scholarly journals Synthesis of silica nanoparticles to enhance the fire resistance of cement mortars

Fire Research ◽  
2019 ◽  
Vol 3 (1) ◽  
Author(s):  
Joana Vaz-Ramos ◽  
Aldina Santiago ◽  
António Portugal ◽  
Luísa Durães
Keyword(s):  
Thermal Conductivity ◽  
Silica Nanoparticles ◽  
Fire Resistance ◽  
Room Temperature ◽  
Sol Gel ◽  
Cementitious Materials ◽  
Pozzolanic Reactivity ◽  
Cement Mortars ◽  
Hydrolysis And Condensation ◽  
Strength And Durability

Silica nanoparticles are known to enhance the strength and durability of cementitious materials, due to their nanofilling effect and their high pozzolanic reactivity. They also have the potential to improve their thermal properties and fire resistance. However, these improvements are highly dependent on the nanoparticles’ characteristics. In this work, silica nanoparticles were prepared by sol-gel reaction and a design of experiments with four factors was used to conclude about the parameters that have more influence in the synthesis of these nanoparticles and, thus, optimize this process and the particles’ properties. Using a lower ethanol/water, higher hydrolysis and condensation time and higher volume of catalyst, the smallest particle size was obtained (118 nm). The effect of the incorporation of these silica nanoparticles into cement mortars was studied in terms of density and thermal conductivity of these mortars, after curing at room temperature. The presence of silica nanoparticles led to an increase in density and decrease of thermal conductivity. The mortars were also exposed to high temperature, which originated a significant reduction (~50%) in their thermal conductivity.

scholarly journals Effect of High-Dispersible Graphene on the Strength and Durability of Cement Mortars

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 915
Author(s):  
Xiaoqiang Qi ◽  
Sulei Zhang ◽  
Tengteng Wang ◽  
Siyao Guo ◽  
Rui Ren
Keyword(s):  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Cement Mortar ◽  
Chloride Ion ◽  
Cementitious Materials ◽  
Chloride Ion Penetration ◽  
Cement Mortars ◽  
Strength And Durability ◽  
Durability Performance

Graphene’s outstanding properties make it a potential material for reinforced cementitious composites. However, its shortcomings, such as easy agglomeration and poor dispersion, severely restrict its application in cementitious materials. In this paper, a highly dispersible graphene (TiO2-RGO) with better dispersibility compared with graphene oxide (GO) is obtained through improvement of the graphene preparation method. In this study, both GO and TiO2-RGO can improve the pore size distribution of cement mortars. According to the results of the mercury intrusion porosity (MIP) test, the porosity of cement mortar mixed with GO and TiO2-RGO was reduced by 26% and 40%, respectively, relative to ordinary cement mortar specimens. However, the TiO2-RGO cement mortars showed better pore size distribution and porosity than GO cement mortars. Comparative tests on the strength and durability of ordinary cement mortars, GO cement mortars, and TiO2-RGO cement mortars were conducted, and it was found that with the same amount of TiO2-RGO and GO, the TiO2-RGO cement mortars have nearly twice the strength of GO cement mortars. In addition, it has far higher durability, such as impermeability and chloride ion penetration resistance, than GO cement mortars. These results indicate that TiO2-RGO prepared by titanium dioxide (TiO2) intercalation can better improve the strength and durability performance of cement mortars compared to GO.

Preparation and Characterization of Cu-SiO2 Nanoparticles

2007 ◽  
Vol 121-123 ◽  
pp. 255-258 ◽  
Author(s):  
Young Hwan Kim ◽  
Beong Gi Jo ◽  
Jee Hean Jeong ◽  
Young Soo Kang
Keyword(s):  
Silica Nanoparticles ◽  
Room Temperature ◽  
Sio2 Nanoparticles ◽  
Hybrid Structures ◽  
Cu Nanoparticles ◽  
Stöber Method ◽  
X Ray ◽  
Transmission Electron ◽  
Hydrolysis And Condensation

A room temperature route for doping silica particles with Cu nanoparticles to achieve hybrid structures is introduced. First, silica nanoparticles were synthesized according to the well-known Stöber method by hydrolysis and condensation of TEOS in a mixture of ethanol with water, using ammonia as catalyst to initiate the reaction. These SiO2 nanoaprticles were dried at 100 oC. We measured the size of these nanoparticles with transmission electron microscopy (TEM). Second, Cu-SiO2 nanoparticles were synthesized by reaction with CuCl2 and SiO2 nanoparticles in presence of catalyst at room temperature for 12 hrs. Results show silica nanoparticles of about 70 nm size with regularly deposited Cu nanoparticles. Cu-SiO2 nanoparticles were investigated with TEM images, energy dispersive X-ray analysis (EDX) spectrum and so on.

Sol Gel Characterization of Nano Kaolin

2013 ◽  
Vol 856 ◽  
pp. 285-289
Author(s):  
M.S. Muhd Norhasri ◽  
M.S. Hamidah ◽  
A.G. Abd Halim ◽  
A. Mohd Fadzil
Keyword(s):  
Particle Size ◽  
Surface Area ◽  
Sol Gel ◽  
High Energy ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Process Time ◽  
Strength And Durability ◽  
Clay Kaolin

Nano kaolin is product from kaolin also known as white clay. Kaolin was established as supplementary cementitious materials in concrete. The inclusion of kaolin in concrete enhances strength and durability properties and prolongs concrete life span. In this research, nanokaolin will be develop by using sol gel technique by that involves high energy milling. The process of milling been influenced by time of milling, ball and jar type. Ceramic type Zirconia (Zi) is been used as jar and ball type in this process. Time of milling was set from four (4) hours and one (1) days. Sample will be analyse by using particle size analyser to see the particle size and surface area of kaolin. From the result shows the optimum milling period for nanokaolin is one day base on particle size compare to 4 hours. Furthermore, one day milling produces a massive increment of surface area compare to others. In conclusion, one day can be considered as the optimum cycle time in the production of nano kaolin.

Effects of Mg Substitution on the Thermoelectric Properties of Ca3Co4O9-Based Materials

2011 ◽  
Vol 84-85 ◽  
pp. 671-675 ◽  
Author(s):  
Xiao Ling Qi ◽  
You Yu Fan ◽  
Ling Ke Zeng ◽  
Dong Sheng Zhu
Keyword(s):  
Thermal Conductivity ◽  
Thermoelectric Properties ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Lattice Thermal Conductivity ◽  
Sol Gel ◽  
Dopant Content ◽  
Mg Doping ◽  
Mg Content ◽  
Mg Substitution

Polycrystalline Ca3-xMgxCo4O9(x=0-0.3)ceramics were prepared by the sol–gel method combined with the ordinary pressing sintering and the thermoelectric properties were measured from room temperature to 673 K. The substitution of Mg2+for Ca2+had a greater impact on the thermoelectric properties of Ca3Co4O9. The electrical conductivity and the thermal conductivity reduced significantly with increasing Mg content, and the Seebeck coefficient increased simultaneously. The influence of Mg doping on the thermal conductivity is mainly embodied in the lattice thermal conductivity of Ca3Co4O9. The lattice thermal conductivity showed a significant change with the increase of the dopant content, while the carrier thermal conductivity had no obvious change with the doping increasing. These results indicated that the thermoelectric properties of the material could be optimized remarkably with the substitution of Mg. The figure of meritZreached 1.08×10-4K-1at 573 K for the sample of Ca2.8Mg0.2Co4O9.

Thermal Transport Properties of Ca3Co4O9 with Mg Substitution

2011 ◽  
Vol 71-78 ◽  
pp. 959-962
Author(s):  
Xiao Ling Qi ◽  
Ling Ke Zeng ◽  
You Yu Fan
Keyword(s):  
Thermal Conductivity ◽  
Transport Properties ◽  
Room Temperature ◽  
Sol Gel ◽  
Dopant Content ◽  
Gel Method ◽  
Sol Gel Method ◽  
Mg Doping ◽  
Mg Substitution ◽  
Thermal Conductivities

Polycrystalline Ca3-xMgxCo4O9（x=0-0.3）ceramics were prepared by the sol–gel method combined with the ordinary pressing sintering and the thermal conductivities were measured from room temperature to 673 K. The influence of Mg2+ substitution for Ca2+ on the thermal conductivities of Ca3Co4O9 ceramics was investigated systematically. The influence of Mg doping on the thermal conductivities is mainly embodied in the lattice thermal conductivities, which shows a significant decrease with the increase of the dopant content for the samples with x ≤ 0.2, while the carrier thermal conductivity had no obvious change with Mg doping increasing. These results indicated that the thermal conductivities of the material could be reduced remarkably with the substitution of Mg from 1.427 W/m·K to 0.731 W/m·K at 573 K with x = 0.2.

Enhancement of photocatalytic degradation of furfural and acetophenone in water media using nano-TiO2-SiO2 deposited on cementitious materials

2016 ◽  
Vol 74 (7) ◽  
pp. 1689-1697 ◽  
Author(s):  
Sahar Soltan ◽  
Hoda Jafari ◽  
Shahrara Afshar ◽  
Omid Zabihi
Keyword(s):  
Uv Irradiation ◽  
Room Temperature ◽  
Sol Gel ◽  
Oxygen Demand ◽  
Dip Coating ◽  
Cementitious Materials ◽  
Nano Particles ◽  
High Porosity ◽  
Visible Absorption ◽  
Operation Conditions

In the present study, silicon dioxide (SiO2) nanoparticles were loaded to titanium dioxide (TiO2) nano-particles by sol-gel method to make a high porosity photocatalyst nano-hybrid. These photocatalysts were synthesized using titanium tetrachloride and tetraethyl orthosilicate as titanium and silicon sources, respectively, and characterized by X-ray powder diffraction (XRD) and scanning electron microscope methods. Subsequently, the optimizations of the component and operation conditions were investigated. Then, nano-sized TiO2 and TiO2-SiO2 were supported on concrete bricks by the dip coating process. The photocatalytic activity of nano photocatalysts under UV irradiation was examined by studying the decomposition of aqueous solutions of furfural and acetophenone (10 mg/L) as model of organic pollutants to CO2 and H2O at room temperature. A decrease in the concentration of these pollutants was assayed by using UV-visible absorption, gas chromatography technique, and chemical oxygen demand. The removal of these pollutants from water using the concrete-supported photocatalysts under UV irradiation was performed with a greater efficiency, which does not require an additional separation stage to recover the catalyst. Therefore, it would be applicable to use in industrial wastewater treatment at room temperature and atmospheric pressure within the optimized pH range.

scholarly journals Thermal Conductivity of Pure Silica MEL and MFI Zeolite Thin Films

2010 ◽  
Author(s):  
Thomas Coquil ◽  
Laurent Pilon ◽  
Christopher M. Lew ◽  
Yushan Yan
Keyword(s):  
Thin Films ◽  
Thermal Conductivity ◽  
Room Temperature ◽  
Sol Gel ◽  
Silica Matrix ◽  
Simultaneous Increase ◽  
Crystallization Time ◽  
Mfi Zeolite ◽  
Relative Crystallinity ◽  
Pure Silica

This paper reports the room temperature cross-plane thermal conductivity of pure silica zeolite (PSZ) MEL and MFI thin films. PSZ MEL thin films were prepared by spin coating a suspension of MEL nanoparticles in 1-butanol solution onto silicon substrates followed by calcination and vapor-phase silylation with trimethylchlorosilane. The mass fraction of nanoparticles within the suspension varied from 16 to 55%. This was achieved by varying the crystallization time of the suspension. The thin films consisted of crystalline MEL nanoparticles embedded in a non-uniform and highly porous silica matrix. They featured porosity, relative crystallinity and MEL nanoparticles size ranging from 40 to 59%, 23 to 47% and 55 to 80 nm, respectively. PSZ MFI thin films were made by in-situ crystallization, were b-oriented, fully crystalline and had a 33% porosity. Thermal conductivity of the PSZ thin films was measured at room temperature using the 3ω method. The cross-plane thermal conductivity of the MEL thin films remained constant around 1.02 ± 0.10 Wm−1K−1 despite increases in (i) relative crystallinity, (ii) nanoparticle size and (iii) yield as the nanoparticle crystallization time increased. Indeed, the effect of increases in these parameters on the thermal conductivity was compensated by the simultaneous increase in porosity. PSZ MFI thin films were found to have the same thermal conductivity as MEL thin films even though they had smaller porosity. Finally, the average thermal conductivity of the PSZ films was three to five times larger than that reported for amorphous sol-gel mesoporous silica thin films with similar porosity and dielectric constant.

Research on Preparation and Structure of Ca3Co4O9

2013 ◽  
Vol 743-744 ◽  
pp. 111-115
Author(s):  
Wei Rong Zhang ◽  
Zhan Yong Wang ◽  
Wen Qing Liu
Keyword(s):  
Thermal Conductivity ◽  
Citric Acid ◽  
Ethylene Glycol ◽  
Ethyl Alcohol ◽  
Room Temperature ◽  
Sol Gel ◽  
Calcium Nitrate ◽  
Cobalt Nitrate ◽  
Optimal Parameters ◽  
Absolute Ethyl Alcohol

Ca3Co4O9 particles were synthesized using cobalt nitrate, calcium nitrate, and citric acid as the starting precursors by sol-gel method. The absolute ethyl alcohol was selected as the solvent. LFA447 was applied to measure the thermal conductivity from room temperature to 300 as the reference to decide the optimal parameters. And the optimal parameters obtained are as follows: ethyl alcohol 100ml, ethylene glycol 5ml, citric acid 12.11g (the mole ratio of citric acid to metal ions is 1.1:1), and pH=3 to prepare samples with total weight of 5 g.

Improved Sol-Gel Materials for Efficient Solid State Dye Lasers

1993 ◽  
Vol 329 ◽  
Author(s):  
Michael Canva ◽  
Patrick Georges ◽  
Jean-Fran^ois Perelgritz ◽  
Alain Brun ◽  
Fréddric Chaput ◽  
...  
Keyword(s):  
Solid State ◽  
Physical Properties ◽  
Room Temperature ◽  
Sol Gel ◽  
Tunable Lasers ◽  
Optical Quality ◽  
Dye Lasers ◽  
Laser Dyes ◽  
Host Matrix ◽  
Host Matrices

AbstractPhotoresistant laser dyes were trapped in silica based xerogel host matrices to obtain solid state tunable lasers. For this purpose very dense xerogel samples with improved chemical and physical properties were prepared at room temperature by the sol-gel technology. The as-prepared materials were polished to obtain optical quality surfaces and were used as new lasing media.Lasing action of such different dyes as rhodamine, perylene and pyrromethene doping dense sol-gel matrices was demonstrated. Efficiencies of 30 % or lifetimes of more than 100,000 shots were achieved with different new ≤dye dopant/host matrix≥ couples. Their different performances are reviewed and discussed.

Incorporation of Iraqi Rocks in the Production of Eco-Friendly Cement Mortar

2020 ◽  
Vol 38 (10A) ◽  
pp. 1522-1530
Author(s):  
Rawnaq S. Mahdi ◽  
Aseel B. AL-Zubidi ◽  
Hassan N. Hashim
Keyword(s):  
Mechanical Properties ◽  
Thermal Conductivity ◽  
Compressive Strength ◽  
Water Absorption ◽  
Structural Properties ◽  
Mechanical Milling ◽  
Cement Mortar ◽  
Cement Mortars

This work reports on the incorporation of Flint and Kaolin rocks powders in the cement mortar in an attempt to improve its mechanical properties and produce an eco-friendly mortar. Flint and Kaolin powders are prepared by dry mechanical milling. The two powders are added separately to the mortars substituting cement partially. The two powders are found to improve the mechanical properties of the mortars. Hardness and compressive strength are found to increase with the increase of powders constituents in the cement mortars. In addition, the two powders affect water absorption and thermal conductivity of the mortar specimens which are desirable for construction applications. Kaolin is found to have a greater effect on the mechanical properties, water absorption, and thermal conductivity of the mortars than Flint. This behavior is discussed and analyzed based on the compositional and structural properties of the rocks powders.

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