Novel Intermetallic Catalysts to Enhance PEM Membrane Durability

The research examined possible sources of degradation of platinum based anode catalysts under long term use. Scientists at the United Technologies Research Center had shown that the anode as well as the cathode catalysts degrade in hydrogen fuel cells. This goal of this research was to see if mechanisms of anode degradation could be understood using forefront electrochemical techniques in an aqueous system. We found that this method is limited by the very low levels of impurities (perhaps less than a part per trillion) in the electrolyte. This limitation comes from the relatively small catalyst surface area (a few sq cm or less) compared to the electrolyte volume of 10 to 25 ml. In real fuel cells this ratio is completelyreversed: high catalyst surface area and low electrolyte violume, making the system much less sensitive to impurities in the electrolyte. We conclude that degradation mechanisms should be studied in real fuel cell systems, rather than in ex-situ, large electrolyte volume experiments

Alkaline Earth Metal Oxyhalides Revisited -Syntheses and Crystal Structures of Sr 4 OBr 6 , Ba 4 OBr 6 and Ba 2 OI 2

Single crystals of the compounds Ca 4 OCl 6 , Sr 4 OBr 6 , Ba 4 OBr 6 , and Ba 2 OI 2 were obtained by solid-state reactions. The crystals of Ba 2 OI 2 are transparent and colorless and isopointal to K 2 ZnO 2 adopting the orthorhombic space group Ibam (no. 72, Z = 4) with the cell parameters a = 747.20(9), b = 1392.02(18), and c = 678.12(9) pm. Sr 4 OBr 6 and Ba 4 OBr 6 are isotypic to Ba 4 OCl 6 (or isopointal to K 6 ZnO 4 ) and crystallize in the hexagonal space group P6 3 mc (no. 186, Z = 2) exhibiting the cell parameters a = 982.20(4) and c = 750.41(7) pm for Sr 4 OBr 6 and a = 1030.10(2) and c = 785.92(4) pm for Ba 4 OBr 6 . In the ternary systems Ca-O-X (X = Cl, Br or I) the only compound found other than the starting materials was the already known Ca 4 OCl 6 which is also isotypic to Ba 4 OCl 6 crystallizing in the hexagonal space group P6 3 mc (no. 186, Z = 2) with the cell parameters a = 903.30(6) and c = 683.27(8) pm

Cornell Fuel Cell Institute: Materials Discovery to Enable Fuel Cell Technologies

The discovery and understanding of new, improved materials to advance fuel cell technology are the objectives of the Cornell Fuel Cell Institute (CFCI) research program. CFCI was initially formed in 2003. This report highlights the accomplishments from 2006-2009. Many of the grand challenges in energy science and technology are based on the need for materials with greatly improved or even revolutionary properties and performance. This is certainly true for fuel cells, which have the promise of being highly efficient in the conversion of chemical energy to electrical energy. Fuel cells offer the possibility of efficiencies perhaps up to 90 % based on the free energy of reaction. Here, the challenges are clearly in the materials used to construct the heart of the fuel cell: the membrane electrode assembly (MEA). The MEA consists of two electrodes separated by an ionically conducting membrane. Each electrode is a nanocomposite of electronically conducting catalyst support, ionic conductor and open porosity, that together form three percolation networks that must connect to each catalyst nanoparticle; otherwise the catalyst is inactive. This report highlights the findings of the three years completing the CFCI funding, and incudes developments in materials for electrocatalyts, catalyst supports, materials with structured and functional porosity for electrodes, and novel electrolyte membranes. The report also discusses developments at understanding electrocatalytic mechanisms, especially on novel catalyst surfaces, plus in situ characterization techniques and contributions from theory. Much of the research of the CFCI continues within the Energy Materials Center at Cornell (emc2), a DOE funded, Office of Science Energy Frontier Research Center (EFRC)

Cosputtered composition-spread reproducibility established by high-throughput x-ray fluorescence

We describe the characterization of sputtered yttria-zirconia composition spread thin films by x-ray fluorescence (XRF). We also discuss our automated analysis of the XRF data, which was collected in a high throughput experiment at the Cornell High Energy Synchrotron Source. The results indicate that both the composition reproducibility of the library deposition and the composition measurements have a precision of better than 1 atomic percent

Cosputtered composition-spread reproducibility established by high-throughput x-ray fluorescence

We describe the characterization of sputtered yttria-zirconia composition spread thin films by x-ray fluorescence (XRF). We also discuss our automated analysis of the XRF data, which was collected in a high throughput experiment at the Cornell High Energy Synchrotron Source. The results indicate that both the composition reproducibility of the library deposition and the composition measurements have a precision of better than 1 atomic percent

Getter sputtering system for high-throughput fabrication of composition spreads

We describe a sputtering system that can deposit composition spreads in an effectively UHV environment but which does not require the high-throughput paradigm to be compromised by a long pump down each time a target is changed. The system deploys four magnetron sputter guns in a cryoshroud (getter sputtering) which allows elements such as Ti and Zr to be deposited with minimal contamination by oxygen or other reactive background gases. The system also relies on custom substrate heaters to give rapid heating and cool down. The effectiveness of the gettering technique is evaluated, and example results obtained for catalytic activity of a pseudoternary composition spread are presented

Getter sputtering system for high-throughput fabrication of composition spreads

We describe a sputtering system that can deposit composition spreads in an effectively UHV environment but which does not require the high-throughput paradigm to be compromised by a long pump down each time a target is changed. The system deploys four magnetron sputter guns in a cryoshroud (getter sputtering) which allows elements such as Ti and Zr to be deposited with minimal contamination by oxygen or other reactive background gases. The system also relies on custom substrate heaters to give rapid heating and cool down. The effectiveness of the gettering technique is evaluated, and example results obtained for catalytic activity of a pseudoternary composition spread are presented

Penerapan Metode Pembelajaran Numbered Heads Together (Nht) Untuk Meningkatkan Motivasi Dan Hasil Belajar Kelarutan Dan Hasil Kali Kelarutan Kelas XI IPA 4 Sman 8 Surakarta Tahun Pelajaran 2012/2013

Tujuan penelitian ini adalah untuk meningkatkan (1) motivasi belajar kelarutan dan hasil kali kelarutan dan (2) hasil belajar kelarutan dan hasil kali kelarutan melalui penerapan metode pembelajaran Numbered Heads Together (NHT). Penelitian ini merupakan penelitian tindakan kelas (Classroom Action Research) yang dilaksanakan dalam dua siklus dimana setiap siklusnya terdiri atas empat tahapan, yaitu perencanaan, pelaksanaan, pengamatan, dan refleksi. Subjek penelitian adalah siswa kelas XI IPA 4 SMAN 8 Surakarta Tahun Pelajaran 2012/2013. Pengumpulan data dilakukan melalui pengamatan, wawancara, kajian dokumen, angket, dan tes. Data yang diperoleh divalidasi menggunakan teknik triangulasi sumber dan dianalisis menggunakan analisis deskriptif kualitatif yang mengacu pada Miles dan Huberman. Hasil penelitian menunjukkan capaian motivasi belajar pada siklus I dan siklus II masing-masing mencapai 58,33% dan 79,17%. Hasil belajar yang diukur pada aspek kognitif dan afektif menunjukkan pada siklus I mencapai 29,17% dan 62,5% serta pada siklus II mencapai 70,83% dan 83,33%. Simpulan penelitian ini adalah penerapan metode pembelajaran Numbered Heads Together (NHT) mampu meningkatkan (1) motivasi belajar kelarutan dan hasil kali kelarutan dan (2) hasil belajar kelarutan dan hasil kali kelarutan kelas XI IPA 4 SMAN 8 Surakarta

Thermal Transport in Micro- and Nanoscale Systems

Small-scale (micro-/nanoscale) heat transfer has broad and exciting range of applications. Heat transfer at small scale quite naturally is influenced – sometimes dramatically – with high surface area-to-volume ratios. This in effect means that heat transfer in small-scale devices and systems is influenced by surface treatment and surface morphology. Importantly, interfacial dynamic effects are at least non-negligible, and there is a strong potential to engineer the performance of such devices using the progress in micro- and nanomanufacturing technologies. With this motivation, the emphasis here is on heat conduction and convection. The chapter starts with a broad introduction to Boltzmann transport equation which captures the physics of small-scale heat transport, while also outlining the differences between small-scale transport and classical macroscale heat transport. Among applications, examples are thermoelectric and thermal interface materials where micro- and nanofabrication have led to impressive figure of merits and thermal management performance. Basic of phonon transport and its manipulation through nanostructuring materials are discussed in detail. Small-scale single-phase convection and the crucial role it has played in developing the thermal management solutions for the next generation of electronics and energy-harvesting devices are discussed as the next topic. Features of microcooling platforms and physics of optimized thermal transport using microchannel manifold heat sinks are discussed in detail along with a discussion of how such systems also facilitate use of low-grade, waste heat from data centers and photovoltaic modules. Phase change process and their control using surface micro-/nanostructure are discussed next. Among the feature considered, the first are microscale heat pipes where capillary effects play an important role. Next the role of nanostructures in controlling nucleation and mobility of the discrete phase in two-phase processes, such as boiling, condensation, and icing is explained in great detail. Special emphasis is placed on the limitations of current surface and device manufacture technologies while also outlining the potential ways to overcome them. Lastly, the chapter is concluded with a summary and perspective on future trends and, more importantly, the opportunities for new research and applications in this exciting field

Thermoelectric Cooling and Power Generation

In a typical thermoelectric device, a junction is formed from two different conducting materials, one containing positive charge carriers (holes) and the other negative charge carriers (electrons). When an electric current is passed in the appropriate direction through the junction, both types of charge carriers move away from the junction and convey heat away, thus cooling the junction. Similarly, a heat source at the junction causes carriers to flow away from the junction, making an electrical generator. Such devices have the advantage of containing no moving parts, but low efficiencies have limited their use to specialty applications, such as cooling laser diodes. The principles of thermoelectric devices are reviewed and strategies for increasing the efficiency of novel materials are explored. Improved materials would not only help to cool advanced electronics but could also provide energy benefits in refrigeration and when using waste heat to generate electrical power