bluuebunny/crossref_metadata_2025 huggingface dataset:
White piedra and Trichosporon species in equatorial Africa. I. History and clinical aspects: an analysis of 449 superficial inguinal specimens
Authors: Thérizol‐Ferly M. , Kombila M. , de Diaz M. Gomez , Duong T. H. , Richard‐Lenoble D.
Published: July 2010

Summary. White piedra is a hair infection characterized by nodules composed of fungal elements which envelop the hair shaft. Classically, this infection was considered to be produced by an asexual yeast‐like fungus, Trichosporon beigelii. At present, in accordance with studies carried out previously, this species is subdivided into six newly defined distinct species (T. asshu, T. ovoides, T. inkin, T. mucoides, T. asteroides and T. cutaneum), all belonging to the class Basidiomycetes. Although widespread, white piedra has not previously been described in tropical regions of Africa. The present study, carried out in Libreville (Gabon), an equatorial region of Africa, shows that the incidence of this infection is quite high (18% of 449. inguinal specimens) in the female population aged 15–60 years, with a predominance in young patients (15–44 years). The relationship between the clinical manifestations and the specific hair lesions is also detailed. Three species belonging to the genus Trichosporon were identified: T. mucoides, T. asahii and T. inkin.

Zusammenfassung. Die weiße Piedra ist eine Haarinfektion, charakterisiert durch harte Knötchen, die aus Pilzelementen bestehen und den Haarschaft umgeben. In der klassischen Definition wurde diese Infektion als durch Trichosporon beigelii verursacht angesehen, einem asexuellen, hefeähnlichen Pilz. In Übereinstimmung mit neueren Untersuchungen wird diese Art jetzt in sechs selbständige Arten unterteilt: T. asahii, T. ovoides. T. inkin, T. mucoides, T. asteroides and T. cutaneum, die alle zur Klasse der Basidiomyzeten gerechnet werden. Obgleich weit verbreitet, wurde die weißie Piedra niemals in den tropischen Gebieten Afrikas beschrieben. Die vorliegende Studie, durchgeführt in Libreville (Gabun), einer äquatorialafrikanischen Region, zeigt, daß die Häufigkeit dieser Infektion ganz beträchtlich ist, nämlich bei 18% von 449 Untersuchungsproben der Inguinalregion in der weiblichen, zwischen 15 und 60 Jahre alten Bevölkerung, vorherrschend bei jüngeren Patientinnen im Alter von 15–44 Jahren. Die klinischen Manifestationen und die spezifischen Haarbefunde werden im Einzelnen dargestellt. Es wurden drei Arten der Gattung Trichosporon gefunden: T. mucoides, T. asahii, T. inkin.
Candidosis of the urinary tract with padding phenomenon of the renal pelvises in an infant with obstructive uropathy
Authors: Walther F. , Kaben Ursula , Radke M. , Terpe Ranghild , Stolpe H.J.
Published: July 2010

Summary. A male infant with obstructive uropathy developed yeast cell agglomerations which were detectable macroscopically and by imagegenerating techniques within both renal pelvises after Candida albicans infection of the urinary tract. Therapy with flucytosine induced excretion of ‘fungal balls’ via the urethra. Continuation of therapy with liposomal amphotericin B (AmBisome®) prevented a relapse after development of fungal resistance against flucytosine. Sonographically or radiographically detectable formation of ‘concrements’ within the urinary tract of patients with an immature or compromised immune system and additional features such as obstructive urinary tract should suggest a localized or systemic mycosis, particularly in the context of long‐term antibiotic treatment.

Zusammenfassung. Bei einem Säugling mit obstruktiver Uropathie manifestierte sich eine Infektion der Harnwege durch Candida albicans, die zur Entwicklung von makroskopisch und durch bildgebende Verfahren nachweisbaren Hefezellag‐glomerationen führte. Während einer Therapie mit Flucytosin kam es zur Ausscheidung von “Hefepilzbällen”über die Urethra. Durch Fortführung der Behandlung mit liposomalem Amphotericin B (AmBisome®) nach Resistenzentwicklung gegen Flucytosin wurde ein Rezidiv verhindert. Die sonografisch oder röntgenologisch nachweisbare Bildung von “Konkrementen” im Harntrakt von Patienten mit unreifem oder geschwächtem Immunsystem und eventuell zusätzlich vorhandenem locus minoris resistentiae in Gestalt einer Obstruktion der Harnwege sollte insbesondere im Zusammenhang mit langzeitigem Einsatz von Antibiotika an eine lokalisierte oder systemische Mykose denken lassen.
Screening of different keratin baits for isolation of keratinophilic fungi
Authors: Rai M. K. , Qureshi S.
Published: July 2010

Summary. Twenty different keratin‐rich substrates were screened as keratin baits for isolation of keratinophilic fungi from different soil sample of Chhindwara District, India. Fungi easily formed colonies on different baits. However, hair, feathers and horns were found to be more suitable than nails, fish fins and fish scales.

Zusammenfassung. Zwanzig unterschiedliche Keratin‐Substrate wurden auf ihre Eignung als Keratin‐Köder zur Isolierung keratinophiler Pilze aus Bodenproben des Chhindwara‐Distrikts, Indien, untersucht. Auf verschiedenen Keratinen wuchsen die Pilze gut an. Haare, Federn und Hornmaterialien erwiesen sich als geeigneter als Nägel, Fischflossen und Fischchshuppen.
Pathogenicity of yeasts and algae isolated from bovine mastitis secretions in a murine model
Authors: Jensen H. E. , Aalbæk B.
Published: July 2010

Summary.The pathogenicity of strains of yeasts and algae isolated from bovine mastitis secretions was evaluated in immunosuppressed mice. Strains ofCandida tropicalis (n= 3) were the most pathogenic, but all strains ofGeotrichum capitatum (n= 5) and the colourless algaPrototheca zopfii (n= 5) were also lethal to mice at the highest dose of 1 times 107CFU per mouse. Reisolation of the inoculated micro‐organisms and the occurrence of histopathological lesions within organs of mice challenged with 1 times 103to 1 times 107CFU per animal revealed strains ofC. krusei (n= 17),C. kefyr (n= 6) andC. rugosa (n= 6) to have a moderate pathogenicity, whereas strains ofC. valida (n= 1) andC. catenulata (n= 2) were weakly pathogenic and non‐pathogenic respectively.

Zusammenfassung.Die Pathogenität von Hefe‐ und Algen‐Isolaten aus Rindermastitis‐Sekreten wurde in immunsupprimierten Mäusen untersucht.Candida tropicalis‐Stämme (n= 3) zeigten die stärkste Pathogenität, aber auch Stämme vonGeotrichum capitatum (n= 5) und der farblosen AlgePrototheca zopfii (n= 5) waren in der höchsten Inokulationsdosis von 1 times 107CFU für Mäuse letal. Rückisolierungsversuche und histopathologische Läsionen an Organen von Mäusen, die mit 1 times 103‐1 times 107CFU pro Tier inokuliert worden waren, belegten eine mäßige Pathogenität vonC. krusei (n= 7),C. kefyr (n= 6) undC. rugosa (n= 6), während sichC. valida (n= 1) undC. catenulata (n= 2) nur als schwach oder nicht pathogen erwiesen.
Itraconazole in the treatment of tinea pedis and tinea manuum: comparison of two treatment schedules: Itraconazol bei der Behandlung der Tinea pedis und Tinea manuum: Vergleich zweier Behandlungsschemata
Authors: Schuller J. , Remme J. J. , Rampen F. H. J. , Van Neer F. C. J.
Published: July 2010

Summary.A multicentre, randomized, doubleblind, parallel‐group trial was conducted to compare the efficacy and safety of two dosages of itraconazole in the treatment of tinea pedis or manuum. Of the 135 patients recruited, 66 received itraconazole 400 mg daily for 1 week and 69 received itraconazole 100 mg daily for 4 weeks. In the evaluable patients observed‐case analysis, mycological cure was seen in 63% of patients in the 400 mg/1 week group and in 75% in the 100 mg/4 weeks group at the end of a 6‐week follow‐up period (not significantly equivalent). In the evaluable patients worst‐case analysis and the intention‐to‐treat analysis, mycological cure rates in the two groups were borderline significantly equivalent at the end of follow‐up (range 51–57%). Clinical response was seen in 81% of evaluable patients in the 400 mg/1 week group and in 75% in the 100 mg/4 weeks group at the end of follow‐up; equivalence testing showed the 400 mg/1 week regimen to be at least equivalent to the 100 mg/4 week regimen. Similar results were found in the intention‐to‐treat analysis, and tolerability ratings for the two treatment regimens were significantly equivalent. This trial has shown that itraconazole 400 mg/1 week and itraconazole 100 mg/4 weeks are both effective regimens for the treatment of tinea pedis or manuum. The two treatment schedules were equally well tolerated and safe.

Zusammenfassung.Zum Vergleich der Wirksamkeit und Sicherheit von zwei Itraconazol‐Dosierungen bei der Behandlung der Tinea pedis oder manuum wurde eine randomisierte, doppelblinde Multicentre‐Parallelgruppenstudie durchgeführt. Von den 135 Patienten wurden 66 Patienten 1 Woche lang mit 400 mg Itraconazol täglich und 69 Patienten 4 Wochen lang mit 100 mg Itraconazol täglich behandelt. Bei der Observed‐case‐Analyse der evaluierbaren Patienten wurde bei der Nachuntersuchung nach 6 Wochen bei 63% der Patienten der Gruppe mit 400 mg/1 Woche und 75% der Patienten der Gruppe mit 100 mg/4 Wochen eine mykologische Heilung festgestellt (nicht signifikant äquivalent). In der Worst‐case‐Analyse der evaluierbaren Patienten und der Intention‐to‐treat‐Analyse waren die mykologischen Heilungsergebnisse bei der Nachuntersuchung grenzwertig signifikant äquivalent (51–57%). Bei der Nachuntersuchung wurde bei 81% der evaluierbaren Patienten der Gruppe mit 400 mg/1 Woche und bei 75% der Gruppe mit 100 mg/4 Wochen ein klinischer Respons beobachtet. Äquivalenztests ergaben, daß die Behandlungspläne mindestens äquivalent waren. Die Intention‐to‐treat‐Analyse führte zu ähnlichen Ergebnissen, und die Verträglichkeitsbewertung war bei beiden Therapien signifikant äquivalent. Diese Studie ergab, daß Itraconazol 400 mg/1 Woche und Itraconazol 100 mg/4 Wochen wirksame Therapien für die Tinea pedis oder manuum sind. Beide Behandlungsschemata sind gleich gut verträglich und sicher.
Safety and efficacy of intermittent therapy with itraconazole in finger‐ and toenail onychomycosis: a multicentre trial: Sicherheit und Wirksamkeit der intermittierenden Itraconazol‐Therapie von Onychomykosen der Finger und Zehen. Eine Multizenter‐Studie
Authors: Haneke E. , Abeck D. , Ring J.
Published: July 2010

Summary. The efficacy and safety of intermittent itraconazole therapy were investigated in patients with onychomycosis. Patients were divided into two groups according to site and extent of infection. Group A comprised 635 patients with toenail onychomycosis (at least one nail with ≥ 20% involvement; n 560) or fingernail onychomycosis (at least one nail with > 75% involvement; n= 63) or both (n=12). These patients received itraconazole 400 mg day‐1 for 1 week per month for 3 months. Group B comprised 48 patients with fingernail onychomycosis (at least one nail with ≥ 20% involvement but no nail with >75% involvement) who received itraconazole 400 mg day‐1 for 1 week per month for 2 months. Patients were followed for a further 18 weeks without treatment, and received another treatment cycle if not cured or markedly improved 6 weeks after the end of the last cycle. An additional cycle was administered to 76 patients with fingernail onychomycosis (group A, n= 43; group B, n= 28) and to 316 patients with toenail onychomycosis. Clinical response rates and mycological cure rates at study end point were 89.0% and 68.4% respectively for toenails, 91.4% and 85.3% respectively for group A fingernails and 84‐4% and 77‐1% respectively for group B fingernails. Most adverse events occurred infrequently; major changes in liver function tests were not noted. In conclusion, intermittent itraconazole therapy is highly effective and safe in patients with onychomycosis.

Zusammenfassung. Die Wirksamkeit und Sicherheit einer intermittierenden Itraconazol‐Therapie wurden bei Patienten mit Onychomykosen untersucht. Die Patienten wurden nach Infektionsort und ‐ausmaß in 2 Gruppen eingeteilt. Gruppe A: 635 Patienten mit Zehennagel‐Onychomykose (mindestens 1 Nagel mit >20% Befall; n= 560) oder Fingernagel‐Onychomykose (mindestens 1 Nagel mit ≥75% Befall; n= 63) oder beidem (n= 12) erhielten 400 mg Intraconazol täglich jeweils eine Woche pro Monat über 3 Monate. Gruppe B: 48 Patienten mit Fingernagel‐Onychomykose (mindestens 1 Nagel mit >20% Befall, aber kein Nagel mit mehr als 75% Befall) erhielten 400 mg Intraconazol/Tag jeweils eine Woche pro Monat über 2 Monate. Die Patienten wurden nach Abschluß der Therapie noch 18 Wochen lang nachuntersucht und erhielten einen weiteren Behandlungszyklus, falls 6 Wochen nach Ende des letzten Behandlungszyklus keine Heilung oder wesentliche Verbesserung zu beobachten war. Ein zusätzlicher Behandlungszyklus wurde bei 76 Patienten mit Fingernagel‐Onychomykose (Gruppe A, n= 43; Gruppe B, n= 28) und bei 316 Patienten mit Zehennagel‐Onychomykose durch‐
Precise Tensile Properties of Ceramic Bodies
Authors: DUCKWORTH W. H.
Published: July 2010

Factors in obtaining and interpreting tensile data on ceramic bodies are discussed, with particular attention given to the use of bending. A bend test can be used conveniently to obtain precise tensile data as long as stress is directly proportional to strain in both tension and compression. The moduli of elasticity in tension and in compression need not be equal. To account for any such inequality, strain in both bottom and top longitudinal fibers should be considered in computing the tensile stress. Extraneous stresses in bending can be essentially eliminated through proper specimen design and manner of loading. Details for the consideration of extraneous stresses in practice are presented, along with an equation for computing tensile stress precisely from bend‐test data. Limited experimental work on oxide‐base and silicate‐base bodies supported the theoretical analysis of bending and indicated the suitability of a refined bend test for precise ceramic work.
The Past, Present, and Future of Ferrites
Authors: Sugimoto Mitsuo
Published: July 2010

Ferrites—ceramic ferromagnetic materials—have been considered as highly important electronic materials for more than half a century. During this time, the characteristics of commercial ferrite materials, both soft and hard ferrites, have come to approach theoretical values. The quality of commercial ferrites has been improved through accumulated scientific knowledge and advanced technology. This article provides a comprehensive survey of the historical development of the science and technology of ferrite materials as well as applications of the ferrites. The article also offers a forecast of the future of ferrites in terms of their chemistry.
Preparation of Undoped Lead Titanate Ceramics via Sol‐Gel Processing
Authors: Kim Sunuk , Jun Myong‐cheol , Hwang Soon‐cheol
Published: July 2010

Crack‐free, undoped PbTiO3 ceramics were fabricated successfully using sol–gel‐synthesized powder prepared from chelated titanium alkoxide and lead acetate. The sintered ceramics, 8.3 mm in diameter and 6–8 mm thick, were 96% dense. In the present study, PbTiO3 ceramics with excess lead (Pb:Ti = 1.1:1.0) had large grains, averaging 14.3 μm. Lower‐lead ceramics (Pb:Ti = 1.0:1.0 and 0.9:1.0) had smaller grains, averaging 1.8 μm. The PbTiO3 ceramics with a high lead content cracked during sintering at 1150°C, whereas the other ceramics did not crack. Excess lead, in a more‐than‐stoichiometric ratio, promoted grain growth and caused disintegration of the ceramics. Therefore, uncracked PbTiO3 ceramics apparently can be fabricated by avoiding excess lead, possibly because restricted grain growth in low‐lead ceramics causes low residual stress over many small grains during transition. The electrical properties measured in the present study for PbTiO3 ceramics with a Pb:Ti ratio of 1:1 are d33= 35 pC/N, K3= 64, kp= 0.59, and kt≈ 0.
Phase Development and Shrinkage of Reaction‐Bonded Mullite Composites with Silicon Carbide of Different Particle Sizes
Authors: Scheppokat Sven , Janssen Rolf , Claussen Nils
Published: July 2010

Mullitization temperatures and mechanical properties of reaction‐bonded mullite composites were investigated using silicon carbide (SiC) of two different particle sizes (180 nm and 2.5 μm) as one of the starting components. The smaller SiC particle size resulted in earlier mullitization, lower final densities, and lower strength of these composites. The sintering shrinkage of these composites was investigated. Low‐to‐zero shrinkage was rendered possible via volume expansions that were associated with the oxidation of SiC and aluminum in the green material. Green bodies that contained 55 vol% aluminum were compacted to 70% of the theoretical density. The materials showed a linear sintering shrinkage of <1% and had a four‐point bend strength of 430 MPa. Samples that were made from precursors with the coarse (2.5 μm) SiC were covered by a porous outer layer after firing in air. This layer led to anisotropy in shrinkage. The porosity of this outer layer was attributed to the oxidation of residual SiC during sintering and the trapping of gaseous oxidation products. Samples that were made from the fine (180 nm) SiC did not exhibit such a layer and showed isotropic shrinkage.
High‐Temperature Oxidation of Boron Nitride: I, Monolithic Boron Nitride
Authors: Jacobson Nathan , Farmer Serene , Moore Arthur , Sayir Haluk
Published: July 2010

High‐temperature oxidation of monolithic boron nitride (BN) is examined at 900–1200°C. Hot‐pressed BN and both low‐ and high‐density chemically vapor‐deposited BN are studied. The oxidation product is B2O3(l) and the oxidation kinetics are sensitive to crystallographic orientation, porosity, and impurity levels. The B2O3 product also reacts readily with ambient water vapor in the test furnace (ppm levels) to form the volatile species HBO2(g), leading to overall paralinear kinetics. The linear rate constant extracted from these experiments agreed with that predicted from diffusion of HBO2(g) across a static boundary layer.
High‐Temperature Creep and Microstructural Evolution of Chemically Vapor‐Deposited Silicon Carbide Fibers
Authors: Lewinsohn Charles A. , Giannuzzi Lucille A. , Bakis Charles E. , Tressler Richard E.
Published: July 2010

The creep behavior of three types of silicon carbide fibers that have been fabricated via chemical vapor deposition is described. The fibers exhibit only primary creep over the range of conditions studied (1200°–1400°C, 190–500 MPa). A transmission electron microscopy study of the microstructural development that is induced by the creep deformation of SCS‐6 silicon carbide fibers at 1400°C is presented. Significant grain growth occurs in all silicon carbide regions of the fiber during creep, in contrast to the reasonably stable microstructure that is observed after annealing at the same temperature and time.
Transverse Fracture of an Aluminosilicate Fiberboard
Authors: Olbert Blain H.
Published: July 2010

Mode I transverse fracture of an aluminosilicate fiberboard was studied under ambient conditions. The material showed tension softening behavior when loaded perpendicular to the isotropic plane. The measured softening curve was treated as the cohesive bridging stress function in a fictitious crack model. The observed peak loads, fracture energy, apparent fracture toughness, and load–displacement curves of various double cantilever beam specimens were shown to be consistent with model predictions.
Microstructure and Mechanical Properties of alpha‐Silicon Carbide Sintered with Yttrium‐Aluminum Garnet and Silica
Authors: Kim Jae‐Yeon , Kim Young‐Wook , Mitomo Mamoru , Zhan Guo‐Dong , Lee June‐Gunn
Published: July 2010

The effect of glassy‐phase chemistry, using Y3Al5O12 (YAG) and SiO2 as sintering additives, on the microstructure and mechanical properties of liquid‐phase‐sintered, and subsequently annealed, α‐SiC materials was investigated. The microstructural development of annealed materials was insensitive to changes in glass chemistry. The mechanical properties vs SiO2/YAG ratio curve had a maximum; i.e., there was a small glass composition range at which optimum mechanical properties were realized. The best results were obtained when the ratio was ∼0.5. The flexural strength and fracture toughness of the material were >450 MPa and >6 MPa·m1/2, respectively.
Acoustic Emission from a Porcelain Body during Cooling
Authors: Ohya Yutaka , Takahashi Yasutaka , Murata Minori , Nakagawa Zenbe‐e , Hamano Kenya
Published: July 2010

Quartz grains in porcelain bodies cause cracking. Under the present conditions, acoustic emission (AE) has shown that the cracking occurred in a temperature range of 900°–800°C during cooling from firing at a temperature of 1200°C. This cracking can be explained by a large thermal expansion mismatch that was due to the negative thermal expansion of quartz at temperatures >1000°C and no stress relaxation of the glass phase. At a temperature of 573°C, which is the transition temperature of quartz, AE was not detected by the measuring system that was used, although there were many peripheral cracks around the large quartz grains. The energy release rate of the peripheral cracks at a temperature of 573°C was too low to be detected by the equipment that was used.
Mechanisms of Reaction of Hydratable Aluminas
Authors: Ma Weiping , Brown Paul W.
Published: July 2010

The reactivities of four hydratable aluminas were investigated. Rates of heat liberation during hydration from 15° to 55°C were determined by isothermal calorimetry. Rates of heat evolution show two peaks. An initial mixing peak is due to wetting and initial dissolution reactions. A second, main heat peak is associated with the hydration step. The hydration product was bayerite in all cases. Although the specific surface areas for the aluminas studied were as high as about 260 m2/g, they did not react completely. The origin of incomplete reaction is related to the microstructure of the hydratable alumina grains. The particles are approximately 10 μm in size. High surface areas are not the result of small particle size, but are the result of high internal surface areas. The Bayerite formation appears to block the porosity in the grains, thereby inhibiting further reaction.
Synthesizing Nanocrystalline Pb(Zn1/3Nb2/3)O3 Powders from Mixed Oxides
Authors: Wang John , Dongmei Wan , Junmin Xue , Beng Ng Wei
Published: July 2010

The attempt to synthesize a Pb(Zn1/3Nb2/3)O3 (PZN) powder of perovskite structure via both traditional ceramic and chemistry‐based novel processing routes over the last three decades has failed. Difficult‐to‐synthesize nanocrystallite PZN powders have, for the first time, been successfully prepared via a mechanochemical reaction either among PbO, ZnO, and Nb2O5 or between PbO and pre‐reacted ZnNb2O6 from ZnO and Nb2O5 for more than 15 h in a high‐energy mechanochemical reaction chamber. The resulting PZN powders exhibit a well‐established perovskite structure and their crystallite sizes are in the range of 10 to 15 nm, as has been indicated from the peak broadening of X‐ray diffraction and direct observation using a high‐resolution transmission electron microscope.
Monotonic and Cyclic Fatigue Behavior of High‐Performance Ceramic Fibers
Authors: Chawla N. , Kerr M. , Chawla K. K.
Published: July 2010

Monotonic and cyclic fatigue behavior of single fibers or fiber fabrics are of significant interest, since fiber assemblies or fiber‐reinforced composite materials in structural applications are often subjected to cyclic loading. Studying the cyclic fatigue behavior of fibers is particularly difficult because of their small diameter (∼10 μm) and high aspect ratio. In this paper, we report results of monotonic tension and tension–tension fatigue behavior of two sol–gel‐derived ceramic fibers: Al2O3–SiO2–B2O3 (Nextel 312) and Al2O3 (Nextel 610). Nextel 312 exhibited a great deal of variability in tensile strength, reflected by a Weibull modulus of 4.6, versus Nextel 610, which had a Weibull modulus of 10.5. Our experiments showed clearly that cyclic loading was more damaging than static loading and, thus, resulted in a lower cyclic fatigue life compared with static loading. The fracture behavior under fatigue loading was distinctly different from that under monotonic loading. It is believed that processing‐induced flaws acted as crack initiation sites, and that the cyclic loading induced subcritical cracking, followed by coalescence of cracks immediately prior to failure.
Formation of BaCrO4 NanoCrystallites within Thermally Evaporated Sodium Bis‐2‐Ethylhexyl‐Sulfosuccinate and Stearic Acid Thin Films
Authors: Rautaray Debabrata , Sinha Kaustav , Sainkar Sudhakar R. , Pasricha Renu , Pavaskar Neela R. , Sastry Murali
Published: July 2010

This paper describes the growth of barium chromate (BaCrO4) nanocrystallites within thermally evaporated thin films of stearic acid (StA) and sodium bis‐2‐ethylhexyl‐sulfosuccinate by a process of Ba2+ ion entrapment followed by in situ reaction with CrO42− ions. Dense spherical assemblies of BaCrO4 nanocrystallites of very uniform size (∼50 nm) were obtained within the two different host matrices. The spherical assemblies were composed of smaller (ca. 5–10 nm size) BaCrO4 crystals indicating that efficient size control over crystal size may be exercised by the matrix. Contact angle measurements of the BaCrO4–StA and BaCrO4–sodium bis‐2‐ethylhexyl‐sulfosuccinate films indicated that they were hydrophobic, thus pointing to the possible role of hydrophobic interaction between the StA and sodium bis‐2‐ethylhexyl‐sulfosuccinate monolayer‐covered BaCrO4 crystals in the assembly process.
Pressure‐Assisted Combustion Synthesis of Dense Layered Ti3AlC2 and its Mechanical Properties
Authors: Khoptiar Yuri , Gotman Irena , Gutmanas Elazar Y.
Published: July 2010

A near‐single‐phase Ti3AlC2 ternary carbide was synthesized from 3Ti–1.1Al–1.8C powder blend, both by the wave propagation and thermal explosion (TE) modes of self‐propagating high‐temperature synthesis. The application of a moderate (28 MPa) pressure immediately after TE at 800°C (reactive forging) yielded a 95% dense material containing, in addition to Ti3AlC2, an appreciable amount of TiC1−x. By adjusting the starting composition, a 99% dense material containing up to 90 vol.% Ti3AlC2 was obtained. The material had a fine‐layered microstructure with Ti3AlC2 grain size not exceeding 10 μm. The samples were readily machinable and had a high compressive strength of ∼800 MPa up to 700°C.
Sonochemical Preparation of PbTiO3 Fine Powders
Authors: Wang Junzhong , Hu Yuan , Liu Jie , Chen Zuyao
Published: July 2010

The sonochemical preparation of PbTiO3 fine powders with lead acetate trihydrate and tetrabutyl titanate as precursors is reported in this paper. Narrow size distribution (40–60 nm) of gel‐derived PbTiO3 nanocrystallites at 520°C was revealed by transmission electron microscopy. The preparation processings with ultrasonic irradiation and a control test without ultrasonic irradiation for comparison were investigated. Results of phase evolution, microstructure, and thermal analysis of gels were characterized and discussed between the control test and the ultrasonic preparations. Acoustic cavitation exerted an important influence on nucleation, gelation, and homogenization of as‐prepared gel, which contributed to the evolution of the resulting gel on further heat treatment. The sonochemical gel was detected to crystallize at temperature, as low as about 410°C, which was confirmed by X‐ray powder diffraction and thermogravimetric analysis and differential thermal analysis (TGA–DTA).
Zircon Formation from Nanosized Powders Obtained by a Reverse Micelle Process
Authors: Tartaj Pedro
Published: July 2010

Dense zircon (ZrSiO4) bodies composed of equiaxed grains have been obtained from uniform nanosized powder compacts. The nanosized powders (20 nm in diameter) were prepared by the controlled hydrolysis with ammonium hydroxide of zirconyl chloride and tetraethoxysilane within reverse micelle nanocavities. The crystallochemical characteristics of the as‐prepared powders and their thermal evolution up to the formation of the thermodynamically stable ZrSiO4 were also examined.
Thermodynamic Modeling of Alkali Metal Oxide‐Silica Binary Melts
Authors: Romero‐Serrano Antonio , Gomez‐Yañez Carlos , Hallen‐Lopez Manuel , Araujo‐Osorio Jorge
Published: July 2010

The evaluation of the thermodynamic properties as well as the phase diagrams for the binary Na2O–SiO2, K2O–SiO2, and Li2O–SiO2 systems are carried out with a structural model for silicate melts and glasses. This thermodynamic model is based on the assumption that each metallic oxide produces the depolymerization reaction of silica network with a characteristic free‐energy change. A least squares optimization program permits all available thermodynamic and phase diagram data to be optimized simultaneously. In this manner, data for these binary systems have been analyzed and represented with a small number of parameters. The resulting equations represent the thermodynamic and phase diagram data for these alkali metal oxide–silica systems within experimental error limits. In particular, the measured limiting liquidus slope at

is well reproduced.
Tribological Behavior of Mo5Si3‐Particle‐Reinforced Silicon Nitride Composites
Authors: Iizuka Tateoki , Kita Hideki
Published: July 2010

The tribological behavior of Mo5Si3‐particle‐reinforced silicon nitride (Si3N4) composites was investigated by pin‐on‐plate wear testing under dry conditions. The friction coefficient of the Mo5Si3–Si3N4 composites and Si3N4 essentially decreased slowly with the sliding distance, but showed sudden increase for several times during the wear testing. The average friction coefficient of the Si3N4 decreased with the incorporation of submicrometer‐sized Mo5Si3 particles and also as the content of Mo5Si3 particles increased. When the Mo5Si3–Si3N4 composites were oxidized at 700°C in air, solid‐lubricant MoO3 particles were generated on the surface layer. Oxidized Mo5Si3–Si3N4 composites showed self‐lubricating behavior, and the average friction coefficient and wear rate of the oxidized 2.8 wt% Mo5Si3–Si3N4 composite were 0.43 and 0.72 × 10−5 mm3 (N·m)−1, respectively. Both values were ∼30% lower than those for the Si3N4 tested in an identical manner.
A ZrO2 (3Y) Matrix Composite Toughened with Fe3Al Intermetallic
Authors: Li Jia , Yin Yan‐Sheng , Tan Xun‐Yan , Zhang Jin‐De
Published: July 2010

Near fully dense ZrO2(3Y)/Fe3Al composites with significantly improved fracture toughness were synthesized by hot‐press sintering at 1350°C. High fracture toughness and bending‐strength values, 36 MPa·m1/2 and 1321 MPa, respectively, were achieved in 40 vol% Fe3Al composite ceramics, whereas those same values for ZrO2(3Y) alone were 10 MPa·m1/2 and 988 MPa, respectively. Microscopic observation of the crack path revealed that Fe3Al particle uniformly dispersed in the matrix have obvious crack‐bridging effect. Improved thermal‐shock resistance was also obtained, which was attributed to higher toughness, thermal conductivity, and lower Young's modulus by adding of Fe3Al particles.
Dry Sliding Wear Behavior of Al2O3–SiC Submicro‐ and Nano‐Composites
Authors: Guicciardi Stefano , Sciti Diletta , Melandri Cesare , Bellosi Alida
Published: July 2010

The wear behavior of a pure alumina matrix and two Al2O3‐based composites, one with 5 vol% SiC nanosized particles (mean size 52 nm) and the other with 5 vol% SiC sub‐microsized particles (mean size 230 nm), was studied in two different experimental conditions corresponding to mild and severe wear regime, respectively. Whether considering the friction or the wear resistance, in the mild regime no difference was observed among the materials. In the severe regime, the composites performed much better than the matrix alone due to stronger grain boundaries. The SiC particle size had no influence on the mean wear resistance.
Numerical Simulation of Anisotropic Shrinkage in a 2D Compact of Elongated Particles
Authors: Tikare Veena , Braginsky Michael , Olevsky Eugene , Johnson D. Lynn
Published: July 2010

Microstructural evolution during simple solid‐state sintering of two‐dimensional compacts of elongated particles packed in different arrangements was simulated using a kinetic, Monte Carlo model. The model used simulates curvature‐driven grain growth, pore migration by surface diffusion, vacancy formation, diffusion along grain boundaries, and annihilation. Only the shape of the particles was anisotropic; all other extensive thermodynamic and kinetic properties such as surface energies and diffusivities were isotropic. We verified our model by simulating sintering in the analytically tractable cases of simple‐packed and close‐packed, elongated particles and comparing the shrinkage rate anisotropies with those predicted analytically. Once our model was verified, we used it to simulate sintering in a powder compact of aligned, elongated particles of arbitrary size and shape to gain an understanding of differential shrinkage. Anisotropic shrinkage occurred in all compacts with aligned, elongated particles. However, the direction of higher shrinkage was in some cases along the direction of elongation and in other cases in the perpendicular direction, depending on the details of the powder compact. In compacts of simple‐packed, mono‐sized, elongated particles, shrinkage was higher in the direction of elongation. In compacts of close‐packed, mono‐sized, elongated particles and of elongated particles with a size and shape distribution, the shrinkage was lower in the direction of elongation. The results of these simulations are analyzed, and the implication of these results is discussed.
Positron Annihilation Lifetime Spectroscopy of Air‐Fired Ca(1−x)(La)xTiO3 Perovskites
Authors: Hadley J. H. , Hsu F. H. , Vance E. R. , Begg B. D.
Published: July 2010

In polycrystalline air‐fired perovskites of Ca(1−x)(La)xTiO3 stoichiometry (x=0.00–0.15), the positron annihilation lifetime increased monotonically with x, and showed an ∼40% increase of the lifetime at x∼0.1, at which value the lifetime increase saturated. These data, together with measured perovskite stoichiometry, indicate that equal numbers of Ca and Ti vacancies were the prime charge compensators. Thermal gravimetric data are consistent with charge compensation occurring via the cation vacancies in the air‐fired samples and Ti3+ in equivalent samples prepared under reducing conditions.
Synthesis of Uniform Titanium Nitride Nanocrystalline Powders via a Reduction–Hydrogenation–Dehydrogenation–Nitridation Route
Authors: Guo Qixun , Xie Yi , Wang Xinjun , Lv Shichang , Hou Tao , Bai Chuannan
Published: July 2010

A novel reaction of TiCl4and NaNH2at 450°–500°C for 12–24 h was performed for the preparation of TiN nanocrystalline powders. Powder XRD patterns indicated that the as‐synthesized powder was cubic‐phase TiN with a lattice constanta=4.225 Å. Transmission electron microscopy images showed that the TiN powders consisted of uniform particles with an average diameter of 10–20 nm. The binding energies of Ti2p3/2and N1s core levels at the position of 455.50 and 396.96 eV, respectively, were detected by X‐ray photoelectron spectra. Four peaks, related to transverse acoustic, longitudinal acoustic, second‐order acoustic, and transverse optical (TO) modes of TiN, respectively, were observed in the Raman spectra of TiN particles. A very reasonable formation mechanism of TiN nanocrystalline powders was proposed.
Powder XRD, SEM, and Multinuclear MAS‐NMR Investigations of the Interactions Between Glass and Crystalline Phases of Li, Na, or K Ceramic Waste Forms
Authors: Lambregts Marsha J. , Frank Steven M.
Published: July 2010

Interactions between the glass and crystalline phases of ceramic waste forms were investigated via powder X‐ray diffraction, scanning electron microscopy, and 29Si, 27Al, 23Na, 7Li, and 35Cl magic angle spinning nuclear magnetic resonance spectroscopy. LiCl, NaCl, or KCl waste form samples were made with or without glass. The waste forms containing glass consist of sodalite and glass phases with minor amounts of nepheline. Samples without glass form varying amounts of sodalite and nepheline. The glass frit, intended to bind the zeolite particles together, changes in composition, showing marked increases in aluminum and alkali content.
Fabrication of a Continuously Oriented Porous Al2O3 Body and Its In Vitro Study
Authors: Lee Byong‐Taek , Kang In‐Cheol , Cho Soon‐Hee , Song Ho‐Yeon
Published: July 2010

Continuously oriented porous Al2O3 bodies were fabricated by a multi‐pass extrusion process using C powders and ethylene vinyl acetate as an agent for pore forming and as a binder, respectively. The main pore size can be easily controlled by increasing the number of extrusion passes. The edges of the pore frame showed a rough surface having many fine pores about 0.2–1 μm in size. In the continuously porous Al2O3 bodies having 150 μm pore size, the values of the relative density and bending strength were about 63% and 90 MPa, respectively. These values were higher than those of an Al2O3 porous body made by a common process. From the in vitro study using human osteoblast‐like MG‐63 cells, it was confirmed that the cells grew well and adhered to the top surface and inside pores, as well as the outside wall of the continuously porous Al2O3 body. Without the directionality, the cells showed some spindle‐shaped, three‐dimensional, and network‐type structures.
Electrical Conduction in Nano‐Structured La0.9Sr0.1Al0.85Co0.05Mg0.1O3 Perovskite Oxide
Authors: Basu Santanu , Chakraborty Amitava , Sujatha Devi Parukuttyamma , Sekhar Maiti Himadri
Published: July 2010

Nanocrystalline La0.9Sr0.1Al0.85Co0.05Mg0.1O3 oxide powder was synthesized by a citrate–nitrate auto‐ignition process and characterized by thermal analysis, X‐ray diffraction, and impedance spectroscopy measurements. Nanocrystalline (50–100 nm) powder with perovskite structure could be produced at 900°C by this process. The powder could be sintered to a density more than 96% of the theoretical density at 1550°C. Impedance measurements on the sintered samples unequivocally established the potential of this process in developing nanostructured lanthanum aluminate‐based oxides. The sintered La0.9Sr0.1Al0.85Co0.05Mg0.1O3 sample exhibited a conductivity of 2.40 × 10−2 S/cm in air at 1000°C compared with 4.9 × 10−3 S/cm exhibited by La0.9Sr0.1Al0.85Mg0.15O3.
High‐Temperature Stiffness and Damping Measurements to Monitor the Glassy Intergranular Phase in Liquid‐Phase‐Sintered Silicon Carbides
Authors: Roebben Gert , Van der Biest Omer , Sciti Diletta , Bellosi Alida , Sarbu Corneliu , Lauwagie Tom
Published: July 2010

Detailed stiffness and internal friction (Q−1) versus temperature curves were obtained for liquid‐phase‐sintered silicon carbides using advanced resonant beam analysis up to 1400°C. As‐sintered materials display a stableQ−1‐peak near 1100°C, superimposed on an increasing background. The change of stiffness associated with the damping peak is quantitatively related to the amount of matter in pockets of the amorphous intergranular phase in which the refractory SiC matrix grains are embedded. The successful removal of the amorphous pockets by annealing at 1900°C is deduced from the disappearance of the damping peak and confirmed with transmission electron microscopy.
A Mathematical Description of the Kinetics of the Electrophoretic Deposition Process for Al2O3‐Based Suspensions
Authors: Anné Guy , Vanmeensel Kim , Vleugels Jef , Van der Biest Omer
Published: July 2010

The yield during electrophoretic deposition is modeled incorporating the changing electric field over the suspension, due to a potential drop over the growing deposit, assessed from on‐line measurements of the current flowing through the deposition cell and the conductivity of the suspension during electrophoretic deposition. The kinetic model is validated for Al2O3 suspensions with different powder loads based on methylethylketone with n‐butylamine and ethanol with polyethyleneimine or HNO3, suspensions with, respectively, a constant and a decreasing electric field during deposition. The need for a powder concentration correction, even at volume fractions down to 0.03, and the incorporation of a changing electric field is experimentally proven to be essential in order to describe the deposition yield more accurately than predicted from the Hamaker equation.
Processing and Properties of ZrO2‐Containing Reaction‐Bonded Aluminum Oxide with High Initial Aluminum Contents
Authors: Sheedy Paul M. , Caram Hugo S. , Chan Helen M. , Harmer Martin P.
Published: July 2010

The reaction‐bonded aluminum oxide (RBAO) process relies upon the oxidation of Al/Al2O3 powder compacts, and many of its associated advantages stem from the presence of the aluminum in the green powder. Higher aluminum contents in the starting powders allow for higher green strengths, densities, and lower overall shrinkage, all while producing a fine‐grained, high‐strength sintered material. However, it is evident that the reaction and sintering of ZrO2‐containing RBAO with higher aluminum contents are more challenging. Therefore, in this study, the effects of aluminum content on the processing, structure, and properties of RBAO ceramics were comprehensively characterized. It was found that RBAO samples with high aluminum contents were more prone to cracking during reaction and even when successfully fired were not able to be sintered to full density. Despite these characteristics, RBAO samples with increasing aluminum contents showed no significant degradation in mechanical properties.
Functionality Diagrams for Hybrid Mechanical Seals with Silicon Nitride Rings
Authors: Carrapichano João M. , Oliveira Filipe J. , Silva Rui F. , Gomes José R.
Published: July 2010

Ring‐on‐ring tribological experiments were performed with hybrid mechanical seals with silicon nitride (Si3N4) rings. The K×PV product, where K is the wear coefficient, P the sealing pressure, and V the linear speed, is proposed as a novel parameter to characterize the total working range of a mechanical seal system, with the advantage of directly indicating the thickness reduction for a certain time of service. The K×PV criterion is represented in a map form called “functionality diagram.” The rotary Si3N4 rings show the better behavior (K×PV=0.05 μm/h) against WC–Co mating faces.
Correlation Between Grain‐Boundary Segregation and Grain‐Boundary Plane Orientation in Nb‐Doped TiO2
Authors: Pang Ying , Wynblatt Paul
Published: July 2010

Grain‐boundary (GB) segregation has been measured in Nb‐doped TiO2 (rutile) by Auger electron spectroscopy analyses of the two surfaces exposed by inter‐granular fracture. In addition, the orientations of the exposed GB planes on both sides of the fracture surface have been determined. A strong anisotropy of GB composition is found. Measurements on 166 individual GB fracture surfaces show that boundary planes with low and high levels of segregation tend to be clustered along the (110)–(010) and (001)–(011) regions of the stereographic triangle, respectively. The matching halves of GB planes with either high or low segregation also tend to be terminated by planes in the same respective regions of orientation space. High and low levels of segregation occur in regions of GB plane orientation space estimated to correspond to high and low GB energy, respectively. This trend is consistent with qualitative arguments based on Gibbsian adsorption.
Effect of Metallization on the Lifetime Prediction of Mechanically Stressed Low‐Temperature Co‐Fired Ceramics Multilayers
Authors: Dannheim Henning , Roosen Andreas , Schmid Ulrich
Published: July 2010

Multilayer ceramics based on Low‐Temperature Co‐fired Ceramics (LTCC) are gaining increasing interest in the manufacturing of high‐integrated devices for microelectronic and sensor applications. In many applications the parts are exposed to mechanical stresses, which is an important issue regarding the reliability of the device. To predict the lifetime of LTCC multilayer devices, and to extend their application range, basic mechanical data of this material are needed. In this paper metallized LTCC multilayers are investigated concerning their flexural strength, crack growth rate, and lifetime prediction. The results show that the electronic layout concerning the location of vias and metallization has a strong influence on the reliability and lifetime prediction of such co‐fired LTCC devices. Mass flow sensors for the measurement of injected fuel quantities, which were fabricated on the basis of LTCC and which are exposed to a stress level of 100 MPa, achieve sufficient lifetimes. Therefore, LTCC is an interesting material to fabricate devices, in which LTCC fulfils the requirements of a functional and structural material.
Stress Concentrations and Notch Sensitivity in Woven Ceramic Matrix Composites Containing a Circular Hole—An Experimental, Analytical, and Finite Element Study
Authors: Haque Anwarul , Ahmed Laboni , Ramasetty Arun
Published: July 2010

In this paper, the stress concentrations associated with a circular hole and subjected to uniform tensile loading in woven ceramic matrix composites (CMCs) have been determined experimentally through strain gauge measurements. The stress concentrations were calculated from the measured strain distributions surrounding the holes during the initial loading period. Then, the load‐carrying capacity of notched CMCs with various hole radius to width ratios (a/w) has been determined. The objective is to study the stress concentrations due to circular notch, and then evaluate the notch sensitivity in woven CMCs. Both quasi‐isotropic [0/90/+45/−45]s and cross‐ply [0/90/0/90]s laminates of woven SiC/SiNC composites were considered. The experimental data of stress concentrations were compared with the results obtained from a complex variable method and finite element analysis. The notched strength data were also analyzed on the basis of some existing theories. The results show significant stress concentrations in the range of 3.75–4.75 near the notch edges during the early stage of loading. But in most cases, the notched strength data show notch insensitivity in CMCs, particularly with small hole diameters. This occurs mostly due to stress redistribution effects during inelastic deformation in ceramic matrix composites. The degree of notch insensitivity in CMCs is observed to decrease with comparatively larger diameter holes. For notch insensitivity, the limiting value of a dimensionless parameter n, comprising of fracture toughness, un‐notched strength, and width of the specimen, has been determined on the basis of existing notch sensitivity theories. The stress concentration factors are seen not to be influenced by the lay‐up sequence of the laminate. Reasonable agreement was observed between the theory and experimentally determined stress concentration factors, particularly for small hole diameters.
Modeling the Influence of Reactive Elements on the Work of Adhesion between Oxides and Metal Alloys
Authors: Bennett I. J. , Kranenburg J. M. , Sloof W. G.
Published: July 2010

A method is presented that allows determination of the work of adhesion between oxides and metals using a macroscopic atom model. The method allows complex interfaces to be modeled easily and the influence of additives and impurities to be assessed. The model is used to study the work of adhesion between α‐Al2O3 and β‐NiAl. This interface is of importance for the performance of thermal barrier coatings as applied to jet turbines. The model shows that the work of adhesion is not significantly altered by so‐called reactive element additions. Reactive elements are known to improve the durability at the alloy/oxide interface and include elements such as Zr, Y, and Hf added in concentrations of less than 1 at.%. A significant weakening of the interface is predicted when impurities such as sulfur and carbon are present. The model also predicts a large interaction enthalpy between the reactive elements and impurities. It is proposed that the primary effect of reactive element additions is impurity scavenging. The impurities are fixed in the bulk of the alloy by the reactive elements and cannot diffuse to the oxide/metal interface to weaken it.