Showing papers in "Platinum Metals Review in 2007"

"Organic Light-Emitting Devices: Synthesis, Properties and Applications"

Abstract: 1 Inorganic Semiconductors for Light-emitting Diodes (E Fred Schubert, Thomas Gessmann, and Jong Kyu Kim) 11 Introduction 12 Optical Emission Spectra 13 Resonant-cavity-enhanced Structures 14 Current Transport in LED Structures 15 Extraction Efficiency 16 Omnidirectional Reflectors 17 Packaging 18 Conclusion References 2 Electronic Processes at Semiconductor Polymer Heterojunctions (Arne C Morteani, Richard H Friend, and Carlos Silva) 21 Introduction 22 Charge Capture at Polymer Heterojunctions 23 Exciton Dissociation at Polymer Heterojunctions 24 Morphology-dependent Exciton Retrapping at Polymer Heterojunctions 25 Summary Acknowledgments References 3 Photophysics of Luminescent Conjugated Polymers (Dirk Hertel and Heinz Bssler) 31 Introduction 32 Spectroscopy of Singlet States 33 Optically Induced Charge Carrier Generation 34 Triplet States 35 Resum Acknowledgement References 4 Polymer-Based Light-Emitting Diodes (PLEDs) and Displays Fabricated from Arrays of PLEDs (Xiong Gong, Daniel Moses and Alan J Heeger) 41 Introduction 42 LEDs Fabricated from Semiconducting Polymers 43 Accurate Measurement of OLED/PLED Device Parameters 44 Fowler-Nordheim Tunneling in Semiconducting Polymer MIM Diodes 45 Pixilated Displays 46 Thickness Dependence of Electroluminescence Efficiency 47 Limits on the Electroluminescence Efficiency 48 White-light emission 49 Conclusion Note Acknowledgement References 5 Metal/Polymer Interface Studies for Organic Light-Emitting Devices (Man-Keung Fung, Chun-Sing Lee, and Shuit-Tong Lee) 51 Review of Organic Light-Emitting Diodes and their Fundamental Interface Studies 52 Polymer Materials, their Preparations, and Experimental Details 53 Chemistry and Electronic Properties of Metal/F8BT 54 Role of Ytterbium and Ytterbium/Cesium Fluoride on the Chemistry of F8BT 55 Highly Efficient and Substrate-Independent Ytterbium/Cesium Fluoride Cathodes 56 Conclusions Acknowledgements References 6 The Synthesis of Electroluminescent Polymers (Andrew C Grimsdale) 61 Introduction 62 Poly(arylene vinylene)s 63 Poly(arylene ethynylene)s 64 Polyarylenes 65 EL Polymers with Isolated Chromophores 66 Stability of EL Polymers 67 Conclusion References 7 Charge-transporting and Charge-blocking Amorphous Molecular Materials for Organic Light-emitting Diodes (Yasuhiko Shirota) 71 Introduction 72 Amorphous Molecular Materials 73 Requirements for Materials in OLEDs 74 Amorphous Molecular Materials for Use in OLEDs 75 Charge Transport in Amorphous Molecular Materials 76 Outlook References 8 Dendrimer Light-Emitting Diodes (John M Lupton) 81 Introduction 82 The Dendrimer Concept 83 Electroluminescent Dendritic Materials 84 Electronic Properties 85 Dendrimer Devices 86 Dendronized Polymers 87 Conclusions References 9 Crosslinkable Organic Semiconductors for Use in Organic Light-Emitting Diodes (OLEDs) (Klaus Meerholz, Christoph-David Mller, Oskar Nuyken) 91 Introduction 92 Multiple-Layer Deposition 93 Patterning 94 Conclusion and Outlook Acknowledgements References 10 Hybrid OLEDs with Semiconductor Nanocrystals (Andrey L Rogach and John M Lupton) 101 Introduction 102 LEDs in the Visible based on Composites of Semiconductor Nanocrystals and Polymers or Nanocrystals and Small Organic Molecules 103 Near-infrared LEDs based on Composites of Semiconductor Nanocrystals and Polymers or Small Organic Molecules 104 Concluding Remarks References 11 Polymer Electrophosphorescence Devices (Xiaohui Yang and Dieter Neher) 111 Introduction 112 Phosphorescent Dyes 113 Transfer Processes in Polymer Hosts Doped with Phosphorescent Dyes 114 Polymer Phosphorescence Devices based on PVK 115 Phosphorescent Devices with Other Host Polymers 116 Fully Functionalized Polymers 117 Conclusion and Outlook Acknowledgement References 12 Low-threshold Organic Semiconductor Lasers (Daniel Schneider, Uli Lemmer, Wolfgang Kowalsky, Thomas Riedl) 121 Introduction 122 Fundamentals of Organic Semiconductor Lasers 123 Low-threshold Organic Lasing 124 Comparison of Organic Laser Properties 125 Electrically Driven Organic Lasers 126 Summary and Outlook References Subject Index

Enhancement of Industrial Hydroformylation Processes by the Adoption of Rhodium-Based Catalyst: Part I

Abstract: The adoption of a low-pressure rhodium-based catalyst system in place of high-pressure cobalt for the hydroformylation of propylene by reaction with carbon monoxide and hydrogen to produce butyraldehydes (an ‘oxo’ reaction) has brought large cost benefits to oxo producers. The benefits derive from improved feedstock efficiency, lower energy usage and simpler and cheaper plant configurations. The technical and commercial merits of the ‘LP Oxo SM Process’ for producing butyraldehydes have made it one of the best known applications of industrialscale chemistry using a platinum group metal (pgm). Today, practically all butyraldehyde is made by rhodium catalysis, and this should provide convincing encouragement to researchers who are keen to exploit pgms as catalyst research materials, but are apprehensive as to the implications of their very high intrinsic value. It should also encourage developers and designers responsible for turning pgm chemistry into commercial processes, who may be daunted by problems such as containment and catalyst life. This article (Part I) reviews the background to the LP Oxo SM Process, and its development to the point of first commercialisation. Part II, covering some of the key improvements made to the process and its use in non-propylene applications, will appear in a future issue of Platinum Metals Review.

Palladium-Polyaniline and Palladium-Polyaniline Derivative Composite Materials

Abstract: polymers from metals is their low electrical conductivity. A new class of organic polymers capable of conducting electricity has recently been developed (1, 2). These polymers become conductive upon partial oxidation or reduction, a process commonly referred to as ‘doping’. The electrical properties of conductive polymers can be changed reversibly over the full range of conductivity from insulators to metallic conductors. Their potential as novel materials in value-added industrial and consumer products is opening up wholly new avenues of application for polymeric materials. Among conducting plastics, polyaniline has become a particular focus of interest because of its environmental stability (3), controllable electrical conductivity (4), and interesting redox properties associated with the chain nitrogen (5). The electrical properties of the aniline polymers can be improved substantially by secondary doping (6). Polyaniline compounds can be designed to achieve the particular conductivity required for a given application. The resulting blends can be as conductive as silicon and germanium or as insulating as glass. Additional advantages are that the compound can be mixed simply with conventional polymers, and it is easy to fabricate polyaniline products into specific shapes. The conductivity of polyaniline makes it an ideal shield against static electric discharges, and as a consequence polyaniline compounds have been used in the packaging of electronics products. Polyaniline compounds are being tested for use as protective materials against electromagnetic radiation. Further, scientists hope that one day printed circuit boards, electrochromic windows in houses and cars, and conductive fabrics will contain polyaniline compounds. The presence of a number of intrinsic redox states (Figure 1) has substantially increased the number of potential applications of aniline polymers for use in practical devices. The aniline polymers have a general formula of the type [(–B–NH–B–NH–)y (–B–N=Q=N–)1–y]x, in which B and Q denote respectively the C6H4 rings in the benzenoid and the quinoid forms. In polyaniline, the neutral intrinsic redox states (Figure 1) can vary from that of the fully oxidised pernigraniline (PNA; y = 0), to that of the

Building a Thermodynamic Database for Platinum-Based Superalloys: Part III

Abstract: Work has been ongoing in building a thermo-dynamic database for the prediction of phaseequilibria in Pt-based superalloys (1–7). The alloys arebeing developed for high-temperature applications inaggressive environments. The database will aid thedesign of alloys by enabling the calculation of thecomposition and proportions of phases present inalloys of different compositions. This paper is arevised account of work presented at the conference:Southern African Institute of Mining and Metallurgy‘Platinum Surges Ahead’ at Sun City, South Africa,from 8th to 12th October 2006 (7).Part I, describing initial results for the Pt-Al-Rusystem from the compound energy formalism model,was published in the July 2007 issue of

Vapour Pressure Equations for the Platinum Group Elements

Abstract: 130 Calculation of Vapour Pressure Values Vapour pressure values are calculated from thermodynamic data following the procedure described in Appendix A. Since free energy functions are given for one bar standard-state pressure, then the vapour pressure will also be given in bars. Values for the free energy functions and the selected heats of sublimation are given in the reviews on platinum (1) and the other five pgms: palladium (2), ruthenium (3), osmium (4), rhodium (5) and iridium (6). Since the behaviour of the specific heat capacities of the solids and their effect on the free energy functions is more complicated than for the liquids, then vapour pressure values were evaluated for the solids at 25 K intervals and the melting point, and for the liquids at 50 K intervals and the melting point, so as to give approximately equal numbers of data points. In the review on platinum (1), a minimum lower temperature of 1200 K was considered. This gives a vapour pressure of about 10 bar, which is considerably below practical measurements. For the other metals, the use of rounded temperatures gives a vapour pressure between 10 and 10 bar, which was used as the lower bound.

Novel Chiral Chemistries Japan 2007

Abstract: 172 The second Novel Chiral Chemistries Japan (NCCJ) Conference and Exhibition was held in Tokyo from 16th to 17th April, 2007. The first meeting in the series had been held in 2006 and a similar format was followed. There were three keynote addresses with supporting lectures. Professor Takao Ikariya (Tokyo Institute of Technology) did an excellent job as the conference organiser. During the coffee and lunch breaks there was a small exhibition by companies associated with chiral chemistry. The exhibitors ranged from companies that provide biocatalysts, metal catalysts and ligands through to service providers associated with the implementation of methodologies. Some scientific instrumentation was also on display. There were about 100 delegates, most coming from the Japanese fine chemicals industry.

Platinum-Copper on Carbon Catalyst Synthesised by Reduction with Hydride Anion

Abstract: With a view to improving the catalytic performance of supported bimetallic platinum-copper catalysts in hydrogen-assisted dechlorination of halogenated alkanes, a range of catalysts were prepared by reduction of oxide precursors by the hydride anion H, using both sodium and calcium hydrides (NaH and CaH2). The catalytic performance of the resulting catalyst samples in the hydrodechlorination (HDCl) of 1,2-dichloroethane at 220oC was investigated, to gain understanding of metal alloying phenomena governing the variation in ethene selectivity with time on stream (TOS). Metal dispersion was also investigated by O2 chemisorption and transmission electron microscopy (TEM). PtCuCaH(b) catalyst, synthesised by reduction with CaH2 at 450oC, showed a high selectivity towards ethene in comparison with that of catalysts synthesised by reduction with either NaH or hydrogen. In view of the chemisorption and TEM results, the significant high selectivity of this catalyst towards ethene was attributed to the fact that reduction by CaH2 enhanced alloying of Pt and Cu. On the other hand, the ethene selectivity of PtCuCaH(b) catalyst did not show any variation with TOS, but reached a steady state at early TOS. This suggested that Pt and Cu alloying did not take place during the course of the reaction, but might have occurred during the reduction process. DOI: 10.1595/147106707X214316

The 20th Santa Fe Symposium on Jewelry Manufacturing Technology

Abstract: The 25th annual Santa Fe Symposium attracted a record attendance of 165, with delegates from 11 countries worldwide, confi rming the more opti-mistic outlook by the US jewellery industry noted last year. Held in Albuquerque, New Mexico, USA, from 15th–18th May 2011, the Symposium had a very strong programme of presentations covering a wide range of topics (1). Platinum featured and, as usual, attracted much interest. The major sponsors were given the opportunity to have a display table in the lobby area, as last year, and thus both Johnson Matthey New York and Platinum Guild International USA had a strong presence.Platinum AlloysThe soldering of platinum received attention this year with Jurgen Maerz (Platinum Guild Interna-tional, USA) reviewing the topic in his presentation, ‘Platinum Solders: Proper Use and Application of Plati-num Solders in Jewelry Making’. Maerz fi rst addressed the types of solder used in soldering platinum jewel-lery: this categorised platinum solders into those con-taining up to 95% platinum and those which contained no platinum, perhaps better classed as plumb and tra-ditional solders respectively. Traditional solders con-tain no or very little platinum and come in a range of soldering or fl ow temperatures in grades from extra easy 1000 to extra hard 1400 with additional grades of platinum welding 1500, platinum special welding 1600, platinum seamless 1700 and platinum weld 1773, where the number refers to the approximate fl ow tem-perature in oC.In contrast, plumb platinum solders have a high platinum content and fl ow temperatures in the range 1300oC for the easy fl ow grade (contains 90% plati-num) to 1500oC for the hard fl ow grade that contains 95% platinum. Maerz makes the point that these sol-ders enable soldering without fear of under-carating of the platinum jewellery in the USA where there is a zero tolerance on assay. To ensure compliance with this standard, he noted, platinum alloys are often ‘sweetened’ to 952 fi neness to allow use of non-plat-

Strengthening of platinum-5 wt.% copper by heat treatment

Abstract: The mechanical properties of the widely used jewellery alloy Pt-5% Cu have been investigated by several researchers (see, for example, (1–3)) for the cast, cold worked and annealed conditions. It is however not widely known that platinum containing around 5 wt.% copper undergoes an ordering transformation after low-temperature heat treatment (4, 5). Recent work in the Centre for Materials Engineering (6) showed that the Pt7Cu ordered phase, which can form after heat treatment at temperatures as low as 200oC, can improve the hardness of Pt-5% Cu. If the alloy is cold worked before heat treatment, the increase in hardness after heat treatment is significant. If the alloy is first quenched from high temperatures, an increase in hardness on heat treatment is measurable but not as great. Given the widespread use of Pt-5% Cu in platinum jewellery, it is surprising that there is little information on this phenomenon in the technical literature. The hardness increase for this alloy has important implications for the manufacture of jewellery, since using low-temperature heat treatment as a final step in the manufacture of a jewellery piece can produce a better finish and improved scratch resistance. Conversely, hardness may be inadvertently increased by heating during manufacture, leading to difficulty in subsequent working of the piece. An understanding of the effect of heating on strength accordingly allows optimal planning of the manufacturing route. The effect of the Pt7Cu ordering transformation on mechanical properties other than hardness has not previously been investigated. In this paper we investigate the effect on the strength and ductility of Pt-5% Cu of heat treatments which result in ordering. The tensile mechanical properties of platinum and its alloys have not been studied extensively, owing to the costs associated with tensile specimens of conventional (American Society for Testing and Materials (ASTM)) scale (7). These costs can be considerably reduced by microsample tensile testing, described previously in this Journal (3). Mechanical properties such as yield strength, tensile strength and ductility can be measured using specimens just 8 mm in length. In the present work the mechanical properties of Pt5% Cu, before and after heat treatments which result in ordering, are fully characterised by microsample tensile testing and hardness testing.