scholarly journals Temperature Distribution in Microwave Sintering of Alumina Cylinders

1994 ◽  
Vol 347 ◽  
Author(s):  
J. R. Thomas ◽  
Joel D. Katz ◽  
Rodger D. Blake
Keyword(s):  
Temperature Distribution ◽  
Sintering Temperature ◽  
Microwave Sintering ◽  
Heat Transfer Process ◽  
Microwave Energy ◽  
Heating Process ◽  
Temperature Dependent ◽  
Fiber Sensors ◽  
Temperature Dependent Properties ◽  
Multi Mode

ABSTRACTSmall cylinders of high-purity alumina were encased in a “casket” of low-density zir-conia insulation and heated to sintering temperature in a large multi-mode microwave oven. Optical fiber sensors were used to monitor the temperature at several locations in the system. It was found that the alumina samples heat faster than the zirconia insulation at temperatures above 1000°C, and that the temperature distribution in the sample is essentially uniform during the heating process.A two-dimensional mathematical model of the heat transfer process was developed which reproduces the essential features of the observed phenomena. Literature data for all temperature-dependent properties were incorporated into the model. The model suggests that the alumina samples absorb a significant fraction of the microwave energy.

Mechanical Properties of La2O3-Al2O3 Ceramics Prepared by Microwave Sintering

2012 ◽  
Vol 519 ◽  
pp. 265-268 ◽  
Author(s):  
Yun Long Ai ◽  
Fei He ◽  
Bing Liang Liang ◽  
Wen He ◽  
Wei Hua Chen
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Draw Ratio ◽  
Sintering Temperature ◽  
Microwave Sintering ◽  
Microwave Energy ◽  
Pure Alumina ◽  
Sintering Time ◽  
Microstructure Evaluation ◽  
Columnar Grains

The influence of La2O3 on the phase and microstructure evaluation and mechanical properties of La2O3-Al2O3 ceramics sintered with 2.45 GHz microwave energy was investigated. The results showed that La2O3 could densify the pure alumina with a lower sintering temperature and a short sintering time. La2O3 reacted with Al2O3 to form LaAl11O18 completely and the amount of LaAl11O18 increased with the increasing content of La2O3, distributing at the Al2O3 grain boundaries. The specimen doped with 10 vol.% and 15 vol.% La2O3 sintered at 1500 °C exhibited plenty of columnar grains with draw ratio about 1:4. The existence of columnar grains enhanced the microhardness and fracture toughness of La2O3-Al2O3 ceramics.

Dynamic Model for Calculating Heating Patterns During Microwave Sintering

1992 ◽  
Vol 269 ◽  
Author(s):  
James Tucker ◽  
Ray Smith ◽  
Magdy F. Iskander ◽  
Octavio M. Andrade
Keyword(s):  
Heat Transfer ◽  
Temperature Distribution ◽  
Microwave Sintering ◽  
Companion Paper ◽  
Heating Process ◽  
Transfer Program ◽  
Ceramic Samples ◽  
Step Procedure ◽  
Picket Fence ◽  
And Control

ABSTRACTAnalysis of dynamic development of heating patterns during microwave sintering provides vital information on the evolution of the heating process and the contributions from the various components in a complex sintering arrangement (picket fence) to the heat-transfer mechanism. Measured heating patterns often provide overall effects, and it is difficult to isolate and control the various contributions. To this end, results from numerical simulation may be significant.In this paper we describe a thermal model that calculates the temperature distribution in ceramic samples and insulation under realistic sintering conditions. The calculation process involves a two-step procedure. The first step is to calculate the microwave power deposition in the sample and surrounding insulation. 3D FDTD calculations described in a companion paper are used for this purpose [1] The other step involves calculation of the temperature distribution using a 3D finite-difference heat-transfer program developed in our department.Results illustrating the effect of thickness of insulation and the placement of SiC rods in picket-fence arrangement are presented. Also, the need to measure additional parameters such as thermal conductivity and density of green samples as a function of temperature during sintering is discussed.

Investigation of Cooling Process of a High-Temperature Hollow Cylinder in Moving Induction Heat Treatment

2012 ◽  
Vol 4 (1) ◽  
Author(s):  
H. Shokouhmand ◽  
S. Ghaffari
Keyword(s):  
Heat Treatment ◽  
Temperature Distribution ◽  
Moving Boundary ◽  
Work Piece ◽  
Cooling Process ◽  
Temperature Dependent ◽  
Time Step ◽  
Heat Treated ◽  
Rate Of Cooling ◽  
Temperature Dependent Properties

The hardness of heat treated steel and probability of occurrence of quenching cracks depend on the cooling time and temperature distribution. Therefore, the investigation of cooling process is a crucial issue in heat treatment to evaluate the obtained structure of the work-piece. In the present work, a vertical hollow circular cylinder is heated up to a specific temperature by a moving coil at a given velocity along it, and the heated parts then quenched by a moving water–air spray. After passing the spray, the cylinder is cooled by natural convection with the surrounding air. An analysis of coupled magnetic problem and transient conjugated thermal problem between the solid and the surrounding air is performed using finite-element method to obtain temperature field in each time step. This procedure includes moving boundary conditions, effect of radiation with ambient, temperature-dependent properties, and change in magnetic permeability of specified alloy at the Curie temperature. The obtained results show how both spray and natural cooling affect the temperature distribution and rate of cooling of the cylinder. Furthermore, the effect of geometry and velocity of coil on the rate of cooling and chance of quenching cracks are investigated.

scholarly journals Investigation of Waves Generated in Transversely Isotropic Micropolar Generalized Thermoelastic Half Space Under Temperature Dependent Properties

2019 ◽  
Vol 24 (4) ◽  
pp. 53-65
Author(s):  
R.R. Gupta ◽  
R.R. Gupta
Keyword(s):  
Temperature Distribution ◽  
Quality Factor ◽  
Half Space ◽  
Elastic Properties ◽  
Transversely Isotropic ◽  
Temperature Dependent ◽  
Phase Velocities ◽  
Generalized Thermoelastic ◽  
Temperature Dependent Properties ◽  
Propagation Of Waves

Abstract The present study deals with the propagation of waves in a transversely isotropic micropolar generalized thermoelastic material possessing temperature dependent elastic properties. After developing the solution for LS, GL and CT theory, the phase velocities and attenuation quality factor have been obtained. The expressions for amplitudes of stresses, displacements, microratation and temperature distribution have been derived and computed numerically. The numerically evaluated results have been plotted graphically. Some particular cases of interest have also been obtained.

Microwave Sintering BaTiO3 Ceramics Using Liquid Phase Sintering

2006 ◽  
Vol 317-318 ◽  
pp. 131-134 ◽  
Author(s):  
Yutsuki Nishimura ◽  
Masaki Yasuoka ◽  
Takaaki Nagaoka ◽  
Yoshiaki Kinemuchi ◽  
Koji Watari
Keyword(s):  
Dielectric Properties ◽  
Liquid Phase ◽  
Sintering Temperature ◽  
Microwave Sintering ◽  
Microwave Energy ◽  
Liquid Phase Sintering ◽  
Electrical Characteristics ◽  
Electronic Components ◽  
Semiconducting Properties ◽  
Material Energy

Microwave sintering is a process in which target materials absorb microwaves and heat themselves from the inside. When microwave energy is effectively absorbed by the material, energy consumption for the sintering can be reduced. Our study is focused on the microwave sintering of BaTiO3 to more rapidly obtain dense ceramics with specific characteristics. For BaTiO3-based electronic components, the sintering temperature is too high for manufacture, so various additives are used to decrease the sintering temperature without undue worsening of the electrical characteristics. In this work, during microwave sintering, BaCO3, H3BO3, BaB2O4 and LiF were added to form a liquid. The effects of the amount of liquid phase on density and dielectric properties were investigated. BaTiO3 sintered with BaCO3 and H3BO3 showed dielectric properties, whereas BaTiO3 sintered with BaB2O4 had semiconducting properties with PTCR characteristics. Also, LiF-added BaTiO3 indicated a dielectric constant in which the peak shifts to lower temperatures with higher LiF concentrations.

scholarly journals Strain Transfer Characteristics of Multi-Layer Optical Fiber Sensors with Temperature-Dependent Properties at Low Temperature

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 495
Author(s):  
Taolue Yang ◽  
Huaping Wang ◽  
Xingzhe Wang
Keyword(s):  
Low Temperature ◽  
Optical Fiber ◽  
Optical Fiber Sensors ◽  
Large Temperature ◽  
Temperature Dependent ◽  
Fiber Sensors ◽  
Strain Transfer ◽  
Transfer Characteristics ◽  
Temperature Dependent Properties ◽  
Temperature Loads

Optical fiber sensors have been potentially expected to apply in the extreme environment for their advantages of measurement in a large temperature range. The packaging measure which makes the strain sensing fiber survive in these harsh conditions will commonly introduce inevitable strain transfer errors. In this paper, the strain transfer characteristics of a multi-layer optical fiber sensing structure working at cryogenic environment with temperature gradients have been investigated theoretically. A generalized three-layer shear lag model incorporating with temperature-dependent properties of layers was developed. The strain transfer relationship between the optical fiber core and the matrix has been derived in form of a second-order ordinary differential equation (ODE) with variable coefficients, where the Young’s modulus and the coefficients of thermal expansion (CTE) are considered as functions of temperature. The strain transfer characteristics of the optical sensing structure were captured by solving the ODE boundary problems for cryogenic temperature loads. Case studies of the cooling process from room temperature to some certain low temperatures and gradient temperature loads for different low-temperature zones were addressed. The results showed that different temperature load configurations cause different strain transfer error features which can be described by the proposed model. The protective layer always plays a main role, and the optimization geometrical parameters should be carefully designed. To verify the theoretical predictions, an experiment study on the thermal strain measurement of an aluminum bar with optical fiber sensors was conducted. LUNA ODiSI 6100 integrator was used to measure the Rayleigh backscattering spectra shift of the optical fiber at a uniform temperature and a gradient temperature under liquid nitrogen temperature zone, and a reasonable agreement with the theory was presented.

scholarly journals Processing of CNTs Reinforced Al-Based Nanocomposites Using Different Consolidation Techniques

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
N. Al-Aqeeli
Keyword(s):  
Temperature Distribution ◽  
Spark Plasma Sintering ◽  
Sintering Temperature ◽  
Microwave Sintering ◽  
The Other ◽  
Milling Parameters ◽  
The Poor ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Hardness Values

In this work, the development of two types of Al-based alloys with different concentrations of Si reinforced with MWCNT’s at 0.5–2.0 wt% is presented. Sonication of the CNT’s in ethyl alcohol was carried out for dispersion, and the mixtures were ball milled for 1, 3, and 5 hrs. SEM/EDS were used to study the morphology and the effects of changing milling parameters in addition to changes caused due to increasing concentration of the CNT’s. Furthermore, three sintering techniques, namely, Spark Plasma Sintering (SPS), Microwave Sintering (μWS), and Hot Isostatic Press Sintering (HIP) were employed to consolidate the ball milled powders at varying temperatures of 400, 450, and 500°C. It was found that SPS consolidated samples showed the most promising results amongst the three with the highest hardness values; around 100% densification, as well as the finest microstructure. On the other hand, microwave sintered samples showed the least appealing results, this could be attributed to the poor temperature distribution and the pressureless nature of the technique. A sintering temperature of 500°C was found to be the most suitable for these types of alloys.

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