Sintered disks

The sources most commonly used so far consisted of sintered disks containing about 100 mg ZnO enriched with 90% Zn. The disks were irradiated with 12 MeV deuterons or 30 MeV He particles, to yield the 78 h activity of Ga, and then annealed by heating in oxygen to 700-1,000 K for about 12 h and cooling down slowly (about 50 K h ) to room temperature. A Nal scintillation counter, 2-3 mm thick, is suitable for the detection of the 93 keV y-rays. Because of the relatively high transition energy, both source and absorber are generally kept at liquid helium temperature. 

XVIII. Bubble Formation under Intermediate Conditions and at Sintered Disks. . 356... 

A sintered disk contains an extremely large number of potential sites for bubble formation, only a fraction of which form the operative sites. ... 

A typical set of data for an air-water system on a sintered disk of 3.61 cm2 area is presented in Fig. 30. The increase in average bubble volume and the decrease in effective number of sites with increasing flow rate are evident from Fig. 30. The solid lines correspond to those calculated on the basis of the model. The agreement between the theoretical and the experimental values is very satisfactory. 

The success of the model, apart from helping in the evaluation of bubble volume from sintered disks, demonstrates the applicability of the simple single-site analysis to an obviously complex situation. 

Fig. 4. Steps in the manufacture of a disk thermistor A, ball-milled powder B, pressed disk C, sintered disk D, soldered disk E, edge-ground disk F, lead...

Pack the Sepharose into a suitable chromatography column (e.g, a syringe barrel fitted with a sintered disk), and wash with 50 mL of PBS Store at 4°C in PBS containing 0 1% sodium azide. 

La0 2Sro8Feo55Tio 4503 8 (LSFTO) powder, synthesized by using the spray pyrolysis method, was obtained from Praxair Specialty Ceramics (Woodinville, WA). The powder was preheated at 1250°C for 10 h in air with a 3°C/min ramp rate. The preheated powder was ground with ethanol in a mortar for more than 30 min. After drying to remove the ethanol, the powder was pressed into a cylindrical shape at 5000 psi with a 1 in. diam die. Dense ceramic disks were obtained by sintering in air at 1300°C for 20 h and 1400°C for 10 h. The sintered disks had a density of 90.3% of the theoretical den-... 

Editor s note The filtration under nitrogen can be effected by use of a Schlenk tube or a similar tube with a sealed sintered disk inserted in place of the gas exit tube. See Figs. 1-3, pages 10,16, and 20. 

The mixture is heated under reflux in a nitrogen atmosphere with mechanical stirring for 4 hours. It is then filtered in air, rapidly to avoid hydrolysis, by using a coarse sintered-disk funnel having a large plate diameter (50 to 100 mm.) and a capacity of at least 200 ml. The crude crystals may be washed on the filter with ether in order to dissolve any precipitated Grignard reagent. 

Another route, applicable to the RESS process, consists in using a sintered disk as the fluid distributor, as proposed by Domingo et al. (77), although this system s performance is limited by the imperfect sintered disk porosity distribution that is continuously modified by the unavoidable plugging of the finest pores by nanoparticles generated inside the disk. 

Bag filters are traditionally used for very fine-particle collection. The filtering media are either woven textile or nonwoven paper or fiber mats. In the present case, the filtering media should be chosen in materials both compatible with the processed fluids (especially for antisolvent processes where the filter is contacted with SCF and organic solvents) and acceptable for drug manufacture. We currently tested various filter types woven or nonwoven polymer (like PTFE or polyamides) fibers to form bags or paper bags (as for vacuum cleaners), woven stainless-steel fibers to from a disk, or filter paper supported by a sintered disk at the bottom of a basket at a smaller scale ceramic filters can also be considered favorably. 

HlPing at 1350°C/3h is able to transform N2 derived sintered disks, which have a BDa>97.5 %TD, into transparent pieces like those shown in Fig. 4. Obtainment of reasonably transparent parts from N1 sintered disks requires HlPing at I700°C. The average grain size of the N2 parts is I pm, while that of the N2 disks is 100 pm. 

The total forward transmission (TFT) - which includes the RIT and the forward scattered radiation - of HlPed specimens is given in Fig. 5. The transmission of an as-sintered disk (=specimen "e" of Fig. 4) derived from N2 powder is also given. The real transmission is a bit higher than shown in Fig. 5 reflection, by the two major surfaces, is higher than theoretical, owing to the imperfect polishing level that could be achieved. 

RESS is a very attractive process as it is simple and relatively easy to implement at least at a small scale when a single nozzle can be used. However, extrapolation to a significant production size or use of a porous sintered disk through which pulverization occurs is extremely difficult to carry out. The reason is that in both cases, particle size distribution is not easy to control, and may be much wider than in the case of a single nozzle. Moreover, particle harvesting is complex, as it is in any process leading to very small particlesP l... 

C for 10 min, the sintered disk was about 30 mm in diameter and 3 mm in thickness. In addition, for the heating rates of 8 and 50 °C min, sintering time was varied between 0 and 5 h, in order to examine the grain growth behavior. The mechanical pressure was unloaded before annealing. 

Our own work d involved measurement of potentials developed by exposure of NASICON to H2 at different pressures in a gaseous concentration cell. The NASICON was prepared both by the sol-gel method and the hydrothermal route. Pressed sintered disks were then prepared which were approximately 1.27 cm ( ") in diameter and 1 mm thick. The disk separated two chambers, one of which contained Nj at 1 atm and the other Hj. The potential of this cell was measured on open circuit as a function of hydrogen pressure and the results at 25 °C are plotted in Fig. 15.4. The slope of the line is close to that expected for Nernst type behaviour. At elevated temperatures, the voltage increased considerably but large deviations from Nernstian behaviour were observed presumably due to conduction of the sodium ions. These results are comparable to those obtained with P-alumina . By applying a potential across the... 

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