Chemical Engineering Commons^™

High Performance Zno Varistors Prepared From Nanocrystalline Precursors For Miniaturised Electronic Devices, Suresh Pillai, Declan Mccormack, John Kelly, Raghavendra Ramesh

Articles

An industrially viable solution-based processing route using minimal amounts of solvent has been used to prepare bulk quantity nanopowders (average particle size 15.3 nm) for the fabrication of ZnO varistors. The xerogels, calcined powders and sintered materials were fully characterised. The preparation of varistors from nanopowders has been optimised by studying the effect of temperature on grain growth, densification and breakdown voltage. The varistors are prepared by sintering at 1050 C for 2 hours, a temperature that is significantly lower than that used in the current industrial process. Highly dense varistor discs prepared from the sintered material produce devices, with …

Process For Formation Of Cationic Poly (Lactic-Co-Glycolic Acid) Nanoparticles Using Static Mixers, Yamuna Reddy Charabudla

University of Kentucky Master's Theses

Nanoparticles have received special attention over past few years as potential drug carriers for proteins/peptides and genes. Biodegradable polymeric poly (lactic-co-glycolic acid) (PLGA) nanoparticles are being employed as non-viral gene delivery systems for DNA. This work demonstrates a scalable technology for synthesis of nanoparticles capable of gene delivery. Cationic PLGA nanoparticles are produced by emulsiondiffusion- evaporation technique employing polyvinyl alcohol (PVA) as stabilizer and chitosan chloride for surface modification. A sonicator is used for the emulsion step and a static mixer is used for dilution in the diffusion step of the synthesis. A static mixer is considered ideal for the …

Study Of Interaction Between Indium Species And Dna In The Formation Of Dna -Templated Nanowires, Shivashankar Suryanarayanan

Doctoral Dissertations

A primary goal of semiconductor industry is to improve device performance and capability by downscaling feature size and upscaling packaging density. As optical-lithography, the mainstream technology for microfabrication, is being stretched to its limit, new unconventional fabrication techniques are being explored as alternatives. A "Bottom-up" approach for manufacturing is emerging as an answer to limitations posed by the traditional "Top-down" approach. Nanowires, bearing the potential of being the basic building blocks for such an approach, are gaining tremendous attention in nanoelectronics. Metal nanowires fabricated using DNA as templates have potential for precise control of length, diameter and positioning. However, wires …

Improved Li-Ion Battery Performance By Coating Cathode Nano-Particles Using Atomic Layer Deposition, Renske Beetstra, John Nijenhuis, Erik M. Kelder, J. Ruud Van Ommen

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The use of nanoparticles as a cathode in Li-ion batteries is very promising. However, many of the cathode materials that could be economically attractive suffer from degradation. Therefore, an objective is to stabilise the surface, in order to reduce the degradation. A setup was build to coat the nanoparticles by atomic layer deposition in a fluidised bed reactor. The first fluidisation results for the nanoparticles are presented in this paper.

Role Of Sound Vibration During Aeration Of Nano-Sized Powders, Paola Ammendola, Riccardo Chirone

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

The behaviour of two different nano-sized powders, Al2O3 (40 nm) and SiO2 (15 nm), during aeration has been investigated in a laboratory scale fluidized bed. The fluidization quality of both powders is very poor without application of acoustic fields even if some bed expansion has been found. The application of acoustic fields of intensities larger than 135 dB and frequencies close to 120 Hz is able to increase the fluidization quality of both powders. Sound is also able to promote an apparent self-fluidization of a relatively thin portion of the upper part of the bed. The possibility that there is …

Mechanistic Study Of Nano-Particle Fluidization, X. S. Wang, F. Rahman, Martin J Rhodes

The 12th International Conference on Fluidization - New Horizons in Fluidization Engineering

Degussa Aerosil R974 powder, with a primary particle size of 12 nm, was fluidized using nitrogen in a cylindrical vessel, 50-mm-id and 900 mm in height. Characteristics of incipient fluidization are analysed in relation to variations in the initial packing conditions. Bed collapse experiments were performed and the results are used for assessing fluidization characteristics of the particles. It was found that nanoparticles exhibit characteristics of both Group A and Group C powders. Various methods for estimating the cohesion forces between nanoparticle aggregates are discussed.

Enhancement Of Fluidization And Filtration Using Nanoparticle Agglomerates And Aerogels, Jose A. Quevedo

Dissertations

Previous works have classified the fluidization behavior of nanoparticles as Agglomerate Particulate Fluidization (APF) and Agglomerate Bubbling Fluidization (ABE). These fluidization behaviors are quite different in regard to the fluidized bed expansion, the presence of bubbles and the smoothness of the bed surface, with APF nanopowders showing a much more homogeneous fluidization and a much better dispersion than ABE nanopowders which are generally very difficult to fluidize and show vigorous bubbling. In the present work, the fluidization of APF as well as ABF nanopowders is studied in depth, both conventionally, and in the presence of extemal assistance; several related topics …

Novel Pemfc Cathodes Prepared By Pulse Deposition, Subasri M. Ayyadurai, Yoon-Seok Choi, Prabhu Ganesan, Swaminatha P. Kumaraguru, Branko N. Popov

Faculty Publications

A pulse electrodeposition method of preparing thin platinum catalyst layers for polymer electrolyte membrane fuel cell (PEMFC) cathodes has been developed through surface activation of the gas diffusion layer (GDL) by a wetting agent. The performance of the catalyst layer was optimized by wetting agent type, immersion time in the wetting agent, and pulse deposition parameters such as total charge density, peak current density, and duty cycle ratio. The T_off time played a more important role than the T_on time in determining the electrode characteristics such as high concentration of Pt, smaller particle size, and loading. Pt cathodes …

On One-Dimensional Self-Assembly Of Surfactant-Coated Nanoparticles, Jee-Ching Wang, Partho Neogi, Daniel Forciniti

Chemical and Biochemical Engineering Faculty Research & Creative Works

Nanometer-sized metal and semiconductor particles possess novel properties. To fully realize their potential, these nanoparticles need to be fabricated into ordered arrays or predesigned structures. A promising nanoparticle fabrication method is coupled surface passivation and self-assembly of surfactant-coated nanoparticles. Due to the empirical procedure and partially satisfactory results, this method still represents a major challenge to date and its refinement can benefit from fundamental understanding. Existing evidences suggest that the self-assembly of surfactant-coated nanoparticles is induced by surfactant-modified interparticle interactions and follows an intrinsic road map such that short one-dimensional (1D) chain arrays of nanoparticles occur first as a stable …

Fabrication Of Core-Shell Nanoparticles, Zhanhu Guo

LSU Doctoral Dissertations

Metallic Cu and Au shells were fabricated around cobalt nanoparticles. A new technique to coat nanoparticles with carbon coatings and poly(methyl methacrylate) (PMMA) was developed. The copper shell formation is a self-limiting process. A thin copper shell (0.82 nm) around the cobalt nanoparticle (1.56 nm) enhanced the magnetic property by increasing the blocking temperature from 124 K to 235 K for nanoparticles with a copper shell. The formed gold shell (0.67 nm) enhanced the cobalt nanoparticle magnetic property by increasing the blocking temperature above room temperature. The magnetic moment in the Co-Cu and Co-Au core-shell nanoparticle is much higher than …

Fluidization Of Nanoparticles, Caroline Hijung Nam

Dissertations

During the past decade, nanoparticles (1-100 nm) and nanocomposites have become the focus of many studies due to the unique properties of nanostructured materials that make them attractive for various applications. Due to their atomic and molecular interactions, nanoparticles and nanocomposites have unique and often favorable catalytic, mechanical, optical, electronic and / or other properties. For instance, nanocrystalline copper is up to 5 times harder than conventional micron sized copper particles. Nanocomposites, such as a homogenous mixture of different nanoparticles, can also exhibit improved properties. Other examples include coating and reacting nanoparticles with a second nanostructured phase. These processes are …

Fluidization Of Agglomerates Of Nanoparticles Under Different Force Fields, Jose A. Quevedo

Theses

Nanoparticles are the focus of many research activities, and in the near future they will be handled in large amounts by industry. Fluidization is a very important unit operation which is applied in several industrial processes.

In the present work, fluidization experiments with agglomerates of nanoparticles were done under different force fields: (1) gravity force or conventional fluidization; (2) a magnetic force field, which uses magnetic particles under the influence of a magnetic field; and (3) a centrifugal force, generated by a rotating frame that simulates higher gravity conditions.

Among the significant results with agglomerates of nanoparticles, conventional fluidization was …