Publications de Paul Bowen | EPFL Graph Search

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By following the densification kinetics of nanocrystalline γ alumina and corresponding microstructural evolution we showed that the diffusive transformation gamma-alpha involves several processes such as nucleation of alpha phase, rearrangement of gamma cr ...

Calcium silicate hydrate (C-S-H) is the most abundant synthetic phase on the planet. However, its atomic-level structure remains only partially resolved. In the present study, the atomic-level structure, water content, and energetics of bulk C-S-H are investigated by molecular dynamics (MD). It is shown that experimentally observed water retention in the C-S-H structure is closely associated by the calcium oxygen coordination environment. This coordination environment affects the cohesion and hydration ener

Thirteen different commercial TiO2 powders with specific surface areas varying from 9 to 335 m/g and with isoelectric points (IEP) from 3 to 7.5 were investigated for their catalytic activity in E. coli inactivation. The TiO2 samples zeta potential, attenu ...

A new Python code for the automated generation of realistic bulk calcium silicate hydrate (C-S-H) structures is introduced. The code was used to generate 400 structures with Ca/Si of 1.3, 1.5, 1.7, and 1.9. The generated structures are in excellent agreeme ...

The performance of the electrolytic ozone generation using a solid polymer electrolyte (SPE) and Pb anode is described. This anode has been prepd. by application of Pb powder on a porous Ti substrate coated with IrO2 layer (Ti/IrO2/Pb anode). Electrochem. measurements and XRD analyses have shown that, after anodic polarization in deionized water a and b-PbO2 are formed at the electrode-membrane-water interfaces. The effect of electrolysis time, anolyte temp., applied c.d. and cell design on the efficiency o

CuO powders with a high specific surface area are shown to be able to produce H2O2 in aqueous solution under simulated light irradiation. The highest rate of peroxide production was observed under mild experimental conditions using O2 and a large surface a ...

In the quest for high real in-line transmittances for transparent polycrystalline alumina (PCA), we need defect free processing. One of the biggest advances in producing high density defect free ceramics over recent years has been the advent of spark plasm ...

Spark Plasma Sintering (SPS) has been successfully applied in the sintering of nanocrystalline BaTiO3 and γ-Al2O3 in order to reach fully dense nanostructured ceramics at moderate pressure and temperature. BaTiO3 compacts with densities exceeding 97% and grain size of 50 nm have thus been prepared at temperatures not exceeding 850 oC using a uniaxial pressure of 100MPa. The selection of sintering temperature is critical for the purpose of minimizinggrain growth and there is a demarcation temperature (820 oC

Microstructural control is a key aspect in producing ceramics with tailored properties and is often achieved by using dopants in a rather empirical fashion. Atomic scale simulations could provide much needed insight but the long-standing challenge of linki ...

LiMnPO4 was synthesized using a sol–gel method and tested as a cathode material for lithium ion batteries. After calcination at temperatures between 520 and 600 ◦C, primary particle sizes in the range of 140–220 nm were achieved. Subsequent dry ball millin ...

This study presents a comparative approach to investigate the potentials of two innovative methods for the synthesis of ZnO and Al-doped ZnO. The first method is a precipitation system working in mild hydrothermal conditions (90°C) using a tubular reactor (Segmented Flow Tubular Reactor, SFTR). The second method is a microwave-assisted hydrothermal process working at 250°C - 38 atmospheres. Nanocrystalline ZnO with a high specific surface area (49–68 m2/g) was obtained with both systems. Smaller equiaxed pa

Portlandite is an important constituent of cementitious materials. Consequently the growth of portlandite is of great interest to fully understand the hydration of cement, a process still posing many scientific challenges. In this paper the growth of portlandite in aqueous systems is studied by simulating the adsorption of Ca2 + and OH− at different portlandite surfaces. For the simulation an adapted version of the Freeman (Freeman et al., 2007) in combination with the TIP4P/2005 (Abascal and Vega, 2005) fo

An overarching computational framework unifying several optical theories to describe the temporal evolution of gold nanoparticles (GNPs) during a seeded growth process is presented. To achieve this, we used the inexpensive and widely available optical exti ...

The surface of a biomaterial can play a major role in its biological fate since the surface is the primary pathway for its interaction with the body. As the natural response of the body to a foreign material is to encapsulate it with a fibrous material, th ...

The possibility of controlling materials properties by tailoring their substructure at the nanometer scale is a current topic of great interest. To do so, a fundamental understanding of the growth mechanism is of key importance and an analytical challenge ...

This paper is a discussion of a recent publication by Sekkal and coworkers, which investigated the elasticity, cohesion, and stability of the C-S-H (001) surface as a function of porosity using molecular dynamics simulations. In our discussion, we highligh ...

The question whether beta-tricalcium phosphate (beta-TCP) can form a solid solution with beta-calcium pyrophosphate (beta-CPP) and/or hydroxyapatite (HA) has still not been solved. For this reason, wet-chemically synthesized beta-TCP powders with only 20 p ...

Nanoparticles and method for producing uniform silicate-based nanoparticles are disclosed. The method comprises a step of injecting into tubular branched elements comprising static mixers a first aqueous solution comprising a water-soluble silicate compoun ...

Deciphering the calcium silicate hydrate (C-S-H) surface is crucial for unraveling the mechanisms of cement hydration and property development. Experimental observations of C-S-H in cement systems suggest a surface termination which is fundamentally differ ...

The percolation behavior of alumina suspensions is studied by computer simulations. The percolation threshold phi(c), is calculated, determining the key factors that affect its magnitude: the strength of colloid-colloid attraction and the presence of hydro ...

Paul Bowen

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Phase Transformation and Densification of Nanostructured Alumina. Effect of Seeding and Doping

Interlayer structure and hydration energetics of calcium silicate hydrate

Catalytic activity of commercial of TiO2 powders for the abatement of the bacteria (E. coli) under solar simulated light: Influence of the isoelectric point

pyCSH: Automated atomic-level structure generation of bulk C-S-H and investigation of their intrinsic properties

Preparation and characterization of Ti/IrO2/Pb electrodes for ozone production in a SPE electrochemical cell

Photocatalytic Storing of O2 as H2O2 Mediated by High Surface Area CuO. Evidence for a Reductive-Oxidative Interfacial Mechanism

Comparison of apparent activation energies for densification of alumina powders by pulsed electric current sintering (spark plasma sintering) and conventional sintering-toward applications for transparent polycrystalline alumina

Spark Plasma Sintering of Nano-crystalline Ceramics

Atomistic modeling of dopant segregation in alpha-alumina ceramics: Coverage dependent energy of segregation and nominal dopant solubility

Effect of particle size on LiMnPO4 cathodes

Comparison of two innovative precipitation systems for ZnO and Al-doped ZnO nanoparticle synthesis

Atomistic simulation of the absorption of calcium and hydroxyl ions onto portlandite surfaces - towards crystal growth mechanisms

Kinetics and Mechanism of Metal Nanoparticle Growth via Optical Extinction Spectroscopy and Computational Modeling: The Curious Case of Colloidal Gold

Interaction of biologically relevant ions and organic molecules with titanium oxide (rutile) surfaces: A review on molecular dynamics studies

Precipitation of Nanostructured Copper Oxalate: Substructure and Growth Mechanism

A discussion on the paper "Role of porosity on the stiffness and stability of (001) surface of the nanogranular C-S-H gel"

Chemically pure beta-tricalcium phosphate powders: Evidence of two crystal structures

Nanoparticles and method for producing uniform silicate-based nanoparticles

Atomic-Level and Surface Structure of Calcium Silicate Hydrate Nanofoils

How colloid-colloid interactions and hydrodynamic effects influence the percolation threshold: A simulation study in alumina suspensions