Effect of Laser Powder Bed Fusion Parameters and Hot Isostatic Pressing on the Microstructure and Mechanical Properties of C22 Alloy

A nickel-based Hastelloy C22 powder with a nominal composition of Ni-21.30Cr-13.36Mo-1.92Co-2.94W-3.85Fe-0.23Mn-0.3V(wt%) and particle size distribution of D₁₀=23.8±0.3 μm, D₅₀=37.5±0.2μm, and D₉₀=59.3±1.1 μm was gas atomized to be used as a feedstock in Laser Powder Bed Fusion (LPBF). In this study, laser power and scanning speed were optimized to manufacture specimens with the highest density. Samples manufactured with power of 150 W and scanning speed of 200 mm/s showed relative density of 99.6%. Additionally, for higher production rate, samples were manufactured with power of 225 W and scanning speed of 1200 mm/s. Additively manufactured parts were post processed by conducting solution heat treatment, hot isostatic pressing and hot isostatic pressing+ solution heat treatments. Total 8 conditions were evaluated for phases and microstructure using optical microscope, X-ray diffraction, scanning electron microscopy, and electron backscatter diffraction. Furthermore, microhardness and tensile test were performed on all optimized and post processed samples. Typical cellular and columnar dendritic structure were founded in the as-printed samples. Mo-rich nanoparticles were observed in both as-printed samples and HIPPed samples and were responsible for higher strength. HIP effectively eliminated most of defects in the as-printed samples, but fine precipitates were observed in HIPPed samples. Solution heat treatment led to a full recrystallization with annealing and complete dissolution of the Mo-rich second phases into the Ni matrix. LPBF followed by HIP seems necessary to achieve full density parts with the desired mechanical properties, whereas role of solution treatment on enhancing mechanical properties was not as significant as HIP

Mineralization of pH-Sensitive Doxorubicin Prodrug in ZIF-8 to Enable Targeted Delivery to Solid Tumors

The zeolitic imidazolate framework (ZIF-8), composed of zinc ion and dimethylimidazole, is widely used in drug delivery because of the easy fabrication process and the good biosafety. However, ZIF-8 suffers from low affinity to nonelectric-rich drugs and does not have surface functional groups. Here, to deliver doxorubicin (DOX) with ZIF-8 to specific target sites, DOX was first modified with a pH-sensitive linker containing two carboxyl groups to form the inactive prodrug CAD and subsequently seeded inside ZIF-8 by a 5 min mineralization process. CAD has high affinity to ZIF-8 because of the carboxyl groups and can anchor to the ZIF-8 surface to enable the surface modification with folic acid for tumor targeting. Moreover, the DOX release is precisely controlled by three steps of acidic pH response, with the dissociation of the FA layer, the breakdown of the ZIF-8 structure, and the cleavage of the pH-sensitive linker in prodrug. This novel "prodrug-ZIF-8" strategy has opened a new horizon in drug delivery

CRL4 antagonizes SCFFbxo7-mediated turnover of cereblon and BK channel to regulate learning and memory

Intellectual disability (ID), one of the most common human developmental disorders, can be caused by genetic mutations in Cullin 4B (Cul4B) and cereblon (CRBN). CRBN is a substrate receptor for the Cul4A/B-DDB1 ubiquitin ligase (CRL4) and can target voltage- and calcium-activated BK channel for ER retention. Here we report that ID-associated CRL4CRBNmutations abolish the interaction of the BK channel with CRL4, and redirect the BK channel to the SCFFbxo7ubiquitin ligase for proteasomal degradation. Glioma cell lines harbouring CRBN mutations record density-dependent decrease of BK currents, which can be restored by blocking Cullin ubiquitin ligase activity. Importantly, mice with neuron-specific deletion of DDB1 or CRBN express reduced BK protein levels in the brain, and exhibit similar impairment in learning and memory, a deficit that can be partially rescued by activating the BK channel. Our results reveal a competitive targeting of the BK channel by two ubiquitin ligases to achieve exquisite control of its stability, and support changes in neuronal excitability as a common pathogenic mechanism underlying CRL4CRBN–associated ID

Dynamic Analysis of the Switched-Inductor Buck-Boost Converter Based on the Memristor

The direct current (DC)–DC converter presents abundant nonlinear phenomena, such as periodic bifurcation and chaotic motion, under certain conditions. For a switched-inductor buck-boost (SIBB) converter with the memristive load, this paper constructs its state equation model under two operating statuses, investigates its chaotic dynamic characteristics, and draws and analyzes the bifurcation diagrams of the inductive current and phase portraits, under some parameter changing by the MATLAB simulation based on the state equation. Then, by applying certain minor perturbations to parameters, the chaotic phenomenon suppression method is explored by controlling peak current in continuous current mode (CCM) to keep the converter run normally. Finally, the power simulation (PSIM) verifies that the waveforms and the phase portraits controlling the corresponding parameters are consistent with those of the MATLAB simulation

Instrumental Variable-Based OMP Identification Algorithm for Hammerstein Systems

Hammerstein systems are formed by a static nonlinear block followed by a dynamic linear block. To solve the parameterizing difficulty caused by parameter coupling between the nonlinear part and the linear part in a Hammerstein system, an instrumental variable method is studied to parameterize the Hammerstein system. To achieve in simultaneously identifying parameters and orders of the Hammerstein system and to promote the computational efficiency of the identification algorithm, a sparsity-seeking orthogonal matching pursuit (OMP) optimization method of compressive sensing is extended to identify parameters and orders of the Hammerstein system. The idea is, by the filtering technique and the instrumental variable method, to transform the Hammerstein system into a simple form with a separated nonlinear expression and to parameterize the system into an autoregressive model, then to perform an instrumental variable-based orthogonal matching pursuit (IV-OMP) identification method for the Hammerstein system. Simulation results illustrate that the investigated method is effective and has advantages of simplicity and efficiency

Preparation and electrochromic properties of indium tin oxide nanocrystal films

Indium tin oxide (ITO) nanocrystals with different shapes and sizes were synthesized by one-pot method, and ITO nanocrystal films were prepared by spin-coating process. The near-infrared spectrum regulation properties of the films prepared by ITO nanocrystals with different morphologies and sizes were studied. The results show that the visible light transmittance of ITO nanocrystal film is 89.2%, and the resistivity is 54 Ω·cm after 5 spin coatings. The films prepared by uniform spherical ITO nanocrystals with an average diameter of (6.88±1.53) nm exhibit the best near-infrared spectrum regulation ability. After applying a voltage of ±2.5 V, the spectrum regulation at 2000 nm is 39.3%, and the optical density change is 0.43. The ITO nanocrystal film maintains high visible light transmittance before and after electrochromism. The electrochromism of ITO nanocrystals is caused by change of frequency and intensity of localized surface plasmon resonance(LSPR) caused by electron injection/extraction, and its electrochromic process is realized by capacitor charging and discharging

Infrared Electrochromic Devices Based on Thin Metal Films

Abstract Tunable emissivity technology is promising for the dynamic regulation of infrared radiation. Herein, infrared electrochromic devices based on thin metal films that operate via a novel hydrogen‐induced metal–insulator transition are demonstrated. The use of thin magnesium–nickel (MgxNi) alloy films as both a variable emissivity material and top conductive electrode simplifies the device structure and ensures that large changes in emissivity can be achieved. The constructed sandwich‐structured electrochromic devices also have polyethyleneimine (PEI) as a middle proton‐conducting electrolyte layer and hydrogen tungsten bronze (HxWO3)/indium tin oxide (ITO) as a bottom ion‐storage layer. Upon application of a voltage of ±2.6 V, the emissivity of the MgxNi/Pd/PEI/HxWO3/ITO device can be reversibly regulated, with emissivity changes of 0.48 and 0.43 in the 3–5 and 7.5–14 µm atmospheric windows, respectively. Under open‐circuit conditions, the high‐emissivity state of the device can be stably maintained for 3 h. The emissivity change is affected by the composition and thickness of the MgxNi film and the device failure mechanism involves the breakage and oxidation of this film after cycling. Corresponding flexible devices that exhibit electrochromism in the visible region have great potential for adaptive thermal camouflage, smart thermal management, and dynamic information displays

Study on Adsorption of Dye Wastewater by Modified Fly Ash

Used fly ash as raw material, it was modified by acid, alkali and high temperature to produce modified fly ash adsorbent, sulfuric acid modified fly ash adsorbent, sodium hydroxide modified fly ash adsorbent and high temperature modified fly ash adsorbent. In this paper, the effects of adsorbent dosage, adsorbent adsorption time, initial dye concentration, wastewater pH and temperature on dye adsorption were studied. The results showed that: the acid modified fly ash adsorbent had a good treatment effect on the dye; when the dosage of fly ash was 1.00 g, the adsorption time was 90 min, the pH of wastewater was 4, and the temperature was 45 °C, the decolorization rate of 60 mg/L methyl orange dye can reached more than 70%; when the dosage of fly ash was 0.20 g, the adsorption time was 60 min, the pH of wastewater was 3, and the temperature was 35 °C, the decolorization rate of 20 mg/L methyl orange dye can be achieved. The decolorization rate of Congo red can reached more than 80%