Surface treatment cleanliness

Nondestructive Testing. Nondestructive testing (NDT) is far more economical than destructive test methods, and every assembly can be tested if desired. Several nondestructive test methods are used to check the appearance and quality of structures made with adhesives or sealants. The main methods are simple ones such as visual inspection, tap, proof, and more advanced physical monitoring such as ultrasonic or radiographic inspection. The most difficult defects to find are those related to improper curing and surface treatments. Therefore, great care and control must be exercised in surface preparation procedures and shop cleanliness. 

This is the most important step in the surface treatment. The purpose is primarily to get a surface with high cleanliness and adequate roughness. The pre-treatment can mainly be divided in two groups a) degreasing and b) removal of mill scale and rust, and simultaneously roughening the surface. 

Testing is important in all aspects of materials science and engineering, but it is especially so in adhesives. Such tests evaluate not only the inherent strength of the adhesive, but also the bonding technique, surface cleanliness, effectiveness of surface treatments, etchings of surfaces, application and coverage of the adhesive, and the curing cycle. 

Visual inspection. Visual inspection, with the help of a strong light, can be used to detect gross flaws and defects. Table 12.2 lists the characteristics of faulty joints that can be detected visually. The most difficult to detect by any means are those defects related to improper curing and surface treatments. For this reason, great care and control must be given to surface preparation procedures and shop cleanliness. ... 

As with adhesive bonding, surface treatment emd cleanliness is of primary importance when decorating plastic parts. Prior to decoration, the svirface of the plastic part must be cleaned of mold release, internal plastics lubricants, and plasticizers. Plastic parts can also become electrostatically charged and attract dust. This could disrupt the even flow of a coating or interfere with adhesion. Solvent or destaticizers may be used to clean and eliminate static from plastic parts prior to decorating. Cleaning of the plastic part requires an understanding of the plastic material to be cleaned and the effect of the solvents and processes on that plastic. 

High Vacuum insulation is used for applications below (—) 200°F in double wall cryogenic vessels, as opposed to insulation between the inner and outer vessel walls. Surface reflectivity and emissivity are important factors for these applications and are a function of surface treatment, flnish and cleanliness. High vacuum systems are designed to 10 torr and less. The better the surface flnish and the higher emissivity, the better the insulating properties. 

Advanced surface treatments often require the use of vacuum chambers to ensure proper cleanliness and control. Vacuum processes are generally more expensive and difficult to use than liquid or air processes. Facilities can expect to see less-complicated vacuum systems appearing on the market in the future. In general, use of the advanced surface treatments is more appropriate for treating small components (e.g., ion beam implantation, thermal spray) because the treatment time for these processes is proportional to the surface areas being covered. Facihties will also have to address the following issues when considering the new techniques ... 

The treatment protocols identify the base plasma inert gas chemistry, assisted by a reactive oxygen component, which was determined to optimize treatment results relative to the solar cell application. For example, specific peel adhesion benchmarks were targeted for PVC adhesion to a solvent-base adhesive. To meet cleanliness benchmarks, pre-specified low level organic particle contamination concentrations were established to optimize lamination adhesions. The required power densities applied to each protocol were predetermined with regard to the required surface effect by laboratory trials on commercial roll-to-roll and tangential atmospheric plasma surface treatment systems. 

We have undertaken a series of experiments Involving thin film models of such powdered transition metal catalysts (13,14). In this paper we present a brief review of the results we have obtained to date Involving platinum and rhodium deposited on thin films of tltanla, the latter prepared by oxidation of a tltanliua single crystal. These systems are prepared and characterized under well-controlled conditions. We have used thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES) and static secondary Ion mass spectrometry (SSIMS). Our results Illustrate the power of SSIMS In understanding the processes that take place during thermal treatment of these thin films. Thermal desorption spectroscopy Is used to characterize the adsorption and desorption of small molecules, In particular, carbon monoxide. AES confirms the SSIMS results and was used to verify the surface cleanliness of the films as they were prepared. 

The values of PRE for duplex stainless steels are given in Table 4.13. It is useful to note that the PRE relationship does not take into account factors such as surface condition, internal cleanliness, heat treatment and related properties that influence... 

Similar to XPS in terms of the analysis and interpretation of spectra, the cost of LEISS analysis is relatively high with regard to the preparation of the sample. This is because constraints on vacuum quality and the cleanliness of the sample surface are stricter. A pre-treatment operation lasting several hours is often required. 

The importance of oxygen is also seen in the next paper on methanation over Co and Ni foils. Palmer and Vroom" used AES to monitor surface cleanliness and a line-of-sight mass spectrometer to study products. Pre-treatment with O2 followed by H2 reduction produced a very active Ni or Co surface believed to result from subsurface O. These authors also invoke the breakdown of CO via the Boudouard reaction, 2CO(g)->C(s) + CO 2(g), to explain their results in that the methanation rate in the presence of H2 matches the rate of disproportionation of CO. 

Treatment of steel with calcium enhances, for example, the mechanical properties such as formability, drawing, impact, tensile, machinability, resistance to cracking and tearing and leads to an improved surface and internal cleanliness calcium alloys are used to deoxidize magnesium, to strengthen electrodes, and to produce special aluminum alloys, etc. 

Table 14.4 contains a small selection of the reported product distributions, but a fuller recapitulation is not warranted because in much of the earlier work (and some of the later) there is a lack of awareness of the importance of experimental variables in determining product selectivities. Relevant factors include (i) surface cleanliness (especially carbon ) and type of pre-treatment, (ii) temperature, and (iii) the hydrogen/MCP ratio used. There is however some disagreement as to the importance of the latter. 

Prior to metallization or plasma treatment, all polymers were annealed in the spectrometer preparation chamber to drive off any residual solvent, water, or adsorbed gases. The annealing temperature corresponded to a value slightly higher than the polymer Tg, except for low Tg polymers which were annealed at -lOO C. After annealing, the polymer surfaces were characterized with XPS to verify the surface cleanliness and stoichiometry. 

The cleaning protocol may include polishing, ultrasonic treatment in different solvents and solutions, plasma and UV/ozone etching, or sputtering a fresh surface from the IRE material, depending on the system under study. The surface cleanliness may be checked by comparing the ATR spectrum of the cleaned sample IRE with the spectrum of a new reference IRE. 

Pretreatment of the titanium surface is an essential prerequisite for reproducible silanization. Untreated titanium films (as sputtered) gave imsatisfactory results. Optimum surface cleanliness and reactivity were achieved through water—vapor—plasma treatment, although other pretreatments such as H2O2 or HCl also gave satisfactory results. 

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