The monitoring of the stuff belongingss of complex liquids and polymers used across industries has become really relevant because a assortment of companies are progressively utilizing these stuffs in their daily production activities and this would assist to avoid bad lucks or accidents. A assortment of ways exist that aid in the monitoring of these belongingss but of peculiar involvement to this work are the Ultrasonic and Dielectric methods.
This work proposes real-time coincident measurings of complex liquids and polymer stuffs utilizing both Ultrasonic and Dielectric Spectroscopy. It tries to reply the inquiry ‘Will holding real-time coincident measurings utilizing the two different techniques be executable and helpful for industry usage? There are presently detectors used in industries which employ either of the individual engineerings and a critical rating of uniting both engineerings is presented in this work.
The processing of complex liquids and the mechanical unity, wellness and safety of complex technology constructions need to be invariably monitored so as to place jobs such as weariness and harm that might happen. Continuous procedure monitoring in gaseous, liquid or liquefied media is a cardinal demand for procedure control ( Hauptmann et al, 2002 ) A and supersonic detector systems have been used to significantly observe and heighten stuff belongingss. Dielectric detectors have besides been used for procedure control in industries. Supersonic Detectors utilize supersonic transducers which convert electrical signals into supersonic moving ridges and frailty versa ( Hauptmann et al, 1998 ) , while the Dielectric detectors — — – . A A
Correlations have been made between supersonic parametric quantities, such as speed, fading and backscattering, and stuff belongingss commanding the mechanical behavior and the ground for these correlativities is that A the same microstructural characteristics which affect the supersonic measuring such as grain size, grain boundaries and inclusions besides play an of import function in finding stuff belongingss of involvement ( Thompson, 1996 via Achenbach, 2000 ) .
AIMS AND OBJECTIVES
RELEVANCE TO INDUSTRIES
2.0 BACKGROUND OF STUDY
Introduction and what is expected in the chapter
2.1 NON DESTRUCTIVE EVALUATION ( NDE )
Non-Destructive Evaluation ( NDE ) , besides called Non-Destructive Testing ( NDT ) is a general term used for any appraisal, trial or rating carried out on stuffs and constructions to guarantee it is fit for service without doing any harm to them in any manner. The American Society of Non-destructive proving provinces that NDE is the scrutiny of an object with engineering that does non impact the object ‘s future utility ( Shull, Introduction to NDE ) . It has become the prima merchandise proving criterion.
Non-destructive rating has become an built-in portion of virtually every procedure in industry where merchandise failure can ensue in accidents or bodily hurt ( Hellier, 2001 ) .
There are a broad scope of NDT techniques available in industries which include:
– Visual/Optical testing
– Eddy Current Testing
– Acoustic Emission
– Ultrasonic NDE
This is presently the most commercially successful NDE method because it is comparatively inexpensive to implement. Non-destructive Evaluation ( NDE ) has a assortment of applications including defect sensing, dimensional measurings and finding stuff belongingss. It requires the trial constituent to keep its original province prior any trial process and is good used in technology and quality confidence for merchandise continuity and to fulfill dependability criterions ( Tong, 2001 ) . Merchandises can besides be tested without disrupting the fabrication procedure. Non-destructive Evaluation and Non-destructive Testing ( NDT ) are frequently used interchangeably but the former defines a more quantitative attack.
Talk about who uses NDE presently in the industry?
Legislation of criterions on proving e.g. British criterions
Number of companies that produce and sell Ult/Diel kits already
– Insulator NDE
Ultrasonic engineering can be traced back to work done by a French physicist, Pierre Curie in 1880 on the piezoelectric consequence. Pierre and his brother Jacques discovered that asymmetrical crystals such as vitreous silica and Rochelle salt ( potassium Na tartrate ) generate an electric charge when mechanical force per unit area is applied ( Angelfire, 2010 ) . In 1881, they discovered that the same crystals were deformed and mechanical quivers were generated on application of an electrical field.
One of the first utilizations of Ultrasonics was medical imaging diagnosing and this dates back to the 1930s and 1940s. In 1937, Karl Theodore Dussik, a head-shrinker and brain doctor began analyzing echography in concurrence with his brother Friederich, a physicist. They attempted to utilize ultrasound to name encephalon tumours but unluckily, it was subsequently determined by Guttner, in 1952, that the images produced by the Dussiks were fluctuations in bone thickness and non of encephalon tumors ( Newman et al, 1998 ) . Consequently, the United States Atomic Energy Commission reported that ultrasound had no function in the diagnosing of encephalon tumours. There is besides Douglass Howry, another innovator from the 1940s, who concentrated more on the development of supersonic equipment and the applied theory of ultrasound instead than its clinical applications. However, it was non until the seventiess that the work of these and other innovators came into fruition.
Testing of non-human stuffs can be done either destructively or non-destructively. Ultrasonics has evolved with promotions in engineering whereby testing can be done while besides retaining the original construction of the trial object prior to proving. This is referred to as Non-destructive Evaluation. Some of the advantages of NDE over destructive trials for industries include its ability to be used in process monitoring like chemical reactions and crystallisations ( Unwin, 2010 ) and its cheap nature in footings of equipment costs and clip. Soon, there are assorted applications of Ultrasonics NDE to assorted industries among which are defect sensing in stuffs, dimensional measurings and word picture of stuffs. However, for the intent of our survey, more accent will be on Supersonic NDE as a agency of analyzing word picture of complex liquids and polymer stuffs.
Ultrasonics is a subdivision of Acoustics ( Ensminger,1988 ) that involves the application of high-pitched sound energy to stuffs, normally at frequences beyond the human hearable scope between 20kHz and 25MHz. The mechanical vibrations/ultrasound signals so propagate through the stuff at a speed dependant on the belongingss of the stuff. The signal will besides undergo some signifier of fading which is besides specific to the stuff belongingss. If a discontinuity exists in a construction ( for illustration, where two stuff types are in contact ) so contemplations or reverberations may happen.
It differs from other signifiers of energy because it can non go through a vacuity ; it requires a medium to propagate. Sound energy going at higher frequences have shorter wavelengths, leting them to reflect from objects more readily ( Angelfire, 2010 ) . The standard information is besides much easier to analyze because of their high declaration. However, they are hard to bring forth and step.
A discontinuity nowadays in the way of the moving ridge would do a part of the incident energy from the transducer is reflected from the surface of the defect and perchance scattered as extra mechanical moving ridges throughout the object. These contemplations are picked up by the same transducer in a pulse-echo set-up or a 2nd receiving transducer in a through-transmission set-up ( Schmerr,1998 ) .
The informations received are represented in the undermentioned ways for analysis:
A typical Ultrasonic apparatus is fundamentally made up of the undermentioned functional units:
( SCHEMATIC DIAGRAM OF A TYPICAL ULTRASONIC SET-UP )
– The Pulser/Receiver: It produces short continuance electrical pulsations and receives the reverberations in signifier of electrical energy. The receiver portion of the pulser/receiver besides has an amplifier that amplifies the standard electrical signals as they are really little in size.
– The Transducer: is used for excitement and normally contains a piezoelectric crystal which transforms the electric signals produced by the pulser into high frequence supersonic energy that propagates through the stuff in signifier of mechanical acoustic moving ridges of peculiar wavelengths dependant on the material features of the object being tested. It besides transforms the reflected reverberation back into electric signals which are picked up by the receiving system and shown on a show as A-scans.
– The Digitizer: This transforms the parallel signals which are represented as a electromotive force versus clip hint on the CRO into digital signals for farther signal processing and analysis by the computing machine ( Schmerr, 1998 ) .
– The Oscilloscope: This provides a show of the signal as a electromotive force versus clip graph.
Single technique Ultrasonic detectors have been in usage in industry since…
Propagation of moving ridges
The basic rules of moving ridges and beckon extension are important to this survey as detection will be done with the interior music director moving as a wave guide. Sound travels as mechanical moving ridges in solids, liquids and gases in the signifier of quivers and oscillations of atoms about a average place. The way of extension of these sound moving ridges is comparative to the supplanting or oscillation of the material atom quivers, doing assorted moving ridge manners to be. These include:
( DIAGRAMS )
( DIAGRAMS )
Surface Waves: Authoritative surface wave extension illustration includes surface moving ridges, Lamb waves, and Stonely moving ridges ( Rose, 2002 ) .
( DIAGRAMS )
Supersonic NDT guided wave extension differs from Bulk wave extension in the sense that it requires a boundary to propagate. Propagating moving ridges along the boundaries of thin home bases result in contemplations, manner transitions and some superposing with countries of constructive and destructive interventions that eventually result in nicely behaved guided wave packages that can go in the construction ( Rose, 2002 ) .
( DIAGRAMS )
Acoustic belongingss of moving ridges
Waveguide ; Acoustic belongingss, fading, speed, stuff, dimensions, form, extension xtics, manners etcaˆ¦
The speed, wavelength and frequence of sound in an elastic stuff are related by the undermentioned equation:
V = A I».f A A A ( 1.1 )
V = speed ( m/s )
I»= wavelength ( m )
f= frequence ( Hz )
Acoustic Impedance ( Z )
Transmission and Contemplation coefficients:
( Pressure )
Supersonic Transducer Features:
Applications of ultrasounds
Measurement of the viscousness of fluids
Remedy supervising procedure of epoxy
Determining the composing of stuffs
Measurement of the viscousness of fluids
Viscosity is a step of the forces ( shear emphasis or tensile emphasis ) that oppose the comparative gesture of an object through a fluid. It can besides be defined as the opposition per unit country of a fluid to distortion or to flux [ 1 ] . The flow belongingss of fluids can be divided into three chief groups ( I ) Newtonian ; ( two ) Non-Newtonian, clip dependent ( three ) Non-Newtonian, clip independent. The viscousness of a Newtonian fluid is changeless and independent of the applied shear rate ( shear emphasis ) [ 1 ] , hence does non increase or diminish with an addition or lessening in shear rate. However viscousness of a Newtonian liquid depends on temperature and force per unit area ( and besides the chemical composing of the fluid if the fluid is non a pure substance ) .
The relation between the applied shear rate and the obtained shear emphasis is changeless over the whole shear rate scope [ 1 ] . Liquids which show Newtonian flow behavior are frequently simple, single-phase liquids and solutions of liquids with low molecular weights [ 2 ] . Example of this type of liquid is H2O.
In both non-Newtonian clip dependent and non-Newtonian clip independent, the relationship between the shear emphasis and the strain emphasis is non additive. Therefore a changeless coefficient of viscousness can non be defined ( non changeless ) . In Non-Newtonian clip dependent liquid viscousness additions or lessenings with the continuance of the applied shear emphasis illustrations of these types of liquids are pigments and yogurt. While in a Non-Newtonian, clip independent f viscousness either increases or decreases with increased emphasis. Examples of these types of liquid are suspensions of maize amylum or sand in H2O, Paper mush in H2O, latex pigment, ice, blood, sirup, and molasses.
There are many assorted techniques for mensurating viscousness such as Coaxial-Cylinder method, glass viscosimeter, piezoelectric response electromotive force and ultrasonics, each suited to specific fortunes and stuffs. The choice of the right viscosimeter from the tonss of instruments available to run into the demand of any application is a hard proposition [ 3 ] , due to the complexness of the application and in some instances the restrictions of the proposed instrument. Ultrasound techniques are the most widely applied in the survey of liquid provinces ( most complicated amongst the three provinces of affair ) due to its simpleness and truth. In a diary titled “ Comparison between different methods for viscousness Measurements ” by M. Mekawy, H. Afifi and Kh. El-Nagar concluded that the viscousness measured by capillary glass, Coaxial-Cylinder rheometer supersonic pulsation reverberation method showed a good correlativity and can be applied industrially. This will add the standardization of viscosimeters in industry. From the supersonic consequences obtained, it is of involvement to reason that the supersonic parametric quantities are really suited as qualifying parametric quantities for oils in the scope mentioned.
Ultrasound has been used to mensurate the viscousness of fluids every bit early as 1949 [ 4 ] . However prior to World War II ( 1935-1945 ) , sonar, the technique of directing sound moving ridges through H2O and detecting the returning echoes to qualify submersed objects, inspired early ultrasound research workers to research ways to use the construct to medical diagnosing [ 5 ] .
In 1929 and 1935, Sokolov studied the usage of supersonic moving ridges in observing metal objects. Mulhauser, in 1931by utilizing two transducers to observe defects in solids. Firestone ( 1940 ) and Simons ( 1945 ) developed pulsed supersonic proving utilizing a pulse-echo technique [ 5 ] . Ultrasonic speed and soaking up measurings have proved to be utile in covering with the jobs of construction of liquids and interaction between the molecules. Supersonic pulse-echo method is in broad spread usage for these measurings [ 1 ] .
Supersonic speed in a liquid system is conditioned by the province of molecular belongingss of the system [ 6-9 ] . In add-on to temperature, the supersonic speed in a liquid system is antiphonal to viscousness every bit good [ 10 ] .
Measuring the supersonic viscousness
Pulse reverberation is the most appropriate method of mensurating viscousness when utilizing supersonic techniques. In pulse reverberation method, a short sinusoidal electrical moving ridge activates the supersonic transducer. The transducer so produces sound moving ridge train into the liquid inside the cell [ 1 ] . This cell is made up of chromium steel steel, which avoids any chemical reactions between the chemicals and the cell. Some advantages of this method are that the sound speed can be measured at the same clip as the fading.
Polarized shear moving ridges may be used every bit good as longitudinal moving ridges, and a broad scope of sound frequence may be employed.
Using an CRO ( 60 MHz clip base CRO, Philips, Netherlands ) direct measuring of the clip required for the pulsations to go twice the length of the specimen is possible, which allows immediate computation of the supersonic moving ridge speed as given in the undermentioned equation:
Where L is the liquid length and I”t is the clip interval. The speed measurings utilizing this method were carried out at a nominal frequence of 4 MHz ( cardinal frequence of 0.7 MHz and band breadth of 1.4 MHz ) at temperature of 25oC. The estimated truth of the speed measuring is about 0.6 % .
The supersonic fading and supersonic viscousness are given in the signifier ;
Where An / An+1 is the ratio between two consecutive reverberations An, An+1, I? is the denseness of the oil and degree Fahrenheit is the supersonic frequence. The uncertainness of the measurings of supersonic fading and viscousness are A±0.01 dB/cm and A±0.03 mPa.s severally.
The experiment was performed over 10 oil samples at different densenesss and individual temperature 25oC. Each experiment was repeated three times and through three yearss consecutively, and the median was chosen as an terminal consequence.
Viscosity is a chief parametric quantity when any flow measurings of fluids, such as liquids, semi-solids, gases and even solids are made. Viscosity measurings are made in concurrence with merchandise quality and efficiency. In industries, the cognition of a stuff ‘s viscousness behavior and rheological features gives makers an of import merchandise dimension. It is indispensable in foretelling pumpability and pourability factors, public presentation in dunking or surfacing operation, or the easiness with which it may be handled, processed and used. The interrelatedness between rheology and other merchandise dimensions frequently makes the measuring of viscousness the most sensitive or convenient manner of observing alterations in colour, denseness, stableness, solids content, and molecular weight [ 3 ] .
Many makers now regard viscosimeters as a important portion of their research, development, and procedure control plans. Viscosity measurings are frequently the quickest, most accurate and most dependable manner to analyse some of the most of import factors impacting merchandise public presentation.
There are many different techniques for mensurating viscousness, each suited to specific fortunes and stuffs. The choice of the right viscosimeter from the tonss of instruments available to run into the demand of any application is a hard proposition. Today ‘s instruments vary from the simple to the composite: from numbering the seconds for a liquid to run out off a stick to really sophisticated automatic recording and commanding equipment. This places the instrument user in a place in which his ain grasp of the flow phenomena involved, coupled with the instrument maker ‘s “ cognize how and experience ” , must be brought to bear.
Experimental Set up ( Pulse Echo )
Generator ( what are the ideal features, signal types, signal types i.e. tone explosion, sine explosion
Examples of kit?
Monetary values of kit.materials
Transducers ( give a basic definition of transducers, types, beginnings ( do we purchase or do ourselves? )
Amplifier + receiving system ( an amplifier is needed because the standard signal would be little )
How would you put it up?
-Pulse reverberation systems
-Through-transmisison ( No demand to advert angles as it ‘s non relevant to our design )
– Experimental process
-What does the informations look like? Data analysis and procedure?
Experimental set-up for pulse reverberation
Pulse Echo Mode
The general set-up for a pulse-echo technique is shown in fig.1. At low frequences, it is convenient to excite longitudinal and torsional moving ridges by agencies of magnetostrictive transduction. A subdivision of the magnetostrictive wave guide is for good magnetised [ 1 ] . A spiral, moving both as a sender and receiving system ( transducer ) is placed at one terminal of the magnetic subdivision and an alternating current is applied [ 2 ] . This provides an extra clip changing axial magnetic field [ 1 ] . Longitudinal emphasis moving ridges ( manners ) are created in the wire if it is axially magnetised by the clip changing field inside the spiral ( joule consequence ) ; if it is circumferentially magnetised, torsional emphasis moving ridges ( manners ) are excited ( Wiedemann consequence ) [ 3 ] .
2.3 DIELECTRIC SPECTROSCOPY
Dielectric Spectroscopy is the measuring of the dielectric belongingss of a stuff as a map of the frequence of an applied jumping electric field. It is a technique used to analyze the kineticss of a stuff when subjected to an electromagnetic field. The kineticss of the stuff is related to its polarisability under the consequence of an applied electric field. Different stuffs characterized by different structural and molecular belongingss exhibit different types of polarization which contribute to the overall polarization in the dielectric stuff. The polarization mechanisms find the fluctuation of the complex permittivity of the dielectric stuff with frequence. The complex permittivity of the trial medium is related to the electrical capacity and conductance by its existent and fanciful constituents severally. A alone feature of dielectric spectrometry is its usage with a broad scope of frequences from 10-5Hz to 1016Hz and this enables measuring of dielectric response to both slow ( low frequence ) and fast ( high frequence ) molecular events [ 11, B ] .
The term “ dielectric ” was coined byA William WhewellA ( from “ dia-electric ” ) in response to a petition fromA Michael Faraday. The word “ Defense Intelligence Agency ” is a Grecian word significance to cut across or block and “ electric ” implies exposing belongingss of electronic conductivity. Thus insulators are frequently thought of crudely as non-conductors or “ dielectrics ” . However, Von Hippel ( a widely respected “ dielectrician ” ) , gave a more precise definition of insulators as non a narrow category of alleged dielectrics, but the wide sweep of non-metals considered from the point of view of their interaction with electric, magnetic, of electromagnetic Fieldss. Therefore, this definition gave a better and broader apprehension of insulators in the scientific discipline community because it implies that insulators concerns gases every bit good as with liquids and solids, and besides the storage of electric and magnetic energy every bit good as its dissipation.
Dielectric Spectroscopy goes back to the terminal of the 19th century. Majority of the parts on dielectric spectrometry can be attributed to Dutch-born U.S. physical chemist, Prof. Peter Joseph Wilhelm Debye. This is majorly due to his extended work and his first of import research, onA electric dipoleA minutes. Polarization can be defined to be the vector summing up of all single dipole minutes in a stuff and since Polarisation and the kineticss of electric charges are at the bosom of insulators, and are frequently described in footings of macroscopic belongingss such as permittivity, dielectric loss and breakdown strength, Prof. Debye ‘s work plays an of import function in understanding Dielectric Spectroscopy.
Over the old ages, after the visual aspect of the original Debye parts between 1912 and 1913, on the topic, there had been an increasing involvement in the field of Dipole minute and particularly its part to the survey of dielectric belongingss. Get downing in 1955 at least three monographs that summarize progresss in the topic included: C. P. Smyth, “ Dielectric Behavior and Structure, ” United States ; N. E. Hill, W. E. Vaughan, A. H. Price, and M. Davies, “ Dielectric Properties and Molecular Behavior, ” Great Britain ; and V. I. Minkin, O. A. Osipov, and Yu. A. Zhdanov, “ Dipole Moments in Organic Chemistry, ” the Soviet Union.
As already noted, polarisation plays an of import function in the survey of insulators. There are four mechanisms of polarisation viz. : Electronic, Ionic Interfacial and Orientation Polarization. These mechanisms are described in item subsequently in this study but of major importance to Dielectric Spectroscopy is the Orientation Polarization. The construct of the orientation of dipolar molecules in an jumping electric field was applied by Debye ( 1913 ) in the account of the behavior of the existent and fanciful parts of two dielectric invariables: Permittivity and dielectric loss factor which are better footings when frequence dependance is involved.
The basic rule of Orientation Polarization is that when the field is applied, or released, a finite clip will be required for the molecules to come to their equilibrium orientation because there is a syrupy opposition to these revolutionary gestures. The scope of frequence over which the existent dielectric invariable is variable extends from the inactive field to one that oscillates so quickly as non to supply for any rotational gesture of the polar molecule at all ; the theory therefore describes a typical molecular relaxation procedure. The attach toing invariable, called the clip of relaxation, is made available from measurings of the frequence fluctuation of either the existent dielectric invariable or the energy soaking up for the system ; in solutions this clip changeless may be related to molecular size and form and therefore, it ‘s rather utile in remedy monitoring of Polymers. The statements and equations presented in connexion with the frequence dependance job have been of greatest involvement in electrical technology.
Early applications of Dielectric Spectroscopy in the surveies of Polymers day of the month back every bit far as 1951 when Debye along with F. Bueche, applied the comparatively simple thought of internal rotary motions to an organic high-polymer system. Although, it is necessary to observe that one may besides derive information about the mean size of coiled polymer molecules in solution from light dispersing measuring. The dielectric belongingss of stuffs have come to play a cardinal function in the description of physical phenomena in many subdivisions of modern scientific discipline, engineering, and technology. Over the last several decennaries, the tantamount frequence scope of Dielectric Spectroscopy ( DS ) has been expanded by assorted experimental techniques so dielectric relaxation processes of systems can be measured over an highly broad scope of characteristic times ( 10A 5A s – 10A -12A s ) .
As a consequence, these techniques now occupy a particular topographic point among legion modern methods used in physical and chemical analyses of stuffs. Since dielectric spectrometry measures the clip development of molecular polarisation, the technique is particularly sensitive to intermolecular interactions and their function in molecular concerted procedures. Dielectric spectrometry provides a nexus between the kineticss of molecular gesture of the single components of the complex stuff and the word picture of its majority belongingss. The recent successful developments of the Time Domain Dielectric spectrometry methods and Broadband Dielectric Spectroscopy have radically changed the function of dielectric spectrometry as an effectual tool for structural probe in solids and liquids on macroscopic, microscopic and mesoscopic degrees.
A dielectric stuff is an dielectric -with a high characteristic resistivity- in which electrostatic dipoles exist either for good or as a consequence of an applied electric field. Dielectrics act as nonconductive Bridgess between two carry oning home bases ( in most instances metals ) . Depending on design specifications, the agreement of the conducting home bases can follow several capacitance theoretical accounts such as parallel home base and cylindrical capacitance theoretical accounts ( shown in figure 1.1 ) . A really cardinal belongings of insulators is their high polarisability. Electric polarisability is the comparative inclination of a charge distribution, like the negatron cloud of an atom or molecule, to be distorted from its normal form by an external electric field, which may be caused by the presence of a nearby ion or dipole [ 1 ] . Permittivity is a characteristic of dielectric stuffs and it is related to polarization and response to an applied electric field.
1.2.1 DIELECTRIC PROPERTIES OF MATERIALS
1.2.2 DIELECTRIC IN CAPACITORS
Polarization is the attendant consequence of using an electric field to a dielectric stuff. Dielectric stuffs fundamentally consist of positively charged karyon and a cloud of uniformly distributed negatrons around the karyon. When an electric field is applied, there is supplanting of charges in the way of the electric field ( positive charges ) and in an opposite way ( negative charges ) . The consequence of the applied electric field ( E ) and attendant supplanting is an induced dipole minute ( m ) defined by
m = qr
R A is the supplanting between the charges ;
m and R are vector measures.
The dipole minute ‘s way points towards the positive charge as shown in figure 1
Figure 1. Supplanting of charges due to applied electric field.
The magnitude of the induced dipole minute is related to an atom or atom and these single dipole minutes are summed up for the whole volume of the dielectric stuff. This vector summing up is the polarization ( P ) of the dielectric stuff and is defined by
P = m
1.3.1 TYPES OF POLARISATION
The polarization mechanisms that contribute to the permittivity of the stuff vary for different stuffs. For polymeric stuffs, the major polarization mechanism are polarization due to bear down migration ( atomic polarization ) and polarization due to orientation of lasting dipoles ( orientation polarization ) [ 2,8,9 ] . In emulsions, gels, Electro-rheological fluids ( ERF ) and other heterogenous systems, the major polarization mechanisms are the Maxwell-Wagner ( interfacial ) polarization and orientation polarization [ 3-7 ] . There are four types of polarization depending on the initiation mechanism and these are electronic, ionic, orientation and inter-facial polarization and are briefly described below.
18.104.22.168 Electronic polarization
This type of polarization is induced as a consequence of supplanting of negatrons from their equilibrium places with regard to the karyon of the atom and therefore induces a dipole minute. It is sometimes referred to as atomic polarisation and is highly fast with resonating frequence in the UV or seeable scope of the electromagnetic spectrum [ 2 ] .
22.214.171.124 Ionic polarization
This occurs chiefly in ionic crystals and it is related to the supplanting of positive ions ( cations ) and negative ions ( anions ) under the influence of an electric field. These supplantings are made with slower dynamicss when compared with electronic polarization. Its resonating frequence is in the infrared scope of the electromagnetic spectrum.
126.96.36.199 Orientation polarization
This type of polarization occurs when an electric field is applied to stuffs that have lasting dipoles. The attendant consequence is the alliance of the dipoles of the stuff in the way of the electric field. Orientation polarization varies reciprocally with absolute temperature and its scattering has a broad frequence scope depending on the stuff [ 10 ] . The confining frequence can be every bit high as 1011 Hz in the microwave spectrum.
188.8.131.52 Interfacial polarization
This polarization is related to heterogenous systems and is besides referred to as space-charge polarization or Maxwell-Wagner polarization. It is due to accretion of charges at the interface ( or inter-phase ) between constituents in the heterogenous insulator when subjected to a low frequence electric field ( 10-1 to 102 Hz ) [ 8,9 ] .
1.4 FREQUENCY RESPONSE/ FREQUENCY DEPENDENCE
1.5 TEMPERATURE DEPENDENCE
1.6 EXPERIMENTAL METHOD
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hypertext transfer protocol: //wapedia.mobi/en/Permittivity
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[ 8 ] Blitz J, “ Fundamentalss of Ultrasonics ” , Butterworths, 1963.
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