Effect Of Metal Dilution Research Articles

Electro-Elastic Modeling of Thermal Spin Transition in Diluted Spin-Crossover Single Crystals.

Spin-crossover solids have been studied for many years for their promising applications as optical switches and reversible high-density memories for information storage. This study reports the effect of random metal dilution on the thermal and structural properties of a spin-crossover single crystal. The analysis is performed on a 2D rectangular lattice using an electro-elastic model. The lattice is made of sites that can switch thermally between the low-spin and high-spin states, accompanied by local volume changes. The model is solved by Monte Carlo simulations, running on the spin states and atomic positions of this compressible 2D lattice. A detailed analysis of metal dilution on the magneto-structural properties allows us to address the following issues: (i) at low dilution rates, the transition is of the first order; (ii) increasing the concentration of dopant results in a decrease in cooperativity and leads to gradual transformations above a threshold concentration, while incomplete spin transitions are obtained for big dopant sizes. The effects of the metal dilution on the spatiotemporal aspects of the spin transition along the thermal transition and on the low-temperature relaxation of the photo-induced metastable high-spin states are also studied. Significant changes in the organization of the spin states are observed for the thermal transition, where the single-domain nucleation caused by the long-range elastic interactions is replaced by a multi-droplet nucleation. As to the issue of the relaxation curves: their shape transforms from a sigmoidal shape, characteristic of strong cooperative systems, into stretched exponentials for high dilution rates, which is the signature of a disordered system.

Spin transition properties of metal (Zn, Mn) diluted Fe(phen)2(NCS)2 spin-crossover thin films

We report here the effect of metal (Zn and Mn) dilution on the spin transition of Fe(phen)2(NCS)2 thin film spin-crossover (SCO) complex. The SCO complexes are deposited on glass and indium-tin-oxide (ITO) coated glass by dip-coating technique. The growth of the films is clearly confirmed by the appearance of the sharp optical absorption band at 521–540 nm corresponding to 1A1g to 1T1g ligand field absorption of the SCO complex. Although the microstructure of the films remains unaffected by metal dilution, substitution of Fe(II) by either Zn(II) (diamagnetic) or Mn(II) (paramagnetic) results in subtle changes in the bonding environment of the host metal as inferred form X-ray diffraction and Raman studies. The high spin to low spin (or vice versa) transition can be triggered either by electric field or magnetic field as revealed in the measured current (I)–voltage (V) profile or magnetization data of the films. The data further shows the effect of metal dilution on the spin transition temperatures(T1/2), produced hysteresis loop width and loop area, which are the crucial parameter for fabricating spin-based room temperature switching devices.

Adding a Suite of Chemical Abundances to the MACER Code for the Evolution of Massive Elliptical Galaxies

Abstract We add a suite of chemical abundances to the MACER (Massive AGN Controlled Ellipticals Resolved) 2D code, by solving 12 additional continuity equations for H, He, C, N, O, Ne, Mg, Si, S, Ca, Fe, and Ni with sources from AGB stars and Type Ia and II supernovae with metal yields based on standard stellar physics. New stars, formed in Toomre unstable circumnuclear disks (of a size ≲150 pc), are assumed to have a top-heavy initial mass function with a power index of 1.65. The metal dilution effects due to cosmic accretion are also included. With a high resolution of a few parsecs in central regions, resolved black hole accretion, and active galactic nucleus (AGN) feedback, we can track the metal enrichment, transportation, and dilution throughout the modeled massive elliptical galaxy of velocity dispersion ∼280 km s−1. We retrieve the chemical composition of the broad absorption line (BAL) winds launched by the central AGN, synthesize the X-ray features of the hot ISM, and find that (1) the simulated metallicity in the BAL winds could be up to ∼8 Z ⊙, while that of the hot ISM in the host galaxy is ∼2.3 Z ⊙, matching well with SDSS observations of BLR gas; (2) the X-ray emitting hot gas is metal-enriched with a typical value ∼2.5 Z ⊙; (3) the circumunuclear cold gas disk, where the metals are condensed, further enriched, and recycled, plays a critical role in the metal enrichment; (4) the black hole accretion rate linearly correlates with the star formation rate in the circumnuclear disk, i.e., , but lagged in time by roughly 106 yr.

High-spin → low-spin relaxation kinetics and metal dilution effects in 1D spin-crossover chain compounds

Light-Induced Excited Spin-State Trapping (LIESST) is a well-known phenomenon in spin-crossover (SCO) materials, studied since 1982 in solution and 1984 in the solid state, as it offers some interesting prospects in data storage. In this paper we discuss the influence of metal dilution on the lifetime of the photo-induced state in two 1D chain solid solution series: [FexZn1−x(btzp)3](BF4)2 and [FexZn1−x(endi)3](BF4)2 {btzp = 1,2-bis(tetrazol-1-yl)propane and endi = 1,2-bis(tetrazol-1-yl)ethane}. For each composition, we have determined the thermal spin transition temperature, T1/2, and the relaxation temperature of the photoinduced high-spin state, T(LIESST). A detailed analysis of the relaxation kinetics allowed a discussion of the evolution of this lifetime as a function of metal dilution.

Metal Dilution Effects on the Reverse Spin Transition in Mixed Crystals of Type [Co(1-x)Zn(x)(C16-terpy)2](BF4)2 (x = 0.1-0.7).

Metal dilution effects on reverse spin transition (rST) in mixed crystals of type [Co(1-x)Zn(x)(C16-terpy)2](BF4)2 (x = 0.1-0.7) were investigated by comparison with behavior of [Co(1-x)Fe(x)(C16-terpy)2](BF4)2 (x = 0.1-0.4). In the mixed crystals, the Zn complexes increased rST temperatures linearly with increasing values of x, without changing the hysteresis width, while the Fe complexes decreased rST temperatures. Moreover, the strength of the metal dilution effects in the CoZn mixed crystals is weaker than what occurs in the CoFe mixed crystals.

Microstructure and creep characteristics of dissimilar T91/TP316H martensitic/austenitic welded joint with Ni-based weld metal

This paper deals with characterization of microstructure and creep behavior of dissimilar weldment between the tempered martensitic steel T91 and the non-stabilized austenitic steel TP316H with Ni-based weld metal (Ni WM). Microstructure analyses were performed using light microscopy, scanning and transmission electron microscopy and energy-dispersive X-ray spectroscopy. The martensitic part of the welded joint exhibited a wide heat-affected zone (HAZ) with typical microstructural gradient from its coarse-grained to the fine-grained/intercritical region. In contrast, the HAZ of austenitic steel was limited to only a narrow region with coarsened polygonal grains. The microstructure of Ni WM was found to be very heterogeneous with respect to the size, morphology and distribution of grain boundaries and MC-type precipitates as a result of strong weld metal dilution effects and fast non-equilibrium solidification. Cross-weld creep tests were carried out in a temperature range from 600 to 650 °C at applied stresses from 60 to 140 MPa. The obtained values of apparent stress exponents and creep activation energies indicate thermally activated dislocation glide to be the governing creep deformation mechanism within the range of used testing conditions. The creep samples ruptured in the T91 intercritical HAZ region by the “type IV cracking” failure mode and the creep fracture mechanism was identified to be the intergranular dimple tearing by microvoid coalescence at grain boundaries. The TEM observations revealed pronounced microstructural differences between the critical HAZ region and the T91 base material before as well as after the creep exposure. ► Phase transformations affect the microstructures of T91 and TP316H HAZ regions. ► High weld metal dilution results in heterogeneous microstructure with MC carbides. ► Creep behavior of the studied weldment is controlled by its martensitic T91 part. ► The lowest hardness of T91 ICHAZ region corresponds with its lowest creep strength.

Microstructure and Mechanical Properties of Dissimilar Ferritic and Austenitic Steel Joints with an Intermediate Inconel-182 Buttering Layer

In this study, microstructure and mechanical properties of dissimilar weld joints between 2.25Cr-1Mo ferritic steel and 316L austenitic stainless steel, with and without an Inconel-182 buttering layer, have been investigated. The buttering layer widths produced on the machined edges of the ferritic steel plate were 3 and 5 mm. The dissimilar weld joints were butt-welded using a SMAW process with Inconel-182 electrodes. The results indicate that the ferritic base metal dilution effects are minimized due to buttering and a more uniform distribution of Fe, Ni, Cr and Nb contents is established over a broad region within the fusion zone. Moreover, a microstructure consisting of combined columnar and equiaxed dendrite with interdendritic Nb-rich particles is developed within the fusion zone as a result of buttering. Mechanical tests show that the average hardness, tensile ductility and impact energy of the weld metal were enhanced with increasing width of the buttering, while tensile strength properties were unaffected. It is observed that fracture surfaces of tensile specimens exhibit ductile features composed of ductile tear ridges with numerous interspersed dimples. However, the dominant fracture mode is noted to change from interdendritic to transdendritic with the use of a buttering layer.

Metal dilution effects on the switching properties of CoFe Prussian blue analogues

Recent years have seen the discovery of unusual and fascinating electronic properties in Prussian blue analogues. Thus, some CoFe Prussian blue analogues exhibit a photomagnetic effect. Here, we present the first study of metal dilution effect on the switching properties in two different CoFe Prussian blue analogues. This investigation shows that metal dilution strongly depends on the stoichiometry of the compounds and the nature of the diluting agents. The switching properties can either be totally killed for low dilution rate or be persist at a CoFe pair scale.

Effect of metal dilution on the light-induced spin transition in [FexZn1−x(phen)2(NCS)2] (phen = 1,10-phenanthroline)

The thermal and light-induced spin transitions in [Fe(x)Zn(1-x)(phen)2(NCS)2] (phen = 1,10-phenantholine) have been investigated by magnetic susceptibility, photomagnetism and diffuse reflectivity measurements. These complexes display a thermal spin transition and undergo the light-induced excited spin state trapping (LIESST) effect at low temperatures. For each compound, the thermal spin transition temperature, T1/2, and the relaxation temperature of the photo-induced high-spin state, T(LIESST), have been systematically determined. It appears that T1/2 decreases with the metal dilution while T(LIESST) remains unchanged. This behaviour is discussed on the basis of the kinetic study governing the photo-induced back conversion.

Effect of metal dilution on the thermal and light-induced spin transition in [FexZn1 –x(mtz)6][ClO4]2(mtz = 1-methyl-1H-tetrazole)

Download options Please wait... Article information DOI https://doi.org/10.1039/DT9940002285 Article type Paper Download Citation J. Chem. Soc., Dalton Trans., 1994, 2285-2288 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Effect of metal dilution on the thermal and light-induced spin transition in [FexZn1 –x(mtz)6][ClO4]2(mtz = 1-methyl-1H-tetrazole) T. Buchen, P. Poganiuch and P. Gütlich, J. Chem. Soc., Dalton Trans., 1994, 2285 DOI: 10.1039/DT9940002285 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Thomas Buchen Peter Poganiuch Philipp Gütlich

Magnetic Behavior of Spin-Crossover Iron(III) Complexes Adsorbed on the Surface of Silicon Dioxide and Metal Dilution Effects on Magnetism

Abstract The effects of metal dilution and adsorption on the surface of silicon dioxide on the spin-crossover behavior of [Fe(acpa)2]PF6, [Fe(acpa)2]BPh4, and [Fe(bzpa)2]PF6, which undergo fast spin-state interexchange on the 57Fe Mössbauer timescale have been studied by using 57Fe Mössbauer and EPR spectroscopies, powder X-ray diffraction and magnetic susceptibility, where Hacpa is N-(1-acetyl-2-propylidene)-2-pyridylmethylamine and Hbzpa N-(1-benzoyl-2-propylidene)-2-pyridylmethylamine. Solid solution compounds, [FexCo1−x(acpa)2]BPh4(x=0.035 and 0.074) and [Fe0.05Co0.95(bzpa)2]PF6 exhibit spin-crossover phenomena. No difference in the spin-state interexchange rate is observed between the diluted compound and the corresponding undiluted one as far as the rates are evaluated by Mössbauer spectroscopy. Mössbauer spectra for [Fe0.074Co0.926(acpa)2]PF6 exhibit only a pair of quadrupole doublets assigned to the low-spin state in the temperature range from 78 to 298 K. The spin-state interexchange rates for [Fe(acpa)2]BPh4 and [Fe(bzpa)2]PF6 adsorbed on the surface of silicon dioxide become slow compared to those for the corresponding pure complexes and the narrowing of the spin-state transition temperature range is observed. On the contrary no detectable differences in the spin-state interexchange rates are observed between the Mössbauer spectra for [Fe(acpa)2]PF6 adsorbed on the surface of silicon dioxide and that for the pure complexes. These observations are interpreted in terms of a spin-state transition behavior in these complexes which is affected by the packing state in the solid state, which is dependent on the characteristic structure of the respective complex.

Effect of metal dilution on the spin-crossover behavior in [FexM1-x(phen)2(NCS)2] (M = Mn, Co, Ni, Zn)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffect of metal dilution on the spin-crossover behavior in [FexM1-x(phen)2(NCS)2] (M = Mn, Co, Ni, Zn)P. Ganguli, P. Guetlich, and E. W. MuellerCite this: Inorg. Chem. 1982, 21, 9, 3429–3433Publication Date (Print):September 1, 1982Publication History Published online1 May 2002Published inissue 1 September 1982https://doi.org/10.1021/ic00139a032RIGHTS & PERMISSIONSArticle Views424Altmetric-Citations69LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (570 KB) Get e-Alerts Get e-Alerts

Mössbauer effect study of the electronic ground state of iron(II) in [ 57Fe xM 1−x(bipy) 3](ClO 4) 2 (M = Mn, Ni, Zn) and [ 57Fe xM 1−x(phen) 3](ClO 4) 2 (M = Ni, Zn) at very lowiron concentrations

Earlier work in our laboratory on the effect of metal dilution on the 5T 2(O h ⇌ 1A 1(O h) equilibrium in polycrystalline spin crossover systems of iron(II) has shown that the relative stability of the high spin state, 5T 2(O h), at a given temperature, increases markedly with decreasing iron concentration. These results have initiated the present work. Using 57Fe Mössbauer spectroscopy, we have investigated the electronic ground state of iron(II) in the highly diluted solid solutions [Fe xM 1−xL 3] with L = bipy, M = Mn, Ni, Zn, x ≲ 0.005 and L = phen, M = Ni, Zn, x ≲ 0.005. Although the critical field potential (V c) of the pure iron complexes, which are known to be low spin, is reported to be not far from the crossover point V c = P ( P , the mean spin pairing energy), the effect of metal dilution does not reduce the difference ¦ V c - P ¦ sufficiently as to thermally populate the 5T 2(O h) state at room temperature to any noticeable extent. ¦ V c - P ¦ has been estimated to be ≳ 1200 cm −1. The quadrupole splitting and the resonance line width are nearly the same in the pure compounds and the solid solutions. The isomer shift, however, is found to increase slightly in the order M = Fe < Ni < Zn < Mn, and parallels the increase in the ionic radii of the M ++ host ions.

Spin crossover in solid solution

The temperature dependent high spin (HS) ⇌ low spin (LS) transition, otherwise called spin crossover, has been well established for many first-row transition metal complexes, particularly for complexes of iron(II) [1]. The phenomenon has been observed mostly in the crystalline state, but also in solution. The spin crossover characteristics have been found to depend on various chemical influences, such as ligand substitution, the nature of the non-coordinating anion and the crystallizing solvent. It has been shown by 57Fe Mössbauer spectroscopy that the spin crossover behaviour in the solid solutions of [Fe xZn 1−x(2-pic) 3] Cl 2·EtOH (2-pic = 2-picolylamine) is also susceptible to metal dilution [2, 3]. At a given temperature, the HS state becomes favoured over the LS state with decreasing x. This may be qualitatively interpreted on the grounds of a cooperative domain model [2]. A phenomenological thermodynamic treatment [4] yields estimates of the changes of enthalpy and entropy as well as the domain size. A statistical model has also been successfully applied, which also allows to estimate the domain size and, in addition, an average effective frequency of the metalligand vibrational modes in each of the two spin states. Mössbauer effect studies of the solid solution of [Fe xCo 1−x(2-pic) 3] Cl 2·EtOH show similar results. The relative stability of the HS state, at a given temperature, also increases with decreasing x. The Fe x/CO 1−x/2-pic system, however, shows higher transition temperatures, at a given x, than the Fe x/Zn 1−x/2-pic system, apparently due to the more rigid lattice of the former system. The effect of metal dilution in solid solutions of [Fe xM 1−x(phen) 2(NCS) 2] (M = Co, Mn, Ni) as studied by Mössbauer spectroscopy [5] follows the same line: at a given temperature, the 5T 2(O h) state becomes favoured over the 1A 1(O h) state upon lowering x.