Magnesium titanate (MT), as one of the important dielectric materials, is widely used as dielectric resonators for the low dielectric loss and good temperature stability. However, the agglomerate behavior of MT particles limit the application areas in organic materials, especially for polymer materials. In this work, the surface of MT particles was modified by three coupling agents, i.e. bis-(γ-triethoxysilylpropyl) tetrasulphide (Si69), γ-(methacryloyloxy) propyltrimethoxysilane (KH570) and stearic acid (SA). Modification effects were characterized via Fourier transform infrared (FTIR) and contact angle analysis. These characterizations showed an excellent surface modification effect, especially for samples modified by Si69 and SA. The contact angle test presents that the surface of modified MT particles was transformed from hydrophilic (35°) to hydrophobic (135°). The content of coupling agent on particle’s surface was investigated by thermal gravimetric analysis (TGA). X-ray diffractometer (XRD) results indicate that surface modification has no effect on the type of MT particle’s crystals. Surprisingly, Ultraviolet–Visible-Near infrared (UV–Vis-NIR) measurement shows that MT particles present a better solar reflectance effect than titanium dioxide. The micro-morphology of particles is analyzed by Scanning electron microscope (SEM). Herein, the potential application areas of surface organic modified MT particles can be used in polymer-ceramic composites and solar reflectance materials.
Fresnel’s law and Maxwell’s equation indicate that the greater the dielectric constant of the material, the greater the refractive index of the material, which makes the material present higher solar reflectance. Magnesium titanate (MT) is an important dielectric ceramic material. It is necessary to investigate the solar reflectance effect of MT particles in practical application areas. In this work, the cooling engineering polymer-ceramic composites were prepared by MT particles and polypropylene (PP)/styrene-ethylene-butylene-styrene copolymer (SEBS)/processing oil matrix. The cooling efficiency of composites was analyzed by solar reflectance, IR thermography analysis, emissivity and solar simulation analysis. The results indicate that solar reflectance enhanced from 16.09% to 60.51% with the content of MT particles increased from 0 to 10 phr. Meanwhile, solar simulation result presents that the inner temperature decreased from 50.4 to 31.5 °C, meaning the fabricated polymer-ceramic composites has a cooling effect of 18.9 °C. Thus, MT dielectric ceramic material can be used as a solar reflectance filler to fabricate cooling engineering polymer-ceramic composites for energy saving application areas.
Song Jiamei,Fan Dawei,Huang Shijie,Zhang Shanrong,Wu Mengzeng,Chen Wei,Zhou Wenge
The unit-cell parameters and volumes of geikielite (MgTiO 3 ) and ilmenite (FeTiO 3 ) were investigated at high temperatures up to 700 K and ambient pressure, using in-situ angle-dispersive synchrotron X-ray diffraction. No phase transition was detected over the experimental temperature range. Using (Berman in J Petrol 29:445–522, 1988. 10.1093/petrology/29.2.445) equations to fit the temperature-volume data, the volumetric thermal expansion coefficients at ambient conditions ( α V 0 ) of MgTiO 3 and FeTiO 3 were obtained as follows: 2.55 (6) × 10 –5 K −1 and 2.82 (10) × 10 –5 K −1 , respectively. We infer that the larger effective ionic radius of Fe 2+ (VI) (0.78 Å) than that of Mg 2+ (VI) (0.72 Å) renders FeTiO 3 has a larger volumetric thermal expansivity than MgTiO 3 . Simultaneously, the refined axial thermal expansion coefficients under ambient conditions are α a 0 = 0.74 (3) × 10 –5 K −1 and α c 0 = 1.08 (5) × 10 –5 K −1 for the a -axis and c -axis of MgTiO 3 , respectively, and α a 0 = 0.95 (5) × 10 –5 K −1 and α c 0 = 0.92 (12) × 10 –5 K −1 for the a -axis and c -axis of FeTiO 3 , respectively. The axial thermal expansivity of MgTiO 3 is anisotropic, but that of FeTiO 3 is nearly isotropic. We infer that the main reason for the different axial thermal expansivity between MgTiO 3 and FeTiO 3 is that the thermal expansion mode of the Mg-O bond in MgTiO 3 is different from that of the Fe–O bonds in FeTiO 3 .
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