Surface Modification of Ti6Al4V Open Porous Structures Produced by Additive Manufacturing

Additive manufacturing techniques can be used to produce micro‐porous structures with global morphological properties that are highly controlled through robust computer design. Despite these advantages, most of these techniques still hold several functional constraints, resulting from present technical device limits and consequently the inability to control surface morphology at a microscale level. In this study, a novel protocol for surface modification of 3D titanium alloy‐based open porous structures is developed, which applies a combination of chemical etching (CHE) and electrochemical polishing (ECP) using HF‐based solutions. This protocol achieves significant and controllable roughness reduction of additive manufactured 3D Ti6Al4V open porous structures. Chemical etching mainly removes the attached powder grains, while ECP further decreases the roughness. In this way the heterogeneity of the strut surface roughness throughout the full 3D structure is effectively removed.     

An economical, semi-automatic system for measuring cellular tree structures in three dimensions, with special emphasis on Golgi-impregnated neurons.

The hardware and software of a semi-automatic system are described for the measurement of cellular tree structures in thick microscopical sections such as the process of Golgi-impregnated neurons. With this system, the morphologist--viewing the neuron directly through the microscope--measures the tree structures using three cartesian coordinates of characteristic points, e.g. centre of cell, origin of processes, bifurcation points, end points, deflection points, etc. The system requires an on-line computer, but does not demand a dedicated computer since a joy-stick generator usually drives the microscopical stage during cell tracking. A digital computer is utilized for acquisition of data, and, when needed, to return the stage to a required position. The microscope stage is coupled to three stepping motors with 0.5 micron as the smallest step. The stepping motor for movement of the stage parallel to the optical axis (z-direction) is coupled directly to a spindle mechanism, replacing the original cog wheel mechanism. This construction shows no measurable backlash. The practical advantages of this new measuring system in relation to the existing digital systems currently in use, its accuracy and its costs, are discussed.     

Near-field microwave scanning probe imaging of conductivity inhomogeneities in CVD graphene

We have performed near-field scanning microwave microscopy (SMM) of graphene grown by chemical vapor deposition. Due to the use of probe-sample capacitive coupling and a relatively high ac frequency of a few GHz, this scanning probe method allows mapping of local conductivity without a dedicated counter electrode, with a spatial resolution of about 50?nm. Here, the coupling was enabled by atomic layer deposition of alumina on top of graphene, which in turn enabled imaging both large-area films, as well as micron-sized islands, with a dynamic range covering a low sheet resistance of a metal film and a high resistance of highly disordered graphene. The structures of graphene grown on Ni films and Cu foils are explored, and the effects of growth conditions are elucidated. We present a simple general scheme for interpretation of the contrast in the SMM images of our graphene samples and other two-dimensional conductors, which is supported by extensive numerical finite-element modeling. We further demonstrate that combination of the SMM and numerical modeling allows quantitative information about the sheet resistance of graphene to be obtained, paving the pathway for characterization of graphene conductivity with a sub-100?nm special resolution.     

Flavour release from rehydrated French beans (Phaseolus vulgaris) influenced by composition and volume of artificial saliva

Influence of saliva composition and volume on flavour release from rehydrated French beans (Phaseolus vulgaris) was studied in three types of mouth model systems; dynamic headspace (DH), dynamic headspace and mastication (DHM) and a purge-and-trap (PT) model system. Volatile compounds were analysed by gas chromatography, using flame ionization detection (FID), mass spectrometry and sniffing port detection. Areas of FID peaks were largest in the PT system, followed by those of the DHM and DH systems, respectively. Saliva composition as well as volume influenced the release of volatile compounds from rehydrated French beans. Generally, FID data showed a decrease in release by the saliva component mucin, because of interactions between volatile compounds and protein, and an increase in release by its α-amylase, probably due to degradation of inclusion complexes of starch. The decrease in flavour release by the enlarged saliva volume was evaluated by a model study. Sniffing patterns of odour active compounds were barely influenced by either saliva composition or volume.     

Theory of Cast Formation in Electrophoretic Deposition

The rate of cast formation in electrophoretic deposition is described by a combination of the equation of continuity for the suspension phase with expressions for the particle velocity and the movement of the cast-suspension boundary. The assumptions necessary to arrive at the well-known equations of Hamaker (1940) and Avgustinik (1962) are summarized, and it is shown that, in both equations, a factor is missing that tends to unity only for diluted suspensions. After incorporation of this factor, it is possible to understand better the more-than-linear increase of cast formation with increasing suspension concentration as reported by several authors.     

First principle‐based simulation of ethane steam cracking

A consistent set of ab initio‐based kinetic and thermodynamic data is applied for the simulation of an ethane steam cracking furnace. The thermodynamic data are calculated using accurate quantum chemical CBS‐QB3 calculations including corrections for hindered internal rotation. The kinetics are obtained from CBS‐QB3‐based group additive models. With these thermodynamic and kinetic data, simulations for pilot and industrial ethane steam cracking reactors over a wide range of process conditions are performed. It is shown that, without adjusting any parameter, the main product yields can be predicted within 15% rel. of the experimentally observed cracking yields. This indicates the tremendous potential of integrating ab initio methods with engineering models for accurate reactor simulations. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Micellar morphology of a semifluorinated diblock copolymer

The diblock copolymer of methyl methacrylate and 1H,1H,2H,2H-perfluorooctyl methacrylate was shown to form micelles which could be deposited and imaged on a flat substrate upon casting from a solvent which is selective for the PMMA block, e.g. toluene and THF. The micelle formation was significantly affected by a small content of PMMA homopolymer. While the pure blockcopolymer formed cylindrical micelles, the presence of the PMMA shifted the associated equilibrium to the side of spherical aggregates. Received: 31 October 1997/Revised version: 15 December 1997/Accepted: 18 December 1997     

Low surface energy polymeric films from partially fluorinated photocurable solventless liquid oligoesters

Summary We have recently shown that low surface energy polymeric films can be readily obtained from partially fluorinated hydroxyl-end-capped solventless liquid oligoesters by thermal curing [1]. Photocurable liquid oligoesters can be prepared by further substituting the remaining hydroxyl end groups with acrylic double bonds. A conventional photoinitiator containing 2-hydroxy-2-methylpropiophenone was used to cure the liquid oligoesters. As the fluorine content increases from 0 to about 1.57 wt %, the surface energy decreases by about 14 mN/m. The fluorine level in the outer few nanometers is significantly greater than that in the bulk, as revealed by XPS studies. The driving force for the surface segregation of fluorinated species comes from the large difference in surface energy between the oligoesters and their fluorinated counterparts. Received: 14 August 2001/Revised version: 10 October 2001/Accepted: 10 October 2001