Search

Titanates are one of promising sorbents for toxic heavy metal ions and radionuclides due to various chemical formulas and crystal structures, and their functional properties. Herein, we present a unique seaweed-like sodium titanate mat (SST) with randomly distributed layered sodium dititanate nanofibers synthesized by a simple hydrothermal process. We focused on the effect of NaOH concentration during the hydrothermal process on crystallographic properties and investigated the synthesis conditions for SST. Furthermore, Sr2+ sorption properties of SST and related titanates, which were synthesized by hydrothermal process, was studied by batch tests. SST, which consist of a dititanate phase, was synthesized at 10 mol/L NaOH concentration and trititanate phase was formed when the NaOH concentration was increased to 15 mol/L. The SST showed a high ion-exchange selectivity of Sr2+ against H+ and a high maximum sorption capacity (2 mmol/g), compared with the case of trititanate phase (0.49 mmol/g), which shows the precipitation of SrCO3. This was presumably due to the difference of crystal structure of two titanates. This study demonstrates that the design of the crystal structure is important for controlling the sorption mechanism of sorbents for water treatment. [ABSTRACT FROM AUTHOR]

Using a horizontal batch dry bead mill newly developed by our company, talc raw material was ground in air, and its grinding performance and mechanochemical effect on the sample were evaluated from various perspectives. First, the average diameter of the ground product as a grinding performance decreases with the increase in grinding time or power source unit, reaching the submicron size. In addition, when mill operation is continued, talc changes fine particle aggregation and crystal structure change due to mechanochemical effects, and the phenomenon of detachment of the (OH) group around Mg in the crystals becomes remarkable. The flowability of the ground product is inhibited by the withdrawal of (OH) from the talc crystal, but this flowability is restored when it is dried. When the power source unit in the grinding approaches 3 kWh/kg2 it asymptotes to the maximum value of 9% in the weight reduction percentage. [ABSTRACT FROM AUTHOR]

In this paper, we report on our group’s efforts to improve the coercivity of Sm2Fe17N3 powder, especially on reducing the particle size to submicron scale, smoothing the particle surface, and suppression of the formation of coarse particles by developing a new reduction-diffusion process. During the course of a series of these works, it was revealed that the washing step, which is performed to remove excess Ca, supplied hydrogen into the Sm2Fe17N3 crystal structure, and induced unfavorable elongation of the crystal structure along the c-axis. To avoid this problem, the powders were subjected to dehydrogenation treatment, demonstrating reasonably high coercivity values that we expect from the known relationship between particle size and coercivity. It was also found that the conventional dissolution and the removal of impurities by acetic acid were roughening the particle surfaces. Thus, development of an alternative process to acetic acid cleaning prevented the surface roughening and showed the further improvement of the coercivity. Finally, the development of a new uniform reduction-diffusion reaction using a rotary furnace brought about a breakthrough for further improvement of coercivity by suppressing the formation of coarse particles. As a result, we succeeded in synthesizing Sm2Fe17N3 anisotropic powder with an ultra-high coercivity (i.e. the current world record) of 31.7 kOe, and also showed that the powder can maintain a coercivity higher than 10 kOe at 200°C. [ABSTRACT FROM AUTHOR]

In recent years, high-precision gears are expected to be used in vehicles and robots. Currently, gear hobbing is widely used as a roughing process while shaving and grinding are used as finishing processes to improve the accuracy and surface quality of the gears. The increasing demand for gears requires a gear machining method that is more efficient than the conventional machining processes. In this study, high-speed gear hobbing that achieves accuracy comparable to shaving and grinding was performed at a cutting speed 12 times that of conventional hobbing. Experiments were conducted using Cr-Mo steel as the workpiece and cemented carbide as the hob cutter in the cutting speed range of 200 - 2450 m/min. The relationship between the hardness and the depth from the gear surface was investigated with a comparison with the change in the material structure of the gear surface layer. The results showed that the hardness of the gear surface layer increased in the high-speed hobbing process compared to the conventional hobbing due to the strain and crystal grain refinement caused by the high cutting speed. In addition, experiments were performed at each cutting speed in the range of 400 - 1200 m/min to investigate the possible changes in machining characteristics when the number of machined pieces increased to 30. The results showed that despite the number of machined gears, the surface hardness increased at high cutting speeds. The effects of the number of machined gears on tool wear and surface roughness were also insignificant, indicating that high-speed hobbing is a promising efficient production method of gears with high surface quality.

The photoluminescence (PL) intensities of Li-Ta-Ti-O:Mn4+ red phosphors were successfully improved under various oxygen partial pressures in an air-pressure control atmosphere furnace (APF). The Mn phosphors were synthesized using an APF and a conventional electric furnace (EF) with the composition formula Li1.33Ta0.67Ti0.33O3 as the host material. The effects of oxygen partial pressure on the Mn4+ ratio and crystal structure for the PL intensity were investigated. As a result, the PL intensity was enhanced under high oxygen partial pressure, showing about 2.6 times higher than the phosphor synthesized by EF. [ABSTRACT FROM AUTHOR]

The GRRM program is a computational program for automated chemical reaction path search. The Artificial Force Induced Reaction (AFIR) method implemented in the GRRM program enables automatic reaction path searches for gas and liquid phase reactions. Recently, the AFIR method has been extended to solid phase systems such as crystals and surfaces. This article reviews applications of the AFIR method to crystal structure prediction and surface reactions. [ABSTRACT FROM AUTHOR]

This study investigated the combustion synthesis of an Eu,Si-doped AlN blue phosphor for white light emitting diodes (LEDs) using Al, AlN, Eu2O3 and Si3N4 powders as raw materials. The photoluminescence (PL) property, crystal structure, and location of Eu of the synthesized phosphor were studied. When Eu is doped without Si doping, Eu does not locate into the AlN crystal but exists at the grain boundary as an oxide. When Eu and Si are co-doped, the Si-Eu-O rich layer generates in the AlN crystal, which exhibits the blue emission under ultraviolet irradiation. Eu is doped as divalent cations in the crystal and the large distance between Eu and surrounding ligands might reduce the crystal field splitting, resulting in the blue emission. [ABSTRACT FROM AUTHOR]

It is known that the anisotropic magnetic fields are improved by La and Co substitutions for M-type ferrite sintered magnets, and the coercive forces are significantly improved. On the other hand, since W-type ferrites have a crystal structure similar to that of M-type ferrites, it is expected that La-Co substitution would improve magnetic properties in the same way. However, evaluations of the effects of La and Co substitution are difficult because sintered bodies with a single phase of W-type has not been obtained and sintering at high temperatures is required. Recently, a method to determine the anisotropic magnetic fields using the saturation asymptotic law was proposed by T. Kuno et al., J. Jpn. Soc. Powder Powder Metallurgy 63 (2016) 1053, which makes it possible to evaluate the anisotropic magnetic fields. In this study, La-Co substituted W-type ferrite powders in the Ba, Sr and (Ba-Sr) based systems were prepared, and the effects of La-Co substitution and the ratio of Ba and Sr on the anisotropic magnetic fields were investigated. [ABSTRACT FROM AUTHOR]

In this study, we synthesized blue-emitting new phosphors of P-doped Ca2SiO4:Ce3+ using the formula (Ca2-(x+y)/2-yCey□(x+y)2)(Si1-xPx)O4. The host material Ca2SiO4 has five polymorphs (γ, β, α, α'L, and α'H), and the crystal structure changes by doping of P or annealing temperatures. The relationship between the photoluminescence (PL) property and crystal structure is our focus point. The phosphors were characterized using X-ray diffraction, X-ray absorption fine structure, and fluorescence spectrophotometry. Results revealed that the P-doped Ca2SiO4:Ce3+ phosphor produced a bright blue emission, with the highest photoluminescence PL values achieved when Ce content (y) = 0.04 and the annealing temperature was 1473 K. [ABSTRACT FROM AUTHOR]

Mechanical synthesis of lithium titanate hydrate (LHTO: Li1.81H0.19Ti2O5·xH2O) in liquid phase was investigated using a bead mill. LHTO has layered crystal structure which leads to form thin plate particles. As starting materials, lithium hydroxide which was dissolved in water and titanium dioxide nanoparticles were used. As bead media, 0.3, 0.5 and 1 mm diameter of zirconia balls were employed. At least some amount of LHTO was formed at each bead size condition. In cases of 0.3 and 0.5 mm beads, crystallization of LHTO looked not to proceed after some hours. After 5 hours, the most crystallized LHTO was synthesized at 1 mm beads. Some of observed particles showed thin plate shape but the greater part of particles were fine particles in the obtained powder. It was supposed that synthesized LHTO particles were broken faster than crystals of LHTO grew up since small bead media performed high grinding ability. [ABSTRACT FROM AUTHOR]

A machine learning method was developed, which predicts ionic conductivity based on chemical composition alone, aiming to develop an efficient method to search for lithium conductive oxides. Under the obtained guideline, the material search was focused on the Li2O-SiO2-MoO3 pseudo-ternary phase diagram, which is predicted to have high ionic conductivity (>10−4 S • cm−1). We investigated the formation range, ionic conductivity, and crystal structure of the lithium superionic conductor (LISICON) solid solution on the Li4SiO4-Li2MoO4 tie line. The ionic conductivity of the LISICON phases is about 10−7 S • cm−1, which is higher than that of the end members; however, two orders of magnitude lower than that of the analogous LISICON materials. In addition, the experimental values were two or three orders of magnitude lower than the predicted conductivity values by machine learning. The crystal structure analysis revealed that the distance between the lithium sites and the occupancy of each lithium site in the crystal structure contributed to the decrease in ionic conductivity. This strong correlation between crystal structure and ionic conductivity was one of the reasons for the discrepancy between the predicted ionic conductivity based on chemical composition alone and the experimental value. [ABSTRACT FROM AUTHOR]

The effects of Cr or V substitution on the crystal structure and mechanical properties of Mo2NiB2 were investigated by experiments and first principles calculation. Mo2Ni1-xCrxB2 and Mo2Ni1-xVxB2 samples were synthesized via the powder metallurgy method. The XRD analysis revealed that the tetragonal Mo2NiB2 phase appeared with the addition of the Cr or V in both Mo2Ni1-xCrxB2 and Mo2Ni1-xVxB2 samples, and increased with the increase of the Cr or V content x. Orthorhombic Mo2NiB2 phase decreased with the increase of the Cr or V content x, and completely disappeared at x = 0.75. The Vickers hardness of Mo2Ni1-xCrxB2 and Mo2Ni1-xVxB2 samples improved with increasing Cr or V additions, and the maximum values of 20.4 GPa and 19.8 GPa for x = 0.75 samples, respectively. The calculated shear modulus of the tetragonal Mo2Ni1-xCrxB2 and tetragonal Mo2Ni1-xVxB2 increase with increasing Cr or V content x. The calculated Vickers hardness of orthorhombic Mo2NiB2, tetragonal Mo2CrB2 and tetragonal Mo2VB2 are 21.915 GPa, 22.492 GPa and 24.656 GPa, respectively. The Crystal Orbital Hamilton Population (COHP) analysis indicates the excellent mechanical properties of tetragonal Mo2CrB2 and tetragonal Mo2VB2 are due to the strong bonding between Mo-(Cr or V) and (Cr or V)-B atoms. [ABSTRACT FROM AUTHOR]

A cutinase-like enzyme from a thermophilic isolate, Saccharomonospora viridis AHK190, Cut190, has the ability to depolymerize polyethylene terephthalate (PET). The catalytic activity and thermal stability of Cut190 are increased by Ca2+ binding. The structural analysis of Cut190 mutants in complex with metal ions and substrates elucidated the reaction mechanism regulated by Ca2+. The metal ion-binding properties, analyzed using isothermal titration calorimetry were correlated with the effects on Cut190 activity and stability, which could be improved using protein engineering. The Cut190 mutant will be used for PET chemical recycling. [ABSTRACT FROM AUTHOR]

In this work, we investigated the crystal structure and photoluminescence (PL) property of Ca2(Si,P)O4:Eu2+ phosphor doped with Al3+ ions. Changes in the crystal structure were evaluated via X-ray diffraction and X-ray absorption fine structure measurements. With increasing concentrations of Al and P ions, the crystal structure transforms from β to α'L phase. The emission color of phosphor changes from green to blue. However, Al ions exerted only a modest effect on the crystal structure and PL property of the material compared with the absence of Al ions. [ABSTRACT FROM AUTHOR]

Cytochrome c oxidase in the mitochondrial respiratory chain mostly exists as an independent monomer, or as a monomer associated with the complexes I and III in the supercomplex, although its molecular mechanism has been elucidated based on the crystal structure of its dimeric form. Here, we report detailed comparison of the activity and crystal structure between the monomer and the dimer, and the possibility that the monomer is an activated form, whereas the dimer can be regarded as a physiological standby form in the mitochondrial membrane. [ABSTRACT FROM AUTHOR]

When we have food intake, pH of the stomach reaches around 1. This highly acidic environment is indispensable for the digestion. Gastric proton pump, H+,K+-ATPase is a membrane protein responsible for the gastric acid secretion. Its crystal structures now reveal how this proton pump extrudes H+ even into the pH 1 environment of the stomach. [ABSTRACT FROM AUTHOR]

Hydrogenases play crucial roles in the hydrogen metabolism by catalyzing the simple reaction: H2 ⇄ 2H+ + 2e–. While the enzymes are of industrial importance, there are a number of serious obstacles to the applications such as the catalytic electrode in the fuel cells, which include the stability to O2. Here we summarize the structural and functional properties of [NiFe]-hydrogenases with focusing the protective mechanism against O2. The recent our studies have revealed that not the catalytic site itself but the Fe-S cluster equipped as the electron pathway is of functional importance for preventing from the attack by O2. [ABSTRACT FROM AUTHOR]

We investigated the crystal structure and ferroelectric domains of Bi4Ti3O12 by the single-crystal X-ray diffraction and transmission electron microscopy (TEM) techniques. The space group in the ferroelectric phase was found to be P1a1. We successfully refined the crystal structure based on this space group. The calculated spontaneous polarization by the point charge model is good agreement with the reported experimental value. The 180° and 90° ferroelectric domain structures were observed by the [001]-zone dark-field TEM imaging. In the 180° domain structure, we determined that one component of the polarization vector is along the a-axis. The annular bright-field scanning transmission electron microscopy images displayed every atomic position in spite of the highly distorted structure of Bi4Ti3O12. The tilting and distortion of the TiO6 octahedra were also clearly observed. Therefore, we directly evaluated the ferroelectric displacements of Bi and Ti ions. [ABSTRACT FROM AUTHOR]

In order to assess the fatigue damage of austenitic stainless steels by electron backscatter diffraction (EBSD) method more simply and easily, it should be more preferable to use a commercially available general-purpose EBSD analysis software rather than to employ an in-house developed EBSD analysis programme. In the present study, EBSD measurement was performed for Type 316 austenitic stainless steels subjected to cyclic loading, and the applicability of the EBSD parameter relevant to the pattern quality, which could be obtained by the commercial software, to the fatigue damage assessment was discussed by comparing the other EBSD parameter of the averaged local misorientation (Mave), which could be calculated by the in-house developed programme. As a result, the EBSD parameter relevant to the pattern quality, which signified the full width at half maximum (FWHM) of the histogram distribution of the image quality (IQ), was saturated at the beginning stage of the fatigue cycles, while Mave was increased monotonically with the cycles. This suggested that the FWHM of IQ could be useful to detect the initial stage of the fatigue damage, while Mave was suitable for the quantitative evaluation of the fatigue damage. XRD measurement was also carried out for the same samples employed in the EBSD measurement, and the XRD data was compared with the EBSD data to discuss the crystallographic mechanism of the change in the FWHM of IQ. As a result, it was found that the FWHM of the (111) XRD peak correlated well with the FWHM of IQ. Because the (111) plane in fcc metal such as austenitic stainless steel was most preferable for slip system, this implied that the change in the distribution of the pattern quality generated by the fatigue loading could be due to the slip deformation.

Copyright of Kobunshi Ronbunshu is the property of Society of Polymer Science and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

DNA damage tolerance (DTT) is a cell function to avoid replication arrest by DNA damage during DNA replication. DTT includes two pathways, translesion DNA synthesis (TLS) and template-switched DNA synthesis (TS), regulated by various molecular interactions. TLS is transient DNA synthesis using a damaged template by error-prone DNA polymerases specialized for DNA damage (TLS polymerases). TS, in which one newly synthesized strand is utilized as an undamaged template for replication by replicative polymerases, is error-free process. This review article describes recent progress in structural studies of proteins involved in TLS and TS. [ABSTRACT FROM AUTHOR]

New lithium ion conductors of M-doped LiScO2 (M = Zr, Nb, and Ta) were synthesized by a solid-state reaction method. Peak shifts of the X-ray diffraction patterns revealed the formation of solid solutions with aliovalent cation doping. In addition, increase in the ionic conductivity by the M doping is indicated. The highest total conductivity of 7.94 x 10-6 S cm-1 at 623 K with an activation energy of 88 ± 5 kJ mol-1 was observed for the Zr4+ doped sample in the systems. The Zr4+ doped system showed the largest solid solution limit in Li1-xSc1-xZrxO2 (x ≈ 0.1) and continuous increase of the conductivity with increasing x. Structural analysis by Rietveld refinement indicated that the lattice expansion and lithium-ion vacancy formation by the Zr doping in the structure, which could contribute to the increase in the ionic conductivity. [ABSTRACT FROM AUTHOR]

Poly(lactic acid) (PLA) is an environmentally-friendly biodegradable polymer. It is often used in packages, in automobiles, and for electronics. We can even expected that PLA replaces petroleum-based plastics. PLA crystallization can be controlled by cooling and heating, organic solvents, and vacuum ultraviolet irradiation. This paper focuses on controlling the crystalline structure by thermal-, solvent-, and photo-induced crystallization. The effect of the crystalline structures on PLA membranes on gas transport properties was systematically investigated. Interestingly, unlike common crystalline polymer membranes, the permeability through a crystalline PLA membrane was larger than that through an amorphous PLA membrane. PLA is an interesting polymer, whose gas permeability is not significantly affected by its isomer ratio and crystallinity in the L:D-donor ratio range of 98.7:1.3-50:50 and in the crystallinity range of 0-25%. [ABSTRACT FROM AUTHOR]

F- and V-ATPases are unique bio- and nano-molecular rotary motors among many types of bioenergy-transducing machineries. The rotational catalysis of F1 -ATPase has been investigated in detail, and the molecular mechanisms have been proposed on the basis of crystal structures of the complex and extensive single-molecule observation of the rotation. Recently, we have obtained crystal structures of bacterial V1-ATPase (A3B3 and A3B3DF complexes) with and without nucleotide. On the basis of these new structures, we present a novel model of the rotational catalytic mechanism for V1-ATPase, which is apparently different from those of F1-ATPases. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride) (PVDF) has three crystal structures: form I, II, and III. The relationship between the PVDF crystal structure and physical properties had not been investigated. We have previously reported that three crystal structures were made from a single solvent. In this study we evaluated the thermal, optical, and electrical properties of all three PVDF crystal structures which can be made by solvent casting using a single solvent. Light transmittance (wavelength: 800nm, 33 lam film thickness) was 93% (form II), 95% (form III), and 97% (form I). Melting point was 165°C (form I), 174°C (form II), and 173°C (form III). The relative permittivity was 13 (form I), 6 (form III), and 11 (form III). From these results, we confirmed that the physical properties of PVDF depended on the difference in the crystal structure. [ABSTRACT FROM AUTHOR]

Hydrogenases play crucial roles in the hydrogen metabolism by catalyzing the production and decomposition of H2. The membrane-bound [NiFe]-hydrogenase is a representative member of O2 -tolerant hydrogenases, but the mechanism of which is poorly understood. Recently, we and other groups have reported the crystal structures of membrane-bound [NiFe]-hydrogenases, which revealed an unprecedented structure of one of three iron-sulfur clusters in the enzyme. Together with the spectroscopic study that shows the unique iron-sulfur cluster takes three oxidation states under physiological redox potentials, we concluded that the iron-sulfur cluster plays a key role in the O2-tolerant mechanism of the membrane-bound [NiFe]-hydrogenase. [ABSTRACT FROM AUTHOR]

This paper discusses the fabrication method of Poly(vinylidene fluoride) (1) crystal having excellent dielectric properties. We tried to control crystal structure of PVDF in the blend films of PVDF and Poly(methyt methacrylate) (PMMA) prepared by solvent casting. PVDF/PMMA = 60/ 40wt.% blend was dissolved in DMF solvent at 120°C. After casting, the PVDF/PMMA blend films were baked at 150°C (B). Each film was quenched (Q) from melting state and then was annealed at 120°C (QA). As a result, we demonstrated that PVDF (I) crystal grows preferentially under the existence of PMMA. That the crystallization speed of the quenched and annealed PVDF/PMMA blend films (QA) with the blend ratio of PVDF/ PMMA = 60/40wt.% is comparatively slow and forms the PVDF (I) crystal. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride) (PVDF) has three crystal structures: forms I, II, and III. Each structure was fabricated by solvent casting using various solvents. In this study, we demonstrated how to fabricate forms I, II, and III using one solvent (hexamethylphosphoric triamide), The results and revealed that the crystal structure of PVDF depended on the evaporation rate of the solvent. Eventually, Form I was formed into when the evaporation rate was slow, Form II was formed when it was fast, and form III was formed at the evaporation rate between form I and II. [ABSTRACT FROM AUTHOR]

We focused on the crystal structure of cyclodextrin (CD) to develop new solid CD complexes. There are two large spaces in the columnar structure of CD crystals: one inside a CD cavity and another between CD columns. New solid CD complexes can be designed by incorporating guest drugs between the CD columns. We succeeded in preparing a solid drug/[polyethylene glycol (PEG)/γ-CD-polypseudoraxane (PPRX)] complex by a sealed-heating method via the gas phase. A drug/(PEG/γ-CD-PPRX) complex has a structure in which PEGs are included in a γ-CD cavity, and guest drugs are incorporated between the γ-CD columns. Screening by a sealed-heating method determined that a variety of guest drugs with varying molecular size and log P could be incorporated into the spaces between γ-CD columns, following a stoichiometric rule. Another method, via solid phase using cogrinding and subsequent heating, was developed to prepare drug/(PEG/γ-CD-PPRX) complex. This method enabled us to prepare the complex with a thermally unstable drug, as well as a drug/(PEG/α-CD-PPRX) complex not formed using the sealed-heating method. Both the structure and molecular state of each drug in the complexes were characterized by powder X-ray diffraction and solid-state NMR measurements. The dissolution character and thermal stability of the drug incorporated in the complex could be improved by the specific complex formation. The solid CD complexes thus developed have potential for drug-encapsulation and as drug-release carriers, owing to their unique structural and pharmaceutical properties.