Polished Glass Research Articles

Modeling and analysis of the material removal rate for ultrasonic vibration–assisted polishing of optical glass BK7

The emergence of ultrasonic vibration–assisted polishing technology has effectively improved the machining accuracy and efficiency of hard and brittle materials in the modern optical industry; however, the material removal mechanism of ultrasonic vibration–assisted polishing (UVAP) still needs to be further revealed. This paper focuses on the material removal mechanism of ultrasonic vibration–assisted polishing of optical glass (BK7), the application of ultrasonic to axial vibration, and the atomization of the polishing slurry; the material removal model was established. Based on the analysis of the relationship between the nominal distance d of the polishing pad and the actual contact area distribution, the prediction of the material removal profile is realized. In addition, the effects of different parameters on the material removal rate (MRR) were analyzed, including polishing force, spindle speed, abrasive particle size, ultrasonic amplitude, feed rate, and flow rate of polishing slurry. Based on the motion equation of abrasive particles, the trajectory of abrasive particles in the polishing slurry was simulated, and the simulation results show that the introduction of the ultrasonic vibration field changes the motion state and trajectory of embedded and free abrasive particles. The new model cannot only qualitatively analyze the influence of different process parameters on MRR, but also predict the material removal depth and MRR, providing a possibility for deterministic material removal and a theoretical basis for subsequent polishing of complex curved surfaces of optical glass.

Material removal profile prediction and experimental validation for obliquely axial ultrasonic vibration-assisted polishing of K9 optical glass

K9 optical glass is one of the typical components in optical systems. However, because of its poor fracture resistance, it is difficult to polish it with ultra-precision and high-efficiency and without any surface damage simultaneously. The emergence of the obliquely axial ultrasonic vibration-assisted polishing (UVAP) method can solve this problem which encounters in polishing efficiency and shape accuracy. However, due to the unclear material removal profile (MRP) mechanism, obliquely axial UVAP is not widely used in the processing field. This paper introduces the obliquely axial UVAP method in research processes, mainly focusing on the fixed point MRP analysis of the obliquely axial UVAP. Based on Hertz's contact theory, polishing pressure, the length of the semi-long axis (LLA) and the length of the semi-short axis (LSA) of the contact area are calculated under ultrasonic vibration conditions. Meanwhile, the relative linear velocity distribution of the oblique polishing tool in the instantaneous contact area is modeled by mathematical geometry method. A novel model of the MRP distribution for obliquely axial UVAP is proposed following the Preston equation. Subsequently, a series of polishing experiments were carried out to verify this model. The results show that the numerical model has good agreement with the experimental results on MRP, LLA, LSA, material removal depth and material removal rate (MRR). In addition, the material removal capability can be significantly improved by larger ultrasonic amplitude and larger oblique angle. This model not only more clearly elucidates the processing mechanism of obliquely axial UVAP, but also provides theoretical support for the polishing of free-form optical lenses.

A note on Guillaume Amontons and the laws of friction

Amontons’ widely cited paper of December 1699 on the subject of friction in machines is not the first to contain his statement of the laws of friction. An earlier paper on a novel heat engine, presented to the Académie Royale des Sciences 6 months earlier, describes the measurements of forces in glass polishing and contains a clear statement that the friction force is independent of contact area and proportional to normal load. The comments in Amontons’ paper on the physical origins of the friction force at surface irregularities (asperities) do not appear in the contemporary record of his lecture in December 1699, but were included in the published version after similar ideas had been presented by Philippe de la Hire; credit for these ideas should be given to La Hire rather than to Amontons.

Effect of the addition and processing of glass polishing waste on the durability of geopolymeric mortars

The waste from the flat glass polishing process for civil construction is generally discarded in landfills. Despite some researchers evaluating its application in the development of alternative building materials, its added value is still a barrier. The objective of this research is to evaluate the physical-mechanical behavior of the addition of glass polishing waste on the durability of geopolymeric mortars to be used for small external structural repairs and their processing methods. Cylindrical specimens (50 × 100 mm) were made with metakaolin (MK) and natural sand as precursors, whereas a mixture of NaOH in pearls + glass polishing waste, dissolved in water in two different orders (A: dry mixing of both activators and B: NaOH was dissolved in water and then the glass waste was added) was used as an alkaline solution, in addition to a reference mixture (without waste). The dosage used a SiO2/Al2O3 ratio = 2.5 and 3.0. The specimens were subjected to ambient and thermal curing (60 °C) for 7 days and then submitted to laboratory for measuring the durability of wetting and drying cycles, saline environment and thermal shock. It can be observed that in the evaluation of wetting and drying cycles, the type A mixture with a molar ratio of 3.0 in ambient cure obtained a weight loss of 10 %, while in mechanical strength with a molar ratio of 2.5 and thermal cure the reduction was 27.34 %. Meanwhile, in the durability to salt exposure, both processing conditions were satisfactory, with a molar ratio of 3.0, with type A and thermal cure with a loss of mass of 11.25 %. In the evaluation of thermal shock, the mixture with the smallest loss of mechanical strength was the molar ratio of 2.5, type A with ambient cure. It can be concluded that forthe conditions evaluated, the mixture with a molar ratio of SiO2/Al2O3 = 2.5, using type A processing in the ambient cure, presented the smallest losses in mass and mechanical strength in comparative terms, adapting to the values of literature for mortars.

Shear Thickening Polishing of Quartz Glass.

Quartz glass is a typical optical material. In this research, colloidal silica (SiO2) and colloidal cerium oxide (CeO2) are used as abrasive grains to polish quartz glass in the shear thickening polishing (STP) process. The STP method employs the shear-thickening mechanism of non-Newtonian power-law fluid to achieve high-efficiency and high-quality polishing. The different performance in material removal and surface roughness between SiO2 and CeO2 slurries was analyzed. The influence of the main factors including polishing speed, abrasive concentration, and pH value on the MRR, workpiece surface roughness, and the surface topography was discussed. Two different slurries can both achieve fine quartz surface in shear thickening polishing with the polishing speed 100 rpm, and pH value 8. The quartz glass surface roughness Ra decreases from 120 ± 10 to 2.3 nm in 14 minutes’ polishing with 8 wt% 80 nm SiO2 slurry, and the MRR reaches 121.6 nm/min. The quartz glass surface roughness Ra decreases from 120 ± 10 to 2.1 nm in 12 minutes polishing by 6 wt% 100 nm CeO2 slurry and the MRR reaches 126.2 nm/min.

Effect of chemical activity of bulk and pad materials on the redeposition layer during polishing of glass

A near-surface redeposition layer is formed in the chemical mechanical polishing process of silicate glasses. In this work, secondary ion mass spectroscopy analyzer and transmission electron microscope are used to investigate the effect of bulk and pad materials on the microstructure and contaminations of the redeposition layer. The results suggest that the polishing materials with higher chemical reactivity will generate a deeper redeposition layer with higher concentration of contaminant elements, which will improve the surface quality by mitigating the mechanical abrasion effect. Then, a more detailed chemical mechanism of the redeposition layer formation has been concluded according to the chemical reaction and arrhenius equation, which can explain the effect of bulk materials and polishing pad on the redeposition layer well. These findings are helpful to understand the chemical process of polishing and improve the lifetime and quality of optical components especially in UV or high-power laser systems.

Recovery of rare earths from glass polishing waste for the production of aluminium-rare earth alloys

The circular economy demands waste utilization for the production of high-value products, and this requires the development of novel processing routes. In this study, rare earth (La and Ce) oxides were completely (>99%) recovered from polishing waste by a combined novel reductive acid leaching and alkali treatment process. About 70% of rare earths were dissolved during the first leaching step. The undissolved rare earth compounds are converted to oxides/hydroxides by alkali treatment and dissolved in the acid solution – the 2nd leaching step – for the complete recovery of rare earths. The recovered rare earth oxides were used for producing in-situ high-value Al-La-Ce alloys with fused salt electrolysis. Mechanical properties of our Al-La-Ce alloys are similar to the known high temperature Al-Ce alloys. This development of new alloys by our novel process helps in utilization of both overproduced primary La and Ce oxides as well as La and Ce recovered from polishing waste.

Circular economy and durability in geopolymers ceramics pieces obtained from glass polishing waste

AbstractThe development of new building materials based on alkaline activation technology is very promising, mainly linked to products that need significant technological properties and durability due to their adverse service conditions and environmental exposure. The objective of this research was to evaluate the development of a circular economy within the scope of durability of ceramic pieces incorporating glass polishing waste aimed at the production of roof tiles, obtained by the geopolymerization process. Two methodologies to evaluate the sample's durability were studied: wetting and drying cycles; and exposure to salt spray; both simulating conditions that tiles typically face in normal conditions. Prismatic specimens were made with an alkaline solution/(metakaolin + waste) ratio = 0.26; a SiO2/Al2O3 molar ratio = 3.5, 4, and 4.5; and with ambient and thermal cure at 7 days. Samples were evaluated in their mechanical strength, mass loss, and water absorption. Results showed that the SiO2/Al2O3 = 4.0 ratio with thermal curing had the best behavior in aggressive conditions, and therefore, this formulation can be used for the production of tiles.

Ultrasonic dispersion method used in glass polishing experiment

To solve the problems of low processing efficiency and poor glass surface quality when using rare earth polishing powder to grind super-hard K9 glass. The potential, phase structure, surface morphology, and particle size distribution of the nano-rare earth polishing powder were characterized. Compare the evaluation indexes such as polishing efficiency, surface morphology, and contact angle after the polishing process is changed. The results of the comparative study show that the average surface roughness of the glass after heating ultrasonic polishing process is 0.9064 nm, the polishing rate reaches 0.748 μm/min, the average surface roughness of the glass without heating ultrasonic polishing process is 1.3175 nm, and the polishing rate reaches 0.586 μm/min, the ultrasonic assisted polishing process is superior to the conventional polishing process. The heating ultrasonic method provides experimental basis for precise and rapid processing.

Oriented surface nucleation in diopside glass

Oriented surface crystallization on polished diopside glass surfaces has been studied with scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy and laser scanning microscopy. An orientation preference of [001] parallel to the glass surface was detected for separately growing diopside crystals even as small as 700 nm in size. This finding shows that crystal orientation occurs in the outermost surface layer without crystal-crystal interaction and indicates that the crystal orientation is a result of oriented nucleation. Depending on surface preparation, monomodal crystal orientation distributions with [100] perpendicular to the surface or bimodal distributions with [100] and [010] perpendicular to the glass surface were detected. It was also shown that the degree of crystal orientation increases with decreasing surface roughness. The observed orientation of diopside crystals could be explained in terms of the interfacial energies of different crystal faces.

Fundamental study on CNC polishing method with inner channel liquid supply

The various optical components have wide applications in aerospace industries. In the manufacturing process of optical components that are made of optical glass materials, the main challenges still are how to ensure the high requirements in dimensional accuracy and surface quality. In this paper, the CNC polishing method with inner channel liquid supply (ICLS) is proposed to polish glass materials based on the chemical mechanical polishing mechanism. The comparative experiment with both inner and external liquid supply was designed, and it is found that the successive and steady material removal rate (MRR) can be achieved by using the proposed polishing method. Then, the effect of polishing pressure, tool rotation speed, and polishing time on polishing quality was analyzed with single-factor experiments. Finally, the optimal polishing parameters were obtained with the orthogonal experiment. The results show that the average surface roughness is reduced from 238.16 to 1.34 nm, and the nanoscale super-smooth surface is achieved, which proves the feasibility of the CNC polishing method with ICLS.

FDTD modeling of sputtered Mo–Al2O3 nanocomposites

Ceramic-metal nanocomposites (NCs) are the one of the most promising materials for selective solar absorbers (SSAs) in renewable energy applications. Design of efficient SSAs demands precise modeling of light propagation in NCs. We report on the synthesis, detailed characterization, and analytical and numerical modeling of Molybdenum (Mo)-alumina (Al2O3) NCs. In this study, Mo–Al2O3 NC films with thicknesses of 45 nm and 60 nm and nominal metal volume fraction (f) of 30%, 40%, and 60% were grown on polished glass substrates, using sequential DC and RF sputtering. TEM analysis of the samples with f = 40% showed that most 2 nm-diameter Mo particles are spherical and isolated. The reflectance (R) and transmittance (T) curves of the NC were measured in the spectral range of 300 nm and 1700 nm. The measured R and T characteristics were compared with the calculated FDTD simulations to analyze the prediction accuracy of the approach.

Study optical properties of the thin HfO2 coatings deposited by DC reactive magnetron sputtering

Thin HfO2 films were deposited on polished microscope glass substrates by DC magnetron sputtering at bias voltages of -85 V, -100 V, -115 V, -130 V and -145 V. The deposited films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and UV-VIS-NIR spectrophotometry. The XRD results show the presence of a polycrystalline monoclinic phase. The roughness calculated from the AFM images increases as the bias voltage is raised to -130 V and then starts decreasing. The effect was also investigated of the bias voltage on the optical properties of the HfO2 films.

Multi-layer Laser Mirrors for Optical Sensors Deposited by Electron Beam Deposition and Ion Assisted Electron Beam Deposition

High reflectivity and low loss mirrors are very much essential for state-of art sensors like Ring Laser Gyroscopes widely used for navigation of moving platforms. Surface scattering is the main source of loss for the Laser mirrors of high reflectivity. Surface scattering also lead to coupling of back reflected light leading to dead band of optical sensors at low input rotation. Super polished glass substrates have been prepared from low expansion glass ceramic material. Surface roughness is achieved about 3-5Å (RMS value) for the ceramic glass substrates prior to thin film coating. The substrates are deposited with 41 alternative layers of SiO2 and Ta2O5 of Quarter-Wave optical thickness with Electron Beam Deposition (EBD) technique. Ion beam Assisted Electron Beam Deposition (IAEBD) is used for another batch of substrates to coat identical stack of layers on glass substrates of the same surface quality. The key process parameters of both the coating processes are presented. The optical constants of the films are evaluated with spectroscopic Ellipsometer from 400nm to 1600nm. Total Integrated Scattering is estimated from the achieved surface finishing of mirrors deposited. The multi-layer coatings are characterized with UV-Vis-IR Spectrophotometer and Cavity Ring Down(CRD) loss meter. The quantitative optical loss of the mirrors is measured at 45o angle of incidence with CRD loss meter. The merits of ion assisted EB process over simple EB coating processes are evaluated against optical constants of thin films and performances of mirrors. Fitness of the processes for realizing Laser mirrors for optical sensors at 632.8nm is evaluated.

Effect of workpiece curvature on the tool influence function during hemispherical sub-aperture tool glass polishing.

The influence of workpiece curvature on the tool influence function spot during polishing of fused silica glass with cerium oxide slurry, while using a rotating hemispherical pad-foam tool for a wide variety of process conditions (tool displacement, inclination angle, and rotation rate), has been investigated. (Workpiece curvature ranged from 500 mm radius concave to 43 mm radius convex.) The TIF spot decreases in diameter and increases in the peak removal rate on more convex workpieces. In contrast, the TIF spot increases both in diameter and peak removal rate on more concave workpieces. For the range of workpiece curvatures investigated, both the spot size and the peak removal rate changed significantly, as much as 2 times. An elastic sphere-sphere contact mechanics model, which utilizes both a modified displacement (that leads to a change in the applied load) as well as a mismatch factor (that influences the pressure distribution shape), has been developed. The model was validated using both offline load-displacement measurements and finite-element analysis simulations. The model quantitatively describes the measured change in the relative contact diameter and relative pressure distribution, as well as semiquantitively describes the change in the relative volumetric removal rate on a large variety of TIF spots. The change in the volumetric removal rate for convex workpieces is a result of the balance between a decreasing spot size (reducing removal) and an increasing peak pressure (increasing removal), which usually results in relatively small changes in volumetric removal. In the case of concave workpieces, the volumetric removal rate change is also governed by a similar balance, but the spot size increase contribution dominates, resulting in a significant increase in volumetric removal rate. Understanding these trends can enable methods to add greater determinism during the fabrication of freeform optics by adjusting polishing parameters (such as dwell time) while the tool translates along a workpiece surface with different local curvatures.

The Resource Base of Silica Glass Sand versus Glass Industry Development: The Case of Poland

The production of glass in Poland, especially of container and flat glass, has constantly risen for at least 30 years. New investments in this sector, which have recently been completed or are currently in progress, create optimistic prospects for further development of this industry, whose total annual production capacities in the next few years is expected to exceed 4 million tons. This will result in increasing demand for basic glass-making raw materials, especially high-quality silica sand (glass sand), which can be satisfied almost entirely from domestic sources. Poland as a country with a considerable resource base of these mineral raw materials, has noted a constantly growing production level that currently reaches approximately 2.8 million tons per year. This paper aims to characterize and interpret the development trends in the Polish glass industry in an international context, as well as the resulting increase in demand for glass sand. In this context, an attempt was made to answer questions concerning the sufficiency of the Polish domestic resource base for the production of glass sand. For this study, the leading recent international and Polish analyses, related to glass industry development, the resource base of glass silica sand, and the management of these types of sand, were taken into account, and were complemented by official statistical data and surveying of domestic glass producers. The performed analysis showed that when taking into account the available glass sand resources in developed deposits in Poland, it is possible to continue production at the existing or a slightly increasing level for another 20–25 years. Based on a more comprehensive perspective, however, it would be a good approach to continue providing access to those parts of currently extracted deposits of silica sand and sandstone that are now located outside of the existing exploitation licenses, as well as enabling the development of some satellite deposits in the Tomaszów Basin, which may prove difficult due to environmental factors.

Damage-free highly efficient plasma-assisted polishing of a 20-mm square large mosaic single crystal diamond substrate

Plasma-assisted polishing (PAP) as a damage-free and highly efficient polishing technique has been widely applied to difficult-to-machine wide-gap semiconductor materials such as 4H-SiC (0001) and GaN (0001). In this study, a 20-mm square large mosaic single crystal diamond (SCD) substrate synthesized by microwave plasma chemical vapor deposition (CVD) was polished by PAP. Argon-based plasma containing oxygen was used in PAP to modify the surface of quartz glass polishing plate, and a high material removal rate (MRR) of 13.3 μm/h was obtained. The flatness of SCD polished by PAP measured by an interferometer was 0.5 μm. The surface roughness measured by both scanning white light interferometer (SWLI) (84-μm square) and atomic force microscope (AFM) (5-μm square) was less than 0.5 nm Sq. The micro-Raman spectroscopy measurement results of mosaic SCD substrate processed by PAP showed that residual stress and non-diamond components on the surface after PAP processing were below the detection limit.

VP45.21: Clinical correlation of severe and non‐severe infection by SARS‐CoV2 in pregnant women

To correlate the characteristics and clinical course in pregnant women with severe and non-severe infection by SARS-CoV2 in General Hospital of Mexico. Observational and descriptive study of clinical features, laboratory and cabinet studies of pregnant with SARS-CoV2 who requested obstetric care at the General Hospital of Mexico, from April to May 2020. It was used to graph graphpad prism 8. In General Hospital of Mexico April-May 2020, 16 patients confirmed for SARS-CoV2 by rt-PCR. Symptoms: cough 13/16 (81.2%), fever, myalgia or arthralgia and dyspnea 9/16 (56.2%), pharyngodynia 7/16 (43.7%), fatigue 6/16 (37.5%). Morbidities: obesity 6/16 (37.5%), gestational diabetes 4/16 (25%), no morbidity 4/16 (25%), gestational hypertension 2/16 (12.5%). Chest x-ray: polished glass 9/16 (56.2%), parenchymal consolidation 7/16 (43.7%) and 7/16 (43.7%) no radiography was performed. Chest tomography 3/16 parenchymal consolidation and polished glass. Severe infection 2/16 (12.5%) and non-severe infection 9/16 (56.2%), and a subgroup of patients who required ambulatory management in 5/16 (31.2%). 2/16 required invasive mechanical ventilation (12.5%), presented sepsis, admission to the intensive care unit. 9/16 (56.2%) without oxygen, 4/16 (25%) nasal tips, 2/16 (12.5%) with invasive mechanical ventilation and 1/16 (6.2%) with a reservoir mask. 3/16 showed clinical improvement during hospitalisation and fetal well-being corroborated by Doppler flowmetry, with hospital discharge and telephone follow-up. Caesarean section 6/8 (75%), 2/8 vaginal delivery (25%). In 6/7 Caesarean sections was oligohydramnios. Neonates 8/8 (100 %) of newborns with rt-PCR negative for SARS-VOC-2 and without reported neonatal mortality. Pregnant women are among vulnerable groups to complicate before a respiratory infection, therefore it is important to identify clinical characteristics and morbidities that complicate the SARS-CoV2 infection, which will allow timely diagnosis and multidisciplinary treatment balancing the clinical course of COVID-19 disease with perinatal results.

Synergy between surface mechanochemistry and subsurface dissolution on wear of soda lime silica glass in basic solution

AbstractThe polishing of oxide glass in aqueous solution is sensitive to not only the mechanical conditions applied by abrasives but also the chemistry of solution. This study elucidates the synergistic interactions of mechanical and chemical effects—especially, the synergetic effects of surface mechanochemical wear and subsurface dissolution are studied by measuring the material removal rate of soda lime silica (SLS) glass upon rubbing with a Pyrex glass ball in noncorrosive (neutral pH) in corrosive solutions (pH 10 and 13 NaOH) as a function of sliding speed. Based on the synergetic model of surface wear and subsurface dissolution, it is found that the mechanochemical surface reaction dominates the wear behavior of SLS glass in neutral and pH 10 solution conditions; the wear of SLS glass in pH 10 is enhanced, compared to the neutral pH case, due to the presence of OH‐ ions at the sliding interface. In the case of pH 13, the dissolution of the densified subsurface region, which is formed due to interfacial friction during the surface wear, becomes significant, further enhancing the material removal yield. The finding provides an insight for designing an efficient polishing process in manufacturing of oxide glass materials with a good surface finish.

Controlling the Magnetic Structure of CoNi Microparticles by Mechanical Stress

The changes in the domain structure of CoNi microparticles under action of mechanical stresses have been studied. With this purpose, an array of identical planar square CoNi particles has been formed on the surface of a polished glass substrate. An elastic bending of the substrate has been used to induce mechanical stresses in the particles. It is shown, using magnetic-force microscopy, that the magnetic structure of the particles can be changed from the multidomain to quasi-homogeneous magnetization using mechanical stresses.