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The deposition of selected monomers on the surface of high modulus carbon fibers was studied. The fundamental principles which provide the basis for the design of a predictable interfacial bond between carbon fibers and polymeric matrices are described.
Fast spin manipulation in magnetic heterostructures, where magnetic interactions between different materials often define the functionality of devices, is a key issue in the development of ultrafast spintronics. Although recently developed optical approaches such as ultrafast spin-transfer and spin–orbit torques open new pathways to fast spin manipulation, these processes do not fully utilize the unique possibilities offered by interfacial magnetic coupling effects in ferromagnetic multilayer systems. Here, ultrafast optically controlled interfacial exchange interactions in the ferromagnetic Co 2 FeAl/(Ga,Mn)As system at low laser fluence levels are experimentally demonstrated. The excitation efficiency of Co 2 FeAl with the (Ga,Mn)As layer is 30–40 times higher than the case with the GaAs layer at 5 K due to the modification of exchange coupling interaction via photoexcited charge transfer between the two ferromagnetic layers. In addition, the coherent spin precessions persist to room temperature, excluding the drive of pump-modulated magnetization in the (Ga,Mn)As layer and indicating a proximity-effect-related optical excitation mechanism. The results highlight the importance of interfacial exchange interactions in ferromagnetic heterostructures and how these magnetic coupling effects can be utilized for ultrafast, low-power spin manipulation.
This work investigates the effects of plasma surface treatment on both the local adherend–adhesive interfacial strength and the global lap shear strength (LSS) of adhesively-bonded joints composed of metals, CFRTPs, and metal-CFRTP combinations, using AA6061 and CFRPPA as representative examples. Experimental and computational results show that plasma treatment improved the ratio of CFRPPA–adhesive interfacial normal strength to adhesive tensile strength (sint,n/scri,t,adhesive) from 0.59–1.00 to 0.91–1.73, leading to an average 90% increase in LSS for CFRPPA-related joints. In contrast, the LSS and sint,n/scri,t,adhesive values of AA6061–AA6061 joints (>=2.27) remained nearly unchanged after plasma treatment. The enhanced joint bonding was further supported by post-failure surface morphologies from three-dimensional profilometry and simulations, showing a transition from dominant interfacial failure to mixed modes involving interfacial, cohesive, and slight fiber-peeling failures. The LSS evolution with respect to sint,n/scri,t,adhesive was numerically established until the saturation of the LSS of various joints, and the behavior of AA6061–CFRPPA T-joints with varying interfacial strengths was also modeled. This study highlights the importance of local interfacial bonding strength, rather than global LSS, for understanding and optimizing the mechanical performance of adhesively-bonded composite–metal and composite-composite structures via different surface modification strategies.
The transition to electric vehicles (EVs) is pivotal for achieving energy security and integrating grid stability, with lithium-ion batteries (LIBs) playing a central role in this transformation. However, the conventional wet electrode manufacturing relying on N-methyl-2-pyrrolidone (NMP) solvent is energy intensive and costly. Dry processing (DP) has emerged as a promising alternative, eliminating solvents and using polytetrafluoroethylene (PTFE) binder for electrode fabrications. Despite its advantages, DP faces a critical challenge: poor interfacial adhesion between the hydrophobic PTFE binder and the hydrophilic cathode active material (CAM), particularly LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811), which undermines electrode performance. Here, to address this, we introduced a novel vapor-phase trimethoxymethylsilane (TMMS) coating to hydrophobize the CAM surface, enhancing compatibility with PTFE. This surface modification significantly enhances binder – CAM interactions, enabling uniform mixing and robust electrode integrity without damaging the CAM particles. Our findings advance the feasibility of environmentally sustainable and cost-effective dry processing, representing a significant step toward sustainable battery manufacturing.
Transfer hydrogenation (TH) of unsaturated hydrocarbons with formic acid (FA) is an attractive processing pathway for the reduction of lignocellulosic pyrolysis oils. The low solubility of hydrophobic bio-oil species in water and FA in oil necessitates the use of a biphasic system as the reaction environment. Here, we report the effects of Pd/silica catalyst surface wettability on the TH reaction rate. Modification of the surface with short chain (C1–C4) alkyl silanes resulted in an increase in the reaction rate as compared to the unmodified catalyst. In contrast, modification of the surface with sulfonate (hydrophilic) and C18 alkyl silanes (hydrophobic) resulted in a decrease in the reaction rate as compared to the unmodified catalyst. Here, the results are discussed in terms of the catalyst interfacial activity and relative affinity of the reagents to the Pd active sites. An observed change in the apparent reaction order in styrene for a hydrophilic catalyst suggests that changing catalyst surface wettability from hydrophilic to hydrophobic resulted in a switch from a transport-limited to a kinetic-limited reaction regime.
Slowing non-desirable electron transfer reactions at metal oxide-dye interfaces is important for many technologies. Specifically, after an interfacial photoinduced charge separation event at a metal oxide-dye interface, it is critically important to limit the rate of electron transfer reactions back to sensitizers and to limit electron transfer reactions between the electrolyte and the metal oxide. Ruthenium-based dyes at metal oxide interfaces are widely used in many fields; however, these dyes often have poor surface insulation resulting in fast recombination kinetics with transition metal-based redox shuttles in an electrolyte. This work explores two semiconductor surface modification strategies designed to minimize recombination events of electrons in TiO 2 with oxidized redox shuttles using a fluorinated siloxane insulator (PFTS) and a metal oxide insulator (MgO) with a well-known Ru dye, B11. Additionally, the influence of these treatments on the rate and duration of photoinduced interfacial charge separation at the TiO 2 -dye interface was examined. The TiO 2 -dye-redox shuttle systems were studied via dye-sensitized solar cell current-voltage curve, incident photon-to-current conversion efficiency, small-modulated photovoltage transient, time-correlated single photon counting, and transient absorption spectroscopy measurements. MgO was found to decrease the rate of the electron transfer reaction from the metal oxide to the electrolyte, decrease the rate of the electron transfer reaction to the oxidized dye from TiO 2 , increase the electron transfer reaction rate from a reduced redox shuttle to an oxidized dye, and decrease the electron injection rate from the photoexcited dye to TiO2. Interestingly, PFTS was found to desirably improve on these rates relative to MgO or untreated TiO 2 . Here, a model based on electrostatic interactions is presented to explain the exceptional behavior of PFTS with DFT computational analysis of PFTS supporting this model.
The long-term durability prospects of halide perovskite solar cells are rapidly improving; however, the interface between the hole transport layer (HTL) and the perovskite remains a source of degradation. Alone, polymer- or carbazole-based HTLs suffer from incomplete coverage of the underlying indium tin oxide glass, leading to degradation and compromised performance. Here, we show a multi-HTL approach whereby a polymer HTL is reinforced using a phosphonic acid modification leading to better protection of the buried perovskite interface and more columnar growth of perovskite film, resulting in an ~40-mV open-circuit voltage (VOC) improvement indicative of suppressed interfacial recombination across multiple p-i-n device architectures. Solar cells with this reinforced HTL show higher tolerance to several accelerated stress tests. We report, among the best durabilities for unencapsulated cells, a T90 ~3,000 h (T80 ~5,900 h) at 65 degrees C under continuous 1.2 sun AM 1.5G illumination and maximum power point tracking, representing a nearly 4-fold increase compared with [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz)-only devices. Furthermore, we deployed a device with this reinforced HTL on a cube satellite, with long-duration operational space testing results exceeding T80 for the complete mission duration of ~100 days in low Earth orbit.
Mitigation of lunar dust contamination is one of the greatest challenges to be overcome to realize a sustained lunar presence. Likely solutions will integrate active mitigation strategies, requiring the input of external energy, and passive materials, exhibiting an intrinsic resistance to lunar dust adhesion. In this work, a series of copolyimide alkyl ethers containing per fluorinated side-chains were generated to evaluate the influence surface modification agents have on surface chemical, topographical, and mechanical properties. An expanded testing protocol to characterize the adhesion interaction between lunar dust simulant and the copolyimide substrate was carried out. The interfacial adhesion strength was in-situ measured by a custom-built particulate adhesion instrument, utilizing a sonic wand. Surface mechanical properties were characterized by nanoindentation, utilizing the continuous stiffness measurement approach. A nominal presence of surface modifying agents, 1 wt%, resulted in a six-fold reduction in adhesion strength of the interface. A strong inverse correlation between the adhesion strength and Young’s modulus of the substrate was identified. The reduction was attributed to a synergistic interaction between the surface energy, surface roughness, and modulus of the copolyimide alkyl ethers film.
We have examined the ALD of Al 2 O 3 using TMA as the precursor and t-BuOH and H 2 O as the co-reactants, focusing on the effects of the latter on both the ALD process and the possible modification of the underlying substrate. We have employed a quartz-crystal microbalance (QCM) to monitor ALD in situ and in real-time, and the deposited thin films have been characterized using X-ray photoelectron spectroscopy, spectroscopic ellipsometry, and X-ray reflectivity. Growth of thin films of Al 2 O 3 using TMA and either t-BuOH or H 2 O as the co-reactant at T = 285 °C produces thin films of similar physical properties (density, stoichiometry, minimal carbon incorporation), and the growth rate per cycle is similar for the two co-reactants at this temperature. At a lower temperature of T = 120 °C, the behavior is starkly different, where growth occurs with H 2 O but not with t-BuOH. At either process temperature, we find no evidence for significant coverages of a long-lived tert-butoxy species from the reaction of t-BuOH. Deposition of thin films of Al 2 O 3 on metal surfaces of Cu and Co has been examined for evidence of interfacial oxidation. While growth with either co-reactant does not lead to the oxidation of the underlying Cu substrate, use of H 2 O leads to the oxidation of Co, while use of t-BuOH as the co-reactant does not. Thermodynamic factors may affect early stages of growth as Al species will likely scavenge all free O species. In contrast, at later times diffusion of species through the deposited Al 2 O 3 thin film could result in oxidation at the Al 2 O 3 |metal interface, a process that is strongly hindered in the case of t-BuOH due to its size. Furthermore, this observation highlights the importance of the choice of the co-reactant concerning ALD of oxides on metal surfaces.
Deposition techniques, like atomic layer deposition (ALD), are used to form high-quality dielectrics for GaN-based metal–oxide–semiconductor (MOS) gate structures due to the lack of a reliable thermal oxide in GaN. Moreover, interfacial GaO x from pre-existing native oxides is thought to adversely impact channel carrier dynamics and induce undesired threshold voltage shifts in GaN-based MOS gate structures. Exposure of the GaN surface to the trimethylaluminum (TMA) precursor prior to standard alumina ALD decreases the native oxide layer on GaN, but the extent of chemical modification has not been well studied in the context of interface composition in a MOS gate structure. Herein, we compare annealed 55 nm Al 2 O 3 dielectric films on GaN grown using either a water-first ALD process or a process including sequential pulses of TMA immediately before the initiation of Al 2 O 3 ALD. Time-of-Flight Secondary Ion Mass Spectrometry measures differences in the interfacial GaO x content between each ALD film. Here, it also detects surface contaminant species like Si, F, S, and C. Furthermore, we report the formation of an AlN species at the Al 2 O 3 /GaN interface, which is more prominent for the film grown using the TMA pre-pulse step. In general, this work demonstrates that the TMA pre-pulse step is an effective strategy for cleaning substrate surfaces prior to ALD.
A rationalized interfacial design strategy was applied to tailor the porous transport layer (PTL)-catalyst layer (CL) contact and the PTL bulk-phase architecture. Particularly, at the PTL-CL interface, our results reveal that laser ablated sintered titanium power-based PTLs improve electrolyzer performance at both the H2NEW Consortium baseline catalyst loading of 0.4 mgIr cm -2 as well as at the ultra-low catalyst loading of 0.055 mgIr cm -2 . Under ultra-low catalyst loadings, the laser ablated PTL demonstrates maximum reduction of 230 mV compared to the commercial PTL at 4 A cm -2 , and reduces by 68 mV at 3.2 A cm -2 under H2NEW baseline loading. Laser ablation alters the titanium phase at the interface, so it forms more uniform structure like a microporous layer or a backing layer, leading to an increase in the surface area in contact with the catalyst layer while preventing the membrane from deforming into the PTL. Moreover, we reveal that bulk-phase architecture modification of the PTL by ablating patterned pores at the flow field-PTL interface improves mass transport without sacrificing contact at the CL-PTL interface. Overall, laser ablation of the PTL is an effective method to customize interfacial design to enhance proton exchange membrane electrolyzer performance.
The self-assembly of high-χ low-N block copolymers (BCPs) can give patterns with sub-10 nm full pitch, serving as a promising alternative to photolithographic methods. Here, in this work, we synthesized poly(solketal methacrylate)-block-polystyrene copolymers, PSM-b-PS, with various volume ratios of the two blocks. After hydrolysis of the PSM block into poly(glycerol monomethacrylate), PGM, the BCPs had both lamellar and cylindrical microdomain morphologies in the bulk phase and in thin films. In addition to our previously developed solid-state hydrolysis strategy involving trifluoroacetic acid vapor, we developed a new photoinduced solid-state hydrolysis using photoacid generators, PAGs, embedded within the polymer films. After exposure to UV followed by a postexposure baking or solvent vapor annealing, the BCPs transitioned from the disordered, phase-mixed state into laterally ordered cylindrical patterns. In comparison to linear BCPs that rely on a random copolymer layer to modify interfacial interactions with the substrate to promote an orientation of the microdomains normal to the interface, we found that the microdomains in bottlebrush multiblock copolymers oriented normal to the interface absent substrate modification due to the chain architecture.
Lithium batteries with Si, Al or Bi microsized (>10 µm) particle anodes promise a high capacity, ease of production, low cost and low environmental impact, yet they suffer from fast degradation and a low Coulombic efficiency. In this paper, we demonstrate that a rationally designed electrolyte (2.0 M LiPF 6 in 1:1 v/v mixture of tetrahydrofuran and 2-methyltetrahydrofuran) enables 100 cycles of full cells that contain microsized Si, Al and Bi anodes with commercial LiFePO 4 and LiNi 0.8 Co 0.15 Al 0.05 O 2 cathodes. Alloy anodes with areal capacities of more than 2.5 mAh cm -2 achieved >300 cycles with a high initial Coulombic efficiency of >90% and average Coulombic efficiency of >99.9%. These improvements are facilitated by the formation of a high-modulus LiF–organic bilayer interphase, in which LiF possesses a high interfacial energy with the alloy anode to accommodate plastic deformation of the lithiated alloy during cycling. Lastly, this work provides a simple yet practical solution to current battery technology without any binder modification or special fabrication methods.
We demonstrate that both the magnitude and sign of the Dzyaloshinskii-Moriya interaction can be tuned by modifying the type and thickness of an oxide layer adjacent to a ferromagnet. In this work, we focus on Ti/Cu/Co 90 Fe 10 /Ta($d_{\text{Ta}}$)/Oxide/Ta structures, where the Ta interlayer thickness $d_{\text{Ta}}$ ranged from 0 nm to 3 nm, followed by an exposure to oxygen and “Oxide” can mean CoFeO x and/or TaO x . We used Brillouin light scattering spectroscopy to directly determine the volume-averaged Dzyaloshinskii-Moriya interaction from the nonreciprocity of the spin-wave frequency. The magnitude of the interfacial Dzyaloshinskii-Moriya interaction, $D_{\text{DMI}}$, ranges from – 0.17 to +0.09(±0.02) mJ/m 2 , clearly showing a change in both sign and magnitude, with an increase of Ta interlayer thickness. The modification of the oxide interface allows us to systematically change the hybridization of the 3$\textit{d}$–CoFe orbitals from 3$\textit{d}$–5$\textit{d}$ to 3$\textit{d}$–2$\textit{p}$ and analyze the influence on the Dzyaloshinskii-Moriya interaction. Importantly, we can vary the Dzyaloshinskii-Moriya interaction while maintaining a relatively small value of the damping parameter.
Ni-rich LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes are investigated to realize high energy density Li ion batteries for long life electric vehicle applications. However, capacity decay and thermal instability due to cathode-electrolyte interfacial degradation remain challenges that require sophisticated surface stabilization methods to address. Here, we propose a strategy, for the first time, to form an artificial Li + -conducting cathode-electrolyte interphase (ALCEI) on the NCM811 cathode surface using a nucleophilic reaction between polysulfides and vinylene carbonate (VC). Furthemore, the as-formed ALCEI layer simultaneously protects the NCM particles from electrolyte corrosion and facilitates Li + ion transport, thus enabling stable and high rate cycling of NCM811. As a result, the ALCEI-modified NCM811 cathode exhibits a high capacity (211.6 mA h g -1 at 0.1C), notable rate capability (134 mA h g -1 at 10C), and superior cycle stability (94.2% over 200 cycles at 1C). These results underscore the use of interfacial engineering in high voltage cathode material development and provide a feasible strategy for stabilizing Ni-rich cathode interfaces in practical Li ion battery applications.
Lithium metal batteries (LMBs) enable much higher energy density than lithium–ion batteries (LIBs) and thus hold great promise for future transportation electrification. However, the adoption of lithium metal (Li) as an anode poses serious concerns about cell safety and performance, which has been hindering LMBs from commercialization. To this end, extensive effort has been invested in understanding the underlying mechanisms theoretically and experimentally and developing technical solutions. In this review, we devote to providing a comprehensive review of the challenges, characterizations, and interfacial engineering of Li anodes in both liquid and solid LMBs. Finally, we expect that this work will stimulate new efforts and help peer researchers find new solutions for the commercialization of LMBs.
Perovskite solar cells fabricated with carbon-based counter electrodes demonstrate decreased cost, enhanced simplicity and speed of production, and increased stability compared to those produced with standard metallic electrodes. This significant improvement of device stability, cost reduction, and production scalability indicates a promising direction for commercial development and availability of perovskite solar technology. The main limitation of carbon-based perovskite devices is the flawed contact between the carbon electrode and perovskite film which decreases device quality and performance, thereby necessitating treatment of the carbon/perovskite interface. This review provides an overview of the current state of carbon-based perovskite devices, discusses progress in carbon/perovskite interface modification methods, and suggests future directions for the research of carbon electrode/perovskite film interface manipulation.
The goal of this proposal is to field test the novel technology of engineered water (modifying ionic composition and/or adding surfactants or nanoparticles) injection to improve oil recovery from the carbonate matrix in fractured reservoirs. Carbonate reservoirs tend to be oil-wet/mixed-wet due to positively charged carbonate mineral surfaces and negatively charged acidic/asphaltic components in the oil. Many carbonate reservoirs are also highly fractured. Water injection does not work efficiently in fractured oil-wet reservoirs because water does not imbibe into the matrix. The water composition can be engineered with ionic modification, surfactants and nanoparticles which can change the wettability of carbonate rocks towards more water-wet conditions which can imbibe water into the matrix and push the oil into the fractures. The engineered water can also lower interfacial tension and minimize capillary forces so that gravity can push the oil up and out of the matrix. Wettability alteration also increases water relative permeability which can also improve oil recovery in non-fractured carbonate reservoirs. This technology, if successful, can be a game changer for West Texas carbonates.