X-Ray, thermal, and Dehydration studies on Magnesium oxychlorides

Abstract

X-ray, differential thermal analysis, and dehydration methods have been used to study the magnesium oxychlorides 3Mg(OH)2.MgCl2.8H2O and 5Mg(OH)2.MgCl2.8H2O formed at temperatures below 100 �C, and 2Mg(OH), . MgCl2.5H2O and 9Mg(OH)2.MgCl2.6H2O formed at temperatures at and above 100 'C. Lower hydrates of the 3-form exist with 5 and 4 molecules of water, results which differ from those of Feitknecht and Held (1944), Feitknecht (1953), and Wehner (1933). It 1s not clear from the new results whether the lower hydrates for the 5-form hare 5 and 3 or 4 and 3 molecules of water, but the latter seems the more likely ; the results of Feitknecht and Held suggested the former. For the 2- and 9-forms a lower hydrate with 2 molecules of water exists. In addition all forms have an anhydrous phase with the crystal structure of Mg(OH)2. The stability of all phases under natural atmospheric conditions is discussed.

An initial investigation of the properties and performance of magnesium oxychloride-based foam thermal insulation

“…A comparison of the TG results of the present study (Table 3) with those of Cole and Demediuk [10] suggests that the foam insulation is neither a pure 3-form or 5-form magnesium oxychloride cement, or a combination of the two. In particular, the percent loss in mass of the insulation specimens in the present study was considerably less, particularly over the low temperature range, than reported by Cole and Demediuk for the magnesium oxychlorides.…”

“…4 The results of the thermogravimetric analyses in the present study can be compared to those reported by Cole and Demediuk [10] for the 3-form and 5-form magnesium oxychloride cements. Their data (included Table 3) may be categorized into two major temperature regimes over which mass loss occurred: a low range from about 100°C (212°F) to about 175°C (347°F), and a high range of about 300 to 460°C (572 to 860°F)…”

“…In the low range, the magnesium oxychloride cements underwent dehydration to the same anhydrous phase [10]. The 3-form and 5-form lost about 34 and 27 percent of their mass, respectively when heated to about 175°C (347°F).…”

“…They had lengths of about 10 The results of the thermal conductivity measurements are given in Table 2. The values are comparable to those measured for other retrofit insulations such as mineral fiber or cellulose [9].…”

“…The results are presented in Fig. 4, and summarized in The ranges were selected so that comparisons could be made (see below) with data for magnesium oxychloride cements presented by Cole and Demediuk [10].…”