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Ce3+ and Pr3+ co−doped Lu3Al5O12 phosphors were synthesized by the sol–gel process, and their crystal structure, photoluminescence (PL) properties, and energy transfer (ET) from the Ce3+ to Pr3+ were studied. The Lu2.94−yAl5O12:0.06Ce3+, yPr3+ phosphors (0.002 ≤ y ≤ 0.008) showed the green−yellow emission from the 2D3/2 → 2F5/2, 7/2 transition of Ce3+ and the red emission at 610 and 637 nm, which were caused by the 1D2→3H4 and 3P0→3H5 transitions of Pr3+, respectively. The optimal concentration of Pr3+ for efficient ET was found to be x = 0.006. The electric quadrupole−quadrupole interaction was responsible for the concentration quenching in the Lu2.94−yAl5O12:0.06Ce3+, yPr3+ phosphors, based on Dexter's theory. The incorporation of Pr3+ for Lu3+ enhanced the red PL intensity in the Lu2.94Al5O12:0.06Ce3+ phosphor.

Fast recovery, high sensitivity, high selectivity, and room temperature (RT) sensing characteristics of NO gas sensors are essential for environmental monitoring, artificial intelligence, and inflammatory diagnosis of asthma patients. However, the conventional semiconductor-type gas sensors have poor sensing characteristics that need to be solved, such as slow recovery speeds (>360 s), low sensitivity (3.8), and high operating temperatures (>300 °C). We propose here a memristor-based NO gas sensor as a gasistor (gas sensor + memory resistor) with SnO2, Ta2O5, and HfO2 films, which successfully demonstrated the feasibility of fast reaction/recovery (

A linear aerospike nozzle is a kind of altitude adaptive nozzle that has optimum performance over the entire operational range. In this work, flow characteristics of a linear plug nozzle and a trun...

In this study, the dynamic characteristics of water droplets impinging on a heated cylinder were investigated using a high-speed camera regarding the diameter ratios between droplet and cylinder. Water droplets generated by a needle in the range of 2.5 mm to 5.0 mm in diameter were impinged onto a cartridge heater with surface temperature of 25 °C and 300 °C. The diameter of the cartridge heater was 6.0 mm. The recording rate of the high-speed camera was set to 10,000 Hz, and the Weber number was controlled from 17.4 to 217 by adjusting the free-fall height of the water droplets. As a result, the dynamic characteristics of water droplets impinging on cylinder were different depending on the diameter ratio and Weber number. In the high-temperature region, the water droplets were detached from the cylinder after the impingement by Leidenfrost effect. Under conditions of low Weber number and low diameter ratio, the water droplets were rebounded in the opposite direction of the impingement, maintaining its shape. However, as the Weber number increases, the water droplets impinging on cylinder were broken-up and detached by the Leidenfrost effect regardless of the diameter ratio. This study is expected to be utilized to determine the dynamic characteristics of droplet, and be applied such as phenomenon analysis of the heat transfer and cooling.

In this study, we explore the structural, optical, and chemical properties of ZnO nanorods (NRs) grown through various transition metal (TM) dopings of Cu, Ni, Co, Ni-plus-Cu, and Ni-plus-Co, while investigating the effect of these external dopings on the performance of ZnO NR-based ultra-violet photodetectors (PDs) implemented on polyethylene terephthalate substrates. The TM dopings, especially Ni-plus-Cu or Ni-plus-Co co-doping, not only improve the crystalline quality but also significantly suppress the density of deep-level emission defects in as-grown ZnO NRs, as demonstrated by X-ray diffraction and photoluminescence. Furthermore, increased O/Zn stoichiometry from 0.55 (undoped) to 0.78 and 0.83 is achieved when the NRs doped with Ni-plus-Cu and Ni-plus-Co, respectively, as revealed by X-ray photoelectron spectroscopy. The highest current on–off ratio of ~51 and spectral responsivity of ~136 A/W are obtained from the PDs fabricated with the NRs doped with Ni-plus-Co. The response time of the PDs is also improved with TM dopings, and rise time and fall time are reduced to ~1/5 and ~1/4, respectively, in the case of Ni-plus-Co doping compared to the values of the device fabricated with undoped NRs.

This study demonstrates the feasibility of applying La0.8Sr0.2MnO3 (LSM)-Ni oxide-metal composite to an interconnect layer for anode-supported solid oxide cells (SOCs) operated at 700 °C. The sintering behavior of LSM-Ni composites and the electrical properties of LSM-Ni composite in both reducing and oxidizing atmospheres were systematically examined. The densification and final microstructure of LSM-Ni composites are tailored by varying the size and content of Ni particles. A part of smaller Ni particles reacts with LSM matrix and forms a second phase, Sr-doped La2NiO4. The addition of Sr to La2NiO4 decreases the melting temperature of La2NiO4, which causes the liquid phase sintering and increases the density of the sintered of LSM-Ni composites. It is also found that LSM-Ni composites are electrically conductive, regardless of the atmosphere. In oxidizing atmospheres, LSM perovskite serves as the major conductive matrix. In reducing atmospheres, on the other hand, embedded Ni forms metallic percolation path and compensates for the decrease in the electrical conductivity of reduced LSM ceramics. This LSM-Ni is used to coat the multilayer thick film of LSM-Ni and LSM. The multilayer film exhibits higher and more stable electric conductivity than the single layer thick film of LSM in a simulated SOC operation environment. This shows that LSM-Ni composite can be a useful component of the interconnect of SOC, which maintains the good electric conductivity in both air and H2.

In this study, we present a self-rectifying resistive switching property observed in Ti/Zr3N2/p-Si and Ti/Zr2N/p-Si metal-insulator-semiconductor (MIS) capacitors for array applications. Compared to the Zr2N film, the Zr3N2 film has a higher trap density due to weaker bonding energy and a higher trap generation rate. In the experimental results for the Zr3N2 sample, we observed a higher on/off ratio, a larger read margin, more stable retention, and more stable DC cycling. In addition, both the trap concentrations increased at the LRS compared to of the common HRS, which was a result of analyzing the nitride trap density (Nnt) within the ZrxNy film and an interface trap (Nit) between the ZrxNy and the p-Si layers. Particularly, it is found in the Zr3N2 film that the Nnt is rapidly increased, which results in an increased current ratio and an increased read margin.

The present study is to explore an active mass flow control technology for an emerging bypass dual throat nozzle. A new arc-shaped bypass system has been applied to replace the previous V-shaped bypass for the bypass dual throat nozzle, which can decrease the total pressure loss significantly. The bypass passage has a contraction part with a variable area ratio. The vector control effectiveness is discussed with different contraction area ratios of the bypass passage. The obtained results reveal that friction choking and geometry choking play crucial roles to affect the bypass mass flow, respectively. When the bypass passage is fully open, the choking location of the bypass flow occurs at the bypass exit, owing to the viscous boundary layer along the constant area passage. A contraction area ratio less than 0.5 does not change the choking position of the bypass flow, because the viscous boundary layer is larger than the geometry contraction height. While the contraction area ratio reaches or exceeds 0.5, the geometry choking takes place in the contraction section. The vectoring angle and bypass mass flow ratio decrease with an increase in the contraction area ratio, whereas thrust coefficient, thrust efficiency, and total pressure loss increase.

The role of oxygen vacancies in temperature-dependent photoluminescence of SnO2 nanowires was investigated by X-ray absorption spectroscopy. Two types of oxygen vacancies are present in the nanowir...

Mixing is an inseparable part of many industries. Static mixers are motionless inserts that are widely used for mixing. In this study, planar laser-induced fluorescence (PLIF) was used to study the mixing characteristics of a multilayer static mixer. The effects of the arrangement angle of layer elements of the static mixer were examined. Arrangement angles of 0°, 45°, and 90° were investigated at four different flow-rate ratios of two mixing fluids. The mixing performance of each angle was evaluated with both qualitative and quantitative approaches. The volume fractions of the flows were obtained from the PLIF results, and the mixing index was calculated. The friction factor was measured to assess the pressure loss of each arrangement angle. The results show that the arrangement angles do not affect the mixing index for higher flow ratios. However, at the lowest flow ratio, the angle of 45° resulted in the highest mixing index of 74.9%, while at 0° and 90°, the values reached 66.4% and 69.8%, respectively. In regard to pressure loss, 45° also resulted in the lowest friction factor.

Controlling the morphology and surface properties of gold nanocrystals (AuNCs) can facilitate tailoring their localized surface plasmon resonance (LSPR) and surface-enhanced Raman scattering (SERS) properties for biomedical applications. However, the shape-controlled synthesis of AuNCs for bioapplications remains challenging, given its critical issues, such as the use of toxic reagents and multiple complicated steps. This study demonstrates the facile, biocompatible, and shape-controllable synthesis of AuNCs. This method employs human α-elastin (HαE) self-assemblies as a shape-directing template, reducing agent, and surfactant. Since HαE is a ubiquitous protein present in human tissue, it is non-toxic and non-immunogenic. This method is thus simple and biocompatible. Of particular note, the sheet-type HαE template enables the shape-controlled synthesis of AuNCs—gold nanoparticles, nanosheets, and a rose-flower-like nanostructure (AuRF) stacked with multiple nanosheets. Among the AuNCs, the AuRF exhibits unique optical and electromagnetic properties—an LSPR peak in the near-infrared (NIR) region and characteristic SERS peaks—given the rough surface with sharp edges. To the best of our knowledge, this is the first report on the biosynthesis of AuNCs using human-derived biomolecules such as HαE. The shape-controllable biosynthesis of AuNCs based on HαE may open up possibilities for a wide range of biomedical applications of AuNCs.

We report on Ba1-xNdxFeO3-δ, a cobalt-free perovskite material, with a view to its use as a next-generation air electrode material in reversible solid oxide cells (RSOCs). BaFeO3-δ (BFO) has long been considered a potential candidate cathode material due to its high oxygen vacancy concentration and electrical conductivity; however, it is difficult to synthesize in a single phase. To overcome this problem, Nd3+ is doped into Ba-sites to reduce impurity phases and create a single perovskite phase. In-situ high temperature and room temperature X-ray diffraction analyses are carried out to investigate Nd3+-doped BFO. We find that Ba0.97Nd0.03FeO3-δ shows the highest electronic conductivity and lowest TEC value among the various doping concentrations tested, making this material most suitable for application in RSOCs. In addition, the polarization resistance of Ba0.97Nd0.03FeO3-δ has the lowest value in yttria-stabilized zirconia symmetric cells. To determine the reasons for the high catalytic activity of Ba0.97Nd0.03FeO3-δ, X-ray photoelectron spectroscopy and iodometric titration are carried out, the results demonstrate that the lower doping concentration of Nd3+ results in an advantage in terms of the number of additional oxygen vacancies created. Moreover, electrical conductivity relaxation measurements show that the Ba0.97Nd0.03FeO3-δ has a fast bulk diffusion coefficient and fast surface exchange coefficient. Hence, the solid oxide fuel cell and electrolysis mode performances when using Ba0.97Nd0.03FeO3-δ are excellent and a high power output of 1.2 W cm−2 at 800 °C can be achieved.

In this work, we reported improved resistive switching (RS) of SnO2-based resistive random access memory (RRAM) devices according to the post microwave treatment (MWT), working pressures (WP), and the electrode. As a result, as the deposition pressure increased, the operational current of all the devices became commonly lower, and when comparing SnO2 RRAM devices, the optimal RS characteristics are obtained from the sample with Ag top-electrode deposited at WP of 10 mTorr and after the MWT process. The filament was also investigated, for the sample deposited at 5 mTorr, the diameter of the filament was wider in both the high resistive state and the low resistive state as a result of increasing the number of cycles. As a result, the larger the diameter of the filament, the longer the time for the filament formation and rupture was found.

CNT fibers (CNTFs) are excellent platforms for fiber-shaped supercapacitors, offering both high electric conductivity and mechanical resilience. Here, we propose a polyaniline (PANI)/CNTF composite...

The surface of conventional carbon nanotube (CNTs) were modified into 4-aminobenzoyl functionalized CNTs (ABCNT) and benzoxazine functionalized CNTs (BZCNT) to improve their surface interaction with bisphenol A based benzoxazine resins (BA-a). Polybenzoxazine (PBZ) composites using these materials were prepared to investigate the effect of different functional groups on the thermal and electrical properties of the composites. The surface modification of CNTs was characterized by Fourier Transform Infrared spectroscopy and thermogravimetric analysis. The PBZ composite with BZCNT showed the better conductivity and thermal properties than the composite with ABCNT due to the chemical bond between BZCNT/BA-a during the curing process which does not exist in the ABCNT/BA-a composite.

We present the principal components of the dielectric tensor for α-SnSe biaxial single crystal in the spectral range from 0.74 to 6.42 eV at room temperature (300 K) using spectroscopic ellipsometry. Aspnes’ first-order approximation method was applied to obtain approximated pseudodielectric response from the pseudodielectric tensor measured at an angle of incidence of ϕ = 68.8°. Multilayer calculations were then performed to extract the pure dielectric tensor without surface roughness artifacts. The Tauc–Lorentz model was applied to describe the critical point structures, and the optical constants along the principal axes of biaxial α-SnSe single crystal can be now calculated at arbitrary wavelength for device applications.

The double divergent nozzle is a type of altitude adaptive nozzle. The double divergent nozzle does not have any mechanical parts, leading to reduced nozzle weight and requires minimum modifications to the existing launch system. The planar double divergent nozzle is a type of double divergent nozzle, having a rectangular cross section. The present study involved the numerical analyses of a single divergent nozzle, and five double divergent nozzle geometries. The flow is simulated on five different double divergent sections having the same area ratio, but with different inflection angles/extension length. All geometries are studied with similar boundary conditions. Flow pattern, wall static pressure, side load, and specific impulse are studied for pressure ratios ranging from 1.5 to 8.5 with cold air as working fluid. The results obtained are compared with a single divergent nozzle having the same area ratio. It is inferred that the flow pattern, side load, and specific impulse of a double divergent nozzle have a strong dependence on the inflection angle.

Prestressed steel beams with a prestressing cover plate (PBCP), which are expected to overcome the limitations of prestressed steel girders using tendons, were investigated in this study. Experiments and finite element analyses (FEA) were performed to present a design procedure. The maximum compressive force according to flange slenderness, which could be applied to steel beams subjected to bending moment due to ultimate load, was investigated for rolled W-shape beams. The flexural capacity and elastic flexural stiffness of steel beams could be significantly increased by using a cover plate attached at a fixed distance from the bottom flange of a steel beam as a prestressing member. A PBCP with W920 × 1377 could achieve a maximum span of 72 m for a two-lane, single-span composite bridge with five girders when the span-to-depth ratio is limited to around 38.0, whereas an ordinary composite beam with the same W-shape section, having a span-to-depth ratio of 36.0, could achieve a maximum span of around 50 m. The limitations of maximum bridge length, minimum steel amount and maximum span-to-depth ratio that rolled flexural members can achieve were able to be efficiently overcome by using the PBCP. The span-to-depth ratio of PBCPs was about 2.08 times larger on average than that of plate girders for bridge lengths of 50 m to 72 m. The PBCP could employ a smaller steel volume than plate girders for the same span-to-depth ratio. Therefore, it could be seen that the PBCP could be an alternative to plate girders for the limited span-to-depth ratio and even for the cost efficiency.

Numerical simulations have been carried out for a supersonic three-dimensional rectangular arc nozzle, where a secondary flow toward the center of the curvature occurs due to the shape of the nozzle. It is known that secondary flow causes longitudinal vortices to form near the wall of the nozzle corner, making the nozzle outlet flow unstable and induces loss of transport energy. When the working fluid is a condensable gas with relatively large latent heat such as moist air or steam, rapid accelerated expansion in the nozzle causes non-equilibrium condensation due to supersaturation. After the release of latent heat during phase transition, nozzle flow continues expanding at an equilibrium saturation condition. In the absence of foreign particles, e.g. ions or dust particles, condensation nuclei are formed in the gas itself causing non-equilibrium homogeneous condensation. Supersonic nozzle flow properties vary considerably due to the occurrence of condensation phenomenon. The objective of this study is to investigate the effect of non-equilibrium homogeneous condensation on the longitudinal vortices which form in the range close to the corner of rectangular arc nozzle numerically.

Despite the recent substantial progress in reversible protonic ceramic cells (RPCCs) it remains essential to further develop oxygen electrode materials that show superior activity and stability for oxygen reduction and evolution reactions due to the intrinsically sluggish kinetics of oxygen electrode reactions at lower temperature (

In this study, we investigated the self-rectifying characteristics of $p$ -Si/O-doped ZrN/TiN structures in order to overcome a disturbance between neighboring cells in array structures. The proposed device shows a nonlinear selection characteristic and a Schottky diode property in the positive bias region. We also observed the rectifying region within −2 V, which suppresses the interference with neighboring cells that occurs during a reading operation. Any RS phenomena is not observed especially for the reverse bias sweep to reset the proposed device, which indicated that the proposed device has an intrinsic rectifying property. The proposed device shows the highest current ratio of $6\times 10 ^{2}$ at −4.5 V and a maximum current limiting capability in the bias region above −2 V. In addition, the O-doped ZrN memory device shows a stable retention up to 104 seconds at 125 °C as well as a high read margin of 380. Therefore, the proposed device suppresses interference in the read operation without additional selector elements, enabling stable memory operation.

We report the dielectric function e = e1 + ie2 and the critical point (CP) energies of the orthorhombic SnS0.52Se0.48 alloy for the zigzag (a)and thearmchair(6) directions in the spectral energy range from 0.74 to 6.42 eV and the temperature range from 27 to 350 K using spectroscopic ellipsometry. The CP energies were determined from the 2nd derivative spectra by using the standard analytic method. We observed sharpenings and blue-shifts of the CPs with decreasing temperature. We found thirteen and twelve CPs for the a-and the b-directions, respectively, at the lowest temperature while only eight and nine CPs were detected at room temperature. Also, an exciton effect was observed only in the armchair direction at low temperatures. The temperature dependences of the CP energies were determined by fitting the data to a phenomenological expression that contain the Bose-Einstein statistical factor and the temperature coefficient to describe the electron-phonon interaction.

Here, we report parameter values for the model dielectric function (e = e1 + ie2) of the SnSxSe1−x alloy in the spectral range from 0.74 to 6.4 eV and the composition range 0 ≤; x ≤ 1 by using the Tauc-Lorentz (TL) model. The experimentally reported dielectric function data for SnSxSe1−x along the zigzag (a) and the armchair (b) directions were borrowed from a previous study for selected compositions. We successfully reproduced the asymmetric nature of the dielectric function with TL lineshapes. The e data are parameterized by using six and seven TL components for the zigzag and the armchair directions, respectively. The obtained parameters at several compositions were fit with cubic polynomials, which can be used to determine the dielectric function and the refractive index as continuous functions of the energy and the composition. Our results will be useful for optoelectronic device design based on SnSxSe1−x materials.

Amorphous iron hydroxide-based material was selected as a suitable adsorbent for the siloxanes from biogas and landfill gas. The adsorptive characteristics of the desiloxanation (DeSiloxs) process were studied through a lab-scale experiment using a simulated gas containing a mixture of siloxanes (D4, and D5) and a field experiment on an actual environment scale. The iron hydroxide-based adsorbents exhibited high activity in adsorption of siloxanes during lab-scale experiments, where the obtained adsorption capacity was about 26.3 % with N2 as a carrier gas. However, from an applicability point of view, the effectiveness of the siloxane removal process was significantly affected by the space velocity during the in-situ test in anaerobic digestion gas plant using wastewater sludge. In the experimental case of various space velocities (50, 100, 300 h−1), a very high removal efficiency (100 %) was obtained.

We present parameters that allow the dielectric function (ε = ε1 + iε2) of perovskite SrTiO3 (STO) to be calculated for spectral range from 0.74 to 6.42 eV and temperatures from 26 to 674 K. The ε data of STO were reproduced from a previous report. We use the Tauc-Lorentz model to express ε of STO analytically for each temperature. The ε spectra are successfully parameterized with six Tauc-Lorentz components and a pole. To obtain ε data for arbitrary energies and temperatures over the range given above, we interpolated the parameterized results using cubic polynomials. It is well known that STO has phase transitions near 40 and 105 K, which are reflected well in our modeling. Our data allow complex refractive indices to be calculated at any temperature for device design.

The GaAsxSb1−x; alloys are particularly promising materials for near-infrared light-emitting diode and detector devices. The optical properties, such as the dielectric function, complex refractive index, and absorption coefficient, are needed to properly design and understand semiconductor devices. Here, we report a method to obtain the optical properties of GaAsxSb1−x for the energy range from 1.5 to 6 eV and for an As composition from 0 to 1 at arbitrary wavelengths and compositions. The parameterization of the dielectric function of GaAsxSb1−x for specific compositions at x = 0, 0.183, 0.397, 0.528, 0.8, and 1 were realized by using the dielectric function parametric model.

The isolator plays a critical role in the scramjet engine situated between the inlet and the combustion chamber. The flow field is more complex with shock–shock interaction and shock boundary layer interaction result in a series of compression waves reffered to as “shock train”. The presence of such flow inside the isolator can degrade the performance of the scramjet engine. The present study focus on the characteristic of the shock train flow field in an isolator and its control by partial removal of the boundary layer. The results examine the variation of the inlet to outlet pressure ratio along with different suction flow ratio. Numerical results indicate that boundary layer suction will cause the slight downstream movement of shock train location and the length of the shock train is reduced. Also when the suction flow gets choked, the transformation of shock train into a single curved normal shock is observed. The effect of varying the upstream boundary layer plays a major role in the suction flow ratio. Furthermore, a significant improvement in the total pressure loss and static pressure rise is obtained by boundary layer suction. The location of the shock train has a greater impact on the performance of the isolator.

In this paper, we provided an efficient way to reduce the power consumption of sensor nodes in an IoT ecosystem. In many cases, IoT objects are battery powered and need to be energy efficient as the most important requirement in order to have a stable operation over long periods of time. The deep sleep mode is used for low power monitoring of NodeMCU. Commercial humidity sensors normally sleep and wake up once an hour to measure soil humidity. The measured humidity data was transmitted wirelessly to Google Sheets via a NodeMCU Wi-Fi module. The user can check the humidity of the soil by referring to the transmitted data values. The power consumption was reduced by about 83% for 1 h than compared to the always awake mode.

Organic-inorganic hybrid perovskites are promising candidates for several optoelectronic devices, such as solar cells, light-emitting diodes, and photodetectors. Particularly, methylammonium lead i...

Silicate glasses based on SiO2–B2O3-BaO-WO3 (SBBW) are synthesized with varying added Al2O3 content, and their thermal and structural properties are examined as a sealing material for reversible solid oxide fuel cells (RSOCs). When up to 17.5 mol%, Al2O3 is added, glass stability is improved at the expense of viscosity at sealing temperature. The glass transition temperature (Tg), coefficient of thermal expansion (CTE) and flow at sealing temperature are investigated while varying Al2O3 content, to find the proper composition for RSOC sealing. The structural changes in the glasses resulting from the Al2O3 are inspected using Raman spectroscopy and an X-ray diffractometer. The adhesion characteristics of the glasses are examined by applying the glasses between NiO-yittria stabilized zirconia (NiO-YSZ) and Crofer22APU. A RSOC stack with 15 cells is prepared with glass containing 10 mol% of Al2O3 as a sealing material, and the practical feasibility of the glass is successfully demonstrated. The open circuit voltage is monitored while cycling the RSOC stack between water electrolysis mode and fuel cell mode.

Acrylonitrile butadiene styrene (ABS) polymer nanocomposite thin films with carbon-based nanofillers (CBNs: fullerene, carbon nanotubes, and graphene) were fabricated in a wet reversal process followed by hot pressing. To understand the effect of CBNs on the fabricated nanocomposites, tensile tests and nanoindentation tests were performed. The tensile strength of the fullerene composite was about 30 MPa based on the specimen containing 1 wt% of CBNs, which was measured to be up to 35% higher than the other two composites. In the nanoindentation test, the elastic modulus and hardness value decreased as the amount of CBNs increased. This is considered to be because the nanoindentation test reflects more mechanical behavior of the local part of the composite than the tensile test. In the tensile and nanoindentation tests, all of the nanofillers exhibited the mechanical properties of ABS polymers, among which the ABS composites with fullerene exhibited the best properties. It is concluded that nanofillers should be added appropriately, and in the case of polymers, nanofillers, which may be located between polymer chains such as fullerene, may be more efficient.

In recent year, vanadium-doped tribological films have become available as possible candidates for self-lubrication at high temperatures. In this work, quaternary Al–Cr–V–N films were deposited onto silicon wafer and WC-Co substrates by an unbalanced magnetron sputtering using high purity (99.99%) CrAl2 and V targets with argon-nitrogen reactive gases. EPMA results revealed that vanadium atoms can incorporated from 0 to 13 at.% into the films. The maximum hardness value was ~32 GPa at vanadium content of 7.1 at.% in the Al–Cr–V–N films. The high-temperature tribometer was used to analysis the friction characteristics of the films with elevated temperature. As a result of the high temperature friction test after heating up to 700 °C, the average friction coefficient decreased from 0.62 to 0.35 with increasing of vanadium contents in the Al–Cr–V–N films. It is concluded that the reduction of the friction coefficient is attributed to the formation of V2O5, which is a Magnéli phase that acts as a lubrication at high temperature.

High temperature oxidation behavior of nanocomposite films is very important characteristics for application of machining and cutting tools. Quaternary Cr–Al–Si–N nanocomposite films with various compositions were deposited onto WC-Co and Si wafer substrates using a filtered arc ion plating technique. The composition of the films were controlled by different combinations of CrAl2 and Cr4Si composite target power in a reactive gas mixture of high purity Ar and N2 during depositions. The instrumental analyses revealed that the synthesized Cr–Al–Si–N films with Si content of 2.78 at.% were nanocomposites consisting of nano-sized crystallites (3–7 nm in dia.) and a thin layer of amorphous Si3N4 phases. The nanohardness of the Cr–Al–Si–N films exhibited the maximum values of ~42 GPa at a Si content of ~2.78 at.% due to the microstructural change to nanocomposite as well as solid-solution hardening. The Cr–Al–Si–N film shows superior result of oxidation resistance at 1050 °C for 30 min in air. Based on the XRD and GDOES analyses on the oxidized films, it could be revealed that the enrichment of Al (17.94 at.%) and Cr (26.24 at.%) elements in the film leads to form an Al2O3 and Cr2O3 layer on the Cr–Al–Si–N film surface. Therefore, in this study, the microstructural changes on the mechanical properties and oxidation behavior with various compositions in the Cr–Al–Si–N nanocomposite films were discussed and correlated with the deposition parameters.

Several rare earth elements (Sc, La, Pr, Sm, Gd, Dy, Er, and Yb) were evaluated to develop a sintering additive for transparent γ-AlON. After adding 0.2 wt. % of each of the rare earth additives to the α-Al2O3 and AlN starting material, hot pressing was performed at 1850 °C for 1 h under 20 MPa as a screening test, whereby the γ-AlON with Pr-nitrate showed the highest transmittance of 60.4 % at 632 nm. Two-step pressureless sintering was conducted as a separate test for the same starting material after adjusting the amount of Pr-nitrate to 0, 0.1, or 0.2 wt. % to enhance transmittance. The γ-AlON with 0.1 wt. % Pr-nitrate showed the highest transmittance of 80.36 % after 1st and 2nd sintering steps at 1610 and 1940 °C, respectively, indicating that Pr can be an alternative sintering additive to conventional Y2O3, MgO, and La2O3 for the fabrication of transparent γ-AlON.

The transuranic (TRU) ingot is considered to be the most prominent target material of pyroprocessing in terms of safeguards since it contains almost all of the Pu of the feed spent fuel. Due to the...

The long-term goal of the Penning trap system for the heavy ion accelerator named RAON in Korea is to obtain an order of magnitude higher mass accuracy for short-lived rare isotopes. For that purpose, we are developing a sympathetic cooler for highly charged ions by exploiting laser-cooled Ca+ ions. We installed a prototype octagon chamber with a calcium atom source, a Paul trap, and a helical resonator for the high-voltage RF supply. The laser system is composed of three extended cavity diode lasers (423, 397, 866 nm) plus one UV diode laser (375 nm). The optical frequency stabilization setup is made up of a wavelength meter, a multichannel fiber switch and a PXI system with an 8-channel analog output module. After having obtained a resonant ionization signal from the calcium atomic beam, we applied the RF voltage to the trap electrodes and illuminated the cooling lasers at the center of the trap. We successfully observed a laser-cooled ion bunch and a linearly aligned ion string by using imaging optics and an electron multiplying charge coupled device (EMCCD) camera. In addition to the experimental effort, we performed a simulation study for cooling 132Sn10+ ions inside a laser-cooled 40Ca+ Coulomb crystal by using a parallel computation technique.

Voltage transformers (VTs) must be highly reliable as they are essential components of the electric power industry. VT failures can cause a significant impact for important facilities such as nuclear power plants. In fact, VTs which passed the international standard, were damaged and sometimes resulted in the shutdown of the nuclear power plants. In order to improve the reliability, VTs with various iron core was studied. The electromagnetic field simulation, a saturation characteristics test, and an overvoltage breakdown test were conducted. The result shows that the magnetic flux density significantly affects the reliability of VTs. To increase the reliability of VTs, it is required to reduce the magnetic flux density by increasing the knee-point and voltage factor. Owing to limited installation space, increasing the size of the iron core is difficult. Instead, VT by decreasing the thickness of the conductor and increasing the number of turns, it was possible to reduce the magnetic flux density without the size change. Therefore, improved VTs were obtained by decreasing the thickness of the conductor and increasing the number of turns, and the improved reliability was verified through a comparison test with existing VTs. The fabricated VTs shows a significantly higher saturation voltage and breakdown time than existing VTs. Thus, by proposed VTs can contribute the stable operation of the nuclear power plant and improve the manufacturer’s quality.

The refrigerator unit based on electrically driven vapor compression technology consumes high energy, associated with high cost and loss of ecosystem. Recently, solar thermal energy emerges as a key research area and introducing it in refrigerator application has happened extremely fast. Solar thermal refrigeration systems based on ejector compression technology are thriving because of its utilization of low-grade energy sources, straight forward design, non-moving parts, lower maintenance costs, and durability. In this present work, the performance of a solar ejector refrigeration system (ERS) is calculated analytically using one-dimensional model. The performance parameters are calculated with the assumption that both the condensation and evaporation processes occur along the saturation line. Initially, the influence of the ejector area ratio, generator temperature, condenser temperature, and evaporator temperature on the performance of the ERS is analyzed in critical mode with water (R718) as the working fluid. The analysis shows that the coefficient of performance increases more than two times on increasing the ejector area ratio from 6.4 to 12.8. The results also show that a higher coefficient of performance (COP) is obtained at a higher ejector area ratio. The COP is found to be inversely related to the generator temperature, meanwhile the coefficient of performance increase more than 74% on increasing the refrigeration temperature from Tc = 8 °C to Tc = 15 °C. Then, the performance of ERS is obtained at the subcritical conditions at varying generator temperatures. At subcritical mode, COP is found to be directly proportional to the generator temperature, and the highest COP occurs at an optimum generator temperature. The performance of the ERS with various refrigerants as R717, R718, R245fa, R123, R141b, and R365fa is calculated at the critical mode. With refrigerant R717, the system shows higher performance as well as a cooling effect than other refrigerants. However, most environmental benign refrigerant R718 shows comparatively low performance, but it is found that R718 produces a significant cooling effect than other refrigerants excluding R717 refrigerant.

Compound semiconductor heterojunctions have enabled various optoelectronic devices. Nonetheless, the formation of heterojunctions is limited by the lattice matching between the two materials. On th...

In this study, we observe the effect of Cu doping on the ZnO nanorod (NR) structure grown on a polyethylene terephthalate flexible substrates by hydrothermal growth of sol–gel method proceeded at 150 °C. Copper (II) nitrate trihydrate (Cu-nitrate) and copper (II) acetate monohydrate (Cu-acetate) are employed as precursors for Cu dopants in aqueous growth solution to examine the evolutionary change of the growth morphology, optical characteristics, and chemical composition of as-grown ZnO NRs. A significant influence of dopant molarity on the morphology of wurtzite ZnO nanocrystals is observed by field-emission scanning electron microscopy. X-ray diffraction analysis also reveals more enhanced crystalline quality from Cu-doped NR crystals prepared by Cu-acetates than that grown with Cu-nitrate precursor. Near band-edge emission of 2 mM Cu-acetate doped NRs is greatly enhanced by 2.5 times compared to those grown with Cu-nitrate precursors. A great reduction in visible emissions is also realized, and this phenomenon is associated with overall improvement in NR crystalline quality by suppressing the oxygenated carbon groups or hydroxyl introduced by the aqueous solution-based growth. X-ray photoelectron spectroscopy also shows that a very high O/Zn atomic ratio of 0.73 can be achieved in the case of NR crystals prepared by 2 mM Cu-acetate. Cu doped ZnO nanostructures of improved optical and structural properties achieved in this study can be utilized in the wide emerging field of flexible device applications such as laser diodes, light-emitting diodes, piezoelectric transducers and generators, gas sensors, and ultraviolet detectors.