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Combined Effect of Silicon Dioxide and Titanium Dioxide Nanoparticles on Concrete Properties

100%

Al-Rbaihat R. , Al-Marafi M. N.

tom Vol. 24, nr 12

319--335

Nanoconcrete is an attractive research area because of its recent practical applications in building materials technologies. This study investigates the individual and combined effects of using nanoparticles in concrete mixtures as a cement substitute. Microscopic images are also used to determine changes in the microstructure of modified concrete in the present study. Concrete’s thermal and mechanical properties, including thermal conductivity (k), specific heat capacity (C), thermal diffusivity (α), and compressive strength (σ), are the leading concrete characteristics examined. The current study used different percentages (0%, 1%, 3%, and 5%) of nano-SiO2, nano-TiO2, and combined nano-SiO2/TiO2 particles as cement substitutes for 7 and 28 days of curing to examine the characteristics of nanoconcrete compared to conventional concrete (CC). The results indicated that adding individual nanoparticles to CC could improve concrete’s thermal and mechanical properties. Among the investigated nanomaterials (nano-SiO2, nano-TiO2, and combined nano-SiO2/TiO2 particles), nano-SiO2 was superior in that context. The optimal thermal properties of nanoconcrete were achieved when 5% nano-SiO2 (C-S5 specimen) was added. The k and α coefficients of sample C-S5 compared to the CC specimen were reduced by 65.6% and 80.3%, respectively, while the C coefficient was increased by 12.8%. Meanwhile, the optimal compressive strength coefficient of nanoconcrete was achieved when 3% nano-SiO2 (C-S3 specimen) was added, where the compressive strength coefficient of sample C-S3 compared to sample CC was increased by 19.6%. In contrast, for the combined effect, the thermal properties of concrete were improved, but the compressive strength coefficient of concrete was reduced. Overall, the present experimental findings offer valuable information about the impact of nanotechnology on high-performance concrete to save energy in buildings.

Pojemność cieplna właściwa stopów γ-TiAl z dodatkiem chromu i niobu

84%

Przeliorz R.

tom R. 52, nr 6

361-364

Przedstawiono wyniki pomiarow pojemności cieplnej właściwej stopu γ-TiAl (L1o) z dodatkiem chromu (2 % at.) i niobu(2, 5, 7 % at.). Pomiary wykonano na różnicowym kalorymetrze kaningowym (DSC) w zakresie temperatury temperatury 423-1243 K. Krzywe cp można podzielić na trzy zakresy temperatury: T < 673 K, wysoki 673 K < T < 1073 K i bardzo wysoki T > 1073 K. Pojemność cieplna właściwa w zakresie temperatury od niskiej do umiarkowanej jest w przybliżeniu proporcjonalna do T3. W bardzo wysokiej temperaturz T>1073K na krzywej cp obserwuje się anomalię polegającą na gwałtownym wzroście pojemności cieplnej.

In the article there are presented results of measurements of specific heat cap(acity alloy γ-TiAl(L1o) with addition chrome (2 % at.) and niobium (2, 5, 7 % at.). The measurements were performed on differential scanning calorimeter (the DSC) in range of temperature 423-1243 K. Curves cp can be divided on three ranges of temperature: moderate T<673 K, high 673K 1073 K. The specific heat capacity in range of temperature from low to moderate is in approximation proportional to T3. At very high temperature T > 1073 K we notice the beginning of an anomalous rise in the specific heat curve.