Machine Learning Customized Novel Material for Energy-Efficient 4D Printing.

Existing commercial powders for laser additive manufacturing (LAM) are designed for traditional manufacturing methods requiring post heat treatments (PHT). LAM's unique cyclic thermal history induces intrinsic heat treatment (IHT) on materials during deposition, which offers an opportunity to develop LAM-customized new materials. This work customized a novel Fe-Ni-Ti-Al maraging steel assisted by machine learning to leverage the IHT effect for in situ forming massive precipitates during LAM without PHT. Fast precipitation kinetics in steel, tailored intermittent deposition strategy, and the IHT effect facilitate the in situ Ni3 Ti precipitation in the martensitic matrix via heterogeneous nucleation on high-density dislocations. The as-built steel achieves a tensile strength of 1538 MPa and a uniform elongation of 8.1%, which is superior to a wide range of as-LAM-processed high-strength steel. In the current mainstream ex situ 4D printing, the time-dependent evolutions (i.e., property or functionality changes) of a 3D printed structure occur after part formation. This work highlights in situ 4D printing via the synchronous integration of time-dependent precipitation hardening with 3D geometry shaping, which shows high energy efficiency and sustainability. The findings provide insight into developing LAM-customized materials by understanding and utilizing the IHT-materials interaction.

Carbon dioxide sequestration accompanied by bioenergy generation using a bubbling-type photosynthetic algae microbial fuel cell.

This study developed a bubbling-type photosynthetic algae microbial fuel cell (B-PAMFC) to treat synthetic wastewater and capture CO2 using Chlorella vulgaris with simultaneous power production. The performance of B-PAMFC in CO2 fixation and bioenergy production was compared with the photosynthetic algae microbial fuel cell (PAMFC) and bubbling photobioreactor. Different nitrogen sources for C. vulgaris growth, namely sodium nitrate, urea, ammonium acetate and acetamide were studied. The maximum CO2 fixation rate in B-PAMFC with 2.8 g L-1 urea reached 605.3 mg L-1 d-1, 3.86-fold higher than that in PAMFC. Urea also enhanced the solution absorption of CO2. Furthermore, the B-PAMFC reached a high lipid productivity of 105.9 mg L-1 d-1. An energy balance analysis indicated that B-PAMFC had a maximum net energy of 1.824 kWh m-3, making it a lab-scale energy-positive system. The B-PAMFC with urea as nitrogen source would provide an attractive strategy for simultaneous CO2 sequestration and bioenergy production.

Enhancement of CO2 biofixation and bioenergy generation using a novel airlift type photosynthetic microbial fuel cell.

This study developed a novel airlift type photosynthetic microbial fuel cell (AL-PMFC) using Chlorella vulgaris to enhance the CO2 biofixation and bioenergy (bioelectricity and biodiesel) generation. The performances of AL-PMFC in CO2 fixation rate, lipid accumulation and power output were investigated and compared with a bubbling-type photosynthetic microbial fuel cell (B-PMFC). Due to the enhanced mass transfer, the CO2 fixation rate of AL-PMFC reached 835.7 mg L-1 d-1, 28.6% higher than that of B-PMFC. Besides, the analysis of energy balance indicated that a maximum net energy of 2.701 kWh m-3 was achieved in AL-PMFC, which performed better than B-PMFC. After optimization of C. vulgaris inoculum density, CO2 concentration and aeration rate, the maximum CO2 fixation rate, lipid productivity, and power density in AL-PMFC reached 1292.8 mg L-1 d-1, 234.3 mg L-1 d-1, and 5.94 W m-3, respectively. The AL-PMFC provided an attractive approach for CO2 fixation and bioenergy generation.

Microbial fuel cell (MFC) power performance improvement through enhanced microbial electrogenicity.

Within the past 5 years, tremendous advances have been made to maximize the performance of microbial fuel cells (MFCs) for both "clean" bioenergy production and bioremediation. Most research efforts have focused on parameters including (i) optimizing reactor configuration, (ii) electrode construction, (iii) addition of redox-active, electron donating mediators, (iv) biofilm acclimation and feed nutrient adjustment, as well as (v) other parameters that contribute to enhanced MFC performance. To date, tremendous advances have been made, but further improvements are needed for MFCs to be economically practical. In this review, the diversity of electrogenic microorganisms and microbial community changes in mixed cultures are discussed. More importantly, different approaches including chemical/genetic modifications and gene regulation of exoelectrogens, synthetic biology approaches and bacterial community cooperation are reviewed. Advances in recent years in metagenomics and microbiomes have allowed researchers to improve bacterial electrogenicity of robust biofilms in MFCs using novel, unconventional approaches. Taken together, this review provides some important and timely information to researchers who are examining additional means to enhance power production of MFCs.

Selective laser melting of high-performance pure tungsten: parameter design, densification behavior and mechanical properties.

Selective laser melting (SLM) additive manufacturing of pure tungsten encounters nearly all intractable difficulties of SLM metals fields due to its intrinsic properties. The key factors, including powder characteristics, layer thickness, and laser parameters of SLM high density tungsten are elucidated and discussed in detail. The main parameters were designed from theoretical calculations prior to the SLM process and experimentally optimized. Pure tungsten products with a density of 19.01 g/cm3 (98.50% theoretical density) were produced using SLM with the optimized processing parameters. A high density microstructure is formed without significant balling or macrocracks. The formation mechanisms for pores and the densification behaviors are systematically elucidated. Electron backscattered diffraction analysis confirms that the columnar grains stretch across several layers and parallel to the maximum temperature gradient, which can ensure good bonding between the layers. The mechanical properties of the SLM-produced tungsten are comparable to that produced by the conventional fabrication methods, with hardness values exceeding 460 HV0.05 and an ultimate compressive strength of about 1 GPa. This finding offers new potential applications of refractory metals in additive manufacturing.