Friction welding of carbon quality steel

The aim of the work is to study the possibility of using, instead of manual arc welding with a covered electrode, a method of friction welding of fittings and small-diameter branch pipes of hull power plants. The solution to this problem is possible on the basis of the application of the friction welding process of small diameter nipples and nipples. Given the insufficient theoretical and experimental study of the problem, it was necessary to solve the following scientific and technical problems: to develop the design of the models and the connected (conical) surfaces of the choke and branch pipe assemblies; substantiate the choice of optimal angles for preparing surfaces for welding; justify the choice and experimentally confirm the values of the welding mode parameters; to assess the quality of welded joints by non-destructive and destructive methods. The obtained positive results of the experimental study confirmed the technological feasibility and economic feasibility of using friction welding of carbon steel fittings and small-diameter nozzles.

Methane Production Rate during Anoxic Litter Decomposition Depends on Si Mass Fractions, Nutrient Stoichiometry and Carbon Quality

While Si influences nutrient stoichiometry and decomposition of graminoid litter, it is still unclear how Si influences anoxic litter decomposition and CH4 formation in graminoid dominated fen peatlands. First, Eriophorum vaginatum plants were grown under different Si and P availabilities, then shoots and roots were characterized regarding their proportions of C, Si, N and P and regarding C quality. Subsequently the Eriophorum shoots were subjected to anoxic decomposition. We hypothesized; that (I) litter grown under high Si availability would show a higher Si but lower nutrient mass fractions and a lower share of recalcitrant carbon moieties; (II) high-Si litter would show higher CH4 and CO2 production rates during anoxic decomposition; (III) methanogenesis would occur earlier in less recalcitrant high-Si litter, compared to low-Si litter. We found a higher Si mass fraction that coincides with a general decrease in C and N mass fractions and decreased share of recalcitrant organic moieties. For high-Si litter, the CH4 production rate was higher, but there was no long-term influence on the CO2 production rate. More labile high-Si litter and a differential response in nutrient stoichiometry led to faster onset of methanogenesis. This may have important implications for our understanding of anaerobic carbon turnover in graminoid-rich fens.

COMPARATIVE STUDY ON THE SYNTHESES OF CARBON NANOMATERIALS USING POLYETHYLENE AND RISK HUSK AS CARBON PRECURSOR

The study compares the syntheses of carbon nanostructures (CNS) using polyethylene (PE) and Rice husk (RH) as carbon precursor via commercial microwave oven at 2.45 GHz. The Microwave energy offers the requisite temperature for catalytic disintegration of the carbon precursors at 750 °C under atmospheric pressure. The CNS were grown on coated silicon dioxide. The as-synthesized CNS was analysed with Raman spectroscopy which shows carbon quality was found to be 0.92 and 1.01 in PE and RH respectively, indicating good graphitic nature with average diameter at (16.0 to 20.0) ± 0.5 nm. The high intensity ratio is attributed to the defect mode in the CNS. The Field Emission Scanning Microscope (FESEM) analysis shows a warped and randomly oriented structures with an interlayer spacing of about 0.35 nm in the internal structure of most CNS. Furthermore, the level of purity in the graphitic nature of the CNS were obtained with Thermogravimetric Analysis (TGA) technique with 90 % in PE and 50 % in RH. Hence, a fast and cheaper method of synthesizing CNS utilizing microwave energy was demonstrated at 750 °C under atmospheric pressure. Lastly, the presence of catalyst, carbon precursors and plasma are necessary for the microwave heating and synthesis process.

Landscape Influence on the Browning of a Lake Watershed in the Adirondack Region of New York, USA

Watershed recovery from long-term acidification in the northeastern U.S. has been characterized by an increase in the influx of dissolved organic matter (DOM) into surface waters. Increases in carbon quantity and shifts to more aromatic and “colored” OM has impacted downstream lakes by altering thermal stratification, nutrient cycling and food web dynamics. Here, we used fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) to model predominant carbon quality fractions and their seasonal changes within surface waters along landscape positions of Arbutus Lake watershed in the Adirondack region of NY, USA. All DOM components were terrestrial in origin, however their relative fractions varied throughout the watershed. DOM in headwater streams contained high fractions of recalcitrant (~43%) and microbial reprocessed humic-like OM (~33%), sourced from upland forest soils. Wetlands above the lake inlet contributed higher fractions of high molecular weight, plant-like organic matter (~30%), increasing dissolved organic carbon (DOC) concentrations observed at the lake inlet (492.5 mg L−1). At the lake outlet, these terrestrial fractions decreased significantly during summer months leading to a subsequent increase in reprocessed OM likely through increased microbial metabolism and photolysis. Comparisons of specific ultraviolet absorbance between this study and previous studies at Arbutus Lake show that OM draining upland streams (3.1 L·mg C−1 m−1) and wetland (4.1 L·mg C−1 m−1) is now more aromatic and thus more highly colored than conditions a decade ago. These findings provide insight into the emerging role that watersheds recovering from acidification play on downstream water quality.

Pemanfaatan Gulma Siam (Chromolaena odarata L.) Sebagai Adsorben Logam Timbal

This study aims to utilize (Chromolaena odorata L) as a metal adsorbent. The methods used to make activated charcoal are dehydration, carbonization, and activation. The activated carbon is then characterized to obtain activated charcoal that can be applied, then optimized. The results of activated carbon characterization obtained have reached the activated carbon quality requirements based on the Indonesian Industry Standard (SII No. 0258-88). Based on the adsorption test, the optimum pH of Pb2+ (Pb (NO3) 2 (in distilled water) Chromolaena odorata L charcoal activated by NaOH 0.2 M under varying pH (2,3,4,5,6) is at pH 5 with 69.00% absorption. The optimum contact time required for Pb ion adsorption is 4 hours at variation (1-5 hours) with 70.19% absorption. The optimum concentration at variation (concentration 20; 40; 60; 80; 100 ppm) on Pb ion adsorption is 100 ppm with 76.15% absorption. The optimum heating time is a variation of 1.5; 2; 2.5; and 3 hours of Pb ion adsorption is one hour 30 minutes with an absorption of 65.95%. Based on the optimization results, the activated carbon from the Chromolaena odorata L can be used as an adsorption material against the contamination of lead heavy metals (Pb).