Aluminum Coated Micro Glass Spheres to Increase the Infrared Reflectance

Abstract

The reflective properties of micro glass spheres (MGS) such as Solid Micro Glass Spheres (SMGS, “glass beads”) and Micro Hollow Glass Spheres (MHGS, “glass bubbles”) are utilized in various applications, for example, as retro-reflector for traffic road stripe paints or facade paints. The reflection behavior of the spheres can be further adapted by coating the surfaces of the spheres, e.g., by titanium dioxide or a metallic coating. Such coated spheres can be employed as, e.g., mid infrared (MIR)-reflective additives in wall paints to increase the thermal comfort in rooms. As a result, the demand of heating energy can be reduced. In this paper, the increase of the MIR-reflectance by applying an aluminum coating on MGS is discussed. Aluminum coatings are normally produced via the well-known Physical Vapor Deposition (PVD) or Chemical Vapor Deposition (CVD). In our work, the Liquid Phase Deposition (LPD) method, as a new, non-vacuum method for aluminum coating on spherical spheres, is investigated as an alternative, scalable, and simple coating process. The LPD-coating is characterized by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), and reflection measurements. The results are compared to a reference PVD-coating. It is shown that both sphere types, SMGS and MHGS, can be homogeneously coated with metallic aluminum using the LPD method but the surface morphology plays an important role concerning the reflection properties. With the SMGS, a smooth surface morphology and a reflectance increase to a value of 30% can be obtained. Due to a structured surface morphology, a reflection of only 5% could be achieved with the MHGS. However, post-treatments showed that a further increase is possible.

Preparation of Melamine Formaldehyde Foam and a Melamine-Formaldehyde-Organo-Clay Nanocomposite and Hybrid Composites

“…The XRD pattern of the MF-organo-clay-pumice-hollow-glass-sphere hybrid composite (MFCPHHC) in Figure 5 shows the overlapping MF, pumice and amorphous silica peaks and the smectite peak almost disappeared. Thus, as expected, the pumice plates and hollow glass spheres encapsulated by spherical polymer clay nanocomposites exhibited an ordered and relatively discrete arrangement (see Figures 2f and 3f) [79,87,93].…”

Preparation and Characteristics of High-Performance, Low-Density Metallo–Ceramics Composite

“…Special attention has been paid to the coating of microspheres with various materials for properties improvement: to increase porosity and decrease density, preserve compressive strength, in some cases catalytic properties, modification of thermal conductivity or dielectric properties, achieve higher thermal resistance than materials which exhibit similar density. Therefore, coatings prepared from different materials such as copper [46], molybdenum oxide [47], and aluminum [48] were developed.…”

Special Issue: Current Research in Thin Film Deposition: Applications, Theory, Processing, and Characterisation

“…Schwinger et al [25] discuss a novel, non-vacuum, liquid phase method of depositing thin films of aluminium on spherical glass substrates, comparing the results to those obtained by a more conventional physical vapour deposition (PVD) process for reference. It is reported that reflectance of solid micro glass spheres can be increased by around 30%, a comparable result to that achieved using PVD.…”