Glass Processing Techniques Research Articles

Low-temperature 3D printing of transparent silica glass microstructures.

Transparent silica glass is one of the most essential materials used in society and industry, owing to its exceptional optical, thermal, and chemical properties. However, glass is extremely difficult to shape, especially into complex and miniaturized structures. Recent advances in three-dimensional (3D) printing have allowed for the creation of glass structures, but these methods involve time-consuming and high-temperature processes. Here, we report a photochemistry-based strategy for making glass structures of micrometer size under mild conditions. Our technique uses a photocurable polydimethylsiloxane resin that is 3D printed into complex structures and converted to silica glass via deep ultraviolet (DUV) irradiation in an ozone environment. The unique DUV-ozone conversion process for silica microstructures is low temperature (~220°C) and fast (<5 hours). The printed silica glass is highly transparent with smooth surface, comparable to commercial fused silica glass. This work enables the creation of arbitrary structures in silica glass through photochemistry and opens opportunities in unexplored territories for glass processing techniques.

A Temperature-Insensitive Bidimensional Curvature Sensor Employing C-Fiber-Based Fabry–Pérot Air Cavity

A bidirectional curvature sensor based on C-fiber-based Fabry-Pérot interferometer (FPI) is proposed and validated in this work. Well-established glass processing techniques and fiber drawing procedures are used to fabricate the C-fiber, which is then fusing-spliced between two single-mode fibers (SMFs) to form an FPI. When the FPI cavity undergoes bending deformation, the variation of the optical path will cause a change of the interference phase difference, resulting in a spectral shift. The shifting direction of the interference spectrum could also be used to identify the bending direction. Moreover, the FPI cavity length has a direct influence on the curvature sensing performance of the proposed sensor, and the smaller the length, the higher the sensitivity. Bending measurement and orientation recognition are experimentally investigated in two opposite directions, namely, the 0°and 180°direction. The maximum sensitivity as high as 3.434 nm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> is obtained within a curvature range of 0.373-1.585 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in the 0°direction using a FPI cavity length of 104.81 um. It also features a low thermal sensitivity of 0.893 pm/°C. The proposed sensor is ultra-compact, easy-to-fabricate and cost effective, which makes it a promising candidate for the bending monitoring at some specific points or ultra-short distances, such as the bend-determination of joint of a robot arms or micron-scale thin films.

In-depth comparison of conventional glass cutting technologies with laser-based methods by volumetric scribing using Bessel beam and rear-side machining.

With the development of industrial lasers and novel glass processing techniques, which offer high speed, quality and precision, this becomes an attractive alternative to conventional methods, such as mechanical scribing and cleaving, diamond saw and waterjet cutting, commonly used in the industry. However, the emerging techniques lack thorough validation with respect to well-established methods. To this end, we present a detailed comparison of different glass cutting methods, taking into account surface quality, side-wall roughness, residual stresses and flexural strength. In addition, samples were examined after fracture, and the flexural strength was estimated according to the quarter elliptical corner flaws, which were the main reason of glass failure. Two laser glass processing techniques were investigated - the rear-side glass processing with tightly focused nanosecond laser pulses and sub-nanosecond laser volumetric scribing with asymmetrical Bessel beam. Results were compared to mechanical scribing and breaking, diamond saw and waterjet cutting.

Multi-objective optimization of glass multi-station bending machining for smartphone curved screen

Glass multi-station bending machining (GMBM) is a high-precision and efficient glass processing technique for smartphone curved screen in 3C industry. In this paper, simulation model of the GMBM of smartphone curved screen was researched by using MSC Marc software. The stress relaxation and structural relaxation models of glass material were used in the numerical model to accurately predict the forming process of the glass component. The effects of process parameters of GMBM, namely heating rate (HR), holding time, bending temperature (BT), bending pressure and cooling rate (CR), on the product quality characteristics (residual stress and shape deviation) and energy efficiency were analyzed based on orthogonal experiments. It can be found that the BT, CR and HR have extremely important effects on product residual stress, shape deviation and energy efficiency. Furthermore, a multi-objective optimization method based on NSGA-III (a non-dominant sorting genetic algorithms based on reference points) was applied to efficiently solve the optimization problem between glass product quality and energy efficiency. The optimal parameter schemes with high quality and low energy efficiency were obtained by the Pareto front of multi-objective, and the average prediction errors of the numerical results by the optimized schemes are no more than 20% through confirm experiments. The optimized schemes improve the stability of the process of GMBM, which can deal with the challenge of green manufacturing.

Mechanism of electric field-induced softening (EFIS) of alkali silicate glasses

Electric field-induced softening (EFIS) has been suggested as an innovative glass processing technique to reduce the furnace temperature required for softening of alkali silicate glasses. Although its overall mechanism was proposed previously, further investigation is required to fully understand the beginning of the EFIS process from initial polarization onwards. Accordingly, we have investigated the effect of externally applied DC voltage across glass on thermally stimulated currents during EFIS. The role of alkali ion migration has been investigated using two binary alkali (lithium and sodium) disilicate glasses, two mixed alkali lithium-sodium disilicate glasses and a sodium aluminosilicate glass of varying electrical resistivity. Comparison of thermally stimulated poling currents between single and mixed-alkali disilicate glasses has delineated the role of alkali ion migration and charge transport mechanisms. Activation energies corresponding to polarization mechanisms and charge transport processes have been calculated from experimental data. Based on these observations, the complex viscous flow response of glass during EFIS is explained as comprising of following phenomena: the formation of an alkali ion depletion layer, development of large internal electric fields, electrolysis and charge injection processes followed by dielectric breakdown, ultimately leading to thermal runaway by resistive heating.

Magnetic polymer nanocomposites for environmental and biomedical applications

Hybrid nanomaterials have received voluminous interest due to the combination of unique properties of organic and inorganic component in one material. In this class, magnetic polymer nanocomposites are of particular interest because of the combination of excellent magnetic properties, stability, and good biocompatibility. Organic–inorganic magnetic nanocomposites can be prepared by in situ, ex situ, microwave reflux, co-precipitation, melt blending, and ceramic–glass processing and plasma polymerization techniques. These nanocomposites have been exploited for in vivo imaging, as superparamagnetic or negative contrast agents, drug carriers, heavy metal adsorbents, and magnetically recoverable photocatalysts for degradation of organic pollutants. This review article is mainly focused on fabrication of magnetic polymer nanocomposites and their applications. Different types of magnetic nanoparticles, methods of their synthesis, properties, and applications have also been reviewed briefly. The review also provides detailed insight into various types of magnetic nanocomposites and their synthesis. Diverse applications of magnetic nanocomposites including environmental and biomedical uses have been discussed.

Gas bubble formation in fused silica generated by ultra-short laser pulses.

During processing of glass using ultra-fast lasers the formation of bubble-like structures can be observed in several glass types such as fused silica. Their formation can be exploited to generate periodic gratings in glasses but for other glass processing techniques such as waveguide-writing or glass welding by ultra-fast lasers the bubble formation proves often detrimental. In this work we present experiments and their results in order to gain understanding of the origins and on the underlying formation and transportation mechanisms of the gas bubbles.

In-plane spectroscopy with optical fibers and liquid-filled APEX™ glass microcuvettes

Chemical etching and laser drilling of microstructural glass results in opaque or translucent sidewalls, limiting the optical analysis of glass microfluidic devices to top down or non-planar topologies. These non-planar observation topologies prevent each layer of a multilayered device from being independently optically addressed. However, novel photosensitive glass processing techniques in APEX™ have resulted in microfabricated glass structures with transparent sidewalls. Toward the goal of a transparent multilayered glass microfluidic device, this study demonstrates the ability to perform spectroscopy with optical fibers and microcuvettes fabricated in photosensitive APEX™ glass.

Integrated chalcogenide waveguide resonators for mid-IR sensing: leveraging material properties to meet fabrication challenges

In this paper, attributes of chalcogenide glass (ChG) based integrated devices are discussed in detail, including origins of optical loss and processing steps used to reduce their contributions to optical component performance. Specifically, efforts to reduce loss and tailor optical characteristics of planar devices utilizing solution-based glass processing and thermal reflow techniques are presented and their results quantified. Post-fabrication trimming techniques based on the intrinsic photosensitivity of the chalcogenide glass are exploited to compensate for fabrication imperfections of ring resonators. Process parameters and implications on enhancement of device fabrication flexibility are presented.

Progress and Perspective of Processing Glass Forming Melts in Low Gravity

A review of the results from previous low-gravity experiments conducted on glass-forming melts is presented with particular emphasis on nucleation, crystallization, glass formation, and chemical homogeneity for high-temperature melts in low gravity. A review of this kind is important for 1) understanding the kinetics of glass formation (conversely, nucleation and crystallization) and the mechanism(s) of homogenization of high-temperature melts in low gravity, 2) avoiding duplication in future low-gravity experiments, and 3) properly utilizing low-gravity conditions for improving present-day glass processing techniques and, hence, the quality of glasses on Earth. It is consistently observed that glasses prepared in low gravity are more chemically homogeneous and more resistant to crystallization than those of the comparable glasses prepared on Earth, which is somewhat surprising. A hypothesis based on shear thinning of a melt is proposed as an explanation for these low-gravity results. A scheduled flight experiment, whose purpose is to acquire data on nucleation and crystal growth kinetics for Li 2 O.2SiO 2 glass prepared in low gravity, is discussed.

A micromachined pressure/flow-sensor

The micromechanical equivalent of a differential pressure flow-sensor, well known in macro mechanics, is discussed. Two separate pressure sensors are used for the device, enabling to measure both, pressure as well as volume flow-rate. An integrated sensor with capacitive read-out as well as a hybrid, piezo-resistive variant is made. The fabrication processes are described, using silicon and glass processing techniques. Based on the sensor layout, equations are derived to describe the sensor behavior both statically as well as dynamically. With the derived equations, the working range of the sensor and the thermal and time stability is estimated. The computed results of the stationary behavior are verified with the measured data. A good similarity in linearity of the pressure/flow relation is found. The computed hydraulic resistance, however, differs from the measured value for water with 21%. This difference can be explained by the high sensitivity of the resistance to the resistor channel cross-section parameter in combination with the difference between the rounded etched shape and the rectangular approximation. From fluid dynamics simulations, a working range bandwidth of about 1 kHz is expected. Thermal influences on the sensor signal due to viscosity changes are in the order of 2% flow signal variation per Kelvin. From these results, it can be concluded that the sensor can be used as a low cost, low power consuming flow and pressure-sensing device, for clean fluids without particles and without the tendency to coat the channel walls. If a high accuracy is wanted, an accurate temperature sensing or controlling system is needed.

Polymeric Precursors for Inorganic Materials

Abstract Standard ceramic processing centers around the growth, compaction, and sintering of compact colloidal particles. Recently, however, it has become clear that numerous glass and ceramic processing techniques cannot be understood in terms of standard colloid physics. The purpose of this talk is to demonstrate several areas where polymer concepts are not only necessary for the understanding of ceramic processing, but also provide the insights necessary to tailor the properties of ceramic materials to achieve specific goals. The talk will center on the polymerization of silicates in solution. By control of the growth conditions such as catalysis, pH, and reaction sequence, it is possible to create a variety of structures from dense colloidal particles to randomly branched polymers. By mapping the polymerization process onto simple fractal models, it is possible to identify the essential factors that control the structure.

High Tc superconductivity in Bi[sbnd]Ca[sbnd]Sr[sbnd]Cu[sbnd]O-based materials synthesized via glass ceramic methods

Superconducting glass ceramics composed of quasi-oriented platelets 100 to 600μ in size have been obtained by controlled heat treatment of glasses with compositions in the Bi2(CaSr)n+1CunOy (n=1,2,3) family. Samples have Tc=85 K, reaching zero resistance around 70 K. This method of preparation allows for the use of glass processing techniques to form superconducting devices.

ChemInform Abstract: MELT PROCESSING AND PROPERTIES OF BARIUM‐SIALON GLASSES

Bulk oxynitride glasses in the system Ba-Sialon were prepared by cooling homogenized melts from ∼1740°C at ∼50°C/min. The microchemistry, microstructure, and properties of these materials were studied by DTA, dilatometry, electron microscopy, and energy dispersive X-ray analysis. Up to ∼7 at.% nitrogen was retained in the glasses by the conventional glass-processing techniques used. Microscopically homogeneous glasses were obtained despite macroscopic segregation of millimeter-sized metallic spheres consisting of Si and Fe. Incorporation of nitrogen in the glass network led to decreasing thermal expansion coefficients, higher glass-transition temperatures, and greater values of indentation hardness with increasing nitrogen content.

Melt Processing and Properties of Barium-Sialon Glasses

Bulk oxynitride glasses in the system Ba-Sialon were prepared by cooling homogenized melts from ∼1740°C at ∼50°C/min. The microchemistry, microstructure, and properties of these materials were studied by DTA, dilatometry, electron microscopy, and energy dispersive X-ray analysis. Up to ∼7 at.% nitrogen was retained in the glasses by the conventional glass-processing techniques used. Microscopically homogeneous glasses were obtained despite macroscopic segregation of millimeter-sized metallic spheres consisting of Si and Fe. Incorporation of nitrogen in the glass network led to decreasing thermal expansion coefficients, higher glass-transition temperatures, and greater values of indentation hardness with increasing nitrogen content.