The elimination of possible defects is indispensable in making zeolite membranes popular in process industries. A novel counter‐diffusion chemical liquid deposition (CLD) technique is proposed and developed for selective defect‐patching of zeolite membranes. Dodecyltrimethoxysilane (DMS) is employed as the silane coupling agent, forming a protective layer on the membrane surface so that intracrystalline pores can be kept intact in the subsequent reparation step. By using tetraethoxy orthosilicate (TEOS) and (3‐chloropropyl)triethoxysilane (3CP‐TES), co‐hydrolysis and co‐condensation at the organic/aqueous interface fabricate the silsesquioxane/silicate hybrid on macro‐, meso‐ and even microdefects. The silicalite‐1 membrane before and after reparation is characterized using contact‐angle measurements, Fourier transform IR spectroscopy, and electron probe microanalysis. Permporometry is conducted to study the pore‐size distribution of the membrane before and after reparation. It is found that the silsesquioxane/silicate hybrid is only deposited at the pore‐mouth of the defects, and the defects can be plugged to less than 1.3 nm pores after patching. After reparation, the separation factor of a 50/50 n/i‐butane‐gas mixture through the membrane can be increased to 35.8 from 4.4, and the separation factor of a CO2/N2 gas mixture through the membrane can be increased to around 15 from 1, while keeping the two‐thirds CO2 permeation flux of the synthesized membrane.
Multi-material additive manufacturing provides a new route for fabricating components with tailored physical properties. Laser-based powder bed fusion (L-PBF), also known as selective laser melting, is a powder bed-based additive manufacturing technology. This technology affords the advantage of manufacturing metallic and non-metallic materials with high geometrical resolution. An emerging field relevant to the foregoing is multi-material L-PBF. This paper reviews the latest progress in this field including multiple material powder deposition mechanisms, molten pool behaviour, process characteristics of printing metal-metal, metal-ceramic, and metal-polymer multiple material components, and potential applications. Finally, scientific and technological challenges are presented.
Porous poly(L-lactic acid) (PLLA) scaffolds with bioactive coatings were prepared by a novel one-step method. In this process, ice-based microporogens containing bioactive molecules, such as hydroxyapatite (HA) and collagen, served as both porogens to form the porous structure and vehicles to transfer the bioactive molecules to the inside of PLLA scaffolds in a single step. Based on scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis, the bioactive components were found to be transferred successfully from the porogens to PLLA scaffolds evenly. Osteoblast cells were used to evaluate the cellular behaviors of the composite scaffolds. After 8 days culturing, MTT assay and alkaline phosphatase (ALP) activity results suggested that HA/collagen could improve the interactions between osteoblast cells and the polymeric scaffold.
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