Glass-like Properties Research Articles

Anharmonic and glass-like phonon transport in the Tetrahedrite-manner Ag6Si6Sn4P12

In this study, the thermal conductivity properties of the tetrahedrite-structures compound Ag6Si6Sn4P12, whose phonon properties have not been reported so far, are investigated in depth using self-consistent phonon calculations that consider up to fourth-order anharmonic terms. Compared to the previously studied Ag6Ge10P12, a tetrahedrite-manner phosphide, Ag6Si6Sn4P12 without lone pairs, has a unique feature in that it exhibits softening of the Ag and Sn phonon modes at 300 K and has a short phonon lifetime owing to its relatively high anharmonicity. This is believed to be the cause of the extremely low lattice thermal conductivity of Ag6Si6Sn4P12. Additionally, we also observed a nonnegligible contribution of the coherent component to the thermal conductivity of Ag6Si6Sn4P12 because of its wide phonon linewidth, suggesting that Ag6Si6Sn4P12 exhibits glass-like phonon transport properties.

Disorder-driven cluster glass state in a geometrically frustrated hexagonal perovskite

We report the observation of cluster glass-like properties in a double perovskite ruthenate Ba$_2$CoRuO$_6$ through structural (neutron and synchrotron X-ray diffraction), magnetic and transport measurements. The system exhibits classic glassy characteristics like a frequency dependence in ac Susceptibility, aging and memory effects along with persistance of short-range correlations upto room temperature. The significant ($\sim30\%$) anti-site disorder on the dimer sites, coupled with the inherent geometrical frustration, allows a variety of exchange (both antiferro- and ferromagnetic) interactions to be distributed randomly across the lattice. On cooling, locally dominant interactions cause spins to nucleate and form local, short-range ordered clusters which grow in size until a global freezing occurs at about $T_f \sim 43K$.

Glassy dynamics in bacterial growth rate temperature dependence

An empirical expression for the temperature dependence of bacterial growth rate, k=b(T−T0), where k is the intrinsic growth rate, T is the ambient temperature, T0 is the hypothetical temperature, and b is the regression coefficient, has been exemplified for practical bacterial growth. Although this relationship has been popularly used as the standard evaluation of the bacterial growth rate, its scientific foundation is not clear. We propose a new relation, k = k0 exp[−Ea/kB(T − Tc)], where k0 is a constant, Ea is the activation energy (eV), kB is the Boltzmann constant, T is the absolute temperature (K), and Tc is the characteristic (frozen-in) temperature (K). The present equation resembles that for temperature-dependent fluidity (inverse viscosity) originally found for glass-forming liquids in inorganic materials. This commonality is attributed to the glass-like properties of the bacterial cytoplasm in accordance with the recent findings of glassy dynamics in active or lived matter.

Investigating structure and dynamics of unentangled poly(dimethyl-co-diphenyl)siloxane via molecular dynamics simulation.

Polysiloxane is one of the most important polymeric materials in technological use. Polydimethylsiloxane displays glass-like mechanical properties at low temperatures. Incorporation of phenyl siloxane, via copolymerization for example, improves not only the low-temperature elasticity but also enhances its performance over a wide range of temperatures. Copolymerization with the phenyl component can significantly change the microscopic properties of polysiloxanes, such as chain dynamics and relaxation. However, despite much work in the literature, the influence of such changes is still not clearly understood. In this work, we systematically study the structure and dynamics of random poly(dimethyl-co-diphenyl)siloxane via atomistic molecular dynamics simulations. As the molar ratio ϕ of the diphenyl component increases, we find that the size of the linear copolymer chain expands. At the same time, the chain-diffusivity slows down by over an order of magnitudes. The reduced diffusivity appears to be a result of a complex interplay between the structural and dynamic changes induced by phenyl substitution.

Synthetic amorphous calcium phosphates (ACPs): preparation, structure, properties, and biomedical applications.

Amorphous calcium phosphates (ACPs) represent a metastable amorphous state of other calcium orthophosphates (abbreviated as CaPO4) possessing variable compositional but rather identical glass-like physical properties, in which there are neither translational nor orientational long-range orders of the atomic positions. In nature, ACPs of a biological origin are found in the calcified tissues of mammals, some parts of primitive organisms, as well as in the mammalian milk. Manmade ACPs can be synthesized in a laboratory by various methods including wet-chemical precipitation, in which they are the first solid phases, precipitated after a rapid mixing of aqueous solutions containing dissolved ions of Ca2+ and PO43- in sufficient amounts. Due to the amorphous nature, all types of synthetic ACPs appear to be thermodynamically unstable and, unless stored in dry conditions or doped by stabilizers, they tend to transform spontaneously to crystalline CaPO4, mainly to ones with an apatitic structure. This intrinsic metastability of the ACPs is of a great biological relevance. In particular, the initiating role that metastable ACPs play in matrix vesicle biomineralization raises their importance from a mere laboratory curiosity to that of a reasonable key intermediate in skeletal calcifications. In addition, synthetic ACPs appear to be very promising biomaterials both for manufacturing artificial bone grafts and for dental applications. In this review, the current knowledge on the occurrence, structural design, chemical composition, preparation, properties, and biomedical applications of the synthetic ACPs have been summarized.

AUSTRALITES. PART 2: EARLY ABORIGINAL PERCEPTION AND USE

This paper reviews the Indigenous perception and use of australites as recorded in the Australian ethnographic literature. Aboriginal people perceived australites as having power derived from their Creation ancestors. There are accounts of australites being ritual objects used for healing, rain-making, hunting, sorcery and conveying messages. There are also descriptions of Aboriginal people using australites as raw material for tool-making, as their glass-like properties enabled specialised microlith tools to be made from them.

Dynamic and static analyses of glass-like properties of three-dimensional tissues.

The mechanical properties of tissues are influenced by those of constituent cells in various ways. For instance, it has been theoretically demonstrated that two-dimensional confluent tissues comprising mechanically uniform cells can undergo density-independent rigidity transitions, and analysis of the dynamical behavior of tissues near the critical point revealed that the transitions are geometrically controlled by the so-called cell shape parameter. To investigate whether three-dimensional tissues behave similarly to two-dimensional ones, we herein extend the previously developed model to three dimensions both dynamically and statically, demonstrating that two mechanical states similar to those of glassy materials exist in the three-dimensional case. Scaling analysis is applied to the static model focused from the rearrangement viewpoint. The obtained results suggest that the upper critical dimension of tissues equals two and is therefore the same as that of the jamming transition.

Water sorption, glass transition, and freeze-concentrated glass-like transition properties of calcium maltobionate–maltose mixtures

The water sorption, glass transition, and freeze-concentrated thermal transition properties of calcium maltobionate (MBCa)–maltose mixtures were investigated. At lower maltose molar fractions, the water content of the mixtures increased sigmoidally with water activity (aw). At higher maltose molar fractions, maltose preferentially crystallized in an aw condition, and water sorption isotherms deviated from sigmoidal behavior. The glass transition temperature (Tg) decreased with increasing water content because of a water-plasticizing effect, described as a Tg curve. The critical water content (Wc) and critical water activity (awc) (i.e., water content and aw at Tg = 298 K) were determined from the water sorption isotherms and Tg curves. The values of Wc and awc decreased linearly with increasing maltose molar fraction. The DSC curve of the MBCa–maltose aqueous solutions showed a large endothermic shift before the endothermic peak due to melting ice, and freeze-concentrated glass-like transition temperature (Tg′) was evaluated from the endothermic shift. The Tg′ of the MBCa–maltose aqueous solutions decreased with increasing maltose molar fraction. These results are useful for predicting the physical stability (collapse, crystallization of maltose, and powder caking) of MBCa–maltose mixtures during freeze-drying and subsequent storage.

Cooling Process Analysis of a 5-Drum System for Radioactive Waste Processing

A cooling system design for the processing of radioactive waste drums is investigated in this work, with the objective of providing insights for the determination of the air flow rate required to ensure an acceptable slag temperature (323 K or below) after 5 days. A methodology based on both 3D and 2D axisymmetric Computational Fluid Dynamics (CFD) modelling is developed. Transient temperature distributions within the drums in time and space determined by the heat transfer characteristics are studied in detail. A sensitivity analysis is also carried out assuming different physical properties of the radioactive slag. It was found out that for all variations analyzed, the maximum temperature of slag at the end of five days cooling is below 323 K, where the maximum outlet air temperature for a minimum air inlet velocity of 1 m/s is between 320 K and 323 K depending on the radioactive slag properties. When glass-like radioactive slag properties are assumed, the internal heat conduction within the slag is limiting the overall heat transfer, therefore requiring significantly longer cooling times.

Spin glass-like properties and exchange bias in La1.5Sr0.5CoIrO6

In this work we report the synthesis and investigation of magnetic properties of La1.5Sr0.5CoIrO6. Study of temperature dependent magnetization on this double-perovskite compound revealed two anomalies at T≃88K and T≃68K, probably related to antiferromagnetic and ferromagnetic couplings of Co and Ir ions, respectively. At T≃27K there is another anomaly, which was confirmed by means of ac magnetic susceptibility measurements to be related to the emergence of a spin glass(SG)-like phase. Magnetization as a function of applied magnetic field measurements revealed exchange bias effect of the same order of magnitude of that found for La1.5Ca0.5CoIrO6 analogue compound. We compare our results for La1.5Sr0.5CoIrO6 with those reported for La1.5Ca0.5CoIrO6, and discuss the magnetic properties of both materials in terms of their structural and electronic properties.

Light-Induced Metastable Magnetic Texture Uncovered by insitu Lorentz Microscopy.

Magnetic topological defects, such as vortices and Skyrmions, can be stabilized as equilibrium structures in nanoscale geometries and by tailored intrinsic magnetic interactions. Here, employing rapid quench conditions, we report the observation of a light-induced metastable magnetic texture, which consists of a dense nanoscale network of vortices and antivortices. Our results demonstrate the emergence of ordering mechanisms in quenched optically driven systems, which may give a general access to novel magnetic structures on nanometer length scales.

Magnetic surfactants as molecular based-magnets with spin glass-like properties

This paper reports the use of muon spin relaxation spectroscopy to study how the aggregation behavior of magnetic surfactants containing lanthanide counterions may be exploited to create spin glass-like materials. Surfactants provide a unique approach to building in randomness, frustration and competing interactions into magnetic materials without requiring a lattice of ordered magnetic species or intervening ligands and elements. We demonstrate that this magnetic behavior may also be manipulated via formation of micelles rather than simple dilution, as well as via design of surfactant molecular architecture. This somewhat unexpected result indicates the potential of using novel magnetic surfactants for the generation and tuning of molecular magnets.

Glasslike versus Crystalline Thermophysical Properties of the Cu–S based Minerals: Tetrahedrite and Colusite

We report the thermal conductivity and specific heat measurements at temperatures down to 0.3 and 0.4 K, respectively, for synthetic Cu–S based minerals, namely, tetrahedrite Cu10Zn2Sb4S13 with rattling Cu atoms and colusite Cu23Zn3V2Sn6S32 without the rattling mode. Because both are semiconducting and diamagnetic, thermal conductivity and specific heat are predominated by the lattice contribution. For the tetrahedrite, thermal conductivity exhibits a plateau at approximately 4 K and T 1.6 dependence at T < 0.7 K. The specific heat C divided by T3 displays a broad peak at around 4 K, almost identical to the so-called boson peak generally observed in structural glasses. This peak indicates the presence of an optical mode with the characteristic temperature θ of 20 K, involving the out-of-plane motion of the threefold-coordinated Cu atom. For the colusite, in contrast, thermal conductivity shows a significant peak at 15 K and specific heat reveals an optical mode with a higher θ of 90 K. The contrasting beh...

Sacrificial adhesive bonding: a powerful method for fabrication of glass microchips.

A new protocol for fabrication of glass microchips is addressed in this research paper. Initially, the method involves the use of an uncured SU-8 intermediate to seal two glass slides irreversibly as in conventional adhesive bonding-based approaches. Subsequently, an additional step removes the adhesive layer from the channels. This step relies on a selective development to remove the SU-8 only inside the microchannel, generating glass-like surface properties as demonstrated by specific tests. Named sacrificial adhesive layer (SAB), the protocol meets the requirements of an ideal microfabrication technique such as throughput, relatively low cost, feasibility for ultra large-scale integration (ULSI), and high adhesion strength, supporting pressures on the order of 5 MPa. Furthermore, SAB eliminates the use of high temperature, pressure, or potential, enabling the deposition of thin films for electrical or electrochemical experiments. Finally, the SAB protocol is an improvement on SU-8-based bondings described in the literature. Aspects such as substrate/resist adherence, formation of bubbles, and thermal stress were effectively solved by using simple and inexpensive alternatives.

Is the cellular and molecular machinery docile in the stationary phase of Escherichia coli?

The bacterial cell envelope retains a highly dense cytoplasm. The properties of the cytoplasm change with the metabolic state of the cell, the logarithmic phase (log) being highly active and the stationary phase metabolically much slower. Under the differing growth phases, many different types of stress mechanisms are activated in order to maintain cellular integrity. One such response in enterobacteria is the phage shock protein (Psp) response that enables adaptation to the inner membrane (IM) stress. The Psp system consists of a transcriptional activator PspF, negative regulator PspA, signal sensors PspBC, with PspA and PspG acting as effectors. The single molecule imaging of the PspF showed the existence of dynamic communication between the nucleoid-bound states of PspF and membrane via negative regulator PspA and PspBC sensors. The movement of proteins in the cytoplasm of bacterial cells is often by passive diffusion. It is plausible that the dynamics of the biomolecules differs with the state of the cytoplasm depending on the growth phase. Therefore, the Psp response proteins might encounter the densely packed glass-like properties of the cytoplasm in the stationary phase, which can influence their cellular dynamics and function. By comparing the properties of the log and stationary phases, we find that the dynamics of PspF are influenced by the growth phase and may be controlled by the changes in the cytoplasmic fluidity.

The Bacterial Cytoplasm Has Glass-like Properties and Is Fluidized by Metabolic Activity

The physical nature of the bacterial cytoplasm is poorly understood even though it determines cytoplasmic dynamics and hence cellular physiology and behavior. Through single-particle tracking of protein filaments, plasmids, storage granules, and foreign particles of different sizes, we find that the bacterial cytoplasm displays properties that are characteristic of glass-forming liquids and changes from liquid-like to solid-like in a component size-dependent fashion. As a result, the motion of cytoplasmic components becomes disproportionally constrained with increasing size. Remarkably, cellular metabolism fluidizes the cytoplasm, allowing larger components to escape their local environment and explore larger regions of the cytoplasm. Consequently, cytoplasmic fluidity and dynamics dramatically change as cells shift between metabolically active and dormant states in response to fluctuating environments. Our findings provide insight into bacterial dormancy and have broad implications to our understanding of bacterial physiology, as the glassy behavior of the cytoplasm impacts all intracellular processes involving large components.

Amorphous Calcium Orthophosphates: Nature, Chemistry and Biomedical Applications

Amorphous calcium orthophosphates (ACPs) represent a unique class of biomedically relevant calcium or- thophosphate salts, having variable chemical but rather identical glass-like physical properties, in which there are neither translational nor orientational long-range orders of the atomic positions. Normally, ACPs are the first solid phases, precipi- tated after a rapid mixing of aqueous solutions containing ions of Ca 2+ and PO4 3- ; however, other production techniques are known. Interestingly, but ACPs prepared by wet-chemical techniques were found to possess a relative constancy in their chemical composition over a relatively wide range of preparation conditions, which suggested the presence of a well-defined local structural unit, presumably, with the structure of Ca9(PO4)6 - so-called a Posner's cluster. However, the presence of similar clusters in ACPs produced by other techniques remains uncertain. All ACPs are thermodynamically unstable com- pounds and, unless stored in dry conditions or doped by stabilizers, spontaneously they tend to transform to crystalline cal- cium orthophosphates, mainly to calcium apatites. This solution instability of ACPs and their easy transformation to crys- talline phases are of a great biological relevance. Namely, the initiating role ACPs play in matrix vesicle biomineralization raises the importance of ACPs from a mere laboratory curiosity to that of a reasonable key intermediate in skeletal calcifi- cation. In addition, due to great chemical and structural similarities to the calcified tissues of mammals, as well as excellent biocompatibility and bioresorbability, all types of ACPs are very promising candidates to manufacture artificial bone grafts. In this review, current knowledge on occurrence, preparation, composition, structure, major properties and biomedical ap- plications of ACPs have been summarized. To assist the readers in looking for the specific details on ACPs, a great number of references have been collected and systematized.

Off-center rattling and cage vibration of the carrier-tuned type-I clathrateBa8Ga16Ge30studied by Raman scattering

To reveal dynamical property of a guest ion in type-I clathrate compound, $n$- and $p$-type clathrates ${\text{Ba}}_{8}{\text{Ga}}_{16}{\text{Ge}}_{30}$ have been investigated by Raman scattering. It is found that the guest ion in a 6d-site cage (6d-cage) rotationally moves for both $n$- and $p$-type since the additional guest mode ${E}_{\text{g}}(\text{A})$ has been observed regardless of its carrier. The potential-energy difference between [100] and [110] directions in the 6d-cage is proportional to the off-center distance of the guest-ion position from the cage center and this off-center distance for $p$-type is much larger than that for $n$-type ${\text{Ba}}_{8}{\text{Ga}}_{16}{\text{Ge}}_{30}$. In addition, the Raman intensity of the cage vibration at a 6c site for $p$-type is weaker than that for $n$-type. Thus, the amplitude of the vibration at the 6c site becomes small for $p$-type, and this small amplitude induces a large movable space for the guest ion, i.e., this vibrational amplitude of the 6c-site atom works as the barrier for the off-center position. For both systems, the guest ion in the 6d-cage shows an anharmonic vibration, judging from the anomalous energy decrease in the guest ion with decreasing temperature. The energy difference between ${T}_{2\text{g}}$ and ${T}_{1\text{u}}$ [T. Mori et al., Phys. Rev. B 79, 212301 (2009)] of the guest mode clearly supports the theoretical prediction of an interacting dipoles picture that explains the glasslike properties of the off-centered clathrate. It is concluded that the off-center rattling plays an important role to suppress a lattice thermal conductivity.

Amorphous Calcium Phosphates

Amorphous calcium phosphates (ACPs) represent a unique class of biomedically relevant calcium orthophosphate salts, in which there are neither translational nor orientational long-range orders of the atomic positions. Nevertheless, the constancy in their chemical composition over a relatively wide range of preparation conditions suggests the presence of a well-defined local structural unit, presumably, with the structure of Ca9(PO4)6 – so-called Posner’s cluster. ACPs have variable chemical but rather identical glass-like physicochemical properties. Furthermore, all ACPs are thermodynamically unstable compounds and, unless stored in dry conditions or doped by stabilizers, spontaneously they tend to transform to crystalline calcium orthophosphates. Although some order within general disorder is the most distinguishing feature of ACPs, the solution instability of ACPs and their easy transformation to crystalline phases might be of a great biological relevance. Namely, the initiating role ACPs play in matrix vesicle biomineralization raises the importance of this phase from a mere laboratory curiosity to that of a key intermediate in skeletal calcification. Furthermore, ACPs are very promising candidates to manufacture artificial bone grafts.

Polarization processes in BaBi2Nb2O9 and SrBi2Ta2O9 ceramics in infralow-frequency fields

The dielectric nonlinearity in BaBi2Nb2O9 and SrBi2Ta2O9 layered ceramics was studied by measuring their polarization loops and reverse dependences of permittivity. It was shown that the features of the dielectric response of BaBi2Nb2O9 and SrBi2Ta2O9 in strong fields can be explained by glass-like properties and the contribution of the domain structure of the ferroelectric material to repolarization processes, respectively.