Wyniki wyszukiwania - BazTech

1

Nowe materiały funkcjonalne w konstrukcji czujników elektrochemicznych przeznaczonych do analiz biochemicznych

Madej Maria

Analityka : nauka i praktyka

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2022

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nr 4

32--36

PL

Ciągły rozwój nowoczesnych technologii stosowanych w przemyśle, diagnostyce medycznej oraz monitoringu środowiska sprawia, że wzrasta zapotrzebowanie na niewielkie, proste urządzenia umożliwiające szybkie i niezawodne określenie składu badanych próbek. Wymogi te spełniają czujniki chemiczne, które łączą w sobie zarówno czułość i selektywność klasycznych metod analitycznych, jak i duże możliwości ich miniaturyzacji i automatyzacji obsługi.

2

Druk 3D i materiały funkcjonalne w chemii analitycznej. Cz. 2

Szynkiewicz Dagmara, Georgiev Paweł, Ulenberg Szymon, Bączek Tomasz, Belka Mariusz

Analityka : nauka i praktyka

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2022

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nr 1

18--24

PL

Szerokie możliwości wykorzystania technik przyrostowych stanowią niemal nieskończoną inspirację do prac badawczych. Już teraz możemy komponować materiały zgodnie ze stawianymi im oczekiwaniami oraz szybko oraz tanio testować je w praktyce.

3

Effect of milling time on microstructure of cobalt ferrites synthesized by mechanical alloying

Tomiczek Anna E.

Archives of Materials Science and Engineering

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2021

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Vol. 111, nr 1

5--13

EN

Purpose: of this paper is to determine the effect of manufacturing conditions, especially milling time, on the microstructure and phase composition of CoFe2O4 cobalt ferrite. Design/methodology/approach: Cobalt ferrite (CoFe2O4) has been synthesised from a stoichiometric mixture of CoCo3 and α-Fe2O3 powders in a high energy planetary mill. Annealing at 1000°C for 6 hours after milling was used to improve the solid-state reaction. Calcinated samples were analysed by X-ray diffraction (XRD), and transmission electron microscopy (TEM). The relationship between the milling time of powders, their microstructure, as well as their properties were evaluated. Particles size distribution and scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX) examination were also made. Findings: CoFe2O4 ferrites were successfully synthesized by mechanical alloying of α-Fe2O3 and CoCO3 powders. The powder particles had undergone morphological changes with the increasing milling time. However, the milling time does not affect the ferrite formation rate. It is expected that the improvement of fabrication parameters can further enhance the properties of cobalt ferrite presented in this work. Research limitations/implications: Contribute to research on the structure and properties of cobalt ferrites manufactured by mechanical alloying. Practical implications: The reactive milling and subsequently annealing is an efficient route to synthesise cobalt ferrite powder. However, using steel milling equipment risks powder contamination with iron and chromium from the vials and balls. Originality/value: The results of the experimental research of the developed ferrite materials served as the basis for determining material properties and for further investigation.

4

Druk 3D i materiały funkcjonalne w chemii analitycznej. Cz. 1

Szynkiewicz Dagmara, Georgiev Paweł, Ulenberg Szymon, Bączek Tomasz, Belka Mariusz

Analityka : nauka i praktyka

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2021

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nr 4

42--47

PL

Dynamiczny rozwój druku 3D skutkuje pojawianiem się coraz większej liczby jego zastosowań w różnych dziedzinach działalności naukowej, w tym laboratorium analityki chemicznej. Podjęto próby drukowania między innymi selektywnych membran, układów przepływowych czy elementów aparatury chemicznej.

5

Sole anionorodnikowe TCNQ z kationami kompleksowymi metali przejściowych

Starodub Tetiana, Starodub Volodymyr

Wiadomości Chemiczne

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2020

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[Z] 74, 11-12

761--796

EN

The unique properties of anion-radical salts (SAR) of 7,7,8,8- tetraethanoquinimethane (TCNQ) with cations [M(N-N)2]2+ (M = Mn, Fe, Co, Ni; N-N = phen, dips) were analyzed. The ability of these SARs to create conductive materials, magnetically ordered structures, including Ferro- and antiferromagnetic, and spin ladders was considered. Particular attention was paid to the possibilities of using these SARs in the electronics of nanomaterials, materials for the production of field-effect transistors, photo-diodes and ion-selective electrodes.

6

Effect of particle shape and imperfect filler-matrix interface on effective thermal conductivity of epoxy-aluminum composite

Pietrak K., Kubiś M., Langowski M., Kropielnicki M., Wultański P.

Composites Theory and Practice

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2017

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R. 17, nr 4

183--188

EN

The predictions of major effective medium models and 2-dimensional numerical models implemented in Ansys Fluent were tested against the results of experimental measurements of macroscopic thermal conductivity for a polymer filled with aluminum powder. The examined composite may be regarded as a representative of materials used for heat management purposes, for example for the manufacture of electronic device housings. The study demonstrates the effect of particle shape and imperfect filler-matrix interface on the theoretical value of thermal conductivity of the considered material. It also creates the opportunity to discuss the versatility and accuracy of various methods devised to predict the effective thermal conductivity of heterogeneous materials. It was found that the effective medium approximation proposed by Duan et al., which considers the effect of the particle aspect ratio, outrivaled other predictive schemes in accuracy and cost-effectiveness. Effective medium approximations that assume spherically-shaped reinforcement as well as finite volume models implemented in Ansys Fluent, greatly underestimated the parameter in question.

PL

Przewidywania popularnych, analitycznych modeli predykcyjnych efektywnej przewodności cieplnej kompozytów cząsteczkowych zostały porównane z danymi eksperymentalnymi uzyskanymi dla kompozytów polimerowych napełnionych proszkiem aluminiowym oraz z wynikami obliczeń numerycznych wykonanych metodą objętości skończonych w programie Ansys Fluent. Testowany materiał reprezentuje grupę materiałów stosowanych w technice cieplnej, np. do wytwarzania obudów urządzeń elektronicznych. Wyniki badania pokazują efekt kształtu wtrąceń oraz niedoskonałego kontaktu termicznego na granicy zbrojenie-osnowa na teoretyczną wartość efektywnej przewodności cieplnej rozważanego materiału. Są też podstawą do dyskusji na temat wad i zalet stosowania analitycznych metod przewidywania przewodności cieplnej materiałów kompozytowych (tzw. effective medium models). Najlepszą zgodność z eksperymentem otrzymano za pomocą jednego z modeli analitycznych (Duan i in.), który uwzględnia wydłużony kształt cząsteczek napełniacza. Przewidywania modeli analitycznych zakładających sferyczny kształt cząsteczek okazały się silnie zaniżone, podobnie jak przewidywania dwuwymiarowych modeli numerycznych zaimplementowanych w środowisku Ansys Fluent.

7

The Effect of Iron Nanoparticles on Physico-Chemical Properties and Functional Activity of Active Carbon from Plant Materials

Revina A. A., Voropaeva N. L., Mukhin V. M., Chekmar L. V., Konovalova A. I., Karpachev V. V.

Inżynieria Mineralna

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2016

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R. 17, nr 2

247--253

EN

Rape, camelina, wheat and Jerusalem artichoke vegetable wastes (straw) as annually renewable raw materials were processed into activated carbons, which were modified with iron nanoparticles for carbonaceous sorbents to acquire specific properties, since carbonaceous sorbents are usually widely used in the food industry, agriculture, medicine and other fields of human activity.

PL

Materiały odnawialne w postaci odpadów roślinnych (słoma) roślin typu: rzepak, len, pszenica, topinambur przetworzono na węgiel aktywny którym poddano modyfikacji za pomocą nanocząsteczek żelaza, tak aby uzyskać materiał o właściwościach sorbcyjnych. Sorbenty są powszechnie stosowane w przemyśle spożywczym, rolnictwie, medycynie i innych dziedzinach działalności ludzkiej.

8

Functional materials produced on an industrial scale

Barska J., Kłysz S.

Prace Naukowe Instytutu Technicznego Wojsk Lotniczych

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2015

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nr 36

19--30

EN

The article presents a wide range of applications of functional materials and a scale of their current industrial production. These are the materials which have specific characteristics, thanks to which they became virtually indispensable in certain constructional solutions. Their basic characteristics, properties, methods of production and use as smart materials were described.

9

Design, fabrication and characterization of ceramic-metal composites: an overview

Konopka K.

Mechanik

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2015

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R. 88, nr 2CD

137--145

EN

Composites are used for many different products in numerous industries applications. They satisfy the demand for new materials which combine dissimilar materials and represent properties which are not achievable by separate material. Among of them are ceramic matrix composites, especially with metal phase. Different systems have been developing. During the last years the composites with Al2O3, ZrO2 ceramic matrix and metals as Ni, Mo, Cu, W, Co have been intensively studied. Metallic particles embedded into ceramic matrix improved mechanical properties such as the toughness, the hardness and the wear resistance. Moreover, other properties as magnetic or electrical of ceramic-metal composites can be significantly changed. Because of that, ceramic- metal composites are considered as structural and functional materials. The final properties of ceramic-metal composites depend on their microstructure, which should be optimize by the design of metal size and distribution into ceramic matrix and selection of the fabrication method. This paper attempts to review the microstructures of ceramic-metal composites based on own experimental results. The following issues will be discussed: design the metal particles distribution into ceramic matrix, opportunities of processing in creating microstructures and fabrication of composites with complex shape and high dimensions, interactions in ceramic/metal interfaces, toughening mechanisms and properties of composites.

PL

Z kompozytów wykonywane są elementy wykorzystywane do różnych zastosowań przemysłowych. Wynika to z możliwości uzyskania w nich właściwości nie spełnianych przez pojedynczy materiał. Wśród kompozytów o osnowie ceramicznej intensywne prace prowadzone są nad kompozytami z wprowadzoną faza metaliczną. Do częściej badanych układów zalicza się ceramikę Al2O3 oraz ZrO2 w połączeniu z metalami jak Ni, Mo, Cu, W czy Co. Wprowadzenie cząstek metalu do osnowy ceramicznej zapewnia zwiększenie odporności na kruche pękanie przy zachowaniu wysokiej twardości. Jednocześnie inne właściwości, jak elektryczne czy magnetyczne, mogą być modyfikowane. Dlatego też coraz częściej kompozyty ceramika-metal są postrzegane jako materiały o możliwości zastosowania jako konstrukcyjne i funkcjonalne. Właściwości kompozytów ceramika-metal zależą od ich mikrostruktury, która powinna być optymalizowana poprzez proces projektowania rozmiaru i rozmieszczenia cząstek metalu w osnowie ceramicznej oraz dobór metody wytwarzania. W artykule przedstawiono przegląd mikrostruktury kompozytów ceramika-metal bazując na własnych pracach w tym zakresie. Analizowano sposób rozmieszczenia cząstek metalu w osnowie ceramicznej, zalety metod wytwarzania pozwalające na wykonywaniu złożonych kształtów próbek kompozytowych oraz o dużych rozmiarach. Omówiono oddziaływania na granicy międzyfazowej ceramika/metal oraz mechanizmy odpowiedzialne za wzrost odporności na kruche pękanie, jak i właściwości kompozytów.

10

Characterization of composite materials with giant magnetostriction

Tomiczek A. E., Dobrzański L. A.

Archives of Materials Science and Engineering

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2014

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Vol. 65, nr 1

5--23

EN

Purpose: This paper concerns manufacturing and researching a new group of the magnetostrictive composite materials, consisting Tb0.3Dy0.7Fe1.9 particles in different polymer matrix. Design/methodology/approach: The following investigation studies have been carried out: the structures of the Tb0.3Dy0.7Fe1.9 powders, the topography of composite materials fractures with the use of electron scanning microscopy; chemical composition of the Tb0.3Dy0.7Fe1.9 powders using the EDS method; phase composition of the Tb0.3Dy0.7Fe1.9 powders and composite materials using X-ray diffraction; as well as properties of the composite materials with polyurethane matrix reinforced with Tb0.3Dy0.7Fe1.9 particles including: density, thermal conductivity (in magnetic field also), electrical and magnetic properties, as well as magnetostriction in magnetic field intensity up to 800 kA/m using a three terminal capacitance technique. Findings: Based on the examination carried out it was found that the highest magnetostriction equals to 805∙10-6 (with magnetic field intensity of 766 kA/m) characterizes a composite material with polyurethane matrix, reinforced with Tb0.3Dy0.7Fe1.9 powder of 20% volume fraction and particles size in the range of 38-106 μm. Simultaneously, the materials is characterized with coercion intensity Hc=5.39 kA/m, remanence Br=0.013 T and magnetic permeability μr=1.13. Moreover, it was found that the maximum magnetostriction value for this material assumes values approximate to the magnetostriction of monolithic Tb0.3Dy0.7Fe1.9 alloy. Additionally, it was confirmed that the correlation exists between the diversification of the volume fraction of Tb0.3Dy0.7Fe1.9 powder in the matrix, its particle distribution and the maximum magnetostriction and magnetic properties of the developed composite materials. The key factor determining the energy transfer efficiency between Tb0.3Dy0.7Fe1.9 and matrix is – in addition to the size and volume fraction of the magnetostrictive particles in the matrix – the method of combining those two phases. Originality/value: The paper presents the research involving the composite material with giant magnetostriction.

11

Conceptual study on a new generation of the high-innovative advanced porous and composite nanostructural functional materials with nanofibers

Dobrzański L. A., Pawlyta M., Hudecki A.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 49, nr 2

550--565

EN

Purpose: The purpose of the paper is to analyse theoretically the possibilities of the development of a new generation of the high-innovative advanced porous and composite nanostructural functional materials with nanofibers and to study into the material science grounds of synthesis and/or production and formulation of such materials’ structure and properties and to characterise and model their structure and properties depending on the compositional, phase and chemical composition and the applied synthesis and/or production and/or processing processes, without the attitude towards any direct practical application or use, but with confirming the highly probable future application areas, using the unexpected effects of formulating such materials’ functional properties. Design/methodology/approach: In general, the study is of priority cognitive importance as theoretical considerations and the author’s initial analyses related to technology foresight concerning this group of issues as well as sporadical results of research provided in the literature, usually in its incipient phase, indicating a great need to intensify scientific research, to develop the new groups of materials with quite unexpected predictable effects, resulting from the use of nanofibers for fabricating super advanced composite and porous materials. Findings: The description of the state of the art for the subject of the study has been limited to the issues initially selected with an analysis with the method of weighted scores. Practical implications: The outcoming materials may have direct influence on the development of electronics and photonics, medicine and pharmacy, environmental protection, automotive industry, space industry, machine industry, textile and clothing industry, cosmetic industry, agriculture and food sector. Originality/value: The value of this paper lies in the fact that it proposes a new generation of the high-innovative advanced porous and composite nanostructural functional materials with nanofibers.

12

Thermal stability of properties in silver - rare earth metals alloys

Głuchowski W., Rdzawski Z. M.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 28, nr 2

143-150

EN

Purpose: The objective of this work was to investigate the changes taking place in the structure and properties of Ag-La (0.5%) and Ag-mishmetal (1 and 4%) alloys caused by severe plastic deformation compared to the Ag+(7.5 wt %)Cu alloy and pure Ag materials. Design/methodology/approach: Tests were made with the samples obtained casting and further plastic working included KOBO® extrusion process and drawing. Wires were annealed in temperature range 50-500° C. The mechanical properties (at room temperature, elevated temperature and after annealing) and microstructure were examined (by the optical, scanning and transmission electron microscopy with EDS and electron diffraction analysis). Findings: Structure of the extruded material was fine and homogenous. The alloys with an addition of lanthanum or mishmetal had high electrical conductivity, which was decreasing with an increase in the content of alloy additives. Fine coherent precipitates were found on the preferred planes in the silver matrix. Practical implications: The alloy with an addition of La or mishmetal could be considered, after further investigations, as a material suitable for use in the production of electrical or electronic components operating at elevated temperatures or exposed to temperature changes. Originality/value: This work has demonstrated that the properties of newly designed silver alloys with an addition of La or mishmetal exhibit temperature stability. It can be concluded from this study that an addition of rare earth metals to silver gives three main benefits: deoxidation during melting in an open furnace, very fine structure and precipitation hardening. The dispersion hardening with coarse particles (size about several žm) is very small. The wire made from this material could be easily produced by the developed processing methods, without the need to use annealing operations.

13

Stabilization of mechanical properties in silver alloys by addition of lanthanides

Głuchowski W., Rdzawski Z. M.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 30, nr 2

129-134

EN

Purpose: Silver alloys intended for industrial application should characterise by high electrical conductivity (as pure silver) as well as high mechanical and functional properties, stable also at elevated temperature. The objective of this work was to investigate the mechanical properties stability of Ag-La (0.5%) and Ag-mishmetal (1 and 4%) alloys caused by severe plastic deformation compared to the Ag+(7.5 wt %)Cu alloy and pure Ag materials. Design/methodology/approach: Tests were made with the samples obtained by casting and further plastic working included KOBO® extrusion process and drawing. Wires were annealed in temperature range 50-500° C. The mechanical properties (at room temperature, elevated temperature and after annealing) and microstructure were examined. The values of yield strength obtained in a tension tests have been compared to the values calculated theoretically. Findings: Additive of rare earth metals contributed to fine structure obtaining, particles formed in grain boundaries stabilized microstructure at elevated temperature. Increase of mechanical properties of investigated alloys was connected with presence of fine precipitations in silver matrix, which confirmed susceptibility to precipitation hardening of silver-mishmetal alloys. Research limitations/implications: Ability of new alloys to precipitation hardening should be confirmed by further investigations, including solution heat treatment and ageing, also for materials prepared in vacuum furnace. Practical implications: Stability of mechanical properties at elevated temperature, gives possibility to use of new silver allays for producing elements designed to operate at elevated temperatures or exposed to rapid temperature changes. Increased mechanical properties and good tarnish resistance indicates possibility of new applications of investigated alloys in jewellery and medicine, after additional and essential investigations. Originality/value: The wire made from this material could be easily produced by the developed processing methods, without the need to use annealing operations.

PL

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14

Silver-mishmetal alloy for application at elevated temperature

Głuchowski W., Rdzawski Z.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 26, nr 2

123-126

EN

Purpose: The aim of this work was to investigate the changes taking place in the structure and properties of silver-mishmetal alloys caused by severe plastic deformation compared to the Ag+(7.5 wt %)Cu alloy and pure Ag materials. Design/methodology/approach: Tests were made with samples obtained by melting and casting in an induction furnace. Further plastic working included KOBO® extrusion process and drawing. The mechanical properties (at a room temperature, elevated temperature and after annealing) and microstructure were examined (by the optical, scanning and transmission electron microscopy). Findings: Structure of the extruded material was fine and homogenous. The alloys with an addition of mishmetal had high electrical conductivity, which was decreasing with an increase in the content of alloy additives. Examination of the mechanical properties has shown that these alloys exhibited (after annealing) an increased stability of properties at elevated temperatures. Practical implications: The alloy with an addition of mishmetal could be considered, after further investigations, as a material suitable for use in the production of electrical or electronic parts operating at elevated temperature or exposed to temperature changes. Originality/value: This work demonstrated that properties of the newly designed silver alloys with an addition of mishmetal exhibit temperature stability. The wire made from this material could be easily produced by the developed processing methods, without the need to use annealing operations. Due to the stable properties and excellent electrical conductivity, this alloy is suitable for use in the production of an advanced electrical or electronic equipment.

15

Thermal stability of functional properties in dispersion and precipitation hardened selected copper alloys

Stobrawa J., Rdzawski Z.

Archives of Materials Science and Engineering

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2008

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Vol. 30, nr 1

17-20

EN

Purpose: The objective of the study was to produce copper-based dispersion hardened materials of submicron grain size, determination of their basic functional properties and stability in high temperature, as well as comparison of those properties with properties of selected precipitation hardened copper alloys made by classical method of melting, casting and thermomechanical processing. Design/methodology/approach: The examination was conducted on copper hardened with WC, Y2O3 and Cr3Si particles and on precipitation hardened copper alloys with addition of Cr and Ni, Si, Cr. The examination of the materials covered changes in hardness, electrical conductivity and stabilities of those properties after various heat treatment options. Findings: Assuming the tendency to softening depending on annealing temperature to be as a criterion of properties stability, temperature ranges of individual alloys applications were determined Research limitations/implications: The study could be supplemented with information on tendencies to high-temperature creep in the examined alloys Practical implications: The materials are used for components operating in high-temperature conditions, such as components of crystallizers for continuous casting of metals, electrodes for welding, in nu clear reactors, etc. Originality/value: The originality lies in examination of dispersion hardened materials (especially Cu – Cr3Si) of controlled submicrometric structure obtained from initial nanocrystalline structure.

16

Structure and properties of dispersion hardened submicron grained copper

Stobrawa J. P., Rdzawski Z. M., Głuchowski W.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 20, nr 1-2

195-198

EN

Purpose: The objective of the work was to investigate changes in structure and properties of Cu-WC microcomposites which take place in the process of controlled hot deformation of materials of nanometric initial structure. Design/methodology/approach: Tests were made with the Cu-WC micro-composites containing up to 2% of a hardening phase. These were obtained by powder metallurgy techniques and further hot deformation. The mechanical properties and microstructure (by the optical, scanning and transmission electron microscopy) were examined. Findings: Analysis of the initial nanocrystalline structure of these materials was made, and its evolution during hot deformation process was investigated with an account of the changes in the mechanical and electrical properties. Research limitations/implications: The powder metallurgy techniques make it possible to obtain copper-based bulk materials. Globular structure and high porosity of this materials result in their limited mechanical properties. This is the reason why additional operations, should be applied. The investigations have revealed that controlled hot deformation, within the temperature range of 500-550 degrees centigrade, gives possiblity for obtaining submicron grain size and more advantageous mechanical properties of Cu-WC microcomposites. Practical implications: A growing trend to use new copper-based functional materials is observed recently world-wide. Within this group of materials particular attention is drawn to dispersion hardened microcomposites with nanometric or submicron grain size of a copper matrix, which exhibit higher mechanical properties. Originality/value: The paper shows instability of nanostructure of Cu-WC microcomposites in the processes of hot deformation. A controlled process, which can lead to destruction of globular structure, significant improvement of density and obtaining of submikron size, gives possibility for significant improvements in functional properties of the materials.

17

Stability of properties in silver - lanthanum alloy

Głuchowski W. J., Rdzawski Z. M.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 2

103-106

EN

Purpose: The objective of the work was to investigate changes in structure and properties of Ag+(0,5%wt)La alloy and its difference to the comparative Ag+(7,5%wt)Cu and pure Ag materials. Design/methodology/approach: Tests were made with samples obtained by melting and casting in inductive furnace. Further plastic deformation was provided by KOBO(R) extrusion and drawing. The mechanical properties (at room temperature, elevated temperature and after annealing) and microstructure (by the optical, scanning and transmission electron microscopy) were examined. Findings: Analysis of the initial microstructure of these materials was made, and its evolution during deformation process was investigated with respect to the changes in the mechanical and electrical properties. Research limitations/implications: Significant changes in microstructure after extrusion were observed. Alloy with addition of lanthanum had an excellent electrical conductivity close to the conductivity of pure silver. Mechanical properties examination after annealing gave grounds to conclude that also this alloy had increased properties stability at elevated temperature. Practical implications: Alloy with addition of lanthanum after further investigations could be considered as a material for producing electric or electronic parts which are designed to work in environment of elevated temperature or with a risk of temperature changes. Originality/value: The paper shows properties stability in new designed silver alloy with addition of lanthanum. Wire made of this material could be easy produced with examined methods, without any annealing process. Having stable properties and excellent electrical conductivity this alloy could be considered as a material for producing advanced electrical or electronic equipment.

18

Microstructure and properties of nanocrystalline copper - yttria microcomposites

Stobrawa J. P., Rdzawski Z. M., Głuchowski W. J.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 2

83-86

EN

Purpose: The objective of the work was to investigate changes in structure and properties of Cu-yttria microcomposites which take place in the process of controlled sintering and deformation of materials of nanometric initial structure. Design/methodology/approach: Tests were made with the Cu-yttria micro-composites containing up to 3 % of a hardening phase. These were obtained by powder metallurgy techniques and further deformation. The mechanical properties and microstructure (by the optical, scanning and transmission electron microscopy) were examined. Findings: Analysis of the initial nanocrystalline structure of these materials was made, and its evolution during deformation process was investigated with an account of the changes in the mechanical and electrical properties. Research limitations/implications: The powder metallurgy techniques make it possible to obtain copper-based bulk materials. Globular structure, high porosity and low sintering temperature of this materials result in their limited mechanical properties. Practical implications: A growing trend to use new copper-based functional materials is observed recently world-wide. Within this group of materials particular attention is drawn to dispersion hardened microcomposites with nanometric or submicron grain size of a copper matrix, which exhibit higher mechanical properties. Originality/value: A controlled process of milling compacting, sintering and cold deformation, allow to obtain nanocrystalline copper based materials with improved functional properties.

19

Interaction of point defects in piezoelectric materials - numerical simulation in the context of electric fatigue

Goy O., Mueller R., Gross D.

Journal of Theoretical and Applied Mechanics

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2006

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Vol. 44 nr 4

819-836

EN

The paper is concerned with the problem of electric fatigue in functional materials such as piezoelectric sensors and actuators. The fatigue degrades electromechanical properties with an increasing number of working cycles during which ionic and electronic charge carriers interact with each other within the bulk and on the interfaces of a material. This, in turn, influences local electric and mechanical fields coupled via the piezoelectric effect. It is assumed in the paper that the electric charges (vacancies) can be modelled as point defects, which tend to agglomerate and finally form clusters, especially in the vicinity of electrodes. As a result, the piled up defects affect the distribution of polarisation. To solve the problem quan\-ti\-tatively, the analysed system is discretised with a grid of square cells and then transformed by FFT. Several numerical examples are formulated. Migration of a single defect, attraction of two and clustering of more point defects are thoroughly discussed and illustrated in the paper.

PL

Praca dotyczy zagadnienia zmęczenia elektrycznego materiałów funkcjonalnych, takich jak piezoelektryki używane do wyrobu czujników i elementów wykonawczych. Zmęczenie elektryczne powoduje degradację właściwości elektromechanicznych z rosnącą liczbą przebytych cykli roboczych, w czasie których jonowe ładunki elektryczne lub elektrony oddziaływują ze sobą wewnątrz i na skraju danego materiału. To z kolei wpływa na lokalne pola elektryczne i mechaniczne sprzężone ze sobą efektem piezoelektrycznym. Założono w pracy, że ładunki elektryczne (dziury) będą zamodelowane defektami punktowymi, które mają skłonność do gromadzenia się i tworzenia skupisk, zwłaszcza w pobliżu elektrod. W rezultacie, nagromadzone defekty zmieniają rozkład polaryzacji układu. Do ilościowego rozwiązania zagadnienia zastosowano dyskretyzację badanego układusiecią kwadratowych komórek i następnie przeprowadzono szybką transformatę Fouriera. Obliczenia wykonano na kilku przykładach. Szczegółowo przedyskutowano problem migracji pojedynczego oraz wzajemnego przyciągania dwóch defektów, by wreszcie zilustrować proces tworzenia skupisk przez całe gromady defektów punktowych.