Apparent Activation Energy in High Frequency Microwave Sintering of Alumina Ceramic

2015 ◽  
Vol 1123 ◽  
pp. 391-396 ◽  
Author(s):  
I. Nyoman Sudiana ◽  
Seitaro Mitsudo ◽  
Shunsuke Inagaki ◽  
La Ode Ngkoimani ◽  
Usman Rianse ◽  
...  
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
High Frequency ◽  
Driving Force ◽  
Microwave Sintering ◽  
High Frequencies ◽  
Conventional Sintering ◽  
Series Of Experiments ◽  
High Frequency Microwave ◽  
Sintering Method

The observed enhancements in the high frequency microwave processing alumina compared to those in conventional method at the same sintering temperatures have been studied. Some possible mechanisms responsible for the enhancements were investigated and are discussed in this paper. The enhancements could be associated with the increase either in driving force or in apparent activation energy of diffusion. An experiment to estimate the driving force of sintering is not easy to perform because the force depends not only on the density and grain size but also on the electric field in the materials. Therefore, a series of experiments to estimate the apparent activation energy were performed in high frequencies microwave and in conventional sintering method, as well. It was observed that the apparent activation energy in conventional sintering was much lower than that of microwave sintering. These activation energy values suggested that diffusion rate in microwaves sintering was faster, which led to the higher densification.

Formation of Tricalcium Silicate Prepared by Electric and Microwave Sintering

2010 ◽  
Vol 148-149 ◽  
pp. 1119-1123
Author(s):  
Kai Ke ◽  
Bao Guo Ma ◽  
Xiao Liang Wang ◽  
Xiang Guo Li
Keyword(s):  
Heating Temperature ◽  
Microwave Sintering ◽  
Electric Heating ◽  
Tricalcium Silicate ◽  
Experimental Results ◽  
X Ray Diffraction ◽  
X Ray ◽  
Conventional Sintering ◽  
Sintering Method

A microwave sintering method was used to prepare C3S from Ca(OH)2, SiO2 and MexOy. f-CaO assay, X-ray diffraction and SEM were used to characterize the sintered samples.The results indicated that ion oxides played a very important role in C3S formation in conventional sintering, the use of MexOy as an additive was so effective in promoting C3S formation. The experimental results showed that samples were heated at an electric heating temperature(1500°C) and then further sintered with microwave for 30~60 min, tricalcium silicate could be formed with kilogram step. The new burning technique can greatly increase the forming speed of tricalcium silicate, MnO2, CuO and Ni2O3 could enhance the microwave sintering.

ELECTRICAL CONDUCTION IN SUBSTITUTED Li-FERRITES PREPARED BY MICROWAVE PROCESSING

2005 ◽  
Vol 19 (21) ◽  
pp. 1051-1055 ◽  
Author(s):  
MAMATA MAISNAM ◽  
SUMITRA PHANJOUBAM ◽  
H. N. K. SARMA ◽  
CHANDRA PRAKASH ◽  
L. RADHAPIYARI DEVI ◽  
...  
Keyword(s):  
Activation Energy ◽  
Lattice Constant ◽  
Electrical Conduction ◽  
Spinel Structure ◽  
Single Phase ◽  
Microwave Sintering ◽  
Microwave Processing ◽  
Conventional Sintering

Samples with representative formula Li 0.45 Ni 0.1 Mn 0.1 Fe 2.35 O 4 have been sintered by conventional sintering technique and microwave sintering technique. Both the samples showed single-phase with spinel structure. The lattice constant for the microwave sintered (MS) sample showed a lower value than the conventionally sintered (CS) sample. The density of the MS sample has been found to be higher than the CS sample. And MS sample showed a higher value of resistivity and activation energy compared to the CS sample. The possible mechanisms are discussed.

Preparation of Rare-Earth Permanent Magnetic Strontium Ferrite by Microwave Sintering Process

2010 ◽  
Vol 177 ◽  
pp. 264-268 ◽  
Author(s):  
Han Han Jiang ◽  
Ming Lin Jin ◽  
Zhan Yong Wang ◽  
Qi Zhong Chen ◽  
Hui Chun Qian
Keyword(s):  
Rare Earth ◽  
Microwave Sintering ◽  
Magnetic Domain ◽  
Strontium Ferrite ◽  
Green Body ◽  
Sintering Process ◽  
Wet Milling ◽  
Conventional Sintering ◽  
Degree Of Orientation ◽  
Sintering Method

In this paper, the green body was prepared by pre-roasted material of strontium ferrite, adding 0.2 to 9% the rare earth additive, by wet milling and forming into pellets Φ30×10 mm under magnetic field. Then, the green body was sintered separately by microwave sintering (MS) method and conventional sintering (CS) technique. The results showed that: the strontium ferrite samples with the same magnetic properties Br and (BH) max were 420 ± 10mT and 33.0 ± 2 kJ/m 3) were synthesized by microwave sintering (MS) method against conventional sintering method, the sintering temperature and time were reduced 150~300°C and 5~6h. Therefore, microwave sintering method will significantly decrease energy consumption. Further analysis revealed that the major improvements in microwave sintering were the material microstructure, the grain size was significantly reduced, the magnetic domain short-range order was increased so that the degree of orientation was increased, and although the fusion was existed between grains, the grain boundaries did not disappear.

Microstructure and Magnetic Properties of Microwave Sintered Ni0.5Zn0.5Fe2O4 Ferrite

2013 ◽  
Vol 328 ◽  
pp. 705-709
Author(s):  
Yuan Dong Peng ◽  
Qing Lin Xia ◽  
Li Ya Li ◽  
Ming Lou ◽  
Jing Zhi Hu ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Microwave Sintering ◽  
Initial Permeability ◽  
Soaking Time ◽  
X Ray ◽  
Intrinsic Coercivity ◽  
Conventional Sintering ◽  
Maximum Permeability ◽  
Sintering Method ◽  
Microstructure And Magnetic Properties

Ni0.5Zn0.5)Fe2O4 ferrite has been sintered via microwave irradiation. The structural, component and magnetic properties of NiZn ferrite was determined by SEM, X-ray powder diffraction (XRD) and automatic hysteresis loop magnetometer. Results showed that the material sintered by microwave energy at 1220°C for 20min had a high purity (Ni0.5Zn0.5)Fe2O4 phase. The sample obtained magnetic properties of intrinsic coercivity 222A/m, saturation magnetization 332mT, initial permeability 0.20mH/m and maximum permeability 0.58mH/m. Compared with conventional sintering method, microwave sintering of NiZn ferrite is more efficient and reducing soaking time.

Effect of High-Frequency Microwaves on the Microhardness of Alumina Ceramic

2016 ◽  
Vol 872 ◽  
pp. 114-117 ◽  
Author(s):  
I Nyoman Sudiana ◽  
Seitaro Mitsudo ◽  
Muhammad Zamrun Firihu ◽  
Haji Aripin
Keyword(s):  
High Frequency ◽  
Microwave Sintering ◽  
Interaction Mechanism ◽  
Microwave Frequency ◽  
Microwave Processing ◽  
Conventional Heating ◽  
Physical Mechanisms ◽  
Microwave Effect ◽  
Series Of Experiments ◽  
Very High

Microwave processing of ceramics has attracted much research interest because of its significant advantages over the conventional one. Most researchers compared processes that occurred during the microwave and conventional heating at the same temperature and time. The enhancements found in the former method are indicated as a microwave effect which is usually used for explaining the phenomena in microwave processing. Numerous recent studies have been focused on the effect to elucidate the microwave interaction mechanism with materials. This paper will present effect of very high microwave frequency to hardness of sintered alumina. The sintering results were taken from a series of experiments to study the microwave effect on properties of alumina. Microwave sintering was performed by using the 300 GHz microwave sintering system. Some possible physical mechanisms are also discussed.

scholarly journals Microwave versus conventional sintering: Estimate of the apparent activation energy for densification of α-alumina and zinc oxide

2014 ◽  
Vol 34 (12) ◽  
pp. 3103-3110 ◽  
Author(s):  
Fei Zuo ◽  
Alexandre Badev ◽  
Sébastien Saunier ◽  
Dominique Goeuriot ◽  
Romain Heuguet ◽  
...  
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Apparent Activation Energy ◽  
Conventional Sintering

scholarly journals Rapid Microwave Synthesis and Structural Phase Diagram of LnxY1−xMnO3

2014 ◽  
Vol 69 (7) ◽  
pp. 761-766 ◽  
Author(s):  
Fred P. Marlton ◽  
Darren J. Goossens ◽  
Reyner White ◽  
Wayne D. Hutchison
Keyword(s):  
Phase Diagram ◽  
Microwave Synthesis ◽  
Single Phase ◽  
Microwave Sintering ◽  
Structural Phase ◽  
Conventional Sintering ◽  
The Stability ◽  
Related Compounds ◽  
Sintering Method

YMnO3 is one of the primary examples of a multiferroic ceramic. We present a novel solid-state microwave sintering method for making high-purity ceramic samples of YMnO3 and related compounds in a few hours. This leads to determination of the structural phase diagram for the formation of single-phase, hexagonal samples when doping lanthanides into YMnO3. It is found that the solidstate microwave synthesis allows manufacture of high-quality samples in hours rather than days. The resulting phase diagram accords well with results from the literature, and from calculations based on the Goldschmidt tolerance factor for the stability of perovskite structures, suggesting that the transformation from hexagonal to perovskite with doping is driven essentially by ion sizes. Some results concerning the microwave synthesis of BaLnInO4 compounds, where Ln is a lanthanide, are noted. Microwave sintering of BaNdInO4 yields single-phase samples where conventional sintering does not.

Permittivity Relaxation Variation for Additive Doping in Cobalt Ferrite at High Frequencies

2019 ◽  
Vol 201 (1) ◽  
pp. 155-162
Author(s):  
S. Bharadwaj ◽  
Suman Kumar Burnwal ◽  
Subimal Deb ◽  
S. Ragini ◽  
S. R. Murthy
Keyword(s):  
Dielectric Relaxation ◽  
Cobalt Ferrite ◽  
Microwave Sintering ◽  
Least Square ◽  
High Frequencies ◽  
Microwave Hydrothermal ◽  
Least Square Fit ◽  
C 30 ◽  
Linear Least Square ◽  
Sintering Method

We present a comparative study of the variation in dielectric relaxation for the additives SiO2, TiO2 and ZrO2 in cobalt ferrite. CoFe2O4 was prepared using microwave hydrothermal system and sintered at 900 °C/30 min using microwave sintering method. Real and imaginary parts of permittivity were measured in the frequency range of 1 MHz to 1.8 GHz for these samples. A shift in the dielectric relaxation towards higher frequencies for doped samples is observed as expected in percolating systems. A non-linear least square fit of the electron oscillator model is used to parameterize absorption in the samples.

STRUCTURAL, ELECTRICAL AND MAGNETIC CHARACTERIZATION OF Ni–Cu–Zn SPINEL FERRITES

2011 ◽  
Vol 25 (03) ◽  
pp. 211-222 ◽  
Author(s):  
M. PENCHAL REDDY ◽  
M. VENKATA RAMANA ◽  
N. RAMA MANOHAR REDDY ◽  
K. V. SIVA KUMAR ◽  
R. RAMA KRISHNA REDDY ◽  
...  
Keyword(s):  
Single Phase ◽  
Sintering Temperature ◽  
Microwave Sintering ◽  
Initial Permeability ◽  
Electromagnetic Devices ◽  
Zn Ferrite ◽  
Conventional Sintering ◽  
Tan Δ ◽  
Sintering Method

Ni – Cu – Zn ferrite materials have been extensively used in multilayer chip inductors because of their remarkable properties at higher frequencies. In the present work, single phase Ni 0.35 Cu 0.05 Zn 0.60 Fe 1.98 O 4-δ ferrite, has been prepared by microwave sintered (MS) method. In comparison with the conventional sintering method (CS), the sintering temperature and time for this MS method were significantly reduced to 30 min and 950°C from 5 h and 1250°C for the CS process. The frequency dependence of the dielectric properties such as dielectric constant (ε'), dielectric loss ( tan δ) were studied. The temperature dependence of magnetic initial permeability (μi) was studied. The saturation magnetization was also studied as a function of magnetic field. These microwave sintered ferrites results were compared with the properties of ferrites prepared by conventional sintering method in normal heating. Microwave sintering improves structural as well as electromagnetic parameters measured and thus makes the ferrite more suitable in microwave applications and electromagnetic devices.

Sign in / Sign up

Export Citation Format

Share Document