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  1. 8 Materials Science Poland
  2. 5 Fibres & Textiles in Eastern Europe
  3. 4 Prace Naukowe Instytutu Podstaw Elektrotechniki i Elektrotechnologii Politechniki Wrocławskiej. Konferencje
  4. 3 International Letters of Chemistry, Physics and Astronomy
  5. 2 Archives of Metallurgy and Materials
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  1. 4 Liu Yuanjun
  2. 3 Wutke M.
  3. 3 Zhao Xiaoming
  4. 2 Bartkowska J. A.
  5. 2 Bochenek D.
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  1. 2 2022
  2. 3 2021
  3. 2 2020
  4. 4 2019
  5. 2 2018
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1
Content available Influence of the Content of Nickel Powders on the Electromagnetic Properties of SingleLayer Coated Polyester-Cotton Plain Weave Fabric
Liu Yuanjun, Xue Huangyu, Wang Ciyi, Han Xiaohui, Zhao Xiaoming
Fibres & Textiles in Eastern Europe
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2022
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Vol. 30, no. 5
47--52
EN
A coated composite was prepared on polyester-cotton plain weave fabric, using PU2540 polyurethane as the matrix. The influences of the content of nickel powders on the dielectric constant (the real and imaginary parts and loss tangent value), reflection loss and shielding effectiveness of single-layer coated composites were mainly investigated. The results showed that within the frequency range of 1-1000 MHz, the value of the real part of the dielectric constant of the coated composites was the largest, and the polarisation ability with regard to electromagnetic waves was the strongest when the content of nickel powders was 40%. Within the frequency range of 15-225 MHz, the value of the imaginary part of the dielectric constant of the coated composites was the largest and the loss ability with regard to electromagnetic waves was the strongest when the content of nickel powders was 40%. Within the frequency range of 250-800 MHz, the loss tangent value of the dielectric constant of coated composites was the largest, and the attenuation ability with regard to electromagnetic waves was the strongest when the content of nickel powders was 40%. Within the frequency range of 1220-3000 MHz, the reflection loss value was the smallest when the content of nickel powders was 40%, and its absorption ability with regard to electromagnetic waves was the strongest. Within the frequency range of 760-3000 MHz, the shielding effectiveness of the coated composite was the largest when the content of nickel powders was 40%.
2
Content available remote An experimental study on the complex resistivity of fractured rock under different saturation conditions
Pan Baozhi, Ruhan A., Guo Yuhang, Zhang Lihua, Wei Boyang, Zhou Weiyi
Acta Geophysica
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2022
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Vol. 70, no 3
1061--1081
EN
The fracture can be a good channel for oil and gas migration, which has a great influence on the permeability of the reservoir. Therefore, it is of major significance to identify fractures and determine the characterization parameters and physical proper ties of fractured reservoirs. In this study, homogeneous sandstone was used to simulate different artificially fractured rocks. The fractured rock samples had different fracture widths, fracture numbers, and fracture dip angles. In addition, the complex impedance and weights of the rock samples were measured during the process of natural evaporation, and the relationships between the water saturation and the complex resistivity values at different frequencies were examined. The frequency range is 100 Hz–10 kHz. It was found that the influence effects of frequency on the resistivity, dielectric constant, and loss factor had differed among the homogeneous samples and the fractured rock sample. The fracturing had led to the resistivity index and the water saturation curves separating under the different frequencies, and the degree of the dielectric constant index and water saturation curve separation became larger. Furthermore, the influencing effects of the fracture widths, fracture numbers, and fracture dip angles mainly occurred in terms of three aspects. The first was the slope of the resistivity index and water saturation curves (IR–Sw). The second was the slope of the dielectric constant index and water saturation curves (Iε–Sw), and the third was the loss tangent D and water saturation Sw curves.
3
Content available remote Influence of zinc substitution on structural, elastic, magnetic and optical properties of cobalt chromium ferrites
Zeeshan Talat, Anjum Safia, Waseem Salma, Majid Farzana, Ali Muhammad Danish, Aslam Ammara
Materials Science Poland
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2021
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Vol. 39, No. 1
139--151
EN
The polycrystalline Co1−xZnxCr0.5Fe1.5O4 series with (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) has been synthesized by conventional ceramic rout method. The structural and elastic properties have been investigated by X-ray diffractometer and Fourier transform spectroscopy. Both XRD and FTIR confirm the formation of single phase cubic spinel ferrites. The cationic distribution for all samples has been proposed. The lattice parameter, X-ray density, hoping length, bond length, and packing factors–in accompaniment with variations in the zinc concentration–have been studied. The IR band position has been explained by the cations involved in the structure. The elastic moduli such as Young's modulus, bulk modulus, rigidity modulus and Poison's ratio have bee calculated using force constants. Scanning electron microscope (SEM) observation conveys information about the agglomeration of particles. The hysteresis curve obtained from vibrating sample magneto meter (VSM) conveys information about the soft nature of prepared compositions. The saturation magnetization decreases with addition of zinc ions and coercivity is almost zero. An increase in band gap energy has been observed with addition of zinc by Ultraviolet Visible Spectroscopy (UV-VIS), which is due to small crystallite size.
4
Content available remote Bio-dielectric based on superconductors yttrium calcium barium copper oxide (YCaBa2Cu3O7−x) from eggshell as calcium oxide source via sol-gel process
Toumvong Wipawadee, Chitcharoentaweechoke Pornnita, Tangboriboon Nuchnapa
Materials Science Poland
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2021
|
Vol. 39, No. 3
305--318
EN
Eggshell is a rich source of calcium that is a dielectric material used for doping in a superconductor. Yttrium calcium barium copper oxide (YxCa1−xBa2Cu3O7) was prepared using the sol-gel process and fired at 900 °C or 1,000 °C. The stoichiometric ratio of the raw materials Y2O3:BaCl2:CuO:CaO was 1:2:3:1 based on the molar mass. The obtained YCaBCO had an orthorhombic crystal structure composed of distorted oxygen-deficient perovskite. The orthorhombic structure was unsymmetrical, providing a substantial increase in the physical electromagnetic properties of the superconductor. The YBCO-900-reference analyzed using an impedance analyzer in the range from 500 Hz to (1 × 106) Hz and at room temperature (27 °C) had the following values for capacitance, electrical conductivity, and dielectric constant ± standard error: 8,286.70 ± 28.49 pF, (3.60 ± 0.01) × 107 S/m, and 1,874.794 ± 6.446, respectively. The YCaBCO-900-eggshell (YxCa1−xBa2Cu3O7) analyzed at 500 Hz at room temperature (27 °C) had high values for capacitance, electrical conductivity, and dielectric constant, namely, 8,540.10 ± 2.00 pF, (1.32 ± 0.00) × 108 S/m, and 1,988.540 ± 0.500, respectively. Furthermore, the YCaBCO-900-eggshell had electrical properties (capacitance, conductivity, and dielectric constant values) higher than those of YCaBCO-900-commercial grade measured under the same conditions. The YCaBCO-900-com grade had capacitance of 8,225.75 ± 0.73 pF, electrical conductivity of (1.40 ± 0.01) × 108 S/m, and dielectric constant of 1,874.59 ± 0.17, respectively. Therefore, eggshell is an alternative dielectric material useful for doping in yttrium barium copper oxide (YBCO) to form YCaBCO, thus causing an increase in its electrical properties. The obtained superconductor is a candidate that could be applied in many industries.
5
Content available Study of the Dielectric Properties and Conductivity of Double Coated Glass Fibre Felt Composites
Liu Yuanjun, Wang Caixia, Ma Yiping, Liu Yanyan, Wu Haiying, Zhao Xiaoming
Fibres & Textiles in Eastern Europe
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2021
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Vol. 29, no. 4 (148)
75--80
EN
Graphite/talcum powder double-coated glass fibre felt composites were prepared using glass fibre felt as the base material, graphite as the surface absorbing agent, talcum powder as the underlying absorbing agent, epoxy resin E44 as the adhesive and low molecular 650 polyamide as the curing agent. The influences of the surface graphite content and underlying talcum powder content on the dielectric properties and conductivity of glass fibre felt composites were the main focus of the investigation. Results showed that when the frequency is less than 103 Hz, the values of the real and imaginary parts of the dielectric constant for double-coated glass fibre felt composites are largest when the surface graphite content is 50%. When the frequency is larger than 106 Hz, the value of the real part of the conductivity is largest when the graphite contents are 40% and 50%. When the frequency is less than 104Hz, the real part of the dielectric constant of the glass fiber mat composites is the largest when the talc content is 40%, and when talc content is 60%, the imaginary part of dielectric constant of glass fiber mat composites is the largest. The maximum loss tangent value for the composites occurs when the talcum powder content is 40%. When the frequency is larger, the value of the real part of the conductivity increases gradually.
PL
W pracy przygotowano podwójnie powlekane kompozyty filcu z włókna szklanego w postaci grafit/talk. Użyto filcu z włókna szklanego jako materiału bazowego, grafitu jako powierzchniowego środka pochłaniającego, talku jako podstawowego środka pochłaniającego, żywicy epoksydowej E44 jako kleju i poliamidu 650 o niskiej masie cząsteczkowej jako środek utwardzającego. Głównym przedmiotem badań było określenie wpływu zawartości grafitu powierzchniowego oraz zawartości proszku talku na właściwości dielektryczne i przewodność kompozytów z filcu z włókna szklanego. Wyniki wykazały, że gdy częstotliwość jest mniejsza niż 103 Hz, wartości części rzeczywistej i urojonej stałej dielektrycznej dla podwójnie powlekanych kompozytów z filcu z włókna szklanego są największe, gdy zawartość grafitu powierzchniowego wynosi 50%. Gdy częstotliwość jest większa niż 106 Hz, wartość rzeczywistej części przewodnictwa jest największa, gdy zawartość grafitu wynosi 40% i 50%. Maksymalna wartość tangensa strat dla kompozytów występuje, gdy zawartość talku wynosi 40%. Gdy częstotliwość jest większa, wartość rzeczywistej części przewodnictwa stopniowo wzrasta.
6
Content available Influence of the Thickness of Graphene Coating on the Electromagnetical and Mechanical Properties of Double-Layer Coated Basalt Fibre Fabrics
Liu Yuanjun, Yang Yanfeng, Yang Zhanhua, Liu Yanyan, Su Ying, Niu Jiarong
Fibres & Textiles in Eastern Europe
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2020
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Vol. 28, no. 5 (143)
69--74
EN
A double-layer coated basalt fibre fabric was prepared using polyurethane as the matrix and applying coating technology to the basalt fibre fabric. The influence of the thickness of the graphene coating on the electromagnetic properties and mechanical properties of the double-layer coated basalt fibre fabric was studied. Results showed that when the thickness of the graphene coating was 2.0 mm, the polarising ability, loss ability and attenuating ability of the fabric with respect to electromagnetic waves were all the largest. Along with the increasing thicknesses of the graphene coating, the electromagnetic shielding effectiveness of the double-layer coated basalt fibre fabric also increased, then the shielding ability against electromagnetic waves became stronger.
PL
W pracy przygotowano dwuwarstwowo powlekaną tkaninę z włókna bazaltowego, stosując poliuretan jako matrycę i stosując technologię powlekania na tkaninę z włókien bazaltowych. Badano wpływ grubości powłoki grafenowej na właściwości elektromagnetyczne i mechaniczne dwuwarstwowo powlekanej tkaniny bazaltowej. Wyniki pokazały, że gdy grubość powłoki grafenowej wynosiła 2.0 mm, polaryzacja, zdolność do strat i zdolność tłumienia tkaniny w odniesieniu do fal elektromagnetycznych były największe. Wraz ze wzrostem grubości powłoki grafenowej wzrastała również skuteczność ekranowania elektromagnetycznego dwuwarstwowo powlekanej tkaniny bazaltowej z włókien bazaltowych, a następnie zdolność ekranowania przed falami elektromagnetycznymi stała się silniejsza.
7
Content available GPR as a support tool in determining the causes of failure of objects built in the “white box” technology
Lejzerowicz A., Wutke M.
Archives of Civil Engineering
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2020
|
Vol. 66, nr 3
173--189
EN
From the construction made in the “white box” technology, first of all tightness is required - on the structural elements there should not be any cracks or scratches, through which water could penetrate, which in consequence may lead to deformation of structural elements and even loosing of their load-bearing capacity. Among the methods enabling the location of weakened places in watertight concrete, the ground penetrating radar (GPR) method is effective because the local occurrence of water in the structure evokes a clear and unambiguous anomaly on the radargram. In addition, the GPR method allows you to indicate places where water flows without the necessity of excluding the object from use and interference in the construction layers. The designation of such locations will make it possible to undertake technical activities that can facilitate the takeover of water and thus ensure the desired load-bearing capacity and usability of the object. Using the GPR method, you can also designate places that have already been deformed – discontinuities or breaking. The article presents a case study of investigations that determine the causes of leakage of tunnels made in the “white box” technology in: twice within the bottom slab of the tunnel (1 GHz air-coupled and 400 MHz ground-coupled antenna) and once in the case of tunnel walls (1.6 GHz ground-coupled antenna).
PL
Od konstrukcji wykonanej w technologii "białej wanny" wymagana jest przede wszystkim szczelność - na elementach konstrukcyjnych nie powinno być żadnych pęknięć ani zadrapań, przez które woda może przenikać, ponieważ to w konsekwencji może prowadzić do deformacji elementów konstrukcyjnych, a nawet utraty ich nośności. Wśród metod umożliwiających lokalizację osłabionych miejsc w wodoszczelnym betonie, metoda georadarowa (ang. ground penetrating radar - GPR), jest skuteczna, ponieważ lokalne występowanie wody w strukturze wywołuje wyraźną i jednoznaczną anomalię na otrzymanym obrazie (radargramie). Ponadto metoda GPR pozwala wskazać miejsca, w których woda przepływa bez konieczności wyłączania obiektu z użytkowania i bez ingerowania w warstwy konstrukcyjne. Wyznaczenie takich miejsc umożliwia podjęcie działań technicznych, które mogą ułatwić przejęcie wody, a tym samym zapewnić pożądaną nośność i użyteczność obiektu. Za pomocą metody GPR można również wyznaczyć miejsca, które zostały już zdeformowane – miejsca nieciągłości lub ugięć czy spękań. Artykuł przedstawia studium przypadku oraz badania, które umożliwiły określenie przyczyny wycieku w obrębie tunelu wykonanego w technologii "białej wanny" - w obrębie płyty dennej tunelu (z wykorzystaniem anteny o częstotliwości 1 GHz sprzężonej z powietrzem oraz z wykorzystaniem anteny o częstotliwości 400 MHz sprzężonej z ziemią), jak również w przypadku ścian tunelu (antena o częstotliwości 1,6 GHz sprzężona z ziemią).
8
Content available remote Growth, electrical, thermal, mechanical and etching studies on 4-chloroanilinium hydrogen (2R, 3R)-tartrate monohydrate-an organic NLO single crystal
Sivakumar R., Nadaraj V.
Materials Science Poland
|
2019
|
Vol. 37, No. 3
310--316
EN
An organic single crystal of 4-chloroanilinium hydrogen (2R,3R)-tartrate monohydrate (4CAHT) was grown by slow evaporation solution growth technique at room temperature. Single crystal XRD study confirmed that the crystal belongs to monoclinic system with the space group P21. Powder XRD analysis confirmed the crystalline nature of the compound. The presence of various functional groups in the compound was revealed by FT-IR analysis. UV studies showed the absence of absorption in the entire visible region. To determine the thermal stability of the grown crystals it was subjected to thermogravimetric and differential thermal analyses. Microhardness and etching studies were also carried out for the crystal. The powder second harmonic generation efficiency of 4CAHT was tested by Kurtz and Perry powder technique and the relative SHG efficiency of 4CAHT was found to be 1.44 times greater than that of standard KDP.
9
Content available Influence of the Yarn Fineness and Stitch Length of Polyester Knitted Fabric on the Dielectric Constant
Liu Yuanjun, Li Wenyue, Zhao Xiaoming
Fibres & Textiles in Eastern Europe
|
2019
|
Vol. 27, no. 6 (138)
63--66
EN
The influence of the yarn fineness and stitch length of polyester knitted fabrics on the dielectric constant was investigated by the single factor test method. As a result of the investigation, polyester knitted fabric parameters were chosen so as to obtain a polyester knitted fabric with the maximum real part and imaginary part of the dielectric constant. The results show that when the yarn fineness is 59 tex and the mark of the stitch length is 75, the polyester knitted fabric displayed the maximum real part and imaginary part of the dielectric constant. Finally, the polyester knitted fabric with these parameters had good microwave absorbing properties.
PL
W pracy, metodą testu jednoczynnikowego, badano wpływ grubości przędzy i długości oczka dzianin poliestrowych na stałą dielektryczną. W wyniku badań dobrano parametry dzianiny poliestrowej, tak aby uzyskać dzianinę o maksymalnej stałej dielektrycznej. Wyniki pokazały, że przy grubości przędzy wynoszącej 59 tex i długości oczka 75, dzianina poliestrowa charakteryzowała się najwyższą stałą dielektryczną i miała dobre właściwości pochłaniania mikrofal.
10
Content available Evaluation of applicability of dielectric constant in monitoring aging processes in engine oils
Gomółka Leszek, Augustynowicz Andrzej
Eksploatacja i Niezawodność
|
2019
|
Vol. 21, no. 2
177--185
EN
This paper reports on the study involving the development of a dependence between the selected physicochemical properties of engine oil and the variation of its dielectric constant, considered as an evaluation parameter for the degree of its exploitation. In order to get to know the selected phenomena that accompany oil aging, a decision was made to perform tests of the condition of engine oils at various stages of their exploitation. In addition to the analysis of the dielectric constant, measurements of total base number and (TBN) and infrared spectroscopy (IR) were also performed. The interdependence between the examined values is developed using the Pearson’s linear correlation coefficient. As a result, the variability of TBN and IR absorbance in the context of the change in the dielectric constant were evaluated. Following the realized experimental tests, it was found that the results demonstrate a satisfactory correlation between the selected physicochemical properties of the oil, which resulted in the adoption of an assumption of a high feasibility of application of dielectric constant as a diagnostic parameter in monitoring the state of exploitation of engine oil.
PL
Celem pracy było określenie związków pomiędzy wytypowanymi właściwościami fizykochemicznymi oleju silnikowego a zmianą jego stałej dielektrycznej, rozważanej jako parametr oceniający stan jego zestarzenia. W celu szczegółowego poznania wybranych zjawisk towarzyszących starzeniu się oleju zdecydowano się na przebadanie oleju w różnych stadiach jego użytkowania. Poza badaniem stałej dielektrycznej wykonano również badania całkowitej liczby zasadowej TBN oraz badania spektrometryczne w podczerwieni IR. Stopień współzależności badanych wielkości przedstawiono wykorzystując do tego współczynnik korelacji liniowej Pearsona. W efekcie oceniono zmienność całkowitej liczby zasadowej oraz absorbancji IR w kontekście zmiany stałej dielektrycznej. Po przeprowadzeniu badań eksperymentalnych, stwierdzono, że uzyskane wyniki wskazują na zadawalającą korelację pomiędzy wytypowanymi własnościami fizykochemicznymi oleju, co pozwoliło z dużą dozą pewności przyjąć, iż stała dielektryczna może być użyta w charakterze parametru diagnostycznego do monitorowania stanu oleju silnikowego.
11
Content available Dielectric Relaxation of Manganese Modified Bi6Fe2Ti3O18 Aurivillius Type Ceramics
Bartkowska J. A., Bochenek D.
Archives of Metallurgy and Materials
|
2019
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Vol. 64, iss. 1
221--225
EN
The five-layer Aurivillius type structures with the general chemical formula Bi5Fe2-xMnxTi3O18, where x = 0, 0.6, 1.2 have been synthesized and tested. The SEM studies showed a significant increase in grain size in the manganese-modified Aurivillius type ceramic material (for x=1.2). The increase in the amount of manganese ions (Mn3+) affects the decrease in the temperature at which the relaxation processes take place. Namely from 525 K (1 kHz) and 725 K (1 MHz) for BFT sample (x=0) to 355 K (1 kHz) and 565 K (1 MHz) for BFM12T sample (x=1.2). Using the Arrhenius’s law and the Vogel-Fulcher’s relationship the activation energy (Ea) and the relaxation time have been calculated. The value of Ea increases with the increase of the Mn amount from 0.737 eV (for x=0) to 0.915 eV (for x=1.2).
12
Content available Charakterystyka technologii georadarowej i możliwe kierunki jej doskonalenia
Wutke M.
Drogownictwo
|
2018
|
nr 9
276--280
PL
Technologia georadarowa (GPR) jest powszechnie stosowana do obrazowania obszarów podpowierzchniowych m.in. nawierzchni drogowych. Jest to metoda nieniszcząca, wykorzystująca do wykrywania sygnałów odbitych od konstrukcji podpowierzchniowych promieniowanie elektromagnetyczne w paśmie mikrofalowym. GPR transmituje do ziemi fale elektromagnetyczne, a gdy te uderzą w zakopany obiekt lub granicę materiałów o różnych stałych dielektrycznych, antena odbiorcza rejestruje zmiany w sygnale zwrotnym. Ważne jest, aby mieć podstawową wiedzę na temat działania georadaru, ponieważ jego możliwości, ale i ograniczenia są bezpośrednio skorelowane z nauką. W artykule charakteryzowano technologię georadarową ze zwróceniem szczególnej uwagi na ograniczenia stosowania metodologii. Opisuje możliwości zwiększenia efektywności pomiarów georadarowych i nowe obszary zastosowań.
EN
Ground Penetrating Radar (GPR) technology is widely used for imaging the subsurface areas, including road structures. It is a non-destructive method that uses electromagnetic waves to detect signals reflected from sub-surface constructions. GPR transmits electromagnetic waves to the ground, and when these hit a buried object or boundary of materials with different dielectric parameters, the receiving antenna registers changes in the reflected signal. It is important to have a basic knowledge related to the operation of GPR, because its capabilities, but also limitations are directly correlated with science. The article describes GPR technology with particular attention to the limitations of the methodology. It describes the possibilities of increasing the GPR efficiency and new areas of applications.
13
Content available The Microstructure and Magnetoelectric Properties of Multiferroic Composites
Bartkowska J. A., Bochenek D., Niemiec P.
Archives of Metallurgy and Materials
|
2018
|
Vol. 63, iss. 2
853--858
EN
Multiferroic composites are very promising materials because of their applicability because the magnetoelectric effect occurs in them. The subject of the study were two multiferroic ceramic composites: leaded obtained from powder of the composition PbFe0.5 Nb0.5 O3 and ferrite powder of the composition Ni0.64 Zn0.36 Fe2 O4 and unleaded which was obtained from the powder of the composition BaFe0.5 Nb0.52 O3 and the same ferrite powder Ni0.64 Zn0.36 Fe2 O4. For the both multiferroic materials the following studies were conducted: SEM, BSE, EDS, XRD and the temperature dependence of dielectric constant ε(T). Using the previously developed method of calculating the magnetoelectric coupling factor (g), based on dielectric measurements, the magnitude of the magnetoelectric effect in the multiferroic composites was determined.
14
Content available Przyczyny uszkodzeń warstw asfaltowych nawierzchni, lokalizacja osłabionych miejsc za pomocą systemu GPR
Wutke M.
Drogownictwo
|
2017
|
nr 12
401--406
PL
W artykule przedstawiono potencjalne przyczyny uszkodzeń warstw asfaltowych nawierzchni przed upływem okresu gwarancyjnego, określone na podstawie specjalistycznych badań: w trakcie realizacji kontraktu, terenowych oraz laboratoryjnych. Omówiono praktyczne zastosowanie metody GPR celem lokalizacji osłabionych miejsc warstw asfaltowych na podstawie map powierzchniowych stałych dielektrycznych.
EN
The article presents potential causes of damages of asphalt pavement layers before the end of the warranty period, determined on the basis of specialized researches: during the contract, during the site works and laboratory researches. The practical application of the GPR method has been discussed in order to locate weakened areas of asphalt layers based on surface maps of dielectric constants.
15
Content available remote Synthesis, investigation on structural and electrical properties of cobalt doped Mn–Zn ferrite nanocrystalline powders
Bhuvaneswari M., Sendhilnathan S., Kumar M., Tamilarasan R., Giridharan N. V.
Materials Science Poland
|
2016
|
Vol. 34, No. 2
344--353
EN
Synthesis of CoxMnyZnyFe2O4 (x = 0.1, 0.5, 0.9 and y = 0.45, 0.25, 0.05) nanocrystalline powders was done by chemical co-precipitation method. The crystal structure was determined by using X-ray diffraction (XRD) studies. The crystallite size and lattice parameters were calculated from the XRD data. The XRD results revealed that the crystallite size of the nanocrystalline powder was found to decrease from 37 nm to 28 nm with the substitution of cobalt. The effect of cobalt ions on the crystallization process, the lattice parameters and electrical properties of Mn–Zn ferrites has been also investigated. The AC conductivity increased with an increase in frequency but it decreased with an increase in cobalt content. The complex impedance analysis of the data showed that the resistive and capacitive properties of the Co–Mn–Zn ferrite are predominant due to the fact that the processes are associated with the grains and grain boundaries. The dielectric constant and dielectric loss dependence on doping level and frequency at room temperature were also studied.
16
Content available remote Structural and electrical properties of chromium substituted nickel ferrite by conventional ceramic method
Jahan N., Chowdhury F. U. Z., Zakaria A. K. M.
Materials Science Poland
|
2016
|
Vol. 34, No. 1
185--191
EN
Polycrystalline Cr substituted Ni ferrites [NiCrxFe2-xO4 (0.0 ≤ x ≤ 1.0)] were synthesized by conventional ceramic method and sintered at 1350 degrees C in air. X-ray diffraction (XRD) patterns showing sharp peaks confirmed the formation of single phase cubic spinel structure. The lattice parameters of the samples were determined from the XRD data using Nelson-Riley extrapolation technique. They were found to decrease with increasing Cr concentration obeying Vegard's law. X-ray density, bulk density and porosity were also calculated from the XRD data. The variation of DC resistivity with temperature was measured by two-probe method. The DC resistivity was found to decrease with increasing temperature indicating the semiconducting nature of the samples. Activation energy was calculated from the Arrhenius plot. AC resistivity, dielectric constant and loss tangent were measured in the frequency range of 1 kHz to 120 MHz at room temperature.
17
Content available remote Dielectric and Raman studies of Ba0.06(Na1/2Bi1/2)0.94TiO3–NaNbO3 ceramics
Roy S. K., Chaudhuri S., Kotnala R. K., Singh D. K., Singh B. P., Singh S. N., Chandra K. P., Prasad K.
Materials Science Poland
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2016
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Vol. 34, No. 2
437--445
EN
In this work the X-ray diffraction, scanning electron microscopy, Raman and dielectric studies of lead free perovskite (1 – x)Ba0.06(Na1/2Bi1/2)0.94TiO3–xNaNbO3 (0 ≤x ≤ 1.0) ceramics, prepared using a standard solid state reaction method, were investigated. X-ray diffraction studies of all the ceramics suggested the formation of single phase with crystal structure transforming from rhombohedral-tetragonal to orthorhombic symmetry with the increase in NaNbO3 content. Raman spectra also confirmed the formation of solid solution without any new phase. Dielectric studies showed that the phase transition is of diffusive character and diffusivity parameter decreases with increasing NaNbO3 content. The compositional fluctuation was considered to be the main cause of diffusivity.
18
Content available Experimental Studies on the Dielectric Behaviour of Polyester Woven Fabrics
Liu Y., Zhao X.
Fibres & Textiles in Eastern Europe
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2016
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Vol. 24, no. 3 (117)
67--71
EN
In this paper, the influence of fabric structure, weft density, end spacing and yarn fineness on the dielectric constant of polyester woven fabrics was studied. The results show that at low frequencies, the dielectric constant of fabric was clearly affected by the processing parameters; when the organisation of the fabric is plain i.e. the warp density is 140/10 cm, weft density 140/10 cm and yarn linear density 32 tex, the absorbing performance of polyester woven fabrics is at its best. At higher frequencies, the effect of the varying parameters on the dielectric constant of the fabrics can be neglected. Polyester woven fabrics have better EM absorbing properties for these parameters. This study offers a new theoretical basis for the development of EM absorptive fabrics.
PL
Badano wpływ struktury tkaniny (gęstości wątku i osnowy oraz masy liniowej przędzy) na dielektryczną stałą poliestrowych tkanin. Wyniki wykazują, że przy niskich częstotliwościach stałe dielektryczne w wyraźny sposób zależą od parametrów procesu tkania. Natomiast przy wyższych częstotliwościach wpływ struktury jest znacznie mniejszy, a nawet może być pomijany. Stwierdzono, że tkaniny poliestrowe mają dobre właściwości absorpcyjne pola elektromagnetycznego. Badania stwarzają nowe podstawy teoretyczne dla opracowywania tkanin absorbujących pole elektromagnetyczne.
19
Content available remote Frequency and temperature dependence of dielectric and electric properties of Ba2-xSm4+2x/3Ti8O24 with structural analysis
Narang S. B., Kaur D., Pubby K.
Materials Science Poland
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2015
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Vol. 33, No. 2
268--277
EN
Dielectric ceramics samples of barium titanium oxide doped with samarium, having a complex structural formula of Ba2-xSm4+2x/3Ti8O24 (referred to as BST), were fabricated by a high temperature solid-state reaction technique with varying x (0.0, 0.2, 0.4, 0.6). X-ray diffraction technique was used to check the formation of particular phases. Scanning electron microscope technique was used to study the surface morphology of the samples. The samples were studied in a temperature range of 298 K to 623 K and frequency range of 10 KHz to 1 MHz. The dielectric constant (εr), loss tangent (tanδ), and AC conductivity (σAC) were measured on sintered disks of BST samples. The DC resistivity of different compositions was measured at room temperature. Detailed studies of dielectric and electrical properties showed that these properties are strongly dependent on composition, frequency and temperature. The compounds showed stable behavior in lower temperature range (up to 523 K), therefore, they can be used in practical applications in this temperature range.
20
Kompozytowa folia LTCC o obniżonej przenikalności elektrycznej do zastosowań mikrofalowych
Synkiewicz B., Kulawik J., Guzdek P., Grzesiak W.
Elektronika : konstrukcje, technologie, zastosowania
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2015
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Vol. 56, nr 9
31-33
PL
O funkcjonalności materiałów w zakresach częstotliwości mikrofalowych decyduje wiele czynników, wśród których istotne miejsce zajmuje m.in. niska przenikalność elektryczna. Materiały o niskiej stałej dielektrycznej stwarzają możliwość zbliżenia linii sygnałowych oraz zagęszczenia połączeń przy zachowaniu kontrolowanej impedancji linii, a także zmniejszenia przesłuchów pomiędzy liniami oraz opóźnień propagacji sygnału. W niniejszym artykule opisano metodę otrzymywania materiału szklano-ceramicznego, bazującego na surowcach nieorganicznych z dodatkiem grafitu, który umożliwił uzyskanie porowatości obniżającej stałą dielektryczną. W oparciu o technologię LTCC, skonstruowano wielowarstwową wytrzymałą mechanicznie strukturę o znacznym udziale porowatości wewnętrznej i równomiernej, nienasiąkliwej powierzchni. Uzyskano statystycznie istotny spadek (ponad 50%) stałej dielektrycznej struktury w stosunku do nieporowatej próbki o tym samym składzie chemicznym.
EN
The functionality of the materials in the microwave frequency range depends on many factors, among them, dielectric constant is one of the most important. In high frequency applications, low dielectric constant of a substrate material is crucial for increasing the speed of signal transmission and reduction of crosstalk between lines in high-speed circuits. This article describes a method of obtaining the glass-ceramic material, based on inorganic components with the addition of graphite powder as pore former, leading to decrease of the electric permittivity. Based on LTCC technology, mechanically resistant multi-layer structure with a high internal porosity and uniform, non-absorbent surface, was constructed. A statistically significant decrease (over 50%) of the dielectric constant in comparison to non-porous sample with the same composition was achieved.
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