Voids in Materials: Adding Functionality during Additive Manufacturing

An often overlooked implication of controlling materials at ever smaller length scales is the control of the inevitable void spaces contained in those materials and components. This miniaturization is widespread and at these small length scales, properties become size dependent, trending toward more ideal material properties. This is corroborated by the extensive selection dispersed phases such as nanotubes and nanometer-scale particles that are available. The technique of additive manufacturing is gaining enormous attention as it offers the ability to make multifunctional components that cannot be made by traditional processing routes. In additive manufacturing, more precise control of material placement presents a unique opportunity to build functionality by the simultaneous control of solid material and voids at multiple length scales. We present an overview of the functionality of voids from the atomic to the millimeter scale, highlighting the current research involving the introduction of voids in additive manufacturing and present future opportunities to incorporate voids by specific additive manufacturing techniques to add functionality

Coated glass microballoons and syntactic foams thereof for environmental cleanup

Titania is of great interest to water purification applications mainly because of its nontoxic nature and its photocatalytic properties. In the presence of ultraviolet (UV) radiation (with energy equal to or greater than its band gap (EG = 3.02 eV) which translates to a wavelength less than or equal to 400 nm) titania exhibits semiconducting properties and creates electron-hole pairs. These electrons and holes give rise to ions, particularly hydroxyl radicals and various superoxides that can be useful in cleaning up a range of organic compounds in their liquid and gaseous phases. We have developed titania coated glass microballoons (GMBs) with high surface area. These hollow GMBs are made of borosilicate glass, have a density of 0.39 g/cm3, and an average diameter of 47µm. The objective is to use syntactic foams made of titania coated GMBs for water purification. This materials system is of great interest because it has the potential of a practical material with broad implications for improving the quality and quantity of drinking water. In this work, we describe the processing by sol-gel of titania-coated glass microballoons (GMBs), followed by making a functional foam for environmental applications by sintering. We will highlight the processing of coated GMBs starting with titanium isopropoxide precursor, the microstructure of the coated GMBs, and some critical materials related issues in environmental cleanup applications

CASTOR: The ALICE forward detector for identification of Centauros and Strangelets in Nucleus-Nucleus Collisions at the LHC

The physics motivation for a very forward detector for the ALICE heavy ion experiment at the CERN LHC is discussed. A phenomenological model describing the formation and decay of a Centauro fireball in nucleus-nucleus collisions is presented. The CASTOR detector which is aimed to measure the hadronic and photonic content of an interaction and to identify deeply penetrating objects in the very forward, baryon-rich phase space 5.6 < eta < 7.2 in an event-by-event mode is described. Results of simulations of the expected response of the calorimeter, and in particular to the passage of strangelets, are presented.Comment: Presented at XXVIII Int. Symp. on Multiparticle Dynamics, Delphi, 6-11 Sept. 1998. 9 pages, 11 figure

Can Centauros or Chirons be the first observations of evaporating mini black holes?

We argue that the signals expected from the evaporation of mini black holes - predicted in TeV-scale gravity models with large extra dimensions, and possibly produced in ultra high energy collisions in the atmosphere - are quite similar to the characteristics of the Centauro events, an old mystery of cosmic-ray physics.Comment: 14 pages, LaTeX, one Table, uses rotate.sty and rotcapt.sty. References added, typos corrected, footnotes moved into the tex

Temporal variability and statistics of the Strehl ratio in adaptive-optics images

We have investigated the temporal variability and statistics of the "instantaneous" Strehl ratio. The observations were carried out with the 3.63-m AEOS telescope equipped with a high-order adaptive optics system. In this paper Strehl ratio is defined as the peak intensity of a single short exposure. We have also studied the behaviour of the phase variance computed on the reconstructed wavefronts. We tested the Marechal approximation and used it to explain the observed negative skewness of the Strehl ratio distribution. The estimate of the phase variance is shown to fit a three-parameter Gamma distribution model. We show that simple scaling of the reconstructed wavefronts has a large impact on the shape of the Strehl ratio distribution.Comment: submitted to PAS

Formation of Centauro and Strangelets in Nucleus-Nucleus Collisions at the LHC and their Identification by the ALICE Experiment

We present a phenomenological model which describes the formation of a Centauro fireball in nucleus-nucleus interactions in the upper atmosphere and at the LHC, and its decay to non-strange baryons and Strangelets. We describe the CASTOR detector for the ALICE experiment at the LHC. CASTOR will probe, in an event-by-event mode, the very forward, baryon-rich phase space 5.6 < \eta < 7.2 in 5.5 A TeV central Pb + Pb collisions. We present results of simulations for the response of the CASTOR calorimeter, and in particular to the traversal of Strangelets.Comment: 4 pages, 4 figures, to appear in the proceedings of the 26th ICR

CASTOR: Centauro and Strange Object Research in nucleus-nucleus collisions at LHC

We describe the CASTOR detector designed to probe the very forward, baryon-rich rapidity region in nucleus-nucleus collisions at the LHC. We present a phenomenological model describing the formation of a QGP fireball in a high baryochemical potential environment, and its subsequent decay into baryons and strangelets. The model explains Centauros and the long-penetrating component and makes predictions for the LHC. Simulations of Centauro-type events were done. To study the response of the apparatus to new effects different exotic species (DCC, Centauros, strangelets etc.) were passed through the deep calorimeter. The energy deposition pattern in the calorimeter appears to be a new clear signature of the QGP.Comment: Talk given by E. Gladysz-Dziadus for the CASTOR group, Intern. Workshop on Nuclear Theory, 10-15 June, 2002, Bulgaria, Rila Mountains, 15 pages, 14 figure

Nano-compression of carbon micro-balloons on a xp-nanoindenter

Microballoons are thin hollow spheres that are bonded together with resins to form 'syntactic foam'. These foams exhibit very high specific compressive strength. Mechanical properties of the microballoons are integral to the mechanical properties of the syntactic foams and will also be useful in modeling of the system. This paper will present nano-compression results obtained for individual carbon microballoons (CMBs) tested between 5 and 50 mN on a XP nano-indentation device (MTS) customized with a special cylindrical tip. Details of the procedure will also be presented. CMBs ranging in diameter from 5 to 80 pm were randomly chosen for testing, which allowed for a statistical analysis (140 tests). Less than 25% of the CMBs were found to be nearly perfect spheres (from comparison between the 'horizontal' diameter measured with a microscope and the 'vertical' compressed diameter). CMBs smaller than 10 pm and greater than 50 pm were markedly ellipsoidal and about one third of the CMBs exhibited 'sequential' cracking, revealing the existence of flaws. SEM and optical microscopy of the foams revealed these flaws as either voids in the wall thickness or compartments in some CMBs. Conventional Berkovich nano-indentation was performed on segments of CMB walls after nanocompresseion and yielded a value of approximately 31 GPa for Young's modulus. The measured thickness was between 0.3 and 2.2 pm, showing no correlation with the diameter of the pristine CMBs

Bose-Einstein correlations of pion pairs in central Pb+Pb collisions at CERN SPS energies

Measurements of Bose-Einstein correlations of pion pairs in central Pb+Pb collisions were performed with the NA49 detector at the CERN SPS for beam energies of 20A, 30A, 40A, 80A, and 158A GeV. Correlation functions were measured in the longitudinally co-moving ``out-side-long'' reference frame as a function of rapidity and transverse momentum in the forward hemisphere of the reaction. Radius and correlation strength parameters were obtained from fits of a Gaussian parametrization. The results show a decrease of the radius parameters with increasing transverse momentum characteristic of strong radial flow in the pion source. No striking dependence on pion-pair rapidity or beam energy is observed. Static and dynamic properties of the pion source are obtained from simultaneous fits with a blast-wave model to radius parameters and midrapidity transverse momentum spectra. Predictions of hydrodynamic and microscopic models of Pb+Pb collisions are discussed.Comment: 22 pages, 23 figure

NA49 results on hadron production: indications of the onset of deconfinement ?

The NA49 experiment at the CERN SPS measured the energy and system size dependence of particle production in A+A collisions. A change of the energy dependence of several hadron production properties at low SPS energies is observed which suggests a scenario requiring the onset of deconfinement.Comment: XXXV International Symposium on Multiparticle Dynamics 200