Hydroxyapatite whiskers have been prepared by the hydrothermal method. The crystals had diameter, length, and aspect ratio in the range of 1–10 μm, 30–50 μm, and 5–20, respectively. Their Ca/P molar ratio varied from 1.59 to 1.62. The morphology of the crystals can easily be controlled by the concentrations of species in the starting solution, while the Ca/P ratio is almost independent of them. Through the reaction with calcite powder at 600 °C, the Ca/P ratio of the whiskers has been improved even to the stoichiometric value of 1.67. Taking into account morphology and chemical composition of the HAp whiskers, they should not be health hazardous and may find applications as substitutes for asbestos and other fibrous materials which presently have restricted use because of their carcinogenic natures.

Epitaxial β-SiC thin films were grown on modified Si(100) substrates from methyltrichlorosilane (CH3SiCl3 or MTS) in a hot wall reactor by using low pressure chemical vapor deposition (LPCVD). At 1150 °C, the growth rate of the β-SiC films was 120 Å/min. Epitaxial β-SiC(100) thin films were deposited after the deposition time of 12.5 min. However, the crystallinity of the deposited films was influenced by the deposition time. For example, the occurrence of rotational β-SiC(100) crystals and polycrystalline β-SiC with a highly preferred orientation of (100) planes was obtained for the deposition time of 50 min. XRD and TEM showed the appearance of polycrystalline β-SiC films with a preferred orientation of β-SiC(111) after further increasing the deposition times (time ≥ 75 min). At 1100 °C, polycrystalline β-SiC films with poor surface morphology were observed even though the film had a preferred orientation of β-SiC(100) for short deposition time (e.g., 12.5 min). Polycrystalline β-SiC(111) film was obtained for the deposition time of 200 min at this temperature.

The microstructural characteristics of melt-spun and heat-treated austenitic Fe−28Mn−8.6Al−0.5Mo−0.7W−0.5Nb−1.1C (in wt. %) alloys have been investigated by means of transmission electron microscopy. The melt-spun alloy contained fine austenitic cells and some intercelluar Nb(C, N) precipitates. Detailed observations revealed fine {100} modulations in the matrix of the cells, as well as a concomitant L′I2 atomic ordering arising from it. These observations indicate that the onset of decomposition of the initial austenite phase occurred during the rapid solidification process. Aging of the melt-spun alloy at 823–1173 K produced various microstructures, including a general precipitation of Nb(C, N) in the matrix. On isochronal annealing for 1 h, this matrix Nb(C, N) precipitation commenced at 1073 K with the formation of metastable coherent K-carbide (K′) near cell boundaries. On annealing at temperatures above 1123 K, only the Nb(C, N) precipitates were formed, on a fine scale, being accompanied by the formation of precipitate-free regions in the vicinity of cell and grain boundaries. Both intercellular and matrix Nb(C, N) precipitates obeyed a cube-to-cube orientation relationship with austenite. The general matrix precipitation of Nb(C, N) and formation of precipitate-free regions are discussed in terms of a vacancy (defect)-depletion effect. Finally, it was demonstrated that, by employing a double heat-treatment schedule of annealing at 1173 K followed by aging at 823 K, a novel microstructure consisting of fine dispersoids of Nb(C, N) carbo-nitride, distributed over the matrix of {100} modulated structure, could be produced.

High transition temperature superconducting YBa2Cu3O7−x (YBCO) thin films have been epitaxially grown on YZ-cut LiNbO3 (LNO) substrates by the pulsed laser deposition technique. The interface between YBCO and LNO has been systematically investigated by scanning electron microscopy, atomic force microscopy, Auger electron spectroscopy, and x-ray photoelectron spectroscopy. Off-stoichiometry LiNbOx phases are found to segregate on the substrate surface because of lithium and oxygen vacancies formed during the high temperature YBCO growth. These submicrometer particles are observed along the Z-axis on the X-Z plane of LNO with height of ∼30 nm above the LNO surface. This rough growth surface results in YBa2Cu3O7−x thin films grown on the LNO surface that have reduced Jc and Tc, possibly limiting the use of YBCO/LNO heterostructures for surface acoustic wave (SAW) devices.

The gas phase densities of CH3 and CH and the hydrogen dissociation fraction are measured in a hot filament diamond deposition system for each of several different hydrocarbon input gases. The crystal growth rate and the appearance of the diamond grown from the different input gases are also examined. A comparison of the measurements indicates that the nature of the input hydrocarbon is relatively unimportant because fast gas phase reactions completely scramble the identities of the input carbon atoms. The addition of oxygen greatly alters the gas phase densities and other experimental factors such as the filament surface condition. Small concentrations of atomic impurities in the gas phase are also detected using high sensitivity absorption spectroscopy.

0.25 μm thick, single crystal, n-type, silicon carbide (β-SiC) films thermally grown on p-type Si(100) were doped with boron by using KrF excimer laser radiation and a spin-on dopant with a boron concentration of 1020/cm3. The threshold fluence for the doping to occur was approximately 0.08 J/cm2. Similarly, p-SiC/n-SiC diodes were fabricated by laser-induced doping of single-crystal β-SiC (n-type, 6 μm thick) films on n-type Si(100). The diodes obtained at 0.25 J/cm2 showed good rectifying characteristics. The threshold fluence for surface modification and/or ablation was approximately 0.3 J/cm2, indicating that doping and diode formation have to be accomplished within the fluence window of 0.08 J/cm2-0.3 J/cm2 for these films.

The electron backscattering pattern technique has been applied to the microstructural investigation of Tl(1223) thick films formed by vapor-phase thallination of Ag-containing Ba–Ca–Cu–oxide precursors. For samples grown on polycrystalline YSZ, considerable biaxial alignment is found in localized, multigrain regions as wide a 100 μm or more. However, on scales above 1 mm the overall texture remains only uniaxial with the c-axes (i.e., [001]) aligned perpendicular to the plane of the substrate. On single-crystal KTaO3 an epitaxial relationship is evident which persists to the surface of a 3 μm thick film. Modest variations in the processing protocol yield films containing grains oriented with the c-axis in the plane, resulting in the degradation of transport properties. The data suggest a growth mode in which sparse nucleation occurs at the substrate followed by rapid lateral crystallization.

The preparation of thick films of the LaBa2Cu3Oy (La-123) phase by using the partial melting technique (PMT) of powders deposited on MgO substrates by drying alcoholic suspensions is reported. The effects of the starting composition, processing time (t), and temperature (T) on the superconducting properties of the La1+xBa2Cu3Oy (−0.25 ⋚ x ⋚ 0.5) system were investigated. The presence of the La4Ba2Cu2O10 (La 422) phase was detected in the samples quenched in liquid N2 after heating up to 1200 °C. The crucial step of the processing is the cooling rate down to the crystallization temperature, Tp, determined by DTA analysis, in order to favor the formation of the La-123 phase from the reaction between the La-422 solid phase and the liquid. The superconducting properties, tested by magnetization measurements, showed a diamagnetic onset temperature (Tc,diam) as high as 89 K.

Important factors governing the size and the morphology of Y2BaCuO5 (Y211) at 1100 °C in air were investigated for three different starting materials having the same nominal composition of Y:Ba:Cu = 1.8:2.4 : 3.4, Y2BaCuO5-BaCuO2-CuO-Pt. Y2O3-BaCuO2-CuO-Pt, and melt-quenched materials from 1400 °C in a Pt crucible. With various amounts of Pt doping, the heating rate and the holding time were employed as the processing parameters. While, with the aid of Pt doping as the effective growth inhibitor, fine round Y211 grains could be obtained by simply employing a refined round Y211 precursor and a rapid healing, there were several important factors for obtaining fine acicular (or needle-like) Y211 grains as follows: (i) The Pt dopants dissolved in the liquid phase should act as the effective heterogeneous nucleation sites. (ii) Y211 grains should grow into the acicular shapes before the system reaches an equilibrium amount of Y211 in the liquid (i.e., reaction-controlled). (iii) A large amount of the liquid phase should be supplied instantly at the partial melt stage with a rapid heating.

Carbon dioxide is an attractive organic solvent in today's chemical process environment, in that it is nonflammable, inexpensive, and exhibits low toxicity. Further, materials solubilized in carbon dioxide are easily and completely recovered/concentrated from solution via a simple pressure quench. Despite these favorable properties, CO2 is nonpolar and therefore is a very poor solvent for materials such as conventional metal chelating agents, thus blocking application of carbon dioxide in metal extraction/recovery. Consequently, we are exploring the molecular design of materials which are highly CO2 phillic, that is, they exhibit solubilities in carbon dioxide which are significantly greater than alkanes with the same number of main-chain atoms. By functionalizing chelating moieties with CO2-phillic oligomers, we have generated materials that both effectively extract metals from solid matrices and that dissolve in carbon dioxide in significant quantities. The application of such chelating agents is not limited to soil cleaning operations. In fact, these chelates make the use of CO2 possible in many applications where precision cleanup/recovery of metal ions are required. For example, CO2 has been promoted as a replacement for CFC's in cleaning processes in the electronics industry. Use of these chelates would allow the removal of metals, along with other impurities in a CO2 cleanup procedure.

Banded structures in combustion-synthesized products have been observed during unstable combustion synthesis. The formation of the banded structures is discussed in this article. It is noted that the band spacing was changed when several initial processing conditions were varied. Any change in the processing parameters that correspondingly caused more unstable combustion was observed to decrease the propagation velocity of the combustion front and increase the band spacing. The correlation of the band spacing and oscillatory frequency of the unstable oscillatory combustion with the propagation velocity was also discussed. From the results studied in this work, it is noted that the change of the band spacing can be used to infer the degree of the instability of the combustion front.

This paper reports on the formation of metastable π phase on mechanical alloying of elemental Ag and Te powders in the composition range of 50 to 75 at. % Te. Contrary to the reported results in vapor-deposited thin films, no amorphous phase could be detected during mechanical alloying. The extent to which the π phase forms on milling is restricted, compared to rapid solidification. Formation of the metastable π phase coincides with the achievement of nanometric grain size and is preceded by the formation of intermetallic compound Ag2Te. An approximate estimation of the free energies of the competing phases has been attempted to provide insight into the phase selection process. It is suggested that tellurium diffusion through the nanoscale grain boundaries plays an important role in the formation of the metastable π phase.

Crystalline MoS2 films were deposited on Si and graphite substrates using MoF6 and H2S as precursors. The crystal orientation and near-interface structure of the MoS2 films were studied using transmission electron microscopy. In general, the preferred orientation of the (002) basal planes of the MoS2 films with respect to the substrate surface changed from parallel to perpendicular with increased deposition temperature from 320 to 430 °C. At 430 °C, the basal planes were primarily oriented perpendicular to the Si substrate, except for the presence of a ∼5 nm interface region in which the basal planes were oriented in the parallel direction. The formation of this transitional region was also observed on the graphite substrate.

GaAs layers grown by close-spaced vapor transport on (100) Ge substrates have been investigated as a function of the experimental growth conditions. The effects on the microstructure of the surface preparation, substrate misorientation, and annealing were studied using optical microscopy and transmission electron microscopy. Microtwins and threading dislocations are suppressed by oxide desorption before deposition. Single domain GaAs layers have been obtained using a 50 nm thick double domain buffer layer on an annealed Ge substrate misoriented 3°toward [011]. The mismatch strain is mainly accommodated by dissociated 60°dislocations. These misfit dislocations extend along the interface by the glide of the threading dislocations inherited from the substrate, but strong interaction with antiphase boundaries (APB's) prevents them from reaching the interface. These results are discussed and compared with previous reports of GaAs growth on Ge(100).

Gold (Au) and silver (Ag) are known to be important contact metals on YBa2Cu3O7−x (YBCO). Both metals have been used as additives in fabricating tapes of YBCO and Bi2Sr2CaCu2O8 (BSCCO) materials, and have favorable results in improving not only the flexibility but also the weighted critical currents of the resulting composites. Previous results on superconductor/normal metal/superconductor junctions made using YBCO/Au/YBCO and YBCO/Au/Nb demonstrated that a supercurrent can be induced in the normal metal layers through the proximity effect. Our transmission electron microscopy study of the Au/YBCO interfaces shows a well-bonded interface with no extraneous phases present. Lattice fringes of the (001) plane in YBCO terminated at the interface abruptly. This observation supports previous results of contact resistance of x-ray photoelectron spectroscopy (XPS). Both (001) integral steps and multiples of 1/3 (001) steps were observed at the Au/YBCO interface. When the top gold layer was absent locally, surface degradation was observed as the (001) lattice fringes stopped short from the surface by 10 nm. Our results support that Au is a desirable contact metal and a dependable surface passivation material for YBCO.

The electroplastic effect in materials is an interesting and potentially useful phenomenon in which an applied electric field affects the plastic flow properties of materials under strain. We have undertaken a study to use optical methods to monitor changes in alkali halide crystals undergoing the electroplastic effect. Some preliminary results from this work are presented along with more conventional quasi-static measurements of the electroplastic effect.

Kikuchi electron diffraction patterns are used extensively to determine crystal orientations via transmission electron microscopy (TEM) or in the electron backscattering pattern (EBSP) mode of scanning electron microscopy (SEM). A new method is presented that is capable of finding crystal orientations, the camera length, and the projection center from only one pattern per grain using a least-squares technique. This method eliminates the need to perform an alignment with a reference crystal in the backscattering mode. Application to a Σ = 13a silicon bicrystal is presented for TEM patterns and EBSP's. A complete analysis of the propagation of random measurement errors into the disorientation axis/angle pair is carried out. The root mean square deviation from the nominal disorientation angle is found to be 0.3°in the case of TEM and 0.5°in the case of EBSP. The root mean square inclination between the nominal and measured disorientation axis is found to be 1°in the case of TEM and 0.5°in the case of EBSP.

We prepared YBa2Cu3Ox films on (100) MgO and (100) SrTiO3 substrates by rf thermal plasma evaporation, and investigated microstructure and growth mechanisms of these films by observation of the surfaces using an AFM technique. As a result, 2D nucleation and further coalescence between vicinal grains were observed in the initial stage of growth. In the films prepared for a deposition time of 3 min, the different complex growth modes, including spiral growth, “birth and spread” growth, and 2D growth, were observed, which might be due to high growth rate over 55 nm/min of this process.

The quasicrystalline (qc) alloy Al65Cu20Cr15, unlike its Ru- and Fe-bearing counterparts like Al65Cu20Ru15 and Al65Cu20Fe15, is a metastable phase. This qc alloy has been shown to possess several structural variants and curious structural characteristics. We have investigated the qc alloy Al65Cu20Cr15 with special reference to the possible occurrence of new structural variants. TEM exploration of the as-quenched qc alloy has indeed revealed the existence of several new phases. These are (i) body-centered cubic (bcc) (a = 12.60 Å, disordered) and simple cubic (s.c.) (a = 12.60 Å, ordered), which are the 1/1 approximants of the primitive icosahedral phase (i phase); (ii) a twice order-induced modulated cubic phase (bcc, a = 25.20 Å) which has been shown to correspond to 1/1 approximant of the ordered i phase [i.e., face-centered icosahedral (FCI)]; and (iii) real crystalline bcc (a = 8.90 Å) and face-centered cubic (fcc) (a = 17.98 Å) phases possessing a specific orientation relationship with the icosahedral matrix phase. Tentative structural models showing the interrelationships between the bcc/fcc phases have been outlined.

The refining of lead blast furnace bullion involves the transfer and handling of hot impure lead bullion. Fugitive emissions of lead-containing fumes create a plant hygiene problem. The cause of the emissions is the high vapor pressure of lead and its compounds when lead blast furnace bullion is transferred in an open ladle at ∼1000 °C from the blast furnace and poured into the drossing kettle, and later during the manual skimming of powdery dross. A laboratory study was conducted on a new concept for lead refining that eliminates contact between hot lead and the cnvironment, and thus abates fugitive lead emissions. The new process takes place in two steps: controlled solidification of bullion as it flows from the blast furnace, followed by remelting in a closed centrifuge to separate lead and dross. Refined lead was produced with <0.05% copper and <0.01% of all other impurities. Suggestions are outlined for implementing the process.