Melt Solution Research Articles

Experimental determination of the enthalpy of formation of the pyrochlore rare‐earth hafnates

In this study, enthalpies of formation of compounds RE2Hf2O7 type (where RE = La, Pr, Nd, Sm, Eu, and Gd), with pyrochlore structure have been measured by high-temperature oxide melt solution calorimetry. Results were compared with literature data, and dependencies of enthalpies of the formation of compounds with the pyrochlore structure from the ionic radius of rare-earth element were analyzed. The enthalpy of formation becomes more positive with the increase in ionic radius, which is in conformity with the results earlier observed for titanates and zirconates.

Linear Viscoelastic Properties of Putative Cyclic Polymers Synthesized by Reversible Radical Recombination Polymerization (R3P)

Linear viscoelastic properties in both melt and solution states are reported for a series of poly(3,6-dioxa-1,8-octanedithiol) (polyDODT) made by reversible radical recombination polymerization (R3P) under conditions designed to produce linear (LDODT), cyclic (RDODT), and linear–cyclic mixtures (LRDODT). PolyDODT is amorphous (Tg < −50 °C) and highly flexible (entanglement molecular weight Me,lin ≈ 1850 g/mol for LDODT). PolyDODT’s low Tg and low Me,lin enable characterization over a wide dynamic range and a wide range of dimensionless weight-average molecular weight Zw = Mw/Me,lin. Measurements at temperatures from −57 to 100 °C provide up to 18 decades of reduced frequency, which is necessary to characterize RDODT melts with Zw from 23 to 300. The two highest-molecular-weight polymers in the present RDODT series have such high Mw (406k and 556k g/mol) that mass spectrometry, NMR spectroscopy, and even chemical assays for chain ends are unable to rule out up to 2 mol % of linear contaminant. By studying the samples in solution (using dilution to reduce Zw), we could compare their dynamics with those of previously established high-purity polystyrene (PS) rings (limited to Zw ≤ 13.6). RDODT solutions with Zw < 15 (concentrations <5 wt % for RDODT-406k and 556k) have dynamic moduli G* that accord with LCCC-purified PS rings in terms of the frequency dependence (including the absence of a plateau), the progression of shapes of G* as a function of Zw, and the linear scaling of their zero-shear viscosity η0 with Mw. The shape of G* as a function of Zw for solutions of RDODT-406k and -556k also accords with lower Mw RDODT melts (which have ≤1.3 mol % of linear contaminant). Thus, the measurement of the linear viscoelastic properties of appropriate concentrations of high Mw (>200k g/mol) putative cyclic polymers, in which linear chains evade spectroscopic detection, may provide an alternative means (though not fully proven) of validation of sample purity. When Zw > 15 (including all seven RDODT melts and eight of their solutions), G* has a rubbery plateau. This suggests that the onset of entanglement-like behavior in rings requires 4–5-fold greater Zw than is required for linear chains. Further, the plateau moduli of RDODT samples are indistinguishable from GNo of the corresponding LDODT (melt or matched-concentration solutions). In entangled linear polymers, the observation that GNo is independent of Zw follows from limitations on lateral fluctuations due to neighboring chains becoming independent of position along a given chain. The present results for RDODT suggest that this holds for sufficiently long endless chains, too. While the RDODTs have the same GNo as entangled LDODTs, when Zw > 60, the terminal relaxation, if reached at all, of RDODT extends to orders of magnitude lower frequency than an entangled linear polymer of the same Zw. Consequently, the viscosity of RDODT with Zw > 60 increases with Zw much more strongly than the 3.4 power observed for entangled linear polymers. Finally, these novel polymers, with a disulfide-linked backbone and broad relaxation time distribution, may prove important in relation to biodegradable elastomers and materials with exceptional low-frequency dissipation, extending at least 12 decades below the onset of the rubbery plateau.

Compositional Analysis of SiOC(H) Powders: A Comparison of X-ray Photoelectron Spectroscopy (XPS) and Combustion Analysis

Accurate chemical analysis of small samples of fine powders in the Si–O–C–H system is challenging. We present a comparison of analysis by X-ray photoelectron spectroscopy (XPS) and combustion analysis, validating XPS as an accurate and simple methodology for Si, C, and O analysis to give bulk and not just surface compositions. The XPS analyses are supported by showing consistency in thermochemical calculations of heats of formation based on high temperature oxide melt solution calorimetry. However, because XPS is not suitable for quantitation of hydrogen, it must be combined with other techniques for samples with substantial H content.

Thermodynamic Properties of Pectolite

Pectolite H1.00Na0.96Ca2.00Mn2+0.02Si3.00O9 from nepheline−feldspathic veins in the Kovdor massif, Kola Peninsula, Russia, was studied by X-ray diffraction (XRD), IR and Raman spectrometry, microprobe analysis (EPMA), and thermal analysis. The enthalpy of formation of pectolite HNaCa2Si3O9.from elements ∆fH° (298.15 K) = –4651.0 ± 4.3 kJ/mol was determined by melt solution calorimetry on a Setaram Tian–Calvet (France) microcalorimeter. The enthalpy of formation of serandite HNaMn2Si3O9, the manganese end member of the pectolite–serandite isomorphic series, was determined to be ΔH(298.15 K) = −4052.6 ± 4.4 kJ/mol. The absolute entropies and Gibbs energies of pectolite and serandite were calculated.

Development of the Composite Thermoluminescent Detectors Based on the Single Crystalline Films and Crystals of Perovskite Compounds.

This work is dedicated to the development of new types of composite thermoluminescent detectors based on the single crystalline films of Ce-doped GdAlO3 perovskite and Mn-doped YAlO3 and (Lu0.8Y0.2)AlO3:Mn perovskites as well as Ce and Pr-doped YAlO3 single crystal substrates. These detectors were obtained using the Liquid Phase Epitaxy growth method from the melt solution based on the PbO-B2O3 fluxes. Such composite detectors can by applied for the simultaneous registration of different components of mixed ionization fluxes using the differences between the thermoluminescent glow curves, recorded from the film and crystal parts of epitaxial structures. For creation of the new composite detectors, we considered using, for the film and crystal components of epitaxial structures (i) the different perovskite matrixes doped with the same type of activator or (ii) the same perovskite host with various types of activators. The thermoluminescent properties of the different types of epitaxial structures based on the abovementioned films and crystal substrates were examined in the conditions of β-particles and X-ray excitation with aim of determination of the optimal combination of perovskites for composite detectors. It was shown that, among the structures with all the studied compositions, the best properties for the simultaneous thermoluminescent detection of α- and X-rays were the GdAlO3:Ce film/YAlO3:Ce crystal epitaxial structure.

Chemical and environmental stability of monazite-cheralite solid solutions Ln1-2xCaxThxPO4 (Ln = Pr, Nd; x = 0–0.15): A thermodynamic study

Monazite-cheralite ceramics are a promising waste form for actinides. To elucidate the long-term behavior of this matrix in aqueous solutions, this study measured thermodynamic data for Th-rhabdophanes Ln1-2xCaxThxPO4·nH2O (with Ln = Pr, Nd; x = 0–0.15) and the associated anhydrous monazite-cheralites Ln1-2xCaxThxPO4. Solubility experiments at 298 K and high temperature oxide melt solution calorimetry were combined for calculation of ΔGf°, ΔHf° and Sm° of Th-rhabdophanes and associated monazite-cheralites. Standard solubility constants were employed in a geochemical simulation using the PHREEQC software, the results of which confirmed the high chemical stability of the monazite-cheralite phases and supported their use as a specific conditioning matrix for the long-term immobilization of actinides.

Probing Capacity Trends in MLi2Ti6O14 Lithium-Ion Battery Anodes Using Calorimetric Studies.

Due to higher packing density, lower working potential, and area specific impedance, the MLi2Ti6O14 (M = 2Na, Sr, Ba, and Pb) titanate family is a potential alternative to zero-strain Li4Ti5O12 anodes used commercially in Li-ion batteries. However, the exact lithiation mechanism in these compounds remains unclear. Despite its structural similarity, MLi2Ti6O14 behaves differently depending on charge and size of the metal ion, hosting 1.3, 2.7, 2.9, and 4.4 Li per formula unit, giving charge capacity values from 60 to 160 mAh/g in contrast to the theoretical capacity trend. However, high-temperature oxide melt solution calorimetry measurements confirm strong correlation between thermodynamic stability and the observed capacity. The main factors controlling energetics are strong acid-base interactions between basic oxides MO, Li2O and acidic TiO2, size of the cation, and compressive strain. Accordingly, the energetic stability diminishes in the order Na2Li2Ti6O14 > BaLi2Ti6O14 > SrLi2Ti6O14 > PbLi2Ti6O14. This sequence is similar to that in many other oxide systems. This work exhibits that thermodynamic systematics can serve as guidelines for the choice of composition for building better batteries.

Structural and thermodynamic evolution of an amorphous SiOC ceramic after swift heavy ion irradiation

Radiation induced structural and energetic changes have been widely studied in crystalline materials, but studied to a much lesser extent in amorphous solids. Using a combination of neutron pair distribution function (PDF) analysis and high temperature oxide melt solution calorimetry, we obtained critical insights into the structural and energetic evolution in a swift heavy ion irradiated amorphous SiOC polymer-derived ceramic. The radiation modified SiOC structure becomes energetically less stable by 24.0±1.6 kJ/mol compared to the unirradiated structure. This destabilization is related to decreased connectivity of the Si-O-C network and destruction of free carbon. In comparison with unirradiated SiOC, the irradiated structure is more likely to become phase separated during subsequent thermal annealing. Our study has important implications for evaluating amorphous SiOC ceramic as a possible radiation resistant structure for nuclear applications.

Mathematical Modeling of Nucleation and Growth Processes of Ellipsoidal Crystals in Binary Melts

The transient behavior of an ensemble of ellipsoidal particles in a supercooled binary melt is considered. The model laws, based on the Fokker-Planck type kinetic equation for the particle-volume distribution function, the thermal and mass integral balances for the binary melt temperature and solute concentration, as well as the corresponding boundary and initial conditions, are formulated and solved analytically. We show that the temperature and concentration increase with time due to the effects of impurity displacement and latent heat emission by the growing ellipsoidal particles. These effects are also responsible for metastability reduction. As this takes place, increasing the initial solute concentration in a metastable binary melt increases the intensity of its desupercooling. The theory is developed for arbitrary nucleation frequency with special consideration of two important nucleation kinetics according to the Meirs and Weber-Volmer-Frenkel Zel’dovich mechanisms. An analytical solution to the integrodifferential model equations is found in a parametric form. The theory contains all limiting transitions to previously developed analytical approaches. Namely, it contains the growth of spherical crystals in binary melts and ellipsoidal crystals in single-component melts.

Asphaltene/polymer composites: Morphology, compatibility, and rheological properties

AbstractIn this study, we investigate the use of asphaltene, a natural waste product that is inevitably formed during heavy oil processing, as a filler in polymer composites. The focus of this work is on the compatibility of various asphaltenes, featuring different polarities, with several polymers, including polypropylene (PP), polystyrene (PS), polymethyl methacrylate (PMMA), and polycarbonate (PC). The Hansen solubility parameters were plotted to predict the compatibility of polymers with different asphaltenes. Then, polymer composites were prepared by two common techniques: melt mixing and solution mixing. The dispersion state of the asphaltenes in each polymer was investigated by using imaging and rheological techniques. This work showed that the network structure of the asphaltenes and, thus, the final properties of the composites can be controlled by the polarity of asphaltenes, mixing technique, and melt viscosity of the polymer. For instance, more polar asphaltene (Asph P) produced smaller aggregates in PMMA, which has a higher polar solubility parameter than PP or PS. At 2.5 wt.% of asphaltene, Asph P showed 26% and 177% larger asphaltene agglomerates in PP and PS, respectively, than the less polar asphaltene (Asph Al). PS/asphaltene and PMMA/asphaltene composites prepared by the solution mixing method exhibited better dispersion compared to their melt‐mixed counterparts. In melt‐mixed composites, the dispersion quality of the asphaltene was better for polymers with higher melt viscosity. Thus, a careful choice of polymer, asphaltene, and preparation conditions can be used to tune the properties of asphaltene/polymer composites.

Surface induced melting of long Al nanowires: phase field model and simulations for pressure loading and without it

In this paper, melting of long Al nanowires is studied using a phase field model in which deviatoric transformation strain described by a kinetic equation produces a promoting driving force for both melting and solidification and consequently, a lower melting temperature is resolved. The coupled system of the Ginzburg–Landau equation for solidification/melting transformation, the kinetic equation for the deviatoric transformation strain and elasticity equations are solved using the COMSOL finite element code to obtain the evolution of melt solution. A deviatoric strain kinetic coefficient is used which results in the same pressure as that calculated with the Laplace equation in a solid neglecting elastic stresses. The surface and bulk melting temperatures are calculated for different nanowire diameters without mechanical loading which shows a good agreement with existing MD and analytical results. For radii R > 5 nm, a complete surface solid-melt interface is created which propagates to the center. For smaller radii, premelting occurs everywhere starting from the surface and the nanowire melts without creating the interface. The melting rate shows an inverse power relationship with radius for R < 15 nm. For melting under pressure, the model with constant bulk modulus results in an unphysical parabolic variation versus pressure in contrast to the almost linear increase of the melting temperature versus pressure from known MD simulations. Such drawback is resolved by considering the pressure dependence of the bulk modulus through the Murnaghan’s equation due to which an almost linear increase of the melting temperature versus pressure is obtained. Also, a reduction of the interface width and a significant increase of the melting rate versus pressure are found. The presented model and results allow for a better understanding of the premelting and melting of different metallic nanowires with various loading conditions and structural defects.

Thermodynamic stabilization of crystalline silicon carbide polymer‐derived ceramic fibers

AbstractThree crystalline SiC fibers were studied: Tyranno, Hi‐Nicalon, and Sylramic. Thermodynamic stability of the SiC fibers was determined by high temperature oxide melt solution calorimetry. Results shed light on the thermodynamic penalty or benefit associated with microstructural modification of the ceramic fibers, and how energetics correlate to mechanical properties. Enthalpies of formation from components (SiC, SiO2, Si3N4, and C, ∆H°f,comp) for Tyranno, Hi‐Nicalon, and Sylramic are −12.05 ± 8.71, −58.75 ± 6.93, and −71.10 ± 8.71 kJ/mol Si, respectively. The microstructure in Sylramic offers the greatest stabilizing effect, thus resulting in its much more exothermic enthalpy of formation relative to elements and crystalline components. In contrast, the microstructure in Tyranno offers the least stabilization. The thermodynamic stability of the fibers increases with increasing mixed bonding (Si bonded to both C and O). From mechanical testing, Young's moduli of Tyranno, Hi‐Nicalon, and Sylramic are 112, 205, and 215 GPa, respectively. Greater thermodynamic stability is correlated with a higher Young's modulus.

Heat capacity and thermodynamic properties of PbS: Optimization based on calorimetric and electrochemical data

Heat capacity of PbS (galena) has been measured in the temperature range from 12 to 338 K using adiabatic calorimetry. Results of the measurements are consistent with previous adiabatic calorimetric data measurements but differ notably from those obtained by relaxation calorimetry. Using experimental data on adiabatic heat capacity measurements in the range of 12–338 K (including our data), results of EMF measurements, and literature data on H0(T) – H0(298.15 K) as inputs, we have optimized the thermodynamic properties of lead sulfide (PbS, galena) based on the quasi-harmonic model vibrational spectrum proposed by Kieffer and advanced to consider intrinsic anharmonicity. In this approach, the volume and temperature dependence of vibrational frequencies are considered, and the enthalpy of formation of PbS, ΔfH0(298.15 K), is treated as an optimized model parameter. The thermodynamic properties of PbS are described with a single set of model parameters over the entire range of its stability (0–1374 K) at a pressure of 1 bar. The model can be optimized based on either the reduced (Cp0 and ΔfG0(T)) or full (Cp0, H0(T) – H0(298.15 K), ΔfG0(T)) datasets. The both variants of the optimization predict the similar thermodynamic properties of PbS, in particular, values of the enthalpies of formation differ less than 0.1 kJ mol−1 and are consistent with ΔfH0(298.15 K) obtained experimentally by oxide melt solution calorimetry. The low-temperature adiabatic calorimetry data and high-temperature results of EMF experiments (or other reliable experimental data on ΔfG0(T)) represent a minimal sufficient set of input data providing optimization of thermodynamic properties at ambient pressure by the technique established in present study.

Characterization of Cross nanofluid based on infinite shear rate viscosity with inclination of magnetic dipole over a three‐dimensional bidirectional stretching sheet

AbstractFluid viscosity manages several engineering processes and keeps its leading role in lubrication models, biological models, polymer processes, melt solutions, colloidal suspensions, and mayonnaise. The cross viscosity model is the most appropriate model, which interprets the key features of non‐Newtonian fluids in the region of shear‐thinning/thickening when very high and very low shear rates are applied. This article focuses on the mathematical model of three‐dimensional Cross nanofluid and interprets its aspect of infinite shear rate of viscosity over the expanding sheet. Velocity is studied through placing inclined magnetic dipole effect, transportation phenomenon is brought by considering the radiation effects, heat generation and chemical process is engaged for concentration of nanoparticles. The geometry of this mathematical model is expanding the stretching sheet with velocity slip, and convective heat conditions are associated. Similarity variables are being utilized for conversion dimensional mathematical model into nondimensional one. For the pursuit of numerical solution of the system of nondimensional mathematical model, the numerical technique Bvp4c is utilized. Furthermore, Matlab graphs and statistical analysis for all physical parameters and physical quantities are shown in the result and debate section. Due to inclination of angle Lorentz force producing in increasing manner, hence flow is opposed, and velocity of fluid is dropped for () and () and for increasing value of n index, the velocity of fluid flow is decreasing.

Exact hydrodynamic solution of a double domain wall melting in the spin-1/2 XXZ model

We investigate the non-equilibrium dynamics of a one-dimensional spin-1/2 XXZ model at zero-temperature in the regime |\Delta|&lt; 1|Δ|&lt;1, initially prepared in a product state with two domain walls i.e, |\downarrow\dots\downarrow\uparrow\dots\uparrow\downarrow\dots\downarrow \rangle|↓…↓↑…↑↓…↓⟩. At early times, the two domain walls evolve independently and only after a calculable time a non-trivial interplay between the two emerges and results in the occurrence of a split Fermi sea. For \Delta=0Δ=0, we derive exact asymptotic results for the magnetization and the spin current by using a semi-classical Wigner function approach, and we exactly determine the spreading of entanglement entropy exploiting the recently developed tools of quantum fluctuating hydrodynamics. In the interacting case, we analytically solve the Generalized Hydrodynamics equation providing exact expressions for the conserved quantities. We display some numerical results for the entanglement entropy also in the interacting case and we propose a conjecture for its asymptotic value.

A Feasibility Study of High-Entropy Alloy Coating Deposition by Detonation Spraying Combined with Laser Melting.

In this work, a new two-stage approach to the deposition of high-entropy alloy coatings is proposed. At the first stage, a composite precursor coating is formed by detonation spraying of the metal powder mixtures. At the second stage, the precursor coating is re-melted by a laser, and the formation of multi-component solid solution phases can be expected upon solidification. The feasibility of the proposed approach was validated using three different mixtures of Fe, Ni, Cu, Co and Al powders. It was shown that detonation spraying allows forming composite coatings with a uniform distribution of the lamellae of different metals. The results of the structural analysis of the laser-treated coatings suggest that complete alloying occurred in the melt and face-centered cubic solid solutions formed in the coatings upon cooling.

Magnetite geochemistry and iron isotope signature of disseminated and massive mineralization in the Kalatongke magmatic Cu[sbnd]Ni sulfide deposit, northwest China

Magnetite is a common accessory mineral and an indicator to magma evolution and sulfide fractional crystallization in magmatic NiCu sulfide deposits. The Kalatongke magmatic sulfide deposit at the southern margin of the Central Asian Orogenic Belt is composed of 11 mafic intrusions. The sulfide orebodies (Y1, Y1 deep, and Y2) are hosted by three small mafic intrusions, and magnetite is common in all mineralized samples. Based on ilmenite exsolution texture, composition, and type of mineralization, three types of magnetite are identified, (1) primary Fe-rich magma-related magnetite (type 1), (2) sulfide liquid-related magnetite (type 2), and (3) hydrothermal magnetite (type 3). We speculate that Fe isotope equilibrium fractionation between early or co-crystallized light 54Fe-enriched sulfide and magnetite may account for the ultra-high magnetite δ56Fe value (0.70‰ to 1.35 ‰) in the magmatic magnetite (types 1 and 2). Enriched compatible elements in type 1 magnetite (TiO2 = 1.52 wt% to 7.89 wt%, V = 775 ppm to 2420 ppm, Cr = 2697 ppm to 14,658 ppm, and Ni contents = 478 ppm to 1256 ppm), reflect the characteristics of primary Fe-rich magmatic magnetite crystallized at relatively high temperature and low oxygen fugacity. Type 2 magnetite in massive ores has Ni (762 ppm to 1769 ppm) and δ56Fe (0.89 ‰ to 1.10 ‰) values similar to type 1 magnetite, but significantly lower TiO2, V and Cr contents (TiO2 = 0.07 to 3.72 wt%, V = 61 to 2314 ppm, Cr = 5 to 2937 ppm), indicating co-crystallization with an evolved sulfide liquid across a wide span of temperature and oxygen fugacity. Type 3 magnetite is of hydrothermal fluid origin, with low δ56Fe (0.29 ‰ to 0.41 ‰) and Ni (177 ppm to 377 ppm).Magnetite composition and Fe isotope signatures at the Kalatongke magmatic sulfide deposit can reveal the genesis of magnetite and the evolution of the melt and sulfide. The Y1 orebody was completely crystallized over a short period of time, while the Y1 deep and Y2 east orebodies underwent a protracted evolution during which magnetite co-crystallized from primitive Fe-rich melt, Fe-rich evolved melt and Cu-rich intermediate sulfide solution. Magnetite and sulfide in the Y2 west massive orebody likely formed last. The compatibility of both lithophile and chalcophile elements, combined with Fe isotopes in magnetite, makes magnetite a good indicator of silicate and sulfide melt evolution.

Vitamin C aqueous solution assisted in-situ reduction of graphene oxide in flexible thermoplastic polyurethane

Graphene oxide (GO) is usually used as a precursor of reduced GO (rGO) in polymer matrices for improving their properties. However, reduction degree of GO in conventional melt mixing is usually limited. In this work, thermoplastic polyurethane (TPU)/rGO nanocomposite is prepared via water-assisted mixing extrusion with vitamin C (VC) aqueous solution injection. In situ chemical reduction (ISCR) by the VC and in situ thermal reduction (ISTR) by the thermal energy from both extruder barrel heating and screw shear are simultaneously enhanced for the GO, which are indicated by disappearances of O–H peak at the FTIR spectrum and O–C=O peak at the XPS spectrum of the rGO powder extracted from the prepared nanocomposite. Thus high reduction degree of the GO is obtained (with C/O atom ratio of 9.83 for the extracted rGO powder). This is attributed to the following two aspects: (1) TPU chains plasticized by water can better intercalate into GO galleries, thus enhancing the stripping of oxygen-containing groups from GO surface and the ISTR of the GO; (2) the screw shear action helps to disperse the VC of the injected VC aqueous solution in the TPU melt and increase the contact between the VC and GO, therefore enhancing the ISCR of the GO. The prepared TPU/GO nanocomposite exhibits enhanced dielectric permittivity.

Energetics and structure of the B‐type solid solution in the Nd2O3–Y2O3 system

AbstractThe system Nd2O3–Y2O3 contains solid‐solution phases with several different structures. Single‐phase B‐type (Nd1−xYx)2O3 solid solutions in the range of were formed at 1873 K and retained on cooling to ambient temperature. They showed a linear composition dependence of lattice parameters, enabling extrapolation to x = 0 and 1 for comparison with the structures of the stable endmembers. A positive enthalpy of formation from A‐type Nd2O3 and C‐type Y2O3 determined using oxide melt solution calorimetry indicated entropic stabilization of the B‐type phase. A positive interaction parameter for mixing in the B‐type solid solution, Ω 47.46 ± 4.04 kJ/mol, was obtained by fitting the data using a regular solution model. This value is significantly more positive than that obtained by previous phase diagram analysis using the CalPhaD approach. Exsolution into two B‐type phases is predicted to occur below 1427 K, making it unimportant for the equilibrium phase relations that will be dominated by other structures at low temperature.

Thermochemistry of 3D and 2D Rare Earth Oxychlorides (REOCls).

The thermodynamic stability of rare earth (RE) materials plays a key role in the design of separation and recycling processes for RE elements. Thermodynamic stability is fundamentally influenced by the lanthanide contraction, as observed in the systematic reduction of unit cell volumes with increasing atomic number. RE materials are found in the form of solids having primary bonds in three dimensions (3D materials) as well as ones with primary bonds in two dimensions (2D materials) whose layers are held together by weak van der Waals (vdW) forces. While studies of synthesis, structure, and physical properties of 2D RE materials are numerous, no systematic research has compared their thermodynamic stability to that of 3D materials. In the present work, RE oxychlorides (REOCls), which display a structural transition from a 3D-polyhedral network (PbFCl-type) to a vdW-bonded layered one (SmSI-type) as the RE size decreases, were all synthesized by the flux method. High-temperature oxide melt solution calorimetry was used to determine their formation enthalpies to enable Born-Haber cycles to calculate lattice energies. Our results indicate that REOCl compounds are thermodynamically stable when compared to their binary oxides and chlorides. The lattice energies of 3D REOCls increase with decreasing RE size yet are insensitive to unit cell volumes for 2D REOCls. This is caused by interatomic interactions parallel and perpendicular to layers in the SmSI-type REOCls, causing a different structure response to the lanthanide contraction than 3D RE materials.