Wyniki wyszukiwania - BazTech

1

Evaluation of hydrophobic properties of organic layers modified with graphene flakes

Stańczyk B., Góra K., Jach K., Dobrzański L.

Materiały Elektroniczne

|

2017

|

T. 45, nr 1

18--24

EN

The paper presents the results of our research on graphene composites with organic polymers in various media. The following composites have been tested: PVDf/DMf/gr, PVDf/nMP/gr, PVDf/acetone/toluene/gr and PMMa/gr. The main purpose of this study is to evaluate hydrophobic properties of the selected materials by the contact measurements angle using the static method. the highest obtained value of the contact angle approached 180º for a superhydrophobic composite PVDf/acetone/toluene/gr.

PL

W artykule przedstawiono rezultaty prac dotyczących kompozytów grafenowych z polimerami organicznymi w różnych ośrodkach. Badano PVDF/DmF/GR, PVDF/NmP/GR, PVDF/aceton/toluen/GR i PmmA/GR. Główny przedmiot badań stanowiła ocena właściwości hydrofobowych wytypowanych materiałów. weryfikowano je za pomocą pomiarów kąta zwilżania metodą statyczną. Najlepszymi parametrami charakteryzował się kompozyt PVDF/aceton/toluen/GR, który wykazywał właściwości superhydrofobowe z wartościami kąta zwilżania wodą zbliżonymi do 180º.

2

Evaluation of Creep Strength of Heterogeneous Welded Joint in HR6W Alloy and Sanicro 25 Steel

Zieliński A., Dobrzański L., Purzyńska H., Sikora R., Dziuba-Kałuża M., Kania Z.

Archives of Metallurgy and Materials

|

2017

|

Vol. 62, iss. 4

2057--2064

EN

This article presents the results of investigations on HR6W alloy and Sanicro 25 steel and the dissimilar welded joint made of them. The characteristic images of microstructure of the investigated materials in the as-received condition and following the creep test, observed with a scanning electron microscope (SEM), are shown. The X-ray analysis of phase composition of the existing precipitates was carried out. The method for evaluation of creep strength based on abridged creep tests carried out at a temperature higher than the design one is presented. The obtained results do not deviate from the values of creep strength determined in long-term creep tests. The maximum difference in creep strength of the investigated materials is ±20%, which is in compliance with the acceptable scatter band. The methodology presented can be used for verification of creep strength (life time) of the material of finished components to be operated under creep conditions.

3

Small-signal microwave measurements and modeling of GaN FET devices manufactured by ITME

Barmuta P., Lewandowski A, Łukasik K., Schreurs D., Dobrzański L.

Przegląd Elektrotechniczny

|

2015

|

R. 91, nr 9

9-12

EN

We present results of small-signal measurements and modeling of GaN FET devices manufactured by Institute of Electronics Materials Technology (ITME). The devices have 500 nm gate length and 100 μm gate width and are grown on 350 μm sapphire substrate. We measured scattering parameters of the devices on-wafer in the frequency range 0.01-15 GHz, and then extracted parameters of their small-signal equivalent circuits. These results show that the devices have repeatable parameters and are capable of delivering at least 14.4 dB of unilateral gain in S-band with fmax of at least 23 GHz.

PL

W artykule przedstawiono wyniki małosygnałowych pomiarów w.cz. oraz modelowania tranzystorów GaN FET wyprodukowanych w Instytucie Technologii Materiałów Elektronowych (ITME). Badane tranzystory miały bramkę o długości 500 nm i szerokości 100 μm gate i zostały wyprodukowane na podłożu szafirowym o grubości 350 μm. Parametry rozproszenia tranzystorów zostały zmierzone na stacji ostrzowej w pasmie 0,01-15 GHz, a następnie na ich podstawie zostały wyznaczone parametry małosygnałowego schematu zastępczego. Otrzymane wyniki pokazują, że badane tranzystory mają powtarzalne parametry, uzyskując co najmniej 14,4 dB wzmocnienia unilateralnego w pasmie S oraz maksymalną częstotliwość generacji co najmniej 23 GHz.

4

Hydrofobowe pokrycia organiczne na gładkich podłożach i na podłożach z rozwiniętą powierzchnią

Stańczyk B., Dobrzański L., Góra K., Jach K., Jagoda A.

Materiały Elektroniczne

|

2015

|

T. 43, nr 3

25--34

PL

W artykule scharakteryzowano własności hydrofobowe warstw organicznych uzyskanych na powierzchniach gładkich i z celowo rozwiniętą powierzchnią, której geometria była przedmiotem badań. Przebadano własności żywic takich jak: polifluorowinyliden, polimetakrylan metylu, octatrichlorosilan. Przedstawiono cechy tych materiałów w zależności od rodzaju nośnika, sposobu przygotowania roztworu roboczego oraz metody osadzania na różnych powierzchniach. Własności hydrofobowe otrzymanych warstw weryfikowano za pomocą pomiarów kąta zwilżania (CA) statycznej kropli wody i metodą dynamiczną. Uzyskano wartości CA na poziomie od ok. 135° do 180°.

EN

In this paper we present the hydrophobic properties of organic layers obtained on both smooth and 3D surfaces. the geometry of which has been the research topic. We have investigated polymers such us: polyvinylidene fluoride, poly (methyl methacrylate), octatrichlorosilane. The properties of these layers depending on their preparation and deposition method have been determined. We have verified the wetting contact angle by performing static and dynamic measurements. The obtained values of the wetting contact angle have been in the 135° - 180° range.

5

Monolityczny mikrofalowy układ scalony GaN/AlGaN

Dobrzański L., Caban P., Kowalik A., Podgórski J., Rudziński M., Góra K., Jagoda A., Stańczyk B., Wojnowski D., Kozłowski A., Przyborowska K., Lewandowski A., Wiatr W., Paszkiewicz R.

Elektronika : konstrukcje, technologie, zastosowania

|

2015

|

Vol. 56, nr 6

6-9

PL

Przedstawiamy opracowanie przyrządów HEMT (High Electron Mobility Transistors) z GaN/AlGaN, a następnie pierwszego w Polsce monolitycznego mikrofalowego układu scalonego, w którym zastosowano przyrządy HEMT z GaN/AlGaN. Opracowanie przyrządów HEMT. Sekwencja warstw epitaksjalnych tworzących strukturę tranzystora była następująca: bufor AlN, kanał GaN, warstwa Schottky’ego AlGaN oraz warstwa podkontaktowa GaN. Strukturę wyhodowano na podłożu szafirowym. Wzór izolacji oraz wzór obszarów drenów i źródeł uzyskano metodą litografii optycznej. Wzór bramki o długości 500 nm i 440 nm otrzymano metodą bezpośredniej elektronolitografii na powierzchni półprzewodnika. Izolację przyrządów uzyskano przez wytrawienie obszaru ‘mesa’ w plaźmie chlorowej. Metalizacja kontaktów tworzyła struktura wielowarstwowa Ti/Al/Ni/Au. Powierzchnię kanału zabezpieczono przez nałożenie warstwy pasywującej Si3N4. Wzmocnienie tranzystorów w pasmie S i X wynosiło odpowiednio 16 i 11 dB (MSG/MAG Maximum Stable Gain). W najlepszym z kilku opisanych wariantów konstrukcyjnych i technologicznych uzyskano częstotliwość graniczną fT = 30 GHz, częstotliwość graniczną fMAX = 30 GHz. Ponadto stwierdzono, że unilateralne wzmocnienie mocy (UPG) równa się jeden dla częstotliwości ok. 30 GHz. Uzysk wynosił 70% co odpowiada 3000 dobrych przyrządów z płytki o średnicy 2”. Opracowanie mikrofalowego monolitycznego układu scalonego (MMIC).Opracowano pierwszy w Polsce mikrofalowy monolityczny układ scalony (MMIC), klucz typu SPDT (Single Pole Double Throw) stosowany zazwyczaj w układach transciever’ów (klucz nadawanie-odbiór). Układ zbudowany jest z czterech tranzystorów HEMT o szerokości bram μm. W paśmie 0-4 GHz straty wtrącenia są mniejsze niż 2 dB, a izolacja lepsza niż 23 dB. Wykazano, że po zmianie konstrukcji układu i stosując tę samą technologię można uzyskać straty wtrącenia mniejsze niż 1 dB. Przedstawiony układ MMIC jest demonstratorem technologii, przy pomocy której można wykonać układy scalone o parametrach na poziomie komercyjnym.

EN

We present the development of HEMT (High Electron Mobility Transistors) and MMIC (Microwave Monolithic Integrated Circuit) made of GaN/AlGaN. Development of HEMTs. The sequence of epitaxial layers grown on sapphire substrate was as follows: AlN buffer, GaN channel, AlGaN Schottky and GaN contact cap. Isolation pattern and ohmic metal pattern were obtained by optical lithography. The gate was 500 nm and 440 nm long and was written using e-beam directly on semiconductor wafer. Then gate metal was evaporated and lifted off. The isolation was obtained by mesa etching in pure chlorine plasma. Ohmic contact consisted of a Ti/Al/Ni/Au sandwich. Finally Si3N4 passivation was made to protect exposed channel surface. Transistors operate in S and X band, showing 16 and 10 dB MSG/MAG gain respectively. For the best layout design transistors exhibited frequency fT=30 GHz, frequency fMAX = 30 GHz, and exhibited UPG=1 (unilateral power gain) for frequency 30 GHz. The yield was 70%, what corresponds to about 3000 good devices form one 2” wafer. Development of monolithic microwave integrated circuit (MMIC). We developed transistor switch of SPDT (Single Pole Double Throw) type which is used in transceivers. The circuit consists of four HEMT devices having gate width of 150 μm, gate length of 440 nm and drain source distance of 3 μm. In the 0-4 GHz bandwidth insertion loss is less than 2 dB and isolation is better than 23 dB. It was demonstrated that increase of the gate width of transistors will improve insertion loss value to the level of 1 dB.

6

Strength analysis of a three-unit dental bridge framework with the Finite Element Method

Reimann Ł., Żmudzki J., Dobrzański L.

Acta of Bioengineering and Biomechanics

|

2015

|

Vol. 17, no. 1

51--59

EN

Purpose: The aim of the study was to analyse the strength of a prosthetic bridge with variable geometry in the connectors between the span and the retention elements on the pillar teeth crowns. Methods: Research was carried using the Finite Elements Method (FEM) on a model of the bridge in the anterior teeth arch in the field 21–22–23, obtained using a contact scanner and computer aided design (CAD) system, with four different cross-sectional areas of the connectors: 4.0, 5.0, 5.5, and 6.0 mm2. For that purpose, the impact of the properties of selected metal alloys on the deflection of the prosthesis was analysed. Results: On the basis of the analyses, it was found that when the loading force acted obliquely, the stress was 19% higher compared to the stress with a loading vertical force. In the case of connectors with the smallest cross-sectional area, the stress exceeded permissible value (with safety factor n = 2) for one of the alloys. Conclusions: Deflection of the bridges tested changed depending on the connector cross-section and the elastic modulus of the selected material.

7

Grafen otrzymywany metodą elektrolityczną na podłożach z węglika krzemu

Stańczyk B., Dobrzański L., Jagoda A., Możdżonek M., Natarajan S.

Materiały Elektroniczne

|

2014

|

T. 42, nr 3

20--25

PL

W artykule przedstawiono nową technikę osadzania warstw grafenu na podłożach z węglika krzemu metodą elektrolityczną. Polega ona na zastosowaniu jako materiału elektrod grafitu i SiC oraz elektrolitu organicznego poli–styrenosulfonianu sodu (PSS). Widma Ramana osadzanych warstw wskazują na to, że otrzymano grafen. Istnienie wiązań typu C=C potwierdza spektroskopia FTIR. Prowadzono także proces z roztworów na bazie tlenku grafenu. Ponadto w procesie z rozcieńczonym elektrolitem uzyskano rzadką odmianę alotropową węglika krzemu - moissanit, który syntetycznie jest produkowany przede wszystkim na potrzeby przemysłu elektronicznego.

EN

We present a new electrochemical deposition method of graphene layers on silicon carbide substrates. The technological arrangement was comprised of graphite, SiC electrodes and organic electrolyte, i.e. poly(sodium-4-styrenesulphonate), and in the case of an alternative technique suspension with graphene oxide was applied. Graphene layers consisting of flakes were obtained on SiC electrodes, which was concluded based on a Raman Spectroscopy analysis. Moreover, during the process with diluted electrolyte solution we achieved a rare allotropic form of silicon carbide called moissanit, which is commonly used in electronic applications.

8

The influence of carbon nanotubes on the mechanical properties of nanocomposites

Dobrzański L., Mucha A., Macek M.

Archives of Materials Science and Engineering

|

2014

|

Vol. 68, nr 2

75--80

EN

Purpose: The paper presents a simply method of preparation of polymer matrix nanocomposite reinforced with carbon nanotubes and their influence on the mechanical properties. Design/methodology/approach: A series of polymer matrix nanocomposite materials at filler weight fractions 5%, 10%, 15%, 20%, 30% and 40% both in the absence and in the presence of multiwalled carbon nanotubes (MWCNTs) at a 0.1% wt. were prepared. The specimens were tested at 3 point-bending and tension using an universal testing machine. Findings: The paper presents the way of preparation of nanocomposite materials. The components were carefully measured and mixed in vacuum. The carbon nanotubes were homogenized using ultrasonicator. After that the mixture was injected into the moulds and heated in the temperature of 50°C by 24h.Practical implications: Polymer composites reinforced with carbon nanotubes are considered to be an important group of materials for many engineering applications. MWCNTs (used as reinforcement in nanocomposites) have greater mechanical strength and endurance and a greater modulus of elasticity comparing to carbon fibers. Polymer nanocomposites reinforced with carbon nanotubes have been used at the production of chemical sensors, materials using emission field phenomenon, media converters, electrical appliances, supercapacitors. Originality/value: Paper presents new polymer matric nanocomposites with high Young’s modulus. Polymer nanocomposites reinforced with carbon nanotubes are characterized by dimensional stability, high stiffness, toughness, heat resistance, low combustibility, reduction of the transmission of liquids and gases, the lower density, low thermal expansion coefficient, and increased electrical conductivity.

9

Technology of dye-sensitized solar cells with carbon nanotubes

Dobrzański L., Mucha A., Prokopiuk vel Prokopowicz M., Drygała A., Łukaszkowicz K.

Archives of Materials Science and Engineering

|

2014

|

Vol. 70, nr 2

70--76

EN

Purpose: The aim of the paper is to fabricate the dye-sensitized solar cells DSSC with carbon nanotube. Design/methodology/approach: The main aim this work was to improve the technological conditions of conventional dye solar cells by the application of nanostructured materials (MWCNTs) as one of the electrodes of the cell and to prove that the use of this type of nanomaterials increases the efficiency of dye solar cell electrodes. Findings: Carbon materials can be used as a counter electrode in dye-sensitized photovoltaic cells by replacing a costly platinum. Research limitations/implications: It has been found that due to the technology of developed conventional DSSC and cells with the carbon nanotubes, it is possible to lowering a production costs. It is advisable to take into account in the further experiments application of variables of different kinds of materials in the selected process parameters, and research for the use them in DSSC cells production. Practical implications: Presented in this paper results showed possibilities of modifying DSSC cells in terms of architecture, which should be correlated with the parameters of current-voltage and optical. DSSC cells are an interesting alternative to silicon solar cells. The stage of scientific research conducted around the world suggests that in the near future DSSC are fully commercially available. Originality/value: It was shown that the DSSC cells can be used as promising materials used in building-integrated photovoltaic.

10

Surface properties and antimicrobial activity of composite nanofibers of polycaprolactone with silver precipitations

Dobrzański L., Hudecki A., Chladek G., Król W., Mertas A.

Archives of Materials Science and Engineering

|

2014

|

Vol. 70, nr 2

53--60

EN

Purpose: The purpose of the article is to investigate the structure and antimicrobial properties of composite nanofibers with silver particles precipitated onto the nanofibers surface. Design/methodology/approach: A solution was prepared in the first place made of the following solvents to fabricate antimicrobial composite nanofibers of polycaprolactone with silver precipitations: formic acid and acetic acid at a rate of 70:30. Then, silver nitrate was introduced into the fabricated solution of the solvents and it was subjected to the interaction of ultrasounds, and after 10 minutes polycaprolactone was added to the solution, and then the solution was mixed for 12 hours and a solution was obtained with a 10% concentration and the mass fraction of 0, 1, 3 and 5% of silver nitrate additives. The solution was forced into a positive voltage electrode placed above a negative voltage electrode; the solution was then subjected to the activity of a strong electrostatic field transforming the solution into micro- and nanofibers. After electrospinning, the fibers obtained underwent the activity of a 2% ascorbic acid solution, by means of which silver was precipitated on the nanofibers surface. Viscosity and electrical conductivity tests were performed of single-component and double-component solutions, of the fibers’ structure in a transmission electron microscope, of the BET, Langmuir specific surface area and DTF porosity with the method of gas adsorption and antimicrobial activity of the nanocomposites produced on the nanocomposites on following bacteria: Staphylococcus aureus, Escherichia coli, Candida albicans. Findings: The use of a formic acid and acetic acid solution at a rate of 70:30 for preparation of a polycaprolactone solution for its electrospinning enables to obtain a non-toxic and fully biodegradable polymer nanofibers of polycaprolactone with PCL/Ag silver precipitations possessing high antimicrobial performance against Gram+, Gram- bacteria and fungi. Practical implications: Antimicrobial composite nanofibers with silver nanoparticles precipitated onto the nanofibers surface can be applied in biodegradable antiseptic dressings in the form of mats or other textiles containing polymer nanofibers of polycaprolactone with PCL/Ag silver precipitations obtained as a result of electrospinning. Originality/value: The research outcomes confirm that it is feasible to manufacture polycaprolactone nanofibers with PCL/Ag silver precipitations possessing high antimicrobial performance against Gram+, Gram- bacteria and fungi.

11

Structure, geometrical characteristics and properties of biodegradable micro- and polycaprolactone nanofibers

Dobrzański L., Hudecki A.

Archives of Materials Science and Engineering

|

2014

|

Vol. 70, nr 1

5--13

EN

The purpose of the paper is to obtain and examine the structure and properties obtained in the electrostatic field of micro- and nanofibers PCL. Design/methodology/approach: The main problem of the study is to examine the impact of properties of the polymer solutions PCL obtained from the mixture of formic acid and acetic acid in a ratio of 70:30, tetrahydrofuran and dimethylsulfoxide in a ratio of 70:30, and chloroform and methanol in a ratio of 70:30 on the structure and and surface properties of polymer micro and nanofibers PCL. Findings: On the basis of out carried researches the impact of the polymer solutions applied to researches on the diameter and the properties of obtained polymer micro- and nanofibers have been shown. It comes out that from the our carried researches of specific surface area of fibers the highest specific surface area BET was obtained for fibers formed from a mixture of acetic acid and formic acid and it is equalled 8.9 m2/g. Significantly smaller surface area was obtained from a mixture of tetrahydrofuran and dimethyl sulfoxide 3.1 m2/g. However, the lowest surface area for fibers obtained from a mixture of chloroform and methanol, which is 0.9 m2/g, in spite of the observation of the porous surface of fibers. Practical implications: Mixture of formic acid and acetic acid may be an alternative solution for preparing nanofibers PCL. Originality/value: The results confirm the possibility of receiving nanofibers PCL from a mixture of non-toxic solvents.

12

Structure and properties of aluminium-silicon matrix composites manufactured by pressure infiltration method

Kremzer M., Dobrzański L., Dziekońska M., Radziszewska A.

Archives of Materials Science and Engineering

|

2014

|

Vol. 68, nr 2

53--58

EN

Purpose: The goal of the paper is to develop technologies for manufacturing composite materials with casting aluminum alloy matrix reinforced by silicon AN AC-AlSi12 and to investigate the effect of the amount of the pore forming agent in the form of graphite MG 192 on the structure and properties of porous ceramic skeleton infiltrated with liquid aluminum alloy. Design/methodology/approach: The composite was manufactured by the use of porous material pressure infiltration method. Hardness test was carried out with Rockwell method in A scale. The wear resistance was measured by the use of TSM Instruments Tribometer. The tribomiter allows to realize dry friction wear mechanism conditions. Additionally the examinations on stereomicroscope of wear tracks were made. Findings: Composite materials reinforced by porous skeleton manufactured on the base Al2O3 particles show superior in mechanical properties and wear resistance than the aluminum alloy EN AC-AlSi12 constituting the matrix. The developed composite materials also have better wear resistance compared to the matrix. Practical implications: Tested composite materials can be applied in many industry branches, among others, in the automotive, aerospace industry and in manufacturing of professional sports equipment. Originality/value:The investigation results shows that the worked out technology of composite materials manufacturing can find the practical application in the production of near net shape and locally reinforced elements.

13

Overview and general ideas of the development of constructions, materials, technologies and clinical applications of scaffolds engineering for regenerative medicine

Dobrzański L.

Archives of Materials Science and Engineering

|

2014

|

Vol. 69, nr 2

53--80

EN

Purpose: of this paper is the general presentation of the synergic utilisation of medical knowledge, tissue engineering and materials engineering for fabrication of functional substitutes of damaged tissues in the case of which medical indications show that classical prosthetics/implantation cannot be completely avoided, and that it is also appropriate to achieve natural ingrowth of the implanted elements into a living tissue in the implant area. Design/methodology/approach: This refers to post-injury losses, post-resection losses, as well as those originating from operative treatment of cancerous tumours or inflammation processes. Implantable biomedical devices are currently aggregately considered to be medical bionic implants where bionics is understood as production and investigation of biological systems to prepare and implement artificial engineering systems which can restore the lost functions of biological systems. Findings: The development of new hybrid technologies of bioactive and engineering materials for personalised scaffolds of tissues and bones requires a number of basic research and application work. They are presented numerous examples of the needs of the research for application of various bioactive and engineering materials, and their respective materials processing and tissue engineering technologies for manufacturing of the hybrid personalised implants and scaffolds. Research limitations/implications: There are no reports in the references about an original concept presented by the Author of introduction of prosthetics/implantation and tissue engineering techniques for the purpose of natural ingrowth of the implanted elements into a living tissue in the implant area without having to use mechanical devices, at least in the connection (interface) zone of bone or organ stumps with prosthetic/implant elements. Practical implications: They are open up vast possibilities for the application of the hybrid technologies of bioactive and engineering materials for personalized scaffolds of tissues and bones in accordance with the concept of the Author, presented in this paper. Medical bionic implants encompass numerous solutions eliminating various disfunctions of a human organism, among other implants of the cardiovascular system (stents, vessel prostheses, heart valves, pacemakers, defibrillators), digestive system implants, neuron devices (implants and neuronal prostheses to the central (CNS) and peripheral nervous system (PNS), the cochlea, retina), orthopaedic prostheses (bone grafts, bone plates, fins and other connecting and stabilising devices, including screws applied in the area of ankles, knees and hands, bars and pins for stabilising fractured limbs), screws and plates in skull-jaw-face reconstructions, dental implants, and also scaffolds of bones and tissues in tissue engineering. Originality/value: The Author’s idea for the embracing hybrid technologies of bioactive and engineering materials with titanium alloys including personalised scaffolds of tissues and bones will be created. It is also a challenge to achieve a synergy of clinical effects obtained with classical prosthetics/implantation of large lost post-injury or post-resection recesses together with the use of achievements in advanced tissue engineering methods at least in the interface zone of bone or organ stumps with prosthetic elements/implants.

14

Influence of the electrospinning parameters on the morphology of composite nanofibers

Dobrzański L., Nieradka B., Macek M., Matysiak W.

Archives of Materials Science and Engineering

|

2014

|

Vol. 69, nr 1

32--37

EN

Purpose: In the paper the fabrication of composite nanofibers using electrospinning Technique was reported. That processing technique was used to synthesis composite Nanofibers with various morphologies using a precursor composed of poly(vinyl) alcohol (PVA), copper acetate (CuAC) and acetic acid (C2H3OH). The morphology of formed Nanofibers depends not only on the spinning parameters, but also on the composition of the Polymer solution. The purpose of the study was to obtain results that allowed to determine The influence of parameters of the electrospinning process on morphology of the composite Nanofibers. Design/methodology/approach: The obtained nanofibers were characterized through High resolution scanning electron microscopy (SEM). It was noticed that the morphology Of composite nanofibers depends on the applied voltage and nozzle-collector distance. The research was carried on a scanning electron microscope. Findings: The influence of parameters of the electrospinning process on morphology of the Composite nanofibers was determined. Research limitations/implications: The research was carried out on samples, not on Final elements. Originality/value: The paper presents the influence of the electrospinning parameters On the morphology of composite nanofibers.

15

Effect of carbon nanotubes content on morphology and properties of AlMg1SiCu matrix composite powders

Dobrzański L., Macek M., Tomiczek B.

Archives of Materials Science and Engineering

|

2014

|

Vol. 69, nr 1

12--18

EN

Purpose: The main purpose of this work is to determine morphology, as well as technological and mechanical properties of aluminium matrix powder reinforced with multi-walled carbon nanotubes (MWCNTs) using powder metallurgy techniques. Dispersion of the multi-walled carbon nanotubes was achieved by using mechanical milling in a high energy ball mill. The addition of MWCNTs cause significant improvement in mechanical properties of Al/MWCNTs nanocomposites what is confirmed with more than a threefold increase in the hardness of composite powders, as compared to this value before milling. Design/methodology/approach: The main problem of the study is the agglomeration and poor distribution of carbon nanotubes in the matrix material. In order to achieve uniform dispersion of carbon nanotubes in aluminium alloy matrix mechanical milling was used. Additional problem is possible formation of the brittle aluminium carbides in the result of reaction between carbon nanotubes and aluminium particles. Findings: On the basis of micro-hardness testing has found that a small addition of carbon nanotubes in an amount of 0.5% by volume increases composites hardness by 13%, while the addition of carbon nanotubes in an amount of 5% by volume results in an increase of 37%.Practical implications: Composite powders carbon nanotubes were prepared using powder metallurgy method which shows the practical implications in manufacturing of nanocomposites. Originality/value: The investigation results shows that the technology of composite materials manufacturing can find the practical application in the production of new light metal matrix composites. It was found that carbon nanotubes, used as reinforcing phase, have influence on the properties of metal matrix composites.

16

Tranzystory z grafenu epitaksjalnego

Dobrzański L., Stankiewicz R., Strupiński W., Gierałtowska S., Borysiewicz M., Góra K., Kozłowski A., Stańczyk B.

Elektronika : konstrukcje, technologie, zastosowania

|

2013

|

Vol. 54, nr 11

9-14

PL

Opracowano technologię tranzystorów potowych z grafenu epitaksjalnego na podłożu z węglika krzemu. Przedstawiono charakteryzację grafenu i przyrządów. Poprzez badanie transportu nośników potwierdzono wysoką jakość grafenu. Otrzymano staloprądowe charakterystyki tranzystorów porównywalne z opisywanymi w literaturze. Na podstawie posiadanego doświadczenia określono drogę przyszłego rozwoju tranzystorów z grafenu i zidentyfikowano technologie konkurencyjne.

EN

We have developed technology of transistors made of epitaxial graphene grown on silicon carbide substrate. Carrier transport investigation confirmed good quality of graphene. DC parameters of developed transistors are similar to reported in the literature. On the basis of own experience we predict the way of future developments of grafene devices and indicate possible competing technologies.

17

Structure of X11MnSiAl17-1-3 steel after hot-rolling and Gleeble simulations

Dobrzański L., Borek W., Czaja M., Mazurkiewicz J.

Archives of Materials Science and Engineering

|

2013

|

Vol. 61, nr 1

13--21

EN

Purpose: The aim of the paper is to compare results after thermo-mechanical simulation using Gleeble 3800 and hot-rolling on LPS module of high-manganese austenitic X11MnSiAl7-1-3 steel. Design/methodology/approach: The hot-working behaviour was determined in continuous, 4- and 8-stage compression tests performed in a temperature range of 850 to 1100°C by the use of the Gleeble 3800 thermo-mechanical simulator and LPS module for semi-industrial hot rolling. The comparison between two processes has been established based on microstructure research and X-ray diffraction analysis. Findings: It was found that austenite microstructure with numerous annealing twins in the initial state was obtained. 4-stage compression tests were realized in the temperature range from 850 to 1050°C with the true strain 4x0.23. 8-stage compression test were performed in the same temperature range and with true strain of 0.4 in the first deformation, and 0.25 and 0.2 in the following deformations. The multi-stage compression examination gives the possibility to refine the austenite microstructure. Based on this research hot-rolling on LPS module in the temperature range from 1100°C to 850°C was realized. Based on microstructures research were found that this process is not perfect due to longer intervals between successive passes and inability to control the temperatures of following passes. Practical implications: The obtained stress-strain curves relationship and microstructure after Gleeble simulations can be useful in determination of power-force parameters of hot-rolling for thin sheets to obtain fine-grained austenitic microstructures. Originality/value: The hot-working behavior and microstructure evolution in various conditions of plastic deformation for new-developed high-manganese austenitic steels were investigated.

18

Influence of introducing silver nanoparticles on tribological characteristics of soft liner

Chladek G., Żmudzki J., Malara P., Dobrzański L., Krawczyk C.

Archives of Materials Science and Engineering

|

2013

|

Vol. 62, nr 1

5--14

EN

Purpose: of this paper is to assess the influence of introducing silver nanoparticles to the material intended for denture lining on tribological properties of obtained composite and retention properties of elastic friction attachments made of it. Design/methodology/approach: Studies of coefficient of frictions and forces conducted using a handle designed for this which allows exerting symmetrical pressure through elastomer samples on counterspecimen, applying different pressure forces and relative velocities of friction elements. The study of forces and retention of elastic friction attachments was conducted on the basis of our own methodology in an environment of artificial saliva. Findings: Results of laboratory tests show that introducing 40 ppm of nanosilver does not influence coefficient of friction values. Simultaneously, some dependencies of coefficient of frictions on pressure forces values were observed, while no dependencies of coefficient of frictions on relative velocities of friction elements were shown. No practically meaningful influence of introducing nanosilver, pressure force or relative velocities of elements on friction force values was noted. Values of retention forces did not depend on the content of nanosilver. Research limitations/implications: Limitations resulting from the specificity of the conditions of laboratory tests of retention characteristics do not allow to fully translate obtained results to expected results of clinical trials. Practical implications: The studies show that introducing a small amount of nanosilver to soft lining material will allow to obtain elastic attachments with unchanged retention characteristics, but they will be characterized with increased antimicrobial resistance. Originality/value: Study results of tribological properties of a new composite were presented. Own methodology of studying coefficient of friction and friction force of silicone rubber was presented here.

19

Effect of water dilution and alcohol mixing on erosive potential of orange juice on bovine enamel

Malara L., Kloc-Ptaszna A., Dobrzański L., Górniak M., Stefański T.

Archives of Materials Science and Engineering

|

2013

|

Vol. 62, nr 1

15--21

EN

Purpose: This in vitro study aimed to evaluate the changes of erosive potential of an orange juice before and after mixing with water and alcohol. Design/methodology/approach: Fifty enamel specimens obtained from bovine teeth were prepared and randomly assigned into the following groups (n=10) with different erosive solution: I. commercially available pure orange juice (Cappy, Coca Cola Co.), II. orange juice diluted with distilled water at a ratio 3:1 (v/v), III. orange juice mixed with vodka (Smirnoff, 40% ethanol, Polmos) at a ratio 3:1 (v/v); IV. Orange juice diluted with distilled water (1:1, v/v), V. Orange juice mixed with vodka (1:1 v/v). The enamel specimens were submitted to a short-term erosion-remineralization cycling model (five 1-min erosion challenges in-between six 10-min remineralization periods in artificial saliva). Erosive potential of the drinks was assessed on the basis of chemical analysis and percent surface microhardness change (%SMHC) calculated from Vickers surface microhardness measurements before and after cycling. In chemical analysis of the experimental drinks, the pH value, titratable acidity, and buffer capacity (β) were determined. Findings: The pH of tested drink remained low even after dilution with water or mixing with alcohol, however, titratable acidity decreased after addition of water and alcohol. Short-term erosion-remineralization cycling resulted in significantly decreased surface microhardness of enamel specimens in all experimental groups. In the proportion of 3:1, juice mixed with alcohol resulted in significantly smaller %SMHC than juice diluted with water. This difference was not observed at a ratio 1:1. Practical implications: Consumers should be aware of tooth damage by drinks with low pH and high titratable acidity, even when mixing them with water and alcohol. Originality/value: To the best of our knowledge, this is the first study comparing the erosive effect of water-diluted orange juice with that of juice mixed with alcohol.

20

Kwantowy efekt Hall'a w epitaksjalnym grafenie otrzymanym w ITME

Dobrzański L., Strupiński W., Stankiewicz R., Borysiewicz M., Góra K., Kozłowski A., Stańczyk B.

Elektronika : konstrukcje, technologie, zastosowania

|

2012

|

Vol. 53, nr 4

7-8

PL

Opracowano technologię i konstrukcję struktur z grafenu wyhodowanego na powierzchni węglika krzemu przy pomocy oryginalnej opatentowanej metody. Wykonano struktury do pomiaru kwantowego efektu Hall'a i przeprowadzono pomiary. Zaobserwowano anomalny kwantowy efekt Hall'a charakterystyczny dla grafenu składającego się z jednej warstwy węgla, w którym występuje transport nośników ładunku o zerowej masie.

EN

We developed technology and construction of devices made of epitaxial graphene grown on silicon carbide using proprietary patented method. Hall bars were processed and characterized. We observed the QHE characteristic for graphene build of single carbon layer in which charge carriers are mass less fermions.