Characterization of microwave-sintered ceramic composites

1993 ◽  
Vol 51 ◽  
pp. 1136-1137
Author(s):  
X. Zhang ◽  
Y. Pan ◽  
T.T. Meek
Keyword(s):  
Matrix Material ◽  
Maximum Output Power ◽  
Ceramic Matrix Composite ◽  
Ceramic Composites ◽  
Processing Technique ◽  
Structure Characterization ◽  
Alumina Powder ◽  
Maximum Output ◽  
Sintered Ceramic

Industrial microwave heating technology has emerged as a new ceramic processing technique. The unique advantages of fast sintering, high density, and improved materials properties makes it superior in certain respects to other processing methods. This work presents the structure characterization of a microwave sintered ceramic matrix composite.Commercial α-alumina powder A-16 (Alcoa) is chosen as the matrix material, β-silicon carbide whiskers (Third Millennium Technologies, Inc.) are used as the reinforcing element. The green samples consisted of 90 vol% Al2O3 powder and 10 vol% ultrasonically-dispersed SiC whiskers. The powder mixture is blended together, and then uniaxially pressed into a cylindrical pellet under a pressure of 230 MPa, which yields a 52% green density. The sintering experiments are carried out using an industry microwave system (Gober, Model S6F) which generates microwave radiation at 2.45 GHz with a maximum output power of 6 kW. The composites are sintered at two different temperatures (1550°C and 1650°C) with various isothermal processing time intervals ranging from 10 to 20 min.

Thermal Diffusivity Imaging of Ceramic Composites

1993 ◽  
Author(s):  
K. Elliott Cramer ◽  
William P. Winfree ◽  
Edward R. Generazio ◽  
Ramakrishna Bhatt ◽  
Dennis S. Fox ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Diffusivity ◽  
Silicon Nitride ◽  
Matrix Material ◽  
Ceramic Matrix Composite ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Ceramic Composites ◽  
Fiber Direction ◽  
Large Area

Strong, tough, high temperature ceramic matrix composites are currently being developed for application in advanced heat engines. One of the most promising of these new materials is a SiC fiber-reinforced silicon nitride ceramic matrix composite (SiCf/Si3N4). The interfacial shear strength in such composites is dependant on the integrity of the fiber’s carbon coating at the fiber-matrix interface. The integrity of the carbon rich interface can be significantly reduced if the carbon is oxidized. Since the thermal diffusivity of the fiber is greater than that of the matrix material, the removal of carbon increases the contact resistance at the interface reducing the thermal diffusivity of the composite. Therefore thermal diffusivity images can be used to characterize the progression of carbon depletion and degradation of the composite. A new thermal imaging technique has been developed to provide rapid large area measurements of the thermal diffusivity perpendicular to the fiber direction in these composites. Results of diffusivity measurements will be presented for a series of SiCf/Si3N4 (reaction bonded silicon nitride) composite samples heat-treated under various conditions. Additionally, the ability of this technique to characterize damage in both ceramic and other high temperature composites will be shown.

Servo Control and Energetic Characterization of a Proportionally Injected Liquid-Fueled Actuator for Power-Autonomous Mobile Robots

2005 ◽  
Author(s):  
Kevin B. Fite ◽  
Michael Goldfarb
Keyword(s):  
State Of The Art ◽  
Direct Injection ◽  
Maximum Output Power ◽  
Servo Control ◽  
Autonomous Mobile Robots ◽  
Maximum Output ◽  
Liquid Propellant ◽  
Hot Gas ◽  
Energetic Characterization

This paper describes and characterizes a chemo-mechanical actuator that incorporates proportionally controlled injection valves for the direct injection of a hot-gas actuator. Proportional control of the liquid propellant provides for high-resolution control without sacrificing the maximum output power of the valves. The design of the proportional injection valves will be briefly discussed, along with the design of the actuator force controller. Experimental results of the force and position tracking of the actuator are presented. Finally, an energetic characterization of the actuator shows improvement relative to prior configurations, and shows marked improvement relative to state-of-the-art batteries and motors.

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%.

Fabrication and Characterization of Pb1-xYbxSe0.2Te0.8 Based Alloy Thin Films Thermoelectric Generators Grown Using Thermal Evaporation Method

2013 ◽  
Vol 756 ◽  
pp. 259-265 ◽  
Author(s):  
Arshad Hmood ◽  
Arej Kadhim ◽  
Abu Hassan Haslan
Keyword(s):  
Thin Films ◽  
Open Circuit Voltage ◽  
Maximum Output Power ◽  
Open Circuit ◽  
Maximum Output ◽  
Thermoelectric Generators ◽  
Thermal Evaporation Method ◽  
Glass Substrates ◽  
In Series

In the current work p-Pb0.925Yb0.075Te:Te and n-Pb0.925Yb0.075Se0.2Te0.8 powders synthesized by solid-state microwave route were used to fabricating thermally evaporated thin films. The micro-thermoelectric devices were composedof 20-pairs and 10-pairs p-Pb0.925Yb0.075Te:Te and n-Pb0.925Yb0.075Se0.2Te0.8 thin films on glass substrates. Overall size of the thin films thermoelectric generators which consist of 20-pairs and 10-pairs of legs connected by aluminumelectrodes were 23 mm×20 mm and 12 mm×10 mm, respectively. The 20-pairs p–n thermocouples in series device generated output maximum open-circuit voltage of 275.3 mV and a maximum output power up to 54.4 nW at temperature difference ∆T= 162 K, and 109.4 mV and 16.7 nW at ∆T=162 K, for 10-pairs, respectively.

Preparation and characterization of NextelTM 720/ alumina ceramic composites via the prepreg process

2021 ◽  
Author(s):  
Hao Li ◽  
Bo-xing Zhang ◽  
Ying Guo ◽  
Weijian Han ◽  
Tong Zhao ◽  
...  
Keyword(s):  
Flexural Strength ◽  
Ceramic Matrix Composite ◽  
Temperature Stability ◽  
Ceramic Matrix Composites ◽  
Ceramic Matrix ◽  
Ceramic Composites ◽  
Alumina Ceramic ◽  
Alumina Powder ◽  
High Temperature Stability ◽  
Aqueous Slurry

Abstract In this work, the continuous Nextel™ 720 fiber reinforced alumina ceramic matrix composites (CMCs) were prepared by the prepreg process. The alumina matrix derived from aqueous slurry, which consisted of organic glue, alumina sol, nanometer alumina powder and micrometer alumina powder. This combination endowed the ceramic matrix composite with the prepreg processing capability, making the low-cost fabrication of complex shape components possible. The ratio of different alumina sources in aqueous slurry was optimized to offer good sintering activity, high thermal resistance, and excellent mechanical properties simultaneously. Furthermore, the preceramic polymer of mullite was used to strengthen the ceramic matrix through multiple impregnation process. The final CMC sample achieved a high flexural strength of 255 MPa and a good high-temperature stability. The maximum flexural strength of the CMC sample still remained 85% after heat-treatment at 1100 ℃ for 24 h.

Treatment of Agricultural Wastewater Using Porous Ceramics Composite of Hydroxyapatite and Silica

2012 ◽  
Vol 622-623 ◽  
pp. 915-918 ◽  
Author(s):  
Supansa Intapong ◽  
Anirut Raksudjarit
Keyword(s):  
Porous Ceramic ◽  
Porous Ceramics ◽  
Ceramic Composites ◽  
Ceramic Filter ◽  
Water Filtration ◽  
Sintered Ceramic ◽  
Agricultural Wastewater ◽  
Flow Through ◽  
Silica Nanopowder

Porous ceramics filter was prepared by sintering of hydroxyapatite (HA) and silica composite nanopowder. Silica nanopowder of 50 wt% are incorporated into HA nanopowder. The mixing powders are uniaxially compact and then sintering at 900°C-1050°C in air. The characterization of the porous was carried out by scanning electron microscopy (SEM). Filtration studies using porous ceramic were performed for agricultural wastewater. The studies of the water filtration and flow through these porous showed that the sintered ceramic filter at all temperatures reduced the TDS, TS, conductivity, and arsenic (As) content. The water permeated through porous ceramic composites could be compared to drinking water quality.

Characterization of Different Piezoelectric Profile for Energy Harvester

2015 ◽  
Vol 793 ◽  
pp. 407-411 ◽  
Author(s):  
Afifah Shuhada Rosmi ◽  
Syed Idris Syed Hasan ◽  
Y. Wahab ◽  
Mazlee Mazalan
Keyword(s):  
Energy Harvester ◽  
Electrical Power ◽  
Maximum Output Power ◽  
Mechanical Vibration ◽  
Electrical Potential ◽  
Low Frequency ◽  
Maximum Output ◽  
Excellent Performance ◽  
Microelectromechanical System

Microelectromechanical system (MEMS) piezoelectric transducer has been widely used as a mechanism for converting mechanical vibration into electrical power energy harvester.This paper presents a simulation result of cantilever-type piezoelectric MEMS generator with four different profiles to characterize the ability in producing a maximum output power at low frequency ambient vibration.Zinc Oxide is chosen as the piezoelectric material during the simulation. The simulation was conducted using IntelliSense’s CAE tool to obtain the natural frequency, electrical potential, and the optimum length dimension for each profile. The simulation result shows an excellent performance from trapezoidal shapetransducer with the electrical potential of 0.914 V at low frequency of 79.92 Hz.

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