bluuebunny/crossref_metadata_2025 huggingface dataset:
Strain‐Induced Deformation in Magnesia–Alumina Layered Composites
Authors: Kim Chang Soo , Lombardo Stephen J. , Winholtz Robert A.
Published: July 2010

Ceramic beams are induced in situ to form complex shapes at elevated temperature without the application of an external stress. This process has been demonstrated for thin alumina substrates coated with a layer of magnesia. The internal strain causing the substrates to deform at elevated temperature arises as a consequence of strain mismatch accompanying the penetration of the coating into the substrate. The magnitude of the deformation depends on the amount of coating applied, on the thickness of the substrate, on the density of the substrate, and on the temperature. During exposure of the beams to elevated temperature, the magnesia coating reacts with the alumina substrate to form the spinel phase; the resulting volume change accompanying the phase transformation is likely the predominant driving force for deformation.
Role of a Small Addition of Acetic Acid on the Setting Behavior and on the Microstructure of a Calcium Aluminate Cement
Authors: Smith A. , El Hafiane Y. , Bonnet J. P. , Quintard P. , Tanouti B.
Published: July 2010

In order to be able to monitor dispersion and setting of cements, admixtures can be added, which usually can consist of large organic molecules. Here, the choice is different since small organic molecules have been used as in ceramic processing. This work concerns the preparation of calcium aluminate cement paste in the presence of acetic acid; the water to cement mass ratio is equal to 0.6 and the acid to cement mass ratio,, ranges between 0 and 0.05. This admixture can have either a retarding or an accelerating effect on cement setting. The retarding effect is because of adsorption of acetate complexes, CaCH3CO2+positively charged, at the surface of CA particles, negatively charged, which leads to the delay (slowing down) of dissolution; it can reach 52 h (case of). When, there is a remarkable accelerating effect. The setting starts 2 h after mixing the cement with the liquid and is fairly constant for higher acetic acid contents. This rapid setting in acid conditions is because of the formation of hydrated calcium acetate in very low quantities and possibly gibbsite; the setting mechanism is quite different since there is no formation of conventional calcium and aluminum hydrates. As an example, with the highest amount of HOAc (), no CxAyHztype of calcium aluminum hydrate is formed after aging for 4 days at 20°C and 95% relative humidity. There is also a densifying effect of acetic acid; the open porosity of set samples left to age for 4 days at 20°C and 95% relative humidity decreases from 35 to 25 vol% whengoes from 0 to 0.005 and remains relatively constant afterwards. Lastly, this decrease in the porosity continues with aging time; at 6 months, we obtain values as low as 9 vol% in samples where.
High‐Toughness Silicon Carbide as Armor
Authors: Flinders Marc , Ray Darin , Anderson Angela , Cutler Raymond A.
Published: July 2010

Silicon carbide, with single‐edge precracked beam (SEPB) toughness greater than 7 MPa·m1/2, was made by hot‐pressing using Al–B–C (ABC) or Al–Y2O3(YAG) as additives. The hardness of SiC processed with a liquid phase was always less than SiC densified without a liquid phase despite having a similar or finer grain size. With increasing Al content, the ABC system changed from trans‐ to intergranular fracture with a drop in hardness and a two‐ to threefold increase in SEPB toughness. Strength and Weibull modulus for materials processed with a liquid phase were higher than those of solid‐state densified SiC. Ballistic testing, however, did not show any improvement over SiC densified with B and C additives. Depth of penetration was controlled by hardness of the SiC‐based materials, whileV50values for 14.5 mm WC–Co cored projectiles were in the range of 720–750 m/s for all materials tested.
Alkoxide Route to La0.5Sr0.5CoO3 Films and Powders
Authors: Pohl Annika , Westin Gunnar
Published: July 2010

An all‐alkoxide route to films and nano‐phase powders of the La0.5Sr0.5CoO3 perovskite is described. To our knowledge, this is the first purely alkoxide‐based route to (La1−xSrx)CoO3, and it yields phase‐pure and elementally homogeneous perovskite at 700°C by heating at 2°C/min. At 700°C, a cubic unit cell was obtained with ac=3.853Å, and after further heating to 1000°C, a rhombohedral cell could be indexed: ar=5.417 Å, αr=59.94°. Ninety to 130 nm thick films of La0.5Sr0.5CoO3 were obtained by spin coating. The gel‐to‐oxide conversion was studied in some detail, using thermo‐gravimetric analysis, differential scanning calorimetry, powder X‐ray diffraction, IR spectroscopy, and transmission electron microscope equipped with an energy‐dispersive X‐ray spectrometer.
Temperature Dependence of Lattice Parameters and Anisotropic Thermal Expansion of Bismuth Oxide
Authors: Yashima Masatomo , Ishimura Daiju , Ohoyama Kenji
Published: July 2010

Temperature dependence of lattice parameters of bismuth sesquioxide (Bi2O3) has been obtained between 26° and 778°C by the Rietveld method using neutron powder diffraction data. Lattice parameters

and unit‐cell volume of α and δ phases increased, while the β angle of α phase decreased with an increase of temperature. Here the

denotes the lattice parameter a of the α phase on the basis of pseudo‐fluorite lattice. The thermal expansion coefficients of α phase were 26.7, 6.6, and 9.0 (× 10−6°C−1) for

and

axes, respectively, indicating a large anisotropy. The α‐ to ‐δ phase transition of Bi2O3 was confirmed between 721° and 760°C on heating. At the α–δ transition point, the lattice parameters and unit‐cell volume discontinuously changed, indicating that the transition is of the first order.
Hydroxyapatites Produced by Wet‐Chemical Methods
Authors: Donadel Karina , Laranjeira Mauro C. M. , Gonçalves Vanessa L. , Fávere Valfredo T. , De Lima João C. , Prates Luiz H. M.
Published: July 2010

Hydroxyapatite samples were produced by two different wet‐chemical methods, and characterized by X‐ray diffraction, infrared (IR), thermal gravimetric analysis (TGA), scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, inductively coupled plasma atomic emission spectrometry, and compression strength measurements. The IR spectra showed the presence of CO32− ions in all samples. After the sintering, the CO32− bands almost disappeared, indicating a large release of CO32− ions by the samples, which were also confirmed by TGA. By mixing samples produced by both methods, a bioceramic was prepared and, after sintering at 900°C for 1 h, compressive strengths of 26–30 MPa were obtained.
XANES and ELNES in Ceramic Science
Authors: Tanaka Isao , Mizoguchi Teruyasu , Yamamoto Tomoyuki
Published: July 2010

Both X‐ray absorption near edge structures (XANES) and electron energy loss near edge structure (ELNES) are important tools in ceramic science offering information on local environment of selected elements not only in crystals but also in amorphous materials. Recent technological progress enables measurements of XANES of ppm‐level dopants using modern synchrotron facilities. Combined with transmission electron microscopy, ELNES can be used to analyze the local structures with subnanometer spatial resolution. First principles methods to reproduce and interpret the spectra have been established just recently. When a core‐hole is adequately taken into account, most of K‐edge spectra can be well reproduced using a modern band‐structure method within one‐electron approximation. The same is true for L2, 3‐edge spectra of non‐transition metal compounds. However, multi‐electron calculations are mandatory to reproduce L2, 3‐edge spectra of 3d transition‐metal elements because of strong electronic correlations. In this paper, some recent results obtained in our group by the combination of XANES/ELNES experiments and theoretical calculations are reviewed.
High‐Temperature Creep Behavior of Mixed Conducting La0.5Sr0.5Fe1−xCoxO3‐δ (0.5≤x≤1) Materials
Authors: Lein Hilde Lea , Wiik Kjell , Einarsrud Mari‐ann , Grande Tor , Lara‐curzio Edgar
Published: July 2010

Steady‐state compressive creep rate of La0.5Sr0.5Fe0.5Co0.5O3−δ (LSFC) and La0.5Sr0.5CoO3−δ (LSC) is reported in the temperature region 900°–1050°C and stress range 5–28 MPa. The stress exponents for the two materials were 1.71±0.18 and 1.24±0.15, respectively. The activation energy for creep was considerably higher for LSC (619±56 kJ/mol) than for LSFC (392±28 kJ/mol). The grain size exponent for LSC was 1.28±0.14. Considerably higher creep rates were observed for both materials in N2 compared with air. Relaxation by creep of chemical‐induced stresses in oxygen‐permeable membranes is addressed, especially at low partial pressure of oxygen.
Binder Removal from Ceramic‐Filled Thermoplastic Blends
Authors: Knapp Angela M. , Halloran John W.
Published: July 2010

Thermogravimetric analysis is used to examine the degradation of a multicomponent polymer binder consisting of a blend of a polyethylene co‐ethyl acrylate with a polyisobutymethacrylate polymer. In the polymer blends without ceramic powder, the methacrylate component degrades at a temperature lower than the ethylene copolymer. Minor additives polyethylene glycol, stearic acid, and paraffinic mineral oil are also considered. The thermal degradation of a five‐component blend is only approximately as expected from the individual components, with retardation of the methacrylate degradation. Oxide ceramic powder significantly alters polymer degradation, retarding degradation in the early stages but accelerating degradation in the later exothermic stages. Polymer–polymer interactions and oxide–polymer interactions make the degradation behavior of blends difficult to predict from single component behavior.
Preparation of a Superhydrophilic Thin Film on Glass Substrate Surfaces with Titanium Alkoxide Solution
Authors: Funakoshi Kunio , Nonami Toru
Published: July 2010

Thin films of anatase titanium dioxide (TiO2) were prepared on slide glass substrate surfaces by a titanium alkoxide hydrolysis operation, and the hydrophilicity and the transparency of their films were examined. The contact angles of water and the transmittances of visible light for their substrates changed with the duration of tetraethyl orthotitanate (TEOT) hydrolysis operations. They were influenced by the thickness of the films and the size of the deposited particles on the silicon dioxide‐coated slide glass substrate surfaces. The contact angles also changed with the irradiating duration of ultraviolet light. When acetylacetone was added to a TEOT solution, the contact angles on the thin films became larger and the transparency was better during the same duration of TEOT hydrolysis operations. On addition of acetylacetone, nucleation of TiO2 particles at the initial stages of TEOT hydrolysis operations was restrained and, subsequently, the supersaturations of TiO2 in the solution became comparatively higher in the later stages of TEOT hydrolysis ones.
Ferroelectric Domain Structures and their Morphology Evolution in Pb(Ni1/3Nb2/3)O3–PbZrO3–PbTiO3 Piezoelectric Ceramics Modified by Bismuth and Zinc Substitutions
Authors: Zhu Xinhua , Zhu Jianmin , Zhou Shunhua , Liu Zhiguo , Ming Naiben , Meng Zhongyan
Published: July 2010

Ferroelectric domain structures and their morphology evolution in the Bi‐ and Zn‐modified (Pb0.985Bi0.01)(Ni1/4Zn1/12Nb2/3)x(ZrσTi1−σ)1−xO3 piezoelectric ceramics (0.20≤x≤0.60 and 0.10≤σ≤0.60) are investigated as a function of the relaxor Pb(Ni1/3Nb2/3)O3 content and the Zr/(Zr+Ti) ratio (σ) by transmission electron microscopy and selected area electron diffraction, and followed by a complete analysis of the nature of the domain walls based on the predicated twinning planes for the formation of domains in these piezoelectric ceramic systems. A systematic variation in the domain morphology was observed as the compositions move from the ferroelectric tetragonal (FT) to pseudocubic (Fpc) phases, and then to the rhombohedral (FR) phase. Wedged‐shaped domains with misoriented {110} domain walls and mixed with herringbone‐like configuration are the main features of the ferroelectric domains in the FT and Fpc phases, whereas in the compositions near the morphotropic phase boundary (MPB) between the Fpc and FR phases, the characteristic feature of the ferroelectric domains is an intricate domain structure exhibiting a fluctuating mottled contrast. However, the domain boundaries in the FR phase exhibit a wavy character. The domain feature for the compositions at/near the MPB between the FT and FR phases with high property coefficients is a 90° domain texture mixed with an intricate domain structure. The different domain configurations observed in the FT and FR phases are due to their different accommodations of local elastic strain fields. The piezoelectric soft behavior and a normal‐relaxor ferroelectric behavior transition observed in this piezoelectric ceramic system are closely related to the above domain morphology evolution as increasing the PNN content or the Zr/(Zr+Ti) ratio.
Stress‐Oxidation Behavior of a Carbon/Silicon Carbide Composite in a High‐Temperature Combustion Environment
Authors: Zhang Yani , Zhang Litong , Cheng Laifei , Xu Yongdong
Published: July 2010

A carbon/silicon carbide composite with a silicon carbide coating was prepared by chemical vapor infiltration. Stressed oxidation testing was performed on the composites in a self‐built high‐temperature combustion environment. The gas in this environment contained oxygen, steam, carbon dioxide, and some nitrogen. Test conditions were controlled at temperatures of 1300°, 1500°, and 1800°C, and the stress was sustained at 40, 80, 120, 160, and 200 MPa. The effect of combustion environment and applied load on stress‐oxidation behavior was discussed by analyzing the residual strength and weight loss. The morphology of the fracture surface of the tested specimens was observed by scanning electron microscopy. The high‐temperature combustion environment and the high sustained stress above 80 MPa enhanced the material failure and led to strength reduction by determining crack openings and thus oxidation of fibers. However, sustained stress below 80 MPa resulted in no strength degradation after exposure for 10 min at 1500°C.
Synthesis and Characterization of Mesoporous SrTiO3 Spheres via a Poly Vinyl Alcohol‐Assisted Hydrothermal Route
Authors: Wei Xiao , Xu Gang , Ren Zhaohui , Wang Yonggang , Shen Ge , Han Gaorong
Published: July 2010

Monodisperse porous SrTiO3 spheres with an average size of ca. 200 nm were synthesized via a hydrothermal route in the presence of poly vinyl alcohol (PVA). Characterization techniques such as X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, SAED, and high‐resolution transmission electron microscopy were used to investigate the products. The results showed that these porous spheres were compared of small primary nanocrystals and pores were formed among them. The nanocrystal and pore diameters increased as the reaction time proceeded. It was suggested that the PVA played an important role in the mesoporous sphere's formation by means of preventing nanocrystal growth through a capping effect.
Preparation of TiO2 Nanoparticles on Different SiO2 Supports by the Adsorption Phase Technique
Authors: Jiang Xin , Wang Ting
Published: July 2010

The influence of supports on the preparation of TiO2 nanoparticles by the adsorption phase technique is studied in detailed. Series temperature experiments of two types of supports (named as SiO2 A and B) were used. Energy‐dispersive analysis by X‐ray indicates that the concentration of TiO2 on both supports decreases with temperature increasing. TiO2 quantity on SiO2 A decreases sharply between 40° and 60°C, whereas the temperature range for SiO2 B is between 30° and 50°C. X‐ray diffraction (XRD) shows that grain size of TiO2 particles on two SiO2 surfaces is all below 7 nm. It is also shown by XRD that particles on SiO2 A decrease sharply as in the quantity curve of TiO2, but particles on SiO2 B all change gradually and TiO2 particles on SiO2 B are more uniform in transmission electron spectroscopy. The similarly of both supports is considered to be the reason for the similar changes in Ti concentration, and the different characteristics of the internal/external surface lead to variant quantity and grain size, as well as characteristics of TiO2.
Oxide Ion Disorder in Nd2Hf2O7
Authors: Ubic Rick , Abrahams Isaac , Hu Yi
Published: July 2010

The compound Nd2Hf2O7 was synthesized via a solid‐state route and the crystal structure determined by electron diffraction and Rietveld refinement of both X‐ray and neutron diffraction data. A small amount of disorder was found on the anion sublattice, while no evidence of disorder in the cation sublattice could be verified. The compound is cubic with space group Fd3m, structurally lying between the ideal pyrochlore and fluorite forms, with 0.26% of the oxide ions residing on the 8a sites usually vacant in pyrochlores. The lattice constant is 10.6469(2) Å, and the overall fit parameter was Rwp=0.0398.
Effects of V Substitution on Dielectric and Polarization Properties for Sr0.5Bi2.25Na1.25(Nb3−xVx)O12 Ceramics
Authors: Yokoi Atsushi , Sugishita Junji , Kan Akinori , Ogawa Hirotaka
Published: July 2010

The effects of V substitution for Nb on the dielectric and polarization properties of Sr0.5Bi2.25Na1.25(Nb3−xVx)O12 ceramics were investigated in this study. From the X‐ray powder diffraction results, no secondary phase was detected in the composition range of 0–0.075. The remanent polarizations (Pr) of the samples in the composition range of 0–0.03 were improved by the V substitution for Nb and the highest Pr value of approximately 15 μC/cm2 was obtained at x=0.03; it was noted that the V substitution for Nb was effective in improving the Pr values in this ceramics. On the other hand, the coercive fields (Ec) of the samples were on the order of approximately 40 kV/cm in such a composition range. Moreover, the anomalous variations in the dielectric constant were observed in the composition range of 0–0.075. Also, it was observed that the dielectric loss increased drastically at the temperature of approximately 500°C.
Structure–Property Relationship in Mn‐Doped (Pb0.94Sr0.06)(Zr0.53Ti0.47)O3
Authors: Rema Kallada Prabhakaran , Kumar Viswanathan
Published: July 2010

Hard piezoelectrics based on PZT with a composition near the morphotropic phase boundary (Pb0.94Sr0.06)(Zr0.53Ti0.47)O3 [PSZT] have been synthesized by the sol–gel method. The influence of B site aliovalent dopant Mn3+ on the crystal structure and electrical properties has been investigated. Mn3+ions (d4) are found to change the crystal structure from tetragonal to rhombohedral as a result of Jahn–Teller distortion of the MnO6 octahedra and are therefore found to impart donor characteristics to PSZT.
Effect of pH on the Carbonate Incorporation into the Hydroxyapatite Prepared by an Oxidative Decomposition of Calcium–EDTA Chelate
Authors: Yusufoglu Yusuf , Akinc Mufit
Published: July 2010

In this study, the carbonate incorporation into the hydroxyapatite (HAp) lattice under various pH conditions was investigated. Crystalline‐sodium and carbonate‐containing calcium HAp (NaCO3HAp) powders were prepared using an oxidative decomposition of calcium–EDTA chelates in a sodium phosphate solution with hydrogen peroxide. The powders obtained were characterized by X‐ray diffraction, infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, and elemental analysis. Depending on pH, spherical particles approximately 3.5 μm in diameter or hexagonal prismatic particles measuring 3–9 μm in length were obtained. Various characterization techniques showed that the precipitates were a single‐phase NaCO3HAp. The carbonate content and the lattice parameters of the HAp were a function of solution pH. Maximum carbonate incorporated into the HAp lattice was at pH=10, corresponding to lattice parameters of a=0.93880 nm and c=0.69070 nm. Furthermore, spectroscopic analyses indicate that the as‐prepared samples are B‐type carbonated HAp, in which carbonate ions occupy the phosphate sites. After heat treatment at 965°C, most of the carbonate is removed from the HAp lattice.
Carbothermal Synthesis of α‐SiC Micro‐Ribbons
Authors: Yushin Gleb N. , Cambaz Z. Goknur , Gogotsi Yury , Vyshnyakova Kateryna L. , Pereselentseva Lyudmila N.
Published: July 2010

We report the synthesis of microscopic α‐SiC ribbons (belts) on the surface of a graphite rod at 1800°–1900°C by a carbothermal process. The width of the ribbons produced ranged from 500 nm to 5 μm and the aspect ratio was up to 400. The ribbon thickness ranged from 50 to 800 nm. Their growth mechanism was explained by accelerated growth along the twin boundary. SiC whiskers grew on the rod along with the ribbons. Frequently, ribbons were growing from the tip of a whisker or whiskers were growing from the edge of a ribbon. SiC ribbons may find applications in high‐temperature sensors, photo‐electronic devices, or robust cantilevers in micro (or nano) electro mechanical systems. Alternatively, they can be used as reinforcements in composite materials, conferring anisotropic mechanical properties, such as unidirectional flexibility, to the composite.
Spark Plasma Sintering of Magnesia‐Doped Alumina with High Hardness and Fracture Toughness
Authors: Chakravarty Dibyendu , Bysakh Sandip , Muraleedharan Kuttanellore , Rao Tata Narasinga , Sundaresan Ranganathan
Published: July 2010

The effect of grain size of magnesia and its content as well as spark plasma sintering conditions on the density, grain size, strength, hardness, and toughness of alumina was investigated. Spark plasma sintering conditions were optimized at 1150°C/5 min/175°C/min. Addition of 100 nm magnesia gave higher density levels (99.5%), while better strength (600 MPa), hardness (25 GPa), and fracture toughness (4.5 MPa·m1/2) were obtained with 15 nm magnesia. The good strength and hardness is attributed to the submicrometer grain size of the matrix, and the improved toughness to the presence of Mg‐rich nanoparticles and nanopores at grain boundaries.
Silver‐Modified CrO2 of Core–Shell Nanoparticles and their Magnetic and Impedance Properties
Authors: Singh Gajendra Prasad , Ram Shanker , Fecht Hans‐Jörg
Published: July 2010

A chemical CrO3→CrO2 transformation reaction occurs in the presence of Ag+ species forming CrO2 core–shell magnetic nanoparticles. The process involves heating CrO3 with AgNO3 in an aqueous solution in ambient air at a low temperature of 330–350 K. Shell thickness (diamagnetic amorphous silver) is controlled to be ∼2 nm tunable to the magnetic and impedance properties. Improved coercivity Hc=75.7 mT and the Curie temperature TC=415 K are found with saturation magnetization Ms=80 Am2/kg after annealing the sample at 573 K in air for 2 h. On heating, the impedance (or electrical resistance) varies steadily through a maximum in the TC point in a typical half‐metallic ceramic behavior. In a dynamic response to frequency f, the TC increases from 418 K at 1 kHz to as high a value as 505 K at 1 MHz. A nearly f independent and low value of dissipation factor ϕ as 0.05 is promising for low power loss high‐frequency applications of such CrO2 particles.
Statistical Analysis of Experimental Parameters in Ultrasonic Machining of Tungsten Carbide Using the Taguchi Approach
Authors: Kumar Vinod , Khamba Jaimal Singh
Published: July 2010

The objective of this paper is to study the influence of operating parameters of ultrasonic machining of tungsten carbide on the machining characteristics. The effectiveness of the ultrasonic machining process with tungsten carbide is evaluated in terms of the material removal rate and the surface finish quality of the work piece produced. Tungsten carbide as a super hard and high wear‐resistant material has been used widely in industries. Powder metallurgy technology is the common method for producing tungsten carbide components. However, this method is obviously too costly and time consuming for small quantity production, such as product prototyping. It is expected to make the prototypes by a material removal process, such as ultrasonic machining. In this paper, an experimental study on the ultrasonic machining of tungsten carbide is presented using a systematic approach. Practical aspects are given on the characteristics of tungsten carbide as functions of the type of abrasive slurry, their size and concentration, nature of the tool material, and the power rating of the machine. The optimum combination of various input factors for the ductile chip formation in the machining of tungsten carbide has been determined by applying the Taguchi approach and the F‐test.
Microstructure and Properties of the Ni–CGO Composite Anodes Prepared by the Electrostatic‐Assisted Ultrasonic Spray Pyrolysis Method
Authors: Chen Jing‐Chiang , Hwang Bing‐Hwai
Published: July 2010

Composite NiO–CGO (Ce0.9Gd0.1O1.95) films were deposited on CGO substrates using the electrostatic‐assisted ultrasonic spray pyrolysis (EAUSP) method. Deposition parameters were varied systematically to investigate their effects on film microstructure and electrochemical performance. The X‐ray diffraction patterns indicate that the desired crystalline phases of NiO and CGO were obtained in the deposited and then the calcined films. The NiO phase was further converted into a crystalline Ni phase after a reduction treatment. Scanning electron microscope examination revealed that the deposition temperature and electric field strength were dominant factors determining the morphology and microstructure of the deposited films. A deposition temperature of 450°C and an electrostatic field introduced by an applied voltage of 12 kV were identified to yield a cauliflower‐like structure with high porosity. A film thus deposited with a NiO:CGO mole ratio of 6:4 performed best as a solid oxide fuel cell anode, as revealed by the ac impedance measurement of Ni–CGO//CGO//Ni–CGO cells in an atmosphere of humidified H2. The representative area‐specific resistance value was 0.09 Ω·cm2 at 550°C, which was considerably smaller than that obtained by conventional sample preparation routes. In view of the simplicity, efficiency, and economy of film deposition and the sound electrochemical characteristics of the films obtained found in the current work, it is concluded that the EAUSP method is a promising method for the preparation of Ni–CGO composite anode films.
Subcritical Water Treatment: A Simple Method to Prepare Porous Glass with a Core–Shell Structure
Authors: Sun Yiwen , Wang Yujun , Lu Yangcheng , Wang Tao , Luo Guangsheng
Published: July 2010

This paper presents a subcritical water treatment method for preparing porous glass with a core–shell structure from ordinary soda‐lime glass beads in one step. In this method, reactive subcritical water rather than any other chemical additive was utilized to selectively corrode the glass and mainly leach the alkali ions from the glass. The core–shell structure has been characterized by scanning electron microscope observation. The mesoporous structure of the porous glass beads has been confirmed by a nitrogen adsorption–desorption measurement. The treated alkali–lime–silicate glass beads have mesopores with a narrow distribution ranging around 4 nm, and a uniform nanoflake array on the surface. The shell structure can be easily tailored by changing the treatment temperature and water flow rate. A possible mechanism of a corrosion‐ion immigrating‐recondensation pattern was hypothesized to explain the formation of the core–shell porous structure.
Influence of the Gas Atmosphere on the Composition and Phase Development of Polymer‐Derived SiOC‐Ceramics
Authors: Liemersdorf Susanne , Riedel Ralf , Oberle Jürgen
Published: July 2010

Silicon oxycarbide (SiOC)‐based ceramics were synthesized by pyrolysis of a commercial polysiloxane containing MoSi2 and ceramic filler particles. The influence of different gas atmospheres on the chemical composition and on the phase formation of the filled Si–O–C ceramic during the pyrolysis process up to elevated temperatures of above 1200°C has been studied. The pyrolysis gas composition in the furnace during pyrolysis was measured with an in situ gas analyzer. Both the core and the surface of bulk samples were investigated with respect to composition in order to take the changes on the rim area of the specimens into account. The influence of hydrogen gas on the compositional gradient of the resulting ceramic material was derived from samples investigated by polarization microscopy, X‐ray diffraction (XRD), and micro‐XRD (μ‐XRD).
Creation of Ferroelectric, Single‐Crystal Architecture in Sm0.5La0.5BGeO5 Glass
Authors: Gupta Pradyumna , Jain Himanshu , Williams David B. , Honma Tsuyoshi , Benino Yasuhiko , Komatsu Takayuki
Published: July 2010

Using a novel, selective heating by Nd:YAG laser, a single‐crystal architecture is created in a model glass system, Sm0.5La0.5BGeO5, which devitrifies congruently into a ferroelectric phase of the same composition as the parent glass. The Sm3+ ions in glass absorb the light and heat the matrix locally resulting in devitrification. Initially, a polycrystalline spot is formed. However, with optimum laser power, scanning speed, and the depth of focus, one of the grains acts as the seed for further growth as a single crystal. By programming the relative displacement of the glass with respect to laser spot, desired single ferroelectric crystal architecture is created. The optical functionalities (guiding of light and second harmonic generation) of the architectures are shown, which demonstrate the viability of this method for constructing active elements in optical integrated circuits. The single‐crystal nature of the architecture is confirmed from the electron backscattered diffraction results.
Large‐Scale Synthesis of Magnenium Silicon Nitride Powders at Low Temperature
Authors: Peng Li , Liqiang Xu , Zhicheng Ju , Zhang Jie , Yang Jia , Qian Yitai
Published: July 2010

Magnesium silicon nitride (MgSiN2) powders have been synthesized by the reaction of SiCl4, N2H4·HCl, and Mg in an autoclave at 450°C for 5 h. The yield of the products is calculated to be about 90% according to the amount of SiCl4. X‐ray powder diffraction patterns indicated that the products are orthorhombic MgSiN2 (cell parameters: a=5.252 Å, b=6.426 Å, and c=4.979 Å) together with little amount of Si. The results of scanning electron microscopy and transmission electron microscopy (TEM) observations indicate that the particles have rough surfaces and have diameters in the range of 0.5–3 μm. The high‐resolution TEM image shows clearly resolved fringes separated by 0.248 nm, which corresponds to the (002) d‐spacing of the orthorhombic MgSiN2. The effects of different synthesis conditions on the final formation of MgSiN2 powder, such as the different ratios of the precursors, reaction temperature, and nitrogen sources were also investigated.
Zirconia Transport by Liquid Convection during Oxidation of Zirconium Diboride–Silicon Carbide
Authors: Karlsdottir Sigrun N. , Halloran John W. , Grundy Anthony Nicholas
Published: July 2010

During high‐temperature oxidation of ZrB2–SiC composites, a multi‐layer oxide scale forms with a silica‐rich borosilicate liquid as the surface oxide layer. Here, a recently proposed novel mechanism for the high‐temperature oxidation of ZrB2–SiC composites is further investigated and verified. This mechanism involves the formation of convection cells in the oxide surface layer during high‐temperature oxidation of the composite. The formation of zirconia deposits found in the center of the convection cells is proposed here to be the consequence of liquid transport. The nature and deposition mechanism of the zirconia is reported in detail, using calculated phase equilibrium diagrams and microstructure observations of a ZrB2‐15 vol% SiC composite tested at 1550° and 1700°C in ambient air for various times. The calculated phase equilibrium diagrams for the binary ZrO2–B2O3 system as well as the ternary B2O3–SiO2–ZrO2 system at 1500°C are reported here to interpret these results.
Solid‐State Compatibility in the System Bi2O3–TiO2–Bi2WO6
Authors: Jardiel Teresa , Villegas Marina , Caballero Angel , Suvorov Danilo , Caballero Amador C.
Published: July 2010

We have studied solid‐state compatibility in the Bi2O3–TiO2–Bi2WO6 ternary system. Based on previously reported data, we prepared different compositions and calcined them in air at 850°C. The crystalline phases and the microstructures were analyzed using X‐ray diffraction and scanning electron microscopy. The results allowed us to determine seven new compatibility triangles: Bi2O3–Bi12TiO20–Bi14W2O27, Bi12TiO20–Bi4Ti3O12–Bi14W2O27, Bi4Ti3O12–Bi6Ti3WO18–Bi14W2O27, Bi6Ti3WO18–Bi10Ti3W3O30–Bi14W2O27, Bi10Ti3W3O30–Bi2WO6–Bi14W2O27, Bi6Ti3WO18–Bi10Ti3W3O30–Bi6Ti5WO22, and Bi2WO6–Bi10Ti3W3O30–Bi6Ti5WO22. The existence of the Bi4WO9 phase, as reported in the Bi2O3–WO3 binary system, could not be confirmed. The Bi4Ti3WxO12+3x (x≤0.05) solid solution was detected and, therefore, the Bi4Ti3O12–Bi2Ti4O11–Bi6Ti3WO18 compatibility triangle was corrected to include two‐phase fields.
OMMOCHROME FROM ANTHOMEDUSAN OCELLI AND ITS PHOTOREDUCTION
Authors: Yoshida M. , Ohtsuki H. , Suguri S.
Published: July 2010

Abstract— The ocellar pigment of Spirocodon saltatrix extractable with phosphate buffer and acidified methanol was considered to be a substance closely related to or identical with xanthommatin, from its behaviour on paper and thin‐layer chromatography and from the position of the absorption maxima in the ultra‐violet and visible ranges of the spectrum in various solvents. The infra‐red spectrum also supported this view. The pigment extracted with cetyltrimethylammonium bromide was gel‐filtered through a column of Sephadex G 100. The pigment was eluted fairly quickly and the elution pattern was narrow, indicating that the eluted pigment is large as well as homogeneous in its molecular size. The gel‐filtered pigments from medusan ocelli and fly ommatidia underwent an almost indentical photoreduction under anaerobic conditions.
CHARGE TRANSFER FROM PHOTOSYSTEM I TO THE CYTOCHROMEb/fCOMPLEX: DIFFUSION AND MEMBRANE LATERAL HETEROGENEITY
Authors: Selak M. A. , Whitmarsh J.
Published: July 2010

Abstract—We discuss here the minimum requirements for diffusion of a charge carrier between appressed and stroma‐exposed membrane regions of chloroplasts based on recent models of the thylakoid membrane and flash‐induced kinetic data. We have investigated the kinetics of the transfer of a positive charge from photosystem I to the cytochromeb/fcomplex in spinach chloroplasts by measuring the light‐induced oxidation of cytochromef.The rate and extent of cytochromefoxidation were measured spectrophotometrically using either long actinic flashes that induced several turnovers of photosystem I or short actinic flashes that induced a single turnover of photosystem I. In the long actinic flashes, in the electron transfer reaction from water to methyl viologen, we observed the rapid oxidation of all of the cytochromefpresent in the membrane. The half‐time of the oxidation was 1.0 ± 0.1 ms. The total amount of the cytochrome was determined by chemical difference spectra to be one molecule of cytochromefper 650 – 30 chlorophyll molecules. Using short actinic flashes we studied the photosystem I‐driven electron transfer reaction from duroquinol to methyl viologen in the presence of the inhibitor 5‐n‐undecyl‐6‐hydroxy‐4,7‐dioxobenzothiazole. Under these conditions a single turnover flash induced the oxidation of 62 ± 5% of cytochromefwith a half‐time of 240 ± 30 μs. An Arrhenius plot of the temperature dependence of the cytochromefoxidation rate revealed an activation energy between 16 and 21 kJ/mol, a value consistent with a diffusion‐controlled reaction. These kinetic data are considered in the context of two models of the thylakoid membrane.
EFFECT OF TISSUE ABSORPTION AND MICROSCOPE OPTICAL PARAMETERS ON THE DEPTH OF PENETRATION FOR FLUORESCENCE AND REFLECTANCE MEASUREMENTS OF TISSUE SAMPLES
Authors: Benson Douglas M. , Knopp James A.
Published: July 2010

Abstract— An equation has been derived that is concerned with the measurements of fluorescence or reflectance intensities in reflectance or incident light microscopy. A theoretical basis for the linear relationship between relative fluorescence and reflectance changes is given. This equation predicts both the contributions of different volume elements below the surface of a tissue sample to the total intensity and the depth of penetration of the measured intensities. The relationship requires knowledge of the effective focal points of the excitation beam and the apparent absorption coefficient of the sample. Two procedures are given to provide the empirical values of the effective focal point. The absorption coefficient of mouse liver tissue at 420 nm was determined to be 3.3/mm. The fluorescence intensities of liver slices of differing thickness containing pyrene butyric acid were measured and were found to compare favorably with the calculated values for tissue absorption of 3/mm.
FLUORESCENCE QUENCHING OF INDOLE BY DIMETHYLFORMAMIDE
Authors: Fucaloro Anthony F. , Forster Leslie S. , Campbell Mary K.
Published: July 2010

Abstract— The effect of dimethylformamide on the lifetime (T) and quantum yield (F) of indole has been determined. Negative Stern‐Volmer deviations prevail for T and F, but F0/F T0/T at all DMF concentrations. The deviation between F0/F and T0/T is ascribed to changes in F0 and T0 induced by the change in solvent composition at the higher quencher concentrations.
PHOTOLYSIS MECHANISM OF AQUEOUS TYROSINE UPON EXCITATION OF THE SECOND ABSORPTION BAND
Authors: Shimizu Okiyasu
Published: July 2010

Abstract—The formation mechanism of tyrosinyl radical was studied for aqueous solutions of tyrosine under irradiation at 235 nm which falls into the second absorption band. The work is based upon the analysis of the rate of bityrosine production for steady‐state excitation at low intensity. The results indicate that monophotonic O‐H bond cleavage of tyrosine, presumably involving the upper excited triplet state, is the initial photoprocess leading to the tyrosinyl radical when tyrosine is excited into the second absorption band.
PHOTOREARRANGEMENT OF AZOXYBENZENE TO 2‐HYDROXYAZOBENZENE: A CONVENIENT CHEMICAL ACTINOMETER*
Authors: Bunce Nigel J. , Lamarre Jon , Vaish Shiv P.
Published: July 2010

Abstract— In ethanolic solution, the intramolecular photorearrangement of azoxybenzene occurs with quantum yield close to 0.02 over the range 250–350 nm. The reaction, which is independent of temperature and of concentration of reactant, is conveniently monitored by measuring the absorbance of the product, 2‐hydroxyazobenzene, as its anion in alkaline solution.
THE PRODUCTION OF SINGLET MOLECULAR OXYGEN BY ZINC(II) PHTHALOCYANINE IN ETHANOL AND IN UNILAMELLAR VESICLES. CHEMICAL QUENCHING AND PHOSPHORESCENCE STUDIES
Authors: Valduga Giuliana , Nonell Santiago , Reddi Elena , Jori Giulio , Braslavsky Silvia E.
Published: July 2010

Abstract— Zn(II)phthalocyanine (ZnPc) generates O2(1Δg) with a quantum yield of ca. 0.4 upon photocxcitation at 354 or 600 nm in ethanolic solution as determined by time‐resolved phosphorescence studies at 1270 nm and photooxidation experiments using 1,3‐diphenylisobenzofuran (DPBF) as substrate. The quantum yield of photooxidation slightly increases upon incorporation of ZnPc into unilamellar liposomes of dipalmitoylphosphatidylcholine. Under our irradiation conditions (600 nm, 18°C, and short light exposure times), DPBF(5–50 μM) undergoes photooxidation by a pure Type II mechanism; the rate constant for the O2(1Δg) + DPBF reaction is (1.1 ±0.1) x 109 M‐1 s_1 in ethanol solution and determined to be about two orders of magnitude smaller when both ZnPc and DPBF are embedded into liposomes.
BIOLOGICAL DEACTIVATION AND SINGLE‐STRAND BREAKAGE OF PLASMID DNA BY PHOTOSENSITIZATION USING TRIS(2,2′‐ BIPYRIDYL)RUTHENIUM(II) AND PEROXYDISULFATE
Authors: Aboul‐Enein, * Ahmed , ScHulte‐Frohlinde Dietrich
Published: July 2010

Abstract—Single‐strand break formation and biological deactivation of plasmid pBR322 DNA in the presence of tris(2,2′‐bipyridyl)‐ruthenium(II), Ru(bpy)2/3;+, and K2S2O8, upon irradiation with visible light(400–500 nm), were studied in aqueous solution at room temperature. Conditions of complete binding of Ru(bpy)2/3;+to the strand were employed. The damage is initiated mainly by the SO2/3;; radical anion. Under anoxic conditions at a ratio of nucleotide to sensitizer concentrations (N/S) of 18 and S2O2/8‐concentrations of 0.5mMthe quantum yield of single‐strand break (ssb) formation is φssb= 8.4 times 10‐3while that of biological deactivation (bd) is Øbd= 7.6 times 10‐3(φssb= 5.2 times 10‐36.4 times 10‐3, 6.0 times 10‐3and φbd= 4.2 times 10‐3, 5.2 times 10‐3, 4.8 times 10‐3at N/S=3, 6, and 9, respectively). The quantum yields are approximately 2.5 times smaller in air‐saturated solutions. At N/S = 18 about 33 SO4‐radical anions are required per one lethal event. φbdincreases linearly with the S2Oφ‐concentration (up to 0.5mM).The damage to DNA is drastically reduced on addition of mono‐ or divalent salts (e.g. NaC104, MgCl2). These additives cause the release of Ru(bpy)2+from the strand. The observed damage to DNA is thus the result of a site specific reaction. When the phenanthroline analogue, Ru(phen)φ+, is used as sensitizer, φssband φbdare three times smaller.
THE EFFECT OF TEMPERATURE AND WAVELENGTH ON PRODUCTION AND PHOTOLYSIS OF A UV‐INDUCED PHOTOSENSITIVE DNA LESION WHICH IS NOT REPAIRED IN XERODERMA PIGMENTOSUM VARIANT CELLS
Authors: Francis Andrew A. , Carrier William L. , Regan James D.
Published: July 2010

Abstract— Ultraviolet light causes a type of damage to the DNA of human cells that results in a DNA strand break upon subsequent irradiation with wavelengths around 300 nm. This DNA damage disappears from normal human fibroblasts within 5 h, but not from pyrimidine dimer excision repair deficient xeroderma pigmentosum group A cells or from excision proficient xeroderma pigmentosum variant cells. The apparent lack of repair of the ultraviolet light DNA damage described here may contribute to the cancer prone nature of xeroderma pigmentosum variant individuals. These experiments show that the same amount of damage was produced at 0°C and 37°C indicating a photodynamic effect and not an enzymatic reaction. The disappearance of the photosensitive lesions from the DNA is probably enzymatic since none of the damage was removed at 0°C. Both the formation of the lesion and its photolysis by near ultraviolet light were wavelength dependent. An action spectrum for the formation of photosensitive lesions was similar to that for the formation of pyrimidine dimers and(6–4) photoproducts and included wavelengths found in sunlight. The DNA containing the lesions was sensitive to wavelengths from 304 to 340 nm with a maximum at 313 to 317 nm. This wavelength dependence of photolysis is similar to the absorption and photolysis spectra of the pyrimidine(6–4) photoproducts
THE ISOLATION AND PARTIAL CHARACTERIZATION OF UV SENSITIVE MUTANTS OF Synechococcus PCC7943 (Anacystis nidulans 602)
Authors: Lanham Patrick G. , Houghton James A.
Published: July 2010

Abstract–Four mitomycin‐C sensitive, UV sensitive mutants of Synechococcus PCC7943 were isolated. They were capable of host‐cell reactivation and showed enhanced UV survival if held under non‐growth conditions for a recovery period immediately after irradiation. One of the mutants was shown to be deficient in Weigle‐reactivation.
MONOCLONAL ANTIBODY WITH SPECIFIC AFFINITY FOR PYRIMIDINE DIMERS IN RNA
Authors: Phillips Roger G. , Kalthoff Klaus
Published: July 2010

Abstract— A monoclonal antibody was prepared which meets three criteria for specific binding to pyrimidine dimers in RNA. (i) UV irradiation at wavelengths greater than 300 nm in the presence of a triplet state sensitizer, or at 270 nm without sensitizer, promotes antibody binding to RNA and polyribonucleotides, (ii) Antibody binding is reduced by exposure to UV radiation of short wavelength (240 nm) following sensitized irradiation (<300 nm). (iii) Antibody binding is dependent upon the presence of adjacent pyrimidine ribonucleotides. The antibody recognizes a single uridine dimer with one or more additional nucleotides at both ends. Affinity for a single uridine dimer with additional nucleotides at only the 3′ end is substantially weaker.
SOLAR UVB‐ALBEDO OF VARIOUS SURFACES
Authors: Blumthaler M. , Ambach W.
Published: July 2010

Abstract— Measurements of the albedo of various surfaces in open grounds show significant differences for solar UVB radiation and total solar radiation (0.3–3μm). Above grassland, that albedo for solar UVB radiation is significantly smaller than that for total solar radiation (UVB: 1.3%, total: 20.7%); contrary to that, the albedo for UVB radiation is significantly higher above new dry snow (UVB: 94.4%, total: 87.0%). Consequences resulting therefrom are being quantitatively discussed with respect to the solar radiant exposure of individuals standing outdoors. Keratitis Solaris, for example, hardly occurs in snow‐free terrain, even at high solar irradiance in summer; it occurs, however, in snow‐covered terrain, in spite of low solar irradiance in winter and spring.
DEPENDENCY OF APPARENT RELATIVE QUANTUM YIELD OF ISORHODOPSIN TO RHODOPSIN ON THE PHOTON DENSITY OF PICOSECOND LASER PULSE
Authors: Kandori Hideki , Matuoka Sinzi , Nagai Hiroshi , Shichida Yoshinori , Yoshizawa Tôru
Published: July 2010

Abstract—The quantum yield of bleaching of isorhodopsin relative to that of rhodopsin was measured by irradiation of both pigments with a steady light source or a picosecond laser pulse. The each pigment was prepared by incubation of 11‐cisor 9‐cisretinal with opsin, respectively. The ratio of isorhodopsin to rhodopsin in the quantum yield was estimated to be 0.37 using irradiation with a steady light, while with a weak picosecond laser pulse (excitation photon density: below 20 μ.J/1.8 mmφ), it was estimated to be 0.39. Both values are in good agreement with each other. On the other hand, excitation with a strong picosecond laser pulse (above 20 μ.J/1.8 mmφ) produced a larger ratio than 0.39, indicating that saturation effects can be easily observed by irradiation with strong picosecond laser pulses.
SINGLE PHOTONS ARE SUFFICIENT TO TRIGGER MOVEMENT RESPONSES IN Chlamydomonas reinhardtii
Authors: Hegemann Peter , Marwan Wolfgang
Published: July 2010

Abstract— The unicellular green alga Chlamy domonas reinhardtii shows two distinct movement responses upon changes in green light irradiance: These are direction changes and stop responses. The dependence of both responses on the intensity of applied flashes was measured and analysed with the help of Poisson statistics. In dark‐adapted cells both responses were ‘single‐photon’ events. Preillumination of cells or background irradiation decreased the sensitivity for the stop response, now requiring two or more photons to trigger it. In the blind, carotenoid‐negative mutant FN 68 the light‐sensitivity for a stop‐response was reconstituted by addition of all trans retinal. This result indicated that not only the receptor for phototaxis but also that for the stop response is a retinal protein. In addition, stimulus‐response curves from the literature were analysed by Poisson statistics.
THE THYMIDINE‐PSORALEN PHOTOADDITION. A MODEL APPROACH
Authors: Décout Jean‐Luc , Lekchiri Yahya , Lhomme Jean
Published: July 2010

Abstract—In order to investigate the photoreactions between the thymidine and the psoralen chromophores and to devise a synthetic route to prepare thymidine‐5‐methoxypsoralen adducts, we have prepared and studied a compound in which thymidine is linked to a 5‐methoxypsoralen derivative by a diester chain. Irradiation at 365 nm carried out at usual concentrations (10–3M) leads exclusively to one diastereoisomer of an intramolecular 3,4cis‐anti[2+2] adduct. No photodimerization is observed in these conditions. These results are compared to those obtained for models studied previously in which the thymine and the psoralen rings are linked by polymethylenic chains of varying length.