bluuebunny/crossref_metadata_2025 huggingface dataset:
Phase Equilibria of the La2O3‐SrO‐CuO System at 950°C and 10 kbar
Authors: Geny Joel , Meen James K. , Elthon Don
Published: October 2005

Phase equilibria of the La2O3‐SrO‐CuO system have been determined at 950°C and 10 kbar (1 GPa). Stable phases at the apices of the ternary phase diagram are CuO, La2O3, and SrO. Stable intermediate phases are La2CuO4 in the LaO1.5‐CuO binary and Sr2CuO3, SrCuO2, and Sr14Cu24O41 in the CuO‐SrO binary. The La2‐xSrxCuO4‐δ solid solution is stable where 0.0 ≤x ≤ 1.3, the La2‐xSr1+xCu2O6+δ solid solution is stable where 0.0 ≤x≤ 0.2, the La8‐xSrxCu8O20‐δ solid solution is stable where 1.3 ≤x≤ 2.7, the LaxSr14‐x‐Cu24O41 solid solution is stable where 0 ≤x≤ 6, and the La1+xSr2‐xCu2O5.5+δ phase is stable where 0.04 ≤x≤ 0.16. The La2O3‐SrO‐CuO phase diagram at 950°C and 10 kbar is almost identical to that determined by other authors at 950°C and 1 atm, in terms of phase stability and solid‐solution ranges.
Effects of Off‐Axis Loading on the Tensile Behavior of a Ceramic‐Matrix Composite
Authors: Lynch Christopher S. , Evans Anthony G.
Published: October 2005

A 0°/90° ceramic‐matrix composite (CMC) comprised of Nicalon fibers in magnesium aluminosilicate (MAS) has been loaded in tension in three orientations relative to the fiber direction: 0°, 30°, and 45°. The off‐axis loaded samples exhibit inelastic deformation at appreciably lower stresses than samples loaded at 0°. Matrix cracking governs the inelastic strains in all orientations. But, important differences in the morphologies and sequencing of the cracks account for the differences in the stress levels. Off‐axis failure also occurs at substantially lower stresses than on‐axis failure. On‐axis composite failure is governed by fiber fracture, but off‐axis failure involves matrix‐crack coalescence. To facilitate interpretation and modeling of these behaviors, the interface friction and debond stresses have been determined from hysteresis measurements.
Sintering of Fine Oxide Powders: I, Microstructural Evolution
Authors: Chen Pei‐Lin , Chen I‐Wei
Published: October 2005

Microstructural evolution during sintering has been investigated using fine powders of CeO2 and Y2O3 with excellent sinterability. A universal pore size distribution, normalized by particle size, has been determined and found to be a function of density only. Microstructure evolves toward the universal distribution, with or without densification, signifying homogenization at all stages. This may even involve the elimination of supercritical pores, at low densities, which are otherwise thermodynamically not sinterable. Theoretical justification for these observations is made by using a network model with a random, but spatially homogeneous, distribution of spherical particles. Final microstructure after full density is reached is also found to evolve toward a universal steady state of grain shape/grain size distribution regardless of initial state.
Transformation and Densification of Nanocrystalline θ‐Alumina during Sinter Forging
Authors: Nordahl C. Scott , Messing Gary L.
Published: October 2005

The sinter forging behavior of α‐Al2O3 seeded and unseeded nanocrystalline θ‐Al2O3 was investigated as a function of temperature, stress, and strain rate. Seeded samples exhibited the highest degree of plastic deformation during the θ‐ to α‐AI2O3 phase transformation. As a result, microstructure control, increased densification, and a higher degree of transformation were obtained. A uniform microstructure of 150 nm α‐Al2O3 grains developed, reaching 57% relative density after sintering 1.5 wt%α‐Al2O3 seeded samples for 30 min at 1060°C. When sinter forged at 0.25 mm/min to 63 MPa and 1060°C for 30 min large deformations during the phase transformation increased the relative density to 74%. When the stress was increased to 235 MPa (1060°C, 30 min), 99.7% dense α‐Al2O3 with a grain size of 230 nm was obtained. By increasing the sinter forging temperature to 1150°C, 99.5% relative density was achieved at 190 MPa for 30 min.
Surface and Internal Crystallization in Glasses as Determined by Differential Thermal Analysis
Authors: Ray Chandra S. , Yang Quanzu , Huang Wen‐hai , Day Delbert E.
Published: October 2005

A differential thermal analysis (DTA) method has been developed that identifies and distinguishes surface and internal (volume) crystallization in glasses. This method is fast, convenient, and requires only a small quantity of sample, ∼500 mg, to identify the dominant crystallization, surface versus internal, in the glass. In this method, either the maximum height of the DTA crystallization peak, (δT”)p, or the ratio T2p/(ΔT)p, where Tp is the temperature at (δT)p and (ΔT)p the peak half width, is plotted as a function of particle size. The composition of the glasses that have been investigated in the present work include (in mol%) 33.3BaO 66.7SiO2 (BS2), 20Na2O‐80TeO2 (NT4), 22.2PbOll.lNb2O5 66.7TeO2 (PNT), 66.7PbO10.0Bi2O3‐23.3Ga2O3 (PBG), and xLi2O(100 ‐ x)SiO2 (lithium silicate, x = 33.3, 35, 37, and 40 mol%). Both (δT)p and T2p/(ΔT)p decrease with increasing particle size when surface crystallization is the dominant mechanism and increase when internal crystallization becomes predominant. The surface and internal crystallization have been identified by crystallizing the glasses at temperatures, as determined by DTA, and then examining the microstructure by scanning electron microscopy. The temperature at the crystallization peak maximum, Tp, shows no dependence on the crystallization mechanism (surface versus internal) and increases with increasing particle size for all the preceding glasses.
Plastic‐to‐Brittle Transition of Saturated, Alumina Powder Compacts
Authors: Franks George V. , Lange Fred F.
Published: October 2005

Alumina slurries, in which different particle pair potentials were produced by adjusting ρH and salt concentration, were used to form cylindrical, consolidated bodies by pressure filtration, at applied pressures between 0.25 and 100 MPa. The mechanical properties of these bodies were investigated by uniaxial compressive loading at a specific rate. Saturated bodies formed from flocced slurries (ρH 9) were plastic at low relative densities (<0.54, formed at filtration pressures < 40 MPa) but were brittle (fractured prior to flow) at higher relative densities. Bodies formed from the dispersed slurries (ρH 4) were always brittle. When initially stressed, plastic bodies consolidated from the coagulated slurries (ρH 4, 5, and 6 with additions of NH4C1) produced a stress‐strain behavior characterized by a peak stress, followed by a much lower flow stress. The peak stress reduced to the flow stress upon several reloading cycles. The peak stress observed during the initial loading rapidly increased with consolidation pressure. These bodies exhibited a transition from plastic to brittle behavior at large consolidation pressures (∼65 MPa), with little change in relative density. It was reasoned that the plastic‐to‐brittle transition occurred for bodies formed from coagulated slurries when a sufficient fraction of the particles were pushed into their primary minimum to form a touching particle network. The reduction of the peak stress to the flow stress was reasoned to occur once the touching network was broken apart to reestablish the weakly attractive, but nontouching, network that existed in the slurry state. This can only occur when the fraction of particles in the touching network is less than that necessary for fracture. It was also noted that the flow stress for certain bodies formed from the coagulated slurry had a nearly identical flow stress as measured for a commercial, throwing clay.
Effect of Oxygen‐Gas Concentration in the Heat‐Treatment Atmosphere and High‐Voltage Pulse Application on the Electrical Properties of Carbon Fibers
Authors: Okubo Atsushi , Miyayama Masaru , Yanagida Hiroaki
Published: October 2005

Semiconductive carbon fibers suitable for infrared‐ray sensor materials were prepared by final heat treatments at 600°‐700°C in an atmosphere with a controlled oxygen‐gas (O2) concentration, and the influence of O2 concentration on the electrical properties and surface composition/micro ‐ structure was investigated. Resistivities at 20°C were almost equal and independent of the O2 concentration of heat treatment in all cases, but the thermistor constant decreased as the O2 concentration increased. Carbon fibers heat‐treated in O2‐mixed nitrogen gas (N2) exhibited higher surface oxygen concentrations than did those treated in pure N2, and surface microstructures differed between the two fibers.
Size‐Effect on the Fracture Toughness and the R‐Curve of Carbon Materials
Authors: Sakai Mototsugu , Kurita Hisashi
Published: October 2005

A theoretical extension of the Bažant size‐effect law to crack propagation problems is made in order to analyze the R‐curve‐related microfracture mechanisms of brittle materials. The specimen's size‐effect on the fracture toughness and crack growth resistance curve (R‐curve) is formulated in a generalized fashion without assuming the similitude restriction of test specimen geometry, being more convenient for the study of R‐curve behavior. Using the size‐effect law proposed in this work, the dimensions of the crack‐tip process zone as well as the crack‐face bridging region are estimated in the fracture mechanics analysis of carbon materials (a polycrystalline graphite and a carbon‐matrix/ carbon‐fiber composite). Microstructural observations confirm these fracture mechanics estimates.
Effect of Variations in Grain Size and Grain Boundary Barrier Heights on the Current‐ Voltage Characteristics of ZnO Varistors
Authors: Nan Ce‐Wen , Clarke David R.
Published: October 2005

Throughout the microstructure at every varistor, there exist variations of the grain size and the electrical properties of the individual grain boundaries. To calculate the effect of such microstructural variations on the overall electrical transport properties, we describe a multibond percolation approach utilizing effective medium theory. The model presented takes into account these variations as well as the electrical conductivity of the ZnO grains themselves. To illustrate the predictions of the model, both the effect of continuous distributions in the grain boundary potential and the grain size are considered, as well as a bi‐lognormal distribution in grain size to represent the effect of a population of anomalously large grains in a smaller grain size varistor.
Sintering of Alumina in Microwave‐Induced Oxygen Plasma
Authors: Su Hunghai , Johnson D. Lynn
Published: October 2005

Small cylindrical tubes were sintered in a microwave‐ induced oxygen plasma, initiated and sustained inside a tunable, single‐mode cavity. Temperature and shrinkage measurements of the specimens were achieved using an optical‐fiber thermometer black‐body sensor and a dilatometer, respectively. Sintering experiments at constant heating rate were accomplished to obtain the activation energy for sintering of alumina in the plasma and in a conventional rapid‐heating furnace. Diffusion of aluminum interstitials along grain boundaries was believed to be the dominant sintering mechanism, with an estimated activation energy of 488 ± 20 kj/mol for conventional sintering and an average activation energy of 468 ± 20 kj/mol for plasma sintering. A comparison of specimens sintered in the plasma to those sintered in a conventional furnace under the same temperature‐time excursions and oxygen pressures showed an athermal effect due to the plasma. To further explore this athermal effect, sintering experiments in plasmas of different oxygen pressure were conducted. The athermal effect was ascribed to an increase of aluminum interstitial concentration during plasma sintering. Sintering data were interpreted using the combined‐stage sintering model.
Master Sintering Curve: A Practical Approach to Sintering
Authors: Su Hunghai , Johnson D. Lynn
Published: October 2005

One of the ultimate objectives for sintering studies is to be able to predict densiflcation results under different thermal histories for a given processing method. It has been reported that the geometric parameters related to sintering often are functions only of density for a given powder and green‐body process, provided that one diffusion mechanism dominates in the sintering process. Based on this report, the concept of a master sintering curve has been developed that characterizes the sintering behavior for a given powder and green‐body process regardless of the heating profiles. The formulation and construction of the master sintering curve are given in this paper. A model experiment on sintering of alumina is used and analyzed to demonstrate this new concept. Examples of the master sintering curves obtained from other powder systems (ZnO, nickel, A12O3(5 vol% TiO2), and A12O3(5 vol% ZrO2)) are presented. When this new method is used, densification behavior can be predicted under arbitrary temperature‐time excursions following a minimal set of preliminary experiments, and these predictions can be used in planning sintering strategies. Moreover, deviations from the assumption of a single mechanism can be observed readily.
Order‐Disorder Phase Formation in the Complex Perovskite Compounds Ba(Ni1/3Nb2/3)O3 and Ba(Zn1/3Nb2/3)O3
Authors: Hong Kug Sun , Kim In‐Tae , Kim Chong‐Don
Published: October 2005

The order‐disorder phase formation of the complex perovskite compounds Ba(Ni1/3Nb2/3)O3 (BNN) and Ba(Zn1/3‐Nb2/3)O3 (BZN) was investigated using X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, and energy‐dispersive spectroscopy. The BNN and BZN samples were sintered over a temperature range of 1200° to 1500°C in air for 2 h. X‐ray diffraction and transmission electron microscopy showed that these compounds exhibited a 1:2 ordering on the B‐site within a narrow temperature range. When BNN and BZN were sintered above 1400° and 1350°C, respectively, a liquid phase formed in the grain boundary which was accompanied by disordering. The composition of the liquid phase resembled that of pyrochlore, with a small amount of nickel for BNN or zinc for BZN. The disordering with the formation of the liquid phase was attributed to the increase in defect concentration.
Rheological Property and Stress Development during Drying of Tape‐Cast Ceramic Layers
Authors: Lewis Jennifer A. , Blackman Kimberly A. , Ogden Andrea L. , Payne James A. , Francis Lorraine F.
Published: October 2005

Rheological property and stress development of tape‐cast ceramic layers derived from nonaqueous alumina (A12O3)‐poly(vinyl butyral) (PVB) suspensions were observed during drying. Casting suspensions exhibited strong shear‐thinning behavior, with a low shear Newtonian plateau apparent viscosity >102 Pa.s. The apparent suspension viscosity displayed a power‐law dependence on the A12O3 volume fraction during the initial stage of drying (<30% solvent loss). Stress development, measured by a cantilever deflection method, and parallel weight loss measurements were performed during the drying of tape‐cast layers and pure binder coatings. Maximum drying stresses (σmax) of 1.37‐0.77 MPa were observed for plasticized tapes cast at gap heights of 150‐400 μm. In contrast, nonplasticized tapes of similar thickness displayed a more gradual stress increase, with σmax values approximately an order of magnitude higher than their plasticized counterparts. The stress histories of the corresponding binder coatings were quite similar to the tape‐cast layers, albeit slightly lower σmax values were observed. Stresses decayed beyond σmax with a logarithmic time dependence to an almost constant value of 0.2‐0.4 MPa for the plasticized tapes. Based on these observations, process methodologies have been offered to minimize stress development and retention in tape‐cast ceramic layers
Effects of Microstructure and Composition on the Curie Temperature of Lead Barium Niobate Solid Solutions
Authors: Hiroshima Takuya , Tanaka Kazuhiko , Kimura Toshio
Published: October 2005

The Curie temperature of normally sintered and hot‐pressed Pb1‐xBaxNb2O6 (x = 0.30, 0.37, 0.41, and 0.50) was dependent on the sample preparation conditions. Samples with large amounts of pores and cracks had higher Curie temperatures than dense samples. Dense samples with fine grains had higher Curie temperatures than those with coarse grains. Comparison between microstructure and the Curie temperature revealed that the variation in Curie temperature was caused by internal stresses developed in the paraelectric‐to‐ferroelectric phase transition. Large internal stresses increased the free energy of the ferroelectric phase, and thus decreased the Curie temperature. The magnitude of internal stresses depended on the microstructure. Pores and cracks relaxed internal stresses, resulting in high Curie temperatures. Grain boundaries also relaxed internal stresses; samples with small grains had high Curie temperatures. Furthermore, the magnitude of internal stresses was dependent on the crystal structure of ferroelectric phases; samples with the tetragonal ferroelectric structure had internal stresses larger than those with the orthorhombic ferroelectric structure. The effect of crystal structure was discussed in terms of the relaxation of internal stresses by the formation of 90° domains
Dynamic Recrystallization during the Sliding Wear of Alumina at Elevated Temperatures
Authors: Xiao Hanning , Senda Tetsuya , Yasuda Eiichi
Published: October 2005

In previous studies, a very fine grain size surface layer of several micrometer thickness has been consistently observed in the wear track of alumina couples after wear at elevated temperatures. Detailed microstructural observations have revealed that dynamic recrystallization is the most probable mechanism for the surface layer formation. In this study, grain size and thickness of the surface layer are reported for the samples tested under various wear conditions. Both the grain size and the thickness are dependent on the testing temperature, nominal contact pressure, and the sliding velocity. The strain rate and the local temperature of the wear surface are estimated taking frictional heat into account and the Zener‐Hollomon parameter Z = exp(Q/RT) is calculated. A logarithmic plot of the grain size and Z yields a good linear relationship. This linearity and the slope of –0.21, similar to that previously reported for metals, further substantiate that dynamic recrystallization occurring in the wear surface is responsible for the formation of the fine grain size surface layer
Crystal Phase and Phonon Densities of States of β'‐SiAION Ceramics, Si6‐zAlzOzN8‐z (0 ≤z≤ 4)
Authors: Loong Chun‐Keung , Richardson James W. , Sukuzi Sugura , Ozawa Masakuni
Published: October 2005

The crystal structure and phonon densities of states (DOS) of β‐SiAlON ceramics, Si6_zAlzOzN8‐z (0 < z < 4), prepared by a novel slipcast method, are studied by neutron‐scattering techniques. The samples with z < 4 form a single‐phase solid solution of Si‐Al‐O‐N isostructural to β‐Si3N4 (space group P63/m). A consistent preferential occupation of the 2c sites by oxygen atoms and the 6h sites by nitrogen atoms exists within this structure. The phonon DOS of β'‐SiAlON displays phonon bands at ∼50 and 115 meV. These features are considerably broader than the corresponding ones in β‐Si3N4 powder.
Synthesis of Red‐Emitting, Small Particle Size Luminescent Oxides Using an Optimized Combustion Process
Authors: Shea Lauren E. , McKittrick Joanna , Lopez Olivia A. , Sluzky Esther
Published: October 2005

A novel ceramic synthesis technique, combustion synthesis, was explored to produce red‐emitting Cr3+‐doped Y3A15O12 and Eu3+‐doped Y2O3 phosphors with improved physical and luminescent properties. This technique involves the reaction of metal nitrates (oxidizers) and an organic fuel (urea, carbohydrazide, glycine) at 500°C. Resulting powders are well‐crystallized, with a large surface area and small particle size. The spectral energy distribution was observed using photoluminescence measurements. The effects of processing parameters such as type of fuel, fuelto‐oxidizer ratio, furnace temperature, and batch water content were studied. An increase in phosphor brightness with increasing reaction temperature was observed. Postreaction heat treatments (1000°, 1300°, and 1600°C) increased the luminous intensity of as‐synthesized powders. Residual carbon content and chromium site symmetry were investigated as possible explanations for the increase in brightness with increasing heat treatment temperature. By tailoring the reaction chemistry, the optimal conditions for producing the most luminescent phosphors have been identified.
Vaporization of LaCrO3: Partial and Integral Thermodynamic Properties
Authors: Peck Dong‐Huyn , Miller Miroslaw , Kobertz Dietmar , Nickel Hubertus , Hilpert Klaus
Published: October 2005

The vaporization of LaCrO3(s) and samples of the composition LaCrO3+ La2O3 was investigated in the temperature range of 1887‐2333 K by Knudsen effusion mass spectrometry using Knudsen cells made of tungsten lined completely with iridium. The species Cr(g), CrO(g), CrO2(g), and LaO(g) were identified in the vapor. Their partial pressures were determined by calibration with pure platinum solid. The thermodynamic activity of Cr2O3, acr2o3 in LaCrO3 for the Cr203‐poor phase boundary of this phase was In aCr2o3= ‐(17953/T) ‐ 0.485 (temperature T given in K) for the temperature range of the measurements with a probable overall error of ± 13%. The following values and temperature dependence of ΔG°f,T resulted for the formation of LaCrO3(s) according to the reaction 0.5Cr2O3(s) + 0.5La2O3(s) → LaCrO3(s): ΔG°f,2100= ‐78.9 ± 1.1 kj/mol, ΔH°f,298= ‐76.8 ± 5.2 kj/mol, and ΔG°r(kJ/mol) = ‐74.7 ‐ 0.00202T. Computations for the vaporization of LaCrO3 were conducted to show the volatility of this material in different atmospheres at high temperatures.
Stereological Observations of Platelet‐Reinforced Mullite‐ and Zirconia‐Matrix Composites
Authors: Cherian Isaac K. , Lehigh Mitchell D. , Nettleship Ian , Kriven Waltraud M.
Published: October 2005

Recently, the effect of solid inclusions on the sintering of ceramic powders has been explained in terms of a “backstress” that opposes densiflcation. Several analyses havebeen proposed to describe this problem. However, little quantitative information exists concerning the effect of reinforcement on microstructural evolution. This study compares the microstructural development of zirconia and mullite matrices in the presence of alumina platelets. The effect of platelet loading on density is similar for both composites. Quantitative stereological examinations reveal that the average grain size and pore size are finer for the zirconiamatrix composite. The platelet loading does not have any noticeable effect on the average grain size of the matrix in either composite. However, the average pore size increases as the volume fraction of platelets increases for both materials. Contiguity measurements have detected some aggregation of platelets in the zirconia‐matrix composite.
PbTiO3‐PbO‐B2O3 Glass‐Ceramics by a Sol‐Gel Process
Authors: Saegusa Kunio
Published: October 2005

PbTiO3 (PT)‐PbO‐B2O3 glass‐ceramics were produced by a sol‐gel process. Achievement of high PT content at levels unattainable by conventional glass‐ceramics preparation methods was semiquantitatively shown. PT content was similar to the designed PT volume fraction and seemed rather unaffected by the composition of the glassforming component at a calcination temperature of 700°C. A higher ratio of PbO to B2O3 in the glassforming component resulted in a low PT crystallization temperature, <500°C. PT crystals 1‐2 μm in size were obtained at calcination temperatures >600°C.
Effect of Cr3C2 Addition on the Sintering of SiC‐TiC Composite
Authors: Chae Ki‐Woong , Niihara Koichi , Kim Doh‐Yeon
Published: October 2005

The densification behavior and mechanical properties of SiC‐30TiC (in volume percent) composites prepared with Cr3C2 additive were investigated. By hot‐pressing a SiC‐30TiC‐lCr3C2 specimen at 1950°C, 98.5% of theoretical density was achieved and the specimen exhibited a fracture strength of 750 MPa. For the SiC‐30TiC‐10Cr3C2 specimen, (β‐α transformation of SiC was observed to occur during hot‐pressing and in situ growth of elongated α‐SiC grains resulted in an increase of fracture toughness. Micro‐structural observations using high‐resolution TEM indi‐cated that no liquid phase was present at the interfaces.
Preparation of an Alkali‐Element‐Doped CeO2‐Sm2O3 System and Its Operation Properties as the Electrolyte in Planar Solid Oxide Fuel Cells
Authors: Mori Toshiyuki , Yamamura Hiroshi , Saito Syoshichi
Published: October 2005

The ionic conductivity of the ceria‐samaria (CeO2‐Sm2O3) system is higher than that of yttria‐stabilized zirconia and other CeO2‐based oxides. In this study, a small amount of alkali‐element‐doped CeO2‐Sm2O3 solid solution was prepared. This solid solution was characterized by measuring the powder density and the chemical composition. Moreover, its electrochemical properties were investigated in the temperature range from 700° to 1000°C. It was found that a small amount of alkali‐element‐doped CeO2 solid solution enhanced the ionic conductivity. The power density of an oxygen‐hydrogen fuel cell for alkali‐element‐doped CeO2‐Sm2O3 ceramics exhibited high values at low temperatures such as 700° to 800°C. It is concluded that the improved fuel cell performance can be attributed to the high stability of this composition in the fuel atmosphere.
Bonelike Coatings onto Ceramics by Reactive Magnetron Sputtering
Authors: Yamashita Kimihiro , Yagi Takeshi , Umegaki Takao
Published: October 2005

Bonelike coating of partially carbonated, calcium hydroxyapatite onto strong ceramics and metals is one of the current objectives in biomaterials science for the development of bioactive implant materials. We recently accomplished bonelike apatite coating onto ceramic alumina by the newly developed reactive rf‐magnetron sputtering method, which was undertaken in a mixed CO2/Ar gas. The key of this method is the use of calcium phosphate glass targets with much lower Ca/P ratios than the stoichiometric value of hydroxyapatite. Surface analyses by XRD, EDX, and FT‐IR identified the formation of bonelike carbonated calcium hydroxyapatite, in which CO2‐3 ions occupied the lattice positions of PO3‐4. The bioactivity of the coated ceramic materials was confimed by in vitro experiments on the bonelike crystal growth on their surfaces in a simulated body fluid, and the growth rate on the coated layers was experimentally proved to be much faster than that on uncarbonated hydroxyapatite
Measurement of Porosity in Ceramic Coatings by Thermogravimetric Volatilization of Liquids
Authors: Craig Bradley D. , Francis Lorraine F. , Abrams Lloyd
Published: October 2005

A simple gravimetric method was developed to determine the open porosity in ceramic coatings. The coating's pore space was filled with a liquid and the weight loss on volatilization of the liquid was measured in a thermogravimetric analyzer. This thermogravimetric volatilization of liquids (TVL) method was used to characterize the porosity in titania coatings, alumina/aluminum phosphate coatings, and free‐standing films of alumina. Several liquids were used; ethylene glycol and 1,3‐propanediol gave the best results due to their low volatilities at room temperature. The measured porosities of the ceramic coatings ranged from 30% to 80% and the pore sizes (as determined by SEM and mercury porosimetry) ranged from 0.1 to 15 μm. The standard deviation of the TVL measurement was smaller for thicker coatings (e.g., ≥20 μm). Porosities determined by TVL were within typically 5‐10% of those determined by mercury intrusion porosimetry on identical samples. Characterization of a series of alumina/aluminum phosphate coatings showed a decrease in porosity consistent with expectations based on density and SEM observations. TVL is nondestructive, can be used for small volumes of sample, and when combined with SEM, provides a good means to characterize coating porosity and pore structure.
Ultrasonic Characterization of Zirconia‐Toughened Alumina Ceramics
Authors: Phani Kalyan K. , Mukherjee Sampad , Basu Debabrata
Published: October 2005

Ultrasonic pulse‐echo technique was used for the characterization of sintered zirconia‐toughened alumina (ZTA) ceramics. The variation of the ultrasonic velocity and elastic constants with the volume fraction of zirconia in the alumina matrix was studied. The ultrasonic velocity variation in these materials also was modeled using a mean‐value approach. The zirconia grains in ZTA were modeled by oblate spheroids, whose aspect ratio was estimated from the two‐dimensional microstructure of the material using stereological relations. The aspect ratio was then used as a parameter to estimate the ultrasonic velocity variation in the material using self‐consistent spheroidal inclusion theory, and the model was validated by comparing the estimated data with the measured velocity values, which showed very good agreement.
Pyroelectric Properties of Diphasic Polar Glass‐Ceramics at Low Temperatures
Authors: Xie Weimin , Ding Zhenya , Zhang Peilin
Published: October 2005

The pyroelectric properties of the diphasic polar glassceramic (Sr2TiSi2O8 and SrTiO3) are investigated in the temperature range from 10 to 300 K. The pyroelectric coefficient of the diphasic polar glass‐ceramic is −1.8 × 10−7 C/ (m2.K) at room temperature. It is interesting that the absolute value of p3 decreases quickly below 100 K and eventually becomes positive below 40 K, corresponding to the structural phase transition of the crystalline SrTiO3 in the glass‐ceramic. XRD, DTA, and SEM were used to investigate the coupling patterns of Sr2TiSi2O8 and SrTiO3 crystallites in the glass‐ceramic and to explain the special coupling effects
Fetal haemoglobin augmentation in E/β0 thalassaemia: clinical and haematological outcome
Authors: Singer Sylvia T. , Kuypers Frans A. , Olivieri Nancy F. , Weatherall David J. , Mignacca Robert , Coates Thomas D. , Davies Sally , Sweeters Nancy , Vichinsky Elliott P. ,   the E/β Thalassaemia Study Group
Published: October 2005

Patients with E/β0 thalassaemia, the most common haemoglobinopathy in many Asian countries, might benefit from drugs that increase fetal and total haemoglobin and thereby decrease the need for transfusions. The long‐term clinical efficacy and safety of such therapy is unknown, limiting its use in countries where resources for safe and regular transfusion are scarce. In this study, 45 patients were treated with hydroxyurea (18–20 mg/kg) for 24 ± 9 months, hydroxyurea with sodium phenyl butyrate (n = 8) and hydroxyurea with erythropoietin (n = 9), each for ∼6 months, and followed for 3 years from study exit. Hydroxyurea had minimal toxicity, resulted in a mean 1·3 g/dl steady‐state increase in haemoglobin in 40% of patients, and a milder response (≤1 g/dl) in the others. Baseline haemoglobin F was significantly associated with an increase in haemoglobin (P < 0·001). Combined treatment with erythropoietin benefited selected patients, but the addition of sodium phenyl butyrate had no effect. Of the 27/45 patients who discontinued regular transfusions before the study, 13 remained transfusion independent during long‐term follow‐up, 6/13 continued hydroxyurea. Hydroxyurea moderately increased steady‐state haemoglobin in a sub‐group of E/β0 thalassaemia patients and can be considered for patients with intermediate severity disease, thus delaying or avoiding the need for life‐long transfusions. Continuous monitoring of toxicity and growth is required.
Differential expression of CD180 and IgM by B‐cell chronic lymphocytic leukaemia cells using mutated and unmutated immunoglobulin VH genes
Authors: Porakishvili N. , Kulikova N. , Jewell A. P. , Youinou P. Y. , Yong K. , Nathwani A. , Heelan B. , Duke V. , Hamblin T. J. , Wallace P. , Ely P. , Clark E. A. , Lydyard P. M.
Published: October 2005

We have studied the surface expression of the Toll‐like receptor family member CD180 on cells from 78 patients with B‐chronic lymphocytic leukaemia (B‐CLL). B‐CLL cells had variable levels of CD180 expression, but this was always less than that expressed by normal blood B cells and was stable for 24 months. Significantly higher levels of CD180 were expressed by B‐CLL cells with mutated IGVH genes compared with those using unmutated IGVH genes. This was in contrast to the higher levels of expression of surface immunoglobulin M by B‐CLL cells using unmutated, rather than mutated IGVH genes. CD180 was functional on B‐CLL cells from some of the patients, as shown by the increased expression of CD86 following incubation in vitro with anti‐CD180. The differential expression of CD180 amongst B‐CLL patients is one more marker that may define more precisely the different biological properties of this heterogeneous disease.
Estimating detailed soil water profile records from point measurements
Authors: Fernández‐Gálvez J. , Simmonds L. P. , Barahona E.
Published: October 2005

Temporal and spatial patterns of soil water content affect many soil processes including evaporation, infiltration, ground water recharge, erosion and vegetation distribution. This paper describes the analysis of a soil moisture dataset comprising a combination of continuous time series of measurements at a few depths and locations, and occasional roving measurements at a large number of depths and locations. The objectives of the paper are: (i) to develop a technique for combining continuous measurements of soil water contents at a limited number of depths within a soil profile with occasional measurements at a large number of depths, to enable accurate estimation of the soil moisture vertical pattern and the integrated profile water content; and (ii) to estimate time series of soil moisture content at locations where there are just occasional soil water measurements available and some continuous records from nearby locations.

 The vertical interpolation technique presented here can strongly reduce errors in the estimation of profile soil water and its changes with time. On the other hand, the temporal interpolation technique is tested for different sampling strategies in space and time, and the errors generated in each case are compared.
Experimental tail shortening in Barn Swallows (Hirundo rustica) affects haematocrit
Authors: CUERVO J. J. , DE AYALA R. M.
Published: October 2005

Recent studies in Scotland suggest that the outermost tail feathers of Barn Swallows (Hirundo rusticaLinnaeus) may be around 10–12 mm longer than the aerodynamic optimum, with sexual selection for long tails accounting for this extra length.

To test this hypothesis, we shortened the outermost tail feathers in male and female Barn Swallows in southern Spain by cutting 1, 11 or 21 mm from the tips of the feathers, and checked for change in haematocrit 1 month later. Haematocrit levels were high when birds arrived at the breeding grounds due to an intense effort for flight during migration, but these levels decreased during the breeding season. We predicted that this decrease would be more pronounced when tail length was closer to the aerodynamic optimum (tails shortened by 11 mm), and less pronounced as tail length was displaced from that optimum (tails shortened by 1 or 21 mm).

Contrary to expectations, we found that the smaller the experimental reduction in tail length, the more pronounced the decrease in haematocrit. Barn Swallows with little parental effort and originally long tail feathers experienced a more pronounced decrease in haematocrit than individuals with strong parental effort and originally short tail feathers, respectively, although only in the group of birds with tails shortened by 21 mm.

These results do not support the hypothesis that outermost tail feathers in Barn Swallows have been elongated because of sexual selection, at least in the population studied, but are consistent with tail length being at an aerodynamic optimum, or very close to it. Differences in tail length among populations might help to understand the disagreement with previous studies.
Psychometric field study of the new haemophilia quality of life questionnaire for adults: The ‘Hemofilia‐QoL’
Authors: Remor E. , Arranz P. , Quintana M. , Villar A. , Jiménez‐Yuste V. , Diaz J. L. , del Rincón C. , Marrero C. , Moreno M. , Lucia J. F. , Martínez E. , Soto I. , Sedano C. , Gonzalez‐Boullosa R. , Prieto M. , Garcia‐Luaces M. , Hernández‐Navarro F. ,   The Hemofilia‐QoL Project Group
Published: October 2005

Summary.  Although there is a worldwide interest in the assessment of health‐related quality‐of‐life (HRQoL) in haemophilia patients, no non‐disease specific instruments (for adults) are readily available. In this paper, a haemophilia‐specific quality‐of‐life assessment measure for adults (the Hemofilia‐QoL questionnaire) has been developed and tested for psychometric properties in 121 adults with haemophilia living in Spain. The Hemofilia‐QoL questionnaire is a self‐report modular instrument that assesses nine relevant HRQoL domains for patients with haemophilia (e.g. physical health, daily activities, joint damage, pain, treatment satisfaction, treatment difficulties, emotional functioning, mental health, relationships and social activity). Psychometric examination involved the assessment of data quality, scaling assumptions, reliability (internal consistency and test–retest) and validity (concurrent; external clinical criterion and sensitivity). The Hemofilia‐QoL 36‐item version questionnaire had acceptable internal consistency and retest reliability values. The questionnaire shows excellent concurrent validity (with the SF‐36 Health Survey) and external clinical criterion validity (haemophilia clinical status) and sensitivity (health status changes) as well. The Hemofilia‐QoL is now available for adult assessment and is ready for use in clinical research in Spain.
Candida vertebra osteomyelitis in a girl with factor X deficiency
Authors: Gursel T. , Kaya Z. , Kocak U. , Erbaş G. , Akyurek N. , Tali E. T.
Published: October 2005

Summary.  Candidal vertebra osteomyelitis is a rare condition which occurs primarily in immunocompromised patients. We report a 14‐year‐old girl with factor X deficiency who developed candida vertebra osteomyelitis during home therapy. The microorganism was probably from a contaminated peripheral cannula used for infusion of factor concentrate. This is the first such case in bleeding disorders to our knowledge.
Microscopic observation of bacteria: review highlighting the use of environmental SEM
Authors: Bergmans L. , Moisiadis P. , Van Meerbeek B. , Quirynen M. , Lambrechts P.
Published: October 2005

Throughout the years, various methods have been adopted to investigate bacteria involved in root canal infection and apical periodontitis. This paper reviews the most commonly used microscopic techniques and discusses their possibilities, limitations and sample preparation. In particular, a recently developed variant of scanning electron microscope (SEM), referred to as environmental SEM (ESEM), is highlighted due to its potential impact across the diverse field of biomaterials research. The performance of this ESEM technique for bacterial observation of endodontic pathogens was illustrated by a practical approach. The paper concludes with a discussion on the possible use of ESEM for testing endodontic treatment modalities under environmental conditionsin situ.
The use of an intra‐oral injection of ketorolac in the treatment of irreversible pulpitis
Authors: Mellor A. C. , Dorman M. L. , Girdler N. M.
Published: October 2005

Aim  To examine whether an intra‐oral injection of a nonsteroidal anti‐inflammatory drug (ketorolac), in association with conventional local anaesthetic techniques, would improve the pulp extirpation rate in teeth with irreversible pulpitis.

Methodology  A two group double‐blind clinical trial was undertaken in the Dental Casualty Department of the University of Manchester School of Dentistry. Patients were randomly allocated to either the test or control group. The test group received an intra‐oral injection of ketorolac (30 mg in 1 mL) in the buccal sulcus adjacent to the tooth being treated. After an interval of 15 min, they then received 2.2 mL of 2% lidocaine with 1 : 80 000 epinephrine by buccal infiltration in the maxilla or by inferior dental block in the mandible. The control group received an intra‐oral injection of normal saline (1 mL) in the buccal sulcus adjacent to the tooth being treated, followed by the same local anaesthetic regime as the test group after the 15 min interval. Fifteen minutes after the local anaesthetic injections, pulp extirpation was attempted.

All patients completed the short‐form McGill pain questionnaire prior to treatment and completed identical questionnaires at 6 and 24 h after treatment.

Results  The study protocol set the number of patients to be treated at twenty. However, as the study progressed it became apparent that the intra‐oral injection of ketorolac caused significant pain to four of the five patients who received it; therefore the study was terminated after ten patients had been treated. The results from the patients treated showed no significant difference in the pulp extirpation rate between the test and control groups. However, patients with higher pain scores at baseline were less likely to have the pulp completely extirpated, irrespective of whether they were in the test or control group. Pain scores for all patients decreased significantly from baseline to 24 h.

Conclusion  An intra‐oral injection of ketorolac did not improve the pulp extirpation rate in a small group of patients with irreversible pulpitis compared with a placebo. In addition, it was associated with such significant pain on injection that it cannot be recommended as a treatment in this situation.
Physical and mechanical characterization and the influence of cyclic loading on the behaviour of nickel‐titanium wires employed in the manufacture of rotary endodontic instruments
Authors: Bahia M. G. A. , Martins R. C. , Gonzalez B. M. , Buono V. T. L.
Published: October 2005

Aim  To analyse the influence of cyclic loading on the mechanical behaviour of nickel‐titanium (NiTi) wires employed in the manufacture of ProFile rotary endodontic instruments.

Methodology  Nickel‐titanium wires, 1.2 mm in diameter, taken from the production line of ProFile rotary endodontic instruments before the final machining step, were tensile‐tested to rupture in the as‐received condition and after 100 load–unload cycles in the superelastic plateau (4% elongation). The wires were characterized by X‐ray energy‐dispersive spectroscopy, X‐ray diffraction and by differential scanning calorimetry and compared with new size 30, .06 taper ProFile instruments. The fracture surfaces of the wires were observed by scanning electron microscopy.

Results  The mechanical properties of the as‐received wires, their chemical composition, the phases present and their transformation temperatures were consistent with their final application. Only small changes, which decreased after the first few cycles, took place in the mechanical properties of the cycled wires. The stress at maximum load and the plastic strain at breakage remained the same, while the critical stress for inducing the superelastic behaviour, which is related to the restoring force of the endodontic instruments, decreased by approximately 27%.

Conclusions  The mechanical behaviour of the NiTi wires was modified slightly by cyclic tensile loading in the superelastic plateau. As the changes tended towards stabilization, the clinical use of rotary NiTi ProFile instruments does not compromise their superelastic properties until they fracture by fatigue or torsional overload, or are otherwise discarded.
Neurological complications following extrusion of sodium hypochlorite solution during root canal treatment
Authors: Witton R. , Henthorn K. , Ethunandan M. , Harmer S. , Brennan P. A.
Published: October 2005

Aim  To report the presentation and management of two cases with neurological complications secondary to the extrusion of sodium hypochlorite solution into the facial soft tissues during root canal treatment.

Summary  The clinical features, with particular emphasis on nerve deficit following inadvertent extrusion of sodium hypochlorite, are discussed and its management highlighted. Early and aggressive treatment is advocated following such incidents in order to reduce potentially serious complications.

Key learning points

Neurological sequelae can follow inadvertent hypochlorite extrusion.

Early recognition may avert a potentially more serious outcome.

Active hospital treatment including intravenous steroids and antibiotics is recommended.
Assessment of a gel‐type chelating preparation containing 1‐hydroxyethylidene‐1, 1‐bisphosphonate
Authors: Girard S. , Paqué F. , Badertscher M. , Sener B. , Zehnder M.
Published: October 2005

Aim  To test an aqueous gel containing 1‐hydroxyethylidene‐1, 1‐bisphosphonate (HEBP) regarding its interactions with sodium hypochlorite, its calcium binding capacity, and its potential in preventing the formation of a smear layer when used in conjunction with rotary root canal preparation.

Methodology  The experimental aqueous gel consisted of (w/v) 2% alginate, 3% aerosil, 10% Tween 80 and 18% HEBP. Interactions of gel components with hypochlorite were assessed using iodometric titration and monochromatic ultraviolet spectrometry. Two commercial paste‐type chelators containing ethylenediaminetetraacetic acid (EDTA) and peroxide (RC‐Prep and Glyde) served as controls. Calcium‐binding capacities were measured in mixtures with a Ca2+ standard solution buffered at pH 10 using a calcium‐selective measuring chain. Finally, root canals of 16 extracted single‐rooted premolars per group were instrumented using ProFile instruments dipped in the experimental gel, RC‐Prep, or nothing. Additionally, canals were rinsed with 10 mL of a 1% NaOCl solution during/after preparation. Smear scores in instrumented teeth were monitored using scanning electron microscopy.

Results  None of the experimental gel components showed short‐term interactions with hypochlorite, whilst EDTA, peroxide, RC‐Prep and Glyde immediately reduced the hypochlorite in solution. The experimental gel chelated 30 mg Ca2+ g−1, compared with 16 mg Ca2+ g−1 and 11 mg Ca2+ g−1 chelated by RC‐Prep and Glyde respectively. Smear scores obtained with the experimental gel were significantly (P < 0.05) lower than with RC‐Prep in coronal and middle root thirds, whilst no differences were observed in apical root thirds.

Conclusions  Under the conditions of this study, an HEBP gel appeared advantageous over currently available products.