The Effect of Glass Additives on the Microwave Dielectric Properties of Ba(Mg 1 /3Ta2/3)03 Ceramics

The effect of glass additives on the densification , phase evolution, microstructure and microwave dielectric properties of Ba(Mg1;3 Ta2i3)03 (BMT) was investigated . Different weight percentages of quenched glass such as B203 , Si02, B203-SiO2, ZnO-B203, 5ZnO-2B2O3, Al203-SiO2, Na20-2B203.10H20, BaO-B203-SiO2, MgO-B203-SiO2, PbO-B203-SiO2 , ZnO-B203-SiO2 and 2MgO-Al203-5SiO2 were added to calcined BMT precursor . The sintering temperature of the glass -added BMT samples were lowered down to 1300 °C compared to solid-state sintering where the temperature was 1650 °C. The formation of high temperature satellite phases such as Ba5Ta4O15 and Ba7Ta6O22 were found to be suppressed by the glass addition . Addition of glass systems such as B203, ZnO-B203, 5ZnO-2B203 and ZnO-B203-SiO2 improved the densification and microwave dielectric properties. Other glasses were found to react with BMT to form low-Q phases which prevented densification . The microwave dielectric properties of undoped BMT with a densification of 93 . 1 % of the theoretical density were Cr = 24 . 8, Tr = 8 ppm/°C and Q„ x f= 80,000 GHz. The BMT doped with 1.0 wt% of B203 has Q„ x f = 124,700GHz, Cr = 24.2, and T f = -1.3 ppm /°C. The unloaded Q factor of 0.2 wt% ZnO-B203-doped BMT was 136,500 GHz while that of 1.0 wt% of 5ZnO-2B203 added ceramic was Q„ x f= 141,800 GHz . The best microwave quality factor was observed for ZnO -B203-SiO2 (ZBS) glass-added ceramics which can act as a perfect liquid-phase medium for the sintering of BMT. The microwave dielectric properties of 0.2wt% ZBS-added BMT dielectric was Q„ x f= 152,800 GHz, F,= 25.5, and Tr = - 1.5 ppm/°C

Alkali insoluble glucan extracted from Acremonium diospyri is a more potent immunostimulant in the Indian White Shrimp, Fenneropenaeus indicus than alkali soluble glucan

E¡ect of an extraction method on the structure of glucan and its immunostimulatory response in Fenneropenaeus indicus was investigated. Here we extracted alkali insoluble glucan (AIG) and alkali soluble glucan (ASG) from a ¢lamentous fungi Acremonium diospyri following alkali^acid hydrolysis and the sodium hypochlorite oxidation and dimethyl sulphoxide extraction method respectively. Structural analysis showed that 85% of glucan in AIG was a (1 !3)-b-D-glucan and it increased the prophenoloxidase and reactive oxygen intermediate activity when administered to F. indicus. On the other hand, ASG, which contained 93% (1 !3)-a-glucan, did not induce signi¢cant immune response in shrimp. Here we report that the di¡erence in immunostimulatory potential between AIG and ASG is due to the di¡erence in the percentage of (1 !3)-b-D-glucans present in each preparation, which varies with the method of extraction employed. Also our observations suggest that glucan can be used as a potential immunostimulant to shrimp, provided it contains (1 !3)-b-D-glucan as the major fraction.