scholarly journals Room-temperature dissolution and chemical modification of cellulose in aqueous tetraethylammonium hydroxide–carbamide solutions

Cellulose ◽  
2019 ◽  
Vol 27 (4) ◽  
pp. 1933-1950 ◽  
Author(s):  
Juho Antti Sirviö ◽  
Juha P. Heiskanen
Keyword(s):  
Chemical Modification ◽  
Charge Density ◽  
Microcrystalline Cellulose ◽  
Room Temperature ◽  
Molar Ratio ◽  
Cellulose Modification ◽  
Tetraethylammonium Hydroxide ◽  
Cellulose Concentration

AbstractThe room-temperature dissolution of cellulose in aqueous tetraethylammonium hydroxide (TEAOH) in the presence of carbamides (ureas) was investigated. Without carbamide, 35 wt% TEAOH was able to dissolve cellulose (microcrystalline cellulose) up to 3 wt%, whereas carbamides—such as urea, N-methylurea, N-ethylurea, 1,3-dimethylurea, and imidazolidone—were able to improve the dissolution of cellulose. At 5 wt% cellulose concentration, the highest carbamide contents in the solvent still able to dissolve cellulose within 1 h were 56 and 55 wt% of 1,3-dimethylurea and N-methylurea, respectively. When using urea, up to 15% of cellulose could be dissolved in a solution containing 22 wt% of urea. To demonstrate the possibility of the use of a carbamide-based solvent in cellulose modification, cationic cellulose was produced using glycidyltrimethylammonium chloride (GTAC). At a molar ratio of 1:3 of cellulose and GTAC, all the studied TEAOH–carbamide solvents produce cationic cellulose with higher charge density compared to the reference NaOH–urea solvent.

scholarly journals Pure hydroxyapatite synthesis originating from amorphous calcium carbonate

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Michika Sawada ◽  
Kandi Sridhar ◽  
Yasuharu Kanda ◽  
Shinya Yamanaka
Keyword(s):  
Calcium Carbonate ◽  
Calcium Phosphate ◽  
Room Temperature ◽  
Molar Ratio ◽  
Final Phase ◽  
Amorphous Calcium Carbonate ◽  
Phosphate Compound ◽  
Synthesis Strategy ◽  
Phosphorylation Reaction ◽  
Subsequent Calcination

AbstractWe report a synthesis strategy for pure hydroxyapatite (HAp) using an amorphous calcium carbonate (ACC) colloid as the starting source. Room-temperature phosphorylation and subsequent calcination produce pure HAp via intermediate amorphous calcium phosphate (ACP). The pre-calcined sample undergoes a competitive transformation from ACC to ACP and crystalline calcium carbonate. The water content, ACC concentration, Ca/P molar ratio, and pH during the phosphorylation reaction play crucial roles in the final phase of the crystalline phosphate compound. Pure HAp is formed after ACP is transformed from ACC at a low concentration (1 wt%) of ACC colloid (1.71 < Ca/P < 1.88), whereas Ca/P = 1.51 leads to pure β-tricalcium phosphate. The ACP phases are precursors for calcium phosphate compounds and may determine the final crystalline phase.

Real space observation of charge density waves in the incommensurate room temperature phase of TaS2

1981 ◽  
Vol 64 (2) ◽  
pp. K105-K106 ◽  
Author(s):  
G. van Tendeloo ◽  
J. van Landwt ◽  
S. Amelinckx
Keyword(s):  
Charge Density ◽  
Room Temperature ◽  
Real Space ◽  
Charge Density Waves ◽  
Temperature Phase ◽  
Density Waves

scholarly journals Crystal structure of the new hybrid material bis(1,4-diazoniabicyclo[2.2.2]octane) di-μ-chlorido-bis[tetrachloridobismuthate(III)] dihydrate

2015 ◽  
Vol 71 (11) ◽  
pp. 1384-1387
Author(s):  
Marwen Chouri ◽  
Habib Boughzala
Keyword(s):  
Crystal Structure ◽  
Aqueous Solution ◽  
Hydrogen Bonds ◽  
Room Temperature ◽  
Molar Ratio ◽  
Water Molecules ◽  
Site Symmetry ◽  
Two Dimensional ◽  
Slow Evaporation ◽  
Solution Ph

The title compound bis(1,4-diazoniabicyclo[2.2.2]octane) di-μ-chlorido-bis[tetrachloridobismuthate(III)] dihydrate, (C6H14N2)2[Bi2Cl10]·2H2O, was obtained by slow evaporation at room temperature of a hydrochloric aqueous solution (pH = 1) containing bismuth(III) nitrate and 1,4-diazabicyclo[2.2.2]octane (DABCO) in a 1:2 molar ratio. The structure displays a two-dimensional arrangement parallel to (100) of isolated [Bi2Cl10]4−bioctahedra (site symmetry -1) separated by layers of organic 1,4-diazoniabicyclo[2.2.2]octane dications [(DABCOH2)2+] and water molecules. O—H...Cl, N—H...O and N—H...Cl hydrogen bonds lead to additional cohesion of the structure.

scholarly journals Ultrafast manipulation of mirror domain walls in a charge density wave

2018 ◽  
Vol 4 (10) ◽  
pp. eaau5501 ◽  
Author(s):  
Alfred Zong ◽  
Xiaozhe Shen ◽  
Anshul Kogar ◽  
Linda Ye ◽  
Carolyn Marks ◽  
...  
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Room Temperature ◽  
Domain Walls ◽  
Density Wave ◽  
Charge Ordering ◽  
Time Resolved ◽  
Insulator Metal Transition ◽  
Femtosecond Light Pulse ◽  
A Charge

Domain walls (DWs) are singularities in an ordered medium that often host exotic phenomena such as charge ordering, insulator-metal transition, or superconductivity. The ability to locally write and erase DWs is highly desirable, as it allows one to design material functionality by patterning DWs in specific configurations. We demonstrate such capability at room temperature in a charge density wave (CDW), a macroscopic condensate of electrons and phonons, in ultrathin 1T-TaS2. A single femtosecond light pulse is shown to locally inject or remove mirror DWs in the CDW condensate, with probabilities tunable by pulse energy and temperature. Using time-resolved electron diffraction, we are able to simultaneously track anti-synchronized CDW amplitude oscillations from both the lattice and the condensate, where photoinjected DWs lead to a red-shifted frequency. Our demonstration of reversible DW manipulation may pave new ways for engineering correlated material systems with light.

Efficient synthesis of pyrido[2,3-d]pyrimidine-7-carboxylic acids catalyzed by a TiO2/SiO2 nanocomposite in aqueous media at room temperature

2018 ◽  
Vol 73 (9) ◽  
pp. 641-645 ◽  
Author(s):  
Sepehr Sadegh-Samiei ◽  
Shahrzad Abdolmohammadi
Keyword(s):  
Heterogeneous Catalyst ◽  
Carboxylic Acids ◽  
Room Temperature ◽  
Aqueous Media ◽  
Reaction Times ◽  
Molar Ratio ◽  
Efficient Synthesis ◽  
Reaction Conditions ◽  
Moderate Reaction ◽  
Recyclable Heterogeneous Catalyst

AbstractA novel and efficient synthesis of eight 5-aryl-1,3-dimethyl-2,4-dioxo-1,2,3,4,5,8-hexahydropyrido[2,3-d]pyrimidine-7-carboxylic acids using a TiO2/SiO2 nanocomposite with a molar ratio of 1:1 as a recyclable heterogeneous catalyst is described. The desired products, five of which are new, are formed in short reaction times (2–3 h) with high to excellent yields (94%–98%) under very moderate reaction conditions (room temperature, aqueous media).

scholarly journals Initial Investigation into the Leaching of Manganese from Nodules at Room Temperature with the Use of Sulfuric Acid and the Addition of Foundry Slag—Part I

Minerals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 565 ◽  
Author(s):  
Norman Toro ◽  
Nelson Herrera ◽  
Jonathan Castillo ◽  
Cynthia Torres ◽  
Rossana Sepúlveda
Keyword(s):  
Particle Size ◽  
Sulfuric Acid ◽  
Acid Concentration ◽  
Room Temperature ◽  
Sulfuric Acid Concentration ◽  
Extraction Rate ◽  
Molar Ratio ◽  
Independent Variables ◽  
Initial Investigation ◽  
Optimization Methodology

In this study, the surface optimization methodology was used to assess the effect of three independent variables—time, particle size and sulfuric acid concentration—on Mn extraction from marine nodules during leaching with H2SO4 in the presence of foundry slag. The effect of the MnO2/Fe ratio and particle size (MnO2) was also investigated. The maximum Mn extraction rate was obtained when a MnO2 to Fe molar ratio of 0.5, 1 M of H2SO4, −320 + 400 Tyler mesh (−47 + 38 μm) nodule particle size and a leaching time of 30 min were used.

Achieving Room‐Temperature Charge Density Wave in Transition Metal Dichalcogenide 1 T ‐VSe 2

2020 ◽  
Vol 6 (5) ◽  
pp. 1901427
Author(s):  
Jiajia Feng ◽  
Resta A. Susilo ◽  
Bencheng Lin ◽  
Wen Deng ◽  
Yanju Wang ◽  
...  
Keyword(s):  
Transition Metal ◽  
Charge Density ◽  
Charge Density Wave ◽  
Room Temperature ◽  
Density Wave ◽  
Transition Metal Dichalcogenide

scholarly journals Synthesis, Characterization and Antifungal Studies of Adducts of p- Ethylphenyldithiocarbonates of Copper(II)

2019 ◽  
Vol 31 (8) ◽  
pp. 1819-1824
Author(s):  
Shivangi Sharma ◽  
Renu Sachar ◽  
G.D. Bajju ◽  
Vikas Sharma
Keyword(s):  
Magnetic Susceptibility ◽  
Electron Spin Resonance ◽  
Room Temperature ◽  
Molar Conductance ◽  
Octahedral Geometry ◽  
Molar Ratio ◽  
Spectral Studies ◽  
Distorted Octahedral Geometry ◽  
Distorted Octahedral ◽  
Spin Resonance

A series of adducts of p-ethylphenyldithiocarbonates of copper(II) [(p-C2H5C6H4OCS2)2Cu] with ethyl pyridines and chloro pyridines have been synthesized in 1:2 molar ratio. They were characterized by elemental analysis, magnetic susceptibility and molar conductance measurements, infrared, electronic, electron spin resonance and mass spectroscopy, NMR and thermogravimetric analysis. In addition, antifungal studies of these adducts were also performed. The results revealed that the adducts have 1:2 stoichiometry, non-electrolytic and paramagnetic at room temperature. On the basis of spectral studies, a distorted octahedral geometry is proposed around copper(II) ion. ESR studies depicted elongated axial symmetry of Cu(II)adducts with nitrogen donors. Moreover, the adducts also showed potential antifungal activity against Fusarium oxysporium.

scholarly journals Charge Density Wave and Narrow Energy Gap at Room Temperature in 2D Pb3–xSb1+xS4Te2−δ with Square Te Sheets

2017 ◽  
Vol 139 (32) ◽  
pp. 11271-11276 ◽  
Author(s):  
Haijie Chen ◽  
Christos D. Malliakas ◽  
Awadhesh Narayan ◽  
Lei Fang ◽  
Duck Young Chung ◽  
...  
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Room Temperature ◽  
Energy Gap ◽  
Density Wave

Desulfurization from Gasoline by Polymer Resin at Room Temperature and Atmospheric Pressure

2011 ◽  
Vol 396-398 ◽  
pp. 1283-1286
Author(s):  
Jian Peng Zhu ◽  
Chun Hu Li ◽  
Jia Ling Chen ◽  
Ying Wei Luo
Keyword(s):  
Reaction Time ◽  
Sulfur Content ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Oxidative Desulfurization ◽  
Sulfur Compounds ◽  
Molar Ratio ◽  
Reaction Conditions ◽  
Polymer Resin ◽  
Mild Conditions

Abstract. Investigation of polymer resin as catalyst in the oxidative desulfurization (ODS) process has revealed that the method can be applied to make a relative high removal of sulfur compounds. The reaction conditions, including temperature, amount of oxidant and reaction time were studied. The best result occurs under mild conditions with respect to room temperature and atmospheric pressure, to remove 75.54% of the totle sulfur content in the presence of H2O2 with an O/S molar ratio of 17. Possible mechanism is also disscussed.

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