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  1. 57 Acta Physica Polonica A

  2. 3 Open Physics

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  1. 9 2017

  2. 13 2016

  3. 12 2015

  4. 7 2014

  5. 3 2013

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  1. 9 Sahin O.

  2. 5 Altan H.

  3. 4 Kale E.

  4. 4 Sahin E.

  5. 3 Adamiak S.

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1
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Iron Aluminides and Petr Kratochvíl

100%
Paidar V.
Acta Physica Polonica A
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2015
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vol. 128
|
issue 4
467-469
EN
Professor Petr Kratochvíl initiated a modern investigation of this class of materials in our country. He has been interested in various methods how to improve iron aluminides by alloying, precipitation and insertion of hard particles. He also restored the results obtained already in fifties of the last century in the development of so called PyroFerAl that was produced in Czechoslovakia and used, for example, for heat treatment installations. Professor Petr Kratochvíl has been cooperating with leading institutions for material research, for instance, with the Institute of Physics of Materials AS CR in Brno on creep studies or with the Technical University in Ostrava on material formation processes. Since aluminium is near the nonmetals on the periodic table, it can bond with metals differently than do other metals and hence the properties of iron aluminides, in particular, are different from the other intermetallics. These alloys can be also used as functional materials due to their magnetic properties. Iron aluminides are being developed for use as structural materials and/or cladding alloys in fossil energy systems. They have good high temperature mechanical properties and excellent corrosion resistance. These alloys offer relatively low material cost, conservation of strategic elements and a lower density than stainless steels, and thus they have a great potential for substituting steels at elevated temperatures. However, a wider use of these materials is partly hampered by their moderate ductility at ambient temperatures.
2
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Scanning Force Microscopy Studies of Implanted Silicon Crystals

100%
Lekki J., Lekka M., Romano H., Cleff B., Stachura Z.
Acta Physica Polonica A
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1996
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vol. 89
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issue 3
315-322
EN
Scanning force microscope has been applied to investigate wear tracks produced during friction coefficient measurements of hard steel ball against ⟨111⟩ silicon crystals implanted with Ar ions. Such treatment causes the stable and significant decrease in friction, despite the total removal of implanted species from the wear track during friction. Scanning force microscope measurements of wear tracks topography supported the former hypothesis assuming the formation of post-implantation dense microcracks structure and subsequent propagation of this structure into the bulk. Such process assures small size of wear particles and a low friction coefficient value. Additionally the microfriction force measurement method was applied to determine the friction coefficient of Si_{3}N_{4} cantilever and a wear track in Si crystal.
3
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Distinguishing Features of Phase Transformation in the Surface Layer of Hardened Steel with (α+γ)-Two-Phase Structure during Plasto-Elastic Loading at Different Rates

100%
Alekseeva L., Sinelnikov V., Filippov G.
|
EN
An effect of loading during uniaxial tension at different rates ranging from 10^{-4} to 10^{-2} s^{-1} on the phase transformation "austenite-martensite" in the surface layer of hardened 0.36%C-14%Ni steel type with an unbalanced (α+γ)-structure has been determined by an X-ray structure analysis. The mechanisms of (γ-α)-transformation through the depth of steel surface layer and character of this transformation propagation along the specimen length depending on external stress value and tension rate have been defined.
4
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The Young Modulus and Microhardness Anisotropy in (Pb,Cd)Te Solid Solution Crystallizing in the Rock Salt Structure and Containing 5% of Cd

100%
Łusakowska E., Adamiak S., Adamski P., Kuna R., Minikayev R., Skupiński P., Szczerbakow A., Szuszkiewicz W.
Acta Physica Polonica A
|
2017
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vol. 132
|
issue 2
343-346
EN
A single crystal of (Pb,Cd)Te solid solution with Cd content equal to 5% was grown by self-selecting vapour growth technique and characterized by powder X-ray diffraction using the X'Pert PANalytical diffractometer and Cu K_{α₁} radiation. The X-ray diffraction pattern refinement demonstrated the fcc structure of the rock-salt type of investigated sample, no precipitates or other crystal phases were detected. The sample chemical composition was determined on the basis of measured lattice parameter value. Next, the Young modulus and microhardness were determined by the nanoindentation for carefully prepared, (001), (011) and (111)-oriented single crystal plates. The slight anisotropy of two parameters mentioned above has been found and compared with available literature data.
5
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Evaluation of Surface Properties of Four Tooth-Colored Restorative Materials

63%
Arslanoglu Z., Altan H., Sahin O., Tekin M., Adigüzel M.
Acta Physica Polonica A
|
2015
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vol. 128
|
issue 2B
B-310-B-313
EN
The aim of this study is to compare microhardness, roughness and micromorphology of the examined materials of a newly developed glass carbomer dental filling material to two different resin modified glass ionomers and a glass ionomer dental filling material. Specimens tested were prepared from a glass carbomer without gloss (Glass Carbomer, GCP), a glass carbomer (Glass Carbomer, GCP) with gloss, two different resin modified glass ionomers (Fuji II LC, GC and Riva LC, SDI) and a glass ionomer (Equia, GC). Seven specimens of each material were prepared according to manufacturer's recommendations. After setting, samples were polished and stored in 37°C distilled water for 24 h. Indentation microhardness of examined restorative materials was measured using the Vickers indenters. In addition surface roughness of the materials was measured using surface profilemeter. Surface morphology was analyzed by using scanning electron microscopy. There was a significant difference in microhardness and roughness between the restorative materials (p<0.05). The highest microhardness was measured for Equia and lowest for glass carbomer with gloss. The roughness was fully definite for the glass carbomer with gloss and indefinite for the glass carbomer without gloss. Small cracks and voids were observed in all groups. High viscosity glass ionomer cement Equia exhibits the high physical strength than RMGIC. Gloss application does not influence the hardness behavior of GCP.
6
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Peculiarities of Plastic Deformation of SPD Al-Li Alloy at 0.5 K

63%
Shumilin S., Isaev N., Zabrodin P., Fomenko V., Grigorova T., Geidarov V.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
536-539
EN
The mechanical properties of Al-Li solid solution were studied in tensile deformation tests at extremely low temperature of 0.5 K. The purpose of this study was to investigate the flow stress and work hardening rate as well as the development of serrated (jump-like) deformation for the polycrystalline samples with different microstructure. The samples obtained by severe plastic deformation via hydroextrusion were initially tensed up to a given intermediate deformation, then unloaded, annealed to modify their microstructure, and once again deformed to fracture. The increase of the grain size and decrease of average dislocation density due to annealing were found responsible for the work hardening rate increases and the flow stress decrease in accordance with the superposition of the Hall-Petch and Taylor contributions. As opposed to the flow stress, the high ductility of the samples remains rather insensitive to the microstructure properties, apparently due to suppressed recovery processes as well as the unstable deformation mode at extremely low temperature. The high ductility makes it possible to compare the work hardening rate and the scale of jump-like plastic deformation along the stress-strain curves for samples with different microstructures. In all cases, the average amplitude of the stress jumps was observed to increase whereas the average work hardening rate decreases with deformation. The observed correlation indicates that the nature of both phenomenons follows from the dislocation density evolution processes.
7
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Mechanical Properties and Lattice Parameters of Lu_{2x}Gd_{2(1-x)}SiO_{5}:Ce Scintillation Crystals

63%
Maksimchuk V., Baumer V., Bondar V., Galich Y., Kurtsev D., Sidletskiy O.
Acta Physica Polonica A
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2010
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vol. 117
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issue 1
146-149
EN
Structural and mechanical characteristics of complex oxide compounds Lu_{2x}Gd_{2-2x}SiO_{5}:Ce (LGSO) crystals were studied at different cation ratio in the host. For this purpose, a series of LGSO crystals with Lu concentration 5-70 at.% has been grown by the Czochralski method. Anisotropy of mechanical properties for these materials has been studied. The obtained results can be useful at choice of optimal growth direction for crystals and at mechanical processing of scintillation elements.
8
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Hardening of (Pb,Cd)Te Crystal Lattice with an Increasing CdTe Content in the Solid Solution

63%
Kuna R., Adamiak S., Petit S., Baroni P., Gas K., Minikayev R., Szczerbakow A., Łażewski J., Szuszkiewicz W.
Acta Physica Polonica A
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2016
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vol. 130
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issue 5
1245-1247
EN
Single crystals of the (Pb,Cd)Te solid solution with CdTe content up to 9% were grown by self-selecting vapour growth method and investigated by powder X-ray diffraction, inelastic neutron scattering, and nanoindentation measurements. The analysis of the linear part of the LA phonon dispersion, determined by the inelastic neutron scattering demonstrated an increase of the sound velocity (thus the hardening of the crystal lattice) with an increase of CdTe content in the solid solution. An important increase of microhardness value for (Pb,Cd)Te was directly confirmed by results of nanoindentation measurements performed for a few samples with various chemical composition.
9
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Nanomechanical Properties of Different Dental Restorative Materials

63%
Altan H., Bilgic F., Arslanoglu Z., Kale E., Köroğlu Kale A., Altan A., Sahin O.
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EN
The aim of this study is to determine the hardness and roughness of glass ionomer cement, glass carbomer, and compomer by nanoindentation. Three different dental restorative materials: glass ionomer cement, glass carbomer cement, and compomer were used. Disc specimens (10 mm × 1 mm) were prepared from each material using teflon mold. All specimens were light cured according to the manufacturer's instructions. The specimens were then mounted in polyacrilic resin. After grinding and polishing the specimens were stored in distilled water at 37°C for 1 day. The specimens were investigated using nanoindenter. The highest nanohardness was measured for glass ionomer cement and the lowest for glass carbomer. Regarding roughness, glass ionomer cement and compomer showed the highest mean values. Glass ionomer cement and compomer exhibited similar nanomechanical properties. Glass carbomer had superior ability to be polished up.
10
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Mechanical Properties of Nanocrystalline Tetragonal Zirconia Stabilized with CaO, MgO and Y_2O_3

63%
Sahin O., Demirkol İ., Göcmez H., Tuncer M., Ali Cetinkara H., Salih Güder H., Sahin E., Rıza Tuncdemir A.
Acta Physica Polonica A
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2013
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vol. 123
|
issue 2
296-298
EN
The citrate gel method, similar to the polymerized complex method, was used to synthesize homogeneous tetragonal zirconia at 1000°C. Nanocrystalline tetragonal phase has been fully stabilized at wide temperature range with 10 mol.% CaO, MgO, and Y_2O_3 addition. Scanning electron microscopy, X-ray diffraction, and microhardness tests are used to characterize synthesized materials. The grain size and dislocation density were calculated from X-ray diffraction data. The examined material exhibits indentation size effect behavior. Results revealed that the Vickers and Knoop microhardness are dependent on indentation test load. Geometrically necessary dislocation model and modified proportional resistance model are used to analyze the load dependence of the microhardness. The highest hardness values were obtained for the samples with CaO addition; however the lowest values were acquired for sample stabilized with Y_2O_3 by using both Knoop and Vickers techniques. This situation might be explained using the Hall-Petch relation.
11
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Hardness Behavior of Alumina-Zirconia Nanocomposites Synthesized by Gel Process

63%
Sahin O., Hasde A., Göcmez H., Tuncer M., Ali Cetinkara H., Salih Güder H., Sahin E., Rıza Tuncdemir A.
Acta Physica Polonica A
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2013
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vol. 123
|
issue 2
299-301
EN
The alumina-zirconia composites are one of the relatively good and promising candidates for biomaterials application, due to biocompatibility and their mechanical properties that combines high flexural strength with a high toughness. The aim of the present work is to analyze the mechanical properties of these composites, where zirconia content was varied from 5 to 50 wt%. The citrate gel method, similar to the polymerized complex method, was used to synthesize these ceramics. Scanning electron microscopy, X-ray diffraction and microhardness tests are used to characterize synthesized materials. The examined material exhibits the behaviour of indentation size effect. Modified proportional resistance model are used to analyze the load dependence of the microhardness. X-ray diffraction analysis was used to calculation of the grain size and dislocation density. It is found that hardness is decreased when the zirconia content increases with enlargement of grain size.
12
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Nanomechanical Behaviour and Surface Roughness of New Generation Dental Fissure Sealants

63%
Arslanoğlu Z., Altan H., Kale E., Bılgıç F., Şahin O.
Acta Physica Polonica A
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2016
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vol. 130
|
issue 1
388-393
EN
The aim of this study is the comparative evaluation of surface roughness, elastic modulus and hardness values of some new generation fissure sealants using nanoindentation method and triboindenter. In this study, we have tested five different materials of dental fissure sealant in five groups with six specimens in each. Tested specimens were prepared from the following materials; Fuji Triage as a glass ionomer, Glass Seal as a glass carbomer, Ultra Seal XT Hydro, Teethmate F-1 and Defence Chroma as three resin composites. In the study, Hysitron Triboindenter TI 950 machine was used for nanohardness measurements. This machine has load resolution of less than 1 nN and displacement resolution of 0.04 nm. Data were statistically analysed using one-way analysis of variance (ANOVA) and Kolmogorov-Smirnov Z tests. Hardness values of Fuji Triage, Glass Seal, Ultra Seal XT Hydro were fairly close. Same situation was seen between Teethmate F-1 and Defence Chroma. However, hardness values of the Teethmate F-1 and Defence Chroma was lower than in other examined materials. We can also say that the Defence Chroma has the lowest elastic modulus and Fuji Triage has the highest one among the examined materials. Surface of Teethmate F-1 was the roughest. On the other hand, Ultra Seal XT Hydro has the smoothest surface.
13
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Influence of Pd Addition of CoCrMo Biomedical Alloys on the Microhardness Behaviour

63%
Sahin O., Uzunoglu S., Sahin E.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2B
B-145-B-148
EN
CoCrMo alloys are often used as the material for metal artificial joint because of their high corrosion resistance and mechanical properties. In this study CoCrMo alloys having different palladium amount of produced by investment casting method. Scanning electron microscopy, X-ray diffraction method and indentation tests were used to examine the mechanical properties of the alloys. Indentation experiments were carried out using Vickers indenter that the loads range from 0.245 to 9.8 N. The alloys exhibit significant load-dependence (i.e., indentation size effect). Meyer's law, proportional specimen resistance model, and Hays-Kendall model were used to analyze the load dependence of the hardness. As a results for load-independent determination of the CoCrMo alloys, the Hays-Kendall model is found to be more effective than the proportional specimen resistance model and microhardness values decreases with increase of the Pd content.
14
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Mechanical Characterization of CoCrMo Alloys Consisting of Different Palladium Ratios Produced by Investment Casting Method

63%
Sahin O., Uzunoglu S., Sahin E.
Acta Physica Polonica A
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2015
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vol. 128
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issue 2B
B-149-B-151
EN
CoCrMo alloys are one of the most commonly used materials for hip arthroplasty, knee and dental because of its mechanical properties, corrosion resistance, wear resistance and biocompatibility. In this study, CoCrMo alloys consisting of 1.68 to 4.33%Pd are produced by investment casting process under argon atmosphere. The microstructures and mechanical properties of CoCrMo alloy were studied using X-ray diffraction, optical microscopy, scanning electron microscopy, Knoop indentation hardness tests, focusing on the influences on the different palladium additives. The measured microhardness values of CoCrMo alloys having different palladium ratio are seen to be load-dependent. The observed load dependence was rationalized using the Hays-Kendall model and it was found that the resultant load-independent hardness decreases with increase of palladium ratios. As a results, microhardness decreases with increase of palladium amount.
15
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Mechanical and Thermal Properties of Individual Phases Formed in Sintered Tungsten-Steel Composites

63%
Matějíček J., Nevrlá B., Čech J., Vilémová M., Klevarová V., Haušild P.
Acta Physica Polonica A
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2015
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vol. 128
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issue 4
718-721
EN
Tungsten is a prime candidate material for plasma facing components in fusion devices, thanks to its advantageous properties with respect to interaction with hot plasma. For its bonding to the supporting structure, composites and graded layers can be used for the reduction of stress concentration at the interface. When tungsten and steel are processed at elevated temperatures, e.g. hot pressing or spark plasma sintering, intermetallic phases may form and their presence and properties will affect the properties of the composite. In this work, mechanical and thermal properties of the individual phases, i.e. steel, tungsten and Fe-W intermetallics are investigated. Mechanical properties were determined by instrumented indentation. Thermal conductivity was determined by the xenon flash method on a range of samples with varying composition, from which the conductivities of each constituent were estimated. The results can be used for the optimization of compositional profiles and processing conditions for manufacturing of plasma facing components.
16
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Effects of Third-generation LED LCU on Nanomechanical Properties of Orthodontic Adhesives

63%
Bilgic F., Altan H., Akinci Sözer Ö., Arslanoglu Z., Kale E., Özarslan S.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
697-701
EN
The aim of this study was to compare the hardness and elastic modulus of orthodontic adhesives cured with different light-curing units, based on light-emitting diodes. Standardized samples of orthodontic adhesives, Transbond™ XT, Opal® Bond™ and Light Bond™ were prepared in cylinder blocks and cured for three seconds with Valo Ortho LED (Ultradent Products, South Jordan, Utah) and Valo LED High-Power Mode. After grinding and polishing, specimens were stored in distilled water at 37°C for one day. Specimens were investigated using nanoindenter. Employment of Valo Ortho unit has resulted in significantly higher elastic modules for Transbond™ XT (p=0.041). The highest nanohardness and elastic modules were measured for Transbond™ XT cured with Valo Ortho (9.47 GPa; 81.85 GPa, respectively) and lowest for Opal® Bond™ for both Valo Ortho (0.44 GPa; 14.52 GPa, respectively) and Valo High-Power groups (0.44 GPa; 11.84 GPa, respectively).
17
Publication available in full text mode
Content available

Embedded Atom Method for Theoretical Strength and Stability of Some fcc Metals

63%
Öztekin Çiftci Y., Çolakoğlu K.
Acta Physica Polonica A
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2001
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vol. 100
|
issue 4
539-551
EN
The structural phase transformation and theoretical strength of fcc metals Ni, Cu, Ag, Al, Au, and Pt under [100] uniaxial loading are studied by using analytical embedded-atom-potential method. In the present calculations the stress-free bcc phase is found unstable and fcc phase is found to be stable. The obtained energy differences of fcc-bcc phases are comparable with those found by the first-principles calculations and experiments for all metals considered. The present pair potential in the embedded-atom method is used for the first time for this purpose. Theoretical lattice parameters, volumes, and energies of the bcc and fcc structures for each metal at zero pressure are calculated and compared with the available experimental values. Third-order elastic constants and pressure-volume curves for studied metals are also investigated and found generally good agreement with experiments.
18
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Influence of CaO on the Nanohardness Behaviour of AZ63 Magnesium Alloys Produced by Mechanical Alloying Method

63%
Boztas M., Ozarslan S., Sahin O.
Acta Physica Polonica A
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2016
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vol. 130
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issue 1
357-361
EN
In this study we aimed to produce AZ63 magnesium alloys containing different amounts of CaO, to investigate the nanohardness behaviour of the resulting alloys. These alloys were produced by mechanical alloying under argon atmosphere. Magnesium based alloys with the initial CaO content of 0.1%, 0.3%, and 0.5% were produced by high-energy ball milling, followed by process that involved cold pressing and sintering. These alloys were characterized using scanning electron microscopy, scanning probe microscopy, X-ray diffraction, and nanoindentation methods. Unloading segments of nanoindentation curves were analyzed using Oliver-Pharr method. Experimental results show that measured nanohardness exhibits a peak load dependence. As a result, in these alloys the microstructure and nanohardness depend on the content of CaO.
19
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Structure and Properties of Metals

63%
Kurzydłowski K.
Acta Physica Polonica A
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1999
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vol. 96
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issue 1
69-79
EN
Metals are one of the most widely used types of engineering materials. Some of their properties, e.g. elastic constants, can be directly related to the nature of the metallic bonds between the atoms. On the other hand, macro- and microstructural features of metals, such as point defects, dislocations, grain boundaries, and second phase particles, control their yield, flow, and fracture stress. Images of microstructural elements can be obtained by modern imaging techniques. Modern computer aided methods can be further used to obtain a quantitative description of these microstructures. These methods take advantage of the progress made in recent years in the field of image processing, mathematical morphology and quantitative stereology. Quantitative description of the microstructures are used for modeling processes taking place under the action of applied load at a given temperature and test (service) environment. These model considerations can be illustrated on the example of an austenitic stainless steel, which is an important material for power generating and chemical industry. Reports recently published also show that properties of materials can be significantly modified by the effect of free surface. Examples of such situations include environmental effect on the mechanical properties of materials. Data for an austenitic stainless steel is used to discuss contribution of the free surface to the mechanical properties of metals.
20
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Investigation of the Crash Boxes Light Weighting with Syntactic Foams by the Finite Element Analysis

51%
Özer H., Can Y., Yazıcı M.
Acta Physica Polonica A
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2017
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vol. 132
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issue 3
734-737
EN
Light-weighting is a new scope in the automotive industry to accommodate new emission regulations. The parts produced with conventional metallic materials are replaced with parts produced by using light weight or high strength materials, to obtain light weighted equivalents of the same strength. Foam core sandwich structures, high strength steels, composite materials are the most used alternative materials. Syntactic foams that show outstanding performance in case of high-speed collisions have an excellent utility as energy absorbers in vehicle crash boxes. Syntactic foams are modeled in crash boxes at various filling rates and filling patterns in the context of this study. As results of the FEM analyses, it is observed that syntactic foams have excellent crash performance, as well as weight-reducing effect in vehicle crash boxes.
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