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Transition metal sulfides, as an important class of inorganics, have been shown to be potential high-performance electrode candidates for lithium-ion batteries (LIBs) in account of their high activity towards lithium storage, rich types and diverse structures. Despite these advantages, structure degradation related with volume variations upon electrochemical cycling restricts their further development. In this present study, a unique hybrid structure with ultrafine heazlewoodite nanoparticles (less than 10 nm) in-situ confined in nitrogen and sulfur dual-doped carbon (Ni3S2@NSC) was constructed though a facile pyrolysis process, using a novel Ni-based metal chelates as the precursor. Specifically, enhanced structure stability, shortened Li+ migration distance and improved reaction dynamics can be obtained simultaneously in the designed structure, thereby allowing to realize high lithium storage performance. Consequently, a remarkable reversible capacity of 955.9 mAh g−1 (0.1 A g−1 after 100 cycles) and a superior long-term cycling stability up to 1200 cycles (863.7 mAh g−1 at 1.0 A g−1) are obtained. Importantly, the fundamental understanding on the improved lithium storage of Ni3S2@NSC based on the synergistic coupling reveals that the combination between Ni3S2 and NSC at the hetero-interface through the doped sulfur atoms contributes to the integrity of electrode and improved kinetics.

Engineering of nanostructured materials with a unique and uniform morphological design is considered to be a competent candidate for a diverse range of electrochemical energy applications. However, the construction of ball-in-ball transition metal sulfide via the vaporization process remains a big challenge of today's research community. In this work, carbon encapsulated nickel sulfide (Ni3S2@C) with a complex hollow interior was synthesized and further studied with nitrogen-doped carbon encapsulated nickel sulfide (Ni3S2@NC) for comparison basis. We used metal salt (nickel nitrate) and organic linker (trimesic acid, TMA) as a precursor to synthesize Ni-TMA via a solvothermal method. Next, the sulfidation process was done under 5% H2 balanced argon gas in a tubular furnace to convert into Ni3S2 with encapsulation of carbon. The prepared hybrid material showed ball-in-ball morphology and heazlewoodite mineral phase structure. Furthermore, the prepared materials were examined for electrochemical energy storage properties owing to their well-known faradaic dominant (battery-type) charge storage features and key positive electroactive material for today's growing hybrid electrochemical capacitor. The nitrogen-doped carbon encapsulated nickel sulfide has demonstrated good electrochemical features like a specific capacity of 442.45 F g−1 at 5 mV s−1 of scan rate and 373.52 F g−1 at 2 A g−1 of current density. Moreover, the material showed excellent capacitance retention of 81% and 70% after 5000 and 10,000 cycles run with 100% of coulombic efficiency at 8 A g−1.

Author(s): Barkov, AY; Bindi, L; Tamura, N; Martin, RF; Ma, C; Winkler, B; Shvedov, GI; Morgenroth, W | Abstract: Fleetite, Cu2RhIrSb2, a new species of platinum-group mineral (PGM), was discovered intergrown with an Os–Ir–Ru alloy in the Miass Placer Zone (Au–PGE), southern Urals, Russia. A single grain 50 lm across was found. Osmium, ruthenium, and iridium are the main associated minerals; also present are Pt–Fe alloys, laurite, Sb-rich irarsite, Rh-rich tolovkite, kashinite, anduoite, ferronickelplatinum, heazlewoodite, PGE-bearing pentlandite and digenite, as well as micrometric inclusions of forsterite (Fo93.7), chromite–magnesiochromite, and Mg-rich edenite. In reflected light, fleetite is light gray; it is opaque, isotropic, non-pleochroic, and non-bireflectant. We report reflectance values measured in air. A mean of seven point-analyses (wavelength-dispersive spectrometry) gave Cu 13.93, Ni 8.60, Fe 0.10, Ir 28.07, Rh 7.91, Ru 1.96, Sb 39.28, total 99.85 wt.%, corresponding to (Cu1.41Ni0.58Fe0.01)R2.00(Rh0.49Ni0.36Ru0.12)R0.97Ir0.95Sb2.08 on the basis of six atoms per formula unit, taking into account the structural results. The calculated density is 10.83 g/cm3. Single-crystal X-ray studies show that fleetite is cubic, space group Fd3m (#227), a = 11.6682(8) A, V = 1588.59(19) A3, and Z = 16. A least-squares refinement of X-ray powder-diffraction data gave a = 11.6575(5) A and V = 1584.22(19) A3. The strongest five reflections in the powder pattern [d in A(I)(hkl)] are: 6.70(75)(111), 4.13(100)(220), 3.52(30)(311), 2.380(50)(422), 2.064(40)(440). Results of synchrotron micro-Laue diffraction experiments are consistent [a ¼ 11.66(2) A]. The crystal structure of fleetite was solved and refined to R ¼ 0.0340 based upon 153 reflections with Fo . 4r(Fo). It is isotypic with Pd11Bi2Se2 and best described as intermetallic, with all metal atoms in 12-fold coordination. Fleetite and other late exotic phases were formed by reaction of the associated alloy phases with a fluid phase enriched in Sb, As, and S in circulation in the cooling ophiolite source-rock. The mineral is named after Michael E. Fleet (1938–2017) in recognition of his significant contributions to the Earth Sciences.

Extremely abundant PGE-minerals (PGM) hosted in chromitites from the Veria ophiolite complex in Macedonia (N. Greece) may be unique among ophiolite complexes. This study focuses on differences between the low- and high-PGE chromitites. New textural, mineralogical and geochemical constraints from those ores are presented, aiming to define factors controlling the PGE enrichment in a supra subduction environment, in the light of post-magmatic processes. The whole ore analyses for mmajor and trace elements indicated an unusually high-IPGE content (up to 25 ​ppm) and higher Fe, Ca, Mn, Zn and V contents in high-PGE compared to low-PGE in massive chromitites. The wide compositional variation of chromite, even in the same polished section, the occurrence of very fine PGM (less than 20 ​μm) as inclusions within chromite and extremely large (>1000 ​μm), angular or fine-grained PGM aggregates ones within a matrix of highly fragmented chromite - Cr-garnet matrix, may indicate crystallization/recrystallization of chromite from more than one precursor phases. Laurite (RuS2) is very limited, occurring as remnants surrounding by Ru–Os–Ir oxides/hydroxides, of a wide compositional variation. Irarsite occurs as euhedral crystals up to 200 ​μm, surrounding by chromite, as anhedral exsolutions 1–200 ​μm within laurite, or creating segregates with platarsite and relics of (Ru, Pt, Rh, Os) sulfarsenides. Platinum–Ru–Rh–Pd-minerals occur commonly as relatively fine-grained assemblages, up to 50 ​μm, along with irarsite and other relics of (Ru, Pt, Rh, Os) sulfarsenides. Pt-alloys show a variation ranging from tetraferroplatinum to Pt–Ir–Fe–Ni alloys. The presence of laurite relics in large IPGM, awaruite, heazlewoodite, and carbon-bearing material reflecting a super-reducing environment, and the transformation of primary PGM into Os–Ir–Ru-alloys and oxides/hydroxides in association with Fe-chromite and Fe3+-bearing garnet (andradite-uvarovite solid-solution series) may reflect changes of the redox conditions from reducing to oxidizing. The relatively high Na content in hydrous mineral inclusions within high-PGE chromitites suggest a hydrous mantle source and provide the possibility for estimation of the P (average 3.0 ​kbar) and T (average 874 ​°C), indicating formation at a shallow mantle environment.

В работе представлена математическая модель гидрохимического окисления хизлевудита в разбавленных растворах азотной кислоты. Дана физико-химическая интерпретация основных кинетических характеристик процесса растворения: константа скорости и эффективная энергия активации. Установлены режимы взаимодействия хизлевудита с азотной кислотой, выявлены вероятные лимитирующие стадии. По наблюдаемым кинетическим закономерностям при моделировании процесса, предложен механизм гидрохимического окисления хизлевудита. The paper presents a mathematical model of the hydrochemical oxidation of heazlewoodite in dilute solutions of nitric acid. A physicochemical interpretation of the main kinetic characteristics of the dissolution process is given: the rate constant and the effective activation energy. The modes of interaction of heazlewoodite with nitric acid have been established, and probable limiting stages have been identified. According to the observed kinetic regularities in modeling the process, a mechanism for the hydrochemical oxidation of heazlewoodite has been proposed.

В работе представлены результаты математического моделирования окислительного растворения хизлевудита в растворах азотной кислоты в условиях равнодоступной поверхности вращающегося диска с применением метода полного факторного эксперимента. Получены и проанализированы зависимости скорости процесса гидрохимического окисления сульфида никеля (W, моль/смс) от продолжительности взаимодействия (τ, с), влияния концентрации азотной кислоты (С, моль/дм), частоты вращения диска (ω, с) и температуры (Т, К). Определены основные кинетические параметры: константа скорости и эффективная энергия активации процесса. Установлены режимы взаимодействия хизлевудита с азотной кислотой, выявлены вероятные лимитирующие стадии взаимодействия. The paper presents the results of mathematical modeling of the oxidative dissolution of hizlewudite in solutions of nitric acid using the rotating disk method and the factor experimental design. The dependences of specific speed of dissolution of sulfide of nickel Nickel sulfide (W, mol/cmc) on the duration of interaction (τ, s), the influence of nitric acid concentration (C, mol/dm), frequencies of rotation disk (ω, s) and temperatures (T, K) were obtained and analyzed. The main kinetic parameters are determined: the rate constant and the activation energy of the process. Established modes of interaction heazlewoodite with nitric acid, identified probable limiting stage of the interaction.

Heazlewoodite, Ni3S2, is one of the most promising bifunctional electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in alkaline media due to its metallic conductivity and low cost. However, the reported HER activity of Ni3S2 is still unsatisfactory. Herein, 3D self-supported phosphorus-doped Ni3S2 nanosheet arrays on Ni foam (P-Ni3S2/NF) are synthesized by a simple one-step simultaneous phosphorization and sulfuration route and exhibit dramatically enhanced HER and OER activity. The introduction of P anions significantly optimized the hydrogen adsorption free energy (ΔGH*) and increased the electrochemical surface area (ECSA). Accordingly, the optimal P-Ni3S2/NF exhibits relatively low overpotentials of 101 mV and 256 mV to drive a current density of 10 mA cm−2 for the HER and OER in 1 M KOH. The reported electrocatalyst activation approach by anion doping can be adapted for other transition metal chalcogenides for overall water splitting, offering great promise for future applications.

A group of accessory ore minerals is revealed in rocks of the Galmoenan mafic-ultramafic massif (Koryak Upland, Kamchatka, Russia), represented by native metals (iron, copper, zinc, and silver), iron-nickel and cobalt-iron intermetallic compounds, sulfides (pentlandite, cobaltpentlandite, pyrrhotite, sphalerite, heazlewoodite, millerite, shandite, pyrite, chalcopyrite, and Cu3S2 phase), arsenides (maucherite, nicolite, orcelite, and modderite), and some other minerals. Their chemical compositions, crystal forms, and paragenetic associations are described. Formation of these minerals is attributed to serpentinization of rocks.

Nickel sulfides are common in nature, and have been found in mantle-related rocks and xenoliths. Their properties exhibit significant differences with silicates in density, conductivity, and elasticity, and may be responsible for the geophysical anomalies in the upper mantle. Whether there is a difference in thermodynamic properties between sulfides and silicates in the upper mantle is not yet known. In the present study, the thermodynamic properties of millerite (NiS), heazlewoodite (Ni3S2), and polydymite (Ni3S4)-violarite (FeNi2S4) series with Fe/(Fe + Ni) = 0, 1/6 and 2/6 are calculated using the first-principles methods together with the quasi-harmonic approximation. The thermodynamics properties of some sulfides, including equation of state, isothermal bulk modulus, thermal expansion coefficient, heat capacity, and entropy are consistent with the available previous calculated and experimental data. The effect of Fe content on the thermodynamic properties of polydymite are also investigated, which show that with the increase of substitution Fe for Ni, the bulk modulus increases while the coefficient of thermal expansion decreases. Our calculations show that the coefficient of thermal expansion of Ni sulfides are higher than that of olivine and pyroxenes, while the adiabatic bulk modulus of Ni sulfides are lower than that of forsterite.

Nielsenite, a rare intermetallide of palladium and copper, was described previously as a late-magmatic formation. A different genetic type of nielsenite was studied in the layered ultrabasite–basite Yoko-Dovyren intrusive. The maximum concentrations of Pd, Pt, Au, and Ag minerals are confined to crosscutting bodies of pegmatoid sulfide-bearing anorthosites within the contact zone between the troctolites and overlapping gabbro-norites strata in this intrusive. Postmagmatic pneumatolytic (fluid-metasomatic) Pd, Pt, Au, and Ag minerals, such as kotulskite, moncheite, michenerite, zvyagintsevite, telargpalite, paolovite, electrum, and sperrillite, compose metasomes in Fe–Ni–Cu sulfides and in the silicate matrix nearby. The Yoko-Dovyren intrusive is tectonized and tilted, crossed by inclined faults with streamlined serpentinized rocks, which contain lizardite, antigorite, clinozoisite, chlorite, actinolite, prehnite, pectolite, and hydrogarnet and are often transformed into rodingites of a prehnite–pumpellyite facies. The serpentinization process is younger than the intrusive rocks by 55 million years. In metamorphosed anorthosites, chalcopyrite is replaced by bornite, chalcocite, digenite, and magnetite; pentlandite is replaced with violarite, heazlewoodite, …; pyrrhotine is replaced by magnetite, …; moncheite is replaced with cuproplatinum–tulameenite; the veins of clinozoisite and pectolite with chlorite inclusions of chalcosine and native copper are well developed. Curved veins of nielsenite in brecciated chalcopyrite occasionally extend such veins. The size of the veins of metamorphogenic-hydrothermal nielsenite reaches up to 200 × 10 microns. Nielsenite metasomes up to 12 microns in diameter are developed nearby. The composition of the Yoko-Dovyren nielsenite is stable and close to stoichiometric with the formula Pd1.01Cu2,81Fe0,17Ni0,01. The Yoko-Dovyren nielsenite differs from the holotype of nielsenite of the Skergaard intrusive by the absence of Pt and Au impurities and a significant impurity of Fe. Yoko-Dovyren nielsenite was likely to appear under conditions of the prehnite–pumpellyite metamorphism facies at a high fugacity of О2 and at an extremely low fugacity of sulfide sulfur (log f S2 < –24 at ≈300°C).

The Jacurici Complex hosts the largest chromite deposit in Brazil in an up to 8-m-thick chromitite layer within a tectonically segmented 300-m-thick intrusion. The ore has been interpreted as the result of crustal contamination-driven crystallization in a magma conduit. This study addresses the stratigraphy, mineralogical and textural relationships, and mineral chemistry of the Monte Alegre Sul segment focusing on chromite-hosted inclusions from the Main Chromitite Layer to understand the role of volatiles in the genesis of the massive chromitite. Silicate inclusions (enstatite, phlogopite, magnesiohornblende, diopside and olivine) are commonly monomineralic and sub- to euhedral, and crystallized prior to, or coeval with, the chromite crystallization. Carbonate inclusions (dolomite and magnesite) are irregular or have negative crystal shapes, suggesting entrapment as melt droplets. Sulfides (pentlandite, millerite, heazlewoodite, polydymite, pyrite, and chalcopyrite) are often polymineralic, irregular, or hexagonal-shaped, indicating entrapment as sulfide melt and as monosulfide solid solution. The inclusions indicate an H2O- and S-saturated resident magma with immiscible droplets of carbonate melt during chromite crystallization. Inclusion-rich and inclusion-free chromites that occur together have similar compositions and are considered to have formed from the same magma in response to variations in the degree of Cr saturation. Hot primitive magma might have heated and mobilized CO2 and probably water from devolatized and assimilated carbonate-rich wall rocks, increasing fO2 and triggering chromite crystallization. We propose that the formation of the chromitite layer started as in situ crystallization with additional material added by slumping of locally remobilized chromite slurries, facilitated by the presence of volatiles.

Djerfisherite in the monticellite rocks of the Krestovskaya Intrusion is found in primary melt inclusions, mono- and polysulfide globules, and in the djerfisherite–hydrogarnet segregations. Melt inclusions are represented by three types. Type I is observed in the cores of perovskite phenocrysts and monticellite grains and corresponds to one of the early crystallization stages of the parental larnite-normative alkali ultrabasic magma enriched in water and other volatiles. Daughter phases of the inclusions are clinopyroxene, serpentine, phlogopite, apatite, nepheline, hydrogarnet, magnetite, djerfisherite, pectolite, and calcite. In some type I inclusions, melt at 1230–1250°C was immiscibly split into two fractions: alkali silicate fraction and highly fluidized water-bearing low-silica fraction enriched in alkali, sulfur, and CO2. The types II and III inclusions in perovskite, monticellite, Ti-garnet, and melilite were formed through the spatial separation of immiscible phases. This follows from the similarity of the modal composition of types II and III melt inclusions to the normative composition of immiscible fractions of type I inclusions. Type II inclusions contain mainly water-bearing silicate daughter phases (hydrogarnet, serpentine, phlogopite, and pectolite), as well as djerfisherite, calcite, and magnetite, Type III inclusions contain clinopyroxene, nepheline, apatite, magnetite, djerfisherite, calcite, and pectolite. The djerfisherite–hydrogarnet segregations are confined to the Ti-magnetite and perovskite phenocrysts and fractures radiating from them in monticellite. The mineral composition of the djerfisherite–hydrogarnet segregations together with their surrounding is similar to the composition of type II inclusions containing similar water-bearing silicates, djerfisherite, calcite, and magnetite. Such similarity gives grounds to relate the formation of the djerfisherite–hydrogarnet segregations, as type II inclusions, with the spatial separation and crystallization of highly fluidized low-silica melt enriched in water, alkalis, sulfur, and CO2. According to the homogenization experiment, the crystallization of highly fluidized melt at 990–1090°C was accompanied by silicate–sulfide immiscibility and the formation of globular, emulsion-like, and myrmekite structures in the djerfisherite–hydrogarnet segregations, as well as mono- and polysulfide globules with djerfisherite in the hydrogarnet–calcite–serpentine substrate. The formation of ferrobrucite–carbonate–hydrogarnet globules in the djerfisherite–hydrogarnet segregations was also related to melt liquation, which again confirms the magmatic origin of the latter. Sometimes, djerfisherite in the djerfisherite–hydrogarnet segregations becomes coarser and forms rims, bands, and veinlets, which is likely explained by the high mobility and low viscosity of sulfide melt. Scarce grains of heazlewoodite, godlevskite, and pentlandite hosted in the djerfisherite–hydrogarnet segregations frequently have the same shape as djerfisherite, which indirectly suggests their simultaneous crystallization from the same melt. The chemical composition of the djerfisherite from mono- and polysulfide globules, djerfisherite–hydrogarnet segregations, and type I inclusions, as most Yakutian kimberlites, is characterized by the high (12.1–16.7 wt %) Ni and low (0.1–0.9 wt %) Cu contents. The composition of the djerfisherite from types II and III inclusions differs in the lowered (3.3–1.6 wt %) Ni and elevated (40.9–53.2 wt %) Fe contents; type III inclusions have high Cu content: from 7.6 to 10.6 wt %.

Nuwaite (Ni_6GeS_2, IMA 2013-018) and butianite (Ni_6SnS_2, IMA 2016-028) are two new chalcogenide minerals, occurring as micrometer-sized crystals with grossular, Na-bearing melilite, heazlewoodite, and Ge-bearing Ni-Fe alloys in veins and as mono-mineralic crack-filling material in igneous diopside in the Type B1 Ca-Al-rich inclusion (CAI) ACM-2 from the Allende CV3 carbonaceous chondrite. The chemical composition of type nuwaite is (wt%) Ni 65.3, S 10.3, Ge 8.2, Te 7.9, Sn 5.1, and Fe 1.7, with a sum of 98.5 and an empirical formula of (Ni_(5.95)Fe_(0.16))(Ge_(0.60)Sn_(0.23))(S_(1.72)Te_(0.33)). The simplified formula is Ni6(Ge,Sn)(S,Te)2, leading to an end-member of Ni6GeS2. The chemical composition of type butianite is (wt%) Ni 62.1, Sn 8.9, Te 10.3, S 8.9, Ge 5.3, Fe 1.3, sum 99.1, giving rise to an empirical formula of (Ni_(5.93)Fe_(0.13))(Sn_(0.52)Ge_(0.41))(S_(1.56)Te_(0.45)). Butianite's simplified formula is Ni6(Sn,Ge) (S,Te)2 and the end-member formula is Ni6SnS2. Both nuwaite and butianite have an I4/mmm inter-growth structure with a = 3.65 A, c = 18.14 A, V = 241.7 A^3, and Z = 2. Their calculated densities are 7.24 and 7.62 g/cm^3, respectively. Nuwaite and butianite are the first known meteoritic minerals with high Ge and Sn concentrations. Nuwaite and butianite are very late-stage, vapor-deposited, alteration products, filling in pores within preexisting grossular-rich alteration veins and cracks in igneous Al,Ti-diopside. These phases and associated heazlewoodite and Ge-bearing alloys are observed only within the Ca-,Al-rich inclusion (CAI) and not outside it or at the inclusion-matrix interface. As only sections in one half of ACM-2 contain nuwaite/butianite, they were probably derived through a relatively low f_(O2)-f_(S2) sulfidation process, in which a highly localized, low-temperature Ge-, Sn-bearing fluid interacted with a portion of the host CAI. It is likely that the fluid became relatively more Sn- and Te-enriched with time and that crack fillings post-date vein fillings, possibly due to a late remobilization of vein sulfides.

The lopolithic Pados-Tundra layered complex, the largest member of the Serpentinite belt&ndash, Tulppio belt (SB&ndash, TB) megastructure in the Fennoscandian Shield, is characterized by (1) highly magnesian compositions of comagmatic dunite&ndash, harzburgite&ndash, orthopyroxenite, with primitive levels of high-field-strength elements, (2) maximum values of Mg# in olivine (Ol, 93.3) and chromian spinel (Chr, 57.0) in the Dunite block (DB), which exceed those in Ol (91.7) and Chr (42.5) in the sills at Chapesvara, and (3) the presence of major contact-style chromite&ndash, IPGE-enriched zones hosted by the DB. A single batch of primitive, Al-undepleted komatiitic magma crystallized normally as dunite close to the outer contact, then toward the center. A similar magma gave rise to Chapesvara and other suites of the SB&ndash, TB megastructure. Crystallization proceeded from the early Ol + Chr cumulates to the later Ol&ndash, Opx and Opx cumulates with accessory Chr in the Orthopyroxenite zone. The accumulation of Chr resulted from efficient cooling along boundaries of the Dunite block. The inferred front of crystallization advanced along a path traced by vectors of Ol and Chr compositions. Grains and aggregates of Chr were mainly deposited early after the massive crystallization of olivine. Chromium, Al, Zn and H2O, all incompatible in Ol, accumulated to produce podiform segregations or veins of chromitites. This occurred episodically along the moving front of crystallization. Crystallization occurred rapidly owing to heat loss at the contact and to a shallow level of emplacement. The Chr layers are not continuous but rather heterogeneously distributed pods or veins of Chr&ndash, Ol&ndash, clinochlore segregations. Isolated portions of melt enriched in H2O and ore constituents accumulated during crystallization of Ol. Levels of fO2 in the melt and, consequently, the content of ferric iron in Chr, increased progressively, as in other intrusions of the SB&ndash, TB megastructure. The komatiitic magma vesiculated intensely, which led to a progressive loss of H2 and buildup in fO2. In turn, this led to the appearance of anomalous Chr&ndash, Ilm parageneses. Diffuse rims of Chr grains, abundant in the DB, contain elevated levels of Fe3+ and enrichments in Ni and Mn. In contrast, Zn is preferentially partitioned into the core, leading to a decoupling of Zn from Mn, also known at Chapesvara. The sulfide species display a pronounced Ni-(Co) enrichment in assemblages of cobaltiferous pentlandite, millerite (and heazlewoodite at Khanlauta), deposited at &le, 630 &deg, C. The oxidizing conditions have promoted the formation of sulfoselenide phases of Ru in the chromitites. The attainment of high degrees of oxidation during crystallization of a primitive parental komatiitic magma accounts for the key characteristics of Pados-Tundra and related suites of the SB&ndash, TB megastructure.

This research has been funded by the Spanish project RTI2018099157-A-I00 granted by the "Ministerio de Ciencia, Innovacion y Universidades". Additional funding for chemical analysis was provided by the Ramon y Cajal Fellowship RYC-2015-17596 to JMGJ. Jesus Montes is acknowledged for his careful preparation of the thin-sections. Isabel Sanchez Almazo and Rocio Marquez Crespo (CIC, University of Granada) are also acknowledged for their assistance with HR-SEM and FE-SEM analysis respectively. We are also indebted to Miguel Angel Hidalgo Laguna (CIC, University of Granada) and Xavier Llovet (Centres Cientifics i Tecnol`ogics of the Universitat of Barcelona) for their careful help with EPMA., A variety of base-metal minerals (BMM) may form during hydration-dehydration of ultramafic rocks within subduction zones. However, the trace element fingerprints of these minerals and their relation to different stages of the subduction cycle are still unexplored. Here, we present the first comprehensive in situ analysis by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) of (semi)-metals (Ni, Fe, As, Sb, Co, Bi, Te, Pb, Cd, Se, Cu, Zn, and Mn) and precious metals (Os, Ir, Rh, Pt, Pd, Au, and Ag) for Ni–Fe–S–As minerals in subducted serpentinites from the La Caba˜na area (South-Central Chile). The targeted rocks are medium- and high-pressure serpentinites recording the entire cycle of burial-exhumation within a subduction zone. A first stage of hydration of upper mantle peridotites within the mantle wedge led to formation of lizardite after magmatic olivine at ~300 ◦C. This stage was followed by prograde hydration (i.e., antigoritization at ~320–400 ◦C; 300 ◦C). The Ni–Fe–S–As minerals in these serpentinites include Ni-Fe-rich sulfides [pentlandite (Ni,Fe)9S8), smythite (Fe9S11), heazlewoodite (Ni3S2), millerite (NiS)], arsenides [orcelite (Ni5-xAs2), nickeline (NiAs) and maucherite (Ni11As8)] and, to a lesser extent, alloy (awaruite, Ni3Fe) and sulfarsenides (gerdorffite, NiAsS). Their abundance, morphology and chemistry strongly vary with the degree of serpentinization and style of deformation of the host rock. Thus, euhedral grains of heazlewoodite ± awaruite ± magnetite formed in equilibrium with lizardite when magmatic olivine was hydrated within the mantle wedge. Once the lizardite-olivine serpentinites were incorporated into the subduction serpentinite channel, the infiltration of hotter (S-As-Sb)-bearing fluids promoted antigoritization under static regime and precipitation of orcelite and pentlandite in equilibrium with antigorite. Channelling of fluids in zones of focussed strain enhanced further antigoritization in some schistose serpentinites at decreasing fO2 and fS2, resulting in the transformation of pentlandite into a second generation of heazlewoodite–awaruite–magnetite. After relic olivine exhaustion, fO2 and fS2 increased promoting the replacement of the secondary heazlewoodite to millerite. No significant variations in terms of trace elements were observed during these mineral replacements associated to hydration upon prograde metamorphism and/or increasing of strain. In contrast, partial dehydration of serpentinites under high-pressure conditions (> 1GPa) generated Ni-rich awaruite in equilibrium with the prograde assemblage antigorite-metamorphic olivine. These awaruites are depleted in trace elements, indicating substantial (semi)-metal and precious metal mobility during high P-T metamorphism within the subduction channel. During the final stage of deformation linked to exhumation inside the accretionary prism some orcelite grains formed during early antigoritization recrystallized without substantial change in trace element concentration. At this stage, nickeline singularly enriched in gold formed in equilibrium with the recrystallizing orcelite. These results demonstrate that Ni–Fe–S–As minerals formed or modified during the entire subduction cycle of upper mantle rocks have their own characteristic trace element signature (i.e., depletion in precious metals and enrichment in As, Sb, Te, Bi and Pb) that distinguish them from magmatic counterparts., "Ministerio de Ciencia, Innovacion y Universidades" RTI2018099157-A-I00, Spanish Government RYC-2015-17596, Miguel Angel Hidalgo Laguna (CIC)

Nickel sulfide based anode materials, featuring rich types, high specific capacities and favorable conversion kinetics, have been proved to be promisingly applied in high-performance sodium-ion batteries (SIBs). Unfortunately, the poor electronic/ionic conductivity, together with the structure change induced degraded capacity upon cycling, restricts their further development. In this work, heazlewoodite nanoparticles decorated on nitrogen doped reduced graphene oxide (Ni3S2/NrGO) were fabricated via a facile combined approach with freeze-drying and subsequent in-situ sulfidation. In the obtained hybrid structure, the synergistic effect between Ni3S2 and NrGO endows the composite with highly conductive pathways, thus accelerating the charge transfer. Benefitting from the buffering matrix offered by NrGO as well as the tight combination between Ni3S2 and NrGO, this novel Ni3S2/NrGO demonstrates satisfying sodium storage performance, with a stable reversible capacity of 299.2 mAh g−1 up to 100 cycles (0.1 A g−1) and a high initial Coulombic efficiency of 76.8%. Importantly, the rational structure design and synthesis method, as well as the insights on the improved electrochemical performance reported in this work, should be helpful for the development of new-type host materials with high performance for SIBs.

Rare nickel hydroxide-hydroxyl carbonate, theophrastite (Ni(OH)2)-zaratite (Ni3(CO3)(OH)4&middot, 4H2O) aggregates were found from a partially serpentinized dunite from Fujiwara, the Sanbagawa metamorphic belt of high-pressure intermediate type, Japan. The dunite was regionally metamorphosed within the Sanbagawa subduction complex of Cretaceous age. The theophrastite-zaratite aggregate from Fujiwara most typically occurs in association with nickel sulfides, which form a composite grain with awaruite and magnetite within an antigorite-rich part of the rock. The theophraste-zaratite formed possibly together with millerite (NiS) from heazlewoodite (Ni3S2). This represents a partial desulfurization of heazlewoodite, which contains or interlocks with laths of antigorite, suggesting their cogenesis. The desulfurization occurred at an early stage of, or during, exhumation of the subduction complex toward the surface, where sulfur was oxidized and removed as sulfate ions. Serpentinization of olivine has not been associated with the formation of theophrastite-zaratite, and an oxidized condition has been kept at this post-serpentinization stage. The sulfate ions liberated in part precipitated anhydrite where calcium was available in the surrounding rocks. This shows one of the shallow migration pathways of sulfur in the subduction zone, especially to the forearc area.

Nickel sulfide minerals, an important type of metal sulfides, are the major component of mantle sulfides. They are also one of the important windows for mantle partial melting, mantle metasomatism, and mantle fluid mineralization. The elasticity plays an important role in understanding the deformation and elastic wave propagation of minerals, and it is the key parameter for interpreting seismic wave velocity in terms of the composition of the Earth&rsquo, s interior. Based on first-principles methods, the crystal structure, equation of state, elastic constants, elastic modulus, mechanical stability, elastic anisotropy, and elastic wave velocity of millerite (NiS), heazlewoodite (Ni3S2), and polydymite (Ni3S4) under high pressure are investigated. Our calculated results show that the crystal structures of these Ni sulfides are well predicted. These Ni sulfides are mechanically stable under the high pressure of the upper mantle. The elastic constants show different changing trends with increasing pressure. The bulk modulus of these Ni sulfides increases linearly with pressure, whereas shear modulus is less sensitive to pressure. The universal elastic anisotropic index AU also shows different changing trends with pressure. Furthermore, the elastic wave velocities of Ni sulfides are much lower than those of olivine and enstatite.

The Abdasht and Soghan ultramafic complexes, Southern Iran, host major actively exploited chromitite bodies, variably enriched in PGE. The Platinum Group Minerals (PGM) – Base Metal Minerals (BMM) assemblage was studied in order to assess PGE remobilization during post-magmatic processes. Studied chromitites have variable textures: massive, banded, nodular and disseminated. Primary silicates are almost completely replaced by serpentine. Ferrian chromitization is present but not widespread. BMM are mostly found in the silicate matrix, while PGM are more common as inclusions within chromites. Primary BMM (pentlandite and bornite) within the silicate matrix are poorly preserved, while primary PGM (laurite) are more abundant. Secondary BMM (heazlewoodite, millerite and Ni Fe alloys) and PGM (PGE-alloys) are the dominant mineralogical species. During serpentinization the pervasive percolation of low fS2 fluids induced the desulfurization of the metallic assemblage. Primary sulfides were replaced by S-poor (heazlewoodite) or S-free (Ni Fe alloys, PGE alloys, PGE-BM alloys) phases. Low fS2 differentially mobilized PGE. The release of IPGE (Ir, Os, Ru) into the fluids follows the order: Ru> > Os>Ir. PPGE (Pt, Pd, Rh) mobility is more difficult to assess, due to their small concentration, but the evidence suggests that Rh is more mobile than Ru, and that Pd and Pt were partially added to the system by fluids. A mass balance calculation on a polyphasic grain, showing differential stages of desulfurization, allowed a semi-quantitative analysis on the desulfurization degree of Abdasht and Soghan complexes, estimated, in the more serpentinized portions, between 75 and 100%.

Generally, sulfur elimination from nickel matte was incomplete in the one-step oxidation roasting process. In this work, X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray spectroscopy, and chemical analysis of the roasted products were carried out to explain this phenomenon. The results indicated that the melting of heazlewoodite was the main limiting factor. Thereafter, the oxidation mechanism of high-grade nickel matte from room temperature to 1000 °C was studied. It was found that the transformation from heazlewoodite (Ni3S2) to nickel sulfide (NiS) took place from 400 °C to 520 °C. Considering that the melting temperature of NiS was much higher than that of Ni3S2, a low-temperature roasting step was suggested to suppress the melting of heazlewoodite. Under the optimum conditions (520 °C for 120 minutes followed by 800 °C for 80 minutes), the degree of desulfurization reached 99.52 pct. These results indicated that the two-step oxidation roasting method could be a promising process for producing low-sulfur calcine from high-grade nickel matte.

In this study, ammonium N-benzyldithiocarbamate was synthesized and used to prepare homoleptic Ni(II) bis(N-benzyldithiocarbamate) (1) and heteroleptic Ni(II) complexes involving isocyanate (2) and cyanide (3) ions. The complexes were characterized by elemental analysis, Fourier transform infra-red (FTIR), and NMR (1H and 13C) spectroscopic techniques. Complex 2 was further characterized by single crystal X-ray diffraction analysis. The FTIR showed bidentate co-ordination for all the complexes as the v(CN) stretching frequency were in the 980–1050 cm−1 region without any splitting. Thermal decomposition profile of the complexes showed decomposition resulting in the formation of nickel sulphides. The homoleptic complex 1 was utilized as single source precursor (SSP) to prepare Nickel sulphide nanoparticles. The synthesis of the nanoparticles was conducted using different capping molecules (with various alkyl chain lengths), and at different reaction temperature and time. Pure phase Heazlewoodite (Ni3S2) nanoparticles were obtained from the X-ray diffraction study. The TEM analysis showed that the type of capping agent, reaction temperature, and time of reaction have significant effect on the morphology and size of the nanoparticles. The optical properties of the nanoparticles were studied using absorption and fluorescence spectroscopies, and they displayed evidence of quantum confinement effect. Keywords: Nickel sulphide, Dithiocarbamate, Nanoparticles, Morphology

Nickel is an important element on Earth, and a major element in the Earth's core, and plays important roles in many geological and biological systems. As an important sink of Ni, Ni sulfides are closely concerned with Ni migration in magma systems and the genesis and evolution of magmatic sulfide deposits. Ni isotopes of Ni sulfides may be a powerful geochemical tracer in magmatic processes and evolution of magmatic sulfide deposits. However Ni isotope fractionation factors of sulfides remain poorly known, which makes the applications of Ni isotopes to geological problems associated with sulfides difficult. In this study, the first-principles methods are used to compute Ni isotope fractionation parameters of polydymite (Ni3S4), heazlewoodite (Ni3S2), millerite (NiS), godlevskite (Ni9S8) and vaesite (NiS2). The reduced partition function ratios of 60Ni/58Ni ( 10 3 ln β 60 – 58 ) for these minerals decrease in the order of polydymite > heazlewoodite > millerite > godlevskite > vaesite. Ni isotope fractionations in these Ni sulfides show an approximately linear dependence on the average Ni S bond lengths, and have a significant negative correlation with the average Ni Ni bond lengths. Furthermore, a change in Fe/Ni ratio can also lead to Ni isotope fractionation, and with substitution Fe for Ni, the reduced partition function ratios of 60Ni/58Ni decrease.

The mining of ultramafic ores is required to meet society’s continued demand for nickel. These deposits, however, are difficult to process due to their high serpentine content. Serpentine, a gangue mineral, increases slurry viscosity, slime-coats the valuable Ni-bearing mineral pentlandite, and reports to and dilutes the froth during flotation via the formation of bubble-fibre aggregates. Microwave pre-treatment can be used to convert the serpentine gangue to olivine, which should improve ore processing. However, the fundamental microwave properties and heating behaviour of ultramafic ores must be understood to develop a robust process. Microwave heating curves were developed for, and high temperature permittivity analysis was conducted on, two ultramafic nickel ores (Pipe and OK ore). Subsequently, TGA/DSC (thermogravimetric analysis/differential scanning calorimetry) and HTXRD (high-temperature x-ray diffraction) tests, along with a thermodynamic analysis using FactSage 7.3, were done to explain the heating behaviours and permittivity data. An unusual peak in the permittivity data was detected at 950 °C for the Pipe ore with both increasing and decreasing temperature; however, no phase transitions were detected in the TGA/DSC analysis. HTXRD of the Pipe ore revealed the presence of heazlewoodite at higher temperatures (950 to 1100 °C). Thermodynamic modeling of the Pipe ore system suggests that melting at higher temperatures is responsible for the decrease in the permittivities of this ore. To mitigate the melting and clumping of the ore particles, it is necessary to ensure that the processing temperature does not exceed 800 °C during microwave treatment. The OK ore, which contained less microwave response minerals than the Pipe ore, reached a maximum temperature of 500 °C after only 5 min of heating time, and therefore overheating was not an issue.

The Northern Ultramafic Centre (NUC) of the Lac des Iles Complex, Northwest Ontario hosts several platinum group element (PGE) occurrences, including the Sutcliffe Zone, which consists of four subparallel, stratiform PGE-enriched intervals exposed within the cyclically layered eastern flank of the NUC. Field relationships, mineral paragenesis and lithogeochemistry allowed for the identification of 14 cyclic cumulate sequences of two distinct types – Cyclic unit type A (CUA) and Cyclic unit type B (CUB). CUA-type and CUB-type units are interpreted to have formed from a Si-enriched and Si-poor parent magmas, respectively. PGE-enriched intervals occur in four of the CUA-type cyclic units (CUA-5, -6, -8 and -11). PGE enriched intervals are commonly associated with websterite, olivine websterite and gabbronorite containing primary disseminated sulfide (0.2–2 vol%) which are dominated by pyrrhotite, chalcopyrite, and pentlandite with minor cubanite, and troilite. In hydrothermally altered rocks enriched in PGE, primary sulfides are locally partially replaced by secondary chalcopyrite, sphalerite, heazlewoodite, and chalcocite. Palladium occurs either in solid solution with primary pentlandite or is associated with platinum group minerals (PGM) such as Pd-plumbide, Pd-telluride, and Pt-bismuthotelluride. PGMs commonly occur within primary sulfides, at contacts between primary sulfide–silicate minerals, or in association with secondary serpentine and actinolite. Gold and silver typically occur as electrum that exhibits similar textural characteristics and mineralogical associations as the PGMs. Two different chemostratigraphic patterns of PGE, Cu and S enrichment can be recognized among the mineralized CUA cycles: The first (top-loaded) occurs near the top of CUA cycles (CUA-6, -8 and -11) in websterite and/or gabbronorite, just below the levels at which CUB magmas were emplaced. The second (middle-loaded), occurs midway through the lower cycle (CUA-5) in the olivine websterite, which is overlain by CUA-6. Within the four mineralized intervals, PGE tenors average 643 ppm Pd + Pt (in 100% sulfide), Pd/Pt and Pd/Ir ratios range from 0.9 to 3.5 and 35 to 537, respectively, and S/Se ratios range between 500 and 6000. The highest PGE tenors (4377 ppm Pd + Pt) are found in the lowermost interval in serpentinized olivine websterite and have an average Pd/Pt ratio of 3.5 and a S/Se ratio of approximately 2000. It is proposed that orthomagmatic processes of fractional crystallization and dynamic magma recharge were the dominant mineralization processes triggering sulfide-saturation and PGE concentration at the Sutcliffe Zone. Textural relationships between PGM, sulfide minerals, and primary and secondary hydrous silicates suggest that late magmatic to postcumulus hydrothermal fluid infiltration occurred locally during and after sulfide mineralization of the PGE-enriched intervals. However, these fluids had a minimal effect on the distribution of PGE in the Sutcliffe Zone. The Sutcliffe Zone shares many similarities with classic stratiform PGE deposits in terms of Pd/Pt ratio, high PGE tenors, low abundance of sulfide, and PGM assemblages. However, it is distinguished from most stratiform PGE deposits by its tectonic environment and lithostratigraphic position and by the intimate spatial association of the two parental magmas that are interpreted to have been responsible for the observed chemostratigraphy and PGE enrichment.

Ultramafic mine wastes are known to react passively with CO 2 to form stable hydrated magnesium carbonates. This study uses kinetic tests to evaluate the carbonation potential of ultramafic mine tailings from the Dumont project (RNC Minerals, Quebec, Canada) during their weathering, and to determine the impact of carbonation on the long-term quality of drainage waters. The weathering of awaruite [(Ni 2.5 Fe)], pentlandite [(Fe,Ni) 9 S 8 ], and heazlewoodite [(Ni 3 S 2 )], which are the main sources of Ni in the studied materials, were also investigated due to their potential to generate contamination. A column test and small-scale weathering cell tests were used to simulate the passive weathering of ultramafic mine wastes, as well as concentrates of awaruite and Ni sulfides. Results from the kinetics tests confirmed that the Dumont tailings have a significant carbon sequestration potential which ranged from 8.5 to 33.6 kgCO 2 /t. The surface-normalized carbonation rates varied from 600 to 2200 g of CO 2 /m 2 /year. Results demonstrated that brucite [Mg(OH) 2 ] content is the main parameter controlling CO 2 uptake by the Dumont wastes. Weathering of brucite and serpentine [Mg 3 Si 2 O 5 (OH) 4 ] are driven by CO 2 dissolution in pore water and by sulfide oxidation. The rapid dissolution of brucite results in leachates with alkaline pH values, thus preventing metal mobility. Metals such as Ni, Zn, Fe, and Cu are suggested to precipitate as hydroxide or carbonate species within the wastes immediately upon being released through sulfide oxidation. The Ni-Fe alloy awaruite is stable and does not release metals in kinetic tests. The Dumont tailings are found to be non-acid generating and CO 2 sequestration is shown to play a significant role in drainage water quality which allow generation of significant alkalinity and the rise of pH.

The activity and durability of electrocatalysts are important factors in their practical applications, such as electrocatalytic oxygen evolution reactions (OERs) used in water splitting cells and metal–air batteries. In this study, a novel electrocatalyst, comprising few-layered graphitic carbon (~5 atomic layers) encapsulated heazlewoodite (Ni3S2@C) nanoparticles (NPs), was designed and synthesized using a one-step solid phase pyrolysis method. In the OER test, the Ni3S2@C catalyst exhibited an overpotential of 298 mV at a current density of 10 mA·cm–2, a Tafel slope of 51.3 mV·dec–1, and charge transfer resistance of 22.0 Ω, which were better than those of benchmark RuO2 and most nickel-sulfide-based catalysts previously reported. This improved performance was ascribed to the high electronic conductivity of the graphitic carbon encapsulating layers. Moreover, the encapsulation of graphitic carbon layers provided superb stability without noticeable oxidation or depletion of Ni3S2 NPs within the nanocomposite. Therefore, the strategy introduced in this work can benefit the development of highly stable metal sulfide electrocatalysts for energy conversion and storage applications, without sacrificing electrocatalytic activity.

Effect of the solution redox potential on the behavior of cobalt-containing phase components of sulfide copper-nickel concentrates in the Cu(II)/Fe(III)–Cl––HCl–Cl2 system was studied. It was shown that, at solution redox potentials in the range 350–650 mV, phases based on heazlewoodite, pentlandite, cobaltous pentlandite, and cobalt pentlandite are transformed to thiospinels from the linneite group (M3S4, where M = Ni, Fe, Co). The resulting thiospinels are dissolved, with the exception of Co3S4, at solution redox potentials of 450 mV and less. The Co3S4 thiospinel is a stable compound in concentrated chloride solutions up to 650 mV, which, in the system under study, may be a reason for the poor cobalt recovery from sulfide concentrates.

Oxides, sulfides, arsenides, native metals, and intermetallic compounds are accessory ore minerals from the rocks of the Mt. Poputnaya ultramafic massif. The Fe–Ni phases containing 55.3–82.3 wt % Ni are the most abundant among them. Magnetite, pyrrhotite, Co–Fe and Fe–Ni phases, and native iron are the comparatively high-temperature minerals, whereas heazlewoodite, orcelite, dienerite, and native copper are formed at low temperatures. The found minerals result from serpentinization at 500°C and below.

The role of post-magmatic processes in the composition of chromitites hosted in ophiolite complexes, the origin of super-reduced phases, and factors controlling the carbon recycling in a supra-subduction zone environment are still unclear. The present contribution compiles the first scanning electron microscope/energy-dispersive (SEM/EDS) data on graphite-like amorphous carbon, with geochemical and mineral chemistry data, from chromitites of the Skyros, Othrys, Pindos, and Veria ophiolites (Greece). The aim of this study was the delineation of potential relationships between the modified composition of chromite and the role of redox conditions, during the long-term evolution of chromitites in a supra-subduction zone environment. Chromitites are characterized by a strong brittle (cataclastic) texture and the presence of phases indicative of super-reducing phases, such as Fe&ndash, Ni&ndash, Cr-alloys, awaruite (Ni3Fe), and heazlewoodite (Ni3S2). Carbon-bearing assemblages are better revealed on Au-coated unpolished sections. Graphite occurs in association with hydrous silicates (chlorite, serpentine) and Fe2+-chromite, as inclusions in chromite, filling cracks within chromite, or as nodule-like graphite aggregates. X-ray spectra of graphite&ndash, silicate aggregates showed the presence of C, Si, Mg, Al, O in variable proportions, and occasionally K and Ca. The extremely low fO2 during serpentinization facilitated the occurrence of methane in microfractures of chromitites, the precipitation of super-reducing phases (metal alloys, awaruite, heazlewoodite), and graphite. In addition, although the origin of Fe&ndash, Cu&ndash, Ni-sulfides in ultramafic parts of ophiolite complexes is still unclear, in the case of the Othrys chromitites, potential reduction-induced sulfide and/or carbon saturation may drive formation of sulfide ores and graphite-bearing chromitites. The presented data on chromitites covering a wide range in platinum-group element (PGE) content, from less than 100 ppb in the Othrys to 25 ppm &Sigma, PGE in the Veria ores, showed similarity in the abundance of graphite-like carbon. The lack of any relationship between graphite (and probably methane) and the PGE content may be related to the occurrence of the (Ru&ndash, Os&ndash, Ir) minerals in chromitites, which occur mostly as oxides/hydroxides, and to lesser amounts of laurite, with pure Ru instead activating the stable CO2 molecule and reducing it to methane (experimental data from literature).

The paper presents the results of research on the influence of nitric acid concentration on the dissolution rate heazlewoodite. The dependence of the amount of Nickel transferred to the solution on the time of the dissolution process was studied. The absence of time influence on the specific dissolution rate was revealed. Specific dissolution rates of Ni2S3 in wide concentration ranges were investigated. From the studied dependence was chosen a range to build a mathematical model of the influencing factors., {"references":["Pichugina, A. I., Lutsik, V. I., Bol'shakov, E. C., & Chursanov, Yu. V. (2015). Vysokotemperaturnyi sintez khizlevudita. Khimicheskaya termodinamika i kinetika: Sb. dokl. V Mezhdunarodnoi nauchnoi konf. g. Velikii Novgorod, (25-29 maya 2015 g.). 169-170.","Lutsik, V. I., & Sobolev, A. E. (2009). Kinetika gidroliticheskogo i okislitel'nogo rastvoreniya sul'fidov metallov. Tver': TGTU, 140.","Lutsik, V. I., & Sobolev, A. E. (2007). Issledovanie kinetiki protsessov gidrokhimicheskogo okisleniya sul'fidnykh mineralov. Mining Informational and Analytical Bulletin (scientific and technical journal), (6). 362-369.","Pichugina, A., Gortsevich, S., & Lutsik, V. (2016). Kinetics of millerite and heazlewoodite dissolution in solutions of nitric acid. Bulletin of Science and Practice, (11), 106–111.","Pichugina, A. I., Lutsik, V. I., & Epifanova, N. I. (2014). The kinetics of hydrolytic and oxidative dissolution of nickel (II) sulphide in an acidic medium. Bulletin of Tver state University. Series Chemistry, (2). 82-88."]}

Serpentinites in the Eastern Desert of Egypt are the most distinctive lithological unit in the Arabian–Nubian Shield (ANS) ophiolite sequence which associated with major suture zones. Khor Um-Safi (KUS) serpentinites represent dismembered fragments of ophiolitic rocks located in the central Eastern Desert (CED) of Egypt. KUS serpentinites exhibit affinity to the typical metamorphic peridotites with harzburgitic protolith compositions. Their opaque mineral assemblage (pentlandite, heazlewoodite and magnetite) is similar to that observed in oceanic serpentinites and implies serpentinization under highly reducing conditions. They have refractory major element compositions with Al2O3 contents comparable to oceanic and active margin peridotites as well as Pan-African serpentinites. The Cr and TiO2 contents reflect evolution within a supra-subduction zone (SSZ) environment. This implication is confirmed by the Al2O3/SiO2 and MgO/SiO2 ratios which akin to ANS ophiolitic peridotites in fore-arc setting. Their enrichment in compatible trace elements (Cr, Ni and Co) reveals a depleted mantle peridotite protolith. Modelling trace elements indicates that they represent the mantle residues from 15 to 20 % melting of spinel peridotite at oxygen fugacity conditions of the QFM + 1 buffer. This range of melt extraction is consistent with the typical range of SSZ peridotite. Oxygen fugacity estimation suggests evolution under more oxidizing regime similar to modern fore-arc basin system. Moreover, this implication indicates that the KUS mantle represents arc lithosphere interacted with arc melt.

Nano-structured Ni3S2 is regarded as one of the most promising supercapacitor (SC) electrode materials due to its unique heazlewoodite phase and high electronic conductivity. However, preparation of Ni3S2 nanostructures with controllable chemical stoichiometry and morphology is still a challenge issue. Herein, we report a novel Ni3S2/3D graphene/nickel foam (Ni3S2/3D G/NF) composite electrode prepared by a chemical vapor deposition (CVD) followed by an electrodeposition. The as-prepared Ni3S2/3D G/NF composite electrode is stable with good chemical stoichiometry, binder-free and exhibits an excellent specific capacitance up to 2585 F/g with current density of 1 A/g,a high capacitance retention rate ~70.68% as the current density increases to 30 A/g, and a capacitance remaining ~88.9% after 5000 cycles of charge and discharge with the current density of 20 A/g. The perfect Ni3S2 heazlewoodite phase and good contact between Ni3S2 and the surface of 3D G/NF are believed to be responsible for the greatly improved conductivity and specific surface area of the as-prepare composite electrode. Our result has provided an effective way to significantly improve the capacitive property of Ni3S2 and shown a great potential for realizing its practical SC applications.

Nickel sulphides and nickel oxides nanoparticles have been synthesized from Ni(II) bis (N-alkyl-N-ethanoldithiocarbamate), represented as NiL12 (L1, with methyl group) and NiL22 (L2, with ethyl group). Both complexes were characterized using Fourier transform infra-red (FTIR), nuclear magnetic resonance spectroscopy and elemental analysis. The sulphides were prepared by solvothermal route in hexadecylamine, and X-ray diffraction analyses revealed that Heazlewoodite Ni3S2 and hexagonal α-NiS1.19 were the phases obtained from compounds NiL12 and NiL22 respectively. The nickel oxides nanoparticles were synthesized via calcination process in air, and presented as NiO1 and NiO2 of which both oxides are Bunsenite phase. The optical and morphology of the nanoparticles were studied using UV–visible spectroscopy and transmission emission microscopy (TEM) techniques. Cyclic voltammetry (CV) and impedance spectroscopy were used for their electrochemical evaluation in 1 M NaOH solution. The Au/NiO2 modified electrode was more electroactive and displayed faster electron transport at the electrode surface than the bare Au and Au/NiO1 electrodes. The modified Au/NiS electrode, showed poor voltammogram which could be due to the poor interaction between the nanoparticles and the electrolyte solution, while the CV of uncapped NiS showed redox peak with oxidation peak potential at 0.36 V and the reduction peak potential at 0.30 V.

Sulfur isotopes are a powerful geochemical tracer in high-temperature processes, but have rarely been applied to the study of mantle metasomatism. In addition, there are very limited S isotope data on sub-continental lithospheric mantle (SCLM) material. For cratonic regions, these data are restricted to sulfide inclusions in diamonds. To provide new constraints on the S isotope composition of the SCLM and on the source(s) of mantle metasomatic fluids beneath the diamondiferous Kimberley region (South Africa), we investigated the S isotope systematics of five metasomatised mantle xenoliths from the Bultfontein kimberlite. Pentlandite and chalcopyrite in these xenoliths were analysed by in situ secondary-ion mass spectrometry (SIMS), with bulk-rock material measured by gas source isotope ratio mass spectrometry techniques. Based on previous studies, the xenoliths experienced different types of metasomatism to one another at distinct times (∼180 and ∼90–80 Ma). Contained pentlandite grains show variable alteration to heazlewoodite (i.e. Ni sulfide) + magnetite. The in situ S isotope analyses of pentlandite exhibit a relatively restricted range between −5.9 and − 1.4 ‰ δ 34 S (compared to VCDT), with no statistically meaningful differences between samples. Chalcopyrite only occurs in one sample and shows δ 34 S values between −5.4 and − 1.0 ‰ . The bulk-rock Ssulfide isotope analyses vary between −3.4 and + 0.8 ‰ δ 34 S . Importantly, the only sample hosting dominantly fresh sulfides shows a bulk-rock δ 34 S value consistent with the mean value for the sulfides, whereas the other samples exhibit higher bulk 34S/32S ratios. The differences between bulk-rock and average in situ δ 34 S values are directly correlated with the degree of sulfide alteration. This evidence indicates that the elevated 34S/32S ratios in the bulk samples are not due to the introduction of heavy S (commonly as sulfates) and are best explained by isotopic fractionation coupled with the removal of light S during serpentinisation, when pentlandite is altered to S-poor mixtures of heazlewoodite and magnetite. Available bulk Ssulfide isotopic data for SCLM peridotite xenoliths are dominated by positive δ 34 S values, which contrasts with the negative values of the sulfides. These results imply that the mantle S isotope values from bulk peridotite samples are commonly modified by isotopic fractionation during serpentinisation. Therefore, the S isotopic composition of the SCLM may require revision. The limited isotopic variability shown by sulfides in the Bultfontein mantle xenoliths is probably due to intermittent tapping of a mantle source with a relatively restricted S isotope composition. While the asthenospheric mantle ( δ 34 S ≤ − 1.4 ‰ ) is a viable candidate, δ 34 S values as low as − 5.9 ‰ require input from recycled crustal material, possibly represented by the sulfur reservoir with negative δ 34 S signature that is missing in the >500 Ma sedimentary record and could have been subducted and stored in the Earth's mantle.

This study reports the first documented occurrence of platinum group minerals (PGM) and silicate inclusions in the podiform chromitites of the Naga-Manipur ophiolite complex, Indo-Myanmar orogenic belt, northeastern India. The studied chromitites were divided into three groups, high-Cr (Cr# = 0.72 to 0.80), intermediate-Cr (Cr# = 0.66 to 0.68), and high-Al (Cr# = 0.46 to 0.47). The bulk PGE content is low and varies in the range of 57–162 ppb. The chondrite normalized PGE patterns show that the studied chromitites are enriched in IPGE (Os, Ir, Ru) over PPGE (Rh, Pt, Pd), which in general is consistent with podiform chromitites hosted in a mantle sequence of ophiolites. All the PGE patterns are characterized by a consistent positive anomaly in Ru and some samples display a slight positive anomaly in Pt, compared with Rh and Pd. Most of the PGM occur in fresh chromite crystals consisting of single or polyphase grains composed of different PGM associated with Ni and Cu sulfides and silicates. The primary PGM paragenesis consists of minerals of the laurite (RuS 2 )–erlichmanite (OsS 2 ) series with minor osmium, iridium, and ruthenium. An unidentified Ir–Ni sulfide mineral, probably kashinite, was also observed. Based on their assemblage, we can argue that the PGM discovered in the Naga-Manipur chromitites are magmatic in origin and formed at relatively high sulfur fugacity, as testified by the presence of Os-rich laurite, erlichmanite, and kashinite. However, the relatively low PGE content of the investigated chromitites suggests that sulfur saturation was not achieved in the parental magma during the early stage of their crystallization. The presence of heazlewoodite in chromite fractures and in the altered matrix reflects its secondary origin, suggesting that it formed progressively during the serpentinization process. The presence of both Cr-rich and Al-rich chromitite suggest that the Naga-Manipur chromitite formed from separate intrusions of magmas derived from different depleted mantle sources ( e.g ., MORB versus boninitic) during evolution of the oceanic lithosphere from the MOR (Al-rich chromitite) towards a supra subduction zone (SSZ). Abundant hydrous silicates inclusions were found exclusively in the Cr-rich chromitites, whereas the Al-rich chromitites contain only clinopyroxene, confirming the proposed geodynamic evolution.

Heazlewoodite nickel sulfide (Ni3S2) has become attractive for electrocatalytic hydrogen evolution reaction (HER). However, strong sulfur–hydrogen bonds (S–Hads) formed on the surface of Ni3S2 greatly hinder the Hads desorption and reduce HER activity. Herein, amorphous NiWO4 nanoparticles-decorated Ni3S2 electrocatalysts (NiWO4/Ni3S2) have been constructed via a two-step hydrothermal method. The heterostructures exhibit much better HER performance than original Ni3S2 by delivering current densities of −10 and −100 mA cm−2 at low overpotentials of 136 and 274 mV, while those for Ni3S2 are 234 and 424 mV, respectively. Moreover, they display ultra-long stability of 75 h. Theoretical calculation proves the improved activity of NiWO4/Ni3S2 heterostructures is attributed to highly active interfaces between amorphous NiWO4 nanoparticles and Ni3S2 electrocatalysts. The strong electronic interaction between NiWO4 and Ni3S2 decreases the local electron density of Ni and S atoms, facilitates water adsorption on Ni-sites and optimizes hydrogen atom adsorption/desorption on adjacent S-sites with weakened S–Hads.