română RAJESH PINNAVASAL VENUKRISHNAN, BASKAR NEELAKANDAN, VINOTH KUMAR SELVARAJ
Abstract
The presented research work explores the fabrication and parametric optimization of β- Tri-Calcium Phosphate (β-TCP) composites reinforced with Zinc Oxide (ZnO) powder, which make them suitable for biomedical applications. TCP is widely recognized for its biocompatibility and bioresorbability, while ZnO offers strong bacterial inhibition and enhanced mechanical strength. The composite is fabricated using a compaction-sintering process, known as Powder Metallurgy technique followed by investigation of physical and mechanical attributes of the as-formed composite specimens. The process parameters viz., particle size of the constituents, volumetric percentage of TCP content and sintering temperature are optimized and the best possible specimen is selected among various combinations using a combinatorial statistical technique namely Historical Data incorporated Additive Ratio Assessment (HD-ARAS). The results demonstrate the performance of β-TCP-ZnO composites with significant enhancement in Particle Density, Microhardness and Compressive Strength. The starting particles and best ranked composite specimen is further subjected to microstructure study using Scanning Electron Microscope (SEM) to validate the results. This research supports the potential candidature of TCP-ZnO composites as viable materials in bone repair and regeneration.
Keywords
tri-calcium phosphate, zinc oxide, mechanical strength, powder metallurgy, bone repair
RĂDUCU-MIHAI GEANTĂU, ANCUȚA ROTARU, TRAIAN-DĂNUȚ BABOR, MARIA TUNKIEWICZ, JOANNA MISIEWICZ, PIOTR KOSIŃSKI
Abstract
Mercury intrusion porosimetry (MIP) within the present study, was not used as a stand-alone proof of pore blocking, but as a complementary microstructural method interpreted in relation to capillarity and surface-level hydrophobic behaviour of the hydrophobised brick specimens, with the aim of contextualising changes in liquid water transport after PDMS–Si biomimetic treatment. The study evaluated a silica nanoparticle-polydimethylsiloxane (Si-PDMS) mixture. Aplication to historical Gothic-type and factory-made fired-clay foundation bricks was made by brush and the homogenization was performed by mechanical agitation at 50 Hz, and no visible sedimentation is observed, phase separation of the materials used or agglomeration was during the preparation and application window. The treatment was applied by brush on the exposed surfaces of the specimens. This methodological position is essential because MIP primarily reflects the smallest accessible constrictions within the pore network and is influenced by ink-bottle effects for the surface pore distribution. The results showed that historic bricks that where tested exhibited higher open porosity and a broader pore-throat distribution than modern bricks, confirming their greater susceptibility to capillary uptake and their higher capacity for treatment penetration. By contrast, denser modern bricks that where tested presented lower baseline porosity and more limited changes after treatment. MIP outputs indicated that the 2% Si mixture produced the clearest refinement of accessible porosity, reducing total porosity from 42.842% to 35.111% for Gothic bricks and from 28.861% to 25.236% for factory-made bricks. In contrast, the 5% Si mixture showed a partial rebound in porosity-related parameters, suggesting diminishing returns at higher solids loading. MIP served as a contextual and plausibility-based tool, helping to explain why reductions in capillary vulnerability were more pronounced in more porous historic materials without implying that hydrophobisation acted by sealing the substrate. The porosity analysis therefore supports the conclusion that the biomimetic PDMS–Si treatment modifies interfacial wetting and partially alters accessible near-surface transport pathways, with implications for reducing liquid water ingress, salt crystallization risk, and freeze-thaw susceptibility. The study explicitly acknowledges its current experimental limitations. Because not all the dimensions of the potential study were addressed water-vapour transmission was not measured, and no standardized durability campaign was completed. We attempted to test freeze-thaw behaviour the results wer inconclusive because it was not performed according to a standardized method and the specimens were damaged during the analysis stage. Mechanical strength remain essential for complete cross-study comparison. Interpreted within these methodological boundaries, MIP provides a credible microstructural framework for understanding the protective action Si-PDMS treatment in conservation-oriented masonry applications.
Keywords
mercury intrusion porosimetry, pore connectivity, porosity, historic bricks, modern bricks, silica nanoparticles, PDMS, durability, solvent-free treatment
RĂDUCU-MIHAI GEANTĂU, ANCUȚA ROTARU, TRAIAN-DĂNUȚ BABOR, MARIA TUNKIEWICZ, JOANNA MISIEWICZ, PIOTR KOSIŃSKI
Abstract
This study evaluates the hydrophobic properties of silica nanoparticle–polydimethylsiloxane (Si–PDMS) treatment developed for fired-clay masonry structures and infrastructures exposed to moisture. The work emerged from a conservation-driven question that also applies to contemporary construction: how to reduce liquid-water penetration without turning a porous substrate into a sealed, vapour-impermeable system with out damaging the material or its apperance. The formulation strategy follows a biomimetic route in which silica nanoparticles generate near-surface roughness and PDMS lowers surface energy, translating lotus-inspired surface. Historical and factory-made fired-clay bricks were dryed to constant mass and treated by brush application. The dispersion was prepared without solvent, homogenized by mechanical agitation at 50 Hz, and visually remained free of sedimentation or agglomeration during the preparation/application window. Wettability was assessed by static contact angle, bulk liquid uptake by 24 h immersion, and capillary transport; lateral faces were sealed during the capillary test. The treatment shifted the surface from highly hydrophilic (11.0°) to hydrophobic/superhydrophobic behavior (105.4–114.7°), reduced 24 h water absorption from 6.70% to 5.56–5.97%, and lowered the capillarity coefficient from 0.0015446 to 0.0013109–0.0013657 g/cm²·s. The highest surface beading was obtained at 2% Si-PDMS mixture, whereas the lowest immersion and capillary uptake occurred at 1% Si-PDMS mixture, indicating a non-linear trade-off between interfacial wetting control and bulk transport. Water-vapour transmission and standardized durability tests were not part of the present article; therefore, compatibility claims remain limited to the wetting and hygric indicators reported here.
Keywords
contact angle, wettability, hydrophobic impregnation, water absorption, capillary uptake, biomimetic coating, silica nanoparticles, PDMS, fired-clay brick, heritage masonry