Dusts 1. Hybrid Mixtures 1. Explosive Mists. Supercritical Fluids 1. Mass and Concentration Units in Process Safety 1. Partial Volumes Gas Phase 1. Mass Fraction Gas and Liquid Phase 1. Parts per Million Gas and Liquid Phase 1. Parts per Million Gas Phase 1. Molar Concentration Aqueous Solutions 1. Concentration Units Conversion Summary 1. Solutions and Chemical Equilibrium 1. Gaseous Solutions 1. Kinetics and Equilibrium in Gas Reactive Mixtures. Liquid Solutions Liquid liquid solutions Vapour liquid equilibrium in liquid solutions 1.
Azeotropic Mixtures 1. Gas Liquid Equilibrium in Liquid Solutions 1. Equilibria in Aqueous Solution 1. Hydrogen Sulphide 1. Sulphuric and Sulphurous Acid 1. Carbon Dioxide 1. Ammonia 1. Chlorine 1. Hydrolysis 1. Absorption With Chemical Reaction 1. Adsorption 1. Applications 1. Kinetics and Equilibrium of Sulphur Oxides 1. Properties of Hydrogen Sulphide 1. Properties of Ammonia 1. Properties of Sulphur Dioxide 1. Properties of Sulphur Trioxide 1. Properties of Carbon Monoxide 1. Properties of Carbon Dioxide 1.
Properties of Chlorine 1. Ideal Gases 2. Standard and Normal Conditions. Real Gases 2. Virial Equation of State 2. Corresponding States 2. State Equations 2. Polytropic Transformations 2. State Functions 2.
Internal Energy 2. Enthalpy 2. Entropy 2. Thermodynamic Properties 2. Specific Heats 2. Vapour Pressure 2. Latent Heat of Vaporisation 2. Sound Speed of Liquids and Gases 2. Heat Transfer Mechanisms 2. Thermal Conduction 2. Thermal Convection Empirical correlations for natural thermal convective flow.
All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.
This book and the individual contributions contained in it are protected under copyright by the Publisher other than as may be noted herein. Notices Knowledge and best practice in this field are constantly changing.
As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary.
Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility.
Accordingly, the intention of the author was not to duplicate or to emulate the many excellent literature works produced since the many years of study on process safety techniques and models, but rather to build-up a logical and fluid thread to overcome doubts, uncertainties, and difficulties often met in calculation exercises. The available literature sources offer either a broad range of different models and approaches or, even when they are calculations oriented, sometimes unavoidably and faultlessly leave some gaps in the calculation criteria; this is a fee to be paid to the richness and variety of data and information.
This book has a different target: to provide a clear indication on where to go in practical applications when a crossroads is met, and when available data are difficult to be converted into figures and findings.
Nevertheless, the theoretical and conceptual background is deemed to be effective in enabling the user to properly frame the topics and, to some extent, some aspects not included in the existing literature sources have also been dealt with, from principles to applications.
The book is the final step of a long trip the author started in , when, more than 10 years after the incidents of Flixborough and Seveso, and some years after the unresolved tragedy of Bhopal, the Seveso I directive was actuated in Italy. It is doubtless that this European legislative act has given a tremendous impulse to the development of systematic methods and techniques in process safety engineering.
In the nineties the author was involved as a teacher in the final part of the Chemical Plants course held at the Chemical Engineering faculty at the University of Salerno Italy , providing some guidance about process risk assessment methodologies. In the same years, a long experience acquired as an instructor within the course for Risk Analysis, managed by the Italian Inspectorates engaged in the Seveso Directive safety reports assessment, clearly showed how difficult and challenging it was to relate theory to real cases.
Specifically, even if chemical engineers, and engineers in general, should have a thorough knowledge of background concepts underpinning process safety studies, the experience has shown that cultural transition from process to process safety engineering is neither automatic nor easy. The author has analysed this aspect in a recent article Benintendi, , where he has pointed out that the effectiveness of adding-on basic process safety concepts to the university background is not always high.
In this respect, this book includes a first part where basic concepts of chemistry, thermodynamics, reactor engineering, hydraulics, and fluid-dynamics are reviewed with a specific focus on process safety scenarios. Dozens of fully resolved examples focusing on process safety applications have been included. This Fundamentals section ends with one chapter dealing with structural analysis for process safety and another one including a statistics and reliability overview, aiming to provide the basic concepts to properly manage the probabilistic aspect of risk assessment studies.
All these first chapters include many literature data, with the intention to provide the users with a complete tool for their calculations. The Consequence Assessment section is organised according to the typical sequential outcomes following a release after loss of containment. Some efforts have been made to ensure that all potential gaps and uncertainties in the calculations were covered and overcome, based on the professional involvement of the author in many projects dealing with oil and gas, petrochemical, pharmaceutical, fine chemistry, food, and environmental subjects.
In this respect, the users will be driven across a relatively simple and direct route, unlike what happens when they go to the literature, where obviously a much wider spread of methods is provided.
Chapter 7 focuses on releases from containments and from pools: on the basis of the theoretical background provided in the Fundamentals section, a systematic analysis of possible scenarios has been carried out, with the support of many fully resolved examples.
Release of carbon dioxide has been dealt with in detail, due to the relatively new hazardous scenarios presented after the introduction of Carbon Capture and Storage CCS process, and to the specific nature of this substance, which shows a solid-liquid equilibrium below the triple point and does not fully behave according to equilibrium thermodynamics. Key parameters have been identified to drive this approach with the support of many examples.
A specific focus has been made on ignition sources, according to the systematic BS EN standard, with the aim to reduce the incompleteness of the approach often followed. Chapter 10 deals with gas and vapour explosions, consisting of all of scenarios potentially resulting in significant overpressures, including BLEVE, Rapid Phase Transition, and thermal runaway.
The Multi Energy Method MEM has been fitted with the findings of the GAME projects, and this has been very effective in removing the traditional large level of subjectivity and uncertainty in blast curve selection. Chapter 11 has been included to cover dust explosions. In addition to the models describing the primary and the secondary xx Preface explosions, some HAZID cases relating to dust processing equipment have been included, according to the great emphasis the machinery and the ATEX directives have put on this specific aspect.
A case study dealing with the Imperial Sugar Company has been analysed and verified against some calculation findings. Some applications have also been given in this chapter. In this book, unless otherwise specified, all units are expressed according to the International System SI or mks system.
This book aims to support scientists and engineers working in process safety engineering. It is worth repeating that it is a book of calculations offering a large number of data useful for this purpose. The author guesses that it is not free from mistakes and defects, and the author apologies in advance for that.
He will be grateful for any contributions readers will wish to give him, to ensure that the objectives the writer had in his mind can be fully achieved. The bridge link between university and industry: a key factor for achieving high performance in process safety.
IChemE, Elsevier. This book is dedicated to his memory as an appreciation for the prestigious Chemical Engineering School he created in Naples, that I had the honour and the pleasure to attend. Simona Rega, for her precious support and for the contribution to the development of the Rapid Phase Transition Phase included in this book. My colleagues, Foster Wheeler and Amec Foster Wheeler, Reading office, who inspired this work through their joint activity and the commitment of the Process Safety Calculations course held in Reading in My students of the master in process safety engineering attended at Sheffield, Leeds, and Paris, whom I tutored, giving me the opportunity to make a much better focus on the subject from this standpoint.
The team of the Project Evaluation Laboratory of the University of Salerno Italy , with whom I am sharing and extending the risk assessment techniques in a much wider perspective, which has resulted in a sharper focus on methods and philosophy. Finally, I would like to express my thanks, gratitude, and appreciation to the Elsevier team for their support and patience: Fiona Geraghty, Anita Koch, Renata Rodrigues, and Maria Convey, without whose advice these pages would have been neither written nor published.
Everything is transformed. Lavoisier 1. Instead, process safety scenarios are variable and often very complex. Considering a portion of space Fig. Wout is the mass leaving the space domain. Wgen is the mass generated or converted. Wacc is the mass inventory variation. Process safety engineering entails a broad range of complex and variable scenarios where full understanding of stoichiometry and mass balances is necessary to properly analyse and assess the related process and plant configurations.
Some cases are discussed here, and specific scenarios have been analysed in the next paragraphs. The system undergoes a chemical reaction that converts all carbon monoxide into carbon dioxide and is assumed to be at thermal equilibrium so that initial ambient temperature is attained.
The consequences of toxic or flammable compound dispersion strictly depend on the jet dynamics. The scenario shown in Fig. The toxic gas is released with a mass flow rate of WH2 S. Air is entrained into the jet as long as this is developed, resulting in a progressive dilution of H2S. Depending on the effect of the entrainment, toxic concentrations are proportionally reduced, while flammability will be promoted by air mixing within a specific region of the jet.
Assuming a steady state value of z Air entrainment H2S Fig. The liquid is forced to vaporise a fraction of it to reach the downstream equilibrium condition.
This is the case with LPG stored at ambient temperature Fig. A typical example is the amine treatment of sour gas Fig. Example 1. Knowing that the off gas contains Solution With reference to Fig. The tank is nitrogen blanketed so that a positive overpressure of Po is maintained. The tank emptying is started with a head free volume of Vo and a liquid flow rate equal to Q.
Find the nitrogen mass to be provided with time by the controller PIC in order to ensure that positive overpressure Po is maintained during all emptying phases Fig. Solution The tank head space is assumed to be occupied by nitrogen only.
This result is intuitive but has been rigorously obtained here via the application of mass balances. Hydrogen and methane have to be regarded as gases at ambient temperature, whereas propane and sulphur dioxide are vapours and can be condensed by compression. They can be in equilibrium with their vapours at any temperature, and vapour pressure is the equilibrium pressure exerted by vapour above the liquids. Liquids can be miscible or immiscible, polar or non-polar, and this behaviour strongly affects the release and dispersion scenarios.
Chemistry of Process Safety 11 1. It has been proved that aerosol sized droplets sub-micron to 50 microns will likely be the most easily ignitable portion of the mist cloud BS-EN V T is the system volume at temperature T.
Chemistry of Process Safety 13 Both states, normal and standard, are assumed in this book to be at In process safety it is very frequent to deal with mixtures and solutions which may exists in any of the three states of matter, gaseous, liquid, and solid. Knowledge of solutions and mixtures chemistry is important to identify and calculate hazardous properties of the involved substances.
Nonreactive gas mixtures present a high degree of homogeneity, so they can always be considered solutions. This is not always true for liquid and solid mixtures. Sulphur molecular weight: 32, nitrogen: 28, oxygen: Solution The combustion reaction is: 79 79 1. Many important reactive mixtures in process safety reach the equilibrium.
Depending on the nature and the behaviour of the dissolved substances solute , and of the liquid solvent , a wide range of physical—chemical scenarios may be obtained, which have to be well understood in order for them to be properly analysed process safety wise.
Liquid—liquid solutions Miscible liquids form homogeneous solutions, whereas immiscible liquids form two phase dispersed emulsions. A general criterion used to establish whether or not two or more liquids are miscible is comparing their polar features. The old saying like dissolves like is a very useful rule of thumb. Therefore, polar species, such as water, have the ability to engage in hydrogen bonding. Alcohols are less polar, but can form hydrogen bonding as well.
Due to its strong polarity, water is an excellent solvent for many ionic species. Non-polar species do not have a permanent dipole, and therefore cannot form hydrogen bonding. Organic covalent liquids, such as many hydrocarbons, fall within this category.
The following general criteria can be adopted to predict solubility of chemicals: - Symmetric structure molecules have a very low dipole moment and are not dissolved by water - Molecules containing OdH and NdH can form hydrogen bonds - Molecules containing fluorine and oxygen are expected to have a high dipole moment - Pure hydrocarbons, oil and gasoline, are non-polar or weak molecules Dipole moment gives just a very general indication of solubility of molecules.
Table 1. A common practice is to assume the following scale of polarity with respect to the dipole moment: - Dipole moment 1. Very polar ionic molecule. Calculate the initial and the final pH. Sulphur dioxide is the main outcome of the combustion of sulphur compounds, even if a small amount of trioxide is formed, especially if a catalytic action is promoted by some metals, such as vanadium.
Sulphuric acid may be considered totally dissociated into hydrogen and sulphate ions. Find the carbon dioxide pressure above the liquid surface. The feedstock is sent to two reactors, which are charged with a catalyst activated by hydrogen chloride. A stabiliser column separates isomerate from overhead vapours, which are sent to a scrubber where hydrogen chloride is removed Fig. On the overhead line a pressure relief valve is connected to the flare. Analyse the operational scenario relevant to the PRV venting into the atmosphere and discuss the findings.
Solution It is assumed that flare combustion is not affected by air humidity, which is a realistic assumption. On this basis, steam partial pressure in the equilibrium equation may be considered equal to the molecular chlorine partial pressure Fig. As per U. It is also seen that temperature affects equilibrium much more than oxygen partial pressure. This process segment is not safeguarded by a scrubber on the pressure relief valve line.
Solutions of sulphides and ammonium salts hydrolyse when dissolved in water. CO3 H2CrO4! S] H2SO3! Housecroft and Sharpe For this purpose, they are absorbed by a liquid solution or adsorbed on porous media. This process depends on the driving force existing between the liquid phase and the gas phase and is governed and limited by the gas—liquid equilibrium condition and, in turn, by the gas solubility.
The lower the dissolved gas 36 Chapter 1 concentration, the greater is the mass transfer. Applying Eq. This works according to the same principles of absorption, but just inverts the driving force with the aim to enhance the gas transfer from the liquid to the gas stream.
Unlike absorption, stripping is promoted by high temperatures and low pressures. Stripping typically removes toxic or hazardous gases such as hydrogen sulphides and ammonia. Chemistry of Process Safety 37 Table 1.
When the molecules of the fluid come in contact with the adsorbent, equilibrium is established between the adsorbed gas or vapour and the fluid remaining in the gas phase. For a given adsorbate at a given temperature an isotherm can be constructed, relating the mass of adsorbate per unit of weight of adsorbent to the partial pressure of the adsorbate in the gas phase.
A family of adsorption isotherms having the shape typical of adsorption on activated carbon is plotted in Fig. EPA, This, along with other isotherms whose shapes are convex upward throughout, are designated Type I isotherms. The Freundlich isotherm, which can be fit to a portion of a Type I curve, is commonly used in industrial design.
Table 3. Due to the very high reactivity, flammability limits and corresponding ignition energy levels are more favourable to promote explosions than oxygen Tables 3.
The lower limits in oxygen, and in a wide variety of oxygen-nitrogen mixtures, are essentially the same as those in air at the same temperature and pressure Tables 3.
These can cause serious and sometimes catastrophic consequences. Incident case history has shown that quite often even simple phenomena, such as dilution and neutralisation, have been ignored, resulting in dramatic outcomes. Heat of combustion values in the Project database are defined as negative values for purposes of sign convention. The quantity known as higher heating value HHV or gross energy, or upper heating value or gross calorific value GCV , or higher calorific value HCV is determined by bringing all the products of combustion back to the original precombustion temperature, and in particular condensing any vapour produced.
This can be an exothermic or an endothermic process. The exothermic energy is often non negligible, and planned or unwanted mixing processes may result in catastrophic failures in storage tanks and vessels. The following table includes heat developed in water at different temperatures for sodium hydroxide and sulphuric acid Table 3. For sulphuric acid, on the basis of the enthalpy of formation provided at different concentrations in water by the U.
NIST and presented by Bhatt and Vora , an interpolation curve has been obtained, which can be used for quick estimation of the thermal effects of dilution. Example 3. Calculate the final temperature of the solution. Solution Sulphuric acid 54, This example shows how potentially dangerous can be the incautious action to mix water and chemicals, or to clean up a spillage by just pouring water.
The effects are comparable to those analysed for the exothermic dissolution of electrolytes in water. The peculiarity of the reaction of neutralisation is that for each mole of water produced, Solving sodium chloride in water is a typical example of an endothermic process.
In closed equipment such as pressure vessels and piping, if not properly vented and accurately foreseen, an endothermic reaction could cause serious structural damages. They do not require an ignition source. Thus, they are considered to have zero minimum ignition energy. The definition of pyrophoricity is not restricted to finely divided powders. According to Housecroft and Sharpe , transition d-block metals present a general pyrophoric behaviour. According to Glassman et al.
NH4 NO3 3. It is deemed that the final products are molecular nitrogen, oxygen, and water Cagnina et al. This is the key parameter to understand the explosive behaviour of ammonium nitrate. High temperature and confinement can trigger explosive phenomena, even if sensitivity to other substances has been statistically the most frequent triggering factor. Furthermore, they can oxidise organic compounds and reducing agents.
Hydrogen peroxide shows a similar behaviour in addition to promoting and increasing fire hazard as chlorates. The traditional theoretical frames utilised to describe the self heating cases are identified as the Semenov model, the FrankKamenetskii model, and the Thomas model. This model is applied in well mixed systems Fig. This is typically the case of large, unmixed, or reacting exothermically systems Fig.
Tsystem Tambient Tambient Fig. Although a relatively limited number of applications have been implemented, these systems may offer significant potential for the reduction of toxic or flammable cloud concentration developing in process areas. Curtains work according to two different mechanisms, each of which can be more or less important depending on factors such as the chemical nature of the hazardous gas, its concentration, and its fluid-dynamic characteristic momentum, density, temperature.
These mechanisms are — — simple dilution of cloud concentration; absorption, and eventually chemical reaction; and can take place simultaneously to a certain extent. Absorption is particularly important when a significant reduction is required, either because of high hazardous gas content or its great potential for harm. In this respect, the effectiveness of absorption is strongly affected by the solubility properties of the substances.
Typically, ammonia and hydrochloric acid are easily absorbed in pure water, whereas hydrogen sulphide has a very low solubility. Affecting parameters are the following: — — — — — Henry constant mass transfer properties such as transfer coefficients in the gas and liquid film surface to volume ratio of the absorbent spray droplet size reactivity towards specific electrolytes The theoretical frame for absorption is the Lewis and Whitman two-film model, depicted in Fig.
This model typically assumes that the interface gas—liquid concentrations are in Henry equilibrium, if applicable. Absorption of substances, like hydrogen sulphide, which show a very low water solubility, may be promoted by solutes, which increase the overall absorption power by one or more orders of magnitude, depending on their concentration in water.
Effective modelling and experimental results have been obtained by means of Na2CO3 water solutions in the range 0. References Albright, L. Babrauskas, V. SFPE Handbook, 2nd ed. Bartkowiak, A. Flammability limits of methane and ethane in chlorine at ambient and elevated temperatures and pressure. BuMines Rept. Benedetti, R. National Fire Protection Association Inc. Benintendi, R. Identification and analysis of the key drivers for a systemic and process-specific reactive hazard assessment RHA methodology.
Design a Safe Hazardous Materials Warehouse. Hydrocarbon Processing. Gulf Publishing. Bhatt, B. Stoichiometry, 4th ed. Tata McGraw-Hill Education. Bodurtha, F. Industrial Explosion Prevention and Protection. McGrawHill Book Company. From Table 3. In general, the photoluminescence PL decay rate is a sum of the radiative and non-radiative decay rates.
Therefore, the origin of the decrease in PL decay rate versus size may be radiative and nonradiative. The possibility may be invoked for the non-radiative process in origin is surface states, responsible for non-radiative decay, which changes as surface-to-volume ratio varies with size. Other possibility for radiative in origin, may be considered for the size dependence as quantum confinement effect may lead to size dependent oscillator strength.
The quantum confinement effect in nanoparticles predicts a decreased radiative decay rate as the size increases [39]. As PL and PLE spectra are dependent on the size of diameter of BAM nanostructures indicating that the quantum confinement effect as well as surface effect both is responsible for change in decay rate. Thus we have chosen YAG as host material in the present investigation by assuming that this high bonding energy may match the VUV excitation.
It is well known that YAG is very stable under e-bombardment, so it may be stable under the plasma [40], the typical environment in PDP. In order to check the stability of prepared nanophosphors with time and temperature, time evolution studies along with annealing treatment are also performed for these samples. Citric acid and ethylene glycol were used as chelating and polymerizing agents, respectively.
All chemicals were of analytical reagent grade and were directly used without any special treatment. In the present work, all the samples were prepared in a clean room of class under ambient conditions. Then ethylene glycol and citric acid were added. Citric acid solution was used to chelate the metal ions and to polymerize with ethylene glycol for gel formation.
Homogeneous colorless solution was obtained after continuous stirring for more than 5 hours. At this stage, excess water evaporates and white gels were obtained. The size and morphology of prepared nanostructures were recorded on transmission electron microscope model Tecnai T G 2 S - Twin electron microscope operated at KV accelerating voltage.
The broadening of XRD peaks i. Scherrer's broadening can be attributed to nanosize and the size, d, of the crystallites in samples were estimated by Debye-Scherrer's equation using Scherrer's broadening FWHM. Figure 3. TEM images were recorded by dissolving the synthesized powder sample in ethanol and then placing a drop of this dilute ethanolic solution on the surface of copper grid.
The crystallite size obtained using XRD data and observed TEM results reveal that these phosphors are in nanometer range. The solgel route using citric acid as polymerizing agent led to the formation of tiny gel cages during polymerization process, subsequently restricting the particle growth within the cage, resulted in formation of nanostructures.
Since many display devices including plasma display panels utilizes nm and nm VUV excitation, generated through typical Xe discharge, we have investigated the emission characteristics of all the three prepared samples particular by the same excitations. Kang et al. Whereas, Van der Weg et al.
They observed that at low doping concentrations, primarily the absorption of excitation wavelength affects the luminescence characteristics without having any direct effect of the process of cross relaxation favoring emission from 5 D 3 state, whereas, at higher concentration the cross relaxation process favors the emission from 5D4 state.
So, in present case, the cross relaxation process dominates. It is notable that the emission intensity of the sample excited with VUV nm is much higher than that of the sample excited with VUV nm. In , Bhargava et al. They reported that the presence of an impurity within a nanocrystal and localization of electron and hole wave function due to quantum confinement leads to faster energy transfer to impurity in smaller particles as compared to transfer rate for band to band transition or surface recombination.
Hence, luminescence efficiency increases with decrease in size of the particle. In , Dijken et al. They also observed that quantum efficiency of the ZnO nanoparticles increases with the decrease in particle size. Further, R. Bhargava etal. This system is known as "Quantum Confined Atom" and the Quantum Confined Atom QCA is a nanocomposite comprising of few isolated atoms and the properties of the caged atoms are retained, protected and significantly amplified via its interaction with the host.
The terbium ion doped YB0 3 nanocrystal host have particle size nm, while, YB0 3 : Tb bulk phosphor particles are of size nm.
In the experiment, 0. In the above solution, ammonia solution was mixed. The pH of the solution was 9. Emission and excitation spectra were carried out on Perkin- Elmer LS 55 spectrometer. Yadav and A. Pandey, ]. Alloys and Comp. Fig 3. From these results it is clear that the peak of the PLE absorption moves to higher energy as the size of the particles decreases and the intensity of the absorption peak PLE increases as the peak position moves to the higher energy.
It means that the product of the absorption and emission intensity i. PLE is greater for nanophosphor and comparable to bulk one. Bhargava et al. Daud et al. In the standard configuration coordinate model as shown in Fig 3. This is shown as two different configuration coordinate parabolas, named as 'bulk' and 'nanoparticle'. From Fig 3.
Opted from R. This is due to the confinement of Tb ions imposed by the YB0 3 host boundary. In this model the excited state of dopant provide a significant overlap with the host boundary. The overlap of the wavefunctions of the extended excited states and host leads to strong modulation of the excited states of the dopant. This modulation leads to efficient and fast transfer of carriers from host to the dopant atom. From Figure 3. Therefore, there will be difference in penetration depth of the excitation photons of UV nm and VUV nm.
As the excitation wavelength becomes short, the penetration depth is decreased due to large absorption coefficient [] and the excitation volume from which photoluminescence is observed moves closer to the surface. Since the particle surface can substantially act as a defect or a source of non-radiative recombination routes, the larger surface area due to nanosized particles end result in diminished luminescent efficiency under VUV irradiation.
It is also notable that the atomic arrangement on the surface of nanosized phosphor is different from the bulk and consequently nanophosphor particles with large surface to volume ratio will be influenced by VUV irradiation. Due to the low penetration depth of VUV irradiation, the ratio of the dead volume in nanophosphor, into which the excited beam cannot reach, would increase.
In bulk phosphor, ratio of the dead volume decreases especially under VUV irradiation. According to the experimental data, the decay time is about 2. The finding of the present study may give insight to printing technology of barrier ribs in PDPs to counts the problem of dead volume by improving the packing fraction and controlling the surface defects with the help of capping agents transparent to VUV photons. Merck Limited, Mumbai- , India. All chemicals were of AR grade and were directly used without any special treatment.
The size and morphology of prepared nanostructures were recorded on transmission electron microscope model Technai 30 G 2 S - Twin electron microscope operated at KV accelerating voltage. PL studies were performed on a Perkin Elmer LS 55 luminescence spectrophotometer using a Xenon discharge lamp, equivalent to 20 kW for 8 microsecond duration as the excitation source at room temperature.
Furthermore, it was also observed that as we go on increase the annealing temperature the XRD peaks become narrow and much intense, indicating enhancement in crystallinity as compared to those for sample annealed at lower temperatures.
The crystallite sizes, estimated by XRD, were increased, from 10 nm to 32 nm, with annealing temperatures and were found to be consistent with TEM results. Opted from P. Sharma, M. Kumar, P. Singh, A. Pandey and V. Singh, J. In order to study the annealing effect on the luminescence behavior of the synthesized samples, photoluminescence PL excitation studies at nm were also carried out.
Due to higher degree of disorder near the surface, nanomaterials generally gives better chromaticity. At higher annealing temperature the maxima of maximum luminescence intensity was found to be improved due to better crystallization.
Singh, ]. Thus, the change in surface to volume ratio, removal of surface defects and non-radiative rates led to improvement in luminous efficiency. While Fig 3. Spectra A were recorded without applying any filter, spectra B was recorded after applying nm filter and spectra C were recorded after applying nm filter. All these spectra were recorded a on the very first day and b after days. On the other hand, for the samples excited by at nm and nm radiations, emission spectra show one sharp intense peak at the position of nm followed by three other weak peaks at nm, nm and nm, respectively.
In this case, the orange peak intensity almost vanished and only strong red peak appeared. In order to do this, we performed time evolution studies on at regular intervals of time for days.
In this section, we are revealing in-depth discussions on the results obtained from of XRD, photoluminescence and VUV-PL results during and after days. These results are in excellent agreement with the XRD results obtained on the very first day. The PL spectra obtained after days are similar to that of obtained for the samples synthesized on the very first day Fig 3. In the same way Similarly, the VUV-PL results also showed exact similarity between the spectra recorded on the very first day and remained same after days.
Thus these nanophosphors can be seen as one of the most feasible candidate for red phosphor which is necessary and condemnatory constituent for flat panel displays, underlying the importance of the current work. Now PRl was added drop wise to PR2 while constantly stirring and then again homogenized for 2 h.
Sharma, R. Dutta and A. Pandey, Opt. By applying the Scherrer formula to the full width at half maximum of the diffraction peaks, the mean particle size could be calculated as 5nm for sample prepared at room temperature. The corresponding TEM images are shown in Fig. The grain sizes are distributed in the range of nm for different samples and consistent with the mean particle size obtained from XRD.
The electron diffraction pattern shown in the inset of Fig. In order to study the effect of doping concentration on the luminescence behavior of the samples synthesized at room temperature, quenching studies were carried out and is shown in Figure 3. The concentration quenching effect is due to dominance of non-radiative transitions over the radiative one, because the particle boundary encumbrance causes the resonance energy transfer only within one particle, whereas the enhanced mobility of the excited state within the host matrix increases the non-radiative de-excitation probability via quenching centers traps [77].
The obtained comparative emission spectra are depicted in Fig 3. The highest luminescence intensity, almost 1. Besides the size of nanoparticles, numerous existing surface defects, consequence to the low temperature synthesis, plays an important role. The reduced decay time makes it possible that the more and more phosphors are ready to contribute without quenching for sustainable emission efficiency.
The quality of phosphor is of great importance for the performance of these modern flat panel display devices as they directly influence the brightness and lifetime.
From above point of view, the phosphor should have good luminescence efficiency as well as high color purity with long term stability [82]. All the metal nitrates and glycine were mixed in double distilled water to form the precursor solution. Then the solution was concentrated by direct flame heating until excess free water evaporated and spontaneous ignition occurred. No peaks attributed to other phases were observed indicating good quality samples.
In order to study the annealing effect on the luminescence behavior of the synthesized samples, PL studies at nm were performed. For figure b black line corresponds to nm excitation and red line corresponds to nm excitation. At higher annealing temperature the maxima of luminescence intensity is improved due to better crystallization. In PDPs, phosphors are excited by vacuum ultraviolet VUV radiation, especially by and nm, from inert gas plasma, which shows the unique requirement for PDP phosphors that they can only be excited by the higher VUV excitations.
So we have explored the luminescence characteristics particularly by the same excitations. For the samples excited at nm and nm, emission spectra show one sharp intense peak at the position of nm followed by four other weak peaks at nm, nm, nm and nm, respectively. The luminescence decay time of the 5D0—»7F2 transition at nm was also calculated against the nm VUV excitation and is shown in the inset of Fig 3.
The calculated decay time for the decay curve shown in the inset of Fig 3. Before going into details, we have briefly discussed about the existing science of plasma display panels with state-of-art history of the development of plasma display panels till date.
Ahead of main focus of the present chapter, we have briefly described the advantages and disadvantages of existing plasma display panels. It is observed that the luminous efficiency and lifetime of plasma display panels PDPs are directly related to the performance of phosphors used in PDPs, thus higher efficiency, higher stability against high temperature processes and a long lifetime along with good color chromaticity against vacuum-ultraviolet VUV radiation are major concerns while selecting suitable phosphors for PDPs.
In the same pursuit, the present chapter talks about the plasma display phosphor of nanosize, usually termed as "Nanophosphors" as better alternatives to the currently used micron-submicron size commercial phosphors. Time evolution studies showed these nanophosphors to be extremely stable, suggesting them to be one of the most feasible candidates for PDP applications and seize great potential in flat panel display application, underlying the importance of the current work.
Further, to improvise the performance of PDP's with nanophosphors, the technological processes of printing of phosphors on ribs for making the pixels have to be looked into differently as low penetration of VUV due to its heavy absorption poses problems in dealing with high dead volume for non-radiative transitions degrading the luminous efficiency.
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DOS Version. Pariah Win Follow Us! Top downloads. List of top downloads. Latest releases. List of new games here Follow us on Facebook or Twitter. An alternative explana- tion that is useful to relate the changes in contact angle and undercooling is that the increase in wettability implies an increase in the area wetted by the metal, and hence an increase in the effective surface where heterogeneous nucleation can occur.
This analysis Figure 13 also implies that as the wett- ability decreases, the undercooling approaches the expected value for homogeneous nucleation. This is the case for the experiments presented in this work: the value of undercool- ing under a condition where a heterogeneous nucleation Fig. They had attributed the decrease of contact angle to lower oxy- gen partial pressures, to the increase in the aluminum dis- solved in the metal. Since, in equilibrium with Al2O3, the lower the oxygen content, the higher the dissolved alumi- num content, this effect could explain the drop in contact angle as the PO2 decreases.
Then, if the decrease in under- cooling observed in the experiments with low PO2 is caused by the increase in the elements introduced in the metal during the substrate dissolution, the undercooling on experiments using steels with high aluminum should show low values of undercooling, as observed by Kudoh. Figure 14 shows the undercooling as a the undercooling.
This is due to the observed effect of the function of melting temperature. As the sample loses aluminum, the disregistry. Many researchers have referred to this parame- to low PO2 and low Al due to limited dissolution of the ter. These results agree with the hypothesis that the steel with different types of inclusions and concluded that decrease in undercooling in the low PO2 range is caused by the undercooling was proportional to the square root of the introduction of Al from the dissolution of the substrate.
For deep Fig. The mod- eling of the growth rate has been published previously. The measured under- in an undercooled liquid than under conditions found when cooling was a strong function of gas phase oxygen content, using a water-cooled copper mold.
The variation in undercooling was related to the wetting of the substrate by the liquid metal, where the deepest undercoolings occurred when the highest contact VI.
The experimental composition for example, oxygen content or aluminum results indicated that the undercooling of liquid iron, in can lead to conditions that vary from low to high under- contact with an Al2O3 substrate, did not have a unique coolings. Eustathopoulos, M. Nicholas, and B. Drevet: Wettability at High the ability of a surface to be a heterogeneous nucleant. Ueda, H. Shi, X.
Jiang, H. Shibata, and A. Cramb: Metall. B, , vol. Ogino, K. Nogi, and Y. Ogino, A. Adachi, and K. Takiuchi, T. Taniguchi, N. Shinozaki, and K. Mukai: J. The authors thank the member companies of the Center Met. Jun and K. Mukai: Iron Steel Inst. Eldred and P. Ownby: Trans. JWRI, , vol. Shinozaki, T. Fujita, and K. Mukai: Metall.
Yuan, K. Mukai, K. Takagi, and M. Ohtaka: J. Hasouna, K. Nogi, and K. Ogino: Trans. Takamura and S. Mizoguchi: Proc. Iron Steel Congr. Nagoya, , pp. Gaskell: Introduction to the Thermodynamics of Materials, 3rd 2. Kluken and O. Grong: Metall.
A, , vol. Fruehan: The Shaping and Treating of Steel, 11th ed. Cross, O. Grong, and M. Mousavi: Scripta Mater.
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