378784-00-0Relevant articles and documents
Abnormal infrared effects of nanostructured rhodium thin films for CO adsorption at solid/gas interfaces
Lin, Wen-Guang,Sun, Shi-Gang,Zhou, Zhi-You,Chen, Sheng-Pei,Wang, Han-Chun
, p. 11778 - 11783 (2002)
Nanometer-scale thin films of rhodium supported on glassy carbon (nm-Rh/GC) were prepared by electrochemical deposition using cyclic voltammetry. STM studies demonstrated that the Rh film is made of layered crystallites of an average size 230 nm (1) ?? 90 nm (w) ?? 10-30 nm (h). In situ FTIR spectroscopic investigations revealed, for the first time, that the nanostructured film exhibits abnormal infrared effects (AIREs) for CO adsorption at solid/gas interfaces. The AIREs are characterized by the inverting of the direction of IR bands of adsorbed CO (COad), an enhancement of IR absorption intensity, and an increase in the full width at half-maximum (FWHM) of the bands. The inversion of the direction of the absorption bands and the increase in the FWHM are observed in spectra of CO on nm-Rh/GC of different Rh film thicknesses; the enhancement of IR absorption depends strongly on the thickness of the Rh film. The maximum enhancement factor has been determined to be 10.38 for an Rh film thickness of 79 nm. The present study demonstrated that the AIREs are general phenomena exhibited by nanostructured thin-film materials at both solid/liquid and solid/gas interfaces; they are of importance in revealing the intrinsic properties of 2D nanomaterials.
Nucleation behavior in electroless displacement deposition of metals on silicon from hydrofluoric acid solutions
Yae, Shinji,Nasu, Noriaki,Matsumoto, Kohei,Hagihara, Taizo,Fukumuro, Naoki,Matsuda, Hitoshi
, p. 35 - 41 (2007)
We investigate the nucleation behavior in the electroless displacement deposition of metal particles (Pt, Rh, Pd, Cu, Ag, and Au) onto n-Si wafers from a metal-salt solution containing HF. The particle density of metals varies widely from 106 (Pt) to 1011 (Au) cm-2, depending on the kind of metal. Deposited metals can be classified into two types of nucleation behavior. One consists of the platinum group elements, including Pt, Rh, and Pd, which display lower particle densities than elements of the other group and depend on the type of pretreatment of the n-Si wafer, and thus the surface conditions of Si. The second group consists of the copper group elements, including Cu, Ag, and Au, which display higher particle density than the first group and are independent of pretreatment. The size of deposited particles decreases from hundreds nm to tens nm as the particle density increases. Moreover, the displacement deposition of the Pt and Ag particles onto n-Si are in progressive and instantaneous nucleation modes, respectively.
New recovery process for rhodium using metal vapor
Kayanuma, Yoshihiro,Okabe, Toru H.,Mitsuda, Yoshitaka,Maeda, Masafumi
, p. 211 - 220 (2004)
Rhodium (Rh) is an essential element as a catalyst in automotive catalytic converters, and the recovery of Rh from scrap is an important issue. However, the chemical inertness of Rh makes it difficult to recover it from scrap. This study focused on a new process for recovering platinum group metals (PGM) from scrap with the purpose of improving Rh dissolution in acid. Reactive metal vapors such as magnesium (Mg) and calcium (Ca) were reacted with powdered Rh in a closed stainless steel reaction vessel at a constant temperature ranging from 873 to 1173 K. Mg and Ca deposited on Rh at temperatures above 973 and 1073 K, respectively. Dissolution experiments of the obtained compounds were conducted at 323-333 K for 1 h using an aqueous HCl solution or aqua regia. After reactive metal treatment 99% of Rh was dissolved by aqua regia leaching. Under the same leaching condition only 8% of the untreated pure Rh powder was dissolved. Rh was recovered from the solution obtained by leaching Mg reacted Rh compound using precipitation or cementation methods, demonstrating the feasibility of such recovery. These results show the possibility of developing a new Rh recovery process utilizing reactive metal vapor treatment.
Preparation and properties of the system Cr2-x RhxO3(2≥ x ≥ 0)
Zhang, Y. C.,Kershaw, R.,Dwight, K.,Wold, A.
, p. 155 - 162 (1988)
Members of the system Cr2-xRhxO3(2≥x≥0) were prepared by thermal decomposition of the nitrates. Magnetic measurements indicate that the chromium-rich members are antiferromagnetic and the spin-only moment, extrapolated from the high-temperature portion of the susceptibility curves, corresponds to Cr(III). Reduction studies indicate that the rhodium was stabilized in the solid solution and that at elevated temperatures between 1100 and 1200°C the mixed oxides were reduced to either the elements or a rhodium-chromium alloy.
Synthesis of a Cu-Filled Rh17S15 Framework: Microwave Polyol Process Versus High-Temperature Route
Roslova, Maria,Golub, Pavlo,Opherden, Lars,Ovchinnikov, Alexander,Uhlarz, Marc,Baranov, Alexey I.,Prots, Yurii,Isaeva, Anna,Coduri, Mauro,Herrmannsd?rfer, Thomas,Wosnitza, Joachim,Doert, Thomas,Ruck, Michael
, p. 11513 - 11523 (2017)
Metal-rich, mixed copper-rhodium sulfide Cu3-δRh34S30 that represents a new Cu-filled variant of the Rh17S15 structure has been synthesized and structurally characterized. Copper content in the [CuRh8] cubic cluster was found to vary notably dependent on the chosen synthetic route. Full site occupancy was achieved only in nanoscaled Cu3Rh34S30 obtained by a rapid, microwave-assisted reaction of CuCl, Rh2(CH3CO2)4 and thiosemicarbazide at 300 °C in just 30 min; whereas merely Cu-deficient Cu3-δRh34S30 (2.0 ≥ δ ≥ 0.9) compositions were realized via conventional high-temperature ceramic synthesis from the elements at 950 °C. Although Cu3-δRh34S30 is metallic just like Rh17S15, the slightly enhanced metal content has a dramatic effect on the electronic properties. Whereas the Rh17S15 host undergoes a superconducting transition at 5.4 K, no signs of the latter were found for the Cu-derivatives at least down to 1.8 K. This finding is corroborated by the strongly reduced density of states at the Fermi level of the ternary sulfide and the disruption of long-range Rh-Rh interactions in favor of Cu-Rh interactions as revealed by quantum-chemical calculations.
Stabilization of decatellurium molecules in isolated and concatenated clusters
Guenther, Anja,Isaeva, Anna,Ruck, Michael
, p. 254 - 260 (2013)
Black, shiny crystals of the molecular cluster compounds (Te 10)[M(TeX4)(TeX3)]2 (M/X = Rh/Cl (1), Ir/Br (2)), (Te10)[Ru(TeI4)(TeI2)] 2 (3), (Te10)[M(TeI4)(TeI2)] 2(TeI4)(Te2I2) (M = Rh (4), Ir (5)) as well as the one-dimensional cluster polymer (Te10I 2)[Ir(TeI4)]2(Te4)I2 (6) were synthesized by melting reactions of an electron-rich transition metal M (M = Ru, Rh, Ir) with tellurium and TeX4 (X = Cl, Br, I). X-ray diffraction on single-crystals revealed that the compounds crystallize in the triclinic space group type P1. 4 and 5 show [3+1]-dimensional modulations of their structures. All compounds contain binuclear complexes with central μ-η4:η4-bridging Te10 units and terminal halogenidotellurate(II) groups. Each of the transition metal cations is in a slightly distorted octahedral coordination by six tellurium atoms; the two [MTe6] octahedra share a common edge. With the tellurium atoms acting as electron-pair donors, the 18 electron rule is fulfilled for the electrophilic M atoms. The central tricyclo[5.1.1.13, 5]- decatellurium molecule consists of two ecliptically stacked Te4 rings, which are linked through two tellurium atoms. The symmetric or asymmetric 3c4e bonds along these almost linear bridges are in analogy to polyanionic forms of tellurium, while the tricyclic conformation is stabilized by the strong bonding to the transition-metal cations. Multi-center bonding (3c4e) is also present in the terminal square [Te+IIX4]2- and the T-shaped [Te+IIX3]- groups. The crystal structures of 4 and 5 are organized in layers of (Te10)[M(TeI 4)(TeI2)]2n+ clusters (n ≤ 2) that are quite robust upon oxidation or reduction as shown by molecular calculations. These clusters alternate with incommensurately modulated layers that probably consist of TeI42- anions and a previously unknown Te2I2 molecule. The uncertainty arises primarily from equal scattering powers of I and Te atoms as well as from the known flexibility of the electron count of the Te10 unit. In 6, neutral Te4 rings concatenate (Te10I2)[Ir(TeI 4)]2 clusters into chains, which run parallel to the a axis. Copyright
Hexatellurium rings in coordination polymers and molecular clusters: Synthesis and crystal structures of [M(Te6)]X3 (M = Rh, Ir; X = Cl, Br, I) and [Ru2(Te6)](TeBr3) 4(TeBr2)2
Guenther, Anja,Ruck, Michael
, p. 317 - 323 (2012)
The reaction of an electron-rich transition metal M (M = Ru, Rh, Ir), tellurium and TeX4 (X = Cl, Br, I) resulted in black crystals of five ternary coordination polymers with the general composition [M III(Te6)]X3 (M = Rh, Ir) and of the molecular cluster compound [RuII2(Te6)](Te IIBr3)4(TeIIBr2) 2. X-ray diffraction on single-crystals revealed that the compounds [M(Te6)]X3 crystallize isostructurally in the trigonal space group type Rβar{3}χ. In their crystal structures linear, positively charged [MIII(Te6)] chains form the motif of a hexagonal rod packing. In the chain, each of the formally uncharged Te 6 molecules with chair conformation acts as a bis-tridentate bridging ligand to two M atoms. The octahedrally coordinated M atoms are spiro atoms in the chain of trans vertices sharing heterocubane fragments. Including the isolated halide ions, which provide charge balance, the entire arrangement resembles a cut-out of the α-polonium structure type.In the monoclinic compound Ru2Te12Br16 (space group P2 1/n), the ruthenium atoms of the hetero-cubane core of the molecular cluster [Ru2(Te6)](TeBr3)4(TeBr 2)2 are saturated by terminal bromidotellurate(II) groups. Again, the Te6 ring is formally uncharged. With the tellurium atoms acting as electron-pair donors the 18 electron rule is fulfilled for the M atoms in all compounds. Copyright
About RhSCl5 - A hexameric, molecular rhodium(III) complex with SCl2 ligands
Herzog, Frank,Thiele, Gerhard
, p. 1461 - 1464 (2002)
Needle-shaped red crystals of RhSCl5 were obtained by reaction of Rh metall or RhI3 with SCl2 in a closed silica ampoule. In the monoclinic crystal structure the Rh atoms are octahedrally coordinated by 5 Cl atoms and a SCl2 ligand. In each case six RhCl5(SCl2) groups are connected with each other by two common edges of Cl atoms to form hexameric molecules [RhCl3(SCl2)]6. In the pseudohexagonal unit cell (monoclinic, space group C2/c, a = 26.215(5) A, b = 6.7750(10) A, c = 26.868(5) A, β = 119.06(3)°, Z = 4) the molecules are stacked in columns and form a hexagonal rod package.
Subsolidus phase relations in the Gd2O3-Rh 2O3 system
Skrobot,Ugolkov,Kuchaeva,Romanov,Grebenshchikov,Gusarov
, p. 1116 - 1121 (2006)
The Gd2O3-Rh2O3 system is studied using the anneal-and-quench technique, X-ray powder diffraction, thermal analysis, and chemical analysis. A schematic subsolidus phase diagram is designed. One double oxide of composition GdRhO3 is found to exist. It was characterized using some physicochemical methods. Pleiades Publishing, Inc., 2006.
Gibbs free energy of formation of calcium rhodite
Banerjee, Aparna,Prasad,Venugopal
, p. 59 - 65 (2004)
The Gibbs free energy of formation of CaRh2O4(s) has been determined using two techniques viz., quadrupole mass spectrometer coupled to a Knudsen cell and solid-state cell incorporating CaF2(s) as the solid electrolyte. In the former method, equilibrium O2(g) pressures were measured over the phase field Rh(s)+Rh2O3(s), in the temperature range 793.7-909.1 K and over the three phase mixture CaRh 2O4(s)+Rh(s)+CaO(s) was measured from 862.1 to 1022.7 K. The Gibbs free energy of formation of Rh2O3(s) from elements in their standard state can be given by ΔfG° (Rh2O3(s)) (kJ mol-1±2.0)=-363.2+0.241T (K). The Gibbs free energy of formation of CaRh2O4(s) from elements in their standard state can be given by ΔfG° (CaRh2O4(s)) (kJ mol-1±2.0)=-1030.5+0. 3437T (K). In the electrochemical technique, the cell configuration employed was (-)Pt/O2(g),{CaO(s)+CaF2(s)}//CaF2//{CaRh 2O4(s)+Rh2O3(s)+CaF 2(s)},O2(g)/Pt(+). The emf values were measured in the temperature range 879.7-1000 K can be represented by the following expression: E (V)(±7.63×10-4)=0.3928-2.374×10-4T (K). From the measured emf of the cell and requisite ΔfG° values from the literature, ΔfG°(CaRh2O 4(s)) from elements in their standard state has been calculated and can be represented by ΔfG°(CaRh2O 4(s)) (kJ mol-1±2.0)=-1079+0.390T (K). The uncertainty estimates for ΔfG°include the standard deviation in the emf and uncertainty in the data taken from the literature. The slope and intercept of the above equation gives the entropy and enthalpy of formation of the compound at the average experimental temperature T av=940 K.
