Control of calcium hexaluminate grain morphology in in-situ toughened ceramic composites

Fully dense samples of TiB2-TiCX and TiB2-TiCX/15SiC ceramic composites were fabricated by in-situ synthesis under hot isostatic pressing from TiH2, B4C and SiC powders. Their oxidized behaviors at different temperatures were tested. Optical micrograph studies and thermo-gravimetric analyses show that the highest effective temperature of oxidation resistance is 700°C for TiB2-TiCX, and 1100°C for TiB2-TiCX/15SiC. The weight gain of TiB2-TiCX/15SiC below 1100°C is quite low, and it rises up suddenly when the temperature reaches 1200°C. Thus, the highest effective temperature of oxidation resistance is 1100°C for TiB2-TiCX/15SiC. The oxidation dynamic curves of TiB2-TiCX/15SiC ceramics accord with the parabola’s law. The activation energy of TiB2-TiCx/15SiC (189.87kJ.mol-1) is higher than that of TiB2-TiCx (96.44kJ.mol-1). In the oxidation process of TiB2-TiCx/15SiC, TiB2 reacts with oxygen and generates TiO2 and B2O3 at first. A layer of whole homogeneous oxide film cannot be formed, in the mean time, the oxidation of TiC begins. When temperature goes up to 1000°C, TiC phase is totally oxidized. SiC is oxidized to SiO2 at about 900°C, Meanwhile, TiO2 forms denser film than B2O3, which grows and covers the surface of the material, and gives better property of oxidation resistance.

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Strengthening Effect of In-Situ Dispersed Hexagonal Boron Nitride in Ceramic Composites

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.317-318.163 ◽

2006 ◽

Vol 317-318 ◽

pp. 163-166

Author(s):

Guo Jun Zhang ◽

Hideki Kita ◽

Naoki Kondo ◽

Tatsuki Ohji

Keyword(s):

Grain Size ◽

Boron Nitride ◽

Hexagonal Boron Nitride ◽

High Strength ◽

Ceramic Composites ◽

Strengthening Effect ◽

Mechanical Shock ◽

Metallic Particles ◽

Reactive Hot Pressing

High strength particulate ceramic composites are in general reinforced by strong dispersoids, such as strong ceramic particles (SiC, TiB2, ZrO2, et al) and strong metallic particles (Mo, W, et al). In this work high strength ceramic composites with in-situ synthesized hexagonal boron nitride (h-BN) have been prepared and characterized. As an example, we manufactured mullite-BN composites by reactive hot pressing (RHP) using aluminum borates (9Al2O3·2B2O3 and 2Al2O3·B2O3) and silicon nitride as starting materials. The obtained material RHPed at 1800°C showed a strength of 540 MPa, which was 1.64 times higher than that of the monolithic mullite ceramics. TEM observation revealed that the composite had an isotropic microstructure with a fine mullite matrix grain size of less than 1 μm and a nano-sized h-BN platelets of about 200 nm in length and 60∼80 nm in thickness. The high strength was suggested to be from the reduced matrix grain size and the small toughening effect by the h-BN platelets. In addition, this kind of ceramic composite demonstrates low Young’s modulus that is beneficial to the thermal/mechanical shock resistance, and excellent machinability.

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Reaction behavior, microstructure and application in coating of in situ ZrC–ZrB2 ceramic composites powders from a Co–Zr–B4C system

Materials & Design (1980-2015) ◽

10.1016/j.matdes.2015.05.022 ◽

2015 ◽

Vol 81 ◽

pp. 65-72 ◽

Cited By ~ 10

Author(s):

Mengxian Zhang ◽

Binglin Zou ◽

Jiaying Xu ◽

Xiaolong Cai ◽

Ying Wang ◽

...

Keyword(s):

Ceramic Composites ◽

Reaction Behavior

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Intermetallic/Ceramic Composites Synthesized from Al–Ni–Ti Combustion with B4C Addition

Metals ◽

10.3390/met10070873 ◽

2020 ◽

Vol 10 (7) ◽

pp. 873

Author(s):

Chun-Liang Yeh ◽

Chih-Yao Ke

Keyword(s):

Combustion Velocity ◽

Ceramic Composites ◽

The Other ◽

X Ray Diffraction ◽

Temperature Synthesis ◽

Reaction Systems ◽

X Ray ◽

High Temperature Synthesis ◽

In Situ Formation

The fabrication of intermetallic/ceramic composites by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) was investigated in the Al–Ni–Ti system with the addition of B4C. Two reaction systems were employed: one was used to produce the composites of xNiAl–2TiB2–TiC with x = 2–7, and the other was used to synthesize yNi3Al–2TiB2–TiC with y = 2–7. The reaction mechanism of the Al–Ni–Ti system was strongly influenced by the presence of B4C. The reaction of B4C with Ti was highly exothermic, so the reaction temperature and combustion velocity decreased due to increasing levels of Ni and Al in the reactant mixture. The activation energies of Ea = 110.6 and 172.1 kJ/mol were obtained for the fabrication of NiAl- and Ni3Al-based composites, respectively, by the SHS reaction. The XRD (X-ray diffraction) analysis showed an in situ formation of intermetallic (NiAl and Ni3Al) and ceramic phases (TiB2 and TiC) and confirmed no reactions taking place between Ti and Al or Ni. The microstructure of the product revealed large NiAl and Ni3Al grains and small TiB2 and TiC particles. With the addition of TiB2 and TiC, the hardness of NiAl and Ni3Al was considerably increased and the toughness was also improved.

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