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Congratulations on “United Nations International Year of Glass 2022.” I would like to acknowledge the efforts made by the International Commission on Glass with the Community of Glass Associations and the Glass Art Society to promote the status of glass. I am very much pleased to contribute an article on the birth of the sol–gel method and its growth in early times for a Special Issue of Journal of Sol–Gel Science and Technology, which is published to celebrate the Year of Glass. At present, the sol–gel method is employed not only for manufacturing optical glass fibers for communication, but also for processing a wide range of functional, high technology materials, such as photonic, electronic, micromechanical, chemical, and bionic materials. The sol–gel method typically involves the following steps: (1) starting from a solution containing pure precursors, (2) conversion of the solution to a sol and then to a gel by hydrolysis and polycondensation, (3) forming into desired shapes such as bulk, film, and fiber during gelation of the sol, and (4) thermal treatment of the gel into a solid material at low temperatures. It should be noted, however, that there are many variants. For instance, the method of fabrication of a solid material by heating the shaped compact of gel powders prepared from a solution or sol is also called the “sol–gel method.” In this case, “starting from a solution” is important.

Glass meeting the GOST requirements concerning stria-free category-1 optical glass was produced in the system Me2O–Ga2O3–GeO2–SiO2 (Me = Li, Na). The subsequent heat treatment results in the precipitation of γ-Ga2O3 nanocrystals in it and triggering of luminescence excited by only UV radiation in the solar-blind range. The integral visible-light transmission and luminescence intensity of the developed material are comparable with these characteristics of glass-crystalline samples for which the glass was obtained by the melt quenching method.

Quantification of friction may provide insights into the material removal behavior of polishing process. In this study, frictional force at the workpiece-polisher interface is measured using customised instrumentation setup (miniature load cell: 0–25 lbf) at different combinations of process parameters during polishing of BK7 optical glass. It is observed that frictional force varies with polishing time and is also a function of process parameters. It is observed that friction coefficient (~0.1) indicates the ductile material removal from the workpiece surface while friction coefficient (~0.3) indicates ductile cum brittle fracture behavior, which is also verified through surface texture observed through optical interferometer. Friction coefficient indicates that workpiece and polisher surfaces are in solid-solid contact mode. Hence, mechanical actions are dominant over chemical actions in removing the material from workpiece surface. Further variation of surface parameters w.r.t. wear index is estimated and way to enhance the polishing process efficiency is suggested.

The microstructures arrays are widely used and have good prospects in different applications because of their special and unique engineering functions. Micro V-grooves array is one of the most common micro structures used for optical and biomedical functions. Precision grinding is one of the micro mechanical machining technologies for a wide range of hard non-ferrous materials to fabricate micro structures array. In this paper, a three-axis computer numerical control (CNC) grinding machine tool is designed for the grinding of micro V-grooves array on hard and brittle materials. Material removal and machining strategy are studied for the grinding of V-grooves array. A machining strategy design (MSD) system is established to generate NC program, simulate the tool paths and machining process as well as predict the total machining time for the grinding of V-grooves array in the developed machine tool. Experiments are designed to grind flat surface and micro V-grooves array on optical glass. The experimental results show that the grinding machine tool can produce high quality surface and micro V-grooves array with sub-micrometer form accuracy.

Optical glass K9 is a critical kind of optical materials, however experiments have indicated that the mechanical grinding of K9 easily led to subsurface damage (SSD). Although substantial SSD measurement methods have been suggested, the problems including the prior knowledge of SSD and slow measurement speed still impede the reported method applications. To this end, this paper has presented an image-process-based method that can identify and measure the grinding-induced SSD in K9 specimens. By performing grinding trials, the method has been found to be able to accurately (with biggest relative error of 3.13% in comparison with the manually measured results) and quickly (with the measurement speed of 1.68 s per image) measure SSD depths. Without any parameter presetting, the method enables automatic SSD measurements, allowing the users without SSD knowledge to be able to use the method. Moreover, the method has shown the good robustness to the input image size, illumination, tilted specimen placement, and material flaws. The method is therefore anticipated to be meaningful for the industrial manufacturing, design and application of optical glass.

Subsurface damages (SSD) induced during grinding of brittle materials influence mechanical and physical properties of the machined specimen. Experimental evaluation of SSD is very expensive and time consuming due to need for performing various grinding testes in one hand and post-grinding processes such as angle polishing in another hand. Meanwhile, theoretical investigation lacks accuracy due to the various simplifications involved with theoretical models. Hence, a numerical study was performed to analyze SSD in optical glass grinding using finite element method. The constitutive material behavior of glass was defined based on the Johnson-Holmquist model. Performing FEM simulations, the SSD depth was obtained for various combinations of process parameters. Based on the statistical analysis of variance, feed velocity was found to be the most significant parameter followed by depth of cut and cutting velocity. The numerical results were then compared with experimental observations using angle polishing technique and Scanning Electron Microscopy. This comparison reveals good performance of FEM in prediction of SSD depth. Finally, an empirical/ mathematical model was developed to express SSD depth as a function of process parameters. The regression model revealed that by increasing feed velocity and cutting depth, SSD depth increases, while by increasing cutting velocity, SSD depth decreases.

Our previous works presented experimental investigations of the brittle material removal fraction (BRF) on the machined surface of optical glass. It is related to the area fraction of brittle material removed on the machined surface and is used to assess the surface roughness of optical glass during precision grinding. In general, subsurface damage (SSD) is considered to be one of the most important machining qualities in grinding of optical glass. This work presents an experimental investigation of the relationship between BRF and SSD depth of optical glass during precision grinding to understand the significance of BRF on sensing the SSD of optical glass. A series of precision grinding experiments were conducted on a precision grinder machine to investigate the influence of grinding parameters on SSD depth. Based on an image processing algorithm developed in previous work, the BRF was calculated by using a microtopography image of a machined surface of K9 glass during precision grinding. The experimental results show that the BRF was determined for different machining parameters (cutting depth, wheel speed, and feed rate) and was dependent on SSD depth in precision grinding, which implies that the BRF has potential for application as a rapid and affordable online vision measurement approach to monitor surface and subsurface qualities during the grinding of brittle materials.

In polishing process, polishers must have a number of proprieties inter alia elasticity to perform their function, which is the achievement of a minimum roughness and a correct form. During the process, the polishers are subjected to compression stress generated by the technological parameters of the process. The efficiency of the polishers and the obtained quality will be influenced when they lost their mechanical properties after some hours of use. This work aims to characterize the polisher’s compression behavior and its influence on the surface quality and the effectiveness during the optical polishing process. The subjects are to define polishers wear reasons and thus to define their lifetime, in addition to the identification of the relationship between the compression behavior and the polishing quality and efficiency. For that, polishing, compression and hysteresis tests were conducted on polyurethane polishers before and after their use and the obtained results were discussed. The found results after 2 h of polishing showed the difference of the elastic properties of the polishers without a big influence on their total wear. Consequently, a very low surface roughness was obtained, with high shape accuracy.

Ultrasound-assisted grinding (UAG) is generally considered as one of the most efficient and cost-effective techniques to machine optical glass. To understand the influence of the UAG parameters on the surface quality of optical glass, a series of experiments was conducted on a precision grinder machine assisted with an axial ultrasonic vibration device. On the basis of the mechanism of removal of hard, brittle materials, we propose a new surface-quality parameter for optical glass subjected to UAG: the brittle material removal fraction (BRF), which is related to the area fraction of brittle material removed from a machined surface. To calculate the BRF, an image-processing algorithm was developed by analyzing microtopographic images of the machined optical glass surface. The BRF was determined for different machining parameters (cutting depth, wheel speed, feed rate, and ultrasonic vibration amplitude) and was found to be dependent on the surface roughness. The grinding force measured in the UAG experiments exhibited a similar trend to the BRF with respect to the different machining parameters. Therefore, the BRF is a reasonable variable for estimating the surface quality of optical glass subjected to UAG.

Optical glass fibres act as a light transmitting conduit, do not conduct electricity, and transmit data with a high speed and over long distances. During winding of special optical glass fibres on spools having flanges, because of generation of axial pressure that causes deformation of the flanges, the marginal coils may slip into the gaps between the winder and the spool flanges, which disrupts parallel arrangement of the fibres in the cut bundle and lengthens packing time. During unwinding of the fibres, because of decrease in axial pressure, the marginal coils may get pinched, leading to tearing of the fibres. In this work, we made an analysis of the axial pressure and flexures of the spool flanges and determined the effect of flange size, winding tension, and thickness of winding on the absence of fibre slipping.

The processes changing the state of polished surfaces of BK10 optical silicate glass are examined and the effect of the ambient environment on them is determined. It is found that hexamethyldisilazane vapor treatment of the polished surfaces of optical components fabricated from this glass results in the formation of a hydrophobic film that protects them from high humidity.

A compound machine tool was designed, which combined rotary ultrasonic assisted grinding, electrical discharge machining (EDM) and multi-axis milling. Experimental results indicated that its positioning accuracy was less than 5.6 µm and its repetitive positioning accuracy was less than 1.8 µm; the vibration amplitude of ultrasonic grinding system was uniform and stable, and the EDM system worked well and stably. A smooth surface of K9 optical glass component was achieved by the grinding method.

As a kind of widely used optical material, optical glass BK7 is machined by first grinding and then polishing in industrial production. However, the polishing process is time-consuming and high-cost. Therefore, it is very meaningful to produce high-quality BK7 workpieces by grinding. To understand the grinding characteristics of BK7, many studies were conducted and reported. But most studies available so far had low industrial relevance and were difficult to be applied to guide real production of BK7 glass. To fill this gap, in this study, BK7 grinding characteristics are investigated and special emphasis is laid on the effects of machining parameters in terms of machined surface morphology, subsurface damage, and grinding force. Results show that wheel depth of cut plays the most important role in BK7 grinding, and a little difference of it leads to completely different material removal modes. Wheel speed is the second important parameter. It cannot change the dominant removal mode but can slightly adjust the characteristics of machined surface, subsurface damage, and grinding force. Workpiece feed rate has a small impact on BK7 grinding. From the viewpoint of industrial application, it suggests that the wheel depth of cut of 1.0 μm, high wheel speed, and high workpiece feed rate are more rational and practical because under this condition the grinding process can produce BK7 workpieces, which possess crack-free surface and sublet subsurface damage, with high removal rates and stable grinding forces. The findings of this paper are expected to be meaningful to provide the experimental references for the studies of the BK7 grinding process and guide industrial production of BK7 optical components.

The materials of glass vessels for making glass produced by different manufacturers are investigated. Conclusions concerning the reasons for fracturing of the vessels are drawn on the basis of data from dilatometric analysis as well as optical and electronic microscopy.

Subjecting the polished surfaces of optical parts fabricated from silicate glass to treatment in vapors of hexamethyldisilazane results in the formation of a protective film that impedes the action of the ambient environment. Increasing humidity and temperature of the ambient environment diminish the protective properties of the film.

Glass material has many fine chemical properties and is widely used in high-technology fields such as aerospace and biomedical. But it is also a typical hard processing material due to its brittle and hard nature. Conventional mechanical processing methods will cause low efficiency, poor surface quality, and even surface damage when processing such materials. In order to get good surface quality, glass material must be processed plastically. This paper adopt micromilling method in processing soda lime glass, analyzed the micromilling mechanism in processing glass material, obtained the critical brittle–ductile transition condition under the consideration of size effect. Processing parameters’ range was obtained according to milling experiment in which ball-end mill was used. Surface roughness was measured and tool wear was observed simultaneously. Experimental results shown that plastic processing of glass material which brought good surface quality can be achieved by changing processing parameters and tool parameters.

A homemade apparatus was used to apply ultrasonic-vibration to assist the glass hot embossing processes. To operate at high temperatures for glass hot embossing, the ultrasonic vibration system was appropri- ately designed with an embedded cooling system, and an ultrasonic horn was specifically modified for high- temperature use. Molds with both V-groove and Fresnel structures were manufactured for hot embossing experi- ments on PSK-100 glass. The heights of the molded structures were increased significantly with the assistance of ultrasonic vibration. This technology demonstrates the capability to upgrade the performance of the glass hot embossing process.

To improve the machinability of optical glass and achieve optical parts with satisfied surface quality and dimensional accuracy, scratching experiments with increasing cutting depth were conducted on glass SF6 to evaluate the influence of cutting fluid properties on the machinability of glass. The sodium carbonate solution of 10.5% concentration was chosen as cutting fluid. Then the critical depths in scratching experiments with and without cutting fluid were examined. Based on this, turning experiments were carried out, and the surface quality of SF6 was assessed. Compared with the process of dry cutting, the main indexes of surface roughness decrease by over 70% totally. Experimental results indicated that the machinability of glass SF6 can be improved by using the sodium carbonate solution as cutting fluid.

The formation of the equilibrium Cu(I)↔Cu(II) in colored optical glasses under the combined action of several factors is examined. It is shown that the oxidation of copper intensifies with increasing total copper content by weight, increasing content of carbonates in the mix, and increasing basicity of the matrix and depends primarily on the ratio of chromium, arsenic, and copper oxides. Afactor is proposed for making a quantitative assessment of the combined effect of the chromium and arsenic oxides on the copper equilibrium.

The possibilities of evaluating the quality of the surface working of optical glass during grinding and polishing are investigated.

The published and patent data on the compositions of glass for optical glass fibres, production technology, and the basic requirements imposed on this glass were analyzed. Synthesis of glass for the light-conducting core in the BaO-B2O3-La2O3-SiO2 system was proposed using modern methods of production of optical glass fibers.

Ge x As y Se100−x−y (33 ≤ x ≤ 39 and 12 ≤ y ≤16) glasses were prepared, and their structure and optical properties were studied by Raman and UV–Vis-IR spectroscopic techniques. Ge-tetrahedrons [GeSe4] dominated in the structural units, and ‘defect’ bonds, such as Ge–Ge, Ge–As and As–As bonds, also occurred in the glasses. A structural model for calculation of the optical band gap energy (E g ) of Ge–As–Se glasses was proposed, and the calculated values are consistent with experimental results. Increasing germanium and decreasing selenium content can reduce both the mean bond energies and optical band gap energies, enhancing the photo-sensitivity of the glasses.

Super-smooth and optical glass and fused silica substates are needed in many high-technology applications. Present paper describes a bowl-feed based technique for polishing super-smooth substrates using conventional optical grinding, polishing machine. Constructions of the polishing setup, polishing-holders, polishing attachments etc. have been discussed. Results for BK-7 and fused silica (Suprasil-I) samples have been presented.

The research of Dickson [1] and Weber et al. [2] about the performance evaluation of suppliers pointed out that quality and delivery are two important assessable items. Chen and Yung [3] indicated that the significance of delivery would only increase in the future. Obviously, customers value quality and delivery. Therefore, a superior quality of product and rapid manufacturing process are the major factors in obtaining orders. Much research has been carried out on quality assurance, but the research on delivery is rare. Thus, this paper uses the manufacturing process of optical glass as an example to propose a performance index for a manufacturing time schedule and related a suite of objective evaluation models used. This evaluation method is very convenient and efficient for management to monitor the multi-manufacturing performance of each stage of a manufacturing process for deliveries of high quality.

Glasses with refractive index 1.60 – 1.65, density 2.80 – 3.08 g/cm3 and dispersion coefficient ≥ 45 have been developed on the basis of the system Na2O(K2O)–MgO–CaO–BaO–ZnO–B2O3–SiO2. These glasses are recommended for use in ophthalmologic lenses.

Radiation from shock‐compressed water at pressures of 10.0–39.5 GPa loaded through targets made of various metals (Al, Mg, and Cu) is studied. It is shown that the radiation intensity depends on both shock pressure and the nature of the metal. At pressures below 25 GPa in the region of water transparency, the radiation intensity considerably exceeds the presumed level of thermal radiation. This effect can partly be explained by the interaction of the target material with water and by nonthermal radiation from shock‐compressed water. For comparison, some experimental data on shock‐induced radiation from a number of transparent materials (Kron‐8 optical glass, glycerin, AND sodium salt) are given.

Optical and structural properties of silica materials with controlled Ge-content were investigated in aerogels samples with Ge concentration up to 100000 molar ppm prepared by a sol-gel method and densified at 1150°C. An optical absorption band centered at 242 nm, commonly ascribed to an under-coordinated germanium point defect, was observed in all doped samples, and its amplitude was found to be almost linearly correlated with the Ge-content. This feature may be ascribed to the new preparation technique so that this is potentially useful to produce materials with controlled defect content for specific optical applications.

Bismuth trioxide (Bi2O3) is the prevalent commercial oxide of bismuth. A precursor to the preparation of other compounds of bismuth, including the chemical reagents, bismuth trioxide has specialized uses in optical glass, flame-retardant paper, and, increasingly, in glaze formulations where it substitutes for lead oxides. In the last decade, bismuth trioxide has also become a key ingredient in flux formulations used by mineral analysts in fire assaying. The production of bismuth trioxide generally begins with the minor metal bismuth. This paper describes bismuth trioxide production and the properties and basis for its use in environmentally sound fire assaying.

A device for creating three-dimensional images in optical materials by means of laser breakdown is described. Features of the phenomenon of laser breakdown in K-8 optical glass and other optical materials are investigated. A dependence of the dimensions of the breakdown on the laser energy is obtained.

In recent years, developments in the mechatronics and telecommunication industry have caused a rapid increase in the use of brittle materials such as sintered carbide, silicon, fine ceramics, and optical glass. The optimum dressing of superabrasive wheels and the development of a microposition system makes possible the mirror-like grinding of these brittle materials, but the present dressing system cannot provide sufficient control for the optimum dressing of the superabrasive wheels. In this study, a new system of optimum in-process electrolytic dressing and a microposition system are developed. This system can carry out optimum in-process dressing of superabrasive wheels, and gives effective control of the unstable dressing current and insulating layer. Therefore, ultraprecision grinding when using an optimum in-process electrolytic dressing system and microposition system is a good method for efficient mirror-like grinding of brittle materials.

Ceramic pigments, which are microgranules of wastes formed in polishing optical glass whose surface is coated with two layers — silica and crystals of α-Fe2O3, α-Al2O3, and FeAl2O4, were synthesized. The pigments obtained can be used for preparation of enamels for glass, metal, and porcelain.

The matrix compositions of silver-free photochromic glasses were optimized by the simplex-lattice design method. The general region of photochromism in such glasses and the optimal region of matrix compositions were determined.

The authors analyze diamond-abrasive tools intended for fine grinding of flat surfaces made of optical glass, glass ceramics, or ceramics, which are based on plate-shaped elements making it possible to vary the space factor of the circular zones and the whole faceplate. The advantages of platelike faceplate elements over spotlike elements are demonstrated based on comparative studies.

The interaction of magnesium-containing refractory materials and optical glasses is considered. It is shown that in most cases such materials cannot be used in glass melting because their corrosion resistance is lower than in conventional refractories owing to the formation of stones and crystalline inclusions in the glass. It is possible to use magnesium-containing refractories for melting high-lead glass.

The interrelation between the chemical composition of spectacle glass and its optical characteristics is considered. A correlation dependence of different cations on the refractive index is established. The possibility of directed synthesis of new glasses with specified optical characteristics is established.

It is demonstrated that the redox potential (ROP) of glass is formed depending on the type of gases released in heating batch materials. The ROP of glass has a significant effect on the valence state of iron and copper and the oxygen coordination number of Cu(II) ions.

A new-generation, high-strength, ultra-heavy, reactive-powder concrete for radiation protection is proposed. This superconcrete is obtained by making total use of TF-10 silicate-lead glass cullet as fine and coarse fillers introduced in dry form into the concrete mix.

An automated line is developed for the production of optical elements (screens, cones) for kinescopes. New molding equipment is designed, and technological parameters for the production of screens and cones 12 cm in the diagonal are developed.