
ISBN: 9783954047048
Category :
Languages : en
Pages : 122

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Author: Yves Huttel
Publisher: John Wiley & Sons
ISBN: 3527340602
Category : Technology & Engineering
Languages : en
Pages : 416

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The first overview of this topic begins with some historical aspects and a survey of the principles of the gas aggregation method. The second part covers modifications of this method resulting in different specialized techniques, while the third discusses the post-growth treatment that can be applied to the nanoparticles. The whole is rounded off by a review of future perspectives and the challenges facing the scientific and industrial communities. An excellent resource for anyone working with the synthesis of nanoparticles, both in academia and industry.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Silica nanoparticles and zirconia coated silica nanoparticles were prepared by Stober method.and various subsequent methods. The nanoparticles obtained were characterized by XRD, SEM, EDAX and IR analytical techniques. The XRD study of pure ZrO2 shows well crystalline characteristics with the presence of 100% monoclinic phase. The coated nanoparticles are found to be amorphous in nature. SEM study indicate the particles to possess disorder morphology with the particle are attached to each other through grain boundary to form agglomerated structure. The zirconia coated silica nanoparticles were used as a efficient catalyst for the synthesis of Bis(indolyl) methane under solvent free condition. The Bis(indolyl) methane were obtained with high yield and purity.

Author: Yves Huttel
Publisher: John Wiley & Sons
ISBN: 3527698426
Category : Technology & Engineering
Languages : en
Pages : 416

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Book Description
The first overview of this topic begins with some historical aspects and a survey of the principles of the gas aggregation method. The second part covers modifications of this method resulting in different specialized techniques, while the third discusses the post-growth treatment that can be applied to the nanoparticles. The whole is rounded off by a review of future perspectives and the challenges facing the scientific and industrial communities. An excellent resource for anyone working with the synthesis of nanoparticles, both in academia and industry.

Author: Brenna Marie Gibbons
Publisher:
ISBN:
Category :
Languages : en
Pages :

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The shift towards a more sustainable energy economy is one of the imperative challenges facing humanity today, and balancing prosperity against the risks of irrevocable climate change will require policy adjustments and scientific innovations on a global scale. In particular, it is essential to move away from burning fossil fuels to meet our energy needs; rising atmospheric CO2 has already contributed to ocean acidification and record high temperatures, and the dangers only increase with every ton of CO2 emitted. Fortunately, wind and solar radiation provide vast resources for renewable energy, and remarkable progress has been made in the past several years towards incorporating these sources. As the use of renewable energy generation rises, so too does the need for efficient energy storage and conversion that are not predicated on the use of fossil fuels. Electrochemistry offers one piece of the solution through fuel cells, batteries, and other technologies. The drive to discover and refine catalysts for these electrochemical reactions is therefore of critical importance to our shared sustainable energy future. Catalyst design has benefited from the close integration of experiment and theory in a cyclical framework whereby new materials are synthesized, characterized, tested for electrochemical performance, and used to improve predictions for future catalysts. A similar framework is used in this dissertation as we delve into each part of the catalyst development cycle. We begin with materials synthesis of nanoparticles, which are of scientific interest for their unique properties compared to bulk materials. Inert gas condensation is introduced as a method for nanoparticle synthesis, and we present several systems including NiFe, Mn oxides, and other transition metals. We observe several unusual morphologies, including cubic particles and the alignment of particles on surface defects. In addition, we study catalytic activity for the oxygen evolution reaction (OER) on both NiFe of varying sizes and Mn oxide promoted with Au. We demonstrate that inert gas condensation is a highly versatile method for synthesizing nanoparticles both for fundamental studies and as electrochemical catalysts. We then focus on the details of one specific catalyst: CuAg for the oxygen reduction reaction (ORR). The ORR is a key component of fuel cells and metal-air batteries, and developing efficient and cost-effective catalysts for this reaction will entail improving our understanding of catalyst activity. We find that CuAg nanoparticles outperform either Cu or Ag nanoparticles, and that they are on par with thin films of similar compositions. To elucidate the origin of this heightened activity we use a combination of density functional theory (DFT) and in situ characterization. X-ray absorption spectroscopy (XAS) allows us to follow the electronic state of our catalyst under reaction conditions, and while we see little change in the electronic or geometric state of the Ag atoms in CuAg, the Cu atoms in CuAg are markedly different than in pure Cu. DFT predicted that Cu atoms in a Ag lattice would have dramatically different d-band states and a smaller oxygen binding energy, and our in situ experiments confirmed that Cu atoms in CuAg are more reduced than in Cu at ORR-relevant potentials. CuAg is revealed to owe its enhanced activity not to a small change in Ag, the more active metal alone, but to a substantial modification of Cu that boosts the overall performance. We hope that better understanding this system will contribute to the design of highly active non-precious catalysts for the ORR. Traditionally new catalysts for a reaction are chosen based on a combination of conventional theory calculations such as DFT and educated guesswork informed by scientific insight. However the vast search space of possible catalyst materials and the wealth of computational and experimental data for reactions studied over decades opens the possibility to use machine learning to speed the iterative design process. In the final portion of this work we consider the application of machine learning to case studies in both computational and experimental materials science. To start, we examine several algorithms for predicting metallic glasses on ternary alloys from a historical dataset based on their compositions alone. Using the two best models, we then investigate combining sparse historical data with new high-throughput data and find that more data is not always better. On the other hand, materials science encompasses many questions for which the data is much less plentiful. One strategy to maximize the value of small datasets is transfer learning, in which the outputs of one model inform subsequent models. We apply transfer learning to experimental Ni superalloy mechanical properties and nitric oxide reduction reaction computational data, and we determine that in both cases transfer learning is an effective way to improve model accuracy without collecting new data. In summary, this dissertation explores each step of the catalyst development cycle, from nanoparticle synthesis, to electrochemical testing, advanced in situ characterization, and predicting new materials via machine learning. This work aims to present fundamental insights on catalytic activity as well as several avenues for future catalyst development with the goal of contributing to a more efficient energy future.

Author: Hooisweng Ow
Publisher:
ISBN:
Category :
Languages : en
Pages : 314

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Author: Michael A. Serio
Publisher:
ISBN:
Category : Science
Languages : en
Pages : 296

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These papers by leading experts look at current methods for synthesizing new materials. The methods presented include chemical vapor deposition synthesis, solution synthesis, pyrolysis and combustion synthesis, and polymer synthesis. Featuring in-depth coverage of ceramic materials, the volume also discusses group III nitrides, fullerenes, and ferroelectrics.

Author: Anjana Devi
Publisher: The Electrochemical Society
ISBN: 9781566774277
Category : Technology & Engineering
Languages : en
Pages : 1128

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Author: Hongyi Dang
Publisher:
ISBN:
Category :
Languages : en
Pages : 188

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Synthesis of silicon nanoparticles is of great interest because of their unique optical and electronic properties. Fundamental understanding of the various interconnected mechanisms involved in the particle formation, such as gas phase and gas-surface phase chemical kinetics and particle size evolution through nucleation, growth, coagulation and coalescence, would be of great value in designing and optimizing processes for producing silicon nanoparticles. On the other hand, the same understanding can also contribute to contamination control in the semiconductor industry, where particles formed by homogeneous nucleation within the processing environment are rapidly becoming the most important source for yield loss as integrated circuits become smaller.^Moreover, silicon particle formation by thermal decomposition of silane is a prototypical example of a system where particle nucleation and growth are believed to occur via a complex network of chemical reactions, as opposed to nucleation from, and condensation of, a supersaturated vapor. First, a general two dimensional (2D) model has been developed for silicon nanoparticle synthesis by silane thermal decomposition driven by laser heating in a tubular reactor. This fully coupled model includes fluid dynamics, laser heating, gas phase and surface phase chemical reactions, and aerosol dynamics, which includes particle transport and evolution by convection, diffusion, thermophoresis, nucleation, surface growth and coagulation processes. A moment method, based upon a lognormal particle size distribution, and a sectional method are used to model the aerosol dynamics. The simulation results obtained by the two methods are compared.^The sectional method is capable of capturing the bimodal behavior that occurs locally during the process, while the moment method is computationally more efficient. The effect of operating parameters, such as precursor concentration, gas phase composition, inlet gas velocity and laser power input, on the characteristics of the particles produced are investigated. Based on the above general 2D model, another 2D model that closely simulates the silicon nanoparticle synthesis by silane thermal decomposition in the six-way cross laser-driven aerosol reactor in our lab was developed. This model incorporates fluid dynamics, laser heating, gas phase and surface phase chemical reactions, and aerosol dynamics, with particle transport and evolution by convection, diffusion, thermophoresis, nucleation, surface growth, coagulation and coalescence processes. Because of the complexity of the problem at hand, the simulation was carried out via several sub-models.^First, the chemically reacting flow inside the reactor was simulated in three dimensions in full geometric detail, but with no aerosol dynamics and with highly simplified chemistry. Second, the reaction zone was simulated using an axisymmetric two dimensional CFD model, whose boundary conditions were obtained from the first step. Last, a two dimensional aerosol dynamics model was used to study the silicon nanoparticle formation using more complete silane decomposition chemistry, together with the temperature and velocities extracted from the reaction zone CFD simulation. A bivariate moment model was used to describe the evolution of particle size and morphology. The model predicted that spherical particles are produced at the center of the reaction zone, while non-spherical particle aggregates are formed at the outlet of the reaction zone.^Precursor concentration, peak temperature and residence time are shown to be major parameters affecting reactor yield and the characteristics of the product particles. Gas phase kinetics are a key component of our model of silicon nanoparticle synthesis. However, description of cluster growth to a critical nucleus size that can be treated as a solid particle can involve thousands of distinct elementary reactions. Exploration of such large reaction mechanisms is facilitated by the use of automated reaction mechanism generation, in which a computer constructs a detailed reaction mechanism according to a pre-specified set of rules. In order to utilize the silane decomposition reaction mechanisms generated in this way, like that published by (Wong et al. 2004), one must translate the mechanism from the compact description used in automated reaction mechanism generation codes to more conventional descriptions used in reacting flow simulations.^Thus, this work set up a framework for translating their mechanisms produced by automated mechanism generation software, into a form that is readily usable in our simulations. First, the string code representation of each species is translated into a bond electron matrix (BEM). Then a group additivity scheme is used to process the BEM to find out the types and quantities of the groups that make up the molecule. A straightforward walking ring finding algorithm is used to find the smallest set of independent rings with smallest sizes. At last, the thermochemical properties are estimated based on the contribution from each group at various temperatures. Those thermodynamics data in turn were fit to a standard polynomial form (NASA format), that can serve as input for CHEMKIN or other similar packages for calculation of thermodynamic, kinetic and transport properties.^We have carried out preliminary studies using this newly translated kinetics model for modeling silicon nanoparticle synthesis by silane decomposition in a plug flow reactor with constant temperature and pressure.

Author: Vineet Kumar
Publisher: CRC Press
ISBN: 1000367207
Category : Technology & Engineering
Languages : en
Pages : 603

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Nanomaterials contain some unique properties due to their nanometric size and surface functionalization. Nanomaterial functionalization also affects their compatibility to biocompatibility and toxicity behaviors. environment and living organism. This makes functionalized nanomaterials a material with huge scope and few challenges. This book provides detailed information about the nanomaterial functionalization and their application. Recent advancements, challenges and opportunities in the preparation and applications of functionalized nanomaterials are also highlighted. This book can serve as a reference book for scientific investigators, doctoral and post-doctoral scholars; undergrad and grad. This book is very useful for multidisciplinary researchers, industry personnel’s, journalists, and policy makers. Features: Covers all aspects of Nanomaterial functionalization and its applications Describes and methods of functionalized nanomaterials synthesis for different applications Discusses the challenges, recent findings, and cutting-edge global research trends on functionalization of nanomaterials and its applications It discusses the regulatory frameworks for the safe use of functionalized nanomaterials. It contains contributions from international experts from multiple disciplines.