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1

Thermal Properties of Various Ti-Al-C Composites Prepared by Hot Shock Compaction Utilizing Combustion Synthesis

Tomoshige R., Tanaka H.

Archives of Metallurgy and Materials

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2014

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Vol. 59, iss. 4

1575--1578

EN

Hot shock compaction method was utilized for the consolidation of MAX phase composites consisting of Ti, Al and C. This paper presents the production of dense, crack-free composites by combining the combustion synthesis with explosive detonation. Another objective is to investigate various properties of the obtained shock-compacts. The shock compacted materials were post-annealed at 1173 K for releasing the shock-induced strain. As a result, these compacts had strong interparticle bonding strength and few macro cracks. Intermetallic compounds (TiAl, Ti2Al and Ti3Al) and non-oxide ceramics (TiC and Ti4Al2C2) were detected in as-synthesized and annealed materials by X-ray diffraction experiments. Also, lamella structures of Ti4Al2C2 phase were observed by SEM. It was known that the coefficient of thermal expansion increased with increasing temperature, and decreased with increasing TiC content.

PL

Metodę udarowego zagęszczania na gorąco wykorzystano do konsolidacji fazy MAX kompozytów na bazie Ti, Al oraz C. Celem przeprowadzonych badań było wytworzenie zagęszczonych, wolnych od pęknięć kompozytów oraz analiza ich właściwości. Zagęszczone z wykorzystaniem technik udarowych materiały wstępnie wyżarzono w 1173 K w celu usunięcia skutków odkształcenia udarowego. Uzyskany materiał charakteryzował się silnym wiązaniem międzycząsteczkowym, ale zaobserwowano równie występowanie mikropęknięć. W syntezowanych i wyżarzonych materiałach, wykorzystaniem techniki dyfrakcji promieni rentgenowskich stwierdzono obecność związków międzymetalicznych typu TiAl, Ti2Al oraz Ti3Al, a także ceramik wolnych od tlenków typu TiC oraz Ti4Al2C2. Przy pomocy SEM analizowanor ównież warstwową strukturę fazy Ti4Al2C2. Zaobserwowano również, iż współczynnik wydłużenia cieplnego wzrastał wraz ze wzrostem temperatury i obniżał się wraz ze zmniejszaniem się koncentracji TiC.

2

Hydrides formed in ZrCo2 - based intermetallic compounds under high hydrogen pressure

Filipek S. M., Ru-Shi Liu Ru-Shi, Kuriyama N., Takeichi N., Tanaka H., Bulyk I. I., Kuo H.-T., Tu M.-H., Kochman M.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 1

223-226

EN

The hydrides of zirconium based pseudobinary alloys Zr(Co1-xTx)2, (T = Fe, V or Cr) and Zr1-xRxCo2 (R = Y, La, Pr) were synthesized under 1.2 GPa of hydrogen pressure. It was revealed that partial substitution of cobalt by V, Cr or Fe increases hydrogen absorption capacity and stability of derived hydrides. Especially, it was found that ZrCo1:8V0:2 alloy exposed to high hydrogen pressure can absorb 50% more hydrogen than pure ZrCo2 and the hydride ZrCo1:8V0:2Hy has surprisingly high stability. Substitution of zirconium by Y, La or Pr in ZrCo2 alloys improved hydrogen absorption but hydrides derived from La and Pr substituted alloys were less stable than ZrCo2H2. Only for Zr0:7Y0:3Co0:2Hy the hydrogen absorption was higher and desorption rate markedly smaller comparing ZrCo2H2.

PL

Pod wysokim ciśnieniem wodoru rzędu 1.2 GPa otrzymano szereg wodorków na osnowie pseudobinarnych stopów cyrkonu o następujących składach: Zr(Co1-xTx)2, (T = Fe, V or Cr) oraz Zr1-xRxCo2 (R = Y, La, Pr). Wykazano, że częściowe podstawienie kobaltu wanadem, chromem lub żelazem zwiększa zdolność absorpcyjną stopów i stabilność tworzących się wodorków. W szczególności okazało się, że pod wysokim ciśnieniem wodoru ZrCo1:8V0:2 absorbuje o 50% więcej wodoru aniżeli ZrCo2, a co więcej otrzymany z tego stopu wodorek ma nieoczekiwanie wysoką stabilność. Częściowe zastąpienie cyrkonu itrem, lantanem lub prazeodymem podwyższało wprawdzie zdolność absorpcyjną wodoru ale jednocześnie otrzymane wodorki zawierające lantan lub prazeodym były mniej stabilne aniżeli ZrCo2H2. Jedynie dla Zr0:7Y0:3Co0:2Hy odnotowano wyższą absorpcje wodoru i niższą szybkość jego desorpcji aniżeli w przypadku ZrCo2H2.

3

Increase in cortisol awakening response after two weeks of self-instruction for good sleep

Nomura S., Suguri K., Okamoto Y., Nomura T., Suzuki K., Tanaka H.

Journal of Medical Informatics & Technologies

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2010

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Vol. 15

169--175

EN

There is growing evidence suggesting that the magnitude of cortisol awaking response (CAR), which is characterized by a profound increase of salivary cortisol secretion after awakening, plausibly reflects the level of a chronic stress, social stress, anxiety, etc. In this study the alternation of CAR at the start and at the end of two weeks session of self-instruction for good sleep was investigated; by which we anticipated that the self-instruction for good sleep would bring-forth a positive affection for the participants, and would result in decline of cortisol awakening response (CAR). Nevertheless, as a result unexpectedly, subjects did not change their sleep and dietary habits along with the instruction, moreover the increased CAR was observed. This result implies that the suggestion of an impractical instruction would solely be taken as a stressful task for participants, even though they know that it is effective to improve their sleep. On the contrary, if one develops an instruction with practicable indication for daily life, it is highly possible to observe a positive effect of the instruction on CAR.

4

Suction and shear wave velocity measurements for assessing sample quality.

Tanaka H., Nishida K.

Studia Geotechnica et Mechanica

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2007

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Vol. 29, nr 1-2

163-175

EN

Sample quality is very important for obtaining reliable geotechnical parameters, especially because the reliability design method has been recently introduced into geotechnical engineering (for example, Eurocode 7). The sample quality is usually assessed by comparing the values of strength, Young's modulus and strain at failure from unconfined compression test as well as the values of pre-consolidation pressure, compression index, and volumetric strain at in situ stresses from oedometer test. However, since the assessment criteria are based on past experience, the above conventional methods should be examined carefully in order to explain whether they can or cannot be applied to the layers tested. In addition, it should be noted that they are destructive, i.e., after assessing the specimen quality, it is cannot be used for testing anymore. In this paper, the possibility of assessing a sample quality by suction (p'r) and shear wave velocity (vv) is examined.

5

Additional evidence on some relationship between seismic electric signals and earthquake source parameters

Varotsos P., Sarlis N., Skordas E., Tanaka H., Lazaridou M.

Acta Geophysica Polonica

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2005

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Vol. 53, nr 3

293-298

EN

We provide recent experimental evidence which further supports the inter-relation between the earthquake source parameters and the selectivity properties of Seismic Electric Signals. The cases of two major earthquakes with magnitudes larger than 6.0, that occurred in Greece during 2004-2005, are presented.

6

Electron impact excitation and dissociation of halogen-containing molecules

Kitajima M., Suzuki R., Tanaka H., Pichl L., Cho H.

Nukleonika

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2003

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Vol. 48, nr 2

89-93

EN

A systematic analysis of the absolute differential cross sections (DCSs) for electron scattering by halogen-containing molecules CF3X (X = H, F, Cl, Br, I) has been performed with impact energy and scattering angle ranging from 1.5 to 100 eV and 15 to 130°, respectively. Three of the results of these experiments are described in the present report. Firstly, a clear difference is demonstrated in the elastic-scattering cross section angular distributions of polar and nonpolar molecules with the substitution of one of the F atoms in CF4 for a H, Cl, Br or I atom. Secondly, vibrational excitation spectra of the unresolved composite modes (mainly CF3 stretching) for CF3X reveal a common broad structure in the region from 7 to 9 eV due to shape resonance. The third result presented is the observation of a low-lying electronic state of CF3Cl, CF3Br, and CF3I. This feature is enhanced at lower incident energies and larger scattering angles. Also discussed are some preliminary results on the formation of negative and neutral fragments from SiF4 and CH4 by electron impact.

7

Plasma Processing of Incineration Ashes

Huczko A., Chojecki G., Golimowski J., Kowalska J., Dziadko D., Tanaka H., Ishigaki T.

Chemia i Inżynieria Ekologiczna

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2002

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Vol. 9, nr 1

9-20

EN

Practical applicability of thermal plasma in the remediation of solid residuals resulting from the incineration of various wastes has been presented. There is a growing concem regarding the final disposal of waste incineration residuals, e.g. bottom and fly ashes. These "secondary" wastes can threaten the environment, mostly due to relatively high leachability of heavy metals and the possibility of desorption of polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs). In the present study plasma melting of incineration residuals was performed in a DC plasma jet, a DC rotating arc and RF plasma. Ashes were pneumatically transported into the plasma. The solidified products were collected and analyzed. SEM observations showed partial spheroidization of powders while their melting was evaluated from the sieve analysis. For DC plasma jet, the degree of transformation, despite the high plasma enthalpy, was relatively low, this is due to a poor mixing of reactants with high velocity plasma jet. To improve the heat transfer between a plasma and processed powders the rotating arc was used. The reactants were introduced directly into the plasma "cone". This system provided for longer reaction times. Effectively, the melting of the ashes was much more efficient (approaching 80%), despite relatively low arc power, comparing to the plasma jet. Microscope observations confirmed partial spheroidization and melting of processed powders. The conversion of processed ashes also depended upon their origin, i.e. the incineration residuals containing more organic matter (elemental analysis) were not only melted, but also pyrolyzed. Comparative physical and chemical analysis (DSC, XRD, XRF, differential voltamperometry) of solid residuals before and after plasma melting show, that plasma processing not only reduces their volume but also can distinctly decrease their leachability.

PL

Zaprezentowano praktyczne zastosowanie plazmy termicznej w przetwarzaniu stałych pozostałości pospaleniowych. Obserwuje się wzrost zainteresowania skutecznym pozbywaniem się pozostałości pospaleniowych, np.: popiołów lotnych i paleniskowych. Owe wtórne odpady mogą zagrażać środowisku przyrodniczemu, szczególnie z uwagi na względnie dużą wymywalność z nich metali ciężkich oraz możliwości desorpcji dibenzodioksyn (PCDD) i dibenzofuranów (PCDF). W niniejszej pracy pokazano możliwości przetapiania plazmowego w przepływowej oraz rotacyjnej plazmie łukowej, a także w plazmie indukcyjnej. Pyły były pneumatycznie transportowane do przepływowej plazmy argonowo-wodorowej. Zestalone produkty były zebrane i przeanalizowane. Badania morfologii wykonane przy użyciu SEM pokazały, że powierzchnia ziaren pyłów została częściowo nadtopiona. Stopień przetopienia oszacowano na podstawie analizy sitowej. Stopień transformacji w plazmie łukowej, pomimo dużej entalpii plazmy, był relatywnie niski. Wynika to ze słabego mieszania reagentów przy równoczesnej dużej szybkości przepływu strumienia plazmy. Aby polepszyć przepływ ciepła pomiędzy plazmą i przerabianymi pyłami, użyto wirującej plazmy łukowej. Reagenty były wprowadzane bezpośrednio do stożka plazmowego, co zapewniało dłuższy czas przebywania ich w strefie reakcyjnej. W rezultacie nastąpił wzrost przetopienia (do 80%) pomimo użycia mniejszej mocy niż w strumieniowej plazmie łukowej. Mikroskopowe badania potwierdziły częściową sferoidyzację i nadtopienia powierzchni przerabianych pyłów. Poza rodzajem użytej plazmy stopień przetworzenia reagentów zależał również od pochodzenia pyłów, np.: odpady pospaleniowe zawierające więcej związków organicznych (co wykazała analiza elementarna) zostały nie tylko stopione, ale uległy również pirolizie. Analizy porównawcze (DSC, XRD, XRF, amperometria różnicowa) stałych odpadów przed i po przeróbce plazmowej pokazują, że taki proces nie tylko redukuje objętość pyłów, lecz jednocześnie może znacznie obniżać wymywalność pierwiastków ciężkich.

8

A new type of dielectric bolometer mode of infrared detector using ferroelectricn thin film capacitors for uncooled focal plane array

Noda M., Hashimoto K., Kubo R., Tanaka H., Mukaigawa T., Xu H., Okuyama M.

Opto-Electronics Review

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1999

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Vol. 7, No. 4

313-320

EN

We have developed a new type of detector pixel circuit operated in an infrared image sensor of dielectric bolometer mode. The detector pixel consists of capacitors of ferroelectric thin film, whose dielectricc constant changes drastically with temperature. After comparing a few kind of ferroelectric materials such as Ba₁₋xSrxTiO₃ (BST) and La modified Sr₁₋xBaxNb₂O₆ (SBN) among each other, the BST is selected as the ferroelectric film in the structure of the detector. Our proposed circuit is a serially connected capacitor-capacitor, where one capacitor is composed of a BST ferroelectric thin film irradiated by infrared light and the other is nonirradiated one. BST film has been prepared on Si membrane structure by pulsed laser deposition method (PLD). Dielectric constant of the BST film, which is about 450 at 25°C, changes by about 1 to 10% K⁻¹ at ambient temperature. As a result of on-board evaluation of the assembled circuit with a source-follower output, the output level is about 40 mV when a relative capacitance change in the capacitor is about 3%. On the other hand, in PSPICE circuit simulations, the output level is about 25 mV when a relative capacitance change in the capacitor of about 100 pF is 1%. The simulated relationship between the output voltage of the assembled circuit and capacitance change of the BST film agrees well with that in the experimental results. It is considered that the circuit has enough output signal level for input of conventional operational amplifier. Voltage responsivity Rv, and specific detectivity D* estimated from temperature change of dielectric constant are 50 kVW⁻¹ and 6.5 x 10⁹ cmHz¹/² W⁻¹, respectively, which means high-sensitivity compared to the other type of IR sensors. The pixel structure also shows a simple configuration, and then is very effective in reducing their pixel size and then increasing the pixel density.

9

Interval regression analysis with polynomial and its similarity to rough sets concept

Tanaka H., Lee H.

Fundamenta Informaticae

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1999

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Vol. 37, Nr 1,2

71-87

EN

This paper proposes interval regression analysis with polynomials. For data sets with crisp inputs and interval outputs, three estimation models called as an upper, a lower, and a possi-bility estimation models can be formulated from the concepts of the possibility and necessity measures. Always there exists an upper and a possibility estimation model when a linear sys-tem with interval coefficients is considered, but it is not assured to attain a solution for a lower estimation model in an interval linear system. If we can not obtain the lower estimation model, it might be caused by adopting a model not fitting to the given data. Thus we consider polynomials to find a regression model which fits well to the given observations. The possibility model is used to check the existence of the lower model. If we can find a proper lower model, the estimated upper and lower models deserve more credit than the previous models in the former studies. We also introduce the measure of fitness to gauge the degree of approximation of the obtained models to the given data. The upper and lower estimation models in interval regression analysis can be considered as the upper and lower approximation in rough sets. The similarity between the interval estimation models and the rough sets concept is also discussed. In order to illustrate our approach, numerical examples are shown.