scholarly journals Improvement of mechanical properties of HfB2-based composites by incorporating in situ SiC reinforcement through pressureless sintering

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Ghadami ◽  
E. Taheri-Nassaj ◽  
H. R. Baharvandi ◽  
F. Ghadami
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Relative Density ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Vacuum Atmosphere ◽  
Sic Reinforcement ◽  
Microstructural Studies ◽  
Composite Samples

AbstractHfB2, Si, and activated carbon powders were selected to fabricate 0–30 vol% SiC reinforced HfB2-based composite. Pressureless sintering process was performed at 2050 °C for 4 h under a vacuum atmosphere. Microstructural studies revealed that in situ SiC reinforcement was formed and distributed in the composite according to the following reaction: Si + C = SiC. A maximum relative density of 98% was measured for the 20 vol% SiC containing HfB2 composite. Mechanical investigations showed that the hardness and the fracture toughness of these composites were increased and reached up to 21.2 GPa for HfB2-30 vol% SiC and 4.9 MPa.m1/2 for HfB2-20 vol% SiC, respectively. Results showed that alpha-SiC reinforcements were created jagged, irregular, and elongated in shape which were in situ formed between HfB2 grains and filled the porosities. Formation of alpha-SiC contributed to improving the relative density and mechanical properties of the composite samples. By increasing SiC content, an enhanced trend of thermal conductivity was observed as well as a reduced trend for electrical conductivity.

scholarly journals Effect of in situ VSi2 and SiC phases on the sintering behavior and the mechanical properties of HfB2-based composites

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Soheil Ghadami ◽  
Ehsan Taheri-Nassaj ◽  
Hamid Reza Baharvandi ◽  
Farzin Ghadami
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Vickers Hardness ◽  
Thermodynamic Calculations ◽  
Sintering Behavior ◽  
Pressureless Sintering ◽  
Vacuum Atmosphere ◽  
Second Phases ◽  
Microstructural Studies

Abstract In situ HfB2–SiC–VSi2 composite was fabricated by reactive pressureless sintering at the temperature of 2150 °C for 4 h under a vacuum atmosphere. In situ SiC and VSi2 reinforcements were formed using VC and Si powders as starting materials according to the following reaction: VC + 3Si = SiC + VSi2. Microstructural studies and thermodynamic calculations revealed that in situ VSi2 and SiC phases were mostly formed and homogeneously distributed in HfB2 skeleton. The results showed that the density of in situ HfB2–SiC–VSi2 composite was 98%. Besides, the mechanical properties of the composite were effectively enhanced by the formation of in situ second phases. The Vickers hardness and the fracture toughness of the composite reached 20.1 GPa and 5.8 MPa m−1/2, respectively.

Preparation and Characterization of SiC/MoSi2 Composites from Powder Resulting from a Mechanical-Assistant Combustion Synthesis Method

2010 ◽  
Vol 105-106 ◽  
pp. 70-74
Author(s):  
Jian Guang Xu ◽  
Hui Qiang Li ◽  
Hou An Zhang
Keyword(s):  
Mechanical Properties ◽  
Cyclic Oxidation ◽  
Room Temperature ◽  
Synthesis Method ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Oxidation Properties ◽  
Mosi2 Composite

SiC reinforced MoSi2 composites have been successfully prepared by pressureless sintering from mechanical-assistant combustion synthesized powders. The sintering temperatures and holding time were 1500°C~1650°C at a heating rate of 10K/min and 1 hour, respectively. The microstructure and mechanical properties of the as-sintered composites were investigated. SEM micrographs of SiC/MoSi2 composites showed that SiC particles were homogeneously distributed in MoSi2 matrix. The Vickers hardness, flexural strength and fracture toughness of the SiC/MoSi2 composites were up to 15.50GPa, 468.7MPa and 9.35MPa•m1/2, respectively. The morphologies of fractured surface of the composites revealed the mechanism to improve mechanical properties of MoSi2 matrix. At last, the cyclic oxidation behavior of the composites was discussed. The results of this work showed that in situ SiC/MoSi2 composite powder prepared by MASHS technique could be successfully sintered via pressureless sintering process and significant improvement of room temperature mechanical and anti-oxidation properties could be achieved.

The Preparation and Properties of Alumina Ceramics through a Two-Step Pressureless Sintering Process

2018 ◽  
Vol 922 ◽  
pp. 47-54
Author(s):  
Chang Suo Yuan ◽  
Zi Jing Wang ◽  
Qiang Zhi ◽  
Ya Ming Zhang ◽  
Xu Dong Wang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Relative Density ◽  
High Purity ◽  
Dominant Factor ◽  
Second Phase ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Alumina Ceramics ◽  
Soaking Time

In this paper, a high-dense alumina ceramics were prepared through the two-step pressureless sintering process with high-purity alumina powder as raw materials and high-purity MgO as sintering aids. The effects of the sintering temperature in the first-step (T1) and the soaking time (t) in the second sintering step (T2) on the density, microstructure and mechanical properties of the alumina ceramics were studied. The results indicated that the relative density increased with the increase of T1 temperature whereas it increased and then decreased with the increase of MgO content. Higher T1 temperature and extended soaking time caused larger grain size, which accompanied with the Ostwald ripening of the grain and led to non-uniformity of grain size distribution. The addition of MgO was beneficial to the decrease in grain size due to pinning effect of the second phase. For samples with shorter soaking time, sintering with higher T1 temperature led to better mechanical properties because of its high density. However, for the long soaking time, all samples after sintering at different T1 temperature were fully-densified, so the grain size become to the dominant factor of strength, thus samples with lower T1 temperature exhibited better mechanical properties due to the refinement grain. Excessive addition of MgO resulted in defects, by which the strength increased firstly and then decreased slightly with the increased MgO content. For the samples with 2.5wt.% MgO, the optimum condition for the two-step pressureless sintering was T1=1450°C and T2=1400°C for 20h, and the obtained sample achieved the relative density of 96% and the strength of 507±32MPa.

Influence of Ca2P2O7 on Sintering Ability, Mechanical Strength and Degradability of β-Ca3(PO4)2 Bioceramics

2007 ◽  
Vol 361-363 ◽  
pp. 23-26 ◽  
Author(s):  
Kai Li Lin ◽  
Lei Chen ◽  
Jiang Chang ◽  
Jian Xi Lu
Keyword(s):  
Mechanical Properties ◽  
Mechanical Strength ◽  
Relative Density ◽  
Dissolution Rate ◽  
Pressureless Sintering ◽  
Sintering Process

In the present study, Ca2P2O7-doped β-Ca3(PO4)2 bioceramics were fabricated by pressureless sintering process. The effect of Ca2P2O7 on the sintering ability, mechanical strength and degradability of the ceramics were investigated. The results showed that the Ca2P2O7 could apparently decrease the sintering ability and mechanical properties of β-Ca3(PO4)2. Moreover, the relative density and mechanical strength of the sintered samples decreased gradually with the increase of the Ca2P2O7 additive amount. However, the dissolution rate of the samples increased with the increase of the Ca2P2O7 additive amount.

MICROSTRUCTURE AND PROPERTIES OF SiC PARTICLES REINFORCED COPPER BASED ALLOY COMPOSITE

2013 ◽  
Vol 27 (19) ◽  
pp. 1341025 ◽  
Author(s):  
YU HONG ◽  
XIAOLI CHEN ◽  
WENFANG WANG ◽  
YUCHENG WU
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Electrical Conductivity ◽  
Relative Density ◽  
Volume Fraction ◽  
Copper Matrix ◽  
Matrix Composites ◽  
Wear Properties ◽  
Sic Particles ◽  
Copper Based Alloy

Copper-matrix composites reinforced with SiC particles are prepared by mechanical alloying. The microstructure characteristics, relative density, hardness, tensile strength, electrical conductivity, thermal conductivity and wear properties of the composites are investigated in this paper. The results indicate that the relative density, macro-hardness and mechanical properties of composites are improved by modifying the surface of SiC particles with Cu and Ni . The electrical conductivity and thermal conductivity of composites, however, are not obviously improved. For a given volume fraction of SiC , the Cu / SiC ( Ni ) has higher mechanical properties than Cu / SiC ( Cu ). The wear resistance of the composites are improved by the addition of SiC . The composites with optimized interface have lower wear rate.

scholarly journals Synthesis of "in situ" reinforced silicon nitride composites

2004 ◽  
Vol 69 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Aleksandra Vuckovic ◽  
Snezana Boskovic ◽  
Ljiljana Zivkovic
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Silicon Nitride ◽  
Pressureless Sintering ◽  
Sintering Additives ◽  
Sintering Time

The objective of this work was to investigate the effect of two different sintering additives (CeO2 and Y2O3 + Al2O3), sintering time and amount of ?-Si3N4 seeds on the densification, mechanical properties and microstructure of self-reinforced Si3N4 based composites obtained by pressureless sintering. Preparation of ?-Si3N4 seeds, also obtained by a pressureless sintering procedure, is described. Samples without seeds were prepared for comparison. The results imply that self-reinforced silicon nitride based composites with densities close to the theoretical values and with fracture toughness of 9.3MPa m1/2 can be obtained using a presureless sintering procedure.

Preparation and Characterization of In Situ Nanocomposites of Graphene Nanosheets/Polyurethane

2019 ◽  
Vol 814 ◽  
pp. 90-95 ◽  
Author(s):  
Guang Lei Lv ◽  
Yuan Yuan Li ◽  
Chen Fei ◽  
Zhi Hao Shan ◽  
Jing Gan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Tensile Strength ◽  
Graphene Nanosheets ◽  
Graphene Sheets ◽  
Microstructural Properties ◽  
Wear Performance ◽  
Polyurethane Composites

Graphene nanosheets/polyurethane (GNS/PU) was prepared in situ by polymerization technique for the manufacture of PU safety shoes soles. The graphene nanosheets/polyurethane composites were characterized for their mechanical properties, thermal conductivity and abrasion resistance, and comparison is made with those of the neat polyurethane. The microstructural properties of GNS/PU were characterized by SEM. The results show that with the increase of the amount of graphene within the range of weight-percentages analyzed, the tensile strength of the composites gradually increases. The tensile strength of the GNS/PU composites increased to 64.14 MPa with 2 wt% GNS, compared with 55.1 MPa for neat PU. When the graphene sheets reached 2 wt%, the abrasion volume reached 71 mm3. Compared with the pure PU, the wear performance of GNS/PU composites was significantly improved.

Elongated Grain Growth Mechanism of Alumina Ceramics with Additives

2010 ◽  
Vol 105-106 ◽  
pp. 844-847
Author(s):  
Yong Chang Zhu ◽  
Shou Fan Rong ◽  
Ji Wei Guo ◽  
Jun Gang Li
Keyword(s):  
Grain Growth ◽  
Growth Mechanism ◽  
Second Phase ◽  
Pressureless Sintering ◽  
Sintering Process ◽  
Alumina Ceramics ◽  
Effect Of Additives ◽  
Sintering Properties ◽  
Columnar Grain

The elongated grain evolution of alumina ceramics doping with Al2O3-CaO-SiO2(CAS), Nb2O5, and 3Y-TZP was studied under pressureless sintering. From in-situ growth elongated grain cooperating with second phase to toughen the alumina ceramics, microstructure and sintering properties were firstly studied systematically. The effect of additives on the alumina ceramics with columnar grain were analyzed by means of TEM, SEM, XRD, etc. Basing on the analyzed sintering process by the principle of dynamics, the elongated grain growth mechanism was further studied.

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