Search

The influence of discharged hydrogen from Pd-Ni based hydrogen storage alloys (HSAs) on cultured cells has been investigated. The susceptibility of cells to discharged hydrogen varied with the kind of cells. No influence was seen in the normal cells, while an effect of killing cancer cells was observed near the HAS and the region where the cell death was observed was limited to an extent of a few mm from the alloy surface. In order to examine the cause of the effects, the amount of gaseous hydrogen and hydrogen radicals released from the alloy surface and pH change of physiological saline aq. solution were measured. The amount of gaseous hydrogen and hydrogen radicals increased with time. The pH of physiological saline aq. solution decreased first and then recovered to the starting value after about 50h. The pH change behavior varied with alloy composition. It is inferred that the hydrogen radicals formed on alloy surface may bring a characteristic change in the cancer cells, leading to the effect of discharged hydrogen on cancer cell death.

In order to develop a new application of cast iron, high niobium cast iron has been developed as a grain refiner for stainless steel. High niobium cast iron was prepared by adding pure niobium to a commercial cast iron. Coarse primary niobium carbide crystals were observed in the microstructure of the cast iron. The effect of the high niobium cast iron as an inoculant on the grain size of austenitic and ferritic stainless steels was examined in various experimental conditions. When the amount of the cast iron inoculant more than 3 mass% was added into the steel melt, fine equiaxed grains were observed and grain size was significantly reduced to 210 μm. The results indicate that the high niobium cast iron is effective as a grain refiner for the austenitic and ferritic stainless steels. From the dissolution rate measurement, the grain refining mechanism was proposed., 9th International Symposium on Science and Processing of Cast Iron, SPCI-9; Luxor; 10 November 2010 through 13 November 2010, Key Engineering Materials, 457, pp.447-452; 2010

text, ナノダイナミクス国際シンポジウム 平成22年1月21日(木) 於長崎大学, Nagasaki Symposium on Nano-Dynamics 2010 (NSND2010), January 21, 2010, Nagasaki University, Nagasaki, Japan, Invited Lecture, Nagasaki Symposium on Nano-Dynamics 2010 (NSND2010), p.23-24; 2010

To synthesize an array of numerous ferromagnetic nanowires, iron-group metals such as Ni, Co, Fe, Ni-Fe and Co-Fe alloys were electrodeposited from aqueous solution into a nanoporous template with numerical cylindrical nanochannels . The shape of nanowires was precisely transferred from the nanochannel template and the aspect ratio reached to around 150. Magnetic hysteresis loops revealed that Ni, Co and Fe nanowires were spontaneously magnetized to the long axis direction. Coercive force of the nanowires with 6000 nm in length was increased in decreasing the pore-diameter. The coercive force of Co nanowires with 40 nm in diameter has increased up to 1084 Oe., 7th Pacific Rim International Conference on Advanced Materials and Processing, PRICM-7; Cairns, QLD; Australia; 2 August 2010 ～ 6 August 2010, Materials Science Forum, 654-656, pp.1724-1727; 2010

ZnTe compound semiconductors were synthesized in acidic aqueous solution using a pulsed current electrodeposition technique. The optimum condition to obtain ZnTe deposits was determined by the cathodic polarization curves measured at a wide potential range. During the co-deposition of Zn and Te, under potential deposition (UPD) of Zn was observed. Increasing the solution temperature up to 353 K, UPD of Zn was promoted by the formation of Zn(OH)2. Crystal phase, structure and chemical composition of electrodeposited ZnTe was controlled by the solution composition and electrolysis condition. The band gap energy of ZnTe films annealed at 573 K was close to 2.26 eV., Materials Science Forum, 654-656, pp.1732-1735; 2010

In order to develop the alumina fiber reinforcements optimized to FRMMCs, the effect of characteristics of alumina fibers on the fabrication process and the characteristics of the alumina fiber reinforced Al alloy composites was investigated. Alumina fibers which have different alumina content were prepared. Alumina content in the fibers was varied from 80% to 100%. Al-4mass%Cu alloy, Al-12mass%Si alloy and Al-10masss%Mg alloy were used as matrix. The FRMMC specimens were fabricated by a low-pressure infiltration process (LPI process). The formability of the preform was improved with increasing alumina content in the fibers. However, broken fibers were observed in the preform when alumina fibers with high alumina content were used. The number of the broken fibers seemed to be increased with increasing alumina content in the fibers. This result could be attributable to a change of fiber strength resulting from a change of alumina content in the fiber. The FRMMC specimens were characterized by using Vickers hardness test. The Vickers hardness of FRMMC specimens depended on the elasticity or the hardness of the fibers. The results obtained suggest that the characteristics of the FRMMCs largely depend on the intrinsic characteristics of the reinforcement fibers., 6th International Conference on Processing and Manufacturing of Advanced Materials - THERMEC'2009; Berlin; 25 August 2009 through 29 August 2009; Code 79243, Materials Science Forum, 638-642, pp.956-960; 2010

Ni-Fe alloy films and nanowires were fabricated using electrodeposition technique. The cylindrical shape of nanowires was precisely transferred from the nanochannels of membrane filters and the aspect ratio reached to around 60. Coercive force in in-plan direction of Ni-Fe alloy films decreased to ca. 1 Oe with increasing Fe content in deposits while, in perpendicular direction, the films were hardly magnetized. Magnetic hysteresis loops revealed that the nanowires were spontaneously magnetized to the long axis direction and the coercive force reached to ca. 200 Oe., 6th International Conference on Processing and Manufacturing of Advanced Materials - THERMEC'2009; Berlin; 25 August 2009 through 29 August 2009; Code 79243, Materials Science Forum, 638-642, pp.787-792; 2010

A nuclear track etched polycarbonate membrane filter with numerous cylindrical nanopores was applied as a nanoporous template for growing metallic nanowires. Nickel, cobalt, and iron nanowires were electrodeposited into the cylindrical nanopores. Cathodic polarization curves were measured to determine an optimum condition for growing nanowires. The shape of nanowires was observed using scanning electron microscope (SEM) and the crystal structure was analyzed using transmission electron microscopy (TEM). Diameter and length of nanowires corresponded to those of nanopores and each nanowire was composed of a single crystal. Anodized aluminum oxide films were also fabricated as a novel nanoporous template. The pore length and diameter was controlled changing anodizing conditions. Ordering behavior of nanopores array in an anodized aluminum oxide film was also investigated to make a novel nanoporous template with a highly ordered honeycomb array of nanopores., Materials and Manufacturing Processes, 22(4), pp.440-443; 2007

To develop a novel separation technique of matrix alloys from metal matrix composite, separation experiments for various kinds of particle reinforced metal matrix composites (PRMMCs) were carried out. The Al-4mass%Cu alloy, Al-7mass%Si alloy and cast iron were used as matrix. The SiC particles (particle size: 75μm) and Al2O3 particles (particle size: 120μm) were used as reinforcement. The PRMMC specimen was placed in a silica tube container with a small nozzle (nozzle size: 0.75mm) at the bottom and was melted by H.F. induction heating. Then the molten PRMMC specimen was forced to flow out through the nozzle by applying a certain pressure of Ar gas. Most of the molten matrix alloy flowed out through the nozzle and the remainder in the container consisted of the reinforcements and a part of the matrix alloy. The amount of separated matrix alloy increased with decreasing the volume fraction of reinforcement particles in PRMMC specimens. With decreasing the fabrication temperature from 1273K to 1073K, the amount of matrix alloy separated from SiCP/Al-7mass%Si alloy composites increased. It is considered that a reaction layer formed on the surface of SiC particles at 1273K improves the wettability between the molten matrix alloy and SiC particle, which prevents the separation of molten matrix alloy from reinforcements. On the other hand, the amount of separated matrix alloy from 20vol% Al2O3P/cast iron composites was very high due to no reaction layer formed at interface between Al2O3 particle and cast iron., THERMEC 2006: 5th International conference on processing and manufacturing of advanced materials, July 4-8, 2006, Vancouver, Canada, Materials Science Forum, 539-543, pp.1028-1032; 2007

The physical and mechanical properties of randomly oriented fiber-reinforced metal matrix composites (FRMMCs) fabricated by LPI process were examined. SiC particles and SiC fibers were used as reinforcement, while Al–4 mass% Cu alloy, Al–7 Si mass% alloy and AZ91 alloy were used as matrix. A mixture consisting of aluminum particles, SiC particles and SiC fibers was prepared as a preform to control the distribution of SiC fibers in FRMMC. Randomly oriented FRMMC specimens were fabricated by infiltrating the molten matrix alloy into the preform by pressing the melt surface with a low pressure of Ar gas. FRMMC specimens showed a high performance in thermal cycling test as well as an excellent wear resistance. The Vickers hardness of FRMMC specimens was almost constant on the different sections and the physical and mechanical properties were found to be isotropic.

Thermal cycling test was carried out for 20 vol% and 40 vol% SiC particle/Al-4 mass%Cu alloy composites to evaluate the bonding strength of the SiC particle/matrix interface in PRMMC fabricated by a low-pressure infiltration process (LPI process). The SiC particles were distributed homogenously in the specimens and a reaction layer of less than I μm thickness was observed at the SiC particle/matrix interface before thermal cycling test. This reaction layer was identified as Al 4 C 3 formed by the reaction between the alloy melt and SiC particle during infiltration. The θ phase, which might form a coherent interface with Al 4 C 3 , crystallized around the SiC particles through the Al 4 C 3 layer. The coefficient of thermal expansion was hardly changed during thermal cycling for both the 20 vol% and 40 vol% SiC particle/Al-Cu composites. No significant change in the microstructure and no detachment at the SiC particle/matrix interface were observed after thermal cycling test. The interfacial structure consisting of SiC. Al 4 C 3 , θ phase and α-Al in order was considered to exhibit a strong bonding of SiC particles to the matrix. The Vickers microhardness measured on the SiC particles in the specimens having a strongly bound interface show hardness values with a small scatter, while those for the specimens having a weakly bound interface exhibit a large scatter in the hardness values. It is suggested that the bonding strength of the reinforcement particle/matrix interface could be ascribed qualitatively from the Vickers microhardness test.

The protection of crack formation by a functionally graded layer at the interface of surface-hardened iron alloys has been investigated using a modified reactive diffusion process which consists of the two-stage diffusion heat-treatment for diffusion species. From the stress analysis on thermal shock test and the microstructure observation, it was known that cracks formed on the thermal shock test were onion cracks arising from a radial stress σ r and radial cracks due to a circumferential stress σ θ . In the specimens subjected to the modified reactive diffusion heat-treatment, a functionally graded layer was formed at the interface between the surface carbide layer/iron substrate, which effectively suppressed the generation of cracks by shifting a location of the maximum tensile stress toward the substrate and relaxing a stress concentration at the interface.

Process parameters to control the microstructure of particle reinforced MMC in the low pressure infiltration process (LPI process), have been investigated. The mixed powder of reinforcement particle and pure aluminum particle in various volume fraction was employed to control the volume fraction of the reinforcement particles in PRMMC . The Al–12 mass%Cu alloy melt was forced to infiltrate into the mixed powder layer by applying a certain pressure of argon gas on the melt surface. The pressure required to infiltrate remarkably increased from 0.05 to 0.5 MPa with a decrease in the particle size from 100 to 20 \\micron, indicating that the pressure at the advancing melt surface decreased due to the resistance based on a capillary force and a friction force between melt and particle. In the microstructure of PRMMC obtained, the reinforcement particles were homogeneously distributed and a linear relationship was obtained between the volume fraction of reinforcement particle in the mixed powder and the observed area fraction. It was found that a homogeneous particle distribution and accurate control of the volume fraction of reinforcement particles could be attained in the LPI process.

The mechanism of crack generation in the surface chromium carbide layer formed by laser cladding of an iron substrate with a mixed powder of raw materials has been investigated for different laser melting procedures. On the vertical section of the specimens subjected to cross laser scanning, vertical cracks across the surface carbide layer were observed on one side or both sides of the laser melted track, and some interfacial cracks were observed at the interface between the carbide layer and the iron substrate. Stress analysis revealed that vertical cracks may be caused by a tensile stress generated just after the solidification of the laser melted region due to the restriction of the unmelted carbide on both sides, while interfacial cracks may be generated due to a stress resulting from a steep temperature gradient beneath the top surface and the difference in the coefficient of thermal expansion between the chromium carbide and the iron substrate.

A polycarbonate membrane filter with numerous cylindrical nanopores was used as a template for growing metallic nanowires such as Ni, Co and Fe. The nanoporous template with pore-diameter of 150 nm, pore-length of 6000 nm, and pore-density of 108 pore?cm-2 was modified as a cathode with sputter-deposited gold layer. Inside the nano-pores, the metallic nanowires were electrochemically deposited from an acidic sulfate solution containing metal ions. The growth rate of metallic nanowires depended on the cathode potential during electrodeposition. The diameter of electrodeposited nanowires corresponded to that of nanopores in the template. TEM diffraction pattern suggested that each metallic nanowire composed of a single crystalline structure., Materials Science Forum, 539-543, pp.1253-1257; 2007

The partition coefficients of chromium between austenite and liquid iron,k Cr A/L , were determined from the experiment of rapid cooling of iron-carbon hypo-eutectic alloys containing a small amount of chromium from coexisting solid—liquid states; the partition coefficients between eutectic and its liquid,k 0,Cr, andk′ 0,Cr, for the stable and metastable eutectic solidifications were obtained from the zone-melting experiment of iron—carbon eutectic alloys containing a small amount of chromium. Chromium was rejected to liquid iron on the crystallization of primary austenite,k Cr A/L 1. The relationship between effective and equilibrium partition coefficients given by Burtonet al. was observed for the results of the zone melting experiment and, from the relationship, the thickness of boundary layer in the liquid ahead of the solid—liquid interface was found to be 0.17 mm for the stable system and 0.11 mm for the metastable system. Thermodynamic calculation of the partition coefficients of chromium and carbon proved to represent the observed partition coefficients well.

During iron-carbon eutectic solidification, the coefficients for partition of a third element between the eutectic liquid and its solid were evaluated thermodynamically. The coefficientkMA/L for the equilibrium partition of the third element (M) between austenite and liquid iron largely depended on the interaction between carbon and the third element and a simplified method for the evaluation ofkMA/L was introduced. The coefficients,KS andKM, for the partition of the element between the eutectic liquid and its solid in the stable and metastable eutectic solidification, respectively, were also calculated fromkMA/L and the coefficientkMC/A for the equilibrium partition of the element between cementite and austenite. It was indicated by the thermodynamics of the free energy for the co-existing phases that the effect of a third element on graphitization occurring during eutectic solidification was related quantitatively to the value of ΔK which was represented byKS-KM. The effect of a third element on the difference between the stable and metastable eutectic temperatures and on the carbon activity of liquid iron was closely related to ΔK or the equilibrium partition coefficient,kMC/A.

The partition of nitrogen between austenite and liquid iron was examined from the measurement of solubilities of nitrogen in these phases. On primary austenite crystallization, nitrogen was rejected into liquid iron at high temperatures and the partition behaviour was reversed at low temperatures. Silicon lowered the critical temperature where the partition behaviour of nitrogen changed. The partition of nitrogen between cementite and austenite was investigated by analysis of nitrogen in iron-carbon-silicon alloys, which were quenched in ice-water from an equilibrium state at subeutectic temperatures, and in the cementite extracted from them. Nitrogen was enriched in cementite for Fe-C-0.5 wt% Si alloy, similar to the case of pure Fe-C alloy. However, silicon reduced the degree of enrichment of nitrogen in cementite. By the use of the partition coefficients, the variations of nitrogen concentrations in the coexisting phases were evaluated during the solidification of cast irons. In the irons with lower carbon concentrations, the supersaturation of nitrogen in liquid iron attained during solidification increased with increasing silicon content, and silicon had a detrimental effect to promote the formation of nitrogen gas blowholes in low-carbon cast irons.

The effects of chromium on the anisotropy of Young's modulus and the thermoelastic coefficient of iron-cementite alloy castings were investigated at temperatures up to 773 K. From regression analysis, the Young's moduli of cementite and pearlite were evaluated as functions of carbon and chromium concentrations. The “young's modu!i and thermoelastic coefficients of iron-carbon-chromium alloy castings are highly anisotropic. Chromium decreases the ΔE effect due to the ferromagnetism of cementite and increases the Young's moduli o cementite and pearlite. An Elinvar property is observed in the alloy Fe-4 wt% C-4 wt % Cr below the Curie temperature.

The hot hardness was measured on the (010) plane of primary cementite in unidirectionally solidified iron-carbon, iron-carbon-chromium, and iron-carbon-boron alloys at temperatures up to 973 K, using a hot hardness tester equipped with an indenterheating system. The hardness of paramagnetic cementite against temperature was represented by the Ito-Shishokin relation. On the other hand, the hardness of ferromagnetic cementite deviated to low values from the Ito-Shishokin relation found for paramagnetic cementite. This deviation occurred from magnetostriction, because the thermal softening coefficient of cementite was found to relate to the thermal expansion coefficient regardless of the magnetic state similar to that found with fcc and bcc metals. Chromium and boron increased the hot hardness of cementite.

Hot hardness was measured on the primary carbides, (Fe, Cr)3C and (Fe, Cr)7C3, in unidirectionally solidified iron-carbon-chromium hypereutectic alloys with chromium more than 4.8 wt %. The hardness-temperature relation was represented by two Ito-Shishokin formulae,Hv =A(— BT), and thus was drawn by two lines on a semilogarithmic graph. The inflection temperature where the two lines intersected was found at 730 to 860 K for (Fe, Cr)3C carbide containing 0 to 14 wt % Cr, increasing with an increase in the chromium concentration in the carbide, and at about 910 K for (Fe, Cr)7C3 carbide containing 36 to 76 wt % Cr. With increasing chromium concentration in each carbide, the hardness of the carbide increased and the thermal softening coefficients decreased. The effect of chromium on the hardness, the inflection temperature and the thermal softening coefficients was more pronounced for (Fe, Cr)3C carbide than for (Fe, Cr)7C3 carbide. Each of the thermal softening coefficients,B1(T Tt), the inflection temperature,Tt, room-temperature hardness,Hv(TRT), and the hardness atTt,Hv(Tt), related linearly to the chromium concentration in the carbides, and hence the hot hardness of the carbides could be expressed as functions of temperature and chromium concentration in the carbides. The relationships betweenHv(TRT) andHv(Tt) and between the thermal softening coefficient,B2, and the activation energy for creep,Qc(kJ mol−1), were represented by the following equations:Hv(Tt)≃0.7Hv(TRT),B2=1.26/Qc.

Changes in the stable and metastable eutectic temperatures and compositions of the iron-carbon system by addition of alloying elements were calculated on the basis of the geometrical thermodynamics. The influences of alloying elements on these temperatures and compositions exhibit periodicities. The periodicities of the influences on the stable and metastable eutectic temperatures have a maximum in raising these temperatures, and the periodicities of the influences on the eutectic compositions have a maximum in lowering them, in each periodic row. The calculation of eutectic temperatures was extended to Fe-C base multicomponent alloys, and the calculated eutectic temperatures Were in good agreement with experimental ones given by Oldfield.