Effect of Annealing on the Surface Microstructure of Y-Ba-Cu-O Superconducting Ceramics

Precusors to the YBa₂Cu₃O_7-δ material were prepared by both the oxalate precipitation method and conventional ceramic processing. Second-phase grains were observed to develop on the exposed fracture surface during annealing at 500° to 600°C in an ambient atmosphere. The second-phase grains were identified to be BaCO₃ using EDX and XRD. The liquid phase, which was formed because of local chemical inhomogeneity in the Y-Ba-Cu-O system, contributed to the formation of second-phase grains as a source of Ba.     

Brazing as a means of sealing ceramic membranes for use in advanced coal gasification processes

Coal is potentially a very inexpensive source of clean hydrogen fuel for use in fuel cells, turbines, and various process applications. To realize its potential however, efficient low-cost gas separation systems are needed to provide high purity oxygen that will enhance the coal gasification reaction and to extract hydrogen from the resulting gas product stream. Several types of inorganic membranes are being developed for hydrogen or oxygen separation, including porous alumina, transition metal oxide perovskites, and zirconia. Because they form the heart of the working device, numerous advances have been made in the fabrication and performance of these membrane materials. However, less emphasis has been placed on the materials that will be used in the balance of the device; in particular, the seals that bond the functional ceramic to the metallic structural component. In an effort to begin addressing this issue, we have examined ceramic-to-metal brazing as a method of sealing a model set of gas separation component materials: yttria-stabilized zirconia and stainless steel. In comparative high-temperature exposure testing of joints prepared using commercial brazes and a newly conceived braze alloy, the commercial material proved to be unsuitable due to excessive oxidation. On the other hand, the new material not only displayed superior oxidation resistance, but also excellent hermeticity in prototypic membrane testing.     

Structural properties of 0.65Pb(Mg1/3Nb2/3)O3–0.35PbTiO3 relaxor ferroelectric thin films on SrRuO3 conducting oxides

Coating of 0.65Pb(Mg_1/3Nb_2/3)O₃–0.35PbTiO₃ (PMN–PT) relaxor ferroelectrics by a sol–gel method is followed by growth of epitaxial SrRuO₃ (SRO) metallic oxide electrodes on SrTiO₃ (STO) single-crystal substrate by pulsed laser deposition. High-quality PMN–PT films on SRO with preferred growth orientation were successfully fabricated by controlling the operation parameters. Structural properties of relaxor ferroelectric PMN–PT thin films on SRO/STO substrates have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). In-plane and out-of-plane alignments of the heterostructure are confirmed and the structural twinning of the materials are also revealed.     

Optical scattering in beef steak to predict tenderness using hyperspectral imaging in the VIS-NIR region

The objective of this research is to develop a non-destructive method for predicting cooked beef tenderness using optical scattering of light on fresh beef muscle tissue. A hyperspectral imaging system (λ = 496–1,036 nm) that consists of a CCD camera and an imaging spectrograph, was used to acquire beef steak images. The hyperspectral image consisted of 120 bands with spectral intervals of 4.54 nm. Sixty-one fresh beef steaks, including 44 strip loin and 17 tenderloin cuts, were collected. After imaging, the steaks were cooked and Warner-Bratzler shear (WBS) force values were collected as tenderness references. The optical scattering profiles were derived from the hyperspectral images and fitted to the modified Lorentzian function. Parameters, such as the peak height, full scattering width at half maximum (FWHM), and the slope around the FWHM were determined at each wavelength. Stepwise regression was used to identify 7 key wavelengths and parameters. The parameters were then used to predict the WBS scores. The model was able to predict WBS scores with an R = 0.67. Optical scattering implemented with hyperspectral imaging shows limited success for predicting current status of tenderness in beef steak.     

Study on Contamination Control for Yield Enhancement in the Manufacturing Line of Cellular Phone Modules

Practical studies on the method of contamination control for yield enhancement in the cellular phone modules production line were carried out. A contamination control method was proposed, consisting of data collection, data analysis, improvement action, verification, and implementation of control. The partition check method and the composition analysis for data collection and data analysis were respectively used in the cellular phone modules manufacturing process, and these methods were evaluated by the variation of yield loss before and after implementing the actions for improvement. In the partition check method, the critical process step was selected, and yield loss reduction through improvement actions was observed, whereas in the composition analysis, critical sources were selected, and yield loss reduction through improvement actions was investigated. From the results, it is concluded that the partition check and the composition analysis are effective solutions for contamination control in cleanroom production lines.     

Influence of the silicon surface treatment by plasma etching and scratching on the nucleation of diamond grown in HFCVD - a comparative study

A comparative study for the nucleation of diamond was carried out using surface treatment like (i) surface scratching with 1 μm diamond paste and (ii) surface etching using chlorine plasma at different RF powers (50, 100 and 150 W). Atomic force microscopic study shows variation in roughness from 31 nm to 110 nm. Scratching results in random scratches, whereas plasma etches a surface uniformly. Scanning electron microscopic observations show well faceted crystallites with a predominance of angular shaped grains corresponding to 〈100〉 and 〈110〉 crystallite surfaces for the scratched as well as plasma etched substrate. Surface etching at 150 W plasma power results in a better growth in comparison with 50 and 100 W plasma powers. Chlorine-radical is found responsible for the changes in the growth morphology. Raman spectroscopy shows a sharp peak at 1,332 cm⁻¹ and a peak at ∼1,580 cm⁻¹ for both samples.     

Characteristics of nitrogen and phosphorus removal in SBR and SBBR with different ammonium loading rates

Laboratory scale experiments were conducted to study the deterioration of enhanced biological phosphorus removal (EBPR) due to influent ammonium concentration, and to compare the performance of two types of sequencing batch reactor (SBR) systems, a conventional SBR and sequencing batch biofilm reactor (SBBR). Both in SBR and SBBR, the total nitrogen removal efficiency decreased from 100% to 53% and from 87.5% to 54.4%, respectively, with the increase of influent ammonium concentration from 20 mg/l to 80 mg/l. When the influent ammonium concentration was as low as 20 mg/l (C: N: P=200: 20: 15), denitrifying glycogen-accumulating organisms (DGAOs) were successfully grown and activated by using glucose as a sole carbon source in a lab-scale anaerobic-oxic-anoxic (A₂O) SBR. In the SBR, due to the effect of incomplete denitrification and pH drop, the nitrogen and phosphorus removal efficiency decreased from 77% to 33.3% when the influent ammonium concentration increased from 20 mg/l to 80 mg/l. However, in the SBBR, simultaneous nitrification/denitrification (SND) occurred, and the nitrification rate in the aerobic phase did not change remarkably in spite of the increase in influent ammonium concentration. Phosphorus removal was not affected by the increase of influent ammonium concentration.     

Zero-valent iron treatment of RDX-containing and perchlorate-containing wastewaters from an ammunition-manufacturing plant at elevated temperatures.

The use of zero-valent iron for treating wastewaters containing RDX and perchlorate from an army ammunition plant (AAP) in the USA at elevated temperatures and moderately elevated temperature with chemical addition was evaluated through batch and column experiments. RDX in the wastewater was completely removed in an iron column after 6.4 minutes. Increasing the temperature to 75 degrees C decreased the required retention time to 2.1 minutes for complete RDX removal. Perchlorate in the wastewater was completely removed by iron at an elevated temperature of 150 degrees C in batch reactors in 6 hours without pH control. Significant reduction of perchlorate by zero-valent iron was also achieved at a more moderate temperature (75 degrees C) through use of a 0.2 M acetate buffer. Based on the evaluation results, we propose two innovative processes for treating RDX-containing and perchlorate-containing wastewaters: a temperature and pressure-controlled batch iron reactor and subsequent oxidation by existing industrial wastewater treatment plant; and reduction by consecutive iron columns with heating and acid addition capabilities and subsequent oxidation.     

Application of artificial neural networks to the analysis of two‐dimensional fluorescence spectra in recombinant E coli fermentation processes

A two‐dimensional (2D) spectrofluorometer was used to monitor various fermentation processes with recombinant E coli for the production of 5‐aminolevulinic acid (ALA). The whole fluorescence spectral data obtained during a process were analyzed using artificial neural networks, ie self‐organizing map (SOM) and feedforward backpropagation neural network (BPNN). The SOM‐based classification of the whole spectral data has made it possible to qualitatively associate some process parameters with the normalized weights and variances, and to select some useful combinations of excitation and emission wavelengths. Based on the classified fluorescence spectra a supervised BPNN algorithm was used to predict some of the process parameters. It was also shown that the BPNN models could elucidate some sections of the process's performance, eg forecasting the process's performance. Copyright © 2005 Society of Chemical Industry