scholarly journals Influence of Structure-Directing Additives on the Properties of Poly(methylsilsesquioxane) Aerogel-Like Materials

Gels ◽  
2019 ◽  
Vol 5 (1) ◽  
pp. 6 ◽  
Author(s):  
Marta Ochoa ◽  
Alyne Lamy-Mendes ◽  
Ana Maia ◽  
António Portugal ◽  
Luísa Durães
Keyword(s):  
Specific Surface ◽  
Bulk Density ◽  
Surface Area ◽  
Specific Surface Area ◽  
High Porosity ◽  
Poly Ethylene Glycol ◽  
Optimum Amount ◽  
Molar Ratios ◽  
Fine Control ◽  
Poly Ethylene

The effect of glycerol (GLY) and poly(ethylene glycol) (PEG) additives on the properties of silica aerogel-like monoliths obtained from methyltrimethoxysilane (MTMS) precursor was assessed. The tested molar ratios of additive/precursor were from 0 to 0.1 and the lowest bulk densities were obtained with a ratio of 0.025. When a washing step was performed in the sample containing the optimum PEG ratio, the bulk density could be reduced even further. The analysis of the material’s microstructure allowed us to conclude that GLY, if added in an optimum amount, originates a narrower pore size distribution with a higher volume of mesopores and specific surface area. The PEG additive played a binder effect, leading to the filling of micropores and the appearance of large pores (macropores), which caused a reduction in the specific surface area. The reduction of the bulk density and the microstructural changes in the aerogels induced by adding a small amount of these additives confirm the possibility of fine control of properties of these lightweight materials. The achieved high porosity (97%) and low thermal conductivity (~35 mW·m−1·K−1) makes them suitable to be used as thermal insulators.

Physical Properties Variability of Zinc Powders Obtained by Electrochemical Method

2021 ◽  
Vol 316 ◽  
pp. 689-693
Author(s):  
K.D. Naumov ◽  
V.G. Lobanov
Keyword(s):  
Particle Size ◽  
Specific Surface ◽  
Bulk Density ◽  
Surface Area ◽  
Specific Surface Area ◽  
Current Density ◽  
Zinc Concentration ◽  
Regulatory Change ◽  
Average Particle ◽  
Zinc Powders

The aim of this paper is to establish a regulatory change of zinc powders key physicochemical properties with varying electroextraction conditions. It was studied influence zinc concentration, alkali concentration and current density. Quantitative dependencies of zinc powders particle size and specific surface area from mentioned electroextraction parameters are shown. At increasing of zinc concentration, decreasing of NaOH concentration and decreasing of current density of powders particle size growth, correspondingly specific surface area is declined. It is indicated, that electrolytic zinc powders bulk density varies from 0.61 g/cm3 to 0.75 g/cm3 with a decrease of average particle size from 121 μm to 68 μm. In comparison, spherical powders bulk density used in various industries is currently 2.45-2.6 g/cm3. In all experiments, metal zinc content varied in the range of 91.1-92.5%, the rest - ZnO. To a greater extent, this indicator depends on powder washing quality from alkali and storage conditions.

In-situ controlled synthesis of NiFe MOF materials with excellent electrocatalytic performances for water splitting

2021 ◽  
Vol 14 (02) ◽  
pp. 2151011
Author(s):  
Jingwen Jia ◽  
Longfu Wei ◽  
Ziting Guo ◽  
Fang Li ◽  
Changlin Yu ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Water Splitting ◽  
Specific Surface Area ◽  
High Performance ◽  
Alkaline Condition ◽  
High Porosity ◽  
Large Specific Surface Area ◽  
Electrocatalytic Performance

Metal–organic frameworks (MOFs) are the electrocatalytic materials with large specific surface area, high porosity, controllable structure and monodisperse active center, which is a promising candidate for the application of electrochemical energy conversion. However, the electrocatalytic performance of pure MOFs is seriously limited its poor conductivity and stability. In this work, high-performance electrocatalyst was fabricated through combining NiFe/MOF on nickel foam (NF) via in-situ growth strategy. Through rational control of the time and ratio in reaction precursors, we realized the effective manipulation of the growth behavior, and further investigated the electrocatalytic performance in water splitting. The catalyst presented excellent electrocatalytic performance for water splitting, with low overpotential of 260 mV in alkaline condition at a current density of 50 mA[Formula: see text], which is benefited from the large specific surface area and active sites. This study demonstrates that the rational design of NiFe MOF/NF plays a significant role in high-performance electrocatalyst.

Effect of Synthesis Temperature and Ca/P Ratios on Specific Surface Area of Amorphous Calcium Phosphate

2016 ◽  
Vol 721 ◽  
pp. 172-176 ◽  
Author(s):  
Jana Vecstaudza ◽  
Janis Locs
Keyword(s):  
Calcium Phosphate ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Amorphous Calcium Phosphate ◽  
Calcium Phosphates ◽  
Synthesis Temperature ◽  
Molar Ratios ◽  
Different Temperatures ◽  
Low Crystalline

Amorphous and low crystalline calcium phosphates are prospective candidates for bone implant manufacturing. Amorphous calcium phosphate (ACP) preparation technologies could be improved in terms of specific surface area (SSA) of obtained products. Current study is dedicated to the effect of synthesis temperature and Ca and P molar ratios (Ca/P) on SSA of ACP. Higher SSA can improve bioactivity of biomaterials. ACP was characterized by XRD, FT-IR, SEM and BET N2 adsorption techniques. Spherical nanoparticles (<45 nm in size) were obtained independently of initial Ca/P ratio and synthesis temperature. For the first time comparison of SSA was shown for ACP obtained at different temperatures (0 °C and 20 °C) and Ca/P molar ratios (1.5, 1.67 and 2.2).

Using Activated Diatomite as Adsorbent for Treatment of Arsenic Contaminated Water

2020 ◽  
Vol 850 ◽  
pp. 16-21
Author(s):  
Hoc Thang Nguyen ◽  
Phong Thanh Dang
Keyword(s):  
Specific Surface ◽  
Adsorption Capacity ◽  
Surface Area ◽  
Specific Surface Area ◽  
Contaminated Water ◽  
Viet Nam ◽  
High Porosity ◽  
Room Condition ◽  
Main Chemical Composition ◽  
Adsorbent Capacity

Diatomite or diatomaceous earth (DE) is one of materials which can be used as an adsorbent to treat heavy metal ions from waste water, even there are many factories used it to clean the water for drinking. However, natural DE (raw DE) has very low adsorption capacity because of low specific surface area. In this work, natural DE from Lam Dong province, Viet Nam was demagnetized to remove iron and activated by HCl solution for 90 minutes with concentration of 10% at room condition. Adsorbent capacity was evaluated using As solution and the results show that the activated diatomite has adsorption capacity three times higher than that of raw DE, and the specific surface area of activated diatomite was increased 47.5% with the main chemical composition of 90.8% SiO2 and high porosity

scholarly journals Manufacture of Fine-Pored Ceramics by the Gelcasting Method

2017 ◽  
Vol 2017 ◽  
pp. 1-6 ◽  
Author(s):  
Bronisław Psiuk ◽  
Anna Gerle ◽  
Małgorzata Osadnik ◽  
Andrzej Śliwa
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Design Theory ◽  
Nanoporous Materials ◽  
Silica Sol ◽  
High Porosity ◽  
Simple Method ◽  
Fine Grained ◽  
Wide Range

The fine-pored materials represent a wide range of applications and searches are being continued to develop methods of their manufacturing. In the article, based on measurements on fine-grained powders of Al2O3, TiO2, and SiO2, it has been demonstrated that gelcasting can be relatively simple method of obtaining of nanoporous materials with high values of both specific surface area and open porosity. The powders were dispersed in silica sol, and the gelling initiator was NH4Cl. The usefulness of experiment design theory for developing of fine-pored materials with high porosity and specific surface area was also shown.

Effect of pH, Molar Ratio of Fuel to Nitrates and Calcination Temperature on the Glycine-Nitrate Synthesis of Nano CoAl2O4

2010 ◽  
Vol 68 ◽  
pp. 176-181 ◽  
Author(s):  
Seyyed Hamid Jazayeri ◽  
Federica Bondioli ◽  
Shiva Salem ◽  
Ali Allahverdi ◽  
Mansoor Shirvani ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Calcination Temperature ◽  
Specific Surface Area ◽  
Precursor Solution ◽  
Molar Ratio ◽  
Effect Of Ph ◽  
Molar Ratios ◽  
Metal Nitrates ◽  
Powder Characteristics

In this research, solution-based combustion synthesis is applied to prepare the spinel CoAl2O4 pigment from precursor solution of Al(NO3)3 .9H2O, Co(NO3)2 .6H2O and glycine. Effect of pH values (2.5, 7, 10.5), molar ratio of fuel to metal nitrates in the precursor solutions (1.5, 2) and subsequent calcination temperature (800, 1000, 1200 °C) on the powder characteristics are described. Gel formation, morphologies, specific surface area and colour of the powder are characterized using DTA/TG, XRD, TEM, BET and UV-Vis. The results indicate that the crystalline spinel CoAl2O4 is formed at all different Gl/(metal nitrates) molar ratios, pH and temperatures and higher temperature promote the increase of the crystallite size. According to TEM figures most of the particles calcined at 800 and 1000 °C has sizes less than 50 and 100 nm, respectively. Corresponding to results of BET experiment, specific surface area has its maximum values at pH 7 and decreases with increasing of temperature. Finally, colorability test indicates the complete stability of the synthesized powder in the glass matrix.

Novel Al2O3–SiO2composite aerogels with high specific surface area at elevated temperatures with different alumina/silica molar ratios prepared by a non-alkoxide sol–gel method

RSC Advances ◽  
2016 ◽  
Vol 6 (7) ◽  
pp. 5611-5620 ◽  
Author(s):  
Xiaodong Wu ◽  
Gaofeng Shao ◽  
Xiaodong Shen ◽  
Sheng Cui ◽  
Ling Wang
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Elevated Temperatures ◽  
Inorganic Salt ◽  
Sol Gel ◽  
High Specific Surface Area ◽  
Gel Method ◽  
Molar Ratios ◽  
Composite Aerogels

We have developed a new sol–gel route to synthesise Al2O3–SiO2composite aerogels with different alumina/silica (Al/Si) molar ratios using an inexpensive inorganic salt.

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