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Search Results: 1 - 10 of 144335 matches for " F. Starzyk "
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Humidification and drying of granular matter – correlation of mass change and effective dielectrometry.
F. Starzyk
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: The purpose of this paper was to record and mutualy correlate mass changes of population of micro-granules ofrye starch and effective dielectric permittivity of this system taking places during humidification and drying processes.Design/methodology/approach: Mass changes of biopolymeric mirco-granular sample occuring during itsexposition on saturated water vapour at room temperature, was recorded in the time by means of precise torsionalbalance equipped with special chamber. The same was done in case of drying. Monitoring of effective dielectricpermittivity was performed by means of interdigit comb capacitor and precise RLC meter equipped with PCprogram. Specially designed and constructed measuring chamber was applied to control temperature and relativehumidity (RH %) of ambient sample atmosphere.Findings: Interdigit dielectric spectroscopy method turned out to be more sensitive technique to follow detailsof humidification as well as drying processes. Correlation of changes of effectife dielectric permittivity withsimultaneously occurring mass increase or decrease can be a way to describe the humidification and dryingprocesses of micro-granular biopolymeric sample.Practical implications: Effective dielectric permittivity monitoring of humidification and drying processesturned out to be much more selective than only gravitational measurement of mass change. For modeling purposecorrelation of both is giving new possibilities of modelling approach.Originality/value: For the first time practically important humidification and drying processes were monitoredin statu nascendi, without disturbing geometry of granules starch by means of ε’ values evolution record. It wasenabled by application of interdigit comb capacitor as sensing unit.
Interdigit dielectrometry of water vapour induced changes in granular starch
F. Starzyk
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: of this paper was a practical approval whether fringe field interdigit dielectrometry (FFID) can beuseful for sensible monitoring of water molecules behavior within granular-starch-population sample during it’shumidification process.Design/methodology/approach: used was to design methodology and perform series of measurementsinvolving calibration of a measuring system, sample preparation and to record initial stage of starch-granulespopulationsamples humidification process as dielectric parameters response on the step of ambient atmosphererelative humidity (~0 to ~100%) at room temperature.Findings: it was found that FFID enables to follow and isolate new features and characteristic stages of watervapors behavior during humidification of vacuum- dried starch granules population. The measurement of dielectricproperties of freely stacked granules population with unperturbed inter-granular contacts areas differs from the one,during which this contacts are being broken.Research limitations/implications: the possibility of new insight into humidification of micro-granularmatter sample (starch granules population). It implies the necessity of collective (of global scale) model of dielectricproperties creation. The evolution of dielectric permittivity is correlated with mass increase (water dipoles number)and adsorption rate as well as with absorption of water molecules within the granules population. Dielectric energylosses are correlated with evolution of interaction between water molecules and bio-polymeric matrix.Practical implications: huge amounts starch granules are produced transported and stored so properunderstanding of wheat response on humidity change is also of great practical importance.Originality/value: of this paper relays on the fact that FFID was applied for the first time to starch granulespopulation and it turned out to be effective tool in monitoring and modeling of dielectric properties of microgranularmatter population and for granular starch in particular. It is important in modeling of collective dielectricproperties of this kind of matter as well as of practical reasons specified above.
Parametrisation of interdigit comb capacitor for dielectric impedance spectroscopy
F. Starzyk
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: The purpose of this paper was to collect full description of interdigit capacitor (IDC) used in interdigitdielectrometry and to point out on the way how it should be applied in practice.Design/methodology/approach: The full graphical representation of IDC geometry and its descriptionwas demonstrated and described. Capacity of IDC and electric potential distribution as well as charge densitydistribution on flat comb electrodes were demonstrated.Findings: Though the analytical formulas of effective IDC capacity and potential distribution are complicated, thepractical application of IDC in dielectric measurements is much simpler than those of flat or cylindrical capacitors.Research limitations/implications: Practical limitations were formulated and specified together with their meanings.Practical implications: Universality of measuring procedure with IDC application was pointed out and completed.Originality/value: Complete description of IDC parameters will make easier for potential investigator frommany scientific disciplines to see how one have to understand and apply in practice IDC dielectrometry techniqueas well as potentially make the IDC parameter optimal for given application.
Elevated temperature induced dispersion phenomena in Ba 1-xNaxTi1-xNbxO3
W. B?k,F. Starzyk,C. Kajtoch,E. Nogas - ?wikiel
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: of this paper was to investigate features of the dispersion of dielectric permittivity induced by elevated temperature (473K-723K) in polycrystalline solid solution of Ba1-xNaxTi1-xNbxO3 (for x=0.3 and x=0.4).Design/methodology/approach: used to perform this purpose was dielectric spectroscopy application to measure dielectric and electric parameters within the frequency range (20Hz-1MHz).Findings: Analysis of temperature and frequency dependences of real (ε’) and imaginary (ε”) parts of dielectric permittivity had pointed out on relaxor type of dielectric behaviour for both investigated samples in paraelectric phase. The thermal activation energy values of ac conductivity (for 100Hz) are similar to those of semiconductors. Values of ε’ for both materials (x=0.3, x=0.4) are consistent with literature quotations. Thus the polarisation behaviour of our materials seems to be similar to those described in the literature. Different behaviour of dielectric energy losses is postulated as originating from differences of samples microstructure.Research limitations/implications: Further investigations should be carried out in the range of low temperatures (down to 100K) and within a broaden frequency range (up to 1.8GHz) in order to establish the influence of chemical structure on ferroelectric-paraelectric phase transition.Originality/value: Dielectric properties for two new material prepared from nanopowders of BaTiO3 and NaNbO3 were described.
Water induced evolution of dielectric and micro-structural properties of rice starch
F. Starzyk,A. Chrzanowska,W. ?u?ny,M. ?niechowski
Archives of Materials Science and Engineering , 2009,
Abstract: Purpose: The purpose of this paper was to record and correlate mass (m) changes of population of rice starch micro-granules and their effective dielectric permittivity(ε′), as well as X-ray diffraction (XRD) changes observed in this system during humidification.Design/methodology/approach: Changes of mass of bio-polymeric-granular sample occurring during its exposition on saturated water vapour at room temperature, was recorded in the time. The ε′ evolution was recorded by means of fringe-field-interdigit-dielectric spectroscopy (FFIDS) method. The temperature and relative humidity (RH %) of ambient atmosphere were controlled. Microstructure changes induced by water absorption were recorded by means of XRD diffractometer.Findings: The FFIDS method turned out to be sensitive technique to follow details of humidification process. Correlation between changes of ε′ with simultaneously occurring mass increase can be a way to describe the humidification and drying processes of micro-granular bio-polymeric sample. The changes observed by means of XRD should enable to point the regions within granules structures where water molecules effectively interact with internal granules physical organisation on macromolecular level.Research limitations/implications: The time length of m(t) record was limited to ~11000 s in case of humidification by the nature of the process. The whole range of measurements was limited to max ~23 % of water uptake in order to prevent the molecular structure irreversible changes.Practical implications: The ε′ monitoring of humidification turned out to be much more selective than only gravitational measurement of mass change. The correlation of both is giving new possibilities of modelling approach. The XRD observed changes within physical structures of rice starch granules seems to be of great importance for modelling of water behaviour in starch.Originality/value: For the first time humidification process was monitored in statu nascendi, without disturbing geometry of granules starch by means of ε’ evolution record. It was enabled by application of interdigit comb capacitor as sensing unit. The high quality of XRD records enables a new insight into details of reversible swelling process of rise starch granules.
The dielectric behaviour of polycrystalline Ba0.96Na0.04Ti0.96Nb0.04O3 solid solution
W. B?k,M. Gabry?,W. Tejchman,F. Starzyk
Archives of Materials Science and Engineering , 2009,
Abstract: Purpose: The purpose of this work was to measure and investigate dielectric properties of new material, polycrystalline solid solution Ba0.96Na0.04Ti0.96Nb0.04O3 (BNTN4) within the temperature range 153 K-473 K.Design/methodology/approach: The dielectric spectroscopy method has been applied to measure dielectric and electric parameters within the frequencies from 20 Hz to 1 MHz.Findings: The dielectric permittivity(ε’) dependence on temperature (T) within the range of 473 K-225 K consist of two components: the reversly proportional one and the second one in the form of small local, transient peak at about 400 K. The global maximum is frequency dependent and above ~400 K along the T decrease, the dispersion of ε’ is initiated and low frequency dispersion of ε’ prevails below 250 K. Energy losses measure (ε”), correlated with ε’(T), is generally shifted towards lower T values. Its frequency dependence undergoes inversion which develops with T decrease and is initiated at about 370 K. The whole temperature induced phase transition turned out to be of relaxor kind and diffused process. The detailed analysis of this transition and its features was performed.Research limitations/implications: In order to determine the details of polycrystalline structure of BNTN4 new material for modelling of ferroelectric properties the precise X-ray diffraction measurements should be performed as function of T. The nature of ferroelectric - paraelectric (FE - PE) transition diffusive character will be studied by means of dielectric measurements within frequency range 1 MHz-1.8 GHz.Originality/value: The new kind of ferroelectric solid solution (BNTN4) was synthesized. The specific features of this material at low T range involves among others, the T-dependent dispersion of dielectric properties on low T side of broad ε’(T) peak
AC impedance and microstructure of rye starch exposed to water vapour
F. Starzyk,A. Chrzanowska,W. ?u?ny,M. ?niechowski
Archives of Materials Science and Engineering , 2009,
Abstract: Purpose: The purpose of this paper was to record and analyse mass (m) changes of population of micro-granules of rye starch, effective alternative current (AC), (electric) complex impedance (EACI) of this system taking place during humidification as well as insight into microstructure evolution by X-ray diffraction (XRD).Design/methodology/approach: Mass changes of biopolymeric micro-granular sample occurring during its exposition to saturated water vapour at room temperature, was recorded in time by means of precise torsional balance equipped with special chamber. The same was done in case of microstructure by XRD method. Monitoring of EACI was performed by means of interdigit comb capacitor and precise RLC meter equipped with PC software. Specially designed and constructed measuring chamber was applied to control temperature and relative humidity (RH %) in ambient sample atmosphere. Electric measurements were carried out for 5 selected frequencies.Findings: Interdigit dielectric spectroscopy method turned out to be more sensitive technique to follow details of long lasting humidification than only mass changes recording. Correlation of changes of EACI with simultaneously occurring mass increase can be a way to describe the humidification stages processes involving water molecules adsorption and absorption by micro-granular biopolymeric sample. Frequency dependence of EACI gives insight into mechanism of water molecules inclusion, binding and immobilization on the starch granules surface as well as inside of its internal physical structure.Research limitations/implications: The recording duration of m(t) was limited to ~104 s in case of humidification by balance resolution and character of the process. The whole range of measurements was limited to max ~23 RH % of water uptake in order to prevent over molecular structure irreversible changes. The above limitations enable us to collect data for modelling reversible water uptake and connected EACI micro-granular biopolymeric population sample.Practical implications: EACI monitoring of humidification turned out to be much more selective than only gravitational measurement of mass change. Modelling purpose correlation of both can give new possibilities to modelling approach. Achieved data can contribute to better understanding of active adsorption and absorption centres in starch granules.Originality/value: For the first time practically important humidification process was monitored in statu nascendi, without disturbing geometry of starch granules population by means of EACI evolution record. It was enabl
Influence of electric field DC-component on AC-response of ferroelectric powder
F. Starzyk,W. B?k,C. Kajtoch,M. Gabry?
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: of this work was to establish whether ac-response of freely stocked micro-granular ferroelectric matter on fringe measuring electric field depends on constant component presence VDC (or DC-Bias).Design/methodology/approach: used involves measurements of effective dielectric permittivity (and other effective dielectric quantities) by means of interdigit dielectrometry. Fringe measuring electric field was applied to BaTiO3 micro-powder by interdigit comb sensor (ICS) Netzsch of Ms25 type. ICS was driven by measuring generator with sinusoidal voltage: v(t)= VDC+VACsin(ωt), within frequency range 20Hz-100kHz and for DC-Bias values ranging as VDC=(0-20)V.Findings: The interdigit dielectrometry was applied to measure complex dielectric permittivity, complex dielectric modulus and others dielectric functions of ferroelectric BaTiO3 powder. The influence of constant component of electric stimulus was investigated in the frequency range 100 kHz to 20 Hz. It was established that in the low frequency range constant component of electric field enhances effective dielectric permittivity, and changes two weak relaxation processes occurring in the ferroelectric micro-granular net. It turned out that effective dielectric complex modulus of this net is most sensitive quantity for application of constant component of electric stimulus.Research limitations/implications: The density solution effect is a source of small effective dielectric permittivity of micro-granular ferroelectric powder (ε’). ε’ values are being enhanced by presence of non zero VDC value. The same effect was established for effective energy loss coefficient (ε”). The two relaxational processes connected with VDC≠0 seems to be a key feature of freely stocked ferroelectric matter.Originality/value: of this work relays on the fact, that this is a first report of the VDC influence on effective dielectric properties of ferroelectric micro-granular matter. It is opening the way to a new approach in modelling of effective dielectric properties of granular matter in nature and powders technology.
Evolution of electric polarisation in paraelectric phase of BaTiO3
W. B?k,C. Kajtoch,F. Starzyk,J. ?mija
Archives of Materials Science and Engineering , 2008,
Abstract: phase. On the basis of the obtained results mechanism of dipolar polarization has been discussed.Design/methodology/approach: Polycrystalline samples of barium titanate were prepared using calcinations method, at the temperature about 1670 K. Dielectric measurements were carried out by means of Quatro Cryosystem 4.0 and Agilent Precision LCR meter HP4284A equipped with WinDETA 5.62 software Novocontrol. The samples were refreshed before measurements by annealing at 700 K. The dielectric measurements were carried out within the frequency range 20 Hz - 1 MHz under cooling with 2 K/min speed.Findings: The results show occurrence of maxims of dielectric permittivity (ε’) and phase angle (Φ) within the “cross – over” region. The temperatures related to these maxims depend on the frequency of electric field and are higher for higher frequencies. A positive temperature coefficient (PTC) of conductivity has been found in paraelectric phase of BT.Research limitations/implications: It has been postulated, on the basis of the obtained results, that at the temperatures above 400 K (paraelectric phase) two types of polarization exist in BT: the polarization due to free dipoles (Pf) and the polarization (Pd) related to polar clusters formed by the dipoles.Originality/value: The results confirm existence of two types of polarization in paraelectric phase of BaTiO3.
Study of phase transition specific in polycrystalline Pb(Cd1/3Nb1/3)O3
C. Kajtoch,W. B?k,F. Starzyk,M. Gabry?
Archives of Materials Science and Engineering , 2008,
Abstract: Purpose: of this paper was to isolate and attempt to identify experimentally specific features of paraelectric diffused phase of Pb(Cd1/3Nb2/3)O3 (PCN) not reported yet in the literature.Design/methodology/approach: we used was to measure and analyse the temperature and frequency dependence of polarization, energy loss, phase angle and ac-conductivity components.Findings: we have isolated four specific processes visible as specific behaviour of ε’(T, ν); on ε” and phase angle also temperature and frequency dependences and three contributions to ac-conductivity.Practical implications: processes isolated will be used to construct a model of polarizability and energy loss as well as ac-conductivity in diffused paraelectric phase of PCN. Originality/value: of the paper rely on the possibility of experimental verification of temperature induced evolution of polar regions structure and dynamics created in high temperature region of paraelectric phase of PCN.
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