Low-temperature Process Research Articles

Polymer‐based filaments with embedded magnetocaloric Ni‐Mn‐Ga Heusler alloy particles for additive manufacturing

AbstractOne important issue associated to magnetocaloric materials that hinders its technological application is the poor processability and structural integrity of those with the highest performance, usually intermetallics undergoing first‐order magnetic phase transitions. Additionally, the performance of these magnetocaloric materials highly depends on the structural stability of the magnetocaloric phase, which is, in many cases, very sensitive to temperature and mechanical processes. Additive manufacturing via the extrusion of polymer‐based composites is regarded as a promising way to overcome these issues. A recently presented manufacturing method of encapsulating functional fillers into polymer capsules has been used to produce a composite filament with a large load of magnetocaloric off‐stoichiometric Ni2MnGa Heusler alloy fillers with a uniform distribution throughout the polymer matrix as demonstrated by x‐ray tomography characterization. The incorporation of these metallic particles causes changes in the thermal behavior of the polymer as well as an increase in the flowability of the composite with respect to the polymer at the same temperature. The increased flowability of the composites found during manufacturing can be compensated by lowering the extrusion temperatures, making this technique even more convenient for preserving the filler properties, which is an important concern when additive manufacturing magnetocaloric materials. This is confirmed by the magnetic and magnetocaloric behavior of the composites, with responses proportional to the fraction of fillers.Highlights Ultrasonic‐atomization produces highly spherical Ni‐Mn‐Ga Heusler alloy particles. Ni‐Mn‐Ga filled polymer capsules allow a direct extrusion of composites for AM. X‐ray tomography shows uniform volumetric filler distribution within the filaments. Decreased viscosity of the matrix favors the lowering of the processing temperature. The low processing temperatures avoid altering the MCE of the alloy fillers.

Connecting visual metamictization to radiation damage to expand applications of zircon (U-Th)/He thermochronometry

Zircon (U-Th)/He (ZHe) thermochronometry quantifies the timing and tempo of low-temperature processes and is used to deconvolve tectonic and erosional histories. Accumulation and annealing of radiation damage impacts He diffusion in zircon and resulting ZHe dates. Resolving complex histories requires building relationships between ZHe date, effective U (eU), and radiation damage in grains sharing a common thermal history. Prior work demonstrated that purposefully selecting grains with a spectrum of visual metamictization yields a broad range of intrasample eU values (Ault et al., 2018), but it remained unclear if visual metamictization tracks effective radiation damage. Here we evaluate relationships between visual metamictization, effective damage calculated from Raman spectroscopy, and ZHe dates from a new suite of grains from some of the same Precambrian samples investigated in Ault et al. (2018) and Phanerozoic detrital grains from Armstrong et al. (2022). New ZHe analyses (n = 21) confirm increasing visual metamictization corresponds with increasing eU concentration and dates fall along previously reported ZHe date-eU trends for each sample, despite grain selection by different analysts in different sessions. Raman-based alpha dose calculations from multiple spot analyses from transects across the surface and interior of each grain (n = 480 total analyses) range from 3.19 × 1016 to 1.52 × 1019 α/g across the whole dataset. Alpha dose increases in samples characterized by a clear increase in visual metamictization from different types of ZHe date-eU patterns, supporting that visual metamictization reflects effective radiation damage in these samples. Complexities in visual metamictization-damage trends are due to damage zonation observed in cathodoluminescence, comparative internal and external spot analyses, and 2-D Raman maps, as well as limited spread in intrasample visual metamictization and user grain selection bias. Overall, visual metamictization provides a qualitative estimate of effective damage and should be leveraged when selecting grains for traditional ZHe analyses to build ZHe date-eU-damage patterns.

Visible-Light-Induced photocatalytic oxidation of gaseous ammonia on Mo, c-codoped TiO2: Synthesis, performance and mechanism

Ammonia gas (NH3) is a notorious malodorous pollutant with detrimental effects on environment and human health. Removing NH3 through photocatalytic oxidation remains a challenging task due to unclear reaction mechanisms. In this study, DFT simulation results revealed that Cdoped TiO2 could extend the photo-response range to the visible region, but the introduction of deep impurity levels was found to accelerate photogenerated carrier recombination. Fortunately, the rational doping of Mo was found to mitigate this negative effect. Accordingly, Mo, C co-doped TiO2 was synthesized via a facile low-temperature calcination process, resulting in unique band structure that enhanced the photocatalytic oxidation of NH3. Notably, in-situ DRIFTS and DFT results demonstrated that the gradual reaction of NH3 adsorbed on Mo atoms with oxygen species through the N2H4 mechanism, promoting the formation of N2. These findings offer insights into the design of efficient photocatalysts for NH3 removal under visible light, and present a promising technology for indoor air pollution control.

Microstructure-mechanical properties evolution of hot-rolled medium Mn steel: Effects of short-time holding and low-temperature tempering following ultrafast heating

In this work, the mechanical properties of hot-rolled 7Mn steel are significantly sensitive to the short-time isothermal holding after ultrafast heating (UFH). These samples also exhibited significant disparities in sensitivity of mechanical properties to subsequent low-temperature tempering. Through a combination of multi-scale experimental characterization, calculations of yield strength, and numerical simulations of elemental diffusion, we discussed the sensitivities described above. The results indicate that mechanical properties of the samples subjected to ultra-fast heating is not sensitive to subsequent low-temperature tempering. This due to the preferential segregation of C atoms at dislocation sites during the ultra-fast heating, leading to less noticeable C atoms segregation during low-temperature tempering. Short-time isothermal holding after ultrafast heating results in the precipitation of numerous nanoscale carbides within the martensite, thereby reducing solid solution strengthening and significantly decreasing the yield strength. Simultaneously, the low-temperature tempering process induces the segregation of C atoms towards dislocations, grain boundaries, or phase interfaces. This significantly mitigates the Portevin-Le Chatelier (PLC) effect in the sample, increasing the elongation rate of the steel from about 10% to 19%. Additionally, the combined effects of strengthening induced by Cottrell atmosphere and phase boundary segregation contribute to an elevation in yield strength.

Experimental analysis of a CO2 closed heat pump drying system combined with rotary dehumidification for drying banana slices drying

A CO2 closed heat pump drying system combined with rotary dehumidification (HPRD) was investigated using both experimental and theoretical approaches. The advantages of HPRD over traditional CO2 closed heat pump drying systems (THPSs) for drying banana slices were analyzed. After drying, the drying kinetics and quality of banana slices were investigated. The results demonstrated that HPRD reduced the banana slice drying time during low-temperature processing while retaining more color and vitamin C content than THPS. In particular, HPRD increased the drying rate of banana slices dried at low temperatures by up to 41 % compared to the rate obtained by THPS. In addition, it increased the vitamin C content by an average of 12 % and reduced the total color difference by an average of 16 %. And the specific moisture extraction rate of HPRD increases by 26 % compared to THPS. The highest-quality banana slices, which were 3 mm thick and dried by HPRD at 43 °C, maintained a high drying rate and high drying quality. The optimal model of Henderson & Pabis predicted the drying behavior within the experimental range. The results indicated that the drying rate and quality of banana slices dried at low temperatures using HPRD were superior to those dried using THPS.

Practical classical molecular dynamics simulations for low-temperature plasma processing: a review

Practical classical molecular dynamics simulations for low-temperature plasma processing: a review

Interface Engineering Enables Multilevel Resistive Switching in Ultra-Low-Power Chemobrionic Copper Silicate.

Memristor is assuming prominence due to its exceptionally low power consumption, adaptable, and parallel signal processing capabilities that address the limitations of the von Neumann architecture to meet the growing demand for advanced technologies such as artificial intelligence, Internet of Things (IoTs), and neuromorphic computation. In this work, we demonstrate resistive switching in copper silicate-based hollow tube-forming self-organized membrane structures belonging to the category of chemobrionics or chemical gardens to demonstrate cost-effective and highly efficient memristor devices. The device architecture is configured as ITO/PEDOT:PSS/active layer (copper silicate)/PMMA/Ag, an arrangement that serves to stabilize current-voltage hysteresis and exhibit a low SET voltage ∼0.2 V with a 0.8 nJ power consumption while manifesting robust data endurance and multilevel resistive switching. The inherent self-rectifying behavior, characterized by a high rectification ratio of 60, underscores the potential utility of these devices across a spectrum of electronic applications. To emulate the functionality of biological synapses, fundamental synaptic characteristics are assessed, including paired-pulse facilitation (PPF) and potentiation and depression (P&D). We validate the potential of copper silicate chemical garden-based memristor devices for applications that require real-time synaptic processing. Importantly, the fabrication of these devices was accomplished through a comprehensive solution-based, low-temperature process conducted under ambient environmental conditions, obviating the need for specialized glovebox facilities.

Comparison of H2O2 and H2O oxidations on TDMAT absorbed on silicon(100) surface during reaction step of ALD–TiO2 process: A DFT study

Atomic layer deposition (ALD) is a thin film technology with high potential in nano fabrication. There is industrial demand to produce an ALD–TiO2 thin film using a low temperature process for applications of bending electronic devices and biomaterials. TDMAT has gained the most attention as a suitable titanium source to grow an ALD–TiO2 film at extremely low temperatures. In this process, almost all published reports have focused on metal-oxide precursors. The current work investigates the effects of oxidizing agents. For the first time, a theoretical investigation was carried out on the oxidation of H2O2 and H2O on TDMAT absorbed on a silicon (100) surface during the reaction step of the ALD–TiO2 process. We simulated the oxidation process, which continued from the adsorption step of the ALD–TiO2 process, where the TDMAT was used as a titanium precursor. The cluster of the Si9H12 =O2 =Ti[N(CH3)]2 surface model was used to represent the remaining TDMAT molecule absorbed on the Si(100) substrate. The reaction mechanisms of H2O2 oxidizing on this surface were evaluated based on their reaction pathways. The reaction pathway of H2O oxidizing on this surface was calculated at the same level to compare the effect of oxidizers. The DFT at the B3LYP 6–311 G+ (2d,p) and 6–31 G(d,p) theoretical levels were used to calculate the potential energy surface and to optimize the electronic structures in this process. It was found that the reaction mechanism depended on the nature of chemical bond dissociation within the oxidizer molecules during the oxidation process. In the oxidation of H2O2, the H2O2 molecule contained O–O and O–H bonds, which were dissociated during the oxidation process, resulting in different product structures. Only the O–O bond dissociation pathway produced the TiO2 structure. The two species of TDMAT ligands at the surface were completely oxidized using a single H2O2 molecule. The H2O2 oxidation produced more –OH groups (double) compared to H2O oxidation. In H2O oxidation, the H2O molecule contained only the O–H bond within its molecule and required activation energies significantly less than for all pathways of H2O2. The HOMO–LUMO properties and IR frequency characteristics (cm−1) of the plausible product structures were discussed. The results should be useful in guiding the selection of suitable precursors for use in the co–reactant system of the ALD–TiO2 process.

Enhancing sustainability: co-pyrolysis of date palm branches and wastewater microalgae for tailored biochar production

The use of waste products in different applications contains prime importance in today’s research and industry. Researchers are working on producing innovative technologies and processes to utilize waste and produce valuable products for different applications. Microalgae-derived char contains low aromaticity and heating values with relatively higher nitrogen content than lignocellulosic char. This study presents the use of waste from date palm branches and wastewater-derived microalgae through co-pyrolysis to produce char of improved properties. Two batches of experiments were conducted (a) single-step pyrolysis (SSP) and (b) two-step pyrolysis, in the range of highest treatment temperature of 400–600 °C. Single-step pyrolysed char showed lower aromaticity, higher yield, ash content and heating values of the char than two-step pyrolysed char. Similarly, ignition temperature and activation energy were higher during combustion by single-step pyrolysed char than two-step char. Economic analysis also showed slightly higher prices for single-step pyrolysed char. Hence, two-step pyrolysed char is suitable for energy applications, whereas low-temperature processing (400–500 °C) will result in optimum properties in terms of yield and heating values.

Oxygen-deficient tungsten oxide inducing electron and proton transfer: Activating ruthenium sites for hydrogen evolution in wide pH and alkaline seawater

The design of electrocatalysts for the hydrogen evolution reaction (HER) that perform effectively across a broad pH spectrum is paramount. The efficiency of hydrogen evolution at ruthenium (Ru) active sites, often hindered by the kinetics of water dissociation in alkaline or neutral conditions, requires further enhancement. Metal oxides, due to superior electron dynamics facilitated by oxygen vacancies (OVS) and shifts in the Fermi level, surpass carbon-based materials. In particular, tungsten oxide (WO3) promotes the directed migration of electrons and protons which significantly activates the Ru sites. Ru/WO3-OV is prepared through a simple hydrothermal and low-temperature annealing process. The prepared catalyst achieves 10 mA cm−2 at overpotentials of 23 mV (1 M KOH), 36 mV (0.5 M H2SO4), 62 mV (1 M PBS), and 38 mV (1 M KOH + seawater). At an overpotential corresponding to 10 mA cm−2 in 1 M KOH and 1 M KOH + seawater, the mass activity of Ru/WO3-OV is about 7.7 and 7.86 times that of 20 wt% Pt/C. The improvement in activity and stability arises from electronic modifications attributed to metal-support interaction. This work offers novel insights for modulating the HER activity of Ru sites across a wide pH range.

Directly prepared Al-doped FeMoO4 materials from spent hydrogenation catalysts via a low-temperature green process

Environmental-friendly recovery of critical metals from solid wastes directly for new energy materials received lots of concerns. In this paper, the FeMoO4(FMO) materials for new energy storage materials are directly prepared from spent hydrogenation catalysts by “low temperature sodium roasting-water leaching” process. The leaching rates after roasting of main metal element Mo, Al and Ni from wastes are: 91.8 %, 1.7 % and 0.1 %, respectively, then the leachate was directly generated Al-doped FMO materials (Mo/Al = 50:1). As for the application of lithium ion battery anode, the specific capacity is 363.5 mAh/g after 200 cycles, 55 % improvement compared with bare FMO. The tunable phase transformation by roasting temperature regulation is the core to achieve the selective water leaching of Mo, and the intrinsic mechanism have been investigated by calculation and experiments. Finally, the economic evaluation of the whole process shows that for every 1 kg of spent catalyst processed and made into FMO, a profit of $20.8 can be obtained, indicating promising economic benefits. This process provides an environmental technology route for the development of new energy industries under carbon neutrality goals.

Minimum oxygen supply rate for smouldering propagation: Effect of fuel bulk density and particle size

Smouldering is a low-temperature, flameless, and persistent combustion process driven by heterogeneous oxidations. Oxygen supply is a key parameter of smouldering and is sensitive to fuel density and particle size, but our understanding is still limited. Herein, we explore the oxygen threshold for smouldering propagation under upward internal airflow velocities up to 5 mm/s. Pine needles with different bulk densities (55–120 kg/m3) and wood samples with different particle sizes (1–50 mm) are tested. We found that the minimum airflow velocity for sustaining smouldering propagation increases with the decrease of the bulk density or the increase of the particle size. By increasing the airflow velocity, the smouldering front first propagates unidirectionally (opposed) and then bidirectionally (opposed + forward). Nevertheless, when the pore size is large (the fuel particle size is large or the fuel bulk density is small), bidirectional propagation always occurs, because the oxygen can leak through the opposed smouldering front. A simplified thermochemical analysis is proposed to reveal the influence of interparticle heat transfer on the minimum oxygen supply rate of smouldering propagation. This work advances the fundamental understanding of smouldering on solid fuel particles and their smouldering fire risks and helps optimize the efficiency and safety of smouldering processes.

Tungsten stable isotope composition of the upper continental crust

Tungsten (W) stable isotope data for twenty-four composites made from the fine-grained matrix of glacial diamictites, deposited between the Mesoarchean and the Paleozoic, as well as two Archean tonalite-trondhjemite-granodiorites (TTG) are used to refine the W isotope compositions (expressed as δ186W deviations from the NIST 3163 W standard) of the upper continental crust (UCC). To do this we evaluate W isotope fractionation in the diamictites as the result of both magmatic and low-temperature processes. The δ186W values of the diamictites are heterogeneous (0.017 ± 0.011 ‰, 2SE to 0.182 ± 0.007 ‰, 2SE), encompassing the range of previously published values for igneous rocks. We find that δ186W correlates positively with the diamictite’s chemical index of alteration (CIA), a measure of the degree of chemical weathering in the provenance, suggesting that the continental regolith (i.e., surface material composed of weathered residues) is isotopically heavy for W. Since W in rivers and ocean water is also isotopically heavy, this suggests that equilibration with Fe-Mn-oxides controls the W isotope composition of surface waters and that such oxides are not important constituents of the regolith, whose W is likely accommodated in clays. Using diamictites with low CIA (<60, n = 9), we calculate an average δ186W of 0.046 ± 0.036 ‰ (2SD) for the UCC, from 2.3 to 0.3 Ga. This average is combined with the TTG data of this study, as well as data from the literature for upper crustal rocks to obtain a representative δ186W value of the UCC of 0.046 ± 0.046 ‰ (2SD). The W stable isotope composition of the UCC is lighter than that of mantle-derived melts (MORB and OIB, with an average δ186W = 0.082 ± 0.026 ‰, 2SD), and much lighter than the weighted average δ186W of intra-oceanic arcs (δ186W = 0.104 ± 0.052 ‰, 2SD), though the spread in the arc rocks is large. The significant difference in δ186W between average intra-oceanic island arc lavas and UCC is intriguing given that continental crust is thought to form primarily via arc magmatism. This difference suggests that not all modern intra-oceanic arcs are representative of those that formed the continental crust. Rather, only arcs that are enriched in incompatible trace elements, which also tend to have lighter W isotope compositions, may have been involved in making new continental crust. Alternatively, there may have been a secular change in the W isotope composition of arc magmas.

Increased hardness value due to the diffusion of low-temperature carburizing process

This research to determine the effect of the tensile load on the carburizing process and the heating temperature lower than the normal carburizing temperature on the hardness of carbon steel with a percentage of 80% buffalo bone charcoal and 20% BaCO3, 20 mesh grain size, 4 hours holding time, and slow cooling with a tensile load of 1/4σp 1/2σp 3/4σp, and σp (proportional stress). The heating temperatures below normal carburizing temperatures, namely 6000C, 6500C, 7000C, and 7500C while being pulled by 1/4σp, 1/2σp, 3/4σp, and σp. After reaching the heating temperature, the material is held in the furnace for 4 hours and cooled slowly. After the material is cold, mechanical testing is carried out with Vickers microhardness. Hardness value at a temperature of 6000C is 103.93 HRB, at a temperature of 6500C is 104.33 HRB, at a temperature of 7000C is 104.80 HRB, and at a temperature of 7500C is 106.60 HRB, while the process of pack carburizing without tensile at a heating temperature of 8000C is 105.2 HRB. This proves that the application of loads at lower heating temperatures during the heating process can exceed the hardness value without tensile loads at higher temperatures of 8000 C.

Reduction of internal stress in InGaZnO (IGZO) thin film transistors by ultra-thin metal oxide layer

In this study, the modification of indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) with an ultrathin metal oxide layer successfully reduces internal film stress. The introduction of an Al2O3 metal oxide layer effectively diminishes defects within the film and minimizes distortion in the film densification process. A low-temperature annealing process at 200 °C was employed to mitigate thermal expansion differences between the film and the substrate, thus reducing internal stress within the device. Furthermore, we have discovered that this structural modification holds the potential to enhance mechanical stress resistance. This paper offers a novel perspective and an experimental foundation for the stress analysis of flexible TFTs.

Low-temperature process design for inversion mode n-channel thin-film-transistor on polycrystalline Ge formed by solid-phase crystallization

We fabricated an inversion mode n-channel thin-film-transistor (TFT) on polycrystalline (poly-) Ge at low temperatures for monolithic three-dimensional large-scale IC (3D-LSI) and flexible electronics applications. Based on our previously reported solid-phase crystallization (SPC) method, we designed an n-channel TFT fabrication process with phosphorous ion implantation to provide the source/drain (S/D). We succeeded in fabricating an n-channel TFT with typical electrical characteristics on poly-Ge and confirmed its operation mode to be inversion mode. However, the fabrication process included a high temperature (500 °C) step for S/D activation. To reduce the process temperature, we used a metal-induced dopant activation method and successfully reduced the activation temperature to 360 °C. This combination is expected to pave the way for high-performance 3D-LSI and flexible electronic devices based on SPC-Ge.

Biotrapping Ureolytic Bacteria on Sand to Improve the Efficiency of Biocementation.

Microbially induced calcium carbonate precipitation (MICP) has emerged as a novel technology with the potential to produce building materials through lower-temperature processes. The formation of calcium carbonate bridges in MICP allows the biocementation of aggregate particles to produce biobricks. Current approaches require several pulses of microbes and mineralization media to increase the quantity of calcium carbonate minerals and improve the strength of the material, thus leading to a reduction in sustainability. One potential technique to improve the efficiency of strength development involves trapping the bacteria on the aggregate surfaces using silane coupling agents such as positively charged 3-aminopropyl-methyl-diethoxysilane (APMDES). This treatment traps bacteria on sand through electrostatic interactions that attract negatively charged walls of bacteria to positively charged amine groups. The APMDES treatment promoted an abundant and immediate association of bacteria with sand, increasing the spatial density of ureolytic microbes on sand and promoting efficient initial calcium carbonate precipitation. Though microbial viability was compromised by treatment, urea hydrolysis was minimally affected. Strength was gained much more rapidly for the APMDES-treated sand than for the untreated sand. Three injections of bacteria and biomineralization media using APMDES-treated sand led to the same strength gain as seven injections using untreated sand. The higher strength with APMDES treatment was not explained by increased calcium carbonate accrual in the structure and may be influenced by additional factors such as differences in the microstructure of calcium carbonate bridges between sand particles. Overall, incorporating pretreatment methods, such as amine silane coupling agents, opens a new avenue in biomineralization research by producing materials with an improved efficiency and sustainability.

Developing high strength/high toughness grades steels by dual-precipitates co-configuration during aging process

Development of new ultrahigh strength steels with high strength and high toughness requires thorough comprehension of nanoscale precipitation mechanisms. In this investigation, a comprehensive array of techniques including atom probe tomography, transmission electron microscopy, scanning electron microscopy, electron backscatter diffraction, small angle x-ray Scattering and thermodynamic calculations were employed. These methods unveiled an intriguing co-precipitation mechanism involving NiAl and carbide nanoparticles in a 2.2 GPa grade strength steel. The results demonstrate that the precipitation mechanisms of NiAl and carbides at different aging temperatures have a significant impact on the strength and toughness of the steel. Sub-micron ε-carbide at the interface of martensite lath and uniformly distributed NiAl cluster in the matrix are independent nucleation during the low-temperature aging process. The high distribution density of NiAl cluster in the matrix results in an increase in the impact absorbed energy of the steel to 136 J, albeit with a slight decrease in strength. On the other hand, the NiAl with minimal lattice misfit and low interfacial energy preferentially nucleates uniformly in the matrix, inducing the nucleation of M2C and increasing the number density of M2C precipitates at the secondary hardening temperature. The homogeneous precipitation of spherical NiAl, along with needle-shaped M2C in the martensite, significantly enhances the strength of the steel, with a tensile strength reaching up to 2216 MPa and an impact absorbed energy of 21 J.

Process optimization of osmotic membrane distillation for the extraction of valuable resources from water streams

The rising demand for sustainable wastewater management and high-value resource recovery is pressing industries involved in, e.g., textiles, metals, and food production, to adopt energy-efficient and flexible liquid separation methods. The current techniques often fall short in achieving zero liquid discharge and enhancing socio-economic growth sustainably. Osmotic membrane distillation (OMD) has emerged as a low-temperature separation process designed to concentrate valuable elements and substances in dilute feed streams. The efficacy of OMD hinges on the solvent’s migration from the feed to the draw stream through a hydrophobic membrane, driven by the vapor pressure difference induced by both temperature and concentration gradients. However, the intricate interplay of heat and mass processes steering this mechanism is not yet fully comprehended or accurately modeled. In this research, we conducted a combined theoretical and experimental study to explore the capabilities and thermodynamic limitations of OMD. Under diverse operating conditions, the experimental campaign aimed to corroborate our theoretical assertions. We derived a novel equation to govern water flux based on foundational principles and introduced a streamlined version for more straightforward application. Our findings spotlight complex transport-limiting and self-adjusting mechanisms linked with temperature and concentration polarization phenomena. Compared with traditional methods like membrane distillation and osmotic dilution, which are driven by solely temperature or concentration gradients, OMD may provide improved and flexible performance in target applications. For instance, we show that OMD—if properly optimized—can achieve water vapor fluxes 50% higher than osmotic dilution. Notably, OMD operation at reduced feed temperatures can lead to energy savings ranging between 5 and 95%, owing to the use of highly concentrated draw solutions. This study underscores the potential of OMD in real-world applications, such as concentrating lithium in wastewater streams. By enhancing our fundamental understanding of OMD’s potential and constraints, we aim to broaden its adoption as a pivotal liquid separation tool, with focus on sustainable resource recovery.

First principles study on polarization and piezoelectric properties of group substitution regulated lead-free organic perovskite ferroelectrics

Organic ferroelectrics are desirable for the applications in the field of wearable electronics due to their eco-friendly process-ability, mechanical flexibility, low processing temperatures, and lightweight. In this work, we use five organic groups as substitution for organic cation and study the effects of organic cations on the structural stability, electronic structure, mechanical properties and spontaneous polarization of metal-free perovskite &lt;i&gt;A&lt;/i&gt;-NH&lt;sub&gt;4&lt;/sub&gt;-(PF&lt;sub&gt;6&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt; (&lt;i&gt;A&lt;/i&gt; = MDABCO, CNDABCO, ODABCO, NODABCO, SHDABCO) through first-principles calculations. Firstly, the stabilities of the five materials are calculated by molecular dynamics simulations, and the energy values of all systems are negative and stable after 500 fs, which demonstrates the stabilities of the five materials at 300 K. The electronic structure calculation shows that the organic perovskite materials have wide band gap with a value of about 7.05 eV. The valence band maximum (VBM) and Cconduction band minimum (CBM) are occupied by different elements, which is conductive to the separation of electrons and holes. We find that organic cations have an important contribution to the spontaneous polarization of materials, with a contribution rate over 50%. The presence of hydrogen atoms in the substituting groups (MDABCO, ODABCO) enhances the hydrogen bond interaction between the organic cations and &lt;inline-formula&gt;&lt;tex-math id="Z-20240616143151"&gt;\begin{document}${\rm PF}_6^- $\end{document}&lt;/tex-math&gt;&lt;alternatives&gt;&lt;graphic specific-use="online" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20240385_Z-20240616143151.jpg"/&gt;&lt;graphic specific-use="print" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="12-20240385_Z-20240616143151.png"/&gt;&lt;/alternatives&gt;&lt;/inline-formula&gt; and increases the displacement of the organic cation, resulting in an increase in the contribution of the polarization of the organic cation to the total polarization. In addition, we observe large piezoelectric strain components, the calculated value of &lt;i&gt;d&lt;/i&gt;&lt;sub&gt;33&lt;/sub&gt; is 36.5 pC/N for CNDABCO-NH&lt;sub&gt;4&lt;/sub&gt;-(PF&lt;sub&gt;6&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;, 32.3 pC/N for SHNDABCO-NH&lt;sub&gt;4&lt;/sub&gt;-(PF&lt;sub&gt;6&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;, which is larger than the known value of &lt;i&gt;d&lt;/i&gt;&lt;sub&gt;33&lt;/sub&gt; of MDABCO-NH&lt;sub&gt;4&lt;/sub&gt;-I&lt;sub&gt;3&lt;/sub&gt;(14pC/N). The calculated value of &lt;i&gt;d&lt;/i&gt;&lt;sub&gt;14&lt;/sub&gt; is 57.5 pC/N for ODABCO-NH&lt;sub&gt;4&lt;/sub&gt;-(PF&lt;sub&gt;6&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;, 27.5 pC/N for NODABCO-NH&lt;sub&gt;4&lt;/sub&gt;-(PF&lt;sub&gt;6&lt;/sub&gt;)&lt;sub&gt;3&lt;/sub&gt;. These components are at a high level among known organic perovskite materials and comparable to many known inorganic crystals. The large value of &lt;i&gt;d&lt;/i&gt;&lt;sub&gt;14&lt;/sub&gt; is found to be closely related to the large value of elastic compliance tensor &lt;i&gt;s&lt;/i&gt;&lt;sub&gt;44&lt;/sub&gt;. The analysis of Young’s modulus and bulk’s modulus shows that these organic perovskite materials have good ductility. These results indicate that these organic materials are excellent candidates for future environmentally friendly piezoelectric materials.