Large Smooth Surface Research Articles

Nanometer Order Separation Control of Large Working Area Nanogap Created by Cleavage of Single-Crystal Silicon Along {111} Planes Using a MEMS Device

Nanogaps with a large working area and a precisely controlled separation of about 1 to 20 nm has important applications in nano photonics, thermal management, power generation, chemical sensing, etc. However, an effective method of fabricating such nanogaps has not yet been established. In addition, it has been necessary to evaluate the dependence of physical characteristics of nanogaps on the separation, but it has been technically and economically difficult to develop such a system. In this study, we developed a MEMS device, which can produce nanogaps with a large area and parallel smooth surfaces by the (111) plane cleavage of a single crystal silicon beam and can change and measure the separation of nanogaps. Using this device, nanogap fabrication by cleavage and separation control were uninterruptedly carried out while maintaining the cleanliness of the gap surfaces in vacuum; a nanogap with a large smooth surface area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$30 ~\mu \text{m}$ </tex-math></inline-formula> 2 was successfully controlled in the range of 14 nm– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.5 ~\mu \text{m}$ </tex-math></inline-formula> . For a small separation of less than 100 nm, the control resolution was sufficiently high at 1 nm. This method is fully compatible with conventional fabrication technologies for not only MEMS but also other semiconductor devices and should contribute to the fabrication of devices that exhibit useful quantum effects with only minor modifications. [2022-0073]

Directly fabricated Al2O3/GdAlO3 eutectic ceramic with large smooth surface by selective laser melting: Rapid solidification behavior and thermal field simulation

Selective laser melting (SLM), a novel approach for one-step melting and solidifying ceramic powder beds layer by layer without post-process of degreasing and sintering, has been developed to directly prepare highly dense (>95 %) Al2O3/GdAlO3(GAP) eutectic composite ceramics with large smooth surfaces. Compact net-shaped plates with the maximum size of 73 × 24 × 5 mm3 are obtained by different strategies of laser pre-heating and multi-tracks’ deposition without any binders. Combined with the finite element thermodynamic coupling simulation results, it is proved that the stress between the substrate and depositions during SLM can be greatly reduced by the step-up preheating, and thus effectively improving the ceramic forming quality. The macro-morphology, microstructure evolution, rapid solidification behavior and mechanical properties of the SLM-ed eutectic ceramics are systematically investigated at different laser processing parameters. The microstructure transforms from ultra-fine irregular eutectic to complex regular eutectic with the increase of the scanning rate. The average eutectic spacing, and solidification rate has an approximately linear relationship consistent with the Jackson-Hunt (JH) model. The microhardness and fracture toughness can reach 17.1 ± 0.2 GPa and 4.5 ± 0.1 MPa·m1/2, respectively. The results indicate that SLM method is a highly effective technique for fabricating high-performance net-shaped structural composite ceramics.

Spherical Li Deposited inside 3D Cu Skeleton as Anode with Ultrastable Performance.

Porous current collectors are conducive to enhance the property of Li metal anode. Unfortunately, congestion in diffusion path during plating process damages the effects of current collectors. Herein, we developed a 3D Cu skeleton with open micrometer-sized pores by NaCl-assisted powder-sintering method. The unobstructed pores of 3D Cu skeleton help to reduce congestion during plating, thus most of Li deposited inside the current collector. Besides, the large smooth surface promotes the deposition of Li with smooth spherical shape, which mitigating Li dendrite growth. As a result, better safety and rechargeability of Li metal anode were achieved in this design.

Synthesis and surface enhanced Raman scattering performance of Ag dendritic nanoplates with ultrasmall nanogaps

Ag dendritic nanoplates were synthesized by a facile reduction method with the assistant of trisodium citrate and hydrogen peroxide. The nanoplates exhibited large smooth surfaces full of ultra-small gaps with the diameters of 2–20nm. The as-synthesized dendritic nanoplates showed significant surface-enhanced Raman scattering (SERS) activity with an enhancement factors of 6.0×105, attributing to the enhanced local electromagnetic field around these nanogaps on the surfaces. Particularly, a detection limitation of 1×10−9M for 4-mercaptobenzoic acid was obtained. Other excellent properties such as good homogeneity and reproducibility were also achieved in the Ag dendritic nanoplates with relative standard derivation values of about 8% for different test dots on just one sample and 10% for different pitches of samples.

Marching-on-in-Degree Method With Delayed Weighted Laguerre Polynomials for Transient Electromagnetic Scattering Analysis

The large cost of computing resources has become a bottleneck of the marching-on-in-degree (MOD) solver of time-domain integral equation (TDIE). A set of delayed weighted Laguerre polynomials is proposed to address this problem in this paper. By incorporating the phase propagation information into itself, the proposed temporal basis function can model the phase variation of the induced current at different places of the scatterer, leading to a great reduction in the spatial unknowns. Moreover, the curvilinear Rao-Wilton-Glisson (CRWG) basis functions are adopted for the spatial discretization to improve the modeling precision of curve surfaces. Numerical results show that the proposed method can greatly reduce the mesh density of the scatterer and save the computing resources. It is both stable and efficient for the transient scattering analysis of perfect electrically conducting (PEC) objects with large smooth surfaces.

Time Domain Analysis of Electromagnetic Scattering Problems by Using Integral Equation Method With Space-Delayed Temporal Basis Functions

This communication presents a new numerical method for the efficient solution of marching on in time (MOT)-based time domain integral equations (TDIE) for electromagnetic scattering from perfect electrically conducting (PEC) object with large smooth surfaces. A set of space-delayed temporal basis functions is proposed for the temporal discretization, and the curvilinear Rao-Wilson-Glisson (CRWG) basis functions for the spatial discretization. The space-delayed temporal basis functions are firstly extended to the time domain electric field integral equations (TDEFIE), then easily to the time domain combined field integral equations (TDCFIE). Numerical results demonstrate that the new method is stable and effective for the transient scattering problems from PEC objects with large smooth surfaces and a single plane wave incidence. A significant reduction of the number of spatial unknowns is achieved by using the space-delayed temporal basis functions.

Effect of Fe content on the fracture behaviour of Al–Si–Cu cast alloys

Castings were prepared from 319.2 alloy melts, containing Fe levels of 0.2–1.0 wt%. Sr-modified (∼200 ppm) melts were also prepared for each alloy Fe level. The end-chilled refractory mold used provided directional solidification and a range of cooling rates (or dendrite arm spacings, DAS) within the same casting. Impact test samples were machined from specimen blanks sectioned from the castings at various heights above the chill end provided DASs of 23–85μm. All samples were T6-heat-treated before testing keeping with Aluminum Association recommendations. The results show that at low Fe levels and high cooling rates (0.4% Fe, 23 μm DAS), crack initiation and propagation in unmodified 319 alloys occurs through the cleavage of β-Al5FeSi platelets (rather than by their decohesion from the matrix). The morphology and the size of the platelets (individual or branched) are important in determining the direction of crack propagation. Increasing the DAS to 83μm leads to cleavage fracture. In this case, the fracture path follows a transgranular plane that is usually a well-defined crystallographic plane as judged by the relatively large smooth surfaces of the β-Al5FeSi phase platelets. Cracks also propagate through the fracture of undissolved CuAl2 or other Cu-intermetallics, as well as through fragmented Si particles. In Sr-modified 319 alloys, cracks are mostly initiated by the fragmentation or cleavage of perforated β-phase platelets, in addition to that of coarse Si particles and undissolved Cu-intermetallics.The amount of undissolved Cu- intermetallics is directly related to the applied cooling rate. Slow cooling rate (DAS ≈83µm) results in the precipitation of Cu- containing phases on the β-platelets, amplifying the likehood for crack propagation through these loacations.

Vertically oriented few-layer graphene as an electron field-emitter

Field emission from flat graphene sheets is a challenge due to fewer emission sites. Here, we have synthesized free-standing vertically oriented few-layer graphene (FLG) films directly on dielectric substrates by hot-filament chemical vapor deposition (HFCVD) without any catalyst or special substrate treatment. The fabricated FLGs with a large smooth surface topography, standing roughly vertical to the substrate are found to grow according to the Stranski–Krastanov growth mechanism. The ease of large-area preparation and the low turn-on field of 22 V µm−1 in addition to the large field enhancement factor of ≈6520 for electron field emission suggest that the vertically oriented FLGs could be used as a potential edge emitter. Scanning electron microscopy image of vertically oriented few-layer graphene on a SiO2/Si substrate with the schematic of field electron emission.

Scaffold-free 3D cellulose acetate membrane-based cultures form large cartilaginous constructs

Scaffold-free three-dimensional (3D) cultures provide clinical potential in cartilage regeneration. The purpose of this study was to characterize a scaffold-free 3D membrane-based culture system, in which human articular chondrocytes were cultivated on a cellulose acetate membrane filter, and compare it to pellet and monolayer cultures. Chondrocytes were expanded in monolayer culture for up to 5 passages, transferred to membrane-based or pellet cultures and harvested after 7 or 21 days. The chondrogenic potential was assessed by histology (toluidine blue, safranin-O), immunohistochemistry for collagen type II and quantitative analysis of collagen type II α(1) (COL2A1). Membrane-based cultures (P1) formed flexible disc-like constructs (diameter 4000 µm, thickness 150 µm) with a large smooth surface after 7 days. Positive safranin-O and collagen type II staining was found in membrane-based and pellet cultures at P1-3. Expression of COL2A1 after 7 days was increased in both culture systems compared to monolayer culture up to P3, whereas cells from monolayer > P3 did not redifferentiate. The best results for COL2A1 expression were obtained from membrane-based cultures at P1. After 21 days the membrane-based cultures did not express COL2A1. We concluded that membrane-based and pellet cultures showed the ability to promote redifferentiation of chondrocytes expanded in monolayer culture. The number of cell passages had an impact on the chondrogenic potential of cells. Membrane-based cultures provided the highest COL2A1 expression and a large, smooth and cartilage-like surface. As these are appropriate features for clinical applications, we assume that membrane-based cultures might be of use in cartilage regeneration if they displayed similar results in vivo.

PAC/Edge Performance Festival (review)

Reviewed by: Pac/Edge Performance Festival Roger Bechtel Pac/Edge Performance Festival. Performing Arts Chicago, Athenaeum Theatre, Chicago. 02, 04, 1104 2004. "You smell nice," remarked the smoky female voice as I rushed into the men's room at the Athenaeum Theatre. Persevering through the flash of panic that I had burst into the wrong quarters, I quickly discovered that I was in fact the inadvertent victim of art, a video installation by Sandra Binion titled watercloset(s), mounted and running on the wall that screens the urinals from the gaze—real or imagined—of the open doorway. Timing, of course, was the source of my initial discomfort, but Binion's relentless, insinuating colloquialisms ultimately touched a deeper nerve. For beneath the seductive voice was a broad-shouldered invasion of that most private of public spaces, the refusal to allow even a moment's respite from the endless demands of performance—theatrical, social, or biological. This kind of aggressiveness has long been a hallmark of the Chicago aesthetic, and it was on abundant display at the second annual PAC/edge Festival, a collection of the best of Chicago's performance vanguard. Crammed into every theatre and hallway, coatroom and restroom of the Athenaeum building, an enormous, converted, turn-of-the-century recreation center and schoolhouse, the Festival presented some forty-four performance, theatre, and dance events, nine workshops, and seven ongoing visual installations. And while most of the forty companies represented enjoy only a local reputation, some have recently begun to garner national attention, including such Chicago stalwarts as Goat Island and Plasticene. As with most festivals of this size and inclusiveness, the quality of the events varied widely, but even the least fully realized of the performances offered its own rewards. From among the twenty-something pieces I saw, here then is a look at some of the Festival's more outstanding performances. If anything separated the veteran companies from the neophytes at the Festival, it was the precision, cohesiveness, and sheer ease that come from amassing a sustained body of work. Nowhere were these qualities better exemplified than in Plasticene's Blank Slate, a trenchant examination of the ecstasies and depravities of language and learning. Founded in 1990 under the direction of Dexter Bullard, Plasticene is composed of four athlete-actors (Mark Comiskey, Dominic Conti, Tere Parkes, and Brian Shaw), whose physical aesthetic lies somewhere between Meyerhold and the World Wrestling Federation. But while the company is best known for the extremity and daring of its physicality, its work is also marked by an abiding intelligence and subtlety, as Blank Slatepersuasively demonstrates. Although the performers remain silent throughout, language itself becomes a gymnastic event here through the use of three mobile chalkboards of various heights and dimensions, as well as small, individual slates for each of the actors. The piece opens with a frenzy of writing, actors rushing from one chalkboard to the next, inchoate scratches gradually forming words, words gradually forming sentences, sentences engendering confusions that propel bodies into battle. At the peak of this sequence, the chalkboards themselves become weapons, spinning and rotating crazily, careering from one side of the stage to the other. Yet the violence of this controlled chaos finally gives way to an unexpected moment of sublimity as the three chalkboards come to rest center stage, each board cantilevered over the one in front of it, forming a large smooth surface running directly down toward the audience. From the hidden upstage edges of the chalkboards a rush of water washes over the dusty, scribbled surfaces, erasing all misinterpretations and misunderstandings, leaving them, with much relief, blank. If the synoptic first half of Blank Slateexamines the language of war, the second half focuses more specifically on the personal dimensions of language, the language of self and love. Early in this section, in perhaps the most arresting conceptual moment of the piece, each performer looks intently into the chalkboard as if it were a mirror, smoothing hair, licking lips, preening, despairing. It is the face that becomes the blank slate here, on which are written the social conventions of sexual attractiveness. This collective private moment is interrupted by the warped strains of...

Free-standing subnanometer graphite sheets

Free-standing graphite sheets with thickness less than 1nm, “carbon nanosheets,” were synthesized on a variety of substrates by radio-frequency plasma-enhanced chemical vapor deposition without any catalyst or special substrate treatment. The nanosheets consist of one to three graphene layers with a large smooth surface topography, standing roughly vertical to the substrate. Due to the atomic thickness and corrugated nature of nanosheets, low-energy vibrational modes are present in the Raman spectra. The low turn-on field of 4.7 V/μm for electron field emission suggests that the carbon nanosheets could be used as a potential edge emitter.

Ordered arrays of intramembrane particles on the surface of fish gills

Freeze fracture of euryhaline fish gill epithelium reveals large smooth surfaces with intramembrane particles or corresponding pits often aggregated into hexagonal arrays. They belong to the outer plasma membranes of respiratory cells, the main surface of contact between the internal and external milieu of the fish. Possible functions for the arrays are discussed in relation to the fine structure of the respiratory cell.

Vapour phase chemical transport properties of the cadmium telluride-iodine system

The vapour phase chemical transport properties of the CdTe : I2 system have been investigated. By comparing the experimental transport rate with the theoretical transport rate calculated on the basis of a three reaction transport model, it was shown that no iodine chemical transport is possible in closed tubes in the hot-cold direction, but only vapour phase transport controlled by the source sublimation. Thin platelets with large smooth surfaces were observed growing on the source charge under small temperature gradients. Their growth was explained in terms of a reverse (cold-hot) iodine transport associated with a reduced sublimation tendency of the facetted crystallized material with respect to the unfacetted powdered material of the charge.

Some Studies on the Rotating Bending Fatigue of Large Mild Steel Specimens : Part 4, Effect of Size on Fatigue Strength of Cracked Specimen and Propagation Rate of Fatigue Crack

This paper is succeeded by No.2 and No.3 reports of the same title in which propagation of fatigue caracks on large smooth surface and fillet specimens has been dealt with. In this paper, the author has studied the following two problems : (1) The fatigue strength of large smooth specimens having a diameter of 130 mm with fine cracks artificially produced beforehand by sea water corrosion. (2) The influence of size on the fatigue strength of cracked specimens and propagation speed of fatigue cracks. The test results have revealed that the fatigue limit of steel specimens, 130 mm in diameter with fine corrosion cracks on the surface is about ±11.0 kg/mm2. This limit coincides with the result assumed by studying the crack propagation of specimens, 120 mm in diameter. Analytical investigation of the propagation speed of fatigue cracks of 60 φmm and 20 φmm specimens has shown that the fatigue limit of these specimens are assumed to be about ±12.0 kg/mm2 and ±15.0 kg/mm2 respectively, when fine cracks may previously exist on their surfaces. From the above results, it may be stated that the fatigue limit of smooth specimens having fine cracks on their surface will tend to increase as the diameter decreases. On the other hand, from the analytical studies on the shape of shelly patterns on the fracture surface, the propagation of fatigue crack may be given approximately by the following formulae in connection with the diameter of specimen : σo≤νbσn<σo+σs, [numerical formula] where : υc is propagation speed of fatigue crack μ/c, νbσn : stress on the edge line of fracture surface kg/mm2, σn : stress on the specimen having no crack, νb : stress magnifying factor due to crack, σo : fatigue limit of cracked specimen kg/mm2, σs : yielding point of the material kg/mm2, K and k : constants varying according to the properties of material and range of νbσn, d : diameter of specimen mm.

Some Studies on Fatigue of Large Steel Specimens : Part 5, Effect of Size on Fatigue Strength of Cracked Specimen and Propagating Speed of Fatigue Crack

This paper is succeeded by No.2 and No.4 reports of the same title in which propagation of fatigue cracks on large smooth surface and fillet specimens has been dealt with. In this paper, the author has studied the following two problems : (1) The fatigue strength of large smooth specimens having a diameter of 130 mm with fine cracks artificially produced beforehand by sea water corrosion. (2) The influence of size on the fatigue strength of cracked specimens and propagation speed of fatigue cracks. The test results have revealed that the fatigue limit of steel specimens, 130 mm in diameter with fine corrosion cracks on the surface is about ±11.0 kg/mm2. This limit coincides with the result assumed by studying the crack propagation of specimens, 120 mm in diameter. Analytical investigation of the propagation speed of fatigue cracks of 60 φmm and 20 φmm specimens has shown that the fatigue limit of these specimens are assumed to be about ±12.0 kg/mm2 and ±15.0 kg/mm2 respectively, when fine cracks may previously exist on their surfaces. From the above results, it may be stated that the fatigue limit of smooth specimens having fine cracks on their surface will tend to increase as the diameter deccreases. On the other hand, from the analytical studies on the shape of shelly patterns on the fracture surface, the propagation of fatigue crack may be given approximately by the following formulae in connection with the diameter of specimen : [numerical formula] Where : υc is propagation speed of fatigue crack μ/c, υσn : stress on the edge line of fracture surface kg/mm2, σn : stress on the specimen having no creck, υ : stress magnifying factor due to crack, σ0 : fatigue limit of cracked specimen kg/mm2, σ8 : yielding point of the material kg/mm2, K and k : constants varying according to the properties of material and range of υσn, d : diameter of specimen mm.