Existence Of Impurities Research Articles

Characterization and magnetic properties of Sm- and Gd-substituted CoFe 2O 4 nanoparticles prepared by forced hydrolysis in polyol

Pure nanoparticles of the CoFe 2− x RE x O 4 (RE = Gd, Sm; x = 0.0, 0.1) system have been prepared by forced hydrolysis in polyol. The insertion of Sm 3+ and Gd 3+ cations into the cobalt ferrite structure has been investigated. X-ray micro-analysis (EDX) shows that the RE contents are close to the nominal ones. X-ray diffraction (XRD) evidences a cell size increase with slight distortions in the spinel-like lattice indicating the entrance of RE 3+ ions. Micro-Raman spectroscopy confirms the cubic inverse-spinel structure and rules out the existence of impurities like hematite. Magnetic measurements (SQUID) show important differences in the magnetic properties of the unsubstituted and substituted particles. All the particles are superparamagnetic at room temperature and ferrimagnetic at low temperature. However, their main magnetic characteristics appear to be directly dependent on the RE content.

Nanoscale Evaluation of Strength and Deformation Properties of Ultrahigh-Purity Aluminum

In order to investigate the strength and the deformation properties of metals in nearly perfect crystals, the nanoindentation test is performed on aluminum samples with various purities: 99.9999% (6 N), 99.99% (4 N) and 99% (2 N). It is widely known that the strength decreases with increasing purity of metals. On the nanoscale, however, the strength has been revealed to be close to the ideal shear strength, because a nanoscale area is expected to behave as a perfect crystal. In this study, a nanoindentation system that is able to provide indentation load vs penetration depth curves is employed. The experiment is performed on ultrahigh-purity aluminum (99.9999%), and high-purity aluminum (99.99%) and commercial-purity aluminum (99%) so as to discuss the relationship between the purity level and the mechanical properties at room temperature. It is revealed that the penetration depth decreases with increasing purity, and the critical shear stress estimated from the experimental results is close to the ideal shear strength. These results suggest that a perfect crystal is harder than an imperfect crystal. Furthermore, the indentation load vs penetration depth curves indicate a discontinuous deformation of the metals. It is considered that these discontinuities are caused by the existence of impurities or the initiation and the multiplication of dislocations in these samples. [doi:10.2320/matertrans.48.1]

超高純度アルミニウムの強度および変形特性の微視的評価

In order to investigate the strength and the deformation properties of metals in nearly perfect crystals, the nanoindentation test is performed on aluminum samples with various purities: 99.9999% (6 N), 99.99% (4 N) and 99% (2 N). It is widely known that the strength decreases with increasing purity of metals. On the nanoscale, however, the strength has been revealed to be close to the ideal shear strength, because a nanoscale area is expected to behave as a perfect crystal. In this study, a nanoindentation system that is able to provide indentation load vs penetration depth curves is employed. The experiment is performed on ultrahigh-purity aluminum (99.9999%), and high-purity aluminum (99.99%) and commercial-purity aluminum (99%) so as to discuss the relationship between the purity level and the mechanical properties at room temperature. It is revealed that the penetration depth decreases with increasing purity, and the critical shear stress estimated from the experimental results is close to the ideal shear strength. These results suggest that a perfect crystal is harder than an imperfect crystal. Furthermore, the indentation load vs penetration depth curves indicate a discontinuous deformation of the metals. It is considered that these discontinuities are caused by the existence of impurities or the initiation and the multiplication of dislocations in these samples. [doi:10.2320/matertrans.48.1]

Using singular value ratio for resolving peaks in HPLC-DAD data sets

A simple chemometrical method is proposed for resolving peaks in liquid chromatography with photodiode-array detection (HPLC-DAD). The approach is based on the technique of moving fixed-size windows along the retention time axis. Visual inspection of the ratio of singular values (SVR) may detect the existence of impurities. The proposed technique was tested for several real data sets, including a complex mixture with 12 components. Its high sensitivity for detecting impurities and determining the number of selective regions were confirmed for both simulated data sets and real cases.

The effects of procedural variables on the maximum capture efficiency of CO 2 using a carbonation/calcination cycle of carbonate rocks

The effect of procedural variables–mass and heating and cooling rate–on the maximum capture efficiency of CO 2 is studied, using a carbonation/calcination cycle, for a series of carbonation rocks with different stoichiometries of dolomite and calcite. The extent of carbonation and the cyclability depends particularly on dolomite presence and at the same time seems to be influenced by the existence of impurities. Samples having the highest percentage of calcite and the lowest percentage of impurities seemed to be independent on the above variables. In limestone samples with small quantity of dolomite, impurities or a combination of both of them was observed a very small increase in the extent of carbonation due to the increase in the initial mass of the samples, while these samples in the case of the same initial mass presented an increase in the extent of carbonation due to the decrease in the cooling and the second heating rate.

Dynamic behavior of a continuous autothermal isobutylene polymerization reactor

Industrial autothermal cationic isobutylene polymerization reactors may present very complex dynamic behavior and difficult operation. A mathemathical model was developed to describe the operation of an autothermal solution industrial reactor, and some possible sources of complex dynamical behavior were analyzed. The results obtained indicate that the most probable source of the complex behavior observed industrially is the existence of adventitious impurities in the feeed stream. The effects caused by the presence of adventitious impurities on process operation and product properties were investigated for both polymerization and oligomerization. In the first case, impurities influence the reactor productivity but do not change the polymer quality. In the oligomerization, both the polymer quality and the reactor productivity are seriously affected by the existence of impurities in the feed stream. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 1403–1413, 1997

Effects of carbon monoxide on the hydriding reactions of the untreated and fluorinated LaNi4.7Al0.3 alloys

A method for the surface treatment of the hydriding alloys has been developed to improve the hydriding properties. After F-treatment, LaF3 was formed on the outer surface and metallic Ni was precipitated in a subsurface for the LaNi4.7Al0.3 alloy. By utilizing the unique surface characteristics, the effects of carbon monoxide on hydriding reaction rates and hydrogen absorbing capacities were investigated by cyclic hydriding/dehydriding (H/D) tests. The degradation of hydriding reaction rate and hydrogen capacity of the fluorinated alloy was found considerably small even under the existence of the extremely poisonous impurity CO (H2 + 1000 ppm CO) at lower temperatures. In contrast, the gas mixture deactivates the untreated alloy severely under the same conditions. It was also found that even if the fluorinated alloy was deactivated after repeating many H/D cycles in the gas mixture, the reactivity can be easily recovered by only a cycle of H/D reaction in pure hydrogen. This offers the possibility to move toward practical metal hydride-based applications, especially under the existence of impurities.

Degradation of the holmium—barium—copper oxide superconductor, HoBa2Cu3O6.92, under the action of H2O and D2O: a study by the radiothermoluminescence method

Information about the existence of impurities and defects on the surfaces of high-T{sub c} superconductors (HTSC) can be obtained by radiothermoluminescence (RTL). The degradation of HTSC materials results from their interaction with water and CO{sub 2}. It has been established that the intensity of RTL is very insignificant for freshly prepared HTSC or for samples stored in a dry atmosphere. However, a large increase in RTL intensity occurs if specimens are in contact with water. Barium hydroxide, carbonate, and oxides make the largest contribution to RTL of superconducting ceramics with degraded surfaces. The RTL curves for Ba(OH){sub 2} and BaCO{sub 3} differ slightly from each other, which makes it difficult to estimate the contribution of each of them to the luminescence observed.

Characteristics and comparison of metastability of alkoxy-derived tetragonal ZrO2 powders, gels and films

Abstract The metastability of t-ZrO 2 in the form of ZrO 2 powders, gels and films prepared by hydrolysis of zirconium n -butoxides using different techniques, including the sol-gel process, was investigated. The morphologies of the powders, gels and films were observed by the scanning electron microscopy. Differential thermal analysis and differential thermal gravimetric curves were used to determine the crystallization temperatures and thermal behavior of the materials. The experimental results indicated that the metastability of t-ZrO 2 , investigated in terms of relative content and crystalline size by X-ray diffraction, could not be explained simply by the effect of crystallite size, the existence of impurities or unpaired electrons. In this work it is proposed that the strain energy existing among the crystallites is an important factor in determining the metastability of t-ZrO 2 .

A theoretical study of electron–hole pair formation due to the collision of an atom with a solid surface

Electronic excitation in a semiconductor induced by the collision of energetic atoms with the solid surface is investigated theoretically. The modeling has been performed for a one-dimensional independent-electron system where the solid is described by a chain of 10–20 atoms. The time evolution of the nuclei (i.e., colliding atom and chain atoms) has been described by classical mechanics while quantum mechanical description has been used for the electronic dynamics. The two systems (i.e., the atoms and the electron) were coupled to each other and the equations of motion were solved self-consistently. Energy dissipation from the chain to the rest of the solid was included via the GLE approach. This study establishes the relationship between the probability of electron–hole formation and various parameters of the system such as collider translational energy, magnitude of the band gap, and existence of impurities in the solid. In addition, two excitation mechanisms were examined, electronic excitation due to a direct coupling between the electron and the colliding atom and an indirect mechanism due to electron–phonon coupling.

PIXE in Determination of Argon Impurity in Ion Beam Sputter-Deposited Co–Cr Films

Co–Cr films prepared by the method of argon ion beam sputtering are analyzed by the proton-induced X-ray emission (PIXE) technique. The PIXE spectra show a clear peak of Ar Kα X-ray, indicating the existence of impurities. The content of argon impurity is in the order of 102 ng, and the content is found to increase as the argon ion beam energy increases and the argon pressure decreases. The argon impurity is attributed to the scattering processes of argon ions at the Co–Cr alloy target surface.

Characterization of the implantation damage in SiO2 with x-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy (XPS) has been applied to characterize the damage introduced into SiO2 by ion implantation. By measuring the peak width of Si2p from SiO2 which corresponds to perturbation of the SiO2 network, good depth profiles of the damage have been obtained for implanted samples and subsequently annealed samples. The results show that the damage distributed more widely than that calculated from energy deposition and that the perturbation of the network is caused not only by radiation damage but also by the existence of impurities in the network. It has been found that the XPS method is effective to understand the atomic structure, and thus, electrical properties of SiO2.

Effect of carbon on mechanical properties in Fe0�5Co0�5 alloys

Effects of carbon addition on brittleness and ductility in equiatomic iron-cobalt alloys have been investigated. In alloys containing 0.5 to 2 at % C, which are ductile when quenched from 800° C, it is found that brittleness occurs due to decarburization, but ductility is reobtained by the recarburizing of the specimens when preceded by decarburization. This is shown to be independent of factors, such as coarsening of the grains occurring during heat treatments, existence of impurities and the formation of texture produced during cold rolling, and the existence of carbon is an important factor. In addition, it is described that the alloys, having generally been very brittle in the ordered state, have not always shown embrittlement even after ordering, if only cold rolled severely. The effectiveness of carbon in improving the ductility has been discussed under a proposal that host atoms, iron or cobalt, react with carbon atoms to precipitate carbides; around the individual carbides, zones, with the deviation from the equiatomic composition, are formed, thus rendering the ordering difficult; in other words, since production of the resultant unequiatomic zones corresponds to that of disordered ones, it would be expected that the ductility of such specimens depends on the morphology of distribution of the zones, such as volume fraction, uniformity and density.

Conversion of halophilic algae into extractable oil. 2. Pyrolysis of proteins

The pyrolysis reactions with different solvents and reagents on different proteins, e.g., albumin, soyaprotein, lysozyme and algae-protein, show that there are no significant differences between the behaviour of proteins under those conditions. The reactions yield rather low conversions in the presence of water in spite of the existence of carbonates and catalysts, e.g. nickel sulphate. The presence of benzene improves the yield and the presence of a mixture of K-Mg-Mn salts is beneficial for such a reaction. The nitrogen content of liquid oil decreases in the presence of carbonates and other catalysts. The maximum amount of protein converted into liquid oil was 27% by weight for algae-proteins containing 5.7 wt% nitrogen. The existence of impurities does not affect the yield which is similar to the one obtained from pure proteinic compounds. The behaviour of the proteins under different temperatures and in various reaction mixtures is very similar to that found with algae.