Control Of Layer Thickness Research Articles

Large-area synthesis of high electrical performance MoS2 by a commercially scalable atomic layer deposition process

This work demonstrates a large area process for atomically thin 2D semiconductors to unlock the technological upscale required for their commercial uptake. The new atomic layer deposition (ALD) and conversion technique yields large area performance uniformity and tunability. Like graphene, 2D Transition Metal Dichalcogenides (TMDCs) are prone to upscaling challenges limiting their commercial uptake. They are challenging to grow uniformly on large substrates and to transfer on alternative substrates while they often lack in large area electrical performance uniformity. The scalable ALD process of this work enables uniform growth of 2D TMDCs on large area with independent control of layer thickness, stoichiometry and crystallinity while allowing chemical free transfers to application substrates. Field effect transistors (FETs) fabricated on flexible substrates using the process present a field effect mobility of up to 55 cm2/Vs, subthreshold slope down to 80 mV/dec and on/off ratios of 107. In addition, non-volatile memory transistors using ferroelectric FETs (FeFETs) operating at ±5 V with on/off ratio of 107 and a memory window of 3.25 V are demonstrated. These FeFETs demonstrate state-of-the-art performance with multiple state switching, suitable for one-transistor non-volatile memory and for synaptic transistors revealing the applicability of the process to flexible neuromorphic applications.

Chiral Perovskite Nanoplatelets with Tunable Circularly Polarized Luminescence in the Strong Confinement Regime

AbstractChiral perovskite nanocrystals have emerged as an interesting chiral excitonic platform that combines both structural flexibility and superior optoelectronic properties. Despite several recent demonstrations of optical activity in various chiral perovskite nanocrystals, efficient circularly polarized luminescence (CPL) with tunable energies remains a challenge. The chirality imprinting mechanism as a function of perovskite nanocrystal dimensionality remains elusive. Here, atomically thin inorganic perovskite nanoplatelets (NPLs) are synthesized with precise control of layer thickness and are functionalized by chiral surface ligands, serving as a unique platform to probe the chirality transfer mechanism at the organic/perovskite interface. It is found that chirality is successfully imprinted into mono‐, bi‐, and tri‐layer inorganic perovskite NPLs, exhibiting tunable circular dichroism (CD) and CPL responses. However, chirality transfer decreases in thicker NPLs, resulting in decreased CD and CPL dissymmetry factors for thicker NPLs. Aided by large‐scale first‐principles calculations, it is proposed that chirality transfer is mainly mediated through a surface distortion rather than a hybridization of electronic states, giving rise to symmetry breaking in the perovskite lattice and spin‐split conduction bands. The findings described here provide an in‐depth understanding of chirality transfer and design principles for distorted‐surface perovskites for chiral photonic applications.

Increased Magnetoelectric Coupling in Porous Nanocomposites of CoFe2O4 and BiFeO3 with Residual Porosity for Switchable Magnetic Devices

In this work, multiferroic thin-film nanocomposites were synthesized by coating the inside of mesoporous, cobalt ferrite (CoFe2O4 or CFO) with varying thicknesses of piezoelectric bismuth ferrite (BiFeO3 or BFO) grown by atomic layer deposition (ALD). Since ALD allows for precise control of the BFO layer thickness, the amount of residual porosity inside the pores can be controlled. Upon electrical poling, the piezoelectric BFO strains to be under out-of-plane tension, and since BFO is covalently bound to CFO, this tensile stress is transferred from BFO to CFO. CFO is a negative magnetostrictive material, meaning its magnetization should decrease in the direction of tension. This decrease in magnetization was observed in out-of-plane magnetometry experiments. Interestingly, the magnetization changes were found to be largest in the samples with the most residual porosity, despite the fact that they contained the smallest volume of BFO. Indeed, while the fully filled samples had a similar magnetoelectric coefficient to other dense nanostructured BFO-CFO composites reported in the literature, composites with the most residual porosity showed an exceptionally large converse magnetoelectric coefficient of 1.2 × 10–6 s m–1, an order of magnitude higher than dense composites. Strain transfer was confirmed using high-resolution X-ray diffraction. Samples with more residual porosity showed larger strain changes, corroborating the magnetization data. This suggests that magnetoelectric coupling can be optimized by engineering residual porosity into multiferroic composites. Such systems have profound effects for a broad range of switchable magnetic devices, particularly in the microwave and spintronic space.

Controlling the Carrier Injection Efficiency in 3D Nanocrystalline Silicon Floating Gate Memory by Novel Design of Control Layer.

Three-dimensional NAND flash memory with high carrier injection efficiency has been of great interest to computing in memory for its stronger capability to deal with big data than that of conventional von Neumann architecture. Here, we first report the carrier injection efficiency of 3D NAND flash memory based on a nanocrystalline silicon floating gate, which can be controlled by a novel design of the control layer. The carrier injection efficiency in nanocrystalline Si can be monitored by the capacitance-voltage (C-V) hysteresis direction of an nc-Si floating-gate MOS structure. When the control layer thickness of the nanocrystalline silicon floating gate is 25 nm, the C-V hysteresis always maintains the counterclockwise direction under different step sizes of scanning bias. In contrast, the direction of the C-V hysteresis can be changed from counterclockwise to clockwise when the thickness of the control barrier is reduced to 22 nm. The clockwise direction of the C-V curve is due to the carrier injection from the top electrode into the defect state of the SiNx control layer. Our discovery illustrates that the thicker SiNx control layer can block the transfer of carriers from the top electrode to the SiNx, thereby improving the carrier injection efficiency from the Si substrate to the nc-Si layer. The relationship between the carrier injection and the C-V hysteresis direction is further revealed by using the energy band model, thus explaining the transition mechanism of the C-V hysteresis direction. Our report is conducive to optimizing the performance of 3D NAND flash memory based on an nc-Si floating gate, which will be better used in the field of in-memory computing.

Effects of deposition temperature on the wear behavior and material properties of plasma enhanced atomic layer deposition (PEALD) titanium vanadium nitride thin films

This work investigates the effects of deposition temperature on the wear behavior and material properties of recently developed plasma enhanced atomic layer deposited (PEALD) TiVN films. ∼50–100 nm thick TixV1-xN (x ~ 0.5, hereto referred to as TiVN) films were deposited using PEALD on Si substrates with thermal oxide at a range of deposition temperatures (150 °C, 200 °C, 250 °C, 300 °C, 350 °C). Wear testing was performed on each film using a linearly reciprocating tribometer in a controlled humidity environment. Wear rates of the TiVN films varied with deposition temperature, with the 250 °C sample achieving ultralow wear(5.4 × 10−7 mm3/Nm), while the 150 °C sample wore through the film completely in early sliding cycles. Along with their low wear properties, these PEALD TiVN films were found to have low electrical resistivity when deposited above 150 °C. Film density and crystallite size increased with increasing deposition temperature up to 250 °C, where these properties plateaued. High compressive residual stresses were measured, ranging from 2.7 to 7.7 GPa. XRD Bragg peak intensities showed that films with increasing deposition temperatures had higher degrees of crystallinity. XPS indicated that above 150 °C deposition temperatures, impurities in the film were reduced by ∼4x. Higher deposition temperatures allow for increased adatom mobility, which can lead to higher densities and crystallinity, which are typically associated with lower wear rates. At deposition temperatures below 200 °C, precursor reactivity is sluggish and there is insufficient energy for complete surface reactions to occur, leading to film contamination and less dense films. The subtle differences in wear rates above 200 °C deposition temperature indicated that there are competing material properties that can either contribute to or detract from the wear behavior of the film, and a combination of desirable mechanical, physical, structural, and chemical properties are required for ultra-low wear rates to be achieved. The low wear and friction properties and low electrical resistivity of these films combined with the low deposition temperature, conformality, and atomic layer thickness control of PEALD make them potential candidates for applications such as thermally sensitive microelectronics and MEMS/NEMS.

Lasing by Template‐Assisted Self‐Assembled Quantum Dots

AbstractMiniaturized laser sources with low threshold power are required for integrated photonic devices. Photostable core/shell nanocrystals are well suited as gain material and their laser properties can be exploited by direct patterning as distributed feedback (DFB) lasers. Here, the 2nd‐order DFB resonators tuned to the photoluminescence wavelength of the QDs are used. Soft lithography based on template‐assisted colloidal self‐assembly enables pattern resolution in the subwavelength range. Combined with the directional Langmuir–Blodgett arrangement, control of the waveguide layer thickness is further achieved. It is shown that a lasing threshold of 5.5 mJ cm−2 is reached by a direct printing method, which can be further reduced by a factor of ten (0.6 mJ cm−2) at an optimal waveguide thickness. Moreover, it is discussed how one can adjust the DFB geometries to any working wavelength. This colloidal approach offers prospects for applications in bioimaging, biomedical sensing, anti‐counterfeiting, or displays.

Dissolution of WO3 modified with IrOx overlayers during photoelectrochemical water splitting

AbstractWO3, an abundant transition metal semiconductor, is one of the most discussed materials to be used as a photoanode in photoelectrochemical water‐splitting devices. The photoelectrochemical properties, such as photoactivity and selectivity of WO3 in different electrolytes, are already well understood. However, the understanding of stability, one of the most important properties for utilization in a commercial device, is still in the early stages. In this work, a photoelectrochemical scanning flow cell coupled to an inductively coupled plasma mass spectrometer is applied to determine the influence of co‐catalyst overlayers on photoanode stability. Spray‐coated WO3 photoanodes are used as a model system. Iridium is applied to the electrodes by atomic layer deposition in controlled layer thickness, as determined by ellipsometry and x‐ray photoelectron spectroscopy. Photoactivity of the iridium‐modified WO3 photoanodes decreases with increasing iridium layer thickness. Partial blocking of the WO3 surface by iridium is proposed as the main cause of the decreased photoelectrochemical performance. On the other hand, the stability of WO3 is notably increased even in the presence of the thinnest investigated iridium overlayer. Based on our findings, we provide a set of strategies to synthesize nanocomposite photoelectrodes simultaneously possessing high photoelectrochemical activity and photostability.

MOF Structure engineering to synthesize core-shell heterostructures with controllable shell layer thickness: Regulating gas selectivity and sensitivity

Metal-organic framework (MOF)-derived metal oxide semiconductors have received significant attention for gas sensing applications. Herein, we reported core-shell In2O3@ZnO n-n heterostructures by depositing ZIF-8 derivative onto wrinkled In2O3 sphere, realizing the control of ZnO shell thickness (12.6–72.4 nm) through controlling MOF growth time. Due to the formation of n-n heterojunction at the core-shell interface, the tuning of shell thickness can lead to the radial modulation of the electron-accumulation layer in ZnO, and realizing the control of free charge carrier concentration that participated in gas sensing reaction. What’s more, the MOF-derived ZnO shell with rich oxygen vacancies is beneficial for oxygen chemisorption. Accordingly, compared with the In2O3 based sensor, the In2O3@ZnO based sensor exhibits higher sensitivity to trace-level acetone (100 ppb), faster response time (2 s vs. 100 ppm), better selectivity, and stronger anti-humidity capacity at operating temperature 300 °C, while the thickness of ZnO shell is 55.3 nm. In addition, the increase of ZnO shell thickness can lead to the selectivity change from ethanol to acetone of In2O3@ZnO owing to the inherent catalytic oxidation activity. Thus, the remarkable performance of the In2O3@ZnO sensor mainly relies on ZnO shell layer.

Spacer Layer Thickness Dependence of the Giant Magnetoresistance in Electrodeposited Ni-Co/Cu Multilayers.

Electrodeposited Ni65Co35/Cu multilayers were prepared with Cu spacer layer thicknesses between 0.5 nm and 7 nm. Their structure and magnetic and magnetoresistance properties were investigated. An important feature was that the Cu layers were deposited at the electrochemically optimized Cu deposition potential, ensuring a reliable control of the spacer layer thickness to reveal the true evolution of the giant magnetoresistance (GMR). X-ray diffraction indicated satellite reflections, demonstrating the highly coherent growth of these multilayer stacks. All of the multilayers exhibited a GMR effect, the magnitude of which did not show an oscillatory behavior with spacer layer thickness, just a steep rise of GMR around 1.5 nm and then, after 3 nm, it remained nearly constant, with a value around 4%. The high relative remanence of the magnetization hinted at the lack of an antiferromagnetic coupling between the magnetic layers, explaining the absence of oscillatory GMR. The occurrence of GMR can be attributed to the fact that, for spacer layer thicknesses above about 1.5 nm, the adjacent magnetic layers become uncoupled and their magnetization orientation is random, giving rise to a GMR effect. The coercive field and magnetoresistance peak field data also corroborate this picture: with increasing spacer layer thickness, both parameters progressively approached values characteristic of individual magnetic layers. At the end, a critical analysis of previously reported GMR data on electrodeposited Ni-Co/Cu multilayers is provided in view of the present results. A discussion of the layer formation processes in electrodeposited multilayers is also included, together with a comparison with physically deposited multilayers.

Heterointerface Engineering of ZnO/CdS Heterostructures through ZnS Layers for Photocatalytic Water Splitting.

Solar-driven water splitting to produce clean and renewable hydrogen offers a green strategy to address the energy crisis and environmental pollution. Heterostructure catalysts are receiving increasing attention for photocatalytic hydrogen generation. ZnO/ZnS/CdS and ZnO/CdS heterostructures have been successfully designed and prepared according to two different strategies. By introducing a heterointerface layer of ZnS between ZnO and CdS, a Z scheme charge-transfer channel was promoted and achieved superior photocatalytic performance. A highest hydrogen generation rate of 156.7 μmol g-1 h-1 was achieved by precise control of the thickness of the heterointerface layer and of the CdS shell. These findings demonstrated that heterostructures are promising catalysts for solar-driven water splitting, and that heterointerface engineering is an effective way to improve the photocatalytic properties of heterostructures.

Membrane assisted reactive crystallization with multiple interfacial flow regimes for effective mass transfer control

Herein, membrane-assisted reactive crystallization (MARC) with effective interfacial flow regimes was proposed to achieve the effective mass transfer control during reactive crystallization. Three tube-shell side solution systems (EtOH-H2O, Butanol-H2O and H2O-H2O) were chosen to form different flow regimes on the membrane surface, including the microscale liquid layer and the uniform droplets. The fundamental mechanisms of ‘rising and falling tide’ phenomenon, and flexible layer thickness control were uncovered. A force analysis model was established to illustrate the transition behavior of the droplet and liquid layer on the membrane surface. Molecular simulations additionally demonstrated that MARC implemented various ion diffusion conditions in different solution systems. Compared to the conventional reactive crystallization, MARC with multiple flow regimes can achieve effective control of CaCO3 crystal size ranging from 700 nm to 3 μm and obtain uniform size distribution (coefficient of variation less than 15.1 %), which shed light on the advanced material manufacture with reactive crystallization process.

Study on the Structural Degradation of the Polyaniline(PANi) Coated LiNi0.90Co0.85Mn0.15o Particles

The nickel content of the layered lithium transition metal oxide cathodes is proportional to the discharge capacity of energy storage systems. Ni2+ ion, the oxidation state of Ni, moves to the Li sites when Li+ ion is deintercalated during discharge process due to the similar size of ion (Ni2+: 0.069 nm, Li+: 0.076 nm). The spatial transition of Ni2+ ion causes gradual cation mixing and structure degradation of cathode, resulting in the failure of the battery. Also, thick cathode-electrolyte interphase (CEI) is formed on the cathode surface because of the transition metal dissolution, the degradation of electrolyte, and the residual gas such as H2O and CO2.Coating technology is one of the strategies for the physical protection of the cathode surface and the control of CEI layer thickness. Polyaniline(PANi) is a conductive polymer with stable oxidation state. PANi can enhance the electrochemical property and structural stability as a protective layer. In this study, we synthesized PANi material by the oxidative polymereization and coated NCM with the synthesized PANi by sonication method.The PANi-coated NCM(PANi@NCM) has uniform coating layer with 5 nm thickness. PANi@NCM exhibits an initial discharge capacity of 208 mAhg-1 and a capacity retention of 81% after 50 cycles at 45 oC in Figure 1(a) and (b). After the cycling test, pristine and coated cathodes were disassembled for the comparison of the microstructure. Pristine NCM only shows the structural transition from layered structure to structure in the XRD pattern of Figure 1(c). Cross-sectional SEM image of the pristine NCM after cycling test shows micro and macro cracks are distributed from the bulk to the surface of the cathode as shown in Figure 1(d). On the other side, cracks are barely observed on the PANi@NCM particles in Figure 1(e). The layered structure of PANi@NCM is maintained even after cycling test, which are confirmed by TEM analysis with FFT patterns and HAADF images. Figure (f) and (g) show the FFT pattern of the two cathode surfaces after cycling test. Mixed phase is observed on the pristine cathode surface, while the layered structure is maintained on the PANi@NCM surface. Also, the PANi@NCM maintains a thinner passivation layer compared with that of the pristine NCM (6 nm vs 35 nm). In conclusion, the PANi coating layer prevents the degradation of structure and the formation of thick CEI layer. The structural stability enhances the electrochemical performance. Figure 1

Influence of plasma species on the early-stage growth kinetics of epitaxial InN grown by plasma-enhanced atomic layer deposition

Plasma-enhanced atomic layer deposition (PEALD) enables the epitaxial growth of ultrathin indium nitride (InN) films at significantly reduced process temperatures and with greater control of layer thickness compared to other growth methods. However, the reliance on plasma-surface interactions increases the complexity of the growth process. A detailed understanding of the relationship between the plasma properties and the growth kinetics is therefore required to guide the tuning of growth parameters. We present an in situ investigation of the early-stage PEALD growth kinetics of epitaxial InN within three different plasma regimes using grazing incidence small-angle x-ray scattering (GISAXS). The GISAXS data are supported by diagnostic studies of the plasma species generation in the inductively coupled plasma source as a function of the relative concentrations of the nitrogen/argon gas mixture used in the growth process. The growth mode is found to be correlated to the production of nitrogen species in the plasma, with high concentrations of the atomic N species promoting Volmer–Weber growth (i.e., island growth) and low concentrations promoting Stranski–Krastanov growth (i.e., layer-plus-island growth). The critical thickness for island formation, island center-to-center distance, and island radius are found to increase with ion flux. Furthermore, the island center-to-center distance and areal density are observed to change only during plasma exposure and to continue changing with exposure even after the methylindium adlayer is believed to have fully reacted with the plasma. Our results demonstrate the potential to control the growth kinetics during PEALD of epitaxial films by intentionally accessing specific regimes of plasma species generation.

Structural and Optical Characteristics of Flexible Optically Rewritable Electronic Paper

A comprehensive theory of light-reflective characteristics and experimental technique of liquid crystal layer thickness control for flexible optically rewritable electronic paper is presented. Cylindrical pillars were used to control the gap between flexible substrates. The introduced prototype of optically rewritable electronic paper has shown very promising performance. In this regard, we report theoretical results of structural photosensitive alignment of nematic liquid crystals on flexible substrate. The focus of theoretical study is on understanding the self-assembled complex structure, governed by the interplay between surface anchoring and liquid crystal elasticity. Mueller matrix spectroscopic ellipsometry was used to study light-reflecting characteristics and polarization properties of the twisted nematic film.

Asphalt Layer Cracking Behavior and Thickness Control of Continuously Reinforced Concrete and Asphalt Concrete Composite Pavement

Based on thermal–mechanical coupling simulation analysis and physical engineering tracking observation, the mechanical behavior and response of a continuously reinforced concrete and asphalt concrete (CRC + AC) composite pavement layer were analyzed, and the causes of cracking on the surface and bottom of the asphalt layer were revealed. Studies have shown that under normal driving conditions, the AC layer, which is usually in the position of the wheel load gap and wheel load side, more easily generates a longitudinal “corresponding crack”. Compared to normal driving, longitudinal cracks are generated more easily inside of the curve, and transverse cracks occur more easily on poor stadia curves. When the AC layer thickness is less than 8 cm, the AC layer is more prone to bottom-up cracking, and it is more prone to top-down cracking when it is more than 8 cm thick. Comprehensively considering the tensile stress, shear stress, and the thickness of the AC layer, it is recommended that the suitable thickness range of the AC layer is 8 cm~14 cm. The calculated results show good agreement with the physical engineering investigation. The research results can provide a theoretical and scientific basis for cracking control and the rational design of a CRC + AC composite pavement layer.

Tunable photochemical deposition of silver nanostructures on layered ferroelectric CuInP2S6

Two-dimensional layered ferroelectric materials, such as CuInP2S6 (CIPS), are promising candidates for novel and high-performance photocatalysts, owing to their ultrathin layer thickness, strong interlayer coupling, and intrinsic spontaneous polarization, while how to control the photocatalytic activity in layered CIPS remains unexplored. In this work, we report for the first time, the photocatalytic activity of ferroelectric CIPS for the chemical deposition of silver nanostructures (AgNSs). The results show that the shape and spatial distribution of AgNSs on CIPS are tunable by controlling layer thickness, environmental temperature, and light wavelength. The ferroelectric polarization in CIPS plays a critical role in tunable AgNS photodeposition, as evidenced by layer thickness and temperature dependence experiments. We further reveal that AgNS photodeposition process starts from active site creation, selective nanoparticle nucleation/aggregation, to continuous film formation. Moreover, AgNS/CIPS heterostructures prepared by photodeposition exhibit excellent resistance switching behavior and good surface enhancement Raman Scattering activity. Our findings provide new insight into the photocatalytic activity of layered ferroelectrics and offer a new material platform for advanced functional device applications in smart memristors and enhanced chemical sensors.

Thermoelectric properties of 2D semiconducting Pt2CO2

Quantum confinement effect in 2D materials leads to the reduction of the degree of freedom of space and the weakening of the correlation between the thermoelectric factors. Only by adjusting a certain physical quantity can optimized the thermoelectric performance. MXenes as a new class of 2D material have attracted widely attention due to their good mechanical and chemical stability, controllable layer thickness, easily functionalized surface and excellent electrical conductivity. In the present paper, using first-principles calculations, we design and study the stability, electronic and thermoelectric properties of 2D monolayer Pt2CO2. Results show that the Pt2CO2 is a new non-magnetic semiconductor, and can bear its own weight, and maintain its free-standing planar structure without substrate support. Futher, the stable calculations indicate that the Pt2CO2 meets thermodynamic, mechanical and dynamic stabilities. Finally, using the Boltzmann transport theory combined with Slack model, we calculate the Seebeck coefficient S, electrical conductivity σ/τ, and the thermal conductivity κ, and then obtain the ZT value from 300 K to 1000 K. It is found that the largest ZT value closes to 1.05 at 1000 K, implying the Pt2CO2 potential application as thermoelectric material.

Characterizing CO2 Reduction Catalysts on Gas Diffusion Electrodes: Comparing Activity, Selectivity, and Stability of Transition Metal Catalysts.

Continued advancements in the electrochemical reduction of CO2 (CO2RR) have emphasized that reactivity, selectivity, and stability are not explicit material properties but combined effects of the catalyst, double-layer, reaction environment, and system configuration. These realizations have steadily built upon the foundational work performed for a broad array of transition metals performed at 5 mA cm–2, which historically guided the research field. To encompass the changing advancements and mindset within the research field, an updated baseline at elevated current densities could then be of value. Here we seek to re-characterize the activity, selectivity, and stability of the five most utilized transition metal catalysts for CO2RR (Ag, Au, Pd, Sn, and Cu) at elevated reaction rates through electrochemical operation, physical characterization, and varied operating parameters to provide a renewed resource and point of comparison. As a basis, we have employed a common cell architecture, highly controlled catalyst layer morphologies and thicknesses, and fixed current densities. Through a dataset of 88 separate experiments, we provide comparisons between CO-producing catalysts (Ag, Au, and Pd), highlighting CO-limiting current densities on Au and Pd at 72 and 50 mA cm–2, respectively. We further show the instability of Sn in highly alkaline environments, and the convergence of product selectivity at elevated current densities for a Cu catalyst in neutral and alkaline media. Lastly, we reflect upon the use and limits of reaction rates as a baseline metric by comparing catalytic selectivity at 10 versus 200 mA cm–2. We hope the collective work provides a resource for researchers setting up CO2RR experiments for the first time.

Modeling and optimization of metal-organic frameworks membranes for reverse osmosis with artificial neural networks

Metal-organic frameworks (MOFs) have recently attracted tremendous attention as membrane materials for desalination owing to their diversified structures, permselectivity, and tunable functionalities. However, the structure-performance relationship of MOF membranes still has not been elucidated. Herein, artificial neural networks (ANN) were developed to form prediction model of MOF thin film nanocomposite (TFN) membrane performances in reverse osmosis applications. Key parameters including MOF size, MOF pore diameter, MOF loading, selective layer thickness, salt concentration, and pressure were collected from literature to predict the water permeability and salt rejection. 5-fold cross-validation and hyperparameter tuning method were employed to acquire a better performing model. When the node structure was 6–9–9–8–2 with the learning rate of 0.001, the developed ANN model attained a remarkable prediction R2 of 90.62%. By introducing mean impact value algorithm into the model, the feature importance of each factor on the membrane performance was also calculated. Rather than the MOF loading and size, proper control of selective layer thickness and MOF pore diameter was key to breaking the permeability-selectivity tradeoff. Finally, ANN proved its ability to predict the membrane performance for water purification and further provide guidance for MOF-based membrane design, or even other TFN membrane design.

Effect of Gas Counter Pressure on the Surface Roughness, Morphology, and Tensile Strength between Microcellular and Conventional Injection-Molded PP Parts.

Microcellular injection-molded parts have surface defect problems. Gas counter pressure (GCP) is one of the methods to reduce surface defects. This study investigated the effect of GCP on the surface roughness, morphology, and tensile strength of foamed and conventional injection-molded polypropylene (PP) products. GCP is generated by filling up the mold cavity with nitrogen during the injection-molding (IM) process. It can delay foaming and affect flow characteristics of microcellular and conventional injection-molding, which cause changes in the tensile strength, flow length, cell morphology, and surface quality of molded parts. The mechanism was investigated through a series of experiments including tuning of GCP and pressure holding duration. Surface roughness of the molded parts decreased with the increase in GCP and pressure holding duration. Compared to microcellular IM, GCP-assisted foaming exhibited much better surface quality and controllable skin layer thickness.