The Microstructure of Ceramic Whiskers

1991 ◽  
Vol 49 ◽  
pp. 918-919
Author(s):  
L. F. Allard ◽  
T. A. Nolan
Keyword(s):  
Silicon Carbide ◽  
Second Phase ◽  
Tin Whisker ◽  
Ferrous Alloys ◽  
Vapor Liquid Solid ◽  
Rice Hulls ◽  
Aspect Ratios ◽  
Silicon Carbide Whiskers ◽  
Synthetic Materials ◽  
Sic Whiskers

The internal structure and surface crystallography of ceramic whiskers are of interest because of their increasing importance as second phase reinforcements in a variety of matrix materials. Whiskers are typically 0.5 to 5 um in diameter with aspect ratios of 10 to 100 or more. Silicon carbide whiskers are the best known; they are usually grown by vapor-liquid-solid (VLS) or other processes from either natural (e.g. rice hulls) or synthetic materials. Titanium nitride whiskers are also of interest because of their potential for applications where SiC whiskers are not suitable (e.g. ferrous alloys). This paper highlights some of the details of SiC and TiN whisker ultrastructure.

Silicon Carbide Whiskers and the VLS Mechanism

1985 ◽  
Vol 43 ◽  
pp. 234-235
Author(s):  
S.R. Nutt ◽  
R.W. Carpenter
Keyword(s):  
Silicon Carbide ◽  
Core Region ◽  
Hrem Image ◽  
Rice Hulls ◽  
Second Stage ◽  
Silicon Carbide Whiskers ◽  
Crystal Growth Mechanism ◽  
Wide Range ◽  
Mechanism Research ◽  
Sic Whiskers

Silicon carbide whiskers can be grown by pyrolysis of silica and cellulose derived from rice hulls. Whiskers grown by this process are useful as composite reinforcements in a wide range of matrix materials. Due to the scarcity of published information regarding the crystal growth mechanism, research was devoted to analysis of inclusions and defects in the whiskers. Most SiC whiskers exhibited microinclusions (<10nm in size) confined to a central core region (Fig. 1). The distribution implies a two-stage growth process in which the core region grows in the first stage, followed by lateral growth in the second stage. An HREM image of a single twinned inclusion is shown in Fig. 2. The whisker orientation is [0001] and the inclusion exhibits crossed 0.45nm lattice fringes running parallel to type II prism planes in the SiC lattice. The lattice fringes often did not span the entire inclusion diameter, and radiation damage to the inclusion was observed with increasing dose using a 200 kV electron beam.

Effect of Combined Addition of Silicon Carbide Whiskers and Fullerene Nanoparticles on Properties of Thermoelectric Zinc Antimonide

2007 ◽  
Vol 1044 ◽  
Author(s):  
Takashi Itoh ◽  
Nobuhisa Asari ◽  
Nobuyuki Kanetake ◽  
Akira Okada
Keyword(s):  
Power Generation ◽  
Silicon Carbide ◽  
Flexural Strength ◽  
Thermoelectric Power ◽  
Ball Milling ◽  
Thermoelectric Power Generation ◽  
Silicon Carbide Whiskers ◽  
Planetary Ball Milling ◽  
Fullerene Nanoparticles ◽  
Sic Whiskers

AbstractThermoelectric power generation is a hopeful method harnessing waste thermal energy particularly covering a middle temperature range between 500 and 800K. A Zn4Sb3 compound is a promising “phonon glass electron crystal” material applicable to thermoelectric power generation around 700K. This material, however, has a problem of its brittleness. In this research, the silicon carbide whiskers were added into the Zn4Sb3 compound for overcoming the brittleness, and the fullerene nanoparticles were also added for improving the thermoelectric performance. The Zn4Sb3 compound was synthesized from mixture of pure zinc and antimony powders by a liquid-solid phase reactions method. Firstly, the synthesized compound powder was mixed with the fullerene nanoparticles. The planetary ball milling method was used in order to disentangle the fullerene agglomerate and to obtain a uniform mixture. Subsequently, the mixture was uniformly mixed with the SiC whiskers by the planetary ball milling. The final mixture was consolidated by the pulse discharge sintering. The synthesized phases were identified by XRD. The morphology of the whiskers after mixing was observed. The flexural strength and the thermoelectric properties of the sintered samples were measured. The length of SiC whiskers and the flexural strength were decreased with the mixing time. Though the addition of SiC whiskers lowered the thermoelectric performance, the combined addition of SiC whiskers and fullerene nanoparticles restored the performance by especially decrease of the thermoelectric conductivity owing to the phonon scattering.

Synthesis of Silicon Carbide Whiskers in Electric Field Furnace

2008 ◽  
Vol 368-372 ◽  
pp. 831-833
Author(s):  
Chang Hong Dai ◽  
Zu Wei Song ◽  
Ru Zhao
Keyword(s):  
Activation Energy ◽  
Silicon Carbide ◽  
Carbon Black ◽  
Electric Field ◽  
Influencing Factors ◽  
High Voltage ◽  
Raw Materials ◽  
Silicon Carbide Whiskers ◽  
Sic Whiskers ◽  
Reaction Speed

A new heating apparatus for synthesizing SiC whiskers was introduced. SiC whiskers were synthesized in electric field furnace with carbon black and SiO2 powders as raw materials and some influencing factors were discussed. SiC whiskers with diameter of 0.1-0.4μm, length of 5-70μm and average purity of 99.6% were acquired at lower temperatures of 1200-1400°C for a shorter holding time of 2-4h. The results showed that the high voltage field has great catalysis action on synthetic of SiC whiskers by reducing activation energy and enhancing reaction speed.

Formation and Structure of Silicon Carbide Whiskers from Rice Hulls

1984 ◽  
Vol 67 (11) ◽  
pp. 715-720 ◽  
Author(s):  
N. K. SHARMA ◽  
WENDELL S. WILLIAMS ◽  
A. ZANGVIL
Keyword(s):  
Silicon Carbide ◽  
Rice Hulls ◽  
Silicon Carbide Whiskers

Tribological Properties of SiC Whisker Containing Silicon Nitride Composite

1988 ◽  
Vol 110 (3) ◽  
pp. 434-438 ◽  
Author(s):  
H. Ishigaki ◽  
R. Nagata ◽  
M. Iwasa ◽  
N. Tamari ◽  
I. Kondo
Keyword(s):  
Silicon Carbide ◽  
Silicon Nitride ◽  
Wear Rate ◽  
Block Type ◽  
Hot Press ◽  
Sliding Speed ◽  
Wear Characteristics ◽  
Silicon Carbide Whiskers ◽  
Sic Whiskers ◽  
Hot Press Sintering

The friction and wear characteristics of SiC whisker containing composite silicon nitride were studied. Silicon nitride powder which contains densification aids of Y2O3 and La2O3 was mixed with silicon carbide whiskers (10, 20, and 30 wt percent) and then hot-pressed at a temperature of 1800° C. Wear experiments were carried out with a ring on block type apparatus at the sliding conditions of the sliding speed of 314 mm/sec and the load of 5 N and experimental results showed that the SiC whisker had an evident effect to reduce the wear rate of silicon nitride blocks. Silicon carbide whiskers are not dispersed isotropically, but they are oriented to the direction which is perpendicular to the pressure of hot-press sintering. Therefore, wear characteristics of the composite ceramics are anisotropic. The effect of SiC whisker on wear rate of silicon nitride is larger for the surface which is perpendicular to the direction of pressure of hot-press sintering that than that for the surface which is parallel to the pressure. Although SiC whiskers have no evident effect on friction coefficient of silicon nitride at the above sliding condition, even small contents of SiC whiskers, such as 10 wt percent, reduce considerably the coefficient of friction and show similar frictional characteristics to that of monolithic silicon carbide at the lower sliding speed of 10 mm/min.

Characterization of silicon carbide platelet-reinforced alumina

1990 ◽  
Vol 48 (4) ◽  
pp. 1032-1033
Author(s):  
K. B. Alexander ◽  
P. F. Becher ◽  
S. B. Waters
Keyword(s):  
Silicon Carbide ◽  
Hot Pressing ◽  
Slow Crack Growth ◽  
Ceramic Composites ◽  
Alumina Powder ◽  
Platelet Volume ◽  
Silicon Carbide Whiskers ◽  
Sic Whiskers ◽  
Ceramic Matrices

The incorporation of silicon carbide whiskers into ceramic matrices has been shown to result in significant increases in toughness, strength, resistance to thermal shock, slow crack growth, and creep. The health hazards associated with the handling of silicon carbide whiskers, however, can be considerable. Silicon carbide platelets are therefore being considered as an alternative to whiskers for reinforcing ceramic composites.The silicon carbide platelets used in this study were supplied by Alcan International Ltd. The platelets varied from 1 to 5 μm in thickness and 5 to 45 μm in diameter. Sumitomo alumina powder was mixed with the platelets and the composites were fabricated by hot-pressing in vacuum at 1600°C for 1.5 h. The resultant composites had the platelet faces oriented primarily perpendicular to the hot-pressing axis. Specimens containing 7 vol% SiC platelets had a fracture toughness of 6.6 MPa m½, which is about the same value as observed for alumina of equivalent grain size containing 7 vol% SiC whiskers. Considerable porosity was observed in specimens with platelet volume fractions larger than 7 vol%.

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