scholarly journals Chemical polymerization of aniline in phenylphosphinic acid

2005 ◽  
Vol 70 (10) ◽  
pp. 1169-1182 ◽  
Author(s):  
Nicoleta Plesu ◽  
Gheorghe Ilia ◽  
Geza Bandur ◽  
Simona Popa
Keyword(s):  
Average Density ◽  
Inherent Viscosity ◽  
Polymerization Process ◽  
Chemical Polymerization ◽  
Molar Ratios ◽  
Synthesis Parameters ◽  
Maximum Value ◽  
Thermogravimetric Data ◽  
Pani Salt ◽  
Pani Base

The chemical polymerization of aniline was performed in phenylphosphinic acid (APP) medium using ammonium peroxidisulfate as the oxidizing agent, at 0 ?C and 25 ?C. The yield of polyaniline (PANI) was about 60?69 %. The polymerization process required an induction time 8?10 times greater than in other acids (hydrochloric, sulfuric). The average density of the obtained polymer was 1.395 g cm-3 for PANI-salt and 1.203 g cm-3 for PANI-base. The acid capacity of PANI depends on the synthesis parameters and the maximum value was 15.02 meq/g polymer. The inherent viscosity of PANI was 0.662 dl/g at aniline/oxidant molar ratios >2 and 0 ?C. The oxidation state was a function of the synthesis parameters and lay between 0.553?0.625, as determined from UV-VIS and titration with TiCl3 data. The PANI samples were characterized by measurements of their density, inherent viscosity conductivity, acid capacity, FTIR and UV-VIS spectrum, and thermogravimetric data.

scholarly journals Density Variations in Alpine Snow

1967 ◽  
Vol 6 (46) ◽  
pp. 495-503 ◽  
Author(s):  
Donald Alford
Keyword(s):  
Physical Property ◽  
Average Density ◽  
Western Montana ◽  
Snow Pack ◽  
Snow Layer ◽  
Near Surface ◽  
Annual Layer ◽  
Maximum Value ◽  
Air Temperatures ◽  
Density Values

AbstractStratigraphic studies of the annual snow layer in the Beartooth Mountains of south-western Montana and on Mount Logan in the St. Elias Range have disclosed a similiar distribution of at least one physical property of the snow pack in the two areas. The average density of the pack, obtained by integrating a series of measurements taken at 5–10 cm. vertical intervals over the total thickness of the annual layer, reaches a maximum value near a mid-point of the total elevation covered by each traverse and decreases linearly toward the elevation extremes. A preliminary hypothesis, relating the distribution of average snow-density values along slopes to a semi-stable zonation of near-surface air temperatures, is presented.

Influence of ethanol on the chain-ordering of carbonised polyaniline

2013 ◽  
Vol 67 (8) ◽  
Author(s):  
Zuzana Morávková ◽  
Miroslava Trchová ◽  
Elena Tomšík ◽  
Jaroslav Stejskal
Keyword(s):  
Molecular Structure ◽  
Pure Water ◽  
Nitrogen Atmosphere ◽  
Ethanol Mixture ◽  
Electron Microscopies ◽  
X Ray Scattering ◽  
Transmission Electron ◽  
Pani Salt ◽  
Chain Ordering ◽  
Pani Base

AbstractPolyaniline (PANI) was prepared by the oxidation of aniline hydrochloride with ammonium peroxydisulphate in water or in a water-ethanol mixture. In the presence of ethanol, PANI nanotubes and nanorods were observed. Both products were carbonised in a nitrogen atmosphere at 650°C. Initial and carbonised products were characterised by scanning and transmission electron microscopies, thermogravimetric analysis and wide-angle X-ray scattering. Their molecular structure was studied by UV-VIS, infrared, and Raman spectroscopies. Carbonised sample obtained from the PANI salt prepared in the presence of ethanol exhibits Raman spectrum which corresponds to a more ordered carbon-like material than carbonised samples obtained from the PANI base and the PANI salt prepared in pure water. The influence of ethanol present in the reaction mixture on the molecular and supra-molecular structure of PANI and, consequently, on the enhancement of chainordering of carbonised PANI is discussed.

A Combined Physical–Chemical Polymerization Process for Fabrication of Nanoparticle–Hydrogel Sensing Materials

2012 ◽  
Vol 45 (20) ◽  
pp. 8382-8386 ◽  
Author(s):  
Qingzhou Cui ◽  
Wei Wang ◽  
Baohua Gu ◽  
Liyuan Liang
Keyword(s):  
Polymerization Process ◽  
Chemical Polymerization ◽  
Physical Chemical

Precipitation and surface polymerizations of aniline at different aniline:oxidizer molar ratios

e-Polymers ◽  
2007 ◽  
Vol 7 (1) ◽  
Author(s):  
Lucia Helena Mascaro ◽  
Débora Gonçalves
Keyword(s):  
Oxidative Polymerization ◽  
Reaction Times ◽  
Ammonium Persulfate ◽  
Open Circuit ◽  
Polymerization Process ◽  
Pani Film ◽  
Electrode Surfaces ◽  
Molar Ratios ◽  
Pt Electrodes ◽  
Vis Spectroscopy

AbstractThe oxidative polymerization of aniline was monitored by means of open-circuit potential (OCP) measurements of Pt electrodes immersed in an aqueous acidic medium containing different aniline:oxidizer (ammonium persulfate) molar ratios. Thin polyaniline (PANI) films were formed on the Pt electrode surfaces during the OCP measurements, and they were studied by SEM and cyclic voltammetry in a monomer-free solution at different reaction times. A precipitate also obtained during the polymerization process was analyzed by UV-VIS spectroscopy in 1-methyl-2-pyrrolidinone. It is observed that aniline or short oligomeric species are necessary to initiate the growth of a PANI film, which takes place at the first few minutes of the reaction.

scholarly journals Hybrid RF-Si Xerogels: A Cost-Effective Proposal for Insulator Materials

Materials ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 265
Author(s):  
Samantha L. Flores-López ◽  
Sara F. Villanueva ◽  
Natalia Rey-Raap ◽  
Ana Arenillas
Keyword(s):  
Cost Effective ◽  
Material Design ◽  
Structural Features ◽  
Polymerization Process ◽  
Drying Methods ◽  
Molar Ratios ◽  
Starting Point ◽  
Good Starting Point ◽  
Hybrid Xerogels ◽  
Lengthy Process

Hybrid xerogels RF/Si were synthesized by controlling the chemical variables involved in the polymerization process (i.e., molar ratios, dilution ratio, catalysts, etc.) and evaluated as insulator materials. Higher insulating performances were recorded for these hybrids compared with their counterparts made from only one of their components (i.e., RF or Si xerogels with similar porous characteristics). The analysis of chemical and structural features correlated with heat transfer methods was useful in understanding the sum of contributions involved in the thermal conductivity of RF/Si xerogels. Variables such as roughness and tortuosity can be used to improve the performance of xerogels from a different perspective. In this way, thermal conductivities of 25 mW/mK were achieved without lengthy process steps or special drying methods. Knowledge of material design and the use of microwave heating during the synthesis allowed us to approach a simple and cost-effective process. These results suggest that the hybrid materials developed in this work are a good starting point for the future of the massive production of insulation materials.

scholarly journals The Effects of Promoter Cs Loading on the Hydrogen Production from Ammonia Decomposition Using Ru/C Catalyst in a Fixed-Bed Reactor

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 321
Author(s):  
Yen-Ling Chen ◽  
Chin-Fang Juang ◽  
Yen-Cho Chen
Keyword(s):  
Hydrogen Production ◽  
Fixed Bed ◽  
Space Velocity ◽  
Ammonia Decomposition ◽  
Fixed Bed Reactor ◽  
Molar Ratio ◽  
Carbon Catalyst ◽  
Molar Ratios ◽  
Maximum Value ◽  
Ammonia Conversion

The hydrogen production from ammonia decomposition on commercial 5 wt.% Ru/C (C: activated carbon) catalyst with different cesium (Cs) loadings at lower temperatures of 325–400 °C in the fixed-bed reactor was experimentally investigated. Based on the parameters used in this work, the results showed that the ammonia conversion at 350 °C is increased with the increasing Cs/Ru molar ratio, and it reaches its maximum value at the Cs/Ru molar ratio of 4.5. After that, it is rapidly decreased with a further increase of Cs/Ru molar ratio, and it is even smaller than that of the pure Ru/C case at the Cs/Ru molar ratio of 6. The Cs promotion at the lower Cs/Ru molar ratios may be due to the so-called “hot ring promotion”. The possible mechanisms for Cs effects on the ammonia conversion at higher Cs/Ru molar ratio are discussed. At optimum Cs loading, the results showed that all the ammonia conversions at 400 °C are near 100% for the GHSV (gas hourly space velocity) from 48,257 to 241,287 mL/(h·gcat).

STUDIES ON CHEMICALLY SYNTHESIZED DOPED POLY(O-ANISIDINE) AND COPOLY{ANILINE-(O-ANISIDINE)}

2006 ◽  
Vol 20 (23) ◽  
pp. 1461-1470 ◽  
Author(s):  
S. B. KONDAWAR ◽  
M. J. HEDAU ◽  
V. A. TABHANE ◽  
S. P. DONGRE ◽  
U. B. MAHATME ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Oxidation States ◽  
Polymerization Process ◽  
Ftir Analysis ◽  
Orthorhombic Crystal ◽  
Orthorhombic Crystal Structure ◽  
Chemical Polymerization ◽  
X Ray ◽  
Increasing Temperature ◽  
Polymerization Method

Substituted polyaniline poly(o-anisidine) and copoly{aniline-(o-anisidine)} were synthesized by the oxidative chemical polymerization method. Sulfuric acid was used as the dopant during the polymerization process. Synthesized polymers were subjected to the spectroscopic, X-ray and thermal analysis. Formation of different oxidation states of the polymer were confirmed by the spectroscopic (UV-VIS and FTIR) analysis. Polymers reveal polycrystalline nature and orthorhombic crystal structure. Three step decomposition patterns similar to that of polyaniline are observed in the thermogram. The conductivity is found to be higher in copoly{aniline-(o-anisidine)} than poly(o-anisidine). Increase in conductivity with increasing temperature was observed in both of the polymers.

Preparation and Mechanical Properties of Potassium Metakaolin Based Geopolymer Paste

2019 ◽  
Vol 31 ◽  
pp. 38-45
Author(s):  
Hiep Le Chi ◽  
Petr Louda ◽  
Totka Bakalova ◽  
Vladimír Kovačič
Keyword(s):  
Compressive Strength ◽  
Mechanical Strength ◽  
Potassium Hydroxide ◽  
Silicate Solution ◽  
Curing Temperature ◽  
Polymerization Process ◽  
Strength Development ◽  
Early Age ◽  
Molar Ratios ◽  
Additional Water

In this study, geopolymer samples were prepared by mixing metakaolin (MA) with activator solution made of potassium alkali silicate solution, potassium hydroxide flakes, and additional water. The aim of the experiment is to evaluate the mechanical strength of hardened samples based on four test variables including the SiO2/K2O molar ratios, K2O concentration, H2O/MA water coefficient, and curing temperature. The results reveal that K2O concentration and H2O/MA water coefficient impact strongly on the compressive strength, whereas varying of SiO2/K2O molar ratios in the range from 1.0 – 1.4 does not significantly change the compressive strength of geopolymer samples. On the other hand, high-temperature curing leads to higher mechanical strength of the samples in the early-age compared to curing at room temperature, due to the faster establishment of hard structure in the early-age of geo-polymerization process. However, curing at a temperature range of 80°C – 100°C contributes the non-linear strength development of the samples over the time.

Effects of Synthesis Parameters on Hydrothermal Synthesis of NaA Zeolite

2010 ◽  
Vol 148-149 ◽  
pp. 1444-1448
Author(s):  
Lin Lin Yuwen ◽  
Meng Fu Zhu ◽  
Hong Bo Su ◽  
Xiu Dong You ◽  
Cheng Deng ◽  
...  
Keyword(s):  
Particle Size ◽  
Molar Ratio ◽  
Crystallization Time ◽  
X Ray Diffraction ◽  
Molar Ratios ◽  
Naa Zeolite ◽  
Optimum Synthesis ◽  
Synthesis Parameters ◽  
Particle Size Analyzer ◽  
Crystal Particle

In this research, NaA zeolite samples were synthesized from aluminosilicate solution through hydrothermal method. The effects of different parameters such as the SiO2/Al2O3, OH-/Si and H2O/Na2O molar ratios of the initial gel solution, crystallization time and temperature on the crystallinity and morphology of the synthesized zeolites were investigated. The final products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser particle size analyzer. The experiment results indicated that the SiO2/Al2O3 molar ratio had influence on morphology and size of the synthesized zeolites, the optimum range of SiO2/Al2O3 molar ratio for synthesizing NaA zeolite was 1.5-2. Alkalinity (OH-/Si and H2O/Na2O molar ratio) had a significant effect on particle sizes of the synthesized zeolites, the higher the alkalinity, the smaller the crystal particle size. In addition, it was found that crystallization temperature during hydrothermal treatment played an important role in reducing the over all reaction time. The crystallization time had effect on the crystallinity of the synthesized zeolites. Finally, the optimum synthesis parameters can be proposed in order to synthesize NaA zeolite with desirable particle size, crystallinity and morphology.

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