Non-Invasive Assessment of PVA-Borax Hydrogel Effectiveness in Removing Metal Corrosion Products on Stones by Portable NMR

The cleaning of buildings, statues, and artworks composed of stone materials from metal corrosion is an important topic in the cultural heritage field. In this work the cleaning effectiveness of a PVA-PEO-borax hydrogel in removing metal corrosion products from different porosity stones has been assessed by using a multidisciplinary and non-destructive approach based on relaxation times measurement by single-sided portable Nuclear Magnetic Resonance (NMR), Scanning Electron Microscopy—Energy Dispersive Spectroscopy (SEM-EDS), and Raman Spectroscopy. To this end, samples of two lithotypes, Travertine and Carrara marble, have been soiled by triggering acidic corrosion of some copper coins in contact with the stone surface. Then, a PVA-PEO-borax hydrogel was used to clean the stone surface. NMR data were collected in untreated, soiled with corrosion products, and hydrogel-cleaned samples. Raman spectroscopy was performed on PVA-PEO-borax hydrogel before and after cleaning of metal corrosion. Furthermore, the characterization of the dirty gel was obtained by SEM-EDS. The combination of NMR, SEM-EDS and Raman results suggests that the mechanism behind the hydrogel cleaning action is to trap heavy metal corrosion products, such as Cu2+ between adjacent boron ions cross-linked with PVA. Moreover, the PVA-PEO-borax hydrogel cleaning effectiveness depends on the stone porosity, being better in Carrara marble compared to Travertine.

Charge and elemental composition of plasma generated by sputtering of powder target from amorphous boron

One of the effective and widespread methods of surface hardening of metal products is an ion-plasma saturation of the surface of machine parts and mechanisms with various elements (nitrogen, oxygen, carbon). Less investigated method is the process of ion-plasma saturation of the metals and alloys surface with boron. The purpose of the present work is to develop a method for the formation and study of parameters (electron temperature, plasma potential and concentration), elemental and charge composition of plasma generated at sputtering of a target from amorphous boron powder. To achieve the stated goal, a discharge system with a hot anode made of powder boron, as well as a pulse arc evaporator with a hot cathode made of sintered boron powder, was developed, designed, created and tested. Charge and elemental composition of boron-containing plasma generated during powder target sputtering from amorphous boron are defined by optical spectrometry method. It is shown that the generated plasma contains mainly neutral atoms and single-charge boron ions, as well as iron, silicon, copper and argon particles.

The Cerium/Boron Insertion Impact in Anatase Nano-structures on the Photo-Electrochemical and Photocatalytic Response

Boron- and cerium-doped titania (Anatase) were prepared via sol-gel method. Phase composition and morphology were assessed by X-ray diffraction (XRD), scanning electronic microscopy (SEM), BET, diffuse reflectance spectra (DRS), and XPS. Photo-electrochemistry of these materials, deposited onto fluorine-doped SnO2 (FTO), was investigated in acid and acid-containing methanol. The boron-doped sample showed the best opto-electronic properties among the investigated samples. On the other hand, the cerium-doped titania samples annihilate to a certain extent the titania surface states, however, photogenerated charge separation was limited, and certainly associated to surface Ce3+/Ce4+ species. The substitutional effect of boron ions for O sites and interstitial sites was confirmed by XRD and XPS analyses.

Structure and properties of the surface layer of zirconium-niobium alloy subjected to high-dose implantation with 10B+ boron isotope ions

The creation of layers implanted with boron isotope 10B on the elements of the core of a nuclear reactor can, due to the anomalously large neutron capture cross-section, provide a decrease in the reactivity of the reactor at the beginning of the company for its operation. The aim of this work is to study the effect of high-dose implantation with 10B + boron isotope ions (ion energy 22 keV, exposure doses from 1×1016 to 7×1016 ion/cm2) on the structure and properties of the surface of E110 alloy samples. It was found that implantation with 10B+ boron ions with an energy of 22 keV at a dose of 7×1016 ions/cm2 leads to an increase in the surface microhardness from 3 GPa for the initial one to 3.7 GPa for the implanted sample. It was found that the corrosion rate of E110 alloy samples in 1% HF solution after implantation (ion energy 10B + 22 keV, dose 7×1016 ion/cm2) is 1.2-1.4 times lower than for the initial alloy. It is shown that the implantation of the E110 alloy with 10B + boron ions is accompanied by the formation of a subgrain structure with dimensions 100-200 nm in the surface layer, an increase in the scalar dislocation density, and the release of nanosized 1.8-2.3 nm zirconium boride particles.

Vinylene-Bridged Cyclic Dipyrrin and BODIPY Trimers

Vinylene-bridged cyclic boron–difluoride complex of dipyrrin (BODIPY) trimers were successfully prepared from expanded dimethyl-vinylene bridged hexaphyrin(2.1.2.1.2.1) Me-Hex that has the structure of alternate dipyrrins and vinylene bridges. The hexaphyrin(2.1.2.1.2.1) Me-Hex can coordinate with boron ions to afford five kinds of cyclic BODIPYs given by step-by-step boron complexations. Crystal structures of all cyclic BODIPYs except for 3BF2-Me-Hex(b) formed non-planar structures. The theoretical calculation predicted that mono-/bis-boron cyclic BODIPYs show the intramolecular charge transfer (ICT) characteristics, whereas tri-boron cyclic BODIPYs have no ICT characteristics. Reflecting these electronic properties, tri-boron cyclic BODIPYs exhibit weak fluorescence in the red region, but mono-/bis-boron cyclic BODIPYs exhibit no emission. Vinylene bridged cyclic dipyrrin trimer Me-Hex is the novel porphyrinoid ligand allowed to control the boron coordination under different reaction conditions to form various boron complexes.

Toroidal plasma conditions where the p-11B fusion Lawson criterion could be eased

We examine the theoretical conditions in which the Lawson ignition criterion for p-11B fusion in a magnetized toroidal plasma can be reduced substantially. It is determined that a velocity differential between the protons and the boron ions of the order of the plasma sound speed (Mach number of 1 or 2 at a plasma temperature of ~102 keV) could raise the p-11B fusion reaction rate to ~2x10-22 m3/s or ~6x10-22 m^3/s, respectively, from the ~1x10-22 m3/s level in a static plasma. The Lawson triple product (ni τE Ti) required for ignition can thereby be reduced to as low as ~1023 m-3 s keV, which is one order of magnitude above the ITER requirement for D-T burn. Since order-unity Mach numbers in velocity differentials between deuterons and impurity carbon ions have been maintained in tokamak plasmas under excellent confinement conditions, similar levels of velocity differentials between protons and minority boron-11 ions could in principle be maintained also. A theoretical possibility of achieving p-11B fusion ignition in a toroidal plasma of ~102 keV in ion temperature is hereby presented. Similar p-13C plasmas, for example, will introduce a possibility of measuring the CNO fusion chain reaction rates in a laboratory.