scholarly journals An On-Line System for High Temperature Dielectric Property Measurement of Microwave-Assisted Sintering Materials

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 665 ◽  
Author(s):  
Li Wu ◽  
Yi Zhang ◽  
Fengxia Wang ◽  
Weiquan Ma ◽  
Tian Xie ◽  
...  
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Dielectric Property ◽  
High Temperatures ◽  
Dielectric Measurement ◽  
Line System ◽  
Microwave Assisted ◽  
On Line ◽  
Property Measurement ◽  
Properties Of Materials

Microwave-assisted sintering materials have been proven to deliver improvements in the mechanical and physicochemical properties of the materials, compared with conventional sintering methods. Accurate values of dielectric properties of materials under high temperatures are essential for microwave-assisted sintering. In view of this, this paper, proposes an on-line system to measure the high temperature dielectric properties of materials under microwave processing at a frequency of 2450 MHz. A custom-designed ridge waveguide is utilized, where samples are heated and measured simultaneously. An artificial neural network (ANN) trained with the corresponding simulation data is integrated into this system to reverse the permittivity of the measured materials. This whole system is tested at room temperature with different materials. Accuracies of measuring dielectric property with an error lower than 9% with respect to theoretical data have been achieved even for high loss media. The functionality of the dielectric measurement system has also been demonstrated by heating and measuring Macor and Duran ceramic glass samples up to 800 °C. All the preliminary experiments prove the feasibility of this system. It provides another method for dielectric property measurement and improves the understanding of the mechanism between microwave and media under high temperatures, which is helpful for optimizing the microwave-assisted sintering of materials.

Density Dependence of High Temperature Dielectric Properties of Debased Alumina and the Effect of a High Loss Additive

1994 ◽  
Vol 347 ◽  
Author(s):  
N. G. Evans ◽  
M. G. Hamlyn
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Dielectric Property ◽  
Density Dependence ◽  
Measurement Technique ◽  
Process Technology ◽  
High Loss ◽  
Property Data ◽  
Powder Samples ◽  
Property Measurement

Research into microwave firing at Staffordshire University has been carried out since 1988 and dielectric property measurements have been used to help in developing process technology. The dielectric property measurement technique (cavity perturbation [1]) is that designed by Atomic Energy of Canada Ltd (A.E.C.L) [2]. The technique was chosen because of it's ability to analyse powder samples as well as solids. In order for dielectric property data to be of use in developing microwave processing, measurements have to be made on the starting materials of the process (i.e powders). When measurements are made on powders it is important to quote the bulk density at which the measurement was made since dielectric properties vary with density as well as frequency and temperature.

Improvement of Dielectric Performance of a Prototype AlN High Temperature Chip-level Package

2011 ◽  
Vol 2011 (HITEN) ◽  
pp. 000052-000057 ◽  
Author(s):  
Liang-Yu Chen
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
High Temperatures ◽  
Substrate Surface ◽  
Substrate Material ◽  
Glass Coating ◽  
Temperature Dependent ◽  
High Temperature Electronics ◽  
Dielectric Performance ◽  
Parasitic Parameters

Aluminum nitride (AlN) has been proposed as a packaging substrate material for reliable high temperature electronics operating in a wide temperature range. However, it was discovered in a recent study that the dielectric properties of some commercial polycrystalline AlN materials change quite significantly with temperature at high temperatures. These material properties resulted in undesired large and temperature-dependent parasitic parameters for a prototype chip-level package based on an AlN substrate with the yttrium oxide dopant. This paper reports a method using a coating layer of a commercial thick-film glass on the AlN substrate surface to significantly reduce both the parasitic capacitances and parasitic conductances between neighboring inputs/outputs (I/Os) of a prototype AlN chip-level package. The parasitic parameters of 8-I/Os low power chip-level packages with the insulating glass coating were characterized at frequencies from 120 Hz to 1 MHz between room temperature and 500°C. These results were compared with the parameters of AlN packages without the glass coating. The results indicate that the parasitic capacitances and conductances between I/Os of the improved prototype AlN packages are significantly reduced and stable at high temperatures. The method using a glass coating provides a feasible way to mitigate the temperature dependence of dielectric properties of AlN and further utilize AlN as a reliable packaging substrate material for high temperature applications.

Dielectric Relaxation Process and Microwave Heating Mechanism in ε-Caprolactone as a Function of Frequency and Temperature

2014 ◽  
Vol 931-932 ◽  
pp. 205-209 ◽  
Author(s):  
Mohd Johari Kamaruddin ◽  
Anwar Johari ◽  
Ramli Mat ◽  
Tuan Amran Tuan Abdullah ◽  
Siti Hamidah Mohd Setapar ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Microwave Heating ◽  
Processing System ◽  
Debye Model ◽  
Microwave Energy ◽  
Dielectric Relaxation Process ◽  
Microwave Assisted ◽  
Heating Mechanism ◽  
Wide Range ◽  
Properties Of Materials

Dielectric properties of materials play a significant role in design of microwave assisted processing system. This paper is focused on the dielectric properties of ε-caprolactone (ε-cap) which is the monomer for the biodegradable polymer, Poly (ε-caprolactone) (PCL). The dielectric properties of ε-cap were measured across a wide range of frequencies (0.1 GHz5.0 GHz) and temperatures (20-150oC). Then the measured dielectric properties data was modelled using Debye model in order to relate quantitatively the dielectric properties to microwave heating mechanisms. The analysis carried out gives a clear picture of interaction of ε-cap with microwave energy and its heating mechanism in microwave assisted polymerisation process. This study concluded that microwave heating mechanism of the ε-cap in the measured range may be dominated by the dipole reorientation.

scholarly journals Dynamic Measurement of Dielectric Properties of Materials at High Temperature During Microwave Heating in a Dual Mode Cylindrical Cavity

2015 ◽  
Vol 63 (9) ◽  
pp. 2905-2914 ◽  
Author(s):  
Jose M. Catala-Civera ◽  
Antoni J. Canos ◽  
Pedro Plaza-Gonzalez ◽  
Jose D. Gutierrez ◽  
Beatriz Garcia-Banos ◽  
...  
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Microwave Heating ◽  
Cylindrical Cavity ◽  
Dynamic Measurement ◽  
Dual Mode ◽  
Properties Of Materials

Dielectric Properties of Alumina Ceramics in the Microwave Frequency at High Temperature

2007 ◽  
Vol 124-126 ◽  
pp. 743-746 ◽  
Author(s):  
Min Kyu Park ◽  
Ha Neul Kim ◽  
Seung Su Baek ◽  
Eul Son Kang ◽  
Yong Kee Baek ◽  
...  
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Room Temperature ◽  
Microwave Frequency ◽  
Dielectric Measurement ◽  
Alumina Ceramics ◽  
Frequency Range ◽  
Beam Focusing ◽  
Half Wavelength ◽  
Optimum Specimen

The dielectric properties of alumina ceramics have been measured using a free-space time-domain technique from room temperature to 1400 oC in the frequency range 8.2 – 12.4 GHz. The effects of thickness and lateral size of specimen were investigated with comparing the measured values to the calculated ones based on the half-wavelength and the Gaussian beam focusing. From these results the optimum specimen dimension for the high temperature dielectric measurement was suggested with experimental verification.

FDTD Simulation of an Open-Ended Metallized Ceramic Probe for Broadband High-Temperature Dielectric Properties Measurements

1994 ◽  
Vol 347 ◽  
Author(s):  
Shane Bringhurst ◽  
Magdy F. Iskander ◽  
Paul Gartside
Keyword(s):  
High Temperature ◽  
Dielectric Properties ◽  
Microwave Sintering ◽  
Fdtd Method ◽  
Fdtd Simulation ◽  
Minimum Thickness ◽  
University Of Utah ◽  
Coaxial Probes ◽  
On Line ◽  
The University

ABSTRACTOpen-ended coaxial probes have been used in broadband dielectric properties measurements for several years. To aid in the ongoing numerical simulation and microwave sintering research at the University of Utah, we have found it necessary to make dielectric properties measurements up to temperatures as high as 1400 °C. The available cavity perturbation techniques were unsuitable in this application due to their relatively narrow band, and the available metal probes are also unsuitable due to the differential thermal expansions of the inner and outer conductors, which makes it difficult to carry out accurate and on-line calibration procedures for these probes.To help us achieve both broadband and high-temperature dielectric properties measurements, we have developed a new metallized ceramic coaxial probe. The detailed design of this probe is described and the metallization procedure is discussed.Also to optimize the design of the probe and in particular to increase the penetration of fields in samples under test and hence improve the probe sensitivity to variation in properties of a larger class of materials, and to determine the required minimum thickness of various samples to obtain accurate results, we modeled and simulated the probe performance using the Finite-Difference Time-Domain (FDTD) method. Results from the FDTD simulation are presented and some guidelines that may be used to optimize the design of the probe are discussed.

High Temperature n- and p-type Doped Microcrystalline Silicon Layers Grown by VHF PECVD Layer-by-Layer Deposition

2003 ◽  
Vol 762 ◽  
Author(s):  
A. Gordijn ◽  
J.K. Rath ◽  
R.E.I. Schropp
Keyword(s):  
Activation Energy ◽  
High Temperature ◽  
High Temperatures ◽  
Continuous Wave ◽  
Hydrogen Plasma ◽  
Silicon Layer ◽  
Dark Conductivity ◽  
High Deposition Rate ◽  
Layer By Layer ◽  
Microcrystalline Silicon

AbstractDue to the high temperatures used for high deposition rate microcrystalline (μc-Si:H) and polycrystalline silicon, there is a need for compact and temperature-stable doped layers. In this study we report on films grown by the layer-by-layer method (LbL) using VHF PECVD. Growth of an amorphous silicon layer is alternated by a hydrogen plasma treatment. In LbL, the surface reactions are separated time-wise from the nucleation in the bulk. We observed that it is possible to incorporate dopant atoms in the layer, without disturbing the nucleation. Even at high substrate temperatures (up to 400°C) doped layers can be made microcrystalline. At these temperatures, in the continuous wave case, crystallinity is hindered, which is generally attributed to the out-diffusion of hydrogen from the surface and the presence of impurities (dopants).We observe that the parameter window for the treatment time for p-layers is smaller compared to n-layers. Moreover we observe that for high temperatures, the nucleation of p-layers is more adversely affected than for n-layers. Thin, doped layers have been structurally, optically and electrically characterized. The best n-layer made at 400°C, with a thickness of only 31 nm, had an activation energy of 0.056 eV and a dark conductivity of 2.7 S/cm, while the best p-layer made at 350°C, with a thickness of 29 nm, had an activation energy of 0.11 V and a dark conductivity of 0.1 S/cm. The suitability of these high temperature n-layers has been demonstrated in an n-i-p microcrystalline silicon solar cell with an unoptimized μc-Si:H i-layer deposited at 250°C and without buffer. The Voc of the cell is 0.48 V and the fill factor is 70 %.

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