In situ alumina/aluminum titanate bulk ceramic composites prepared by SPS from different structured composite powders

The paper describes an investigation of Al2O3 samples and NiAl–Al2O3 composites consolidated by pulse plasma sintering (PPS). In the experiment, several methods were used to determine the properties and microstructure of the raw Al2O3 powder, NiAl–Al2O3 powder after mechanical alloying, and samples obtained via the PPS. The microstructural investigation of the alumina and composite properties involves scanning electron microscopy (SEM) analysis and X-ray diffraction (XRD). The relative densities were investigated with helium pycnometer and Archimedes method measurements. Microhardness analysis with fracture toughness (KIC) measures was applied to estimate the mechanical properties of the investigated materials. Using the PPS technique allows the production of bulk Al2O3 samples and intermetallic ceramic composites from the NiAl–Al2O3 system. To produce by PPS method the NiAl–Al2O3 bulk materials initially, the composite powder NiAl–Al2O3 was obtained by mechanical alloying. As initial powders, Ni, Al, and Al2O3 were used. After the PPS process, the final composite materials consist of two phases: Al2O3 located within the NiAl matrix. The intermetallic ceramic composites have relative densities: for composites with 10 wt.% Al2O3 97.9% and samples containing 20 wt.% Al2O3 close to 100%. The hardness of both composites is equal to 5.8 GPa. Moreover, after PPS consolidation, NiAl–Al2O3 composites were characterized by high plasticity. The presented results are promising for the subsequent study of consolidation composite NiAl–Al2O3 powder with various initial contributions of ceramics (Al2O3) and a mixture of intermetallic–ceramic composite powders with the addition of ceramics to fabricate composites with complex microstructures and properties. In composites with complex microstructures that belong to the new class of composites, in particular, the synergistic effect of various mechanisms of improving the fracture toughness will be operated.

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Oxidation Behaviors of TiB2-TiCX and TiB2-TiCX/15SiC Ceramics

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.105-106.179 ◽

2010 ◽

Vol 105-106 ◽

pp. 179-183 ◽

Cited By ~ 3

Author(s):

De Gui Zhu ◽

Hong Liang Sun ◽

Yu Shu Wang ◽

Liang Hui Wang

Keyword(s):

Oxidation Resistance ◽

Effective Temperature ◽

Hot Isostatic Pressing ◽

Ceramic Composites ◽

Optical Micrograph ◽

Different Temperatures ◽

The Mean ◽

Mean Time ◽

Oxidation Behaviors

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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Microstructure evolution and growth behavior of rod-shaped ZrB2 in situ preparation of ZrB2-SiC composite powders

Ceramics International ◽

10.1016/j.ceramint.2018.11.080 ◽

2019 ◽

Vol 45 (3) ◽

pp. 4016-4021 ◽

Cited By ~ 5

Author(s):

Yuehua Lin ◽

Jinghang Liu ◽

Shaolei Song ◽

Jingbo Liu ◽

Sajid Bashir ◽

...

Keyword(s):

Microstructure Evolution ◽

Growth Behavior ◽

Composite Powders ◽

In Situ Preparation

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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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