Low-temperature Glass Research Articles

Impacts of urban buildings on microclimate and cooling systems efficiency: Coupled CFD and BES simulations

The present research investigates thermal and aerodynamic effects of urban buildings on microclimate and, subsequently, on cooling systems performance. To this end, a real heterogeneous urban area in the Mediterranean climate is considered. By employing open-source tools of OpenFOAM and EnergyPlus, coupled CFD-BES simulations are conducted. In this regard, the Detailed Surface Boundary Condition Coupling (DSBCC) algorithm is proposed. It mainly focuses on meticulously detaching any patches with different thermal properties or orientation to capture their effects on cooling units. Numerical simulations are validated by performing on-site measurements. Results elucidate the wind pattern’s pivotal role in alleviating or aggravating the local Urban Heat Island (UHI) intensity. Research outcomes indicate a stabilized efficiency for split units in all situations. The effect of hot solid walls on the adjacent air is neutralized by low-temperature glass windows. On the other hand, highly irradiated roofs create thermally critical zones, where local UHI is escalated by 3.5 K and the efficiency of rooftop units (RTU) is detracted by 46.7 %. A stronger wind speed (6 instead of 2 m/s) can enhance RTUs performance by 20.7 %. Ultimately, an optimal location for RTUs can elevate their efficiency by 42.4 % and 14.4 %, regarding shadowing effect and wind ventilation, respectively. Video AbstractSupplementary data associated with this article can be found, in the online version, at https://doi.org/10.1016/j.scs.2021.102740. [Display omitted]

Influence of lithium amount on vitreous enamel properties

Lithium is the lightest of all metals and the third element in the periodic table. Recent years, lithium salts have become an important input for the energy industry. Lithium carbonate and hydroxides are the basic building blocks of Li-ion battery production. The usage areas of lithium compounds are not limited to only energy; they are also utilized in heavy-duty machines, in the aluminum industry, in nuclear power plants and for glass, ceramics, frit, and coatings in industrial sectors. Lithium has also been found to be very useful in the development of harder, smoother, and more resistant low-temperature glasses, glazes, and enamels. It is also used in very-low-melting-point vitreous compositions like aluminum enamels, colors, fluxes, and glass-seals. The use of lithium also helps in the development of low-expansion bodies, glazes, and glasses. In this study, it is intended to explore the adherence forces in the steel sheet application of different amounts of lithium in enamel frit composition and to examine surface characteristics such as ease of cleaning, gloss, and color. For chemical characterization, X-ray fluorescence (XRF) spectrometry and color measurements were done with a Minolta CM-700d spectrometer device. Bond adherence tests were performed in accordance with the TS EN 10209 standard.

Improved ion dissociation and amorphous region of PEO based solid polymer electrolyte by incorporating tetracyanoethylene

Solid polymer electrolytes (SPEs) are key materials in safety and flexibility of rechargeable lithium-ion batteries but their ionic conductivities are very low compared with that of liquid electrolytes. One of the reasons for the low ionic conductivity was the low ion dissociation due to low dielectric constant of polymer. So, it should be required to increase the dielectric constant of polymer matrix. We prepared poly (ethylene oxide) (PEO)-based composite polymer electrolyte incorporated with tetracyanoethylene (TCNE) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Compare with dielectric constant of pure PEO (k = 5), TCNE has high dielectric constant (k ≈ 148). The dielectric constant of polymer matrix increased to 50.83 by the incorporation TCNE into PEO. Hence, incorporating LiTFSI into PEO12-TCNE complex, the ion dissociation fraction was also increased from 42.61% to 77.88%. The DSC results showed that the melting temperature (Tm) shifted to low temperature region and glass transition temperature (Tg) also decreased. After incorporation of tetracyanoethylene, the maximum ionic conductivity was obtained as 1.11 × 10−4 S/cm at room temperature.

Joining of Hypereutectic Al-50Si Alloys Using Lead-Free Brazing Filler Glass in Air.

Hypereutectic Al-Si alloys are attractive materials in the fields of electronic packaging and aerospace. A Bi2O3-ZnO-B2O3 system lead-free brazing filler glass was employed to braze hypereutectic Al-50Si alloys in air. The hypereutectic Al-50Si alloys were pre-oxidized and the low-temperature glass powder was flake-shaped in the brazing process. The effects of brazing temperature and time on joints microstructure evolution, resulting mechanical strength, and air tightness were systematically investigated. The results indicated that the maximum shear strength of the joint was 34.49 MPa and leakage rate was 1.0 × 10−10 Pa m3/s at a temperature of 495 °C for 30 min. Crystalline phases, including Bi24B2O39 and Bi2O3, were generated in the glass joint. The formation of a diffusion transition layer with a thickness of 3 μm, including elements of Al, Si, Zn, Bi, Na, and B, was the key to form an effective joint. The elements of Al, Si, and Bi had a short diffusion distance while the elements of Zn, Na, and B diffused in a long way under brazing condition.

Study the atomistic structure of monatomic vanadium under different cooling rates by molecular dynamics simulation

We performed molecular dynamics (MD) simulations with the LAMMPS code in order to understand the rapid solidified processes of refractory body-centered-cubic (BCC) metals V under five different cooling rates (γ1 = 1 × 1011K/s, γ2 = 1 × 1012K/s, γ3 = 1 × 1013K/s, γ4 = 5 × 1013K/s, γ5 = 1 × 1014K/s). It is found that the evolution of energy, volume and density of V are strongly dependents on the cooling rates during the rapid solidification. By analyzing the Abraham-Wendt parameter, discovering the magnitudes of the first minimum and maximum of the radial distribution function (RDF) are more effective parameters for specifying the phase boundary between liquid and super-cooled liquid. Compared to the initial crystallizing occurred in the interface with linked atom chain, the growth model of vitrification is presented through icosahedral medium-range orders (IMROs) with shell structure cored by isolated icosahedra. Further analyzing the variation of the number of icosahedra (ICO), hexagonal-close-packed (HCP), face-centered-cubic (FCC) and BCC clusters as a function of temperature by polyhedral template matching method (PTMM), it is found that the variation of tracking clusters not only occurs in the liquid and super-cooled liquid, but also exist in low temperature region (below the crystallization temperature (Tc) or glass transition temperature (Tg)), which breaks through our previous understanding for the evolution of clusters should only in high temperature region rather than in lower temperature region. In addition, both of the evolution of the density field for crystal and non-crystal exhibited obviously non-homogeneous, which maybe lead to non-uniformity of nucleation and vitrification in some degree, respectively.

Fabrication of red-emitting CaAlSiN3: Eu2+ through phosphor-in-glass approach for application in rear combination lamp

In this study, the red-emitting phosphor-in-glass (PiG) using the CaAlSiN3: Eu2+ (CASN) phosphor is reported for the first time. The CASN: Eu2+ PiG samples with a maximum luminous flux of 25.1–29.4 for l minute at laser power of 1 W/mm2 was obtained using a low-temperature glass frit and GPS furnace. Despite the increase in the phosphor from 15 to 25 wt%, the PiG produced at low temperature of 380 °C showed robust properties. Finally, the red PiG module designed for rear lamp applications maintains over 90% lumens for a minute at 350 mA and achieves an intense red light having a color temperature of 4589 K.

A Simple Low-Temperature Glass Bonding Process with Surface Activation by Oxygen Plasma for Micro/Nanofluidic Devices.

The bonding of glass substrates is necessary when constructing micro/nanofluidic devices for sealing micro- and nanochannels. Recently, a low-temperature glass bonding method utilizing surface activation with plasma was developed to realize micro/nanofluidic devices for various applications, but it still has issues for general use. Here, we propose a simple process of low-temperature glass bonding utilizing typical facilities available in clean rooms and applied it to the fabrication of micro/nanofluidic devices made of different glasses. In the process, the substrate surface was activated with oxygen plasma, and the glass substrates were placed in contact in a class ISO 5 clean room. The pre-bonded substrates were heated for annealing. We found an optimal concentration of oxygen plasma and achieved a bonding energy of 0.33–0.48 J/m2 in fused-silica/fused-silica glass bonding. The process was applied to the bonding of fused-silica glass and borosilicate glass, which is generally used in optical microscopy, and revealed higher bonding energy than fused-silica/fused-silica glass bonding. An annealing temperature lower than 200 °C was necessary to avoid crack generation by thermal stress due to the different thermal properties of the glasses. A fabricated micro/nanofluidic device exhibited a pressure resistance higher than 600 kPa. This work will contribute to the advancement of micro/nanofluidics.

Photofunctional Cyclometalated Iridium(III) Polypyridine Complexes Bearing a Perfluorobiphenyl Moiety for Bioconjugation, Bioimaging, and Phototherapeutic Applications.

In this article, we report the design, synthesis, and characterization of a series of cyclometalated iridium(III) polypyridine complexes containing a perfluorobiphenyl (PFBP) moiety [Ir(N^C)2(bpy-PFBP)](PF6) (bpy-PFBP = 4-(S-(perfluoro-(1,1'-biphenyl)-4-yl)-N-mercaptoethylaminocarbonyloxymethyl)-4'-methyl-2,2'-bipyridine; HN^C = 2-phenylpyridine (Hppy) (1a), 2-(4-hydroxymethylphenyl)pyridine (Hppy-CH2OH) (2a), 2-((1,1'-biphenyl)-4-yl)pyridine (Hpppy) (3a), 2-((4'-hydroxymethyl-1,1'-biphenyl)-4-yl)pyridine (Hpppy-CH2OH) (4a), 2-phenylquinoline (Hpq) (5a), 2-(4-hydroxymethylphenyl)quinoline (Hpq-CH2OH) (6a)). Their PFBP-free counterparts [Ir(N^C)2(bpy-C4)](PF6) (bpy-C4 = 4-(N-n-butylaminocarbonyloxymethyl)-4'-methyl-2,2'-bipyridine; HN^C = Hppy (1b), Hppy-CH2OH (2b), Hpppy (3b), Hpppy-CH2OH (4b), Hpq (5b), Hpq-CH2OH (6b)) were also prepared for comparison studies. Upon irradiation, all the complexes displayed intense and long-lived greenish-yellow to orange luminescence in solutions under ambient conditions and in low-temperature alcohol glass. Reactions of the PFBP complexes with peptides containing the FCPF sequence via the π-clamp-mediated cysteine conjugation afforded luminescent peptide conjugates that exhibited rich photophysical properties. Using complex 3a as an example, we demonstrated that the conjugation of complexes to organelle-targeting peptides is an effective means to modulate their intracellular localization behavior, which was further shown to be important to their performance in photodynamic therapy. The results of this work will contribute to the development of photofunctional transition metal complexes as theranostic agents.

Evaluation of the Curing of Adhesive Systems by Rheological and Thermal Testing.

The analysis of thermal processes associated to the curing of adhesives and the study of mechanical behavior once cured, provide key information to choose the best option for any specific application. The proposed methodology for the curing characterization, based on thermal analysis and rheology, is described through the comparison of three commercial adhesives. The experimental techniques used here are Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Rheology. TGA provides information about the thermal stability and filler content, DSC allows the evaluation of some thermal events associated to the cure reaction and to thermal changes of the cured material when subjected to temperature changes. Rheology complements the information of the thermal transformations from a mechanical point of view. Thus, the curing reaction can be tracked through the elastic modulus (mainly the storage modulus), the phase angle and the gap. In addition, it is also shown that although DSC is of no use to study the curing of moisture curable adhesives, it is a very convenient method to evaluate the low temperature glass transition of amorphous systems.

Joining ZnS ceramics by using PbTiO3-doped PbO–B2O3–ZnO

ZnS ceramic has been extensively used in various optical applications, e.g., full-wave band infrared window. The attractiveness of this material is explained by its wider transmission radiation range and higher infrared transmittance. An infrared window has often to be bonded to the protective metal frame due to high risk of involving demanding operational conditions, e.g., a vibration. So, an innovative joining technique must be necessarily uncovered. The objective of this work was designed to use a low-temperature glass powder to directly solder/braze ZnS ceramics during the temperature range between 400 and 450 °C. Our hypothesis was that the mechanical strength between ZnS glass and PbO–B2O3–ZnO powder would be significantly enhanced by doping the solder/braze by PbTiO3 particles. The formed interfacial reaction layer consists of PbS and the uniformly dispersed PbTiO3 particles. A heuristic explanation of the bonding mechanism is offered, and it is found that the use of sintering remelting can reduce defects within the glass joints. Owning to the second-phase diffusion strengthening of PbTiO3 particles and an interfacial chemical bonding in the joint, the mechanical properties are enhanced.

Low Temperature Glass Sintering Based on Silico Sodium Resins

By using silicate inorganic binders and glass waste it is possible to mould technical and artistic elements which later can be compacted by means of low temperature, and subsequently apply the sintering through high-temperature processing, which is generally lower than current melting glass processes, close to 1250 °C. The experimental phase established thermal ranges from 600°C to 750°C, a fact that allows for an effective sintering temperature (of around 650°C/18 hours). The mixtures and proportions for this experiment were fixed including ethyl silicate as a fluidizer in mixtures,as well as the size of glass grains.The results indicate good compaction of the samples after the initial phase (80°C/24h), allowing proper handling without alterations in samples edges.During heating treatment, mechanical resistance increases gradually (600-750°C), although the volume of porosity was inversely proportional. According to the matrix vs grain size relationship, the partial fusion of both materials is evident in the rounding of the glass grains as well as the resin bonds joined between them. The resins appeared in a homogenous fashion, covering and gluing the grains, a development which improves the joining of sintered samples. Samples with a mixture of sodium silicate and ethyl silicate resins experienced less melting between grains due to a lower volume of fluxing elements, which means a lower percentage volume of sodium (Na). This study concludes that a sintering process for new vitreous composites could be carried out between 650°C and 700°C, offering the opportunity for a substantial reduction in the amount of energy required to produce industrial glass.
 Keywords: Water-glass, glass recycling, low temperature

LOOKING AT THE GLASS TRANSITION: CHALLENGES OF EXTREME TIME SCALES AND OTHER INTERESTING PROBLEMS

ABSTRACTThe behavior of glass-forming materials is examined with emphasis on the below-glass transition behavior. A major question that is related to the super-Arrhenius behavior of the dynamics of glass-forming systems is whether the apparent divergence at finite temperature continues below the kinetic or laboratory glass transition that is related to the limits of measurement and is standardized so that the material relaxation time is near 100 s. The problem arises because as the temperature decreases, the time scales required to reach equilibrium (or metastable equilibrium) become geologically long. Yet the apparent finite temperature divergence is fundamental to many theories of glasses; therefore, it becomes essential to find ways to finesse the extreme time scales related to the so-called Kauzmann paradox to bring new information to the ongoing conversation concerning the existence or not of an ideal glass transition at either the Kauzmann temperature or the Vogel–Fulcher–Tammann temperature. After describing the framework of the glassy state that is formed by the early ideas of a fictive temperature, we examine the use of extremely low fictive temperature glasses as a means to potentially get around the long time-scale problem. The challenge is to find ways to create such glasses and measure their properties. In addition to looking at the dynamic behavior of a 20-million-year-old amber and a vapor-deposited amorphous perfluoropolymer whose fictive temperature was the same as the Kauzmann temperature for the material, we also examine the possibility of directly testing the thermodynamics of an ideal glass transition by making athermal solutions of a poly(α-methyl styrene) and its pentamer, where we find that the entropy surface determined from extrapolation of the heat capacity to zero pentamer shows no distinct transition at as much as 180 K below the Kauzmann temperature. The significance of the dynamics of the stable glasses and the thermodynamics of the polymer solutions is discussed in terms that challenge the idea of an ideal glass transition. We also look in more detail at the ability to use vapor deposition to make ethylbenzene, a small-molecule organic, into an ultra-stable glass with a fictive temperature that is possibly below the Kauzmann temperature of this material. We end with remarks on the question of decoupling of different relaxation mechanisms as something not treated by current theories of glass, and we consider some open questions related to the fact that the glass transition remains an unresolved and important problem.

Acoustic resonance in periodically sheared glass: damping due to plastic events.

Using molecular dynamics simulation, we study acoustic resonance in a low-temperature model glass by applying a small periodic shear at a boundary wall. Shear wave resonance occurs as the frequency ω approaches ωl = πc⊥l/L (l = 1, 2…). Here, c⊥ is the transverse sound speed and L is the cell width. At resonance, large-amplitude sound waves appear after many cycles even if the applied strain γ0 is very small. They then induce plastic events, which are heterogeneous on the mesoscopic scale and intermittent on timescales longer than the oscillation period tp = 2π/ω. We visualize them together with the extended elastic strains around them. These plastic events serve to damp sounds. We obtain the nonlinear damping Q-1 = tan δ due to the plastic events near the first resonance at ω ≅ ω1, which is linear in γ0 and independent of ω. After many resonant cycles, we observe an increase in the shear modulus (measured after switching-off the oscillation). We also observe catastrophic plastic events after a very long time (∼103tp), which induce system-size elastic strains and cause a transition from resonant to off-resonant states. At resonance, stroboscopic diffusion becomes detectable.

Electron Paramagnetic Resonance in HoxLu1−xB12 Dodecaborides

The high-frequency (60 GHz) electron paramagnetic resonance is studied in HoxLu1−xB12 single crystals at low temperatures (2–80 K) in an applied magnetic field up to 7 T within a wide doping range, 0.01 ≤ x ≤ 1. These compounds are characterized by the presence of a low-temperature cage glass phase with random displacements of magnetic holmium ions from the centrosymmetric position in B12 boron cuboctahedra. For the samples with x ≥ 0.1, it is demonstrated that the electron paramagnetic resonance in the form of a single broad line with a g-factor of about 5 appears in the cage glass phase at T 0.3, the pronounced broadening of the resonance line and a steep decrease in the g-factor related to antiferromagnetic correlations is observed on cooling at T < 30 K. The performed simulation of the electron paramagnetic resonance spectra suggests the dominant role of the exchange interaction effects and positional disorder in determining the characteristic features of spin dynamics in HoxLu1−xB12.

Luminescent Molecular Octopuses with a Polyhedral Oligomeric Silsesquioxane (POSS) Core and Iridium(III) Polypyridine Arms: Synthesis, Aggregation Induced Emission, Cellular Uptake, and Bioimaging Studies.

A new class of luminescent molecular hybrids in which eight cyclometalated iridium(III) polypyridine complexes are grafted onto a polyhedral oligomeric silsesquioxane (POSS) unit [POSS-{Ir(N^C)2 (py-im)}8 ](PF6 )8 [py-im=pyridine imine; HN^C=N-phenylpyrazole (Hppz) (1 a), 2-phenylpyridine (Hppy) (2 a), 2-phenylquinoline (Hpq) (3 a)] were synthesized and characterized. On photoexcitation, the complexes showed intense and long-lived orange-red to red emission in fluid solutions at room temperature and in low-temperature glasses. The photophysical properties including aggregation-induced emission and biological properties of these complexes were studied and compared with those of their POSS-free counterparts [Ir(N^C)2 (py-im)](PF6 ) [HN^C=Hppz (1 b), Hppy (2 b), Hpq (3 b)]. The (photo)cytotoxicity of the complexes was examined by the MTT assay, and their cellular uptake and intracellular localization were investigated by inductively coupled plasma-mass spectrometry and laser-scanning confocal microscopy.

Isolating Single Euglena gracilis Cells by Glass Microfluidics for Raman Analysis of Paramylon Biogenesis.

Time-course analysis of single cells is important to characterize heterogeneous activities of individual cells such as the metabolic response to their environment. Single-cell isolation is an essential step prior to time-course analysis of individual cells by collecting, culturing, and identifying multiple single-cell targets. Although single-cell isolation has been performed by various methods previously, a glass microfluidic device with semiclosed microchannels dramatically improved this process with its simple operation and easy transfer for time-course analysis of identified single cells. This study demonstrates isolating single cells of the highly motile microalgae, Euglena gracilis, by semiclosed microchannels with liquid flow only. The isolated single cells were identified in isolating channels and continuously cultured to track, by Raman microscopy, for the formation of subcellular granules composed of polysaccharide paramylon, a unique metabolite of E. gracilis, generated through photosynthesis. Through low-temperature glass bonding, a thin glass interface was incorporated to the microfluidic device. Thus, the device could perform the direct measurements of cultured single cells at high magnification by Raman microscopy with low background noise. In this study, the first demonstration of sequential monitoring of paramylon biogenesis in a single identified E. gracilis cell is shown.

Tunable white light in trivalent europium single doped tin fluorophosphates ultra-low melting glass

In recent years, low melting temperature glasses have received wide attention as the hosts of phosphor-converted light emitting diodes (pc-WLED). In this work, a series of trivalent europium doped tin fluorophosphates glasses were prepared by conventional melting method. Under ultraviolet excitation, the blue-green broadband emission from Sn2+ activation centers in the glass matrix and the red emission of Eu3+ ions together constituted a cool white luminescence. The spectra analysis was used to demonstrate the energy transfer between Sn2+ centers and Eu3+ ions. The results showed that Sn2+ and Eu3+ possessed independent intrinsic emission and mutual energy transfer simultaneously. The 5D4 and 5G2 excited states of Eu3+ ion favored the energy transfer to Sn2+ center, the 5L6 excited state of Eu3+ ion would absorb more of the energy by the Sn2+ ground state excitation to contribute on red emission. Therefore, the fluorescent glass can transform cool white light to warm white light by changing the excitation wavelength. The tunable white light is obtained in the WLED devices built with the glass and commercial UV chips.

Potable water by solar thermal distillation in solar salt works and performance enhancement by integrating with evacuated tubes

Solar salt farms are located in remote coastal regions where the ground water is saline. During the salt harvesting season, the salt workers face difficulties owing to shortage of potable water at-site. Nevertheless such locations are blessed with plenty of sunshine and in-situ desalination for potable water in solar distillation system or still, benefits the workers to a great extent. Since such solar stills are directly applied in field, the design and operation approach ought to be such, that water output is high and maintenance easy. In this work, we report analysis of stepped type basin still and enhancement of output by integrating with evacuated tube collectors (ETC). The average augmentation of productivity was 24% by the integration during the period of March to May 2018. The study of warm feed water charging time from ETC was an important aspect and it was found that highest production could be obtained by night-charging, due to low top glass temperature which led to increased condensation and more productivity. 8.1 L per day from 2 m2 basin area was the maximum productivity from ETC integrated unit. The novelty of the work involves incorporation of particular operational features like (a) single basin stepped tilted absorber with triangular exposure area, avoiding shadow effect; (b) distance between glass and water surface minimum for facile evaporation; (c) easy cleaning of the deposited salts by overflowing water from tilted surface; and (d) endurance of glass tubes of ETC in corrosive salty environment.

Structural switch for fast switching

Phase-Change Memory Phase-change materials are important for computer memory. They can quickly switch from glassy to crystalline using a thermal pulse and then lock in that structure for a long time at lower temperature. Zalden et al. probed the underlying atomic structure of two phase-change materials during this switching using ultrafast x-rays and simulations (see the Perspective by Rao et al. ). A liquid-liquid phase transition in both materials allowed fast switching at high temperatures. The lower-temperature glass locks in the structure, allowing for long-term memory storage. Science , this issue p. [1062][1]; see also p. [1032][2] [1]: /lookup/doi/10.1126/science.aaw1773 [2]: /lookup/doi/10.1126/science.aax6333

Viscous Flow Behavior of (90-x)SiO2-xNa2O-10RO (x = 15–40) Glasses with Low Sintering Temperature

Silicate glasses with varying SiO2 and Na2O contents were prepared and their viscous flow property at the elevated temperature was studied. When the glass powders were packed and sintered at 550°C to examine their feasibility as a low sintering temperature glass frit, contrary to expectations, glasses with lower SiO2 content than 60 mol% showed no vitrification after sintering. High temperature microscopy revealed the viscous flow change of the silicate glasses with varying temperature and duration time and also indicated that the viscous flow was limited at low SiO2 content. X-ray diffraction (XRD) on the sintered samples and Raman spectroscopy were carried out to shed light on the compositional dependency of viscous flow of silicate glasses. Key words: Silicate, Glass, Glass frit, Viscosity