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Dense, uniform and crack-free mullite (3Al 2 O 3 ·2SiO 2 ) coatings were deposited on SiC by chemical vapor deposition. The coatings were compositionally graded, with the Al/Si ratio increasing towards the outer surface of the coatings for improved corrosion resistance. The coatings were found to start out as a nanocrystalline layer, which is an intimate mixture of γ-Al 2 O 3 nanocrystallites imbedded in a vitreous silica-rich matrix at the substrate/coating interface. Mullite grains nucleated when the surface composition of the growing coating was in a narrow range close to that of stoichiometric mullite. The phase transformations occurring in these coatings during high-temperature anneals in the range 1100–1400 °C were studied. These phase transformations, which include a tetragonal-to-orthorhombic transformation, mullitization and devitrification of silica in the nanocrystalline layer, and α-alumina precipitation and twinning of the alumina-rich mullite, are discussed in light of the adhesion and corrosion resistance of the coatings.

Dense, uniform, and adherent chemically vapor-deposited mullite coatings were deposited on SiC substrates using the AlCl3–SiCl4–H2–CO2 system. Typical coating morphology consisted of a thin interfacial layer of γ–Al2O3 nanocrystallites embedded within a vitreous SiO2-based matrix. When a critical Al/Si ratio of 3.2 ± 0.29 was reached within this nanocrystalline layer, mullite crystals nucleated and grew as columnar grains. The thickness of the nanocrystalline layer decreased as the input AlCl3/SiCl4 ratio was increased. In all cases, the Al/Si composition in the coating increased from the coating/substrate interface to the coating surface. Critical factors leading to the nucleation and growth of mullite crystals are discussed in this article.

Dense, uniform, mullite coatings have been deposited by chemical vapor deposition on SiC substrates, using a AlCl3-SiCl4-CO2-H2 system. The typical coating microstructure consisted of a thin layer of nanocrystallites of γ-Al2O3 in vitreous silica at the coating-substrate interface, with columnar mullite grains over this interfacial layer. The composition of the coating was graded such that the outer surface of the coating was highly alumina rich. The changes in the coating microstructure with processing parameters are discussed. The ability of mullite to incorporate such large composition variations is discussed in the light of vacancy formation as theAl/Si ratio is increased and the ordering of these vacancies leads to changes in lattice parameters. The formation of domains was studied by measuring the spacing of superlattice spots in electron diffraction patterns and the relationship between domain size andAl/Si ratio is discussed.

Dense mullite coatings have been deposited on SiC and Si 3 N 4 substrates by chemical vapor deposition (CVD). The coatings were compositionally graded with the Al/Si ratio increasing from 1.5 at the substrate/coating interface, to a value of 8 at the coating surface. This gradation of composition is discussed in light of changes in the concentration of oxygen vacancies, ordering of the vacancies, formation and size of domains and the observed changes in lattice parameters.

Quantitative modeling of oxygen tracer (18O) concentration profiles obtained during double oxidation experiments has been carried out. An existing model in the literature, involving combined grain‐boundary and lattice diffusion of oxygen with exchange, has been extended to cases where the grain size of the oxide is allowed to vary over its thickness. The model predicts tracer profiles in the entire oxide for the case of scale growth by inward oxygen diffusion. A computer program has been developed along with a graphical user interface for easy generation and visualization of simulated tracer profiles. The sensitivity of the simulated profiles to variations in volume (Dv) and grain‐boundary (Db) diffusivities of oxygen in the oxide scale as well as the oxide grain‐size variation have been studied. The results indicate that the normalized tracer profiles are sensitive to variations in Db, although to a lesser extent as compared to similar variations in Dv. Also, incorporation of variable grain size leads to profiles very different from those obtained from a constant oxide grain‐size assumption. The computer program has been used to fit an experimental profile reported in the literature to obtain values of Dv and Db.

The surfaces of [001] SrTiO 3 substrates were modified by implantation of 400 keV Ne 2+ ions at 77 K at doses of 5 × 10 14 , 10 15 and 5 × 10 15 ions / cm 2 . Superconducting YBa 2 Cu 3 O 7 − x thin films were then deposited on these substrates by the electron beam co-evaporation and post-annealing process. The microstructure and properties of these films were characterized by various techniques and compared to a reference film that was grown on an unirradiated SrTiO 3 substrate. The film on the substrate irradiated at the highest dose (5 × 10 16 ions / cm 2 ) showed a deterioration of its properties as reflected by a loss in epitaxy, decrease in transition temperature and increase in transition width. However, films grown on the substrates irradiated at the lower doses showed improvements in the properties as compared to the reference film. The best film was obtained on the substrate irradiated at 10 15 ions/cm 2 . This film exhibited a significant improvement in epitaxy and an increase in the transition temperature as compared to the reference film.

Austenitic Fe-18Cr-20Ni-1.5Mn alloys containing 0, 0.6, and 1.5 wt.% Si were produced both by conventional and rapid solidification processing. The cyclic oxidation resistance of these alloys was studied at 900°C in a SO 2-O 2 gas mixture to elucidate the role of alloy microstructure and Si content on oxidation properties in bioxidant atmospheres. All the large-grained, conventionally processed alloys exhibited breakaway oxidation during cyclic oxidation due to their poor rehealing characteristics. The rapidly solidified, fine-grained alloys that contained less than 1.5 wt.% Si exhibited very protective oxidation behavior. There was considerable evidence of sulfur penetration through the protective chromia scale. The rapidly solidified alloys that contained 1.5 wt.% Si underwent repeated scale spallation that led to breakaway oxidation behavior. The scale spallation was attributed to the formation of an extensive silica sublayer in the presence of sulfur in the atmosphere.

Irradiation effects on thin foils of bulk YBa2Cu3O7−x have been studied in a transmission electron microscope using 100‐, 150‐, 200‐, 250‐, and 300‐keV electrons at 83 and 300 K. The disordering of the oxygen atoms and vacancies in the O(4) and O(5) sites in the Cu‐O planes during irradiation was monitored by measuring the splitting of the (110) diffraction spots in the [001] diffraction pattern. The results show that YBa2Cu3O7−x is insensitive to 100‐keV electron irradiation. Irradiation by higher‐energy electrons leads to irradiation‐induced oxygen disordering of the oxygen atoms and vacancies, mainly by single displacement events. The excellent fit of the data to a disordering model suggests that the displacement threshold energy for oxygen in YBa2Cu3O7−x is around 18 eV and that irradiation‐assisted oxygen reordering occurs in YBa2Cu3O7−x at 300 K, but not at 83 K.

A two-stage intercritical annealing treatment has been attempted to develop dual-phase structure and properties in a commercial grade microalloyed steel containing Nb and V. Manganese concentration in austenite enhanced the hardenability which attributes to martensite formation on air cooling after annealing. The volume fraction of martensite and the manganese distribution were found to depend on both annealing time and temperature. Different morphologies of martensite were identified for various intercritical annealing conditions, e.g. dispersed type, ring type, acicular type. The tensile data and behaviour confirmed the dual-phase characteristics in the microalloyed steel.

Functionally graded mullite coatings have been deposited on flat SiC substrates and on SiC fibers by chemical vapor deposition. The composition of the coating was varied from near-stoichiometric mullite (3Al 2 O 3 2SiO 2 )at the coating/substrate interface to approximately i-Al 2 O 3 , a derivative of the mullite structure in which all Si had been replaced by Al, at the coating surface. These mullite coatings were adherent on thermal cycling and exhibited excellent high temperature oxidation and hot corrosion resistance. Mullite has a close CTE match with SiC, accounting for superior coating adhesion, while the coating surface in contact with aggressive environments was virtually Si-free, accounting for improved hot-corrosion resistance.

A laser‐based ultrasonic system is used to measure the mechanical properties and thickness of mullite environmental barrier coatings deposited on SiC substrates. Narrow‐band surface acoustic waves (SAWs) are generated with an amplitude modulated laser source, and a photorefractive crystal based interferometer coupled to a lock‐in amplifier is used to detect the resulting surface displacement. The complex displacement field is mapped over a source‐to‐receiver distance of approximately 500 μm in order to extract the wavelength of the SAW at a given excitation frequency, from which the phase velocity is determined. Dispersion curves measured over a frequency range of 100–180 MHz are used to extract mean values for the elastic modulus and thickness of the coating over the measurement region. These values are compared to the mean elastic modulus and thickness of the coating measured using nanoindentation and optical microscopy, respectively. It is shown that porosity in the substrate can have a significant impact on the experimental results, particularly over short measurement distances. Experiments on SiC with 1–4% porosity show a linear increase of the mean SAW velocity with decreasing porosity. Additionally, measurements made on a sample with a given bulk porosity indicate that the SAW velocity varies locally, leading to additional error in the measurement of coating properties. This error can be reduced through spatially averaging the velocity measurements.

A combination of laser‐based ultrasonic (LBU) inspection and nanoindentation testing is used to evaluate the thickness uniformity and through‐thickness mechanical property distributions in 5–20 μm thick CVD environmental barrier coatings. Mullite (3Al2O3⋅2SiO2) coatings grown on silicon carbide substrates are studied in order to provide feedback on the growth process under a range of operating conditions. Nanoindentation tests are performed on polished coating cross sections, and the depth dependence of the elastic modulus of each coating is found. In the LBU experiments, a modulated continuous wave (CW) source is used for surface wave generation. The source is held at a fixed temporal frequency as it is scanned over the surface of the coating. At each temporal frequency of interest, the spatial frequencies of the acoustic modes are found, allowing for phase velocities to be determined. The mean values of elastic moduli found using the LBU approach compare well with the nanoindentation results.

Functionally graded mullite (3Al2O3.2SiO2) coatings were deposited on SiC substrates by Chemical Vapor Deposition (CVD) using the AlCl3-SiCl4-CO2-H2 system. It was found that due to preferential adsorption, coatings on SiC started off being Si-rich, while coatings on alumina substrates started out being Al-rich. In either case, if the coating composition was not close to stoichiometric mullite, the microstructure consisted ofg-Al2O3 nanocrystallites imbedded in a vitreous SiO2-rich matrix (nanocrystalline microstructure). On grading the composition, mullite grains nucleated when the composition of the growing nanocrystalline coatings reached a narrow surface composition range of Al/Si molar ratio of 2.9-3.4. Once nucleated, columnar mullite grains could be graded to highly nonstoichiometric Al-rich compositions. However, if the nucleated mullite grains were graded to be Si-rich, the mullite structure could not be sustained, and the coating reverted back to the nanocrystalline microstructure. This phenomenon is explained on the basis of the linkage of coordination polyhedra in the atomic structure of mullite.

The retrospective data on childhood poisoning from eight regional hospitals in India has been reviewed. The demographic features and types of poisonings encountered have been compared. The analysis of the data indicated that pediatric poisonings constituted 0.23-3.3% of the total poisoning. The mortality ranged from 0.64-11.6% with highest being from Shimla. Accidental poisoning was common involving 50-90% of children below 5 years of age and males outnumbered the females. Suicidal poisoning was seen after 13 years of age and was due to drugs and household chemicals. One of the hospitals in Delhi recorded a very high incidence (66.6%) of drug poisoning in children. The drugs consumed belonged to phenothiazines, antiepileptics and antipyretics. Iron poisoning was seen in younger children. Kerosene was one of the causes of accidental poisoning at all hospitals except Shimla and rural Maharashtra were probably wood charcoal is widely used. Pesticide poisoning was more prevalent in Punjab and West Bengal whereas plant poisoning was very common in Shimla. Significant number of snake envenomation has been recorded from rural Maharashtra. Other less common accidental poisonings in children included alcohol, corrosives, heavy metals, rodenticides, detergents and disinfectants. Thus various regions in the country showed some variation in types and frequency of childhood poisoning which could be attributed to different geographical and socio-economic background. Language: en

The authors evaluated nursing home residents with a prior history of hip fracture for osteopenia and its risk factors, and attempted to learn to what extent the residents' bone status had been considered by their primary care physicians. Thirty-one hip fracture residents in the Milwaukee VA nursing home were studied to determine their status with regard to bone mineral density of the proximal femur, and the following risk factors or predictors of osteopenia: history of smoking; history of fractures; calcium and vitamin D intake; underweight; immobility; hypogonadism; and administration of drugs that may accelerate bone demineralization. Data were also collected on the evaluation and management of the post hip fracture residents in three other nursing homes. In the Milwaukee nursing home, out of 31 hip fracture survivors, 74% had sustained a hip fracture before admission to the nursing home; 29% had a history of second fracture. In 84% of patients, there was no mention of osteopenia in the active medical problem list and, therefore, there was no intervention plan in place to improve or prevent further bone loss. Thirty-two percent were underweight, 36% were currently smoking, 55% were immobile, 64% were consuming at least one medication that might increase bone loss, calcium intake was less than 1,000 mg daily in 52%, and 66% were hypogonadal (serum testosterone level less than 300 ng/dL). Chart reviews of the hip fracture survivors at three other nursing homes revealed similar findings. Approximately 5-15% of nursing home residents are hip fracture survivors. They usually have severe osteopenia and multiple risk factors for further bone loss and future fractures.(ABSTRACT TRUNCATED AT 250 WORDS)

Mullite (3Al2O3.2SiO2) is an ideal candidate for coatings on SiC due to its toughness, corrosion resistance and coefficient of thermal expansion (CTE) match. We have deposited alternating layers of Al2O3 and SiO2 followed by post deposition heat treatment to induce mullite formation at the interface. We found that the devitrification of silica to cristobalite led to spallation of the multilayered coatings due to the fracture within the crystalline silica layers. To understand this transformation better, we studied the effect of pressure and temperature on devitrification of silica in both bulk and in coating form. We have demonstrated that the difference in specific volumes of the two phases plays a key role in the vitreous to crystalline transformation in silica.

We report on the rapid thermal processing (RTP) of YBa2Cu3O7 (Y-123) fibers. Unsintered fibers are densified by RTP. We show that fibers which were originally semiconducting and tetragonal before RTP form normal twinned orthorhombic material after processing for 2–4 seconds above 1000°C with a 3 min. cool down in oxygen. They subsequently show Tc to 90K and magnetization indicative of substantially shielding. We present the effects of varying the RTP parameters on the morphology, phase, and superconducting properties of a number of tetragonal and orthorhombic Y-123 fibers.

The mechanisms and kinetics of forming misfit dislocations in heteroepitaxial films are studied. The critical thickness for misfit dislocation formation can be found by considering the incremental extension of a misfit dislocation by the movement of a “threading” dislocation segment that extends from the film/substrate interface to the free surface of the film. This same mechanism allows one to examine the kinetics of dislocation motion and to illuminate the importance of dislocation nucleation and multiplication in strain relaxation. The effects of unstrained epitaxial capping layers on these processes are also considered. The major effects of such capping layers are to inhibit dislocation nucleation and multiplication. The effect of the capping layer on the velocity of the “threading” dislocation is shown to be small by comparison. A new substrate curvature technique for measuring the strain and studying the kinetics of strain relaxation in heteroepitaxial films is also briefly described.

A 900 Å as-deposited multilayered structure of alternating Fe and Ti on hardened tool steel has been examined for tribological and mechanical properties. The multilayer in contact with a 52100 steel ball counter surface possessed a 0.16 friction coefficient and showed good wear character after 1000 cycles in pin-on-disk experiments. Nanoindentation experiments show a 20 % increase in hardness for material in the wear track. Electron microscopy data suggests that the as-deposited bcc-Fe plus hcp-Ti multilayer composite transforms to a nanocrystalline alloy plus bcc-Fe by solid state reaction during pin-on-disk friction and wear test. The low friction observed in these surface films is attributed to the formation of a hard nanocrystalline alloy and improved interlayer and film/substrate adhesion which result during solid state reaction.

The microstructure of YBa2Cu3O7−x thin films grown on (001) SrTiO3 and LaAlO3 substrates by electron beam co-evaporation and laser ablation techniques have been examined. Examination of a 15000A thick film on SrTiO3 grown by electron beam co-evaporation showed a switchover from c-perpendicular to c-parallel growth at a thickness of around 2000A. Thinner films (1500A thick), grown on SrTiO3 by this technique were found to have a fully c-perpendicular microstructure. However, this required the substrate surface to be not only highly oriented but also microscopically smooth. Formation of surface steps on the substrates due to surface roughness caused c-parallel growth in the films, leading to a deterioration of their properties. In contrast, a 5000A thick film formed by laser ablation on LaAlO3 was found to have a completely c-perpendicular microstructure. The reasons for the development of these microstructures are discussed.

The Interfacial stability of a high strength TiB2/Cu multilayer structure was examined by subjecting the layers to ion irradiation by 400 keV Ne++ ions up to a maximum dose of 12×1015 ions/cm2. Even at the highest dose, with a maximum dpa value of 4.92, the TiB2/Cu interface did not show any mixing. This stability of the multilayers has been explained by examining the maximum thermodynamic driving force for Interfacial reactions in this system.

Oxidation resistance of stainless steels, which rely on the formation of a Cr2O3 (chromia) scale, can be further improved through minor alloying additions such as Al or Si, or by application of coatings to the exposed surfaces. Although, additions of Si to austenitic steels have demonstrated an improvement in oxidation resistance, high Si contents can be detrimental to the mechanical properties of these alloys. The application of a silica coating on the surface of the stainless steel provides improved oxidation resistance without detrimental effects on the mechanical properties. This study examines the effect of the grain size of the stainless steel on the effectiveness of a silica coating as an oxidation barrier.Fully austenitic stainless steel of composition Fe-18(wt%)Cr-20Ni-1.5Mn was produced in both coarsegrained and fine-grained form. The coarse-grained alloy, with a grain size of approximately 100 μm, was produced by casting and hot rolling. The fine-grained alloy, with a grain size of approximately 5 μm, was produced by rapid solidification powder processing, followed by consolidated by hot isostatic pressing and swaging.

A study was carried out on the causes of liquefaction of tamarind kernel (TK) paste used in jute warp sizing. Mill- decomposed pastes, added as inocula to fresh paste, strongly liquefied the latter under aerobic as well as crudely anaerobic conditions. Aerobic bacteria isolated from mill pastes were mostly unable to liquefy, either singly or jointly. On the other hand, 9 of the 11 fungal species tested (some isolated from mill pastes) caused strong liquefaction. The enzymes in the crude filtrates of some of these liquefied TK paste at a faster rate than mineral acids at boil. In laboratory experi ments simulating mill conditions of sizing, these results were generally confirmed, fungal action being much stronger than bacterial. Aspergillus fumigatus and its enzyme were the most potent. Accumulated fungal enzymes appear to be the chief cause of liquefaction in mills. While the strongly liquefying fungi could be inhibited by small doses of common antiseptics, these had little effect on their enzymes. Sodium sulfide at 0.16% concentration inhibited all these enzymes.

Exposure to heat, light, acids and alkalis was found to render jute more resistant to attack by aerobic bacteria. The resistance imparted by the physical agencies appears to be due to the formation of decomposition products, apparently from the non-cellulosic portion, while tho chemical agencies seem to contribute to resistance by removing some micro- and possibly macro-nutrients.

Chaetomium brasiliensis requires aneurin for growth, and calcium (strontium or barium), aneurin and a low nutrient level for the formation of ascospores. Decreasing suboptimal doses of calcium progressively decrease the number of fertile perithecia until none is formed, the average perithecial size is reduced, but not the total number of perithecia. Above the optimum level, calcium delays formation of perithecia and ascospores and, ultimately, spore germination; it has no favourable effect on vegetative growth. The fungus appears able to synthesize aneurin slowly after growth is complete.

The decomposition of jute and cellulose by aerobic bacteria from soil has been investigated. Bacterial decomposition of jute is rapid under aerobic conditions only when the fibre is actually wet. The mean optimum temperature for the growth of these bacteria is near 37°C and the optimum pH is near the neutral region. Jute leached in hot water is more resistant to bacterial attack owing to the removal of micro-nutrients. Lignin is not only the most resistant constituent of jute, but it also offers some protection to the cellulosic fraction of the fibre. Hemicellulose is the most easily assimilable major fraction of jute and its presence also leads to increased consumption of α-cellulose. However, about 25% of the xylan content of jute is as resistant to bacterial attack as the α-cellulose fraction. Jute α-cellulose occupies an intermediate position between cotton α-cellulose and filter paper in susceptibility to attack. Bacterial decomposition of cellulose appears to be favoured by increase in surface and a...

The vertebral abnormalities in this case were limited to the thoracic region. The defect in fusion of the laminae of the fourth thoracic vertebra could not be visualised properly, though was evident clinically. The parents and other siblings of the case did not reveal any abnormality on clinical examination, but they could not be persuaded to have roentgenological investigations, so hereditary influence could not be studied. The deformity was less obvious in infancy but became more apparent as the child grew up.

SUMMARY: The influence of certain carbohydrates, nitrogen compounds and accessory substances on the growth and sporulation of Chaetomium globosum and Memnoniella echinata has been studied. It has been confirmed that M. echinata needs an external supply of biotin, which has also a slight effect on the growth of Chaetomium globosum. For C. globosum, a very low level of soluble sugar in the medium was essential for the production of perithecia. With adequate biotin, Memnoniella echinata sporulated in the presence of considerable concentrations of sugar, but at low biotin levels no sporulation occurred until soluble sugar approached exhaustion. Jute extract stimulated growth and accelerated sporulation of Chaetomium globosum; this was not due to the presence in the extract of any of nine well-known B-group vitamins. Jute extract had no more influence on Memnoniella echinata than would be due to its biotin content.

A case having multiple sagittal cleft or “butter-fly” vertebrae and hemivertebrae is presented. The record of such coincidence of two rare anomalies in one case could not be found in the literature. Roentgenological investigations of parents and siblings could possibly throw some more light on the case.

(1948). FUNGAL DECOMPOSITION OF JUTE FIBRE AND CELLULOSE: Part 2—The Effect of Some Environmental Factors. Journal of the Textile Institute Transactions: Vol. 39, No. 7, pp. T237-T248.

SUMMARY: The effect of temperature and some chemical substances on the fruiting of strains of nine species of Chaetomium was studied. The optimum temperature for fruiting was generally lower than that for growth. Micro-nutrients of the nature of growth factors and starvation with respect to nutrients may both stimulate fruiting, whereas staling inhibits it, the ultimate balance between these effects determining the fruiting behaviour of a given species. These factors had no significant effect on the final amount of the vegetative growth within the conditions of the experiments.

Fifty cases of acquired hemiplegias in infancy and childhood have been studied. No definite cause could be found in 29 cases but in 16 others, there was a strong possibility that tuberculosis might have played a significant role in the causation of their hemiplegia. Appropriate investigations to exclude tuberculosis, therefore, appear rational in all cases of acquired hemiplegias in infancy and childhood in places where tuberculosis is highly prevalent.

Fifty-eight cases of non-traumatic paraplegia of the upper motor neurone type in children have been reviewed. Myelitis was found to be the most frequent cause, followed by tuberculosis of the spine in this series.

Fertilizer Promotion and Agricultural Research Division, H. F. C. Ltd., Sindri Indian School of Mines, Dhanbad-826 004. Manuscript received 15 September 1984, revised 13 November 1985, accepted 8 May 1986 Freshly prepared and digested forms of aluminium and ferric phosphates were mixed with an acid Ranchi soil, a neutral Madhubani soil and a calcareous Samastipur soil, and the mixtures were kept in contact with an anion-exchange resin contained in a cellophane bag under waterlogged conditions. The phosphorus uptake by the resin was determined as a function of time. The values of phosphorus release from ferric and aluminium phosphates of the soils of different locations were compared along with the pH values.