KJ/mole Figure 5. Framework stability as a function of Al-Al distance related to the location of Ni2+ ions in Ni-Aluminosilicate mordenite. Decreasing means increasing Ni2+ localization preference. The line is drawn as guide for the eye.vations. Firstly, the small differences in the relative lattice energies for Ni2+ located at the four different extra-framework sites indicate hardly any preferences on structural grounds. Secondly, the relative lattice energies of the Ni-alumina mordenites are observed to depend on the existence of specific Al-O-fSi-O^Al sequences in combination with a Ni2+ ion in close proximity (compare relative lattice energies in Tables III and IV). In particular, sequences with TV = 1 turned out to be very stable in comparison to sequences with TV > 1.Not only the value of TV but also the specific location of the Al-O-Si-O-Al sequences in the mordenite structure proves to be important. In this case (TV = 1), our calculations clearly show that Ni2+ is preferentially located in the 8-ring side pocket, followed by location in the 8-ring secondary pore system. Location of Ni2+ in the 12-ring main channel proves to be less favorable. These findings are illustrated in Figure 4.

No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

Abstract:In the present work, hybrid sintering technique which couples the resistive heating and microwave heating is employed to sinter infrared transparent La 0.15 Y 1.85 O 3 to 99.2% of the theoretical density for the first time to the best of our knowledge. The presence of La 3+ in the yttria matrix improves the hardness properties to a greater extent without affecting the transmittance properties, but there is a deterioration in the thermal properties of the sample. So we have limited our studies to La 0.15 Y 1.85 O 3 which shows better optical, thermal, and hardness properties. The pellets fabricated from the ultra-fine nano powder with average particle size of ~12 nm synthesized by combustion technique and sintered at 1430 ℃ with an average grain size of 0.22 µm show ~80.1% transmittance in the UV-visible region and 81% in mid infrared region. For a comparative study of the optical, mechanical, and thermal properties, two other variants of sintering strategies namely conventional sintering and microwave sintering are also employed. A comprehensive analysis on the hardness reveals that the hardness of the pellets sintered via hybrid heating is 9.73 GPa and is superior to the pellets sintered using the other two techniques. The thermal conductivity of the sample is also analyzed in detail. The results clearly indicate that the La 0.15 Y 1.85 O 3 ultra-fine nano powder synthesised by the single-step combustion method and sintered via microwave hybrid heating shows better transmittance properties without compromising the mechanical properties, and can be used very effectively for the fabrication of infrared transparent windows and domes.