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Modeling Of The Size Effects On The Behavior Of Metals In Microscale Deformation Processes, Gap-Yong Kim, Jun Ni, Muammer Koc
Modeling Of The Size Effects On The Behavior Of Metals In Microscale Deformation Processes, Gap-Yong Kim, Jun Ni, Muammer Koc
Gap-Yong Kim
For the accurate analysis and design of microforming process, proper modeling of material behavior at the micro/mesoscale is necessary by considering the size effects. Two size effects are known to exist in metallic materials. One is the “grain size” effect, and the other is the “feature/specimen size” effect. This study investigated the feature/specimen size effect and introduced a scaling model which combined both feature/specimen and grain size effects. Predicted size effects were compared with three separate experiments obtained from previous research: a simple compression with a round specimen, a simple tension with a round specimen, and a simple tension in …
Effect Of Chain Architecture And Surface Energies On The Ordering Behavior Of Lamellar And Cylinder Forming Block Copolymers, V. Khanna, Eric W. Cochran, A. Hexemer, G. E. Stein, G. H. Fredrickson, E. J. Kramer, X. Li, J. Wang, S. F. Hahn
Effect Of Chain Architecture And Surface Energies On The Ordering Behavior Of Lamellar And Cylinder Forming Block Copolymers, V. Khanna, Eric W. Cochran, A. Hexemer, G. E. Stein, G. H. Fredrickson, E. J. Kramer, X. Li, J. Wang, S. F. Hahn
Eric W. Cochran
We investigate the effect of surface energy and chain architecture on the orientation of microdomains in relatively thick films (600-800 nm) of lamellar and cylindrical block copolymers of poly(cyclohexylethylene) (C) and poly(ethylene) (E). The E block has 26 ethyl branches per 1000 backbone carbon atoms. Melt surface energies of the C and E blocks are 22.3 and 20.9 mJ/m 2, respectively. Grazing-incidence small-angle X-ray scattering (GISAXS), scanning force microscopy (SFM), and cross-sectional transmission electron microscopy (TEM) show that cylindrical and lamellar CEC triblock copolymers orient their microdomains normal to the surface throughout the film thickness. However, a lamellar CE diblock …
Posterminaries: After Nabarro, Alexander H. King
Posterminaries: After Nabarro, Alexander H. King
Alexander H. King
With the passing of Frank Nabarro in July of this year, we have lost one of the founding fathers of materials science. His name appears in many of the textbooks from which we train our students today, and also on the spines of several volumes on dislocation theory, including his classic monograph on the subject. He rightly stands among the gods of our field. Ninety years old at his death, he was a sprightly dancer at the frontiers of knowledge, right up to the end.
Modeling Of The Semi-Solid Material Behavior And Analysis Of Micro-/Mesoscale Feature Forming, Gap-Yong Kim, Muammer Koc, Rhet Mayor, Jun Ni
Modeling Of The Semi-Solid Material Behavior And Analysis Of Micro-/Mesoscale Feature Forming, Gap-Yong Kim, Muammer Koc, Rhet Mayor, Jun Ni
Gap-Yong Kim
One of the major challenges in simulation of semi-solid forming is characterizing the complex behavior of a material that consists of both solid and liquid phases. In this study, a material model for an A356 alloy in a semi-solid state has been developed for high solid fractions (>0.6) and implemented into a finite element simulation tool to investigate the micro-/mesoscale feature formation during the forming process. Compared to previous stress models, which are limited to expressing the stress dependency on only the strain rate and the temperature (or the solid fraction), the proposed stress model adds the capability of …
An Experimental Investigation On Semi-Solid Forming Of Micro/Meso-Scale Features, Gap-Yong Kim, Jun Ni, Rhett Mayor, Heesool Kim
An Experimental Investigation On Semi-Solid Forming Of Micro/Meso-Scale Features, Gap-Yong Kim, Jun Ni, Rhett Mayor, Heesool Kim
Gap-Yong Kim
The potentials of semi-solid forming technology have generated much interest regarding its application in micromanufacturing. This study investigates the feasibility of using semi-solid forming technology to produce parts with micro/meso features. An experimental setup has been developed to study the effects of die/punch temperature, initial solid fraction, punch speed, and workpiece shape on the semi-solid forming process. A part has been produced for a microreactor application and has been analyzed with an optical measurement system for feature formation. The results indicated complex interaction among the process parameters and the material flow, which affected the final pin formation. The punch temperature …
Modification Of Multi-Walled Carbon Nanotubes By Microwave Digestion Method As Electrocatalyst Supports For Direct Methanol Fuel Cell Applications, Fang-Tzu Chuang
Modification Of Multi-Walled Carbon Nanotubes By Microwave Digestion Method As Electrocatalyst Supports For Direct Methanol Fuel Cell Applications, Fang-Tzu Chuang
Fang-Tzu Chuang
Multi-walled carbon nanotubes (MWCNTs) which were directly synthesized on carbon cloth were modified by a microwave digestion method in 5M HNO3 for supporting Pt nanoparticles. The characterizations of modified CNTs were carried out by TEM, XPS, FTIR and Raman spectroscopy. The HRTEM image shows the caps of MWCNTs are opened after modifying by microwave digestion method. The open-end and undamaged MWCNTs can provide a larger surface area for supporting more catalysts. Furthermore, the methanol electrocatalytic oxidation of microwave digestion treated Pt/MWCNTs electrode shows higher current density than pristine and nitric acid-treated MWCNTs from cyclic voltammograms. This can be an effective …
Semicrystalline Thermoplastic Elastomeric Polyolefins: Advances Through Catalyst Development And Macromolecular Design, Atsushi Hotta, Eric W. Cochran, Janne Ruokolainen, Vikram Khann, Glenn H. Fredrickson, Edward J. Kramer, Yong-Woo Shin, Fumihiko Shimizu, Anna E. Cherian, Phillip D. Hustad, Jeffrey M. Rose, Geoffrey W. Coates
Semicrystalline Thermoplastic Elastomeric Polyolefins: Advances Through Catalyst Development And Macromolecular Design, Atsushi Hotta, Eric W. Cochran, Janne Ruokolainen, Vikram Khann, Glenn H. Fredrickson, Edward J. Kramer, Yong-Woo Shin, Fumihiko Shimizu, Anna E. Cherian, Phillip D. Hustad, Jeffrey M. Rose, Geoffrey W. Coates
Eric W. Cochran
We report the design, synthesis, morphology, phase behavior, and mechanical properties of semicrystalline, polyolefin-based block copolymers. By using living, stereoselective insertion polymerization catalysts, syndiotactic polypropylene-block-poly(ethylene-co-propylene)-block-syndiotactic polypropylene and isotactic poly propylene-block-regioirregular poly propylene-block- isotactic polypropylene triblock copolymers were synthesized. The volume fraction and composition of the blocks, as well as the overall size of the macromolecules, were controlled by sequential synthesis of each block of the polymers. These triblock copolymers, with semicrystalline end-blocks and mid-segments with low glass-transition temperatures, show significant potential as thermoplastic elastomers. They have low Young's moduli, large strains at break, and better than 90% elastic recovery at …
Hydrogen And Deuterium Exchange On Pt(111) And Its Poisoning By Carbon Monoxide Studied By Surface Sensitive High-Pressure Techniques, Max Montano, Kaitlin M. Bratlie, Miquel Salmeron, Gabor A. Somorjai
Hydrogen And Deuterium Exchange On Pt(111) And Its Poisoning By Carbon Monoxide Studied By Surface Sensitive High-Pressure Techniques, Max Montano, Kaitlin M. Bratlie, Miquel Salmeron, Gabor A. Somorjai
Kaitlin M. Bratlie
Catalytic hydrogen/deuterium exchange on a platinum (111) single crystal and its poisoning with carbon monoxide was studied using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), sum frequency generation vibrational spectroscopy (SFG), and mass spectrometry under reaction conditions at pressures in the mTorr to atmospheric range. At 298 K and in the presence of 200 mTorr of hydrogen and 20 mTorr of deuterium the surface is catalytically active, producing HD with activation energy of 5.3 kcal/mol. Addition of 5 mTorr of CO stops the reaction completely. In situ STM images reveal an ordered surface structure of chemisorbed CO. At 353 …
Sum Frequency Generation Vibrational Spectroscopic And High-Pressure Scanning Tunneling Microscopic Studies Of Benzene Hydrogenation On Pt(111), Kaitlin M. Bratlie, Max O. Montano, Lucio D. Flores, Matti Paajanen, Gabor A. Somorjai
Sum Frequency Generation Vibrational Spectroscopic And High-Pressure Scanning Tunneling Microscopic Studies Of Benzene Hydrogenation On Pt(111), Kaitlin M. Bratlie, Max O. Montano, Lucio D. Flores, Matti Paajanen, Gabor A. Somorjai
Kaitlin M. Bratlie
Sum frequency generation (SFG) vibrational spectroscopy and high-pressure scanning tunneling microscopy (HP-STM) have been used in combination for the first time to study a catalytic reaction. These techniques have been able to identify surface intermediates in situ during benzene hydrogenation on a Pt(111) single-crystal surface at Torr pressures.
Effect Of Disorder On The Thermal Transport And Elastic Properties In Thermoelectric Zn4Sb3, S. Bhattacharya, R.P. Hermann, Veerle Keppens, T. M. Tritt, G. J. Snyder
Effect Of Disorder On The Thermal Transport And Elastic Properties In Thermoelectric Zn4Sb3, S. Bhattacharya, R.P. Hermann, Veerle Keppens, T. M. Tritt, G. J. Snyder
Veerle Keppens
Zn4Sb3 undergoes a phase transition from α to β phase at T1≈250 K. The high temperature β-Zn4Sb3 phase has been widely investigated as a potential state-of-the-art thermoelectric (TE) material, due to its remarkably low thermal conductivity. We have performed electronic and thermal transport measurements exploring the structural phase transition at 250 K. The α to β phase transition manifests itself by anomalies in the resistivity, thermopower, and specific heat at 250 K as well as by a reduction in the thermal conductivity as Zn4Sb3 changes phase from the ordered α to the disordered β-phase. Moreover, measurements of the elastic constants …
Comment On “Structural Stability Of Complex Hydrides: Libh4 Revisited”, Duane D. Johnson, Nikolai A. Zarkevich
Comment On “Structural Stability Of Complex Hydrides: Libh4 Revisited”, Duane D. Johnson, Nikolai A. Zarkevich
Duane D. Johnson
A Comment on the Letter by Zbigniew Łodziana and Tejs Vegge, Phys. Rev. Lett. 93, 145501 (2004).
Structure Effects Of Benzene Hydrogenation Studied With Sum Frequency Generation Vibrational Spectroscopy And Kinetics On Pt(111) And Pt(100) Single-Crystal Surfaces, Kaitlin M. Bratlie, Christopher J. Kliewer, Gabor A. Somorjai
Structure Effects Of Benzene Hydrogenation Studied With Sum Frequency Generation Vibrational Spectroscopy And Kinetics On Pt(111) And Pt(100) Single-Crystal Surfaces, Kaitlin M. Bratlie, Christopher J. Kliewer, Gabor A. Somorjai
Kaitlin M. Bratlie
Sum frequency generation (SFG) surface vibrational spectroscopy and kinetic measurements using gas chromatography have identified at least two reaction pathways for benzene hydrogenation on the Pt(100) and Pt(111) single-crystal surfaces at Torr pressures. Kinetic studies at low temperatures (310-370 K) show that benzene hydrogenation does not proceed through cyclohexene. A Langmuir-Hinshelwood-type rate law for the low-temperature reaction pathway is identified. The rate-determining step for this pathway is the addition of the first hydrogen atom to adsorbed benzene for both single-crystal surfaces, which is verified by the spectroscopic observation of adsorbed benzene at low temperatures on both the Pt(100) and Pt(111) …
Posterminaries: The Scales Of Judgement, Alexander H. King
Posterminaries: The Scales Of Judgement, Alexander H. King
Alexander H. King
Materials scientists are generally well-versed in physics, and physics, above all, is a science of measurements. The first instinct of a physicist is to parse a problem in terms of its measurables in the dimensions of mass, length, and time, and it is the shifting of attention down the scale of length that particularly characterizes our present times as the Nano Age.
Direct Experimental Evidence For Atomic Tunneling Of Europium In Crystalline Eu8Ga16Ge30, Raphaël P. Hermann, Veerle Keppens, Pierre Bonville, George S. Nolas, Fernande Grandjean, Gary J. Long, Hans M. Christen, Bryan C. Chakoumakos, Brian C. Sales, David Mandrus
Direct Experimental Evidence For Atomic Tunneling Of Europium In Crystalline Eu8Ga16Ge30, Raphaël P. Hermann, Veerle Keppens, Pierre Bonville, George S. Nolas, Fernande Grandjean, Gary J. Long, Hans M. Christen, Bryan C. Chakoumakos, Brian C. Sales, David Mandrus
Veerle Keppens
Mössbauer-effect and microwave absorption experimental evidence unambiguously demonstrates the presence of slow, ∼450 MHz, tunneling of magnetic europium between four equivalent sites in Eu8Ga16Ge30, a stoichiometric clathrate. Remarkably, six of the eight europium atoms, or 11% of the constituents in this solid, tunnel between these four sites separated by 0.55 Å. The off centering of the atoms or ions in crystalline clathrates appears to be a promising route for producing Rabi oscillators in solid-state materials.
Study Of Chemical Surface Modifications Of Cnts As Cathode Electrode For Dmfc, Fang-Tzu Chuang
Study Of Chemical Surface Modifications Of Cnts As Cathode Electrode For Dmfc, Fang-Tzu Chuang
Fang-Tzu Chuang
In this study, multi-wall carbon nanotubes (MWNTs) are used as Pt catalyst support for cathode electrode in the direct methanol fuel cell (DMFC). Thus, a lot of well-align MWNTs are fabricated on carbon cloth directly. The method in the cathode electrode of DMFC is easy to constructed and sticking on the carbon cloth tightly. Then, MWNTs are modified by HNO3, H2SO4, and KOH at high temperature may produce different functional groups to attract more Pt ions nucleating uniformly and densely. Moreover, there are the other parameters, temperature, time, and concentration, in the function of chemical modification for MWNTs. In this …
Fabrication Of Pdms (Polydimethylsiloxane) Microlens And Diffuser Using Replica Molding, Fang-Tzu Chuang
Fabrication Of Pdms (Polydimethylsiloxane) Microlens And Diffuser Using Replica Molding, Fang-Tzu Chuang
Fang-Tzu Chuang
This paper reports the fabrication method of PDMS (polydimethylsiloxane) microlens array based on the replica molding process, casting a liquid PDMS into concave microlens molds. Concave microlens molds were fabricated through spin-coating processes suspended a liquid PMMA film on the micro-drilled hole, leading to the formation of the special curvature. Then, PDMS microlens arrays and diffusers were fabricated by replica molding and discussed in this study. The fabricated microlenses have both good surface roughness and high-quality optical properties. Therefore, diffusers were fabricated by two-step replica molding. A high-intensity He–Ne laser beam was uniformly spread through diffusers. Experimental tests demonstrated that …
A Development Framework For Hands-On Laboratory Modules In Microelectromechanical Systems (Mems), John Lee, Stacy H. Gleixner, Tai-Ran Hsu, David W. Parent
A Development Framework For Hands-On Laboratory Modules In Microelectromechanical Systems (Mems), John Lee, Stacy H. Gleixner, Tai-Ran Hsu, David W. Parent
David W. Parent
This paper presents work-in-progress in terms of a framework that we have structured to support effective joint development among faculty from different engineering backgrounds, spanning mechanical engineering (ME), electrical engineering (EE), and materials engineering (MatE). The framework is organized in short instructional modules designed to span not only major device types and different fabrication technologies, but also different levels of resource requirements. An example of using functional prerequisites--rather than course prerequisites—is presented for one module, wherein each functional prerequisite must be satisfied by at least one member of each student team that will undertake the module. Roles of the faculty …
Dynamics Of Surface Catalyzed Reactions; The Roles Of Surface Defects, Surface Diffusion, And Hot Electrons, Gabor Somorjai, Kaitlin Bratlie, Max Montano, Jeong Park
Dynamics Of Surface Catalyzed Reactions; The Roles Of Surface Defects, Surface Diffusion, And Hot Electrons, Gabor Somorjai, Kaitlin Bratlie, Max Montano, Jeong Park
Kaitlin M. Bratlie
The mechanism that controls bond breaking at transition metal surfaces has been studied with sum frequency generation (SFG), scanning tunneling microscopy (STM), and catalytic nanodiodes operating under the highpressure conditions. The combination of these techniques permits us to understand the role of surface defects, surface diffusion, and hot electrons in dynamics of surface catalyzed reactions. Sum frequency generation vibrational spectroscopy and kinetic measurements were performed under 1.5 Torr of cyclohexene hydrogenation/dehydrogenation in the presence and absence of H2 and over the temperature range 300-500 K on the Pt(100) and Pt(111) surfaces. The structure specificity of the Pt(100) and Pt(111) surfaces …
Study Of Leading Factors In Formation Of Surface Wavy Structures On A Rubber Material, Fang-Tzu Chuang
Study Of Leading Factors In Formation Of Surface Wavy Structures On A Rubber Material, Fang-Tzu Chuang
Fang-Tzu Chuang
Wavy structures are often observed on the surface of a rubber material (polydimethylsiloxane, PDMS) covered with a thin metallic film. In this study we demonstrate that the orientation, periodicity, location of formation, and range of periodicity of the wavy structures can be regulated by three leading factors including the surface pattern, substrate hardness and the thickness of the metallic film. Results show the orientation of the wavy structures can be adjusted by the location, shape and size of the surface patterns. Enhancement of the substrate hardness can prevent forming random wavy structures. The thickness of surface metallic film significantly influenced …
In Situ Sum Frequency Generation Vibrational Spectroscopy Observation Of A Reactive Surface Intermediate During High-Pressure Benzene Hydrogenation, Kaitlin M. Bratlie, Lucio D. Flores, Gabor A. Somorjai
In Situ Sum Frequency Generation Vibrational Spectroscopy Observation Of A Reactive Surface Intermediate During High-Pressure Benzene Hydrogenation, Kaitlin M. Bratlie, Lucio D. Flores, Gabor A. Somorjai
Kaitlin M. Bratlie
Sum frequency generation surface vibrational spectroscopy and kinetic measurements using gas chromatography have been used to identify a reactive surface intermediate in situ during hydrogenation of benzene on a Pt(111) single crystal surface at Torr pressures. Upon adsorption at 310 K, both chemisorbed and physisorbed benzene coexist on the surface, a result which has not previously been observed. Kinetic measurements show a linear compensation effect for the production of both cyclohexane and cyclohexene. From these data the isokinetic temperature was identified and correlated to the chemisorbed benzene species, which were probed by means of vibrational spectroscopy. Additionally, chemisorbed benzene was …
Magnetic And Electronic Properties Of Eu4Sr4Ga16Ge30, G.T. Woods, J. Martin, M. Beekman, Raphaël P. Hermann, Fernande Grandjean, Veerle Keppens, O. Leupold, Gary J. Long, G.S. Nolas
Magnetic And Electronic Properties Of Eu4Sr4Ga16Ge30, G.T. Woods, J. Martin, M. Beekman, Raphaël P. Hermann, Fernande Grandjean, Veerle Keppens, O. Leupold, Gary J. Long, G.S. Nolas
Veerle Keppens
Magnetization, static and ac magnetic susceptibility, nuclear forward scattering, and electrical resistivity measurements have been performed on polycrystalline Eu4Sr4Ga16Ge30, a type I clathrate that has divalent strontium and europium ions encapsulated within a Ga-Ge framework. These data are compared with those of type I clathrates Eu8Ga16Ge30 and Eu6Sr2Ga16Ge30. The ferromagnetic ordering of these Eu-containing clathrates is substantially altered by the incorporation of strontium, as compared to Eu8Ga16Ge30. Ferromagnetism, accompanied by a relatively large negative magnetoresistance, is observed below 15 and 20 K in Eu4Sr4Ga16Ge30 and Eu6Sr2Ga16Ge30, respectively. An effective magnetic moment of 7.83 μB per Eu ion is observed above …
Stability Of The Gyroid Phase In Diblock Copolymers At Strong Segregation, Eric W. Cochran, Carlos J. Garcia-Cervera, Glenn H. Fredrickson
Stability Of The Gyroid Phase In Diblock Copolymers At Strong Segregation, Eric W. Cochran, Carlos J. Garcia-Cervera, Glenn H. Fredrickson
Eric W. Cochran
The gyroid phase in diblock copolymers at strong segregation was stabilized. The intriguing topology of the network structure has inspired a diverse array of potential applications ranging from high-performance separation membranes to photonic crystals. The pressure field enforces incompressibility, while the exchange field is conjugate to the composition pattern in the melt. The Laplacian operator is treated implicitly with a fourth-order backward differentiation formula (BDF4), whereas the source term is discretized explicitly using fourth-order accurate Adams-Bashford.
Modeling Energetics And Noise In Dislocation Patterning, Robb Thomson, M. Koslowski, Richard Alan Lesar
Modeling Energetics And Noise In Dislocation Patterning, Robb Thomson, M. Koslowski, Richard Alan Lesar
Richard Alan Lesar
We explore the underlying physics of dislocation ordering in deforming metals, where we focus on the competing role of energy relaxation and the fluctuations (noise) in the local stress field. We investigate the competition by employing a simple two-dimensional model that exhibits the essential physics, while avoiding extraneous mechanisms that might cloud the issues. We show that noise and energetics are equally important in determining the final state of the system. Quantitative functions for the energetic driving force for ordering and the resistive force owing to the noise are developed that balance one another at the relaxed state. These features …
Theoretical Analysis Of Auto-Stability In Laser Resonator With Thermal Lenses Effect, Juan José Soto-Bernal, Adrian Bonilla-Petriciolet
Theoretical Analysis Of Auto-Stability In Laser Resonator With Thermal Lenses Effect, Juan José Soto-Bernal, Adrian Bonilla-Petriciolet
Adrian Bonilla-Petriciolet
In this work a numeric analysis is carried out to calculate the thermal lens effect in the stability of a barside-pumpedresonator at 808 nm. The active medium is a Nd:YVO4 crystal. It is demonstrated that the thermal effects produced by the radiative process, in certain conditions can take one of the planes to a non consistency, having as a consequence an oscillator that will work in intermittent form.
Characterization Of Cement And Concrete Exposed To Laser Radiation At 10.6 Um, María Del Rosario Moreno-Virgen, Juan José Soto-Bernal, Claudio Frausto-Reyes, Adrian Bonilla-Petriciolet
Characterization Of Cement And Concrete Exposed To Laser Radiation At 10.6 Um, María Del Rosario Moreno-Virgen, Juan José Soto-Bernal, Claudio Frausto-Reyes, Adrian Bonilla-Petriciolet
Adrian Bonilla-Petriciolet
In this paper, we report preliminary results of molecular structural changes in cement and concrete caused by laser radiation at 10.6 um. One of those structural changes is the generation of glazes. At low laser powers, the glazes are small and lined up while at high powers, the glazes are bigger and randomly distributed. In the not exposed to laser radiation concrete, the Raman spectrum presents weak peaks at 200 cm-1, 550 cm-1, 700 cm-1, 750 cm-1 and 1 150 cm-1. However, these peaks are amplified by laser exposure and other peaks appear at 800 cm-1 and 1 050 cm-1. …
The Synthesis Of Ultrafine And Nanocomposite Powders Based On Copper, Silver And Alumina, Zeljko J. Kamberovic
The Synthesis Of Ultrafine And Nanocomposite Powders Based On Copper, Silver And Alumina, Zeljko J. Kamberovic
Zeljko J Kamberovic
Contemporary materials with predetermined properties can be successfully synthesized by utilising the principles of hydrometallurgy and powder metallurgy. The results of developing a new procedure for the synthesis of ultrafine and nanocomposite powders based on copper, silver and alumina are presented in this paper. A two-component nanocomposite powder, Cu-Al2O3, was synthesized by a thermochemical procedure, by deposition from an aqueous solution of soluble metal salts, Cu(NO3)2 and Al(NO3)3. A three-component Cu-Ag-Al2O3 powder was produced by mechanically alloying nanocomposite Cu-Al2O3 powder and Cu-Ag powder, synthesized by the thermochemical procedure. The produced powders were characterized by determining the particle specific area, pouring …
Sulphated Almcm-41: Mesoporous Solid Brønsted Acid Catalyst For Dibenzoylation Of Biphenyl, Eng-Poh Ng, Hadi Nur, Mohd Nazlan Mohd Muhid, Halimaton Hamdan
Sulphated Almcm-41: Mesoporous Solid Brønsted Acid Catalyst For Dibenzoylation Of Biphenyl, Eng-Poh Ng, Hadi Nur, Mohd Nazlan Mohd Muhid, Halimaton Hamdan
Eng-Poh Ng
Sulphated mesoporous solid Brønsted acid catalyst (SO4-AlMCM-41) was prepared by impregnation of sulphuric acid on the surface of H-AlMCM-41. Characterization of SO4-AlMCM-41 by pyridine adsorption studies and 27Al MAS NMR showed that the presence of Brønsted acidity was correlated with octahedrally coordinated aluminium and solvent environment. Catalytic study demonstrated that the SO4-AlMCM-41 catalyst has a higher activity in the dibenzoylation of biphenyl with benzoyl chloride than sulphuric acid, H-AlMCM-41 and sulphated amorphous silica.
Cluster-Type Basic Lanthanide Iodides [M6(Μ6-O)(Μ3-Oh)8(H2o)24]I8(H2o)8 (M = Nd, Eu, Tb, Dy), Anja V. Mudring, Tudor Timofte, Arash Babai
Cluster-Type Basic Lanthanide Iodides [M6(Μ6-O)(Μ3-Oh)8(H2o)24]I8(H2o)8 (M = Nd, Eu, Tb, Dy), Anja V. Mudring, Tudor Timofte, Arash Babai
Anja V. Mudring
Ln6(μ6-O)(μ3-OH)8(H2O)24]I8(H2O)8 (Ln = Nd, Eu, Tb, Dy) compounds are obtained as the final hydrolysis products of lanthanide triiodides in an aqueous solution. Their X-ray crystal structure features a body-centered arrangement of oxygen-centered {Ln6X8}8+ cluster cores: [Nd6(μ6-O)(μ3-OH)8(H2O)24]I8(H2O)8 [Pearson code oP156, orthorhombic, Pnnm (No. 58), Z = 2, a = 1310.4(3) pm, b = 1502.1(3) pm, c = 1514.9(3) pm, 3384 reflections with I0 > 2σ(I0), R1 = 0.0340, wR2 = 0.0764, GOF = 1.022, T = 298(2) K], [Eu6(μ6-O)(μ3-OH)8(H2O)24]I8(H2O)8 [Pearson code oP156, orthorhombic, Pnnm (No. 58), Z = 2, a = 1306.6(2) pm, b = 1498.15(19) pm, c = 1499.41(18) pm, 4262 …
Homoleptic Alkaline Earth Metal Bis(Trifluoromethanesulfonyl)Imide Complex Compounds Obtained From An Ionic Liquid, Arash Babai, Anja V. Mudring
Homoleptic Alkaline Earth Metal Bis(Trifluoromethanesulfonyl)Imide Complex Compounds Obtained From An Ionic Liquid, Arash Babai, Anja V. Mudring
Anja V. Mudring
The first homoleptic alkaline earth bis(trifluoromethanesulfonyl)imide (Tf2N) complexes [mppyr]2[Ca(Tf2N)4], [mppyr]2[Sr(Tf2N)4], and [mppyr][Ba(Tf2N)3] were crystallized from a solution of the respective alkaline earth bis(trifluoromethanesulfonyl)imide and the ionic liquid [mppyr][Tf2N] (mppyr = 1,1-N-methyl-N-propylpyrrolidinium). In the calcium and strontium compounds, the alkaline earth metal (AE) is coordinated by four bidentately chelating Tf2N ligands to form isolated (distorted) square antiprismatic [AE(Tf2N)4]2- complexes which are separated by N-methyl-N-propylpyrrolidinium cations. In contrast, the barium compound, [mppyr][Ba(Tf2N)3], forms an extended structure. Here the alkaline earth cation is surrounded by six oxygen atoms belonging to three Tf2N- anions which coordinate in a bidentate chelating fashion. Three further oxygen …
The First Homoleptic Bis(Trifluoromethanesulfonyl)Amide Complex Compounds Of Trivalent F-Elements, Anja V. Mudring, Arash Babai
The First Homoleptic Bis(Trifluoromethanesulfonyl)Amide Complex Compounds Of Trivalent F-Elements, Anja V. Mudring, Arash Babai
Anja V. Mudring
The synthesis and crystal structures of the first true homoleptic bis(trifluoromethanesulfonyl)amide complex compounds of trivalent f-elements are reported with [bmpyr]2[Ln(Tf2N)5], Ln = Nd, Tb and [bmpyr][Ln(Tf2N)4], Ln = Tm, Lu.