Silicone rubber (SR) composites are candidate radiation-shielding materials, but their irradiation and annealing responses remain incompletely understood. Three predefined formulations containing boron carbide (B₄C), lead (Pb)/B₄C, or Pb were exposed to 100 kGy gamma irradiation in air and then annealed under nitrogen at 60–120 °C for 30–240 min. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectra retained the same characteristic band positions after irradiation, although their normalized band areas changed. Shore A hardness increased after irradiation in all formulations and remained above the corresponding pre-irradiation values after annealing. Electron paramagnetic resonance (EPR) spectra of the SR-B₄C formulation varied qualitatively with the annealing conditions, but absolute radical quantification and assignment of a unique reaction pathway were not possible. Because filler identity, filler loading, and silicone content varied simultaneously, differences among the formulations cannot be independently attributed to Pb, B₄C, or filler–matrix interactions. Based on one independently prepared parent specimen per formulation, these results describe irradiation and annealing responses in composites with micrometer-sized fillers. They may inform future comparisons with silicone-based shielding nanocomposites under matched compositions and treatment conditions.

Silica aerogel, a prototypical transparent nanoporous material with ultralow density and a widely tunable refractive index, is employed as a Cherenkov radiator for precision gamma-ray diagnostics in inertial confinement fusion experiments. However, its optical transmittance is highly sensitive to sol–gel chemistry. Here, silica aerogels were prepared from tetraethyl orthosilicate (TEOS), ethanol, water, and aqueous ammonia, followed by aging, solvent exchange, and supercritical drying. The study examined how catalyst, ethanol, and water concentrations regulate nanostructure and optical transmittance. Increasing ammonia content accelerated gelation, produced smaller framework particles, and enlarged the pore size and pore volume. These changes increased the transmittance at 550 nm from 79.6% for C1 to 84.9% for C7. Increasing ethanol concentration diluted TEOS and its hydrolysis products, extended gelation, and narrowed the particle-size distribution. The average particle size decreased from 21.79 to 17.01 nm, while the transmittance at 550 nm increased from 57.4% for E1 to 65.2% for E5. Water produced a non-monotonic response: insufficient water limited TEOS hydrolysis, whereas excessive water promoted structural heterogeneity. Intermediate water content provided the most favorable optical response. These findings define a process–structure–transmittance relationship in which formulation-dependent nanoscale network formation governs scattering losses and optical clarity.