Preparation of the Substrate

One of the most important factors in the field of the strengthening systems with composite materials is the transmission of stresses from the support of the member to be reinforced to the reinforcement materials. If such a transfer of loads is not ensured, the correct functioning of the reinforcement systems will be affected. 

In the preliminary stage of the drawing up of the reinforcement plan, besides the evaluation of the mechanical properties of the members making up the structure, tests for the mechanical properties of the substrate should also be performed. The higher or lower incidence of the substrate characteristics is a function of the kind of application that is to be used either with reference to adherence applications (bending or shear reinforcement) or contact applications (passive confinement of masonry columns or pillars). In order to increase the mechanical properties of the substrate, it is possible to intervene in advance and apply composite materials by laying a suitable primer using special products. 

The decision on the kind and number of tests to be performed should be made for each individual appUcation by assessing  

In the case of operations on a masonry surface not requiring any restoration, but possibly just being of a poor quahty, an evaluation of the possible application of a consolidating agent on it before the laying of the primer is advisable. 

Moreover, it must be made sure that the parts of the members concerned with the reinforcement with composite are perfectly clean, by removing dust, fats, hydrocarbons, and surface-actives from them. 

Preparation of the substrate at which the layer is deposited is critically important. Some deposition techniques operate at an elevated temperature of the substrate 

Reactive group 1 (e.g. on surface) Intermediate Reactive group II (e.g. on terminal reagent) Coupling linkage type  

Surface characterization techniques, such as photoelectron spectroscopy, can be used to verify the quality of the surface of such layers. 

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Poor preparation of the substrate can result in loss of adhesion, pitting, roughness, lower corrosion resistance, smears, and stains. Because electroplating takes place at the exact molecular surface of a work, it is important that the substrate surface be absolutely clean and receptive to the plating. In the effort to get the substrate into this condition, several separate steps may be required, and it is in these cleaning steps that most of the problems associated with plating arise. 

Scheme 33 Preparation of the substrate (220) for an intramolecular Knoevenagel condensation...

For preparation of the substrate solution, it is common practice to dissolve bilirubin at alkaline ])H (pH 11-12.5) and subsequently to lower the pH to the required value, usually pH 7.4-8.2. The bilirubinate solu-... 

The nucleophilic vinylic substitution (S mV) of heteroatom-substituted alkylidene Meldrum s acids has been intensively studied and kinetics of the reaction <1998JOC6266, 1999CJC584, 2004JOC9248> as well as synthetic applications have been reported <19978567, 2002JHC15, 2005EJ04870> (cf. Section 8.11.4.2, Scheme 10). The preparation of the substrates and a sample application is shown in Scheme 90 <2001J(P2)1534>. 

STEP 2 PREPARATION OF THE substrate(s). While ahnost any substrate can be used, we will use glass microscope slides in this example this is a common substrate and makes it easy to see the CdS film. The microscope slide can be cut to whatever size and shape is convenient. The slide should be cleaned well, since films usually do not adhere well to dirty surfaces. Suitable cleaning agents are trichloroethylene or/and sulphochromic acid, and the slide should be well rinsed with pure water. If the slide is clean, water dropped onto it will form a film (hydrophilic surface), while on a dirty (hydrophobic) slide the water will form drops. Needless to say, the part of the slide where deposition is to occur should not be touched with the hands after this treatment. 

As a general procedure, the first step is preparation of the substrate, which may include cleaning, sizing and applying thin overlay by lamination to cover surface imperfections. Metal surfaces often need a primer coat to assure a good bond of the first coat to the metal. The first coat is then applied to the pretreated substrate. 

Surface Preparation of the Substrate. This is extremely important for all methods of paint and coatings application. The failure of a paint system is often due not to the paint itself, but because of a failure in surface preparation. For example, an anticorrosive paint applied to a rusty surface will not be effective if the rust falls off taking the new paint with it. For wood and plastic surfaces, old paint or a weathered surface layer may have to be removed. For older metal objects, the removal of corrosion is often required. Sandblasting is one method to remove both the old paint and any corrosion. For new metal objects, a phosphate or chromate layer is often chemically bonded to the metal to provide a surface to which a coating can easily adhere. 

Initial experiments with thin films indicated that the surface preparation of the substrate plays an important role. Homogeneous films were obtained on zinc and steel substrates only if the substrate was alkaline-cleaned after mechanical polishing. 

Growth Procedures. The exact procedures for the growth of devicequality epitaxial films by LPE vary with the deposited material, the design of the growth equipment, and the structure to be fabricated. The general procedure involves preparation of the substrate, loading of the melt constituents and pretreatment of the system, and growth. 

The first stage of the synthesis is the preparation of the substrate for enzymatic polymerization, the polyprenyl pyrophosphate-galactosy1-rhamnosy1-mannose XXI. Since the most convenient way to control the polycondensation reaction is the use of isotopic methods, a procedure for incorporation of tritium into trisaccharide I was developed (2 5). Labelled trisaccharide was then converted into the glycosyl phosphate XIX through interaction of its peracetate III with anhydrous phosphoric acid (26). Conditions were found under which the reaction is accompanied by minimal destruction and yields the Ot-phosphate of the trisaccharide. 

It should be noted that a Z2 dependence of the cross section makes the process very sensitive for heavier elements but proportionately less so for lighter elements. This effect can be observed in Figure 1 when it is noted that the Au peak indicates the presence of only about 0.04j Au compared to about 5056 for the 0 peak. In the latter case the sensitivity is further degraded by the superposition of the 0 peak from the thin film with the distribution from the thick underlying Si substrate. It should be further noted here that the Si substrate is prevented from interfering with other elements by the special preparation of the substrate by placing a film of C on its surface before deposition of the sample thin film. This technique is useful when one has the opportunity to choose the substrate. 

On the other hand, the preparation of the substrate is far from easy and demands considerable technical skill. Another drawback is the strong electroendosmosis which amounts to half the main electrophoretic mobility and drives (1- and y-globulins toward the cathode. This means that the application zone lies in the middle of the run and disturbs photometric scanning. Microelectrophoresis, according to Scheidegger (SI), is among the promising developments in this field of electrophoresis. With this substrate it becomes possible to perform an electrophoresis on an ultramicroscale with as little as 0.1-1 (ig protein, which needs about 3 minutes (Wl). 

Fig. 2.33. Mitsunobu inversion a typical substrate, the reagents, and products (possible preparation of the substrate Figure 2.27). "DEAD" stands for diethyl-azodicarboxylate.

Fig. 3.38. Diastereoselective Sharpless epoxidation of chiral primary allylic alcohols (for the preparation of the substrate see Figure 17.63)...

Fig. 17.63. DIBAL reduction of an a,/3-unsaturated ester to an allylic alcohol. (See Figure 11.6 for a preparation of the substrate.)...

With regard to the preparation of the substrates, which has not been thoroughly discussed here, we will only remark that the efficiency of the synthetic methods so far reported for preparation of some of the most widely used... 

In view of the excessive length of the 10-step preparation of the substrate 30 from 19, we planned to develop a more convenient route to 30. Our improved route is depicted in Scheme 4. The Payne rearrangement of 19 with KN(TMS)2 in the presence of 18-crown-6 ether in THF at -18 °C afforded the epoxy-migrated compound 20 in 62% yield along with 30% recovery of 19. This Payne rearrangement produced the equilibrium mixture of 20 and 19. We explored this rearrangement by changing the base and reaction temperature. The most... 

Surface preparation of the substrates for both adhesive bonding and resistance welding... 

A separate section of this book discusses the selection and design of substrate structures which are required to support chemically-resistant masonry. This section will not duplicate what appears therein, except to warn the designer of three things. (1) The designer must verify that the substrate selection and design are adequate to provide the necessary support for the full load anticipated with a safety factor of not less than 1V2, without visible deflection. (2) He must check with the materials manufacturers and installers of all the materials he has selected which will be in direct contact with the substrate to determine what surface strength and surface preparations of the substrate should be provided, and then be certain that these requirements are included in his specifications. (3) He must verify that there is nothing in the materials that will be in contact... 

Typically, STM is the method of choice to receive high resolution images and to gain insight into the electronic structure of molecules on conductive substrates. STM data depend on the electronic interaction of the molecule with the substrate and therefore require a careful choice and preparation of the substrate. 

Many books have been dedicated over the years to the topic of electrodeposition (see, for example, Refs. 1-6). These books deal with a variety of sub-topics such as surface preparation of the substrate prior to deposition, thermodynamics and kinetics of electrodeposition, the reactions that take place on an atomistic level, the mechanisms of growth, the effect of bath chemistry and operating conditions, the deposition of specific metals and alloys, the structure and properties of deposits, etc. 

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