Laser Zone Melting and microstructure of waveguide coatings obtained on soda-lime glass

This study presents a Laser Zone Melting method with potential for producing planar waveguides at large scale, based on the surface coupling of two chemically compatible glass layers which exhibit distinct indices of refraction. The method is based on a recent patent, particularly applicable to process glass and ceramics with low thermal shock resistance. Glass coatings containing 76.24% by weight PbO are thus here reported, as obtained by this method on commercial soda-lime planar glass substrates. Their higher indices of refraction (1.58 vs 1.52 for commercial soda-lime glass) result in attractive waveguiding potential, as demonstrated with measurements using focused light from a He-Ne laser beam. Scanning and transmission electron microscopy studies reveal excellent integration and compatibility between the observed coatings and substrates, where diffusion in the proximity of the interface was studied by EDS analysis. Crystalline phases have not been found within the coating, or within the substrate, as concluded from the absence of Bragg-peaks in XRD experiments.     

Fabrication of superhydrophobic surfaces on a glass substrate via hot embossing

This study developed a new hot pressing process to prepare superhydrophobic surfaces with controllable shape and size on a glass substrate. Microstructures were fabricated on tungsten carbide mold via picosecond laser processing. Microgroove structures were reproduced on glass during the hot embossing process and SiO₂ nanoparticles laid on the mold were also embedded into the glass surface under the action of heat and pressure to provide nanostructures. The contact angle of the superhydrophobic glass surface reached up to 161.8°, and the sliding angle was only 3°. The structures and chemical composition of superhydrophobic glass surface were identified by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometer (EDS), X-ray diffraction (XRD), and Fourier transformed infrared (FTIR) spectroscopy. The 3D laser scanning microscopy result showed the height (20 μm) of the microgroove structures, while white light interferometry revealed the surface roughness (Ra 2.725 μm). The superhydrophobic glass surface demonstrated satisfactory temperature resistance and chemical stability through temperature and acid and alkali solution immersion tests. The surface exhibited certain mechanical stability by friction and wear test. This work provides a new hot embossing method for solving the problem of structural consistency and mass production of superhydrophobic glass, and will have great application prospects in the engineering field.     

Femtosecond laser micro-milling dental glass ceramics: An experimental analysis and COMSOL finite element simulation

Dental glass ceramic materials are widely used in all-ceramic restoration technology. In order to effectively solve the problems existing in the process of traditional diamond cutter milling dental glass ceramic materials, such as severe needle loss, large tool wear and general milling efficiency, a new method of ultrafast laser milling dental glass ceramics is proposed. In this paper, 1030 nm femtosecond laser with pulse width of 600fs was used to micro-mill dental glass ceramics. Confocal laser microscopy was used to measure the milling depth and surface roughness of single-layer milling under selected laser processing parameters. The pre-layered milling software was developed to control the z-axis lifting and to compensate the focal length synchronously. Scanning electron microscope (SEM), Raman spectrometer and Vickers micro-hardness tester were used to characterize the dental glass ceramics after femtosecond laser milling. The results showed that under the specific laser processing parameters, the infrared femtosecond laser milling system can achieve a good processing morphology without changing the surface composition and surface hardness of dental glass ceramics. This new dental glass ceramics processing method based on ultrafast laser technique indicated a new direction for further chair processing of dental all-ceramic restoration technology.     

One second growth of carbon nanotube arrays on a glass substrate by pulsed-current heating

We report the very rapid growth of carbon nanotubes (CNTs) at high temperatures that can be tolerated by glass substrates. Glass substrates with metal microelectrodes and sputtered catalysts are heated by a pulsed current in a chemical vapour deposition gas environment for 0.5–1 s to synthesize CNTs of several micrometres in height without damaging the glass substrate. CNTs with structures from single-walled to multi-walled and morphologies from entangled networks to vertically aligned forests are grown simply by changing the nominal thickness of the catalyst, and such CNTs grown selectively on the microelectrodes worked as field emitters for cathodoluminescence. Rapid, easy growth of patterned CNT arrays on glass substrates without using furnaces/heaters or vacuum pumps will be useful for various applications of CNTs.     

Surface characterization of glass and poly(methyl methacrylate) soiled with a mixture of fat,oil, and starch

Micro-organisms on food contact surfaces provide a 'biotransfer potential', i.e. the ability to contaminate foods during processing or preparation. Surfaces coated with organic materials can act as sites for microbial attachment. This investigation into the surface properties of glass and poly(methyl methacrylate) substrates soiled with a milk powder, oil, and starch composite has found that fatty acid esters dominate the surface chemistry. A lower concentration of proteinaceous material was also detected, with the concentration dependent on both the underlying substrate and the thickness of the soiling material. The physical surface structure of the fouled surfaces showed a complicated surface topography with features of the order of tens of micrometres wide and up to 2 μm high, which increased in size with increasing thickness of the soiling layer. The features reflect bulk incompatibilities between the components of the soiling material and demonstrate the heterogeneity of the surface as presented to micro-organisms.     

Bioactive glass coating using aerosol deposition

This work demonstrates the successful deposition of bioactive glass (BG) 45S5 coatings on various metallic and ceramic substrates at room temperature under low vacuum condition by using aerosol deposition (AD). This room temperature and particle impact consolidation-based deposition method enabled us to deposit well-adhered and dense BG coatings directly on metallic and ceramic substrates. In vitro tests with human osteoblast-like cells on substrates with a 45S5 BG coating demonstrated high cell activity on the surfaces. All tested materials exhibited high in vitro biocompatibility as no inhibition in cell proliferation could be observed. The utilization of AD process for achieving non-crystalline BG coatings is promising for practical bio-medical applications, e.g., bioactive coatings on bioinert metallic and ceramic substrates.     

Additive manufacturing of glass with laser powder bed fusion

Its transparency, esthetic appeal, chemical inertness, and electrical resistivity make glass an excellent candidate for small- and large-scale applications in the chemical, electronics, automotive, aerospace, and architectural industries. Additive manufacturing of glass has the potential to open new possibilities in design and reduce costs associated with manufacturing complex customized glass structures that are difficult to shape with traditional casting or subtractive methods. However, despite the significant progress in the additive manufacturing of metals, polymers, and ceramics, limited research has been undertaken on additive manufacturing of glass. In this study, a laser powder bed fusion method was developed for soda lime silica glass powder feedstock. Optimization of laser processing parameters was undertaken to define the processing window for creating three-dimensional multilayer structures. These findings enable the formation of complex glass structures with micro- or macroscale resolution. Our study supports laser powder bed fusion as a promising method for the additive manufacturing of glass and may guide the formation of a new generation of glass structures for a wide range of applications.     

Indentation behavior of polymer coatings on glass

For relatively soft polymer coatings on soda-lime glass substrates the indentation load increases substantially when the indenter penetrates into the glass substrate since the glass can now directly support some of the indenter load. A model for the indentation load-depth behavior is developed by accounting for the indentation load shared by the coating and substrate. This model accounts for the additional load supported by the coating due to the pile-up of coating material underneath the indenter. The model predicts the indentation behavior as a function of coating and substrate hardnesses and coating thickness. Comparison of the model to experimental data for a wide range of polymer coatings (two epoxies, epoxy acrylate, and urethane acrylate) on soda-lime glass substrates shows good agreement.     

Mechanical properties of poly(vinyl chloride)/wood flour/glass fiber hybrid composites

Short glass fibers were added to poly(vinyl chloride) (PVC)/wood flour composites as reinforcement agents. Unnotched and notched impact strength of PVC/wood flour/glass fiber hybrid composites could be increased significantly without losing flexural properties by adding type L glass fibers and over 40% of PVC. There was no such improvement when using type S glass fiber. The impact strength of hybrid composites increased along with the increment of the type L glass fiber content at a 50% PVC content. At high PVC contents, impact fracture surfaces were characterized by wood particle, glass fiber breakage and pullout, whereas interfacial debonding was the dominant fracture mode at higher filler concentrations. The significant improvement in impact strength of hybrid composites was attributed to the formation of the three‐dimensional network glass fiber architecture between type L glass fibers and wood flour.     

Silicon Carbide Films by Laser Pyrolysis of Polycarbosilane

Thin films of polycarbosilane were deposited on Si and SiO₂ substrates. Instead of conventional oven annealing (high temperatures, inert atmosphere), laser pyrolysis was used to achieve the polymer-to-ceramic conversion. In some conditions, especially when laser radiation absorption was enhanced by depositing a carbon layer on the surface of as-deposited films or by embedding graphite particles, this processing method yielded SiC ceramic coatings, without damaging the substrate. Processing in air or low vacuum did not result in oxidized coatings, contrary to what happens for oven pyrolysis. Laser-converted films were similar to oven-heated films processed at 1000° to 1200°C.     

Altering the wettability of bitumen-treated glass surfaces with ionic surfactants

The abilities of three ionic surfactants—sodium methylnaphthalene sulfonate (SMNS), sodium dodecyl sulfate (SDS), and cetyl trimethylammonium bromide (CTAB)—to alter the wettability of bitumen-treated glass surfaces was examined. Surface wettability was characterized by contact angles, and all measurements were carried out under alkaline conditions by having sodium carbonate (Na₂CO₃) dissolved in the aqueous phase. It was found that Na₂CO₃ alone could slightly increase the hydrophilcity of bitumen-treated glass surfaces. With surfactants added to the system, it was demonstrated that SMNS and SDS (both anionic surfactants) were much more effective in enhancing the water wettability of bitumen-treated glass in comparison to CTAB (a cationic surfactant). X-ray photoelectron spectroscopy (XPS) analyses were also conducted to determine the functional groups and relative mass concentrations of various elements on the glass substrates. Based on these results, we speculate that most or all of the adsorbed hydrocarbon material could be removed from a glass substrate through synergistic effects between sodium carbonate, which provides the alkaline condition, and anionic surfactants, which likely interacted with adsorbed cationic materials. This resulted in dramatic alteration in the wettability of bitumen-treated glass surfaces—from oil-wet to water-wet.     

Hot embossing of moth eye-like nanostructure array on transparent glass with enhanced antireflection for solar cells

Antireflection (AR) silicon and glass surfaces are necessarily required for solar cells, because a reflective silicon solar cell with a glass covering will reflect a percentage of sunlight. In this work, we demonstrate a universal and scalable net-shape nanofabrication method for broadband nanostructured AR surface on transparent glass, intended for solar cell applications. Moth eye-like glass nanopillars with various diameters were successfully fabricated by a combination of precision hot embossing and ultrasonic vibration demolding process. The morphologies of nanopillars were detected to characterize different profiles formed by glass flow at elevated temperatures. Facile optical experiments were designed and conducted to measure the AR performance at varying wavelengths and angle of incidences and the proposed nanostructures exhibit excellent AR property. Additionally, a feasible optical modeling is developed and compared with the measurement to evaluate the theoretical optical behaviors of glass nanostructures based on their embossed shapes. The inexpensive and environmental hot embossing method with ultrasonic vibration demolding is expected to create AR glass nanostructured surfaces for widespread applications such as solar cells, displays and laser systems.     

Growth and morphology of ZnO nanorods prepared from Zn(NO3)2/NaOH solutions

ZnO nanorods on ZnO-coated seed surfaces were fabricated by a solution chemical method using supersaturated Zn(NO₃)₂/NaOH solution. The seed surfaces were coated on glass substrates by sol–gel processing and PEG addition. The mechanism of crystal growth and the factors affecting the rod growth were elucidated. The morphology and structure of both the seed surface and successive nanorods were analyzed by using SEM, XRD, TEM and SAED. Nucleation on the ZnO seed surface is crucial for rod growth since rods can only be observed on ZnO-coated substrates. Supersaturation is also required for rod growth and the Zn²⁺ ion and NaOH concentrations must be varied synchronously to maintain the high level of supersaturation. The average diameter and length of the ZnO nanorods increase to different degree with increasing precursor concentration. The dependence of rod growth on temperature shows that the maximum rod growth rate at any given concentration of Zn²⁺ occurs at a specific temperature, and the optimal temperature increases with Zn²⁺ ion concentration. Densely thick nanorods oriented perpendicularly to the substrate can be obtained by controlling the seed surface with PEG assistance.     

Preparation of scratch resistant superhydrophobic hybrid coatings by sol–gel process

Organic–inorganic hybrid coatings on glass substrates with superhydrophobic properties and with improved scratch resistance were obtained by means of applying a multilayer approach including multiple sol–gel processes. The coatings exhibited a water contact angle (WCA) higher than 150°. Ultraviolet (UV)-curable vinyl ester resins and vinyltriethoxysilane (VTEOS) as coupling agent were employed to increase the adhesion between substrate and the inorganic layers. The surfaces were characterized by means of dynamic contact angle and roughness measurements. Indeed, the occurrence of superhydrophobic behavior was observed. The scratch resistance of the hybrid coatings was tested to evaluate the adhesion of the coatings to the glass substrate. The proposed preparation method for scratch resistant, mechanically stable, superhydrophobic coatings is simple and can be applied on large areas of different kinds of substrates.     

Plasma resistance of quartz with a glass coating layer by aerosol deposition

ABSTRACT

To improve the plasma resistance behaviour, glass frits of SiO₂–Al₂O₃–Y₂O₃ with various powder sizes were coated onto quartz substrates by the aerosol deposition (AD) method. The thickness and microstructure of the coating layers were observed using a surface profiler and scanning electron microscopy. Plasma resistance was measured via the quartz substrate, after exposure to an inductively coupled plasma etcher. The coating layers were densely formed on the quartz substrates without additional heat treatment, and the layer thickness changed for the glass frit size distribution and AD process conditions. The SiO₂–Al₂O₃–Y₂O₃ glass coating layer showed a higher plasma resistance than quartz. Furthermore, the AD coating layer was evenly etched after plasma exposure. This study improves the lifetime of plasma chamber components in the semiconductor industry.     

Multi-step derivatization and analysis of the surface of nonporous silicate glass

Multi-step heterogeneous phase chemical reaction schemes were used to develop different surface chemistries on nonporous glass substrates. Reliable analysis of the products of reaction was needed, because many of the functional groups introduced to the surface were intended to serve as reactive sites for further chemical tailoring to meet specific applications. Because the mass of the surface derivatization layer was only parts per million of the substrate mass, analysis of the reaction products was daunting. However, surface evaluation was accomplished by using several analysis methods in combination and by using the particular glass geometry most suitable to each analysis method.     

Silicon contamination of substrates in fluorocarbon plasmas produced in glass reactors

Extensive research has been carried out in recent years using fluorocarbon plasmas for modification and depositions on polymer substrates. In some cases anomalous results have been obtained that are not explainable based on conventional fluorine chemistry. In this investigation pure polypropylene films were exposed to carbon tetrafluoride plasmas in a Pyrex glass reactor. At short reaction times (less than 1 min) significant amount of silicon was detected by ESCA on the surface of the films. Analysis of liquid nitrogen trapped fluorocarbon plasma gases and molecular fragments indicated high concentrations of silicon and carbon containing species, the former indicative of ablation and etching reactions of the glass reactor walls. The production of a relatively high quantity of fluorosilicon derivatives was explained by the greater affinity of silicon for fluorine than for carbon, with the tendency to readily form SiF₄. These fluorosilicon radical and ionic species generated under cold plasma conditions can easily react with polymeric substrates causing unexpected surface modifications. In addition Si–F bonds could be readily hydrolyzed to SiOH islands on the surface of the substrate to impart anomalous characteristics. © 1994 John Wiley & Sons, Inc.     

Adhesion and interfacial healing between supramolecular hybrid networks and glass substrates

Adhesion towards glass and interfacial healing of partially supramolecular hybrid polymer networks featuring a range of H-bonds content were investigated through two dedicated adhesion test methods. In a first series of tests, adhesion strength was measured by separating two substrates containing a cured inner resin layer, and shown to decrease with increasing H-bonds content in the polymer network (from 0 to 50%) as the mechanical strength of the polymer also decreased while the failure mechanism shifted from adhesive to cohesive due to the possibility to form hydrogen bonds with glass substrates. In a second step, the test was used to evaluate interface restoration through healing of the polymer matrices and results showed an increased from none to a tensile strength recovery up to 70% after 1 h healing time for the 50% H-bond polymer. Then, self-adhesion of freshly cut polymer surfaces to glass substrates was investigated, showing increasing tack with increasing H-bonds content. The influence of glass surface treatments on adhesion and interfacial recovery properties was also explored: while aminosilanes did not influence the interfacial behavior of partially supramolecular self-healing polymers towards glass, trimethoxy (octadecyl)silane (ODS) modification strongly hindered their adhesion abilities, further highlighting the fundamental role of hydrogen bonds interaction with the substrates.     

Mechanically inspired laser scribing of thin brittle materials

Laser processing of thin flexible ceramics and glasses is challenging due to the incurred brittleness and unfavorable thermal and optical properties of such materials. We describe an alternative laser cutting method which utilizes surface stress raisers to cleave brittle substrates along a defined path. An ultrashort laser source is used to precisely pattern a plurality of aligned elliptical recesses on the material surface. The apex of an ellipse concentrates applied tensile stresses. Depending on the elliptical dimensions, the achievable stress concentration factor can be up to 50. The orientation of the ellipses defines a preferred scribing path. The technique was successfully applied to thin flexible yttria stabilized zirconia ceramic and borosilicate glass substrates. The form and properties of the material play an important role during the fracture process. Polycrystalline ceramics were found to accurately auto cleave along the path due to stresses produced during the laser ablation. The resulting fractured surface is of higher quality and strength than surfaces cut using full body laser cutting techniques, while the crystalline phase is preserved. The optical setup is simple, low cost, and compatible with roll‐to‐roll manufacturing.     

Improvement of polyurethane adhesion to glass using novolac primer

The adhesion of polyurethane (PU) coatings based on toluene diisocyanate, poly(propylene glycol) (PPG) 2000, polyethylene adipate (PEA) 2000 and castor oil (CO) was studied. The coatings were applied to glass slides with and without novolac primer (due to the high functionality of castor oil, the resultant PU coatings have limited shelf life). Our studies showed that satisfactory adhesion strengths were achievable for immediate bonding. Furthermore, our study also found that the adhesion of polyurethane to glass surfaces was increased by using a thin layer of novolac primer.