Hot Press Lamination Research Articles

Large-area graphene on polymer film for flexible and transparent anode in field emission device

We present the fabrication and electrical characterization of large graphene structure on polyethylene terephthalate (PET) flexible substrate. Graphene film was grown on Cu foil by thermal chemical vapor deposition and transferred to PET by using hot press lamination. The graphene/PET film shows high quality, flexible transparent conductive structure with unique electrical-mechanical properties; ∼88.80% light transmittance and ∼1.1742 kΩ/sq sheet resistance. We demonstrate application of graphene/PET film as flexible and transparent electrode for field emission displays. Our proposed techniques can be tailored for any flexible substrate and large scale production, which could open up exciting device applications in foldable electronics.

Alumina–tantalum composite for femoral head applications in total hip arthroplasty

Dense composite laminates of alumina (Al 2O 3) and tantalum (Ta) were fabricated by hot pressing and tested in vitro for potential use as a femoral head material in total hip arthroplasty (THA). Al 2O 3–Ta composite laminates hot pressed at 1450 °C and 1650 °C had flexural strengths of 940 ± 180 MPa and 1090 ± 340 MPa, respectively, which were far larger than the values of 420 ± 140 MPa and 400 ± 130 MPa for Al 2O 3 hot pressed at 1450 °C and 1650 °C, respectively. The interfacial shear strength, determined by a double-notched specimen test, was 310 ± 80 MPa for the composite laminate hot pressed at 1650 °C, indicating strong interfacial bonding between Al 2O 3 and Ta. Scanning electron microscopy (SEM), energy dispersive X-ray (EDS) analysis, and X-ray mapping of polished sections of the hot-pressed laminates showed the presence of an interfacial region formed presumably by diffusion of O (at 1450 °C) or O and Al (1650 °C) from Al 2O 3 into Ta. Composite femoral heads of Al 2O 3 and Ta could combine the low wear of an Al 2O 3 articulating surface with the safety of a ductile metal femoral head.

Deformation and fracture behavior of Nb in Nb 5Si 3/Nb laminates and its effect on laminate toughness

The mechanical behaviour of the Nb reinforcement (250 μm thick foils) in Nb 5Si 3/Nb/Nb 5Si 3 laminates were investigated under a variety of stress states and test temperatures. Tests were conducted at room temperature (298 K) and 77K on as-received Nb foils, on Nb 5Si 3/Nb/Nb 5Si 3 laminates, on Nb foils extracts from the hot pressed laminates, and on Nb foils simply exposed to vacuum at high temperature. It is shown that Nb grain size, solid solution of Si in Nb, degree of constraint, and test temperature significantly affect the mechanical behavior of Nb. All unconstrained Nb foils failed via ductile rupture at room temperature, while a mixture of cleavage and ductile fracture was exhibited by the constrained Nb present in the laminates. A similar ductile-to-brittle transition in fracture appearance was observed for some foils tested at 77 K, accompanied by a reduction in total energy to fracture. The peak toughness exhibited by the laminates tested at 77 K was only reduced 28% from that exhibited at 298 K, despite this drastic change in fracture mode from ductile to brittle. The effects of composition, interface strength and test conditions on the mechanical behavior of the Nb and its subsequent role on the toughness of the laminates are discussed.

Physical design and fabrication of a multiple element slab waveguide spectrograph for multimode fiber-optic WDM systems

The materials and processes for fabricating a compact multiple-element slab waveguide spectrograph suitable for multimode fiber-optic wavelength-division-multiplexing (WDM) applications are described. A fabrication scheme based on thick-film solder glass glazing, hot-press lamination and optical finishing was chosen to produce a precisely dimensioned glass-ceramic spectrograph blank structure that is compatible with grating replication manufacturing technology and suitable for hermetic packaging. The laminated blank consists of alternating layers of glass-ceramic spacer plates and optical glass wafers bonded together with a screen-printed solder glass adhesive. The exact interlayer optomechanical registration, achieved in the laminated spectrograph blank was essential for obtaining spectral referencing functionality and a passive alignment packaging scheme. A spectrograph optical subassembly package was developed and implemented as part of a multichannel spectrum analyzer receiver in a prototype optical WDM sensor interface system.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

An FT-IR Study on Interfacial Interactions in Ethylene Copolymers/Aluminium Laminates in Relation to Adhesion Properties

Abstract The effect of three different functional groups in ethylene copolymers on the adhesion with aluminium was studied. The interface in polymer/metal laminates was analyzed by FT-IR, and the adhesion mechanism for each functional group was evaluated. Laminate samples were prepared by solution casting or by hotpressing polymeric film onto the aluminium substrate. In the latter case, the interface was exposed by solvent extraction. The interfacial structures developed by the different copolymers were correlated to the mechanical strength of hotpressed laminates, which was measured by a peel test. The polymer surfaces were further characterized by contact angle measurements. Polar functional groups, carboxylic acid and butyl ester in hotpressed laminates were found to form Lewis acid/base interactions with the aluminium oxide. The strength of the interfacial interactions was correlated to the concentration and acidity/basicity of the group, the acid group being the most efficient. A silane functional gr...

Thermal Characteristics of Multilayer Printed Wiring Boards During Lamination

This paper presents the results of a study to identify the thermal characteristics of the laminating process for multilayer printed wiring boards (MLB's). MLB's with 5 and 15 conducting layers were studied by embedding thermocouples into the epoxy/glass bonding sheets during the "hot-press" lamination process. An effort was made to isolate the important parameters governing thermal variation during hot-press lamination and to determine the thermal timing "window" for cure-pressure application necessary for uniform resin flow. The results show that whereas the temperature of the bonding sheets in a 5-layer MLB are practically identical, the temperature in 15-layer MLB's differs in excess of 37°F (20.50°C). The study also concludes that the lag between the time the lay-up is inserted and the press is closed governs temperature differences for a given MLB. Under laboratory conditions, the lag can be as small as 4 s;typically in production, however, the lag is 80 s for multiopening presses. It is these temperature variations that can cause voids, cured thickness variations, measle tendencies, and delamination, resulting in high proportions of defective MLB's. These temperature differences can be reduced either by increasing the padding thickness or by employing a "cold-press" lamination process. The effectiveness of these methods is also discussed.