Effect of High-Temperature Defibration on the Chemical Structure of Hardwood

Holzforschung ◽  
2002 ◽  
Vol 56 (1) ◽  
pp. 51-59 ◽  
Author(s):  
P. Widsten ◽  
J.E. Laine ◽  
P. Qvintus-Leino ◽  
S. Tuominen
Keyword(s):  
High Temperature ◽  
Lignin Content ◽  
Bulk Composition ◽  
Chemical Properties ◽  
Water Extract ◽  
Fiber Surface ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Groups ◽  
Surface Chemical ◽  
Alkyl Aryl

Summary The present paper aims at elucidating the effect of high-temperature defibration at different temperatures on the bulk and surface chemical properties of defibrated birch, aspen and eucalypt. The results indicate that defibration of these hardwoods results in partial depolymerization of fiber lignin via (homolytic) cleavage of interunit alkyl-aryl (β-O-4) ether bonds. This increases the phenolic hydroxyl content and produces relatively stable (phenoxy) radicals. Syringyl-type lignin is more extensively depolymerized than guaiacyl-type lignin. Defibration generates water-extractable material, which is enriched in hemicellulose-derived carbohydrates and has a substantial content of aromatic compounds rich in phenolic hydroxyl groups. The amount of water-extract and the extent of lignin interunit ether bond cleavage increase with an increase in defibration temperature. The differences between various hardwood species in this respect are small. The surface chemical composition of the fibers differs considerably from their bulk composition, but is not significantly influenced by variations in defibration temperature. Lipophilic extractives cover a large portion of the fiber surface, while the lignin content of lipophilic extractives-free fiber surfaces is 2–3 times as high as the bulk lignin content of the fibers.

The Reactions of Lignins with High Temperature Hydrogen Peroxide Part 2. The Oxidation of Kraft Lignin

Holzforschung ◽  
1999 ◽  
Vol 53 (3) ◽  
pp. 277-284 ◽  
Author(s):  
J.F. Kadla ◽  
H.-m. Chang ◽  
H. Jameel
Keyword(s):  
Hydrogen Peroxide ◽  
High Temperature ◽  
Molecular Oxygen ◽  
Kraft Lignin ◽  
Phenolic Hydroxyl ◽  
Hydroxyl Groups ◽  
Peroxide Oxidation ◽  
Alkaline Hydrogen Peroxide ◽  
Phenolic Hydroxyl Groups ◽  
Increasing Temperature

Summary A technical pine kraft lignin was subjected to alkaline hydrogen peroxide oxidation in the presence of DTMPA and molecular oxygen at various temperatures. In the presence of DTMPA the lignin was found to undergo increasing levels of oxidation and degradation with increasing temperature. At 110°C over 80% of the kraft lignin was degraded. Analyses of the degraded lignins indicated that both phenolic and nonphenolic lignin moieties were degraded. At 90°C the addition of molecular oxygen resulted in further lignin demethoxylation, but did not decrease the amount of phenolic hydroxyl groups or hydrogen peroxide consumed. In the absence of DTMPA the hydrogen peroxide was rapidly degraded, and accompanied by only minimal lignin oxidation.

Near-surface stoichiometry of high temperature superconducting YBaCuO thin films

1990 ◽  
Vol 5 (7) ◽  
pp. 1392-1396 ◽  
Author(s):  
A. J. Drehman ◽  
M. W. Dumais ◽  
J. A. Horrigan ◽  
G-C. Wang ◽  
Y-F. Liew
Keyword(s):  
Thin Films ◽  
High Temperature ◽  
Chemical Composition ◽  
Bulk Composition ◽  
Depth Profiling ◽  
Sputter Deposition ◽  
Surface Chemical ◽  
Furnace Annealing ◽  
Near Surface ◽  
High Temperature Superconducting

The surface morphology and near-surface chemical composition of high temperature superconducting Y–Ba–Cu–O thin films have been studied by Scanning Electron Microscopy (SEM) and Auger Electron Spectroscopy (AES) depth profiling. These films were fabricated on SrTiO3 substrates by RF diode sputter deposition and subsequent furnace annealing in oxygen. The chemical composition at and near the surface of thin films was found to differ from the bulk composition. At about 500 Å below the surface the Y, Ba, and Cu stoichiometry, as determined by AES, gradually approach that of the film interior. These results suggest that, for furnace annealed films, there may exist a minimum deposited Y–Ba–Cu–O film thickness in which superconductivity is possible. It was also found that the calculated copper concentration determined by AES during depth profiling is significantly lower than its actual value.

scholarly journals Potential of Biochar Derived from Agricultural Residues for Sustainable Management

2021 ◽  
Vol 13 (15) ◽  
pp. 8147
Author(s):  
Sasiwimol Khawkomol ◽  
Rattikan Neamchan ◽  
Thunchanok Thongsamer ◽  
Soydoa Vinitnantharat ◽  
Boonma Panpradit ◽  
...  
Keyword(s):  
Chemical Properties ◽  
Agricultural Residues ◽  
Hydroxyl Groups ◽  
Asian Countries ◽  
Heating Value ◽  
Coconut Husk ◽  
High Heating Value ◽  
Horizontal Drum ◽  
Physical And Chemical ◽  
And Chemical Properties

A horizontal drum kiln is a traditional method widely used in Southeast Asian countries for producing biochar. An understanding of temperature conditions in the kiln and its influence on biochar properties is crucial for identifying suitable biochar applications. In this study, four agricultural residues (corncob, coconut husk, coconut shell, and rice straw) were used for drum kiln biochar production. The agricultural residues were turned into biochar within 100–200 min, depending on their structures. The suitability of biochar for briquette fuels was analyzed using proximate, ultimate, and elemental analysis. The biochar’s physical and chemical properties were characterized via bulk density, iodine number, pHpzc, SEM, and FTIR measurements. All biochars had low O/C and H/C ratios and negative charge from both carbonyl and hydroxyl groups. Coconut husk and shell biochar had desirable properties such as high heating value and a high amount of surface functional groups which can interact with nutrients in soil. These biochars are thus suitable for use for a variety of purposes including as biofuels, adsorbents, and as soil amendments.

scholarly journals Reactive plasma cleaning and restoration of transition metal dichalcogenide monolayers

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Daniil Marinov ◽  
Jean-François de Marneffe ◽  
Quentin Smets ◽  
Goutham Arutchelvan ◽  
Kristof M. Bal ◽  
...  
Keyword(s):  
High Temperature ◽  
Transition Metal ◽  
Field Effect Transistors ◽  
Removal Rate ◽  
2D Materials ◽  
Scale Up ◽  
Transition Metal Dichalcogenides ◽  
Chemical Properties ◽  
Plasma Cleaning ◽  
Transition Metal Dichalcogenide

AbstractThe cleaning of two-dimensional (2D) materials is an essential step in the fabrication of future devices, leveraging their unique physical, optical, and chemical properties. Part of these emerging 2D materials are transition metal dichalcogenides (TMDs). So far there is limited understanding of the cleaning of “monolayer” TMD materials. In this study, we report on the use of downstream H2 plasma to clean the surface of monolayer WS2 grown by MOCVD. We demonstrate that high-temperature processing is essential, allowing to maximize the removal rate of polymers and to mitigate damage caused to the WS2 in the form of sulfur vacancies. We show that low temperature in situ carbonyl sulfide (OCS) soak is an efficient way to resulfurize the material, besides high-temperature H2S annealing. The cleaning processes and mechanisms elucidated in this work are tested on back-gated field-effect transistors, confirming that transport properties of WS2 devices can be maintained by the combination of H2 plasma cleaning and OCS restoration. The low-damage plasma cleaning based on H2 and OCS is very reproducible, fast (completed in a few minutes) and uses a 300 mm industrial plasma etch system qualified for standard semiconductor pilot production. This process is, therefore, expected to enable the industrial scale-up of 2D-based devices, co-integrated with silicon technology.

A New Method of Producing Carbon Anode by High-Temperature Mould Pressing

2011 ◽  
Vol 415-417 ◽  
pp. 611-616
Author(s):  
Yao Wu Wang ◽  
Nai Xiang Feng ◽  
Jing You
Keyword(s):  
High Temperature ◽  
Bulk Density ◽  
Electrical Resistance ◽  
Chemical Properties ◽  
New Method ◽  
Carbon Anode ◽  
Crushing Strength ◽  
Industrial Carbon ◽  
Physico Chemical ◽  
Carbon Anodes

Laboratory-scale carbon anodes were produced by a new method of high-temperature mould pressing, and their physico-chemical properties were studied in laboratory. The results showed that the bulk density of carbon anodes produced by high-temperature mould pressing are 1.61-1.63g/cm3, they are higher than industrial carbon anode by 0.06 g/cm3, but the specific electrical resistance is higher and crushing strength is lower.

Influence of Regeneration Condition on Physical and Chemical Properties of High Temperature Coal Gas Desulfurization Sorbent

2014 ◽  
Vol 521 ◽  
pp. 658-661
Author(s):  
Lei Yang ◽  
Shang Guan Ju ◽  
Yu Kun Gao ◽  
Yan Hui Hu
Keyword(s):  
High Temperature ◽  
Circulatory System ◽  
Chemical Properties ◽  
Space Velocity ◽  
Physical And Chemical Properties ◽  
Coal Gas ◽  
Regeneration Condition ◽  
Atmosphere Temperature ◽  
Physical And Chemical ◽  
And Chemical Properties

Physical and chemical properties are closely related to desulfurization, regeneration performance and cycle stability for high temperature coal gas desulfurizer. This review focuses on influence rules of changes in regeneration atmosphere, temperature and space velocity on physical and chemical properties. A large number of experimental researches have shown that regeneration atmosphere, regeneration temperature, space velocity have an important influence on mechanical strength, active component and texture change for high temperature coal gas desulfurizer. The different regeneration atmosphere obviously results in different active ingredients for desulfurization sorbent after regeneration, and regeneration at a higher regeneration temperature will easily cause desulfurizer sintering, as well as small regeneration space velocity can lead to the formation of sulfates. In order to make the circulatory system of sulfidation-regeneration-sulfidation need to the requirements in industrial application, the further research of influence rules of regeneration condition on physical and chemical properties will be crucial.

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