Теплота сгорания облагороженного древесного топлива

THE extent of degradation of natural organic mixtures largely determines their utility as records of depositional history, and their potential to act as nutritional substrates and fossil fuel sources. The degree of decomposition is usually inferred from the physical setting of the deposits1 or from bulk chemical composition2, but in both these cases the interpretation can be obscured by several factors3. We report here a study of aldoses and amino acids in samples collected from a variety of marine depositional environ-ments and representing widely different stages of alteration. We identify consistent trends in three compositional characteristics: the percentage of organic carbon in the form of aldoses and protein amino acids, the percentage of total nitrogen present as protein amino acids, and the percentage of total amino acids present as β-alanine and γ-aminobutyric acid. Each of these parameters is sensitive to a different stage of alteration, and they appear to be uncompromised by source variations. Applied together, they offer concordant information on the relative diagenetic stage and reaction potential of natural organic mixtures under both aerobic and anaerobic depositional conditions.

Fine-structure bands have been located in electronic absorption spectra of polyvinyl alcohol (PVA) films decomposed thermally in air at 80–150°C. Doping of the PVA film with aluminum chloride (thermolysis catalyst) was found both to enhance the degree of thermal decomposition and to reduce the starting temperature for formation of poly-π-conjugated chains although it had no effect on the spectral positions of the polyene-unit absorption bands. Values of the band gap of heat-treated PVA films were determined to be in the range 1.65–1.78 eV based on an analysis of the electronic spectra long-wavelength edge.

In order to attain the fruitful effects of wood properties by aging, we conducted the thermal treatment at a moderately high temperature (85°C), which does not cause drastic thermal degradation, under a cyclic humidity changes between 30 and 80% R.H. for 3 months. For wood and cellulose samples, the weight losses were significantly accelerated by the existence of moisture, however the weight loss of cellulose was 1 order lower than wood sample. Loss tangent of wood specimens decreased for a few percent by the heating for 3 months without humidity change, whereas it increased under cyclic humidity changes. By the heating accompanied with humidity change, the degradation may excessively occur even only 1 month and as low as 85°C. The decrease of holocellulose content and relative increase of Klason lignin content were observed, which were remarkable under the heating with humidity change. Because plural factors may participate to the changes of equilibrium moisture content and crystallinity, the changing behaviors were complicated. In conclusion, it was proved that the existence of moisture merely accelerated the thermal degradation and positive effect was not virtually founded.

Hydraulic properties of fen peat soils in Poland

Effects of charring on mass, organic carbon, and stable carbon isotope composition of wood

Odporność drewna buka zwyczajnego (Fagus syłvaticaL.), z drzew o zróżnicowanym stanie zdrowotnym, na rozkład powodowany przez grzyby

Decomposition and humification were studied within three types of forest humus (mull, moder, and mor) by means of CPMAS13C NMR spectroscopy combined with degradative methods. The NMR data show that O‐alkyl carbon decreases in all soils, and alkyl as well as carboxyl carbon increase as depth and decomposition increase; the percentage of aromatic carbon remains constant at about 25%. With increasing depth the amount of carbon that can be identified as belonging to specific compound classes by wet chemical methods decreases from 60% to 40%. Microbial polysaccharides and the proportion of non polysaccharide O‐alkyl carbon increase with depth. A selective preservation of recalcitrant, condensed lignin structural units is also observed.In order to relate the spectroscopic and chemical data from investigations of whole soils with studies of humification, samples were fractionated into fulvic acid, humic acid, and humin fractions. The fulvic acid fraction contains large concentrations of carbohydrates irrespective of the soil horizon. The humic acid fraction contains less polysaccharides, but high amounts of alkyl carbon and aromatic structures. The percentage of aromatic carbon existing in the humic acid fraction increases with depth, probably reflecting the amount and degree of oxidative decomposition of lignin. A loss of methoxyl and phenolic groups is evident in the13C NMR spectra of the humic acid fraction. The humin fraction resembles relatively unchanged plant‐derived materials as evident from the lignin parameters and carbohydrate contents. All the observed data seem to indicate that humic acids originate form oxidative degradation of humin or plant litter.

Study on the isothermal decomposition of CL-20/HMX co-crystal by microcalorimetry

Variations of apparent activation energy based on thermodynamics analysis of zeolitic imidazolate frameworks including pyrolysis and combustion

The forest plantations of eucalyptus of fast growing in Brazil and other regions of the world are under the effect of climate change, water stress and low soil fertility, affecting growth and wood quality. The study aimed to analyze the interaction of growth and quality of the wood of eucalyptus trees, subjected to reduced rainfall and nutrition of K and Na. The dynamics of the formation of the wood with monthly assessment of the cambial activity, an increase in trunk diameter and the physical, chemical and anatomical characteristics of the wood of trees of E. grandis on the 12th, 24th and 36th month of age were evaluated in experimental plots established in May/2010 in Experimental Station of Itatinga -SP. Treatments were defined by two water regimes (100% and 66% of rainfall, artificial reduction with polyethylene tarps) and three types of nutrition : K (K -4.5 kmol/ha ), N (Na -4.5 kmol/ha) and control. 54 trees of eucalyptus were selected to 18th month of age by evaluating the increase in trunk diameter every thirty days, from November/2011 by October/2013, using steel dendrometers. The cambial seasonality was assessed monthly by sampling of the wood and anatomical analyzes of the cambial layer performed in the first year of assessment. The climatic variables and soil moisture were correlated with the increase in trunk diameter and seasonality of cambial activity of trees. In the sample of the wood have been selected four trees per treatment in the 12th, 24th and 36th months of age for the determination of the density in the longitudinal direction of the trunk. Samples of wood from DAP were evaluated in relation to fibers and vessels, basic density and chemical composition. The results showed the effect of seasonality on cambial activity and increase in diameter of trees, beyond the influence of lag in growth. The treatment of applying K and 100% water availability (K/+A) induced larger increment value and the total height of the trunk of the trees. There was a significant difference in nutrition and water availability of the treatments in relation to the growth of trees, density of wood, fiber dimensions and vessels and chemical composition of wood. Digital images of the samples obtained by X-ray, allowed to analyze the variation of the apparent density of the wood. The colorimetric analysis allowed to detect the formation of heartwood in the wood of trees in the 36th month. The results may be used as subsidies for the adoption of silvicultural practices in forest plantations in areas with water and/or affected by climate change stress as well as the partial replacement of K by Na.

Summary 1 Large pools of dead wood in mangrove forests following disturbances such as hurricanes may influence nutrient fluxes. We hypothesized that decomposition of wood of mangroves from Florida, USA ( Avicennia germinans , Laguncularia racemosa and Rhizophora mangle ), and the consequent nutrient dynamics, would depend on species, location in the forest relative to freshwater and marine influences and whether the wood was standing, lying on the sediment surface or buried. 2 Wood disks (8‐10 cm diameter, 1 cm thick) from each species were set to decompose at sites along the Shark River, either buried in the sediment, on the soil surface or in the air (above both the soil surface and high tide elevation). 3 A simple exponential model described the decay of wood in the air, and neither species nor site had any effect on the decay coefficient during the first 13 months of decomposition. 4 Over 28 months of decomposition, buried and surface disks decomposed following a two-component model, with labile and refractory components. Avicennia germinans had the largest labile component (18 ± 2% of dry weight), while Laguncularia racemosa had the lowest (10 ± 2%). Labile components decayed at rates of 0.37‐23.71% month − 1 , while refractory components decayed at rates of 0.001‐0.033% month − 1 . Disks decomposing on the soil surface had higher decay rates than buried disks, but both were higher than disks in the air. All species had similar decay rates of the labile and refractory components, but A. germinans exhibited faster overall decay because of a higher proportion of labile components. 5 Nitrogen content generally increased in buried and surface disks, but there was little change in N content of disks in the air over the 2-year study. Between 17% and 68% of total phosphorus in wood leached out during the first 2 months of decomposition, with buried disks having the greater losses, P remaining constant or increasing slightly thereafter. 6 Newly deposited wood from living trees was a short-term source of N for the ecosystem but, by the end of 2 years, had become a net sink. Wood, however, remained a source of P for the ecosystem. 7 As in other forested ecosystems, coarse woody debris can have a significant impact on carbon and nutrient dynamics in mangrove forests. The prevalence of disturbances, such as hurricanes, that can deposit large amounts of wood on the forest floor accentuates the importance of downed wood in these forests.

Degradation of MDI-based polyether and polyester-polyurethanes in various environments - Effects on molecular mass and crosslinking

Laser sintering of polyamide 12 with limited thermal degradation

NN′-Bis(dimethylsilyl)tetramethylcyclodisilazane (NSCDSN) was selected for plasma polymerization as a model monomer representing N-silyl-substituted cyclodisilazanes. Owing to the aromatic character resulting from the strong (d-p)π coupling between silicon and nitrogen atoms, these compounds manifest the highest thermal stability among the organosilicones. GC/MS examination of a low-molecular-weight fraction evaporated from the plasma polymer revealed the presence of various monomer derivatives having mostly the general structure of N-silyl-substituted cyclodisilazane (Si4N2) units. GC/MS and ATR/IR studies have shown that the Si4N2 skeleton displays a high resistance to plasma fragmentation and that it was incorporated as such into the polymer film. A radical mechanism for plasma polymerization was postulated assuming the formation of and propagation precursors. The low value found for the polar component of the surface free energy confirmed the contribution of Si4N2 units to the polymer film. TGA investigation showed the rate and degree of thermal decomposition of plasma-polymerized (PP) NSCDSN to be lower than those of plasma polymers from N-hydrogen-substituted silazanes. Vacuum pyrolysis, at 800°C, converted the polymer film into a glassy, dense, and almost inorganic material with a strong adhesion to the metal substrates.

1. The chemical conversions which accompany the rectification of raw synthetic fatty acids and result in a loss of the fractions suited for soap manufacture are the most intensive in the boilers of the fourth and fifth columns. 2. During rectification of synthetic fatty acids under a rigorous regime, the weight-average of the acid number drops by 10–15% and the content of unsaponifiable substances is doubled or more than doubled, as is the content of resins. The changes of the carbonyl and the acid numbers pass through a maximum. 3. Synthetic fatty acids of high-molecular weight are sufficiently stable during heating to 320°C in 3–8 min and during rapid overheating of the feeds to the fourth and fifth columns (310–320°C); rapid overheating decreases the degree of thermal decomposition during rectification by almost 50% and increases the yield of acids suited for soap manufacture by 6.1%.