Preparation and Characterization of NTC NiMn2O4-La1-xCaxMnO3 (0≤x≤0.3) Composite Ceramics

2013 ◽  
Vol 716 ◽  
pp. 78-83 ◽  
Author(s):  
Hui Min Zhang ◽  
Fang Guan ◽  
Ai Min Chang ◽  
Li Jun Zhao
Keyword(s):  
Electrical Resistivity ◽  
Perovskite Structure ◽  
Spinel Structure ◽  
Thermal Constant ◽  
Inrush Current ◽  
Composite Ceramics ◽  
Sem Images ◽  
Conventional Solid State Reaction ◽  
Different Temperatures ◽  
Xrd Patterns

Composite ceramics made of spinel structure NiMn2O4 and CaO-doped perovskite structure LaMnO3 were prepared by a conventional solid state reaction and sintered at different temperatures. The XRD patterns have shown that the major phases presented in the sintered samples are NiMn2O4 compounds with the spinel structure, La1-xCaxMnO3 with the perovskite structure and NiO with a monoclinic structure. SEM images show that the density and grain size of the composite ceramics increases with sintered temperature increasing. The electrical resistivity of the composite ceramics at 25°C is found to change significantly depending on the CaO content, while the thermal constant B is still reasonably large in the range of 2400 to 3000 K. For the composition x = 0.1, the composite with a low electrical resistivity (ρ25°C=4.46Ω·cm) and moderate B value (B25/50=2762K) was obtained. These composites could be applied as potential candidates for NTC thermistors in the suppression of the inrush current.

Investigation of the Structural and Magnetic Properties of BaM Hexaferrites Prepared from Scrap Iron Filings

2021 ◽  
Vol 14 (4) ◽  
pp. 287-299
Keyword(s):  
Magnetic Properties ◽  
Magnetic Recording ◽  
Barium Carbonate ◽  
Oxide Phase ◽  
Magnetic Oxide ◽  
Sem Images ◽  
Conventional Solid State Reaction ◽  
Scrap Iron ◽  
Xrd Patterns ◽  
High Density Magnetic Recording

Abstract: In this work, we demonstrate the feasibility of preparing a commercially important type of magnetic oxide, BaM (BaFe12O19) hexaferrite, using scrap iron filings as an iron source. The hexaferrites were prepared by conventional solid state reaction and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and magnetization measurements. XRD patterns of samples prepared by mixing powders extracted from the iron filings with appropriate amounts of barium carbonate and sintering at 1200 °C revealed the presence of a major BaM hexaferrite with small amounts of nonmagnetic α-Fe2O3 oxide phase. On the other hand, SEM images of the samples showed clear crystallization of perfect hexagonal platelets of BaM hexaferrite, which was further confirmed by the Curie temperature determined from the thermomagnetic measurements. The saturation magnetization of the samples was in the range of 45.1– 52.1 emu/g and the remnant magnetization in the range of 14.8 – 19.0 emu/g. These values and the moderate coercivity of ~ 1 kOe suggest that the prepared samples could potentially be useful for high-density magnetic recording. Keywords: Hexaferrite, Solid waste, Magnetic Properties, Structural properties, Magnetic recording.

scholarly journals Existence of Partially Degenerate Electrical Transport in Intermetallic Cu2SnSe3 Thermoelectric System Sintered at Different Temperatures

2021 ◽  
Author(s):  
K. Gurukrishna ◽  
H. R. Nikhita ◽  
S. M. Mallikarjuna Swamy ◽  
Ashok Rao
Keyword(s):  
Electrical Resistivity ◽  
High Temperatures ◽  
Electrical Transport ◽  
Minority Carrier ◽  
Upward Movement ◽  
Temperature Dependent ◽  
Conventional Solid State Reaction ◽  
Different Temperatures ◽  
Transport Behaviour ◽  
Small Polarons

AbstractA detailed investigation on the temperature dependent electrical properties of Cu2SnSe3 system, synthesized via conventional solid-state reaction at different sintering temperatures are presented in this communication. All the samples exhibit degenerate semiconducting nature at low temperatures. The existence of small polarons and hence electron–phonon interactions are confirmed at temperatures below 400 K. A transition was observed from degenerate to non-degenerate semiconducting behaviour at high temperatures (T > 400 K). The study confirms the unusual transition in electrical resistivity as well as thermopower at high temperatures in all the compounds, demonstrating the existence of minority carrier excitation along with temperature-triggered ionisation of the defects. The transport behaviour is further supported by an upward movement of Fermi level away from the valence band. Highest weighted mobility of 8.2 cm2 V−1 s−1 at 673 K was obtained for the sample sintered at 1073 K. A considerable decrease in electrical resistivity with increase in temperature (T > 400 K) has driven the power factor to increase exponentially, thereby achieving highest value of 188 µV/mK2 (at 673 K) for the sample sintered at 673 K. Graphic abstract

scholarly journals Investigation of The Dielectric Properties Of (Cu, Tl) 1234 Added with Graphene

2019 ◽  
Vol 13 (4) ◽  
pp. 12
Author(s):  
Ibrahim. Younes ◽  
Hadi. Basma ◽  
Mohamad. Anas ◽  
Ramadan. Awad
Keyword(s):  
Dielectric Properties ◽  
Normal Pressure ◽  
Superconducting Transition ◽  
Solid State Reaction Technique ◽  
Sem Images ◽  
Conventional Solid State Reaction ◽  
Different Temperatures ◽  
One Step ◽  
Dielectric Constant Increase ◽  
Frequency Temperature

Superconducting samples of type (Cu­0.5Tl0.5)-1234 were prepared at normal pressure via one step of conventional solid state reaction technique, and added with x wt.% of graphene (0≤x≤0.1). X-ray powder diffraction (XRD) shows that the addition of graphene does not alter the tetragonal structure and the lattice parameters of the samples. Fourier Transform Infrared (FTIR) measurements indicate the non-uniform distribution of graphene inside the (Cu­0.5Tl0.5)-1234 phase. While the Scanning Electron Microscope (SEM) images reveal the increase of the inter-grain connectivity. The superconducting transition temperature Tc, obtained from Ac magnetic susceptibility measurements, shows an enhancement up to x=0.04 Wt. %, followed by a deterioration for x >0.04. The frequency dependence of the dielectric properties of the samples was experimentally investigated at different temperatures (110 K ≤ T ≤ 260 K). The real and imaginary parts (ε' and ε'') of dielectric constant increase up to x=0.1. The study of ε' and ε'', the dielectric loss (tan δ) and the ac-conductivity (σac) have shown that the variation of frequency, temperature and addition of graphene allows the tuning of these parameters for various applications.

Properties of Pressureless Sintered SiC-TiB2 Composites

2010 ◽  
Vol 177 ◽  
pp. 369-372 ◽  
Author(s):  
Yu Hong Chen ◽  
Liang Jiang ◽  
Xue Hong Jia
Keyword(s):  
Mechanical Properties ◽  
Electrical Conductivity ◽  
Pressureless Sintering ◽  
Composite Ceramics ◽  
Sem Images ◽  
Sintering Additive ◽  
Xrd Patterns ◽  
New Phase ◽  
Full Densification ◽  
Sic Particle

Silicon carbide( SiC) – titanium diboride (TiB2) composite was prepared with boron (B) and carbon (C) as sintering additive via pressureless sintering at 2180°C. The density of sintered samples achieved 96% of full densification. The mechanical properties and electrical conductivity of composite ceramics with different SiC content were researched. The results showed that with the increasing of SiC content the hardness and electrical resistivity of composites decreased, while the strength increased. Although the XRD patterns of sintered samples showed that non new phase was produced, SEM images showed that SiC particle enlarged and surrounded by TiB2 grain during sintering. In this case the fracture mode was intergranular fracture.

Property Comparison of CuInSi Films Prepared by Multilayer Synthesized and Magnetron Co-Sputtering

2011 ◽  
Vol 110-116 ◽  
pp. 3755-3761
Author(s):  
Jian Sheng Xie ◽  
Jin Hua Li ◽  
Ping Luan
Keyword(s):  
Grain Size ◽  
Film Surface ◽  
Nanocomposite Films ◽  
X Ray Diffraction ◽  
Sem Images ◽  
X Ray ◽  
Absorption Studies ◽  
Nanocomposite Thin Films ◽  
Different Temperatures ◽  
Xrd Patterns

Using magnetron sputtering technology, the CuInSi nanocomposite thin films were prepared by magnetron co-sputtering method and multilayer synthesized method respectively,and followed by annealing in N2 atmosphere at different temperatures. The structure of CuInSi nanocomposite films were detected by X-ray diffraction (XRD); X-ray diffraction studies of the annealed films indicate the presence of CuInSi, the peak of main crystal phase is at about 2θ=42.308°,meanwhile,there are In2O3 peak and other peaks in the XRD patterns of films. The morphology of the film surface was studied by SEM. The SEM images show that the crystalline of the film prepared by multilayer synthesized method was granulated, But the crystalline of the film prepared by magnetron co-sputtering with needle shape. The grain size is a few hundred angstroms. The band gap has been estimated from the optical absorption studies and found to be about 1.40 eV for the sample by magnetron co-sputtering, and 1.45eV for the sample by multilayer synthesized, but all changes with the purity of CuInSi.

The Research on the Piezoelectric and Dielectric Properties of Bi0.5(Nak)0.5-BaTiO3 Lead-Free Ceramics

2014 ◽  
Vol 1035 ◽  
pp. 422-425
Author(s):  
Jian Yong Guo ◽  
Tao Sheng Zhou ◽  
Ji Hong Liao
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Perovskite Structure ◽  
Relative Dielectric Constant ◽  
Lead Free ◽  
Reactive Sintering ◽  
Lead Free Ceramics ◽  
Xrd Patterns ◽  
Sintering Method

The Bi0.5(Na1-xKx)0.5-yBaTiO3(BNK-BT) lead-free ceramics have been prepared by the solild reactive sintering method. XRD patterns show the BNK-BT ceramics had a perovskite structure. Piezoelectric and dielectric properties of the ceramics also have been studied. The results show that the samples had the best piezoelectric and dielectric properties when x=0.20, y=0.10. And the maximum of d33is 149 pC/N, while the relative dielectric constant is 1087.

Synthesis, Characterization and Properties of PANI/(La-Nd Doped BaFe12O19) Composites

2017 ◽  
Vol 727 ◽  
pp. 327-334
Author(s):  
Yan Wang ◽  
Jun Wang ◽  
Xiao Fei Zhang ◽  
Ya Qing Liu
Keyword(s):  
Sol Gel ◽  
Network Analyzer ◽  
X Ray Diffraction ◽  
Sem Images ◽  
Structure Morphology ◽  
Xrd Patterns ◽  
Hexagonal Platelet ◽  
Peak Value ◽  
Properties Of Composites

La-Nd co-doped barium hexaferrites, Ba0.7(LamNdn)0.3Fe12O19 (D-BaM), were successfully prepared by sol-gel method. PANI / D-BaM composites were synthesized by in-situ polymerization in solution. The structure, morphology and properties of samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), four-probe conductivity tester and vector network analyzer. The XRD patterns showed that the crystal structure of all the samples exist as M-type phases. The SEM images revealed that the particles presented a hexagonal platelet-like morphology. The magnetic properties could be improved by substitutions of La and Nd ions. The saturation magnetization (Ms) and coercive force (Hc) increased with the change of La / Nd ratio to the maximum at La / Nd = 3:1. The doped particles have also been embedded in conductive PANI to prepare electromagnetic materials, and the conductivity kept on the order of 10-2. The microwave absorbing properties of composites at 30 MHz-6 GHz improved obviously, the peak value of reflection loss could reach-7.5 dB.

Preparation of catalyst as Au doped Mn1Co9Ox/ceramic system for total oxidation of CO

2021 ◽  
Vol 10 (4) ◽  
pp. 39-45
Author(s):  
Phuong Pham Thi Mai ◽  
Hoan Nguyen Quoc ◽  
Quan Do Quoc ◽  
Hung Nguyen Thanh
Keyword(s):  
Sol Gel ◽  
Active Phase ◽  
Catalyst System ◽  
Oxidation Of Co ◽  
Sem Images ◽  
Total Oxidation ◽  
Wet Impregnation ◽  
Modern Analysis ◽  
Catalyst Powder ◽  
Xrd Patterns

In this paper, the Au doped Mn1Co9Ox was investigated for total oxidation of CO. The sol-gel method was applied to prepare this catalyst and some modern analysis methods as XRD, EPR, TPx, SEM were utilized to characterize its properties. The XRD patterns showed only Co3O4 phase without any peaks belonging to Mn or Au. However, the presence of Au and Mn was confirmed by EPR and O2-TPD results. With the aim to further apply catalyst in reality, the Au doped Mn1Co9Ox was deposited on ceramic by sol-gel, wet impregnation. The SEM images displayed the successful coating of active phase on substrate. However, the complete catalyst system didn’t have the high activity in total CO oxidation like the catalyst powder because of large agglomerations on coatings.

Characteristics of FeCuAl Powder Compacts Formed through Uniaxial Die Compaction Route

2017 ◽  
Vol 264 ◽  
pp. 103-106 ◽  
Author(s):  
M.M. Rahman ◽  
M.A. Ismail ◽  
H. Y. Rahman
Keyword(s):  
Electrical Resistivity ◽  
Relative Density ◽  
Bending Strength ◽  
Axial Loading ◽  
Homogeneous Distribution ◽  
Volumetric Expansion ◽  
Different Temperatures ◽  
Die Compaction ◽  
Powder Compacts ◽  
Interconnected Pores

This paper presents the development of FeCuAl powder compacts through uniaxial die compaction process. Iron powder ASC 100.29 was mechanically mixed with other elemental powders, i.e., copper (Cu), and aluminum (Al) for 30 minutes at a rotation of 30 rpm. The feedstock was subsequently shaped at three different temperatures, i.e., 30°C, 150°C, and 200°C through simultaneous upward and downward axial loading of 325 MPa. The as-pressed samples termed as green compacts were then sintered in argon gas fired furnace at 800°C for three different holding times, i.e., 30, 60, and 90 min at a rate of 10°C/min. The sintered samples were characterized for their relative density, electrical resistivity, and bending strength. The microstructure of the sintered samples was also evaluated through scanning electron microscopy (SEM). The results revealed that the sample formed at 150°C and sintered for 30 min obtained the best final characteristics, i.e., higher relative density, lower volumetric expansion and electrical resistivity, and higher bending strength. Microstructure evaluation also revealed that the sample formed at 150°C and sintered for 30 min obtained more homogeneous distribution of grains and less interconnected pores compared to the other samples.

scholarly journals TWO-STEP CROSSLINKING OF PVP/GEL NANOFIBERS

2021 ◽  
Vol 2021 ◽  
pp. 164-170
Author(s):  
H.K. Güler ◽  
F.C. Çallıoğlu
Keyword(s):  
Fiber Diameter ◽  
Experimental Studies ◽  
Water Soluble ◽  
Diameter Distribution ◽  
Sem Images ◽  
Crosslinking Process ◽  
Different Temperatures ◽  
Ft Ir ◽  
Ir Analysis ◽  
Gel Polymers

In this study, it was achieved that crosslinking of PVP/GEL nanofibers with two-steps. Crosslinking is a process highly important for water-soluble polymers in terms of application areas and mechanical properties. Firstly, crosslinking of PVP polymers experimental studies were carried out via heat treatment at different temperatures and times. Then, GEL polymers were crosslinked with GTA vapour at different times. Morphological analysis was carried out via SEM images and chemical characteristics were determined via FT-IR analysis. Moreover, after the crosslinking process, SD and WL values were calculated. All results showed that before crosslinking of SEM images, nanofibers were smooth, fine and without beads. The average fiber diameter is 196 nm and the fiber diameter distribution is quite uniform. After crosslinking of SEM images, it is expected that all nanowebs will turn from fibrous surfaces to membranous. Generally, SD and WL values decrease with crosslinking time increase. According to all of the SEM images, SD and WL values, optimum conditions were determined for PVP as 4 hours at 180oC and for GEL as 24 hours. Lastly, the presence of PVP and GEL polymers in the nanofiber structure was verified chemically with FT-IR analysis.

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