Fig. 5From: Green construction and release mechanism of lignin-based double-layer coated ureaSEM images of the LPUCU (a1: 1000×; a2: 5000×), EPCU (b1: 1000×; b2: 5000×), and DLCU (c1: 1000×; c2: 5000×). Among them, a1, b1, and c1 appeared surface images, but a2, b2, and c2 showed section imagesBack to article page