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Badanie olejów napędowych metodą dielektrometrii opartą na spektroskopii impedancyjnej

Macioszek Ł.

Pomiary Automatyka Kontrola

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2014

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R. 60, nr 11

942--944

PL

W pracy podjęto próbę oceny przydatności dielektrometrii w badaniu właściwości olejów napędowych typu premium. Przy użyciu systemu pomiarowego do spektroskopii impedancyjnej wykonano wstępne badania, na podstawie których wyznaczono względną przenikalność elektryczną badanych próbek. Wyniki badań pozwalają stwierdzić, że przy uwzględnieniu pewnych ograniczeń, dielektrometria oparta o spektroskopię impedancyjną może pozwolić na analizę olejów napędowych.

EN

In the paper an attempt was made to evaluate the diesel fuels using dielectric spectroscopy to verify experimentally that it can be used to characterize these fuels. Five samples of winter premium diesels from different vendors were examined. Impedance of diesel fuels was measured in the frequency range of 0.01 Hz – 5 kHz with the use of EG&G/Princeton Applied Research laboratory system for impedance spectroscopy. Measurement results are presented in the form of Bode plot in Fig. 1. Complex resistivity of the samples was calculated on the basis of measured impedance and is presented on fig. 2. The simplest electrical equivalent circuit of the measuring cell (parallel R-C circuit) was used to calculate the capacitance and thus dielectric constant of diesel fuels (expression 5) from the collected measurements of impedance. Dielectric constant of diesel fuels’ samples is presented in Fig. 3. In the Fig. 1 and 2 one can notice a diversity in the obtained results that depend on the supplier and hence the exact chemical composition of the tested diesel. This diversity is not so noticeable in Fig. 3 what may be very important in cases when dielectric spectroscopy is used to detect some substances that can be harmful for the engine. The tests’ findings show that dielectric spectroscopy can be used to determine some of the properties of diesel fuels. Ability to detect additional substances in diesel would however depend on the difference in values of dielectric constant of the matters.

2

Water induced evolution of dielectric and micro-structural properties of rice starch

Starzyk F., Chrzanowska A., Łużny W., Śniechowski M.

Archives of Materials Science and Engineering

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2009

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Vol. 39, nr 2

111-115

EN

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. Keywords: Bio-polymers; Micro-granular matter; Water uptake; Interdigit dielectrometry; Biological water

3

AC impedance and microstructure of rye starch exposed to water vapour

Starzyk F., Chrzanowska A., Łużny W., Śniechowski M.

Archives of Materials Science and Engineering

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2009

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Vol. 40, nr 1

23-26

EN

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 &sim104 s in case of humidification by balance resolution and character of the process. The whole range of measurements was limited to max &sim23 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 enabled by application of interdigit comb capacitor as a sensing unit. This is the first report of four stages for EACI evolution as well as the first XRD direct record of granular starch reversal swelling.

4

Physicochemical changes in epoxy-amine systems studied by ionic conductivity and ionic carriers mobility measurements

Friedrich K., Ulański J., Boiteux G., Seytre G.

Polimery

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2006

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T. 51, nr 9

648-655

EN

The main objective of this work was to find the correlations between the ionic conductivity, viscosity and physicochemical changes occurring during the isothermal cure of the epoxy-amine systems. The studies of the ionic conductivity evolutions have been performed using dielectric and direct-current techniques. The measurement data were compared with the ion mobility values evaluated from the time-of-flight investigations and with the dynamic viscosity determined by dynamic mechanical analysis. Different epoxy-amine reacting systems have been analyzed: the diglycidyl ether of bisphenol A with diamino-4,4'-dimethyl-3,3'-dimethyldicyclohexylmethane (DGEBA-3DCM) which gelates and vitrifies during the cure and the diglycidyl ether of 1,4-butanediol with 4,9-dioxa-1,12-dodecane diamine (DGEBD-4D) which only gelates during its polycondensation. It was found that even with an appearing of gelation or viscoelastic properties the conduction process could be described as thermally activated. The inconsistencies between ionic conductivity and ion mobility evolutions indicate that the concentration of the mobile charge carriers in the medium changes during the reaction. It was also observed that the vitrification could be responsible for the large changes of free volume in the system influencing the ionic conduction mechanism and therefore the ionic conductivity evolutions. It was also found that the Stokes's law is fulfilled at the beginning of the cure only.

PL

Głównym celem tej pracy było znalezienie korelacji pomiędzy przewodnictwem jonowym, lepkością oraz zmianami fizykochemicznymi pojawiającymi się podczas izotermicznego utwardzania układów epoksydowo-aminowych. Badania zmian przewodnictwa jonowego dokonane zostały przy użyciu technik dielektrycznych i stałoprądowych (rys. 2-6). Następnie wyniki pomiarów porównano z wartościami ruchliwości jonów oszacowanymi z badań czasu przelotu jonów metodą time-of-flight (TOF) oraz z wartościami lepkości dynamicznej określonymi metodą dynamicznej analizy mechanicznej (DMA) (rys. 7). Analizowano różne układy reaktywne epoksydowo-aminowe: eter diglicydowy bisfenolu A z diamino-4,4'-dimetylo-3,3'-dimetylodicyklohexylometanem (DGEBA-3DCM), który żeluje i ulega zeszkleniu podczas procesu utwardzania oraz eter diglicydylowy 1,4-butanodiolu z 4,9-dioksa-1,12-dodekano diaminy (DGEBD-4D), który podczas polikondensacji wyłącznie żeluje (tabela 2). Stwierdzono, że nawet w przypadku pojawienia się żelowania lub właściwości elastycznych proces przewodzenia może być opisany jako aktywowany termicznie. Niezgodności pomiędzy zmianami przewodnictwa jonowego i ruchliwości jonów wskazują, że w procesie utwardzania następują zmiany koncentracji ruchliwych jonów. Wykazano, że prawo Stokesa może być spełnione wyłącznie na początku procesu utwardzania.