Zhen Li

Fabrication, sintering and characterization of cordierite glass–ceramics for low temperature co-fired ceramic substrates from kaolin

Non-stoichiometric α-cordierite glass ceramic doped with H3BO3 and NH4H2PO4 as additives has been fabricated successfully from sandy kaolin as low temperature co-fired ceramics (LTCC) substrate materials. The sintering and crystallization behaviors of the glass–ceramics were investigated by the differential scanning calorimetry, X-ray diffraction, and field emission scanning electron microscope. In addition, various physical properties were characterized, such as dielectric properties, thermal expansion and flexural strength. The results indicated that there was only onefold α-cordierite formed from MgO–Al2O3–SiO2 glasses in the temperature range from 875 to 925xa0°C. The glass–ceramics could been highly densified at any experimental temperature and they showed excellent properties: low dielectric constants in the range of 5.5–7.5, low dielectric losses in the range of 0.015–0.025, low coefficients of thermal expansion between 1.22–4.32xa0×xa010−6xa0K−1 and applicable flexural strength at the level from 110 to 145xa0MPa. All of the performance qualified cordierite glass ceramic to be used as potential LTCC substrate.

Adsorption Properties of Modified Clinoptilolite for Methane and Nitrogen

Coalbed methane (CBM) is a kind of unconventional gas. CBM often contains a great deal of air when it comes out of the well. So, it must be condensed and purified before it can be applied. In this paper, raw clinoptilolite (Cp) was treated with grinding, gravimetric concentration, and ion-exchange using different aqueous solutions of salts. Then, the modified Cp powder was prepared into particles as adsorbents. Then, the adsorbents were used for nitrogen/methane separation in pressure swing adsorption (PSA) at the same condition of 0.2 MPa and 298 K. Research results indicated that there were micropores and lots of mesopores in the Cp, and the pores were mainly slit holes formed by sheet stacking. The adsorbents of NH4-Cp, Cs-Cp, and Cu-Cp showed good equilibrium selectivity for CH4, and the equilibrium separation factors of CH4 and N2 were 2.56, 2.31, and 1.95, respectively. The adsorbents of Na-Cp and Ag-Cp showed good equilibrium selectivity for N2, and the equilibrium separation factors of N2 and CH4 were 7.25 and 6.53, respectively. Consequently, the adsorbent of Na-Cp was suitable for nitrogen/methane mixture separation, which could make the concentration of methane concentrated from 19.7% to 30.72%.