Hot Press Sintering and Superplastic Forming of Fine-Grained Si3N4-Si2N2O Composites

2006 ◽  
Vol 532-533 ◽  
pp. 25-28 ◽  
Author(s):  
Qing Zhang ◽  
Jun Ting Luo ◽  
Kai Feng Zhang
Keyword(s):  
Grain Size ◽  
Complex Shape ◽  
Sintering Temperature ◽  
Superplastic Forming ◽  
Hot Press ◽  
Fine Grained ◽  
Sinter Forging ◽  
Average Grain Size ◽  
Hot Press Sintering

Si3N4- Si2N2O composites were fabricated with amorphous nano-sized silicon nitride powders by the hot press sintering(HPS). The Si2N2O phase was generated by an in-situ reaction 2Si3N4(s)+1.5O2(g)=3Si2N2O(s)+N2(g). The content of Si2N2O phase up to 60% was accepted when the sintering temperature was 1650°C and decreased whether the sintering temperature was increased or not, which indicated that the reaction was reversible. The mass loss, relative density and average grain size increased with raising of sintering temperature. The average grain size was less than 500nm if the sintering temperature was below 1700°C. The sintered body crystaled completely at 1600°C . The microstructure crystaled in 1600°C indicated that most of the grain size was in 150-250nm. The aspect ratio of some grains reached 1.5. The superplastic deep-drawing forming could be undertaken at 1550°C with a forming velocity of 0.2mm/min. The complex-shape gears could be formed by a sinter-forging technology when the sintering temperature was 1600°C and the superplastic forging temperature was 1550°C.

Superplastic Sinter-Forging of Fine-Grained Si3N4-Si2N2O Composite at Low Temperature

2007 ◽  
Vol 551-552 ◽  
pp. 487-490 ◽  
Author(s):  
Jun Ting Luo ◽  
Qing Zhang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Complex Shape ◽  
Sintering Temperature ◽  
Xrd Analysis ◽  
Liquid Phase Sintering ◽  
Sintered Body ◽  
Fine Grained ◽  
Sinter Forging ◽  
Average Grain Size

The Si3N4- Si2N2O composites are fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering (LPS) method. XRD analysis shows sintered body consists of β-Si3N4 and Si2N2O. SEM experiment conforms that the average grain size of sintered body is less than 300nm. The complex-shape gears can be formed by a sinter-forging technology when the sintering temperature is 1600°C and the superplastic forging temperature is only 1550°C. Rod-shaped grains aligned along the perpendicular direction of pressure and the mechanical properties increase about 10% after the materials were forged.

Superplasticity and Sinter-Forging of Fine-Grained Si3N4-Si2N2O Composite

2005 ◽  
Vol 475-479 ◽  
pp. 2987-2990 ◽  
Author(s):  
Jun Ting Luo ◽  
Kai Feng Zhang ◽  
Guo Feng Wang ◽  
Wen Bo Han
Keyword(s):  
Grain Size ◽  
Complex Shape ◽  
Sintering Temperature ◽  
Xrd Analysis ◽  
Liquid Phase Sintering ◽  
Sintered Body ◽  
Fine Grained ◽  
Sinter Forging ◽  
Average Grain Size ◽  
Cavitation Failure

The Si3N4- Si2N2O composites are fabricated with amorphous nano-sized silicon nitride powders by the liquid phase sintering(LPS) method in this article. XRD analysis shows that the sintered body consists of β-Si3N4 and Si2N2O. SEM experiment conforms that the average grain size of sintered body is less than 300nm. The superplastic deep-drawing forming can be proceed at a low temperature of 1550°C with a forming velocity of 0.2mm/min. There are only a few small sintered defects before forming, but there are a lot of cavity groups after forming. Cavitation failure occurs by nucleation, growth and interlinkage of cavities. The complex-shape gears can be formed by a sinter-forging technology when the sintering temperature is 1600°C and the superplastic forging temperature is 1550°C.

Hot Press Sintering Behavior of Nano-Sized AlN Powders

2010 ◽  
Vol 105-106 ◽  
pp. 720-722
Author(s):  
Hong Bo Li ◽  
Jun Ting Luo ◽  
Yong Fei Gu ◽  
Yan Xia Xu
Keyword(s):  
Grain Size ◽  
Relative Density ◽  
Elevated Temperatures ◽  
Sintering Temperature ◽  
Hexagonal Wurtzite Structure ◽  
Sintering Behavior ◽  
Mechanical Resistance ◽  
Hot Press ◽  
Average Grain Size ◽  
Hot Press Sintering

Aluminum nitride (AlN) is a stoichiometric compound with the hexagonal wurtzite structure. AlN has excellent thermal conductivity and good properties as electronic insulator. It displays good mechanical resistance up to elevated temperatures and is resistant against corrosion by molten metals. Bulk AlN may therefore be used as a refractory structural material as well as a substrate for high power microelectronic devices. However, it is very difficult for sintering high-density AlN at lower temperature than 1800°C. Nano-sized AlN powders were sintered by hot press sintering at low temperature of 1500~1700°C and mechanical properties were investigated. β-AlN and β-Al2O3 were detected when the sintering temperature is 1600°C. The phase transition β-AlN to α-AlN was discovered at a 1700°C sintering temperature. Relative density and average grain size were increasing with the increasing of sintering temperature, and fracture form is intercrystalline crack in 1500°C and transcrystalline crack in 1700°C. 97.3% relative density and 850nm average grain size were deserved at 1700°C.

scholarly journals Effect of Sintering Temperature on Microstructure and Mechanical Properties of Hot-Pressed Fe/FeAl2O4 Composite

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 422
Author(s):  
Kuai Zhang ◽  
Yungang Li ◽  
Hongyan Yan ◽  
Chuang Wang ◽  
Hui Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
Sintering Temperature ◽  
Raw Materials ◽  
Hot Press ◽  
Microstructure And Mechanical Properties ◽  
Powder Particles ◽  
Hot Press Sintering ◽  
Sintering Method

An Fe/FeAl2O4 composite was prepared with Fe-Fe2O3-Al2O3 powder by a hot press sintering method. The mass ratio was 6:1:2, sintering pressure was 30 MPa, and holding time was 120 min. The raw materials for the powder particles were respectively 1 µm (Fe), 0.5 µm (Fe2O3), and 1 µm (Al2O3) in diameter. The effect of sintering temperature on the microstructure and mechanical properties of Fe/FeAl2O4 composite was studied. The results showed that Fe/FeAl2O4 composite was formed by in situ reaction at 1300 °C–1500 °C. With the increased sintering temperature, the microstructure and mechanical properties of the Fe/FeAl2O4 composite showed a change law that initially became better and then became worse. The best microstructure and optimal mechanical properties were obtained at 1400 °C. At this temperature, the grain size of Fe and FeAl2O4 phases in Fe/FeAl2O4 composite was uniform, the relative density was 96.7%, and the Vickers hardness and bending strength were 1.88 GPa and 280.0 MPa, respectively. The wettability between Fe and FeAl2O4 was enhanced with increased sintering temperature. And then the densification process was accelerated. Finally, the microstructure and mechanical properties of the Fe/FeAl2O4 composite were improved.

Nanopowder and Fine-Grained Ceramics for Multilayer PTCR Elements

2008 ◽  
Vol 368-372 ◽  
pp. 453-455 ◽  
Author(s):  
Jun Zhao ◽  
Shu Ping Gong ◽  
Chun Fang Cheng ◽  
Zhi Ping Zheng ◽  
Huan Liu ◽  
...  
Keyword(s):  
Grain Size ◽  
Sintering Temperature ◽  
Boundary Effect ◽  
Sol Gel ◽  
Tape Casting ◽  
Casting Technique ◽  
Fine Grained ◽  
Average Grain Size ◽  
Sol Gel Process ◽  
Different Temperatures

BaTiO3 nanopowders prepared by sol-gel process were used for multilayer PTCR ceramics in order to utilize grain boundary effect and lower sintering temperature. The precursor gel was calcined at different temperatures and the powders were characterized by XRD and TEM. The average grain size was about 26nm when calcined at 800°C for 2h. Effects of acceptor/donor concentration and sintering temperature on PTCR ceramics were also investigated. The optimal concentration of the donor was found to be 0.6mol with the acceptor concentration being 1/8 of the donor. Multilayer PTCR elements were fabricated by tape-casting technique. The jump ratio of PTCR chips sintered at 1240°C was above 103 with the average grain size smaller than 1~2 μm, which is suitable for the multilayer PTCR elements.

scholarly journals C0.3N0.7Ti-SiC Toughed Silicon Nitride Hybrids with Non-Oxide Additives Ti3SiC2

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1428
Author(s):  
Heng Luo ◽  
Chen Li ◽  
Lianwen Deng ◽  
Yang Li ◽  
Peng Xiao ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Silicon Nitride ◽  
Flexural Strength ◽  
Mechanical Performance ◽  
Sintering Temperature ◽  
Hot Press ◽  
Pull Out ◽  
Hot Press Sintering ◽  
Si3n4 Ceramics

In situ grown C0.3N0.7Ti and SiC, which derived from non-oxide additives Ti3SiC2, are proposed to densify silicon nitride (Si3N4) ceramics with enhanced mechanical performance via hot-press sintering. Remarkable increase of density from 79.20% to 95.48% could be achieved for Si3N4 ceramics with 5 vol.% Ti3SiC2 when sintered at 1600 °C. As expected, higher sintering temperature 1700 °C could further promote densification of Si3N4 ceramics filled with Ti3SiC2. The capillarity of decomposed Si from Ti3SiC2, and in situ reaction between nonstoichiometric TiCx and Si3N4 were believed to be responsible for densification of Si3N4 ceramics. An obvious enhancement of flexural strength and fracture toughness for Si3N4 with x vol.% Ti3SiC2 (x = 1~20) ceramics was observed. The maximum flexural strength of 795 MPa for Si3N4 composites with 5 vol.% Ti3SiC2 and maximum fracture toughness of 6.97 MPa·m1/2 for Si3N4 composites with 20 vol.% Ti3SiC2 are achieved via hot-press sintering at 1700 °C. Pull out of elongated Si3N4 grains, crack bridging, crack branching and crack deflection were demonstrated to dominate enhance fracture toughness of Si3N4 composites.

Liquid Phase Sintering Behavior of Amorphous Nano-Sized Silicon Nitride Powders

2007 ◽  
Vol 336-338 ◽  
pp. 1069-1071 ◽  
Author(s):  
H.B. Li ◽  
Jun Ting Luo ◽  
Kai Feng Zhang
Keyword(s):  
Grain Size ◽  
Silicon Nitride ◽  
Liquid Phase ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
Sintering Behavior ◽  
Average Grain Size ◽  
Sintering Method ◽  
Amorphous Si3n4

The amorphous nano-sized silicon nitride powders were sintered by liquid phase sintering method. Si3N4-Si2N2O composites were in-situ fabricated. The Si2N2O phase was generated by an in-situ reaction 2Si3N4(s)+1.5O2(g)=3Si2N2O(s)+N2(g). The content of Si2N2O phase up to 60% was obtained at a sintering temperature of 1650°C and reduced when the sintering temperature increased or decreased, which indicates that the reaction is reversible. The mass loss, relative density and average grain size increase with increasing of sintering temperature. The average grain size is less than 500nm when the sintering temperature is below 1700°C. During the sintering procedure, there is a complex crystallization and phase transition: amorphous Si3N4 → equiaxial α-Si3N4→ equiaxial β-Si3N4 → rod-likeSi2N2O → needle-like β-Si3N4. Small round-shaped β-Si3N4 particles are entrapped in the Si2N2O grains and a high density of staking faults are situated in the middle of Si2N2O grains at a sintering temperature of 1650°C.

scholarly journals Effect of Vanadium Reinforcement on the Microstructure and Mechanical Properties of Magnesium Matrix Composites

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 806
Author(s):  
Liqing Sun ◽  
Shuai Sun ◽  
Haiping Zhou ◽  
Hongbin Zhang ◽  
Gang Wang ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Refinement ◽  
Milling Process ◽  
Mg Alloy ◽  
Matrix Composites ◽  
Magnesium Matrix Composites ◽  
Pinning Effect ◽  
Average Grain Size ◽  
The Matrix ◽  
Hot Press Sintering

In this work, vanadium particles (VP) were utilized as a novel reinforcement of AZ31 magnesium (Mg) alloy. The nanocrystalline (NC) AZ31–VP composites were prepared via mechanical milling (MM) and vacuum hot-press sintering. During the milling process, the presence of VP contributed to the cold welding and fracture mechanism, resulting in the acceleration of the milling process. Additionally, increasing the VP content accelerated the grain refinement of the matrix during the milling process. After milling for 90 h, the average grain size of AZ31-X wt % Vp (X = 5, 7.5, 10) was refined to only about 23 nm, 19 nm and 16 nm, respectively. In the meantime, VP was refined to sub-micron scale and distributed uniformly in the matrix, exhibiting excellent interfacial bonding with the matrix. After the sintering process, the average grain size of AZ31-X wt % VP (X = 5, 7.5, 10) composites still remained at the NC scale, which was mainly caused by the pinning effect of VP. Besides that, the porosity of the sintered composites was no more than 7.8%, indicating a good densification effect. As a result, there was little difference between the theoretical and real density. Compared to as-cast AZ31 Mg alloy, the microhardness of sintered AZ31-X wt % VP (X = 5, 7.5, 10) composites increased by 65%, 87% and 96%, respectively, owing to the strengthening mechanisms of grain refinement strengthening, Orowan strengthening and load-bearing effects.

Effects of MgO and Y2O3 on the Microstructure and Mechanical Properties of Al2O3 Ceramics

2013 ◽  
Vol 589-590 ◽  
pp. 572-577 ◽  
Author(s):  
Hua He Liu ◽  
Han Lian Liu ◽  
Chuan Zhen Huang ◽  
Bin Zou ◽  
Ya Cong Chai
Keyword(s):  
Mechanical Properties ◽  
Sintering Temperature ◽  
Hot Press ◽  
Composite Ceramics ◽  
Microstructure And Mechanical Properties ◽  
Suitable Amount ◽  
Hot Press Sintering ◽  
Grains Refinement ◽  
Better Than

Al2O3-MgO, Al2O3-Y2O3 and Al2O3-MgO-Y2O3 composite ceramics were fabricated respectively by hot-press sintering technique. With the analysis of the mechanical properties and microstructure, it was found that single additive MgO could be more favorable to the grains’ refinement and densification than Y2O3; the composite additive including both MgO and Y2O3 was better than single additive MgO or Y2O3, because their interactions could improve the mechanical properties of the Al2O3 ceramics; The sintering temperature could be reduced by adding the suitable amount of composite additives.

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