Preparation and Characterization of 17O-Enriched Alumina for Nuclear Fusion Damage Experiments

Alumina enriched in ¹⁷O was successfully fabricated from aluminum isopropoxide and water containing the ¹⁷O isotope. This material was necessary for an experiment to study the radiation damage expected in alumina exposed to a nuclear fusion reactor environment. The enrichment levels of specimens subjected to different preparation schedules were measured using a nuclear reaction analysis technique. Replacement of the ¹⁷O isotope in the ceramic by atmospheric oxygen occurred readily. Therefore, successful fabrication of suitably enriched alumina specimens required that all processing steps be performed under vacuum or inertgas environments. The optimum fabrication procedure produced enriched alumina specimens of >99.5% of theoretical density, ∽10-μm grain size, and a flexural strength of 280 MPa.     

Surface Preparation of Tantalum for Encapsulation and Adhesive Bonding

A number of methods of surface preparation of tantalum for encapsulation in silicone rubber and for structural adhesive bonding were explored. The only ones which could be generally useful were boiling for 24 hours in distilled water (28% improvement) or boiling for 4 hours in 20% sodium hydroxide solution followed by boiling for 2 hours in dilute hydrochloric acid (34% improvement). An alternative, which could sometimes be used, was heating in air for at least 2 hours at 100°C.     

Applications of laser Raman microprobe spectroscopy to the characterization of coals and cokes

Optical microscopy is widely used in the characterization of coals and cokes. This Paper shows that the laser Raman microprobe (MOLE) which combines an optical microscope and a Raman spectrometer can provide useful additional information. Three main areas were investigated: identification of minerals in coal and coke; structural characterization of coals and cokes; and the interaction of inorganic additives and coal. Where possible, the results were compared with conventional optical microscopy measurements whereby it was shown that the optical texture and Raman spectra of cokes are not closely related. The Raman spectra of high temperature cokes were used to estimate the size of microcrystalline regions.     

Effects of experimental endogenous hyperlipemia on circulating leukocytes and erythrocytes

Effects of hyperlipemia on circulating leukocytes and erythrocytes were studied in dogs which were given repeated, intravenous injections of a nonionic detergent, Triton WR-1339. Erythrocyte lipid concentrations increased from 3.6±0.9 mg/10¹⁰ cells in control animals to 9.3±1.5 mg in the hyperlipemic group. This increase was accompanied by a shift in the distribution of total fatty acids toward a higher percentage of saturated and monounsaturated acids. In contrast to the changes observed in erythrocytes, the leukocyte lipid content remained unaltered in dogs with serum cholesterol levels ranging from 500 to more than 2,000 mg/100 ml. Leukocyte counts rose whereas hematocrit values, hemoglobin concentrations, and erythrocyte counts decreased. Oxygen utilization studies showed no significant metabolic differences between leukocytes which were isolated from hyperlipemic or control animals. Circulating leukocytes in dogs with an endogenously induced hyperlipemia were shown therefore to maintain normal lipid concentrations and did not participate in lipophage formation, as reported for certain diet-induced lipemias.     

Note: The Use of Triallyl Cyanurate in Bonding PVC Plastisols to Steel

The use of diallyl phthalate as the basis for a non-extractable plasticizer for poly(vinylchloride) (PVC) is well-known. Used in conjunction with a primary plasticizer and a polymerization initiator, a plastisol coating for steel can be formulated which is oil or grease tolerant and can also be used for bonding some structural steel parts if the area is relatively large compared with the load to be applied. Defrayne and Twiss¹ describe the bonding of automobile hood assemblies by vinyl plastisol adhesives and Schneberger² emphasizes their use in the automobile industry though neither article gives the formulations employed. Commercial formulations giving pull-off strengths of the order of 1 to 4 MN. m^-2 always incorporate a proportion of a phenolformaldehyde resin or even an epoxy, but sound-deadening and other coatings of steel do not necessarily need this reinforcement. Phillips and Longworth³ particularly studied the use of diallylphthalate (DAP) as a polymerizable plasticizer and the consequent improvement in adhesion to mild steel. Sherlock⁴ used a simple formulation without additives when investigating the effect of surface cleaning and conversion coatings (oxides and phosphates). It was suggested that, as outlined below, improved adhesion would be expected if a small proportion of triallyl cyanurate (TAC) were added to the polymerizable plasticizer. This paper shows this expectation to be achieved although the proportion of the more expensive TAC needed for substantial increase in bond strength is greater than was hoped.     

A two‐station embossing process for rapid fabrication of surface microstructures on thermoplastic polymers

An embossing strategy involving a hot station and a cold station for sequentially heating and cooling the embossing tool was investigated to reduce cycle times in hot embossing polymer microstructures. Experimental studies showed that aluminum stamps with a thickness of 1.4 mm can be rapidly heated from room temperature to 200°C in 3 s using contact heating against a hot station at 250°C. Microchannels and microlenses were successfully embossed onto high‐density polyethylene and acrylonitrile–butadiene–styrene substrates using a heating time less than 3 s and a total cycle time around 10 s. The two‐station embossing process for the microlens was also numerically studied. The simulated filling behavior agreed with the experimental observation and the predicted thermal and deformation history of the polymer offered a good explanation on the experimentally observed process characteristics. POLYM. ENG. SCI., 47:530–539, 2007. © 2007 Society of Plastics Engineers.     

Factors influencing the photofading of commercial anthraquinone dyes in solution

The photofading of two anthraquinone dyes has been studied in aqueous solution using ultraviolet-visible absorption spectroscopy and flash photolysis. The influence of alcohol concentration, pH, atmosphere, photosensitisers and stabilisers have been examined and these lead to some important conclusions on the mechanism of dye fading. Essentially, the results indicate the photoexcited triplet state of the dye undergoes a process of either electron or hydrogen-atom abstraction depending on the nature of the environment. Other factors such as aggregation and singlet oxygen also appear to play an important role in solution photofading. The relevance of these results to photofading in a polymeric phase is discussed.     

From surface science to catalysis: Surface “explosions” observed on Rh crystals and supported catalysts

Phenomena called surface explosions have been reported for decomposition reactions on single crystals, and have been identified by the use of desorption methods. In particular, in TPD, they are manifested by extremely narrow peaks (as little as 3 K in width) and a desorption rate which increases with time in isothermal experiments. In this paper we report such observations for acetate species on Rh single crystals, but extend this to show for the first time that such effects are not restricted to single crystal/UHV experiments, but can also be found on a Rh/Al₂O₃ catalyst under ambient pressure conditions. These reactions can be classified as second order autocatalytic surface processes, where free surface Rh sites are an essential component of the reaction. It is shown that coadsorbed adatoms are also essential for such explosions to be seen and their role is proposed to be that of a template layer acting to order the acetate in self-poisoning configurations.     

Effect of aluminum on the low temperature properties of relatively high purity ferrite

True stress-strain data on alloys of pure iron with up to 2.4 pct Al were obtained in the temperature range +100° to ?185°C. Aluminum was found to reduce yield and flow stresses of iron at low temperatures but to have little or no effect on ductility. The effects of temperature and composition on strain hardening are discussed.