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Background Trimetallic hollow core-frame nanocrystals with open structures and defects have potential applications in electrochemical sensing and catalytic reaction. Methods Herein, we synthesized trimetallic Ag@Au-Rh hollow core-frame nanocubes via selective growth of Au and Rh atoms on high energy facets of Ag nanocubes. Then, voltammetric detection of dopamine and catalytic degradation of organic dye were investigated. Significant Findings It was found that Ag@Au-Rh hollow core-frame NCs-based electrochemical sensor can measure DA in phosphate buffer solution (0.16–200 μM) with a logical limit of detection (LOD) of 0.43 µM. Moreover, Ag@Au-Rh hollow core-frame NCs showed extraordinarily higher catalytic activity towards the degradation of organic dyes than the bimetallic Ag@Au core-frame nanocubes. The superior electrochemical catalytic selectivity and sensitivity might be due to their high mass activity, unsaturated coordinated sites of the frame nanostructures, and the synergistic electronic effect of their trimetallic composition. These results demonstrate that the trimetallic hollow core-frame nanocrystals, such as Ag@Au-Rh, could be used for sensitive sensors and ultrafast environmental remediation.

The purpose of this study was to solve the chloride corrosion damage problems of the rebar in reinforced concrete structures under the chloride environment. The effects of 1.0% triethanolamine (abbreviated as 1.0% TEA), 1.0% Ca(NO2)2, and 0.5% TEA + 0.5% Ca(NO2)2 (abbreviated as 1.0% composite corrosion inhibitor) on the electrochemical performance and modification mechanism of the mortar specimens were investigated by combining macro experiment and microanalysis. The results showed that the electrode potential of the rebar was effectively improved by incorporating the 1.0% composite corrosion inhibitor. This composite corrosion inhibitor displayed the ability to stabilize the electrode potential of the rebar; it also formed a passive film on the surfaces of the rebar, protected the rebar from chloride attack, and achieved satisfactory electrochemical performance. In addition, it could also effectively improve the strength of the mortar specimens and possessed the strong ability to bind chloride ions, thus signifying that it could promote cement hydration and accelerate the formation of cement to form AFt crystals. Therefore, the results of this investigation confirmed that this composite corrosion inhibitor could be effectively used in practical engineering to prevent the corrosion of reinforced concrete structures.

Sodium alginate (SA) limits its application due to its low stability and poor performance. This study explored the synergy between SA and gum ghatti (GG) to improve the performance of biodegradable SA film. In this study, the chemical structure, rheological properties, morphology, thermal stability, and physical properties of the films were evaluated. Attenuated Total Reflection Fourier Transform Infrared Spectroscopy analysis (FTIR-ATR) revealed that hydrogen bonds are established between SA and GG, as well as strong electrostatic interactions. scanning electron microscopy and X-ray diffraction confirmed that SA has good compatibility with GG. Differential scanning calorimetry data demonstrated the excellent thermal properties of the SA/GG blend films. The film with an SA/GG ratio of 5:1 exhibited an elongation at break (EB), tensile strength (TS) and water vapor permeability (WVP) of 15.27% and 34.11 MPa and 7.19 × 10−11 g/(m s Pa), respectively. In addition, the light barrier properties of the blend film were improved 65.17%. Thus, there is a strong interaction between SA and GG to improve the properties of the blend films. SA/GG blend films offer wide application prospects as packaging materials and biomaterials in food industries.

The deposition of NH4HSO4 and the poisoning effect of SO2 on SCR catalyst are the main obstacles that restrict the industrial application of CeO2-doped SCR catalysts. In this work, deposited NH4HSO4 decomposition behavior and SO2 poisoning over V2O5-MoO3/TiO2 catalysts modified with CeO2 and SiO2 were investigated. By the means of characterization analysis, it was found that the addition of SiO2 into VMo/Ti-Ce had an impact on the interaction existed between catalyst surface atoms and NH4HSO4. Temperature-programmed methods and in situ diffused reflectance infrared Fourier transform spectroscopy (DRIFTS) experiments indicated that the doping of SiO2 promoted the decomposition of deposited NH4HSO4 on VMo/Ti-Ce catalyst surface by reducing the thermal stability of NH4HSO4 and enhancing the NH4HSO4 reactivity with NO in low temperature. And this improvement may be the reason for the better catalytic activity than VMo/Ti-Ce in the case of NH4HSO4 deposition. Accompanied with cerium sulfate species generated over catalyst surface, the conversion of SO2 to SO3 was inhibited in SiCe mixed catalyst. The addition of SiO2 could promote the decomposition of cerium sulfate, which may be a potential strategy to enhance the resistance of SO2 poisoning over CeO2-modifed catalysts.

Limestone-gypsum wet flue gas desulfurization (WFGD) process has a significant influence on the emission characteristics of soluble ions in particulates. In this study, a simulated limestone-gypsum WFGD platform was used to study the emission characteristics of water-soluble ions in flue gas after desulfurization. The experimental results indicated that the entrainment of desulfurization slurry droplets was the main source of water-soluble ions emission while water-soluble ions cannot be carried by vaporous water in flue gas. The limestone-gypsum desulfurization process can form soluble ionic particles with particle size less than 1 μm. In addition to Ca2+, Mg2+, SO42- and Cl-, which were the main ion components in the slurry, NH4+ was also the main ion composition of the soluble ionic particles, indicating that the entrainment and evaporation of slurry droplets and condensation of volatile components were the formation mechanism of the soluble ionic particles. Reducing the gas velocity and liquid-gas rat...

The purposes of this study were to validate modified atmosphere packaging (MAP) pre-storage for reducing surviving populations and thermal resistance of E. coli ATCC 25922 in almond kernels. A 6 kW, 27.12 MHz radio frequency (RF) assisted hot air heating system was used to conduct thermal treatments of 1.5 kg MAP pre-storage samples. Surviving populations of E. coli ATCC 25922 in almond kernels with 8.0% wet basis were determined weekly for 12-week pre-storage and samples were removed at five different time intervals during thermal treatments to achieve at least 4-log reduction. The results showed that reduction levels of E. coli for MAP and regular atmosphere packaging (RAP) were 1.47 ± 0.08 and 0.61 ± 0.05 log CFU/g after 12-week pre-storage. The 4-log reduction time of E. coli in MAP was 18 ± 1 min holding after RF assisted heating to 75 ± 2 °C, reducing 40% pasteurization time as compared with RAP pre-storage. Fatty acid and peroxide values remained within acceptable range (FA 0.05) different from those of untreated ones. MAP pre-storage assisted thermal treatments induced by RF energy may hold potential as an effective and environmentally friendly method to control E. coli ATCC 25922 in almond kernels.

Selective catalytic reduction (SCR) may affect the emission characteristics of fine particulate matter due to NH3 slip during denitrification. In this study, an experimental facility equipped with a coal-fired boiler, SCR unit, electrostatic precipitator (ESP), and wet flue gas desulfurization (WFGD) unit was adopted to investigate the effect of SCR on final fine particulate matter emission characteristics. The migration and transformation of the generated ammonium sulfates and NH3 slip in the downstream ESP and WFGD were also investigated. The results indicate that SCR can increase the final emissions of submicron particles due to the formation of (NH4)2SO4 and NH4HSO4 aerosols. In the ESP system, the generated ammonium sulfate particles can be effectively captured by the electric field force, which can also improve the capture efficiency of ESP on fine particles. Nonetheless, the operation of SCR with an NH3 injection still leads to an increase in fine particle emission levels at the ESP outlet. In the WFGD system, ammonium sulfates and ammonia can be partly removed by desulfurization through slurry scrubbing. However, the accumulated NH4+ in slurry will generate new ammonium species and ammonia through the entrainment and evaporation of the slurry. Finally, although both ESP and WFGD have a good removal effect on the generated fine particles, the SCR operation with the NH3 slip still results in an increase in the emission of fine particles and NH4+. As the formation and transformation mechanism of ammonia slip and ammonium sulfates generated by SCR is complex and affected by many factors, further research will be required.

Structures are easily corroded in the Salt Lake areas of China, especially in sulfate solution. This study was intended to settle the problem of sulfate corrosion failure of concrete structures, the influences of different contents of super absorbent polymer (abbreviated as SAP) on the working performance, mechanical properties, corrosion resistance and expansion performance of cement mortar were studied. The mechanism of SAP in mortar was analyzed and studied by SEM. The results showed that although SAP could slightly decrease the fluidity and strength of cement mortar, but it could remarkably improve the coefficient of resistance erosion of specimens and the inflation coefficient of cement paste. When the content of SAP was 0.3%, the sulfate corrosion resistance and expansion performance of specimens showed the best (the coefficient of resistance erosion and inflation coefficient of mortar specimens were 0.95 and 0.97, respectively). Besides, SAP could release much water in the hydration process, form irregular holes, and increase the porosity of mortar specimens. There would more hydration products generated and filled in the pores during the hydration process, thereby improving the sulfate resistance of mortar specimens. Therefore, this research provides theoretical guidance and basis for the study of sulfate corrosion damage of concrete structures in the future.

Ink-printing method emerges as a viable way for manufacturing large-scale flexible Cu(In,Ga)Se2 (CIGS) thin film photovoltaic (TFPV) devices owing to its potential for the rapid process, mass production, and low-cost nonvacuum device fabrication. Here, we brought the femtosecond laser annealing (fs-LA) process into the ink-printing CIGS thin film preparation. The effects of fs-LA treatment on the structural and optoelectronic properties of the ink-printing CIGS thin films were systematically investigated. It was observed that, while the film surface morphology remained essentially unchanged under superheating, the quality of crystallinity was significantly enhanced after the fs-LA treatment. Moreover, a better stoichiometric composition was achieved with an optimized laser scanning rate of the laser beam, presumably due to the much reduced indium segregation phenomena, which is believed to be beneficial in decreasing the defect states of InSe, VSe, and InCu. Consequently, the shunt leakage current and rec...

Concrete use in construction sector getting demand due to its availability, cheap rate handling malleability, flexibility and the process of development country. As the concrete is widely used in the construction practice, the time for the construction to competition was also a crucial argument. Thus, with the addition of calcium nitrate (Hardening Accelerator), this study attempts to explore the effect of silica fumes on early concrete stage. This research assessed multiple tests which are slump test, compressive strength test, flexural strength test and ultrasonic pulse velocity. The concrete mix proportioning of silica fumes in the percentage of 0%, 5%, 10%, and 15% of replacement with cement. Each specimen was being cured in water and tested according to its testing age (3 hours, 6 hours, 1 days, 7 days and 14 days). The synergistic interaction between silica fumes and calcium nitrate (hardening accelerator) was analysed to be used in the concrete. Thus, with the enhanced silica fumes content, the compressive strength and the flexural strength of the concrete was improved.

Reinforced concrete structures are easily corroded in the Salt Lake areas of China, especially in harsh environmental circumstance, such as freezing-thawing cycles, wetting-dry, et al, thus causing a lot of damage problems (concrete deterioration and steel bars corrosion). This research investigation was a research study which was to solve the corrosion problem of reinforced concrete structures under the chloride environmental circumstance through the electrochemical performance and mechanical properties test of the reinforced mortar specimens, the effect of single or compound doping of two organic and two inorganic corrosion inhibitors to the electrode potential, electrochemical impedance spectroscopy and mechanical properties of the reinforced mortar were investigated. The experimental conclusion demonstrated that the organic or inorganic corrosion inhibitors after single and compound doping showed some degree influence on the electrode potential and mechanical properties of the reinforced mortar specimens. Meanwhile, when the ratio of triethanolamine (TEA):triisopropanolamine (TIPA) was 7:3, sodium monofluorophosphate (MFP):sodium molybdate was 5:5, the compressive strength and flexural strength of mortar after curing for 28 days were greater than 90%, it indicated that these proportions showed the best corrosion resistance performance of steel bars. Therefore, these proportions of corrosion inhibitors could be used in reinforced concrete structures. The significant was that these results could provide theoretical guidance and technical basis for the study of corrosion damage of reinforced concrete structures in the future.

The purpose of the study was to validate effects of radio frequency (RF) heating under controlled atmosphere (CA) on thermal inactivation of E. coli ATCC 25922 in almond kernels. A 2.4 kW, 27.12 MHz, 50 Ω RF heating system was used to treat 1.5 kg size almond kernel samples with the adjusted moisture content of 8.0% wet basis under regular atmosphere (RA, 21% O2, 79% N2) and CA (2% O2, 20% CO2, 78% N2) conditions. The power level of 900 W under an electrode gap of 11.5 cm was used at the ramping stage for quick heating, and a maximum temperature difference of 3 °C in the inoculation area was achieved by continuing the RF heating at reduced power level during the 40 min holding stage. A 4-log reduction time under CA treatment was achieved with 21 ± 1 min holding at 75 ± 3 °C, reducing treatment time by 38% as compared with RA environment. The various quality attributes of treated samples remained within acceptable range based on nut industry standards. The RF heating under CA conditions may hold potential as an effective treatment method to control E. coli ATCC 25922 in raw almond kernels and be possibly extended for pasteurization applications.

The out-of-plane deformation of the Portevin–Le Chatelier (PLC) band is investigated during tensile tests in an Al alloy using digital shearography for the first time. The fringe patterns, which reflect the out-of-plane displacement gradient, indicate that the PLC bands also appear in the out-of-plane deformation field corresponding to the serrations in the stress–strain curve. Unlike the results obtained from other methods, the true bandwidth is determined by subtracting the shearing amount from the observed bandwidth. The continuous propagation of type-A PLC bands is traced at three different shearing amounts. The out-of-plane displacement of a PLC band is obtained based on the gray-level distribution in a frame of fringe pattern. The maximum displacement is approximately 250 nm in an interval of 1/15 s during a continuous propagation. The displacement gradient is greater in the front of the PLC band than in the back. Moreover, the position change process of the PLC band is presented, i.e., a band disappearing and a new band forming concurrently in another place. The inclination transition process, such that the inclination direction of the PLC band turns from the “ / ” direction to the “ ⧹ ” direction, is also shown in detail. The results prove that the vibrations-proof and high sensitivity digital shearography is a valuable and important method in the investigation of the out-of-plane deformation of the PLC band.

Real-time phase-shifting interferometry based on pixelated micropolarizer array (PMA) has recently been used to achieve real-time phase measurement, and the requirement of vibration resistance is greatly reduced. In this paper, a 320×240 Aluminum PMA with 7.4 μm pitch is successfully fabricated by the electron beam lithography (EBL). The period of the grating is 140nm, and the polarization directions of each 2×2 units are 0°, 45°, 90°, and 135°. The PMA is integrated to the CCD sensor to achieve real-time phase measurement. Four fringe patterns of different polarization directions are obtained from only one single frame image by linear interpolation method, and then the object wave phase is calculated in real-time. Moreover, dynamic phase caused by temperature change is obtained in real-time, which verify the feasibility of this method in real-time dynamic phase measurement.

A variety of experimental methods have been proposed for Portevin-Le Chatelier (PLC) effect. They mainly focused on the in-plane deformation. In order to achieve the high-accuracy measurement, three-dimensional digital image correlation (3D-DIC) was employed in this work to investigate the PLC effect in 5456 Al-based alloy. The temporal and spatial evolutions of deformation in the full field of specimen surface were observed. The large deformation of localized necking was determined experimentally. The distributions of out-of-plane displacement over the loading procedure were also obtained. Furthermore, a comparison of measurement accuracy between two-dimensional digital image correlation (2D-DIC) and 3D-DIC was also performed. Due to the theoretical restriction, the measurement accuracy of 2D-DIC decreases with the increase of deformation. A maximum discrepancy of about 20% with 3D-DIC was observed in this work. Therefore, 3D-DIC is actually more essential for the high-accuracy investigation of PLC effect.

The critical strain of the Portevin–Le Chatelier (PLC) effect marks the boundary between stable and unstable flow. In this paper, tension tests were conducted at different temperatures ranging from 173 to 333 K. The PLC effect is present at temperatures of 223–328 K. Normal behavior of the critical strain is observed at temperatures of 223–298 K, while inverse behavior is observed at 298–333 K. By comparing the stress–strain curves at different temperatures, the curves for 173 and 333 K are identified as the lower and upper envelope curves, respectively. Before the critical strain, the stress follows the lower envelope curve at low temperatures, whereas it follows the upper envelope curve at high temperatures. The subsequent serrations, which are upward at low temperatures but downward at high temperatures, oscillate between the two envelope curves. Furthermore, different dislocation states for the lower and upper envelope curves are proposed. The lower envelope curve implies that few dislocations are pinned by solute, while the upper envelope curve implies that some dislocations are pinned by the solute prior to escape. The dominant factor of the critical strain is the diffusibility of the solute at low temperatures and the pinning strength at high temperatures. Finally, based on dynamic strain aging, two critical mechanisms in relation to the first pinning at low temperatures, and the first unpinning at high temperatures, are proposed and are highly consistent with the experiment.

As one of the simplest MEMS sensors, microcantilever can sense temperature faster and more sensitively than traditional thermometers as its small size and low thermal mass. In this paper, an Au/SiNx bi-material microcantilever temperature sensor based on optical readout is presented. The deflection of the cantilever varies with the change of temperature due to the differences in thermal expansion coefficients between gold and silicon nitride. Then, the temperature could be accurately measured by detecting the deflection of the cantilever with optical lever method. By experiments, the theoretical model is verified and the temperature characteristics of the sensor are also determined. With a commercial microcantilever, the temperature resolution of the sensor is tested to be 0.02 K when 25 mm length of optical arm set. By optimizing the microcantilever parameters, the temperature resolution of the sensor could be 0.1 mK. High sensitivity makes it suitable for some special precise temperature measurements.

Furfuryl alcohol (FA) was polymerized in aqueous solutions consisting of polyvinyl pyrrolidone (PVP) as a surfactant together with hydrochloric acid, phosphoric acid, or acetic acid as a catalyst, respectively. The polymerization degree of FA and the resulting structural difference after carbonization were examined. Experiments revealed that the presence of acids does indeed promote polymerization of FA, leading to a reduced defect population and an eventual formation of a more ordered structure in the carbonized products. This is particularly pronounced when hydrochloric acid was used as a catalyzer, forming “nonstick” polyfurfuryl alcohol (PFA) particles with a diameter ca. 0.5–1 μm. The polymeric particles were then converted into microporous carbon spheres with a specific surface area of 297 m2/g when calcined at 600 °C in argon atmosphere. On the contrary, FA in the rest of catalyst systems showed aggregated form with a pronouncedly reduced specific surface area ranging from 0.3 to 5.2 m2/g.

θ-Al2O3 powders in slurry form were coated by boehmite nanoparticles prepared from alumina sol that consists of aluminum tri-sec-butoxide (Al(OC4H9)3) as a precursor. The θ-Al2O3 powders presented an iso-electrical point (IEP) at pH ∼ 9.2, and formed stable suspensions without notable gravity settling at acidic conditions (pH 3–4). Boehmite nanoparticles with a mean particle size ca. 68 nm were derived from the hydrolysis of Al(OC4H9)3 sol. Well-dispersed boehmite/θ-Al2O3 aqueous mixtures consisting of 3 and 9 wt.% of boehmite were then prepared by addition of θ-Al2O3 powder into the Al(OC4H9)3 sol followed then by vigorous agitation at 90 °C and in a pH range 3–4. IR and particle-size measurement both revealed possible coating of boehmite on the θ-Al2O3 particles. From TEM observation, “thickness” of the boehmite layer did not vary much with the boehmite concentration. Agglomeration of the particles became nonetheless apparent as the boehmite concentration was increased. The boehmite coating on θ-Al2O3 surface inhibited grain growth during the θ- to α-phase transformation upon heating. Mean grain size of the boehmite-coated alumina was substantially smaller than that of the un-coated one.

The non-toxic and wide bandgap material TiO2 is explored as an n-type buffer layer on p-type Cu(In,Ga)Se2 (CIGS) absorber layer for thin film solar cells. The amorphous TiO2 thin film deposited by atomic layer deposition process at low temperatures shows conformal coverage on the CIGS absorber layer. Solar cells from non-vacuum deposited CIGS absorbers with TiO2 buffer layer result in a high short-circuit current density of 38.9 mA/cm2 as compared to 36.9 mA/cm2 measured in the reference cell with CdS buffer layer, without compromising open-circuit voltage. The significant photocurrent gain, mainly in the UV part of the spectrum, can be attributed to the low parasitic absorption loss in the ultrathin TiO2 layer (~10 nm) with a larger bandgap of 3.4 eV compared to 2.4 eV of the traditionally used CdS. Overall the solar cell conversion efficiency was improved from 9.5% to 9.9% by substituting the CdS by TiO2 on an active cell area of 10.5 mm2. Optimized TiO2/CIGS solar cells show excellent long-term stability. The results imply that TiO2 is a promising buffer layer material for CIGS solar cells, avoiding the toxic CdS buffer layer with added performance advantage.

Utilizing different rare-earth cations R 3+ to the Ba 6 − 3 x R 8 + 2 x Ti 18 O 54 compounds is one of effective route to tailor the dielectric constant, quality factor and temperature coefficient of frequency. In this study, densification, microstructural evolution, and microwave dielectric properties of Ba 6 − 3 x (Sm 1 − y Nd y ) 8 + 2 x Ti 18 O 54 compound, with x ranging from 0.3 to 0.7; and y from 0 to 1.00, were investigated. The ceramics with x = 0.7 [Ba 3.9 (Sm 1 − y Nd y ) 9.4 Ti 18 O 54 ] has a higher densification compared with others, due to the formation of vacancy, in the perovskite-like tetragonal cavity of the tungsten bronze-type framework structure. Differential thermal analysis and density results show that the densification of Ba 6 − 3 x (Sm y Nd 1 − y ) 8 + 2 x Ti 18 O 54 ceramics during sintering is primarily resulting from the solid state sintering process. The phase homogeneity for the Ba 6 − 3 x (Sm 0.5 Nd o.5 ) 8 + 2 x Ti 18 O 54 system is at least extended in the range of x between 0.3 and 0.7. Combining different rare-earth cations appears not alter the single phase range in tungsten bronze-type Ba 6 − 3 x R 8 + 2 x Ti 18 O 54 ceramics. The size of the columnar-grain in the microstructure increases with increasing the Nd/Sm ratio as well as the x value. Dielectric constant changes from 91.0 to 84.2 as the x increases from 0.3 to 0.7. Variation of the Nd/Sm ratio allows one to control the τ f value to the nearly 0 ppm/°C.

A novel scheme for hybridizing inkjet-printed thin film Cu(In,Ga)Se2 (CIGS) solar cells with self-assembled clusters of nanocrystal quantum dots (NQDs), which provides a 10.9% relative enhancement of the photon conversion efficiency (PCE), is demonstrated. A non-uniform layer of NQD aggregates is deposited between the transparent conductive oxide and a CdS/CIGS p-n junction using low cost pulsed-spray deposition. Hybridization significantly improves the external quantum efficiency of the hybrid devices in the absorption range of the NQDs and in the red to near-IR parts of the spectrum. The low wavelength response enhancement is found to be induced by luminescent down-shifting (LDS) from the NQD layer, while the increase at longer wavelengths is attributed to internal scattering from NQD aggregates. LDS is demonstrated using time-resolved spectroscopy, and the morphology of the NQD layer is investigated in fluorescence microscopy and cross-sectional transmission electron microscopy. The influence of the NQD dose on the PCE of the hybrid devices is investigated and an optimum value is obtained. The low costs and limited material consumptions associated with pulsed-spray deposition make these flexible hybrid devices promising candidates to help push thin-film photovoltaic technology towards grid parity.

Pixelated micropolarizer array (PMA) is a novel concept for real-time visible imaging polarimetry. A 320 × 240 aluminum PMA fabricated by electron beam lithography is described in this paper. The period, duty ratio, and depth of the grating are 140 nm, 0.5, and 100 nm, respectively. The units are standard square structures and the metal nanowires of the grating are collimating and uniformly thick. The extinction ratio of 75 and the maximum polarization transmittance of 78.8% demonstrate that the PMA is suitable for polarization imaging. When the PMA is applied to real-time polarization imaging, the degree of linear polarization image and the angle of linear polarization image are calculated from a single frame image. The polarized target object is highlighted from the unpolarized background, and the surface contour of the target object can be reflected by the polarization angle.

Scanning probe microscopy, having the capability of nano-positioning and nanomanipulation, enables the characterization of material properties at a very small scale. In our previous work, the investigation of localized electrochemical reactions in Si3N4-TiC ceramic nanocomposites had been demonstrated using a single conductive scanning probe in a scanning impedance microscope (SIM). The results have provided experimental evidence that links the relations among microstructural heterogeneity, electrochemical property, and sintering behavior of spark plasma sintered ceramics. This single-probe SIM measurement gave through-body electrochemical information of specific surface feature of interest; however, the characterization of across-surface material properties in nanoscale is still much desired and unavailable.To further investigate the heterogeneity of materials, we have designed and developed a dual-electrode scanning probe (DESP), which is capable of localized electrochemical characterization across the surface of a material. These probes were designed based on computer simulation and iterations, and fabricated using common semiconductor processing techniques. The span of two probes (electrodes) in our first prototypes was 10∼15 microns, which can be further reduced with optimized parameters. The DESP probes have been evaluated on Si3N4-TiC nanocomposites to demonstrate their functionality in topography scanning and in-situ impedance measurement. The impedance spectroscopy revealed two distinct impedance patterns for measurements across TiC-rich and Si3N4-rich surface regions. The design, fabrication, and evaluation of DESP were discussed in addition to the analysis of Si3N4-TiC nanocomposites.

Repeated plastic instability accompanying serrated yielding in stress–strain curves and localization of deformation is observed during plastic deformation of many metallic alloys when tensile specimens are deformed under certain experimental conditions of temperature, strain rate, and pre-deformation. This phenomenon is referred to as the Portevin- Le Chatelier (PLC) effect. TMW alloy, a newly developed Ni–Co base superalloy for aircraft engine application, also exhibit PLC effect during tensile test at temperatures ranging from 300 ℃ to 600 ℃, which are also the temperature range for engine working. In this paper, a 3D digital image correlation (3D DIC) measurement system was established to observe the localization of deformation (PLC band) in a tensile test performed on TMW alloy specimen at temperature of 400 ℃. The 3D DIC system, with displacement measurement accuracy up to 0.01 pixels and strain measurement accuracy up to 100 μe, has a high performance in displacement field calculation with more than 10000 points every second on a 3.1G Hz CPU computer. The test result shows that, the PLC bands are inclined at an angle of about 60° to the tensile axis. Unlike tensile test performed on aluminums alloy, the widths of PLC bands of TMW alloy specimen, ranging from 4 mm to 4.5 mm, are much greater than the specimen thickness (0.25 mm).

In this study, we used antibody-immobilized AlGaN/GaN high electron mobility transistors (HEMTs) for detecting a short peptide, and revealing the number of binding sites of the antibody for the peptide and the dissociation constants of the antibody-peptide complex. In our case, two binding sites were found on the ferritin heavy chain (FHC) antibody and the dissociation constants of the antibody-peptide complex were 2.723×10−11M and 6.994×10−9M for the two binding sites, respectively. The estimated dissociation constants are consistent within the reasonable range of the IGg antibody-antigen complexes binding constants. It also reveals the limit of detection is not only decided by the performance of the transistors but also the dissociation constant of the detected molecules. To our knowledge, it is the first time that AlGaN/GaN HEMTs using on the study of protein-peptide binding affinity. The results show that AlGaN/GaN HEMTs can not only be used as biosensors, but also a good tool and platform for analytical chemistry with numerous advantages since they are label-free, low-cost, biocompatible, stable in high temperature, real-time detection. Compared with other methods and techniques investigating the binding and kinetics of biological molecules, we do demonstrate AlGaN/GaN HEMTs have great potential to compete with conventional or proposed methods.

CIGS solar cell has yielded the high efficiency beyond 20% on glass substrate [1], but some drawbacks such as heavy, not portable, toxic and costly need to be met for future manufacture. In this study, ZnS(O,OH)/CIGSeS solar cells were fabricated on flexible stainless steel substrate by low-cost nano-particle printing process. The flexible and non-toxic CIGSeS solar cell shows the efficiency as high as 13.37% without anti-reflection layer. The high efficiency was attributed to good thin film quality in absorption layer and buffer layer. Besides, the ZnS(O,OH) buffer layer with thickness only 15 nm shows good coverage, which enhances photocurrent and leads to high efficiency. Moreover, the CIGSeS solar cells were placed to dark room for 3 days to test light soaking effects, the results show that only 0.14% efficiency decay was measured. The results implies that the non-toxic and flexible CIGSeS solar cells prepared by nanoparticle printing process shows high potential for portable power source and building integrated photovoltaic system.

The members of viperidae crotalinae (pit viper) family have special pit organs to detect infrared radiation in normal room conditions, whereas most artificial uncooled infrared focal plane arrays (FPAs) operate only in a vacuum chamber. Dissection shows that the pit membrane is a unique substrate-free structure. The temperature rise advantage of this pit organ was verified in comparison with an assumed substrate pit organ (as an artificial FPA structure). Inspired by the pit viper, we introduced this structure to infrared FPA, replacing the conventional substrate FPA. The substrate-free FPA was fabricated by micro-elctromechanical systems (MEMS) process and placed into an infrared imaging system to obtain thermal images of the human body in atmosphere and vacuum working conditions. We show that the infrared capability of the substrate-free pit organ was achieved.

Based on a bi-material micro-cantilever thermal deformation principle, an uncooled infrared focal plane array (FPA) with optical readout has been developed from a substrate-based structure to a substrate-free structure. Infrared imaging of the substrate-free FPA indicates that this structure does not satisfy temperature-constant substrate conditions when the FPA unit size decreases from 200 μm to 60 μm. To evaluate the performance of the FPA, this paper puts forward an analytical model of heat transfer in the substrate-free FPA, by using a holistic approach and an electrical circuit analogy. The analytical model provides a fast and convenient way to calculate the temperature gray response and the response time of the substrate-free FPA. A substrate-free FPA with a unit size of 50 μm was fabricated. Infrared imaging experiments validate the model and indicate a noise equivalent temperature difference value of 170 mK has been achieved.

Optical sensitivity is a major issue to improve the sensor responsivity and the spatial resolution of uncooled optomechanical focal plane arrays (FPA). The optical sensitivity is closely related to the mirror length and the undesired mirror deformation induced from the imbalanced residual stresses in different layers. In this paper, the influences of mirror length and deformation on the optical sensitivity are discussed by Fourier Optics. Theoretical analysis and experiments demonstrate that the optical sensitivity is seriously degraded by undesired mirror deformation, and that there exists an optimal mirror length which makes the optical sensitivity achieve its maximum under a certain mirror deformation. Based on the results, an optimized mirror configuration is presented to increase the optical sensitivity of substrate-free bi-material microcantilever array (SFBMA).

The original research proposal to ONR/SDIO had outlined two major goals to be accomplished during the three and half year period from July 1987 to December 1990. The first task was (i) the fabrication and characterization of thin film superconductors with the high-temperature oxide materials and secondly was (ii) the fabrication and characterization of Josephson tunnel junctions. These tasks included the following: (i) fabrication and characterization of thin film superconductors and (ii) fabrication and characterization of Josephson tunnel junctions. Although the administration/contracting of funds was not formally authorized until January 1988, the progress has been quite successful with regards to the first goal of fabrication and characterization of thin/film superconducting oxide films. Similar to all other research groups in being unable to fabricate simple Josephson tunnel junctions with superconducting oxides, we have however been unable to initiate some characterization of the electromagnetic response observed in these films due to the inherent granular Josephson-coupled networks. In the following pages we outline in more detail the progress attained in the research proposal to date, a summary of the major accomplishments, and index of publications attributable to the present funding period, and the proposed program for continued research.