The native platinum group elements (PGE), namely, the light PGE (ruthenium, rhodium and palladium) and the heavy PGE (osmium, iridium and platinum), are important historically, scientifically and industrially. Some of the scientists who discovered and refined these metals in the 18th and early 19th centuries, besides being chemists, were also physicians, but all were also knowledgeable of mineralogy. We cannot but be impressed by their achievements because of the complexity of the minerals they studied. The PGE alloys occurred as a fraction of the heavy minerals concentrated from alluvial deposits. Today we can understand why some details of their discovery and mineralogy have not been well understood because of a lack of modern mineralogical studies and misunderstandings of some of the early literature, especially for native palladium and platinum. Though reported widely, highlights of the historical discoveries are here assembled in a single paper and discussed with respect to the mineralogy of the samples studied.
New dilatometric measurements allow the evaluated thermal expansion of osmium to be increased from the previous limit of 1300 K to the melting point at 3400 K. The new data is reported in the form of Equations and Tables. The revision confirms that osmium is the densest solid at all temperatures above room temperature. A new equation is given for the density of liquid osmium.
Renewable and low-carbon hydrogen will contribute to a future climate-neutral economy as a fuel, clean energy carrier and feedstock. One of the main concerns when considering its production by the present proton exchange membrane water electrolysers (PEMWE) is the use of scarce and expensive noble metals as catalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), because they contribute to increase the cost of the technology. Several strategies have been developed to overcome this drawback, such as optimising the catalyst loading in the electrodes and alloying or using alternative catalyst supports, always with the aim to maintain or even increase electrolyser performance and durability. In this review, we examine the latest developments in HER and OER catalysts intended for practical PEMWE systems, which point in the short term to the use of platinum and iridium nanoparticles highly dispersed at low loadings on conductive non-carbon supports.
Bushings made of platinum-rhodium alloys are a key component in glass fibre production. While bushings have grown in size and functionality since their introduction in the early 20th century, manufacturing constraints still limit their full potential. Both in terms of design and quality, traditional manufacturing methods such as milling, drilling and welding limit the potential of precious metal bushings. The technical feasibility of the use of additive manufacturing for the production of bushings is greatly dependent on the material properties. For the purpose of this work, an additively manufactured alloy consisting of 90 wt% platinum and 10 wt% rhodium (PtRh10) is investigated with regard to density, electrical resistivity, creep performance and the contact angle of E-glass on the PtRh10 samples.
Additive manufacturing of jewellery alloys has been actively investigated for the past 10 years. Limited studies have been conducted on gold and platinum jewellery alloys. Platinum is of increased interest due to the technological challenges in investment casting. In the present paper, typical platinum jewellery alloys have been tested by laser track experiments on sheet materials. The effect of alloy composition on width and depth of the laser tracks was studied by metallography. Optimum parameters of the laser powder bed fusion (PBF-LB) process were determined for a typical 950Pt jewellery alloy by the preparation of dedicated test samples. Densities of >99.8% were reached for a wide range of processing parameters. However, for real jewellery parts the resulting density was found to depend significantly on the part geometry and on the chosen support structure. The supports must take into account the geometrical orientation of the part relative to the laser build direction and the orientation on the build plate. Local overheating gives rise to porosity in these areas. Therefore, the supports play an important role in thermal management and must be optimised for each part. The design of suitable supports was successfully demonstrated for a typical jewellery ring sample.
Jewellery-specific standardised tests as well as bulk metallic glass (BMG)-specific testing methods were performed on a series of platinum-based BMGs with and without phosphorus, to evaluate their suitability as jewellery items. Their mechanical properties (elasticity, Young’s modulus and yield stress) were determined by three-point beam bending measurements. Hardness, wear and corrosion resistance were tested in comparison to state-of-the-art crystalline platinum-based jewellery alloys. The platinum-BMG alloys exhibit elastic elongation of about 2%. Compared to conventional crystalline platinum-alloys, their fracture strength of ca. 2 GPa and their hardness of ca. 450 HV1 is four and two times higher, respectively. However, the BMGs show less abrasion resistance in the pin-on-disc test than the conventional benchmark alloys due to adhesive wear and microcracking. Regarding the corrosion resistance in simulated body fluids, the BMG alloys reveal a slightly higher release of metals, while the tarnishing behaviour is comparable to the benchmark alloys. The phosphorus-free platinum-BMG alloy showed pronounced tarnishing during exposure to air at elevated temperature. The outstanding thermoplastic formability, a special feature of amorphous metals that can be crucial for enabling novel and filigree designs, was determined and quantified for all BMG alloys.
Carbon-hydrogen bond activations and their subsequent functionalisation have long been an important target in chemistry because C–H bonds are ubiquitous throughout nature, making C–H derivatisation reactions highly desirable. The selective and efficient functionalisation of this bond into many more useful carbon-element bonds (for example, C–B, C–Si, C–O and C–S bonds) would have many uses in pharmaceutical and bulk chemical synthesis. Activation of the C–H bond is, however, challenging due to the high strength and low bond-polarity of this bond rendering its cleavage unfavourable. With the correct choice of reagents and systems, especially those utilising directing groups, kinetically and thermodynamically favourable catalytic processes have been developed. However, a key remaining challenge is the development of undirected, intermolecular reactions using catalysts that are both selective and active enough to make useful processes. In this review, the progress towards optimising Group 9 C–H activation catalysts is discussed, particularly focusing on undirected reactions that are kinetically more difficult, starting with a brief history of C–H activation, identifying the importance of auxiliary ligands including the nature of anionic ligand (for example, cyclopentadienyl, indenyl, fluorenyl and trispyrazolylborate) and neutral ligands (such as phosphines, carbonyl, alkenes and N-heterocyclic carbenes (NHCs)) that contribute towards the stability and reactivity of these metal complexes. The tethering of the anionic ligand to strong σ-donating ligands is also briefly discussed. The focus of this review is primarily on the Group 9 metals rhodium and iridium, however, C–H activation using Group 8 and 10 metals are compared where useful. The most recent advances in this field include the development of C–H borylation of many small hydrocarbon substrates such as arenes, heterocycles and n-alkanes as well as the more challenging substrate methane.
The synthesis of platinum-cobalt nanocrystals (NCs) using colloidal solvothermal techniques is well understood. However, for monodisperse NCs to form, high temperatures and environmentally detrimental solvents are needed. We report a room temperature, aqueous method of platinum-cobalt NC synthesis using electrochemical reduction as the driving force for nucleation and growth. It is found that colloidal NCs will form in both the presence and absence of surfactant. Additionally, we report a monodisperse electrochemical deposition of NCs utilising a transparent conducting oxide electrode. The methods developed here will allow for a synthetic method to produce nanocatalysts with minimal environmental impact and should be readily applicable to other NC systems, including single- and multi-component alloys.
Johnson Matthey’s annual review of the platinum group metal (pgm) markets was published on 15th May 2023, providing an outlook for pgm supply and demand for 2023. The report contains a comprehensive review of developments in the automotive market, covering production and powertrain trends and their implications for pgm use as well as an update on future emissions legislation. It also features an in-depth discussion of the ruthenium and iridium markets in view of increasing interest in the use of these metals in the net zero transition.
Platinum has only been known to Europe since the 16th century. This was impure platinum, found as grains of native metal in alluvial deposits and comprising mainly platinum alloyed with the other five platinum group metals. They were exploited by pre-Colombian native populations of Ecuador and Colombia. In more recent times, the use of platinum in jewellery dates from the late 19th or early 20th centuries, often as a basis for diamond (and other precious gemstone) jewellery. Early jewellery alloys tended to be based on the existing industrial alloys and comparatively little development of specific jewellery alloys was carried out. Its acceptance as a hallmarkable jewellery metal came in 1975 when, with wider availability of the metal, platinum was promoted as a high-value jewellery metal. Platinum jewellery started to grow in popularity, mainly at 950 and 900 fineness qualities. Since that time there has been alloy development specifically for jewellery application and tailored to the requirements of different manufacturing technologies. This review examines the evolution of platinum jewellery alloys over the past century against the challenges presented in developing improved alloys for jewellery application. There has been a substantial increase in alloy development over the past 30 years, particularly focused on improved investment (lost wax) casting alloys as well as better mechanical properties.
Dependence of mechanical properties of binary platinum-rhodium alloys on valence electron ratio (VER), number of valence electrons (ev) and average atomic number of the alloys (Z) are investigated. The alloys have a high number of valence electrons (9 ≤ ev ≤ 10) and a wide range of average atomic numbers (Z = 45–78). Clear correlations between VER of the alloys and their mechanical properties are found. By increasing the VER of the alloy from 0.13 to 0.20 following the increase of rhodium content in the composition, the hardness, elastic modulus and ultimate tensile strength (UTS) of the alloy increases. Creep rates of the selected alloys clearly decrease with increasing VER at high temperatures (1500–1700°C), while stress rupture time at different temperatures consistently increases because of higher rhodium content in the alloy solid solution chemistry. Dependence of mechanical properties on valence electron parameters is discussed with reference to the atomic bonding.
Definitive equations are suggested to represent the variation with temperature of the densities and molar volumes of the liquid platinum group metals whilst the previously unknown initial slopes of the melting curves for iridium, rhodium and ruthenium are estimated. 1. Introduction Paradis et al. (1) summarised determinations of the densities of the liquid platinum group metals but a...
Ruthenium targets were prepared by vacuum hot pressing of ruthenium powder with different morphologies. Ruthenium films were then deposited on a SiO2/Si(100) substrate for different times by radio frequency (RF) magnetron sputtering. The relationship in terms of the microstructure and electrical properties between the ruthenium targets and resultant films at different conditions were studied by means of field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), atomic force microscopy (AFM) and four-point probe. The results showed that parameters such as the average deposition rate, surface roughness, crystallisation properties and growth rate were directly related to the homogeneity of the microstructure of the ruthenium targets, but there was no correlation between the crystal orientations of the films and the targets. Moreover, the resistivity of ruthenium films was positively correlated with that of the ruthenium targets.
The elastic, mechanical, thermophysical and ultrasonic properties of platinum group metal (pgm) carbides XC (X = rhodium, palladium, iridium) have been investigated at room temperature. The Coulomb and Born-Mayer potential model was used to compute second- and third-order elastic constants (SOECs and TOECs) at 0 K and 300 K. The obtained values of SOECs were used to evaluate mechanical properties such as Young’s modulus, bulk modulus, shear modulus, Pugh’s indicator, Zener anisotropic constant and Poisson’s ratio at room temperature. The materials show brittle nature as the value of Pugh’s indicator for pgm carbides is ≤1.75. The values of SOECs were used to compute the ultrasonic velocities along <100>, <110> and <111> directions for the longitudinal and shear modes of wave propagation. Further, the values of Debye temperature, thermal conductivity, specific heat per unit volume, energy density, average value of ultrasonic Grüneisen parameter, thermal relaxation time and non-linear parameter were calculated with the help of SOECs, TOECs, ultrasonic velocities, density and molecular weight. Finally, the ultrasonic attenuation due to phonon-phonon interaction and due to thermoelastic relaxation mechanisms were calculated with the use of all associated parameters. The calculated values of elastic, mechanical, thermophysical and ultrasonic properties are compared with available literature and discussed.
