Honeycomb Surface Research Articles

Macromol. Rapid Commun. 14/2011

Back Cover: Hierarchically structured smart honeycomb surface was elaborated, from PS-b-P4VP pH-responsive block copolymer, using the breath-figure process. The reversible pH-sensitive wettability is associated to the ordering at the micrometer length scale and to the copolymer nano self-assembly. Further information can be found in the communication by P. Escalé, L. Rubatat, C. Derail, M. Save,* and L. Billon* on page 1072.

Coadsorption of n Monomer Species on Terraces and Nanotubes

The knowledge of the partition function, Z, of a system of particles adsorbed on a surface is all that is required to determine the occupational characteristics of the adsorbates and the thermodynamic properties of the system. The surface considered is a terrace or a nanotube of arbitrary periodic lattice geometry, L atomic sites in length, and M' sites in the width of the terrace or in the normal cross section of the nanotube. The matrix method introduced in 2007 to obtain Z for the adsorption study of one species of monomers is now generalized to the study of the coadsorption of any number, n, of monomer species. We provide proof that Z can be related to the eigenvalues of a real and non-negative matrix (T matrix) of rank (n + 1)(M), where M is an integer multiple of M'. In the infinite-L limit, we also prove that Z is the largest eigenvalue of the T matrix, raised to the power of (1)/(M). Because the rank of this matrix increases exponentially with M, we develop a technique for its recursive construction applicable to any lattice geometry, which is easily programmed and efficiently adaptable for supercomputing and multiparallel processing. As examples, we consider the coadsorption on square, equilateral triangular, and honeycomb surfaces. This general formulation can now be applied to model a whole new set of experiments involving the coadsorption of two or more monomer species, on terrace or nanotube surfaces with various periodic lattice structures.

Friction Factor Behavior From Flat-Plate Tests of Smooth and Hole-Pattern Roughened Surfaces With Supply Pressures up to 84 bars

A flat-plate tester was used to measure the friction factor behavior for a hole-pattern roughened surface apposed to a smooth surface. The tests were executed to characterize the friction factor behavior of annular seals that use a roughened-surface stator and a smooth rotor. Friction factors were obtained from measurements of the mass flow rate and static pressure measurements along the smooth and roughened surfaces. In addition, dynamic pressure measurements were made at four axial locations at the bottom of individual holes and at facing locations in the smooth plate. The test facility is described, and a procedure for determining the friction factor is reviewed. Three clearances were investigated: 0.635 mm, 0.381 mm, and 0.254 mm. Tests were conducted with air at three different inlet pressures (84 bars, 70 bars, and 55 bars), producing a Reynolds numbers range from 50,000 to 700,000. Three surface configurations were tested, including smooth-on-smooth, smooth-on-hole, and hole-on-hole. The hole-pattern plates are identical with the exception of the hole depth. For the smooth-on-smooth and smooth-on-hole configurations, the friction factor remains largely constant or increases slightly with increasing Reynolds numbers. The friction factor increases as the clearance between the plates increases. The test program was initiated to investigate a friction-factor jump phenomenon cited by Ha et al. (1992, “Friction-Factor Characteristics for Narrow-Channels With Honeycomb Surfaces,” Trans. ASME, J. Tribol., 114, pp. 714–721) in test results from a flat-plate tester where, at elevated values of Reynolds numbers, the friction factor began to increase steadily with increasing Reynolds numbers. They tested apposed honeycomb surfaces. For the present tests, the phenomenon was also observed for tests of apposed roughened surfaces but was not observed for smooth-on-smooth or smooth-on-rough configurations. When the phenomenon was observed, dynamic pressure measurements showed a peak-pressure oscillation at the calculated Helmholtz frequency of the holes.

Fundamental aerodynamics of a new volleyball

This study compared the basic aerodynamic characteristics of conventional volleyballs with those of new designs in a wind tunnel. Furthermore, to examine the aerodynamic instability near the critical Reynolds regime (14 m/s), balls were propelled with an impact-type ball ejection device and the variation in the coordinates of the landing point was measured. It was found that the critical Reynolds number for a conventional volleyball (Molten MTV5SLIT) was approximately 2.7 × 105, whereas that for a design with honeycomb surface protrusions (Molten V5M5000) was slightly lower at approximately 2.2 × 105. The honeycomb-type balls showed a drag coefficient of approximately 0.17 when supercritical, which is rather large compared with that of conventional balls (0.1). It is believed that the honeycomb surface protrusions increase the roughness of the ball surface, and this presumed increase in roughness implies a trend towards reduced aerodynamic instability close to critical Reynolds numbers.

Fabrication of micropatterned thermosensitive gel with highly-ordered honeycomb surface and inverse opal structure

Thermosensitive poly(N-isopropylacrylamide) gels with highly-ordered honeycomb surface and inverse opal structure were successfully fabricated by several microfabrication methods using closely packed silica beads as a template. The gels are able to reversibly change the shapes and sizes of the pores with swelling-deswelling by temperature changes. In particular, regular buckling was induced due to compression with swelling. Such a thermoregulation of surface topography might be useful for design of functional surfaces with tunable physical properties.

Performance assessment of novel side firing flexible optical fibers for dental applications

Use of lasers in dentistry in root canals of teeth and in periodontal pockets for disinfection would be more effective if energy was delivered laterally. This study examined the energy emission profiles of fibers modified in various ways to enhance their lateral emissions for dental use. Commercial optical fibers were altered by tube etching with hydrofluoric acid, modified tube etching (after removing the protective polyimide coating), alumina abrasive particle beams, and by etching and particle beams used in combination. Three free-running pulsed infrared lasers (Nd:YAG, Er:YAG, and Er,Cr:YSGG) were employed to test the modified fibers, with 25 fibers for each laser (modified or unmodified). Surface topography of fibers was examined using SEM. Laser emissions forward and laterally were measured, and thermally sensitive paper used to record the emission profiles. Visible tracing of emissions was undertaken using coaxial He-Ne or InGaAsP diode laser emissions. The etching/abrasion/etching combination gave a unique honeycomb surface configuration with grating-like properties, whilst etching alone gave a conical end. Conical and honeycomb tips showed greater lateral and lower forward emissions compared with plain fibers, with fourfold improvements in lateral emission. The most regular lateral emissions were from the honeycomb configuration. The honeycomb and the conical fiber modifications show dramatic improvements in lateral emissions. The unique emission profile obtained for the honeycomb fibers could play a significant role in increasing the efficiency of laser delivery for endodontic and periodontal applications in dentistry, as well as in other fields.

Fabrication of Micropatterned Thermo-responsive Gel Array with Ordered Honeycomb Surface and Inverse Opal Structure

Fabrication of Micropatterned Thermo-responsive Gel Array with Ordered Honeycomb Surface and Inverse Opal Structure

D-α-Tocopheryl polyethylene glycol 1000 succinate (TPGS) modified poly( l-lactide) (PLLA) films for localized delivery of paclitaxel

d-α-Tocopheryl polyethylene glycol 1000 succinate (TPGS) was used as a novel additive to the poly( l-lactide) (PLLA) films for local drug delivery with paclitaxel as a prototype therapeutic agent. Paclitaxel-loaded PLLA/TPGS films were prepared by the solvent casting technique with dichloromethane as the solvent. Effects of TPGS component on the films’ physicomechanical properties and the drug release profile were investigated. It was found by field emission scanning microscopy (FESEM) that a biphasic honeycomb surface was formed for the PLLA/TPGS films, while the PLLA film exhibited a smooth and homogeneous surface. There was no significant effect of the drug loading on the morphological structure of the PLLA/TPGS films. Differential scanning calorimetry (DSC) demonstrated that the PLLA/TPGS films was a phase-separated system. Tensile testing showed that the flexibility of the PLLA/TPGS films was much higher than that of the PLLA film. The elongation at break for the PLLA/TPGS film of 5%, 10% and 15% TPGS content was 6.8, 8.9 and 19.4 times of that for the PLLA film, respectively. In vitro drug release studies found that incorporation of TPGS considerably facilitated paclitaxel release.

The Use of a Honeycomb Surface for Controlling the Boundary Layer

The results are given of an experimental investigation of the boundary layer forming on the wall of a diffusor channel made of a honeycomb structure. The distribution of the averaged velocity and turbulent pulsations and the integral characteristics of the boundary layer are described.

Preparation of ZSM-5 thin film on cordierite honeycomb by solid state in situ crystallization

Thin films of ZSM-5 zeolite were prepared on porous cordierite honeycombs by a solid state in situ crystallization method and were characterized by XRD, FTIR, SEM and nitrogen gas adsorption. The zeolite films were formed by coating the zeolite precursor sol on the cordierite honeycomb substrate and gelling it in the surface pores of the substrate. This gel was then converted into ZSM-5 by heating the coated substrate in an autoclave without adding solution. The amount of coating was increased by forming an interfacial layer of microporous silica on the cordierite substrate by acid leaching. The maximum specific surface area of the honeycomb coated with zeolite film was 249 m 2/g. Recoating the substrate with zeolite film was effective not only in increasing the amount of zeolite film and its surface area but also in reducing the macropores in the honeycomb surface. The zeolite film was found to retain its porous properties up to the calcining temperature of 900°C. The zeolite film is considered to be formed by a vapor transport mechanism initiated by the water included in the gel.

Hydrothermal Synthesis and Characteristics of Porous Mullite Honeycomb Coated with Silicalite Film.

The formation and some properties of sintered kaolin honeycomb monolith with thick silicalite film, prepared by a hydrothermal reaction, were investigated. To enhance the adhesion strength of the silicalite film onto the honeycomb surface and the mechanical strength of the honeycomb body, the Malaysian kaolin was sintered at 1500°C and then treated in 1M NaOH solution at 180°C to form a partially porous mullite layer on the honeycomb. Silicalite film was hydrothermally prepared on porous honeycomb from colloidal silica, NaOH, tetrapropylammonium bromide and H2O at 180°C. The effect of hydrothermal reaction time on the formation of the silicalite film onto the porous honeycomb surface and Teflon vessel was studied. Due to the formation of a porous mullite layer of 150 to 160μm in thickness on the honeycomb surface by leaching silica in the honeycomb, the adhesion strength of silicalite film on the honeycomb was improved, and a sintered kaolin honeycomb monolith with high strength which was coated with a silicalite film of 100 to 150μm in thickness at 180°C for 25 to 30h could be prepared by hydrothermal reaction.

A New Friction Factor Model and Entrance Loss Coefficient for Honeycomb Annular Gas Seals

A new experimental friction factor model for a honeycomb surface was developed using a static seal tester. Three clearances and three lengths were tested for the seals, and Reynolds number ranged from 3000 to 49,000. It was found that the friction factor was a function of Reynolds number and seal clearance only. The clearance effect was dominant and the friction factor was found to increase with increased clearance. A new uncertainty analysis was developed for the experimental friction factor when calculating friction factor using Mach number curve fit. The entrance loss coefficient was found to be constant for both smooth and honeycomb seals. The entrance loss coefficient of Honeycomb seals was found to be 50 percent higher than that of smooth seals. [S0742-4787(00)02102-0]

Reduction of Nitrogen Oxide with Methane: Activity and Methane Conversion on In-HZSM-5 and PdIn-HZSM-5 Honeycomb Catalysts

In-HZSM-5 and PdIn-HZSM-5 honeycomb catalysts have been prepared by the ion exchange method within the scope of the examination of NO x reduction with methane. Comparing the two different catalysts, it was shown that there is a better conversion of methane on the PdIn-HZSM-5 catalyst than on the In-HZSM-5 catalyst; however, the reduction rate of NO is much lower. Another investigation revealed that the deactivation of the PdIN-HZSM-5 catalyst by water vapor is irreversible. For the improvement of the methane conversion, a series connection of an In-HZSM5 honeycomb and a three-way catalyst was used. According to the dependence on the oxygen concentration, the reduction of nitrogen oxide is susceptible to the rate of NO and NO 2 in the gas stream. The study of the honeycomb surface by means of an electron microscope showed that the indium content of the honeycomb is concentrated on the surface.

Solar pond with honeycomb surface insulation system

A solar pond consisting of transparent compound honeycomb encapsulated with Teflon film and glass plates at the bottom and top surface respectively, floating on the body of a hot water reservoir is considered and analysed for the heat transfer processes in the system. A mathematical model is developed where the energy balance equation of the convective water is formulated by considering its capacity effects, various heat losses and solar energy gain through the surface insulation and is solved by the finite difference method. Transient rate of heat collection and storage characteristics are investigated. Explicit emphasis is laid on the effect of the thickness of the bottom encapsulation on the year-round thermal performance of the system and results seem to favour the minimum thickness. The annual average efficiency of the transparent honeycomb insulated solar pond is found to be higher than the conventional salt gradient pond by a factor of about 2.

Fabrication and transport measurements of honeycomb surface superlattices

We study a novel surface superlattice structure formed by a honeycomb gate pattern on GaAs/AlGaAs heterostructures with a high-mobility two-dimensional electron gas. The hexagonal gate arrays, fabricated by electron beam lithography, had pitches as small as 150 nm, corresponding to hexagons with 87 nm between adjacent vertices. Magnetoresistance measurements show features which reflect the presence of the induced hexagonal superlattice potential.

Scanning electron microscopy of dimethylbenzanthracene (DMBA)-treated hamster cheek pouch.

The aim of the present study was to describe changes which could be regarded as a result of neoplastic rather than inflammatory processes. Fifty-five weeks after 6 weeks of DMBA application to the cheek pouches of 5 male hamsters there were 4 types of lesion: larger ulcerated sessile; smaller non-ulcerated sessile; non-ulcerated pedunculated; conical projections. These and the rest of the pouches were examined by scanning electron and light microscopy. The interlesional mucosa, non-ulcerated sessile lesions and conical projections were covered by flat polygonal cells with either a honeycomb surface pattern of interconnecting microridges, or microridges arranged into more parallel lines. Cell imprints and boundaries were formed by linear ridges, grooves or both. Pedunculated lesions had flat smooth-surfaced cells and cells with a honeycomb surface pattern. None of these lesions were carcinomas by light microscopy but the ulcerated sessile lesions were. The appearance of the cells on the ulcerated lesions varied: flat, with a variable number of short microvilli that were often knob-like, isolated short microridges, or both; plump, giving a cobblestone appearance with surfaces that were smooth, covered by microvilli, short microridges or both. Such appearances have been described as characteristic for dysplastic and malignant stratified squamous epithelium in a number of sites. Further study of both experimental and naturally occurring mucosal disease is needed to validate this.

Honeycomb and other anomalous surface pictures of graphite

Scanning tunneling microscope pictures of graphite ordinarily show only half of the atoms, the B-site atoms, in closepacked hexagonal symmetry. The pictures do not show the expected honeycomb structure with A- and B-site atoms. We have obtained STM pictures showing the graphite honeycomb structure along with well resolved A- and B-site atoms and the electronic bridge structure using tungsten and graphite-coated tungsten probes. Repeated scanning, however, changed the geometry of the pictures, eventually giving pictures with closepacked hexagonal symmetry.

Structure of hamster palatal gingiva and intermolar mucosa after intraperitoneal dosing with N-methyl-N-nitrosourea: a scanning electron microscope study

The palatal gingiva and intermolar mucosa from normal hamsters and from hamsters that had received N-methyl-N-nitrosourea (NMU) intraperitoneally were examined by scanning electron microscopy over a 22-week period. The normal gingiva and rostral two-thirds of the intermolar mucosa were covered by flat polygonal cells that had a regular honeycomb surface pattern of interconnecting micro-ridges, distinct cell boundaries and imprints of cells that had been desquamated. The caudal third of the intermolar mucosa in normal and NMU-treated hamsters was covered by soft-palate type mucosa whose smooth surfaced cells surrounded scattered fungiform-like papillae. In NMU-treated hamsters changes were more common in the rostral two-thirds of the intermolar mucosa than in the gingiva. At 10 weeks there were sessile and conical surface projections and saucer-shaped and conical epithelial-lined depressions. At 16 weeks these projections and depressions were larger and more numerous, and groups of conical projections formed papillomatous-like lesions. At 22 weeks the projections and depressions were further increased in number and size and there were distinct papillomas. At 10 and 16 weeks the entire epithelium showed cells, cell boundaries and cell imprints resembling those in the controls, except that there were defects or dilated intercellular spaces at the base of the conical depressions and some of the cells were thicker. Much of the 22-week epithelial had a similar structure, but in some areas that did not show the projections or depressions the cells varied in size and shape and were covered by elongated micro-ridges. Here the surface was irregular as were the cell boundaries. Examination of sections by light microscopy, both from these irregular areas and from areas that appeared normal by scanning electron microscopy, revealed that the deeper epithelial strata could be either normal, dysplastic or at times malignant. However, scanning electron microscopy failed to reveal dysplastic or malignant epithelium.

Annular Honeycomb-Stator Turbulent Gas Seal Analysis Using a New Friction-Factor Model Based on Flat Plate Tests

A new empirical friction-factor model for honeycomb surfaces based on flat plate test results has been developed as a function of Mach number and dimensionless pressure and honeycomb geometry variables. A rotordynamic analysis for centered, turbulent-annular-honeycomb-stator seals has been developed incorporating the new empirical friction-factor model for honeycomb-stator surfaces. The results of the new analysis in predicting the rotordynamic and leakage characteristics have been compared to: (a) Moody’s friction-factor model analysis, and (b) experimental data for short (L/D = 1/6, 25.4 mm long) seal. The comparisons show that the new honeycomb friction-factor model greatly improves the predictions of leakage and rotordynamic coefficients compared to Moody’s friction-factor model, especially, for direct and cross-coupled stiffness.

Friction-Factor Characteristics for Narrow Channels With Honeycomb Surfaces

The experimental determination of friction-factors for the flow of air in a narrow channel lined with various honeycomb geometries has been carried out. Test results show that, generally, the friction-factor is nearly constant or slightly decreases as the Reynolds number increases, a characteristic common to turbulent flow in pipes. However, in some test geometries this trend is remarkably different. The friction factor dramatically drops and then rises as the Reynolds number increases. This phenomenon can be characterized as a “friction-factor jump.” Further investigations of the acoustic spectrum and friction-factor measurements for a broad range of Reynolds numbers indicate that the “friction-factor jump” phenomenon is accompanied by an onset of a normal mode resonance excited coherent flow fluctuation structure, which occurs at Reynolds number of the order of 104. The purpose of this paper is not to present the friction-factor data but to explain the friction-factor-jump phenomenon and friction-factor characteristics.