Surface Substructure Research Articles

Low temperature soldering technology based on superhydrophobic copper microlayer

Cu–Cu soldering is realized under certain pressure and low temperature conditions by using a surface silver film to modify the copper microlayer structure, thus solving the problems of high thermal stress and signal delay aggravation caused by high temperature in the traditional reflow soldering process. The copper microlayer modified with silver film is obtained by electrodeposition. The surface substructure of the Cu microlayer is a nano cone-shaped protrusion. The diameter of the bottom of the cone is 500 nm∼1 μm, and the height of the cone is 1∼2 μm. The thickness of the silver film is about 320 nm, and the modification of the copper layer with silver film can effectively prevent the oxidation of the copper layer. Two silver-modified copper microlayers are placed in face-to-face contact as a soldering couple. A certain pressure and low temperature are applied to the contact area to realize the soldering and interconnection.The morphology of the soldered interface and the average shear strength of the soldered joints are analyzed by scanning electron microscopy, transmission electron microscopy and solder joint tester. It is found that under the optimal soldering parameters of soldering temperature 220 °C, soldering pressure 20 MPa and soldering time 20 min, the nano-conical projections of the Cu micrometer layer are inserted into each other to produce a physical blocking effect. The highly surface-meltable silver film effectively connects the surrounding copper layer as an intermediate buffer layer. The average shear strength of soldering joints is significantly increased. Heat treatment experiments have shown that the average shear strength can be effectively increased by heat treatment for an appropriate period of time. Prolonged exposure to heat has little effect on the average shear strength. With the special morphology of the copper microlayer structure and the nano-size effect of the silver layer, soldering can be done at low temperatures. The quality of the soldering interface is good and small soldering dimensions can be obtained.

Integration of Multiple Sensors into an ROV for Remote Measurement in the Fukushima Daiichi Nuclear Power Station

To measure and analyze the distribution and criticality of submerged fuel debris “in situ” in the decommissioning process of the Fukushima Daiichi Nuclear Power Station (1F), we developed a system for remote measurement using multiple sensors consisting of the neutron sensor, the sonar, and the sub-bottom profiler (SBP) mounted on a small remotely operated underwater vehicle (ROV). First, the locations presumed to contain fuel debris were explored based on the information of the water bottom shape obtained using the sonar and the bottom surface substructure obtained using the SBP. Second, the system identified the location of fuel debris by detecting neutrons emitted by spontaneous fissions of fuel debris using the neutron sensor with diamond elements. Simulated fuel debris was placed at the bottom of a test water tank that simulated the pedestal. In the primary containment vessel (PCV) of 1F, and a verification test of remote measurement was conducted using the ROV mounted on the multiple sensors. The desired results were obtained.

Research on Microstructure Evolution of Deposited Metal of Low Nickel High Nitrogen Austenitic Stainless Steel

In this paper, in situ observation of the cooling process of the deposited metal of low nickel high nitrogen austenitic stainless steel obtained by laser‐arc hybrid surfacing welding with shielding gas containing only Ar and only N2, respectively, is carried out using the ultra‐high‐temperature confocal laser scanning microscope (CLSM). An in‐depth analysis of the microstructural changes is conducted with SEM, EDS, and EBSD. The results showed that the surface substructure is refined during crystallization with shielding gas Ar. However, grains are seriously coarsened in the δ phase area. Widmanstatten γ and intragranular γ are formed as a result of δ ⟶ γ phase transition through the shear‐diffusion mechanism. In the cooling process with shielding gas N2, the temperature range of each phase area narrowed obviously. Blocky γ began to appear because of the δ ⟶ γ phase transition through the diffusion mechanism. Generally, Ar and N2 have a strong effect only on the very shallow range from the surface. The area with a larger local misorientation with shielding gas Ar is at lath γ on the surface. With shielding gas N2, the large local misorientation area is the last contact position of γ during the δ ⟶ γ phase transition on the surface and cross section.

Surface-controlled galvanic replacement for the development of Pt-Ag nanoplates with concave surface substructures

Galvanic replacement, a spontaneous redox reaction arising from contact between a nanotemplate and a replacing ion, has been widely used for its convenience, stability, and ability to form various complex nanostructures. In this study, the two-dimensional nanosurface adsorption of polymeric micelles is performed for substructure formation through advanced galvanic replacement strategies. Polymeric micelles adsorbed on the nanotemplate surface form a nano-array structure of hydrophobic and hydrophilic domains, resulting in surface controlled galvanic replacement and the formation of concave surface substructures. The hydrophobic domain formation and blockage region expansion due to nanotemplate curvature and solvent composition contributes greatly to the surface substructure formations. The results can be summarized as a successful attempt to design the nanostructure by coordinating all potential factors involved in conventional galvanic replacement to create an unprecedented high-complexity nanostructure. Manufactured Pt-Ag nanoplates with concave surface substructures exhibited the successful hydrogen evolution electrocatalytic efficiency as demonstration. The Pt-Ag nanoplates with concave surface substructures exhibit the enhanced HER activity in strong acidic solutions with a low Tafel slope. The enhancement of the HER performance can be attributed to concave surface substructures, which greatly improve the edge sites and defects, resulting in a high density of exposed active sites. The galvanic replacement-based material design strategy demonstrated here exemplifies a novel and versatile approach to developing electrocatalysts with high activity and durability for advanced electrochemical water-splitting systems.

Experimental Investigation of Contact Welding Characteristics of Electromechanical Relays

Contact dynamic welding failure problems seriously limit the electrical lifetime of electromechanical relay. However, the welding behavior occurred in contact making and breaking process and relevant influencing factors are still unknown. In this article, a series of experiments are carried out in make only, break only, and make & break (M&B) operation modes individually to differentiate the effects of making and breaking processes on contact dynamic welding. The typical dynamic force and electrical waveforms of contact making and breaking processes are obtained and the statistical results of welding force are presented. The roles of bounce arc and molten bridge in welding force are interpreted explicitly by using the variations in electrical parameters such as bounce energy, contact resistance, molten bridge energy, break arc energy, and surface substructure morphologies. It is determined that the bounce arc plays a crucial role in the formation of weld nugget and strength, and the strongest welding occurs in the M&B operation mode.

Non-covalent modification of glassy carbon electrode with isoorientin and application to alpha-fetoprotein detection by fabricating an immunosensor

In this study, the glassy carbon electrode (GCE) surface substructure and geometry were originally modeled by first principles density functional theory (DFT) methods with a simple basis set AFPD/3−21 G. Isoorientin was then used as a model to explore the adsorbates bonding effect on GCE surface with experimental and computational methods. It was confirmed that the modification of the electroactive molecule, isoorientin onto GCE was no-covalent. Further, it was found that the Isoorientin/Anti-alpha-fetoprotein (AFP) antibody modified GCE, prepared by in turn depositing isoorientin and anti-AFP antibody (Ab) onto the GCE surface, could be used as an immunosensor for detecting the cancer biomarker AFP at GCE with differential pulse voltammetry (DPV). The peak current of isoorientin fixed at the modified GCE was negatively proportional to the concentration of AFP in solution with a linear range from 0.001–10 ng mL−1 and a detection limit of 0.0002 ng mL−1 by DPV. The practical determination of AFP in human serum is also investigated, indicating a potential application of the presented immunosensor in clinical tests and disease diagnosis.

Synthesis Peculiarities of CNT “Forest” Under Conditions of Adding a Regulated Plasma Component of the Working Gas

It has been shown that in case of adding a regulated plasma component of gas to the working gas mixture, the synthesis by the PECVD method of carbon nanotubes (CNT) on catalytic centers formed from a thin film deposited by vacuum-arc sputtering of a catalyst leads to the formation of nanotubes of two morphological types: forest and multiwall CNTs with surface substructure. Carbon nanotubes have their growth centers located either on solid crust formed on the substrate surface owing to the plasma component or directly on the substrate surface, when sufficiently small (5–20 nm) catalytic high-density centers are formed on this substrate. Plasma component forms a well-developed surface on multiwall nanotubes that is important for their practical application.

Effect of Heat Shotblast Treatment Exerted on the Contact Fatigue of Carburised Heat-Resistant Steel C0.12Cr2NiWV

Studies are performed to improve the working capacity of high-loaded gears made of heat-resistant carburised steel C0.12Cr2NiWV using a method of heat shotblast treatment. Basic regularities of change in the surface substructure and properties that determine contact fatigue are presented.

Surface Substructure and Properties of ZrB2p/6061Al Composite Treated by Laser Surface Melting under Extreme Cooling Conditions

Abstract Particulate reinforcement composite ZrB2p/6061Al was fabricated from Al-K2ZrF6-KBF4 by a direct melt reaction. Laser surface melting was used to improve the surface strength of the in situ ZrB2p/6061Al composite, which includes a series of laser-melted composites with different laser power and cooling conditions processed by a 2-kW yttrium aluminum garnet laser generator. The surface substructure of these laser-treated specimens was investigated by light optical microscopy, scanning electron microscopy, energy-dispersive spectroscopy, X-ray diffractometry and transmission electron microscopy. The penetration depth of the molten pool increases with increases in power density, and decreases with increases in the degree of undercooling. The Vickers hardness of the laser-melted composites reached 60–75.2 HV in liquid nitrogen and 56–64.0 HV in air, and increased by 50.4 % and 28 %. Grain refinement with decreased cellular spacing is important in strength performance. Because of a thermocapillary flow vortex and α-Al phase precipitation, nano-ZrB2 particles were distributed along the cellular dendrite boundary as observed by scanning electron microscopy. This was considered to be a key factor responsible for the improved mechanical composite properties. When cooling under liquid nitrogen, the thermal mismatch stress between particles and the matrix generates a high dislocation density. The dislocation grows along the interface between the matrix and particles and provides the laser-melted composites with additional strength.

Gradient Structural-Phase States in the Thermostrengthened Low-Carbon Steel Reinforcement

Thermomechanical strengthening increases the strength and plasticity of low-alloy low-carbon steel reinforcement and provides an alternative to expensive alloying. Scanning and transmission electron microscopy investigations of the failure surface, phase composition, morphology, and defect substructure of 0.25% carbon steel (St3 ps) after thermal strengthening by discontinuous quenching in the rolling-mill line reveals the formation of a gradient states in the rod cross-section.

Centrality dependence of the parton bubble model for high-energy heavy-ion collisions and fireball surface substructure at energies available at the BNL relativistic heavy ion collider (RHIC)

In an earlier paper we developed a QCD-inspired theoretical parton bubble model (PBM) for RHIC/LHC. The motivation for the PBM was to develop a model that would reasonably quantitatively agree with the strong charged particle pair correlations observed by the STAR Collaboration at RHIC in $\mathrm{Au}+\mathrm{Au}$ central collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV in the transverse momentum range 0.8 to 2.0 GeV/$c$. The model was constructed to also agree with the Hanbury Brown and Twiss (HBT) observed small final-state source size $~2$ fm radii in the transverse momentum range above 0.8 GeV/$c$. The model assumed a substructure of a ring of localized adjoining $~2$ fm radius bubbles perpendicular to the collider beam direction, centered on the beam, at midrapidity. The bubble ring was assumed to be located on the expanding fireball surface of the $\mathrm{Au}+\mathrm{Au}$ collision. These bubbles consist almost entirely of gluons and form gluonic hot spots on the fireball surface. We achieved a reasonable quantitative agreement with the results of both the physically significant charge-independent (CI) and charge-dependent (CD) correlations that were observed. In this paper we extend the model to include the changing development of bubbles with centrality from the most central region where bubbles are very important to the most peripheral where the bubbles are gone. Energy density is found to be related to bubble formation and as centrality decreases the maximum energy density and bubbles shift from symmetry around the beam axis to the reaction plane region, causing a strong correlation of bubble formation with elliptic flow. We find reasonably quantitative agreement (within a few percent of the total correlations) with a new precision RHIC experiment that extended the centrality region investigated to the range 0%\char21{}80% (most central to most peripheral). The characteristics and behavior of the bubbles imply they represent a significant substructure formed on the surface of the fireball at kinetic freezeout.

Nanostructural self-organization under selective laser sintering of exothermic powder mixtures

Topology of the surface substructure induced by the synthesis of intermetallic compounds under selective laser sintering is studied by scanning electron microscopy. The data is then analysed by image processing software for identification and discussion of common features and peculiarities of the structure-formation process. A dependence between the fractal dimension D of low-dimensional nanostructures and laser energy input A is found. It is shown that particularities of the structural-phase transformations under intermetallic synthesis in the Ni–Al, Ti–Al, Fe–Ti and Ni–Ti systems determine the appearance of ordered nanosubstructures as honeycomb-like, dendritic or mosaic. The change of the fractal dimension of low-dimensional structures clearly correlates with the change of roughness, while the increase of the laser energy input influences the fractal dimension D in different ways. Sharp variations of the D orientation indicate a change of the phase-formation mechanism.

Substructure and properties of thick palladium films

Thick (up to 9 μm) condensates are deposited by electron-beam evaporation (EBE) and magnetron sputtering of palladium. The surface substructure and morphology of these condensates are studied by electron microscopy. The strength and hydrogen permeability of these vacuum condensates are measured. It is found that condensation-stimulated processes give rise to a gradient substructure across the film thickness and that the gradient films are substantially stronger than epitaxial films. The epitaxial films grown by EBE proved to be most permeable to hydrogen.

Structural and phase states in austenitic steel subjected to high-cycle fatigue

The destruction surface and defect substructure of the Fe-0.1C-1.71Mn-0.92Ti-18.2Cr-10.4Ni-0.71Si steel subjected to high-cycle fatigue tests is investigated by the methods of scanning and transmission electron microscopy. It is demonstrated that the fatigue tests, irrespective of the loading scheme (continuous or under conditions of intermediate stimulation by pulse current), result in the formation of a structural gradient in the material manifested through regular changes of the relief parameters of the destruction surface and defect substructure with increasing distance from the loading surface (face or back specimen side). It is revealed that scalar and excess dislocation density, volume fraction of grains that comprise deformation microtwins, and degree of dislocation substructure organization maximize near the free specimen surface.

TEM Observation of Vacancy Clustering Process in FeAl Single Crystal

AbstractNanoporous surfaces are formed in B2-type FeAl single crystals by quenching into iced water, followed by surface treatment and aging heat treatment. From our previous works, it was indicated that the nanoporous phenomenon is caused by the clustering of supersaturated thermal vacancies. In this study, the clustering process of supersaturated thermal vacancies was systematically investigated by transmission electron microscopy (TEM). An irreversible exothermic peak was detected for as-quenched specimens by differential scanning calorimetry (DSC). The isochronal changes of surface morphology and substructure around the exothermic peak temperature were clarified by TEM observation. The average size of the surface pores monotonously increased with increasing the temperature. Dislocations whose Burgerse vectors are parallel to <100> existed in the isochronally-heated single crystals, and its density was changed with heat treatment temperature. On the other hand, there was no dislocation zone from surface to the depth of several tens nanometers. A growth model of the surface pores is discussed

Size Effects on Yield Instabilities in Nickel

AbstractDislocation events are seen as excursions, or pop-in events, in the load-displacement trace of nanoindentation experiments. When indenting single crystal metals these events occur frequently during quasi-static and dynamic loading. A single crystal of Ni (111) has been indented quasi-statically using three different loading rates (10, 100, and 1000 μN/s) as well as with three different radii diamond indenter tips (1000 nm cone, 300 nm Berkovich, and 50 nm cube corner) to examine the occurrences of excursions. As expected, excursions at higher loads have larger displacements, and that initial loading follows Hertzian behavior up to the point of yield. Also, as the tip size is reduced the excursion loads are reduced. The excursion events depend mostly on the statistical distribution of surface sources and substructure dislocation arrangements.

Confocal Imaging of Scale Development on Butterfly Wings

Both surfaces of the butterfly wing are covered with thousands of colored scales that are arranged in precise linear arrays. Each scale contributes a single color to the overall pattern, which is usually different on the upper and lower surface of the wing. Moreover, the scales have a characteristic surface substructure that is visible using confocal autofluorescence (fig. 1). The ridges on the surface of all of the scales function to control the flow of air across the wing surface during gliding flight, and they contribute to the interference colors in a subset of the scales.The fruit fly Drosophila melanogaster is the closest relative of butterflies for which detailed developmental, genetic and confocal imaging protocols have been established. Specimen preparation techniques for butterfly imaginal discs were largely developed from those for Drosophila tissues. The various stages of butterfly wing development have presented new challenges for confocal imaging. For example, butterfly fifth instar wing imaginal discs are much larger and thicker than those of the fruit fly.

The Surface Substructural Effects on Reststrahlen Bands in Reflectance of Alumina Ceramics with Different Sized Grains.

Directional hemispherical reflectance (DHSR) of alumina ceramics was measured in the reststrahlen band (500-1000cm-1). Three different samples with different grain sizes of 3-5μm, 11-13μm, and 28-34μm were used. Comparing the measured DHSR to the calculated reflectance using published optical constants of α-Al2O3 single crystal, we observed some difference between these reflectance data. The origin of this difference was identified as the surface substructure on the grains after some calculations based on the effective medium approximation. The distribution of the probability of the effective polarization factor of the surface substructure was determined by the fitting of the calculated reflectance by taking account its effect. The obtained in homogeneity well corresponds to the surface morphology observed by SEM and AFM.

Scanning Electron Microscopy of antennal sensilla of the Japanese tusser, Antheraea vamamai

Antennal surface structure of the Japanese tusser, Antheraea yamamai was observed by scanning electron microscope. The antennae of male and female were bipectinate with scape, pedicel and 33--37 flagellar segments. There were two pairs of equal long branch on eacli flagellar segment of male (Fig.1), but a pair of longer and a pair of shorter on female's (Fig.2).Seven types of sensillum, namely sensillum trichodeum, sensillum cheaticum, sensillum coeloconicum, sensillum campaniformlum, sensillum styloconicum, Bohm's bristle and sensillum squamiformium wer found on the antenna both of male and female. The sensillum trichodeum could be subdivided into long and short according to the shape and surface substructure. The long sensillum trichodeum had a diameter of 4.8μm at its base. It was reratively stright and slightly curved at the tip (Fig.3). The short sensillum trichodeum was 2.5--3.6 μm in diameter at the base. It was shorter, strongly bend down near its base and run parallel with the surface of the antenna (Fig.4). The surface of long and short sensilla trichodea were covered with annular ridges (Fig.5).

Alterations in surface substructure and degranulation of subapical cytoplasmic granules by mezereinu (MZ) in toad urinary bladder epithelia

The increase in transepithelial water flow induced by antidiuretic hormone (ADH) occurs through the ADH V2 receptor, and includes the stimulation of adenylcyclase, an increase in cAMP synthesis and the activation of protein kinase A. These biochemical events in amphibian urinary bladder tissues are reported to be accompanied by apical membrane transformations including the induction of numerous microvilli, and an increase in apical surface area as a result of incorporation of water channels. Amphibian epithelia also contain an ADH V1 receptor coupled to phosphoinositide metabolism and inositol phosphate release. Recently, it was demonstrated that mezerein (MZ), a non-phorbol activator of protein kinase C (PKC)increased transepithelial water flow when added to mucosal surface. The magnitude of water transport was less and occurred over a longer period of time than compared to ADH-stimulated tissues (7,and also Table 1). However, there is little or no information available on ultrastructural studies linking the events due to the ADH V1 receptor and osmotic water flow. Presently, we report on morphological and cytological observations which suggests that the ADH V1 receptor cascade may play a role in the insertion of water channels into the apical membrane possibly through the activation of PKC. The present study utilizes mezerein (MZ), a non-phorbol activator of protein kinase C (PKC) to examine the effect of MZ on epithelial cytomorphology.