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Tytuł:
Road to Quantum Boxes
Autorzy:
Chang, L. L.
Powiązania:
https://bibliotekanauki.pl/articles/1946514.pdf
Data publikacji:
1996-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
73.61.-r
78.66.-w
Opis:
Quantum wells and superlattices have evolved over the last two decades to become a prominent multi-disciplinary field in condensed matter science. From the first observation of resonant tunneling to the recent realization of the quantum box, in this work we provide a summary description of the historical development of the field, known today as quantum structures. The focus is on the physics aspect with emphasis on important experimental observations that collectively define the field and set its direction of development.
Źródło:
Acta Physica Polonica A; 1996, 90, 4; 603-612
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
How To Construct Support Vector Machines Without Breaching Privacy
Autorzy:
Zhan, J.
Chang, L.
Matwin, S.
Powiązania:
https://bibliotekanauki.pl/articles/92993.pdf
Data publikacji:
2006
Wydawca:
Uniwersytet Przyrodniczo-Humanistyczny w Siedlcach
Tematy:
privacy
security
support vector machine (SVM)
Opis:
This paper addresses the problem of data sharing among multiple parties in the following scenario: without disclosing their private data to each other, multiple parties, each having a private data set, want to collaboratively construct support vector machines using a linear, polynomial or sigmoid kernel function. To tackle this problem, we develop a secure protocol for multiple parties to conduct the desired computation. In our solution, multiple parties use homomorphic encryption and digital envelope techniques to exchange the data while keeping it private. All the parties are treated symmetrically: they all participate in the encryption and in the computation involved in learning support vector machines.
Źródło:
Studia Informatica : systems and information technology; 2006, 1(7); 233-244
1731-2264
Pojawia się w:
Studia Informatica : systems and information technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Multi-Party Scheme for Privacy : Preserving Clustering
Autorzy:
Zhan, J.
Matwin, S.
Chang, L.
Powiązania:
https://bibliotekanauki.pl/articles/93043.pdf
Data publikacji:
2006
Wydawca:
Uniwersytet Przyrodniczo-Humanistyczny w Siedlcach
Tematy:
privacy
security
clustering
Opis:
Preserving data privacy while conducting data clustering among multiple parties is a demanding problem. We address this challenging problem in the following scenario: without disclosing their private data to each other, multiple parties, each having a private data set, want to collaboratively conduct k-medoids clustering. To tackle this problem, we develop secure protocols for multiple parties to achieve this dual goal. The solution is distributed, i.e., there is no central, trusted party having access to all the data. Instead, we define a protocol using homomorphic encryption and digital envelope techniques to exchange the data while keeping it private.
Źródło:
Studia Informatica : systems and information technology; 2006, 1(7); 217-232
1731-2264
Pojawia się w:
Studia Informatica : systems and information technology
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Impact of mesh quality on the numerical estimation of saturated water conductivity of pore media
Autorzy:
Gackiewicz, B.
Lamorski, K.
Slawiński, C.
Hsu, S.-Y.
Chang, L.-C.
Powiązania:
https://bibliotekanauki.pl/articles/2082923.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Agrofizyki PAN
Tematy:
porous media
numerical modelling
hydraulic
conductivity
mesh accuracy
Opis:
The numerical modelling of transport phenomena in porous media often requires a compromise between grid precision and the accuracy of simulation results. This study demonstrates the impact of errors on the accuracy of the reproduction of the actual pore space by the numerical grid on the estimated values of the saturated water conductivity. Four types of computational grids with varying levels of complexity were prepared for each of the 12 tomographic images of the porous specimens. The specific surfaces and total porosities were calculated for each of the meshes and compared with those parameters calculated for binarized tomographic images. Simulations of steady flow were performed on the computational grids, and the saturated water conductivity values were calculated. It has been shown that an insufficiently accurate mesh only reproduces the largest pore spaces in the analysed sample, which most often leads to an underestimation of the water conductivity coefficient. The following criterion for the optimal accuracy of the computational grid is proposed, it is based on the voxel size of the tomographic images of the porous media: the minimum size of the cell in the mesh used for simulations has to be at most two times the size of the voxel used in the tomographic scans of the porous medium.
Źródło:
International Agrophysics; 2020, 34, 4; 473-483
0236-8722
Pojawia się w:
International Agrophysics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Paleomagnetic analyses on Badenian–Sarmatian drill cores from the North Carpathian Foredeep (Middle Miocene, Poland)
Analizy paleomagnetyczne rdzeni wiertniczych z utworów badenu–sarmatu z północnej części zapadliska przedkarpackiego (środkowy miocen, Polska)
Autorzy:
Sant, K.
Leeuw, A. de
Chang, L.
Czapowski, G.
Gąsiewicz, A.
Krijgsman, W.
Powiązania:
https://bibliotekanauki.pl/articles/2061987.pdf
Data publikacji:
2015
Wydawca:
Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
Tematy:
Badenian-Sarmatian boundary
paleomagnetic dating
Northern Carpathian Foredeep
granica baden–sarmat
datowania paleomagnetyczne
zapadlisko przedkarpackie
Opis:
Accurate dating of the Badenian–Sarmatian transition, a boundary between two regional Middle Miocene stages of the semi-isolated Paratethys Sea, is crucial to understand what event caused the corresponding major turnover in faunal assemblage at that point in time. The general opinion is that this event resulted from a sudden isolation of the Eastern Paratethys from ocean water, due to the closure of the Eastern Anatolian seaway to the Indian Ocean, but it remains debated if the final isolation had a tectonic or climatic cause. This pilot study presents paleomagnetic analyses of two drill cores from the North Carpathian Foredeep in Poland that straddle the Badenian–Sarmatian transition. Rock magnetic experiments, including thermomagnetic runs in air on a Curie balance, and hysteresis measurements on a MicroMag, indicate that the dominant magnetic carrier is the iron sulphide greigite. This is in agreement with the observed gyroremanence obtained during alternating field demagnetization above 40 mT. Alternating field and thermal demagnetization results are in good agreement and show a weak, mixed-polarity, signal for most of the Badenian, rapidly shifting to a much stronger and dominantly normal polarity signal in the Sarmatian part of the cores. First order reversal curves diagrams indicate that the greigite in the Sarmatian part is clearly of diagenetic origin, it thus most likely concerns a secondary overprint by the present-day field that cannot be used for magnetostratigraphic correlations. We conclude that the Paratethys-wide paleoenvironmental change that occurred at the Badenian–Sarmatian transition had probably also created different conditions for the formation and/or preservation of magnetic minerals.
Dokładne datowanie przejścia baden–sarmat, granicy dwóch regionalnych pięter środkowego miocenu na terenie częściowo izolowanego morza Paratetydy, jest istotne dla zrozumienia przyczyny wyraźnej zmiany zespołów faunistycznych, która towarzyszyła temu wydarzeniu. Według powszechnie akceptowanych poglądów wydarzenie to było wynikiem nagłego odcięcia obszaru Paratetydy Wschodniej od otwartego oceanu wskutek zamknięcia cieśnin na terenie wschodniej Anatolii, które stanowiły łącznik z Oceanem Indyjskim. Obecnie przedmiotem dyskusji jest tektoniczna lub klimatyczna przyczyna tego wydarzenia. Paleomagnetyczne badania pilotowe rdzeni z dwóch otworów wiertniczych, położonych w północnej części zapadliska przedkarpackiego na terenie Polski, dotyczą przejściowej, badeńsko-sarmackiej sukcesji osadowej. Badania petromagnetyczne (w tym analizy termomagnetyczne na wadze Curie oraz histerezy na instrumencie MicroMag) wskazują, że dominującym minerałem magnetycznym jest siarczek żelaza – greigit, co potwierdza obecność składowej giromagnetycznej podczas rozmagnesowywania próbek zmiennym polem magnetycznym powyżej 40 mT. Wyniki polowej i termicznej demagnetyzacji są zgodne i wskazują na słaby sygnał, o mieszanej polarności, dla większości sukcesji badeńskiej, wzmocniony i zmieniający charakter na normalny dla części sarmackiej profilu. Odwrócone krzywe pierwszego rzędu dowodzą, że greigit w osadach sarmackich jest minerałem diagenetycznym, co bardziej wskazuje na wtórne nałożenie oddziaływania współczesnego pola magnetycznego i tym samym nie pozwala na przeprowadzenie korelacji magnetostratygraficznych. Autorzy stwierdzają, że zmiana paleośrodowiskowa w Paratetydzie na pograniczu badenu i sarmatu wpłynęła na powstanie i/lub dalsze przemiany minerałów o właściwościach magnetycznych.
Źródło:
Biuletyn Państwowego Instytutu Geologicznego; 2015, 461; 179--192
0867-6143
Pojawia się w:
Biuletyn Państwowego Instytutu Geologicznego
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Si/ZnO nanorods with Ag nanoparticles/AZO heterostructures in PV applications
Autorzy:
Gwóźdź, K.
Płaczek-Popko, E.
Gumienny, Z.
Zielony, E.
Pietruszka, R.
Witkowski, B. S.
Wachnicki, Ł.
Gierałtowska, S.
Godlewski, M.
Chang, L. B.
Powiązania:
https://bibliotekanauki.pl/articles/201432.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
solar cells
ZnO
Si
heterojunction
nanorods
nanoparticles
ogniwa słoneczne
nanopręty
nanocząstki
Opis:
Our studies focus on test structures for photovoltaic applications based on zinc oxide nanorods grown using a low-temperature hydrothermal method on a p-type silicon substrate. The nanorods were covered with silver nanoparticles of two diameters – 20–30 nm and 50–60 nm – using a sputtering method. Scanning electron microscopy (SEM) micrographs showed that the deposited nanoparticles had the same diameters. The densities of the nanorods were obtained by means of atomic force microscope (AFM) images. SEM images and Raman spectroscopy confirmed the hexagonal wurtzite structure of the nanorods. Photoluminescence measurements proved the good quality of the samples. Afterwards an atomic layer deposition (ALD) method was used to grow ZnO:Al (AZO) layer on top of the nanorods as a transparent electrode and ohmic Au contacts were deposited onto the silicon substrate. For the solar cells prepared in that manner the current-voltage (I-V) characteristics before and after the illumination were measured and their basic performance parameters were determined. It was found that the spectral characteristics of a quantum efficiency exhibit an increase for short wavelengths and this behavior has been linked with the plasmonic effect.
Źródło:
Bulletin of the Polish Academy of Sciences. Technical Sciences; 2016, 64, 3; 529-533
0239-7528
Pojawia się w:
Bulletin of the Polish Academy of Sciences. Technical Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exploring senior high school students’ difficulties and strategies for reading L1 and L2 texts in Taiwan
Autorzy:
Tsai, Cheng-Chang
Powiązania:
https://bibliotekanauki.pl/articles/2011738.pdf
Data publikacji:
2015-09-30
Wydawca:
Wydawnictwo Adam Marszałek
Tematy:
L1 and L 2 reading difficulties
L1 and L 2 reading strategies
reading strategy curriculum and instruction
Opis:
This study is an attempt to explore proficient Taiwanese senior high school students’ difficulties and strategies in L1 (Chinese) and L 2 (English) Reading. A total of eight proficient students participated in this study. An in-depth face to face interview was adopted for data collection. Thanks to the enthusiastic response of the students, we could gain an overall understanding of their reading difficulties and strategies in Chinese and English reading. This study shows that there are some similarities and differences between Chinese and English reading perceptions. Based on the findings of this study, classroom teachers will be able to design more effective reading strategy curricula and instruction geared to their students’ needs.
Źródło:
The New Educational Review; 2015, 41; 39-51
1732-6729
Pojawia się w:
The New Educational Review
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Weighted integrability and L¹-convergence of multiple trigonometric series
Autorzy:
Chen, Chang-Pao
Powiązania:
https://bibliotekanauki.pl/articles/1291177.pdf
Data publikacji:
1994
Wydawca:
Polska Akademia Nauk. Instytut Matematyczny PAN
Tematy:
multiple trigonometric series
rectangular partial sums
Cesàro means
weighted integrability
L¹-convergence
conditions of generalized bounded variation
Opis:
We prove that if $c_{jk} → 0$ as max(|j|,|k|) → ∞, and $∑_{|j|=0±}^∞ ∑_{|k|=0±}^∞ θ(|j|^⊤)ϑ(|k|^⊤)|Δ_{12}c_{jk}| < ∞$, then f(x,y)ϕ(x)ψ(y) ∈ L¹(T²) and $∬_{T²} |s_{mn}(x,y) - f(x,y)|·|ϕ(x)ψ(y)|dxdy → 0$ as min(m,n) → ∞, where f(x,y) is the limiting function of the rectangular partial sums $s_{mn}(x,y)$, (ϕ,θ) and (ψ,ϑ) are pairs of type I. A generalization of this result concerning L¹-convergence is also established. Extensions of these results to double series of orthogonal functions are also considered. These results can be extended to n-dimensional case. The aforementioned results generalize work of Balashov [1], Boas [2], Chen [3,4,5], Marzuq [9], Móricz [11], Móricz-Schipp-Wade [14], and Young [16].
Źródło:
Studia Mathematica; 1994, 108, 2; 177-190
0039-3223
Pojawia się w:
Studia Mathematica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Recovery mechanisms of sericite in microcrystalline graphite flotation
Autorzy:
Li, H.
Ou, L.
Feng, Q.
Chang, Z.
Powiązania:
https://bibliotekanauki.pl/articles/110055.pdf
Data publikacji:
2015
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
microcrystalline graphite
sericite
flotation
entrainment
entrapment
Opis:
Sericite is the main contaminant of concentrate in commercial microcrystalline graphite ore flotation. It was necessary to identify its recovery mechanisms so that the appropriate solution can be selected. In this study, the influence of sericite on flotation selectivity of microcrystalline graphite ore and its recovery mechanisms were investigated. Artificial mixtures flotation test suggested that sericite seriously reported into concentrate leading to poor flotation selectivity of microcrystalline graphite ore. However, the aggregation/dispersion behavior of artificial mixtures indicated that a large repulsive energy existed between sericite and microcrystalline graphite particles at pH 7.4, and sericite was not likely to report into graphite concentrate by slime coating. The results obtained from contact angle measurements and a technique of Warren showed that the floated sericite reached the froth via a combination of both entrainment and entrapment mechanisms, not via true flotation.
Źródło:
Physicochemical Problems of Mineral Processing; 2015, 51, 2; 387-400
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Tools for Scaffolding the Development of L2 Speaking in English-medium Higher Education: Lessons from Poland and Australia
Autorzy:
Pitura, Joanna
Chang, Heejin
Powiązania:
https://bibliotekanauki.pl/articles/22446738.pdf
Data publikacji:
2023
Wydawca:
Wydawnictwo Uniwersytetu Śląskiego
Tematy:
scaffolding
L2 speaking
higher education
Polska
Australia
Opis:
Participating in oral L2 communication may be challenging for English-medium higher education students. While literature suggests that scaffolding facilitates the development of L2 speaking, research has not addressed the notion of tools for scaffolding its development. The aim of this study is twofold: (1) to investigate how scaffolding can be embodied in tool design to support L2 speaking and (2) to obtain and analyse student perceptions of the tools. We draw on questionnaire data gathered in two iterations of a larger design-based research study conducted in two contexts: English Studies students in Poland (N = 26) and culturally and linguistically diverse L2 learners in Australia (N = 12). This study illustrates how features of scaffolding were applied to map instructor, peer- and technology-based tools in terms of learning activities, resources, technology and feedback. The results suggest that these tools may cater to the multiple levels of student understanding and skill with regard to the development of L2 speaking found in modern L2 classrooms.
Źródło:
Theory and Practice of Second Language Acquisition; 2023, 9, 2; 1-35
2450-5455
2451-2125
Pojawia się w:
Theory and Practice of Second Language Acquisition
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Mild Method to Synthesize TATB by Amination of 1,3,5-Trialkoxy-2,4,6-Trinitrobenzene under Phase Transfer Catalysis Conditions
Autorzy:
Chang, T.
Li, B.
Chen, L.
Ge, L.
Lu, M.
Powiązania:
https://bibliotekanauki.pl/articles/358103.pdf
Data publikacji:
2017
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
TATB
phase transfer catalysis
atmospheric amination reaction
Opis:
Nucleophilic amination, as a vital step in the synthesis of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) using 1,3,5-trialkoxy-2,4,6-trinitrobenzene (TORTNB) and aqueous ammonia as the starting materials and catalyzed by phase transfer catalysis (PTCs) under mild conditions is described. Various phase transfer catalysts, such as crown ethers, tertiary amines, quaternary ammonium salts, poly ethers and cyclodextrin, and various experimental parameters, such as no. of equivalents of PTC, mole ratio of ammonium hydroxide to the starting material, reaction time, reaction temperature and cycle times of the organic phase were investigated. The crown ethers, especially 18-crown-6, show good catalytic activity and re-usability for the amination of 1,3,5-triethoxy-2,4,6-trinitrobenzene giving a yield of 96.52%. This makes for a safe process and suitable for scale-up, because the reactions are carried out under atmospheric conditions. The material synthesised by the new system was characterized by DSC, SEM and LPS.
Źródło:
Central European Journal of Energetic Materials; 2017, 14, 1; 47-59
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Numerical Assessment of a One-Mass Spring-Based Electromagnetic Energy Harvester on a Vibrating Object
Autorzy:
Chiu, M.-C.
Chang, Y.-C.
Yeh, L.-J.
Chung, C.-H.
Powiązania:
https://bibliotekanauki.pl/articles/177720.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
spring
harvester
generator
permanent magnet
simulated annealing
optimization
buckling
Fatigue
Opis:
The paper is an exploration of the optimal design parameters of a space-constrained electromagnetic vibration-based generator. An electromagnetic energy harvester is composed of a coiled polyoxymethylen circular shell, a cylindrical NdFeB magnet, and a pair of helical springs. The magnet is vertically confined between the helical springs that serve as a vibrator. The electrical power connected to the coil is actuated when the energy harvester is vibrated by an external force causing the vibrator to periodically move through the coil. The primary factors of the electrical power generated from the energy harvester include a magnet, a spring, a coil, an excited frequency, an excited amplitude, and a design space. In order to obtain maximal electrical power during the excitation period, it is necessary to set the system’s natural frequency equal to the external forcing frequency. There are ten design factors of the energy harvester including the magnet diameter (Dm), the magnet height (Hm), the system damping ratio (ζsys), the spring diameter (Ds), the diameter of the spring wire (ds), the spring length (ℓs), the pitch of the spring (ps), the spring’s number of revolutions (Ns), the coil diameter (Dc), the diameter of the coil wire (dc), and the coil’s number of revolutions (Nc). Because of the mutual effects of the above factors, searching for the appropriate design parameters within a constrained space is complicated. Concerning their geometric allocation, the above ten design parameters are reduced to four (Dm, Hm, ζsys, and Nc). In order to search for optimal electrical power, the objective function of the electrical power is maximized by adjusting the four design parameters (Dm, Hm, ζsys, and Nc) via the simulated annealing method. Consequently, the optimal design parameters of Dm, Hm, ζsys, and Nc that produce maximum electrical power for an electromagnetic energy harvester are found.
Źródło:
Archives of Acoustics; 2016, 41, 1; 119-131
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Noise Elimination of Reciprocating Compressors Using FEM, Neural Networks Method, and the GA Method
Autorzy:
Chang, Y.-C.
Chiu, M.-C.
Xie, J.-L.
Powiązania:
https://bibliotekanauki.pl/articles/178126.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
finite element method
polynomial neural network model
genetic algorithm
group method of data handling
reciprocating compressor
optimization
Opis:
Industry often utilizes acoustical hoods to block noise emitted from reciprocating compressors. However, the hoods are large and bulky. Therefore, to diminish the size of the compressor, a compact discharge muffler linked to the compressor outlet is considered. Because the geometry of a reciprocating compressor is irregular, COMSOL, a finite element analysis software, is adopted. In order to explore the acoustical performance, a mathematical model is established using a finite element method via the COMSOL commercialized package. Additionally, to facilitate the shape optimization of the muffler, a polynomial neural network model is adopted to serve as an objective function; also, a Genetic Algorithm (GA) is linked to the OBJ function. During the optimization, various noise abatement strategies such as a reverse expansion chamber at the outlet of the discharge muffler and an inner extended tube inside the discharge muffler, will be assessed by using the artificial neural network in conjunction with the GA optimizer. Consequently, the discharge muffler that is optimally shaped will decrease the noise of the reciprocating compressor.
Źródło:
Archives of Acoustics; 2017, 42, 2; 189-197
0137-5075
Pojawia się w:
Archives of Acoustics
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of an N-policy GI/M/1 queue in a multi-phase service environment with disasters
Autorzy:
Jiang, T.
Ammar, S. I.
Chang, B.
Liu, L.
Powiązania:
https://bibliotekanauki.pl/articles/330836.pdf
Data publikacji:
2018
Wydawca:
Uniwersytet Zielonogórski. Oficyna Wydawnicza
Tematy:
N-policy
GI/M/1 queue
multiphase service environment
disaster
sojourn time
kolejka GI/M/1
katastrofa
czas pobytu
Opis:
This paper investigates an N-policy GI/M/1 queue in a multi-phase service environment with disasters, where the system tends to suffer from disastrous failures while it is in operative service environments, making all present customers leave the system simultaneously and the server stop working completely. As soon as the number of customers in the queue reaches a threshold value, the server resumes its service and moves to the appropriate operative service environment immediately with some probability. We derive the stationary queue length distribution, which is then used for the computation of the Laplace– Stieltjes transform of the sojourn time of an arbitrary customer and the server’s working time in a cycle. In addition, some numerical examples are provided to illustrate the impact of several model parameters on the performance measures.
Źródło:
International Journal of Applied Mathematics and Computer Science; 2018, 28, 2; 375-386
1641-876X
2083-8492
Pojawia się w:
International Journal of Applied Mathematics and Computer Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Vacuum Hot-Press Process on The Sintered Characteristics and Mechanical Properties of A High-Density Cr-31.2 Mass% Ti Alloy
Autorzy:
Chang, S.-H.
Li, C.-L.
Huang, K.-T.
Yang, T.-H.
Powiązania:
https://bibliotekanauki.pl/articles/356911.pdf
Data publikacji:
2018
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
Cr-31.2 mass% Ti alloy
vacuum hot-press sintering
relative density
TRS
electrical conductivity
Opis:
In this study, two different compositions of submicron-structured titanium (760 nm) and micron-structured chromium (4.66 μm) powders were mixed to fabricate Cr-31.2 mass% Ti alloys by vacuum hot-press sintering. The research imposed various hot-press sintering pressures (20, 35 and 50 MPa), while the sintering temperature maintained at 1250°C for 1h. The experimental results showed that the optimum parameters of the hot-press sintered Cr-31.2 mass% Ti alloys were 1250°C at 50 MPa for 1h. Also, the relative density reached 99.94%, the closed porosity decreased to 0.04% and the hardness and transverse rupture strength (TRS) values increased to 81.90 HRA and 448.53 MPa, respectively. Moreover, the electrical conductivity is enhanced to 1.58 × 104 S·cm-1 However, the grain growth generated during the high-temperature and high-pressure of the hot-press sintering process resulted in the grain coarsening phenomenon of the Cr-31.2 mass% Ti alloys after 1250°C hot-press sintering at 50 MPa for 1h. In addition, the Cr-31.2 mass% Ti alloys were fabricated with the submicron-structured titanium (760 nm) and chromium (588 nm) powders showed more effective compaction than the micron-structured titanium (760 nm) and chromium (4.66 μm) powders did. The closed porosity decreases to 0.02% and the hardness values increase to 83.23 HRA. However, the agglomeration phenomenon of the Cr phase and brittleness of the TiCr2 Laves phases easily led to a slight decrease in TRS (400.54 MPa).
Źródło:
Archives of Metallurgy and Materials; 2018, 63, 4; 1715-1723
1733-3490
Pojawia się w:
Archives of Metallurgy and Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 18

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