Wyniki wyszukiwania - Biblioteka Nauki

1

Spark Plasma Sintering of Mn-Zn Ferrite Powders by High Energy Ball Milling

100%

Suh J. Y. , Song Y.-S. , Chang S. Y.

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2019

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tom Vol. 64, iss. 2

565--569

EN

The Mn-Zn ferrite powders prepared by high energy ball milling were heat-treated, subsequently compacted and sintered by spark plasma sintering (SPS). Based on the observation of microstructure, the characteristics of samples after SPS were investigated and compared with ones after conventional sintering. The size of initial powders was approximately 650 nm and decreased to 230 nm after milling at 300 rpm for 3 h. After heat treatment at 973 K for 1 h, the milled powders became larger to approximately 550 nm in size again and the peaks of Mn2 O3 disappeared in XRD patterns. In the samples after SPS, the Fe2 O3 and MnZnFe2 O4 phases decomposed at the higher temperatures than 1173 K and 1373 K, respectively, while only MnZnFe2 O4 phase was detected in the samples conventionally sintered at 1273~1673 K. As the sintering temperature increased, the relative density after SPS increased more quickly than that after conventional sintering. In particular, it reached approximately 99% after SPS at 1473 K.

2

Microstructure Evolution of Ti/ZrO2 and Ti/Al2O3 Composites Prepared by Powder Metallurgy Method

100%

Dercz G. , Matuła I. , Gurdziel W. , Kuczera N.

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2019

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tom Vol. 64, iss. 2

443--450

EN

The current study were performed in order to assess the fabrication possibility of the metal-ceramic composites based on nanocrystalline substrates. The influence of the variable time of the high energy ball-milling (10, 30 and 50 h) on the structure, pores morphology and microhardness of Ti/ZrO2 and Ti/Al2O3 compositions was studied. The X-ray diffraction analysis confirmed the composite formation for all milling times and sintering in the case of Ti/ZrO2 system. Decomposition of substrates during milling process of Ti/Al2O3 system was also observed. Additionally, the changes of lattice parameter as a function of milling time were studied. The morphology of powders and the microstructure of the sintered samples were observed by scanning electron microscopy (SEM). Also, analysis of microhardness and pores structure were performed.

3

Microstructure and microhardness of ball milled/hot pressed aluminium with Mg3N2 addition

86%

Gajewska M. , Dutkiewicz J. , Morgiel J.

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tom Vol. 58, iss. 2

433--436

EN

The microstructure and microhardness of a ball milled and hot pressed aluminium powder with 10 vol.% of magnesium nitride (Mg3N2) were investigated. It was expected that the addition of a Mg3N2 as an nitrogen-bearing substrate would allow to obtain an in situ reaction leading to a formation of an aluminium nitride (AlN) strenghtening phase. The powders were milled in a high energy planetary ball mill for up to 40 h and then compacted in vacuum at 400ºC/600 MPa. The material was investigated by means of X-ray diffraction measurements (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and microhardness tests. The performed investigations showed that the composite preparation method provided a significant structure refinement of the material - the average matrix grain size of composite compact was about ˜140 nm. Energy Dispersive Spectrometry (EDS) analysis of Al/ Mg3N2 compact combined with X-ray diffraction (XRD) technique indicated a presence of Mg3N2 as well as Mg-Al-O phase, which were probably formed during hot pressing. Microhardness tests showed nearly 40% increase in the hardness of Al/ Mg3N2 composite over the non-reinforced aluminium compact.

PL

W niniejszej pracy przedstawiono wyniki obserwacji mikrostruktury i pomiarów mikrotwardości kompozytu o osnowie z aluminium z dodatkiem 10% objętościowych azotku magnezu wytworzonego drogą wysokoenergetycznego mielenia połączonego z prasowaniem na gorąco. Zakładano, że dodatek Mg3N2 jako substratu azotonosnego pozwoli na uzyskanie reakcji in situ prowadzącej do wytworzenia fazy wzmacniającej w postaci azotku aluminium. Proszki poddano mieleniu w wysokoenergetycznym młynku kulowym przez okres 40. godzin, a następnie sprasowano w próżni pod ciśnieniem 600 MPa w temperaturze 400ºC. Przeprowadzone obserwacje mikrostruktury materiału wykazały, że zastosowana metoda wytwarzania kompozytu pozwala na uzyskanie znacznego rozdrobnienia struktury materiału - średnia wielkość ziaren osnowy wynosiła ˜140 nm. Pomiary składu chemicznego technika EDS w połączeniu z analizą XRD wskazały na obecność zarówno azotku magnezu, jak również fazy Mg-Al-O w wyprasce kompozytowej. Pomiary mikrotwardości wykazały natomiast 40%-owy wzrost twardości kompozytu Al/ Mg3N2 w porównaniu z wypraska z niezbrojonego aluminium.

4

Effect Of Heat-Treatment On Microstructure And Magnetic Properties Of Nanocrystallized Mn-Zn Ferrite Powders

72%

Lee W. H. , Hong C. S. , Chang S. Y.

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tom Vol. 60, iss. 2B

1347--1350

EN

The initial ferrite powders were subjected to high energy ball milling at 300rpm for 3h, and subsequently heat-treated at 573-1273K for 1h. Based on the observation of microstructure and measurement of magnetic properties, the heat-treatment effect was investigated. The size of initial powders was approximately 70μm. After milling, the powders with approximately 230nm in size were obtained, which were composed of the nano-sized particles of approximately 15nm in size. The milled powders became larger to approximately 550nm after heat-treatment at 973K. In addition, the size of particles increased to approximately 120nm with increasing temperature up to 973K. The coercivity of initial powders was almost unchanged after milling, whereas the saturation magnetization increased. As the heat-treatment temperature increased, the saturation magnetization gradually increased and the maximum coercivity was obtained at 773K.

5

The FeCuAl-Al2O3 coatings deposited by means of supersonic technique – microstructure and properties

58%

Kusiński J. , Kac A. , Matteazzi P. , Colella A. , Dosta S. , Fernandez J. , Celis J. P. , Georgiou E.

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2012

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tom Vol. 33, nr 6

576--579

EN

The basic scientific and technological aim of the research was the generation of nanostructural FeCuAl-Al2O3 coatings having thickness of about 100 μm. The high energy ball milling allowed to produce powders characterized by a fine and homogeneous chemical distribution of elements and an ultrafine (the nanometric size) crystalline structure. A new powerful deposition technology (Supersonic Cold Gas Spray – SCGS) was used to transfer nanophased powder onto the substrate in the form of dense coating with very small or none change of crystal structure and properties. The microstructure and composition of all prepared nanopowders and deposited coatings were investigated using the light microscopy, TEM/HRTEM, STEM, SEM/EDS and XRD techniques. Hardness, Young’s modulus, friction coefficient and wear resistance measurements were carried out on the deposited coatings. It has been found that microstructure of deposited coatings remains that of the powder used for deposition. Thanks to nanophase structure, with an appropriate balance of hard and soft phases, the SCGS coatings exhibited better tribological properties than that of the examined benchmark materials.

PL

Naukowym i technologicznym celem badań było wytworzenie nanostrukturalnych powłok FeCuAl-Al2O3 o grubości ok. 100 μm. Nanoproszki charakteryzujące się strukturą krystaliczną i równomiernym rozmieszczeniem składników otrzymywano, stosując wysokoenergetyczną syntezę mechaniczną. Proszek o strukturze nanokrystalicznej był nanoszony na podłoże bez istotnych zmian jego struktury i właściwości. Wykorzystano nową technologię naddźwiękowego natryskiwania zimnym gazem (SCGS) pozwalającą uzyskiwać powłoki o dużej gęstości. Mikrostrukturę oraz skład chemiczny nanoproszków i nanoszonych powłok analizowano, wykorzystując mikroskopię świetlną, TEM/HRTEM, STEM, SEM/EDS oraz XRD. Ponadto mierzono twardość, moduł Younga, współczynnik tarcia oraz odporność na ścieranie powłok. Przeprowadzone badania wykazały, że mikrostruktura powłok odpowiada strukturze nanoszonych proszków. Dzięki nanostrukturalnej budowie powłok, właściwej proporcji faz twardych i miękkich, natryskiwane zimnym gazem powłoki wykazują lepsze własności tribologiczne od materiału porównawczego.