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Sawada H.,Materials Characterization Research Laboratory | Ozaki T.,Japan Advanced Institute of Science and Technology
Nippon Steel Technical Report | Year: 2013

The precipitates in steel play an important role to strengthen steel. One of the important factors of controlling growth of the precipitate is interface energy between precipitate and iron. It is necessary for the interface energy to calculate more than 1,000 atoms. The calculation is achieved by the use of O(N) method of large scale first-principles electronic structure calculation on TSUBAME 2.0. The interface energy of the semi-coherent interface is the value between the coherent interface energy where Fe atom is located next to Nb atom and that where Fe atom is located next to C atom.

Kanehashi K.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2011

It is important to analyze structure of slag and mold flux in the steel-making process with complicated multi-component systems from the viewpoint of appropriate management of the process and their effective use. Nuclear magnetic resonance (NMR), a nuclide specific method, is a powerful tool for structural analysis of slag with complicated structure. We have developed in situ high temperature NMR technique for analysis of melt structure and dynamics up to 1,500 degrees Celsius and some information have been obtained: (1) an averaged coordination number around Al increases with elevating temperature and (2) atomic-scale motion is closely related to macroscopic viscous flow.

Sugiyama M.,Materials Characterization Research Laboratory | Shigesato G.,Materials Characterization Research Laboratory | Ikematsu Y.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2011

The progress on the focused ion beam fabrication method provides us several kinds of advanced techniques for the sample preparation of transmission electron microscopy. With improvement of the beam convergence and the increase of the ion accelerating voltage, the ability of its scanning ion microscope becomes glade up with a good image resolution. The scanning ion microscope is now powerful tool to investigate the three dimensional microstructure to cut and view in any places under the observation and recently the FIB serial sectioning method is developed to one of the method to reconstruct the 3D image in the computer using a series of sliced cross sectioning images, in the research filed of steel microstructure. As another application filed of the scanning ion microscopy, the high temperature in situ observation technique has been developed, and the melting behavior of metal particles have been observed.

Fujioka Y.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2011

I tried to apply the Infrared emission spectroscopy to identify the organic substances on the non-smooth or non-flat metallic surface. The organic substances like oils, fats and coating materials play an important role to enhance the lubricant property just like a processing property of steel and to protect it from corrosion. An organic substance on the flat metallic materials like a steel plate can be analyzed by the spectroscopic analysis that uses reflection method. But, the organic substances on non-flat materials like a fiber, wire rod, ball and powder must be removed and then preceded to various analyses. On the other hand, this infrared emission spectroscopy method can practice contactless analysis of the organic substances getting infrared spectral information just by heating up the target samples and references without any pre-treatment. And this emission is isotropic; therefore it can easily detect the organic substances of the non-flat surface of the metallic surface with limited influence of the surface shape of a material. This method is very simple and easy to expand in application.

Takahashi T.,Materials Characterization Research Laboratory | Kanehashi K.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2011

In NMR measurements of quadrupolar nuclei, the spectral analysis has troublesome because of large line width of NMR peak that is caused by second-order quadrupolar interaction. As a result of application of MQMAS to structural analyses of coal and clay minerals, the substantial increase of spectral resolution archived has enabled us to elucidate their fine chemical structures. On the other hand, we have addressed establishment of STMAS method, because sensitivity of MQMAS is too low to perform the analysis of trace amounts of elements. A new developed NMR probe with feature of very precise adjustment of magic angle, which is critical in STMAS, has attained sensitivity enhancement of up to approximately 5 times compared to MQMAS. Since sensitivity and resolution of these methods are furthermore improved by the combination with high magnetic field strength, their application are promised for low-sensitive nuclei and low-level elements, which have been regarded as quite difficult to measure.

Yanagihara K.,Materials Characterization Research Laboratory | Yamazaki S.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2011

Oxidation behavior of Fe-Si alloys strongly depends on oxygen potential of an annealing atmosphere. In the present study, X-ray diffraction, Auger electron spectroscopy, X-ray electron photoelectron spectroscopy, glow discharge optical emission spectrometry and transmission electron microscope have been applied to characterize the microscopic features of oxides formed on an Fe-3mass%Si alloy. The samples were oxidized at 850°C under a 75%H2-25%N 2 atmosphere with various partial pressures of water vapor. The macroscopic results of an oxidized Fe-3mass% Si alloy agree well with prediction based on the thermodynamic data of oxidation of elements. The oxidation in higher oxygen potential generates the surface roughness and Fe layer, which caused by the internal oxidation. In case of SiO2 film forms on the surface in early stage of oxidation, the internal oxidation is suppressed in the next stage. Consequently, internal oxidation occurs locally and it causes large surface roughness.

Hayashi S.-I.,Materials Characterization Research Laboratory | Tsuji N.,Materials Characterization Research Laboratory | Suzuki T.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2011

For monitoring of hazardous organic compounds, we have been developing an on-line analytical instrument based on a supersonic jet resonance enhanced multiphoton ionization (Jet-REMPI) mass spectrometry. We have attempted to apply this technique to monitor transient emission phenomena of hazardous organic compounds in the exhaust gas. The real time monitoring of the gaseous compounds in the atmosphere could be done by our instrument with a continuous sample introduction. We demonstrated the emission phenomena of monochlorobenzene generated from the chimney could be monitored every 10 seconds with below 100 ppt concentration level. This technique was proven to become pretreatment-free and high sensitivity analysis for hazardous organic compounds.

Kanehashi K.,Materials Characterization Research Laboratory | Aimoto M.,Materials Characterization Research Laboratory
Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan | Year: 2013

A new approach to quantifying free magnesium oxide (f-MgO) in steelmaking slag has been proposed by using solid-state 25Mg nuclear magnetic resonance (NMR) spectroscopy. Although 25Mg (I=5/2) signals in solid materials often suffer from the second-order quadrupolar broadening, a quite narrow and symmetric signal of MgO is obtained in the 25Mg NMR spectrum thanks to its highly symmetric Mg sites. By contrast, other Mg-containing compounds (e.g. magnesium hydroxide, diopside and akermanite) are more or less affected by the second-order quadrupolar interaction, resulting in severe broad signals buried in the spectral noise. Therefore, the MgO peak can be only detected for steelmaking slag in the 25Mg NMR spectrum without any hindrance. It is significant to select the optimum internal standard (e.g. Mg2Si and MgS) showing the narrow 25Mg signal being free from the second-order quadrupolar broadening like MgO to obtain reliable data. Accuracy of f-MgO concentration obtained by the present method has been demonstrated by using the standard samples in which f-MgO concentration is known. The advantages of the present method to quantify f-MgO in steelmaking slag, no need to dissolve slag in any solvent and detection of surface f-MgO as well as inner f-MgO of slag particles, should outweigh the disadvantages of poor signal-to-noise ratio which is surmounted by using a larger sample rotor and/or a higher magnetic field. These ideas for quantification of f-MgO by NMR should be explicated to that of free calcium oxide (f-CaO) which is responsible for hydrated expansion of steelmaking slag as well.

Kimura M.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2012

The magnetization of iron depends on its crystal orientation. Electrical steel is a material whose magnetic property is dramatically improved by controlling the orientation of iron grains in the steel. In its manufacturing process, the process in which grains exceeding 10 mm in size are formed from grains tens of microns in size is especially important. On the other hand, implementing an atomic-level observation of the behavior of a catalyst in the actual environment requires a sophisticated observation technique. Therefore, knowledge of catalyst behavior is still insufficient. This has been one of the obstacles to efficient development of catalysts. Concerning the process in which the state of the active noble metal in the catalyst changes according to the change in composition of engine exhaust fumes, Nippon Steel succeeded in performing in situ observation of the process within tens of milliseconds.

Hayashi S.-I.,Materials Characterization Research Laboratory
Nippon Steel Technical Report | Year: 2012

The steel industry is now in the midst of global competition. From the standpoint of developing a new steelmaking process to impart denser and more complex structures to steel products, characterization technology that enables researchers to understand every phenomenon involved in the process on the basis of fundamental principles has become indispensable. The STEM was also applied to study the behavior of grain boundary segregation of trace amounts of boron, which is important from the standpoint of understanding the mechanism of improving the hardenability of high-strength steels used for ocean structures. It permits determining the types and spatial arrangement of the atoms that exist in the tip of the specimen, and its lateral resolution is 0.2 nm or less. Thanks to positron microscopy developed recently, however, the application of the technique is expanding, as in the observation of plastic deformation-induced defects in iron-copper alloys. It is expected that our technique will make it possible to obtain information about the distribution and density, etc. of dislocations and precipitates.

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