Microstructure and Ablation Behavior of Low-Pressure Plasma Sprayed ZrB2 Coatings Down to 100 Pa.

The effect of chamber pressure on the microstructure and ablation behavior of ZrB2 coatings deposited by low-pressure plasma spraying was investigated. The results showed that as the spray chamber pressure further was reduced to less than 50 kPa, the porosity of the coating deposited at the same distance decreased with the chamber pressure, and the coating prepared under 100 Pa presented the lowest porosity of about 0.89%. The ablation performance test subjected to high-temperature plasma jet revealed that the linear ablation rate of ZrB2 coating increased with the porosity of the coating. As a result, among the ZrB2 coatings deposited at chamber pressures of 100 Pa, 5 kPa, 10 kPa and 50 kPa, the dense coating deposited at 100 Pa showed the lowest ablation rate of 0.33 µm/s. The dense ZrB2 coating with a thickness of about 100 µm was able to withstand 300 s ablation by a plasma flame with a net power of 25 kW resulting in an ablating coating surface temperature of about 2000 °C. The ablation mechanism of the coating was also examined.

The design and application of an automated microscope developed based on deep learning for fungal detection in dermatology.

BACKGROUND: Light microscopy to study the infection of fungi in skin specimens is time-consuming and requires automation. OBJECTIVE: We aimed to design and explore the application of an automated microscope for fungal detection in skin specimens. METHODS: An automated microscope was designed, and a deep learning model was selected. Skin, nail and hair samples were collected. The sensitivity and the specificity of the automated microscope for fungal detection were calculated by taking the results of human inspectors as the gold standard. RESULTS: An automated microscope was built, and an image processing model based on the ResNet-50 was trained. A total of 292 samples were collected including 236 skin samples, 50 nail samples and six hair samples. The sensitivities of the automated microscope for fungal detection in skin, nails and hair were 99.5%, 95.2% and 60%, respectively, and the specificities were 91.4%, 100% and 100%, respectively. CONCLUSION: The automated microscope we developed is as skilful as human inspectors for fungal detection in skin and nail samples; however, its performance in hair samples needs to be improved.

Plasma-Sprayed High-Performance (Bi2O3)0.75(Y2O3)0.25 Electrolyte for Intermediate-Temperature Solid Oxide Fuel Cells (IT-SOFCs).

Rare earth element-doped bismuth oxides with the fluorite structure (δ-Bi2O3) exhibit high oxygen ion conductivity at low temperature, which is promising electrolyte materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). However, traditional co-sintering process is not applicable to the manufacturing of IT-SOFCs using low melting point Bi2O3-based electrolyte, while further high-temperature processing is not required for deposition Bi2O3-based electrolytes. In this study, plasma spraying was used to examine the possibility to deposit high-performance Bi2O3-based electrolytes without the following high-temperature process. (Bi2O3)0.75 (Y2O3)0.25 (YSB) spray powders were prepared by the sinter-crushing method. The YSB electrolytes were fabricated by plasma spraying at different deposition temperatures. The effects of deposition temperature on the coating microstructure, crystalline stability, and ion conductivity were investigated. Results showed that the as-sprayed YSB electrolytes present a dense microstructure with well-bonded lamellar interfaces. The pure δ-phase YSB electrolyte was deposited with 37.5-75 µm powders at a deposition temperature of 350 °C. The deposited YSB electrolyte presented the excellent ionic conductivity of 0.19 S cm-1 at 700 °C in comparison with 0.21 S cm-1 for sintered bulk.

Effect of Powder Particle Size and Spray Parameters on the Ni/Al Reaction During Plasma Spraying of Ni-Al Composite Powders.

It was known for long that Ni-Al composite powders can be used to deposit self-bonding coating as a bond coat for common ceramic coatings due to the exothermic reaction between Ni and Al. However, it was found that with commercial Ni-Al composite powders with a large particle size, it is difficult to ignite the self-propagating reaction between Ni and Al to form Ni-Al intermetallics by plasma spraying. In this study, Ni-Al composite powder particles of different sizes were used to prepare Ni-Al intermetallics-based coatings by plasma spraying. The dependencies of the exothermic reaction between Ni and Al and the coating microstructure on powder particle size and spray parameters were investigated. The phase composition, microstructure, porosity and oxide content of the coatings were characterized by x-ray diffraction, scanning electron microscope and image analyzing. The results show that particle size of Ni-Al composite powders is the dominant factor controlling the exothermic reaction for the formation of Ni-Al intermetallics during plasma spraying. When the powders larger than about 50 µm are used, the reaction forming aluminide cannot complete even by heating of plasma flame generated at high plasma arc power. However, when smaller powders less than 50 µm are used, the exothermic reaction can completely occur rapidly in plasma spraying, contributing to heating of Ni-Al droplets to the highest temperature for development of the self-bonding effect. The positive relationship between molten droplet temperature and tensile adhesive strength of the resultant coatings is recognized to confirm the contribution of high droplet temperature to the adhesive or cohesive strength.

Tuning morphology and photovoltaic properties of diketopyrrolopyrrole-based small-molecule solar cells by taloring end-capped aromatic groups.

In this article, we selected BDT­DPP­BDT (DPP = diketopyrrolopyrrole and BDT = 4,8-di-2-(2-ethylhexyl)-thienyl-benzo[1,2-b:4,5-b']dithiophene) as the model backbone and end-capped it with hydrogen, octyl 2-cyano-3-(thiophen-2-yl)acrylate (CNR), and 2-hexylbithiophene (HTT), respectively, forming three small molecule donors: BDB, CNRBDB and HTTBDB. Introduction of a polar and planar electron-withdrawing unit of CNR to both ends of the BDB backbone enhances the hole mobility from 4.14 × 10(−4) to 7.75 × 10(−3) cm(2) V(−1) s(−1) and raises the fill factor from 27 to 57% when blended with PC71BM. This is associated with the PC71BM phase size decreasing from 70 to 20 nm. When the electron-donating unit of HTT with poorer planarity is linked to both ends of the BDB backbone, both donor and acceptor phase sizes are decreased to 20 nm. The short-circuit current density is greatly improved from 4.22 to 9.66 mA cm(−2), and the fill factor is enhanced to 46%. Overall, this work demonstrates that the end-capped aromatic groups play an important role in tuning the phase size and photovoltaic properties of DPP-based small molecule solar cells.

A potential perylene diimide dimer-based acceptor material for highly efficient solution-processed non-fullerene organic solar cells with 4.03% efficiency.

A highly efficient acceptor material for organic solar cells (OSCs)--based on perylene diimide (PDI) dimers--shows significantly reduced aggregation compared to monomeric PDI. The dimeric PDI shows a best power conversion efficiency (PCE) approximately 300 times that of the monomeric PDI when blended with a conjugate polymer (BDTTTT-C-T) and with 1,8-diiodooctane as co-solvent (5%). This shows that non-fullerene materials also hold promise for efficient OSCs.

Phenyl-1,3,5-trithienyl-diketopyrrolopyrrole: a molecular backbone potentially affording high efficiency for solution-processed small-molecule organic solar cells through judicious molecular design.

Finding new molecular backbones is necessary for further advances in solution-processed small-molecule organic solar cells (SM-OSCs). Increasing molecular π conjugation generally enhances the light-harvesting ability, and the resulting strong π-π-stacking interactions improve the charge-carrier transport ability; both increase the efficiency. In this study, we focus on the phenyl-1,3,5-trithienyl (3T-P) backbone because of its C3 symmetry, planarity, and particularly high conjugation between the three arms through the core phenyl unit. When the three arms were functionalized with diketopyrrolopyrrole (DPP) units to afford 3D-T-P, only modest efficiency was achieved (1.16%). Introduction of 4,8-bis(2-(2-ethylhexylthienyl)) benzodithiophene (BDT) between the 3T-P and DPP units to give 3D-B-T-P enhanced the light-harvesting ability, and particularly improved the hole mobility by 1.5 orders of magnitude (5.91×10(-2) versus 1.05×10(-3) cm(2) V(-1) s(-1)). When using PC71BM as the acceptor material, 3D-B-T-P gave the best power conversion efficiency (PCE) of 2.27%, which is about 1.9 times higher than the best efficiency from 3D-T-P (≈1.16%). The efficiency can be improved up to 3.60% with 3% (v/v) of 1,8-diiodooctane (DIO) as the cosolvent and thermal annealing at 100 °C for 10 min. This PCE is, to the best of our knowledge, the highest efficiency reported to date among the phenyl-1,3,5-based C3-symmetric molecules. Removing one DPP unit from 3D-T-P to form 2D-T-P, or from 3D-B-T-P to form 2D-B-T-P both decreased the light-harvesting ability and the hole mobility, thereby affording lower efficiency. Taken together, our results demonstrate that the planar phenyl-1,3,5-trithienyl-based C3 -symmetric structure can be a promising backbone, and enhancing the conjugation of the 3D-T-P backbone can effectively improve the device performance.

Chromism based on supramolecular H-bonds.

Normal solvatochromic phenomena are induced by different polarities of the ground and excited states of a compound when it is dissolved in a solvent. A compound such as the perylene diimide (PDI) derivative, which has a small difference in the dipole moments of the excited and ground states, generally shows a weak color change. Herein, we found that a dilute dichloromethane (DCM) solution of the PDI derivative 1,6,7,12-tetra(4-tert-butylphenoxyl) PDI (1) with a typical concentration of 1 × 10(-5) M distinctly changed colour from red to dark blue with a distinct red-shift of both the absorption (Δλ(a)max = 32 nm) and the fluorescence (Δλ(f)max = 45 nm) when 50,000 equivalents of trifluoroacetic acid (TFA) were added. Such a new chromism originates from the stronger decrease of the energy level of the LUMO than that of the HOMO after the step-by-step H-bonding of TFA with the PDI chromophore: firstly, the imide C[double bond, length as m-dash]O functionality, then the bridged -O- and finally the TFA molecules undergo H-bonding, forming a highly polar TFA shell around the PDI molecule, as proved by the concentration variable UV-vis absorption, fluorescence, (1)H NMR, (13)C NMR, and NOE spectra, cyclic voltammetry, and quantum chemical calculations. The degree of the solution's color change (Δλ(a)max/Δλ(f)max) depends (1) on the number of the bay-substituted 4-n-butylphenoxyl groups: it amounts to 25/38 and 17/22 nm for 1,7-bis(4-tert-butylphenoxyl) PDI (2) and the bay-unsubstituted PDI 3, respectively, and (2) on the polarity of the -OH functionality: in HOOC-CX3, for example, the value of Δλ(a)max/Δλ(f)max of PDI 1 amounts to 9.5/17 nm for trichloroacetic acid (TClA, X = Cl) and 0/3.6 nm for acetic acid (AA, X = H). The protons are necessary for the chromism, and thus ethyl trifluoroacetic acid ester, EtOTFA, cannot produce any obvious red-shifting of the absorption and fluorescence for 1-3. However, 2,2,2-trifluoroethanol (TFEtOH) produces an obvious red-shift.

Solution-processed DPP-based small molecule that gives high photovoltaic efficiency with judicious device optimization.

A solution-processed diketopyrrolopyrrole (DPP)-based small molecule, namely BDT-DPP, with broad absorption and suitable energy levels has been synthesized. The widely used solvents of chloroform (CF) and o-dichlorobenzene (o-DCB) were used as the spin-coating solvent, respectively, and 1,8-diiodooctane (DIO) was used as additive to fabricate efficient photovoltaic devices with BDT-DPP as the donor material and PC71BM as the acceptor material. Devices fabricated from CF exhibit poor fill factor (FF) of 43%, low short-circuit current density (Jsc) of 6.86 mA/cm(2), and moderate power conversion efficiency (PCE) of 2.4%, due to rapid evaporation of CF, leading to poor morphology of the active layer. When 0.3% DIO was added, the FF and Jsc were improved to 60% and 8.49 mA/cm(2), respectively, because of the better film morphology. Active layer spin-coated from the high-boiling-point solvent of o-DCB shows better phase separation than that from CF, because of the slow drying nature of o-DCB, offering sufficient time for the self-organization of active-layer. Finally, using o-DCB as the parent solvent and 0.7% DIO as the cosolvent, we obtained optimized devices with continuous interpenetrating network films, affording a Jsc of 11.86 mA/cm(2), an open-circuit voltage (Voc) of 0.72 V, an FF of 62%, and a PCE of 5.29%. This PCE is, to the best of our knowledge, the highest efficiency reported to date for devices prepared from the solution-processed DPP-based small molecules.

A self-assembly phase diagram from amphiphilic perylene diimides.

Supramolecular forces govern self-assembly and further determine the final morphologies of self-assemblies. However, how they control the morphology remains hitherto largely unknown. In this paper, we have discovered that the self-assembled nanostructures of rigid organic semiconductor chromophores can be finely controlled by the secondary forces by fine-tuning the surrounding environments. In particular, we used water/methanol/hydrochloric acid to tune the environment and observed five different phases that resulted from versatile molecular self-assemblies. The representative self-assembled nanostructures were nanotapes, nanoparticles and their 1D assemblies, rigid microplates, soft nanoplates, and hollow nanospheres and their 1D assemblies, respectively. The specific nanostructure formation is governed by the water fraction, R(w), and the concentration of hydrochloric acid, [HCl]. For instance, nanotapes formed at low [HCl] and R(w) values, whereas hollow nanospheres formed when either the HCl concentration is high, or the water fraction is low, or both. The significance of this paper is that it provides a useful phase diagram by using R(w) and [HCl] as two variables. Such a self-assembly phase diagram maps out the fine control that the secondary forces have on the self-assembled morphology, and thus allows one to guide the formation toward a desired nanostructure self-assembled from rigid organic semiconductor chromophores by simply adjusting the two key parameters of R(w) and [HCl].