Comparing Surface Finish Properties

Table 32.12 compares surface finishes by type and property and summarizes the material presented in this chapter. 

Ni-AI Bronze. Cast Ni-Al bronze has been friction stir processed (FSP), as reported by Ref 26. Yield strength of the FSP material (420 MPa, or 61 ksi) was more than double that of the cast alloy (193 MPa, or 28 ksi). Tensile strength also increased substantially due to the processing (700 MPa compared with 420, or 102 ksi compared with 61). However, elongation dropped to 14%, compared with 20% in the as-cast material. Surface finish and tool life were both excellent. In addition to the improvement in as-cast properties, FSP was demonstrated to reduce or eliminate internal porosity due to casting defects. 

It should be noted that most optical properties are greatly affected by the condition of the surface, so that the method of preparation of test pieces is most important and needs to be carefully controlled if comparative results are required. To obtain a very high standard of surface finish, molding against platens of borosilicate glass without a release agent has been recommended,... 

The glass-reinforced thermoplastic polyester resins are nnusual in that they are the first thermoplastic that can compare with, or are better than, thermosets in electrical, mechanical, dimensional, and aeep properties at elevated temperatures (approximately 150°C), while having superior impact properties. The glass fiber concentration usually ranges from 10 to 30 percent in commercially available grades. In molded parts, the glass fibers remain slightly below the surface so that finished items have a very smooth surface finish as well as an excellent appearance. 

Every material has frictional (tribologic) properties. Some are naturally lubricating, such as Sn-Pb alloys, and others are notably nonshppery, such as tin or copper. Copper is one of the least slippery of the surface finishes and typically requires more pressing force than Sn-Pb or gold finishes for a comparably sized hole. Tin s crystalline structure is also rather resistant to sliding. In some cases, extra attention to PTH finished hole size (FHS) is required. The PWB vendor should be alerted to the fact that holes are being placed in the board for press-fit, so FHS and surface finish conditions are appropriate for the press-fit component. In some cases, for some materials such as copper, the holes could be specified for the upper end of its FHS as expressed by the connector vendor to aid in insertion. FHS should be just that the hole size after surface finish is applied. 

The method using GC/MS with selected ion monitoring (SIM) in the electron ionization (El) mode can determine concentrations of alachlor, acetochlor, and metolachlor and other major corn herbicides in raw and finished surface water and groundwater samples. This GC/MS method eliminates interferences and provides similar sensitivity and superior specificity compared with conventional methods such as GC/ECD or GC/NPD, eliminating the need for a confirmatory method by collection of data on numerous ions simultaneously. If there are interferences with the quantitation ion, a confirmation ion is substituted for quantitation purposes. Deuterated analogs of each analyte may be used as internal standards, which compensate for matrix effects and allow for the correction of losses that occur during the analytical procedure. A known amount of the deuterium-labeled compound, which is an ideal internal standard because its chemical and physical properties are essentially identical with those of the unlabeled compound, is carried through the analytical procedure. SPE is required to concentrate the water samples before analysis to determine concentrations reliably at or below 0.05 qg (ppb) and to recover/extract the various analytes from the water samples into a suitable solvent for GC analysis. 

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