Aluminum Mold Research Articles

Nanopillared Chitosan/Gelatin Films: A Biomimetic Approach for Improved Osteogenesis

Biomimicry strategies, inspired from natural organization of living organisms, are being widely used in the design of nanobiomaterials. Particularly, nonlithographic techniques have shown immense potential in the facile fabrication of nanostructured surfaces at large-scale production. Orthopedic biomaterials or coatings possessing extracellular matrix-like nanoscale features induce desirable interactions between the bone tissue and implant surface, also known as osseointegration. In this study, nanopillared chitosan/gelatin (C/G) films were fabricated using nanoporous anodic alumina molds, and their antibacterial properties as well as osteogenesis potential were analyzed by comparing to the flat C/G films and tissue culture polystyrene as controls. In vitro analysis of the expression of RUNX2, osteopontion, and osteocalcin genes for mesenchymal stem cells as well as osteoblast-like Saos-2 cells was found to be increased for the cells grown on nano C/G films, indicating early-stage osteogenic differentiation. Moreover, the mineralization tests (quantitative calcium analysis and alizarin red staining) showed that nanotopography significantly enhanced the mineralization capacity of both cell lines. This work may provide a new perspective of biomimetic surface topography fabrication for orthopedic implant coatings with superior osteogenic differentiation capacity and fast bone regeneration potential.

Development and application of an anticorrosion type water release agent

Water based release agents have attracted widely attention in recent years due to their advantages, such as environmental and convenience. However, during the application process, the resistance to the steel mould is not obvious, and the concrete surface is easy to rust, which affects the appearance of the concrete surface. The application of aluminium mould can’t solve the problem of bubble and surface ash. The ZJTM anticorrosion type water release agent developed in this paper can effectively solve the corrosion of the concrete surface, bubble and surface ash, and the effect is remarkable in all kinds of engineering.

Platinum-Nickel Nanotubes Array as Cathode for PEMFC

Pt-based catalysts such as Pt-Co, Pt-Cu, Pt-Ni etc. have been shown to exhibit higher oxygen reduction reaction (ORR) activity than platinum for Proton Exchange Membrane Fuel Cells. This paper describes the synthesis of a new carbon-free structure of electrodes made of vertically aligned PtNi Nanotubes. The process is based on an electrochemistry route of Ni electrodeposition inside nonporous alumina mold, followed by a step of controlled galvanic displacement, annealing and acid treatment leading to the formation of nanotubes. The latter are transferred onto a Nafion® membrane using an optimized hot pressing process.

Fabrication of Plano-Concave Plastic Lens by Novel Injection Molding Using Carbide-Bonded Graphene-Coated Silica Molds.

Injection molding of plastic optical lenses prevails over many other techniques in both efficiency and cost, however polymer shrinkage during cooling, high level of uneven residual stresses and refractive index variations have limited its potential use for high precision lenses fabrication. In this research, we adopted a newly-developed strong graphene network to both plain and convex fused silica mold surfaces and proposed a novel injection molding of plano-concave lenses with graphene coated fused silica molds. The unique combination of the graphene coating and fused silica substrate maximize the mechanical properties of the mold and coating materials, namely high hardness, low surface friction, and high heat preservation effect during cooling since fused silica has low thermal conductivity. This advanced injection molding process was implemented in molding of plano-concave lenses resulting in reduced polymer shrinkage. In addition, internal residual stresses, and refractive index variations were also analyzed and discussed in detail. Meanwhile, as a comparison of conventional injection mold material, aluminum mold inserts with the same shape and size were also diamond machined and then employed to mold the same plano-concave lenses. Finally, a simulation model using Moldex3D was utilized to interpret stress distributions of both graphene and aluminum molds and then validated by experiments. The comparison between graphene and aluminum molds reveals that the novel injection molding with carbide-bonded graphene coated fused silica mold inserts is capable of molding high quality optical lenses with much less shrinkage and residual stresses, but more uniform refractive index distribution.

One-pod preparation of anodic porous alumina molds with tapered holes for moth-eye structures by nanoimprinting

An anodic porous alumina mold with tapered holes was formed by a one-pod preparation process. In this process, one-pod of a mixed solution containing oxalic acid and phosphoric acid was used for both anodization and pore widening. The anodization proceeded during the on state of the applied voltage, while the pore widening proceeded during the off state. The shape of the tapered holes in anodic porous alumina could be controlled by adjusting the program composed of on and off periods. Moth-eye structures were formed by nanoimprinting using the obtained molds. These moth-eye structures effectively suppressed the reflection of incident light.

Freeze Casting of Tubular Anode Supports for High-Performance Solid Oxide Fuel Cells

Freeze casting method has received significant attention in recent years for the fabrication of porous materials with unique pore geometries. A typical freeze casting process involves freezing of a liquid suspension forming solvent crystals that grow in the direction of solidification. When these solvent crystals are removed by sublimation under a reduced pressure, a porous structure with unidirectional and gradient pores is achieved. Such a porous structure is considered ideal for solid oxide fuel cell (SOFC) electrodes because it allows for rapid gaseous diffusion through the bulk of the electrode and a large number of active sites toward the electrolyte–electrode interface for electrochemical reactions. In the present work, we developed a freeze casting and freeze drying process to fabricate tubular SOFC anode supports using an aqueous NiO–yttria-stabilized zirconia (YSZ) slurry. Freeze casting was performed in an aluminum mold that contained peripheral coils for flowing a coolant. After complete freezing of the slurry, the mold was connected to a vacuum chamber for freeze drying. With a proper control of the experimental setup and adjustments in the freeze drying profile, we were able to reduce the total drying time from several days to a few hours. The fabricated anode supports were coated with the thin layers of YSZ electrolyte and strontium-doped lanthanum manganite (LSM)-YSZ cathode to obtain the single cells. The electrochemical performance of the single cells was evaluated by the I–V polarization curves and electrochemical impedance spectra. Owing to the favorable gas transport properties of the freeze-cast anode, the concentration polarization was found to be greatly reduced and thus a high power density was achieved. Figure 1

Evaluation of properties of anti-adhesive coatings on the surface of injection moulds made of Al alloys

Purpose: The aim of the research was to determine the most favourable fluoropolymer coatings, deposited on the surface of aluminium moulds, which will be used to share improvements in automotive sectors. Design/methodology/approach: The paper presents the results of the coatings thickness and surface roughness measurements, AFM analysis, contact angle measurements and surface free energy calculation, wear test and adhesion force measurement of three fluoropolymer coatings. Findings: On the basis of the investigation, it can be stated that the properties of the tested coating and their adhesion to the aluminium substrate are different. Based on the obtained results it can be concluded that the coating named Coat_134 was characterized by the optimum properties - well anti-adhesion properties and good mechanical properties. Research limitations/implications: Coating must be applied on the surface of injection tools, with complex shape and wide range of dimensions. Practical implications: Injection moulds for polyurethane foam, reduction of release agent consumption. Originality/value: The paper presents comparative research of fluoropolymer coatings in order to determinate adhesion to polyurethane foam with low density.

A digital MEMS gyroscope with 40∘/h instability variation in −40∘C to 85∘C

This paper presents a digital MEMS gyroscope with 40[Formula: see text]/h instability variation in −40[Formula: see text]C to 85[Formula: see text]C, performing 5[Formula: see text]/h instability variation at normal temperature and 0.01% nonlinearity in the range of ±400[Formula: see text]/s. This stability was achieved by using temperature compensation for the zero-output value changed after the temperature signal. As the resonant frequency of the mechanical structure varied according to the temperature linearly, a frequency calculator was adopted to detect the temperature of the mechanical structure. And the resolution of the frequency could be up to 0.01 Hz with a 1 MHz clock frequency used, obtaining a 10 Hz bandwidth. The driving mode used a PI controller to control a VGA to maintain at a fixed effective value of the driving signal. The sensing mode contained a low noise C/V convertor and a switch demodulation, which could give the angular velocity signal to the A/D convertor. Then the output data of A/D will be compensated in the digital domain. Finally, the digital output of the gyroscope will be available through a normal SPI serial port. The whole circuit was realized on one chip with an active circuit area of 3.5 mm × 5.2 mm fabricated in a 0.35 [Formula: see text]m CMOS technology. And the MEMS structure and circuit are packaged in a 2.5 cm × 2.5 cm × 2.5 cm aluminum mold. The digital output of the gyroscope earned a noise floor of 0.0024[Formula: see text]/s.

Processing, manufacturing, and characterization of vibration damping in epoxy composites modified with graphene nanoplatelets

This research aims to characterize the vibration and damping properties of epoxy composites modified with pristine and amino‐functionalized graphene nanoplatelets (GNPs) at four different nanofiller loadings (0.2, 0.4, 0.6, 1.2 wt%). The GNPs/acetone solution was mixed with epoxy through mechanical stirring. The mixture was then heated by means of a hot plate to evaporate the acetone. Once the mixture was cooled down, the hardener was added and the mixture injected into aluminum molds to form the nanocomposite test coupons. A shaker generated a periodic signal to excite the cantilever nanocomposite specimens at the fixed end. The frequency response functions (FRFs), damping ratios and natural frequencies measured using the forced vibration technique. The experimental results confirmed the beneficial effect of graphene nanoplatelets on the damping ratio of high content epoxy nanocomposites. POLYM. COMPOS., 40:3914–3922, 2019. © 2019 Society of Plastics Engineers

Phase Transition Evaluation of a Medium Using Acoustic Reverberation Time

Non-destructive monitoring of a material’s state during its physico-chemical transformation is of interest for several industrial fields including food processing and industrial manufacturing. Recent research trends have focused on the monitoring of elastic properties (Young’s modulus, shear modulus) of sol-gel products. The use of ultrasound to provide reliable information about physico-chemical properties is becoming increasingly popular. In fact, ultrasonic techniques have the main advantage of being rapid and non-invasive methods that allow parameters such as product composition, structure and physical state to be obtained. Yet, classical techniques are limited to the characterization of the medium along the propagation path using first wave packets. In this paper, an alternative technique based on studying the reverberated signals is used, by analogy with those classically used in room acoustics. These complex signals contain useful quantitative and qualitative information about medium properties and are sensitive to structural changes. In previous works, this method has shown its capability to characterize materials. Compared to classical techniques, it has the advantage of studying a medium as its whole structure. Using this method, the determination of sol-gel phase transition of Salol is presented. Measurements were performed using an aluminum mould and nine piezoelectric (PZT) patches randomly distributed on the mould rear face. One of them is used as a source and the others are connected to an eight-channel oscilloscope and are used as receivers. The mean reverberation time over four receivers has been studied and its evolution can be linked to a sol-gel phase transition.

Fundamental evaluation of burnishing process with DLC-coated carbide tool targeting aluminum mold for plastic injection molding

Fundamental evaluation of burnishing process with DLC-coated carbide tool targeting aluminum mold for plastic injection molding

THE USE OF ALUMINUM SLAG RECYCLING PRODUCTS IN INVESTMENT CASTING TECHNOLOGIES

The studies of fractional, chemical and phase compositions of aluminum-containing slags of different origin found that slags are multi-component systems consisting of metal and non-metal parts. The non-metal part contains water-soluble and water-insoluble components. A practical scheme for recycling aluminum-containing slags was proposed in order to isolate the water-insoluble component to be further used a secondary refractory dusting material. It was found that the secondary refractory dusting material has a positive effect on the quality of refractory ceramic molds in investment casting and the surface finish of experimental aluminum castings. This material improves the strength of refractory ceramic molds by 9 times in comparison with silica sand molds and increases gas permeability by 15 % to 33 % in comparison with fused alumina and silica sand molds, respectively. The study covers the processes used to produce refractory ceramic molds based on the secondary refractory dusting material. The mechanism of interaction between dusting material particles and suspension is theoretically justified in terms of colloid chemistry. Negatively charged aluminum hydroxide micelles appear when ceramic mold layers are formed using the secondary refractory dusting material. Interaction between differently charged Al(OH)3 and SiO2 micelles makes secondary refractory dusting material particles come in close contact with each other. The theoretically justified processes of ceramic mold layer formation with the secondary refractory dusting material make it possible to explain the reduction in the surface roughness of castings made of AK9ch aluminum casting alloy using investment casting by 3.7 times compared with standard production processes.

Multi-Purpose Usage of Super Low Reflective Film “Moth-Eye Film”, Nanoimprinted by the Anodic Oxidized Alumina Mold

Multi-Purpose Usage of Super Low Reflective Film “Moth-Eye Film”, Nanoimprinted by the Anodic Oxidized Alumina Mold

Effect of Morphological Changes due to Increasing Carbon Nanoparticles Content on the Quasi-Static Mechanical Response of Epoxy Resin.

Mechanical failure in epoxy polymer and composites leads them to commonly be referred to as inherently brittle due to the presence of polymerization-induced microcrack and microvoids, which are barriers to high-performance applications, e.g., in aerospace structures. Numerous studies have been carried out on epoxy’s strengthening and toughening via nanomaterial reinforcement, e.g., using rubber nanoparticles in the epoxy matrix of new composite aircraft. However, extremely cautious process and functionalization steps must be taken in order to achieve high-quality dispersion and bonding, the development of which is not keeping pace with large structures applications. In this article, we report our studies on the mechanical performance of an epoxy polymer reinforced with graphite carbon nanoparticles (CNPs), and the possible effects arising from a straightforward, rapid stir-mixing technique. The CNPs were embedded in a low viscosity epoxy resin, with the CNP weight percentage (wt %) being varied between 1% and 5%. Simplified stirring embedment was selected in the interests of industrial process facilitation, and functionalization was avoided to reduce the number of parameters involved in the study. Embedment conditions and timing were held constant for all wt %. The CNP filled epoxy resin was then injected into an aluminum mold and cured under vacuum conditions at 80 °C for 12 h. A series of test specimens were then extracted from the mold, and tested under uniaxial quasi-static tension, compression, and nanoindentation. Elementary mechanical properties including failure strain, hardness, strength, and modulus were measured. The mechanical performance was improved by the incorporation of 1 and 2 wt % of CNP but was degraded by 5 wt % CNP, mainly attributed to the morphological change, including re-agglomeration, with the increasing CNP wt %. This change strongly correlated with the mechanical response in the presence of CNP, and was the major governing mechanism leading to both mechanical improvement and degradation.

The Influence of Thermal Load on Composite Coating PTFE

This article deals with the thermal stability of the PTFE coating and the composite coating composed with the PTFE matrix and titanium dioxide particles. These coatings have application in production of aluminium moulds in the automotive industry, specifically in the vulcanization of rubber materials. The first type of coating (PTFE coating) is already applied in the production and thanks to its application on the Al mould surface, the maintenance interval was increased by up to 400% compared to the uncoated state. Vulcanization of rubber compounds usually take place at a temperature 150 - 170°C. This temperature can be increased after addition of additives to a temperature 220°C. For this reasons, there is the research focused on degradation of these coatings at various thermal loads. Thermal stability was tested on coatings - PTFE a PTFE + TiO2 - applied on aluminium substrate (type Al - Si). Experimental samples were loaded at temperatures 150°C, 200°C, 250°C, 300°C, 350°C, 400°C a 500°C at a time 30 minutes and 60 minutes. The samples after thermal load were performed to tribometric analysis, and to the surface roughness measurement of selected parameters. The samples were also evaluated from the point of view of surface morphology and state of the surface with SEM and EDS analysis.

Vertically Aligned Platinum Copper Nanotubes as PEM Fuel Cell Cathode: Elaboration and Fuel Cell Test

AbstractThis paper describes the elaboration via an electrochemistry route of a PEM carbon‐free cathode made of a periodic array of vertically aligned platinum copper nanotubes. Nanotubes synthesis is assisted with a porous alumina mold made on a silicon substrate to perform growth of copper nanowires. After optimization of an original confined galvanic displacement with H2PtCl6 salt, PtCu nanotubes are embedded into porous alumina template and directly integrated onto a Nafion® membrane. Therefore, our process does not need any step of purification or catalyst dispersion. The performances in fuel cell of these new electrodes are compared to conventional structures made of Tanaka Pt/C with the same electrocatalytic surface area. Significant improvement in the specific activity at 0.9 V and reduction in mass transport limitations are observed compared with standard Tanaka Pt/C catalyst in real operating conditions.

Development of shape memory alloy actuator integrated flexible poly-ether-ether-ketone antenna with simultaneous beam steering and shaping ability

Active control of antenna radiation by mechanical reconfiguration has large potential applications in space as well as in ground segment. Such reconfigurable antenna primarily has two functionalities: beam steering and beam shaping. While previous research has shown individual control of these functions; we have developed a suitable antenna actuation system which takes care of both the functionalities. To demonstrate our concept, we have fabricated a 1-m diameterC-band flexible reflector of poly-ether-ether-ketone using precisely machined aluminum mold. A periphery feed structure is connected to the center of the reflector by a goose-neck-shaped supporting frame. Next, we have designed and developed a smart control-disk containing two types of shape memory alloy actuator-based self-locking devices. A group of actuators are used for locking/unlocking the rotational degree of freedom of the antenna; while the other group generates deformation of antenna at the desired direction. An 8-bit absolute encoder is installed with each locking device to sense and feedback the displacement of a control point. We have achieved a controllable deflection up to 25 mm with a precision of 0.3 mm with this system. A directional precision of [Formula: see text] is also achieved simultaneously. Presently, we have developed eight such actuation points on the disk to control the shape of the antenna. For numerical simulation of the structural deformation and study of the radio frequency pattern, finite element analysis is carried out using ABAQUS, and the far-field radiation pattern corresponding to the deformed shape is obtained. The electromagnetic patterns are analyzed using geometric optics technique. Finally, a methodology of achieving surface coordinates for desired radiation pattern is presented. The study provides useful insights into the design of flexible and reconfigurable antenna system.

Solar Powder Metallurgy: Preparation of TiC – TiB2 Ceramic Foam

The solar powder metallurgy was used to prepare TiC–TiB2 ceramic foams in 40kW horizontal solar furnace at Plataforma Solar de Almeria (PSA), Spain. The foams were prepared using self-propagating high-temperature synthesis from the green compacts of powder mixture of Ti + 15 vol.% B4C. The foaming was performed under protective argon atmosphere at various heating rates. It was shown that it is possible to prepare successfully TiC–TiB2 ceramic foams with porosity around 45%. The foaming temperature or ignition temperature was found to be around 1380 °C. The optimal heating rate for foam preparation was found to be 220°C/min. It was confirmed that 2 pieces of precursor will join successfully to create single foam. Further, graphite and alumina moulds were tested for possible preparation of 3D shapes. The EDS investigations confirmed the creation of TiB2, TiC and complex TiBxC1-x phases.

Fabrication of Line & Space Structure and Wiring on 3D Surface Features with Imprinting Process

In recent years, electronic devices made by polymers with wiring materials are widely used, such as FPC (Flexible Printed Circuit) in a PC (Personal Computer), and smartphones. Fine Pitch Wiring technologies on 3D objects are needed for coming IoT(Internet of Things) trends. Therefore, in this research, we conducted a fundamental study of the low-cost replication process with etching less wiring method in order to replicate microstructure on the curved polymer surfaces by using the hybrid nanoimprint technology. The first imprinting step was carried out to produce the intermediate mold on COP (Cyclic Olefin Polymer) surface by thermal nanoimprint process. The aluminum mold with a concavo-convex structure called L/S (Line & Space; concave width of 500 µm, concave depth of 100 µm) was used. The obtained intermediate structure was coated with UV (Ultraviolet) curable resin and it was applied to the 3D substrate (curved surface region: lens shape) having planar region and curved surface region as shown in Fig. 1. In this step, UV imprinting was applied with the pressure of 5 MPa and UV irradiation time of 300 seconds to transfer the L/S structure to the 3D substrate. Thereafter, the silver nanoink was dropped and filled in the concave portion of the L/S structure using a dispenser and sintered at 160 oC for 1 hour. SEM (Scanning Electron Microscope) image revealed that the 3D structure can be precisely transferred on the curved surface by using this hybrid nanoimprint technology (See Fig. 2). In Fig. 3, the transfer rates in the planar region (flat) and curved region were 100 and 60%, respectively. It is considered that the liquid UV curable resin may flow downward from the upper part to the lower part along the inclination of the substrate during the crimping and curing steps, resulting in the decrease in filling amount from the intermediate mold structure. The L/S patterned wired with silver nanoink is shown in Fig. 4. This result proposes that the hybrid nanoimprint technology is considered to be an effective method for the replication of wiring on the curved surface. Figure 1

Performance Analysis of Enhanced 3D Printed Polymer Molds for Metal Injection Molding Process

Conventionally, molds for metal injection molding (MIM) process are fabricated using metallic materials using conventional machining processes. Machined metal molds are resilient and therefore could be suitable for mass production of MIM parts. However, with the process of mass production leading to permanent hard tooling, the design is subjected to rigorous testing and iteration before finalization. During design analysis and the iteration process, the demand for MIM parts (part demand) is at low-volume. Therefore, machined metal molds could be costly and time consuming for low volume and customized end-use products. 3D printed molds could be a suitable choice for MIM production for such applications. The present study compares the performance of Fused Deposition Modelling (FDM) 3D printing (3DP) process made polymer molds with an aluminum mold for potential use in MIM process. It was observed that 3DP molds could successfully be used for a limited number of MIM cycles.