Glass Mold Research Articles

Amorphous Carbon Coated Silicon Wafer as Mold Insert for Precision Glass Molding

Press molding of glass is an emerging research area for micro-optics manufacturing. Despite advancements on coating layers of precision molds for glass molding, challenges still exist towards tailoring non-stick coating to provide consistent replication accuracy in thousands of repetitive molding cycles. In this study, atmospheric pressure chemical vapor deposition (APCVD) is introduced to synthesize nanoscale-thickness amorphous carbon layer on the surface of silicon wafer with liquid benzene as the carbon source and silicone rubber as the silicon oxycarbide (SiOC) source. The micro-morphologies of the coating layers under different conditions are obtained and analyzed. In the press molding, the coating exhibits extraordinary physical properties and can remarkably prevent silicon-glass adhesion under elevated temperature. Typical micro-structures, such as micro-pillar and micro-lens arrays on the amorphous carbon coated silicon wafers, are used as mold inserts in precision glass molding to replicate high-precision optical components. The results indicate that this amorphous carbon coated silicon wafer can replicate intricate micro-structures to glass substrates with high-precision dimensions without macroscopic adhesion. This coating technology will protect the mold materials with low adhesion and improve precision glass molding process.

The effect of hydroxyapatite concentration on the mechanical properties and degradation rate of biocomposite for biomedical applications

Biocomposite is a material that have potential to heal injured bones and teeth due to their biocompatible, non-toxic, non-inflammation, and bioactive properties which can prevent infections that occurs frequently during surgical processes. Biocomposites made of PLA, PCL, and HA from bovine bone as a substitute for metal materials in medical applications have been widely studied. However, there are limited studies on the biocomposites made of PLA, PCL, and HA from green mussel shells. Therefore, this study aims to produce biocomposites from Polylactic Acid (PLA), Polycaprolactone (PCL), and Hydroxyapatite (HA) from green mussel shells and to determine the effect of HA concentration on the mechanical properties and degradation rate of the resulting biocomposite. 80 ml of chloroform was used to dissolve 16 grams of a PLA/PCL mixture with a composition of 80% and 20%. After 30 minutes, the solution was agitated for 30 minutes with a magnetic stirrer at 50°C and 300 rpm. After obtaining a homogenous solution, hydroxyapatite was added in percentages of 5%, 10%, 15%, and 20% of the total weight of the PLA/PCL mixture. The resulting mixture is poured into a glass mold in accordance with ASTM D790. Three-point bending, density, and biodegradable test were performed to investigate the effect of HA content on the mechanical properties and degradation rate of the biocomposite. The results of this study indicate that the mechanical properties of the biocomposite improved with the HA concentration increases. However, the more HA content used, the faster the biocomposite degrades.

Demonstration of Molded Glass Primary Optics for High-Efficiency Micro-Concentrator Photovoltaics

Demonstration of Molded Glass Primary Optics for High-Efficiency Micro-Concentrator Photovoltaics

Study the effect of reinforcement material in particles on the properties of unsaturated polyester

This study dealt with the preparation of compounds (1, 2, 3) of chemical composition (pure unsaturated polyester), (96% unsaturated polyester reinforced with 4% zeolite), (96% unsaturated polyester reinforced with 4% white cement), respectively, The models were prepared by hand casting method with glass molds prepared with dimensions (25 × 25 cm) and a height of (5 mm). It was cut into dimensions to suit each examination. And then a number of mechanical tests were performed, which included Bernel hardness and compressive strength for all vehicles, as well as measuring the coefficient of thermal conductivity and electrical conductivity, in addition to measuring Miller's coefficients by conducting an X-ray diffraction test for all models. From the results, it was concluded that the highest values of thermal conductivity coefficient were for the first compound consisting only of unsaturated polyester resin, then the values decreased significantly for the compound reinforced with zeolite and reinforced with white cement, as well as for the electrical conductivity where the highest value given by the first compound - Ω.cm- 1 (6.163), while the lowest value was given by the white cement-reinforced compound with a value of −1 (3.33) Ω.cm.While the mechanical properties had a direct relationship with the reinforcement in minutes, as the highest values of hardness were given by the third compound reinforced with white cement, then followed by the second compound reinforced with zeolite with values (48) and (59), respectively. The same is the case with the compressive strength, which gave the highest values at the reinforcement in minutes. The first compound, which consisted only of unsaturated polyester, gave the lowest value of compressive strength, Mpa (34.5).

Deformation Analysis of the Glass Preform in the Progress of Precision Glass Molding for Fabricating Chalcogenide Glass Diffractive Optics with the Finite Element Method.

Precision glass molding (PGM) technology is a cost-efficient process for the production of micro/nanostructured glass components with complex surface geometries. The stress distribution, surface profile, and reduced refractive index of the molded lens are based on the lens being fully formed. The process of the deformation of the glass preform is rarely discussed, especially in the case of multi-machining parameters in the experiment. The finite element method (FEM) was adopted to analyze the glass preform deformation. Due to the phenomenon of incomplete deformation of the glass preforms in the experiments, two groups of finite element simulations with different boundary conditions were carried out with MSC.Marc software, to reveal the relationship between the deformation progress and the parameters settings. Based on the simulation results, a glass preform deformation model was established. The error between the model result and the simulation result was less than 0.16. The establishment method of the glass preform deformation model and the established model can be used as a reference in efficiently optimizing PGM processing parameters when the designed lens has two different base radii of curvature.

Characterization of Bacterial Nanocellulose - Graphite Nanoplatelets Composite Films

Bacterial cellulose (BC) was synthesized from pineapple peel extract media with addition of fermentation agent bacteria Acetobacter xylinum. BC was disintegrated from the pellicle into bacterial nanocellulose (BNC) by using a high-pressure homogenizer (hph) machine, which has a three-dimensional woven nanofibrous network. The synthesis of composite films started when BNC, graphite nanoplatelets, and cetyltrimethylammonium bromide (CTAB) were homogenized using an ultrasonic homogenizer then baked on a glass mold at a temperature of 80 degrees Celcius for 14h. A scanning electron microscope (SEM) was used to analyze its morphology. X-Ray diffraction spectra were used to analyze the composite films structure. The functional groups of the composite films were analyzed using the FTIR spectrum. SEM micrograph shows that GNP was evenly distributed into BNC matrix after CTAB addition. GNPs are shown as flat and smooth flakes with sharp corners. Some peak corresponds O-H, C-H, C≡C, and CH3 stretching was identified by using FTIR spectroscopy at wavenumber 3379, 2893, 2135, and 1340 cm-1, respectively. XRD analysis shows that Crystalline Index (C.I) of BNC increases after 2.5 wt% addition of GNP. The presence of CTAB decreases C.I value of composite films. BNC/GNP composite films have the best mechanical properties with Young’s modulus about 77.01 ± 8.564.

Study of the Transcription Effects of Pressing Dies with Ultrasonic Polishing on Glass Molding

The micro lens array (MLA) has played an important role in optical systems for the past few years, and the precision of pressing dies has dominated the quality of MLAs in glass molding. Few studies have covered the transcription effects on surface roughness of pressing dies for this technology. Therefore, this research utilized pressing dies to produce a sine-wave lens array on glass molding, to transform the Gauss-distributed spotlight into a uniform straight one and then characterize the transcription effects of these lenses. Pressing dies with a sine-wave shape were firstly cut by wire electrical discharge machining (WEDM), and then ultrasonic polishing using diamond abrasives was applied to finish the sine-wave surface with an original roughness of 0.2 μm Ra. Next, the sine-wave lens arrays were pressed by glass molding at the appropriate pressure and temperature, before evaluating the transcription effects of transforming the Gauss-distributed spotlight into a uniform straight one. The result showed that the sine-wave lens array stuck easily to the pressing die and then ruptured during glass molding due to the poor surface roughness of pressing tool. However, the diamond abrasive with appropriate sizes could establish good surface roughness on pressing dies via ultrasonic polishing, and the pressing die with a low surface roughness of 0.08 μm Ra was able to successfully perform MLA in the glass molding. However, only pressing dies with a surface roughness smaller than 0.023 μm Ra could produce precision glass lenses to transform the Gauss-distributed spotlight into a uniform straight one.

Superplastic Nanomolding of Highly Ordered Metallic Sub‐Micrometer Pillars Arrays for Surface Enhanced Raman Scattering

AbstractOrdered metallic nanostructures, due to their superior electronic and photonic properties, have played a vital role in wide range of applications, such as metamaterials, plasmonic sensing, electrocatalysis, and energy devices. However, traditional fabrication strategies based on bottom‐up self‐assembly and top‐down lithography are either poor in uniformity or time‐consuming with low scalability. Here, a robust and cost‐effective approach for the fabrication of highly ordered metallic pillars arrays in centimeter scale is presented. This is realized by superplastic nanomolding of metals with highly ordered anodic aluminum oxide templates which are fabricated by the prepatterning of aluminum sheets with bulk metallic glass (BMG) mold, followed by anodizing. The nanopatterning process is rationalized with finite element simulation to avoid the damage of BMG mold. Finally, it is shown that the molded metallic sub‐micrometer pillars arrays can be used for the surface‐enhanced Raman scattering (SERS) with enhancement factor of ≈106. It is found that the SERS performance is influenced by the specific surface area of the pillars in addition to the near‐field intensity. This simple and cost‐effective method not only opens new opportunities for rapid prototyping of large‐scale ordered metallic nanostructures for various applications but also provides guidance for the quantitative analysis on sub‐micrometer scale.

A Wavy-Structured Highly Stretchable Thermoelectric Generator with Stable Energy Output and Self-Rescuing Capability

A Wavy-Structured Highly Stretchable Thermoelectric Generator with Stable Energy Output and Self-Rescuing Capability

Methodological Aspects of Obtaining and Characterizing Composites Based on Biogenic Diatomaceous Silica and Epoxy Resins.

Diatomaceous earth are sediments of unicellular algal skeletons with a well-defined hierarchical structure. Despite many tests conducted on systems using diatomaceous earth and epoxy resins, we can find many differences in the methods of acquisition and characteristics of the composite, which may considerably affect the results. In our study, we have conducted tests to verify the impact of the method of obtaining samples and the degassing of the composite on its mechanical properties and standard deviation. The samples were cast in glass moulds and silicone moulds and then subjected to testing for their mechanical and functional properties, imaging with the use of an optical microscope and a scanning electron microscope. The tests have shown that, for samples cast in glass moulds, there is no heterogeneity within the area of the tested sample, as in the case of samples cast in silicone moulds. Silicone moulds allow for quite effective self-degassing of the resin due to the large area-to-mass ratio, and the small remaining air vesicles have a limited effect on the mechanical properties of the samples. The filler used also played a significant role. For systems containing base and rinsed diatomite, it is clear that the degassing of mixtures increases the tensile strength. For treated diatomite, the elongation at break grew along with increasing filler concentration, while for base diatomite, the improvement was observed for flexural strength and impact strength. A non-modified epoxy resin shows a tensile strength at 19.91 MPa (silicone mould cast). At the same time, the degassed, glass mould-cast systems containing 12% of base and rinsed diatoms showed a tensile strength of 27.4 MPa and 44.7 MPa, respectively. We have also observed that the higher the filler concentration, the higher were the tensile strength values, which for the rinsed diatoms reached over 55.1 MPa and for the base diatoms were maximum of 43.8 MPa. The tests, therefore, constitute a set of guidelines and recommendations for testing with the use of fillers showing an extended inner structure.

Fabrication of large-scale infrared diffractive lens arrays on chalcogenide glass by means of step-and-repeat hot imprinting and non-isothermal glass molding

In this study, a new cost-effective and high-precision process chain for the fabrication of large-scale infrared (IR) diffractive lens arrays on chalcogenide glass is proposed. First, a positive diffractive lens array is fabricated on a polymethylmethacrylate (PMMA) master substrate by employing a step-and-repeat hot imprinting process. The direct hot imprinting can transfer microstructures from a heated mold to the polymer substrate accurately. Repeating the hot imprinting process along a predetermined path, the desired diffractive lens array is obtained. Unlike photolithography and electron-beam writing, which are expensive technologies with sophisticated process steps, the hot imprinting is an easier, cheaper, and more eco-friendly method for fabricating diffractive features with continuous profile. Afterwards a casting process is applied to create a polydimethylsiloxane (PDMS) mold with negative features. The diffractive lens array is successfully transferred from the master substrate to the PDMS elastomer, which is used as a mold in subsequent precision glass molding. Finally, microstructures on the PDMS mold are replicated to the chalcogenide glass by non-isothermal glass molding. In this process, the PDMS mold and workpiece are set at different temperatures. Specifically the PDMS mold at low temperature maintains enough rigidity to press the features onto the softened chalcogenide glass, which is kept at a relatively higher temperature, resulting in a replica of high-fidelity diffractive lens array on the chalcogenide glass. Surface profiles and optical performance of the fabricated components are characterized quantitatively. Results showed that large-scale diffractive lens array can be successfully fabricated on chalcogenide glass by this proposed process chain with high quality and integrity.

A Comprehensive Review of Micro/Nano Precision Glass Molding Molds and Their Fabrication Methods

Micro/nano-precision glass molding (MNPGM) is an efficient approach for manufacturing micro/nanostructured glass components with intricate geometry and a high-quality optical finish. In MNPGM, the mold, which directly imprints the desired pattern on the glass substrate, is a key component. To date, a wide variety of mold inserts have been utilized in MNPGM. The aim of this article is to review the latest advances in molds for MNPGM and their fabrication methods. Surface finishing is specifically addressed because molded glass is usually intended for optical applications in which the surface roughness should be lower than the wavelength of incident light to avoid scattering loss. The use of molds for a wide range of molding temperatures is also discussed in detail. Finally, a series of tables summarizing the mold fabrication methods, mold patterns and their dimensions, anti-adhesion coatings, molding conditions, molding methods, surface roughness values, glass substrates and their glass transition temperatures, and associated applications are presented. This review is intended as a roadmap for those interested in the glass molding field.

INFLUENCE OF AN ORGANIC ADDITIVE ON THE STRUCTURE OF AN AQUEOUS SODIUM SILICATE FILM ON THE SURFACE OF A REFRACTORY CHROMITE FILLER

Formation of the structure of a film of hydrous sodium silicate on the surface of a refractory chromite filler. Wastes of contact cleaning of oils were used as organic additives, which are calcium bentonite impregnated with oils. The structure of liquid glass films on the surface of a refractory filler, cured at a temperature of 180-400-600-900 ° C, is investigated, which is comparable to the temperature convective system of liquid glass molds and rods, as well as the temperature system of molds after pouring with hot metal.

High-temperature friction characteristics of N-BK7 glass and their correlation with viscoelastic loss modulus

It is fundamentally important to investigate the interfacial friction between softened glass and rigid molds for controlling the product quality in glass hot forming techniques. However, the underlying mechanism has not been fully understood in terms of the contribution of viscous dissipation to the viscoelastic friction of softened glass. In this paper, a dry rotary sliding scheme using the ball-on-disc pair is employed to investigate the high-temperature friction characteristics of a typical borosilicate crown glass N-BK7 from 500 °C to 660 °C. Experimental results show that the friction coefficients in the steady stage remarkably increase with the applied temperatures. For softened glass, friction could originate from adhesion, ploughing and dissipation. Furthermore, with careful estimations on both the scratch deformation frequency and the induced flash temperature during sliding, the increase in friction coefficient with temperature is well correlated with the loss modulus ratio, which presents the viscous energy dissipation by macroscale ploughing. Additionally, the friction coefficients at 500 mm/s are slightly larger than those at 250 mm/s, because the effect of more frictional heat prevails. Lastly, the influences of temperature and frequency shifting on the loss modulus ratio are summarized to explain the experimental evolution of friction coefficient. It is confirmed for N-BK7 glass that the dependences of friction coefficients on temperature and sliding velocity, also follow the classical superposition master curve of viscoelastic friction.

Study on Mechanism of Glass Molding Process for Fingerprint Lock Glass Plates

Curved glass is widely used in 3C industry, and the market demand is increasing gradually. Glass molding process (GMP) is a high-precision, high-efficiency 3D glass touch panel processing technology. In this study, the processing parameters of fingerprint lock glass panels were deeply analyzed. This paper first introduces the molding process of the glass panel, discusses the glass forming device, and explains the heat conduction principle of the glass. Firstly, it introduces the forming process of the glass panel, discusses the glass forming device, and explains the heat conduction principle of the glass. Secondly, the simulation model of a fingerprint lock glass plate was simulated by MSC. Marc software. The stress relaxation model and structure relaxation model are used in the model, and the heat transfer characteristics of glass mold are combined to accurately predict the forming process of glass components. The effects of molding temperature, heating rate, holding time, molding pressure, cooling rate and other process parameters on product quality characteristics (residual stress and shape deviation) were analyzed through simulation experiments. The results show that, in a certain range, the residual stress is inversely proportional to the bending temperature and heating rate, and is directly proportional to the cooling rate, while the shape deviation decreases with the increase of temperature and heating rate. When the cooling rate decreases, the shape deviation first decreases and then increases. Furthermore, a verification experiment is designed to verify the reliability of the simulation results by measuring and calculating the surface roughness of the formed products.

Molded Vial Manufacturing and Its Impact on Heat Transfer during Freeze-Drying: Vial Geometry Considerations

Recent advances in molded vial manufacturing enabled manufacturers to use a new manufacturing technique to achieve superior homogeneity of the vial wall thickness. This study evaluated the influence of the different manufacturing techniques of molded vials and glass compositions on vial heat transfer in freeze-drying. Additionally, the influence of using empty vials as thermal shielding on thermal characteristics of edge and center vials was investigated. The vial heat transfer coefficient Kv was determined gravimetrically for multiple vial systems. The results showed superior heat transfer characteristics of the novel manufacturing technique as well as differences in heat transfer for the different glass compositions. Empty vials on the outside of the array did not influence center vial Kv values compared to a full array. The direct contact area and vial bottom curvature and their correlation to heat transfer parameters were analyzed across multiple vial systems. A new approach based on light microscopy to describe the vial bottom curvature more accurately was described. The presented results for the contact area allowed for an approximation of the pressure-independent heat transfer parameter KC. The results for the vial bottom curvature showed a great correlation to the pressure-dependent heat transfer parameter KD. Overall, the results highlighted how a thorough geometrical characterization of vials with known heat transfer characteristics could be used to predict thermal characteristics of new vial systems as an alternative to a time-consuming gravimetric Kv determination. Primary drying times were simulated to show the influence of Kv on drying performance.

Functionalized Three-Dimensional Multilayer Ceramic Modules

Three-dimensional interconnect devices are still strongly related to plastic materials. Since the use of these materials is limited in harsh environments, there is an application gap, which could be filled by ceramic circuit carriers. Low-temperature cofired ceramics (LTCC) offer promising solutions to fill this gap. This work provides a feasibility study, including the whole technological chain of ceramic multilayer processing. Targeting a curved multilayer substrate, fully equipped with SMD (Surface-mounted device) components, the particularities of single process steps are investigated. Two shaping methods based on quartz glass molds are compared with regard to shape fidelity and technological effort. The investigation of internal conductor lines and via connections reveals that the metallization should have a minimum width of 200 µm and the via diameter is limited to 150 µm. Further considerations focus on the possible footprint of components and use of cavities to increase the footprint of components. The limits of wire bonding on curved surfaces were inspected. Finally, the work presents a demonstrator of a fully equipped four-layer ceramic circuit, including internal wiring. Hence, the transfer of the 2.5-dimensional multilayer ceramic technology into the third dimension is proven.

Fabrication of high-precision freeform surface on die steel by ultrasonic-assisted slow tool servo.

The mold core fabrication of a freeform surface on die steel by ultra-precision machining can make the optical elements of freeform be mass-produced by plastic injection and glass mold pressing. However, because steel is a typical difficult-to-cut material, the technical limitations of existing machining methods hardly meet the current requirements of design. In this paper, a novel machining method, one-dimension ultrasonic-assisted slow tool servo (UASTS) turning, is proposed to manufacture the freeform surface with high-precision and large-steepness on the die steel. Aiming at the characteristics of UASTS turning, the tool trajectory is generated by analyzing the compensation of tool radius and confirming the position of ultrasonic displacement. The 2D surface model contours of residual tool marks are established for predicting the 3D surface topography based on considering the effects of kinematics, material elastic recovery and plastic side flow. In the experiments, the large-amplitude bidirectional sinusoidal wave grid (BSWG) surface is successfully fabricated by UASTS technology on the material, Polmax steel, for which the value Rt of surface roughness is less than 70nm and the value Ra of surface roughness can achieve to 3.298nm. The results show that the freeform surface with high-precision and large-steepness can be machined by UASTS turning technology on mold steel.

Annealed high-phosphorus electroless Ni–P coatings for producing molds for precision glass molding

An annealed high-phosphorus electroless Ni–P coating was developed as the mold material for precision glass molding. The coating with a phosphorus content of 11.6 wt% was prepared on heat-resistant stainless steel via an intermittent ultrasonic-assisted electroless plating method. The effects of annealing temperature and heating rate on phase transformation, grain size variation, and mechanical properties were investigated. An annealing temperature of 600 °C with a heating rate of 5 °C/min was determined to be the optimal choice for heat treatment. Microgrooves were machined on the coating surface. After heat treatment, the increased hardness and modulus helped the microgrooves on the coating resist thermal deformation during the PGM process. The PV value decreased from 0.58 to 0.32 μm, and the surface roughness decreased from Sa 104.5 to Sa 62.6 nm. The mold produced by heat-treated coating was beneficial for improving the forming accuracy of precision glass molding.

Multi-Scale Characterization by Neutronography and Electron Diffraction of Ni Coating on Cu-Ni-Al or Cast-Iron Glass Molds after Laser Cladding

Laser cladding of a Ni based powder on Cu-Ni-Al or cast iron was performed with a 4kW continuous Nd: YAG laser. The Cu-Ni-Al and cast-iron substrates are used for their thermal properties in glass mold industry. But the issue of these materials is their lack of resistance on corrosion and abrasion. The role of the Ni based alloy is to protect the mold without affecting its thermal properties (Heat Affected Zone (HAZ)). The purpose of this research is to produce a well bonded Ni based melted powder without pores or cracks on a non-planar surface (curvilinear section). An investigation of the impact of the processing parameters, power (1500-3200 W), scanning speed (2.5-10 mm/s) and powder feeding rate (24.5-32.5 g/min) on the bonding quality, the porosity propagation and HAZ appearance is performed. The used methods are neutronography, Scanning Electron Microscopy, Energy Dispersive Spectroscopy and Electron BackScatter Diffraction (EBSD). These multi-scale techniques are obviously complementary. Neutronography is a well-adapted non-destructive method to observe the porosity in the volume thanks to the contrast between materials. EBSD analysis allows us to analyze the microstructural evolution of the coating notably by observing the dendrites growth. This same method also permits to observe the HAZ nature according to the laser cladding parameters. Those methods allowed to optimize the processing parameters in a way to obtain perfect bonding, to avoid porosity propagation and to limit the HAZ emergence.