General Pans

Most general and hermetic DSC pans are punched out of thin aluminum sheet that is contaminated with small amounts of machine oil. If these pans are used 

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In general, pan filters are selected for freely filtering soHds and thick filter cakes. Cake washing can be introduced easily. Most appHcations are in the mining and metallurgical industries for small-scale batch filtration. 

FIGURE 2.7 Comparison of the effect of increasing the heating rate upon the initial start up transient of a DSC. Empty general pans were placed in both the sample and reference positions. Nitrogen purge gas at 25 ml/min. 

FIGURE 2.9 Heat flow and derivative temperature data for the first 5 min of a DSC experiment on 2.780 mg of indium heated at 10°C/min in an aluminum general pan. Nitrogen purge gas at 25 ml/min. 

Although the first two cultural renderings of the problem of climate change were generally panned for their sensationalism and implausibility, Robinson s Science... 

These structural differences may be important selection criteria in view of battery applications. In general, PAN-based membranes, having characteristics somewhat approaching those of a "tme" polymer electrolyte entity, are be expected to be more stable than PMMA-based membranes or, generally, than membranes having characteristics of purely hybrid systems. 

At high enough concentrations, PAN is a potent eye irritant and phytotoxin. On a smoggy day in the Los Angeles area, PAN concentrations are typically 5 to 10 ppb in the rest of the United States PAN concentrations are generally a fraction of a ppb. An important formation route for formaldehyde [50-00-0] HCHO, is reaction 9. However, o2onolysis of olefinic compounds and some other reactions of VOCs can produce HCHO and other aldehydes. 

Pan and cascade burners are generally more limited ia flexibiHty and are useful only where low sulfur dioxide concentrations are desired. Gases from sulfur burners also contain small amounts of sulfur trioxide, hence the moisture content of the air used can be important ia achieving a corrosion-free operation. Continuous operation at temperatures above the condensation poiat of the product gases is advisable where exposure to steel (qv) surfaces is iavolved. Pressure atomiziag-spray burners, which are particularly suitable when high capacities are needed, are offered by the designers of sulfuric acid plants. 

Carbon fibers are generally typed by precursor such as PAN, pitch, or rayon and classified by tensile modulus and strength. Tensile modulus classes range from low (<240 GPa), to standard (240 GPa), intermediate (280—300 GPa), high (350—500 GPa), and ultrahigh (500—1000 GPa). Typical mechanical and physical properties of commercially available carbon fibers are presented in Table 1. 

More than 95% of current carbon fiber production for advanced composite appHcations is based on the thermal conversion of polyacrylonitrile (PAN) or pitch precursors to carbon or graphite fibers. Generally, the conversion of PAN or pitch precursor to carbon fiber involves similar process steps fiber formation, ie, spinning, stabilization to thermoset the fiber, carbonization—graphitization, surface treatment, and sizing. Schematic process flow diagrams are shown in Eigure 4. However, specific process details differ. 

Pitch-based fibers generally have higher moduh but lower strengths than theh PAN-based counterparts. The specific properties of the various types of carbon fibers are compared in Figure 4. Pitch-based fibers also have higher electrical conductivity, which can be an important consideration in certain circumstances, for example, for use in electromagnetic inductance (EMI) shielding. 

General References Pan N. Garay, P. E., Tump Application Desk Book,... 

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