Infiltration temperatures

It was observed that the factors contributing to the variation of leachate data are solid waste characteristics, for example, the composition and size of the waste and degree of compaction, the moisture content and degree of rainwater infiltration, temperature, sampling, and analytical methods.47... 

The preceding analysis predicts that it will be difficult to form a TiB2/TiC/Ti composite using furnace infiltration temperatures near the Ti melting point. On the other hand, a different composite, a TiB/TiC/Ti material, has been successfully formed by reacting at 2000°C for times of 6 to 24 h. Under these conditions, molten Ti is in equilibrium with the... 

Process conditions for CVI of SiC vary considerably. For isothermal infiltration of Nicalon 2D cloth preforms 4 x 5 X 50 mm in size and containing 40 to 50 vol.% fiber, Fitzer and Gadow [122] recommend an infiltration temperature of 1050°C, a total pressure of 3 kPa, and a time of 14 days. A yield (efficiency with which the MTS was utilized) of 60% was quoted but it may not have pertained to this exact set of process conditions. Deposition rates increase with temperature and pressure for isothermal processing [122, 123]. 

Figure 4. Noble gas components in a shallow ground-water sample. All concentrations are normalized to the respective atmospheric equilibrium concentration (given as 100 %). Note that the excess air component for Xe and the radiogenic component for He are too small to be clearly visible on this scale. The data represent an actual sample from southern France, which was interpreted assuming unfractionated excess air. It has an infiltration temperature of 10.8°C, an excess air...

Vapor silicon has a very low pressure, facilitating its superior infiltration ability and low exothermal heat during reaction. Based on theory calculations, VSI was conducted for the fabrication of Ci/SiC composites. As the infiltration temperature increased from 1873K to 1973K the bulk density of the composites increased from I.68g/cm to 2.25g/cm while the open porosity decreased from 28% to 6%. Strength increased and then kept nearly the same, but the work of fracture decreased with... 

Infiltration rate of the metallic binder from the substrate is influenced by pressure gradients created by the applied external load, pressure gradients inside the capsule and the pore size of the diamond compact at the onset of infiltration, temperature, and the substrate binder mean free path and chemistry. 

After the parts were fully dried, they were heat treated above 1000 C in a furnace under an Ar/5% H2 atmosphere with a residence time at heat treat temperature of 1-2 hours. After heat treatment, the infiltration furnace was loaded with the porous B4C parts, with the appropriate amount of aluminum 6061 alloy ingot placed in contact with each individual part. The furnace was evacuated to 1 torr, backfilled with Ar gas, and then pumped to high vacuum (10" torr) for the aluminum infiltration furnace run. The residence time at infiltration temperature was typically 1 hour. After infiltration, the GEN3 composition was post heat-treated in an air furnace at 800°C for several hours to obtain the GEN4 composition. 

The bulk density and the open porosity of C(/SiC composites prepared by VSl are shown in Fig.6 as a function of infiltration temperature. The sintered density reached 2.2S g(cm with the porosity as 6% at 1700°C. The fracture surface (Fig. 7 a) showed the dense matrix after VSl at 1700 C. An obvious fiber pull-out (Fig. 7 b) was observed after fracture although the silicon content is quite high (14.5 vol %). 

The samples generated for this paper were all produced as stated in the introduction with some minor variations. A systematic set of samples were made by varying the carbon of the preform, and the infiltration alloy composition. Lower infiltration temperatures were used with the AI additions. The SiC powders used were primarily the 6H polytype, and consisted of a bi-modal distribution of 45 and 10 pm particles. 

In this study, CVR approach using SiO vapor was utilized to form thin SiC coatings on graphite foams. For the production of SiO gas, commercially available Patinal SiO pellets were used. These pellets have congruent vaporization and by optimizing infiltration temperature and time... 

Pyrolytic graphite was first produced in the late 1800s for lamp filaments. Today, it is produced in massive shapes, used for missile components, rocket nozzles, and aircraft brakes for advanced high performance aircraft. Pyrolytic graphite coated on surfaces or infiltrated into porous materials is also used in other appHcations, such as nuclear fuel particles, prosthetic devices, and high temperature thermal insulators. 

Example 5 Cooling and Dehumidification Find the cooling load per pound of dry air resulting from infiltration of room air at 80 F dry-bulb temperature and 67 F wet-bulb temperature into a cooler maintained at. 30 F dry-bulb and 28 F wet-bulb temperature, where moisture freezes on the coil, which is maintained at 20 F. 

Many metals are naturally brittle at room temperature, so must be machined when hot. However, particles of these metals, such as tungsten, chromium, molybdenum, etc., can be suspended in a ductile matrix. The resulting composite material is ductile, yet has the elevated-temperature properties of the brittle constituents. The actual process used to suspend the brittle particles is called liquid sintering and involves infiltration of the matrix material around the brittle particles. Fortunately, In the liquid sintering process, the brittle particles become rounded and therefore naturally more ductile. 

This fortuitous infiltration is essential in otherwise unventilated buildings, since it allows ingress of air providing oxygen for us to breathe and for combustion equipment to burn. The infiltration is, however, effectively uncontrolled, and is often insufficient in quantity, at the wrong temperature or too contaminated to maintain satisfactory internal environmental conditions. 

Cold outside air introduced to the system by infiltration or by design of the plant will require heat to be added by the plant or directly in the room to maintain the room temperature. The heat required is... 

Depending on the degree of oxygen infiltration, the temperature of the condensate and the presence of other gases such as carbon dioxide, various corrosion reactions may take place in the steam distribution and CR systems. The most basic reaction associated with oxygen infiltration results in oxygen corrosion, which can produce deep pitting in the pipework and is described later in this chapter. 

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