Importance of the support material in thin palladium composite membranes for steady hydrogen permeation at elevated temperatures.

Hydrogen permeation performance of palladium membranes supported on porous alpha-alumina and yttria-stabilized zirconia (YSZ) was studied at 300-850 degrees C. The hydrogen permeation flux across the palladium-alpha-alumina membrane decreased markedly during permeation tests conducted at >600 degrees C. The SEM and XPS studies of the post-test membrane revealed the presence of aluminium in the palladium layer. Such migration of aluminium was not observed by heating the palladium-alpha-alumina membrane under an argon atmosphere, indicating that hydrogen is responsible for this phenomenon. Hydrogen-induced strong metal-support interaction might be related to this considerable loss of the hydrogen flux. Reduction of alumina to Al(0) by active hydrogen at the membrane-support interface and subsequent migration of Al(0) into the palladium layer represents the most plausible mechanism for the aluminium diffusion. Actually, Al(0) that migrated into the palladium membrane layer generated less hydrogen-permeable palladium-aluminium alloy or inter-metallic compound phase. In contrast, no such strong interaction was found between the YSZ support and the palladium membrane. This composite membrane exhibited a steady permeation of hydrogen at 650 degrees C for 336 h. Having a remarkably high reduction potential, Y(III) is unlikely to be reduced to Y(0), although Zr(IV) has a comparable reduction potential to that of Al(III). A binary phase diagram shows a liquid alloy phase present for the Pd/Al couple at temperatures greater than 615 degrees C (eutectic point), while an inter-metallic compound or liquid alloy phase in the Pd-Zr binary system is not apparent at temperatures less than 750 degrees C. Consequently, inter-diffusion of zirconium with palladium did not occur during operations at 650 degrees C.

Laparoscopy in the management of scirrhous gastric cancer.

BACKGROUND: Scirrhous gastric cancer frequently shows extensive tumor spread, and gastrectomy for cure of the disease is not possible in the presence of peritoneal dissemination, which is often overlooked by conventional computed tomography. The aim of this study was to evaluate our experience of 16 patients who underwent laparoscopy in the management of scirrhous gastric cancer, and to examine whether peritoneal dissemination could be diagnosed accurately by laparoscopy.METHODS: All patients had nonobstructed, nonbleeding scirrhous gastric cancer and had no evidence of metastatic disease by ultrasonography and computed tomography. Laparoscopy was performed under general anesthesia with CO(2) pneumoperitoneum. A Hasson trocar and two manipulating forceps were inserted, and the surfaces of the peritoneum, omentum, stomach, spleen, pancreas, liver, and diaphragm were examined.RESULTS: The mean time for laparoscopy was 20 min. Peritoneal dissemination was disclosed in 4 patients (25%), and systemic and intraperitoneal chemotherapy was done without laparotomy. In 12 patients, subsequent gastrectomy with a curative intent was successfully performed. Pathology revealed that the tumor diffusely invaded the whole thickness of the gastric wall; the mean size of resected tumors was 12 cm, and the mean number of positive nodes was 17. Nine patients died of the disease with a mean survival period of 10 months, and 7 patients were alive without recurrence during a mean follow-up period of 11 months.CONCLUSIONS: Laparoscopy is useful for the evaluation of peritoneal spreads of advanced gastric cancer, can avoid unnecessary laparotomy because of peritoneal dissemination, and is important for the choice of treatments in patients with scirrhous gastric cancer.