The equilibrium diagram of a part of the ternary system lime-ferric oxidesilica is presented. A comparison with the diagram of the lime-alumina-silica system shows that the presence of ferric oxide results in extension of the stability fields of the calcium silicates and the lowering of the liquidus and eutectic temperatures in much of the area investigated. Evidence from thermal analyses is offered of a limited solid-solution series between dicalcium silicate and ferric oxide, substantiated by an X-ray investigation. The amount of reduction of ferric oxide a t the liquidus temperature of representative t ernary mixtures is recorded. The applications to iron-rich cements are discussed. CONTENTSPage I. Introduction ___ ______ __________________________________________ 475 II. Experimental methods ___________________________ ___ ____________ _ 476 III. Stability fields __ ________________________________________________ 476 1. Si0 2 ________________ ________ ____________________________ 476 2. CaO.SiC 2 _ ________ ___ _____________ __ __ _ __________________ 477 3. 3CaO.2Si0 2 ______________________________________________ 479 4. 2CaO.Si0 2 _______________________________________________ 480 5. 3CaO.Si0 2 _ _____________________ ____ _____________________ 484 6. CaO ____________________________________________________ 485 IV. Reduction of ferric oxide in ternary mixtures _______________________ 485 V.

Fused uranium dioxide was separated into fractions of varying particle size by air separation. Specimens of the nominal size of l / 8 by 1/4 by 11/* in. were formed by hydrostatic pressing, firing, and lapping. Specimens prepared from the 0 to 5 p fraction were the strongest and most dense. The room-temperature density was about 92y0 of theoretical and the room-temperature flexural strength was about 12,000 Ib. per sq. in. When tested at 1000°C., the strength was about 18,000 lb. per sq. in. The flexural strength of specimens decreased and their density decreased as the starting particle size was increased. The crystallization of the urania fragments which had occurred during the firing treatment was observed.

The ge neral physical properties of practically imperviou s porcelains within t he beryllia (BeO) field of the system beryllia-alumina-zirconia (BeO-Ah03-ZrOz), whose base composit ions approximate t hat of NBS Body No. 4811C, were found to be: maturing range, 1,500° to 1,600 0 C; apparent density, 2.9 to 3.4 g/ cm3 ; shrinkage, 17.8 to 20.5 p ercent; roomtemperature compressive strength, 238,000 to 305,000 lb/in. 2 ; room-temperature transverse strength, 17,200 to 34,100 lb/in.z; room-temperature transverse stI"ength after t hermal shocking, 17,800 to 31,900 Ib/in.2; transverse stre ngth a t 1,800° F (982° C), 15,100 to 25,100 Ib/in. 2 ; approximate Young's modulus at 1,800 0 F , 28,000,000 to 38,000,000 Ib/ in.2 ; relative thermal shock resistance, good; and Knoop hardness numbers (500-g load), 550 to 830. An adm ix ture of 2 weight p ercent of calcia (CaO) to t he base compositions of t hese porcelains (without which the specim ens would not mature to an impervious structure) caused the appearance of unidentified isotropic phases.

In connection with creep studies of graph ite, t he need a rose for accu rate ther mal expansion data on the three grades of graphite being investigated. Therefore, the linear thermal expansion of specimen s of the t hree grades, cut in t hree direction s with respect to the direction of extrusion or of molding press ure, was determ in ed at various t e mperatures between 20° and 1,370° C in vacuum. Resul ts show that specime ns cut perpendicular to the extrusion direction or paralJel to the direction of molding pressLil e had greater expan sion s than specimen s cut parall el to t he extrusion d irection or p erpendicular to the molding pressure. The data obtain ed are tabulate d.

Flexural strengths of specimens prepared from four uranium dioxide powders were determined at room temperature and at 1000°C. The relation of the strength ( S ) to porosity ( P ) and to grain size (G) could be represented by the expression S = kG-.e-hP, where k, a, and b are empirical constants which differed with test temperature but did not differ for the different urania powders used. Additions of titania were very effective in promoting sintering and additions of 0.50 or 0.75% by weight markedly increased the strength of the specimens.