Ceramic Methodology Research Articles

The effect of La–Co–Mn–Nd substitution on the microstructure and magnetic properties of the strontium ferrites

M-type strontium hexaferrites Sr1−xLaxFe12−2xCox(Mn0.5Nd0.5)xO19 (x = 0, 0.1, 0.2, 0.3, 0.4) were prepared by the ceramic methodology. Crystalline structure, morphology and magnetic properties of the samples were studied via X-ray diffraction (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer (VSM), respectively. Single-phase have been observed at x value in the ranged from 0.0 to 0.2. When x ≥ 0.3, the LaCoO3 phase is observed. The results of scanning electronic microscopy show that the grains are regular hexagonal platelets with sizes from 1 to 4 µm. It is observed that the value of saturation magnetization (Ms) and the coercivity force (Hc) all increased after doping. The values of saturation magnetization first increases at low substitutions (x ≤ 0.2), and then decreases at x ≥ 0.3. The Hc has a similar trend with Ms, but the coercivity force is small change with the x value in the ranged from 0.1 to 0.4. In this experiment, the magnetic properties of the sintered magnets at x = 0.2 reach the maximum values.

Synthesis and Characterization of Zeolite Based Porous Ceramic Membranes

New porous zeolite based membranes were synthesized using a ceramic methodology and characterized by means of XRD, SEM, EDAX and permeation tests. The membranes were produced by thermal transformation of natural clinoptilolite. The XRD study showed clinoptilolite amorphization at 600–900°C. A posterior recrystallization to a siliceous phase and a compact aluminosilicate phase at 900–1150°C was also produced. The Permeability [B] and Permeance [Π] of H2 and CO2 were measured using the Darcy Law correlation. It was also applied for gaseous laminar flow using the Carman‐Kozeny equation. With the help of this equation the membrane pores sizes were measured. It was shown that the membrane porosity can be controlled by the grain size of the original natural zeolite powder. The membranes were further transformed by hydrothermal synthesis to obtain materials covered with an AlPO4‐5 molecular sieve. In conclusion, novel, inexpensive, strong, high permeation rate, and high temperature membranes were produced with natural clinoptilolite, a low cost and available material.

The preparation of high T c superconductors from nitrates

The preparation of high T c superconductors, in most cases, proceeds by ceramic methodology from the metal oxides and carbonates. In this paper we show that the same materials can easily be derived, as well, from nitrates. Nitrates are a potentially useful class of starting materials because of their solubility and thus possible use in technologies that require the deposition of thin films of precursors to the high T c superconductors. When the appropriate mixture of nitrate salts is prepared and ground together, then fired, first in air, and then in pure oxygen, the superconducting material results. Both the La 1.85Sr 0.15CuO 4 and Ba 2YCu 3O 7 materials have been prepared in this way. Their authenticities have been confirmed by comparison of their x-ray powder patterns and resistivity properties with those published for known materials. In addition we have demonstrated that solutions of nitrate salts can be analyzed for purity by a simple spectroscopic method.