Wyniki wyszukiwania - Biblioteka Nauki

1

Nanocrystalline Ti obtained by torsion under 2GPa

100%

Kuśnierz J.

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2007

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tom Vol. 7, nr 4(14)

63-67

EN

The methods of intensive shear deformation such as the equal-channel angular pressing (ECAP), accumulative roll-bonding (ARB) or high pressure torsion (HPT) are commonly used to produce submicron grain size bulk materials, characterized by unique properties like the high strength, accompanied by improved ductility in comparison with conventional coarse-grained materials. The high pressure torsion method, enabling torsion under high hydrostatic pressure is very effective in gram refinement although rarely used because of difficulty in arranging the high pressure equipment. In the paper, the transmission electron microscopy observations were used to document the evolution of microstructure during HPT processing under 2 GPa hydrostatic pressure. The results demonstrated that torsion up to equivalent deformation E-18 produced already the most grain-refined titanium with gram diameter d- 50 nm. The titanium deformed by HPT is compared with that deformed one by ECAP.

2

Nanomaterials: friends or foes?

100%

Lewandowska M. , Roguska A.

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tom Vol. 31, nr 3

773-776

EN

Within the field of nanomaterials the main emphasis has been placed, so far, on the development of technology and applications, while the potential risks for human health and the environment received marginal attention. The specific properties which make nanomaterials so interesting for industrial applications may also lead to specific risks. For instance, smaller particles have a greater surface area per unit mass than larger particles, which may render them more reactive and possibly more toxic. In addition, the small particle size may allow nanomaterials to penetrate more easily through the body compared to large particles. Data for some nanomaterials on their toxicity are now emerging and need to be carefully interpreted before generalizing for all nanomaterials. There is, however, a clear need to carry an extensive research of the potential hazards and possible benefits of nanomaterials.

PL

Wraz z postępującym rozwojem nanotechnologii i coraz powszechniejszym wykorzystaniem rożnych nanomateriałów w produktach codziennego użytku konieczne jest określenie realnego zagrożenia, jakie niesie nanotechnologia. Problem potencjalnej szkodliwości nanomateriałow dla człowieka i środowiska naturalnego odnosi się w szczególności do nanocząstek. Ich negatywne oddziaływanie wynika z faktu, że mają wymiar znacząco mniejszy w porównaniu z komórkami tkanek organizmów żywych. Stwarza to potencjalną możliwość ich wnikania do tkanek i zmian ich funkcjonowania. Wydaje się jednak, że obecnie największe ryzyko związane z nanomateriałąmi polega na braku kontroli, w sensie braku środków technicznych do monitorowania środowiska naturalnego, co do obecności i oddziaływania nanocząstek i nanomateriałów. Niezwykle potrzebna jest wyważona debata na temat rzeczywistych korzyści i zagrożeń wynikających z rozwoju tej dziedziny nauki.

3

Nanocrystalline materials prepared by torsion under pressure of 2 GPa

80%

Kuśnierz J. , Dutkiewicz J. , Malczewski P. , Kurowski M.

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2006

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tom Vol. 51, iss. 4

575-579

EN

Improved mechanical properties of materials with ultra-fine grained structure (nanostructure) are very frequently reported and severe plastic deformation is commonly proposed as a method to obtain such materials. High pressure torsion, although it cannot supply big dimension samples, generally leads to the highest degree of grain refinement The paper shows the influence of the phenomenon of intensive shear deformation during high pressure torsion (HPT) processing on the changes in structure, grain size, mechanical properties and solid solubility. The study is performed on copper brasses exemplified by CuZn30, CuZn37 and CuZn29Mn11, severely deformed up to high deformation degree (ε = 18.1 under 2 GPa pressure). The α + β brasses are particularly interesting as the deformation of two-phase α +β brasses shows the ability to superplastic deformation; additionally the better grain refinement and relation of α/β phase contents influence superplastic deformation.

PL

Polepszenie własności mechanicznych w materiałach o ultradrobnokrystalicznej strukturze jest powszechnie zauważane, a metody intensywnego odkształcenia plastycznego są wykorzystywane do wytwarzania takich materiałów. Taką metodą jest skręcanie pod wysokim ciśnieniem (metoda HPT), które chociaż nie dostarcza próbek o znacznych wymiarach jednak prowadzi do największego rozdrobnienia ziarna. W pracy przedstawiono wpływ intensywnego odkształcenia postaciowego wytwarzanego technika HPT na zmiany mikrostruktury, wielkości ziarna, własności mechanicznych i rozpuszczalności w stanie stałym. Badania prowadzono na mosiądzach: CuZn30, CuZn37 i CuZn29Mn11 intensywnie skręcanych do ε = 18.1 pod cisnieniem 2 GPa. W szczególności zwrócono uwagę na rozdrobnienie ziarna i wzajemny udział faz α i β, które mają wpływ na zdolność do odkształcania superplastycznego dwufazowych mosiądzów α + β.

4

Enhancement of XPS surface sensitivity in nanocrystalline material

80%

Wróbel R.

Polish Journal of Chemical Technology

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2010

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tom 12

|

nr 4

62-63

EN

The influence of the particle size on the surface sensitivity in XPS analysis was investigated. Previous reports about such influence were qualitatively only. In this report there are given mathematical description of XPS sensitivity and quantitative results. It was found that influence due to nanometric size on XPS analysis can be noticeable for particles below 15 nm of diameter and increases dramatically with reduction of the size.

5

Structural and Magnetic Properties of Cobalt Ferrite Nanopowders Synthesis Using Contact Non-Equilibrium Plasma

80%

Frolova L. , Derimova A. , Butyrina T.

Acta Physica Polonica A

|

2018

|

tom 133

|

nr 4

1021-1023

EN

Different grades of magnetic cobalt ferrite (Co_xFe_{3-x}O₄) nanoparticles were synthesized with various molar ratios of Fe²⁺ to Co²⁺ ions in the initial salt solutions method with using contact non-equilibrium plasma. The crystal structure and morphology of the nanoparticles are obtained from X-ray diffraction and transmission electron microscopy studies. With an increase in the value of x, the saturation magnetization for the samples of CoFe₂O₄ has decreased from 150.9 emu/g to 1.2 emu/g. The dependence of the coercive force on x is extremal with a plateau maximum corresponding to the x=0.5-1.25.

6

Optical properties of ZnO nanoparticles synthesized by varying the sodium hydroxide to zinc acetate molar ratios using a Sol-Gel process

80%

Dejene F. , Ali A. , Swart H. , Botha R. , Roro K. , Coetsee L. , Biggs M.

Open Physics

|

2011

|

tom 9

|

nr 5

1321-1326

EN

Material property dependence on the OH−/Zn2+ molar ratio of the precursor was investigated by varying the amount of NaOH during synthesis of ZnO. It was necessary to control the water content and temperature of the mixture to ensure the reproducibility. It was observed that the structural properties, particle size, photoluminescence intensity and wavelength of maximum intensity were influenced by the molar ratio of the precursor. The XRD spectra for ZnO nanoparticles show the entire peaks corresponding to the various planes of wurtzite ZnO, indicating a single phase. UV measurements show the absorption that comes from the ZnO nanoparticles in visible region. The absorption edge of these ZnO nanoparticles are shifted to higher energies and the determined band gap energies are blue shifted as the OH−/Zn2 molar ration increases, due to the quantum confinement effects. The photoluminescence characterization of the ZnO nanostructures exhibited a broad emission band centred at green (600 nm) region for all molar ratios except for OH−/Zn2+ = 1.7 where a second blue emission around 468 nm was also observed. The photoluminescence properties of ZnO nanoparticles were largely determined by the size and surface properties of the nanoparticles.

7

Molecular Clusters to Nanomaterials

70%

Singh N. , Lee H. , Suh S. , Kołaski M. , Kim K.

|

2007

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tom Vol. 81, nr 5-6

1021-1035

EN

Theoretical investigations of gas phase clusters enable the evaluation of intrinsic molecular properties and intermolecular interactions. Based on the microscopic determination of the properties of individual atoms, molecules, or clusters, one can predict the macroscopic properties of bulk matter. With the aid of theoretical insights into the interaction forces holding these clusters and subsequent properties of a large number of cluster systems (ranging from simple water clusters to large pi-systems), we have investigated the properties of various novel molecular systems including endo/exohedral fullerenes, nanotori, nonlinear optical materials, ionophores/receptors, polypeptides, enzymes, organic nanotubes, nanowires, and electronic and nano-mechanical molecular devices. This mini-review highlights some of the interesting results obtained in the course of our extensive theoretical investigations of clusters toward the molecular design approach of nanomaterials.

8

Template Assisted Growth of Molybdenum Oxide Nanocrystals Through Hydrothermal Process

70%

Farzaneh F. , Najafi M.

|

2009

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tom Vol. 83, nr 9

1523-1528

EN

Rod shaped MoO3 nanocrystals were prepared from ammonium heptamolybdate tetra - hydrate (AHM) and ethylene diamine (en) as template agent in water via a hydrothermal process at 180 graduate C. The prepared nanocrystals were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The range size of nanorods are from a few nanometers (nm) to micrometers in length and 50 to 200 nm in diameter. It was also found that nanostructures of varied dimensionality such as plates and helical plates are formed using citric acid (CA), and starch as template respectively.

9

Synthesis and spectroscopic properties of LiIn(WO4)2 nanopowders and single crystals doped with chromium(III) ions

70%

Skibiński T. , Fuks H. , Kaczmarek S. , Bodziony T. , Hermanowicz K. , Maczka M. , Ptak M. , Hanuza J.

Open Physics

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2013

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tom 11

|

nr 11

1559-1566

EN

LiIn(WO4)2 single crystals and nanopowders doped with chromium(III) ions were synthesized and investigated, including their EPR spectra and magnetic properties. The EPR spectra have shown low and high field lines attributed to isolated chromium ions with an electron spin S=3/2 and complex chromium centers with higher spin value, respectively. Magnetic susceptibility measurements revealed an almost linear dependence on the magnetic field. The electron resonance and magnetic properties have been related to the structural and spectroscopic data of the studied material.

10

Chemical characteristics of new nanopowder of titania doped with nitrogen atoms

70%

Szybowska K. , Gazda M. , Lisowska-Oleksiak A.

|

2009

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tom Vol. 9, nr 3(21)

23-38

EN

Characteristics of new nitrogen doped TiO2 prepared in an one-pot synthesis where titania (IV) complexes with ligands containing nitrogen atoms were used as a precursor are presented in this paper. The pale yellow nanopowder with crystallite size of 9 – 12 nm is obtained as a product of calcination at 310°C and repeated washing procedure. Elemental analysis shows that nitrogen (1.087 at. pct.) is present in obtained material. The morphology and microstructure of samples were examined by XRD, AFM, UV-VIS and FTIR-ATR techniques. These studies confirm that obtained powder demonstrates a significant decrease in the band gap energy value (Eg = 2.83 eV) comparing to pure TiO2 (Eg 3.22 eV). Presence of N-Ti-O bonds was confirmed via FTIR ATR. Products of the powder thermal decomposition were detected using TG-DSC technique coupled with mass spectrometry (MS). The report presents electrochemical studies which allow estimation of a flatband potential Efb on the basis of the Mott-Schottky relation.

11

Silver nanoparticles – possible applications and threats

70%

Kędzierska M. , Miłowska K.

Acta Universitatis Lodziensis. Folia Biologica et Oecologica

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2021

|

tom 17

14-31

EN

Silver is known for its biocidal properties. This metal has been used for decorations and food preservation since ancient times and has also been used in medicine. Silver foil has been used to cover wounds and burns. In addition, silver solutions were created to help fight the microorganisms responsible for causing infections, which helped the wound healing process. Currently, to increase and optimize the properties of silver, it is used on a nanometric scale. Nanosilver, due to its expanded spectrum of properties, is used in many economic sectors, including in the production of disinfectants and food films, as well as in animal farms. Nanoparticles are also the basis of nanomedicine action. Creating new drug complexes with nanosilver and modifying the medical materials used in implantology or dentistry allow the lives of many people to be saved every day. In addition, nanosilver particles are commonly used as a specific disinfectant in the production of hospital materials: dressings, bandages, surgical masks, hospital clothing and shoes, and equipment. With the growing use of nanosilver, there are concerns about its harmful effects on living organisms, because not all its mechanisms of action are known. As is well known, the dose determines the toxicity of a given substance; the case is similar for nanosilver. However, is the dose providing antibacterial and antifungal properties non-toxic to animals and humans? This review presents a summary of the scientific research showing the scope of nanosilver activity and the resulting threats.

12

Otrzymywanie materiałów magnetycznie twardych Nd-Fe-B w procesie mielenia w podwyższonej temperaturze

60%

Kaszuwara W. , Michalski B.

|

tom Vol. 32, nr 1

9-12

PL

Wysokokoercyjne proszki Nd-Fe-B otrzymuje się wieloma metodami (melt-spinning, HDDR, mechanical milling, mechanical alloying). W większości z wykorzystywanych procesów można wyróżnić etap destrukcji gruboziarnistej fazy Nd2Fe14B oraz etap jej rekombinacji do struktury o znacznie mniejszym ziarnie. Taka sekwencja zmian struktury występuje na przykład w metodzie mechanical milling, gdzie mielenie doprowadza stop Nd-Fe-B do amorfizacji, a późniejsze wyżarzanie prowadzi do ponownej krystalizacji fazy Nd2Fe14B w postaci nanokrystalicznej. W pracy opisano metodę mielenia w wysokiej temperaturze, gdzie oba etapy: destrukcji i rekombinacji są nałożone na siebie w czasie. W efekcie takiego procesu po samym mieleniu, które w całości lub tylko w ostatnim etapie odbywa się w wysokiej temperaturze, otrzymuje się proszek o dobrych właściwościach magnetycznych. Proszek stopu o składzie Nd14Fe80B6 poddawano wysokoenergetycznemu mieleniu przez 17 h (do amorfizacji materiału), a następnie ogrzewano w trakcie mielenia pojemnik z proszkiem i kontynuowano mielenie w odpowiedniej temperaturze przez dalsze 0,5 h. Badania dyfrakcyjne wykazały, że proszek po takim procesie zawiera fazę Nd2Fe14B. Właściwości magnetyczne uzyskanych proszków zależały od zastosowanej temperatury. Najwyższe właściwości miały proszki mielone w temperaturze z zakresu 520÷540°C, jednak nawet po mieleniu w temperaturze 455°C uzyskano materiał o wysokiej koercji. Proszek mielony w temperaturze pokojowej przez 17 h, wyżarzany w niezależnym procesie w piecu w temperaturze 520°C, osiąga wyraźnie niższe właściwości magnetyczne niż po mieleniu przeprowadzonym w końcowym etapie w tej temperaturze. Przeprowadzono również proces, w którym całe mielenie odbywało się w podwyższonej temperaturze (520°C). W tym przypadku również uzyskano proszek o wysokiej koercji. Przeprowadzone w pracy badania dowiodły, że jednoczesne działanie mielenia i temperatury daje lepszy efekt niż rozłączne stosowanie mielenia i późniejszego wyżarzania.

EN

High-coercivity Nd-Fe-B powders are obtained using various methods (such as melt-spinning, HDDR, mechanical milling, mechanical alloying) - Figure 1. In most of these techniques the process is conducted in two stages: in the first stage the coarse-grained Nd2Fe14B phase is destructed and in the next stage it is recombined so as to crystallize in significantly smaller grains. This sequence of structural reconstruction is realized in e.g. mechanical milling in which the milling operation brings the Nd-Fe-B alloy to an amorphous form, whereas the annealing, which is the next operation, leads to the recombination of the Nd2Fe14B phase to the nanocrystalline form. The present paper describes a method in which the milling operation is carried out, entirely or only in the final stage, at high temperatures, so that the destruction of the material and its recombination occur simultaneously. In this way a powder with good magnetic properties immediately after milling was obtained. In the present experiments, the Nd14Fe80B6 powder was subjected to high-energy milling for 17 h (until the material becomes amorphous - Figure 2a) and, then, the milling was continued for 0.5 h with the powder container being heated to an appropriate temperature. Diffraction examinations have shown that the powder thus processed contains the Nd2Fe14B phase (Fig. 2b, c, e). Its magnetic properties appear to depend on the temperature applied (Fig. 4). The best magnetic properties were achieved in the powder milled at a temperature between 520 and 540°C, but we found that even milling at a temperature of 455°C gave a material with a high coercivity. The powder milled at room temperature for 17 h and then heated to 520°C in a separate furnace shows much worse magnetic properties than the powder subjected to heating at the same temperature realized during the final stage of the milling (Fig. 5). We also experimented with a process in which the milling was all the time conducted at a high temperature (520°C). This process also yielded a powder with a high coercivity (Fig. 6). Therefore our experiments have proved that the milling and heating operations conducted simultaneously give better results than processes in which the two operations are performed separately.

13

Structure and properties of dispersion hardened submicron grained copper

60%

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

|

2007

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tom 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.

14

Fabrication of nano-structured materials by high-pressure sintering

60%

Czepelak M. , Staszewski M. , Wrona A. , Lis M. , Osadnik M.

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2008

|

tom Vol. 30, nr 2

109-112

EN

Purpose: The aim of this work was to fabricate nanocrystalline powders and high-density bulk materials using a sintering method with limited grain growth so as to maintain nanocrystalline structure of the materials also after sintering. Design/methodology/approach: The size of crystallites and physical properties of the obtained nanocrystalline powders and sinters made from these powders were examined. The studied materials were pure copper and the following powders: Cu+1%WC, Cu+3%WC, Cu+3%AlNi and AlNi. The technology for preparation of nano-structured powders was used, which included milling the powders in ball mills and their sintering in a pressing furnace. Findings: It was found that the objective of this work can be achieved provided that high-pressure sintering is used, in which the stages of compacting and sintering proceed simultaneously over a short period of time. Research limitations/implications: It is recommended to perform further studies aimed at checking the possibility of using the proposed method of nanomaterials fabrication in the case of the materials with other chemical composition. Practical implications: This work broadens possibilities of metal powder sintering technology by fabrication of bulk nanocrystalline materials. Originality/value: The results from his work shall be useful in determining conditions for fabrication of nanocrystalline or sub-microcrystalline materials by the sintering method.

15

Inorganic nanomaterials prepared with the use of alkalides.

60%

Grobelny Z. , Stolarzewicz A.

|

2006

|

tom Vol. 27, nr 2-3

111-119

EN

Alkalides are salts containing alkali metal anions and complexed alkali metal cations. They reduce various organic compounds easily. Alkalides can be also used for the reduction of soluble transition and post transition metal salts in mild homogeneous conditions. Nanoparticles of metals are products of this process. Their further reactions result in nanocrystalline metal oxides, nitrides and carbides as well as electroceramics. This review article presents papers dealing with this subject and shows possible applications of the nanomaterials obtained.

16

Nanorurki węglowe jako warstwa pośrednia na powierzchni katalitycznego reaktora utleniającego w układzie oczyszczania spalin

60%

Ciałkowski M. , Giersig M. , Iskra A. , Kałużny J. , Babiak M.

|

2009

|

tom nr 6

CD-CD

PL

Nanomateriały i nanorurki stanowią stosunkowo nowy obszar nauki i praktyki przemysłowej. Niniejszy artykuł obejmuje przegląd zastosowań nanomateriałów w przemyśle samochodowym. Obszary zastosowań nanomateriałów podzielono na dwie grupy w zależności od stopnia zaawansowania procesu wdrożeniowego nanomateriałów. Szczególną uwagę poświęcono przy tym obszarom innowacyjnych zastosowań nanomateriałów, zastosowaniom w których możliwe byłoby wykorzystanie unikalnych własności nanomateriałów. Autorzy artykułu zaproponowali utworzenie warstwy pośredniej reaktora katalitycznego z nanorurek, oczekując istotnego zwiększenia powierzchni kontaktu warstwy katalitycznej ze spalinami. W artykule przedstawiono wstępne wyniki badań stopnia konwersji reaktora zbudowanego według zaproponowanej koncepcji oraz przedyskutowano kierunki dalszego rozwoju konstrukcji.

EN

The nanotubes and nanotechnologies are relatively new areas of science and engineering practice. This article should be concerned as a review of the selected nanotechnology applications in the automotive industry. The applications were divided into groups in respect of implementation advance level. Special attention was devoted to innovative nanomaterials application in areas where taking advantage of their unique features is possible. Authors presented the catalytic converter for combustion engine exhaust system application in which the nanotubes were used in order to increase the contact area of exhaust gases with catalytic layer. In the paper preliminary results of proposed catalytic reactor conversion ratio were presented and future directions of development were discussed.

17

Nanoroboty w aspekcie bezpieczeństwa jednostki

60%

Niedbała M. P.

SECRETUM. Służby specjalne, bezpieczeństwo, informacja

|

2016

|

nr 1(4)

130-141

PL

Idee nanotechnologii z końca XX w. urzeczywistniły się z początkiem XXI w. Szybki rozwój tej młodej dziedziny naukowej niesie ze sobą wiele obiecujących rozwiązań dotyczących przede wszystkim medycyny, ale także technologii informatycznych, w tym komunikacyjnych. Rozwój wytwarzania samych nanotechnologii, jak i nanorobotówdowodzi, że człowiekowi udało się zmienić wadliwy genotyp zwierząt i dąży on do zastosowania tej samej metody u człowieka w oparciu o nanoroboty biologiczne. Z wielką uwagą należy obserwować wykorzystanie nanotechnologii szczególnie na polu medycznym. Istnieje bowiem uzasadniona obawa użycia wspomnianych technologii, w tym budowy nanorobotów opartych na biologii, przeciwko człowiekowi. Niniejszy artykuł ma na celu zwrócenie uwagi czytelnika na możliwości i skutki ich niekontrolowanego użycia.

EN

The ideas of nanotechnology become reality at the beaginning of XXI century. The rapid development of this young scientific field entails a number of promising solutions mainly related to medicine, as well as information technology, including communication. Development of nanotechnology manufacturing and nanobots proves that man has already managed to change defective genotype of animals, and seeks to apply the same method in humans, based on biological nanorobots. However, great attention should be paid to observe the use of nanotechnology particularly in the medical field. There is a reasonable fear to use these technologies, including the construction of nanobots based on biology, against man. This article is intended to draw the reader's attention to the possibilities and consequences of their uncontrolled use.

18

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

60%

Stobrawa J. , Rdzawski Z.

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2008

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tom 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.

19

Wear characteristic of exfoliated graphite nano sheets/copper metal matrix composite

60%

Ashraf A. A.

|

2008

|

tom z. 73 [253]

19-26

EN

Powder Metallurgy technique has been used to prepare composite samples made of exfoliated graphite nano sheets (EGNS)and graphite flakes (GF) of 1, 3 and 5 weight % with copper chips. Effect of both graphite and its size on morphological, mechanical, and tribological behavior of copper matrix camposite has been investigated. Same unexpected characteristics have been identified due to the addition of graphite flakes and its exfoliated nano sizes with copper metal matrix. Nano-like grain boundary (NLGB) phenomenon has been reported. A decrease in hardness has been measured within the used weight fractions. Surprisingly, there was an increase in wear rates with an increase in wt % GF added to the copper matrix. In the case of EGNS, an increase in wear rate is reported for a weight fraction of 1%, which then decreases as more EGNS is added until it reaches approximately the same wear rate of pure Cu matrix at 5% EGNS. It is believed that the increase in wear at 1% EGNS is due to delamination domination theory. Measuring the counter part wear characteristics more deeply, evaluating the dispersion quantitatively, and explaining the delaminating theory of the EGNS/Cu metal matrix composites is recommended for future work.

20

Structure and magnetic properties of powder HITPERM material

60%

Konieczny J. , Dobrzański L. A. , Frąckowiak J. E.

|

2007

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tom Vol. 28, nr 3

156-164

EN

Purpose: The aim of the work is to investigate the structure and magnetic properties of the cobalt based HITPERM amorphous alloy Co68Fe4Mo1Si13.5B13.5 subjected high-energy ball milling and to the isothermal annealing to a combination of these two technologies. Design/methodology/approach: The nanocrystalline ferromagnetic powders were manufactured by highenergy ball milling of metallic glasses ribbons in as state. Using the HFQS program the distributions of the magnetic hyperfine P(H) fields were determined for spectra smoothed in this way, employing the Hesse-Rübartsch method. Observations of the structure of powders were made on the OPTON DSM-940 scanning electron microscope. The diffraction examinations and examinations of thin foils were made on the JEOL JEM 200CX transmission electron microscope equipped in equipped with the EDS LINK ISIS X- ray energy dispersive spectrometer made by Oxford. Graphical analyses of the obtained X-ray diffraction patterns, as well as of the HC=f(TA) relationship were made using the MICROCAL ORIGIN 6.0 program. Findings: The analysis of the structure and magnetic properties test results of the HITPERM powders alloy Co68Fe4Mo1Si13.5B13.5 obtained in the high-energy ball of milling process proved that the process causes significant decrease in the magnetic properties. The magnetic properties of this material and structure and may be improved by means of a proper choice of parameters of this process as well as the final thermal treatment. Research limitations/implications: For the soft magnetic powder material, further magnetical, composition examinations and structure are planed. Practical implications: Feature an alternative to solid alloys are the amorphous and nanocrystalline metal powders obtained by milling of metallic glasses and make it possible to obtain the ferromagnetic nanocomposites, whose dimensions and shape can be freely formed. Originality/value: The paper presents results of influence of parameters of the high-energy ball milling process on magnetic properties and structure of soft magnetic powder HITPERM alloy obtained in this technique. The paper compares magnetic properties and structure of the HITPERM alloy obtained in high-energy ball milling process, melt spinning technique and in a combination of these two technologies.