Molten Glass Surface Research Articles

Thermo‐rheological snapshot of melter feed conversion to glass

AbstractSlurry feed charged into an electric melter creates a layer of reacting and melting material (termed cold cap) that floats on the surface of molten glass. The rheological behavior of heated melter feed affects the spreading of slurry at the top of the cold cap and the stability of the primary foam, affecting cold‐cap coverage and melter plenum temperatures. The apparent viscosity of a high‐alumina high‐level waste melter feed was assessed by thermomechanical analysis, high‐temperature viscometer, and the hot stage microscopy method, yielding viscosity estimates from ≈107.5 Pa s at 550°C to ≈102.5 Pa s at 1050°C. As the temperature of feed materials increased, their state changed from rigid solid to dilatant fluid, to pseudoplastic bubbly liquid with dissolving solids, to fully developed foam, and finally to Newtonian glass melt.

Ultrafast Growth of Large‐Area Uniform, Millimeter‐Size MoSe2 Single Crystals on Low‐Cost Soda‐Lime Glass

Abstract2D semiconducting transition metal dichalcogenides (TMDCs) have emerged as essential building blocks for engineering next‐generation integrated electronics. To achieve this, the controllable synthesis of monolayer TMDCs with high crystal quality, low cost, and high yield is crucial, while it remains challenging. Herein, the direct synthesis of large‐area uniform, millimeter‐size monolayer MoSe2 single crystals on a 6‐centimeter‐long soda‐lime glass template, by using a designed “beam‐bridge” assisted metal oxide precursor feeding strategy via chemical vapor deposition (CVD), is reported. Notably, several tenths of millimeter‐scale, triangular‐shaped monolayer MoSe2 single crystals are obtained in one batch within 25 s’ growth, affording so far the fastest growth rate (≈50 µm s−1). This ultrafast growth behavior is proposed to be mediated by the sufficient, homogeneous release of Mo‐based precursor, the catalytic property of sodium atoms on soda‐lime glass substrate, as well as the improved surface kinetics on the molten glass surface. Moreover, the thickness‐controlled growth from monolayer to bilayers is also realized. This work provides brand new insights for the batch production of large single‐crystal TMDCs, which should propel its practical applications in versatile fields.

Improved Design of Two-Screw Batch Charger for Glass Furnaces

An improved design of a two-screw batch charger for glass furnaces is presented. It is noted that a change in the shape of the pushing shutter equipped with two trapezoidal side sections makes it possible to optimize by means of an additional pivot turn of the pusher arm around its axis the distribution of the batch over the molten-glass surface in a sealed doghouse.

Resources and Problems of the Mathematical Simulating Thermo-Technological Processes

The paper presents the combustion of natural gas in a short flame in entourage of the very hot air had produced extremely elevated temperature of the flame, reaching 2300...2500 °C at the front of burning. In the stagnant part of the gas space beyond the short flame, the temperature of gases had gone down, approaching gradually to temperature of the molten-glass surface. As it is well known, a relatively low temperature level of the stagnant gas space allows zones of glass cooling to be organized at the end of the molten-glass basin of the glass furnaces with returned gas flow.

Influence of the bulk diffusion of rubidium and sodium atoms in glass on their surface dwell time

This paper presents the results of measurement of the surface potential and the dwell time of Rb and Na atoms on the surface of S-52 molybdenum glass. It is found that at temperatures below the glass transition temperature, the temperature dependence of the dwell time of Rb atoms is well described by the Arrhenius formula. The surface potentials for Rb and Na are measured to be 0.67 and 1.37 eV, respectively. At temperatures above the glass transition temperature, the dwell time of these atoms increases abnormally. The reason for this is that during impact of an atom on the surface of molten glass, it can penetrate into the volume of the window and then return by diffusion and desorb from the surface. In this case, the dwell time of the atom on the glass is determined by the diffusion time and can be very significant, despite the relatively low potential barrier at the surface and high temperature.

Chemical Vapor Deposition of Large-Size Monolayer MoSe2 Crystals on Molten Glass.

We report the fast growth of high-quality millimeter-size monolayer MoSe2 crystals on molten glass using an ambient pressure CVD system. We found that the isotropic surface of molten glass suppresses nucleation events and greatly improves the growth of large crystalline domains. Triangular monolayer MoSe2 crystals with sizes reaching ∼2.5 mm, and with a room-temperature carrier mobility up to ∼95 cm2/(V·s), can be synthesized in 5 min. The method can also be used to synthesize millimeter-size monolayer MoS2 crystals. Our results demonstrate that "liquid-state" glass is a highly promising substrate for the low-cost growth of high-quality large-size 2D transition metal dichalcogenides (TMDs).

Nuclear waste vitrification efficiency: Cold cap reactions

Batch melting takes place within the cold cap, i.e., a batch layer floating on the surface of molten glass in a glass-melting furnace. The conversion of batch to glass consists of various chemical reactions, phase transitions, and diffusion-controlled processes. This study introduces a one-dimensional (1D) mathematical model of the cold cap that describes the batch-to-glass conversion within the cold cap as it progresses in a vertical direction. With constitutive equations and key parameters based on measured data, and simplified boundary conditions on the cold-cap interfaces with the glass melt and the plenum space of the melter, the model provides sensitivity analysis of the response of the cold cap to the batch makeup and melter conditions. The model demonstrates that batch foaming has a decisive influence on the rate of melting. Understanding the dynamics of the foam layer at the bottom of the cold cap and the heat transfer through it appears crucial for a reliable prediction of the rate of melting as a function of the melter-feed makeup and melter operation parameters. Although the study is focused on a batch for waste vitrification, the authors expect that the outcome will also be relevant for commercial glass melting.

Distribution of impurities on nonlattice substraes influence for fractal aggregates

According to the experimental observation of Au atomic aggregations on a molten glass surface, we established a computational model to simulate Improved Restricted Cluster-Cluster Aggregation (IRCCA) on nonlattice substrates with regularly and randomly distributed impurities. In the model, the random diffusion step and rigidity rotation around the mass center of cluster were considered. The aggregation process was simulated and the influence of the distribution of impurity on the properties of aggregations was systemically investigated. The results show that regularly distributed impurities play a more important role in restricting the aggregation of clusters than randomly distributed impurities, resulting in a higher number density of fractal aggregates with smaller radius of gyration and fractal dimension.

A numerical investigation on the thermal impact of foam on an oxy-fuel-fired glass furnace

Gas evolution during the melting and refining of raw materials in glass melting furnaces may result in the formation of a layer of foam on the molten glass surface. The foam layer presents an additional thermal resistance to melting and refining between the furnace crown and combustion products and the raw materials/molten glass. A simple foam thermal model has been incorporated into an advanced comprehensive model for the prediction of the primary thermal phenomena in a prototypical oxy-fuel-fired industrial glass furnace. Heat fluxes and temperatures at the interfaces between the combustion space, the batch, the glass melt tank and the foam layer are calculated in an iterative procedure in order to simulate the entire furnace in an integrated fashion. The thermal impact of the foam on furnace behaviour is studied by comparing model simulations using different values of foam thickness and effective thermal conductivity in a 150-tonne-per-day, oxy-fuel-fired glass furnace to predictions in the same furnace without the presence of foam. The numerical results obtained quantify the effect of foam on important furnace operating parameters such as glass surface temperature, crown temperature and exhaust gas temperature.

Compositional Heterogeneity in NIST SRM 610‐617 Glasses

Extensive compositional heterogeneity is shown to affect at least twenty four of the doped trace elements in the NIST SRM 610‐617 glasses.Compositional profiling and mapping using laser ablation ICP‐MS reveals that all NIST SRM 610‐617 wafers examined here contain domains that are significantly depleted in Ag, As, Au, B, Bi, Cd, Cr, Cs, Mo, Pb, Re, (Rh), Sb, Se, Te, Tl and W, and antithetically enriched in Cu (and Pt), with large enrichments in Cd, Fe and Mn also being encountered in some cases. These domains are visible in doubly polished wafers by unaided visual inspection and by transmitted light and schlieren microscopy. They occur in close proximity to the wafer perimeters and also as stretched and complexly folded forms within wafer interiors. The chemical and optical properties of these heterogeneous domains are consistent with those of compositional cords, a phenomenon of glass manufacture where glass bulk composition and physical properties are modified by loss of volatile components from the molten glass surface. The NIST SRM 610‐617 glasses may be considered reliable reference materials for microanalysis of only between one half and two thirds of the trace elements with which they were doped, including Be, Mg, Sr, Ba, Sc, Y, REE, V, Zr, Hf, Nb, Ta, Th, U, Ga, In, Sn, Co, Ni and Zn. These elements show no evidence of significant heterogeneity, indicating that the original glass constituents and possible residues remaining in the furnace from preceding glass batch fusions were well homogenised during manufacture.

Laser-Induced Breakdown Spectroscopy for the On-Line Multielement Analysis of Highly Radioactive Glass Melt Simulants. Part II: Analyses of Molten Glass Samples

The paper presents the application of laser-induced breakdown spectroscopy (LIBS) for the on-line multielement analyses of glass melts in a vitrification process of high level liquid waste (HLLW). The third harmonic pulse of an Nd:YAG laser is used for the generation of plasma on the molten glass surface and the plasma emission is monitored by an echelle spectrometer with an intensified charge-coupled device (ICCD), which simultaneously covers the wavelength range from 200 to 780 nm. Twelve different reference HLLW glass melts with a complex composition of about 27 chemical elements are simulated on a laboratory scale, varying the HLLW component concentration. By real-time analyses of the reference glasses at 1200 °C, the analytical method is calibrated. A multivariate regression approach with partial least squares (PLS) is used for the data evaluation. The LIBS method thus calibrated is then applied for the multielement analysis of molten glass samples from the prototype vitrification plant under operation in our institute. The results underline that the LIBS method can be applied to a vitrification process for the on-line multielement analysis of highly radioactive glass melts.

AGGREGATION CHARACTERISTICS OF GOLD ATOMS DEPOSITED ON MOLTEN GLASS SURFACES

The diffusion,aggregation and crystallization characteristics of gold atoms deposited on molten glass surfaces are studied.Experimental results indicate that the gold atoms first form a characteristic web-shaped Au film on the colloid glass surface,and the average diameter of the crystal grains in the film is about 20 nm.The area of the meshes gradually increases and then the whole film tatters.Thus the compact clusters are formed.The saturated diameter of the compact clusters is about 1.2μm and its diffusion coefficient D is of the order of 107—108cm2/s.The compact clusters diffuse on the molten glass surface quickly and quasi-randomly,and finally large ramified aggregates with diameter of about 50 μm from.

Device for removing siliceous foam from the surface of molten glass

Device for removing siliceous foam from the surface of molten glass