Bulky Crystals Research Articles

Bright Self-Trapped Exciton Emission in Alkali Iodide Nanocrystals via Sn(II)-Doping

Lead-free alkali halides have gained increasingly attentions due to their desire optoelectronic properties across a variety of light-emitting applications. However, state-of-the art alkali halide emitters commonly are bulky crystals functionalized...

Growth of large norsethite crystals in aqueous ammonium nitrate solutions

Crystallization of norsethite [BaMg(CO3)2] receives considerable attention as a key for solving geological problems, and environmental and resource issues. Noresthite is poorly soluble in water, and is synthesized via witherite [BaCO3] by solution-mediated transformation. In contrast, owing to the difficulties such as tremendous growth time and consideration of multi-step reactions, the shape and size of norsethite were not satisfactory for further investigations so far. Here we tried to increase the solubility of the crystals to overcome these difficulties of the growth by adding NH4NO3. The solubilities of norsethite and witherite in the presence of NH4NO3 were ∼35 and ∼45 times higher than those in the absence of NH4NO3, respectively. At 90 °C, the growth rate of norsethite in NH4NO3 solutions was ∼17 times higher than that in NH4NO3-free solutions, and norsethite in NH4NO3 solutions nucleated immediately after mixing the raw materials. Finally, we succeeded in synthesizing bulky norsethite crystals of 170 μm size only in one month, utilizing 0.1–1 M NH4NO3 solutions of 90 °C. We could explain the appearance of large norsethite, considering that norsethite dominantly consumes the solute by adding NH4NO3 compared with witherite. The findings provide a breakthrough in the growth technique of double carbonates.

Polarization Engineering of Entangled Photons from a Lithium Niobate Nonlinear Metasurface.

Complex polarization states of photon pairs are indispensable in various quantum technologies. Conventional methods for preparing desired two-photon polarization states are realized through bulky nonlinear crystals, which can restrict the versatility and tunability of the generated quantum states due to the fixed crystal nonlinear susceptibility. Here we present a solution using a nonlinear metasurface incorporating multiplexed silica metagratings on a lithium niobate film of 300 nm thickness. We fabricate two orthogonal metagratings on a single substrate with an identical resonant wavelength, thereby enabling the spectral indistinguishability of the emitted photons, and we demonstrate in experiments that the two-photon polarization states can be shaped by the metagrating orientation. Leveraging this essential property, we formulate a theoretical approach for generating arbitrary polarization-entangled qutrit states by combining three metagratings on a single metasurface, allowing the encoding of the desired quantum states or information. Our findings enable miniaturized optically controlled quantum devices by using ultrathin metasurfaces as polarization-entangled photon sources.

Directing Highly a-Axis-Oriented ZSM-5 Nanosheets with Pre-estimated Bifunctional Imidazole Cations.

An MFI-topology nanosheet zeolite with a highly a-axis-oriented structure has rarely been reported but with a great potential for industrial applications. Theoretical calculations on the interaction energies between the MFI skeleton and ionic liquid molecules indicated the possibility of preferential crystal growth along a specific direction, according to which highly a-oriented ZSM-5 nanosheets were synthesized from commercially available 1-(2-hydroxyethyl)-3-methylimidazolium and layered silicate sources. The imidazolium molecules directed the structure formation and meanwhile acted as zeolite growth modifiers to restrict the crystal growth perpendicular to the MFI bc plane, which induced unique a-axis-orientated thin sheets with ∼12 nm thickness. The a-oriented ZSM-5 exhibited more competitive propylene selectivity and longer lifetime than bulky crystals in methanol-to-propylene (MTP) reaction. This research would provide a versatile protocol for the rational design and synthesis of shape-selective zeolite catalysts with promising applications.

Synthesis and Structure of Bulky Single Crystals of High-Entropy Ferrites BaFe12–x(Ti, Mn, In, Ga)xO19

Synthesis and Structure of Bulky Single Crystals of High-Entropy Ferrites BaFe12–x(Ti, Mn, In, Ga)xO19

Photon pair generation from lithium niobate metasurface with tunable spatial entanglement [Invited

The two-photon state with spatial entanglement is an essential resource for testing fundamental laws of quantum mechanics and various quantum applications. Its creation typically relies on spontaneous parametric downconversion in bulky nonlinear crystals where the tunability of spatial entanglement is limited. Here, we predict that ultrathin nonlinear lithium niobate metasurfaces can generate and diversely tune spatially entangled photon pairs. The spatial properties of photons including the emission pattern, rate, and degree of spatial entanglement are analyzed theoretically with the coupled mode theory and Schmidt decomposition method. We show that by leveraging the strong angular dispersion of the metasurface, the degree of spatial entanglement quantified by the Schmidt number can be decreased or increased by changing the pump laser wavelength and a Gaussian beam size. This flexibility can facilitate diverse quantum applications of entangled photon states generated from nonlinear metasurfaces.

Electrochemical Exfoliation to Produce High-Quality Black Phosphorus.

To obtain high-quality two-dimensional (2D) materials from the bulky crystals, delamination under an externally controlled stimulus is crucial. Electrochemical exfoliation of layered materials requires simple instrumentation yet offers high-quality exfoliated 2D materials with high yields and features straightforward upscalability; therefore, it represents a key technology for advancing fundamental studies and industrial applications. Moreover, the solution processability of functionalized 2D materials enables the fabrication of (opto)electronic and energy devices via different printing technologies such as inkjet printing and 3D printing. This paper presents the electrochemical exfoliation protocol for the synthesis of black phosphorus (BP), one of the most promising emerging 2D materials, from its bulk crystals in a step-by-step manner, namely, cathodic electrochemical exfoliation of BP in the presence of N(C4H9)4∙HSO4 in propylene carbonate, dispersion preparation by sonication and subsequent centrifugation for the separation of flakes, and morphological characterization by scanning electron microscopy (SEM), atomic force microscopy (AFM), and transmission electron microscopy (TEM).

Promoting hydroisomerization selectivity using channel axis reduced ZSM-48 fabricated by a combined bead-milling and porogen-assisted recrystallization method

ZSM-48 is a unidimensional zeolite that is frequently used as acid component of bi-functional hydroisomerization catalyst. As selectivity towards unwanted cracking products increases with retention time of isomerized products inside micropores, shortening their retention time inside the micropores by reducing channel length offers an effective way to improve isomerization selectivity. Direct synthesis of unidimensional zeolitic crystals with reduced channel axis is particularly difficult, since they habitually grow into rod-like shape along their channel direction. Post-synthetic bead-milling is a cost effective, mechanochemical method to decrease crystal size of zeolites from micro meter to nano meter scale, but suffers from amorphization or partial destruction of zeolitic crystals. Consequently, a post-milling recrystallization process is often entailed to remedy the destructed domains, which, nonetheless, readily causes secondary crystal growth and formation of bulky crystals that compromises the effect of bead-milling. Here, we show that porogen-assisted recrystallization can overcome the problem to fabricate channel axis reduced ZSM-48 nanocrystals. The Si/Al ratio is tunable between 30 and 200 and the acidity is largely preserved after recrystallization. The catalytic advantages of the obtained material are demonstrated in catalytic n-heptane hydroisomerization. The obtained ZSM-48 nanocrystal with Si/Al ratio of 100 outperforms the rest samples and shows enhanced isomerization yield (72% vs 62%) with respect to the parent sample. By combined diagnoses of the impact of diffusion length on product selectivity (product shape selectivity) and kinetic studies, selectivities to monomethyl branched isomers (2-methyl hexane and 3-methyl hexane) and small bulky dimethyl branched isomers (2,3- and 2,4-dimethyl pentane) are attributed to product shape selectivity, whereas the formation to bulky dimethyl branched isomers (2,2- and 3,3-dimethyl pentane) is hindered mainly by transition-state shape selectivity. The combined destructive-constructive synthetic protocol and the revelation of the origin of shape-selectivity in n-heptane hydroisomerization are useful for hydroisomerization catalyst design.

Spatially entangled photon pairs from lithium niobate nonlocal metasurfaces.

Metasurfaces consisting of nanoscale structures are underpinning new physical principles for the creation and shaping of quantum states of light. Multiphoton states that are entangled in spatial or angular domains are an essential resource for many quantum applications; however, their production traditionally relies on bulky nonlinear crystals. We predict and demonstrate experimentally the generation of spatially entangled photon pairs through spontaneous parametric down-conversion from a metasurface incorporating a nonlinear thin film of lithium niobate covered by a silica meta-grating. We measure the correlations of photon pairs and identify their spatial antibunching through violation of the classical Cauchy-Schwarz inequality, witnessing the presence of multimode entanglement. Simultaneously, the photon-pair rate is strongly enhanced by 450 times as compared to unpatterned films because of high-quality-factor resonances. These results pave the way to miniaturization of various quantum devices by incorporating ultrathin metasurfaces functioning as room temperature sources of quantum-entangled photons.

A novel modified LiCl solution for three-phase absorption thermal energy storage and its thermal and physical properties

• A novel LiCl solution for three-phase absorption thermal energy storage is proposed. • The energy storage density of the solution is enhanced by adding two types of additives. • The LiCl crystal slurry overcomes the fluidity problem caused by crystallization. • Thermal and physical properties of the modified solution are measured by experiments. Absorption thermal energy storage (TES) is gaining increasing attention due to its large energy storage density (ESD), mobility and long-term thermal storage capability. Expanding the working concentration difference of a solution can significantly enhance its ESD; however, this may result in crystallization, influencing fluidity and blocking flow channels in a TES device. Furthermore, bulky crystals are difficult to dissolve during energy discharge. In this paper, a novel modified LiCl solution is proposed for three-phase absorption TES, which allows the growth of fine crystals and the formation of well suspended slurry. For the first time, two types of additives with competing mechanism are introduced into the solution: ethylene glycol as a crystallization inhibitor and SiO 2 nanoparticles (SNPs) as a nucleating agent. Compared with traditional working fluids, the proposed solution has a larger ESD and good fluidity. The expanded concentration difference is determined by experiments on solubility and suspension. The optimal mass ratio of the LiCl solution, ethylene glycol and SiO 2 nanoparticles are obtained considering both ESD and fluidity. Heat and cold storage density using this novel LiCl crystal slurry can be enhanced by 24.8% and 156.0% respectively. Measurements on thermal and physical properties including vapor pressure, density and viscosity are also carried out.

Postsynthesis of hierarchical core/shell ZSM-5 as an efficient catalyst in ketalation and acetalization reactions

Hierarchical core/shell Zeolite Socony Mobil-five (ZSM-5) zeolite was hydrothermally postsythesized in the solution of NaOH and diammonium surfactant via a dissolution-reassembly strategy. The silica and alumina species were firstly dissolved partially from the bulky ZSM-5 crystals and then were in situ reassembled into the MFI-type nanosheets with the structure-directing effect of diammonium surfactant, attaching to the out-surface of ZSM-5 core crystals. The mesopores thus were generated in both the core and shell part, giving rise to a micropore/mesopore composite material. The micropore volume and the acidity of the resultant hybrid were well-preserved during this in situ recrystallization process. Possessing the multiple mesopores and enlarged external surface area, the core/shell ZSM-5 zeolite exhibited higher activity in the ketalation and acetalization reactions involving bulky molecules in comparison to the pristine ZSM-5.

Adiabatic nonlinear optical frequency conversion based on the electro-optic effect

We propose a novel, to the best of our knowledge, adiabatic nonlinear optical frequency conversion method based on the electro-optic effect, which can be applied in a plethora of bulky nonlinear crystals. Within our method, an electric field gradient is applied on the crystal, which causes the phase mismatch to also gradually vary in space, thus achieving adiabatic frequency conversion. We demonstrate the validity and feasibility of this new approach by providing a theoretical framework and experimental evidence. In the experiment, the second harmonic generation of 532 nm is conducted in K D 2 P O 4 . Conversion efficiency approaching 47.2% is achieved, with a corresponding temperature acceptance bandwidth of 4.56°C, which is about 4.3 times the temperature without the external electric field. We argue that the approach based on the electro-optic effect is promising for extending the range of applications of adiabatic frequency conversion and, consequently, for achieving efficient and robust frequency conversion.

Seismic phononic crystals by elastodynamic Navier equation.

The phenomenon, known as a complete band gap in photonic crystals consisting of periodically arranged manmade nanostructures, caused a huge sensation in photonics. Inspired by the physical methodology, we extend it to large-scale wave propagation for seismic waves. In particular, we exploit the elastodynamic Navier equation in the medium for seismic phononic crystals to induce complete band gaps of body (P) and shear (S) waves. We also show a technique that uses weak formulation to analyze band structures. Estimation of evanescent modes by complex-valued wave vectors yields propagation length, then we redesign bulky phononic crystals to be as thin as possible. We also investigate how material properties affect the relation between propagation length and effective particle velocity. This study will contribute to seismic-resistant techniques in seismology.

Photoconductive Properties of Dibenzotetrathiafulvalene-Tetracyanoquinodimethane (DBTTF-TCNQ) Nanorods Prepared by the Reprecipitation Method.

Charge-transfer complex crystals have been extensively studied because of their metallic conductivity, photoconductivity, ambipolar charge transport, and high career mobility. Numerous studies of their applications for organic electric devices such as organic field effect transistors and solar cells have reported. However, bulky single crystals of charge-transfer complexes are difficult to handle, specifically to be made into a form of a thin film. Recently, nano/micro crystallization of charge-transfer crystal is attracted to realize thin film applications. In this paper, charge transfer complex nanorods composed of dibenzotetrathiafulvalene-tetracyanoquinodimethane (DBTTF-TCNQ) were prepared by the reprecipitation method. The as-formed nanorods possess a kinetically metastable crystal structure different from the thermodynamically stable bulk crystal prepared by slow evaporation of the solvent. From photoconductive measurement, nanorod stacks show a significant photosensitivity (354.57 μA/W) on par with bulk crystal (417.14 μA/W). These results suggest dibenzotetrathiafulvalene-tetracyanoquinodimethane (DBTTF-TCNQ) nanorods have a favorable crystal structure for carrier transport due to the difference of molecular stacking assembly.

Utilization of lithium incorporated mesoporous silica for preventing necrosis and increase apoptosis in different cancer cells

There are many molecules used as a drug carrier. TUD-1 is a newly synthesized mesoporous silica (SM) molecule possess two important features; consists of mesoporous so it is very suitable to be drug carrier in addition to that it has the ability to induce apoptosis in cancer cells. However, the effect of TUD-1 appears to act as cell death inducer, regardless of whether it is necrosis or apoptosis. Unfortunately, recent studies indicate that a proportion of cells undergo necrosis rather than apoptosis, which limits the use of TUD-1 as a secure treatment. On the other hand, lithium considered as necrosis inhibitor element. Hence, the current study based on the idea of producing a new Li-TUD-1 by incorporated mesoporous silica (TUD-1 type) with lithium in order to produce a new compound that has the ability to activate apoptosis by mesoporous silica (TUD-1 type) and at the same time can inhibit the activity of necrosis by lithium. Herein, lithium incorporated in TUD-1 mesoporous silica by using sol–gel technique in one-step synthesis procedure. Moreover, lithium incorporated in TUD-1 with different loading in order to form different active sites such as isolated lithium ions, nanoparticles of Li2O, and bulky crystals of Li2O. The ability of the new compounds to induce apoptosis and prevent necrosis was evaluated on three different types of cancer cell lines, which are; liver HepG-2, breast MCF-7, and colon HCT116. The obtained results show that Li-TUD-1 has the ability to control necrosis and thus reduce the side effects of treatments containing silica in the case of lithium added to them, especially in chronic cases. This opinion has demonstrated by the significant increase in the IC50 value and cell viability compared to control groups. Consequently, the idea is new, so it needs more develop and test with materials that have a more apoptotic impact than silica to induce apoptosis without induction of necrosis.

Epitaxial Growth of Layered-Bulky ZSM-5 Hybrid Catalysts for the Methanol-to-Propylene Process

The hierarchical layered-bulky ZSM-5 (LBZ5) hybrid composites with a core–shell structure were synthesized by epitaxial growth of layered ZSM-5 nanosheets over bulky ZSM-5 crystals. The systematic balance of zeolitic microporosity and interlayered mesoporosity was achieved by elaborate regulation of the ratio between layered phase and bulky phase, resulting in a series of layered-bulky ZSM-5 hybrid composites with the controllable thickness of the layered shell ranging from 98 to 307 nm. The evaluation of catalytic performance in the methanol-to-propylene (MTP) reaction indicated the LBZ5 materials to be candidated catalysts for the MTP process with prolonged catalytic lifetime, superior coke toleration, and enhanced propylene selectivity compared with the parent bulky ZSM-5 (BZ5) and layered ZSM-5 (LZ5) due to their well-retained zeolitic framework, hierarchical meso-/microporosity by the layered-bulky composite structure, and appropriate strong acidity.

The Fabrication of 2D Cu-Based MOF Nanosheets for DNA Detection

The Cu-based metal–organic framework (MOF) analogues, copper 1,4-benzenedicarboxylate (CuBDC), copper 2,6-naphthalenedicarboxylate (Cu(2,6-NDC)), and copper 1,4-naphthalenedicarboxylate (Cu(1,4-NDC)) MOF nanosheets, are prepared as biosensor nanoplatforms for DNA detection by a spray method. With the ultrathin 2D structure, the fabricated MOF nanosheets exhibited better detection of target DNA, in particular when compared with the corresponding 3D MOF bulky crystals, when used as a DNA biosensor platform. The Cu(1,4-NDC) nanosheets display a distinct sensitivity with a detection limit of 0.3nM and linear range of 0–20nM, and selectivity for the target DNA or target DNA mixture. The feasible biosensor nanoplatform composed of 2D MOF nanosheets broadens the application scope of MOF nanosheets.

Microwave Synthesis of Co Doped ZnO Nanoparticles and Their Electrocatalytic Activity for Water Oxidation

Introduction: Fast and efficient conversion of renewable electricity to storable chemical energy is a subject of utmost importance for realization of sustainable society, and development of electrocatalysts out of non-precious elements is the key. Among various metal oxides previously tested, Co3O4 is known to be one of the best catalyst for oxygen evolution reaction (OER), essential for water splitting. Since water oxidation catalysis the surface phenomenon, nano-particles of Co3O4 and Co oxide clusters exhibit higher performance than bulky crystals. In this study, doping of Co ions into nanocrystals of zinc oxide (ZnO) has been achieved by microwave (MW) assisted hydrothermal reaction to form catalytic surface sites for OER combined with highly conductive and stable ZnO for flexible catalyst design and potential enhancement of the catalytic activity. Experiments: Aqueous precursor solutions containing ZnCl2 and CoCl2 at various ratios in a total concentration of 0.2 M were basified with NaOH to ca. pH 13, and subjected to a 2.45 GHz MW to promote reaction at 160°C for 30 min. The products were characterized by FE-SEM, XRD and UV-Vis. Mesoporous electrodes of Zn1-x Co x O (x = 0, 0.02, 0.05, 0.10, 0.20, 1) were fabricated by doctor blading method onto F-doped SnO2 glass substrate for electrochemical analysis in a 0.1 M KCl aqueous solution (pH 7.4). Evolved O2 has been analyzed by gas chromatography (GC). Results and discussion: Minor addition of CoCl2 in the precursor solution turned product into green, exhibiting characteristic absorption peaks at around 560, 610 and 650 nm due to d-d transition of doped Co(II) ion along with a red shift of the bandgap absorption onset, and associated with morphological change of the nanoparticles and slight enlargement of the lattice constants of Wurtzite ZnO. Doping limit of about 10% has been suggested, as phase separation of Co(OH)2 is observed for x > 0.1. Cyclic voltammograms measured at mesoporous ZnO, Zn0.95Co0.05O and Co3O4 electrodes are shown in Fig. 1. While pure ZnO is totally inactive for water oxidation, the Co-doped electrode exhibits an anodic hump at around +0.8 V associated with the oxidation of Co to be followed by a sharp rise of irreversible anodic current above ca. 1 V. The Co3O4 electrode shows even larger anodic peak at 0.8 V, for which, however, Co is reversibly reduced without showing strong rise of anodic current. No systematic increase of the catalytic current was observed by further increasing the x value. Potentiostatic electrolysis at 1.2 V (corresponding to η = 0.545 V) revealed constant anodic current of about 0.9 mA cm-2 for Zn0.95Co0.05O associated with formation of gas bubbled, which was confirmed as O2 by gas chromatography. Although the currently achieved catalytic activity is not satisfactory, the present result reveals new strategies in designing catalysts for OER. Bulk crystals of transition metal oxides are not needed, but reactive sites can be furnished by small doping of transition metals into chemically stable ZnO. Doping of various transition metals such as Mn, Fe, Ni and their alloys is expected to achieve further increase of catalytic activities. Figure 1

Nanocrystallization Process, Structure, and Properties of Charge-Transfer Complex Prepared by the Reprecipitation Method

Charge-transfer (CT) complex crystals composed of organic electron donor (D) and acceptor (A) have been extensively studied because of their attractive properties such as metallic conductivity, photoconductivity, ambipolar charge transport, and high career mobility. Numerous research efforts have been made for their use in devices such as organic field effect transistors and organic photocells. However, bulky single crystals of CT complexes are difficult to handle, specifically to be made into a form of a thin film needed for solar cell applications. Nano/micro crystallization is a promising path to overcome the above mentioned problem. However, the growth of high-quality nanocrystals is imperative for photoconductivity but often hampered, since CT complexes are poorly soluble and vapor pressures of donor and acceptor molecules are imbalanced[1-2]. Here we presente the “reprecipitation method” as facile synthesis route to obtain high quality organic CT complex nanocrystals. The process of nanocrystallization can be explained in four steps[3]; 1) A small amount of a solution of the target compound in its good solvent is injected into a large amount of its poor solvent under vigorous stirring. 2) The tiny droplets formed by the injection diffuse into the poor solvent as the two solvents are chosen to be miscible. 3) Nucleation and crystal growth of the target compound proceed due to its supersaturation at the boundary of good/poor solvents. 4) As the good solvent is completely diffused, nanocrystals are stably dispersed in the poor solvents. All these events are expected to occur in a short time (within tens of milliseconds[4]) and thus nanocrystals with kinetically stable structures are often obtained, which are different from thermodynamically stable single bulk crystal structures[5]. In this work, we have successfully applied the reprecipitation method to dibenzotetrathiafulvalene (DBTTF)-tetracyanoquinodimethane (TCNQ) and tetrathiafulvalene (TTF)-TCNQ to obtain its nanocrystal. The DBTTF-TCNQ nanocrystals were prepared by typical reprecipitation method from D-A mixed solution. The nanocrystals prepared in such a way have been found to possess kinetically stable crystal structure, different from the bulk material. Moreover, a direct current device employing a polycrystalline thin film of the nanocrystals prepared by simple filtration an equivalent photosensitivity (354.57 μA/W) with that of a bulk crystal (417.14 μA/W) despite of the presence of many grain boundaries, indicating a favorable molecular stacking in the nanocrystals for career transport. In addition, the TTF-TCNQ nanocrystals were prepared by two-step reprecipitation method. TTF (TCNQ) solution was injected to TCNQ (TTF) nanoparticle water dispersion. The TTF-TCNQ nanocrystals were formed when the nanoparticles reacted and the dispersion color was changed immediately from yellow to black. Details of morphology, characteristic and crystallization process of the nanocrystals will be discussed in presentation. Reference [1] M. Hiraoka, T. Hasegawa, T. Yamada, Y. Takahashi, S. Horiuchi, and Y. Tokura, Adv. Mater. 19, 3248 (2007). [2] Y. Takahashi, T. Hasegawa, Y. Abe, Y. Tokura, and G. Saito, Appl. Phys. Lett. 88, 073504 (2006). [3] K. Shito, N. Ito, and A. Masuhara, Jpn. J. Appl. Phys. 54, 06FK05-1 (2015). [4] J. Mori, Y. Miyashita, D Oliveira, H. Kasai, H. Oikawa, and H. Nakanishi, J. Cryst. Growth 311, 553 (2009). [5] L. Huang, Q. Liao, H. Fu, J. Ma, and J. Yao, J. Mater. Chem. 20, 159 (2010).

The crystallization and salt expansion characteristics of a silty clay

To investigate the mechanisms and principle for salt expansion, theoretical analysis, micro-fabric observation and salt expansion tests are conducted to a silty clay containing sodium sulfate. The equations for calculating the crystalized sodium sulfate in soil are derived through theoretical analysis. In the microstructure test, long strip crystal bridges and bulky crystals are found in saline soil. When these crystals grow upon cooling, soil is supposed to expand. In salt expansion tests, the effects of compaction effort, water content, and salt content of soil are studied. The salt expansion data demonstrate that the volumetric content of crystal seems to have a linear relation with the volumetric strain of saline soil. Such relation seems to be unique and is applicable to the salt expansion prediction of sulfate soil with any water content, salt content and dry density. As the migration of salt in this study is negligible, the salt expansion tests can be regarded as element tests and the relation obtained can be used to build constitute models for salt expansion.