Effects of heat treatment on microstructure and hardness of Ti-Mo-N coating films were investigated for various N contents. Ti-Mo-N films were deposited onto a stainless steel substrate by a reactive RF sputtering process in the mixture of argon (7.5 ccm) and nitrogen (0~2.0 ccm) gases using Ti50Mo50 target. X-ray results of as-deposited films indicated that the main phase of the Ti-Mo-N film was a bcc-(Ti, Mo) phase at a nitrogen flow rate (fN2)≤0.2 ccm and a δ-(Ti, Mo)N phase at fN2 over 0.3 ccm. The Ti-Mo-N films so obtained were heat treated in argon atmosphere at 300~1100°C for 30 minutes. Hardness was measured by a nanoindentation system. The hardness of the Ti-Mo-N films deposited at fN2=2.0 ccm hardly changed with heat treatment. In contrast, the hardness of the films deposited at fN2=0.2 and 0.3 ccm was drastically increased by heat treatment at temperatures higher than 900°C. In particular, the film deposited at fN2=0.3 ccm showed the maximum hardness of about 35 GPa by heat treatment at 1000°C for 30 minutes. X-ray measurement and TEM observation indicated that the increment of hardness in the Ti-Mo-N film at fN2=0.3 ccm is due to the formation of a bcc-(Ti, Mo) phase in a δ-(Ti, Mo)N phase.
Recently, the development of the high-efficiency technology for gas turbine and jet engine is required to minimize carbon dioxide and nitrogen oxide emission. It is effective way to increase the operational temperature to develop the high-efficiency technology for high temperature instruments. To increase the operating temperature, advanced nickel based superalloys have been developed as a turbine blade material. Even though a nickel based superalloy is used for a structural component, creep damages and creep cracks may be caused due to the external tensile load under high temperature conditions. Therefore, a predictive law of creep crack growth life is necessary to maintain operational safety. This study is aimed to clarify the branch cracking behavior due to the microstructural strengthening mechanism of polycrystalline nickel based superalloy IN100 under the creep condition. The creep crack growth tests were conducted at a temperature of 900°C. The creep crack growth behavior and creep damage formulation were observed by in-situ observational system and SEM/EBSD. Additionally, two dimensional elastic-plastic creep finite element analyses were conducted for the model, which describes the experimental results. The creep crack growth behavior and the creep damage progression were found to be affected by the distribution behaviors of grains and grain boundaries around the notch tip. By comparison of experimental results with mechanical analysis using FEM analyses, mechanisms of the creep crack growth and the creep damage formulation were clarified.
Polarized terahertz (THz) wave spectra were obtained applied for the evaluation of polymer chains in mechanically extensional-deformed ultrahigh-molecular-weight-polyethylenes (UHMWPEs). THz absorption band was seen around 2.2 THz which is due to the B1u translational lattice vibration. For the deformed UHMWPE, the dichroism is appeared in the 2.2 THz band intensity. The absorption intensity is smaller in spectra with the THz wave electric polarization direction parallel to the deformation direction than that with the polarization direction perpendicular. The ratio of absorption intensity in each polarization directions is dependent on the amount of elongation strain. Based on the THz and XRD results, it is suggested that the THz nondestructive diagnosis of the tensile strain in deformed UHMWPE is possible based on the dichroism of B1u band intensities on polarized THz wave spectroscopy.
We have developed a high-resolution and continuous-wave (CW) terahertz spectroscopic system based on difference frequency generation (DFG) with an excitation of phonon-polariton in Gallium phosphide (GaP). The pump and signal near-infrared (NIR) lasers used in this system are an external cavity laser diode (ECLD) and a distributed feedback laser diode (DFB), respectively. Each line width of the NIR laser is less than 4 MHz, thus the quality factor Q of generated THz waves is more than 106. The terahertz wave frequency can be tuned automatically by changing wavelength of the DFB laser. As an example for the THz spectroscopic application for non-destructive inspection of ultra high molecular weight polyethylene (UHMWPE), we have shown terahertz spectra of UHMWPE with some degrees of deformation.
The deterioration mechanism of ferric ferrocyanide (Fe4[Fe(CN)6]3·xH2O) which is called Prussian blue, used as a blue pigment in Ukiyo-e printed in late Edo period, has been investigated. The two Ukiyo-e of the same design differ in their degree of deterioration; one print has good color, but the other is seriously discolored. The conditions of their blue areas are compared. The composition of the Ukiyo-e color pigments are analyzed by EDS (Energy Dispersive X-ray Spectroscopy). FT-IR (Fourier Transform infrared Spectrometer) is used to identify the functional group in the chemical compound. Areas of good blue color in the Ukiyo-e contain Fe, which is the main element in ferric ferrocyanide. In the FT-IR spectra, the absorption peak of around 2090 cm-1 corresponding to the CN triplet combination of ferric ferrocyanide (Fe4[Fe(CN)6]3·xH2O) is recognized. The Fe concentration in the faded blue area in the discolored sample is reduced to one-third that in the nondiscolored sample at the same position. The peak corresponding to the CN group has disappeared. A non discolored sample is subjected to accelerated ageing under the condition of high temperature and high humidity (353 K, 65%rh). The peak intensity of reflectivity in the aged sample decreases gradually with ageing.
The Hencky strain is a logarithmic strain extended to a three-dimensional analysis. By considering logarithm of matrix, components of the Hencky strain are calculated for tensile and shear deformations. ECAP (Equal-Channel Angular Pressing) and HPT (High Pressure Torsion) are giant straining processes based on simple shear deformation. To describe large deformations caused by such giant straining processes, components of the Hencky strain and its equivalent strain are derived for the simple shear deformation. It is shown that the Hencky strain is an appropriate measure to deal with deformations caused by the giant straining processes.
This paper examines the traceability of resource movement across borders by quantifying the global flow of base metals (Fe, Al, Cu, Pb, and Zn) through the used passenger car trade in 2005 using trade statistics and vehicle composition data. An estimation method was developed to deal with the often problematic issues associated with trade statistics. This estimation shows that 3.4×106 metric tons of Fe, 3.1×105 metric tons of Al, 7.5×104 metric tons of Cu, 3.2×104 metric tons of Pb, and 2.7×104 metric tons of Zn in used passenger cars globally were not recycled in the country of origin, but rather moved in a global flow out of the country of manufacture. The destinations of these metals were mainly developing countries with rudimentary recycling technology. These results strongly indicate that in developed countries, many metal resources from automobiles that could have been utilized domestically were instead scattered and lost overseas.
The LI and LIII edges of Hg and the K edge of Rb in Hg-Rb alloys were measured by the absorption spectroscopy of X-rays. On increasing the Rb concentration, the absorption edges of Hg show an opposite behavior from each other, a decrease of LI and an increase of LIII compared with the case of pure liquid Hg. This difference was discussed from the polyanion formation of Hg atoms on alloying. With the increase of alkali concentration, the p like state of polyanion seems to be situated on the lower energy side than that of the s band. The electronic structure of this polyanion was discussed based on a simple LCAO analysis. Such an existence of polyanions may be responsible for the curious phenomena of liquid Hg-alkali alloys, the maximum of the electrical resistivity at 60 at% alkali and the positively enhanced tendency in the intermediate alkali concentration range of the magnetic susceptibility in the overall negative deviation.
High solder wettability and thermal shock resistance are necessary for materials used for soldering tips. The thermal shock resistance of metal/ceramic composites was investigated, and each influencing factor is discussed in this study. The composites that have enough thermal shock resistance to be used as soldering tips are discussed. In addition, the factors that influenced the wettability of the composite material were investigated in order to improve the reliability of the solder wettability. The thermal shock characteristic of a Fe-added composite was clearly superior to a Ni-added composite. Both 20 mass% and 80 mass% Fe-added composites had greater wettability than Ni-added composites, and this led to a decrease in the thermal shock temperature difference ΔTC and bending strength σBT following thermal shock. The solder wettability of metal/ceramic tips are dependant upon the surface temperature and heating time of the specimen. This decreased susceptibility to thermal shock was thought to be due to differences in the surface oxidation behavior caused by the tip heating condition. It is necessary to strictly limit those conditions in order to reliably evaluate wettability.
Microstructural characterization of reactor pressure vessel mode alloys irradiated by neutrons and Fe-ions was performed using three-dimensional atom probe tomography. Ultra-fine clusters of solute atoms, such as Cu, Ni, Mn and Si, with diameter in the range of 2-3 nm were formed at high number density in all the alloys. The cluster number density and the mean diameter of the alloys irradiated by Fe-ion were higher and smaller, respectively, than those of neutron-irradiated alloys. The clusters in Fe-ion irradiated alloys had less Cu and more Ni and Si content than those of neutron irradiated alloys. The increase in hardness of both irradiated alloys had almost linear correlation with the square root of the volume fraction of solute atom clusters.
Hydrogen permeation behavior in carbon steel exposed to gaseous hydrogen was visualized using a hydrogen microprint technique (HMT). Effects of hydrogen gas pressure and charging time on the hydrogen permeation were particularly examined. The amount of permeated hydrogen was dependent on the charging time during the exposure to gaseous hydrogen. It was found that silver particles, which represented the evolution site of hydrogen atoms, were distributed almost uniformly in the matrix after hydrogen gas charging. These particles were arranged at the periphery of the second phase particles such as Al2O3. Area density of the silver particles clearly increased when the time for hydrogen gas charging was increased. Preferential accumulation of silver particles around Al2O3 particles was clearly identified; however, no silver particles were observed directly on the Al2O3 particles. This indicated that hydrogen atoms were diffused not through the inside of the second phase particles but through the interface between the second phase particles and the matrix phase.
In-situ observation of the catalytic action of MgH2-1 mol%Nb2O5 and MgH2-10 mol%Nb2O5 was carried out by using transmission electron microscopy (TEM). In case of MgH2-1 mol%Nb2O5, TEM analysis indicated that MgH2 started to decompose at 150°C and nano-size particle of Mg formed. However, Nb2O5 was not observed in the diffraction pattern and images. In case of MgH2-10 mol%Nb2O5, high resolution images, FFT and IFFT, revealed that the decomposition of MgH2 started with the contact region in Nb2O5 and Mg formed. The result suggested that the reaction of dehydration could proceed due to hydrogen diffusion to the Mg-Nb2O5 interface.
This paper describes the preparation of Fe16N2 nanoparticles by reduction of iron nitrate. First, α-Fe nanoparticles were prepared by reduction of iron nitrate powder under hydrogen flow at 623 K for 5 h. The α-Fe nanoparticles with the size of about 140 nm in SEM image, were then nitrided under an ammonia flow at 423 K for 72 h. The sample consisted of Fe16N2 and α-Fe phases from XRD analyses and showed the magnetization of 207 A m2 kg-1 under magnetic field of 1.43 MA m-1 at room temperature. The average particle size was revealed as 140 nm by TEM observations. To investigate the possibility of the obtained nanoparticles as microwave absorption materials, the electromagnetic wave absorption properties were investigated in a composite of the obtained nanoparticles and resin. The sample showed a good microwave absorption properties (Reflection loss: R.L.<-20 dB) in 15~19 GHz range. Therefore, it is concluded that Fe16N2 nanoparticles have a possibility to become a candidate for microwave absorbers in 10~GHz range.
Bone fracture toughness has been well studied, however, it is also important to investigate the effect of preservative treatment on the mechanical properties of bones. It is necessary to evaluate crack initiation and propagation after fracture because this process may be different in the case of injured bone tissues. In this study, we attempted to analyze the strain distribution on bone tissue surface by using image correlation techniques in order to elucidate the relationship between microscopic bone damage and strain distribution. Bovine femoral cortical bone was employed as the bone specimen and the three-point bend test method was used to determine the fracture toughness, in accordance with the ASTM E399 guidelines. An Instron type machine was used in the fracture toughness test and the loading rate was set to 1 mm/min. Black and white spray paint was applied in a random pattern to the surface of the specimens, and the specimens were loaded until they were ruptured. Bone surface strain analysis was performed using image correlation techniques and the changes were recorded in a digital image. In order to evaluate the effects of preservative treatment on the mechanical properties of bone, we categorized the specimens into 4 groups: the control group included the specimens that were submitted for testing immediately after machining and the preservation group comprised specimens that were analyzed after preservative treatment with different method (formalin, ethanol and physiological saline solution). A strain analysis performed using image correlation techniques allowed the visualization of the increased strain at the forward end of the slit of the specimens. The strain value at the forward end of the slit (the longitudinal direction of specimens) measured at the time of rupture in the control group was approximately 4 times larger than that in the formalin preservation group, thereby suggesting the embrittlement of bone organic constituents due to preservative treatment.
New kinds of cast and wrought (C & W) Ni-Co base superalloys (TMW alloys) have been developed based on the innovative concept of combining two kinds of γ-γ′ two-phase alloys, Ni-base and Co-base alloys, for the applications of turbine disks and high-pressure compressor blades. The results based on testing 20 kg ingots indicate that TMW alloys show excellent high temperature strength and formability, may provide 50°C temperature advantage in 630 MPa/100 h creep performance over C & W alloy U720Li. In this paper, we report our new results on the full-scale pancakes manufactured through the C & W process for real components. The results indicate that TMW alloys had good process-ability in the ingot making and forging into disk pancakes. Pancake disks with fine grain size of about 10 μm were successfully obtained for TMW alloys. TMW alloys provide 58°C to 76°C temperature advantages in 0.2% creep strain life under the 630 MPa condition, over alloy U720Li.