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Creators/Authors contains: "Clark, Nicholas L"

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  1. ; ; ; (, AIP Advances)
    A phase-separated borosilicate glass, with a relative permittivity ranging from 3 to 3.5 and a loss tangent as low as 5.6 × 10−4, is presented for packaging applications for the next generation of mobile communications. Ionic polarizability for each borosilicate composition was calculated from the Clausius–Mossotti relationship for both the vitreous and crystalline structures, and the polarizability difference between the two is proportional to the dielectric loss. Small amounts of alkali modifier were added to improve the glass processability, and the loss tangent increased to the 1–7 × 10−3 range. The resulting glass is phase-separated, which has no impact in the millimeter-wave spectrum, as the wavelengths are considerably greater than the length scale of each immiscible phase. 
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    Free, publicly-accessible full text available November 1, 2025
  2. ; ; ; (, IEEE)
    Accepted Manuscript Full Text Available
  3. ; ; (, Journal of the American Ceramic Society)
    Abstract The impact of microstructure on hardness in phase‐separated calcium aluminosilicate glasses is investigated. Changes in hardness are governed by microstructure deformations that occur during indentation. Phase separation leads to decreased hardness due to the incongruent yielding of the droplet and matrix phases. Moreover, the deformation of microstructures possessing dilute, spherical droplets did not have a significant impact on hardness. Microstructures characterized by concentrated, acicular droplets were found to deform through a process of droplet coalescence. This process absorbs additional energy during yielding and results in glasses that deform through droplet coalescence possessing improved hardness. 
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  4. ; ; (, Journal of the American Ceramic Society)
    Abstract Glasses with nanoscale phase separation have the potential to possess improved hardness and fracture toughness while maintaining their optical transparency. Here we present the results of isothermal heat treatments of phase‐separated calcium aluminosilicate glasses. Our results indicate that a transition from Lifshitz–Slozof–Wagner (LSW)‐type kinetics to a diffusion‐controlled pseudo‐coalescence mechanism occurs at ~17% droplet volume fraction, which results in the droplets becoming increasingly elongated and interconnected. The activation barrier for both mechanisms suggests that calcium diffusion is the underlying means for the coarsening of the silica‐rich domains. Simple approximations show the transition cannot be explained by Brownian motion or Van der Waals attraction between domains, and instead suggest various osmotic forces may be responsible. 
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