Materials In Liquid State Research Articles

Tuning properties of phase-separated magnetic fluid with temperature

Phase-separated magnetic fluids provide a very strong magnetic response (μ>25) in a liquid state material. Even small fields can cause a notable material response, but this depends on its properties, which are often difficult to control. Here, we investigate how temperature affects the properties of the system, where phase separation is induced by an increase in ionic strength. Following the deformations of individual microscopic droplets, we can extract surface tension, magnetic permeability, and viscosity. We find that the temperature increase does not affect the surface tension, while the magnetic permeability and viscosity increase. Applying this knowledge to induce a shape instability for a drop only using temperature shows the potential of applicability of our findings.

Investigating the Cusp Between Dendritic and Supermolecular Architectures in Self‐Organizing Liquid Crystals

AbstractLiquid Crystals are thought of as being complex fluids, underpinned by self‐assembly and self‐organisation within partially ordered fluids, and which sit between solid and liquid states of matter. The realm of the field stretches from low molar mass to polymeric materials, from organic to inorganic substances, and from being functional materials to biological organelles. In this article, we explore the cusp of the change over from nano‐ to macro‐sciences through the formation of ‘supermolecular’ systems, and we debate if such materials are in fact oligomers or materials having giant molecules possessing discrete chemical constitutions? We performed this investigation by synthesising mesogenic materials based upon difluoroterphenyls, terminally substituted with a chiral motif based on (S)‐2‐octanol, and which could be appended onto a variety of siloxane scaffolds. We studied the structures and properties of six mesomorphic materials in which we systematically increased the number of mesogenic units attached to the scaffold.

Theoretical analysis of high-order harmonic generation in liquids by a semiclassical method

The study of high-order harmonic generation in liquid-state materials is still in its infancy. Quantitative models are highly required to understand the mechanisms. Here we develop a semiclassical method to investigate the ultrafast electron dynamics in liquids under monochromatic and two-color laser fields in momentum space. By assuming that different $k$ values are decoupled, we construct a quasienergy band for the liquid model and give the group velocity of the ionized electrons under the driving field. It successfully predicts the caustic enhancement of the liquid harmonic spectrum. We also find that the cutoff of the liquid harmonic spectrum is determined by the $k$-dependent band gap. Our results provide a different perspective for analyzing the nonlinear and nonperturbative liquid-state harmonic generation.

Low- and High-Density Unknown Waters at Ice-Water Interfaces.

Experimental confirmation of liquid polymorphs of water, high-density liquid (HDL) and low-density liquid (LDL), is desired for understanding not only the liquid state of matter but also the origin of the mysterious properties of water. However, this remains challenging because the liquid-liquid critical point of water lies in experimentally inaccessible supercooling conditions known as "no man's land". Here, we show by in situ optical microscopy that droplets and layers of low- and high-density unknown waters (LDUW and HDUW) appear macroscopically depending upon ice polymorphs at non-equilibrium interfaces between water and ices under experimentally accessible (de)pressurization conditions. These unknown waters were found to have characteristic velocities (about 20 and 100 m/s for LDUW and HDUW, respectively) different from water (about 40 m/s) and quasi-liquid layers (QLLs) (about 2 and 0.2 m/s for droplet and layer forms of QLLs, respectively). Our discoveries provide insight on liquid polymorphism of water.

Study on the interfacial thermal conductance between metals and phase change materials

Foam metal phase change composite materials and systems play a crucial role in the heat (cold) storage system. The interfacial thermal conductancebetween different foam metals and phase change materials under different phases isan important factor to affect the heat (cold) storage process of theheat (cold)storagesystem. In this paper, the interfacial thermal conductancebetween the three metals(copper, aluminum and nickel) andtwo phase change materials (paraffin and erythritol) in solid and liquidis measured by time-domain thermoreflectanctechnique. The experiments suggest that regardless of the types (paraffin or erythritol) and phases (solid or liquid) of phase change materials, the interfacial thermal conductance results preserve the same trend that copper < nickel < aluminum. By performing a series of molecular dynamics simulations and phonon-level analyses, the mechanisms for the above trend are identified to be the dominant contribution of lattice vibration in z direction and mismatching degrees of metal/phase change material interfaces. The interfacial thermal conductance of metals/paraffin are bigger than metals/erythritol in the same conditions.Compared with solid state, two kinds of phase change materials in liquid state show biggerinterfacialthermal conductance for all kinds of metals.

One-dimensional quantum droplets under space-periodic nonlinear management

Quantum droplets have recently emerged as a novel liquid state of matter in a mixture of two-component ultracold Bose gases under the equilibrium condition between the competing attractive inter- and repulsive intraspecies forces. Quantum droplets represent a self-bound liquid state in purely nonlinear systems and as such there is not any management applied to their study up to now. We here introduce the nonlinear management via space-periodic Feshbach resonance technique to a binary Bose–Einstein condensate and investigate theoretically the structure, property and dynamics of the one-dimensional quantum droplets therein, three findings are made: small droplets with single hump (solitonlike), moderate droplets composed of two solitons, large droplets feature a modulated flat-top shape. Particularly, by means of linear-stability and direct perturbed simulations, we prove that the droplets have a much wider stable region than their counterparts without taking the nonlinear management. The variational approximation is adopted and validated with numerical results in terms of small droplets. The results predicted here may be realized in the frontier ultracold atoms experiments aided by Feshbach-resonance, opening up a new channel to the quantum droplets studies.

Dynamic change process of a recast layer in Nd:YAG millisecond laser trepan drilling

Laser drilling has extensive applications in modern industry. To improve the quality of microholes drilled by a high-power millisecond pulsed laser, the laser trepan drilling technique was studied in depth in this paper. Processing parameters, such as trepanning speed (TS) and rotation number (RN), were experimentally studied for their influence on a recast layer (RL), and the detailed change process of the RL in laser repairing stage was also analyzed. It was discovered that the RL thickness would decrease with lower TS and larger RN, but micro edge cracks would appear at the hole entrance if the two parameters exceeded some appropriate ranges. The reduction of the RL during laser trepanning was neither linear nor uniform; it was a dynamic change process. The minimal RL obtained in this study was about 1 µm at the hole entrance. The difference in laser trepanning diameter has no influence on the RL. The mechanism of RL reduction in laser trepan drilling is that the recast material may intermittently be remelted by the rotating laser beam, and once it is remelted, it can be pushed downward by the vaporization-induced recoil pressure and assist gas. This process can continue only if the absorbed energy can support and keep the molten material in liquid state; therefore, the thickness of the RL is inversely proportional to the duration of the remelted material remaining in liquid state per unit length. The theoretical analysis is consistent with the experimental results.

Trap characteristics and its temperature-dependence of silicone gel for encapsulation in IGBT power modules

Silicone gel is a prevailing material for encapsulation in insulated gate bipolar transistor (IGBT) power modules. The space charge transport behavior in silicone gel is significant to evaluate the electrical insulation characteristics. This paper focuses on the trap characteristics and electrical properties of the silicone gel, which were rarely studied before. The experiments are performed on the surface potential decay of silicone gel after the charge injection. Then, the energy distributions of electron or hole traps are determined by a double-trap energy level model, which can be fitted by the Gaussian distribution. In addition, the mobilities of positive and negative charges are determined, which are 1.38 × 10 −12 m 2 ·V −1· s −1 and 1.74 × 10 −12 m 2 ·V −1 ·s −1 , respectively. Furthermore, considering the heat as a byproduct resulting in thermal issues, the temperature-dependence of surface potential decay characteristics are also studied in this paper. When temperature rises, the decay rate of surface potential increases, especially when the temperature is higher than 80 °C. Finally, the contrastive analysis illustrates that the trap characteristics of silicone gel are between the trap characteristics in liquid-state material and solid-state material, which supports the phenomenon that silicone gel is more resistive to the sharp edges in power modules. This work can provide a useful reference for the design of encapsulation in high-voltage IGBT power modules.

Laser-induced forward transfer of silver nanoparticle ink using burst technique

Laser-induced forward transfer (LIFT) is an effective approach to print materials in liquid state with high resolution. This procedure, however, suffers from bulging problem when printing continuous lines or patterns. In this study, LIFT of silver nanoparticle ink using burst technique was developed to mitigate this issue during printing continuous lines. Firstly, a set of droplet printing experiments were conducted to investigate the influences of the pulse energy and burst mode on the morphologies of the printed features. It was found that the resolution was enhanced and the phenomenon of splashing was improved with the introduction of burst technique at the same energy level. Thereafter, a group of lines were printed by changing the scanning speed in bursts of 1, 2 or 3 pulses. The results showed that the bulging of the printed line was effectively mitigated and the resolution was significantly improved in burst-3 mode.

Thermal performance of wooden elements exposed to microwave radiation during treatment of building defects

The paper describes application and theory of microwave radiation and experimental optimization of microwave radiation in relation to its growth of temperature inside and outside of wooden elements. The effect of microwave radiation on building structures is first manifested by vibration of water molecules contained in the material, which leads to a change of the state of matter from liquid to steam, which then evaporates from the wet material. During the transformation of energy from liquid state of matter to steam, heat is generated, therefore, wooden elements heat up. Therefore, the irradiated element, a wooden one in this case, gets dried up. More precisely, the paper assesses the effect of the heating times and distance of heated material from the microwave generator (antenna) and reached temperatures on the surface and inside of the irradiated spruce elements. Individual experiments were performed and results were evaluated for all wooden elements. Wooden samples were divided into two groups. Individual groups were exposed to microwave radiation for different times. In total there were two groups of spruce samples, where individual elements were exposed to identical ambient (outdoor) conditions for a long time.

Water photonics, non-linearity, and anomalously large electro-optic coefficients in poled silica fibers

Abstract

On the oscillatory hydrodynamic modes in liquid metal layers with an obstruction located on the bottom

Hydrodynamic disturbances represent the preferred mode of instability of thermogravitational flow for a relatively wide range of substances and conditions (essentially pure or compound semiconductor and superconductor materials in liquid state). As nowadays almost all modern technologies rely greatly on such crystallized materials, targeting an improved understanding of the convective phenomena which occur in the melt has become a subject of great importance. Here an “ad hoc” model is developed to inquire specifically about the role played in such a context by geometrical “irregularities” affecting the melt container. More precisely, results are presented for the case of a fluid with Pr = 0.01 (silicon) filling an open cavity with a single backward-facing or forward-facing step on the bottom wall or with an obstruction located in the centre. It is shown that the presence of sudden changes in the considered geometry can lead to a variety of scenarios with a significant departure from classical situations examined in the past. These configurations have different spatial symmetries and show different dynamics, including rhythmic roll expansions and contractions along the vertical and horizontal directions at different locations, roll nucleation, deformation, transport and merging phenomena. In some circumstances a travelling wave with front perpendicular to the imposed temperature gradient emerges, which has never been reported in the literature. A frequency spectrum analysis is used to support the identification of the multiple convective phenomena enabled by the new geometric features.

Liquefaction of Biopolymers: Solvent-free Liquids and Liquid Crystals from Nucleic Acids and Proteins.

ConspectusBiomacromolecules, such as nucleic acids, proteins, and virus particles, are persistent molecular entities with dimensions that exceed the range of their intermolecular forces hence undergoing degradation by thermally induced bond-scission upon heating. Consequently, for this type of molecule, the absence of a liquid phase can be regarded as a general phenomenon. However, certain advantageous properties usually associated with the liquid state of matter, such as processability, flowability, or molecular mobility, are highly sought-after features for biomacromolecules in a solvent-free environment. Here, we provide an overview over the design principles and synthetic pathways to obtain solvent-free liquids of biomacromolecular architectures approaching the topic from our own perspective of research. We will highlight the milestones in synthesis, including a recently developed general surfactant complexation method applicable to a large variety of biomacromolecules as well as other synthetic principles granting access to electrostatically complexed proteins and DNA.These synthetic pathways retain the function and structure of the biomacromolecules even under extreme, nonphysiological conditions at high temperatures in water-free melts challenging the existing paradigm on the role of hydration in structural biology. Under these conditions, the resulting complexes reveal their true potential for previously unthinkable applications. Moreover, these protocols open a pathway toward the assembly of anisotropic architectures, enabling the formation of solvent-free biomacromolecular thermotropic liquid crystals. These ordered biomaterials exhibit vastly different mechanical properties when compared to the individual building blocks. Beyond the preparative aspects, we will shine light on the unique potential applications and technologies resulting from solvent-free biomacromolecular fluids: From charge transport in dehydrated liquids to DNA electrochromism to biocatalysis in the absence of a protein hydration shell. Moreover, solvent-free biological liquids containing viruses can be used as novel storage and process media serving as a formulation technology for the delivery of highly concentrated bioactive compounds. We are confident that this new class of hybrid biomaterials will fuel further studies and applications of biomacromolecules beyond water and other solvents and in a much broader context than just the traditional physiological conditions.

Densities of selected phase change materials in liquid state

Abstract Temperature dependencies of densities of ten liquid phase change materials were measured: (i) Mg(NO3)2·6H2O; (ii) Ca(NO3)2·4H2O; (iii) 50 wt.% Ca(NO3)2·4H2O + 50 wt.% Mg(NO3)2·6H2O; (iv) 67 wt.% Ca(NO3)2·4H2O + 33 wt.% Mg(NO3)2·6H2O; (v) 33 wt.% Ca(NO3)2·4H2O + 67 wt.% Mg(NO3)2·6H2O; (vi) Mn(NO3)2·6H2O; (vii) Zn(NO3)2·6H2O; (viii) CaCl2·6H2O; (ix) 28 wt.% Na2SO4 + 72 wt.% H2O; (x) 56 wt.% CH3COONa + 44 wt.% H2O. The two last compositions were chosen near the peritectic compositions of incongruently melting compounds Na2SO4·10H2O and CH3COONa·3H2O, respectively. Data are presented in the article.

Optimization of liquid jet system for laser-induced breakdown spectroscopy analysis

A complex optimization of geometrical and temporal parameters of a jet system (developed in Laser-induced breakdown spectroscopy (LIBS) laboratory of Brno University of Technology) for direct elemental analysis of samples in a liquid state of matter using LIBS was carried out. First, the peristaltic pump was synchronized with the flashlamp of the ablation laser, which reduced variation of the ablated sample amount. Also, the fluctuation of the laser ray angle incident on the jet surface was diminished. Such synchronization reduced signal standard deviations and thus increased repeatability of the measurements. Then, laser energy and distance of the focusing lens from the sample were optimized. The gate delay time and the gate width were optimized for single pulse (SP) experiments; the gate delay time and the inter-pulse delay were optimized for the use of double pulse (DP) variant. Results were assessed according to the highest signal to noise ratios and the lowest relative standard deviations of the signal. The sensitivity of the single pulse and the double pulse LIBS for the detection of heavy metals traces, copper (Cu i at 324.754 nm) and lead (Pb i at 405.781 nm), in aqueous solution of copper (ii) sulfate and lead (ii) acetate, was estimated in terms of limits of detection (LODs). As a result, sensitivity improvement of DP LIBS system was observed, the LOD of Cu obtained with DP was calculated 40% lower than LOD gained from SP technique.

Investigation and Analytical Description of Acoustic Production by Magneto-Acoustic Mixing Technology

Magneto-Acoustic Mixing Technology is a novel manufacturing method that combines two magnetic fields to produce high-intensity sonication for liquid-state materials processing. This method may be adapted to the manufacture of various materials that benefit from a combination of high temperature, magnetic fields, and acoustic energy. In this work, acoustic generation mechanisms are described in detail and found to be dependent on the skin depth of the induction currents. Analytical models of acoustic pressure are derived, based on two mutually exclusive vibration mechanisms, crucible and melt vibration. Additionally, grain size evidence of acoustic pressure distribution is presented as preliminary model validation.

The stable conformations of 4,4′-dichloro-trans-stilbene in solution by liquid crystal NMR spectroscopy

The mechanisms conferring to the trans-stilbene derivatives their well known important biological properties are not yet completely clear; then, it is reasonable to suppose that their conformational equilibrium could play some kind of role (as found for many other molecules of pharmacological interest). In this scenario, the 4,4′-dichloro-trans-stilbene (DCS) can be considered as the prototype of a series of stilbenes substituted in 4,4′ positions in order to enhance their properties. Following this starting idea, we decided to study the conformational distribution of DCS in solution by Liquid Crystal NMR Spectroscopy (LXNMR), one of the best techniques to obtain this kind of information in the liquid state of matter. Our results show that the molecule is basically not planar: the most populated conformations we found are (a) the couple of symmetry-related, propeller-like structures, belonging to the C2 point group and characterized by the phenyl rings disrotated of about 18.7° with respect to the vinyl plane and (b) the couple of symmetry-related Ci structures (where the rings are parallel, like the pedals of a cycle) having this time the two rings conrotated of an angle of ∼18.7° with respect to the vinyl fragment.

Two liquid states of matter: A dynamic line on a phase diagram

It is generally agreed that the supercritical region of a liquid consists of one single state (supercritical fluid). On the other hand, we show here that liquids in this region exist in two qualitatively different states: "rigid" and "nonrigid" liquids. Rigid to nonrigid transition corresponds to the condition τ≈τ(0), where τ is the liquid relaxation time and τ(0) is the minimal period of transverse quasiharmonic waves. This condition defines a new dynamic crossover line on the phase diagram and corresponds to the loss of shear stiffness of a liquid at all available frequencies and, consequently, to the qualitative change in many important liquid properties. We analyze this line theoretically as well as in real and model fluids and show that the transition corresponds to the disappearance of high-frequency sound, to the disappearance of roton minima, qualitative changes in the temperature dependencies of sound velocity, diffusion, viscous flow, and thermal conductivity, an increase in particle thermal speed to half the speed of sound, and a reduction in the constant volume specific heat to 2k(B) per particle. In contrast to the Widom line that exists near the critical point only, the new dynamic line is universal: It separates two liquid states at arbitrarily high pressure and temperature and exists in systems where liquid-gas transition and the critical point are absent altogether. We propose to call the new dynamic line on the phase diagram "Frenkel line".

Thermotropic liquid crystalline drugs

Crystalline solids are characterized by long-range positional and orientational order in three dimensions, whereas amorphous liquids lack long-range order in any dimension. Liquid crystals (mesophases) show structural, mechanical and optical properties intermediate to those of crystalline solids and the amorphous, liquid state of matter. There are two principle types of liquid crystals: thermotropic liquid crystals (TLCs) and lyotropic liquid crystals (LLCs). TLCs can be formed by heating a crystalline solid or by cooling an isotropic melt of a TLC-forming molecule (mesogen). In the first part of this review the types of liquid crystals are defined and classified and the structural properties of mesogens are explained. In the second part, ten case studies of thermotropic mesomorphous drugs and pharmaceutically relevant molecules (arsphenamine, nafoxidine hydrochloride, L-660711, palmitoyl propranolol hydrochloride, penbutolol sulfate, itraconazole hydrochloride, fenoprofen sodium, fenoprofen calcium, ciclosporin and cholesteryl esters) are presented and their thermotropic mesomorphism is described. The review closes with a brief discussion of the unusual properties of drug mesophases and a potential use of drugs and excipients in this fourth state of matter.

Bose-Einstein condensation: Where many become one and, therefore, there is plenty of room at the bottom

Bose{Einstein condensation and super∞uidity are well known to occur in the dilute gaseous as well as in the dense liquid state of matter having a flxed number of Bose particles. Very recently, experimental evidence has been obtained for the probable realization of BEC and super∞uidity in 4 He in the solid state too, as revealed through its non-classical rotational moment of inertia { smaller than that for the solid. Such a solid that can also subtend a ∞ow as super∞uid { and hence a supersolid { is indeed a surprise of condensed matter physics. In this conversation, an order-parameter description for the supersolid state will be given in which the super∞uid ∞ow is decoupled from the crystalline density modulation which remains at rest in the laboratory frame, thus giving it a non- classical inertia.