Additive manufacturing (AM) is a promising technology for the rapid tooling and fabrication of complex geometry components. Among all AM techniques, fused filament fabrication (FFF) is the most widely used technique for polymers. However, the consistency and properties control of the FFF product remains a challenging issue. This study aims to investigate physical changes during the 3D printing of polylactic acid (PLA). The correlations between the porosity, crystallinity and mechanical properties of the printed parts were studied. Moreover, the effects of the build-platform temperature were investigated. The experimental results confirmed the anisotropy of printed objects due to the occurrence of orientation phenomena during the filament deposition and the formation both of ordered and disordered crystalline forms (α and δ, respectively). A heat treatment post-3D printing was proposed as an effective method to improve mechanical properties by optimizing the crystallinity (transforming the δ form into the α one) and overcoming the anisotropy of the 3D printed object.

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electrochemical, membrane technology, and photocatalysis. [1][2][3][4][5][6][7][8] Photocatalysis, a process using abundant and eco-friendly solar energy to trigger degradation, is thought of as a strong asset to environmental sustainability. The highly reactive oxidizing species generated from photocatalysts are indispensable for the oxidation of pollutants. The current efforts are focused on the aggregation of powder photocatalyst, catalytic cycles, carrier separation, and utilization of solar light. [9,10] Introducing photocatalytic materials in the membrane matrix gathers the requirement mentioned above and demonstrates the potential in the reusable photocatalyst and the pollution treatments. [11][12][13] TiO 2 is an extensively used photocatalyst due to its thermal and chemical stability, environmental friendliness, and easy preparation. [14][15][16] The photocatalytic performance is highly dependent on its microstructure. Zero-dimensional TiO 2 nanoparticle holds a large surface area and broadened bandgap, and thus it could provide more active sites to enhance photo catalytic activity than that of high-dimensional materials. Developing TiO 2 nanoparticles is popular in the initial stage of the study. However, the drawbacks gradually emerged, such as its slow charge carrier transport caused by its inner defect and its limited light absorption due to its wide bandgap. Oppositely, Cellulose exhibits outstanding chemical stability, nontoxicity, and renewable ability and is regarded as a candidate for next-generation sustainable materials. After the nanofibrillation of cellulose, cellulose nanofiber (CNF) exhibits unique optical properties, good mechanical strength, and a high aspect ratio. It is suitable to be a matrix for the photocatalysts immobilization and applied in pollutant removal owing to its solvent resistance. Combined with 1D TiO 2 , the network structure may be expected and beneficial for the charge transport of TiO 2 nanofibers. In this study, the flexible CNF composites film incorporated with various sizes and morphology of TiO 2 photocatalysts is fabricated. The relationship between the chemical and physical properties of the composite film and morphological features are discussed. The GIWAXS analysis shows that the entanglement of self-precipitated Ag-doped TiO 2 NFs (STNFs) and CNF induce the densely hierarchical stack and regular stacking orientation. For 30 day solvent resistance tests, various CNF composite films show outstanding stability in the acetone and dimethylformamide (DMF). In the photodegradation of methyl orange in ethanol, STNF/CNF film presents a high degradation efficiency of 87% and shows excellent stability of morphology and activity after three cycles. For volatile organic compound degradation, the degradation efficiencies toward methanol and DMF vapor are higher than 90%.

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