Improvement of grain size and crystallization degree of LPSed h-BN composite ceramics by amorphization/nanocrystallization of raw h-BN powders

Pb(Zr0.52Ti0.48)O3was coated on the surface of CaCu3Ti4O12particles that prepared using sol-gel method. Then the composite particles were sintered into composite ceramics using cold press with the two different pressures and pressing time to achieve sufficient higher relative density after sintering. Afterward, the composite particles were sintered into composite ceramics with various sintering time at the same temperature to reach smaller grain size and higher relative density. The results show that the ceramics are composed of Pb(Zr0.52Ti0.48)O3and CaCu3Ti4O12phases, and Pb(Zr0.52Ti0.48)O3phase is mainly exist at the grain boundary even the composite particles sintered for 2h before pellet making. The results exhibit when density of CaCu3Ti4O12/Pb(Zr0.52Ti0.48)O3composite ceramic is kept in higher level using this simple technology, not only The dissipation loss in these giant-dielectric constant materials was reduced to a considerable level of practical applications but also dielectric constant enhance to very high level in the large frequency range. The results show that the improvement of the dielectric loss and dielectric constant enhancing mainly comes from the increase in the density of the CaCu3Ti4O12/Pb(Zr0.52Ti0.48)O3composite ceramics using suitable pressure in cold press, suitable short sintering time that lead to smaller grain size and sufficient grain boundary.

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Grain size effects on dielectric properties of barium strontium titanate composite ceramics

Materials Research Bulletin ◽

10.1016/j.materresbull.2012.11.085 ◽

2013 ◽

Vol 48 (3) ◽

pp. 973-977 ◽

Cited By ~ 22

Author(s):

Qiwei Zhang ◽

Jiwei Zhai ◽

Bo Shen ◽

Haijun Zhang ◽

Xi Yao

Keyword(s):

Grain Size ◽

Dielectric Properties ◽

Strontium Titanate ◽

Barium Strontium Titanate ◽

Size Effects ◽

Composite Ceramics ◽

Barium Strontium ◽

Grain Size Effects

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Different Radiation Tolerances of Ultrafine-Grained Zirconia–Magnesia Composite Ceramics with Different Grain Sizes

Materials ◽

10.3390/ma12172649 ◽

2019 ◽

Vol 12 (17) ◽

pp. 2649

Author(s):

Wenjing Qin ◽

Mengqing Hong ◽

Yongqiang Wang ◽

Jun Tang ◽

Guangxu Cai ◽

...

Keyword(s):

Grain Size ◽

Ion Irradiation ◽

Composite Ceramic ◽

Heavy Ion ◽

Composite Ceramics ◽

Displacement Damage ◽

Inert Matrix ◽

Grain Sizes ◽

Ultrafine Grained ◽

Nuclear Systems

Developing high-radiation-tolerant inert matrix fuel (IMF) with a long lifetime is important for advanced fission nuclear systems. In this work, we combined zirconia (ZrO2) with magnesia (MgO) to form ultrafine-grained ZrO2–MgO composite ceramics. On the one hand, the formation of phase interfaces can stabilize the structure of ZrO2 as well as inhibiting excessive coarsening of grains. On the other hand, the grain refinement of the composite ceramics can increase the defect sinks. Two kinds of composite ceramics with different grain sizes were prepared by spark plasma sintering (SPS), and their radiation damage behaviors were evaluated by helium (He) and xenon (Xe) ion irradiation. It was found that these dual-phase composite ceramics had better radiation tolerance than the pure yttria-stabilized ZrO2 (YSZ) and MgO. Regarding He+ ion irradiation with low displacement damage, the ZrO2–MgO composite ceramic with smaller grain size had a better ability to manage He bubbles than the composite ceramic with larger grain size. However, the ZrO2–MgO composite ceramic with a larger grain size could withstand higher displacement damage in the phase transformation under heavy ion irradiation. Therefore, the balance in managing He bubbles and phase stability should be considered in choosing suitable grain sizes.

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Innovative architectures in ferroelectric multi-materials: Chemistry, interfaces and strain

Journal of Advanced Dielectrics ◽

10.1142/s2010135x15300017 ◽

2015 ◽

Vol 05 (02) ◽

pp. 1530001 ◽

Cited By ~ 7

Author(s):

C. Elissalde ◽

U.-C. Chung ◽

G. Philippot ◽

J. Lesseur ◽

R. Berthelot ◽

...

Keyword(s):

Grain Size ◽

Spark Plasma Sintering ◽

Materials Chemistry ◽

Composite Ceramics ◽

Strain Effects ◽

Great Opportunity ◽

Plasma Sintering ◽

Spark Plasma

Breakthroughs can be expected in multi-component ceramics by adjusting the phase assembly and the micro–nanostructure. Controlling the architecture of multi-materials at different scales is still challenging and provides a great opportunity to broaden the range of functionalities in the field of ferroelectric-based ceramics. We used the potentialities of Spark Plasma Sintering (SPS) to control a number of key parameters regarding the properties: anisotropy, interfaces, grain size and strain effects. The flexibility of the wet and supercritical chemistry routes associated with the versatility of SPS allowed designing new ferroelectric composite ceramics at different scales. These approaches are illustrated through various examples based on our work on ferroelectric/dielectric composites.

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Fabrication and Surface Hardening Properties for SiC/AlN Ceramic Composites with Different SiC Grain Size

Materials Science Forum ◽

10.4028/www.scientific.net/msf.724.143 ◽

2012 ◽

Vol 724 ◽

pp. 143-146 ◽

Cited By ~ 1

Author(s):

Hai Yun Jin ◽

Zhen Huang ◽

Bo He ◽

Nai Kui Gao ◽

Liang Shao ◽

...

Keyword(s):

Grain Size ◽

Bending Strength ◽

Ceramic Composites ◽

Treatment Temperature ◽

Composite Ceramics ◽

Size Change ◽

Hardening Treatment ◽

Change Tendency ◽

Plasma Activated Sintering ◽

Sic Particle

In this research, the SiC/Al/h-BN composite ceramics with different SiC grain size were fabricated by the method of preparing the machinable pre-sintered body through Plasma Activated Sintering (PAS), which has the advantage of complex shape formation for precision parts. By hardening treatment, the SiC/Al/h-BN composite ceramics would be changed to SiC/AlN composites, and the relatively higher hardness and mechanical properties could be obtained accordingly. The phase transformation and microstructure were observed and the mechanical and other properties were also measured. The results showed that, for different matrix SiC particle size, change tendency of the bending strength was different with the heat treatment temperature change. And the bending strength of composites with larger SiC grain size was higher than that with smaller SiC grain size.

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High-Toughness Tetragonal Zirconia/Alumina Nano-Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.317-318.615 ◽

2006 ◽

Vol 317-318 ◽

pp. 615-618 ◽

Cited By ~ 1

Author(s):

Oleg Vasylkiv ◽

Yoshio Sakka ◽

Valeriy Skorokhod

Keyword(s):

Fracture Toughness ◽

Grain Size ◽

Tetragonal Zirconia ◽

Low Temperature Sintering ◽

Tetragonal Zro2 ◽

Composite Ceramics ◽

Nano Composite ◽

High Toughness ◽

Average Grain Size ◽

Alumina Composites

The 0.75 to 3 mol% Y2O3-stabilized tetragonal ZrO2 and Al2O3/Y-TZP nano-composite ceramics with 0.2 to 0.7 wt% of alumina were produced by a colloidal technique and low-temperature sintering. The influence of the resulting density, microstructure, the yttria-stabilizer and the alumina content on toughness was determined. The bulk 2.7Y-TZP ceramic with an average grain size of 110 nm reached fracture toughness of 11.2 MPa·m1/2. A nano-grained alumina/zirconia composite with an average grain size of 92 nm was obtained. Y-TZP ceramics with a reduced yttria-stabilizer content were shown to reach fracture toughness of 13.8 MPa·m1/2 (2Y-TZP), and 14.5 MPa·m1/2 (1.5Y-TZP). Y-TZP/alumina composites with 0.35 wt% of Al2O3 were shown to reach fracture toughness of 15.7 MPa·m1/2 (2Y), 15.3 MPa·m1/2 (1.5Y).

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Effect of SrO/BaO Ratio on the Phase Structure of the BSTN Composite Ceramics

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.280-283.111 ◽

2007 ◽

Vol 280-283 ◽

pp. 111-114 ◽

Cited By ~ 2

Author(s):

Zong Hui Zhou ◽

Pi Yi Du ◽

Gao Rong Han ◽

Wen Jian Weng

Keyword(s):

Grain Size ◽

Phase Structure ◽

Composite System ◽

Perovskite Phase ◽

Tungsten Bronze ◽

Composite Ceramics ◽

Crystal Lattices ◽

Average Grain Size

The effect of SrO/BaO ratio on the phase structure of the (1-x)BaO.xSrO.0.7TiO2.0.3Nb2O5 composite ceramics was investigated by XRD and SEM. The results showed that the SrO/BaO ratio increased in the perovskite phase and kept almost constant in the tungsten bronze phase as the content of SrO increased in the composite system. The constant SrO/BaO ratio in the tungsten bronze phase was about 0.667. The crystal lattices of the perovskite phase in the composite system were larger and smaller respectively than that in pure (1-x)BaO.xSrO.TiO2 system when SrO/BaO ratio were respectively <0.667 and >0.667. The crystal lattices of the perovskite phases in both systems showed the same crystal lattices when SrO/BaO = 0.667. Affected by the SrO/BaO ratio required in the tungsten bronze phase in composite system, the contents and average grain size of the perovskite phase decreased, while the content of tungsten bronze phase increased as the SrO/BaO ratio increased.

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Spark Plasma Sintering and Characterization of Mixed h-BN Powders with Different Grain Sizes

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.281.414 ◽

2018 ◽

Vol 281 ◽

pp. 414-419

Author(s):

Feng Rui Zhai ◽

Min Lu ◽

Ke Shan ◽

Zhong Zhou Yi ◽

Zhi Peng Xie

Keyword(s):

Mechanical Properties ◽

Grain Size ◽

Boron Nitride ◽

Spark Plasma Sintering ◽

Hexagonal Boron Nitride ◽

Orientation Degree ◽

Plasma Sintering ◽

Spark Plasma ◽

Crystallization Degree

Mixtures of two grades of hexagonal boron nitride (h-BN) powder differing in their grain size and crystallinity were spark plasma sintering in a vacuum. The influences of the mixing ratio of h-BN powders on the densification, microstructure and mechanical properties were investigated in detail. The results show that the smaller grain size, the lower crystallization degree and the higher density and mechanical properties. While the orientation degree of flake h-BN grains can be greatly enhanced by using h-BN powder with larger particle size. As the increasing of nanometer h-BN powder adding amount, the relative density has the same “V” shape changing trends with mechanical properties. In addition, the orientation of boron nitride grains varied widely, and a nearly isotropic material was prepared from a mixture containing 90wt.% nanometer powder.

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