Linde alumina

The metal samples, 2x1 1/2 x 1/8 inches, were polished to a mirror finish on a polishing wheel covered with kitten-ear polishing cloth wet with a suspension of Linde alumina (Type B-5125). Each polished metal sample was covered with an evaporated film of the same metal (1000 A. thick) just prior to use. These films were hydrophillic, indicating the absence of organic contamination. 

Linde alumina Lucalox alumina Morganite alumina... 

For the Linde alumina the point at 1400°C was not included in the above line, though it is evident that it falls close to the calculated lines. The values of Dq and obtained from the least squares fits are given in Table II. The Morganite alumina had an activation energy for surface diffusion of 75 kcal/mole, while that for the Lucalox and Linde aluminas is 50-60 kcal/mole larger. 

Fig. 4. Grain boundary grooving on Linde alumina at 1500°C with the addition of 60% Si02-4fl% surface.

The most notable effect that this work demonstrates is that there is a marked difference in the thermal grooving behavior of different aluminas under similar experimental conditions. Hence we must look for differences in the materials to be able to understand the differences in behavior. The composition of the materials is the obvious place to look for differences, and here we immediately run into problems of interpretation. The total impurity content for the two sintered materials are about equal and about twice that of the Linde alumina. Hence the total impurity content does not rationalize the fact that the Linde and Lucalox behave similarly while the Morganite grooves more rapidly. We must then look for differences in the particular impurities present in order to rationalize the observed behavior. 

Carniglia ( ), in a review of the mechanical properties of refractory oxides, has emphasized that small amounts of impurities can have pronounced effects on the material behavior when they segregate to grain boundaries and surfaces. The present experiments are likely to be affected by precisely this type of segregation. The impurity levels in all three of the materials are such that we cannot be assured that we are measuring the intrinsic behavior of alumina on any of them. However, it is possible that we may be approaching intrinsic behavior in the Linde alumina, which has a purity of about 99.99 %... 

Liquid Water Linde Type 4 A Linde Type 5 A Activated Alumina Silicic Acid Gel... 

Dried with Linde type 5A molecular sieves or Na2S04 and fractionally distd at reduced pressure. Alternatively, it was refluxed with, and distd from, BaO. Also purified by fractional crystn from the melt and distd from zinc dust. Converted to its phosphate (m 135°) or picrate (m 223°), which were purified by crystn and the free base recovered and distd. [Packer, Vaughn and Wong J Am Chem Soc 80 905 1958.] The procedure for purifying via the picrate comprises the addition of quinoline to picric acid dissolved in the minimum volume of 95% EtOH to yield yellow crystals which are washed with EtOH and air dried before recrystn from acetonitrile. The crystals are dissolved in dimethyl sulfoxide (previously dried over 4A molecular sieves) and passed through a basic alumina column, on which picric acid is adsorbed. The free base in the effluent is extracted with n-pentane and distd under vacuum. Traces of solvent are removed by vapour phase chromatography. [Mooman and Anton J Phys Chem 80 2243 1976.]... 

Styrene is difficult to purify and keep pure. Usually contains added inhibitors (such as a trace of hydroquinone). Washed with aqueous NaOH to remove inhibitors (e.g. rert-butanol), then with water, dried for several hours with MgS04 and distd at 25° under reduced pressure in the presence of an inhibitor (such as 0.005% p-tert-butylcatechol). It can be stored at -78°. It can also be stored and kept anhydrous with Linde type 5A molecular sieves, CaH2, CaS04, BaO or sodium, being fractionally distd, and distd in a vacuum line just before use. Alternatively styrene (and its deuterated derivative) were passed through a neutral alumina column before use [Woon et al. J Am Chem Soc 108 7990 1986 Collman J Am Chem Soc 108 2588 1986]. 

For high pressure (15-400 psig), two types of acetylene flame arresters were developed by Linde and are still available from Praxair on special order. The first type is available in 1.5-inch diameter by 3- to 4-foot-long cylinders packed with sintered metal, fine wire wool, or finely divided alumina. The second type is available in 6-inch diameter by 15-inch-long cylinders packed with round nickel shot. 

In 1983, Buelens et al. conducted studies using Linde-manufactured 0.05 pm gamma alumina powder [30]. This work using a RDE resulted in incorporation levels of 0.035 and 0.0175 wt%, i.e. no significant incorporation. Work published in 1987 by the same group resulted in codeposition of 1.45, 0.55 and 0.30 wt% [37]. Comparison of this latter work to the work from 1983 shows codeposition increased by more than an order of magnitude. While the absolute amounts may be questionable in accuracy, the relative increase is significant. Neither of the RDE studies [30, 37] involved x-ray diffraction verification of the Linde powders, presumably since Chen et al. [31] had published such verification. 

Mineral. Alumina used in this study was a high purity a- Linde sample purchased from the Union Carbide Corporation. BET surface area was determined to be 15.0 m /g. 

---