Polishing


Tertiary treatment. Tertiary or polishing treatment prepares the aqueous waste for final discharge. The final quality of the effluent depends on the nature and flow of the receiving water. Table 11.3 gives an indication of the final quality required.  [c.318]

CoAsS, are also used as sources. The ore is roasted and Co is precipitated as the hydroxide and then reduced to Co with carbon (hep below 417 - C, cep to m.p.). The metal is silvery white and readily polished. It dissolves in dilute acids and is slowly oxidized in air. Adsorbs hydrogen strongly. The main use of cobalt is in alloys. Cobalt compounds are used in paints and varnishes, catalysts. Cobalt is an essential element in the diet. World production 1976 32 000 tonnes metal.  [c.104]

Petroleum wax is used in the manufacture of candles, polishes, ointments and for waterproofing purposes. Waxes are also used as a cracking feedstock for the production of 1-alkene.s for conversion to detergents.  [c.302]

Applications for these products cover a wide range. When completely dearomatized, paraffins have markets in the food industry, especially in food packaging. Generally containing polymer additives, paraffins are very useful for impregnating paper or cardboard imparting water resistance. Paraffins or waxes are also found in particle board. This non-exhaustive list of applications for waxes and paraffins can not be ended without mentioning the manufacture of candles, polishes, cosmetics and coatings.  [c.285]

As object we used a polished diamond oriented with its flat table vertically. Figure 4 shows a radiograph taken with the table plane parallel to the X-ray beam. The magnification is about 50 times. The inset shows the contrast along an horizontal trace, which is also indicated.  [c.576]

The immobility of the surface atoms of a refractory solid has the consequence that the surface energy and other physical properties depend greatly on the immediate history of the material. A clean cleavage surface of a crystal will have a different (and probably lower) surface energy than a ground, abraded, heat-treated or polished surface of the same material.  [c.259]

Grinding may induce changes in general physical properties such as density in the case of quartz, a deep amorphous layer appears to form [16]. Electron difftaction studies of the surface region indicated that grinding removes surface material without changing its molecular crystallinity, while polishing leaves a fairly deep amorphous surface layer [17, 18] known as the Beilby layer [19, 20]. Apparently the Beilby layer is formed through a softening, if not melting, of the metal surface [21] and this layer can persist 2-10 nm into a metal such as gold or nickel [22]. Cold working of metals also affects the nature of the surface region [23].  [c.259]

The basic device is very simple. A tip of refractory metal, such as tungsten, is electrically heat-polished to yield a nearly hemispherical end of about 10" cm radius. A potential of about 10 kV is applied between the tip and a hemispherical fluorescent screen. The field, F, falls off with distance as kr, and if the two radii of curvature are a and b, the total potential difference V is then  [c.299]

The results of such studies have made it clear that the surfaces of crystalline materials may have quite irregular steps of hundreds or thousands of angstroms in depth and that lapped or ground surfaces may be quite jagged on this length scale. Even polished metal surfaces are not really smooth. As discussed in Section Vn-IB, polishing appears to bring about local melting, and the effect is that ragged asperities are smoothed out but even so, the resulting surface has a waved appearance. In the case of metals, it is also apt to have an oxide coating [4].  [c.432]

Hardy studied a number of lubricants of the hydrocarbon type, such as long-chain paraffins, alcohols, and acids. An excess of lubricant was generally used, either as the pure liquid or as a solution of the solid in petroleum ether. In some cases the metal surface was then polished. The general observation was that fi values of 0.05 to 0.15 were obtained, that is, much lower than for unlubricated surfaces. Also, for a given homologous series, n decreased nearly linearly with increasing molecular weight, although with the fatty acids, n leveled off at about 0.05 at a molecular weight of 200. These relationships are shown in Fig. XII-7.  [c.444]

Once a sample is properly oriented and polished, it is placed into a UHV chamber for the final preparation steps. Samples are processed in situ by a variety of methods in order to produce an atomically clean and flat surface. Ion bombardment and aimealing (IBA) is the most conunon method used. Other methods include cleaving and film growth.  [c.303]

Figure C2.11.5. Scanning electron micrographs showing the microstmcture of an alumina ceramic spark-plug body (a) fracture surface and (b) polished and thennally etched cross section. Figure C2.11.5. Scanning electron micrographs showing the microstmcture of an alumina ceramic spark-plug body (a) fracture surface and (b) polished and thennally etched cross section.
In practice the closed tubes are carefully polished to remove all grease, moisture, etc. and are then allowed to stand for a definite period of time in the air, to pick up a definite amount of water vapour— this process is known as maturing. Unless the atmospheric conditions change very considerably during the experiment (about 2 hours), the amount of water vapour deposited on the polished tubes before and after the combustion will be the same and any systematic error will have been avoided. Unless the tubes have been used in the combustion tube burning-out process, and so are full of oxygen, they must be filled with oxygen before weighing by connecting to the apparatus (both furnace and mortar being cold) and passing oxygen through for 20 minutes, (It is very important not to forget this when a spent absorption tube is replaced by a freshly-packed one.)  [c.475]

The polishing process should take between thirty seconds and one minute and the tube should then be placed on a small stand. The time at which polishing ended should be noted. The other tube is then treated similarly and the time at which polishing was completed again noted the two tubes should always be polished in the same order.  [c.476]

Some authorities recommend that the inside of the side-arms of the absorption tubes should also be polished by rubbing with pipc-cleaner. This, however, is unsatisfactory with the type of absorption tube that has greased taps as there is always a risk of removing traces of grease from the tap and hence of changing the weight of the tube. Although the side-arm interiors are not, therefore, specially polished, care should be taken that no minute pieces of rubber or wax from the impregnated tubing find their way into them. If this does take place, the offending particles should be carefully removed with a piece of very fine copper wire.  [c.476]

The boat is then transferred to the balance pan (narrow-ended meta tweezers are most suitable for this purpose) and weighed the weight of the empty boat should never vary by more than o i mg. during its working life. The boat is transferred to the grooved block (removed from the desiccator) and 20-25 mg. of the sample to be analysed are then transferred to it. This is best carried out using a very small, narrow-ended spatula, and it is essential that only a small amount of material is put in the boat at a time—the 20-25 mg. should be transferred in several operations. The boat is then gripped firmly with the tweezers and carefully tapped on the aluminium block this serves to remove any small particles of substance that may possibly be adhering to the outside of the boat and also to settle the charge of substance thinly and evenly along the whole length of the boat. The face and groove of the block are then carefully wiped with a polishing cloth. The boat is transferred to the balance pan and reweighed. It is then returned to the block and both replaced in the desiccator.  [c.477]

This operation of weighing out the sample of substance to be analysed may conveniently be carried out while waiting for the absorption tubes to mature after polishing.  [c.477]

Many students tend to forget the practical details learnt in elementary courses of chemistry they are therefore repeated here. To cut a piece of glass tubing, a deep scratch is first made with a triangular file or glass knife The tubing is held in both hands with the thumbs on either side of the scratch, but on the side opposite to it. The tubing is then pulled gently as though one wanted to stretch the tube and also open the scratch. A break with a clean edge will result. The cut edge must then be rounded or smoothed by fire polishing. The end of the tube is heated in the Bunsen fiame until the edges melt and become quite smooth the tube is steadily rotated aU the time so as to ensure even heating. Overheating should be avoided as the tube will then partially collapse.  [c.57]

Important sources, e.g. in South Africa, are the basic igneous rock known as kimberlite and also alluvials. The valuable diamond may be colourless or faintly coloured, but must be transparent. The heavily coloured forms, known as carbonado or bort, are of no value as gems, but are used for rock drills, for lathe tools, and when powdered for cutting and polishing clear diamonds. In cutting, the natural crystalline form is obliterated and an artificial shape, which gives rise to a large amount of internal reflection producing the fire of the stone, produced. The diamond is extremely hard, and stands highest in Mohs s scale of hardness. It possesses a high refractive index, and dispersive power. It is relatively much more transparent to X-rays than are its imitations. World production 1979 48 MKT, 62-5% southern Africa including Zaire.  [c.132]

The material seleeted for the production of the quasi-isotropic laminates was a prepreg material Fibredux 6376C-HTA-5-35. Specimens have a [0,+45,90,-45]s stacking sequence. The geometrical characteristics of the produced specimens are shown in Figure 1. The width is 20 mm and the thickness 1 mm. The specimens were subjected to edge polishing and aluminium end tabs were glued at the two ends of each specimen.  [c.46]

Most samples require some initial ex situ preparation before insertion into a vacuum chamber [45]. A bulk single crystal must first be oriented [48], which is usually done with back-reflection Laue x-ray diffraction, and then cut to expose the desired crystal plane. Samples are routmely prepared to be within +1° of the desired orientation, but an accuracy of+1/4° or better can be routinely obtained. Cutting is often done using an electric discharge machine (spark cutter) for metals or a diamond saw or slurry drill for semiconductors. The surface must then be polished. Most polishing is done mechanically, with alumina or diamond paste, by polishing with finer and finer grits until the finest available grit is employed, which is usually of the order of 0.5 pm. Often, as a final step, tlie surface is electrochemically or chemi-mechanically polished. In addition, some samples are chemically reacted in solution in order to remove a large portion of the oxide layer that is present due to reaction with the atmosphere. Note that tliis layer is referred to as the native oxide.  [c.302]

Due to its sensitivity to small forces and its ability to operate in liquids, the AFM has opened up a new avenue of investigation into colloidal systems. A frequently used approach, developed by Ducker et al [170], involves the cementing of a colloidal-sized particle onto an AFM cantilever in place of the usual tip, and then monitoring interactions with some appropriate flat surface, or even another colloidal particle [171], under a variety of conditions. Larson et al [172] used this teclmique to investigate the interactions between a titania (rutile) particle (s=9 pm diameter) and a rutile single-crystal surface under various conditions of pFl and ionic strengdi. From their experiments they were able to measure the van der Waals interaction between rutile surfaces directly, and to calculate the non-retarded Flamaker constant for the system. Biggs et al have applied a similar approach to the venerable subject of gold colloid stability [173], by innnobilizing a 6 pm gold sphere on a cantilever and measuring its interaction with a polished gold plate under solutions containing combinations of gold, citrate, chloride and a number of other ions of relevance to the colloid system. The autiiors were able to demonstrate the presence of a repulsive mteraction between the gold surfaces due to adsorbed citrate or chloride they showed that citrate adsorbed preferentially, and succeeded in measuring the surface potential of the gold as a fiinction of anion concentrations.  [c.1710]

It was the idea of Winterton [2] to glue the otherwise fragile mica sheets onto polished silica discs to give them better mechanical stability, especially for friction experiments. The glue layer detemiines the final  [c.1733]

Infrared spectroscopy has also been widely employed in electrochemistry [105. 106. and 107]. Spectra aid the identification of reactants, of products and of long-lived intennediates and allow changes in the interfacial solvent to be tracked. A variety of spectral sampling and data acquisition methods have been developed to approach in situ detection of species. In external reflection sampling methods, the infrared beam is directed tlnough a polarizer onto the front surface of a highly polished disc-shaped working electrode witli high reflectivity in the infrared spectral region, such as Pt, An or Ag. A special, thin-layer electrochemical cell is used that pennits the infrared beam to enter and strike the disc, where it is reflected out of the cell and detected. In contrast, in attenuated total internal reflection sampling methods, the working electrode is a thin film of metal deposited on one surface of an ATR crystal. The metal film must be sufiBciently thin to allow penetration of the IR evanescent wave beyond the metal solution interface. The ATR crystal fomis the bottom of a chamber that holds the electrolyte solution and the counter and reference electrodes and the crystal is positioned so that the metal film is inside the chamber. This method has not been widely used in electrochemistry partly due to the diflSculty in the preparation of the thin metal film working electrodes. Nonetheless, the latter design overcomes molecular transport limitations imposed by external reflection methods, where a thin solution layer of the order 1-5 pm between the front face of the working electrode and the infrared transparent window is required to minimize absorption of infrared radiation by tlie solvent. In fact, diflfiision of species into and out of the thin-layer region is restricted and can lead to reactant depletion or product accumulation.  [c.1948]

Carnal D, Oden P I, Muller U, Schmidt E and Siegenthaler FI 1995 In situ STM investigation of T1 and Pb underpotential deposition on chemically polished Ag(111) electrodes E/ecfroc/r/m. Acta 40 1223-35  [c.2758]

Chamois cloths are used to polish the tubes and it is essential to have a carefully controlled scheme of polishing, so that any tube is always polished in the same way and for the same length of time. Before polishing is started, one of the taps of the absorption tube should be opened momentarily in order to equalise the gas pressure inside and outside the tube. It is probably simplest to use two cloths and start polishing in the middle of the tube, outwards, first towards one end and then towards the other (always starting towards the same end first) and including the side-arms and taps, care being taken not to dislodge the latter. Once polishing has started, the tubes should no on account be touched w ith the fingers.  [c.475]

The tubes are left on their rack until ten minutes have elapsed since the completion of polishing of the first one the latter is then transferred to a small aluminium rider which holds it firmly and evenly on the balance pan. This transfer may best be accomplished by using a pair of thin metal tweezers of wide aperture, whose ends have been slightly bent inwards, to grip the tube firmly and easily. The time at which the final counterpoising and reading is made is noted. At the end of the combustion when the tubes have been momentarily opened to the air, repolished exactly as before and are reweighed, their weight will be known to within a few milligrams and the weighing will therefore be rather more rapid in the second case than in the first hence the tube is allowed to mature for a slightly longer time in the second case so that exactly the same length of time elapses, between the end of polishing and the final counterpoising, as before the combustion.  [c.476]

A little practice in polishing and wefghing the absorption tubes is desirable before an actual analysis is carried out. It is important that when the taps on the absorption tubes are off, they should be as far "off" as possible (I. e., hole in lap is 180 away from side-arm hole).  [c.476]

The oxygen is turned on, tap Tj carefully opened and the furnace N and the thermostatic mortar P then turned on. The apparatus can conveniently be allowed to attain its equilibrium temperature over the period of about 20 minutes while the absorption tubes are being polished and weighed and the specimen for andysis weighed out it is thus ready for immediate use as soon as the weighings have been completed.  [c.477]

The absorption tubes are then detached from each other, transferred to their stand, and polished, matured and weighed exactly as at the beginning of the experiment, taking care that no particles of rubber or wax are left in the side-arms. They must be repolished, matured and reweighed before they are used for a further determination. Finally when the tube is cool, the tap Tj of the purification train may be closed and the oxygen supply shut off.  [c.481]


See pages that mention the term Polishing : [c.310]    [c.52]    [c.53]    [c.61]    [c.75]    [c.84]    [c.132]    [c.156]    [c.197]    [c.347]    [c.394]    [c.399]    [c.400]    [c.425]    [c.233]    [c.272]    [c.314]    [c.1940]    [c.1941]    [c.99]    [c.196]   
Corrosion, Volume 2 (2000) -- [ c.12 , c.32 ]