Research of process factors increasing metal yield during aluminum waste remelting

The article presents the results of research determining the most effective technologies for increasing metal yield in the processing of aluminum-containing waste. In particular, peculiarities of the processes of melting aluminum alloys were analyzed using complex methods of furnace and off-furnace processing of charge material containing an increased amount of shovelling scrap and swarf. Studies on the impact of charge preparation and aluminum remelting technology were carried out in SAT-0,16 and IAT-0,4 furnaces on the АК12М2 alloy. Experiments proved that batchwise loading 20 kg of swarf briquette preheated to 300–400 °C into the SAT-0,16 furnace with the addition of flux (composition: NaCl – 50 %; KCl –35 %, Na3AlF6 – 15 %) in the amount of 3 % of total metal mass is the most efficient technology. This technology makes it possible to achieve a metal yield of about 94 %. The study of the remelting technology influence on IAT-0,4 furnace metal yield showed that the greatest effect can be obtained in case of furnace charge (95 kg swarf briquette) by batches of 2 kg into the 7 kg liquid bath with modifier flux (composition: NaCl – 62 %; KCl – 13 %, NaF – 25 %) added in the amount of 2 % from the total metal mass. This technology provides up to 93.5 % of metal yield. Data from 10 series of 5–9 melts were also analyzed with the comparison of metal yield results depending on the mass of briquetted swarf charged into the furnace. A histogram of the change in the porosity of AK12M2 and AK9 samples depending on the content of swarf in the charge (from 0 to 45 %) during remelting. It was found that an increase in the content of swarf in the charge, all other things being equal, leads to an increase in the average porosity score, which indicates the need for additional refining of such melts.

Optimization of a 3D Bioprinting Process Using Ultrashort Peptide Bioinks

The field of three-dimensional (3D) bioprinting is rapidly emerging as an additive manufacturing method for tissue and organ fabrication. The demand for tissues and organ transplants is ever increasing, although donors are not as readily available. Consequently, tissue engineering is gaining much attention to alleviate this problem. The process of achieving well-structured 3D bioprinted constructs using hydrogel bioinks depends on symmetrical precision, regulated flow rates, and viability of cells. Even with the mentioned parameters optimized, the printed structures need additional refining by removing excessive liquids, as peptide hydrogel bioprints encapsulate water. However, it is challenging to eliminate the confined fluids without compromising the printing process. In this paper, we introduced a vacuum system to our 3D bioprinting robotic arm and thus optimized the printing quality for complex and refined 3D scaffolds. Moreover, the proposed vacuum system supports printing with cells. Our results show improved printing resolution which facilitates the printing of higher and more stable structures.

Acute, Subchronic, and Developmental Toxicological Properties of Lubricating Oil Base Stocks

Lubricating oil base stocks (LOBs) are substances used in the manufacture of finished lubricants and greases. They are produced from residue remaining after atmospheric distillation of crude oil that is subsequently fractionated by vacuum distillation and additional refining steps. Initial LOB streams that have been produced by vacuum distillation but not further refined may contain polycyclic aromatic compounds (PACs) and may present carcinogenic hazards. In modern refineries, LOBs are further refined by multistep processes including solvent extraction and/or hydrogen treatment to reduce the levels of PACs and other undesirable constituents. Thus, mildly (insufficiently) refined LOBs are potentially more hazardous than more severely (sufficiently) refined LOBs. This article discusses the evaluation of LOBs using statistical models based on content of PACs; these models indicate that insufficiently refined LOBs (potentially carcinogenic LOBs) can also produce systemic and developmental effects with repeated dermal exposure. Experimental data were also obtained in ten 13-week dermal studies in rats, eight 4-week dermal studies in rabbits, and seven dermal developmental toxicity studies with sufficiently refined LOBs (noncarcinogenic and commonly marketed) in which no observed adverse effect levels for systemic toxicity and developmental toxicity were 1000 to 2000 mg/kg/d with dermal exposures, typically the highest dose tested. Results in both oral and inhalation developmental toxicity studies were similar. This absence of toxicologically relevant findings was consistent with lower PAC content of sufficiently refined LOBs. Based on data on reproductive organs with repeated dosing and parameters in developmental toxicity studies, sufficiently refined LOBs are likely to have little, if any, effect on reproductive parameters.