Changes in the Structure of Steel during Quenching in a Magnetic Field

2020 ◽  
Vol 989 ◽  
pp. 79-84 ◽  
Author(s):  
Viktor N. Pustovoit ◽  
Yuri V. Dolgachev ◽  
L.P. Aref'eva
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
Martensitic Transformation ◽  
Specific Surface ◽  
Surface Area ◽  
Constant Magnetic Field ◽  
Surface Relief ◽  
Volumetric Strain ◽  
Transformation Products ◽  
Electron Microscopes

The structure of martensite obtained by quenching steel under the action of a constant magnetic field was studied. The kinetic changes of the martensitic transformation, caused by the action of a magnetic field, are expressed in the structure by an increase in the dispersity of the transformation products. Samples of steels C45, 100CrMn6 and 30HGSA were investigated. Dispersity was evaluated statistically in images obtained on light and electron microscopes. The specific surface area was measured and the parameters of the surface relief caused by martensitic transformation were studied. Experimental data show that after quenching in a magnetic field, a decrease in the volumetric strain of the transformation, an increase in the dispersity of packets of martensitic crystals and components of the packets are observed. It is concluded that an increase in dispersion and a fragmentation of the structure of martensite are mainly the result of multiplicative nucleation.

Preparing of Silica Aerogel and Adsorption Performance on Nitrobenzene

2012 ◽  
Vol 512-515 ◽  
pp. 1980-1985
Author(s):  
Ya Jun Luo ◽  
Xue Li ◽  
Xiao Li Hu ◽  
Deng Liang He ◽  
Peng Lin
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Ph Value ◽  
Adsorption Property ◽  
Infrared Absorption Spectrum ◽  
Nitrobenzene Solution ◽  
Silica Source ◽  
Electron Microscopes ◽  
Scanning Electron Microscopes

SiO2aerogel is prepared under normal conditions by taking tetraethyl orthosilicate (TEOS) as the silica source, N-hexane as the displacer, trimethylchlorosilane hexane as the modifier and hydrolysis environment provided by hydrochloric acid and ammonia water. The effect of pH value, time, temperature, initial concentration on the adsorption of nitrobenzene by aerogel has been studied. The results show that the best range of the pH value for adsorption is 10.72. When adsorption time is 100 min, adsorption equilibrium can be reached. The best temperature for adsorption is 40 °C. The adsorption capacity becomes larger with the concentration increasing of the nitrobenzene solution. When the concentration reaches 500 mg/L, the adsorption reaches 32.402 mg/g. The adsorption equation matches Langmuir model. Scanning Electron Microscopes (SEM), infrared absorption spectrum and specific surface area measurements have shown that the adsorption property of SiO2aerogel for the nitrobenzene is related to cellular structure of the aerogel and large specific surface area.

Study on the kinetics of process for obtaining cobalt nanopowder by hydrogen reduction under isothermal conditions

2021 ◽  
Vol 1 (1) ◽  
pp. 49-56
Author(s):  
Hieр Nguyen Tien
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Hydrogen Reduction ◽  
Average Particle Size ◽  
Chemical Deposition ◽  
Average Particle ◽  
Isothermal Conditions ◽  
Electron Microscopes ◽  
Kinetics Of

The kinetics of metallic cobalt nanopowder synthesizing by hydrogen reduction from Co(OH)2 nanopowder under isothermal conditions were studied. Co(OH)2 nanopowder was prepared in advance by chemical deposition from aqueous solutions of Co(NO3)2 cobalt nitrate (10 wt.%) and NaOH alkali (10 wt.%) at room temperature, pH = 9 under continuous stirring. The hydrogen reduction of Co(OH)2 nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 270 to 310 °C. The crystal structure and composition of powders was studied by X-ray phase analysis. The specific surface area of samples was measured using the BET method by low-temperature nitrogen adsorption. The average particle size of powders was determined by the measured specific surface area. Particles size characteristics and morphology were investigated by transmission and scanning electron microscopes. Kinetic parameters of Co(OH)2 hydrogen reduction under isothermal conditions were calculated using the Gray–Weddington model and Arrhenius equation. It was found that the rate constant of reduction at t = 310 °C is approximately 1.93 times higher than at 270 °C, so the process accelerates by 1.58 times for 40 min of reduction. The activation energy of cobalt nanopowder synthesizing from Co(OH)2 by hydrogen reduction is ~40 kJ/mol, which indicates a mixed reaction mode. It was shown that cobalt nanoparticles obtained by the hydrogen reduction of its hydroxide at 280 °C are aggregates of equiaxed particles up to 100 nm in size where individual particles are connected to several neighboring particles by contact isthmuses.

scholarly journals High Frequency Magnetoimpedance of FeNi/Cu/FeNi Sensitive Elements with Different Geometries

2009 ◽  
Vol 152-153 ◽  
pp. 373-376 ◽  
Author(s):  
Stanislav O. Volchkov ◽  
Andrey V. Svalov ◽  
G.V. Kurlyandskaya
Keyword(s):  
Magnetic Field ◽  
Experimental Data ◽  
External Magnetic Field ◽  
Finite Elements ◽  
Magnetic Anisotropy ◽  
Constant Magnetic Field ◽  
High Frequency ◽  
Complex Impedance ◽  
Rf Sputtering ◽  
Frequency Range

In this work magnetoimpedance (MI) behaviour was studied experimentally for Fe19Ni81(175 nm)/Cu(350 nm)/Fe19Ni81(175 nm) sensitive elements deposited by rf-sputtering. A constant magnetic field was applied in plane of the sandwiches during deposition perpendicular to the Cu-lead in order to induce a magnetic anisotropy. Sandwiches with different width (w) of FeNi parts were obtained. The complex impedance was measured as a function of the external magnetic field for a frequency range of 1 MHz to 700 MHz for MI elements with different geometries. Some of MI experimental data are comparatively analysed with finite elements numerical calculations data. The obtained results can be useful for optimization of the design of miniaturized MI detectors.

Fabrication of Activated Carbon Fibers from Stabilized PAN-Based Fibers by KOH

2004 ◽  
Vol 449-452 ◽  
pp. 217-220 ◽  
Author(s):  
Young Jae Lee ◽  
Jae Hyung Kim ◽  
Jang Soon Kim ◽  
Dong Bok Lee ◽  
Jae Chun Lee ◽  
...  
Keyword(s):  
Experimental Data ◽  
Activated Carbon ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Carbon Fibers ◽  
Potassium Hydroxide ◽  
Chemical Activation ◽  
Activated Carbon Fibers ◽  
High Concentration

Activated carbon fibers were prepared from stabilized PAN-based fibers by chemical activation using potassium hydroxide at different concentration. The experimental data showed variations in specific surface area, microstructure by the activated carbon fibers. Specific surface area of about 2545 m2/g was obtained in the KOH/stabilized PAN-based fiber ratio of 1:1 at 800°. An abrupt reduction of specific surface area was observed in the experiments with the ratio of 3:1 of OH/stabilized PAN-based fiber, being dissimilar with the result of KOH/fiber ratios of 1:1 and 2:1 in the similar experiments. The high concentration of KOH led to the destruction of micropore walls instead of forming mesopores.

scholarly journals Measuring the specific surface area of mesoporous silica using x-ray scattering

2014 ◽  
Vol 70 (a1) ◽  
pp. C599-C599
Author(s):  
Julien Cambedouzou ◽  
Olivier Diat
Keyword(s):  
Experimental Data ◽  
Specific Surface ◽  
Surface Area ◽  
Mesoporous Materials ◽  
Specific Surface Area ◽  
Small Angle ◽  
X Ray ◽  
X Ray Scattering ◽  
Mcm 41 ◽  
Ray Scattering

The development of porous silica or carbon material with high specific surface area raises a high interest in the field of materials science given their potential interest in a wide range of applications including catalysis, water treatment or drug delivery. Among these mesoporous structures, those consisting of one-dimensional pores aligned along a compact hexagonal packing are of prime importance and can be referred to as "hexagonal mesoporous materials" (HMPM). The most famous silica structures of this kind are MCM-41 and SBA-15. The same symmetry can be found in carbon mesoporous materials, for example in FDU-15 structures. The precise characterization of HMPM is necessary for most of the applications envisioned for these materials (pore size, pore density, specific surface and sometimes thickness of the functionalization layer). Small angle X-ray scattering techniques offer the opportunity to determine the mean structural parameters of HMPM. Although different approaches can be found in the literature in order to numerically reproduce the experimental data obtained on HMPM or hexagonal liquid crystals, when the sample is a powder, fitting the experimental data in absolute scale with numerical models becomes necessary. However, with a large scattering contribution of grain at low q vector as well as short range correlation contribution at large q, the analysis is not so simple. In this paper, we propose a comprehensive study [1] devoted to the quantitative interpretation of small-angle scattering patterns of HMPM in terms of structure and specific surface estimation based on the formalism proposed by Spalla et al. [2]. In the case of two real samples, namely a SBA-15 and a MCM-41 powder, the specific surface area of the mesopores is estimated and is discussed in the light of gas adsorption measurements.

scholarly journals SINTESIS ADSORBEN BERBASIS LIGNOSELULOSA DARI KAYU RANDU (Ceiba pentandraL.) UNTUK MENJERAP Pb(II) DALAM LIMBAH CAIR ARTIFISIAL

2014 ◽  
Vol 3 (2) ◽  
Author(s):  
Widi Astuti ◽  
Nova Susilowati
Keyword(s):  
Experimental Data ◽  
Specific Surface ◽  
Surface Area ◽  
Functional Group ◽  
Pore Diameter ◽  
Freundlich Isotherm ◽  
Model Fit ◽  
Adsorption Ability ◽  
Result Show ◽  
Model Isotherm

<p>Pada penelitian ini, limbah kayu randu digunakan sebagai adsorben untuk menjerap ion Pb (II) dalam larutan. Kayu randu yang telah direaksikan dengan NaOH dikarakterisasi dan diuji kemampuan adsorpsinya. Hasil penelitian menunjukkan bahwa pada serbuk kayu hasil reaksi dengan NaOH terlihat adanya pori dengan bentuk dan ukuran yang lebih seragam dengan luas permukaan spesifik 7,420 m2/g dan diameter pori 0.3 nm. Adsorpsi mencapai kesetimbangan pada 120 menit dengan kemampuan penjerapan sebesar 2,47 mg/g. Adsorpsi mengikuti model isotherm Freundlich dengan nilai tetapan KF sebesar 1,986 dan n sebesar 0,649.</p><p>In this research, cotton wood waste was used to adsorb Pb(II) ion in the solution. Sodium hydroxide treated cotton wood was characterized its spesific surface area, pore size, morphology and functional group. Furthermore, it was tested its adsorption ability to adsorb ion Pb(II). The result show that the treated cotton wood has uniform pores. Its specific surface area and pore diameter are 7.420 m2/g and 0.3 nm, respectively. The equilibrium was achieved in 120 minutes. Adsorption ability of the adsorben is 2.47 mg/g. In the adsorption, Freundlich isotherm model fit with the experimental data with the value of KF and n are 1.986 and 0.649, respectively.</p>

Effects of High Magnetic Field and Tensile Stress on Martensitic Transformation Behavior and Microstructure At 4 K in Fe-Ni-C Alloys

1995 ◽  
Vol 398 ◽  
Author(s):  
H. Ohtsuka ◽  
K. Nagai ◽  
S. Kajiwara ◽  
H. Kitaguchi ◽  
M. Uehara
Keyword(s):  
Magnetic Field ◽  
Martensitic Transformation ◽  
Tensile Stress ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
High Magnetic Field ◽  
Constant Magnetic Field ◽  
Critical Magnetic Field ◽  
Transformation Behavior ◽  
The Magnetic Field

ABSTRACTEffects of high magnetic field and tensile stress on martensitic transformation behavior and microstructure at 4 K have been studied in Fe-31Ni-0.4C and Fe-27Ni-0.8C shape memory alloys. It was found that the critical magnetic field to induce martensitic transformation is between 7.5 T and 10 T. In the case of Fe-27Ni-0.8C, martensitic transformation is stress-induced at lower level of stress in magnetic field than in the case when no magnetic Field is applied. The amount of martensite formed by increasing the magnetic field under constant stress is larger than that formed by increasing the stress in the constant magnetic field.

PERMEABILITY STUDIES: II. SURFACE AREA MEASUREMENTS OF INORGANIC PIGMENT POWDERS

1947 ◽  
Vol 25a (4) ◽  
pp. 191-209 ◽  
Author(s):  
J. C. Arnell
Keyword(s):  
Experimental Data ◽  
Electron Microscope ◽  
Specific Surface ◽  
Surface Area ◽  
Satisfactory Agreement ◽  
Surface Measurement ◽  
Inorganic Pigments ◽  
Inorganic Pigment ◽  
Permeability Studies

The modified Kozeny equation has been found to be satisfactory for the measurement of the specific surface of inorganic pigments having particle diameters of the order of 0.1 to 0.2 µ to within ±10%. These powders were too fine for visual microscope counting or standard sedimentation methods of specific surface measurement. The results obtained from experimental data were checked against those calculated from electron microscope counting for two of the powders studied and found to be in satisfactory agreement.

Features of Martensitic Transformation in Steel during Quenching in a Constant Magnetic Field

2019 ◽  
Vol 946 ◽  
pp. 304-308 ◽  
Author(s):  
Viktor N. Pustovoit ◽  
Yuri V. Dolgachev ◽  
L.P. Aref'eva
Keyword(s):  
Magnetic Field ◽  
Martensitic Transformation ◽  
External Magnetic Field ◽  
Constant Magnetic Field ◽  
Electric Resistivity ◽  
Nucleation Center ◽  
Martensite Formation ◽  
Resistivity Method ◽  
Elastic Forces ◽  
Energy Of Formation

The data on the occurrence of martensitic transformation in steel under the action of a magnetic field were obtained by the electric resistivity method. The obtained data indicate the possibility of stress-assisted martensite formation in the temperature range of Ms-Md (in which superplasticity of austenite is observed). This possibility is due to the magnetic heterogeneity of austenite. Nanosized regions with a ferromagnetic order are present in the paramagnetic matrix. They can perceive the energy of the external magnetic field through the magnetostrictive stresses and change the fields of the elastic forces in the crystal lattice. All this leads to a decrease in the energy of formation of the nucleation center.

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