مجله بلور شناسی و کانی شناسی ایران
سال ششم شماره 1 (پیاپی 12، بهار 1377)

Isotropic sa mples of Barium Ferrite are prepared by coprecipit a tion method. To study the effect of sintering temperature on magnetic propeTl ies of Barium ferrite we have sintered the samples in diUerent temperature from 900 up to J 100°C. Mean partieal size and porosity of the samples are dete rmind by scanning electron miecroseop (SEM), magnetic phase and magnetic parameters are measured by X-ray diffractomet ry (XRD) and DC Magne tic Hysteresis Loop. Experimental results show that the best magnetic parameters, coe rcive force He, remanence magnetization B, and maximum stored magenetie energy (BH)mu is found in samples with sintering temperature about 900 to 950°C.

The extensive use of zeolites as catalysts and catalyst suppo rts in heteregenous cll t:tly~i ... in the che mical and petrochemical industries is well established. Kaolin is a suitable aluminosilicate mineral which in appropriate conditions can be transformed to a three dimensional zeolite structure with a high surface area. A vast and dispersed kaolin deposites in the country are high potential sources for studing synthesis of zeoli tes. The kaolins investigated in this study were from Zenoo z ~ Azarba y jan , Rokh·Scf c ed ~ Khora s an and Samirom· Esfahan. Theywere activated by ca lcination at 750°C to convert them to meta kaolin. Synthesis gel was prepared from metakaolin, sodium hydroxide, sodium silicate and sodium chloride. Synthesis was performed by hydrothermal method at 101YC. The products were examined by XRD and EDX/SEM for structural and chemical analysis. All three types kaolins were converted to zeolite Y in specific condition. Silicon to aluminum ratio in the prepared zeolite framework was in the range of 1.7·2.15 where the highest value belongs to the zeolite prepared from Samirom kaolin. ,

For evaluation of the mineral potential of Sirutr area in the north east of Khorasan, 140 stream sediment samples were analyzed for Ni , Co, Ag, Sb, Hg and Au. Results of these analyses ind ica te an unusual assay for most of these elemen ts, especia lly for gold a nd ant imony. Statis tical analyses and co mparison of geologic map with the surrace anomaly maps indicate a posit ive re lations hip between Ni a nd Co with mafic and ultramafic rocks in the area; while the unusual distribution of gold, antimony and to a lesser extent mercury can be related to the hydrotbermal processes. From this study it is concluded th a t the statistical analyses along with the geological and geochemical studies are very useful in recognition of the mineralized areas and understanding of tbe mineralizing processes.

Thermal behaviour of zeolites is an important property regarding their application in different fields. This property mainly is related to the presence of water molecules in their crystalline structures. It is known that zeolites give up water molecules upon heat ing, a phenomena which affects remaining water molecules and other clements in the framework. This effect mainly depends on the cation type, amount of cations present in the framework. heating rate, AJJ Si ratio and type of the framework. In most zeolites dehydration causes unit cell contract ion and in some cases st ructural collapse will happen upon dehydrat ion. In the latter situation t he phenomena is an irreversible process. In this project two samples of zeolite form different deposits were investigated. The chemicnl analysis and unit cell formula of the sample were firstly determined. Different cataionic forms were then propared. The sample were all subjected to thermal analysis a nd the effect of ingoi ng cations were investingated.

Bentonites from Kashmar, Gonabad and Ferdows were studied and compared with imported types. Bentonites have a very wide range of industrial uses. Chemical and mineralogica l composit ion of montmo rillo nite wit hin t he bentonite control its kind of application. Bentonites from Kashmar have the higbest content of Cao and A120) and K20. High expandibiity, good adhesive property a nd having high content of Na20 indicate that Ferdows bentonites are Na-type. Gonabad bentonites are Na-Ca-Type. Kashmar, Ferdows and Gonabad bentonites were treated for acti vat io n. In term of exc hangable ca t io ns, Kashmar bent o nite is compa rable with imported activated be ntonites from China a nd Turkey . Detemination of Ca and Na montmorionite based on the X-Ray pattern is not very e asy. The position of the first peak of montmorillonite we re compared with Na20 content of bentonites. JJ the first peak of montmorillonite is more than 7.3 degree and t he Na20 co nte nt of bentonite is more than 2 percent, therefore montmorillonite is Na-type. If the first peak is less than 7 degree and Na20 content of bentonite is less than 1.5 percent, the montmorillonite is Ca-type.