An improvement in gas permeation properties has been obtained by introducing bulky silyl side groups at sites ortho to either the ether or sulfone linkage of polysulfone and poly(phenyl sulfone) chains. The sizes of the substituents were systematically increased from trimethylsilyl, to dimethylphenylsilyl, and to diphenylmethylsilyl, and the degree of substitution was also controlled. The sterically smallest trimethylsilyl group substituted at the ortho ether site markedly increased the oxygen permeability from 1.1 to 7.1 barrers compared with that of unmodified polysulfone at a small tradeoff in oxygen/nitrogen selectivity. Unexpectedly, the oxygen permeability remained almost unchanged from polysulfone with the introduction of more bulky dimethylphenylsilyl and diphenylmethylsilyl substituents. It was also found that substitution at the sites ortho to ether linkage was more effective than the sulfone linkage in improving transport properties. The improved gas separation properties appear to be associated with increased free volume, evidenced from the increased d-spacing and specific volume. Further, the mobility of pendant substituents, characterized by dynamic mechanical analysis, correlated strongly with the d-spacing and specific volume. This leads us to the conclusion that it is substituent mobility rather than the size of the pendant side group that is the critical factor in determining free volume and transport properties.

Powder bed fusion (PBF) additive manufacturing (AM) is currently used to produce high-efficiency, high-density, and high-performance products for a variety of applications. However, existing AM methods are applicable only to metal materials and not to high-melting-point ceramics. Here, we develop a composite material for PBF AM by adding Al2O3 to a glass material using laser melting. Al2O3 and a black pigment are added to a synthesized glass frit for improving the composite strength and increased laser-light absorption, respectively. Our sample analysis shows that the glass melts to form a composite when the mixture is laser-irradiated. To improve the sintering density, we heat-treat the sample at 750 °C to synthesize a high-density glass frit composite. As per our X-ray diffraction (XRD) analysis to confirm the reactivity of the glass frit and Al2O3, we find that no reactions occur between glass and crystalline Al2O3. Moreover, we obtain a high sample density of ≥95% of the theoretical density. We also evaluate the composite’s mechanical properties as a function of the Al2O3 content. Our approach facilitates the manufacturing of ceramic 3D structures using glass materials through PBF AM and affords the benefits of reduced process cost, improved performance, newer functionalities, and increased value addition.

No abstract

No abstract

No abstract