Thin Block Research Articles

Investigation of Mechanical Properties and Microstructure Analysis of 5356 Al Alloy Thin Plate and Block Fabricated by Directed Energy Deposition-Arc

Investigation of Mechanical Properties and Microstructure Analysis of 5356 Al Alloy Thin Plate and Block Fabricated by Directed Energy Deposition-Arc

Large-area, self-healing block copolymer membranes for energy conversion

Membranes are widely used for separation processes in applications such as water desalination, batteries and dialysis, and are crucial in key sectors of our economy and society1. The majority of technologically exploited membranes are based on solid polymers and function as passive barriers, whose transport characteristics are governed by their chemical composition and nanostructure. Although such membranes are ubiquitous, it has proved challenging to maximize selectivity and permeability independently, leading to trade-offs between these pertinent characteristics2. Self-assembled biological membranes, in which barrier and transport functions are decoupled3,4, provide the inspiration to address this problem5,6. Here we introduce a self-assembly strategy that uses the interface of an aqueous two-phase system to template and stabilize molecularly thin (approximately 35 nm) biomimetic block copolymer bilayers of scalable area that can exceed 10 cm2 without defects. These membranes are self-healing, and their barrier function against the passage of ions (specific resistance of approximately 1 MΩ cm2) approaches that of phospholipid membranes. The fluidity of these membranes enables straightforward functionalization with molecular carriers that shuttle potassium ions down a concentration gradient with exquisite selectivity over sodium ions. This ion selectivity enables the generation of electric power from equimolar solutions of NaCl and KCl in devices that mimic the electric organ of electric rays.

On an X-ray 3-block Laue-interferometer with violation of ideal geometry

An X-ray monolithic 4-block interference system has been developed and manufactured, in which the first 3 blocks are thin and form a 3- block Laue interferometer with disrupted geometry, and the 4th additional block is thick and is in the reflection position. It is shown that fine structures of interference patterns registered from 3-block interferometers with thin blocks and distorted geometry are observed in cases where an additional 4th thick block is used. The calculations show that when the ideal geometry of a 3-block interferometer is violated, an interference pattern is formed in the form of families of parallel stripes (lines) on the recording plate lying perpendicular to the incident beam. The coordinates of the interference stripes maxima, their periods, as well as the coefficient of a linear enlargement in the presence and absence of the 4th thick block, are calculated. It has been experimentally proven that a thick block does not introduce new information into the interference pattern, but will only enlarge its dimensions in the scattering plane. The limits for reducing the period of interference stripes and their complete disappearance are determined depending on the size of violations from the ideal geometry of a 3-block interferometer.

Structure and dynamics of southern Mariana margin: Constraints from seismicity, tomography and focal mechanisms

The southern Mariana margin is a tectonically distinctive and rapidly deforming region with the world deepest trench and unusual deformation and magmatism. However, its related deep structure and dynamics are still poorly understood. In this study, we determine robust 3-D P and S wave velocity models down to 130 km depth beneath the southern Mariana margin by using arrival-time data of local earthquakes recorded at 12 near-field seismic stations. Our tomographic results together with local seismicity and focal mechanisms reveal that the subducted Pacific slab is rapidly rolling back with a steep dip angle and narrowly but strongly coupled with the thin forearc block, which results in the deepest trench. An inferred eastward mantle flow transports the enhanced hydrous mantle melt beneath the southwest Mariana rift to the southern Mariana Trough, causing unusual deformation, magmatism and volcanism in the new oceanic crust. In addition, seismicity in the west Mariana ridge lithosphere may indicate active foundering of the arc lower crust.

Directed energy deposition of PH 13–8 Mo stainless steel: microstructure and mechanical property analysis

Laser metal deposition (LMD) is of the directed energy deposition (DED) process which is widely used for producing large-scale, dense, and functional parts in the field of additive manufacturing (AM). This research work investigates the microstructure and mechanical properties of PH 13–8 Mo martensitic stainless-steel parts produced via LMD. The workshop trials were conducted using an LMD system collaborated with a robotic arm to deposit single-track thin walls and horizontal blocks. The microstructural characteristics of the additively manufactured parts were analyzed using an optical microscope. The mechanical properties were evaluated through hardness measurements and uniaxial tensile tests. The influence of energy density and powder deposition density on the characteristic geometry of straight walls was also investigated. The microstructural analysis showed that the microstructure consisted of columnar dendrites that grew epitaxially from the substrate, with primary austenite cells containing intercellular ferrite and martensite laths that were roughly parallel with the retained austenite. When the energy density increased from 43 to 86 J/mm2 (a doubling of energy density), there was an increase in secondary dendritic arm spacing (SDAS) by approximately 250% in the first layer and approximately 90% in the top layer. The difference in SDAS change between the first and top layers can be attributed to the difference in cooling rates experienced by each layer during the additive manufacturing process. Increasing powder deposition density from 0.5 to 1 g/min results in a decrease in porosity from 3% to less than 1% and an increase in strength from 800 to over 1000 MPa. The hardness of the deposits was found to range from 300 to 400 HV. This variation in hardness can be attributed to differences in microstructure resulting from changes in cooling rates at different heights.

Multisource working condition recognition via nonlinear kernel learning and p-Laplacian manifold learning

Effectively utilizing information from multiple sources and fewer labeled operating condition samples from a sucker-rod pumping system for oil production can improve the recognition effects and engineering practicability. Nevertheless, this is a challenging energy environment scientific application research subject, and therefore, this study proposes an operating state recognition scheme that relies on multisource nonlinear kernel learning and p-Laplacian high-order manifold regularization logistic regress. Specifically, three measured features are selected and extracted, i.e., wellhead temperature signal, electrical power signal, and ground dynamometer cards, based on mechanism analysis, expert experience, and prior knowledge. Finally, we establish the operating condition recognition model to recognize by the multisource p-Laplacian regularization kernel logistic regress algorithm. The experimental data are derived from 60 wells of a common high-pressure and low-permeability thin oil reservoir block of an oil field in China. The corresponding trials highlight that our scheme outperforms traditional recognition methods by exploiting single-source and multiple-feature data. In the context of fewer labeled samples, the proposed method has a greater recognition effect, engineering practicability, and better model robustness than the existing schemes based on other high-order manifold learning, verifying our method's effectiveness.

Development of advanced cementite-free bainitic steel using Ni, Al and Cu additions – Design concept and phase transformations study

A novel concept, consisting of the stabilization of retained austenite with Ni, Al, and Cu additions instead of using Si as the major alloying element to prevent carbide formation, is proposed to design nanocrystalline, cementite-free bainitic steels. In this work, the novel steel (wt.%) Fe-0.40C-0.50Mn-8.0Ni-2.65Al-0.8Cu was designed. Dilatometry investigations were performed to obtain the experimental CCT and TTT diagrams for this material. It was concluded that the bainitic reaction occurs between 400 and 225 °C during a transformation time ranging from 2 h to 66.5 h, respectively. An in-depth analysis performed on the resulting materials confirmed the presence of an ultrafine structure free of cementite consisting of carbon supersaturated laths of tetragonal bainitic ferrite and retained austenite with thin film and block morphologies. The use of Ni, Al and Cu as alloying elements leads to high carbon content in both populations of retained austenite, which prevents, the formation of fresh martensite during cooling to room temperature. The results of this research constitute a novel insight into the design of ultra-fine, cementite-free bainitic steels.

Experimental study on the detection of frozen diffused ammonia blockage in the inactive section of a variable conductance heat pipe

Variable Conductance Heat Pipes (VCHP) are mainly employed to cool down electronic systems in spacecraft applications, as they can handle high temperature fluctuations in their cold source, preventing thus the systems from damaging. These fluctuations, as well as ultra-low temperatures, are always present in outer space, and one of the key steps in a VCHP design is therefore to make sure that they endure these conditions. However, not much has been written about their resilience during and after a long exposition to subfreezing conditions, i.e. temperatures lower than the freezing point of the working fluid. In this paper we implement and validate a computational routine based on a modified Flat-Front Approach to predict the VCHP temperature profile and to determine the location of the gas–vapor front. Then we continuously expose an ammonia/stainless-steel VCHP to temperatures below the ammonia freezing point for 211 h, to later examine the formation and subsequent dynamics of a thin block of frozen ammonia which is diffused into the inactive part of the heat pipe condenser. We describe as well how a strong correlation between the adiabatic section and the reservoir temperatures is maintained (or broken) upon the occurrence (or absence) of the blockage of frozen ammonia.

Photonic crystal fabric reflects heat to keep wearers warm

Textiles woven into a thin photonic crystal block heat from escaping the body as radiation.

Experimental investigation of blended H2/CH4 combustion in combustors with block for micro-thermophotovoltaic

To extend the operation conditions and improve the working performance of micro-thermophotovoltaic system, the combustor with varied block setting and length is proposed, where blended CH4/H2 is employed. Effects of CH4 addition, burner dimensions and parameters on combustion characteristics, energy conversion and multi-factors on working performance are investigated under various flow rates. Results demonstrate that the consumption and production of OH and H radicals are strongly impacted by the CH4 blending ratio, affecting the flame regime, burning heat release and heat transfer in the combustion chamber. And 5–15 % CH4 addition is beneficial to the improvement of burner thermal performance, where the highest radiation temperature is achieved at mCH4 = 15 % in combustor C24-0.4 under lower fuel flow rate, while it is also affected by the burner setting. A higher CH4 mixing ratio contributes to the combustor with thin block and the thicker block with lower CH4 addition can both contribute to achieve a better working performance. Besides, the augment of burner length extends the operating conditions and the radiant area, while it reduces Tw, and combustor C29-0.6 obtains the highest radiation power of 48.1 W and electrical power output of 2.9 W with a system efficiency 2.2 % at mCH4 = 10 %, Vf = 635 mL/min and Φ = 1.0. So, the appropriate CH4 addition, block setting and burner size can yield enhanced system performance.

Mitigation of Potential‐Induced Degradation in Glass‐Encapsulated Perovskite Solar Cells Using a NiOx Barrier Layer

While the efficiency of perovskite solar cells has been increasing rapidly in recent years, studies on potential‐induced degradation (PID) in these devices have so far been very limited. Herein, the first successful mitigation of PID in glass‐encapsulated perovskite solar cells is reported. A thin NiOx blocking layer between the indium tin oxide and the self‐assembled monolayer is proposed to suppress the PID in these solar cells. Two groups of devices are fabricated, with and without the presence of the NiOx layer. When −1000 V is applied between the short‐circuited solar cell and the front glass pane, the original devices without NiOx only retain about 27% of the initial efficiency, and the modified devices with NiOx retained ≈65% after an extended stress duration of 96 h. The Na+ ions from the glass pane occupy NiOx vacancies under high voltage stress and, as a result, the Nax ion migration toward the perovskite layer is heavily suppressed due to the introduction of NiOx. The modified devices also demonstrate good long‐term stability, retaining more than 80% of initial efficiency after the PID stress test. The results of this work are helpful on the journey toward successful commercialization of perovskite solar cells.

Effects of mesoporous TiO2 with addition of V2O5 and rinsing with various solvents on the properties of dye-sensitized solar cells

Dye-sensitized solar cells (DSSC) have received much attention since they are simple, easily manufactured, inexpensive, and offer reasonable conversion efficiency. Mesoporous TiO2 with the addition of V2O5 nano-particles (0, 0.5, 1.0, 1.5 and 2.0 wt%) as a photoanode in DSSC have been successfully fabricated using a spin-coating method. Titanium tetrachloride (TiCl4) was used to synthesize a thin TiO2 blocking layer to enhance the performance of TiO2 photoanode in DSSC. After annealing treatment at 450 °C, the TiO2 blocking layer showed an amorphous structure. Performance was examined after soaking N719 dye and rinsing with five different solvents (ethanol, isopropanol, acetone, methanol, and diethyl ether). The results show that removing unanchored dye molecules using acetone solution can increase the specific surface area and dye adsorption amount of TiO2, resulting in good Jsc and photovoltaic efficiency. A conversion efficiency of 8.5% was achieved using fluorine doped tin oxide glass, a thin blocking layer, mixing 0.5 wt% V2O5 with mesoporous TiO2 and rinsing with an acetone solution.

Evaluation of Properties for Making of Bricks by Using Granite Sludge Powder

Numerous issues arise from the discharge of waste materials. The primary issues are the spot involved by locales of capacity, significance of expenses and the natural effect. The primary objective of this preliminary work is to investigate the possibility of using stone waste as a substitute for raw materials in the production of granite sludge bricks. The exhibition of the Rock ooze block's compressive strength and a correlation of it with the ordinary dirt blocks. Clay,water,sand ,fly ash,cement, and other components make up granite sludge brick. Due to its lower cost and higher compressive strength in comparison to other bricks, its wides preaduse may become an important criterion for evaluation. Granite sludge bricks have been the subject of numerous experiments, and the results indicate that they lack compressive strength. As a result, numerous tests on the granite sludge brick's strength using various additional materials were carried out.These various additions might include fly ash, clay, cement, s and, and soon, the alterations ingranitesl udge bricks' compressive strength caused by these various additional materials.The granite bricks have a moisture content of 20% and measure 22 cm by 10 cm by 7 cm. Hence we involved a modest material for the streng thin rock ooze block. Where they have extra pieces in development, so we involved them in mud blocks. Granites ludge bricks performed better than conventional bricks, as demonstrated by the findings. Clay was added to the mixture in weight amounts of 10%,20%,30%,40%, and 50%.Test for water absorption and compressive strength.

Enhancement of quasi-static compression strength for aluminum closed cell foam blocks shielded by aluminum tubes

Aluminum closed cell foam blocks are created with a volume of 1 inch3 which consist of aluminum foam parts shielded with part of aluminum tube and in some types reinforced with inner aluminum tubes. Blocks have been made to overcome some existing problems in metallic foam used to protect some applications parts from impacts as a sacrificial part. Metallic foam has three main categories sandwich panels, filled tubes and corrugated sheets. Quasi-static compression tests have been applied on 12 blocks with different shapes and compared with pure aluminum foam blocks as a reference. Results display the enhancement of mechanical properties of blocks like yield strength (SY), crushing strength (Sc) and densification strength (Sd), compression at strain 70%, as well as absorbed energy (area of compression under the curve). The highest value for yield strength (5.87 MPa) was registered for Finger phalanxes cube block (FP—0.1 Sq.). While the highest value for densification strength (21.7 MPa) was registered for spine cylinder block (SV8—0.17 C25). The registered results for samples apparent the highest value for energy dissipation density (Edd) is 40.52 J/in3 (91% enhancement) and crushing strength (8.61 MPa) was registered for Finger phalanx cylinder block (FP—0.17 C25). The lowest value for Edd is 14.16 J/in3 (less than pure aluminum foam block value by 33%), SY = 0.42 MPa, Sc = 3.21 MPa, and Sd = 4.46 MPa, registered for thin wall Ear canal cylinder block (EC8—0.075 C26.5). Best mechanical properties had been achieved for Finger phalanx cylinder block (FP—0.17 C25) and spine cylinder block (SV8—0.17 C25).

Design and acoustic tests of the ATHENA WFI filter wheel assembly development model towards TRL5

The filter wheel (FW) assembly (FWA), developed by the CBK Institute, is one of the critical subsystems of the wide field imager (WFI) instrument on board the Advanced Telescope for High Energy Astrophysics—mission of the ESA Cosmic Vision 2015-25 space science program (launch scheduled around 2035). The instrument has to collect soft x-rays with very high quantum efficiency, thus WFI requires extremely thin optical blocking filter (OBF). Due to its thickness (∼150 nm) and large area (∼170 mm × 170 mm) needed to achieve a 40 ′ × 40 ′ instrument field of view, the filter is extremely vulnerable to acoustic loads generated during Ariane 6 rocket launch. On the other side, FW mechanism has to provide high overall reliability, so it is more favourable to launch the instrument in atmospheric pressure (without vacuum enclosure for filter protection). Design efforts of the FW subsystem were focused on two issues: providing maximal possible sound pressure level suppression and smallest possible differential pressure across the OBF, which should prevent filters from damaging. We describe the design of a reconfigurable acoustic-demonstrator model (DM) of WFI FWA created for purposes of acoustic testing. Also, the acoustic test campaign is described: test methodology, test criteria, and results discussion and its implication on future FWA design. In general, tests conducted with the FWA DM showed that current design of WFI is feasible and the project can be continued without introducing a vacuum enclosure, which would significantly increase system complexity and mass.

Non-Bulk Morphologies of Extremely Thin Block Copolymer Films Cast on Topographically Defined Substrates Featuring Deep Trenches: The Importance of Lateral Confinement.

Directed self-assembly of block copolymers is evolving toward applications that are more defect-tolerant but still require high morphological control and could benefit from simple, inexpensive fabrication processes. Previously, we demonstrated that simply casting ultra-thin block copolymer films on topographically defined substrates leads to hierarchical structures with dual patterns in a controlled manner and unraveled the dependence of the local morphology on the topographic feature dimensions. In this article, we discuss the extreme of the ultraconfined thickness regime at the border of film dewetting. Additional non-bulk morphologies are observed at this extreme, which further elaborate the arsenal of dual patterns that could be obtained in coexistence with full placement control. It is shown that as the thickness confinement approaches its limit, lateral confinement imposed by the width of the plateaus becomes a critical factor influencing the local morphology.

Effect of manufacturing deviations on the thermohydraulic performance of printed circuit heat exchangers with zigzag channels

• The etching-induced deformations have subtle effects on thermo-hydraulics; • The bonding-induced deformations is closely related to PCHE thickness; • An estimation model for bonding-induced deformation is proposed and validated; • The semicircular microchannel deformation mechanism is proposed and validated. A printed circuit heat exchanger (PCHE) is an essential component of the supercritical carbon dioxide Brayton cycle ( sCO 2 -BC ), but the effect of manufacturing deviations of PCHEs on thermohydraulic performance is seldom reported. To quantitatively analyse the etching-induced and bonding-induced deformations, 19 test plates/blocks are manufactured for measurement. Numerical simulations are performed to investigate the effects of these geometric deformations. The results indicate that the influences of etching-induced deformations are relatively small, the effect of the channel cross-section shape is more significant than the zigzag angle, and the longitudinal pitch is the weakest contributor. For the oval-shaped channel, the channel width plays a leading role in influencing the heat transfer, while the pressure drop is affected more severely by the channel depth. The channels tend to be narrower and shallower after diffusion bonding, and the bonding-induced channel cross-section deformation can cause large deviations in thermal-hydraulic characteristics, especially for those with thin blocks and few layers. Based on the measurement data, an estimation model for the relative deviation of the channel hydraulic diameter after bonding is proposed for the present manufacturing process.

Catalytic assembly of symmetric diblock copolymers in a thin film: a dissipative particle dynamics simulation study.

Obtaining a thin block copolymer film with a perfect structure by self-assembly is difficult because the system is, in general, trapped in a metastable state. We used dissipative particle dynamics (DPD) to investigate the self-assembly of AB symmetric diblock copolymers in a thin film. We discovered that addition of a small molecule (molecule C) as the third composition could help the system evade the metastable state. Therefore, imperfect structures could be corrected, and ordered structures formed. Analogous to the performance of a catalyst in catalytic chemistry, molecule C could promote assembly into an ordered structure, but was less involved within the polymer phase. Moreover, simulation results showed that the content of molecule C and its repulsive interactions with blocks A and B were quite important for promoting assembly into ordered structures effectively.

Orientation control of the hexagonal and lamellar phases in thin block copolymer films using in-plane AC electric field

Lamellar and hexagonal pattern rearrangements in thin films of polystyrene–block–poly(2-vinyl pyridine) and polystyrene–block–poly(4-vinyl pyridine) copolymers simultaneously exposed to an in-plane AC electric field and saturated chloroform vapor are studied with atomic force microscopy and analyzed via the numerical solution of the self-consistent field theory equations. It is demonstrated that the use of AC field with the root-mean-square strength higher than 8 V⋅μm−1 allows one to effectively orient microphase-separated domains along the field direction on the tens of microns scale. At the same time, the AC field considerably lowers the risk of breakdown and eliminates effects related to ionic transport in the presence of solvent vapor. The role of such factors as the exposure time, field strength and frequency is investigated. Theoretical considerations prove the equivalent effect of AC and DC fields on the structure of the copolymer film in a wide frequency range. Self-consistent field theory calculations of the free energy as a function of film thickness make it possible to exactly identify which phase dominates in the film. In particular, an apparent transformation of standing cylinders into long threads aligned in the field direction should be interpreted as the phase transition from the perpendicular to parallel hexagonal phase, which can take place in a certain range of film thicknesses, provided the electric field strength exceeds a certain threshold value. In the case of a perpendicular lamellar phase, the domain orientation along the direction of the electric field is always profitable. The observed morphological rearrangements under an in-plane field, which preserve connectivity between the film surfaces through the domains of the minor copolymer block, can be important for practical applications.

Van der Waals Heterostructure Photodetectors with Bias-Selectable Infrared Photoresponses.

A bias-selectable photodetector, which can sense the wavelength of interest by tuning the polarity of applied bias, is useful for target discrimination and identification applications. So far, those detectors are generally based on the back-to-back photodiode configuration via exploiting epitaxial semiconductors as optoelectronic materials, which inevitably lead to high fabrication costs and complex device architectures. Here, we demonstrate that our band-engineered van der Waals heterostructures can be applied as bias-selectable photodetectors. Our first prototypical device is mainly composed of black phosphorus (BP) and MoTe2 light absorbers sandwiching a thin MoS2 hole blocking layer. By varying the bias polarity, its spectral photoresponse can be switched between near-infrared and short-wave infrared bands, and our optoelectronic characterizations indicate that the detector can exhibit high external quantum efficiency (EQE) and fast operation speed. With this framework, we further demonstrate the detector with bias-selectable photoresponses within the mid-wave infrared band using BP/MoS2/arsenic-doped BP heterostructures and show that our developed detectors can be integrated into a single-pixel imaging system to capture dual-band infrared imaging.