Wyniki wyszukiwania - Biblioteka Nauki

1

Computer Aided Quantitative Analysis of Advanced Ceramic Materials

100%

Górny G. , Rączka M.

|

1999

|

tom Vol. 47, nr 4

335-352

EN

The paper presents the results of the computer aided quantitative analysis of the three groups of the ceramic composites: [formulas]. The methods of visualization and processing were elaborated and the representative microstructural characteristics for these materials have been thus obtained. The relationship between the microstructure and parameters of synthesis can be thus studied.

2

Effects of B4C addition on the microstructural and thermal properties of hot pressed SiC ceramic matrix composites

84%

Keceli Z. , Ogunc H. , Gokce H. , Addemir O. , Ovecoglu M. L. , Boyraz T.

|

2008

|

tom Vol. 29, nr 1-2

41-49

EN

Ceramic matrix composite (CMC) material systems are receiving a great interest to be used and provides unique properties for aircraft and land-based turbine engines, defence applications, rocket motors, aerospace hot structures and industrial applications. Boron carbide (B4C)-silicon carbide (SiC) ceramic composites are very promising armor materials because they are intrinsically very hard. Advanced SiC-based armor is desired such that the projectile is completely defetaed without penetrating the ceramic armor. The effect of B4C addition on microstructural and thermal properties of the SiC-B4C powder composites were investigated after high energy milling and hot pressing. SiC powders containing 5wt%, 10wt%, 15wt% B4C were mechanically alloyed in a high energy ball mill for 8 h. Microstructural characterization investigations (SEM, XRD) were carried out on mechanically alloyed SiC powder composites containing 5 wt%, 10 wt%, 15 wt% B4C powders and on these powder composites sintered in vacuum at 50 MPa at 2100 degree C. The thermal properties were characterized using DTA, TGA and dilatometer. The results were evaluated.

3

Kinetyka spiekania węglików diamentopodobnych

84%

Gubernat A.

|

2011

|

tom T. 63, nr 4

743-751

PL

Spiekanie swobodne węglików diamentopodobnych, węglika krzemu i węglika boru, wymaga stosowania dodatków aktywujących procesy zagęszczania. W przypadku węglika krzemu dodatkami były węgiel i bor, a w przypadku węglika boru tylko węgiel. Badania nad kinetyką spiekania przeprowadzono w dylatometrze wysokotemperaturowym w atmosferze ochronnej z postępem temperatury równym 15°C/min oraz w warunkach izotermicznych. Analizę uzyskanych wyników dokonano w oparciu o modele Frenkla i Kuczyńskiego. Uzyskane wyniki pozwoliły na pełne scharakteryzowanie procesu spiekania obu węglików oraz na określenie dominujących mechanizmów transportu masy.

EN

In this work, sintering kinetics of SiC and B4C was studied. Sintering of these diamond-like carbides requires activation of the densification process. Small amounts of carbon and boron were used as additives for the activation of silicon carbide sintering. Only carbon was used for the sintering activation of B4C. Measurements of sintering kinetics were made by means of a high temperature dilatometer. Sintering shrinkage as a function of time was recorded under isothermal conditions. An analysis of the sintering kinetics was based on sintering models worked out by Kuczynski and Frenkel. The results of investigations allowed full sintering characteristics of the studied diamond-like carbides to be obtained.

4

Analysis of the structure of castings made from chromium white cast iron resistant to abrasive wear

84%

Kopyciński D.

|

2009

|

tom Vol. 9, iss. 4

109-112

EN

It has been proved that an addition of boron carbide and disintegrated steel scrap introduced as an inoculant to the chromium white cast iron changes the structure of castings. The said operation increases the number of crystallization nuclei for dendrites of the primary austenite. In this case, the iron particles act as substrates for the nucleation of primary austenite due to a similar crystallographic lattice. The more numerous are the dendrites of primary austenite and the structure more refined and the mechanical properties higher. Castings after B4C inoculation revealed a different structure of fine grained fracture. Primary precipitates of chromium carbide also appeared, reducing the mechanical properties of as-cast parts. Properly established heat treatment regime makes chromium iron castings regain their, originally high, mechanical properties.

5

Effect of boron carbide on primary crystallization of chromium cast iron

84%

Studnicki A.

|

2008

|

tom Vol. 8, iss. 1

173-176

EN

In the paper results of the influence of boron carbide (B4C) as inoculant of abrasion-resisting chromium cast iron (about 2,8% carbon and 18% chromium) on primary crystallization researches are presented. Boron carbide dispersion was introduced at the bottom of pouring ladle before tap of liquid cast iron. In this investigations were used three different quantities of inoculant in amounts 0,1%; 0,2% and 0,3% with relation to bath weight. It has been demonstrated that such small additions of boron carbide change primary crystallization parameters, particularly temperature characteristic of process, their time and kinetics.

6

Inoculation of chromium white cast iron

67%

Kopyciński D.

|

2009

|

tom Vol. 9, iss. 1

191-194

EN

It has been proved that an addition of boron carbide introduced as an inoculant to the chromium white cast iron changes the structure of castings. Castings after inoculation revealed a different structure with numerous grains. Primary precipitates of chromium carbide also appeared, reducing the mechanical properties of as-cast parts. Properly established heat treatment regime makes chromium iron castings regain their, originally high, mechanical properties.

7

Mechanical properties of hot-pressed boron carbide materials

67%

Rutkowski P.

|

2013

|

tom R. 13, nr 1

33-39

EN

In the paper, a research study is presented that was carried out for the purpose of obtaining composite materials based on a commercial micron boron carbide. A hot pressing process was performed to produce all the necessary materials. Chromium carbides, chromium silicides, and chromium boride were used as sintering activators, and as the phases generating thermal stresses (to improve fracture toughness). Some additives were introduced, their amounts not exceeding 5% of the total volume of the sample. In the case where large amounts of the introduced phases were applied, the sintering temperature was reduced by 120°C as regards the boron carbide sintered with carbon. The phase composition and the structure of the sinters produced were analyzed. The microstructure of polished and chemically etched (in molten salts) samples was investigated using scanning electron microscopy. The elastic properties, hardness, bending strength, and fracture toughness of the products were also determined.

PL

Przeprowadzone w niniejszej pracy badania dotyczą otrzymywania tworzyw kompozytowych na bazie mikronowego komercyjnego węglika boru. Tworzywa otrzymane zostały w procesie prasowania na gorąco. Jako aktywatory spiekania, a zarazem faz generujących naprężenia cieplne w celu podniesienia odporności na kruche pękanie wykorzystano węglik chromu, krzemki chromu oraz borek chromu. Dodatki wprowadzano w ilościach do 5% obj. W przypadku użycia dużych ilości wprowadzonych faz obniżono temperaturę spiekania o 120°C w stosunku do węglika boru spiekanego z dodatkiem węgla. Wytworzone spieki poddano analizie fazowej oraz strukturalnej. Na wypolerowanych i wytrawionych chemicznie (w stopionych solach) próbkach tworzyw dokonano obserwacji mikrostrukturalnych metodą skaningowej mikroskopii elektronowej. Materiał poddano również badaniom w celu wyznaczenia właściwości sprężystych, twardości, wytrzymałości na zginanie oraz odporności na kruche pękanie.