scholarly journals Influence of Microstructure-Evolution Changes on the Dielectric Properties of Strontium Titanate Prepared via Mechanical Alloying

2019 ◽  
Vol 7 (2) ◽  
Author(s):  
Mutia Suhaibah Abdullah ◽  
Dayang Nur Fazliana Abdul Halim ◽  
Jumiah Hassan ◽  
Mansor Hashim ◽  
Alex See ◽  
...  
Keyword(s):  
Grain Size ◽  
Dielectric Properties ◽  
Mechanical Alloying ◽  
Dielectric Material ◽  
Perovskite Phase ◽  
Morphological Changes ◽  
Milled Powder ◽  
Sudden Increase ◽  
Common Trend ◽  
Lower Frequency Region

SrTiO3 is a dielectric material of considerable interest. However, the relationships between microstructure and dielectric properties have not been studied in detail. Hence, we have undertaken an extensive experimental work to study the evolution of the dielectric properties against morphological changes of SrTiO3. SrTiO3 was prepared using the mechanical alloying method and samples with nano-sized starting powder were obtained. The milled powder was pressed into pellets and sintered at various temperatures ranging from 500 °C to 1400 °C. XRD studies showed that these ceramics completely formed a perovskite phase at 900 °C. FeSEM studies show the presence of small grain sizes ranging from 120 to 600 nm. Dielectric constant (εr’) and dielectric loss tangent (tan δ) were measured as a function of frequency and correlated with the microstructure. εr’ and tan δ against frequency show a falling trend at the lower frequency region due to the changing interfacial effect. For sintering temperatures 1000 °C to 1100 °C, grain size and XRD peak data show a significant increase with the corresponding increase in εr’, suggesting a sudden increase in the polarizability due to significant increase in crystallinity. With increasing sintering temperature, εr’ increased proportionally with XRD peak and grain size increases, further confirming polarizability and crystallinity relationship. tan δ correlation with microstructure does not have a common trend.

The Mechanical Alloying of Magnetite Concentrate with Biochar

2020 ◽  
Vol 10 (2) ◽  
pp. 116-125
Author(s):  
Elif Aranci Öztürk ◽  
Mustafa Boyrazli ◽  
Mehmet Deniz Turan ◽  
Murat Erdemoğlu
Keyword(s):  
Crystal Structure ◽  
Particle Size ◽  
Grain Size ◽  
Mechanical Alloying ◽  
Milled Powder ◽  
Spherical Particles ◽  
Size Analysis ◽  
Biomass Waste ◽  
Magnetic Separator ◽  
Magnetite Concentrate

Aim: In this work, the effect of milling time on the mechanical alloying of the mixture containing the magnetite concentrate and biomass waste was investigated. Materials and Methods: The ore’s grade consisting of hematite and magnetite minerals was increased from 49.87% Fe to 67.29% Fe using the low intensity wet magnetic separator. Biomass waste which was supplied from ÇAYKUR black tea facilities, used as a carbon source was subjected to carbonization processes at 800°C for 1440 min. After the carbonization process, the carbon and sulphur contents of the biomass were measured as 94.68% and 0.03%, respectively. For the mechanical alloying process, a mixture consisting of magnetite concentrate with a grain size of -45 μm and biomass which was added two times the amount of carbon required for the reduction of magnetite to metallic iron was used. Result: After the mechanical alloying process which was carried out at different times, it was observed in the particle size analysis that the particle size of 90% of the mixture was reduced to about 4 μm. In SEM (Scanning Electron Microscopy) images, cube-like particles along with the spherical particles were observed depending on the mechanical alloying times. After 45 minutes of alloying, it was observed that the carbonized product milled together with magnetite concentrate was partially integrated into the crystal structure. Conclusion: The carbonized tea plant waste milled together with magnetite concentrate was partially integrated into the crystal structure. And the mechanical alloying provide to increase in the specific surface area in parallel with the grain size decrease in the study. Thus, in the later stage of the study, the milled powder acquired more ability to react.

scholarly journals Effect of Milling Time on Microstructure, Crystallite Size and Dielectric Properties of Srtio3 Ceramic Synthesized via Mechanical Alloying Method

2011 ◽  
Vol 364 ◽  
pp. 388-392
Author(s):  
Yick Jeng Wong ◽  
Hassan Jumiah ◽  
Mansor Hashim ◽  
Swee Yin Wong ◽  
Leow Chun Yan
Keyword(s):  
Dielectric Constant ◽  
Grain Size ◽  
Dielectric Properties ◽  
Mechanical Alloying ◽  
Crystallite Size ◽  
Single Phase ◽  
Milling Time ◽  
Average Grain Size ◽  
Average Lattice ◽  
Milled Powders

SrTiO3 sample has been successfully prepared by mechanical alloying (MA) method. The effect of milling time on microstructure, crystallite size and dielectric properties of SrTiO3 were studied. The results revealed that the mean crystallite size of milled powders decreased from 84.56 to 12.87 nm with increasing milling time. However, the average lattice strain of milled powders increased from 0.2 to 0.93% with increasing milling time. A single phase SrTiO3 could not be formed with milling alone and required annealing process. A transformation of anatase-TiO2 to rutile-TiO2 was observed at 16 h of milling. After the milled powders were subjected to sintering process at 1200°C, formation of single-phase SrTiO3-type cubic (Pm-3m) perovskite structure was observed. The peak intensities of the sintered SrTiO3 samples decreased as the milling time was increased. For microstructural observations, the average grain size of the sintered SrTiO3 sample milled for 8 h showed the largest. For dielectric measurements, the dielectric constant of the sintered SrTiO3 sample milled for 8 h showed the highest among others. This could be due to the largest grain size obtained for sintered SrTiO3 sample milled for 8 h. The decrease in the grain size with increasing milling time resulted to the decrease in dielectric constant.

scholarly journals The properties of high-energy milled pre-alloyed copper powders containing 1 wt.% Al

2007 ◽  
Vol 72 (1) ◽  
pp. 45-53 ◽  
Author(s):  
Viseslava Rajkovic ◽  
Dusan Bozic ◽  
Aleksandar Devecerski
Keyword(s):  
Thermal Stability ◽  
Electrical Conductivity ◽  
Grain Size ◽  
Morphological Changes ◽  
Milled Powder ◽  
Copper Matrix ◽  
High Energy ◽  
Lattice Parameter ◽  
Good Thermal Stability ◽  
Before And After

The microstructural and morphological changes of inert gas atomized pre-alloyed Cu-1 wt.% Al powders subjected to hith-energy milling were studied. The microhardness of hot-pressed compacts was measured as a function of milling time. The thermal stability during exposure at 800 ?C and the electrical conductivity of compacts were also examined. During the high-energy milling, severe deformation led to refinement of the powder particle grain size (from 550 nm to about 55 nm) and a decrease in the lattice parameter (0.10 %), indicating precipitation of aluminium from the copper matrix. The microhardness of compacts obtained from 5 h-milled powders was 2160 MPa. After exposure at 800?C for 5 h, these compacts still exhibited a high microhardness value (1325 MPa), indicating good thermal stability. The increase of microhardness and good thermal stability is attributed to the small grain size (270 and 390 nm before and after high temperature exposure, respectively). The room temperature electrical conductivity of compacts processed from 5 h-milled powder was 79% IACS. .

Structure and Dielectric Properties of Mg, Cr-Doped LaSrFeO3 Films

2014 ◽  
Vol 538 ◽  
pp. 11-14
Author(s):  
Yang Lu Hou ◽  
Xing Hua Fu ◽  
Wen Hong Tao ◽  
Xin Jin
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Grain Size ◽  
Dielectric Properties ◽  
Perovskite Phase ◽  
Sol Gel ◽  
Doping Amount ◽  
Single Perovskite Phase ◽  
Pure Perovskite Phase ◽  
Mg Doped

Mg-doped LaFeO3 thin film and Mg, Cr-doped La0.5Sr0.5FeO3 thin films were prepared by the sol-gel method. The change rules of structure and dielectric properties of the films were studied by XRD, SEM, and Agilent. The dielectric properties of La0.5Sr0.5FeO3 and LaFeO3 films were improved by the substitute with Mg and Cr. The doping amount of Mg and Cr for the optimal dielectric properties of La0.5Sr0.5FeO3 films is 45mol%, 25mol%, respectively, and for LaFeO3, the doping amount of Mg is 8mol%. The observed pure perovskite phase of the doped films suggested the dissolution of Mn, Co, and Ni in La0.5Sr0.5FeO3 crystal lattice. Mg and Cr were integrate in the lattice of LaFeO3 and La0.5Sr0.5FeO3, and mineral is single perovskite phase. The surface of the film is smooth, without cracks, surface grain size distribution and had uniform grain size.

Structure and Dielectric Properties of Mn, Co, and Ni-Doped LaSrFeO3 Films

2013 ◽  
Vol 575-576 ◽  
pp. 499-503
Author(s):  
Bin Fu ◽  
Yang Lu Hou ◽  
Wei Bing Wu ◽  
Xing Hua Fu
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Dielectric Properties ◽  
Smooth Surface ◽  
Perovskite Phase ◽  
Sol Gel ◽  
Electrical Measurements ◽  
Doping Amount ◽  
Pure Perovskite Phase ◽  
Gel Technique

Mn, Co, and Ni-doped La0.5Sr0.5FeO3thin films were prepared by the sol-gel technique. The structure and dielectric properties of the films were studied by XRD, SEM, and electrical measurements. The morphology observation demonstrated these films had uniform grain size and smooth surface. The dielectric properties of La0.5Sr0.5FeO3films were improved by the replacement of Fe with Mn, Co, and Ni. The doping amount of Mn, Co, and Ni for the optimal dielectric properties of La0.5Sr0.5FeO3films is 5%, 2%, and 3%, respectively. The observed pure perovskite phase of the doped films suggested the dissolution of Mn, Co, and Ni in La0.5Sr0.5FeO3crystal lattice.

Influence of Ti content and sintering temperature on dielectric properties of Bi4Ti3O12 ceramics

2017 ◽  
Vol 31 (16-19) ◽  
pp. 1744057 ◽  
Author(s):  
Yong Chen ◽  
Zhaozhi Li ◽  
Huyin Su ◽  
Simin Xue ◽  
Mengyun Bian ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Curie Temperature ◽  
Relative Permittivity ◽  
Dielectric Material ◽  
Perovskite Phase ◽  
Layered Perovskite ◽  
Microwave Ceramics ◽  
Ti Content

An ultra-broad working temperature dielectric material, Bi4Ti[Formula: see text]O[Formula: see text]([Formula: see text] = 2.96, 2.98, 3.0, 3.02 and 3.04), prepared by a conventional mixed oxide route was investigated which is supposed to replace lead-containing ceramics for its outstanding dielectric properties. Microstructure and dielectric properties of well-sintered samples (at 1040[Formula: see text]C, 1060[Formula: see text]C, 1080[Formula: see text]C, 1100[Formula: see text]C and 1120[Formula: see text]C) were studied. X-ray diffraction analysis indicated that the new material was in a single Bi-layered perovskite phase. The dielectric constant and dielectric loss at different frequencies (10, 100 and 1000 kHz) were measured at 1100[Formula: see text]C. With the increasing frequency, the dielectric constant decreased and the dielectric loss was almost unchanged. While at 100 kHz, there is the highest relative permittivity ([Formula: see text]) of 2822.8 and the lowest dielectric loss of 0.0040 ([Formula: see text] = 2.98), the Curie temperature ([Formula: see text]) is 668.9[Formula: see text]C. At the frequency of 1 MHz, the highest relative permittivity ([Formula: see text]) is 1115.8 when Ti content is 3.02, and the Curie temperature is 672.2[Formula: see text]C. SEM can explain the results of the dielectric spectrum at different Ti content and sintering temperatures. [Formula: see text] plots show that Bi4Ti3O[Formula: see text] ceramics are a kind of dielectrics. Since it possesses large dielectric constant, low dielectric loss and stable temperature character, this material shows promising applications for the ultra-broad temperature range components, such as high-temperature multilayer ceramic capacitors and microwave ceramics.

Investigating the influence of the grain size and distribution on the macroscopic dielectric properties of Antarctic firn

2021 ◽  
Vol 185 ◽  
pp. 103254
Author(s):  
R. Olmi ◽  
M. Bittelli ◽  
G. Picard ◽  
L. Arnaud ◽  
A. Mialon ◽  
...  
Keyword(s):  
Grain Size ◽  
Dielectric Properties

Development of Biodegradable Mg-Ti Alloy Synthesized Using Mechanical Alloying

2016 ◽  
Vol 1133 ◽  
pp. 75-79 ◽  
Author(s):  
Emee Marina Salleh ◽  
Sivakumar Ramakrishnan ◽  
Zuhailawati Hussain
Keyword(s):  
Mechanical Alloying ◽  
Milling Time ◽  
Milled Powder ◽  
Milling Process ◽  
Planetary Mill ◽  
Ti Alloy ◽  
X Ray Diffraction ◽  
Argon Flow ◽  
Diffraction Patterns ◽  
Ti Powder

The aim of this work was to study the effect of milling time on binary magnesium-titanium (Mg-Ti) alloy synthesized by mechanical alloying. A powder mixture of Mg and Ti with the composition of Mg-15wt%Ti was milled in a planetary mill under argon atmosphere using a stainless steel container and balls. Milling process was carried out at 400 rpm for various milling time of 2, 5, 10, 15 and 30 hours. 3% n-heptane solution was added prior to milling process to avoid excessive cold welding of the powder. Then, as-milled powder was compacted under 400 MPa and sintered in a tube furnace at 500 °C in argon flow. The refinement analysis of the x-ray diffraction patterns shows the presence of Mg-Ti solid solution when Mg-Ti powder was mechanically milled for 15 hours and further. Enhancements of Mg-Ti phase formation with a reduction in Mg crystallite size were observed with the increase in milling time. A prolonged milling time has increased the density and hardness of the sintered Mg-Ti alloy.

scholarly journals Snow dielectric properties: from DC to microwave X-band

1994 ◽  
Vol 19 ◽  
pp. 92-96 ◽  
Author(s):  
TH. Achammer ◽  
A. Denoth
Keyword(s):  
Grain Size ◽  
Dielectric Properties ◽  
Water Content ◽  
Liquid Water ◽  
Liquid Water Content ◽  
Frequency Range ◽  
Snow Density ◽  
Cold Room ◽  
X Band ◽  
Grain Size And Shape

Broadband measurements of dielectric properties of natural snow samples near or at 0°C are reported. Measurement quantities are: dielectric permittivity, loss factor and complex propagation factor for electromagnetic waves. X-band measurements were made in a cold room in the laboratory; measurements at low and intermediate frequencies were carried out both in the field (Stubai Alps, 3300 m; Hafelekar near Innsbruck, 2100 m) and in the cold room. Results show that in the different frequency ranges the relative effect on snow dielectric properties of the parameters: density, grain-size and shape, liquid water content, shape and distribution of liquid inclusions and content of impurities, varies significantly. In the low-frequency range the influence of grain-size and shape and snow density dominates; in the medium-frequency range liquid water content and density are the dominant parameters. In the microwave X-band the influence of the amount, shape and distribution of liquid inclusions and snow density is more important than that of the remaining parameters.

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