Circumventing spatter: Laser powder bed fusion is an additive manufacturing technique that laser-melts powder layer by layer to build a three-dimensional (3D) part. Khairallah et al. used experiments and a multiphysics model to determine the origin of the melt spatter and defect formation that degrade the properties of built parts (see the Perspective by Polonsky and Pollock). Informed modulation of laser power is important to avoid disturbing the powder bed and creating laser shadowing. This reduces pore formations and leads to more uniform properties of 3D-printed parts. Science , this issue p. 660 ; see also p. 583

A new class of castable cerium strengthened aluminum alloys has phenomenal high temperature properties without the need for heat treatment.

We found monochromatic electron photoemission from large-area self-assembled monolayers of a functionalized diamondoid, [121]tetramantane-6-thiol. Photoelectron spectra of the diamondoid monolayers exhibited a peak at the low–kinetic energy threshold; up to 68% of all emitted electrons were emitted within this single energy peak. The intensity of the emission peak is indicative of diamondoids being negative electron affinity materials. With an energy distribution width of less than 0.5 electron volts, this source of monochromatic electrons may find application in technologies such as electron microscopy, electron beam lithography, and field-emission flat-panel displays.

The electronic structure of ${\mathrm{TiO}}_2$ aerogels is studied by soft x-ray absorption near-edge structure (XANES) spectroscopy. High-resolution O K-edge and Ti $L_{2,3}$-edge XANES spectra of aerogels are compared with those of rutile, anatase, and unrelaxed amorphous phases of full-density ${\mathrm{TiO}}_2.$ Results show that all the main spectroscopic features of aerogels, reflecting the element-specific partial density of empty electronic states and correlation effects, can be attributed to the absence of long-range order in stoichiometric amorphous ${\mathrm{TiO}}_2.$ Based on these results, we discuss the effects of short- and long-range order on the electronic structure of ${\mathrm{TiO}}_2.$