scholarly journals Effect of different high surface area silicas on the rheology of cement paste

2020 ◽  
Vol 70 (340) ◽  
pp. 231
Author(s):  
J. I. Tobón ◽  
O. Mendoza ◽  
O. J. Restrepo ◽  
M. V. Borrachero ◽  
J. Payá
Keyword(s):  
Surface Area ◽  
Cement Paste ◽  
Water Demand ◽  
Volume Fraction ◽  
Setting Time ◽  
High Surface ◽  
Solid Volume Fraction ◽  
High Surface Area ◽  
High Specific Surface Area ◽  
Cement Pastes

This work studies the effect of nanosilica (NS) on the rheology of cement paste by comparing it with two high specific surface area silicas: silica fume (SF) and pyrogenic silica (PS). Portland cement pastes were produced with different water-to-cementing material ratios and different solid substitutions of cement by silica. Water demand, setting time, and rheology tests were performed. Results showed that NS and SF decreased plastic viscosity, while PS increased it. Only PS was found to have an effect on yield stress. NS showed the most decreasing effect on viscosity, regardless of its higher water demand. It was concluded that the behavior of pastes containing NS and SF is governed by the “ball-bearing” effect from silica particles, by their agglomeration degree, and their impact on the solid volume fraction. The behavior of pastes containing PS is governed by its ability to absorb a portion of the mixing water.

scholarly journals Synthesis and characterization of porous silica and polyaniline-porous silica composite materials with high surface area

2014 ◽  
Vol 49 (1) ◽  
pp. 1-8
Author(s):  
US Akhtar ◽  
MK Hossain ◽  
MS Miran ◽  
MYA Mollah
Keyword(s):  
Electron Microscopy ◽  
Pore Size ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Porous Silica ◽  
Nitrogen Adsorption ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Cylindrical Pore

Porous silica materials were synthesized from tetraethyl orthosilicate (TEOS) using Pluronic P123 (non-ionic triblock copolymer, EO20PO70O20) as template under acidic conditions which was then used to prepare polyaniline (PAni) and porous silica composites (PAnisilica) at a fixed molar ratio. These materials were characterized by nitrogen adsorption-desorption isotherm measured by Barrett-Joyner- Halenda (BJH) method and pore size distribution from desorption branch and surface area measured by the Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), transmission electron microscopy (TEM), TEM-energy dispersive X-ray (EDX) and Fourier transform infrared (FT-IR) spectroscopy. The composite maintains its structure even after the polymerization and the polymer is dispersed on the inorganic matrix. The rod-like porous silica was about 1?m to 1.5 ?m long and on an average the diameter was in the range of 300- 500 nm. The SEM and TEM images show well ordered 2d hexagonal pore, high specific surface area (850 m2g-1) and uniform pore size of ca. 6.5 nm in diameter. After incorporation of PAni inside the silica pore, framework of porous silica did not collapse and the surface area of the composite was as high as 434 m2g-1 which was 5.5 time higher than our previous report of 78.3 m2g-1. Due to shrinkage of the framework during the incorporation of aniline inside the silica, the pore diameter slightly increase to 7.5 nm but still showing Type IV isotherm and typical hysteresis loop H1 implying a uniform cylindrical pore geometry. DOI: http://dx.doi.org/10.3329/bjsir.v49i1.18847 Bangladesh J. Sci. Ind. Res. 49(1), 1-8, 2014

Ultra-high adsorption of tetracycline antibiotics on garlic skin-derived porous biomass carbon with high surface area

2020 ◽  
Vol 44 (3) ◽  
pp. 1097-1106 ◽  
Author(s):  
Shujian Liu ◽  
Mingdi Pan ◽  
Zhongmin Feng ◽  
Yangchun Qin ◽  
Yun Wang ◽  
...  
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Water Environment ◽  
High Specific Surface Area ◽  
Adsorption Properties ◽  
Porous Carbon Material ◽  
Biomass Carbon ◽  
High Adsorption ◽  
Tetracycline Antibiotics

A porous carbon material with ultra-high specific surface area was prepared from waste garlic skin, and exhibited excellent adsorption properties to TCs in a water environment.

Mechanical Design of Spicule-Reinforced Connective Tissue: Stiffness

1982 ◽  
Vol 98 (1) ◽  
pp. 239-267
Author(s):  
M.A. R. KOEHL
Keyword(s):  
Surface Area ◽  
Volume Fraction ◽  
High Surface ◽  
High Surface Area ◽  
Local Strain ◽  
High Volume ◽  
Tensile Behaviour ◽  
Connective Tissues ◽  
Aspect Ratios ◽  
Stiffening Effect

Many animals from different phyla have, embedded in their pliable connective tissues, small bits of stiff material known as spicules. The tensile behaviour of spicule-reinforced connective tissues from various cnidarians and sponges, as well as of model spiculated ‘tissues’, is here investigated in order to elucidate the effects on mechanical properties of spicule size and shape, and of their packing density and orientation within a tissue. The main conclusions are: 1. Spicules increase the stiffness of pliable connective tissues probably by mechanisms analogous to those by which filler particles stiffen deformable polymers-local strain amplification, and interference with molecular re-arrangement in response to a load. 2. The greater the volume fraction of spicules, the stiffer the tissue. 3. The greater the surface area of spicules per volume of tissue, the stiffer the tissue. Thus, a given volume of spicules of high surface-area-to-volumeratio (S/V) have a greater stiffening effect than does an equal volume of spicules of low S/V. Furthermore, a high volume fraction of large spicules in a tissue can have the same stiffening effect as a lower volume fraction of smaller spicules. 4. Spicules that are anisometric in shape have a greater stiffening effect parallel to their long axes. 5. Spicules with very high aspect ratios appear to act like reinforcing fibres-stress is transferred by shearing from the pliable matrix to the stiff fibres, which thus bear in tension part of the load on the composite. 6. Spicule-reinforced tissues exhibit stress-softening behaviour, which is more pronounced in heavily spiculated tissues.

Ion-matching porous carbons with ultra-high surface area and superior energy storage performance for supercapacitors

2019 ◽  
Vol 7 (15) ◽  
pp. 9163-9172 ◽  
Author(s):  
Lifeng Zhang ◽  
Yu Guo ◽  
Kechao Shen ◽  
Jinghao Huo ◽  
Yi Liu ◽  
...  
Keyword(s):  
Energy Storage ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
High Specific Surface Area ◽  
Porous Carbons ◽  
Storage Performance

Polypyrrole (PPy)-derived porous carbons with an ion-matching micropore diameter exhibit ultra-high specific surface area and capacitance when used in supercapacitors.

Preparation of N-Doped Nanoporous Carbon from Crude Biomass and its Electrochemical Activity

NANO ◽  
2016 ◽  
Vol 11 (03) ◽  
pp. 1650028 ◽  
Author(s):  
Zezhong Xu ◽  
Jingyu Si
Keyword(s):  
Surface Area ◽  
Low Cost ◽  
High Surface ◽  
High Surface Area ◽  
Lithium Ion ◽  
Nanoporous Carbon ◽  
High Specific Surface Area ◽  
Electrochemical Sensing ◽  
Potential Candidate ◽  
Surface Areas

H2O2 detection plays an important role in electrochemical sensing since H2O2 often acts as an intermediate product or regulator in various reactions. Nanoporous carbon (NPC) can be a potential candidate in electrochemical sensing because of its high specific surface area, various pore sizes and structures. In this work, we reported the preparation of N-doped NPC derived from the highly available, accessible and recyclable plant Typha orientalis. The products have high surface area (highest surface areas of 1439.0 m2 g[Formula: see text] and a number of nanopores. Highest content of nitrogen atom in the product is 3.66 at.%). Typical product exhibits high electrocatalytic activity for reduction of hydrogen peroxide. The product may have further use for glucose biosensing. We developed a low-cost, simple and readily scalable approach to prepare the excellent carbon electrocatalyst directly from crude biomass. In addition, because of high surface area and doping of nitrogen element, the product may find broad applications in the fields of supercapacitors, lithium-ion batteries, gas uptake and so on.

Tenacious Mass Transfer Limitations Drive Catalytic Selectivity during Electrochemical Carbon Dioxide Reduction

2019 ◽  
Author(s):  
Kailun Yang ◽  
Recep Kas ◽  
Wilson A. Smith
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Catalyst Layer ◽  
Active Surface ◽  
Active Surface Area ◽  
High Concentration ◽  
Copper Electrodes ◽  
Surface Enhanced ◽  
Local Current

<p>This study evaluated the performance of the commonly used strong buffer electrolytes, i.e. phosphate buffers, during CO<sub>2</sub> electroreduction in neutral pH conditions by using in-situ surface enhanced infrared absorption spectroscopy (SEIRAS). Unfortunately, the buffers break down a lot faster than anticipated which has serious implications on many studies in the literature such as selectivity and kinetic analysis of the electrocatalysts. Increasing electrolyte concentration, surprisingly, did not extend the potential window of the phosphate buffers due to dramatic increase in hydrogen evolution reaction. Even high concentration phosphate buffers (1 M) break down within the potentials (-1 V vs RHE) where hydrocarbons are formed on copper electrodes. We have extended the discussion to high surface area electrodes by evaluating electrodes composed of copper nanowires. We would like highlight that it is not possible to cope with high local current densities on these high surface area electrodes by using high buffer capacity solutions and the CO<sub>2</sub> electrocatalysts are needed to be evaluated by casting thin nanoparticle films onto inert substrates as commonly employed in fuel cell reactions and up to now scarcely employed in CO<sub>2</sub> electroreduction. In addition, we underscore that normalization of the electrocatalytic activity to the electrochemical active surface area is not the ultimate solution due to concentration gradient along the catalyst layer.This will “underestimate” the activity of high surface electrocatalyst and the degree of underestimation will depend on the thickness, porosity and morphology of the catalyst layer. </p> <p> </p>

scholarly journals Rugae-like FeP nanocrystal assembly on a carbon cloth: an exceptionally efficient and stable cathode for hydrogen evolution

Nanoscale ◽  
2015 ◽  
Vol 7 (25) ◽  
pp. 10974-10981 ◽  
Author(s):  
Xiulin Yang ◽  
Ang-Yu Lu ◽  
Yihan Zhu ◽  
Shixiong Min ◽  
Mohamed Nejib Hedhili ◽  
...  
Keyword(s):  
Gas Phase ◽  
Surface Area ◽  
Hydrogen Evolution ◽  
Hydrogen Generation ◽  
High Surface ◽  
High Surface Area ◽  
Catalytic Efficiency ◽  
Carbon Cloth ◽  
Nanocrystal Assembly

High surface area FeP nanosheets on a carbon cloth were prepared by gas phase phosphidation of electroplated FeOOH, which exhibit exceptionally high catalytic efficiency and stability for hydrogen generation.

High Surface Area NiCoP Nanostructure as Efficient Water Splitting Electrocatalyst for the Oxygen Evolution Reaction

2021 ◽  
pp. 111312
Author(s):  
Sisir Maity ◽  
Dheeraj Kumar Singh ◽  
Divya Bhutani ◽  
Suchitra Prasad ◽  
Umesh V. Waghmare ◽  
...  
Keyword(s):  
Surface Area ◽  
Water Splitting ◽  
Oxygen Evolution ◽  
Oxygen Evolution Reaction ◽  
High Surface ◽  
High Surface Area

scholarly journals Effect of Calcium Nitrate on the Properties of Portland–Limestone Cement-Based Concrete Cured at Low Temperature

Materials ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1611
Author(s):  
Gintautas Skripkiūnas ◽  
Asta Kičaitė ◽  
Harald Justnes ◽  
Ina Pundienė
Keyword(s):  
Compressive Strength ◽  
Cement Paste ◽  
Setting Time ◽  
Calcium Nitrate ◽  
Curing Temperature ◽  
Hardened Concrete ◽  
Cement Pastes ◽  
Initial Setting Time ◽  
Initial Setting ◽  
Early Strength

The effect of calcium nitrate (CN) dosages from 0 to 3% (of cement mass) on the properties of fresh cement paste rheology and hardening processes and on the strength of hardened concrete with two types of limestone-blended composite cements (CEM II A-LL 42.5 R and 42.5 N) at different initial (two-day) curing temperatures (−10 °C to +20 °C) is presented. The rheology results showed that a CN dosage up to 1.5% works as a plasticizing admixture, while higher amounts demonstrate the effect of increasing viscosity. At higher CN content, the viscosity growth in normal early strength (N type) cement pastes is much slower than in high early strength (R type) cement pastes. For both cement-type pastes, shortening the initial and final setting times is more effective when using 3% at +5 °C and 0 °C. At these temperatures, the use of 3% CN reduces the initial setting time for high early strength paste by 7.4 and 5.4 times and for normal early strength cement paste by 3.5 and 3.4 times when compared to a CN-free cement paste. The most efficient use of CN is achieved at −5 °C for compressive strength enlargement; a 1% CN dosage ensures the compressive strength of samples at a −5 °C initial curing temperature, with high early strength cement exceeding 3.5 MPa but being less than the required 3.5 MPa in samples with normal early strength cement.

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