Magnetic Properties Of Iron/Silica Gel Nanocomposites

1988 ◽  
Vol 132 ◽  
Author(s):  
Robert D. Shull ◽  
Joseph J. Ritter ◽  
Alexander J. Shapiro ◽  
Lydon J. Swartzendruber ◽  
Llawrence H. Bennett
Keyword(s):  
Silica Gel ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Subsequent Treatment ◽  
Ferric Nitrate ◽  
Bragg Scattering ◽  
X Ray Diffraction ◽  
Iron Compounds ◽  
X Ray ◽  
Interconnected Pores

ABSTRACTHomogeneous gelled composites of iron and silica containing 5–30 wt. % Fe have been prepared by low temperature polymerization of aqueous solutions of ferric nitrate, tetraethoxysilane, and ethanol (with an HF catalyst). X-ray diffraction data, characterized by the presence of a diffuse scattering peak centered at 20≈24 degrees and the absence of any strong Bragg scattering from the iron-containing regions, indicates that these bulk materials are comprised of nanometer-sized regions of iron compounds embedded in a silica gel matrix. Scanning electron microscopy observations show that this matrix is characterized by the presence of many interconnected pores and that the size of these pores is related to the particle size of the Fe-containing regions. The paramagnetic nature of these materials at room temperature, as well as the small size of the iron-containing regions, is indicated by the appearance in many of the samples of only a high intensity central doublet in the 57Fe M6ssbauer spectra. The Mössbauer effect data demonstrates that the form of the iron can be changed by a subsequent treatment in an atmosphere of ammonia or hydrogen at elevated temperatures: for a 10 wt. % Fe sample treated with ammonia, only a central doublet was observed but with a much larger quadrupole splitting and isomer shift. Both of these subsequently treated materials became superparamagnetic at room temperature. In addition, magnetic susceptibility measurements indicate that the hydrogen treated material becomes a spin glass at low temperatures.

Synthesis and Luminescence Properties of Chalcopyrite-Type CuAlS2

2006 ◽  
Vol 301 ◽  
pp. 177-180 ◽  
Author(s):  
Yuichiro Kuroki ◽  
Tomoichiro Okamoto ◽  
Masasuke Takata
Keyword(s):  
Diffraction Analysis ◽  
Room Temperature ◽  
Single Phase ◽  
Elevated Temperatures ◽  
Emission Peak ◽  
Maximum Intensity ◽  
X Ray Diffraction ◽  
Ultraviolet Emission ◽  
X Ray ◽  
Copper Aluminum

Copper aluminum disulfide (CuAlS2) powders were synthesized in an evacuated ampoule at elevated temperatures. X-ray diffraction analysis revealed that the powders heated at temperatures higher than 800oC were single-phase CuAlS2. In the cathodoluminescence (CL) spectra measured at room temperature, the powders heated at temperatures higher than 600oC exhibited a visible emission peak at approximately 1.8 eV and a distinct ultraviolet emission peak at 3.45 eV. The powder heated at 700oC showed the maximum intensity of ultraviolet emission which is considered to be associated with excitons.

Effect of Nd on Microstructures and Properties of AZ31 Wrought Mg Alloy

2007 ◽  
Vol 546-549 ◽  
pp. 301-304
Author(s):  
Wei Qiu ◽  
En Hou Han ◽  
Lu Liu
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Mg Alloys ◽  
The Other ◽  
Mg Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Microstructures And Mechanical Properties ◽  
Re Elements

Addition of RE elements to Al-containing Mg alloys can improve properties of Mg alloys at elevated temperatures. In the present investigation, hot-extruded AZ31+x%Nd. (x=0.1,0.3,0.6and1.0 wt%) wrought Mg alloy were prepared .The effects of Nd on microstructures and mechanical properties at room temperature of new alloy were investigated. The investigation found that Nd can bring about two kind of precipitation phases . One is AlNd phase, the other is AlNdMn phase, which were identified as Al11Nd3 and Al8NdMn4 by X-ray diffraction and TEM.

Magnetic Behavior of Nanocomposites Prepared in a Vitreous Alumina Gel

1990 ◽  
Vol 206 ◽  
Author(s):  
R. D. Shull ◽  
J. J. Ritter ◽  
A. J. Shapiro ◽  
L. J. Swartzendruber ◽  
L. H. Bennett
Keyword(s):  
Magnetic Susceptibility ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Bulk Material ◽  
Magnetic Behavior ◽  
Subsequent Treatment ◽  
Ferric Nitrate ◽  
Fe Content ◽  
Alumina Gel ◽  
Aqueous Aluminum

ABSTRACTHomogeneous gelled composites of iron and vitreous alumina containing 10-40% Fe have been prepared by room temperature polymerization of aqueous aluminum alkoxide solutions containing ferric nitrate and nitric acid at low pH. Scanning electron microscopy, x-ray diffraction, and Mossbauer spectroscopy demonstrated that this bulk material is comprised of nanometer-sized regions of iron compounds embedded in a vitreous alumina gel matrix. Magnetization data showed that in the as-cured condition these nanocomposites are paramagnetic at room temperature and become either superparamagnetic or ferromagnetic on cooling to 10 K. The magnetic susceptibility increased with the Fe content and with decreasing temperature. Analysis of the temperature dependence of the magnetic susceptibility indicated the magnetic moment per Fe atom was 1.87 µB for the 10% Fe nanocomposite and that it increased linearly with composition to 1.96 µB for the 40% Fe material. Mössbauer effect data showed that subsequent treatment of these materials in a gaseous environment of hydrogen at elevated temperatures (T<400 C) changed the form of the iron in the magnetic regions. These results are compared to that observed for similar nanocomposites prepared using a silica gel matrix.

Microstructure and texture of Ti-6Al-4V alloy deformed by rotary forging at elevated temperatures

2020 ◽  
Vol 111 (10) ◽  
pp. 807-813
Author(s):  
Shan Jiang
Keyword(s):  
Grain Refinement ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Electron Back Scatter Diffraction ◽  
Dislocation Slip ◽  
Basal Texture ◽  
X Ray Diffraction ◽  
X Ray ◽  
Rotary Forging ◽  
Main Deformation

Abstract Ti-6Al-4V alloy cylinder samples were subjected to rotary forging at temperatures ranging from room temperature to 1 473 K. The microstructure and texture were examined by means of electron back-scatter diffraction and X-ray diffraction. The results indicated that the rotary forging could remarkably promote formability at elevated temperatures but not room temperature. For the 1 073 K and 1173 K samples, dynamic recrystallization led to a notable grain refinement effect and produced a typical basal texture. With the further increase of deforming temperature to 1 473 K, dislocation slip contributed the main deformation and the effect of grain refinement was weakened. The martensitic transformation took place during the cooling process of the 1 473 K sample, forming a strip type microstructure and a special texture different from basal texture.

Effects of NaBH4 Additions on Hydrogen Absorption by Nanostructured FeTi Powders

2008 ◽  
Vol 587-588 ◽  
pp. 921-925 ◽  
Author(s):  
Sofia F. Marques ◽  
Raquel A. Silva ◽  
Jose Brito Correia ◽  
Nobumitsu Shohoji ◽  
Carmen M. Rangel
Keyword(s):  
Hydrogen Absorption ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Low Cost ◽  
Reaction Products ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gas Atmosphere ◽  
Scanning Electron

FeTi intermetallic powders are very promising media for reversible hydrogen storage. However, difficult activation treatments including annealing at elevated temperatures in high pressure H2 gas atmosphere are mandatory. In the present work nanostructured FeTi powders were produced and activated in situ at room temperature using mechanical alloying/milling (MA/MM) of pure metallic constituents, Fe and Ti, added with sodium borohydride. The resultant powders, FeTiHx, already H2 pre-charged, absorbed a significant amount of H2 but require optimization for reversible absorption/desorption. This system has one of the highest volumetric storage capacities and can be produced at low cost. Several parameters of the as-milled powders were controlled. The phase constitution of the reaction products was characterized by X-ray diffraction and scanning electron microscopy and the absorption isotherms of the activated powders were determined.

A high-temperature environmental chamber for nuclear-resonant Bragg scattering studies

1998 ◽  
Vol 5 (3) ◽  
pp. 949-951
Author(s):  
J. Y. Zhao ◽  
X. W. Zhang ◽  
M. Ando
Keyword(s):  
Magnetic Field ◽  
High Temperature ◽  
Room Temperature ◽  
Bragg Scattering ◽  
X Ray Diffraction ◽  
Environmental Chamber ◽  
X Ray ◽  
Compact Size ◽  
Scattering Study

A compact environmental chamber with a furnace operating in the range from room temperature to about 900 K has been built for a high-temperature nuclear-resonant Bragg scattering study. The compact size (75 mm diameter and 70 mm depth) allows an external magnetic field to be applied from outside permanent Nd–Fe–B alloy magnets; a magnetic field up to 1000 G has been obtained. The chamber can be mounted on a precise θ–2θ goniometer so that in situ observations of X-ray diffraction from a single crystal can be carried out. The temperature is measured by two thermocouples placed at the top and back of the sample and controlled by a PID controller. The temperature fluctuation of the chamber is less than ±1 K.

Physicochemical Properties of New Dicationic Ether-Functionalized Low Melting Point Ammonium Salts

2010 ◽  
Vol 63 (7) ◽  
pp. 1122 ◽  
Author(s):  
Minna Kärnä ◽  
Manu Lahtinen ◽  
Pirkko-Leena Hakkarainen ◽  
Jussi Valkonen
Keyword(s):  
Physicochemical Properties ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Side Chain ◽  
Residual Water ◽  
X Ray Diffraction ◽  
Thermal Stabilities ◽  
X Ray ◽  
Heat Transfer Fluids ◽  
High Temperature Synthesis

Eleven new and one previously known but insufficiently characterized dicationic quaternary ammonium (QA) salts were synthesized and characterized. They contain an ethoxy ethyl group either in a side chain and/or as spacer of the diammonium cation and have bromide, hexafluorophosphate (PF6–), bis(trifluoromethanesulfonyl)imide (TFSI), or trifluoromethanesulfonate (TFMS) as an anion. 1H and 13C techniques, mass spectrometry, and elemental analysis together with X-ray diffraction and thermoanalytical methods were used for their characterization both in the liquid and solid state. In addition, residual water content and viscosity measurements were made for the two room temperature ionic liquids (RTILs). Capillary electrophoresis was used to measure the conductivity of the RTILs. Crystal structures of four compounds were determined by X-ray single crystal diffraction, and powder diffraction was used to study the crystallinity of the solid salts and to compare the structural similarities between the single crystals and the microcrystalline bulk form. Two of the TFSI salts were liquids below room temperature, having liquid ranges of ~380 and 350°C, respectively, and seven out of 12 salts melted below 100°C. In addition, both the TFSI and PF6 salts exhibited high thermal stabilities decomposing at about, or above 300°C. Both RTILs presented moderate viscosities at elevated temperatures. The determined physicochemical properties of the reported ILs suggest their applicability for various applications such as heat transfer fluids, high temperature synthesis, and lubricants.

Water confined in silica gel at room temperature, X-ray diffraction study

2001 ◽  
Vol 3 (8) ◽  
pp. 1315-1317 ◽  
Author(s):  
A Fouzri ◽  
R Dorbez-Sridi ◽  
M Oumezzine ◽  
A Missaoui
Keyword(s):  
Diffraction Study ◽  
Silica Gel ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
X Ray

Tribological behaviour of AZ91D/ultra-high-temperature ceramic composites at room and elevated temperatures

2021 ◽  
pp. 135065012110100
Author(s):  
KT Sunu Surendran ◽  
A Gnanavelbabu
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Wear Test ◽  
X Ray Diffraction ◽  
Tribological Behaviour ◽  
X Ray ◽  
The Matrix ◽  
Scanning Electron ◽  
Ultra High Temperature

In this research work, the tribological behaviour of an AZ91D alloy and its composites reinforced with different titanium-based ultra-high-temperature ceramic particulates was investigated. Titanium-based ultra-high-temperature ceramic materials (5 wt%) such as titanium carbide, titanium boride and titanium nitride was used for the fabrication of three different composites, namely ATC, ATB and ATN, respectively. The proposed composites were prepared using a novel ultrasonic treatment-assisted stir-squeeze casting technique. Material characterization was performed using scanning electron microscopy and X-ray diffraction techniques. The porosity and hardness of the composites were determined prior to the wear test. In the pin-on-disc tribometer, the wear test was carried out at room temperature by varying the normal load (12.5–50 N) and the sliding speed (0.25–1 m/s). In addition, at a temperature of up to 200 °C, the tribological behaviour of the composites was assessed. The homogeneous distribution of ultra-high-temperature ceramic particles in the matrix was confirmed by the analysis of the microstructure using scanning electron microscopy images. The X-ray diffraction results showed that the reinforcement materials in the matrix were thermally stable. The hardness of the ATC, ATB and ATN was improved by approximately 31%, 33.8% and 29.6%, respectively. In comparison, at all wear testing conditions, ATB demonstrated superior tribological performance, while the performance of ATN was poor and ATC was moderate. Abrasion, oxidation and delamination were the wear mechanisms at room temperature. At elevated temperatures, oxidation, delamination, thermal softening and plastic deformation wear mechanisms were significant..

Water confined in silica gel and in vycor glass at low and room temperature, x-ray diffraction study

2002 ◽  
Vol 116 (2) ◽  
pp. 791-797 ◽  
Author(s):  
Afif Fouzri ◽  
Rachida Dorbez-Sridi ◽  
Mohamed Oumezzine
Keyword(s):  
Diffraction Study ◽  
Silica Gel ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Vycor Glass ◽  
X Ray
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