Chromium dioxide

Chromium dioxide. Cr02 (HjO plus O2 on Cr03 at high temperature). Black solid with the rutile structure forming chromates(IV) in solid stale reactions. Used in magnetic lap>es. 

Particulate Materials. There are three principal classes of particulate magnetic materials y-ferric oxide, y-Fe202, and its modifications chromium dioxide [12018-01 -8] and iron [7439-89-6]. A comparison of the remanent magnetization, and coercivity, for several y-Fe202... 

Mag netic Tapes. Chromium dioxide, Cr02, is used as a ferromagnetic material in high fidelity magnetic tapes (qv). Chromium dioxide has several technical advantages over the magnetic iron oxides generally used (58,246). 

Scheme 2.3 Oxidation of primary and secondary alcohols with chromium dioxide.

In a Downstream Decomposing facility not the subject of this example, intentional chemistry is performed as ammonium dichromate is heated to decomposition to make chromium dioxide, which is used in the production of magnetic tape products. In the Upstream Feeds facility under study, physical processing is performed as ammonium dichromate is fed through a screw conveyor. The Preliminary Screening Method is to be used as a first-cut determination whether chemical reactivity hazards will need to be managed in the physical processing facility. 

Synonyms Chromium dioxychloride chromium dioxide dichloride chromium oxychloride chromium chloride oxide... 

Properties. Pigments with a coercive field strength of 50-56 kA/m are used in video cassettes, high-bias audio cassettes (chromium dioxide operating point IEC II), and high-density floppy disks. Depending on the quality of the tape, the particle size varies between 0.2 and 0.4 pm (see Section 5.1.1, Table 36). 

Chromium dioxide may also be used in combination with cobalt-modified iron oxides (see Section 5.1.2) in the production of magnetic recording media. The world production of Cr02 in 1995 amounted to 80001, ca. 11 % of the total consumption of magnetic pigments. Producers are BASF and Du Pont. 

Particulate Materials. There arc three principal classes of particulate magnetic materials g-ferric oxide. p-Fe-Oi. and its modihcatmns chromium dioxide. CrO-. and non, A comparison of the icmaneitt magnetization. It. and cncrciv ny. II,. for several material systems is shown in Table 5. 

F. Chromium Dioxide, Europium Monoxide, and Nickel (Metal). .. 46... 

Chromium dioxide, Cr02, of surface 28.5 m2 g I and Tc = 394 0.5 K has been reported by Arias and Selwood (27) to have negligible activity as normally prepared. But pretreatment with pure flowing helium at 623 K produces a surface with conveniently measurable activity at room temperature. All activity was quickly lost in hydrogen near Tc. It is necessary, therefore, to restrict measurements to the ferromagnetic phase. At 298 K and atmospheric pressure k0 = 1.2 /urnol m-2 s-1. At 17.5 kOe the change in conversion rate was less than 0.5%. It cannot be said that there is any measurable field effect. 

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