Short-run statistical process control: Q-Chart enhancements and alternative methods

The first two tables in Reference 1 are incorrect. Corrected tables are provided below. The errors do not affect the conclusions or the discussion in that paper.     

Electrical properties of biomorphic SiC ceramics and SiC/Si composites fabricated from medium density fiberboard

A study has been made of the dependences of the electrical resistivity and the Hall coefficient on the temperature in the range 1.8-1300 K and on magnetic fields of up to 28 kOe for the biomorphic SiC/Si (MDF-SiC/Si) composite and biomorphic porous SiC (MDF-SiC) based upon artificial cellulosic precursor (MDF - medium density fiberboards). It has been shown that electric transport in MDF-SiC is effected by carriers of n-type with a high concentration of ∼10²⁰ cm⁻³ and a low mobility of ∼0.4 cm² V⁻¹ s⁻¹. The specific features in the conductivity of MDF-SiC are explained by quantum effects arising in disordered systems and requiring quantum corrections to conductivity. The TEM studies confirmed the presence of disordering structural features (nanocrystalline regions) in MDF-SiC. The conductivity of MDF-SiC/Si composite originates primarily from Si component in the temperature range 1.8-500 K and since ∼500 to 600 K the contribution of MDF-SiC matrix becomes dominant.     

Process Optimisation of In Situ H2 Generation From Ammonia Using Ni on Alumina Coated Cordierite Monoliths

A catalyst of Ni supported on alumina coated monolith has been prepared, characterized and tested in NH₃ decomposition. The characterization of the catalyst by XPS and TPR showed that there is no formation of aluminates after catalyst use. It is studied the effect of the space velocity, by varying the feed flow rate and the catalyst??s length. Some evidences are shown about the reaction inhibition by produced H₂ and about the reasons for the better performance of the monolith than packed bed catalyst.     

High-Stable Mesoporous Ni-Ce/Clay Catalysts for Syngas Production

Abstract  

A mesoporous-type catalytic support was synthesized through the modification of a smectite with polyvinyl alcohol (PVA) and microwaves. Texture and micro-morphology of the support was determined. Several techniques were employed in order to describe the chemical environment of active species on the surface. Ni⁰ particle sizes were dependent on the structural site of reducible species. High stable Ni-Ce catalysts (calcined at 800 °C) were evaluated in the CO₂ reforming of methane reaction at 700 °C (WHSV = 96 L g⁻¹ h⁻¹, without dilution gas and pre-reduction). The catalysts have presented CH₄ conversions between 40 and 65%, CO₂ conversion between 35 and 65% and H₂/CO ratios between 0.2 and 0.4.     

Synthesis, characterization and use of reactive polymers with diisopropylphenylphosphine groups

The synthesis of linear and crosslinked polymers starting with 4-(diisopropyl-phosphinyl) styrene is described. Treatment with triphosgene yields the corresponding phosphine dichloride group in the polymers. Using these reactive polymers benzyl alcohol was converted to benzyl chloride at room temperature. The regeneration of the reactive polymers using triphosgene was achieved. The yields of benzyl chloride were in general lower than those previously reported using triphenylphosphine dichloride groups in the polymers. The difference in reactivity between triphenylphosphine dichloride- and diisopropylphenylphosphine dichloride substituted-polymers are discussed with the aid of semi-empirical computer calculations. Received: 17 June 1997/Revised: 4 September 1997/Accepted: 9 September 1997     

Formation of Hydroperoxy-, Keto- and Hydroxy-Dienes in FAME from Oils: Influence of Temperature and Addition of α-Tocopherol

The influence of temperature (40, 60 and 80 °C) and addition of α-tocopherol (0, 500 mg/kg) on the formation and distribution of the main oxidation products of linoleic acid, i.e. hydroperoxy-, keto- and hydroxy-dienes, were studied in samples of fatty acid methyl esters (FAME) derived from high-linoleic (HL) and high-oleic (HO) sunflower oils. In the range of temperatures studied, the formation of hydroperoxydienes showed monomolecular and bimolecular rate constants that ranged from 0.01 to 1 mmol^1/2kg^−1/2h⁻¹ and from 0.02 to 0.9 h⁻¹, respectively. The overall activation energies involved were similar for both samples and for the monomolecular and bimolecular periods (63–68 kJ/mol). The relative oxidation of methyl linoleate, which depended on the fatty acid composition of the FAME sample, was unaffected by temperature. At the three temperatures assayed, hydroperoxydienes constituted approximately 90 and 50% of total hydroperoxides in the HL and HO samples, respectively. Formation of keto- and hydroxy-dienes was influenced by temperature in a similar way to hydroperoxydienes and, consequently, changes in the distribution of compounds were not observed. The addition of α-tocopherol not only decreased the overall oxidation rate, but also affected the distribution of compounds. The content of hydroperoxydienes relative to that of total hydroperoxides was not affected by the presence of the antioxidant in the HL sample, whereas a significant increase (75%) was found in the HO sample compared with the control (50%). The addition of α-tocopherol in both samples also resulted in a slight increase of keto- and hydroxy-dienes in relation to hydroperoxydienes.     

Processing of graded anode-supported micro-tubular SOFCs based on samaria-doped ceria via gel-casting and spray-coating

A simple gel-casting method was successfully combined with the spray-coating technique to manufacture graded anode-supported micro-tubular solid oxide fuel cells (MT-SOFCs) based on samaria-doped ceria (SDC) as an electrolyte. Micro-tubular anodes were shaped by a gel-casting method based on a new and simple forming technique that operates as a syringe. The aqueous slurry formulation of the NiO–SDC substrate using agarose as a gelling agent, and the effect of spray-coating parameters used to deposit the anode functional layers (AFLs) and electrolyte were investigated. Furthermore, pre-sintering temperature of anode substrates was systematically studied to avoid the anode–electrolyte delamination and obtain a dense electrolyte without cracks, after co-sintering process at 1450 °C. Despite the high shrinkage of substrate (～70%), an anode porosity of ～37% was achieved. MT-SOFCs with ～2.5 mm of outer diameter, 370 μm thick substrate, 20 μm thick AFLs and 15 μm thick electrolyte were successfully obtained. The use of AFLs with 30:70 and 50:50 wt% NiO–SDC allowed to obtain a continuous gradation of composition and porosity in the anode–electrolyte interface.