Author: Malini DasguptaPublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
Studies on the Synthesis and In-line Coating of Nanoparticles from the Gas Phase
Gas-Phase Synthesis of Nanoparticles
Author: Yves HuttelPublisher: John Wiley & Sons
ISBN: 3527698426
Category : Technology & Engineering
Languages : en
Pages : 416
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.
Studies of Nanoparticle Synthesis and Charging in the Gas Phase
Author: Jingkun JiangSynthesis of Nanoparticles in the Gas Phase for Functional Applications
Author: Frank Einar KruisControlling the growth of nanoparticles produced in a high power pulsed plasma
Author: Rickard GunnarssonPublisher: Linköping University Electronic Press
ISBN: 9176854663
Category :
Languages : en
Pages : 69
Book Description
Nanotechnology can profoundly benefit our health, environment and everyday life. In order to make this a reality, both technological and theoretical advancements of the nanomaterial synthesis methods are needed. A nanoparticle is one of the fundamental building blocks in nanotechnology and this thesis describes the control of the nucleation, growth and oxidation of titanium particles produced in a pulsed plasma. It will be shown that by controlling the process conditions both the composition (oxidationstate) and size of the particles can be varied. The experimental results are supported by theoretical modeling. If processing conditions are chosen which give a high temperature in the nanoparticle growth environment, oxygen was found to be necessary in order to nucleate the nanoparticles. The two reasons for this are 1: the lower vapor pressure of a titanium oxide cluster compared to a titanium cluster, meaning a lower probability of evaporation, and 2: the ability of a cluster to cool down by ejecting an oxygen atom when an oxygen molecule condenses on its surface. When the oxygen gas flow was slightly increased, the nanoparticle yield and oxidation state increased. A further increase caused a decrease in particle yield which is attributed to a slight oxidation ofthe cathode. By varying the oxygen flow, it was possible to control the oxidation state of the nanoparticles without fully oxidizing the cathode. Pure titanium nanoparticles could not be produced in a high vacuum system because oxygen containing gases such as residual water vapour have a profound influence on nanoparticle yield and composition. In an ultrahigh vacuum system titanium nanoparticles without significantoxygen contamination were produced by reducing the temperature of the growth environment and increasing the pressure of an argon-helium gas mixture within whichthe nanoparticles grew. The dimer formation rate necessary for this is only achievable at higher pressures. After a dimer has formed, it needs to grow by colliding with a titanium atom followed by cooling by collisions with multiple buffer gas atoms. The condensation event heats up the cluster to a temperature much higher than the gas temperature, where it is during a short time susceptible to evaporation. When the clusters’ internal energy has decreased by collisions with the gas to less than the energy required to evaporate a titanium atom, it is temporarily stable until the next condensation event occurs. The temperature difference by which the cluster has to cool down before it is temporarily stable is exactly as many kelvins as the gas temperature.The addition of helium was found to decrease the temperature of the gas, making it possible for nanoparticles of pure titanium to grow. The process window where this is possible was determined and the results presented opens up new possibilities to synthesize particles with a controlled contamination level and deposition rate.The size of the nanoparticles has been controlled by three means. The first is to change the electrical potential around the growth zone, which allows for size (diameter) control in the order of 25 to 75 nm without influencing the oxygen content of the particles. The second means is by increasing the pressure which decreases the ambipolar diffusion rate of the ions resulting in a higher growth material density. By doing this, the particle size can be increased from 50 to 250 nm, however the oxygen content also increases with increasing pressure when this is done in a high vacuum system. The last means of size control was by adding a helium flow to the process where higher flows resulted in smaller nanoparticle sizes. When changing the pressure in high vacuum, the morphology of the nanoparticles could be controlled. At low pressures, highly faceted near spherical particles were produced. Increasing the pressure caused the formation of cubic particles which appear to ‘fracture’ at higher pressures. At the highest pressure investigated, the particles became poly-crystalline with a cauliflower shape and this morphology was attributed to a lowad atom mobility. The ability to control the size, morphology and composition of the nanoparticles determines the success of applying the process to manufacture devices. In related work presented in this thesis it is shown that 150-200 nm molybdenum particles with cauliflower morphology were found to scatter light in which made them useful in photovoltaic applications, and the size of titanium dioxide nanoparticles were found to influence the selectivity of graphene based gas sensors.
Gas-phase Synthesis of Nanoparticles
Author: Karsten WegnerPublisher:
ISBN:
Category : Chemical engineering
Languages : en
Pages :
Book Description
Gas Phase Synthesis of Nanostructured Films and Coatings
Author: H. HahnDeciphering Gas Phase Synthesis of Sulfide Nanoparticles
Author: Adithya KaesePublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
With the ever-increasing need for impressively engineered materials, research has taken a shine to nanosized materials. This has been predominantly because matter on a nanoscale exhibits behaviours unusual to their bulk counterparts. Taking advantage of these properties on the nanoscale has been applied in many areas of research. This thesis is focused on a particular group of nanomaterials - metal sulfides and their production through combustion synthesis. Metal sulfide nanoparticles are attractive materials for a wide range of applications. The synthesis of metal sulfide nanoparticles has predominantly been through liquid-phase synthesis. Although it can be highly versatile, challenges of scaling up production and the requirement for post-processing exist. Combustion of liquid precursors using a flame set-up is an established and highly scalable route of synthesis for metal oxide nanoparticles. As combustion requires oxygen, the synthesis of metal sulfides through this route is a challenge. This thesis delves into sources of metal and sulfur sources that are ideal for producing metal sulfide nanoparticles through combustion, tailored precursor-solvent solutions and mechanisms of breakdown and formation. Here, tetrahydrothiophene (THT) is used as an effective source of sulfur to produce metal sulfide nanoparticles such as those of copper and iron. In addition, specific components formed on the high-temperature breakdown of the sulfur source are investigated. Precursor-solvent solutions are poked and prodded using evaporation and distillation, the results of which were unexpected nor have been reported in prior studies.
Synthesis of Non-oxide Semiconductor Nanoparticles and Nanostructured Coatings Through a High Temperature Reducing Jet Process
Author: Saurabh SinghPublisher:
ISBN:
Category :
Languages : en
Pages : 55
Book Description
This dissertation reports the gas-phase synthesis of binary copper chalcogenide nanoparticles and nanostructured coatings. The goals of the research described here are:1. Development of semiconducting nanoparticles and nanostructured coatings. 2. Characterization of their chemical composition, crystalline phase, thermal stability and optical properties. The High Temperature Reducing Jet (HTRJ) reactor was used to produce these nanoparticles and nanostructured coatings. The HTRJ process is an economical and continuous route for the production of non-oxide nanoparticles of a range of metals and semiconductors. The work described in this thesis is the first demonstration of the application of this process to semiconductor, rather than metal, nanoparticles. Copper selenide and copper telluride nanoparticles and nanostructured coating were synthesized and characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Differential Scanning Calorimeter (DSC) combined with Thermo Gravimetric Analysis (TGA), and UV-VIS-NIR optical absorbance spectroscopy.
Author: Benjamin M. Kumfer