To cite this article: Oğuzhan Bilaç & Cihangir Duran (2021): Al 2 O 3 /glass/hBN composites with high thermal conductivity and low dielectric constant for low temperature cofired ceramic applications, Journal of Asian Ceramic Societies,

No abstract

SiO2‐Al2O3‐CaO‐based glass (10–60 wt%)/mullite composites were investigated for the LTCC and radome applications. The optimum densification temperatures decreased from 1550°C (10 wt% glass) to 1400°C (30 wt% glass) by means of liquid‐phase sintering, and to 850°C–825°C (50–60 wt% glass) by means of viscous phase sintering. XRD analysis showed that mullite was the main phase as well as in situ crystallized anorthite after 825°C. The composite with 20 wt% glass was a suitable candidate for the radome applications (bulk density = 2.86 g/cm3 after sintering at 1450°C, dielectric constant (loss) = 7.12 (0.0025) at 5 MHz, thermal expansion coefficient = 4.27 ppm/°C between 25°C and 800°C, thermal shock resistance parameter = 162°C), and the composite with 50 wt% glass was a suitable candidate for the low‐temperature cofired ceramic applications (bulk density = 2.64 g/cm3 after sintering at 850°C, dielectric constant (loss) = 6.79 (0.0043) at 5 MHz, thermal conductivity = 2.11 W/m⋅K at 25°C, and thermal expansion coefficient = 3.93 ppm/°C between 25°C and 300°C).

Elektrolitik kaplamalara alternatif oluşturan ve dışarıdan herhangi bir elektrik ihtiyacına gerek duymadan gerçekleşen otokatalitik akımsız kaplamalar birçok endüstriyel alanda kullanılmaktadır. Homojen bir kaplama kalınlığı elde edilmesi, yüksek sertlik, iyi korozyon ve aşınma direncine sahip olması, akımsız kaplamaları oldukça yaygın hale getirmektedir. Ayrıca karmaşık şekilli parçalara da uygulanabilmesi avantajları arasında yer almaktadır. Bu çalışmada akımsız NiP kaplamaların sertlik, metalik nikel ve fosfor içerikleri, ısıl işlem sonrası oluşan bileşik türleri ve mikroyapısal özellikleri incelenerek sodyum hipofosfit, sıcaklık ve zaman parametrelerinin etkileri ortaya konmuştur.

Mullite/glass/nano aluminum nitride (AlN) filler (1–10 wt% AlN) composites were successfully fabricated for the low‐temperature co‐fired ceramics applications that require densification temperatures lower than 950°C, high thermal conductivity to dissipate heat and thermal expansion coefficient matched to Si for reliability, and low dielectric constant for high signal transmission speed. Densification temperatures were ≤825°C for all composites due to the viscous sintering of the glass matrix. X‐ray diffraction proved that AlN neither chemically reacted with other phases nor decomposed with temperature. The number of closed pores increased with the AlN content, which limited the property improvement expected. A dense mullite/glass/AlN (10 wt%) composite had a thermal expansion coefficient of 4.44 ppm/°C between 25 and 300°C, thermal conductivity of 1.76 W/m.K at 25°C, dielectric constant (loss) of 6.42 (0.0017) at 5 MHz, flexural strength of 88 MPa and elastic modulus of 82 GPa, that are comparable to the commercial low temperature co‐fired ceramics products.