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ONLINE ISSN: 1883-2954
PRINT ISSN: 0021-1575

Tetsu-to-Hagané Vol. 85 (1999), No. 2

  • Rapid Analysis of Steelmaking Slag by Energy-dispersive X-ray Fluorescence Spectrometry

    pp. 85-90

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    An X-ray fluorescence method using a semiconductor X-ray detector was investigated for rapid analysis of slag in steelmaking process.
    Metallic rectangular solid was dipt in molten slag layer, and slag thin piece grew on the solid. Because this slag piece was rapidly solidified and was flat, it could be directly analyzed by X-ray fluorescence method.
    Slag thin pieces obtained by large volume steel sampler were excellent as uniformity and representativity of slag component. These features gave excellent result for the determination of CaO, SiO2, Al2O3, Fe and MnO in steelmaking slag. In this method, the analysis time was shortened to 5 minutes. As the results, rapid and simple analysis of slag for steelmaking was established.
  • Determination of Trace Elements in High Purity Iron as a Certified Standard Material by Instrumental Neutron Activation Analysis

    pp. 91-96

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    Trace elements in high purity iron certified reference materials, JSS001-4 and JSS003-4, prepared by the Iron and Steel Institute of Japan were determined by instrumental neutron activation analysis (INAA).
    Five or seven aliquots of each sample (ca. 130750 mg) were irradiated for a short time (2 min) at a thermal neutron flux of 1.5×1012n cm-2 s-1 (pneumatic transfer) and for a long time (6 h) at a thermal neutron flux of 3.7×1012 n cm-2 s-1 (cental thimble) in the Rikkyo University Research Reactor. The irradiated samples were measured by conventional γ-ray spectrometry using a coaxial Ge detector, and by anticoincidence γ-ray spectrometry with a coaxial Ge detector and a well-type Nal(Tl) detector.
    The concentrations of 7 elements (Na, Cl, V, Co, Zn, As, W) in the JSS001-4 and 1 1 elements (Na, Al, V. Mn, Co, Ni, Cu, As, Mo, Sb, W) in the JSS003-4 were determined by these methods. The determined values were in good agreement with the certified and reference values. The lower limit of determination values for Sm, Ir, Au in the J55003-4 were 0.11 ng/g.
  • Sensitive Determination of Arsenic and Selenium in Steels by High Power Nitrogen Microwave Induced Plasma Atomic Emission Spectrometry Coupled with Hydride Generation Technique

    pp. 97-101

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    An annular-shaped high power nitrogen microwave induced plasma (N2-MIP) produced at atmospheric pressure by an Okamoto cavity in a surface wave mode has been used as a new and efficient excitation source for atomic emission spectrometry (AES). The results show that this kind of MIP source is more stable than conventional low power MIPs and remarkably tolerant to direct and continuous introduction of wet aerosols and molecular gases such as hydrogen, oxygen, air and gaseous hydrides because of its high input microwave power. Under the optimized experimental conditions, the best attainable detection limits at As(I) 228.812 and Se(I) 196.026 nm by use of N2-MIP-AES coupled with hydride generation technique were 2.99 ng As/ml and 0.86 ng Se/ml with a linear dynamic ranges of 5 to 10, 000 ng As/ml and 1 to 5, 000 ng Se/ml. The presence of several diverse elements has been found to cause more or less a depressing interference with the determination of arsenic and selenium by the present technique. Of the several pre-reductants potassium iodide has been found to be the most preferable to reduce As(V) to As(III) prior to hydride generation for the determination of total arsenic, i.e., As(III)+As(V). To the contrary, the heating of sample solutions, previously acidified in 5 M with hydrochloric acid, at 80°C for 20 min was the best way to pre-reduce Se(VI) to Se(IV) before hydride generation for the determination of total selenium, i.e., Se(IV)+Se(VI). The proposed method was applied to the determination of low concentrations of arsenic and selenium in carbon steels and stainless steels, respectively. The results obtained by this method were in good agreement with the certified values.
  • Multi-elemental Determination of Trace Amounts Impurities in Iron Ores by Atomic Absorption Spectrometry using Iron Excluding Method by means of 4-methyl 2-pentanone Extraction

    pp. 102-107

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    In recent year, the high quality steel products were developed by decrease of impurity elements in the steel. Generally speaking the determination of impurity elements of iron ore were performed by JIS (Japanese Industrial Standard) Method. But these JIS method (published in 1983) were specified that the determination limit of impurity elements in iron ores were ranged from 0.01% to 0.003%. To be suited to con-trol of the steel production process, the determination limit of impurity elements were required to 0.001% contents level. At the same time the establishment of multi-elemental determination of impurity elements were required to the time saving on the analytical procedures.
    Analytical precision on the iron excluding atomic absorption method was significantly improved than the direct atomic absorption method. The determination limit at 0.001% contents level were obtained by the iron excluding atomic absorption method. Sulfate ion interfered in the atomic absorption by the molecular absorption from 200 nm to 300 nm. Threrfore in the case of the pretreatmenrt of analytical samples for the trace amounts determination the use of the sulfate reagents must be avoided in the atomic absorption method. The improvements of the accuracy of the calibration were obtained that the standard addition method was applied to compensate of the effect on the residual iron amounts. The multi-elemental determination can be applied to the same pretreatment solution in this method.
  • Determination of Zinc Compounds in the Recovered Dusts from the Electric Furnace Dusts

    pp. 108-113

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    The analytical methods for Zn compounds in the dust recovered from the electric furnace dust have been investigated.
    The recovered dust contains metallic Zn, ZnO, ZnS and trace amount of Zn(OH)2 as Zn compounds. The sample was dissolved in the FeCl3-citric acid solution at room temperature. During the dissolution, metallic Zn reduced Fe(III) to Fe(II) quantitatively. The amount of Fe(II) was determined by the titration with potassium dichromate, and converted to the amount of metallic Zn. The ZnS contained in the residue was dissolved in HNO3 (1 + 1), and the amount of Zn as ZnS was determined by ICP-AES. The amount of ZnO and Zn(OH)2 was obtained by subtracting the amounts of metallic Zn and ZnS from the amount of total Zn.
    The electric furnace dust contained ZnO and ZnFe2O4, and the FeCl3-citric acid solution was used for the separation of ZnO from ZnFe2O4. Only ZnO was dissolved in the FeCl3-citric acid solution, and ZnFe2O4 contained in the residue was determined by ICP-AES after alkali fusion and acid dissolution.
  • Determination of Trace Amounts of Boron in Steel and Silicon by Anion Exchange Chromatography/ICP Mass Spectrometry

    pp. 114-118

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    A rapid and high sensitive analytical method for the trace amounts of boron in high-purity steel and silicon material has been investigated.
    Steel sample was dissolved in HCl-HNO3 mixture, and boron nitride in the sample was decomposed completely by treatment of H2SO4 H3PO4 fuming at 290°C for over 30 min. After masking of Fe by the addition of CyDTA, the pH value of the sample solution was adjusted at 8 by aqueous ammonia. The sample solution was passed through the column of anion exchange resin (Amberlite® IRA-743), and B was adsorbed selectively as boric acid on the resin. After washing the column for the removal of Fe and H2SO4H3SO4, B was eluted by small amount of 2M HCl, and was determined by ICP-MS.
    The limit of detection (estimated by the 3σ of blank values) was 0.016 μg/g for steel, and 0.006 μ/g for silicon material.
  • Determination of Traces of Metals in Steel by Ion-exchange Separation and Atomic Spectrometry

    pp. 119-123

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    Novel two methods for determination of trace metals in steel have been developed by combining ion-exchange separation and atomic spectrometry. Sample is decomposed with hydrochloric acid and hydrogen peroxide. For the determination of Mo of 0.01 m/m % level, the sample is loaded as dilute sulfuric acid solution on a column of anion-exchanger TEVA resin. Iron ion passes through the column and Mo ion retained on the column is then recovered by elution with nitric acid, followed by quantification by inductively coupled plasma atomic emission spectrometry (ICP-AES). For the simultaneous determination of Al, Mn, Ni and Co of 0.001 to 0.1 m/m % level, the sample is loaded as hydrochloric acid-oxalic acid-hydrogen peroxide solution on a cation-exchange resin Bio-Rad AG 50W column. Iron ion passes the column as oxalato-complexes, and Al, Mn, Ni and Co ions retained on the column are eluted with hydrochloric acid to be subjected to the simultaneous determination by ICP-AES (for metals of 0.01 to 0.1 m/m % level) or "one drop" flame atomic absorption spectrometry (for metals of 0.001 m/m level). The analytical results obtained for the steel certified reference materials are in good agreement with certified values and the precision (R.S.D.=1 to 8%) is satisfactory.
  • Determination of Trace Elements in Acidic Solution of Iron and Steels by Graphite Furnace Atomic Absorption Spectrometry

    pp. 124-128

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    Graphite furnace atomic absorption spectrometry (GF-AAS) has been applied to the determination of trace amounts of arsenic, bismuth, cadmium, lead, thallium and zinc in the acidic solutions of iron and steels. The iron and steels were dissolved in nitric acid. After the solution (20 μl) was pipette into a L'vov platform furnace, it was ashed (600°C-30 s, hydrogen 5 ml/s) and then atomized by using argon as a purge gas and atomic absorption of each analyte was measured. The effect of iron concentration was suppressed by the use of peak area measurement. Synthetic calibration solutions were prepared by addition of standard solution of each analyte to iron or nickel matrix solution. For arsenic, bismuth, cadmium, lead, thallium and zinc, the limits of detection (3σ of blank values) were 0.05, 0.025, 0.002, 0.017, 0.025 and 0.003 ppm, respectively, when one gram of the specimen was used. The proposed method is able to be applied to other analyte in iron and steels.
  • Determination of Arsenic in Iron and Steel by Differential Pulse Anodic Stripping Voltammetry at a Rotating Gold-Film Electrode

    pp. 129-134

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    A simple, rapid and reproducible method is described for the direct determination of arsenic at the, μg/g level in iron and steel based on differential pulse anodic stripping voltammetry without any separation of iron matrix. Electroinactive arsenic(V) was chemically reduced to arsenic(III) by potassium iodide prior to the stripping voltammetric determination. The interference of iron(III) was eliminated by reducing it with potassium iodide to iron(II). The generated iodine was reduced with L(+)-ascorbic acid. Arsenic(III) was electrodeposited from a 3 ml aliquot of the acid solution (0.3M HCl-0.1M HNO3-0.15M Kl-0.1M L(+)-ascorbic acid, pH=ca 0.1) containing 3 mg of a sample on a rotating gold-film electrode (gold plated on glassy carbon) at -0.5 V vs. SCE for 180 s. The deposit was then anodically stripped at a scan rate of 40 mV/s to +0.2 V vs SCE.
    The calibration graph (peak height vs. concentration curve) prepared with standard arsenic solutions was linear in the range from 10 ng/ml to at least 40 ng/ml of arsenic and passed through the origin (correlation coefficient >0.998), with a sensitivity of ca. 0.2 μA/(ngAs/ml). Antimony(III), bismuth(III) and copper(II) interfered with the arsenic determination severely. The proposed method has been successfully applied to the determination of 50.4 and 448.8 μg/g of arsenic in iron and steel, with relative standard deviations of less than 2.4% (n=5), without any troublesome preconcentration steps using harmful chemicals. For a deposition time of 180 s, about 80% of arsenic(III) was accumulated and the detection limit (3 σ) was 1.0 μ/g. The time required for an analysis was within 40 min.
  • Spectrophotometric Determination of Trace Amounts of Silicon in Niobium and Tantalum Metals after Fluoride Separation

    pp. 135-137

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    Fluoride separation-molybdosilicic acid blue spectrophotometry was applied to the determination of trace amounts of silicon in niobium and tantalum samples. After the sample was dissolved in hydrofluoric acid and nitric acid, the silicon was evolved by heating to 300°C in the presence of sulfuric acid. The liberated silicon tetra-fluoride was absorbed into the solution containing boric acid by sucking the evolved gas at a flow rate of 300 ml/min. Then the silicon in the absorbent was determined by Molybdenum Blue spectrophotometry. By this method, silicon at ppm level in commercially available metals was successfully determined. Recovery was 105% for niobium sample and the detection limit given by 3σ of blank value was 0.6ppm silicon in the metal sample.
  • Influence of Sample Treatment Methods on the Determination of Trace Oxygen in Iron and Steel

    pp. 138-142

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    Removing the oxide film from the sample surface is an important process for analyzing trace oxygen in iron and steel.
    The depth profiles of oxygen on the surface after electro-polishing in CH3COOH-HClO4, CrO3-H3PO4, and chemical polishing by HF-H2O2 were investigated.
    As for the high-purity iron, thickness of the oxide layer after electro-polishing in CrO3-H3PO4was thicker than any other pretreatment methods. This is because Fe(III) hydroxide was formed on the surface of sample. This could be removed by rinsing with an acid after electropolishing.
    As for the bearing steel, oxygen containing species were found around carbides on the surface of the sample after pretreatment except that the pretreatment was made by electro-polishing in CrO3-H3PO4. Those precipitates influenced the analysis of oxygen.
    Analytical value obtained by conventional methods were 1 or 2 mass ppm higher than those obtained by charged particle activation analysis that is not influenced by surface contamination. This difference corresponds to the oxide layer formed on the sample surface.
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  • Thickness Evaluation of Thin Multilayered Scale by Glow Discharge Spectroscopy Associated with Raman Spectroscopy

    pp. 143-148

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    To make oxidation behavior of stainless steel clear, an in-depth scale structure characterization method tor multilayered scale formea on stainless steel using both Raman spectroscopy and Glow discharge optical emission spectroscopy (GDS) was developed. In this work, cold rolled Type 304 stainless steels containing 1.0 mass% Mn and 1.5 mass% Mn annealed at the temperature range from 1050°C to 1150°C were prepared to investigate glowth mechanism of thin oxide layers of which thicknesses are about 100 nm. Each thickness of spinel structure layer and corundum structure was estimated by GDS on the basis of proposed thickness estimation model.
    The main results obtained are as follows:
    (1) The glowth rate of corundum structure layer was highly dependent on the annealing temperature than that of spinel, (2) the glowth rate of spinel structre layer formed on 1.5 mass% Mn stainless steel was higher than that formed on 1.0 mass% Mn stainless steel, (3) the growth rate of corundum structrue layer formed on 1.0 mass% Mn stainless steel was higher than that formed on 1.5 mass% Mn stainless steel, (4) the glowth rate of corundun structure layer formed on 1.5 mass% Mn was highly dependent on the annealing temperature than that formed on 1.0 mass% Mn stainless steel.
  • Evaluation of Spatial Resolution and Light Elements Analysis of Precipitates in Steel by AES

    pp. 149-154

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    The influence of backscattered electrons on the spatial resolution was investigated in the analysis of Auger electron spectroscopy. The size of the generation area of Auger electrons caused by backscattered electron generation was evaluated for Au/SiO2/Si and Ni/Fe specimens by measuring the line profile of O KLL and Ni LMM, respectively. It was shown that the size of the generation area, measured as the spread till the intensity becomes 5% of its maximum intensity, increased with accelerating voltage and exceeded 1 μ for the accelerating voltage of 20 kV. Cosequently, the accelerating voltage should be less than 5 kV for the sub-micron analysis. The sizes of the generation area were in good agreement with the values calculated from the theoretical equation proposed by Soejima. The quantitative analysis of carbon and boron in a borocarbide precipitate in steel was done under the analytical conditions determined for sub-micron analysis. The analytical errors were less than 3 atomic % when the relative sensitivity factors for carbon and boron obtained experimentally from Fe3C and Fe2B precipitates were used, respectively. On the other hands, when the relative sensitivity factors obtained from pure materials were used, the analytical accuracy was poor because of the influence of the change of spectrum shape due to the difference of chemical state.
  • Separation and Determination of TiC in in-situ TiC Particle Reinforced Fe3Al Based Alloys

    pp. 155-159

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    A method for separation and determination of TiC in in-situ TiC particle reinforced Fe3Al based alloys has been investigated. The results obtained are summarized as follows:
    (1) When samples were dissolved in a 6N hydrochloric acid at 6080°C, TiC remained as a residue. TiC was separated from the acid solution by filtration.
    Amount and composition of separated TiC could be determined quantitatively.
    (2) Fe, Al and Cr in samples were detected as soluble elements in an acidic solution, while Ti was found in the insoluble residue (TiC). Mo was detected in both the acidic solution and insoluble residue.
    (3) Two types of TiC particles were observed. Large ones with sizes of about 530 μ m have well developed facet structure, while small ones less than 1 μm in diameter have dendritic structure.
    (4) Separation procedure along with the particle size was examined. Large particles were sedimented but small particles were dispersed in acetone, so they were able to be separated by filtration. Both large and small particles in samples are identified to TiC independent of the particle size.
  • The Measurement of the Particle Size Distribution of Oxides in High Carbon Si-Mn Killed Steel

    pp. 160-163

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    The measurement of the particle size distribution of oxides in high carbon Si-Mn killed steel was achieved by extraction of oxides and the measurement with laser diffraction particle size analyzer.
    The extraction method of oxide in steel by using nitric acid could not be applied to the present case because nitric acid decomposed the SiO2 formed in steel. On the other hand, bromine-methanol method was suitable for the extraction of these oxide. Otherwise, the dissolving reaction was disturbed because of high carbon content. Decarbonization of the samples in H2H2O atmosphere was found to be effective as a pretreatment of the bromine-methanol extraction in order to avoid the disturbance in the extraction procedure for high carbon content steel.
    The bromine-methanol extracts the free carbon as well as the desired oxides. But the KMnO4 treatment with citric acid could dissolve only free carbon, and the oxides could be separated.
    It was found that the amount of oxides at the surface area of bloom was greater than that at central area of bloom in case of both fine particle size of the oxides and large particle size of the oxides.
  • Magnesium K X-Ray Emission Spectra of Mg, MgO and Olivine [(Mg, Fe)2(SiO4)] by EPMA and XRF

    pp. 164-168

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    Magnesium K X-ray emission spectra of Mg, MgO, and olivine [(Mg, Fe)2(SiO4)] are measured using an electron probe X-ray microanalyzer (EPMA) and an X-ray fluorescence spectrometer (XRF). It is demonstrated that the fine structures in the low energy side of the Kα X-ray emission spectra resemble the genuine X-ray absorption spectra which are measured using a soft X-ray synchrotron radiation beam line. Radial distribution of atoms in metallic magnesium is obtained by the Fourier transform of the measured XRF spectrum. Based on the above experimental results, we propose a convenient X-ray absorption spectroscopic method using an EPMA. Using this method. X-ray absorption spectra of a local area as small as a diameter of a few tens ofμm is observable within a few hours of measuring time.
  • In Situ Observation Technique of High-temperature Reactions Using a New Image-plate System at Synchrotron Radiation

    pp. 169-173

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    A new system has been developed for in situ obsevation of phase transformation at high temperatures. Changes in powder diffraction patterns from a heated specimen can be measured continuously by scanning an image plate located behind a slit. A heating system is designed for a sheet specimen (ca. 5×6 mm2) using Joule-heating, and it can heat the specimen up to 1100K at a rate up to 160K/sec, where effects of thermal expansion are minimized by a mechanism releasing stress.
    This system was applied to Zn-coated steel. At temperatures higher than the melting point of Zn, different types of Fe-Zn intermetallics formed sequentially through rapid inter-diffusion. Changes in phase and crystallographic structure were monitored with a time resolution less than a few seconds. It has been found that an addition of a small amount of elements, such as P, into Fe changes an incubation time before the alloying reaction starts. This system has been shown to have the potential for application to in situ observation of other reactions at high temperatures.
  • Observation of Distribution Images of Light Elements in Metals by the Charged Particle Activation-autoradiography Using Imaging Plate

    pp. 174-179

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    A new method for the observation of the macroscopic distribution images of light elements in metals by the charged particle activation-au-toradiography was developed by the use of the highly sensitive imaging plate (IP) instead of the conventional X-ray film.
    Surfaces of metallic samples (max. size: about 120 mm×120 mm×5 mm) were irradiated by the 3He ion beam of cyclotron, and then were kept in contact with the IP's for appropriate exposure times. Light elements such as B, C and O were activated in higher yields compared with other coexistent elements and the macroscopic two dimensional distribution images of radionuclides produced from those elements (e.g.: 11C from B or C and 18F from O) were obtained by the above-mentioned IP-autoradiography.
    The method developed was applied to observe the distribution images of C and O in steels and B and 0 in Al alloys. The results obtained were consistent with the results by chemical analysis. The method was considered to be useful especially for the evaluation of macroscopic defects in metallic materials such as segregations, inclusions or surface contaminations.
  • In-situ X-ray Diffraction Analysis of Electrodeposition of Zinc Layers by Using Synchrotron Radiation

    pp. 180-183

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    In order to study the dynamic phenomena of electrodeposition of metallic layers, we have newly developed in-situ X-ray diffraction system using an electrochemical cell and an image-plate detector. Electrodepositions of zinc layers on iron (100), (111) single crystals with current densities of 1.0×103 to 1.0×104 A/m2 were demonstrated. It was found that there were two stages for the preferred orientation of zinc layers. It was dominated by the crystallographic orientation of substrate material at the initial stage and the current density (i.e. overvoltage) at the next stage.
    x

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  • Development of Fast Texture Mapping System with Energy Dispersive X-ray Diffraction Method

    pp. 184-188

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    Texture mapping apparatus with energy dispersive X-ray diffraction method has been newly developed. A collimated white X-ray beam in the diameter of 0.1 to 2.0 mmφ was irradiated to a sample in a fixed incidence and the energy spectrum of diffracted X-ray was measured by solid state detector. In this apparatus, fast data transfer system from multi-channel analyzer to computer was adopted to reduce the total measuring time. Sample was mounted on X-Y stage and moved successively to obtain the intensity mapping of diffraction peaks. Some examples are demonstrated in order to show the performance of this apparatus. It is suitable for the analysis of local inhomogeneities of texture, such as colonies of grains in polycrystalline materials.
  • A Characterization Method of Skeletal Structure for Polycyclic Aromatic Hydrocarbons by Molecular Ion Mass Spectrum

    pp. 189-194

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    A new characterization method of skeletal structure for polycyclic aromatic hydrocarbons (PAHs) has been studied by the soft ionization mass spectrum. The soft ionization, such as field desorption (FD), mass spectrum gives molecular weights of PAHs in coal tars and pitches. PAL-Is are classified into two types skeletal structure groups. Type-I is the highest H/C group based on kata-type condensation. Type-II is the lowest H/C group based on pen-type condensation. The general rational formula of each structures are C4nr+2H2nr+4 (Type-I) and C6nr2H6nr (Type-II). In addition, relation between number of aromatic rings (Ra) and molecular weight (Mw), H/C atom ratio and Ra, H/C and Mw are expressed as follows. Ra and Mw Type-I: Ra=(Mw-28)/50, Type-II: Ra={4Mw-13(8Mw+1)1/2+109}/96. H/C and Ra, Type-I: H/C=(Ra+2)/(2Ra+1), Type-II: H/C=6/[{3(4Ra-1)}1/2+3]. H/C and Mw, Type-I: H/C=(Mw+72)/(2Mw-6), Type-II: H/C=24/{(8Mw+1)1/2-1}.
    Coal tar pitch soluble in toluene and carbon black soluble in acetone are characterized by this method. The average molecular weight of the coal tar pitch soluble in toluene by the field desorption mass spectrum is higher than the carbon black soluble in acetone. But classified molecular ion peaks according to number of aromatic rings, carbon contents of each components of the coal tar pitch soluble in toluene are lower than the carbon black soluble in acetone. This example of the application disclose usefulness of the method for the characterization of polycyclic aromatic hydrocarbons in coal tars and pitches.
  • The Structural Analysis of the Rapid Heating Treated Coal Using Solid State NMR Methods

    pp. 195-200

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    A new carbonization process with high temperature preheating has been studied. A mechanism which improve the coking property was examined with coal properties by Solid State NMR and NMR imaging methods. It has been clarified that the molecular structure of coal has been relaxed by the rapid heating treatment and addition there is a close relation in hydrogen bond and relaxation of molecular structure of coal. Furthermore, the specimen of coal show the increase of mobile component by the rapid heat treatment using NMR micro imaging.

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