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

2012 ◽  
Vol 724 ◽  
pp. 143-146 ◽  
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.

Fabrication and Hardening Treatment for SiC/AlN Ceramic Composites

2009 ◽  
Vol 620-622 ◽  
pp. 363-366
Author(s):  
Hai Yun Jin ◽  
Ying Li ◽  
Xiang Ya Jia ◽  
Guan Jun Qiao
Keyword(s):  
Mechanical Properties ◽  
Bending Strength ◽  
High Hardness ◽  
Ceramic Composites ◽  
New Method ◽  
Composite Ceramics ◽  
Hardening Treatment ◽  
Sic Ceramic ◽  
Machinable Ceramic ◽  
Plasma Activated Sintering

In order to obtain machinable ceramic with high hardness and strong mechanical properties, the SiC/Al/h-BN Composite Ceramics were fabricated by a new method which prepared the machinable pre-sintered body by Plasma Activated Sintering (PAS) and increased it's mechanical properties after hardening treatment. The results showed that the machinability and density of the pre-sintered h-BN/Al/SiC ceramic composites were excellent, and after hardening treatment, the mechanical properties (hardness, bending strength and density) increased obviously.

Surface Hardening of BN-Al Ceramic Composites

2010 ◽  
Vol 105-106 ◽  
pp. 112-114
Author(s):  
Ying Li ◽  
Hai Yun Jin ◽  
Xiang Dong Wang ◽  
Guan Jun Qiao
Keyword(s):  
Surface Hardening ◽  
Complex Shape ◽  
Bending Strength ◽  
Ceramic Composites ◽  
Nitrogen Atmosphere ◽  
Nitriding Process ◽  
Vacuum Furnace ◽  
Hardening Treatment ◽  
Residual Al

Ceramic composites containing BN and Al can be machined easily into complex shape, the hardness of the composites can also be improved by surface hardening process of in situ reaction between Al and BN. However, the reaction of Al and BN is a volume reduced one and the porosity will increase during the hardening treatment.. In order to solve this problem, a surface nitriding process was developed. Put the pre-sintering samples (with designed shapes) into a vacuum furnace in nitrogen atmosphere and reheated to high-temperature, so that the residual Al after pre-sintering would react with N2 completely, and change to AlN which has higher hardness. The phase transformation and microstructure were observed and the mechanical and other properties were also measured. The results showed that the surface nitriding process could increase the hardness, bending strength and density obviously. The porosity decreased sharply compared with the general hardening treatment.

Effect of Sintering Pressure on Mechanical Properties of BN-Si3N4 Ceramic Composites Prepared by Spark Plasma Sintering

2016 ◽  
Vol 697 ◽  
pp. 188-192
Author(s):  
Jia Xin An ◽  
Wen Dong Xue ◽  
Feng Rui Zhai ◽  
Ruo Meng Xu ◽  
Jia Lin Sun
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Relative Density ◽  
Spark Plasma Sintering ◽  
Bending Strength ◽  
Raw Materials ◽  
Ceramic Composites ◽  
Composite Ceramics ◽  
Plasma Sintering ◽  
Spark Plasma

BN-Si3N4 composite ceramic wave-transparent materials with excellent mechanical properties were prepared by spark plasma sintering (SPS) using h-BN and α-Si3N4 powders as raw materials, Al2O3 and Y2O3 as sintering aids. The influence of sintering pressure on density and mechanical properties of BN-Si3N4 composite ceramics were studied. The phases were observed by X-ray diffraction (XRD), and the microstructures were identified by scanning electron microscopy (SEM). The results showed that with the sintering pressure increases, the relative density, bending strength and fracture toughness of the composite ceramics were significantly increased, and the porosity decreased rapidly. The effects of pressure on the properties of the composite ceramics was not significant at >40MPa, so 40MPa is optimal for the composite ceramics to gain good overall performance, i.e. the relative density was 89.1%, the porosity was 2.3%, the bending strength reached 215.4 MPa, and the fracture toughness was 3.1/MPa·m1/2.

Holocene sedimentation in the Hupo Trough of the southwestern East Sea (Japan Sea) and development of the East Korea Warm Current

The Holocene ◽  
2021 ◽  
pp. 095968362110032
Author(s):  
Boo-Keun Khim ◽  
Sunghan Kim ◽  
Yu-Hyeon Park ◽  
Jongmin Lee ◽  
Sangbeom Ha ◽  
...  
Keyword(s):  
Grain Size ◽  
Japan Sea ◽  
East Sea ◽  
Eastern Coast ◽  
Size Change ◽  
Sediment Properties ◽  
Warm Current ◽  
The Holocene ◽  
Mean Grain Size ◽  
East Korea Warm Current

Various sediment properties, such as mean grain size, total organic carbon, total nitrogen, C/N ratio, CaCO3, and biogenic opal content, were analyzed for a box core (BC02; 45 cm long) and a gravity core (GC02; 628 cm long), which were collected from the western margin of the Hupo Trough located off the eastern coast of Korea. The study area has been affected by the East Korea Warm Current (EKWC), a branch of the Tsushima Warm Current (TWC). The analytical results obtained for BC02 and the upper part of GC02 were in agreement, affirming the core-top preservation of GC02. Based on the corrected calibrated AMS 14C dates, the sedimentation rate of GC02 changed abruptly at ~8.2 ka from ~4.0–10.2 cm/kyr in the lower part to ~56.6–91.0 cm/kyr in the middle to upper part. This corresponds to the lithologic change from sandy mud to mud sediments showing the mean grain size change from 6.9 to 46.0 μm. Diverse paleoceanographic proxies representing the surface water condition exhibited varying degree of change at ~8.2 ka, after which all the properties remain almost unchanged, implying stable and continuous depositional conditions following the complete development of the EKWC. Furthermore, it indicated that the sediment depositional conditions in the Hupo Trough in response to the EKWC might have stabilized at ~8.2 ka since the opening of the Korea Strait during the Holocene sea level rise. Moreover, microfossil data from previous studies on the establishment of the TWC in the East Sea (Japan Sea) support our interpretation that the sediment properties revealed the Holocene development of the EKWC in the Hupo Trough.

A Study on The Phase Transformation and Exchange-Coupling of (Nd0 95La0 05)9 5FebalCo5Nb2B10.5 Nanocomposites

1999 ◽  
Vol 577 ◽  
Author(s):  
Q. Chen ◽  
B. M. Ma ◽  
B. Lu ◽  
M. Q. Huang ◽  
D. E. Laughlin
Keyword(s):  
Grain Size ◽  
Magnetic Properties ◽  
Phase Transformation ◽  
Thermal Treatment ◽  
Grain Growth ◽  
Exchange Coupling ◽  
Phase Distribution ◽  
Maximum Energy ◽  
Treatment Temperature ◽  
Phase Identification

ABSTRACTThe phase transformation and the exchange coupling in (Ndo095Lao005)9.5FebaICOsNb 2BI05 have been investigated. Nanocomposites were obtained by treating amorphous precursors at temperatures ranging from 650TC to 9500C for 10 minutes. The magnetic properties were characterized via the vibrating sample magnetometer (VSM). X-ray diffraction (XRD), thermomagnetic analysis (TMA), and transmission electron microscopy (TEM) were used to perform phase identification, measure grain size, and analyze phase distribution. The strength of the exchange coupling between the magnetically hard and soft phases in the corresponding nanocomposite was analyzed via the AM-versus-H plot. It was found that the remanence (Br), coercivity (Hci), and maximum energy product (BHmax) obtained were affected by the magnetic phases present as well as the grain size of constituent phases and their distribution. The optimal magnetic performance, BHm, occurred between 700°C to 750°C, where the crystallization has completed without excessive grain growth. TMA and TEM indicated that the system was composed of three phases at this point, Nd2(Fe Co) 14B, ca-Fe, and Fe3B. The exchange coupling interaction among these phases was consistently described via the AM-versus-H plot up to 750°C. The Br, Hci, and BHmax degraded severely when the thermal treatment temperature increased from 750°C. This degradation may be attributed to the grain growth of the main phases, from 45 to 68nm, and the development of precipitates, which grew from 5nm at 750°C to 12nm at 850°C. Moreover, the amount of the precipitates was found to increase with the thermal treatment temperatures. The precipitates, presumably borides, may cause a decrease in the amount of the a-Fe and Fe 3B and result in a redistribution of the Co in the nanocomposites. The increase of the Co content in the Nd 2(Fe Co) 14B may explain the increase of its Curie temperature with the thermal treatment temperatures. In this paper, we examine the impacts of these factors on the magnetic properties of (Ndo 95Lao 05)9 5FebaICosNb2B10.5 nanocomposite.

Machining and Wear of High-Alumina Ceramics for Structural Applications

2009 ◽  
Vol 409 ◽  
pp. 137-144 ◽  
Author(s):  
Stojana Veskovic-Bukudur ◽  
Tanja Leban ◽  
Milan Ambrozic ◽  
Tomaž Kosmač
Keyword(s):  
Grain Size ◽  
Wear Rate ◽  
Abrasive Wear ◽  
Direct Relationship ◽  
Bending Strength ◽  
High Alumina ◽  
Alumina Ceramics ◽  
Large Area ◽  
Structural Applications ◽  
Worn Surfaces

The wear resistances of four standard-grade high-alumina ceramics were evaluated and related to their machining ability. Three of the material grades contained 96% of alumina and 4% of either calcium silicate, or magnesium silicate, or manganese titanate in the starting-powder composition. The nominal alumina content in the fourth material was 99.7%. The specimens were fabricated using a low-pressure injection-molding forming technique, followed by thermal de-binding and sintering. After sintering the four materials differ significantly in their grain size, bending strength and Vickers hardness. No direct relationship between the microstructural parameters and the mechanical properties was found, but there was a grain-size dependence of the surface finish after grinding under industrial conditions. The two silicate-containing ceramics exhibited considerably higher wear resistances than the two silicate-free ceramics, but no direct relationship between the abrasive wear rate during grinding and the cutting time was observed. The cutting ability represents a valuable material characteristic for industrial practice, but it should not be directly used for predicting the wear rate during grinding. Quantitative differences in the cutting time and abrasive wear rate were manifested in the different topographies of the worn surfaces. Cutting resulted in relatively large area fractions of plastically deformed surfaces, whereas pullouts dominated the worn surfaces after grinding.

scholarly journals Influence of the Matrix Grain Size on the Apparent Density and Bending Strength of Sand Cores

2017 ◽  
Vol 17 (1) ◽  
pp. 27-30
Author(s):  
R. Dańko
Keyword(s):  
Grain Size ◽  
Apparent Density ◽  
Bending Strength ◽  
Diffraction Method ◽  
Laser Diffraction ◽  
Grain Sizes ◽  
The Matrix

Abstract The results of investigations of the influence of the matrix grain sizes on properties of cores made by the blowing method are presented in the hereby paper. Five kinds of matrices, differing in grain size compositions, determined by the laser diffraction method in the Analysette 22NanoTec device, were applied in investigations. Individual kinds of matrices were used for making core sands in the Cordis technology. From these sands the shaped elements, for determining the apparent density of compacted sands and their bending strength, were made by the blowing method. The shaped elements (cores) were made at shooting pressures being 3, 4 and 5 atn. The bending strength of samples were determined directly after their preparation and after the storing time of 1 hour.

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

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.

scholarly journals Formation and Properties of the Ta-Y2O3, Ta-ZrO2, and Ta-TaC Nanocomposites

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
J. Jakubowicz ◽  
M. Sopata ◽  
G. Adamek ◽  
P. Siwak ◽  
T. Kachlicki
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Mechanical Alloying ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Ceramic Composites ◽  
Ceramic Phase ◽  
Plasma Sintering ◽  
Average Grain Size ◽  
Bulk Nanocrystalline

The nanocrystalline tantalum-ceramic composites were made using mechanical alloying followed by pulse plasma sintering (PPS). The tantalum acts as a matrix, to which the ceramic reinforced phase in the concentration of 5, 10, 20, and 40 wt.% was introduced. Oxides (Y2O3 and ZrO2) and carbides (TaC) were used as the ceramic phase. The mechanical alloying results in the formation of nanocrystalline grains. The subsequent hot pressing in the mode of PPS results in the consolidation of powders and formation of bulk nanocomposites. All the bulk composites have the average grain size from 40 nm to 100 nm, whereas, for comparison, the bulk nanocrystalline pure tantalum has the average grain size of approximately 170 nm. The ceramic phase refines the grain size in the Ta nanocomposites. The mechanical properties were studied using the nanoindentation tests. The nanocomposites exhibit uniform load-displacement curves indicating good integrity and homogeneity of the samples. Out of the investigated components, the Ta-10 wt.% TaC one has the highest hardness and a very high Young’s modulus (1398 HV and 336 GPa, resp.). For the Ta-oxide composites, Ta-20 wt.% Y2O3 has the highest mechanical properties (1165 HV hardness and 231 GPa Young’s modulus).

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