Millimeters In Length Research Articles

Preparation and characterization of hollow In2O3/Co3O4 heterostructured microribbons by electrospinning process

Long and thin hollow In2O3/Co3O4 heterostructured microribbons have been prepared by a combination method of electrospinning and sol–gel process. The as-prepared microribbons show the well-defined one-dimensional ribbon structure with 5–10 μm in width and tens of millimeters in length. The polycrystalline microribbons calcined at 700 °C for 2 h are still continuous and have the uniform cross section and the thickness to width ratio is around 1:10. It is very interesting that the microribbons present the hollow structure and these novel heterostructured ribbons can potentially be used in micro/nano electronic devices, gas-sensors and catalysts.

Constituent Particle Clustering and Pitting Corrosion

Corrosion is a primary degradation mechanism that affects the durability and integrity of structures made of aluminum alloys, and it is a concern for commercial transport and military aircraft. In aluminum alloys, corrosion results from local galvanic coupling between constituent particles and the metal matrix. Due to variability in particle sizes, spatial location, and chemical composition, to name a few critical variables, corrosion is a complex stochastic process. Severe pitting is caused by particle clusters that are located near the material surface, which, in turn, serve as nucleation sites for subsequent corrosion fatigue crack growth. These evolution processes are highly dependent on the spatial statistics of particles. The localized corrosion growth rate is primarily dependent on the galvanic process perpetuated by particle-to-particle interactions and electrochemical potentials. Frequently, severe pits are millimeters in length, and these pits have a dominant impact on the structural prognosis. To accommodate large sizes, a model for three-dimensional (3-D) constituent particle microstructure is proposed. To describe the constituent particle microstructure in three dimensions, the model employs a fusion of classic stereological techniques, spatial point pattern analyses, and qualitative observations. The methodology can be carried out using standard optical microscopy and image analysis techniques.

Preparation and Characterizations of Na<sub>2</sub>Ti<sub>3</sub>O<sub>7</sub>, H<sub>2</sub>Ti<sub>3</sub>O<sub>7</sub> and TiO<sub>2</sub> Nanobelts

In this paper, the Ti-O-Compound nanobelts from commercial TiO2 (annatase phase) were synthesized via the alkali-hydrothermal process. The as-synthesized nanobelts are sodium titanate, hydrogen titanate and anatase with general formula Na2Ti3O7, H2Ti3O7and TiO2, respectively. The nanobelts are characterized by Thermogravimetric/Differential Thermal Analysis (TG/DTA), X-ray Diffraction (XRD), Infrared Spectra (IR) and Scanning Electron Microscope (SEM) apparatuses. The characterization indicates that the nanobelts with typical widths of 50 to 200 nm, thicknesses of 20 to 50 nm, and up to a few millimeters in length. The conversion mechanisms between the layer titanate and anatase of nanobelts have been discussed in this study.

Dimorphism in methane seep-dwelling ecotypes of the largest known bacteria

We present evidence for a dimorphic life cycle in the vacuolate sulfide-oxidizing bacteria that appears to involve the attachment of a spherical Thiomargarita-like cell to the exteriors of invertebrate integuments and other benthic substrates at methane seeps. The attached cell elongates to produce a stalk-like form before budding off spherical daughter cells resembling free-living Thiomargarita that are abundant in surrounding sulfidic seep sediments. The relationship between the attached parent cell and free-living daughter cell is reminiscent of the dimorphic life modes of the prosthecate Alphaproteobacteria, but on a grand scale, with individual elongate cells reaching nearly a millimeter in length. Abundant growth of attached Thiomargarita-like bacteria on the integuments of gastropods and other seep fauna provides not only a novel ecological niche for these giant bacteria, but also for animals that may benefit from epibiont colonization.

In situ synthesis of high-purity carbon microtube membrane

High-purity carbon microtube membrane was in situ synthesized in a gas pressure furnace using urea as a precursor in the absence of catalyst. The size of the as-prepared membrane is up to 150 cm 2 composed of highly entangled carbon microtubes with 1.5 μm in outer diameter, 15 nm in wall thickness and several millimeters in length. The unique architecture of this membrane may have potential applications in microelectronics and microdevices area.

A pressure enhanced CVD method for large scale synthesis of carbon microtubes and their mechanical properties

Carbon microtubes (CMTs) are a new morphological form of carbon with micrometer scale internal diameters and thin walls made of a few graphitic layers. However, compared with carbon nanotubes, there is lack of a feasible and reliable synthetic method. Furthermore, the mechanical properties of CMTs have not been reported. In this paper, we report a gas pressure enhanced CVD method for large-scale preparation of high-purity, crystalline and thin-walled CMTs in a gas pressure furnace using urea as raw material in the absence of catalyst. The as-obtained CMTs have highly graphitized structure and have a homogenous morphology with an internal diameter of about 1μm, a wall thickness of 5nm and several millimeters in length. The Young's modulus of the CMTs was determined to be 0.652TPa on average, which is comparable to that of carbon nanotubes reported in previous research.

Collembolan Density and Diversity in a Forest and an Agroecosystem

Collembola, commonly called “springtails” are wingless soft-bodied hexapods that are usually between 1 and 3 millimetres in length and occur in varying habits such as, soil surface and litter, under rocks or the bark of trees. The great majority develop in soil, feeding on fungi, bacteria, algae and decaying plant matter, and along with other soil fauna constitute the decomposer community. The present study examines the diversity, density, and seasonal variation patterns of collembolan fauna under different intensities of disturbance, as evidenced in a forest and an agroecosystem. Results indicate that both densities and diversity of collembola was higher in the forest than in the agroecosystem. Seasonal fluctuation exhibited an increase from spring to summer and autumn and a decrease during winter. The coorelation patterns with different chemo-edaphic factors did not show any specific trend.Indices of diversity and significant correlation values are discussed in light of landuse.

Size-Controlled Simple Fabrication of Free-Standing, Ultralong Metal Nanobelt Array

Free-standing, ultralong (up to several millimeters) nanobelts of gold, silver, and copper were fabricated by a template approach. Firstly, a metal nanofin array was prepared on a substrate via metal nanocoating of the template surface and selective removal of the metal top layer and template. Electroless plating and sputtering were employed for the metal nanocoating. In this approach, the minimum width and thickness of the Au nanobelt were 95 and 30 nm, respectively. Systematic control of the nanobelt width (from 95 to 350 nm) was successfully achieved by adjusting the template height. Free-standing nanobelts of several millimeters in length were fabricated and maintained their unique structure and alignment, even on a mesh grid.

Novel coaxial SiC–SiO2–BN nanocable: large-scale synthesis, formation mechanism and photoluminescence property

Novel one-dimensional heterostructures composed of single crystalline cubic SiC cores, intermediate amorphous SiO2 layers, and single crystalline hexagonal BN (h-BN) sheaths (i.e. SiC–SiO2–BN nanocable) have been successfully fabricated in large scale using SiC–SiO2 nanocables and ammonia borane as starting materials. The structure and chemical composition of the as-synthesized products are determined by powder X-ray diffraction, field emission scanning electron microscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and energy filtered TEM based on electron energy loss spectroscopy. The nanocables are approximately 100 nm in diameter and up to 1 millimetre in length. The intermediate amorphous SiO2 layers and the outer h-BN sheaths are about 10 nm and 5 nm thick, respectively. Interestingly, an increase in the amount of ammonia borane leads to the transformation of SiC–SiO2 nanocables into BN nanotubes. Mass spectrometric analysis shows that the vapors decomposed from ammonia borane play crucial roles both in the growth of the BN sheath on the SiC–SiO2 nanocables and in the transformation to the BN nanotubes. The SiC–SiO2–BN nanocable displays similar photoluminescence (PL) characteristics with respect to the original SiC–SiO2 nanocable but with the 488.5-nm emission peak blue shifting. The synthetic route has also been extended to fabricate SiC–BN nanocables and has proved effective and universal for the synthesis of core–sheath nanostructures with BN sheaths.

Oriented Free-Standing Ammonium Vanadium Oxide Nanobelt Membranes: Highly Selective Absorbent Materials

Highly selective, absorbent, free-standing, paper-like membranes made of ammonium vanadium oxide (NH(4)V(4)O(14)) nanobelts have been engineered by taking advantage of the nanoscaled self-assembly of architectures that display a mesh structure with an average periodic pore size of about 5 to 10 nm. The NH(4)V(4)O(14) nanobelts are synthesized by using a simple hydrothermal process, and exhibit the same orientation and assemble into bundles, each about 40 to 80 nm in width, 3 to 5 nm in thickness, and up to several millimeters in length. Importantly, the as-obtained NH(4)V(4)O(14) nanobelt membranes can highly selectively absorb a variety of organic solvents, covering both polar and non-polar solvents, for example, the absorbent capacity of glycol is 28 times as high as the initial weight of the membrane, and it can even separate organic solvents with similar polarities and absorb solid contaminants in organic solvents. These highly selective, absorbent membrane materials can be an ideal candidate for the separation and removal of pollution in industrial and environmental applications.

The Identification of a Hidden Long‐Term Plastic Damage Stage During Splitting Tensile Loading of Concrete: A Fracture Mechanics Approach

Abstract: A new method for the determination of fracture toughness KIC, fracture energy GF and critical crack tip opening displacement CTODc of mortars and concretes with maximum size of aggregates up to 8 mm is presented. This was achieved by using a suitable modification of the conventional splitting tensile test. The values that were obtained are in accordance with those of other researchers. On the basis a clear‐cut fracture mechanics analysis, we extract a set of equations that correlates the above quantities with the crack rate. Specific plastic damage stages that accompany the crack growth were thus easily identified. A pre‐peak damage process of a characteristic bandwidth of 0.1–1 μm and length from a few micrometres to a few millimetres appears first. Damage process of this kind can be diffused and dispersed in bulk of the loading component or it can also be localised and formed into an active attractor cracking path through its chain accumulation. Then another damage stage, coming directly through the formation of the well‐known fracture process zone near the crack tip of 10 μm in bandwidth and a few tens of millimetres in length, must be added. Finally, a large‐scale stage involving the influences of composition and texture of stressed components as well as their loading and geometry conditions must be superimposed on the first two. This third damage process comes directly through the reordering and redistribution of the aforementioned features, during the evolution of fracture, giving an effective length that varies from few tens of millimetres to some metres. All these effective lengths could easily be extracted from the calculated concrete fracture quantities.

Luminescent Porous Silica Fibers as Drug Carriers

Luminescent and porous silica fibers have been successfully prepared by using the electrospinning process. The obtained multifunctional silica fibers, which possess a porous structure and display blue luminescence, can serve as a drug delivery host carrier, using ibuprofen (IBU) as a model drug, allowing the investigation of storage/release properties. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FT-IR), N(2) adsorption/desorption, photoluminescence (PL) spectra, and kinetic decay were used to characterize the structural, morphological, and optical properties of the as-obtained samples. The results reveal that the multifunctional silica materials exhibit an irregular porous structure, and display a fiberlike morphology with dimensions of several hundred nanometers in width and several millimeters in length. The obtained silica fibers exhibit an intense broad bluish emission, which might be attributed to impurities and/or defects in the silica fibers. The IBU-loaded silica fiber system shows blue luminescence under UV irradiation and controlled release behavior for IBU. In addition, the emission intensities of silica fibers in the drug carrier system vary with the released amount of IBU, thus allowing the drug release to be easily tracked and monitored by the change of the luminescence intensity.

Two-Dimensional Single Crystal CdS Nanosheets: Synthesis and Properties

A one-dimensional (1D) to two-dimensional (2D) topotactic transformation has been proposed for the synthesis of 2D CdS nanosheets by promoting the lateral growth of 1D CdS nanobelts. The as-prepared nanosheets are single crystal with hexagonal structure, usually 20−100 nm in thickness, 20−100 μm in width, and up to several millimeters in length. CdS nanosheets show enhanced multiphonon responses and exciton−phonon couplings, which are correlated to their extraordinary anisotropic geometry. Photoluminescence measurement reveals three emission bands at about 1.61, 2.39, and 2.45 eV, which are attributed to the radiative transitions related to surface states, bandgap, and excitonic molecules, respectively; moreover, the formation of the surface states and the excitonic molecules are significantly enhanced due to the anisotropic geometry of the 2D nanosheets. CdS nanosheets show also pronounced photoconduction under visible light irradiation, indicating potentials in assembly of optoelectronic nanodevices.

Thermoacoustic prime mover for thermal management.

Because thermoacoustic prime movers can operate over a wide range of temperature differences across the stack, they can be used in thermal management applications. Depending on their geometry and frequency of operation, the onset temperature differences for oscillation can vary by a few hundred degrees. This is attractive for low‐temperature difference applications, as in computers and electronics, and for high‐temperature differences as in power plants and automotive industry. Thermoacoustic devices developed here for the mid‐audio frequency up to the ultrasonic range require special materials for the stack, heat exchangers, resonators, and assembly components. A critical issue is the thermal coupling of the acoustic device to the source of heat; it is based on mechanical contact and thermal compounds. The above development led to a variety of small thermoacoustic engines, which ranged in size from 5 cm down to a few millimeters in length. An important benefit of the above approach is that the devices can generate electricity by means of piezoelectric elements; this provides energy conversion from heat to sound to electricity. The working fluid is air at 1 atm.

An improved microtensile technique for mechanical characterization of short plant fibers: a case study on bamboo fibers

This article aims to present an improved technique for the mechanical characterization of single plant fibers. In particular, our efforts lie in resolving the difficulties involved in the testing of short plant fibers with only a few millimeters in length and tens of microns in width. Such fibers are potentially used as reinforcement phase in polymer composites. A special fiber gripping system, consisting of a pair of fiber clamps, a 3D positioning stage and two digital microscopes, was developed and combined to a small commercial mechanical tester. The resultant testing system possesses great convenience and reliability for the installation, orientation adjustment, and gripping of short plant fibers, as well as powerful control and data analysis functions. The equipment was then applied to the mechanical characterization of single bamboo fibers under air-dried state. Furthermore, the capability of this equipment for studying moisture content-related mechanical and viscoelastic properties of bamboo fibers was also successfully demonstrated.

Kapundaite, (Na,Ca)2Fe43+(PO4)4(OH)3{middle dot}5H2O, a new phosphate species from Toms quarry, South Australia: Description and structural relationship to melonjosephite

Kapundaite, ideally (Na, Ca)Fe(PO )(OH)·5HO, is a new mineral (IMA2009-047) from Toms phosphate quarry, Kapunda, South Australia, Australia. The new mineral occurs as cavernous aggregates of fibers up to several centimeters across, associated with leucophosphite, natrodufrenite, and meurigite-Na crystals and amorphous brown, black, and/or greenish coatings. Individual kapundaite crystals are very thin flattened fibers up to a few millimeters in length, but typically no more than a few micrometers in thickness. The main form observed is {100}; other forms in the [010] zone are present, but cannot be measured. Crystals of kapundaite are pale to golden yellow, transparent to translucent, have a yellow streak and silky luster, and are non-fluorescent. Mohs hardness is estimated to be about 3; no twinning or cleavage was observed. Kapundaite is biaxial (+), with indices of refraction α = 1.717(3), β = 1.737(3), and γ = 1.790(3). 2V could not be measured; 2V is 64.7°. The optical orientation is Z = b, Y ≈ c with weak pleochroism: X = nearly colorless, Y = light brown, Z = pale brown; absorption: Y > Z > X. No dispersion was observed. The empirical chemical formula (mean of seven electron microprobe analyses) calculated on the basis of 24 O is (CaNa) (Fe MnAl Mg)PO (OH)·5HO. Kapundaite is triclinic, space group P1, a = 6.317(5), b = 7.698(6), c = 9.768(7) A, α = 105.53(1)°, β = 99.24(2)°, γ = 90.09(2)°, V = 451.2(6) A, and Z = 1. The five strongest lines in the powder X-ray diffraction pattern are [d in A (I) (hkl)]: 9.338 (100) (001), 2.753 (64) (211), 5.173 (52) (011), 2.417 (48) (2 13, 202, 014), and 3.828 (45) (021). The crystal structure was solved from single-crystal X-ray diffraction data using synchrotron radiation and refined to R = 0.1382 on the basis of 816 unique reflections with F > 4σF. The structure of kapundaite is based on a unique corrugated octahedral-tetrahedral sheet, which is composed of two types of chains parallel to a. Kapundaite is structurally related to melonjosephite. The mineral is named for the nearest town to the quarry.

The lead fatigue crack concept for aircraft structural integrity

Over many years of quantitative fractographic examination of fatigue cracking from in-service and full-scale fatigue tests of metallic airframe components, it has been consistently observed that the largest cracks formed have grown in an approximately exponential manner. These crack growth observations range from the initiation of cracks and their early growth from a few micrometers through to many millimetres in length. It appears that these lead cracks commence growing shortly after the airframe is introduced to the loading environment. Furthermore these cracks usually initiate from production-induced or, less frequently, inherent material discontinuities. Based on these two observations, an aircraft lifing methodology that is based on the results of fatigue testing programs utilising the lead crack concept has been developed and implemented as an additional tool in the determination of aircraft component fatigue lives in several Royal Australian Air Force (RAAF) fleet types. In this paper the lead crack concept is developed and its strengths and weaknesses are discussed. Examples of crack growth behaviour that are considered typical and representative of lead cracks are presented.

Rapid, Low‐Temperature Synthesis of β‐SiC Nanowires from Si and Graphite

β‐SiC nanowires were synthesized at a temperature as low as 150°C by the reaction of Si and graphite induced by an additional reaction between Na and S. Characterization by X‐ray diffraction, high‐resolution transmission electron microscopy, IR spectra, and Raman spectra demonstrates the formation of curly β‐SiC nanowires with several millimeters in length and 50–70 nm in diameter. Also, a prominent peak at 387 nm is observed in the visible photoluminescence emission. Besides the temperature, the molar ratio of S to Si (or graphite) has significant influence on the synthesis of SiC at relatively low temperatures.

Photolithographically patterned silver nanowire electrodeposition

We report the fabrication of silver nanowires using lithographically patterned nanowire electrodeposition (LPNE). The LPNE synthesis of silver nanowires proceeds by lithographically patterning, and then etching an evaporated nickel film to produce a nickel nanoband 20–80 nm in height. This nanoband, which traces the perimeter of the exposed region, is recessed by ≈500 nm into the photoresist producing a horizontal trench. A silver nanowire, of controlled height and width, is formed within this trench by electrodepositing silver from either of two aqueous solutions at the nickel nanoband. Silver nanowires with controlled widths ranging from 100 to 400 nm were obtained and the height of silver nanowires was independently controllable over the range from 20 to 80 nm. The LPNE process is wafer-scale and continuous silver nanowires millimeters in length are readily obtained. Data for the characterization of these nanowires using AFM, TEM, and XRD is presented.

Tubular Bridges for Bronchial Epithelial Cell Migration and Communication

BackgroundBiological processes from embryogenesis to tumorigenesis rely on the coordinated coalescence of cells and synchronized cell-to-cell communication. Intercellular signaling enables cell masses to communicate through endocrine pathways at a distance or by direct contact over shorter dimensions. Cellular bridges, the longest direct connections between cells, facilitate transfer of cellular signals and components over hundreds of microns in vitro and in vivo.Methodology/Principal FindingsUsing various cellular imaging techniques on human tissue cultures, we identified two types of tubular, bronchial epithelial (EP) connections, up to a millimeter in length, designated EP bridges. Structurally distinct from other cellular connections, the first type of EP bridge may mediate transport of cellular material between cells, while the second type of EP bridge is functionally distinct from all other cellular connections by mediating migration of epithelial cells between EP masses. Morphological and biochemical interactions with other cell types differentially regulated the nuclear factor-κB and cyclooxygenase inflammatory pathways, resulting in increased levels of inflammatory molecules that impeded EP bridge formation. Pharmacologic inhibition of these inflammatory pathways caused increased morphological and mobility changes stimulating the biogenesis of EP bridges, in part through the upregulation of reactive oxygen species pathways.Conclusions/SignificanceEP bridge formation appears to be a normal response of EP physiology in vitro, which is differentially inhibited by inflammatory cellular pathways depending upon the morphological and biochemical interactions between EP cells and other cell types. These tubular EP conduits may represent an ultra long-range form of direct intercellular communication and a completely new mechanism of tissue-mediated cell migration.