bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Evolution in Sol–Gel‐Derived Yttrium Aluminum Garnet–Alumina Precursor Fibers
Authors: Krüger Reinhard , Glaubitt Walther , Löbmann Peer
Published: July 2010

A sol leading to a eutectic Al2O3–Y3Al5O12 composition was spun into fibers. These fibers were dried and pyrolyzed between 200° and 850°C in a nitrogen or water‐vapor atmosphere. Pyrolysis in nitrogen resulted in dense, amorphous fibers with considerable residual carbon content. In water vapor, fibers also remained amorphous, but organics were almost completely removed. The loss of organics created micropores that grew as the pyrolysis temperature increased. The amorphous fiber structures were examined by nitrogen adsorption, helium pycnometry, and transmission electron microscopy. Young's moduli of the pyrolyzed fibers were measured, and porosities of the fibers were calculated from both nitrogen‐adsorption data and elastic behavior. Sintering tests showed the best sinterability for fibers pyrolyzed in water vapor to 385°–500°C.
Effect of Fe and Cr Addition on the Sintering Behavior of ZrB2 Produced by Self‐Propagating High‐Temperature Synthesis
Authors: Mishra Suman Kumari , Das Swapan Kumar , Ray Ajoy Kumar , Ramachandrarao P.
Published: July 2010

An investigation of the sintering behavior of ZrB2 powder with Fe and Cr (0 to 20 wt%) addition was conducted. It was observed that Fe addition helps to enhance the density of ZrB2 only up to 10 wt%. Further addition of Fe degrades the sintering by segregation of Fe‐rich phases. Formation of a eutectic phase containing a Fe:Zr ratio of 92.57:7.43 was also found in Fe‐added samples. The addition of Cr to a ZrB2 matrix was found to result in swelling of the samples, leading to several cracks.
High‐Strength Porous Silicon Carbide Ceramics by an Oxidation‐Bonding Technique
Authors: She Jihong , Yang Jian‐Feng , Kondo Naoki , Ohji Tatsuki , Kanzaki Shuzo , Deng Zhen‐Yan
Published: July 2010

Porous silicon carbide (SiC) ceramics were fabricated by an oxidation‐bonding process in which the powder compacts are heated in air so that SiC particles are bonded to each other by oxidation‐derived SiO2 glass. Because of the crystallization of amorphous SiO2 glass into cristobalite during sintering, the fracture strength of oxidation‐bonded SiC ceramics can be retained to a relatively high level at elevated temperatures. It has been shown that the mechanical strength is strongly affected by particle size. When 0.6 μm SiC powders were used, a high strength of 185 MPa was achieved at a porosity of ∼31%. Moreover, oxidation‐bonded SiC ceramics were observed to exhibit an excellent oxidation resistance.
In Situ Reaction Synthesis of Silicon Carbide–Boron Nitride Composite from Silicon Nitride–Boron Oxide–Carbon
Authors: Zhang Guo‐Jun , Beppu Yoshihisa , Ando Motohide , Yang Jian‐Feng , Ohji Tatsuki
Published: July 2010

This work proposes a new approach, based on the reaction Si3N4+ 2B2O3+ 9C → 3SiC + 4BN + 6CO, to synthesize an SiC–BN composite. The composite was prepared by reactive hot pressing (RHP), at 2000°C for 60 min at 30 MPa under an argon atmosphere, following a 60 min hold at 1700°C without applied pressure before reaching the RHP temperature. TG‐DTA results showed that a nitrogen atmosphere inhibited denitrification somewhat and retarded the reaction rate. The chemical composition of the obtained material was consistent with theoretical values. FE‐SEM observation showed that in situ‐formed SiC and BN phases were of spherical morphology with very fine particle size of ∼100 nm.
Pulse Electric Current Sintering of Al2O3/3 vol% ZrO2 with Constrained Grains and High Strength
Authors: Jayaseelan D. Doni , Kondo N. , Rani D. Amutha , Ueno S. , Ohji T. , Kanzaki S.
Published: July 2010

The pulse electric current sintering technique (PECS) was demonstrated to be effective in rapid densification of fine‐grained Al2O3/3Y‐ZrO2 using available commercial powders. The composites attained full densification (>99% of TD) at 1450°C in less than 5 min. The composites sintered at a high heating rate had a fine microstructure. The incorporation of 3 vol% 3Y‐ZrO2 substantially increased the average fracture strength and the toughness of alumina to as high as 827 MPa and 6.1 MPa·m1/2, respectively. A variation in the heating rate during the PECS process influenced grain size, microstructure, and strength, though there was little or no variation in the fracture toughness.
Thermodynamic Modeling of the FeO–Fe2O3–MgO–SiO2 System
Authors: Decterov Sergei A. , Jung In‐Ho , Pelton Arthur D.
Published: July 2010

The liquid and solid phases in the FeO–Fe2O3–MgO–SiO2 system are of importance in ceramics, metallurgy, and petrology. A complete critical evaluation and thermodynamic modeling of the phase diagrams and thermodynamic properties of this system are presented. Optimized equations for the thermodynamic properties of all phases are obtained that reproduce all available thermodynamic and phase equilibrium data within experimental error limits from 25°C to above the liquidus temperatures at all compositions and oxygen partial pressures. The optimized thermodynamic properties and phase diagrams are believed to be the best estimates presently available. The database of the model parameters can be used with software for Gibbs energy minimization to calculate any type of phase diagram section.
Crystallographic Facetting in Sintered Barium Titanate
Authors: Liou Jing‐Kai , Lin Ming‐Hong , Lu Hong‐Yang
Published: July 2010

A commercial TiO2‐excess BaTiO3 powder has been sintered and its microstructure analyzed for crystallographic facetting via both scanning and transmission electron microscopy (SEM and TEM). Facetted grain surfaces are developed initially from {111} at a low temperature of 1215°C, which are then altered to {111} and {100} at 1290°C in the presence of a grain‐boundary liquid phase. The grain shape is also modified correspondingly from platelike to polygonal. Facetting of the intragranularly located residual pores in BaTiO3 along the {141} planes further develops on the (quasi‐)equilibrium shape after annealing at 1400°C for 100 h from the initially well‐characterized {111}, {110}, and {100} in as‐sintered samples sintered at the same temperature for 10 h. The Wulff plots derived from the residual pores in as‐sintered and annealed samples are constructed for the 〈011〉 zone. Microstructural analysis also suggests that the shape of grains and intragranular residual pores is modified progressively upon annealing. The initial solid–vapor surface energy has become less anisotropic crystallographically. Abnormal grain growth in relation to the surface energy anisotropy is discussed.
Particle Size Comparison of Hydrothermally Synthesized Cobalt and Zinc Aluminate Spinels
Authors: Chen Zhizhan , Shi Erwei , Li Wenjun , Zheng Yanqing , Wu Nanchun , Zhong Weizhuo
Published: July 2010

Nanosized CoAl2O4 and ZnAl2O4 powders with particle sizes of 67 and 6.5 nm are synthesized under hydrothermal conditions at 245°C for 20 h. The precursors are reacted at different temperatures to provide intermediate phase transformations using X‐ray diffraction (XRD), infrared (IR) spectra, and thermal gravity and differential thermal analysis (TG‐DTA). XRD patterns and IR spectra demonstrate that the CoAl layered double hydroxide structure (CoAl‐LDHs) is more stable than ZnAl layered double hydroxide structure (ZnAl‐LDHs) when they are hydrothermally treated. The different thermal stability of the CoAl‐ and ZnAl‐LDHs results in the different aluminum source, e.g., β‐Al(OH)3 for ZnAl2O4 vs γ‐AlO(OH) for CoAl2O4, when the aluminate spinels are formed. The different aluminum sources lead to the particle size difference. The phenomenon is reasonably expounded based on the nucleation theory from the microscopic scale.
Physical Properties of Barrier Ribs of Plasma Display Panels: II, Effects of Fillers
Authors: Hwang Geon‐Ho , Kim Won‐Yong , Jeon Hyung‐Jo , Kim Yong‐Seog
Published: July 2010

The effects of inert fillers, such as quartz and Al2O3, on the sintering behavior and physical properties of lead borosilicate glasses used for barrier ribs of plasma display panels (PDP) were investigated. The effects of volume fraction and type of filler on the sintering temperature, thermal expansion coefficient, dielectric constant, and fracture resistance of the barrier ribs of PDP were investigated. The influence of the filler on sintering behavior was discussed based on the wetting angle of the glass on the fillers. The physical properties and fracture resistance of the glass with fillers were measured and compared with theoretical models.
Sintering of AlN Using CaO‐Al2O3 as a Sintering Additive: Chemistry and Microstructural Development
Authors: Hagen Eirik , Yu Yingda , Grande Tor , Høier Ragnvald , Einarsrud Mari‐Ann
Published: July 2010

The densification of aluminum nitride using Ca12Al14O33 as a sintering aid has been studied with emphasis on the effect of using coarse or fine powder, the amount of sintering aid, the sintering temperature, and embedding. Both crystalline and amorphous grain boundary phases were observed. Significant weight losses were observed for coarse‐grained samples, and if suitable embedding was not used. Porous and coarse‐grained ceramics with high contiguity and minor amounts of secondary phases were obtained by enhanced evaporation while dense ceramics were obtained limiting the evaporation. High weight losses in the graphite environment resulted in formation of a dense AlN surface layer.
Dependence of the Microstructure and the Electrical Properties of Lanthanum‐Substituted (Na1/2Bi1/2)TiO3 on Cation Vacancies
Authors: Yi Jae Yun , Lee Jung‐Kun , Hong Kug‐Sun
Published: July 2010

The sintering and electrical characteristics of La‐modified Na1/2Bi1/2TiO3 (NBT) was investigated from a defect structure viewpoint. To reveal the role of cation vacancies, two series of ceramics, with different cation vacancies, were processed to compensate the excess positive charge of lanthanum ions. In a region of complete solid solution, the grain size of NBLT‐B {[(Na0.5Bi0.5)1−xLax]Ti1−0.25xO3} was smaller than that of NBLT‐A {[(Na0.5Bi0.5)1−1.5xLax]TiO3} and densification was enhanced more effectively in NBLT‐B. With the aid of thermoelectric power, electric conductivity, and electrotransport measurements, it was found that different sintering behaviors between NBLT‐A and NBLT‐B specimens were related to the change in the type of cation vacancies present and that lanthanum ion–cation vacancy pairs played an important role in reducing the grain growth and enhancing the densification process.
Preparation, Structure, and Properties of Thermally and Mechanically Improved Aluminum Titanate Ceramics Doped with Alkali Feldspar
Authors: Takahashi Masahide , Fukuda Masahiro , Fukuda Masaaki , Fukuda Hisato , Yoko Toshinobu
Published: July 2010

Aluminum titanate (AT) ceramic materials doped with alkali feldspar ((Na0.6K0.4)AlSi3O8) have been prepared. These ceramics exhibited high sinterability, large resistance to thermal decomposition, and large flexure strength. The existence of liquid‐phase feldspar at sintering temperatures promoted the formation of AT ceramics as the sintering agent. It was considered that silicon ions substituting for aluminum ions at the surface of AT crystal grains lowered the surface energy and hindered the diffusion of Ti4+ and Al3+, giving rise to the large resistance to thermal decomposition. As a result, doping with alkali feldspar was found to effectively improve the mechanical and thermal properties of AT ceramics.
Grain‐Boundary Wetting‐Dewetting in z= 1 SiAlON Ceramic
Authors: Kleebe Hans‐Joachim , Pezzotti Giuseppe
Published: July 2010

The grain‐boundary structure of a model SiAlON polycrystal with nominal composition Si5AlON7 was characterized by transmission electron microscopy (TEM) both in an equilibrium (as‐processed) state at room temperature and after quenching from elevated temperature. In addition, low‐frequency (1–13 Hz) internal friction data were recorded as a function of temperature, showing a pronounced grain‐boundary sliding peak positioned at 1030°C. High‐resolution transmission electron microscopy (HRTEM) of the equilibrated low‐temperature microstructure revealed residual glass only at multigrain junctions, but no amorphous intergranular films were observed. The detection of clean interfaces in the as‐processed sample contradicts the internal friction data, which instead suggests the presence of a low‐viscosity grain boundary phase, sliding at elevated temperatures. Therefore, a thin section of the as‐sintered material was heated to 1380°C and rapidly quenched. HRTEM analysis of this sample showed, apart from residual glass pockets, wetted grain boundaries, which is in line with the internal friction experiment. This wetting‐dewetting phenomenon observed in z= 1 SiAlON is expected to have a strong impact not only on high‐temperature engineering ceramics but also on geological, temperature‐activated processes such as volcanic eruptions.
Chemical Diffusion Coefficient of H2O in AB(1−x)B′xO(3−x/2)‐Type Perovskites
Authors: Virkar Anil V. , Baek Hyun‐Deok
Published: July 2010

Many oxygen‐deficient oxide perovskites are oxygen ion conductors in a dry environment. However, in a humid atmosphere, they absorb water to fill up oxygen vacancies, release quasi‐free protons into the structure, and thereby become proton conductors. Absorption of water requires the transport of both protons and oxygen ions. This effectively leads to the transport of H2O under its chemical potential gradient. The present manuscript develops relationships between the chemical diffusion coefficient of H2O and the diffusion coefficients of protons and oxygen vacancies with an emphasis on the role of solution thermodynamics.
Origin of the Superlattice Reflections in Pb(Fe2/3W1/3)O3
Authors: Lin Ming‐Hong , Lu Hong‐Yang
Published: July 2010

Two types of superlattice reflections have been observed in pressureless‐sintered Pb(Fe2/3W1/3)O3 perovskite ceramics from selected‐area electron diffraction patterns (SADPs). The presence of commensurate superlattice reflections of the {1/2 1/2 1/2} type found in as‐sintered samples persisted after prolonged postsintering annealing at 800°C for 300 h. These reflections, conventionally termed the F‐spots, represent the existence of the nanoscale cation‐ordered domains of cubic perovskite Pb1−x(Fe1/2W1/2)O3. However, the satellite‐type incommensurate superlattice reflections, appearing as sideband spots to the fundamental reflections and occurring only along 〈111〉, 〈110〉, and 〈100〉, have gradually reduced their intensities and finally disappeared on postsintering annealing at 800°C. Observations via transmission electron microscopy (TEM) suggested that the “black dots” revealed in bright‐field (BF) images have given rise to the incommensurate superlattice sideband spots. These dots of ∼5–10 nm are in fact a different type of nanocrystalline domain whose structure (and chemical composition) differs from those of the disordered Pb(Fe2/3W1/3)O3 matrix and the ordered nanoscale Pb1−x(Fe1/2W1/2)O3 domains. The nanocrystalline precipitates containing the paracrystalline phase are pyrochlore (Pb2(Fe,W)O6.5) formed during powder preparation via the solid‐state mixed‐oxide route. They become dispersed in the Pb(Fe2/3W1/3)O3 perovskite matrix grain and have also undergone phase transformation to perovskite progressively during sintering and postsintering annealing. It is suggested that the nanocrystalline pyrochlore precipitates are metastable and disappear when chemical composition within the perovskite grains becomes homogenized from solid‐state diffusion on postsintering annealing.
Dielectric and Ferroelectric Properties of Nanocrystalline Bi2Ti2O7 Prepared by a Metallorganic Decomposition Method
Authors: Hou Yun , Wang Min , Xu Xiao‐Hong , Wang Dong , Wang Hong , Shang Shu‐Xia
Published: July 2010

Nanopowders of Bi2Ti2O7 were synthesized by a metallorganic decomposition (MOD) technique. Pure Bi2Ti2O7 nanocrystals formed after annealing at 550°C for 5 min. X‐ray patterns show that Bi20TiO32 is a metastable phase during Bi2Ti2O7 formation. It was found that there were two peaks in the curves of the dielectric response as a function of temperature for pressed nanocrystalline Bi2Ti2O7 samples. The Curie temperature decreases with decrease of grain size whereas the ferroelectric‐ferroelectric phase transition temperature increases. The hysteresis loops observed also suggest that Bi2Ti2O7 might belong to a ferroelectric material.
Effect of Composition on Properties of Alumina/Titanium Silicon Carbide Composites
Authors: Luo Yong Ming , Li Shu Qin , Chen Jian , Wang Rui Gang , Li Jian Qiang , Pan Wei
Published: July 2010

In the present study, the room‐temperature properties of Al2O3‐Ti3SiC2 composites with different Ti3SiC2 contents are determined. The composites are prepared by attrition milling Al2O3 and Ti3SiC2 mixture powders followed by spark plasma sintering (SPS) under vacuum. From a closer examination of the dependencies of the electrical conductivity on compositions in this system, we determined the percolation threshold at which an interconnected network of electrically conductive phase arises. Since the hardness of Ti3SiC2 is lower than that of Al2O3, the Vickers hardness decreased with the increasing of Ti3SiC2 content while the fracture toughness and the strength increased. The maximum strength (673 MPa) and the maximum toughness (9.3 MPa·m1/2) were reached in the pure Ti3SiC2 material.
Aluminum Nitride Prepared by Nitridation of Aluminum Oxide Precursors
Authors: Kroke Edwin , Loeffler Lars , Lange Fred F. , Riedel Ralf
Published: July 2010

Aluminum nitride (AlN) powders were prepared from the oxide precursors aluminum nitrate, aluminum hydroxide, aluminum 2‐ethyl‐hexanoate, and aluminum isopropoxide (i.e., Al(NO3)3, Al(OH)3, Al(OH)(O2CCH(C2H5)(C4H9))2, and Al(OCH(CH3)2)3). Pyrolyses were performed in flowing dry NH3 and N2 at 1000°–1500°C. For comparison, the nitride precursors aluminum dimethylamide (Al(N(CH3)2)3) and aluminum trimethylamino alane (AlH3·N(CH3)3) were exposed to the same nitridation conditions. Products were investigated using XRD, TEM, EDX, SEM, and elemental analysis. The results showed that nitridation was primarily controlled by the water:ammonia ratio in the atmosphere. Single‐phase AlN powders were obtained from all oxide precursors. Complete nitridation was not obtained using pure N2, even for the non‐oxide precursors.
Freeform Gelcasting of Porous Tubular Alumina Substrate
Authors: Prabhakaran Kuttan , Babu Natarajan Ramesh , Kumar Sivasankaran Rajesh , Warrier Krishna Gopakumar
Published: July 2010

The present work demonstrates a new method for fabrication of thin‐walled tubular alumina substrate by combining the principles of gelcasting and freeform fabrication. A tube made up of filter paper or organic preform was filled with 4N nitric acid and dipped in a 55 vol% alumina (average particle size 0.34 μm) slurry containing methylolurea and urea. A thin layer of alumina slurry was gelled on the filter paper tube by in situ polymerization of methylolurea and urea monomers present in the slurry by delivering the acid through the walls of the filter paper tube. The thickness of the alumina tube obtained depended on the dipping time. Alumina tubes with thicknesses in the range 0.7–2 mm were obtained for dipping times in the range 1–8 min. The tubes obtained had good surface finishes and profiles. These tubes were sintered at 1150°C and microstructural observation indicated uniform grain size and pore morphology. A porosity of 40% and an average pore size of 300 nm were obtained.
Oxygen Diffusion in Yttria‐Stabilized Zirconia: A New Simulation Model
Authors: Krishnamurthy R. , Yoon Y.‐G. , Srolovitz D. J. , Car R.
Published: July 2010

We present a multiscale modeling approach to study oxygen diffusion in cubic yttria‐stabilized zirconia. In this approach, we employ density functional theory methods to calculate activation energies for oxygen migration in different cation environments. These are used in a kinetic Monte Carlo framework to calculate long‐time oxygen diffusivities. Simulation results show that the oxygen diffusivity attains a maximum value at around 0.1 mole fraction yttria. This variation in the oxygen diffusivity with yttria mole fraction and the calculated values for the diffusivity agree well with experiment. The competing effects of increased oxygen vacancy concentration and increasing activation energy and correlation effects for oxygen diffusion with increasing yttria mole fraction are responsible for the observed dopant content dependence of the oxygen diffusivity. We provide a detailed analysis of cation‐dopant‐induced correlation effects in support of the above explanation.
Preparation and Spontaneous Polarization–Magnetization of a New Ceramic Ferroelectric–Ferromagnetic Composite
Authors: Qi Xiwei , Zhou Ji , Li Baorang , Zhang Yingchun , Yue Zhenxing , Gui Zhilun , Li Longtu
Published: July 2010

Ceramic composites with the composition of xPMZNT·(1 –x)NiCuZn have been prepared using a standard ceramic technique, in which x varies as 0, 0.1, 0.2, 0.4, 0.6, 0.9, and 1.0. PMZNT is the abbreviated form of 0.92Pb(Mg1/3Nb2/3)O3·0.04Pb(Zn1/3Nb2/3)O3·0.04PbTiO3 (PMN‐PZN‐PT). NiCuZn is the abbreviated form of Ni0.2Cu0.2Zn0.6Fe2O4. The presence of ferroelectric PMZNT phase and ferromagnetic NiCuZn ferrite phase has been confirmed using X‐ray diffractometry. Ferroelectric hysteresis loops and magnetic hysteresis loops have been observed and studied. In polarization–electric‐field curves, the remnant polarization and coercive fields display little asymmetric characterization because of the existence of the internal electric field. When the amount of NiCuZn ferrite phase increases, the coercive field increases. Meanwhile, the saturation magnetization decreases and the coercivity of the composites increases with the increase of phase fraction of PMZNT, because the interaction between magnetic grains (or magnetic connectivity) is weakened by the existence of nonmagnetic PMZNT phase distributed in the magnetic phases. Under an applied magnetic and electric field, the magnetization and polarization of the composites can be easily tuned. The sintered composites possess high density and fine‐grained microstructure. The average grain size of NiCuZn ferrite grains is slightly larger than that of the PMZNT grains.
Conversion of Polycrystalline Alumina to Single‐Crystal Sapphire by Localized Codoping with Silica
Authors: Thompson Gary S. , Henderson Peter A. , Harmer Martin P. , Wei George C. , Rhodes William H.
Published: July 2010

The effect of a localized SiO2 codoping on the conversion of polycrystalline, MgO‐doped Al2O3 tubes to single‐crystal sapphire was investigated. Codoping with SiO2 before sintering intentionally triggered abnormal grain growth, which resulted in the full conversion of tube surfaces to single crystal without adversely affecting densification to a almost pore‐free, translucent state. The degree of surface conversion was strongly dependent on experimental variables, which included furnace temperature and codoping amount. Surface‐converted tubes had excellent physical properties, which included good thermal cycling resistance and optical properties superior to unconverted, polycrystalline Al2O3.
Geometry and Electrical Properties of Grain Boundaries in Manganese Zinc Ferrite Ceramics
Authors: Lee Jong‐Sook , Kim Doh‐Yeon , Fleig Jürgen , Maier Joachim
Published: July 2010

For large‐grained manganese zinc (MnZn) ferrite ceramics, grain misorientation determined by electron backscatter diffractions and grain‐boundary resistance measured using microcontact impedance spectroscopy have been correlated. The degree of oxidation of grain boundaries and, hence, the barrier height depends on the overall grain‐boundary network as well as on the individual boundary structure; therefore, a statistical analysis has been performed based on several hundreds of local measurements. When the boundaries are divided into low‐ and high‐resistance groups, statistically significant differences in rotation axis and angle distributions are found. The misorientation distribution of the low‐resistance boundary group is suggested to reflect the low‐energy configurations of boundary planes in MnZn ferrites.
Sol–Gel Preparation and Properties of Fluoride‐Substituted Hydroxyapatite Powders
Authors: Kim Hae‐Won , Li Long‐Hao , Koh Young‐Hag , Knowles Jonathan C. , Kim Hyoun‐Ee
Published: July 2010

Hydroxyapatite (HA) and fluor‐hydroxyapatite (FHA) powders were synthesized by a sol–gel method for usage as bone filler and drug carrier. Calcium nitrate and triethyl phosphite were used as precursors under an ethanol–water‐based solution. Different amounts of ammonium fluoride (NH4F) were incorporated for the preparation of FHA powders. With heat treatment above 400°C, a characteristic apatite phase was observed for all the sol–gel powders. However, the crystallization temperature decreased with increasing fluoride addition. The tricalcium phosphate (TCP) phase formed in the pure HA powder above 800°C was attenuated in the FHA powders, confirming an enhanced phase stability of the FHA powders. Increasing the F− addition improved crystallinity and increased the crystallite size, as was determined from X‐ray diffraction (XRD) analyses. The lattice parameters of the heat‐treated powders varied corresponding to the fluoride addition, i.e., a gradual decrease in the a‐axis, while little change in the c‐axis was observed with increasing fluoride addition, indicating a nearly complete substitution of fluoride within the apatite lattice. However, little difference was observed with heat‐treatment temperatures (400°–1000°C). The powders substituted with fluoride exhibited reduced dissolution rates in an in vitro solution as compared with the pure HA powder, suggesting the possibility of tailoring bioactivity with fluoride substitution.
Mechanochemical Synthesis of Magnesium Aluminate Spinel Powder at Room Temperature
Authors: Domanski Daniela , Urretavizcaya Guillermina , Castro Facundo J. , Gennari Fabiana C.
Published: July 2010

MgAl2O4 spinel was successfully synthesized using a mechanochemical route that avoided the formation and calcination of its precursors at high temperatures. The method involved a single step in which γ‐Al2O3–MgO, AlO(OH)–MgO, and α‐Al2O3–MgO mixtures were milled at room temperature under air atmosphere. The formation of MgAl2O4 occurred faster with γ‐Al2O3 than with AlO(OH) or α‐Al2O3. After 140 h, the mechanochemical treatment of the γ‐Al2O3–MgO mixture yielded 99% of MgAl2O4.
Synthesis of Ordered Zirconium Titanate (Zr,Ti)2O4 from the Oxides Using Fluxes
Authors: Troitzsch Ulrike , Christy Andrew G. , Ellis David J.
Published: July 2010

The crystallization of ordered (Zr,Ti)2O4 from the oxides succeeded for the first time, at 800°–1200°C and 13–20 kbar, using either ammonium carbonate or copper oxide as flux. The composition of the ordered phase, coexisting with either zirconia or rutile, is pressure–temperature dependent, ranging from XTi= 0.60 to 0.68. Its reproducibility and reversibility suggest the ordered compound crystallized at/near thermodynamic equilibrium. The presence of flux permits the equilibration of phase assemblages well below 1200°C, a region previously inaccessible for equilibrium experiments in the ZrO2–TiO2 system due to sluggish kinetics. Thus we were able to determine the ZrO2–TiO2 phase diagram at 20 kbar at temperatures as low as 800°C. In contrast, room‐pressure experiments did not result in the spontaneous nucleation of ordered (Zr,Ti)2O4 from the oxides, and seeds were required to initiate growth. The flux‐aided synthesis of ordered (Zr,Ti)2O4 from the oxides, at constant temperature and in its stability field, has the following advantages over previous crystallization attempts, which consisted of slow cooling of the disordered polymorph through the ordering transition. The ordered compound forms at equilibrium, therefore permitting phase equilibrium studies and thermodynamic interpretation. Large grain sizes facilitate quantitative analysis of the composition with electron microscopy. Microcracks and ZrO2 exsolution, reported from samples cooled through the transition, can be avoided. The composition and the ordering state of the ordered compound can be controlled with pressure and temperature. Using the flux‐based synthesis method, well‐crystallized samples can now be obtained for future crystal structure refinements, calorimetric and dielectric measurements, or investigations into the phase transition.
Synthesis of Ba(Mg1/3Ta2/3)O3 Microwave Ceramics through a Sol–Gel Route Using Acetate Salts
Authors: Tsai Chien‐Cheng , Teng Hsisheng
Published: July 2010

A sol–gel process to unsophisticatedly synthesize Ba(Mg1/3Ta2/3)O3 (BMT) ceramics at low cost has been developed in the present work. This process involves the reaction of TaCl5 with acetates of Ba and Mg in the presence of citric acid. Pure BMT polycrystalline powders can be obtained by calcining the synthesized products at 1000°C. The BMT powders were found to have a primary particle size as small as 100 nm. BMT ceramics with favorable structural characteristics can be obtained from sintering of the sol–gel BMT at temperatures much lower than that for the conventional solid‐state BMT. Sintering the sol–gel BMT in pellet form at 1300°C resulted in an ordering parameter of 0.72 for the pellet, and a relative density of >95% was achieved with sintering at 1500°C. The grain size of the sintered sol–gel BMT was large and uniform in comparison with the products from the solid‐state method. Using the sol–gel route, sintering at temperatures as low as 1400°C gave ceramics with acceptable microwave dielectric properties (a dielectric constant of 16 and Qf factor of 14 400 GHz), while higher temperatures (>1600°C) are needed for the solid‐state route to give similar properties.
Insulating Properties of Lanthanum‐Doped BaTiO3 Ceramics Prepared by Low‐Temperature Synthesis
Authors: Beltrán Héctor , Cordoncillo Eloisa , Escribano Purificación , Sinclair Derek C. , West Anthony R.
Published: July 2010

Samples of composition Ba1−xLaxTi1−x/4O3, x= 0, 0.003, 0.03, and 0.10, were prepared by an alkoxide sol–gel route with final firing of ceramics at 1100°C, 2 h in air. All samples showed bulk insulating behavior with no evidence of semiconductivity caused by either direct donor doping or oxygen loss.
Mechanical Properties of Textured Alumina Made by High‐Temperature Deformation
Authors: Yoshizawa Yu‐ichi , Hirao Kiyoshi , Kanzaki Shuzo
Published: July 2010

The mechanical properties of a textured alumina made by high‐temperature deformation of normal‐purity sintered alumina have been investigated. The textured alumina shows very high bending strength and extremely high fracture toughness. Fracture toughness of more than 10 MPa·m1/2 was measured by the single‐edge precracked beam method, and even using the single‐edge V‐notched beam method, toughness of over 8 MPa·m1/2 was obtained. This high fracture toughness was attributed to a large number of aligned small platelike grains of the textured structure enhancing the grain bridging effect.
Oral rehydration therapy without bicarbonate for prevention and treatment of dehydration: a double‐blind controlled trial
Authors: ELLIOTT E. J. , ARMITSTEAD J. C. M. , FARTHING M. J. G. , WALKER‐SMITH J. A.
Published: July 2010

Forty children (≤ 2 years of age) were admitted to hospital with acute gastroenteritis and were randomly assigned to receive either an oral rehydration solution (ORS) containing bicarbonate (Na 35, K 20, CI 37, HCO3 18, glucose 202 mmol litre−3) or an identical solution in which bicarbonate was replaced by chloride ions. Groups were matched for age, sex, ethnic origin, duration of diarrhoea and nutritional status. On admission, degree of dehydration, biochemical and haematological parameters were similar. The majority had minimal or no dehydration and only 30% had moderate to severe dehydration. All children were treated successfully with no complications. Oral rehydration solution intake by each group was similar. Clinical outcome, as judged by speed of rehydration or maintenance of hydration, duration of diarrhoea, stool frequency and length of hospital stay, was the same in both groups. After 24 h of ORS there was no difference between groups in venous pH, serum bicarbonate, urea and electrolytes. In hospitalized children with acute gastroenteritis in the United Kingdom an ORS without bicarbonate is a safe, effective means to prevent dehydration and maintain hydration and acid—base status where dehydration is not severe. Exclusion of bicarbonate would simplify production, increase stability and reduce the cost of ORS without apparent impairment of efficacy.
Two different dose regimens of cisapride in the treatment of reflux oesophagitis: a double‐blind comparison with ranitidine
Authors: GELDOF H. , HAZELHOFF B. , OTTEN M. H.
Published: July 2010

We conducted a double‐blind study comparing two dosage regimens of a prokinetic drug, cisapride (10 mg q.d.s. and 20 mg b.d.), with a low dose of a H2 receptor antagonist (150 mg ranitidine b.d.) in the treatment of 155 patients with reflux oesophagitis as determined by endoscopy. The active treatment took 8 to 12 weeks depending on whether complete healing was found at endoscopy. Improvement in oesophagitis grades from baseline to endpoint was observed in 68% of patients in the 10 mg cisapride q.d.s. group, 83 % in the cisapride 20 mg b.d. group and 81% in the ranitidine group (N.S.). At endpoint, the percentages of endoscopically cured patients with initial grades I or II were 52% for 10 mg cisapride q.d.s., 71% for 20 mg cisapride b.d. and 80% for ranitidine (N.S.). The proportional improvement of the overall reflux symptom score (60%) also showed no significant difference between the three groups. In the treatment of mild reflux oesophagitis (grades I and II) similar results can be expected from 20 mg cisapride b.d. and 150 mg ranitidine b.d. As the results of the two dosage regimens of cisapride were not different, the 20 mg twice daily regimen is preferred because it will improve patient compliance. It is concluded that in reflux oesophagitis grades I and II, the efficacy of 20 mg cisapride b.d. and 150 mg ranitidine b.d. are broadly similar.
Infliximab regulates lamina propria T lymphocytes in patients with Crohn's disease
Authors: WATANABE O. , ANDO T. , FURUTA R. , MAEDA O. , ISHIGURO K. , TAKAHASHI H. , INA K. , KUSUGAMI K. , GOTO H.
Published: July 2010

Background and Aims

The immune system is a major determinant of the pathophysiological inflammation, which may lead to gastrointestinal mucosal injury in patients with Crohn's disease. Cytokines such as tumour necrosis factor‐alpha are well‐known mediators of the immune system, and treatment with a chimeric anti‐tumour necrosis factor‐alpha antibody (infliximab) has been shown to be highly effective in patients with Crohn's disease. Recent evidence indicates that infliximab induces apoptosis in lamina propria T lymphocytes in these patients. To better understand the mechanisms of infliximab's effect on gastrointestinal inflammation, we investigated changes in the serum level of cytokines after treatment in these patients, and the effect of infliximab in inducing the apoptosis of T lymphocytes.

Methods

Thirteen patients with Crohn's disease were treated with infliximab at a dosage of 5‐mg/kg body weight. Clinical response was evaluated using the Crohn's Disease Activity Index, and serum soluble interleukin‐2 receptor, interleukin‐6, tumour necrosis factor‐alpha levels were analysed by enzyme‐linked immunosorbent assay at 0 and 2 weeks after treatment. Apoptosis of peripheral and lamina propria T lymphocytes after culture with infliximab was detected by flow cytometry.

Results

Crohn's Disease Activity Index decreased in 12 of 13 patients, and serum soluble interleukin‐2 receptor, interleukin‐6 and tumour necrosis factor‐alpha levels decreased in most patients after treatment with infliximab. Tumour necrosis factor‐alpha level before treatment in the six patients in whom Crohn's Disease Activity Index decreased by more than 70 was <5 ng/mL. Infliximab induced the apoptosis of lamina propria but not of peripheral T lymphocytes.

Conclusion

These findings suggest that a low level of serum tumour necrosis factor‐alpha is an indicator for infliximab treatment. The induction of apoptosis of lamina propria T lymphocytes by infliximab may be an important mechanism of its anti‐inflammatory effect in patients with Crohn's disease.
Helicobacter pylori‐induced atrophic gastritis progressing to gastric cancer exhibits sonic hedgehog loss and aberrant CDX2 expression
Authors: SHIOTANI A. , IISHI H. , UEDO N. , ISHIHARA R. , ISHIGURO S. , TATSUTA M. , NAKAE Y. , KUMAMOTO M. , HINOI T. , MERCHANT J. L.
Published: July 2010

Background

The loss of sonic hedgehog is an early change that occurs in the mucosa prior to neoplastic transformation and correlates with the type of intestinal metaplasia. Aberrant expression of CDX has also been shown to correlate with the development of intestinal metaplasia.

Aim

To examine CDX2 expression in the non‐cancerous mucosa of patients with gastric cancer and compared it to CDX2 expression in controls with intestinal metaplasia.

Methods

Sixty patients who had undergone endoscopic mucosal resection for early gastric cancer and 60 gender‐ and age‐matched controls were studied. Two specimens each were obtained from the greater and lesser curves of the corpus and from the greater curve of the antrum. Expression of CDX2 and sonic hedgehog were evaluated by immunostaining.

Results

Gastric cancer was associated with a higher frequency of incomplete intestinal metaplasia (OR = 8.3; 95%CI, 3.7–18.9, P < 0.001). CDX2 negatively correlated with sonic hedgehog expression, however, multivariate analysis revealed that CDX2 correlated with the intestinal metaplasia scores. Sonic hedgehog indices were lower and CDX2 staining in the corpus lesser curve was higher in the cancer group than in the controls. Sonic hedgehog indices in the corpus decreased and CDX2 indices in both areas increased in patients in the ascending order of those without intestinal metaplasia, those with complete intestinal metaplasia and those with incomplete intestinal metaplasia (P < 0.001).

Conclusions

Loss of sonic hedgehog expression and aberrant expression of CDX2 correlates with the type of intestinal metaplasia and may play a role in carcinogenesis.
Efficacy and endoscopic prediction of cytapheresis therapy in patients with refractory and steroid‐dependent ulcerative colitis
Authors: WATANABE K. , OSHITANI N. , KAMATA N. , INAGAWA M. , YAMAGAMI H. , HIGUCHI K. , ARAKAWA T.
Published: July 2010

Background

Recently, it has been proved in Japan that granulocyte and monocyte adsorption apheresis (GCAP) and leukocytapheresis (LCAP) are effective and safe for patients with moderate to severe ulcerative colitis (UC).

Aim

To investigate the efficacy of GCAP and LCAP in patients with active UC, and the use of endoscopic findings in predicting efficacy, especially in refractory and steroid‐dependent cases.

Subjects and methods

Thirty‐four patients with active UC (24 refractory to conventional therapy and 10 steroid‐dependent) were treated with GCAP (n = 21) or LCAP (n = 13). The patients received one or two GCAP or LCAP sessions per week for 5 consecutive weeks, with colonoscopy before and after each session.

Results

About 70% of the patients achieved a clinical response, and no severe adverse effects were observed. Most steroid‐dependent patients or patients who had side effects due to steroids were controlled successfully. Endoscopically, 14 of 16 cases with shallow ulcers and erosion throughout the colon and 10 of 15 with deep ulcerations responded to treatment. However, three with massive ulceration of the whole mucosa did not respond.

Conclusions

GCAP or LCAP are valuable therapies for refractory or steroid‐dependent UC, and endoscopic findings are helpful in predicting clinical effectiveness.
Evaluation of alcohol metabolism in humans using the non‐invasive [13C]‐ethanol breath test – influence of gender, Helicobacter pylori infection and polymorphism of alcohol‐oxidizing enzymes
Authors: SUZUKI M. , TANAKA S. , KOMATSU H. , NAKANE T. , SASAKI N. , MARUYAMA K. , SUZUKI H. , ISHII H. , SUEMATSU M. , HIBI T.
Published: July 2010

Background

The [13C]‐ethanol breath test (EBT) has been proposed as a novel non‐invasive laboratory test to detect the degradation of ethanol into CO2. However, this method has not yet been evaluated clinically.

Aim

To investigate the factors that influence [13C]‐EBT.

Methods

Twenty‐six healthy volunteers were instructed to drink 100 mL of beer (4 g ethanol) containing 100 μL of [13C]‐ethanol. Breath samples were collected every 15 min before and after the intake of ethanol solution and 13CO2‐enrichment was measured using mass spectrometry. CO2 excretion was then calculated, and the results were evaluated using kinetic parameters (Tmax, Cmax, AUC).

Results

T
max (min) was significantly shorter in men than in women but not Cmax and AUC. Infection with H. pylori had no impact on all kinetic parameters. Genetic alcohol dehydrogenase (ADH) polymorphisms did not affect 13CO2 excretion, but Cmax (11.1 ± 3.4% dose/h, n = 16) and AUC (10.5 ± 3.4% dose) were slightly increased in aldehyde dehydrogenase (ALDH)‐deficient individuals (heterozygote of ALDH2*2) (13.2 ± 3.2 and 12.9 ± 4.5, respectively; n = 10).

Conclusions

[13C]‐EBT is capable of assessing the metabolic processing of 100 mL beer in a non‐invasive way. Kinetic parameters are partially influenced by ALDH polymorphism but not by gender, H. pylori infection or ADH polymorphism.
Review article: bacterial translocation in the critically ill – evidence and methods of prevention
Authors: GATT M. , REDDY B. S. , MACFIE J.
Published: July 2010

Background

Delayed sepsis, systemic inflammatory response syndrome (SIRS) and multiorgan failure remain major causes of morbidity and mortality on intensive care units. One factor thought to be important in the aetiology of SIRS is failure of the intestinal barrier resulting in bacterial translocation and subsequent sepsis.

Aim

This review summarizes the current knowledge about bacterial translocation and methods to prevent it.

Methods

Relevant studies during 1966–2006 were identified from a literature search. Factors, which detrimentally affect intestinal barrier function, are discussed, as are methods that may attenuate bacterial translocation in the critically ill patient.

Results

Methodological problems in confirming bacterial translocation have restricted investigations to patients undergoing laparotomy. There are only limited data available relating to specific interventions that might preserve intestinal barrier function or limit bacterial translocation in the intensive care setting. These can be categorized broadly into pre‐epithelial, epithelial and post‐epithelial interventions.

Conclusions

A better understanding of factors that influence translocation could result in the implementation of interventions which contribute to improved patient outcomes. Glutamine supplementation, targeted nutritional intervention, maintaining splanchnic flow, the judicious use of antibiotics and directed selective gut decontamination regimens hold some promise of limiting bacterial translocation. Further research is required.
Oral oligofructose‐enriched inulin supplementation in acute ulcerative colitis is well tolerated and associated with lowered faecal calprotectin
Authors: CASELLAS F. , BORRUEL N. , TORREJÓN A. , VARELA E. , ANTOLIN M. , GUARNER F. , MALAGELADA J.‐R.
Published: July 2010

Background Inulin and oligofructose promote selective growth of saccharolytic bacteria with low inflammatory potential.

Objective To test the effect of oligofructose‐enriched inulin in patients with active ulcerative colitis.

Design Prospective, randomized, placebo controlled pilot trial. Eligible patients had been previously in remission with mesalazine as maintenance therapy or no drug, and presented with a relapse of mild to moderate activity. They were treated with mesalazine (3 g/day) and randomly allocated to receive either oligofructose‐enriched inulin (12 g/day, p.o., n = 10) or placebo (12 g/day of maltodextrin, p.o., n = 9) for 2 week. Primary endpoint was the anti‐inflammatory effect as determined by reduction of calprotectin and human DNA in faeces.

Results Rachmilewitz score decreased in both groups, reaching statistical significance at day 14 (P < 0.05). Oligofructose‐enriched inulin was well‐tolerated and dyspeptic symptoms scale decreased significantly with active treatment but not with placebo. At day 7, an early significant reduction of calprotectin was observed in the group receiving oligofructose‐enriched inulin (day 0: 4377 ± 659 µg/g; day 7: 1033 ± 393 µg/g, P < 0.05) but not in the placebo group (day 0: 5834 ± 1563 µg/g; day 7: 4084 ± 1395 µg/g, n.s.). Changes in faecal concentration of human DNA were not significant.

Conclusion In active ulcerative colitis, dietary supplementation with oligofructose‐enriched inulin is well tolerated and is associated with early reduction in faecal calprotectin.
Review article: management of ascites and associated complications in patients with cirrhosis
Authors: KUIPER J. J. , DE MAN R. A. , VAN BUUREN H. R.
Published: July 2010

Background  Ascites is the most common complication of cirrhosis, associated with an expected survival below 50% after 5 years. Prognosis is particularly poor for patients with refractory ascites and for those developing complications, including spontaneous bacterial peritonitis (SBP) and hepatorenal syndrome (HRS).

Aim  To provide an evidence‐based overview of the pathophysiology, diagnosis and clinical management of ascites secondary to liver cirrhosis.

Methods  Review based on relevant medical literature.

Results  Portal hypertension, splanchnic vasodilatation and renal sodium retention are fundamental in the pathophysiology of ascites formation. The SAAG (serum‐ascites albumin gradient) allows reliable assessment of the cause of ascites. The majority of cirrhotic patients with ascites can be managed with dietary sodium restriction in combination with diuretic agents. Large volume paracentesis with albumin suppletion and TIPS are therapeutic options in patients with refractory ascites. Prophylactic antibiotics for SBP should be given in certain patient populations.

Conclusions  Recent advances in the diagnosis and treatment of ascites and associated complications have improved the medical management and poor prognosis of patients with these manifestations of advanced liver disease. Early diagnosis, adequate treatment and focus on prevention of complications remain essential as well as timely referral for liver transplantation.
Introduction: thrombocytopenia in chronic liver disease – treatment implications and novel approaches
Authors: AFDHAL N.H. , ESTEBAN R.
Published: July 2010

Background  Thrombocytopenia is a common hematologic toxicity among patients with chronic liver disease.

Aim  To give a brief overview of thrombocytopenia and its effects on patients with chronic liver disease.

Results  Thrombocytopenia is generally mild to moderate in severity and can thus be managed relatively easily. Severe thrombocytopenia (platelet count <50,000 /μL), however, may present significant challenges to patient management. Thrombocytopenia can increase the risk of bleeding associated with invasive or surgical procedures. Therefore, while perhaps less widely appreciated than the impact of anemia or neutropenia, effective prevention and management of thrombocytopenia is also critical for patients with liver disease.

Conclusions  This supplement to Alimentary Pharmacology & Therapeutics provides a comprehensive review of the significance of thrombocytopenia in patients with chronic liver disease, its pathophysiology and relationship to coagulation disorders, impact on clinical care and resource utilization, and novel therapies that may be able to supplant platelet transfusions.