Rapid processing of ferrite ceramics with promising magneto-dielectric characteristics

Ferrite ceramics, Ni0.88Zn0.07Co0.05Fe1.98O4, with the addition of 4wt.% Bi2O3 as sintering aid, were fabricated by using a simple one-step processing without involving the step of calcination. X-ray diffraction (XRD) results indicated that single phase ferrite ceramics can be achieved after sintering at 1000∘C for 2h. The samples demonstrated relative densities in the range of 97–99%. Desired magneto-dielectric properties have been approached by adjusting the sintering temperature and sintering time duration. This technique is believed to be applicable to other ceramic materials.Published versio

Hydrothermal fluid activity and the quantitative evaluation of its impact on carbonate reservoirs: A case study of the Lower Paleozoic in the west of Dongying sag, Bohai Bay Basin

By integrating the analyses of core samples, thin sections, homogenization temperature measurement of inclusions, stable isotopic compositions of carbon & oxygen, trace element composition, and conventional physical properties, this research identifies the evidence of Lower Paleozoic hydrothermal fluid activity in the western Dongying sag of Bohai Bay Basin, quantitatively evaluates the hydrothermal dissolution strength in various carbonate reservoirs, and analyzes the longitudinal distribution of effective fractures in reservoirs. The markers of hydrothermal dissolution in the study area include the typical hydrothermal mineral combinations such as fluorite-anhydrite-authigenic quartz combination, the homogenization temperature of inclusions in fracture fillings related to hydrothermal fluid of up to 150 °C−210 °C, and the high FeO, high SiO2, high MnO and low Na2O features of carbonate in hydrothermal fluid karst area. Dissolution of hydrothermal fluid can produce not only new fluorite mineral, but also many pores, micropores, small fractures and micro-fractures, which significantly improve the quality of carbonate reservoirs. During the process of hydrothermal fluid dissolution, calcite precipitated and filled structural fractures as the hydrothermal fluid dissolved host rock. As the hydrothermal fluid went up along faults, its velocity and temperature dropped gradually, the intensity of dissolution and calcite filling differ significantly in different formations of the Lower Paleozoic, for example, the Fengshan and Yeli-Liangjiashan Formations have low fracture filling degree and highly developed dissolved fractures and pores, whereas the Majiagou Formation has high fracture filling degree and poorly developed dissolved fractures and pores. Key words: carbonate, reservoir, hydrothermal fluid, dissolution, Bohai Bay Basin, Dongying sag, Lower Paleozoic, quantitative eveluatio

Optimization of Ni0.95−xZnxCo0.05Fe1.90Mn0.02O4 ceramics with promising magneto-dielectric properties for VHF antenna miniaturization

Magnetic, dielectric and DC conductive properties of Ni0.95−xZnxCo0.05Fe1.90Mn0.02O4 (with x=0-0.20 at an interval of 0.05) ferrite ceramics were studied, in order to develop magneto-dielectric materials with almost equal values of relative permeability and permittivity, for the miniaturization of HF (3–30MHz) and VHF (30–90MHz and 100–300MHz) antennas. The ferrite ceramics were prepared by using the conventional two-step sintering process. The real part of relative permeability is increased almost linearly with increasing concentration of Zn, while that of relative permittivity keeps nearly unchanged. It is found that promising magneto-dielectric materials, with close values of real permeability and permittivity over 30–90 MHz (VHF), can be obtained for the samples at Zn concentrations between x=0.05 and x=0.10

Sintering and electrical properties of commercial PZT powders modified through mechanochemical activation

The effect of high-energy ball mechanochemical activation on microstructure and electrical properties of PZT from commercial PZT powder has been studied in this paper. The mechanochemical treatment destroys the large particles and refines the grains of the commercial PZT powder. The milled PZT powder can be fully sintered at a very low temperature of 950 °C, which is much lower than that of the pristine powder. More importantly, the grain growth is effectively prevented, while electrical properties of the final PZT ceramics are well maintained, due to the significant reduction in sintering temperature. It is believed that this technique can be readily extended to other materials