An Example of Preparation

The elaboration of cordierite tubular supports is described in Fig. 5.9. The values correspond to 3 kg paste preparation and shaping with a laboratory piston extruder. 

There are about 4 parts of cordierite powder for 1 part of organics. The 18 wt% of organics is composed as follows 4 wt% of gel of corn starch as binder. 

5 — CERAMIC PR(XISSING TECHNIQUES OF SUPPORT SYSTEMS FOR MEMBRANES SYNTHESIS 

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Finally, with respect to successive evaporation, Pd-Rh films used for CO oxidation (34) are an example of preparing alloy films where a miscibility gap exists and interdiffusion rates are slow. These Pd-Rh films were prepared by depositing layers of palladium and rhodium at 0°C, followed by annealing in 50 Torr hydrogen at 400°C for 21 hr. The apparent surface compositions, evaluated from the CO oxidation rate as described in Section IV, and information on film structure obtained by X-ray diffraction (XRD) are recorded in Table II. 

In this reaction the source of the azoxy oxygen appears to be the nitroso group [6]. The preparation of t-butyl-OAW-azoxymethane (iV-methyl-A -t-butyldiazine jV -oxide) is an example of preparation of an unsymmetrical azoxy compound which is quite generally applicable. The structure assignment is based on NMR data. 

Copolymers of ethyl- and chloro-p-xylylene were also prepared by pyrolytic polymerization of mixtures of dichloro-di-p-xylylene and diethyl-di-p-xylylene at 50°C. This is an example of preparation of a copolymer by pyrolysis of a mixture of two disubstituted di-p-xylylenes. 

Reference materials are obtained with known uranium concentrations and isotope ratios. These are used to spike base urine to prepare at least two depleted isotopic ratios. If appropriate licensing is available, then an enriched isotopic spike should also be included. An example of preparation follows. 

Active PG fibers can be obtained from PAN fibers by means of a heating at 220 °C in atmospheric pressure for 5 hours, and then saponification with boiling in 1M (molar) NaOH for 30 min, following the process reported in [203], The procedure transforms the original PAN fibers into swollen fibers of amphoteric amino-carboxylic polyelectroljde gels. An example of preparation of PG samples is also reported on the following web site http //ndeaa.jpl.nasa.gov/nasa-nde/lommas/eap/EAP-recipe-UA.htm. 

An example of preparation of CP samples is also reported on the following web site http //ndeaa.jpl.nasa.gov/nasa-nde/lommas/eap/Polypirrole-PrepProcedure. ht m. 

This is an example of preparing a water reducible resin using an emulsion polymerisation technique. In the next section, the preparation of water reducible resins using a solution polymerisation technique is considered. 

This type of coil was prepared from copper cladded printed circuit board material by applying photolithographic techniques. The p.c. board material is available with difierent copper thicknesses and with either a stiff or a flexible carrier. The flexible material offers the opportunity to adapt the planar coil to a curved three dimensional test object. In our turbine blade application this is a major advantage. The thickness of the copper layer was chosen to be 17 pm The period of the coil was 100 pm The coils were patterned by wet etching, A major advantage of this approach is the parallel processing with narrow tolerances, resulting in many identical Eddy current probes. An example of such a probe is shown in fig. 10. 

Thin oxide films may be prepared by substrate oxidation or by vapour deposition onto a suitable substrate. An example of the fomrer method is the preparation of silicon oxide thin-films by oxidation of a silicon wafer. In general, however, the thickness and stoichiometry of a film prepared by this method are difficult to control. 

Beams of metal atoms have been prepared by many researchers tlirough thennal vaporization from a heated cmcible. An example of such a source, employed for the generation of beams of alkaline earth atoms, is described by Irvin and Dagdigian [H]. By striking an electrical discharge within this source, beams... 

Figure C2.17.3. Close-packed array of sub-micrometre silica nanoparticles. Wlren nanoparticles are very monodisperse, they will spontaneously arrange into hexagonal close-packed stmcture. This scanning electron micrograph shows an example of this for very monodisperse silica nanoparticles of -250 nm diameter, prepared in a thin-film fonnat following the teclmiques outlined in [236].

For an example of sublimation, see the preparation of anthra-quinone, p. 259 for semi-micro sublimation, see p. 69. 

The preparation of -butyl bromide as an example of ester formation by Method 1 (p. 95) has certain advantages over the above preparation of ethyl bromide. -Butanol is free from Excise restrictions, and the -butyl bromide is of course less volatile. and therefore more readily manipulated without loss than ethyl bromide furthermore, the n-butyl bromide boils ca. 40° below -butyl ether, and traces of the latter formed in the reaction can therefore be readily eliminated by fractional distillation. 

This preparation is an example of the use of di-M-butyl ether as a solvent in the Grignard reaction. The advantages are it is comparatively inexpensive, it can be handled without excessive loss due to evaporation, simple distillation gives an ether free from moisture and alcohol, and the vapour does not form explosive mixtures with air. n-Butyl ether cannot, of course, be employed when the boiling point of the neutral reaction product is close to 140°. 

This is an example of an acetylenic alcohol. It is prepared from acetone by the following series of reactions ... 

It is convenient to include under Aromatic Amines the preparation of m-nitroaniline as an example of the selective reduction of one group in a polynitro compound. When wt-dinitrobenzene is allowed to react with sodium polysulphide (or ammonium sulphide) solution, only one of the nitro groups is reduced and m-nitroanUine results. Some sulphur separates, but the main reaction is represented by ... 

An example of this is given in Section IV.63—the conversion of 3-bromo-4-aminotoluene into m-bromotoluene. Another application is to the preparation of. iM.-tribromobenzene (Section IV,72) ... 

Here the phenylacetic anhydride, possessing more reactive a-hydrogen atoms, condenses with benzaldehyde to give a-phenylcinnamic acid. The preparation of the latter is an example of the Oglialoro modiflcation of the Perkin reaction. 

Mandelic acid. This preparation is an example of the synthesis of an a-hydroxy acid by the cyanohydrin method. To avoid the use of the very volatile and extremely poisonous hquid hydrogen cyanide, the cyanohydrin (mandelonitrile) is prepared by treatment of the so um bisulphite addition compound of benzaldehj de (not isolated) with sodium cyanide ... 

The preparation of 2 4-dimethyl-3 5-dicarbethoxypyrrole (II) is an example of the Knorr synthesis of pyrrole derivatives, involving the reaction of an -aminoketone (or a derivative thereof) with a reactive methylene ketone (or a derivative thereof). The stages In the present synthesis from ethyl acetoacetate (I) may be represented as follows ... 

The preparation of 4-methylcoumarin is an example of the Pechmann reaction, which consists in the interaction of a phenol with a 3-ketonic ester In the presence of a condensing agent (sulphuric acid, aluminium chloride, phosphorus oxychloride or pho.sphoric oxide) ... 

Crystal violet is an example of a triphenylmethane dye. Its preparation in the laboratory may be illustrated by the condensation of 4 4 -tetramethyl-diaminobenzophenone (Michler s ketone) and dimethylaiiiliue in the presence of phosphorus oxychloride ... 

Vinylation can also be done by Pd-catalysed cross-coupling in which one component is used as a halide or triflate and the other as a stannane (Stille reaction) or boronic acid (Suzuki reaction). Entry 9, Table 11.3, is an example of the use of a vinylstannane with a haloindole. lndole-3-boronic acids, which can be prepared by mcrcuration/boration, undergo coupling with vinyl triflates (Entry 10). 

When propene is polymerized under free radical conditions the polypropylene that results IS atactic Catalysts of the Ziegler-Natta type however permit the preparation of either isotactic or syndiotactic polypropylene We see here an example of how proper choice of experimental conditions can affect the stereochemical course of a chemical reaction to the extent that entirely new materials with unique properties result... 

The elastomer produced in greatest amount is styrene-butadiene rubber (SBR) Annually just under 10 lb of SBR IS produced in the United States and al most all of it IS used in automobile tires As its name suggests SBR is prepared from styrene and 1 3 buta diene It is an example of a copolymer a polymer as sembled from two or more different monomers Free radical polymerization of a mixture of styrene and 1 3 butadiene gives SBR... 

This reaction occurs quickly and is of known stoichiometry. A titrant of SCN is easily prepared using KSCN. To indicate the titration s end point we add a small amount of Fe + to the solution containing the analyte. The formation of the red-colored Fe(SCN) + complex signals the end point. This is an example of a direct titration since the titrant reacts with the analyte. 

Ester interchange reactions are valuable, since, say, methyl esters of di-carboxylic acids are often more soluble and easier to purify than the diacid itself. The methanol by-product is easily removed by evaporation. Poly (ethylene terephthalate) is an example of a polymer prepared by double application of reaction 4 in Table 5.3. The first stage of the reaction is conducted at temperatures below 200°C and involves the interchange of dimethyl terephthalate with ethylene glycol... 

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