Effect of time and temperature

The rate of crystal growth and sintering of the MgO, formed by decomposition of the hydroxide, is controlled primarily by the temperature and time of heat treatment. Crystal growth has been shown to fit an equation of the following form (Lindner and Parfitt, 1957 Riddell, 1972)  

Bouvier, A., Griesser, H. J., and Herzog, G. W. (1980). Radex Rundsch. 231. Boynton, R. S. (1980). Chemistry and Technology of Lime and Limestone, Wiley New York. 

Riddell, D. (1972). PhD thesis, Sheffield University, United Kingdom. 

A variety of furnaces are used in the magnesia industry to calcine either magnesite or magnesium hydroxide filter cake. The most commonly used are the multiple-hearth furnace (MHF) and rotary and shaft kilns. MHFs are primarily used to produce reactive lightly calcined magnesia, while rotary and shaft kilns produce hard and dead-burned grades of magnesia. 

Heat transfer in kilns occurs in a variety of ways. By far the largest transfer of heat from the hot flame to the kiln burden occurs by radiation a much smaller quantity of heat is also transferred by radiative processes from the refractory lining. The hot refractory lining can also transfer heat to the burden by conduction. Heat transfer from the hot combustion gases can also occur by convective processes as well. 

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Fig. 29. Effects of time and temperature of precipitation treatments on yield strength of alloy 2036—T4 sheet. Numbers represent strength in MPa. To...

ISO 10146 1997 Crosslinked polyethylene (PE-X) pipes - Effect of time and temperature on the expected strength... 

ISO 1346 2004 Fibre ropes - Polypropylene split film, monofilament and multifilament (PP2) and polypropylene high tenacity multifilament (PP3) - 3-, 4- and 8-strand ropes ISO 1873-1 1995 Plastics - Polypropylene (PP) moulding and extrusion materials - Part 1 Designation system and basis for specifications ISO 1873-2 1997 Plastics - Polypropylene (PP) moulding and extrusion materials - Part 2 Preparation of test specimens and determination of properties ISO 3213 1996 Polypropylene (PP) pipes - Effect of time and temperature on expected strength... 

Abstract. Grignard reactions are of utmost importance in organic synthesis (Lee, 2005), and finding the prime conditions under which to conduct these reactions is really crucial to their usefulness. This work looks at the effects of time, and temperature on yield in the reaction of isopropyl magnesium bromide with 4-methoxyben-zaldehyde to produce l-(4-methoxyphenyl)-2-methylpropan-l-ol. The reaction was first run for 10 min at 25, 50, 75, and 80 °C. Next it was run at 80 °C for 10, 20, and 30 min (see Methods section for more details). Highest yields (85%) were obtained at 80 °C with 10-20 min reaction times. Utilizing conditions that optimize yields will improve the economic practicality of these reactions, and increase their usefulness as a synthetic tool. 

Solvent absorption measurement has been shown to be a sensitive and useful test method in the manufacture of epoxy powder coatings. A test method was defined and the effects of time and temperature of immersion described. It was shown that solvent absorption is a measure of raw material properties (EEW of the epoxy resin, and CTBN elastomer type and concentration), the homogeneity of the extrudate, as well as the state of cure. The information obtained from solvent absorption measurements has proven to be extremely important not only in quality control analysis but also in providing an insight into the structure function relationships in epoxy resin chemistry. 

Related to the attack of polycrystalline ceramic materials by aqueous media is the hydrolysis of silicate glasses. The following relationship has been developed to describe the effect of time and temperature on the acid corrosion (10% HCl) of silicate... 

Fig. 14. Ni/Si02 (Ni Si02 = 3 1). Effect of time and temperature of reduction on particle size a Slope magnetization curve at

Barrow, N. J., and Shaw, T. C. (1975). The slow reactions between soil and anions. II. Effect of time and temperature on the decrease in phosphate concentration in the soil solution. Soil Sci. 119, 167-177. 

D. J. Hoffmann, E. G. Garcia, Rheology of PVC Dispersions Effect of Time and Temperature, presented at the Third International Symposium on PVC, Cleveland, Aug. 1980. 

This equation provides a fundamental relationship between the effects of time and temperature on a transition mechanism. Time and temperature appear to be equivalent in their effect on the behaviour. At a fixed time scale, T, e.g. 1 sec, the transition temperature, T, is proportional to the energy of activation, AU. The transition temperature can be expressed in the time scale by ... 

Hamosh, M., Ellis, L.A., Pollock, D.R., Henderson, T.R., Hamosh, P. 1996. Breastfeeding and the working mother effect of time and temperature of short-term storage on proteolysis, lipolysis, and bacterial growth in milk. Pediatrics 97, 492-498. 

TABLE 1.2 Effect of Time and Temperature upon Extent of Reduction and Activity of Ni-Kieselguhr ... 

Kinetic data can also be obtained for the structure development process during cooling of biopolymer dispersions. This kind of analysis is difficult due to the combined effects of time and temperature. Usually, the data are obtained using time as an independent variable and changing the temperature and test sample for each run. 

Tobitani, A. and Ross-Murphy, S. B. 1997a. Heat-induced gelation of globular proteins. 1. Model for the effects of time and temperature on the gelation time of BSA. Macromolecules 30 4845-4854. 

Details about products that can crystallize In alpha or beta forms, such as the effect of time and temperature. 

Daly IS, Dodge RA, Glew RH, Keroack MA, Bednarek FJ, Whalen M. Effect of time and temperature on inactivation of aminoglycosides by ampiciUin at neonatal dosages. J Perinatol 1997 17(l) 42-5. 

In addition, the effect of time and temperature on the behavior of the materials manifests a great influence on the rheological properties of the food systems. 

Observations with soil - the effects of time and temperature... 

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