Sectioning technique solution preparation

Both wet-ceramic techniques and direct-deposition techniques require preparation of the feedstock, which can consist of dry powders, suspensions of powders in liquid, or solution precursors for the desired phases, such as nitrates of the cations from which the oxides are formed. Section 6.1.3 presented some processing methods utilized to prepare the powder precursors for use in SOFC fabrication. The component fabrication methods are presented here. An overview of the major wet-ceramic and direct-deposition techniques utilized to deposit the thinner fuel cell components onto the thicker structural support layer are presented below. 

The most important method used in the preparation of polyamides is direct amidation, usually through the intermediate formation of a salt of the diamine and dicarboxylic acid, but without it in the case of aminoacids or for pairs of monomers that do not readily form a salt. Esters can react with diamines to form polyamides with liberation of alcohol or phenol. Diamines can be reacted with diamides yielding polyamides and freeing ammonia. Polyamides have been prepared by acidolysis of acyl derivatives of diamines (compare Section 5.4 for acidolysis in polyester preparation). Bis-anhydrides react with diamines to form polyamides and, if reacted further, polyimides. The low-temperature reaction of acid chlorides with diamines has been used, interfacially or as a solution technique, to prepare certain polyamides (compare Section 5.7 for related reactions in polyester synthesis). 

ICP emission spectroscopy is used primarily for the qualitative and quantitative analysis of samples that arc dissolved or suspended in aqueous or organic liquids. I he techniques for preparation of such solutions are similar lo tho.se described in. Section 9D-1 for flame absorption methods. With plasma emission, however, it is possible to analyze solid samples direclly. These procedures include incorporating electrothermal vaporization, la.ser and S[)ark ablation, and glow-discharge vaporization, all of which were described in Section 8C-2. Suspensions of solids in solutions can... 

Acidic Hydrolysis. In a small round-bottom flask equipped for magnetic stirring under reflux, combine 1 g of the nitrile with 10 ml of concentrated sulfuric acid or concentrated hydrochloric acid and warm the mixture to 50 °C for about 30 min. Dilute the mixture by addition of 20 ml of water. Caution Add the mixture slowly to the water if sulfuric acid has been used. Heat the mixture under gentle reflux for 30 min to 2 h and then allow it to cool. The acid usually forms a separate layer. If the acid solidifies upon cooling, collect it by vacuum filtration. If it is a liquid, extract the acidic mixture with small portions of diethyl ether, dry and decant the ethereal solution, and remove the solvent by one of the techniques described in Section 2.29. Prepare suitable derivatives of the acid (Sec. 25.13). 

Neutraiize the acidic soiution in the receiver, perform the Hinsberg test (Sec. 25.14A), and prepare derivatives of the amine (Sec. 25.14). If the amine is not voiatiie enough to distiii, and thus is not found in the receiver, use small portions of diethyl ether to extract it from the aqueous layer contained in the stillpot. Dry the combined ethereal extracts over potassium hydroxide pellets, decant the solution, and then remove the solvent by one of the techniques described in Section 2.29. Prepare derivatives of the amine from the residue remaining after solvent removal (Sec. 25.14). 

Despite careful operation, errors can stiU occur during sample preparation and due to the wrong choice of sectioning technique. An overview of the most common errors encountered during sectioning is given in [3], and a detailed description of the method, as well as of the errors and solutions, is in the monograph [14]. 

Determination of gold concentrations to ca 1 ppm in solution via atomic absorption spectrophotometry (62) has become an increasingly popular technique because it is available in most modem analytical laboratories and because it obviates extensive sample preparation. A more sensitive method for gold analysis is neutron activation, which permits accurate determination to levels < 1 ppb (63). The sensitivity arises from the high neutron-capture cross section (9.9 x 10 = 99 barns) of the only natural isotope, Au. The resulting isotope, Au, decays by P and y emission with a half-life of 2.7 d. 

Reagents. In view of the sensitivity of the method, the reagents employed for preparing the ground solutions must be very pure, and the water used should be re-distilled in an all-glass, or better, an all-silica apparatus the traces of organic material sometimes encountered in demineralised water (Section 3.17) make such water unsuitable for this technique unless it is distilled. The common supporting electrolytes include potassium chloride, sodium acetate-acetic acid buffer solutions, ammonia-ammonium chloride buffer solutions, hydrochloric acid and potassium nitrate. 

For the application of flame spectroscopic methods the sample must be prepared in the form of a suitable solution unless it is already presented in this form exceptionally, solid samples can be handled directly in some of the non-flame techniques (Section 21.6). 

In addition to the preparation of Langmuir and Langmuir-Blodgett films, the use of self-assembly techniques also plays an important role in the formation of particle films. Both physisorption, as, for example, electrostatic adsorption of charged particles from colloidal solution, and chemisorption onto a substrate have been investigated. In Section V.A, electrostatic adsorption will be reviewed chemisorption is the subject of Section V.B. 

Several review articles have been published about SILAR-grown films.4-7 The SILAR technique, including its advantages and disanvantages and the equipment employed, is presented in Section 8.2. Materials that have been prepared by SILAR are reviewed in Section 8.3. Short descriptions of the related ILGAR, ECALE, and other sequential solution-phase techniques follow in Sections 8.4- 8.6. 

In some manufacturing process analysis applications the analyte requires sample preparation (dilution, derivatization, etc.) to afford a suitable analytical method. Derivatization, emission enhancement, and other extrinsic fluorescent approaches described previously are examples of such methods. On-line methods, in particular those requiring chemical reaction, are often reserved for unique cases where other PAT techniques (e.g., UV-vis, NIR, etc.) are insufficient (e.g., very low concentrations) and real-time process control is imperative. That is, there are several complexities to address with these types of on-line solutions to realize a robust process analysis method such as post reaction cleanup, filtering of reaction byproducts, etc. Nevertheless, real-time sample preparation is achieved via an on-line sample conditioning system. These systems can also address harsh process stream conditions (flow, pressure, temperature, etc.) that are either not appropriate for the desired measurement accuracy or precision or the mechanical limitations of the inline insertion probe or flow cell. This section summarizes some of the common LIF monitoring applications across various sectors. 

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