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A Numerical Study of Densification Behavior of Silicon Carbide Matrix Composites in Isothermal Chemical Vapor Infiltration
摘要： We studied the characteristics of two-scale pore structure of preform in the deposition process and the mass transfer of reactant gas in dual-scale pores, and observed the physiochemical phenomenon associated with the reaction. Thereby, we established mathematical models on two scales, respectively, preform and reactor. These models were used for the numerical simulation of the process of ceramic matrix composites densified by isothermal chemical vapor infiltration (ICVI). The models were used to carry out a systematic study on the influence of process conditions and the preform structure on the densification behaviors. The most important findings of our study are that the processing time could be reduced by about 50% without compromising the quality of the material, if the processing temperature is 950-1 000 ℃ for the first 70 hours and then raised to 1 100 ℃.
关键词： isothermal chemical vapor infiltration,fiber preform structure,densification behavior,ceramic matrix composites,process parameters
更新于2025-09-23 15:23:52
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Microstructural Aspects of Infiltration Growth YBCO Bulks with Chemical Pinning
摘要： Single grain YBa2Cu3O7-x (YBCO, Y123) bulk superconductors were prepared by infiltration growth (IG) process. The solid phase precursor was prepared by solid state synthesis from Y2O3+BaCuO2 powders. The influence of the composition of the source of melt for infiltration and the CeO2 addition on the transition temperature and critical current density was studied. It is shown that the studied samples are doped by Yb from the Yb2O3 substrate. The dependences of Yb concentration on the distance from the bottom of the samples were measured by EDS microanalysis at SEM. Correlation between the fabrication technology, level of Yb doping, microstructure and superconducting properties is discussed.
关键词： infiltration growth,chemical pinning,microstructure,YBCO bulk superconductor
更新于2025-09-23 15:22:29
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PZT/PZT and PZT/BiT Composite Piezo-Sensors in Aerospace SHM Applications: Photochemical Metal Organic + Infiltration Deposition and Characterization
摘要： The composition of fine-ground lead zirconate-titanate powder Pb(Zr0.52Ti0.48)O3, suspended in PZT and bismuth titanate (BiT) solutions, is deposited on the curved surface of IN718 and IN738 nickel-based super alloy substrates up to 100 μm thickness. Photochemical metal organic and infiltration techniques are implemented to produce smooth, semi-dense, and crack-free random orientated thick piezoelectric films as piezo-sensors, free of any dopants or thickening polymers. Every single layer of the deposited films is heated at 200 °C with 10 wt.% excess PbO, irradiated by ultraviolet lamp (365 nm, 6 watt) for 10 min, pyrolyzed at 400 °C, and subsequently annealed at 700 °C for one hour. This process is repeated successively until reaching the desired thickness. Au and Pt thin films are deposited as the bottom and top electrodes using evaporation and sputtering methods, respectively. PZT/PZT and PZT/BiT composite films are then characterized and compared to similar PZT and BiT thick films deposited on the similar substrates. The effect of the composition and deposition process is also investigated on the crystalline phase development and microstructure morphology as well as the dielectric, ferroelectric, and piezoelectric properties of piezo-films. The maximum remnant polarization of Pr = 22.37 ± 0.01, 30.01 ± 0.01 μC/cm2, the permittivity of εr = 298 ± 3, 566 ± 5, and piezoelectric charge coefficient of d33 = 126, 148 m/V were measured versus the minimum coercive field of Ec = 50, 20 kV/cm for the PZT/PZT and PZT/BiT thick films, respectively. The thick film piezo-sensors are developed to be potentially used at frequency bandwidth of 1–5 MHz for rotary structural health monitoring and also in other industrial or medical applications as a transceiver.
关键词： piezoelectric sensor,structural health monitoring,PZT/BiT,composite,characterization,sol-gel PMOD deposition,infiltration,aerospace structure,PZT/PZT,thick film
更新于2025-09-23 15:22:29
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Utiliza??o da termografia infravermelha para detec??o de focos de umidade em paredes internas de edifica??es
摘要： The use of infrared thermography has become the theme of studies in several areas of the construction industry. However, research studies on detecting the presence of moisture in buildings are still under development. The main objective of this article was to study the feasibility of the use of thermography in the detection of infiltrations due to accidental causes in internal walls. The methodology consisted of the construction of masonry walls made of ceramic bricks with different coating configurations: uncoated, with plaster, plaster with latex paint, plaster with acrylic base paint and plaster with ceramic set with plaster glue. In each prototype, a drilled pipe was inserted to simulate water leaks. The infiltration progress was verified by means of thermograms, for a period of 2 hours with constant flow, and at 48 hours and one week after the beginning of the simulation. The results confirm that thermography may be effective in detecting the region containing the focus of hidden infiltration, provided the coating is not impermeable. This fact can be observed in the thermal gradients produced in the porous coatings, where ΔT ranged from 2.6 to 3.8 ° C, whereas coatings with waterproof characteristics had a maximum ΔT of 2.2 °C. In addition, the type of coating directly influences the time required for the appearance of the moisture spot to become apparent.
关键词： Infrared thermography. Coating. Infiltration. Moisture. Pathologies in civil construction.
更新于2025-09-23 15:22:29
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Rise and side infiltration in opals and porous materials for their skin-free replica synthesis
摘要： A floating opal placed on a certain liquid will cause the liquid to climb through the opal gaps, fill all its pores, and stop almost of its upper surface without covering it. A drop of solution with a surface tension much lower than that of water, deposited on a hydrophilic substrate near an opal, rapidly spread over a large surface forming a film which will surround the opal and infiltrate it from the side without covering it. High quality, skin-free, inverse opals can be synthesized by rise and side infiltration of solution in opals. The overlayer absence leads to the fabrication of mechanically robust, crack-free, completely filled photonic crystals which preserve the long rage order of initial opals. Inverse opals of sodium silicate were synthesized starting from polystyrene nanospheres self-assembled through hanging drop technique followed by their rise and side infiltration, casting, and template removal. Crystalline material inverse opals such as glycine, sodium chloride, and sulfur were also synthesized.
关键词： skin-free,photonic crystals,inverse opals,rise infiltration,porous materials
更新于2025-09-23 15:19:57
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Selective infiltration and storage of picoliter volumes of liquids into sealed SU-8 microwells
摘要： This paper describes the selective infiltration and storage of picoliter volumes of water and IPA in arrays of sealed SU-8 microwells. Microwells, with a volume of approximately 300 picoliters, are fabricated employing photolithography and a polymer onto polymer lamination method to seal the structures with a thin cover of SU-8 and PDMS in order to suppress the evaporation of the infiltrated liquids. A glass capillary is used to punch through the SU-8/PDMS cover and to infiltrate the liquid of interest into the microwells. The influence of the mixing ratio of the PDMS and its curing agent is studied and the results show that a lower ratio of 2:1 suppresses the evaporation more when compared to the standard mixing ratio of 10:1. In regards to water and IPA, the dwell time in the reservoirs was increased by approximately 50 % and 450 % respectively. Depending on the physical properties of the microwells and the liquids, the SU-8/PDMS cover suppresses the evaporation up to 32 mins for water and 463 mins for IPA, respectively, until the microwell is completely empty again. Additionally, multiple infiltrations of the same microwell are demonstrated using two immiscible liquids IPA and paraffin oil. Based on the popular polymers SU-8 and PDMS, the sealed microwell structures are scalable and combinable with different glass capillaries according to the needs of future analytical research and medical diagnostics.
关键词： microwells,Lab-on-a-chip,microfluidics,Selective infiltration,PDMS,SU-8
更新于2025-09-16 10:30:52
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Study on Effect of Post Processing on Direct Metal LASER Sintered 420 Stainless steel Infiltrated with Bronze
摘要： Additive manufacturing (AM) of metals is increasing its potential applications in the areas of aerospace, automobile, defense and medical with the processing capability from light to heavy metals, but still low density of the finished products which causes discrimination to functional properties and thus reducing AM process real time efficiency. Current research focus on improving the functional properties of 420 stainless steel specimens which are fabricated by Direct Metal LASER Sintering (DMLS) process and infiltrated with bronze for improving the density. Also post processing i.e. annealing, deep cryogenic treatment and tempering was performed. By studying the mechanical properties like tensile strength, hardness, wear of material of specimens in as fabricated and post processed condition it was observed that post processing treatment will favours in enhancing the functional properties. Also results are compared with SEM and optical microscopy images in order to determine microstructural changes.
关键词： deep cryogenic treatment,Infiltration with bronze,Additive manufacturing,420 stainless steel,annealing,tempering
更新于2025-09-16 10:30:52
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Metal Oxide Heterostructure Array via Spatially Controlled–Growth within Block Copolymer Templates
摘要： Nanofabrication is continuously searching for new methodologies to fabricate 3D nanostructures with 3D control over their chemical composition. A new approach for heterostructure nanorod array fabrication through spatially controlled–growth of multiple metal oxides within block copolymer (BCP) templates is presented. Selective growth of metal oxides within the cylindrical polymer domains of polystyrene-block-poly methyl methacrylate is performed using sequential infiltration synthesis (SIS). Tuning the diffusion of trimethyl aluminum and diethyl zinc organometallic precursors in the BCP film directs the growth of AlOx and ZnO to different locations within the cylindrical BCP domains, in a single SIS process. BCP removal yields an AlOx-ZnO heterostructure nanorods array, as corroborated by 3D characterization with scanning transmission electron microscopy (STEM) tomography and a combination of STEM and energy-dispersive X-ray spectroscopy tomography. The strategy presented here will open up new routes for complex 3D nanostructure fabrication.
关键词： block copolymers,sequential infiltration synthesis,heterostructures,nanofabrication
更新于2025-09-11 14:15:04
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Electrodeposited AgAu nanoalloy enhancing photoelectric conversion efficiency of dye sensitized solar cells
摘要： In this study, an equivalent mechanical model was established for the clogging induced by soil suction under negative pressure during root-zone infiltration irrigation in a crop-free pot, and a state diagram was plotted for the clogging process induced by a single soil suction factor under negative pressure. Three groups of impact factor experiments were conducted using three different emitters: a flow-adjustable emitter with eight horizontal outlets (emitter L), a flow-adjustable emitter with two vertical outlets (emitter Q), and an anti-clogging material wrapped around the outer surface of emitter L (emitter K). The first group of experiments investigated the influence of irrigation pressure, the variation of irrigation pressure (range of 0.02 to 0.12 MPa), and the amount of sediment inside emitter L in Yunnan laterite. For the second group of experiments, two soil types (Yunnan laterite and yellow sand), two single-event irrigation volumes (170 and 250 mL), and two numbers of irrigation events (8 and 16) were used to quantitatively analyze the sediment content in emitter L. The third group of experiments used emitters L, Q, and K and involved quantitative analysis of the clogging differences in the different emitter types with two soil types (Yunnan laterite and yellow sand) and two numbers of irrigation events (24 and 64). Statistical analysis showed that irrigation pressure, soil type, irrigation pattern, and emitter type were significant (p < 0.05) for the amount of sediment due to negative suction inside the emitter. The results demonstrate that emitter clogging induced by negative pressure tends to first decrease and then increase with increasing irrigation pressure. The amount of sediment that accumulates within an emitter is influenced by both the soil suction effect under negative pressure as well as soil flushing under positive pressure. Within emitter L, clogging induced by soil suction under negative pressure was more likely to occur when using Yunnan laterite rather than yellow sand soil. When both soil types were used in the test, emitter L was observed to be more prone to clogging induced by negative pressure compared to emitter Q, whereas emitter K exhibited the best anti-clogging performance. This study provides a quantitative account of the factors associated with clogging induced by negative pressure, and it provides a theoretical and experimental basis for gaining an in-depth understanding of emitter clogging during root-zone infiltration irrigation in Yunnan laterite.
关键词： Negative-pressure clogging,Emitter,Yunnan laterite,Pot environment,Root-zone infiltration irrigation
更新于2025-09-11 14:15:04
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End-pump high efficiency 355 nm laser with a convex–concave cavity and optically-uncoated Brewster angle-cut LiB <sub/>3</sub> O <sub/>5</sub> crystal
摘要： Porous organic polymers (POPs), with features of permanent nanopores and designable frameworks, show great promise as sulfur host materials to restrain the shuttling of polysulfides, one of the main obstacles in the development of lithium–sulfur batteries. However, the simple physical entrapment from weak intermolecular interactions via a typical melt-diffusion method results in the diffusive loss of polysulfides that has thus far restricted their potential. Herein, a facile strategy for introducing chemical covalent interactions between POPs and sulfur via the regulation of sulfur infiltration temperature is reported. The results show that increasing the temperature to a suitable value, e.g., 400 °C, for a fluorinated triazine-based framework (FCTF), enables chemical bonding between the sulfur and aromatic FCTF backbone. Benefitting from the synergetic chemical and physical confinement effect, the shuttling of polysulfides can be efficiently restrained. As a result, the sample features superior sulfur utilization, high-rate performances, and good cycle stability, as compared with the sample with only physical confinement. The proposed strategy can also be extended to other POPs, such as the boroxine-linked covalent organic framework, by judiciously tailoring the infiltration temperatures. The findings disclose the important role of infiltration temperatures in developing efficient cathode host materials for lithium–sulfur batteries.
关键词： porous organic polymers,electrochemical performance,covalent chemical interactions,lithium–sulfur batteries,elevated sulfur infiltration temperature
更新于2025-09-11 14:15:04