Spatial atomic layer deposition (S-ALD) is a potential high-throughput manufacturing technique offering fast and large scale ultrathin films deposition. Here, an S-ALD system with modular injectors is introduced for fabricating binary oxides and their nanolaminates. By optimizing the deposition conditions, both ZnO and TiO2 films demonstrate linear growth and desired surface morphology. The as-deposited ZnO film has high carrier mobility, and the TiO2 film shows suitable optical transmittance and band gap. The ZnO/TiO2 nanolaminates are fabricated by alternating substrate movement between each S-ALD modular units of ZnO and TiO2. The grazing incidence x-ray diffraction spectra of nanolaminates demonstrating the signature peaks are weaker for the same thickness nanolaminates with more bilayers, suggesting tuning nanolaminates from crystalline to amorphous. Optical transmittances of ZnO/TiO2 laminates are enhanced with the increase of the bilayers' number in the visible range. Refractive indices of nanolaminates increase with the thickness of each bilayer decreasing, which demonstrates the feasibility of obtaining desired refractive indices by controlling the bilayer number. The electronic properties, including mobility, carrier concentration, and conductivity, are also tunable with different bilayers.

Microbial metabolisms can impact abiotic mineral-promoted trichloroethene (TCE) reduction in groundwater environments, but mechanistic understanding of these coupled processes is limited. Here, we explore how sulfate-reducing bacteria (SRB) enhance TCE reactivity of iron sulfide minerals, specifically addressing how SRB maintain reactive iron sulfide surfaces after biogenic mineral formation. Iron sulfides were formed either abiotically (ferrous iron and sulfide) or biotically (ferrous iron and sulfate reduction by Desulfovibrio vulgaris) in batch systems. TCE was added, and reaction products were monitored under different ferrous iron:sulfur (Fe:S) ratios. With D. vulgaris present, higher Fe:S ratios showed over an order of magnitude increase in TCE transformation rates. These rates increased with lower reduction potentials (R 2 = 0.66, p = 0.0014), as potentials decreased below −150 mV vs SHE. Mineral precipitate characterization indicated the presence of mackinawite (FeS), and pH and redox potentials confirmed experimental conditions in the FeS stability range. Filtered D. vulgaris media (SRB removed) showed similarly high rates to biotic experiments, implying the role of biogenic redox-active soluble microbial products (SMPs) in maintaining reducing conditions. From these results, we propose a reaction scheme, where iron sulfide surfaces reduce TCE, oxidizing mineral surface species, which are then “re-reduced” by SMPs from D. vulgaris.

A spatial atomic layer deposition apparatus integrated with a modular injector and a linear motor has been designed. It consists of four parts: a precursor delivery manifold, a modular injector, a reaction zone, and a driving unit. An injector with multi-layer structured channels is designed to help improve precursor distribution homogeneity. During the back and forth movement of the substrate at high speed, the inertial impact caused by jerk and sudden changes of acceleration will degrade the film deposition quality. Such residual vibration caused by inertial impact will aggravate the fluctuation of the gap distance between the injector and the substrate in the deposition process. Thus, an S-curve motion profile is implemented to reduce the large inertial impact, and the maximum position error could be reduced by 84%. The microstructure of the film under the S-curve motion profile shows smaller root-mean-square and scanning voltage amplitude under an atomic force microscope, which verifies the effectiveness of the S-curve motion profile in reducing the residual vibration and stabilizing the gap distance between the injector and the substrate. The film deposition rate could reach 100 nm/min while maintaining good uniformity without obvious periodic patterns on the surface.

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To a large extent, the efficiency and durability of the proton exchange membrane fuel cell (PEMFC) depend on the effective control of air supply system. However, dynamic load scenarios, internal and external disturbances, and the characteristics of strong nonlinearity make the control of complex air supply systems challenging. This paper mainly studies the modeling of PEMFC air supply system and the design of a nonlinear controller for oxygen excess ratio tracking control. First, we analyze and calibrate the system’s optimal oxygen excess ratio control target and explore how the system temperature and humidity impact it, respectively; second, a second-order affine oriented control model which can represent the static and dynamic characteristics of the air supply system is derived, and a disturbance observer is designed to estimate and compensate the “lumped error” online. Then, aiming at the problem of unmeasurable cathode pressure, a state observer based on Kalman optimal estimation algorithm is proposed to realize the real-time estimation of cathode pressure; finally, a dynamic output feedback control system based on observer and backstepping nonlinear controller is proposed, and the comparison and evaluation of two control strategies based on constant oxygen excess ratio tracking and optimal oxygen excess ratio tracking are carried out. The simulation results show the effectiveness and superiority of the designed control system compared with the reference controller.