Substitution Of Pt Research Articles

The Effect of d10 Precious Elements on Structural, Magnetic and Elastic Properties of MnPt Alloy: A First-Principles Study.

MnPt's exceptional stability and extremely high Néel temperature have generated a lot of interest in data storage applications. Previously, it was reported experimentally that the MnPt alloy shows ferromagnetic (FM) behavior at room temperature. In this study, the effects of partial substitution of Pt with Pd, Au, and Ag on magnetic properties is investigated using density functional theory. The stability of Mn50Pt50-xMx (M = Pd, Au, Ag, x = 6.25, 12.5, 18.75) alloys was assessed by determining their thermodynamic, magnetic, and mechanical properties. The calculated lattice constants of Mn50Pt50 agree well with available theoretical results. The Mn50Pt50-xMx alloys' formability was assessed by measuring the thermodynamic stability using the heat of formation. It was found that B2 Mn50Pt50-xPdx alloys (0 ≤ x ≤ 18.75) are thermodynamically stable due to the negative heat of formation close to that of a pristine MnPt alloy. Based on the elasticity results, the B2 Mn50Pt50-xPdx is most likely to undergo martensitic transformation for the entire considered composition range. From the calculated values of the Poisson's ratio, it is shown that an increase in Pd, Ag, and Au effectively improves the ductility of the B2 Mn50Pt50-xMx compounds. It was revealed that ferromagnetism is maintained with Pd addition but significantly reduced in the case of Au and Ag. Thus, this work showed that density functional theory can be exploited to propose new possible compositions for future magnets in spintronic applications.

Diffusion-controlled growth and microstructural evolution between Pt and Pd containing B2-NiAl bondcoats and Ni-based single crystal superalloy

Pt-modified NiAl bond coats are used to extend the lifetime of blades in gas turbine engine applications. However, they suffer from the growth of deleterious precipitates within the interdiffusion zone. Partial substitution of Pt by Pd is advantageous in reducing the interdiffusion zone thickness between the bond coat and the superalloy, providing comparable oxidation properties, and critically reducing the propensity to form brittle (Pt,Ni)Al2 precipitates. In this study, we utilize the pseudo-binary diffusion couple method to estimate the interdiffusion coefficients of Ni and Al in Pd, Pd-Pt and Pt-modified nickel aluminides. Additionally, the main and cross-interdiffusion coefficients are estimated in the ternary diffusion couples. The estimated diffusion coefficients in the β-NiAl phase reflect on the thickness of the β phase in the superalloy bond coat interdiffusion zone. Pd reduces the pseudo-binary interdiffusion coefficients of Ni–Al and also decreases the main and cross-ternary interdiffusion coefficients. This correlates with the reduction of the interdiffusion zone thickness by Pd. The diffusion process is strongly assisted by point defects in this phase. Ab initio-informed defect calculations are done to explain diffusion retardation in the presence of Pd (compared to Pt) with decreased defect concentrations. Furthermore, through in-depth microstructure characterization performed by electron probe micro analyser, transmission electron microscopy, and atom probe tomography, the presence of σ, R and μ phases as TCP precipitates in the interdiffusion zone are identified. The results give insights into the coatings’ diffusional properties that influence the service life of the product.

Multi‐Component PtFeCoNi Core‐Shell Nanoparticles on MWCNTs as Promising Bifunctional Catalyst for Oxygen Reduction and Oxygen Evolution Reactions

AbstractThe development of commercially viable fuel cells and metal‐air batteries requires effective and cheap bifunctional catalysts for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). Multi‐component Pt−Fe−Co−Ni nanoparticles on multi‐walled carbon nanotubes (MWCNTs) were synthesized by wet chemistry route via NaBH4 reduction of metal salts, followed by sintering at different temperatures. The catalyst demonstrates an excellent ORR activity and a promising OER activity in 0.1 m KOH, with a bi‐functional over‐potential, ΔE of 0.83 V, which is comparable to the values of Pt/C or RuO2. Furthermore, it shows outstanding long‐term stability in ORR and OER, namely diffusion limited current density at a potential of 0.3 V decreased just by 5.5 % after 10000 cycles in ORR. The results of the PFCN@NT300 indicate a significant effect of the substitution of Pt by the transition metal (TM) and the formation of nanoparticles on the catalytic performance, especially in the OER.

A computational study of the thermodynamic and magnetic properties of Co-alloyed MnPt

Magnetic functional materials remain an area of research interest for applications in electronic devices. Among these materials, Mn50Pt50 alloy has received a great deal of attention in practical potential applications such as spintronics due to its high-thermal and magnetic stability. It was reported previously that L10 Mn50Pt50 alloy shows ferromagnetic ordering at room temperature. In this study, the effect of the partial substitution of Pt with Co was investigated using density functional theory (DFT) approach. The thermodynamic, magnetic and mechanical properties were determined to check the stability of Mn50Pt50-xCox alloys. The results showed that the L10 phase has the lowest heat of formation when the c/a ratio is 1.10 for 6.25 at.% Co. Overall magnetic moments improve with an increase in Co compositions when the c/a ratio is 1.10. The obtained results reveal that Mn50Pt50-xCox alloys exhibit attractive magnetic and mechanical properties for future magnets in spintronics applications.Graphical

Effects of Pt substitution on the formation and magnetic behavior of a Ga–Pd–Tb 2/1 approximant

A systematic study on the formation and magnetic properties of Tsai-type 2/1 approximants in Ga–(Pd, Pt)–Tb alloys was conducted by replacing Pd with Pt in a previously reported antiferromagnetic Ga–Pd–Tb 2/1 approximant. Tsai-type 2/1 approximants were found to form quaternary Ga–(Pd, Pt)–Tb alloys as well as ternary Ga–Pt–Tb alloys. Magnetic susceptibility measurements indicated that the substitution of Pt for Pd in the 2/1 approximants resulted in a change in the magnetism from antiferromagnetic to spin-glass-like behavior.

The effect of increasing hafnium on the microstructure, phase transformation temperatures and hardness of TiPtHf potential shape memory alloys

Shape Memory Alloys (SMAs) are popular due to their ability to regain their original shape after plastic deformation. Binary TiPt alloys have low shape memory effects and as such, alloying elements are added to improve these properties. The effect of alloying and increasing the Hf in binary Ti50Pt50 to form ternary Ti50Pt50−xHfx (x=6.25,12.5 and 18,25 at.%) on the microstructure, transformation temperatures and hardness in the as cast and solution heat treatment conditions were investigated. In the as-cast condition SEM EDS analysis showed that alloying with Hf resulted in the formation of dark grey interdendritic regions comprised of Ti-rich phases and the increase in Hf content (at. %) led to an increase in the size of these interdendrites. Solution heat treatment (SHT) of the alloy led to a decrease in the size of the dark grey interdendritic regions and the formation and increase of dark black regions with increasing Hf content (at. %). Differential scanning calorimetry showed that partial substitution of Pt with 6.25 at. % Hf decreased the transformation temperature of the alloy below that of Ti50Pt50 in both conditions. Increase in to Hf 12.5 and 18.25 at. % increased the transformation temperatures above those of Ti50Pt50 binary alloy in both conditions. SHT of 12.5 at. % Hf significantly reduced the AS and MS temperatures. Alloying and increase in Hf content (at. %) increased the hardness of the alloys above that of Ti50Pt50. SHT increased the hardness of the alloys above that of Ti50Pt50 and the as-cast alloys.

Selective Removal of Isolated Ni of the Electroplated Ni-P Catalyst for High-Performance Hydrogen Evolution Reaction

A commercialization of green hydrogen is necessary to construct a hydrogen economy. In this context, a water electrolysis which is composed by the hydrogen evolution reaction and its anodic counter reaction is evaluated as an optimal generation method of green hydrogen. As compared with replaceable oxidative reaction such as oxygen evolution reaction (OER) and chlorine evolution reaction (COR), the development of efficient electrocatalyst for HER, which is an irreplaceable cathodic reaction of water electrolysis, became the most urgent assignment in both of acidic and alkaline water electrolysis.Acidic HER is divided by two steps: adsorption and desorption of proton, while the difference of Gibbs free energy between the first (M + proton, M means reaction site of catalyst) and final (M + H2) state is zero. Thus, each reaction rate of adsorption and desorption step decreases when the proton adsorbed free energy shows positive and negative value, respectively. Furthermore, an ideal catalyst shows the proton adsorbed free energy of zero. In particularly, alkaline HER needs to separate water molecule to proton and hydride to supply the proton. Therefore, it showed a different free energy at the intermediate though an equal catalyst due to the addition of hydride absorbed free energy, but it also need a zero-like free energy. In this context, platinum (Pt) based catalyst is known as the most zero-like proton adsorbed free energy in alkaline media, however its high cost owing to a high rarity of Pt becomes the research gap of HER catalyst.As a substitution of Pt based catalyst, transition metal phosphide (TMP) has received a lot of attention due to its efficient electron transfer between metal and phosphorus. Furthermore, nickel phosphide (Ni-P) is evaluated as the most suitable catalyst for HER due to the high catalytic activity and practical usefulness. The nickel (Ni) has lower electronegativity than phosphorus (P), and the electron transfers from Ni to P. Therefore, a proton and hydride adsorbed at the negatively charged P and positively charged Ni, respectively. Because the proton desorption step becomes a rate determining step of Ni without P for HER catalyst, the higher interaction between adsorbed proton and hydride increase the kinetic of not only desorption step but also overall HER. Based on the theoretical advantage, a lot of researchers are studying to find the most suitable ratio between Ni and P. For instance, J. Zhang formed P vacancy on Ni12P5 catalyst for alkaline HER to balance the kinetic of adsorption and desorption of proton, while the Ni12P5 compound has negative proton adsorbed free energy without the P vacancy. [1] Although the formation of P vacancy increased the proton adsorbed free energy, there was limitation on variance of P ratio.Unlike the crystalline Ni-P compound, an amorphous Ni-P compound which is fabricated by an electroplating process is facile to control the ratio between Ni and P. However, the electroplated Ni-P has a critical limitation in increasing P ratio up to about 25 at% because P-rich amorphous Ni-P has too low electric conductivity to be electroplated. Furthermore, ‘isolated Ni’ which has low bonding with P is formed due to nonuniformity of crystal structure between Ni and P, then the isolated Ni has lower redox potential than Ni-P. A galvanic corrosion between the grain of isolated Ni and Ni-P becomes a critical cause of high degradation rate of amorphous Ni-P catalyst. In this study, we suggest a surficial engineering process to control the ratio between Ni and P after the electroplating of Ni-P compound on carbon fiber paper (Ni-P/CFP) catalyst to improve the activity and stability for HER in alkaline media.Using the difference of redox potential between the isolated Ni and Ni-P, the surficial engineering is designed as a dealloying cycle of metal alloy to selectively remove the isolated Ni. As a result, The Ni-P/CFPx10 (10 times dealloying-cycled Ni-P/CFP catalyst) catalysts show higher P content of 29.6 at% on the surface (24.9 at% before dealloying treatment). Furthermore, the surficial engineering arouses the recrystallization of Ni-P compound, thus the permeated amount of P increases according to the number of surficial engineering cycle. Because of the mentioned influences, the Ni-P/CFP catalyst shows higher catalytic activity and durability after the surficial engineering. In particular, the Ni-P/CFPx10 catalysts shows the 58 mV lower overpotential at -10 mA cm-2 the pristine Ni-P/CFP catalyst (247 mV) in alkaline HER.[1] Jingjing Duan, Sheng Chen, C8sar A. Ort&z-Ledln, Mietek Jaroniec, and Shi-Zhang Qiao, Phosphorus Vacancies that Boost Electrocatalytic Hydrogen Evolution by Two Orders of Magnitude, Angew. Chem. Int. Ed., 59, 2020, 8181.

Electrochemical Surface Treatment to Enhance the Activity and Stability of Ni-P/CFP Electrocatalysts in Hydrogen Evolution Reaction

To construct an efficient and eco-friendly hydrogen economy, it is necessary to improve a cost competitiveness of green hydrogen. In this respect, a water electrolysis has been considered as an ideal production method of green hydrogen, where hydrogen evolution reaction (HER) is an irreplaceable cathodic reaction, while the various oxidative reactions such as oxygen evolution reaction (OER) or chlorine evolution reaction (CER) can be coupled as an anodic reaction. Because the HER becomes an essential reaction of water electrolysis, to facilitate efficient HER is one of the most important goal in a water electrolysis, in particular, to adopt and design the cost-effective HER catalysts are needed to lower the high activation energy of HER.As a theoretical and practical researches, a platinum (Pt) based compound is known as the most effective catalyst which has a zero-like proton adsorbed free energy in both of acidic and alkaline media, however its high cost owing to a high rarity of Pt becomes the research gap of HER catalyst. As a substitution of Pt based catalyst, transition metal phosphide (TMP) has received a lot of attention among the various non-noble metal based catalyst. Among them, nickel phosphide (Ni-P) is evaluated as the most suitable catalyst for HER due to the high catalytic activity and practical usefulness. The nickel (Ni) has lower electronegativity than phosphorus (P), and the electron transfers from the Ni to P. In other words, a proton and hydride adsorbed at the negatively charged P and positively charged Ni, respectively. Because homogeneous Ni metal has a lower kinetic of proton desorption than adsorption, the higher interaction between adsorbed proton and hydride increases the kinetic of not only desorption step but also overall HER. However, in conventional fabrication methods of Ni-P such as hydrothermal and electroplating, it is difficult to control the ratio of Ni and P, which might maximize the kinetics and moreover, stability.In this context, we suggest a surficial engineering process to control the ratio between Ni and P after the electroplating of Ni-P compound on carbon fiber paper (CFP) for the efficient HER catalyst in both of acidic and alkaline media. Because ‘isolated Ni’ which has a low bonding with P has different redox potential with Ni-P, the surficial engineering is designed as a dealloying cycle of metal alloy to selectively remove the isolated Ni. As a result, The Ni-P/CFPx10 and Ni-P/CFPx20 (10, 20 times dealloying-cycled Ni-P/CFP catalyst) catalysts show higher P content of 29.6 and 36.5 at% on the surface (24.9 at% before dealloying treatment). Furthermore, the surficial engineering arouses the recrystallization of Ni-P compound, thus the permeated amount of P increases according to the number of surficial engineering cycle. In particular, the Ni-P/CFPx20 and Ni-P/CFPx10 catalysts shows the 55 mV and 58 mV lower overpotential at -10 mA cm-2 the pristine Ni-P/CFP catalyst (179 mV for acidic HER and 247 mV for alkaline HER) in acidic and alkaline HER, respectively. Figure 1

Synthesis, structural evolution, and dielectric properties of a new perovskite solid solution (Pb0.5Sr0.5)(Zr0.5Ti0.5)O3–PbTiO3

AbstractTo explore lead‐reduced dielectric materials in the SrTiO3–PbTiO3–PbZrO3 ternary system, a novel solid solution between relaxor ferroelectric (Pb0.5Sr0.5)(Zr0.5Ti0.5)O3 and ferroelectric PbTiO3, namely (1 − x)(Pb0.5Sr0.5) (Zr0.5Ti0.5)O3–xPbTiO3 (lead–strontium–zirconate–titanate [PSZT]–PT), has been synthesized in the perovskite structure by high‐temperature solid‐state reaction method in the form of ceramics. The crystal structure and phase symmetry of the materials synthesized were analyzed and resolved based on X‐ray powder diffraction (XRD) data through both the Pawley and Rietveld refinements. The results of the structural refinements indicate that at low PT‐concentration end of the solid solution system, for example, x = 0.05, the PSZT–PT solid solution exhibits a cubic structural symmetry (with the space group Pm‐3m). As the PT concentration (x) increases, the structure of (1 − x)PSZT–xPT gradually transforms from the cubic to a tetragonal (P4mm) phase. In the composition range of x = 0.10–0.25, a mixture of the cubic and tetragonal phases was identified. As the concentration of PT increases, the proportion of the tetragonal phase increases at the expense of the cubic phase. For a composition of x > 0.25, a pure tetragonal phase is observed. The dielectric properties of the materials were studied by measuring the permittivity as a function of temperature at various frequencies. For the composition of x = 0.05, the temperature dependence of dielectric constant shows typical relaxor behavior. For x = 0.35, the dielectric peaks indicate a normal ferroelectric phase transition. Overall, a structural transformation from a central‐symmetric, nonpolar cubic phase to a non‐centrosymmetric, polar tetragonal phase is induced by the substitution of PT for PSZT in the pseudo‐binary solid solution of (1 − x)PSZT–xPT, which also reveals an interesting relaxor to ferroelectric crossover phenomenon.

Disorder-induced transition from type-I to type-II superconductivity in the Dirac semimetal PdTe2

We report a doping study directed to intentionally induce disorder in ${\mathrm{PdTe}}_{2}$ by the isoelectronic substitution of Pt. Two single-crystalline batches ${\mathrm{Pd}}_{1\ensuremath{-}x}{\mathrm{Pt}}_{x}{\mathrm{Te}}_{2}$ have been prepared with nominal doping concentrations $x=0.05$ and $x=0.10$. Sample characterization by energy dispersive x-ray spectroscopy revealed Pt did not dissolve homogeneously in the crystals. For the nominal value $x=0.10$ small single crystals cut from the batch appeared to have $x=0.09$, as well as the nonstoichiometric composition ${\mathrm{Pd}}_{0.97}{\mathrm{Pt}}_{<0.004}{\mathrm{Te}}_{2.03}$. Magnetic and heat capacity measurements demonstrate a transition from type-I to type-II superconducting behavior upon increasing disorder. From transport measurements we calculate a residual resistivity ${\ensuremath{\rho}}_{0}=1.4\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{\ensuremath{\Omega}}\phantom{\rule{0.16em}{0ex}}\mathrm{cm}$ suffices to turn ${\mathrm{PdTe}}_{2}$ into a superconductor of the second kind.

Reducing the high hydrogen binding strength of vanadium carbide MXene with atomic Pt confinement for high activity toward HER

To construct an efficient electrocatalyst for HER, the high binding energy of MXene must be mitigated through electronic modulation of active sites. Here, we propose atomic Pt substitution in V2CTx MXene to modulate the electronic structure and promote catalytic activity toward HER. Pt–V2CTx exhibits high HER performance with a low overpotential of 27 mV at −10 mA cm−2 in acidic media, comparable to the commercial Pt/C catalyst. X-ray absorption spectroscopy and DFT calculations indicate that the Pt atoms are efficiently confined to the V vacancy sites of V2CTx, accompanied by a unique electronic structure. The atomic substitution of Pt with higher occupied d states at the Fermi energy of Pt and surface oxygen sites can significantly indicate an optimum hydrogen-binding free energy (∆GH*), promoting HER performance. This work introduces further prospects for developing efficient electrocatalysts by feasible electronic regulation and highly improved catalytic activity through rational atomic engineering.

Naldrettite (Pd2Sb): A new find in Brazil and comparison with worldwide occurrences

ABSTRACT Naldrettite (Pd2Sb) is a PGM discovered in 2005 in Mesamax Northwest deposit, Ungava region, Quebec, Canada. Before and after its approval, PGM with the naldrettite type composition have been reported from a number of localities worldwide. Most frequently, naldrettite has been documented in magmatic Ni–Cu–PGE sulfide deposits, hydrothermal veins in porphyry coppers of the Cu–Au type, and PGE deposits of Alaskan-type zoned intrusions. Naldrettite has been occasionally found in metasomatic Sb–As sulfide ore, metamorphic Ni–oxide ore, and podiform chromitites, although these occurrences have not been fully constrained by solid chemical analyses or paragenetic reconstruction. In this paper we report the first discovery of naldrettite in Brazil. This new finding occurs in a chromitite sample collected in the Luanga Complex, a Neo-archaean layered intrusion in the Carajás Mineral Province. Paragenetic association with alteration assemblages (ferrianchromite, Fe-hydroxides, chlorite) suggests precipitation of naldrettite from metamorphic hydrothermal fluids. The average composition of the Luanga sample (Pd1.76Pt0.24)Σ2.00(Sb0.57As0.43)Σ1.00 shows major substitution of Pt and As. These elements were derived from the breakdown of primary sperrylite, and were incorporated in naldrettite deposited by percolating fluids, at temperature below 350 °C (maximum temperature registered by the crystallization of associated chlorite). An overview of documented occurrences indicates that naldrettite can form in a variety of igneous rocks (ultramafic, mafic, felsic), even involving minimal concentrations of Pd and Sb. Crystallization of naldrettite generally occurs in the post-magmatic stage due to the activity of hydrothermal fluids containing volatile species Sb, As, Bi, Te, and Pd due to its higher mobility compared with the other PGE. A major issue concerns the origin of fluids that can be: (1) “residual”, after the main crystallization of the host magma, (2) “metamorphic”, during regional metamorphism or serpentinization, and (3) “metasomatic”, emanating from an exotic magma intrusion. The combination of two or three of these factors is the most likely process observed in the naldrettite-bearing complexes.

Efficient Schottky Junction Construction in Metal-Organic Frameworks for Boosting H2 Production Activity.

Manipulation of the co‐catalyst plays a vital role in charge separation and reactant activation to enhance the activity of metal‐organic framework‐based photocatalysts. However, clarifying and controlling co‐catalyst related charge transfer process and parameters are still challenging. Herein, three parameters are proposed, V transfer (the electron transfer rate from MOF to co‐catalyst), D transfer (the electron transfer distance from MOF to co‐catalyst), and V consume (the electron consume rate from co‐catalyst to the reactant), related to Pt on UiO‐66‐NH2 in a photocatalytic process. These parameters can be controlled by rational manipulation of the co‐catalyst via three steps: i) Compositional design by partial substitution of Pt with Pd to form PtPd alloy, ii) location control by encapsulating the PtPd alloy into UiO‐66‐NH2 crystals, and iii) facet selection by exposing the encapsulated PtPd alloy (100) facets. As revealed by ultrafast transient absorption spectroscopy and first‐principles simulations, the new Schottky junction (PtPd (100)@UiO‐66‐NH2) with higher V transfer and V consume exhibits enhanced electron‐hole separation and H2O activation than the traditional Pt/UiO‐66‐NH2 junction, thereby leading to a significant enhancement in the photoactivity.

Structural disorder and antiferromagnetism in LaNi1–xPtxO3

We report on the B-site substitution of Pt for Ni in the system LaNi1–xPtxO3. The system can only be synthesized between x ​≤ ​0.50, with LaNiO3 (x ​= ​0.00) and the stoichiometric double perovskite La2NiPtO6 (x ​= ​0.50) as the end members. Higher Pt-contents (x ​> ​0.50) are unachievable due to the preference of Pt to being in oxidation state ​+ ​IV in octahedral coordination. Upon introducing Pt into LaNiO3, a phase transformation from rhombohedral (R-3c) to monoclinic (P21/n) symmetry is observed for 0.075 ​≤ ​x ​≤ ​0.125, where all monoclinic samples are B-site ordered, and Pt show a strong preference for the Pt-site (2c-site) for all compositions (x ​≥ ​0.20). Powder X-ray diffraction analysis reveal disorder of the Pt-distribution in several of the non-equimolar samples (0.20 ​≤ ​x ​≤ ​0.40), which point toward cluster formation with domains of high and low Pt-content within each sample. La2NiPtO6 further show an antiferromagnetic transition at ∼ 40 ​K. A similar transition is observed for all monoclinic samples (x ​≥ ​0.20), however, the transition is less pronounced for lower x. This is explained in terms of the structural disorder, i.e. by the coexistence of antiferromagnetic domains with long range order and paramagnetic domains dominated by short range antiferromagnetic interactions.

New minerals and the first mineral occurrences in the Kupferschiefer (U, REE, HgS, chloride minerals PtAs2, Pt(Sb,Bi)2, PtBi2), Poland, and their genetic meaning

Abstract Main U minerals in the Lubin and Polkowice mines in decreasing order of abundance are: uraninite, brannerite, metazunerite, metauranospinite, uranospinite, thucholite, monazite-huttonite, coffinite, and becquerelite. All these minerals are associated mainly with noble metal mineralization at the redox interfaces. Main minerals of REE are: (i) brannerite, monazite-huttonite in Noble Metals Bearing Shale (NMBS), (ii) florencite in Mo-Re shales and (iii) minor phospates in Cu-black shales derived from oxidation of organic matter. The latter, however, are controlling no more than 1/5 of the REE budget. Chloride minerals and sulphates are ubiquitous phases associated with Cu sulphides. They are represented by chlorargylite, cotunnite and penfieldite. Halite and sylvite form cubic inclusions in gypsum, up to 3 mm in chevrel compound, where they occur together with thiosulphates, anna-bergite and erithrite and Ni-Co-diarsenides. Sylvite is most common in lensoidal accumulations of semi massive kaolinite + chalcocite + gypsum at the contact between black shale and the top part of white sandstone. Such lenses have been traced over a distance of up to 30 m in the Lubin West and Polkowice East mines. Sylvite and halite have been so far overlooked during investigations of the Kupferschiefer because of applying standard cuƫng and polishing procedures using water as a lubricant. The Au content in native gold may reach exceptionally up to 97.40 wt% in a dolomitic reef from the Lubin West Mine. Gold forms four characteristic micro to nano-textures. Organic matrix of thucholite indicates correlation of Pt-Ni-V suggesting substitution of Pt in tetrapyrrole ring. Sperrylite, geversite and insizwaite appear at the western perimeter of Cu-sulphide deposit, where the redox gradient is so strong that almost all organic matter is gone. Platinum has forms its own minerals trapped in microfractures in anilite-digenite-spionkopite-yarrowite-bornite composite grains present in the reddened NMBS. Celestine-barite solid solution is one of the main accessory minerals in the Kupferschiefer. It has Sr/Ba ratio around 2.5 and 7.5. Euhedral uraninite associated with celestine-barite yielded U/Pb age of 84 ± 1 Ma, based on four grains measurements.

Evolution of the Structural and Magnetic Properties of Bulk Fe61Co10B20W1Y8−XPtx Alloys through the Partial Substitution of Pt for Y

This paper presents the results of an investigation into rapidly quenched Fe-based alloys with the chemical formula: Fe61Co10B20W1Y8−xPtx (where x = 3, 4, 5). In these alloys, a small quantity of Pt was added, and the Y content was reduced concurrently. Samples of the aforementioned alloys were injection-cast in the form of plates with the dimensions: 0.5 mm × 10 mm × 10 mm. The resulting structure was examined using X-ray diffractometry (XRD), Mössbauer spectroscopy and scanning electron microscopy (SEM). The results of the structural research reveal that, with a small addition of Pt, areas rich in Pt and Y are created—in which Fe-Pt and Pt-Y compounds, with different crystallographic systems, are formed. It has also been shown that an increase in Pt content, at the expense of Y, contributed to the formation of fewer crystalline phases, i.e., it allowed a material with a more homogeneous structure to be obtained. Magnetic properties of the Fe61Co10B20W1Y8−xPtx (where x = 3, 4, 5) alloy samples were tested using a vibrating sample magnetometer (VSM). The magnetic properties of the investigated materials revealed that the saturation magnetisation increased with increasing Pt content, at the expense of Y. This effect is due to the occurrence of different proportions of crystalline magnetic phases within the volume of each alloy.

Improved crystallographic compatibility and magnetocaloric reversibility in Pt substituted Ni2Mn1.4In0.6 magnetic shape memory Heusler alloy

We present here the improved crystallographic/geometric compatibility and magnetocaloric reversibility by measurement of magnetic entropy change using different protocols in 10% Pt substituted Ni2Mn1.4In0.6 magnetic shape memory alloy. The substitution of Pt reduces the thermal hysteresis about 50% to the Ni2Mn1.4In0.6. The origin of the reduced thermal hysteresis is investigated by the crystallographic compatibility of the austenite and martensite phases. The calculated middle eigenvalue of the transformation matrix turned out to be 0.9982, which is very close to 1 (deviation is only 0.18%) suggests for the crystallographic compatibility between the austenite and martensite phases in Ni1.9Pt0.1Mn1.4In0.6. A very small thermal hysteresis and crystallographic compatibility between two phases in this alloy system indicate a stress-free transition layer (i.e. perfect habit plane) between the austenite and martensite phase, which is expected to give reversible martensite phase transition and therefore reversible magnetocaloric effect (MCE) as well. The calculated value of the isothermal entropy change (ΔSiso) using the magnetization curve under three different measurement protocols (i.e. isothermal, loop, and isofield measurement protocol) is found to be nearly same indicating a reversible MCE in the present alloy system. Our work provides a path to design new magnetic shape memory Heusler alloys for magnetic refrigeration and also suggest that any of the above measurement protocol can be used for the calculation of ΔSiso for materials satisfying geometrical compatibility condition.

Factors influencing selectivity in the liquid-phase phenol hydrodeoxygenation over ZSM-5 supported Pt/Ir and Pt+Ir catalysts

The effect of partial Pt substitution by Ir on the catalytic response of bimetallic Pt-Ir/ZSM-5 (Pt/Ir = 1) catalyst in the liquid-phase hydrodeoxygenation (HDO) of phenol was investigated. To evaluate the catalyst intrinsic activity, the ZSM-5 supported Pt, Ir and Pt + Ir catalysts were prepared with similar total metal loading (ca. 3 wt.%) and acidity. The catalysts were characterized by several physical and chemical techniques and tested in the HDO of phenol reaction carried out in a batch reactor at T = 200 °C under H2 pressure of 3.0 MPa. For all the catalysts, the phenol transformation mainly proceeds via hydrogenation + dehydration (HYD reaction route) leading to cyclohexane as the main product (selectivity 60–96%). Partial substitution of Pt by Ir in catalyst formulation (Pt50-Ir50/ZSM-5) enhances both activity and selectivity toward O-free products. This was associated to Ir surface enrichment (from HRTEM). The Ir/ZMS-5 and Pt50-It50/ZMS-5 catalysts having well dispersed Ir nanoparticles were more selective toward dehydration than Pt/ZSM-5 having Pt species with a broad size distribution range. The catalyst activity-structure correlation suggests that the dehydration of cyclohexanol (intermediate product) can occur at the interface between the metal and acid sites of the support.

The Study for Two-dimensional PtX2 (X=S Se Te) Which Have Geometrical Structures Fully Composed of Pentagons.

In this paper, we mainly use the first-principles method based on density functional theory to study the structure and electronic properties of three new two-dimensional materials consisting of five-membered rings, PtS2, PtSe2 and PtTe2. Based on the structure of the pentagon tile of Cairo, the substitution of Pt, S and Pt, Se and Pt, Te between the atoms in the unequal position of the minimum repeating unit will result in different structures, and then different structures will be obtained. The obtained structure is optimized, and the phonon spectrum is calculated. Finally, the three phonon spectrum stable structures of penta-PtS2, penta-PtSe2 and penta-PtTe2 are obtained. Then we proved the stability of these three structures from the aspects of dynamics and thermodynamics. Then their electronic properties were studied. From the calculated energy band diagram, we found that these three structures are indirect band gap semiconductors.

Single Pt atoms stabilized on Mo2TiC2O2 for hydrogen evolution: A first-principles investigation.

Single-atom catalysis offers an effective way to reduce the amount of used noble metals and maximizes their catalytic activity. We systematically explore electrocatalytic performances of Pt doped Mo2TiC2O2 monolayer by the first principles calculations. Our results show that the presence of donor defects in Mo2TiC2O2 can always increase the reaction free energy of hydrogen adsorption and further promotes the performance in hydrogen evolution reaction (HER). More interestingly, the substitution of Pt for O in the Mo2TiC2 can modify the free energy to an ideal value and is responsible for the significantly enhanced catalytic activity. Furthermore, the large value of diffusion barrier indicates that single Pt atoms can be stabilized onto the O vacancy sites, which can effectively prevent them to aggregate into nanoparticles. Our works are useful for understanding the recent experimental observations and pave the way for further experimental improvements of catalytic activity for the HER.