Polished Glass Research Articles

Analytical model of dynamic and overlapped footprints in abrasive air jet polishing of optical glass

Abstract Thanks to the superior machined surface integrity, high machining feasibility, and limited tool wear, the Abrasive Air Jet Polishing (AAJP) has been considered as a widely used finishing process, especially for high-valued small and complex optics products. Therefore, many experimental, theoretical and processing technology studies have focused on this topic. However, experimental studies cannot provide an in-depth understanding of the process principle while most of the theoretical models/methods have been established based on many unrealistic assumptions. To fill this gap, this paper suggests an analytical model of the polished surface topography (or footprint) considering (i) the horizontally asymmetric cross-section profiles of a single-abrasive impact footprint, (ii) the abrasive-workpiece elastic deformation and further springback when the abrasive bounces back, and (iii) the overlapping footprints generated by multiple abrasives having a normal-distributed size. The systematic validation trials proved the model accuracy and feasibility. Based on the validated model, the effects of the polishing parameters including the jet pressure, jet angle, and abrasive size on both machined surface roughness and removed material volume are studied. The proposed model is anticipated for not only exploring and laying the theoretical foundation of the AAJP process in more depth, but also to provide guidance for industrial manufacturing in terms of polishing parameter optimization and polished surface prediction.

Catalyzed chemical polishing of SiO2 glasses in pure water.

A catalytically assisted etching system was developed for the ultra-precision fabrication of optical components, such as X-ray mirrors and extreme-ultraviolet mask blanks. This study demonstrates that an atomically smooth surface with a sub-Angstrom root-mean-square roughness could be achieved on a SiO2 glass substrate using pure water and Pt as the etching solution and catalyst, respectively. Density functional theory calculations confirmed that the mechanistic pathway was involved in catalyzed hydrolysis. The significant roles of the catalyst were clarified to be the dissociation of water molecules and the stabilization of a meta-stable state, in which a hypervalent silicate state is induced, and the Si-O backbond is elongated and loosened. To confirm the role of the catalyst, the Pt metal was replaced by Au, and the observed drastic difference in the removal rate was attributed to the degree of stabilization of the metastable state.

Structural, optical and thermal properties of nickel doped bismuth borate glasses

Nickel doped Bismuth Borate glasses with composition (70B2O3-(30-x)Bi2O3-xNiO) where x = 0,0.5,1.0,1.5,2.0 (wt%) have been synthesized by conventional melt quenching technique. X-Ray Diffractograms have confirmed the amorphous nature of the prepared glasses. The calculated physical parameters such as density, molar volume, average boron‑boron separation, ion concentration and inter ionic distance provided the information about the structural stability of glass samples. DTA and OPD confirmed the decrease in glass transition temperature (Tg) with increase in Ni content. The FTIR and Raman studies clearly revealed that the glass network mainly comprises of [BiO3], [BiO6], [BO3] and [BO4] units. It is also observed that the introduction of dopant (Ni) and modifier (Bi) leads to the conversion of [BO3] trigonal units into the [BO4] tetragonal units due to the increase in non-bridging oxygen atoms which results in the increase of degree of disorder in the glass network. The optical absorption measurements (UV) carried out for well polished glass samples show a decrease in optical band gap with the increase in Ni doping. This observation was further supported by the urbach energy calculations and metallization criterion of the prepared glass samples. The electronegativity and electronic polarizability values revealed the ionic character of glass samples.

An enzyme-free electrochemiluminesce aptasensor for the rapid detection of Staphylococcus aureus by the quenching effect of MoS2-PtNPs-vancomycin to S2O82−/O2 system

In this study, based on gold nanoparticles (AuNPs) and hemin as the regenerable enhancers of S2O82−/O2 electrochemiluminesce (ECL) system, a highly sensitive “on-off” ECL aptasensor was constructed for S. aureus detection by the quenching effect of MoS2-PtNPs. Firstly, the polished glass carbon electrode (GCE) was subsequently modified with reduced graphene oxide (RGO), AuNPs and thiol-terminated aptamer, and MoS2-PtNPs-Vancomycin (MoS2-Pt-Van) was prepared utilizing platinum ammonia bonds. Without S. aureus, a high S2O82−/O2 ECL intensity was achieved by the cooperative enhancements of RGO, AuNPs and hemin (“signal-on”). Then, when S. aureus existed, captured by aptamers, which further combined with MoS2-Pt-Van by the bio-recognition of vancomycin and bacterial cytoderm. As a result, a low ECL intensity was obtained by the highly quenching effect of MoS2-Pt-Van on the S2O82−/O2 ECL system (“signal-off”). The ECL intensity had a linear relationship with the logarithm of S. aureus concentration in a range of 1.5 × 102 to 1.5 × 108 CFU/mL, possessing the detection limit of 28 CFU/mL. In addition, this assay possessed excellent detection specificity, and could be applied to the analysis of S. aureus spiked in urine samples. Therefore, this strategy might become a potential alternative tool for bacteria detection in medical research and early clinical diagnosis.

Experimental study on chemical mechanical polishing of chalcogenide glasses.

Chalcogenide glasses (Ge10As40Se50) are one of the core components of the athermalized infrared optical system. Because of material properties, its processability is limited, and surface defects are difficult to control. The chemical nature of Ge10As40Se50 has been established, which can react with sodium hydroxide and hydrogen peroxide (H2O2). In this paper, experimental studies are further carried out to investigate the effect of chemical-mechanical polishing on the surface. As a result, both agents can improve the surface quality effectively. When the concentration of H2O2 is about 10wt. % to 15wt. %, the best result can be obtained, in which case the surface microdefect and surface roughness are significantly improved with the surface roughness RMS≈0.31 nm.

Characterization and Feasibility Studies on Complete Recovery of Rare Earths from Glass Polishing Waste

One of the main applications of ceria (CeO2) is its use in glass polishing. About 16,000 tonnes of rare earth oxides, which is about 10% of total rare earth production, are used for polishing applications. The waste generated in glass polishing contains rare earths, along with other impurities. In this study, two different glass polishing waste samples were characterized and two different processes were proposed for the complete recovery of rare earths from polishing waste, i.e., an acid-based process and an alkali-based process. The polishing waste samples were characterized with inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), thermo-gravimetric analysis (TGA) and particle size analysis. Chemical analysis showed that sample A (CeO2-rich waste from plate glass polishing) contained a high amount of impurities compared to sample B (CeO2-rich waste from mirror polishing). XRD analysis showed that sample B contained CeO2, LaO0.65F1.7 and LaPO4 compounds, whereas sample A contained CaCO3 in addition to rare earth compounds. SEM-EDX analysis showed the presence of alumino-silicates in sample A. Leaching experiments were carried out at 75 °C at different acid concentrations for the recovery of rare earths from polishing waste samples. The leaching results showed that it is difficult to dissolve rare earths completely in acid solutions due to the presence of fluorides and phosphates. Hence, undissolved rare earths in the leach residue were further recovered by an alkali treatment with NaOH. In another approach, polishing waste samples were directly treated with NaOH at 500 °C. After alkali treatment followed by water leaching, rare earths can be completely dissolved during acid leaching. Rare earths from polishing waste can be recovered completely by both the acid-based process and the alkali-based process.

Fabrication of silver nanoparticles-embedded antibacterial polymer surface through thermal annealing and soft molding technique

The major challenge faced in biomedical field is the formation of biofilm on polymer devices like catheters. It is important to functionalize the biomedical devices with a bactericidal agent through an easy and safe process in order to protect them from bacterial attack. In this article, the new method of impregnation of silver nanoparticles (AgNPs) into polymer film was proposed and tested against bacterial cells. The different sizes of silver nanoparticles were embedded in polystyrene film using thermal annealing and soft molding technique. Silver films having different thickness were deposited on the highly polished machinable glass ceramic (MACOR) substrate using direct current (DC) sputtering and subjected to at 750 °C for 15 min. After the heat treatment, AgNPs were formed on MACOR sample. It was then characterized using field emission scanning electron microscope (FE-SEM). Image-J software was used to analysed shape, size and distribution of AgNPs. The spin coating method was adopted to coat polystyrene film on to MACOR substrate supported AgNPs and allow it to cure for 24 h. After curing, the polystyrene film was peeled off and finally, AgNPs got transferred to polystyrene film. The AgNPs embedded polystyrene film was analyzed using FE-SEM and atomic force microscopy (AFM). Spread plate (plate counting) method was used to evaluate the bacterial killing potential of modified polystyrene film against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. The modified polystyrene film shows effective antibacterial ability against both the types of bacteria compared to the plain polystyrene surface.

Effect of Three Commonly Consumed Beverages on Surface Roughness of Polished and Glazed Zirconia-Reinforced Lithium Silicate Glass Ceramics.

Objectives:This study aimed to assess the effect of three commonly consumed beverages on surface roughness of polished and glazed zirconia-reinforced lithium silicate (ZLS) glass ceramics.Materials and Methods:In this experimental study, 104 rectangular specimens were cut from Vita Suprinity blocks with 2 mm thickness. After ultrasonic cleaning and firing of the specimens, they were finished and polished in two groups. Specimens in the first group were polished using a 2-step polishing kit while the second group specimens were glazed and heated in a porcelain firing oven according to the manufacturer’s instructions. Baseline surface roughness was measured using a profilometer. Specimens in each group were then randomly divided into 4 subgroups (n=13) for immersion in artificial saliva (control group), cola, orange juice and black tea. Surface roughness was measured again and data were analyzed using two-way ANOVA.Results:The highest and the lowest mean Ra were found in orange juice and saliva subgroups, respectively in both glazed and polished groups. The Ra values of both polished and glazed groups significantly increased after immersion in orange juice and cola (P<0.05). The polished surfaces showed insignificantly higher surface roughness compared with glazed surfaces (P>0.05).Conclusion:Orange juice and cola significantly increased the surface roughness of both polished and glazed ZLS ceramics. Type of surface finishing (polishing versus glazing) had no significant effect on the surface roughness of specimens following immersion in different beverages.

Fields of application for laser beam polishing of optical glasses

Fields of application for laser beam polishing of optical glasses

Analysis of the results of the finishing process for manufacturing low-hardness products from non-metallic structural materials

Abstract The methods and results of glass processing, including quartz glass, are considered. Research is aimed at improving the quality of the surface in the physical and chemical methods of exposure to the product, to ensure high precision machining and surface quality without cracks and scratches. Processing was applied to rotation bodies. Polyurethanes with solid inclusions were used as a polishing tool. The parameters of solid inclusions are investigated and their influence on the quality of the surface obtained is evaluated. The results of the study were obtained for the operations of grinding, polishing and etching quartz glass samples with different processing modes. The influence of these processes on the value of the surface roughness parameter of silica glass is estimated. It has been established that the quality of the glass surface during processing is affected by geometry and surface roughness before processing; the quality of the polishing tool, the etching mechanism; time and modes during polishing, as well as the effect of the polishing slurry. In the process of polishing and etching, the division into conditional boundaries of the treatment zones occurs. The formation of roughness and macro geometry is due to the polishing scheme, the size, and geometry of the tool, as well as the accuracy of the alignment of the machine. The results of the study are clearly presented, the obtained data of experiments on polishing and pickling are analyzed, conclusions are made in this work.

Improvement of Fat Suppressing Effect for Finger and Neck MRI by Using Small Glass Beads

The defectiveness of the fat suppression becomes the factor of the decrease of the quality of the diagnosis of magnetic resonance imaging. It is reported that the use of magnetic field uniformity adjuvant pad is effective for reduce poor fat suppression. The ball bullets, polystyrene balls, and polished rice are used for pad packing material, in recently, it was reported that fat suppression effect was good by the use of the small glass beads. Therefore, we tested the utility of small glass beads pad in the neck and fingers in this study. Neck and the fingers of subjects were imaged with T1-weighted image with fat suppression and T1-high resolution isotropic volume excitation image. The fat suppression effect of each image was compared with the polished rice and glass beads as material of pad used by physical, observation, and contact evaluation. In the result, satisfactory results were obtained by using glass beads, and it is suggested that fat suppression effect is improved by using glass beads as a filling material of pad in clinical study as a conclusion.

A new approach to laser polishing and form correction of optical components

The increasing variety of optical components and materials, combined with stricter surface tolerance requirements, necessitate refining existing polishing processes and developing innovative new polishing solutions and metrology technologies. A fast, reproducible laser polishing process would offer considerable economic benefits over conventional mechanical polishing processes and interest a broad variety of optics manufacturers. In this work, a holistic approach is taken to address the various aspects of glass polishing and form correction via a novel laser polishing system design, the use of a measurement strategy that can be integrated inline and simulation results that are correlated with process parameter studies for different materials.

Glass polishing material: Experimental study of manganese oxide powder instead of cerium oxide

Glass polishing material: Experimental study of manganese oxide powder instead of cerium oxide

On the predictive modelling of machined surface topography in abrasive air jet polishing of quartz glass

Abrasive Air Jet Polishing (AAJP) process can be considered as one of the most promising ultra-high-precision finishing methods of quartz glass products due to the superior machined surface integrity, and the high machining feasibility for free-form surfaces. Although many academic and engineering efforts have been paid so far to AAJP process from the theoretical, numerical and experimental aspects, most of the available studies have considered neither (i) the stochastic nature of the abrasive sizes nor (ii) the elastic springback after the impacting abrasives bounced back from the workpiece surface. To fill this gap, this paper proposes the predictive model of the machined surface topography in the AAJP process of quartz glass. A series of experimental trials are performed as well which to a large extent proved the model feasibility and accuracy, and, more importantly, the necessity to consider the normally-distributed abrasive sizes, the stochastic abrasive distribution within the spray airflow, and the elastic workpiece deformation recovery after the AAJP process. Both the experimental and theoretical results also conclude that the small-sized abrasives and the low jet airflow pressure were more effective to achieve the smooth surfaces. The proposed model in this work is expected to be not only helpful to provide the theoretical foundation to study more in-depth mechanism of the AAJP process of brittle materials, but also meaningful to guide the industrial manufacturing in terms of machining parameter optimisation and machined surface quality prediction.

Surface nanocavitation of titanium modulates macrophage activity.

BackgroundNanoscale surface modifications are widely touted to improve the biocompatibility of medically relevant materials. Immune cells, such as macrophages, play a critical role in the initial healing events following implantation.MethodsTo understand the response of macrophages to nanotopography better, we exposed U937-derived macrophages to a distinctive mesoporous titanium surface (TiNano) produced by a process of simple chemical nanocavitation, and to mechanically polished titanium (TiPolished) and glass coverslip (Glass) surfaces as controls. Cell numbers and morphology were evaluated. Osteopontin expression and that of the proinflammatory SPARC protein and its stabilin 1 receptor were analyzed. Release of inflammation-associated cytokines and chemokines was also measured.ResultsCompared to the two control surfaces, there were fewer U937 cells on TiNano, and these exhibited a more rounded morphology with long filopodia. The cells showed areas of punctate actin distribution, indicating formation of podosomes. Of the three proteins examined, only osteopontin’s immunofluorescence signal was clearly reduced. Irrespective of the substrate, the cytokine assay revealed important variations in expression levels of the multiple molecules analyzed and downregulation in a number of chemokines by the TiNano surface.ConclusionThese results indicate that macrophages sense and respond to the physicochemical cueing generated by the nanocavitated surface, triggering cellular and molecular changes consistent with lesser inflammatory propensity. Given the previously reported beneficial outcome of this mesoporous surface on osteogenic activity, it could be presumed that modulation of the macrophagic response it elicits may also contribute to initial bone-integration events.

Mosquitoes modulate leg dynamics at takeoff to accommodate surface roughness

Insects perform takeoffs from a nearly unquantifiable number of surface permutations and many use their legs to initiate upward movement prior to the onset of wingbeats, including the mosquito. In this study we examine the unprovoked pre-takeoff mechanics of Aedes aegypti mosquitoes from two surfaces of contrasting roughness, one with roughness similar to polished glass and the other comparable to the human forearm. Using high-speed videography, we find mosquitos exhibit two distinct leg actions prior to takeoff, the widely observed push and a previously undocumented leg-strike, where one of the rearmost legs is raised and strikes the ground. Across 106 takeoff sequences we observe a greater incidence of leg-strikes from the smoother surface, and rationalize this observation by comparing the characteristic size of surface features on the mosquito tarsi and each test surface. Measurements of pre-takeoff kinematics reveal both strategies remain under the mechanosensory detection threshold of mammalian hair and produce nearly identical vertical body velocities. Lastly, we develop a model that explicates the measured leg velocity of striking legs utilized by mosquitoes, 0.59 m s−1.

Change of electrical conductivity of MoS2 under exposure to protons

A significant drop (by a factor of 10,000) in the electrical resistance of the thin-film semiconductor MoS2 with continuous injection of protons into it under conditions of established dynamic equilibrium was found. With the cessation of proton injection, the effect disappears. These films MoS2 were obtained on polished glass supports by means of mechanical infriction of powder into a rough surface. In order to create a permanent proton flow directed to the sample plasma ion source with cold cathode was used.

Modeling and prediction of surface topography and surface roughness in dual-axis wheel polishing of optical glass

Abstract It is rather difficult to achieve uniform surface texture and high convergence rates of surface roughness (CRSR) at the same time in the conventional optical polishing process. The dual-axis wheel polishing (DAWP) technology, which uses a semi-rigid wheel with combined dual-axis rotational movements, shows a strong capability directly changing the rough ground surface status down to mirror status with nanometer level surface roughness, and achieving a uniform and smooth surface texture. In order to provide a better scientific understanding of the surface texture generation in DAWP process, in this paper, two comprehensive mathematical models are proposed. The first model is to predict the generation of micro-topography and roughness within single-axis TIF (tool influence function) area, based on the abrasive wear theory, abrasives distribution investigation and accumulative removal theory. On the basis of this model, another surface micro-topography generation model is also built to predict the micro-topography and roughness generated on workpiece surface in actual DAWP process (both for single and dual-axis modes). A series of fixed spot polishing tests and uniform polishing tests on BK7 glass were carried out to analyze the influence of polishing parameters and motion modes on the generated surface texture and roughness. The measurement results show that the surface micro-topography and roughness within TIF area and on polished surface can be well predicted by the two models. After actual polishing process, the dual-axis mode tends to produce much lower surface roughness with uniform texture. The single-axis mode tends to generate directional surface textures with relatively higher surface roughness. Under the dual-axis mode, the variation of co-rotating speed has less influence on the polishing quality, very high CRSR and uniform texture can be achieved under different co-rotating speeds.

Recovery of Cerium from Glass Polishing Waste: A Critical Review

Ceria is the main component in glass polishing powders due to its special physico-chemical properties. Glass polishing powder loses its polishing ability gradually during usage due to the accumulation of other compounds on the polishing powder or due to changes in the particle size distribution. The recovery of cerium from the glass polishing waste results in the efficient utilization of natural resources. This paper reviews processes for the recovery of rare earths from polishing waste. Glass polishing powder waste can be reused via physical, physico-chemical or chemical processes by removing silica and/or alumina. The removal of silica and/or alumina only improves the life span up to some extent. Therefore, removal of other elements by chemical processes is required to recover a cerium or cerium-rich product. However, cerium leaching from the polishing waste is challenging due to the difficulties associated with the dissolution of ceria. Therefore, high acid concentrations, high temperatures or costly reducing agents are required for cerium dissolution. After leaching, cerium can be extracted from the leach solution by solvent extraction or selective precipitation. The product can be used either in glass polishing again or other high value added applications.

Designing a Technology of Industrial Sewage Waters Purification from the Spent Polishing Powder Based on Ceric Oxide

The primary activity of an enterprise, where the wastewater samples have been taken, is applying lacquer coatings to glass and the mirrors production. For washing glass before the application of coatings a suspension of powder based on ceric oxide is prepared, which is used as a polishing solution. The physical and chemical properties of industrial sewage waters, generated after glass polishing, and of the initial and spent polishing powder based on ceric oxide have been researched. The optimal doses of flocculating agents for purifying wastewaters in order to reduce turbidity, suspended solids concentration and dry residue have been determined. After the flocculation the advanced treatment of the water was done, by means of filtering elements with pore size 5 and 1 μm, produced by the Pentek Company. The process scheme of wastewater purification, including the physico-chemical method (flocculation) and mechanical purification method by using bag filters, has been developed.