Uncontrolled Precipitation Research Articles

Environmental-assisted simple synthesis and electrocatalytic performance of Ni-MOF nanorods

It is a tough job for the fabrication of metal phosphonate (MP) products with desired morphologies due to their uncontrolled precipitation reactions between metal ions and phosphonic acids in solution. However, the fabrication of MP nanomaterial with unique controlled morphologies is desired for numerous potential applications due to their exceptional properties. We report the facile and rapid synthesis of very uniform one-dimensional (1-D) nickel phenylphosphonate (NiPP) nanorods without the use of any templates through an inexpensive solution-phase method. For the first time, the formation mechanism of NiPP with 1-D nanostructure is systematically investigated using a series of experiment conditions. The present investigation is extremely important and has never been systematically investigated in the literature. The as-prepared NiPP nanorods are further utilized as electrocatalyst for the oxidation of glucose and methanol.

Monodisperse oxidative-sensitive polymer nanoparticles from dispersion polymerization of N-acryloyl thiomorpholine

Aqueous emulsion or suspension polymerizations are well established industrial processes with widespread applications. Dispersion polymerizations, on the contrary, are rarely found for the preparation of stable particle dispersions, which is certainly related to the limited number of suitable monomers. Here, we report that N-acryloyl thiomorpholine (NAT) is an interesting candidate for aqueous dispersion polymerizations, as it is fully miscible with water but forms insoluble polymers at low degrees of polymerization. Polymerization in pure water results in an uncontrolled precipitation but with the addition of a surfactant well-defined dispersions with monomodal size distributions are obtained if low monomer concentrations (≤4 wt%) are used. Higher concentrations (10 wt%) broaden the dispersity of the resulting particles, but still result in stable dispersions, while 30 wt% cause a solidification of the solution as particles start to fuse. Crosslinked particles can be obtained by addition of a bisacrylamide comonomer. The thioether moiety of NAT further enables postpolymerization modifications including its oxidation to a more polar sulfoxide. Kinetic studies revealed that oxidation in H2O2 follows a bulk process causing a swelling of the particles after reaching a critical degree of oxidation (35%). In case of the non-crosslinked particles, disintegration occurs only at ≥ 60% conversion of the thioethers, while the particles remain intact for days at lower degrees of oxidation. The oxidation of the crosslinked particles results in water-swollen microgels. Overall, the straightforward process allows access to monodisperse reactive polymer nanoparticles of variable size (∼ 60 – 100 nm) that could be used as well-defined templates or carrier materials.

Development of a continuous silica treatment strategy for metal extraction processes in operating geothermal plants

The extraction of rare metals like lithium (Li) from geothermal fluids is a promising alternative to conventional mining. Membrane distillation (MD) could support energy-efficient fluid treatment enabling further freshwater production. For the operation of geothermal plants and MD uncontrolled precipitation of silica (Si) represents a major hurdle. Herein, we demonstrate the transfer of a Si treatment from lab to field demonstrator scale, tested under conditions of an operating geothermal power plant.For the treatment, lime precipitation was chosen showing good Si reduction rates using artificial fluids. The high alkaline conditions of this process (pH > 10) in combination with the high salinities of the geothermal brines (TDS > 100 g/L) are transferred into real geothermal environment with a newly developed numerical design calculation. The resulting demonstrator consists of three major process steps - 1) Si-reduction, 2) liquid/solid separation, and 3) post-concentration using MD. The Si treatment efficiently reduced 98 % of Si in <5 min reaction time, without influencing the lithium concentration negatively. The MD resulted in Li concentrations of ∼500 mg/L while producing fresh water. Beyond the approval of the concept, neuralgic points for improvement were identified expanding fundamental knowledge about the material use of geothermal fluids.

Electrostatically Directed Long‐Range Self‐Assembly of Nucleotides with Cationic Nanoparticles To Form Multifunctional Bioplasmonic Networks

AbstractPrecise control over interparticle interactions is essential to retain the functions of individual components in a self‐assembled superstructure. Here, we report the design of a multifunctional bioplasmonic network via an electrostatically directed self‐assembly process involving adenosine 5′‐triphosphate (ATP). The present study unveils the ability of ATP to undergo a long‐range self‐assembly in the presence of cations and gold nanoparticles (AuNP). Modelling and NMR studies gave a qualitative insight into the major interactions driving the bioplasmonic network formation. ATP‐Ca2+ coordination helps in regulating the electrostatic interaction, which is crucial in transforming an uncontrolled precipitation into a kinetically controlled aggregation process. Remarkably, ATP and AuNP retained their inherent properties in the multifunctional bioplasmonic network. The generality of electrostatically directed self‐assembly process was extended to different nucleotide–nanoparticle systems.

Electrostatically Directed Long-Range Self-Assembly of Nucleotides with Cationic Nanoparticles To Form Multifunctional Bioplasmonic Networks.

Precise control over interparticle interactions is essential to retain the functions of individual components in a self-assembled superstructure. Here, we report the design of a multifunctional bioplasmonic network via an electrostatically directed self-assembly process involving adenosine 5'-triphosphate (ATP). The present study unveils the ability of ATP to undergo a long-range self-assembly in the presence of cations and gold nanoparticles (AuNP). Modelling and NMR studies gave a qualitative insight into the major interactions driving the bioplasmonic network formation. ATP-Ca2+ coordination helps in regulating the electrostatic interaction, which is crucial in transforming an uncontrolled precipitation into a kinetically controlled aggregation process. Remarkably, ATP and AuNP retained their inherent properties in the multifunctional bioplasmonic network. The generality of electrostatically directed self-assembly process was extended to different nucleotide-nanoparticle systems.

Tertiary-Butylbenzene Functionalization as a Strategy for β-Sheet Polypeptides.

β-Sheet forming polypeptides are one of the least explored synthetic systems due to their uncontrolled precipitation in the ring-opening polymerization (ROP) synthetic methodology. Here, a new t-butylbenzene functionalization approach is introduced to overcome this limitation by sterically controlling the propagating polymer chains, and homogeneous polymerization with good control over chain growth was accomplished. New bulky N-carboxyanhydride monomers were designed having t-butylbenzene pendant by multistep organic synthesis, and N-heterocyclic carbene was explored as a catalyst to make high-molecular-weight and narrow polydisperse soluble polypeptides. This ROP process was successfully demonstrated for two β-sheet forming polypeptides such as poly(l-serine) and poly(l-cysteine). These new t-butylbenzene-functionalized polypeptides were found to be readily soluble in tetrahydrofuran, chloroform, and so forth, and they were produced in high molecular weights having Mn = 32 kDa with dispersity D̵ ≤ 1.3. ROP kinetics were studied by real-time Fourier transform infrared and 1H NMR to determine the actual content of the secondary structures in the propagating chains. These studies established that the α-helical conformational front in the propagation chain was speeding up the polymerization kinetics with good degree of control in the ROP process. Reversible-conformational transitions in the post-polymerization deprotection were found to restore the β-sheet secondary structures in poly(l-serine)s. The newly developed t-butylbenzene-substituted steric-hindrance approach is valuable in yielding soluble polymers, and this approach could be useful for exploring new polypeptide architectures for long-term impact.

Electrochemical In Situ pH Control Enables Chemical-Free Full Urine Nitrification with Concomitant Nitrate Extraction.

Urine is a valuable resource for nutrient recovery. Stabilization is, however, recommended to prevent urea hydrolysis and the associated risk for ammonia volatilization, uncontrolled precipitation, and malodor. This can be achieved by alkalinization and subsequent biological conversion of urea and ammonia into nitrate (nitrification) and organics into CO2. Yet, without pH control, the extent of nitrification is limited as a result of insufficient alkalinity. This study explored the feasibility of an integrated electrochemical cell to obtain on-demand hydroxide production through water reduction at the cathode, compensating for the acidification caused by nitritation, thereby enabling full nitrification. To deal with the inherent variability of the urine influent composition and bioprocess, the electrochemical cell was steered via a controller, modulating the current based on the pH in the bioreactor. This provided a reliable and innovative alternative to base addition, enabling full nitrification while avoiding the use of chemicals, the logistics associated with base storage and dosing, and the associated increase in salinity. Moreover, the electrochemical cell could be used as an in situ extraction and concentration technology, yielding an acidic concentrated nitrate-rich stream. The make-up of the end product could be tailored by tweaking the process configuration, offering versatility for applications on Earth and in space.

Elastic and biodegradable chitosan/agarose film revealing slightly acidic pH for potential applications in regenerative medicine as artificial skin graft

The aim of this work was to develop new method for the production of chitosan/agarose (CHN/A) film that could serve as a potential artificial skin substitute for regenerative medicine applications. Within this new production method, the concentrations of biomaterial components (chitosan in CH3COOH and agarose in NaOH) were optimized to provide neutralization of the resultant mixture up to pH approx. 6.0 without uncontrolled precipitation (gelation) of chitosan constituent. Produced thin film was subjected to comprehensive evaluation of its biomedical potential by determination of mechanical, physicochemical, and biological properties. It was demonstrated that the developed CHN/A film reveals slightly acidic pH of 5.98 known to support skin regeneration, high exudate absorption capacity, and is prone to biodegradation in simulated enzymatic wound environment. Performed tensile test proved high elastic deformations of the film (Young's modulus = 0.02 MPa, elongation at break = 23%) in a wet state, which would allow suitable stretching after application at the wound site. Moreover, novel biomaterial is non-toxic and supports fibroblast growth on its surface. Based on the obtained results it may be concluded that the produced CHN/A film possesses all necessary features of the artificial skin substitute.

Fast conversion and controlled deposition of lithium (poly)sulfides in lithium-sulfur batteries using high-loading cobalt single atoms

Lithium-sulfur (Li–S) batteries are appealing energy storage technologies owing to their exceptional energy density. Their practical applications, however, are largely compromised by poor cycling stability and rate capability because of detrimental shuttling of polysulfide intermediates, complicated multiphase sulfur redox reactions, and uncontrolled precipitation of the discharge products (lithium sulfide, Li2S). Herein, monodispersed Co single-atom catalyst on conductive nitrogen-doped carbon nanosheet (CoSA-N-C) with high Co content of 15.3 ​wt% was fabricated through a salt-template method and used as a sulfur host material to simultaneously alleviate the polysulfide shuttling, propel the redox kinetics of dissolved polysulfides, and mediate the deposition of Li2S. The robust two-dimensional architecture of CoSA-N-C with large surface area, high porosity, and dual lithiophilic-sulfiphilic Co–N species enable strong physical and chemical polysulfides confinement and fast electrons/ions transfer process. The densely populated Co–N4 coordinated moieties function as electrocatalytic sites to accelerate the reversible conversion between lithium polysulfides and Li2S. Importantly, the CoSA-N-C enables spatially controlled deposition of Li2S nanoparticles during the battery discharge process, as opposed to conventional Li2S passivation layers that fully covered the conductive host. Consequently, the as-fabricated cathodes based on the CoSA-N-C deliver high sulfur utilization (1574 mAh·g−1 at 0.05 ​C), outstanding rate capability (624 mAh g−1 at 5 ​C) and superior long-term stability (capacity fade rate of 0.035% per cycle for 1000 cycles at 1 ​C). Even under a sulfur loading up to 4.9 ​mg ​cm−2, the reversible areal capacity could reach 4.24 mAh cm−2 after 120 cycles at 0.2 ​C, delivering an ultrahigh capacity retention of 91.8%. This work sheds inspiring insights on the important role of single atomic metal with high mass loading in mediating the deposition of lithium sulfides and accelerating the reversible conversion of lithium polysulfides toward decent-performance Li–S batteries.

Effect of dimethylsulfoxide, ethanol, α- and β-cyclodextrins and their association on the solubility of natural bioactive compounds

The use of co-solvents to increase drug solubility is limited mainly due to their toxicity. Many solvents are not biodegradable and have significant environmental impact. Furthermore, uncontrolled precipitation of the compound may arise when solvent-based formulation is introduced into an aqueous medium. Cyclodextrins (CD) can form inclusion complexes resulting in an increase in the guest's solubility. Herein, we evaluated the effect of dimethylsulfoxide (DMSO), ethanol (EtOH), CD, and their association, on the solubility of two natural anti-oxidants, trans-anethole (AN) and caffeic acid (CA). The findings revealed that co-solvents or CD enhanced the solubility of these compounds. Nonetheless, if the concomitant presence of co-solvent and CD induced a loss of the solubilizing efficiency of CD it allowed lowering the quantity of solvent needed to achieve the same solubility. Consequently, the concentration of CD and co-solvent in the complexation media should be optimized to solubilize the required amount of the guest.

Enhanced Chemical Immobilization and Catalytic Conversion of Polysulfide Intermediates Using Metallic Mo Nanoclusters for High-Performance Li-S Batteries.

Rechargeable lithium-sulfur batteries have attracted tremendous scientific attention owing to their high energy density. However, their practical application is greatly hindered by the notorious shuttling of soluble lithium polysulfide (LPS) intermediates with sluggish redox reactions and uncontrolled precipitation behavior. Herein, we report a semiliquid cathode composed of an active LPS solution/carbon nanofiber (CNF) composite layer, capped with a carbon nanotube (CNT) thin film decorated with metallic Mo nanoclusters that regulate the electrochemical redox reactions of LPS. The trace amount (0.05 mg cm-2) of metallic Mo on the CNT film provides sufficient capturing centers for the chemical immobilization of LPS. Together with physical blocking of LPS by the compact CNT film, free diffusion of LPS is significantly restrained and the self-discharge behavior of the Li-S cell is thus effectively suppressed. Importantly, the metallic Mo nanoclusters enable fast catalytic conversion of LPS and regular deposition of lithium sulfide. As a result, the engineered cathode exhibits a high active sulfur utilization (1401 mAh g-1 at 0.1 C), stable cycling (500 cycles at 1 C with 0.06% decay per cycle), high rate performance (694 mAh g-1 at 5 C), and low self-discharge rate (3% after 72 h of rest). Moreover, a high reversible areal capacity of 4.75 mAh cm-2 is maintained after 100 cycles at 0.2 C for a cathode with a high sulfur loading of 7.64 mg cm-2. This work provides significant insight into the structural and materials design of an advanced sulfur-based cathode that effectively regulates the electrochemical reactions of sulfur species in high-energy Li-S batteries.

Analysis of uncontrolled phosphorus precipitation in anaerobic digesters under thermophilic and mesophilic conditions

ABSTRACT This study compares the operation of mesophilic and thermophilic anaerobic digestion of sewage sludge and their effects in uncontrolled phosphorus precipitation. The research has been carried out using a pilot plant consisting of two digesters of 1.6 m3 working volume, treating the mixed sludge of Alzira WWTP (Valencia, Spain). The digesters were operated in parallel, at different conditions: mesophilic (38 ± 2.0°C) and thermophilic (55 ± 2.5°C) temperatures and organic loading rates (OLR) ranging from 1.1 to 1.7 kg volatile solids (VS) m−3 d−1 and different hydraulic retention times (HRT) 20, 15 and 12 days. Uncontrolled precipitation was evaluated through P, Mg and Ca mass balances in both digesters. The results revealed that up to 82% of the available P and 81% of the available Mg precipitated in the mesophilic digester at HRT = 20 days which suggests the possible formation of struvite in both digesters. At lower HRT (HRT = 12 days) Mg and Ca precipitation was negligible and P fixation has been attributed to the possible formation of iron phosphates or adsorption processes on solid surfaces.

Stabilizing Reactive Fe(III) Clusters by Freeze-Dry/Solvent-Exchange To Benchmark Iron Hydrolysis Pathways.

Isolating Fe(III) clusters from water without stabilizing ligands is significantly challenged by the high acidity of Fe3+-bound water, leading to uncontrolled precipitation of iron oxyhydroxides. Here we demonstrate a freeze-drying solvent-exchange method that enabled the isolation of a metastable Fe(III) sulfate decameric cluster formulated [Fe10O2(SO4)12(OCH3)2]·14CH3OH (Fe10). Without stabilization by solvent-exchange, the aqueous species undergoes rapid conversion to the iron sulfate mineral schwertmannite. Monitoring the hydrolysis process from cluster intermediates to schertmannite by small-angle X-ray scattering, we observe the progression from Fe10 to 37 Å soluble nanoparticles prior to the precipitation process. This condensation behavior of Fe10 is further exploited to develop a simple laboratory synthesis of schwetmannite. In addition, we demonstrate the versatility of the freeze-drying solvent-exchange method by isolating Al(III), Zn(II), and Cd(II) substituted Fe(III) sulfate clusters. The freeze-drying solvent-exchange method provides a unique opportunity to isolate cluster intermediates and models to aid in our understanding of metal-ion hydrolysis processes in environmental, material science, and geological studies.

Combined and individual applications of ozonation and microwave treatment for waste activated sludge solubilization and nutrient release

This study focused on the separate and combined applications of ozonation and microwave treatment to enhance the phosphorus and ammonia release from waste activated sludge. Twenty-six batch experiments were run with or without acidic (pH 2) and alkaline (pH 10) pretreatments and different ozone dosages. Also, microwave post-treatments were applied to enhance phosphorus release efficiency. Results showed that ozonation is an effective technology for solubilization and release without any pre or post-treatment, reactive phosphorus content increased from 1.9 to 3.6 mg PO4-P/g MLSSin (89.5% increase) with 19.4% COD release. Alkaline pretreatment enhanced sludge solubilization and phosphorus release at most (23.9% COD release and 152.6% PO4-P increase); however, decreases in ammonia, calcium and magnesium concentrations pointed out a loss of a part of released phosphorus, due to struvite or apatite precipitation. Acidic pretreatment reduced the sludge solubilization during ozonation (10% COD release) but prevented the uncontrolled precipitation and enhanced the phosphorus release (115.8% PO4-P increase). For microwave treatment, acid pretreated sludge showed higher release than alkaline pretreated or neutral sludge. Among different process combinations, acid pretreatment/ozonation/microwave experiments have shown the highest sludge solubilization and nutrient release (48% COD release and 579% PO4-P increase); however, the difference between acid pretreatment/microwave and acid pretreatment/ozonation/microwave was not significant in terms of phosphorus release (479% PO4-P increase, p = 0.082). Thus, pH 2/microwave may be a cost-effective and feasible alternative for nutrient recovery from waste sludge. For struvite precipitation, pH 8.5 were determined as optimum level. Also using fine struvite particles as seed increased struvite precipitation efficiency.

Welding thermal cycle-triggered precipitation processes in steel S700MC subjected to the thermo-mechanical control processing

Abstract This study presents tests concerned with welding thermal process-induced precipitation processes taking place in 10 mm thick steel S700MC subjected to the Thermo-Mechanical Control Process (TMCP) with accelerated cooling. The thermomechanical processing of steel S700MC leads to its refinement, structural defects and solutioning with hardening constituents. Tests of thin foils performed using a transmission electron microscope revealed that the hardening of steel S700MC was primarily caused by dispersive (Ti,Nb)(C,N) precipitates (being between several and less than twenty nanometers in size). In arc welding, depending on a welding method and linear energy, an increase in the base material in the weld is accompanied by the increased concentration of hardening microagents in the weld. The longer the time when the base material remains in the liquid state, the greater the amount of microagents dissolved in the matrix. During cooling, such microagents can precipitate again or remain in the solution. An increase in welding linear energy is accompanied by an increase in the content of hardening phases dissolved in the matrix and, during cooling, by their another uncontrolled precipitation in the form of numerous fine-dispersive (Ti,Nb)(C,N) precipitates of several nm in size, leading to a dislocation density increase triggered by type 2 internal stresses.

Highly Efficient and Thermally Stable K3AlF6:Mn4+ as a Red Phosphor for Ultra-High-Performance Warm White Light-Emitting Diodes.

Following pioneering work, solution-processable Mn4+-activated fluoride pigments, such as A2BF6 (A = Na, K, Rb, Cs; A2 = Ba, Zn; B = Si, Ge, Ti, Zr, Sn), have attracted considerable attention as highly promising red phosphors for warm white light-emitting diodes (W-LEDs). To date, these fluoride pigments have been synthesized via traditional chemical routes with HF solution. However, in addition to the possible dangers of hypertoxic HF, the uncontrolled precipitation of fluorides and the extensive processing steps produce large morphological variations, resulting in a wide variation in the LED performance of the resulting devices, which hampers their prospects for practical applications. Here, we demonstrate a prototype W-LED with K3AlF6:Mn4+ as the red light component via an efficient and water-processable cation-exchange green route. The prototype already shows an efficient luminous efficacy (LE) beyond 190 lm/W, along with an excellent color rendering index (Ra = 84) and a lower correlated color temperature (CCT = 3665 K). We find that the Mn4+ ions at the distorted octahedral sites in K3AlF6:Mn4+ can produce a high photoluminescence thermal and color stability, and higher quantum efficiency (QE) (internal QE (IQE) of 88% and external QE (EQE) of 50.6%.) that are in turn responsible for the realization of a high LE by the warm W-LEDs. Our findings indicate that the water-processed K3AlF6 may be a highly suitable candidate for fabricating high-performance warm W-LEDs.

Crystallizing Elusive Chromium Polycations

Summary Metal-oxo clusters are commonly isolated from water with ligands for preventing the precipitation of metal hydroxides. However, unligated clusters are important for both mechanistic studies and applications. Isolating open-shell transition-metal clusters is especially difficult without ligation. Herein, we elucidate a cluster-isolation process that yields an unligated Zn 2+ -Al 3+ -Cr 3+ polyoxocation. For decades, Cr 3+ -polyoxocations have proved elusive synthetic targets because of hydrolytic instability. We overcame the synthetic challenges by the following strategies: (1) pH-driven hydrolysis by oxidative dissolution of zinc; (2) metal nitrate concentrations 10× higher than conventional syntheses, suppressing cluster assembly; and (3) azeotropic evaporation of HNO 3 -H 2 O, driving cluster assembly and crystallization at the solution surface. Contrary to common cluster growth, the fully assembled cluster is never detected in the reaction solution. Because these reactive clusters do not persist in solution, uncontrolled precipitation of metal hydroxide is avoided. The proposed formation pathway opens opportunities to expand the composition space of metal-oxo clusters.

Coupling Hierarchical Sulfur Composites with in-situ Cross-linked Binder to Build Stable High-areal-capacity Sulfur Cathodes

Lithium-sulfur battery is considered one of the most promising electrochemical system for energy storage, owing to the high theoretical energy density (2600 kWh/kg) and the natural abundance of sulfur. Their practical challenges facing commercial viability lie in the insulating feature of the end-products (S and Li2S), lithium polysulfide dissolution and shuttling between electrodes and random precipitation of Li2S from the dissolved polysulfides. This leads to rapid capacity fading over long-term cycling and relatively low sulfur utilization. This becomes even more problematic for high sulfur loading cells, since the large concentration of dissolved polysulfides can not only lead to uncontrolled precipitation of Li2S that eventually clog the cathodes, but also to increased side-reactions with lithium anodes. Great efforts have been made to address these issues with a focus on the cathode materials, but mostly thin electrodes with sulfur loadings below 2 mg/cm2.[[1]] In order to fabricate high-loading Li-S cells, recently reported approaches are to construct 3D conductive framework composed of graphene or carbon nanofibers. However, one intrinsic problem is the high porosity of the 3D architecture usually requires large volume of electrolyte, leading to high electrolyte/sulfur ratio and thus low volumetric energy density. Therefore, developing high loading electrodes using traditional slurry-based process is critical for practical applications.[[2]] Here we will present a multifaceted strategy to construct stable and high sulfur loading cathodes based on the traditional slurry processing, by coupling a hierarchical sulfur composite with in-situ cross-linked polymer. We incorporated our previously reported highly nitrided material with conductive framework. A light-weight, electrically conductive and highly porous hybrid was thus obtained. The hybrid material exhibit a micrometer sized structure, which is beneficial to fabricate crack-free thick electrodes. This is due to the enhanced connection between individual particles even with lower percentage of binder compared to nanoparticles with low tap density. The XPS survey spectrum shows the presence of a high concentration of nitrogen at 19.9 at%. Our first-principles calculations show that our hybrid has a much higher polysulfide binding energy towards than functionalized polymer or doped carbons. We will further present an integrated cathode enabled by in-situ cross-linked binder and a combination of CNTs and Super P carbon additives. The inter-particle electronic connection is greatly enhanced. Fourier transform infrared spectroscopy (FTIR) confirms the successful cross-linking. The low-magnification SEM images clearly shows that on contrary to the large cracks in the PVDF based electrodes (formed upon evaporation of the slurry solvent), the cross-linking binder based electrode surface is flat and compact, without any cracks. It is worth noting that such an integrated structure was achieved with as low as 5 wt% of binder, which greatly increases the gravimetric energy density. We demonstrate that cathodes with sulfur loading up to 15.0 mg/cm2 have been fabricated with stable cycling performance. Insights into the evolution of the impedance will also be presented.

A Molten Salt Lithium-Oxygen Battery.

Despite the promise of extremely high theoretical capacity (2Li + O2 ↔ Li2O2, 1675 mAh per gram of oxygen), many challenges currently impede development of Li/O2 battery technology. Finding suitable electrode and electrolyte materials remains the most elusive challenge to date. A radical new approach is to replace volatile, unstable and air-intolerant organic electrolytes common to prior research in the field with alkali metal nitrate molten salt electrolytes and operate the battery above the liquidus temperature (>80 °C). Here we demonstrate an intermediate temperature Li/O2 battery using a lithium anode, a molten nitrate-based electrolyte (e.g., LiNO3-KNO3 eutectic) and a porous carbon O2 cathode with high energy efficiency (∼95%) and improved rate capability because the discharge product, lithium peroxide, is stable and moderately soluble in the molten salt electrolyte. The results, supported by essential state-of-the-art electrochemical and analytical techniques such as in situ pressure and gas analyses, scanning electron microscopy, rotating disk electrode voltammetry, demonstrate that Li2O2 electrochemically forms and decomposes upon cycling with discharge/charge overpotentials as low as 50 mV. We show that the cycle life of such batteries is limited only by carbon reactivity and by the uncontrolled precipitation of Li2O2, which eventually becomes electrically disconnected from the O2 electrode.

Weldability of Thermomechanically Treated Steels Having a High Yield Point

Abstract The article concerns the issue of weldability of S700MC steel, treated thermo-mechanically, with high yield point. The weakest area of welded joints of this steel is a high - temperature coarse heat affected zone (HAZ) in which due to the nucleation effect of the dissolved phases, strengthening the matrix and their subsequent uncontrolled separation precipitation in the form of finely disperse and rapid decrease impact strength is observed. Performed arc welding tests here have shown that in order to ensure high quality of welded joints, it is necessary to limit the welding linear heat input. During the welding process of S700MC steel, it is not recommended to use pre heating before the welding process and heat treatment after welding, and the number of repairs should be kept to a minimum, because it leads to a reduction of strength and plastic properties in the HAZ area, as a result of aging processes, dissolution of strengthening phases in the matrix and their subsequent uncontrolled precipitation during cooling.