Joining Titanium by Means of Ceramic Adhesives

Ceramic adhesives are an interesting alternative to traditional methods to join metal to ceramics such as fastening, vacuum brazing and gluing. Ceramic adhesives are made of an inorganic matrix with a filler (alumina, zirconia, silica, etc.), and they require a thermal cure cycle in order to establish adhesion. In this work, the adhesion between two different adhesive and Ti6Al4V is studied in details and the influence of the curing cycle is analyzed. Two different adhesives have been used, the first made of a phosphate matrix with an alumina filler, the second made of a silicate matrix wit an alumina filler. The results indicates that in the case of the first adhesive a high temperature cure it is necessary in order to establish a strong adhesion with the metal; on the contrary the second adhesive is capable to create a strong bonding already at low temperature.

Menshikovite Pd3Ni2As3 and associated minerals of sulphide ores within the Eastern flank of the Oktyabrsky deposit (Norilsk ore field)

Significant amount of menshikovite (rare palladium and nickel arsenide) Pd3Ni2As3 was found on the Eastern flank of the Oktyabrsky deposit (Norilsk ore field), near the contact of solid and impregnation sulfide Co-Ni-Cu ores among magnetite-plagioclase-fassaite skarns. Sulfide material of both ores consists of chalcopyrite, pentlandite, pyrrhotite and cubanite aggregates, which are the products of subsolidus transformations of high-temperature solid solutions Iss3, Iss4 and subordinate Mss; with interpositions of later Se-galenite. Menshikovite in association with mertieite-II, silver-gold (fineness 756–706), golden-electrum (fineness 694–672), kotulskite, moncheite, rare altaite, hessite, naldrettite and melonite forms small (up to 30 microns) metasomatic growths on the contact of silicate matrix and magmatogenic sulfide aggregates. The average composition of menshikovite is close to theoretical data: (Pd2,98Ru0,03)3,01(Ni1,89Fe0,-08Co0,01)1,98 (As2,94Se0,04Bi0,02Sn0,01)3,01. Sperrylite metacrystals cut the borders of menshikovite accretions as well as other minerals of precious metals and contain “corroded” inclusions. This association of minerals of noble metals has arisen under the increased activity of As, Te, Sb, Bi and low activity of Sn in fluids. Menshikovite is typical for Pd-rich ores of the Oktyabrsky Deposit, while mayakite PdNiAs (another palladium and nickel arsenide) is relatively widely developed in ores of the Talnakh Deposit (Mayak mine and partly Komsomolsky mine) and the Norilsk-I. Perhaps, such a distribution of palladium-nickel arsenides is an element of mineral zonality of the Norilsk ore field.

Deconvolution of the composition of fine-grained pyrite in sedimentary matrix by regression of time-resolved LA-ICP-MS data

Pyrite is a common mineral in sedimentary rocks and is the major host for many chalcophile trace elements utilized as important tracers of the evolution of the ancient hydrosphere. Measurement of trace element composition of pyrite in sedimentary rocks is challenging due to fine-grain size and intergrowth with silicate matrix and other sulfide minerals. In this contribution, we describe a method for calculation of trace element composition of sedimentary pyrite from time-resolved LA-ICP-MS data. The method involves an analysis of both pyrite and pyrite-free sediment matrix, segmentation of LA-ICP-MS spectra, normalization to total, regression analysis of dependencies between the elements, and calculation of normalized composition of the mineral. Sulfur is chosen as an explanatory variable, relative to which all regressions are calculated. The S content value used for calculation of element concentrations from the regressions is calculated from the total, eliminating the need for independent constraints. The algorithm allows efficient measurement of concentrations of multiple chalcophile trace elements in pyrite in a wide range of samples, including quantification of detection limits and uncertainties while excluding operator bias. The data suggest that the main sources of uncertainties in pyrite composition are sample heterogeneity and counting statistics for elements of low abundance. The analysis of regression data of time-resolved LA-ICP-MS measurements could provide new insights into the geochemistry of the sedimentary rocks and minerals. It allows quantification of ratios of elements that do not have reference material available (such as Hg) and provides estimates on the content of non-sulfidic Fe in the silicate matrix. Regression analysis of the mixed LA-ICP-MS signal could be a powerful technique for deconvolution of phase compositions in complex multicomponent samples.

Strongly Luminescent Composites Based on Carbon Dots Embedded in a Nanoporous Silicate Glass

Luminescent composites based on entirely non-toxic, environmentally friendly compounds are in high demand for a variety of applications in photonics and optoelectronics. Carbon dots are a recently developed kind of luminescent nanomaterial that is eco-friendly, biocompatible, easy-to-obtain, and inexpensive, with a stable and widely tunable emission. Herein, we introduce luminescent composites based on carbon dots of different chemical compositions and with different functional groups at the surface which were embedded in a nanoporous silicate glass. The structure and optical properties of these composites were comprehensively examined using electron microscopy, Fourier transform infrared transmission, UV-Vis absorption, and steady-state and time-resolved photoluminescence. It is shown that the silicate matrix efficiently preserved, and even enhanced the emission of different kinds of carbon dots tested. The photoluminescence quantum yield of the fabricated nanocomposite materials reached 35–40%, which is comparable to or even exceeds the values for carbon dots in solution.

Microstructure evolution of plagioclase-hosted Fe-Ti-oxide microinclusions in oceanic gabbro

<p>Microinclusions of Fe-Ti-oxides in rock-forming plagioclase are protected from subsea-floor alterations by the silicate matrix and are stable carriers of the paleomagnetic record of oceanic gabbros. We studied plagioclase-hosted microinclusions in oceanic gabbro (“gabbro 1241” from the Vema Lithospheric section, Mid-Atlantic ridge, Pertsev et al., 2015) with a complex petrogenetic history. Important events in the gabbro evolution caused consecutive transformations of the micro-inclusions and presumably affected their paleomagnetic records.</p><p>The earliest generation of the microinclusions was present as ulvospinel and presumably titanomagnetite which were probably formed by sub-solidus oxidation exsolution of early-magmatic plagioclase (An#42-45). An increase of the anorthite component around the early generation of microinclusions to typical values of late-magmatic plagioclase (An#53) suggest involvement of the late-magmatic fluid accompanying residual melt at 800-900°С (Pertsev et al., 2015). Subsequently, the gabbro was locally affected by hydrothermal alteration at about 600°С as a result of interaction of the gabbro with reduced brine containing 20-21% NaCl. The reducing conditions of this process ensured a “non-oxidative” character and primarily cooling driven exsolution of the microinclusions and transformation of the titanomagnetite microinclusions into ulvospinel-magnetite (“Usp-Mt<sub>1</sub>”) intergrowths at about 500°С, which is close or higher than the Curie temperature (Tc) of the exsolving titanomagnetite but lower than the Tc of the newly forming Mt<sub>1,</sub> and the acquired magnetisation may be referred to chemical remanence. The further evolution of the micro-inclusions correlates with low-temperature hydrothermal alteration induced by inflow of seawater-derived fluids during tectonic unroofing of the lithospheric section (Pertsev et al., 2015). The homogeneous ulvospinel inclusions and ulvospinel of the “Usp-Mt<sub>1</sub>”-inclusions were replaced by “Ilm-Mt<sub>2</sub>” -aggregates under more oxidizing conditions: 3 Fe<sub>2</sub>TiO<sub>4</sub>(Ulv) + 0.5 O<sub>2</sub>= 3 FeTiO<sub>3</sub>(Ilm) + Fe<sub>3</sub>O<sub>4</sub>(Mt<sub>2</sub>). The Mt<sub>1</sub> was more stable to increase of fO<sub>2 </sub>that resulted in simultaneous presence of the “Ilm-Mt<sub>2</sub>”-, “Mt<sub>1</sub>/Ilm-Mt<sub>2</sub>“- and “Usp-Mt<sub>1</sub>” -inclusions with two generations of magnetic phases (magnetite) within a single plagioclase grains.</p><p>Thus, despite of protection by silicate matrix the microinclusions of Fe-Ti-oxides in rock-forming plagioclases evolve under the influence of petrogenetic processes. It is important to note that bulk-rock AF demagnetization of 14 specimens (extracted from “gabbro-1241“) in the interval 100-250 Oersted (Oe) and 300-700 Oe revealed both moderately-grouped (k=27.4) and variable (deviated with angle 40-104°) directional components of magnetisation, which may have resulted from the presence of different generations of magnetite. Further magnetic investigation of separates of plagioclase single grains will allow to evaluate capacities of plagioclase-hosted Fe-Ti-micro-inclusions to save initial and “newfound” paleomagnetic information and to serve as stable sources of paleomagnetic record in regions of mid-oceanic ridges.</p><p>Funding by RFBR project 18-55-14003 and FWF project I 3998-N29 is acknowledged.</p><p>Pertsev, A. N., Aranovich, L. Y., Prokofiev, V. Y., Bortnikov, N. S., Cipriani, A., Simakin, S. S., & Borisovskiy, S. E. (2015). Signatures of residual melts, magmatic and seawater-derived fluids in oceanic lower-crust gabbro from the Vema lithospheric section, Central Atlantic. Journal of Petrology, 56(6), 1069-1088.</p>