PL
 |
EN
Preferencje help
Polish version English version Język
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 16

Liczba wyników na stronie
first rewind previous Strona / 1 next fast forward last
Wyniki wyszukiwania
Wyszukiwano:
w słowach kluczowych:  nanocrystalline
help Sortuj według:

help Ogranicz wyniki do:
first rewind previous Strona / 1 next fast forward last
1
Content available Microstructure and Hardness of Cu-22Sn-xC Alloys Fabricated by Powder Metallurgy
Kim Gwanghun, Park Jungbin, Lee Seok-Jae, Kim Hee-Soo
Archives of Metallurgy and Materials
|
2023
|
Vol. 68, iss. 1
71--75
EN
Cu-Sn alloys have been known as bronze since ancient times and widely used as electrode materials, ornaments, tableware and musical instruments. Cu-22Sn alloy fabrication by hot forging process is a Korean traditional forged high-tin bronze. The tin content is 22 percent, which is more than twice that of bronze ware traditionally used in China and the West. Copper and tin have a carbon solubility of several ppm at room temperature, making Cu-Sn-C alloys difficult to manufacture by conventional casting methods. Research on the production of carbon-added copper alloys has used a manufacturing method that is different from the conventional casting method. In this study, Cu-22Sn-xC alloy was fabricated by mechanical alloying and spark plasma sintering. The carbon solubility was confirmed in Cu-Sn alloy through mechanical alloying. The lattice parameter increased from A0 to C2, and then decreased from C4. The microstructural characteristics of sintered alloys were determined using X-ray diffraction and microscopic analysis. As a result of comparing the hardness of Cu-22Sn alloys manufactured by conventional rolling, casting, and forging and Cu-22Sn-xC alloy by sintered powder metallugy, B0 sintered alloy was the highest at about 110.9 HRB.
2
Content available Austenitic Stability and Strain-Induced Martensitic Transformation Behavior of Nanocrystalline FeNiCrMoC HSLA Steels
Park Jungbin, Jeon Junhyub, Seo Namhyuk, Kim Gwanghun, Son Seung Bae, Jung Jae-Gil, Lee Seok-Jae
Archives of Metallurgy and Materials
|
2023
|
Vol. 68, iss. 1
77--80
EN
The austenitic stability and strain-induced martensitic transformation behavior of a nanocrystalline FeNiCrMoC alloy were investigated. The alloy was fabricated by high-energy ball milling and spark plasma sintering. The phase fraction and grain size were measured using X-ray diffraction. The grain sizes of the milled powder and the sintered alloy were confirmed to be on the order of several nanometers. The variation in the austenite fraction according to compressive deformation was measured, and the austenite stability and strain-induced martensitic transformation behavior were calculated. The hardness was measured to evaluate the mechanical properties according to compression deformation, which confirmed that the hardness increased to 64.03 HRC when compressed up to 30%.
3
Content available Effect of Sintering Holding Time and Cooling Rate on the Austenite Stability and Mechanical Properties of Nanocrystalline FeCrC Alloy
Kim Gwanghun, Jeon Junhyub, Seo Namhyuk, Choi Seunggyu, Oh Min-Suk, Son Seung Bae, Lee Seok-Jae
Archives of Metallurgy and Materials
|
2021
|
Vol. 66, iss. 3
759--763
EN
The effects of the sintering holding time and cooling rate on the microstructure and mechanical properties of nanocrystalline Fe-Cr-C alloy were investigated. Nanocrystalline Fe-1.5Cr-1C (wt.%) alloy was fabricated by mechanical alloying and spark plasma sintering. Different process conditions were applied to fabricate the sintered samples. The phase fraction and grain size were measured using X-ray powder diffraction and confirmed by electron backscatter diffraction. The stability and volume fraction of the austenite phase, which could affect the mechanical properties of the Fe-based alloy, were calculated using an empirical equation. The sample names consist of a number and a letter, which correspond to the holding time and cooling method, respectively. For the 0A, 0W, 10A, and 10W samples, the volume fraction was measured at 5.56, 44.95, 6.15, and 61.44 vol.%. To evaluate the mechanical properties, the hardness of 0A, 0W, 10A, and 10W samples were measured as 44.6, 63.1, 42.5, and 53.8 HRC. These results show that there is a difference in carbon diffusion and solubility depending on the sintering holding time and cooling rate.
4
Content available Corrosion Behavior of Amorphous-Nanocrystalline Ni50Ti50 Shape Memory Alloy
Aghabeygzadeh H., Mohammad Sharifi E., Tavoosi M.
Archives of Metallurgy and Materials
|
2021
|
Vol. 66, iss. 1
267--272
EN
In the present study, the corrosion behaviors of amorphous-nanocrystalline Ni50Ti50 shape memory alloy with different crystallite sizes were investigated. The Ni50Ti50 homogenized specimens were hot rolled and annealed at 950°C. Thereafter, the nanocrystalline Ni50Ti50 specimens with different crystalline sizes in the range of 40-350 nm were prepared by cold rolling and annealing at temperature range of 400 to 900°C. The corrosion resistance of Ni50Ti50 specimen with coarse grain size has significantly increased after cold rolling as a result of the formation of amorphous-nanocrystalline structure. The amorphous and nanocrystalline (with the crystallite size of about 40 nm) Ni50Ti50 samples exhibited the best corrosion resistance in the 5% HCl electrolyte with the corrosion potential and corrosion current density of about –197 mV and 2.34×10-6 A/cm2, respectively. This effect can be attributed to the higher density of crystalline defects in amorphous and nanocrystalline structures to quickly form protective films on the surface.
5
Content available Physicochemical properties of pseudobrookite Fe2TiO5 synthesized from ilmenite ore by co-precipitation route
Mahmoud Mohamed H. H., Hessien Mahmoud M., Alhadhrami Abdulrahman, Gobouri Adel A.
Physicochemical Problems of Mineral Processing
|
2019
|
Vol. 55, iss. 1
290--300
EN
Pseudobrookite (Fe2TiO5) is a semiconductor with numerous potential applications. Low-grade ilmenite ore has been used as an inexpensive source of Fe and Ti for preparation of Pseudobrookite. Ilmenite was first leached with 20% hydrochloric acid for 3 h at 70°C. Co-precipitation of soluble Fe and Ti from the rich filtrate was carried out at pH ≥ 9.1 followed by calcination at different temperatures (900-1300oC) for 2 h. X-ray diffraction patterns (XRD) showed that a single-phase nanocrystalline pseudobrookite powder was produced. The pH was a critical parameter for the evolution of formation the different sizes, structural morphology, and the magnetic properties of the product. Scanning electron microscope (SEM) images showed that particles synthesized at pH 11.2 contained more agglomerations and were more porous than those synthesized at pH 9.1. As the calcination temperature increases, the Fe2TiO5 changes from a small rod-like structure to an elongated rod-like structure, and finally to interconnected aggregated crystals. The magnetization of the synthesized Fe2TiO5 was measured using a vibrating sample magnetometer (VSM) and was found steadily increase with increasing calcination temperature from 1000 (≈9 emu/g) to 1300°C (16 emu/g). Such a large saturation of magnetization might be due to the high phase purity and well-defined crystallinity of Fe2TiO5.
6
Content available Quantitative Analysis of Cryomilled Nanocrystalline Ti-6Al-4V Alloy Powder by X-Ray Diffraction
Oh M., Yu H. K., Lee J.-H., Oh M. C., Jung S.-H., Ahn B.
Archives of Metallurgy and Materials
|
2018
|
Vol. 63, iss. 3
1439--1442
EN
A nanocrystalline Ti alloy powder was fabricated using cryomilling. The grain size and lattice strain evolution during cryomilling were quantitatively analyzed using X-ray diffraction (XRD) based on the Scherrer equation, Williamson-Hall (W-H) plotting method, and size-strain (S-S) method assuming uniform deformation. Other physical parameters including stress and strain have been calculated. The average crystallite size and the lattice strain evaluated from XRD analysis are in good agreement with the result of transmission electron microscopy (TEM).
7
Content available Effects of PVA Polymer Type and Calcination Temperature on Synthesis of Nanocrystalline Yttria Powder by Polymer Solution Route
Yang Y.-K., Lee S.-J.
Archives of Metallurgy and Materials
|
2018
|
Vol. 63, iss. 3
1473--1476
EN
Nano-sized yttria (Y2O3) powders were synthesized by a polymer solution route using polyvinyl alcohol (PVA) as an organic carrier. The PVA polymer affected the dispersion of yttrium ions in precursor sol. In this study, three kinds of PVA polymer (different molecular weight) were applied for synthesis of yttria powder. The PVA type as well as calcination temperature had a strongly influence on the particle morphology. Single crystal nano wire particles were observed at the temperature of polymer burn out range and the size was dependent on the PVA type. The stable, fully crystallized yttria powder was obtained through the calcination at 800°C for 1 h. The yttria powder prepared with the high weight PVA (MW: 153,000) revealed a particle size of 30 nm with a surface area of 18.8 m2/g.
8
Content available remote Synthesis and characterization of nanocrystalline barium strontium titanate powder by a modified sol-gel processing
Araghi A. M. E., Shaban N., Bahar M.
Materials Science Poland
|
2016
|
Vol. 34, No. 1
63--68
EN
In this research work, nanocrystalline BST (Ba0.6Sr0.4 TiO3) powders were synthesized through a modified sol-gel process, using barium acetate, strontium acetate and titanium isopropoxide as the precursors. In this process, stoichiometric proportions of barium acetate and strontium acetate were dissolved in acetic acid and titanium (IV) isopropoxide was added to form BST gel. The as-formed gel was dried at 200 °C and then calcined in the temperature range of 600 to 850 °C for crystallization. The samples were characterized by infrared spectroscopy method (FT-IR), X-ray diffraction technique (XRD) and field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectroscopy. EDS analysis of these samples confirmed the formation of the final phase with the special stoichiometry. The formation of a cubic perovskite crystalline phase with nanoscale dimension was detected using the mentioned techniques. The results showed that the obtained crystallite sizes were 33 and 37 nm for BST powder calcined at 750 and 850 °C, respectively.
9
Content available Nanocrystalline Ag-Re Composite as a Potential Material for Electric Contacts Fabrication
Kołacz D., Księżarek S., Woch M., Karwan-Baczewska J., Staszewski M., Rudnicki K., Borkowski P., Sienicki A.
Archives of Metallurgy and Materials
|
2016
|
Vol. 61, iss. 4
1847--1852
EN
A new silver-based composite material with an addition of 1 and 10 mass % of rhenium, for prospective application in the production of electric contacts, has been presented. The paper shows results of the research and experimental works aimed at developing technology for fabrication of semiproducts (wires and bimetallic contacts) by classical powder metallurgy methods and by a method enabling production of nanocrystalline composite. At each stage of the processes involved, physical, mechanical and technological properties of the materials were investigated. Particular attention was given to final products and semiproducts prepared in a form of bimetallic contacts. It was found that the composite with nanocrystalline structure may be a good material for ecological electric contacts.
10
Content available remote Hardening strain and recovery strain in nanocrystalline Ni investigated in tests with multiple stress changes
Sun Z., Blum W.
Archives of Materials Science and Engineering
|
2016
|
Vol. 79, nr 2
53--59
EN
Purpose: Dynamic recovery is interesting as it limits the maximal deformation strength of crystalline materials. Due to its small grain size, nanocrystalline Ni reaches its maximal strength after small strains < 0.1. It is shown that dynamic recovery contributes to strain and that its kinetics differs from that of hardening strain. Design/methodology/approach: The kinetics of recovery was studied by performing a large stress reduction suppressing thermally activated glide of the hardening type. The transition to a new quasi-stationary state at reduced strain rate and stress was accelerated by incremental increases of stress. Findings: During the transition the kinetics of deformation changes from that of recovery strain to the quasi-stationary one where hardening and recovery are coupled. The results are interpreted in terms of thermally activated hardening strain (in the grains) and thermally activated recovery strain (boundary mediated) linked by internal stresses. The activation volume of the hardening strain rate determined from the small stress increments is not inconsistent with the classical theory of thermally activated dislocation glide. Research limitations/implications: It is proposed to better characterize dynamic recovery by performing small stress changes in the period of dominating recovery strain to quantify the kinetics parameters of recovery strain. Practical implications: Disturbing deformation by sudden changes of stress is recommended as a suitable means to describe the kinetics of dynamic recovery. Recovery strains should enter the modeling of plastic deformation. This holds in particular for cases where dynamic recovery is prominent, e.g. at high stresses, high temperatures, and variable stresses (cyclic deformation, stress relaxation). Originality/value: The stress change method described in this work is generally applicable in deformation testing independent of the type of testing machine, where inelastic strains are measured at the usual accuracy.
11
Wpływ domieszkowania europem na właściwości optyczne i fizyko-chemiczne powierzchni cienkich warstw Ti02
Wojcieszak D.
Elektronika : konstrukcje, technologie, zastosowania
|
2013
|
Vol. 54, nr 7
11-14
PL
W niniejszej pracy przedstawiono wpływ domieszkowania europem na właściwości optyczne oraz fizyko-chemiczne powierzchni cienkich warstw Ti02. Cienkie warstwy wytworzono wysokoenergetyczną metodą rozpylania magnetronowego i dodatkowo wygrzewano w temperaturze 400°C i 800°C. Badania wykonane metodami XRD i AFM pokazały, że warstwy domieszkowane europem były nanokrystaliczne i miały strukturę TiO2 - anatazu. Były one stabilne nawet po wygrzewaniu w temperaturze 800°C. Natomiast warstwa niedomieszkowanego Ti02 miała strukturę rutylu już bezpośrednio po naniesieniu (bez dodatkowego wygrzewania), co jest typowe dla procesu wysokoenergetycznego. Wygrzewanie spowodowało m.in. wzrost wielkości krystalitów z około 18 do 28 nm. Oprócz tego stwierdzono, że poziom adsorpcji powierzchniowej oraz intensywność fotoluminescencji zależał od rozmiaru krystalitów z których były zbudowane cienkie warstwy Ti02:Eu. Wyniki badań pokazały, że optymalne do uzyskania silnej PL oraz dużego poziomu adsorpcji powierzchniowej (grup OH oraz cząstek H20) są krystality Ti02:Eu o rozmiarze około 22 nm.
EN
In this work influence of Eu-doping on optical an physicochemical properties of the surface of TiO2 thin films have been described. Thin films were manufactured by magnetron sputtering method and additionally annealed at 400°C and 800°C. Structural investigations with the aid of XRD and AFM methods have shown that doping with europium results in receiving of nanocrystalline films with the Ti02 - anatase structure. They were stable even after annealing at 800°C. Although undoped Ti02 matrix had rutile structure directly after deposition (without additional annealing), which is typical for high energy sputtering process. Annealing caused increase of crystallites size from about 18 to 28 nm. Besides, the level of surface adsorption and the intensity of photoluminescence was dependent from the size of crystallites of Ti02:Eu. It was found that the crystallites in size of about 22 nm are optimal to obtain strong PL and high adsorption (of OH- and H20).
12
Content available A model for abnormal grain growth in nano-crystalline materials based on Zener drag force
Razavi-Tousi S. S., Yazdani-Rad R., Manafi S. A.
Archives of Metallurgy and Materials
|
2012
|
Vol. 57, iss. 1
79-85
EN
Abnormal grain growth of a matrix in which normal grain growth has stagnated due to the presence of fine incoherent ceramic particles is studied. A balance between driving and retarding forces is used as the criteria for estimating the steady state. Random and non-random approaches are applied for coarse and nano-grained structure respectively.
PL
Badano nieprawidłowy wzrost ziaren w materiale, w którym prawidłowy wzrost ziaren został zahamowany z powodu obecności drobnych cząsteczek ceramicznych. Równowaga pomiędzy siłami pędną i opóżniającą zostały przyjęte jako kryterium oszacowania stanu równowagi. Zastosowano przypadkowe i nieprzypadkowe podejście odpowiednio do struktury grubo i drobnoziarnistej.
13
Content available remote Computer aided design of an electromagnetic ignition coil for high speed benzine engines
Tarimer I., Güven M. E., Arslan S.
Przegląd Elektrotechniczny
|
2011
|
R. 87, nr 2
230-235
EN
In this study, since it can be analyzed in term of practically and easily in application, a 15 kV ignition coil was designed, and analyzed in electromagnetic way. In order to benefit from this design in automotive industry, it has been determined an ignition coil construction here. Magneto static designing of the ignition coil have been done as 3 dimensional analytical way with help of finite elements methods (Ansoft Maxwell V12 program). By this way, electrical and magnetic parameters and quantities have been calculated; the static magnetic data obtained have been commented. In this design, the effects of using different electromagnetic materials such as nanocrystalline, amorphous and enni55 as core of the ignition coil have been explored. By using Ansoft-Simplorer program, different types of ignition coil cores could have been obtained. It has been inferred that more accurate dynamic analyzing conclusions for the ignition coil would result in the calculation.
PL
W artykule zaprezentowano projekt 15 KV cewki zapłonowej z przeznaczeniem do silników benzynowych. Projekt wykorzystuje obliczenia magnetostatyczne wykonane z pomocą metody elementów skończonych. Uwzględniono zastosowanie różnych materiałów jak materiałów nanokrystalicznych czy amorficznych. Przedstawiono różne koncepcje projektu cewki.
14
Content available Odporność na korozję nanokrystalicznego tytanu do zastosowań biomedycznych
Ura-Bińczyk E., Garbacz H., Lewandowska M.
Engineering of Biomaterials
|
2010
|
Vol. 13, no. 96-98
40--44
PL
Celem przeprowadzonych badań było określenie wpływu rozdrobnienia ziarna na odporność na korozję w sztucznym płynie ustrojowym (SBF) komercyjnego tytanu Grade 2. Badaniom podano tytan w stanie wyjściowym o strukturze mikrometrycznej (μ-Ti) i po procesie hydroekstruzji o strukturze nanometrycznej (n-Ti) stosując polaryzację potencjodynamiczną, elektrochemiczną spektroskopię impedancyjną (EIS) oraz analizując zmiany potencjału korozyjnego w czasie. Na podstawie otrzymanych wyników stwierdzono, że n-Ti ma wyższy potencjał korozyjny niż jego grubokrystaliczny odpowiednik. Przebiegi obu krzywych polaryzacyjnych są podobne, a istotne różnice występują powyżej 1200 mVSCE. Badania impedancyjne wskazują, że warstwa pasywna wytworzona na n-Ti jest mniej zwarta i bardziej porowata.
EN
Nanocrytalline titanium (n-Ti) produced by hydroextrusion process was evaluated in terms of corrosion resistance in simulated body fluid (SBF) using variation of corrosion potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results obtained revealed higher corrosion potential of n-Ti and similar polarization behavior to that of μ-Ti. The EIS results indicate that the passive film formed on n-Ti is less compact and more porous.
15
Content available remote Effect of impact energy on the formation of nanocrystalline powders in Cu- 50 % Fe immiscible alloy system
Vaezi M.R., Mir Shah Ghassemi S.H., Shokuhfar A.
Materials Science Poland
|
2008
|
Vol. 26, No. 3
602--608
EN
The study of mechanical alloying in the Cu–Fe system, as a model system for those with positive heats of mixing, has been investigated. The effects of impact force which pertains to ball-to-powder ratio, rotation speed and milling time, on the strain and grain size of final powders have been studied. The aim of this research was to find the optimum condition for mechanical alloying of Cu–Fe system by the automatic design and analysis of Taguchi experiments. X-ray diffraction (XRD) was used to analyze the effect of incoming energy on the diffusion rate.
16
Content available remote Photoconductivity in sol-gel TiO2 thin films with and without ammonia treatment
Vomvas A., Pomoni K., Trapalis C., Todorova N.
Materials Science Poland
|
2007
|
Vol. 25, No. 3
809--816
EN
Thin TiO2 sol-gel films, with and without ammonia treatment, were prepared using the dip-coating technique and then heat treated at 500 oC. The time dependences of the photoconductivity at various light intensities were studied in vacuum and in air at 27 oC. The transient photoconductivity is very sensitive to the environment and dramatically higher than the dark one for samples both in vacuum and in air. The results are discussed in terms of the competition of the photogeneration, recombination, thermal release, and the influence of NH3 treatment.
first rewind previous Strona / 1 next fast forward last
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.