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MgCl2 is trigonal omega-like structured and crystallizes in the trigonal R-3m space group. The structure is two-dimensional and consists of three MgCl2 sheets oriented in the (0, 0, 1) direction. Mg2+ is bonded to six equivalent Cl1- atoms to form edge-sharing MgCl6 octahedra. All Mg–Cl bond lengths are 2.53 Å. Cl1- is bonded in a distorted T-shaped geometry to three equivalent Mg2+ atoms.
MgCl2 is trigonal omega structured and crystallizes in the trigonal P-3m1 space group. The structure is two-dimensional and consists of one MgCl2 sheet oriented in the (0, 0, 1) direction. Mg2+ is bonded to six equivalent Cl1- atoms to form edge-sharing MgCl6 octahedra. All Mg–Cl bond lengths are 2.53 Å. Cl1- is bonded in a distorted T-shaped geometry to three equivalent Mg2+ atoms.
MgCl2 crystallizes in the triclinic P-1 space group. The structure is two-dimensional and consists of one MgCl2 sheet oriented in the (1, 0, 0) direction. Mg2+ is bonded to four Cl1- atoms to form a mixture of edge and corner-sharing MgCl4 tetrahedra. There are a spread of Mg–Cl bond distances ranging from 2.35–2.38 Å. There are three inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in an L-shaped geometry to two equivalent Mg2+ atoms. In the second Cl1- site, Cl1- is bonded in a linear geometry to two equivalent Mg2+ atoms. In the third Cl1- site, Cl1- is bonded in a linear geometry to two equivalent Mg2+ atoms.
MgCl2 crystallizes in the tetragonal P-4m2 space group. The structure is two-dimensional and consists of one MgCl2 sheet oriented in the (0, 0, 1) direction. Mg2+ is bonded to four equivalent Cl1- atoms to form corner-sharing MgCl4 tetrahedra. All Mg–Cl bond lengths are 2.37 Å. Cl1- is bonded in a water-like geometry to two equivalent Mg2+ atoms.
MgCl2 crystallizes in the orthorhombic Pmma space group. The structure is two-dimensional and consists of one MgCl2 sheet oriented in the (0, 0, 1) direction. Mg2+ is bonded to six Cl1- atoms to form a mixture of edge, face, and corner-sharing MgCl6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are two shorter (2.38 Å) and four longer (2.67 Å) Mg–Cl bond lengths. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in an L-shaped geometry to two equivalent Mg2+ atoms. In the second Cl1- site, Cl1- is bonded in a 4-coordinate geometry to four equivalent Mg2+ atoms.
Corrosion of materials presents a significant challenge for the long-term operation of molten salt reactors. This study aims to identify the most effective techniques for evaluating the corrosion performance of materials in molten salts, with a focus on the effects of galvanic corrosion and dissimilar materials. A reliable testing methodology for assessing material corrosion in molten chloride salts has been successfully developed. The corrosion of Alloy 316H in molten NaCl-MgCl2 salt was found to be significantly accelerated by galvanic corrosion. Additionally, the presence of dissimilar materials resulted in a slight increase in the corrosion rate of Alloy 316H in NaCl-MgCl2 salt. Microstructural characterization was utilized to understand the corrosion behavior of test samples under different conditions. Common trends observed across samples include chromium depletion and iron enrichment near corroded surfaces. Molybdenum enrichment along grain boundaries and corrosion surfaces was also frequently noted.
MgCl2 crystallizes in the orthorhombic Ama2 space group. The structure is three-dimensional. Mg2+ is bonded to five Cl1- atoms to form corner-sharing MgCl5 trigonal bipyramids. There are a spread of Mg–Cl bond distances ranging from 2.40–2.60 Å. There are two inequivalent Cl1- sites. In the first Cl1- site, Cl1- is bonded in a trigonal planar geometry to three equivalent Mg2+ atoms. In the second Cl1- site, Cl1- is bonded in a linear geometry to two equivalent Mg2+ atoms.
Ionic liquid materials are viable candidates as a heat transfer fluid (HTF) in a wide range of applications, notably within concentrated solar power (CSP) technology and molten salt reactors (MSRs). For next-generation CSP and MSR technologies that strive for higher power generation efficiency, a HTF with wide liquid phase range and energy storage capabilities is crucial. Studies have shown that eutectic chloride salts exhibit thermal stability at high temperatures, high heat storage capacity, and are less expensive than nitrate and carbonate salts. However, the experimental data needed to fully evaluate the potential of eutectic chloride salts as a HTF contender are scarce and entail large uncertainties. Considering the high cost and potential hazards associated with the experimental methods used to determine the properties of ionic liquids, molecular modeling can be used as a viable alternative resource. In this study, the eutectic ternary chloride salt MgCl 2 –NaCl–KCl is modeled using ab-initio molecular dynamics simulations (AIMDs) in the liquid phase. Using the simulated data, the thermophysical and transport properties of eutectic chloride salt can be calculated: density, viscosity, heat capacity, diffusion coefficient, and ionic conductivity. For an initial model validation, experimental pair-distribution function data were obtained from X-ray total scattering techniques and compared to the theoretical pair-distribution function. Additionally, theoretical viscosity values are compared to experimental viscosity values for a similar system. The results provide a starting foundation for a MgCl 2 –NaCl–KCl model that can be extended to predict other fundamental properties.
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A novel and versatile strategy for the amorphous-to-crystalline transformation of boron nitride (BN) with the capability to control the degree of crystallization was developed through an electrochemical pathway using MgCl 2 at low temperature (750 °C). This procedure can be extended to the transformation of amorphous carbon to graphite, which significantly reduces the energy and cost, accelerates the synthesis process and could potentially replace industrial graphite synthesis globally. Therefore, the synthesized graphite exhibits much enhanced electrochemical performance at high charge–discharge rates (5C) compared to commercial synthetic graphite.
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Design of interfaces with thermodynamic and kinetic specificity is of great importance for hydrogen storage from both an applied and fundamental perspective. Here, in order to destabilize the metal hydride and protect the dehydrogenated products from oxidizing, a unique core-shell structure of porous Mg(BH4)2-based framework with a thin layer (no more than 5 nm) of MgCl2 additives on the surface, has been proposed and synthesized via a wet-chemical method. The local structure and electronic state of the present complex system are systematically investigated to understand the correlation between the distribution of additives and dehydrogenation property of Mg(BH4)2. A significant improvement is achieved for hydrogen desorption with chlorides: initial hydrogen release from MgCl2 decorated ..gamma..-phase Mg(BH4)2 particles commences at 100 °C and reaches a maximum of 9.4 wt% at 385 °C. Besides the decreased decomposition temperature, an activation barrier of about 76.4 kJ mol-1 lower than that of Mg(BH4)2 without MgCl2 is obtained. Moreover, MgCl2 decoration can also prevent the whole decomposed system (both Mg- and B- elements) from oxidizing, which is a necessary condition to reversibility.
This progress report describes work performed during FY20 at Sandia National Laboratories (SNL) to assess the localized corrosion performance of container/cask materials used in the interim storage of spent nuclear fuel (SNF). Of particular concern is stress corrosion cracking (SCC), by which a through-wall crack could potentially form in a canister outer wall over time intervals that are shorter than possible dry storage times. Work in FY20 further defined our understanding of the potential chemical and physical environment present on canister surfaces, evaluated the relationship between the environment and the resultant corrosion that occurs, and initiated crack growth rate testing under relevant environmental conditions. In FY20, work to define dry storage canister surface environments included several tasks. First, collection of dust deposition specimens from independent spent fuel storage installation (ISFSI) site locations helped to establish a more complete understanding of the potential chemical environment formed on the canister. Second, the predicted evolution of canister surface relative humidity RH) values was estimated using ISFSI site weather data and the horizontal canister thermal model used by the SNL probabilistic SCC model. These calculations determined that for typical ISFSI weather conditions, seasalt deliquescence to produce MgCl2-rich brines could occur in less than 20 years at the coolest locations on the canister surface, and, even after nearly 300 years, conditions for NaCl deliquescence (75% RH) are not reached. This work illustrates the importance of understanding the stability of MgCl2-rich brines on the heated canister surface, and the potential impact of brine composition on corrosion processes, including pitting and stress corrosion cracking. In an additional study, the description of the canister surface environment was refined in order to define more realistic corrosion testing environments including diurnal cycles, soluble salt chemistries, and inert mineral particles. The potential impacts of these phenomena on canister corrosion are being evaluated experimentally. Finally, work over the past few years to evaluate the stability of magnesium chloride brines continued in FY20. MgCl2 degassing experiments were carried out, confirming that MgCl2 brines slowly degas HCl on heated surfaces, converting to less deliquescent magnesium hydroxychloride phases and potentially leading to brine dryout.