Women and Water-Pumps in Bangladesh

1996 ◽  
Author(s):  
Barbara van Koppen ◽  
Simeen Mahmud
Keyword(s):  
Water Pumps

Structure, Stability and Water Adsorption on Ultra-Thin TiO2 Supported on TiN

2019 ◽  
Author(s):  
Jose Julio Gutierrez Moreno ◽  
Marco Fronzi ◽  
Pierre Lovera ◽  
alan O'Riordan ◽  
Mike J Ford ◽  
...  
Keyword(s):  
Density Functional ◽  
Water Adsorption ◽  
Chemical Potential ◽  
Energy Gap ◽  
Molecular Water ◽  
Structure Stability ◽  
Ambient Conditions ◽  
Rutile Structure ◽  
The Stability ◽  
The One

<p></p><p>Interfacial metal-oxide systems with ultrathin oxide layers are of high interest for their use in catalysis. In this study, we present a density functional theory (DFT) investigation of the structure of ultrathin rutile layers (one and two TiO<sub>2</sub> layers) supported on TiN and the stability of water on these interfacial structures. The rutile layers are stabilized on the TiN surface through the formation of interfacial Ti–O bonds. Charge transfer from the TiN substrate leads to the formation of reduced Ti<sup>3+</sup> cations in TiO<sub>2.</sub> The structure of the one-layer oxide slab is strongly distorted at the interface, while the thicker TiO<sub>2</sub> layer preserves the rutile structure. The energy cost for the formation of a single O vacancy in the one-layer oxide slab is only 0.5 eV with respect to the ideal interface. For the two-layer oxide slab, the introduction of several vacancies in an already non-stoichiometric system becomes progressively more favourable, which indicates the stability of the highly non-stoichiometric interfaces. Isolated water molecules dissociate when adsorbed at the TiO<sub>2</sub> layers. At higher coverages the preference is for molecular water adsorption. Our ab initio thermodynamics calculations show the fully water covered stoichiometric models as the most stable structure at typical ambient conditions. Interfacial models with multiple vacancies are most stable at low (reducing) oxygen chemical potential values. A water monolayer adsorbs dissociatively on the highly distorted 2-layer TiO<sub>1.75</sub>-TiN interface, where the Ti<sup>3+</sup> states lying above the top of the valence band contribute to a significant reduction of the energy gap compared to the stoichiometric TiO<sub>2</sub>-TiN model. Our results provide a guide for the design of novel interfacial systems containing ultrathin TiO<sub>2</sub> with potential application as photocatalytic water splitting devices.</p><p></p>

scholarly journals Design of Molecular Water Oxidation Catalysts Stabilized by Ultrathin Inorganic Overlayers—Is Active Site Protection Necessary?

Inorganics ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 105 ◽  
Author(s):  
Laurent Sévery ◽  
Sebastian Siol ◽  
S. Tilley
Keyword(s):  
Water Oxidation ◽  
Atomic Layer ◽  
Deposition Process ◽  
Operating Conditions ◽  
Molecular Water ◽  
Side Reactions ◽  
Aqueous Environment ◽  
Oxidation Catalysts ◽  
Initial Onset ◽  
Anchoring Groups

Anchored molecular catalysts provide a good step towards bridging the gap between homogeneous and heterogeneous catalysis. However, applications in an aqueous environment pose a serious challenge to anchoring groups in terms of stability. Ultrathin overlayers embedding these catalysts on the surface using atomic layer deposition (ALD) are an elegant solution to tackle the anchoring group instability. The propensity of ALD precursors to react with water leads to the question whether molecules containing aqua ligands, such as most water oxidation complexes, can be protected without side reactions and deactivation during the deposition process. We synthesized two iridium and two ruthenium-based water oxidation catalysts, which contained an aqua ligand (Ir–OH2 and Ru–OH2) or a chloride (Ir–Cl and Ru–Cl) that served as a protecting group for the former. Using a ligand exchange reaction on the anchored and partially embedded Ru–Cl, the optimal overlayer thickness was determined to be 1.6 nm. An electrochemical test of the protected catalysts on meso-ITO showed different behaviors for the Ru and the Ir catalysts. The former showed no onset difference between protected and non-protected versions, but limited stability. Ir–Cl displayed excellent stability, whilst the unprotected catalyst Ir–OH2 showed a later initial onset. Self-regeneration of the catalytic activity of Ir–OH2 under operating conditions was observed. We propose chloride ligands as generally applicable protecting groups for catalysts that are to be stabilized on surfaces using ALD.

Paper 15: Recent Research and Development in Truck Engine Cooling

1969 ◽  
Vol 184 (1) ◽  
pp. 117-124 ◽  
Author(s):  
S. R. G. Taylor
Keyword(s):  
Coolant Temperature ◽  
Analytical Prediction ◽  
Cooling Performance ◽  
Pump Speed ◽  
Power Characteristics ◽  
Engine Cooling ◽  
System Pressure ◽  
Component Design ◽  
Additional Resistance ◽  
Water Pumps

To improve economically the cooling performance of trucks an analytical approach was used to assist development. The component tests undertaken included the complete net pressure and power characteristics of two engine water pumps and four engine fans, the heat transfer and pressure drop performances over appropriate flow ranges of some 14 radiators, the additional resistance to air flow offered by two noise shields, and studies of the effects of pump speed, coolant temperature, system pressure, thermostat resistance, and by-pass resistance on radiator water flow with three different engines. The apparatus and methods used for each type of test are outlined. Using the above and other existing data, cooling performance was predicted for some 80 different configurations and conditions, and fan power consumption was predicted for several of these. These results enabled component design and manufacturing problems to be identified and the selection of the most promising configurations for actual development testing. The agreement between the predicted and actual cooling performances is discussed. The use of computer programmes in component testing and analytical prediction is mentioned, and various possible developments in future cooling systems of still higher performance are discussed.

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