Molten Phase Research Articles

Understanding the bonding mechanism in short-time resistance projection welding: a comprehensive analysis

Capacitor discharge welding (CDW) is characterized by a pulsed electrical current profile. It is primarily utilized for resistance projection welding tasks, offering high power densities and short welding times. According to the latest findings, the welding process can be divided into different phases: contacting, activating, material connection, and holding pressure. During the activation phase, high-speed video-imaging reveals the generation of metal vapor which effectively eliminates impurities and oxide layers from the contact zone. The result of this is an activated surface. The purpose of this paper is to describe the physical effects of the bonding mechanism during short-time resistance welding. The Chair of Joining Technology and Assembly at the Technische Universität Dresden has a laboratory facility that can interrupt the welding current at any desired time during capacitor discharge welding. This allows different welding current profiles with always the same current rise time to be scientifically investigated. The experimental findings were supplemented with simulative analyses to clarify the bonding mechanism in resistance projection welding. Three different surface conditions are considered to generalize the findings on the bonding mechanism. Temperature and current density distributions were assessed to provide a physical description of the activation phase. The power density in the joining zone at different interruption times is determined, which gives an indication of activation by metal vaporization. The material connection is determined experimentally for the same interruption times. The numerical simulation model can be used to describe the bonding mechanism in short-time resistance welding. In resistance welding, the bond is formed due to the molten phase (solidification structure). In short-time resistance welding, the bond is formed due to surface activation by metal vaporization.

A New Look at the Mechanism of Cocrystal Formation and Coformers Exchange in Processes Forced by Mechanical and/or Thermal Stimuli - ex situ and in situ Studies of Low-Melting Eutectic Mixtures.

Three different devices: ball mill, hot stage melting, and magic angle spinning (MAS) NMR rotor were used for the preparation of ethenzamide (ET) cocrystals with glutaric acid (GLU), ethylmalonic acid (EMA) and maleic acid (MAL) as coformers. In each case, well-defined binary systems (ET:EMA, ET:GLU, ET:MAL) were obtained. The common features of the two solvent free methods of cocrystal formation (grinding, melting) are presented on the basis of arguments obtained by solid state NMR spectroscopy. Thermal analysis (Differential Scanning Calorimetry) proved that the eutectic phase arises over a wide range of molar ratios of components for each of the binary systems. NMR techniques, supported by theoretical calculations, allowed to provide details about the pathway of the reaction mechanism with atomic accuracy. It was found that the formation of ET cocrystals is a complex process that requires five steps. Each step has been recognized and described. Variable temperature 1D and 2D MAS NMR experiments allowed to track physicochemical processes taking place in a molten state. Moreover, it was found that in a multicomponent mixture consisting of all four components, ET, EMA, GLU, and MAL, ET in the molten phase behaves as a specific selector choosing only one partner to form binary cocrystals according to energy preferences. The process of exchange of coformers in binary systems during grinding, melting, and NMR measurements is described. The stabilization energies (Estab ) and molecular electrostatic potential (MEP) maps computed for the cocrystals under discussion and their individual components rationalize the selection rules and explain the relationships between individual species.

Optical strain measurements during pulsed laser beam welding to improve the understanding of hot crack formation of EN AW-6082 aluminum alloy

E-mobility turned in the last years to be an emerging market and one solution to fossil fuel free mobility for the future. E-mobility requires, compared to fossil-fueled mobility concepts, a huge amount of welding tasks, which have to guarantee different functionality, as for example high strength, ductility, but also low resistivity and tightness. Last is especially for housing or cases of aluminum in automotive challenging, as pores and cracks can occur. Pulsed laser welding presents, due to the adaptable heat input and the temporal modification of stress state and solidification conditions advantages for this type of applications. EN AW-6xxx group of aluminum alloys is mainly used for such components due to their favorable mechanical properties. However, these alloys are susceptible to hot cracking during solidification from the molten phase. This article aims to present a methodology for demonstrating the resulting strain during pulsed laser beam welding of hot crack susceptible aluminum alloys. It will highlight the influence of factors such as pulse shape, shielding gas, and flow rate on strain and strain rate.

Convergence of dissolving and melting at the nanoscale.

Phase transitions of water and its mixtures are of fundamental importance in physical chemistry, the pharmaceutical industry, materials sciences, and atmospheric sciences. However, current understanding remains elusive to explain relevant observations, especially at the nanoscale. Here, by using molecular dynamics simulations, we investigate the dissolution of sodium chloride (NaCl) nanocrystals with volume-equivalent diameters from 0.51 to 1.75 nm. Our results show that the dissolution of NaCl in aqueous nanodroplets show a strong size dependence, and its solubility can be predicted by the Ostwald-Freundlich equation and Gibbs-Duhem equation after considering a size-dependent solid-liquid surface tension. We find that the structure of dissolved ions in the saturated aqueous nanodropplet resembles the structure of a molten NaCl nanoparticle. With decreasing nanodroplet size, this similarity grows and the average potential energy of NaCl in solution, the molten phase and the crystal phase converges.

Exploring the phase behavior of C8-BTBT-C8 at ambient and high temperatures: insights and challenges from molecular dynamics simulations.

C8-BTBT-C8 is one promising candidate for the development of high-performance electronic devices based on thin-film technologies. Its monoclinic polymorph has a well-established role in thin-film growth. Yet, quite little information is available about its dynamics on the molecular scale, and the structures of the mesophases which form at high temperature (about 100 K above ambient temperature). The present study is devoted to the analysis of such phases, with the ultimate goal of developing molecular models. Already at ambient temperature, our molecular dynamics simulations reveal a rich conformational behavior of the alkyl side chains, with gauche conformations as leading structural defects. Heating promotes the formation of a stacking faulted mesophase (380 K), and a smectic phase, at 385 K, upon side chain melting. Although more disordered, this phase bears several analogies with the smectic A phase, experimentally observed at 382.5 K. At higher temperatures, the increase in configurational disorder is brought by molecular diffusion and other phenomena, finally leading to an isotropic molten phase. Our in-depth analysis, complemented by hot-stage polarizing microscopy data, provides interesting insights into this material, highlighting the challenges associated with the modeling of soft semiconducting systems.

Effect of high Hartmann number on thermal performance of SWCNT-Fe3O4 hybrid nanoenhanced PCM in magnetized minichannel

Numerical investigations are conducted to investigate the impact of the magnetic field on the molten phase formation and thermal performance of phase change material (PCM) incorporated with hybrid nanoparticles within a three-dimensional vertical channel subjected to differential heating. The PCM, lauric acid, is dispersed using nanoparticle pairings consisting of iron oxide combined with aluminum oxide, titanium dioxide, and single-wall carbon nanotubes. This study focuses on examining the melting characteristics under turbulent conditions, specifically at high Rayleigh (Ra) and Hartmann number (Ha) within the specified range of 106≤Ra≤1010 and 0≤Ha≤1500. The enthalpy-porosity method is being considered for evaluating the phase change characteristics with an in-house code. For Ha of 1500, the melting process influenced by thermal convection was effectively suppressed, leading to significant delays in the melting rates. The melting time and molten fraction of the PCM exhibit a decreasing trend in response to the applied magnetic field, which results in an 82.14% reduction in the heat transfer rate. The SWCNT-Fe3O4 nanoparticle pairs demonstrated superior thermal performance, as the melting fraction and convective heat transfer were increased by 84.03% and 43.83%, respectively. The thermal performance exhibits a decreasing relationship with the Hartmann number, resulting in a 23.87% reduction in the heat transfer of nanoenhanced lauric acid. The accuracy of the present mathematical model is confirmed through validation against experimental benchmark data.

A Review of Top-Submerged Lance (TSL) Processing—Part I: Plant and Reactor Engineering

Part I of this series of papers focuses on plant and reactor engineering aspects of the TSL reactor technology. A general flowsheet is presented, while emphasis is given to the definition of different reactor zones in terms of fluid dynamics and occurring reactions. Then, the technical advantages of TSL processing, such as feed flexibility and high conversion rates (due to induced turbulence), low dust generation, and low fugitive emissions, are explained. In addition, the reactor is analyzed part by part, also taking into account patent literature, focusing on furnace design, settling furnaces for molten phase disengagement, feeding systems regarding input material streams such as concentrates and fuels, vessel cooling arrangements, off-gas system, and aspects associated with the refractory lining. Furthermore, specific focus is given to the centerpiece of the TSL reactor, i.e., the reactor lance. Associated developments have focused on establishing a slag coating to hinder lance wear, i.e., the development of cooling mechanisms (e.g., use of fluid-cooled lance and shroud arrangements), the increment of O2 enrichment within the incoming air stream, and influencing of fluid dynamics (e.g., O2 conversion at the lance tip, bubble formation, and bath splashing). Finally, comprehensive tables concerning process developments and commissioned TSL plants are provided thus concluding Part I of the review.

Carbothermal-sulfurization of TiO2 into Ti2SC MAX phase in TiO2/C/FeS2 ternary system

The conventional method for synthesizing Ti2SC depends on the reaction between TiS and TiC, which requires the utilization of costly Ti, TiC, or TiS2 powders. Utilizing TiO2 as the raw material for the synthesis of Ti2SC enables the cost-effective preparation of this compound. However, the optimization of the TiO2/C/XnSm (sulfides) system is of utmost importance when aiming to synthesize Ti2SC through carbothermal-sulfurization of TiO2, as the formation temperature of TiS and TiC greatly depends on the XnSm. In this study, the identification of the thermodynamically dominant region for the formation of TiS and TiC in the TiO2/C/XnSm systems was conducted by utilizing various sulfides (63 types). Considering factors such as the challenges associated with removing by-products, accessibility, and toxicity, FeS2 was ultimately chosen as a highly promising candidate. Thanks to the low melting point of FeS2, Ti3O5, the preliminary carbothermal reduction product of TiO2, has achieved rapid-deep deoxidation and phase reconstruction processes in the molten phase. Meanwhile, unlike the conventional solid-solid sintering reaction, which often results in residual reactants that are challenging to eliminate. This novel one-step phase transformation process that occurs in the molten phase exhibits minimal impurity phases, apart from the by-product Fe. Ti2SC with a purity greater than 99 wt% was obtained when the TiO2/C/FeS2 was pickled to remove Fe after sintering at 1600 °C for 5 min. This work will provide the theoretical basis and a new path for the low-cost preparation of sulfur-containing MAX phases.

Na6Li4MO4(CO3)4 (M = W and Mo): An Alternative Electrolyte for High-Temperature Electrochemical Cells.

Two new acentric oxycarbonates Na6Li4MO4(CO3)4 (M = W and Mo) were synthesized via a conventional solid-state route. Their structure was determined from X-ray diffraction data on single crystals. Na6Li4MO4(CO3)4 (M = W and Mo) crystallizes in the acentric cubic P-43m space group (a ≈ 7.15 Å). It is composed of MLi4O16 units built from MO4 and LiO4 tetrahedra and linked by CO32- groups to form a three-dimensional framework in which Na+ ions are inserted. We showed from differential scanning calorimetry and powder X-ray diffraction experiments that the melting is congruent (T ∼525 °C). In the solid and molten forms, conductivity was measured for both oxycarbonates by electrochemical impedance spectroscopy with three various gas compositions (CO2 100 vol %, CO2-air 70-30 vol %, and CO2-air 20-80 vol %). Each time, the stability of the electrical behavior was checked via heating and cooling cycles. The conductivity of both solid and molten phases is purely ionic and in the same order of magnitude as for the classical molten alkali electrolyte made of Li-Na or Li-K carbonates. As activation energies are also comparable, those new oxycarbonates appear to be promising electrolytes for electrochemical devices.

Density and surface tension measurements of molten Al–Si based alloys

AbstractThis study is part of a series of studies aimed at measuring the thermophysical properties of molten phase change material-type metallic thermal energy storage materials near 873 K (600°C). The target material is Al–Si based alloys. First, as a feasibility study, density measurements of the molten state of three Al–Si binary alloys (Al–12.2Si, Al–50Si and Al–90Si in atomic%) were performed. A highly accurate non-contact density measurement method based on the static magnetic field superposition electromagnetic levitation (EML) method was employed as the density measurement method. The validity of this experimental method was confirmed, and density of molten Al–Si base alloys (ADC12 and Al–5.9mass%Si–1.6mass%Fe) were measured as a function of temperature with an expanded uncertainty of 1.2%. In addition, the surface tension of the alloys was measured by the droplet oscillation method using the EML technique. The surface tension was successfully obtained as a function of temperature with expanded uncertainty of 2.3%.

Highly efficient separation of titanium minerals from a modified bauxite residue through direct reduction: A comparison study

Bauxite residue, which is a solid waste generated during the production of alumina, contains significant amounts of iron (Fe) and titanium (Ti) resources. The large-scale utilization of bauxite residue has become an urgent concern from both an environmental and resource perspective. In this study, a calculation of phase diagram (Calphad) was conducted to analyze the changes in mineral phases during the direct reduction process of both the current and reductive Bayer bauxite residue. Additionally, a comparison experiment was performed to investigate the enrichment and separation characteristics of iron and titanium minerals. The results indicated that during the carbon thermal reduction process, titanium existed as CaTiO3 and Na-Al-Si-Ti molten phase slag in the current and reductive Bayer bauxite residue, respectively. Furthermore, NaFeO2 was observed in the latter slag phase, which facilitated the migration and reduction of iron-containing minerals. The reductive Bayer bauxite residue was carbon thermal reduced for 1 h at a temperature of 1200 °C, with the addition of 7.5% Na2CO3. Following grinding and separation under a magnetic field strength of 0.08 T, the iron grade of the concentrate, iron recovery, and TiO2 grade in the tailing increased to 95.30%, 98.40%, and 50.50%, respectively. This was in comparison to the bauxite residue from current Bayer digestion, which showed values of 78.90%, 87.18%, and 14.87% under the same conditions. The findings of this work contribute to the potential utilization of iron and titanium present in bauxite residue from a modified Bayer digestion process.

Enhancing thermal performance of latent heat storage unit for solar cooling: A hybrid approach with C-shaped fins and nano-additives

The performance of solar cooling systems is significantly affected by the intermittent nature of solar energy. To address this problem, thermal energy storage systems such as sensible and latent heat storage systems can be a viable option. Among these, the latent heat storage systems are promising due to their high energy storage density and nearly isothermal charging/discharging characteristics. However, the low thermal conductivity of the phase change material used within the storage unit hinders heat transfer, leading to longer charging and discharging periods. To overcome this problem, a hybrid approach that uses fins and nano additives is proposed in this study. A novel C-shaped fin design is introduced that effectively utilises the natural convection current in the molten phase change material. A comprehensive geometrical and material optimisation study is performed to determine the optimal shape, position, and material of the fins. The study also investigates the effect of the inclusion of graphene nanoplatelets (GnP) on the latent heat storage units. An experimental study is conducted to characterise the composite phase change material, and empirical correlations for viscosity and thermal conductivity are developed. The performance of an optimally designed LHS stacked with nano PCM composite of varying mass fractions is also evaluated. The study reveals that the C-shaped fins can reduce melting time by up to 59% compared to conventional fin designs, while PCM dispersed with 1% GnP reduces melting time by 27% when compared to the base PCM. Finally, a two-bed solar vapour adsorption cooling system with a 500 W capacity is considered to conduct a case study for demonstrating the performance of the proposed LHS. The result shows that the solar adsorption system integrated with the proposed heat storage unit can operate up to 3.3 h longer than it currently does. Thus the study presents a promising solution to overcome the obstacles limiting the widespread utilisation of solar cooling systems.

Numerical modeling to predict threshold fluence for material ejection in Laser-Induced forward transfer of metals

Laser-induced forward transfer (LIFT) uses a pulsed laser beam to propel material from a donor (containing a glass coated with a thin material film) onto a receiving substrate, resulting in pixellated material deposition. The deposition characteristics depend on the material ejection modes that vary with film thickness and laser parameters. This study develops a computational model based on the finite volume method for LIFT of gold films using nanosecond pulses, which captures two different ejection modes for droplet depositioncap ejection and jet ejection. The model computes the temperature distribution and predicts potential ejection regimes for different film thicknesses, providing an understanding of the material removal process. Cap ejection occurs at lower laser fluences when the entire film thickness in the irradiated zone is in the molten phase. In comparison, jet ejection occurs at higher laser fluences caused by vapor pocket formation at the glass-film interface. The model predicts threshold fluences with greater than 90% accuracy for film thickness less than 583 nm. However, for the film thickness of more than 583 nm, the simulations underpredict the threshold fluence, suggesting that laser absorption by the film decreases due to vapor formation at the glass-film interface. Besides, it is observed that higher fluences can cause melting and vaporization of the glass at the interface leading to possible contamination of the deposited material. The proposed model can be used to choose the operating window for laser parameters for droplet deposition in LIFT, which otherwise is challenging using experiments.

Exploring the origins of surface cracks in forged ingots: Impurity element influence and temperature-induced formation of detrimental phases in case hardening steel

Surface hot shortness is a critical defect affecting the performance and reliability of steel components. This study investigates the factors influencing surface hot shortness in DIN 16MnCr5 steel, with a particular focus on the role of impurity elements and temperature. Experimental analysis reveals that copper and zinc, as impurity elements, play a significant role in the formation of detrimental phases and the initiation of surface cracks. Copper enrichment occurs due to its lower affinity to react with oxygen, resulting in its aggregation at the oxide layer/iron interface. Zinc contamination contributes to the formation of intermetallic phases and the initiation of hot shortness, likely due to its low melting point and reactivity. Furthermore, the impact of temperature during hot tensile testing on the ductility and formation of detrimental phases is investigated. Below 950 °C, fractures primarily occur due to proeutectoid ferrite formation at grain boundaries, with limited formation of Cu-rich phases. However, temperatures above 950 °C exhibit increased Cu-rich phase formation, leading to decreased ductility and the formation of hot cracks. The critical temperature range of 1000 °C shows minimum ductility and the highest content of Cu-rich compounds.Grain boundary penetration of Cu-rich melt is identified as a crucial mechanism in the nucleation and propagation of cracks during surface hot shortness. Exceeding a certain copper concentration along grain boundaries leads to the formation of a molten phase at the crack tip, facilitating wetting of the grain boundaries and the subsequent formation of surface cracks. Understanding the influence of impurity elements, such as copper and zinc, as well as the effect of temperature on surface hot shortness is essential for mitigating this defect and improving the performance of steel components. The findings of this study contribute valuable insights toward the development of effective strategies for preventing and controlling surface hot shortness in DIN 16MnCr5 steel.

Molecular dynamic simulation of the [N(C4H9)4]BF4 / (110) α-Al2O3 interface

The structure and transport properties of the pure salt [N4]BF4 and this salt located in the contact with the (110) surface of a-Al2O3 were studied using a MD computer simulation in order to reveal the effect of the salt/oxide interface on the structure and properties of the salt. The radial distribution functions of the ions and their mean square displacements were analyzed as a function of the temperature during the cooling of the salt. It was found that in all the cases anions are more mobile than cations. The molten phase of [N4]BF4 tends to crystallize at temperature 420 K which is close to the experimental melting point. The salt located in the [N4]BF4/(110)Al2O3 interface exhibits high values of anion self-diffusion coefficients which are higher by 1.2–2 orders of magnitude than in pure salt. This effect is likely to be caused by the formation of a layered atomic structure located within a characteristic thickness of 5 nm. Despite the structuring, the structure of the salt is amorphous, no crystallization-related effect is observed. The results of MD simulations agree with the experimental effect of the conductivity enhancement observed previously in [N4]BF4-Al2O3 nanocomposites.

The foaming mechanism and properties of SiO2–Al2O3–CaO-based foamed ceramics with varied foaming agents

To select suitable high-temperature foaming agents, SiO2–Al2O3–CaO-based foam ceramics (SACFC) were successfully prepared with different foaming agents based on phosphorus tailings and coal gangue. The effects of high-temperature foaming agents (CaCO3, carbon black, MnO2 and Fe2O3) on the microstructure and compressive strength of the SACFC were investigated, and the corresponding foaming mechanism was revealed. The results indicated that CaCO3 could increase the porosity of SACFC due to high-temperature decomposition. However, the precipitation of needle-like anorthite reduced the mechanical properties. Because the high-temperature oxidation temperature of carbon black was lower than the molten phase formation temperature, bubbles floated up and gathered on the surface of SACFC, leading to a decrease in strength. The continuous release of O2 from MnO2 during the sintering process promoted the growth and aggregation of large pores, which was detrimental to the strength. The CO2 generated by the redox of Fe2O3 by CO/C was the main factor for the foaming of SACFC. During the high-temperature foaming, the synergy effect of Fe2+ and Fe3+ promoted the formation of a uniformly distributed pore structure. When 2 wt.% Fe2O3 was added, SACFC obtained the optimal comprehensive performance with bulk density and compressive strength of 0.78 g/cm3 and 3.50 MPa.

Direct Fabrication of Sub-10 nm Nanopores in WO3 Nanosheets Using Single Swift Heavy Ions.

Extending the fabrication methodology of solid-state nanopores in a wide range of materials is significant in the fields of single molecule detection, nanofluidic devices, and nanofiltration membranes. Here, we demonstrate a new method to directly fabricate size- and density-controllable sub-10 nm nanopores in WO3 nanosheets using single swift heavy ions (SHIs) without any chemical etching process. By selecting ions of different electronic energy losses (Se), nanopores with sizes from 1.8 to 7.4 nm can be created in WO3 nanosheets. The creation efficiency of nanopores achieves ∼100% for Se > 20 keV/nm, and there exists a critical thickness below which nanopores can be created. Combined with molecular dynamics simulations, we propose that the viscosity and surface tension of the transient molten phase caused by SHIs are the key factors for the formation of nanopores. This method paves a way to fabricate solid-state nanopores in materials with a low viscosity and surface tension.

Consistent description of phase-change processes in substances with density contrast: A finite volume based approach

Phase-change is an important phenomenon and usually it causes a concomitant change in the density of the underlying materials. As applications of phase-change grow, it is important to develop numerical tools that can model this phase-change behaviour accurately; many efforts have improved the ability of numerical algorithms to do so; however, with materials in which phase-change causes significant change in density, these approaches are inadequate in predicting the phase-change interface or the temperature profiles during this process. To address these limitations, we present a “moving mesh” method that explicitly accounts for volumetric expansion during the melting (or, evaporation) process by introducing liquidus or vapour cells at appropriate locations adjacent to the interface. This moving mesh approach is used in conjunction with the apparent heat capacity method implemented through a finite volume scheme to represent the one-dimensional propagation of the melting (or, vapour) front during heating. This new algorithm has been validated for the Stefan's analytical solution, in addition to verifying the conservation of energy principle. We subsequently use our approach to investigate phase-change phenomena for a host of materials with a large gamut of density contrasts between the various phases, and compare the results to those obtained using a fixed-grid approach. The moving mesh method forecasts an early commencement of melting (or, evaporation) at a given position, a comparatively rapid movement of the front, and a larger volume fraction of the molten (or, vapour) phase, for substances that expand upon phase change, while the opposite is observed for the melting of ice, considered as a special case in this study. We hope that the proposed scheme will be adopted in addressing phase-change problems involving significant density contrasts.

Porous 8YSZ Ceramics Prepared with Alkali Halide Sacrificial Additives.

8 mol% Y2O3-stabilized ZrO2 (8YSZ) ceramics were prepared with KCl and LiF additions to obtain porous specimens with high skeletal density. Thermogravimetric and differential thermal analyses (TG/DTA) were carried out on 8YSZ and on 8YSZ mixed to 5 wt.% KCl or 5 wt.% LiF as sacrificial pore formers that were thermally removed during sintering. The melting and evaporation of the alkali halides were evaluated by differential thermal analysis. Dilatometric analysis was also carried out following the same TG/DTA temperature profile with results suggesting rearrangement of the 8YSZ particles during LiF and KCl melting. The dilatometric data of 8YSZ green pellets mixed to KCl or LiF exhibited an initial expansion up to the melting of the alkali halide, followed by shrinkage due to sintering evolution with grain growth and pore elimination. The time that the alkali halide molten phase was kept during sintering was found to be an important parameter for obtaining 8YSZ-sintered specimens with specific pore content; bulk density and open porosity could then be tuned by controlling the time the alkali halide remained liquid during sintering. Scanning electron microscopy images of the pellet fracture surfaces showed pores that contributed to increasing the electrical resistivity as evaluated by impedance spectroscopy analysis.

Planar Sodium‐Nickel Chloride Batteries with High Areal Capacity for Sustainable Energy Storage

AbstractHigh‐temperature sodium‐nickel chloride (Na‐NiCl2) batteries are a promising solution for stationary energy storage, but the complex tubular geometry of the solid electrolyte represents a challenge for manufacturing. A planar electrolyte and cell design is more compatible with automated mass production. However, the planar cell design also faces a series of challenges, such as the management of molten phases during cycling. As a result, cycling of planar high‐temperature cells until now focused on moderate areal capacities and current densities. In this work, planar cells capable of integrating cost‐efficient nickel/iron electrodes at a substantially enhanced areal capacity of 150 mAh cm−2 is presented. Due to a low cell resistance during operation at 300 °C, these cells deliver a specific discharge energy of 300 Wh kg−1 at high discharge current densities of 80 mA cm−2 (C/2, 10%–100% state‐of‐charge). This results represent the first demonstration of planar Na‐NiCl2 cells at a commercially relevant combination of areal capacity, cycling rate, and energy efficiency. It is further identified the secondary molten NaAlCl4 electrolyte to contribute to the cell capacity during cycling. Mitigating electrochemical decomposition of NaAlCl4 will play an important role in further enhancing both cycling rates and cycle life of high temperature Na‐NiCl2 batteries.