Binder Jetting of Silicon Steel, Part I: Process Map of Green Density

This study focuses on developing and demonstrating a straightforward workflow for identifying pathways to increase green part density in binder jetting additive manufacturing using statistically-driven process maps. The workflow was applied to investigate the effects of process parameters toward improving green part density, with a direct application in manufacturing of Fe-Si components. Specifically, a half-factorial experimental design was used to study the effects of four key parameters - layer thickness, powder spreading speed, roller rotational speed, and binder saturation - on Fe-Si spherical powder with D50 of 32.40 µm. The study discusses bulk density as well as localized density variation in the printed parts, which is attributed to both parameter selection and inherent process variability. A regression analysis was employed to reveal the significance of main effects and second order interactions. The regression model (R2 = 0.915) was used to derive an expression for green density as a function of the parameters, and had a prediction error of 0.96%. Based on the regression model, an optimized set of parameters was obtained that would maximize green density up to 57.96% for the machine and material system.

Detailed study of 137Cs distribution in soil-litter-moss cover within the undisturbed woodland test site in the Chernobyl abandoned zone, Russia

<p>Cs-137 distribution was studied in the regular grid and in landscape cross-sections characterizing the ELGS system (top-slope-closing depression) in the “Vyshkov-2” test site located in the Chernobyl abandoned zone, the Bryansk region, Russia. The test site (70×100 m) located on the Iput’ river terrace in a pine forest formed on sod-podzolic soils is characterized by a pronounced elevation gradient (ca 4.5 m). In 1986 the level of <sup>137</sup>Cs contamination of the area varied from 1480 kBq/m<sup>2</sup> to 1850 kBq/m<sup>2</sup>. The distribution of <sup>137</sup>Cs was studied in the topsoil, soil, moss and litter cover in a grid manner with a step of 10 m and along cross-sections with 1 m step. To assess the influence of water regime on radiocaesium migration moisture content was also determined in the studied objects. The data showed that the major part of <sup>137</sup>Cs is now fixed in the soil layer 2-10 cm thick while the highest activity of radiocaesium is found at a depth of 2-8 cm that can be explained mainly by the burial of the initially contaminated layer under the annual leaf fall. In the ELGS system the content of <sup>137</sup>Cs in the top soil layer (0-2 cm) determined in laboratory conditions by Canberra gamma-spectrometer with HPGe detector correlated with the surface Cs-137 activity measured by field gamma-spectrometer Violinist III (r=0.643, n=15). Cs-137 activity in the green part of moss samples correlated with the radionuclide activity in soil layer samples 4-6 cm deep (r=0.627, n=15). In the moss samples the highest correlation was observed between the green and rhizoid moss parts (r<sub>0.01</sub>=0.718, n=60, along cross-sections), (r<sub>0.05</sub>=0.858, n=20, in regular grid). Correlation between radiocesium activity of the green part of mosses and the underlain litter samples was lower, but also significant (r<sub>0.01</sub>=0.617, n=60, along cross-sections), (r<sub>0.05</sub>=0.481, n=20, in regular grid). Cs-137 activity in the rhizoid part of moss and in litter were also positively linked, but to a lower degree (r<sub>0.01</sub>=0.402, n=60). Studies performed in 2015-2019 confirmed our earlier finding that radiocaesium had not moved in unidirectional manner down the slope to the closing depression, but formed a more complex polycentric structure in ELGS.</p><p>The study was financially supported by the Russian Foundation for Basic Research (grant # 19-05-00816).</p>

A mutant of the phototoxic protein KillerRed that does not form DsRed-like chromophore

Genetically encodable photosensitizers based on fluorescent proteins produce reactive oxygen species when illuminated with light. Although widely used as optogenetic tools, existing photosensitizers with green fluorescence possess suboptimal properties motivating for a search of new protein variants with efficient chromophore maturation and high phototoxicity. Here we report a mutant of the phototoxic fluorescent protein KillerRed protein with fluorescence in the green part of the spectrum. The mutant variant carries mutations I64L, D114G, and T115S and does not form a DsRed-like chromophore. The protein can be used as a template to create new genetically encodable photosensitizers that are spectrally different from KillerRed.

A mutant of the phototoxic protein KillerRed that does not form DsRed-like chromophore

We report a mutant of the phototoxic fluorescent protein KillerRed protein with fluorescence in the green part of the spectrum. The mutant variant carries mutations I64L, D114G, and T115S and does not form a DsRed-like chromophore. The protein can be used as a template to create new genetically encodable photosensitizers that are spectrally different from KillerRed.

Effect of powder characteristics on parts fabricated via binder jetting process

PurposeThis study aims to experimentally investigate the effect of the powder material characteristics on the qualities of the binder jetting additive manufacturing parts both before and after post processing (sintering).Design methodology/approachThree different types of the 316L stainless steel powder feedstock with various mean particle sizes and size distributions were studied. The influence of the powder particle size distributions and pore sizes on the powder bed packing densities and on the dynamics of the binder droplet-powder bed interactions were characterized. In addition, the surface roughness and densities of these parts both in the green state and after sintering were studied.FindingsThe results revealed the significant role of the powder feedstock characteristics on the liquid binder/powder bed interaction and consequently on the dimensional accuracies of the green parts. It was observed that the parts printed with the smaller mean particle sizes resulted in better surface finish and higher final densities after sintering. Furthermore, the hardness of the sintered parts produced with smaller powder particles exhibited higher values compared to the parts fabricated with the larger particles. On the other hand, larger particle sizes are advantageous for various green part qualities including the dimensional accuracies, green part densities and surface roughness.Originality/valueThis study establishes more comprehensive correlations between the powder feedstock characteristics and various quality criteria of the printed binder jetting components in both green and sintered states. These correlation are of critical importance in choosing the optimal process parameters for a given material system.

Synthesis, structure and anion binding properties of 1,8-bis(dimesitylboryl)anthracene and its monoborylated analog

1,8-Bis(dimesitylboryl)anthracene binds the toxic fluoride and cyanide anion to afford the corresponding 1 : 1 complexes that display a red shifted emission in the green part of the spectrum.