Centrifugal Deposition Research Articles

Preparation of efficient all-inorganic perovskite solar cells from large grain via 1-heptanamine stabilised CsPbI2Br nanoparticles with NH4SCN additive

CsPbI2Br is a potential material for perovskite solar cells (PSCs) due to its better thermal stability and high efficiency. Centrifugal deposition for film formation greatly simplifies the steps of the conventional anti-solvent spin coating method, but there are still problems hindering progress, such as small grain size and poor photoelectric performance. In this work, NH4SCN was introduced as an additive during the preparation of heptylamine (C7H17N) stabilised CsPbI2Br nanoparticles (NCs) and the films were prepared by centrifugal deposition. The results show that the low melting temperature compounds which formed by thiourea from NH4SCN decomposition during annealing and unreacted PbX2 would link the small grains together by melting and flowing; after PbX2 precipitation and reaction with CsX, the grain size was significantly increased by about 95 % compared to that of the untreated film. Due to large grains, less defects and high crystallinity, the final power conversion efficiency and fill factor reached 12.25 % and 0.70, respectively.

Tuning surface morphology of AuNPs film via thiourea as a stable SERS platform for methylene blue

Gold nanoparticles (AuNPs) have been extensively utilized in various fields such as sensors, life sciences, and catalysis. In this study, AuNPs were synthesized using a reduction method and subsequently treated with thiourea in an ethanol-water environment to prepare AuNPs film using a centrifugal deposition method for first time, resulting in the aggregation of the initial small-sized AuNPs into larger microsphere-like structures. The addition of thiourea facilitated the interconnection between AuNPs, ultimately leading to the formation of large stable gold microspheres. The sheet resistance of the AuNP films transitioned from being non-conductive to exhibiting a sheet resistance of 42.6 Ω/sq following thiourea treatment. The transformation from a flat surface to tightly connected particles resembling microspheres was observed from SEM images. The thiourea treatment not only altered the morphological characteristic of the AuNPs films but also significantly increased the number of scattering sites on their surface, leading to a substantial enhancement in the Raman scattering effect for methylene blue. This structural configuration also improved the electronic conduction and stability of the treated AuNPs films. Consequently, these findings suggest that AuNPs have promising application prospects in surface-enhanced Raman scatting (SERS), as well as in flexible electronics, catalysis, adsorption, and energy fields.

Fabrication of a YSZ electrolyte layer via co-pressing/co-sintering for tubular NiO-YSZ anode-supported SOFCs

• A simple and effective method to fabricated semi-cells of tubular Ni-YSZ anode-supported electrolyte film is proposed. • The method is the combination of centrifugal deposition, co-pressing and co-sintering techniques. • The YSZ films are dense with the thickness of 21.4∼27.3 μm. A simple and effective method to fabricated semi-cells of tubular NiO-YSZ anode-supported electrolyte film is proposed. This method is the combination of centrifugal deposition technique, cold isostatic co-pressing and co-sintering. The X-ray diffraction patterns showed that the presence of NiO and YSZ, and YSZ grains of electrolyte film grow preferentially on (2 2 0), (3 1 1), (2 2 2), (4 0 0). The YSZ films are dense with the thickness of 21.4∼27.3 μm. At 1400℃, the YSZ crystallite size in the electrolyte film is largest with the size of ∼4.6 μm, which confirms the crystallite growth during co-sintering. The EDX mapping at the same location of EDS further reveals the presence of O, Ni, Y and Zr in the calcined powders.

Preparation and activity study of monolithic three-dimensional ordered macroporous La0.7Ce0.3CoO3 with different loading methods

The innovative mixed impregnation method was used to realize the combination of polymethylmethacrylate(PMMA) template, active components and cordierite carrier in the preparation of monolithic catalyst. Compared with the samples prepared by centrifugal deposition method and deposition curing method, three-dimensional ordered macroporous(3DOM) La0.7Ce0.3CoO3 cordierite catalysts prepared by mixed impregnation method have obvious advantages over other samples in morphology, microstructure, surface properties and redox capacity. Through a series of characterization, it was found that the active components of the catalyst prepared by mixed impregnation method(3DOM La0.7Ce0.3CoO3/MIM) were highly dispersed on the surface of cordierite carrier, and the most complete La0.7Ce0.3CoO3 perovskite crystal structure was formed. At the same time, 3DOM La0.7Ce0.3CoO3/MIM formed a macroporous-mesoporous structure, which provided a good diffusion environment for the reactants. In addition, catalysts prepared by mixed impregnation method had excellent catalytic activity (T50 = 103 ℃, T90 = 218 ℃) and good stability due to its large specific surface area (10.57 m2/g), high Oads/Olatt concentration and good redox ability. The apparent activation energy of 3DOM La0.7Ce0.3CoO3/MIM was 59.56 kJ·mol−1, which was lower than that of catalysts prepared by centrifugal deposition method (72.07 kJ·mol−1) and deposition curing method (71.38 kJ·mol−1). It can be concluded that the high activity of 3DOM La0.7Ce0.3CoO3/MIM can be attributed to the high dispersion of active components, permeable pore structure, high surface adsorbed oxygen concentration and good low temperature reduction.

Fabrication of X-ray absorption gratings by centrifugal deposition of bimodal tungsten particles in high aspect ratio silicon templates

Grating-based X-ray imaging employs high aspect ratio absorption gratings to generate contrast induced by attenuating, phase-shifting, and small-angle scattering properties of the imaged object. The fabrication of the absorption gratings remains a crucial challenge of the method on its pathway to clinical applications. We explore a simple and fast centrifugal tungsten particle deposition process into silicon-etched grating templates, which has decisive advantages over conventional methods. For that, we use a bimodal tungsten particle suspension which is introduced into a custom designed grating holder and centrifuged at over 1000×g. Gratings with 45 µm period, 450 µm depth, and 170 mm × 38 mm active area are successfully processed reaching a homogeneous absorber filling. The effective absorbing tungsten thickness in the trenches is 207 µm resulting in a filling ratio of 46.6% compared to a voidless filling. The grating was tested in a Talbot–Lau interferometer designed for clinical X-ray dark-field computed tomography, where visibilities up to 33.6% at 60 kV were achieved.

Investigation on pool-scrubbing hydrodynamics with VOF interface-capturing method

Pool scrubbing with bubble swarm generated by gas jet is an effective technique for aerosol retention at severe accidents, owing to large interfacial area and long residence time. Correct understanding of the process and thus enhancing its efficiency relies on analysis of the hydrodynamic behaviour of the gas, since it affects particle removal mechanisms directly. The objective of the present work is to explore the gas jet structure in detail by means of VOF interface-capturing method and additional techniques for tracking bubble characteristics and trajectories. The main findings are: (a) The breakup of globules in the injection zone becomes significant at high gas flow rates and has a great contribution in particle removal; (b) The increase of bubble size and velocity with the injection velocity will promote the inertial and centrifugal deposition of aerosol particles; (c) However, the coalescence probability of rising bubbles is found to increase with the gas flow rate, which may influence particle retention by re-enclosing particles from liquid film and reducing surface area; (d) Furthermore, the reduction in bubble residence time as they rise through the pool is unfavourable for particle removal. Nevertheless, liquid recirculation originated from violent interaction between the gas jet and the pool surface as well as swarm effects helps to prolong the residence of bubbles. The effect of gas flow rates on the decontamination factor is found to be associated with a variety of gas–liquid hydrodynamic phenomena. The proposed numerical approach is capable of acquiring detailed local information that is required for model development. Both the time-averaged spatial distribution of void fraction and the instantaneous size/rise velocity of individual bubbles obtained from the simulation conform to the experimental data. In the next step it will be extended to include aerosol particles.

Technical advantages of the city sedimentation water reconstruction system

The work designs a system of production components of urban infrastructure to create an energy efficient city. Hydraulic, hydrological, heat exchange processes of interaction of water structure and elements of treatment structures for centrifugal deposition of suspended matter have been investigated. Depending on the degree of contamination, devices for resource recovery are calculated. The duration of recovery operations was investigated. The technological cycle of re-water recovery and the number of cycles of cavitation generator for controlled conditioning of conditionally clean and dirty waters have been determined. Reverse osmosis devices for the recovery of conditionally pure water have been investigated. Categorized potential effluents of industrial waters as appropriate for restoration. Samples of experimental sediments for the needs of the construction industry at operating and supercritical modes of operation of the technological stream were obtained. A mathematical model of the productivity of irrigation of agro-centers in drought conditions with drip irrigation by repeated water has been developed.

Investigation of Vs – based liquefaction charts using a heavily preshaken silty sand centrifuge deposit

Preshaking by previous seismic activity can significantly affect the liquefaction resistance of saturated sands. Field evidence, cyclic laboratory testing and centrifuge modeling show that: (i) earthquake events that build up excess pore pressures short of liquefaction strengthen the soil; and (ii) liquefying earthquakes may weaken the soil. The paper presents the results of a centrifuge test (Experiment 2), where a 6 m saturated loose silty sand deposit was subjected to 52 successive base shakings. Three types of shakings were used: preshaking Events A, with a shaking duration of 5 cycles, and stronger Events B and C having a duration of 15 cycles, with Events C having the largest input accelerations. A total of 35 Events A, 9 Events B, and 8 Events C were applied at the base of the model in an alternating sequence. All Events C liquefied the deposit, with the Events B inducing liquefaction at the beginning but not at the end of Experiment 2. Events A generally induced excess pore pressures but not liquefaction. In addition to the pore pressures, horizontal accelerations, settlement and densification, and the soil shear wave velocity, Vs, were also monitored during the test. The results were compared with those of Experiment 1, reported in a previous publication, where a similar 6 m deposit of the same silty sand was subjected to a different sequence of shakings A and B which did not include any Event C. Conclusions are drawn on the effect of the strong Events C on the deposit's response. Events A, B and C of Experiment 2 are plotted on existing Vs –based liquefaction charts. The charts predict well the liquefaction response of the deposit at the beginning of Experiment 2. On the other hand, for shakings near the end of the test, the charts predict liquefaction for the Events B, which by this time have stopped liquefying the deposit due to the previous history of shakings. This result is consistent with the field evidence including the presence of a number of “false positives” in the charts for silty sand sites in the Imperial Valley of California, an area of intense seismic activity.

Contraction and pore pressure behavior of a silty sand deposit subjected to an extended shaking history

The paper presents the implementation of an identification technique to characterize the pore pressure behavior of a silty sand centrifuge deposit subjected to more than 70 seismic shakings with full pore pressure dissipation between shakings. The seismic shakings were meant to crudely simulate the seismic history of field deposits in some very seismically active zones in California. The technique estimates shear stresses and strains based on acceleration and pore pressure recorded using a vertical array of sensors in the deposit. A constitutive model was implemented to identify optimal material parameters controlling the contractive behavior of the soil based on the recorded response of all shakings. It was found that the seismic history of soil deposits plays an important role in determining the contractive tendency of the material, significantly influencing the pore pressure response of the deposit. That is, the seismic history can reduce or increase the resistance of a deposit to contraction and liquefaction.

Centrifugal Deposited Au-Pd Core-Shell Nanoparticle Film for Room-Temperature Optical Detection of Hydrogen Gas.

In the present work, centrifugal deposited Au-Pd core-shell nanoparticle (NP) film was proposed for the room-temperature optical detection of hydrogen gas. The size dimension of 44, 48, 54, and 62 nm Au-Pd core-shell nanocubes with 40 nm Au core were synthesized following a solution-based seed-mediated growth method. Compared to a pure Pd NP, this core-shell structure with an inert Au core could decrease the H diffusion length in the Pd shell. Through a modified centrifugal deposition process, continues film samples with different core-shell NPs were deposited on 10 mm diameter quartz substrates. Under various hydrogen concentration conditions, the optical response properties of these samples were characterized by an intensity-based optical fiber bundle sensor. Experimental results show that the continues film that was composed of 62 nm Au-Pd core-shell NPs has achieved a stable and repeatable reflectance response with low zero drift in the range of 4 to 0.1% hydrogen after a stress relaxation mechanism at first few loading/unloading cycles. Because of the short H diffusion length due to the thinner Pd shell, the film sample composed of 44 nm Au-Pd NPs has achieved a dramatically decreased response/recovery time to 4 s/30 s. The experiments present the promising prospect of this simple method to fabricate optical hydrogen sensors with controllable high sensitivity and response rate at low cost.

Thin Films Constructed by Centrifugal Deposition of Highly Deformable, Charged Microgels.

Thin films composed entirely of microgel building blocks were fabricated using two kinds of self-cross-linked, oppositely charged microgels, via centrifugal deposition. Atomic force microscopy studies revealed that both microgels form very thin monolayer films due to a large degree of microgel deformation during deposition. Meanwhile, centrifugal deposition from a mixture of these two kinds of microgels resulted in the formation of microgel bilayers with a total thickness of around 20 nm. The film thickness increased linearly with the deposition time. Additionally, isotropic stretching/release by heating/cooling of the dried microgel films generated complicated buckling patterns, while anisotropic (uniaxial) stretching/release resulted in parallel buckling perpendicular to the stretching direction. The damage caused by anisotropic stretching and 100 °C treatment can be healed by addition of water, while damage caused via treatment at 150 °C cannot be healed due to the occurrence of polymer cross-linking, which inhibits the mobility of the microgel building blocks.

Centrifugal deposition of iron oxide magnetic nanorods for hyperthermia application

Centrifugal deposition of iron oxide was performed to manufacture magnetic nanorods in an aqueous solution. The nanorods were examined by electron microscopy. The diameter of the nanorods ranges from 10 to 20 nm. The length is about 150 nm. The nanorods were incorporated into a silicone polymer to simulate body tissues injected with magnetic nanomaterials. Then the magnetic nanorod-containing silicone samples were put into a microwave to examine the external electromagnetic field induced heating behavior. Dramatic increase in temperature was observed when the nanorods were exposed to the external electromagnetic field for 2 seconds. It is concluded that the nanorods generate intensive heating effect and they have the potential for hyperthermia application.

Morphometric Analysis and Immunocytochemical Staining on Cytospin Preparation in Effusion Cytology: A Study

Introduction: Morphological differentiation between reactive mesothelial proliferation and metastatic carcinoma cells may be extremely difficult in conventional centrifuge deposit smears stained with papanicolaou and romanowsky dyes. In the present study immunocytochemistry and morphometric analysis were performed on cytospin preparation of effusion categorized as atypical/suspicious on toluidine blue stained wet films. Materials and methods: A total of 100 cases comprising 26 benign (control group) and 74 malignant (study group) effusions were included in the study. Samples showing atypical /suspicious cells on preliminary conventional centrifuged wet film stained with toluidine blue; 63 were aspirated from pleural, 36 from peritoneal and 1 from pericardial effusions. These samples were processed for 6 cytospin preparations, 1 air dried stained with giemsa and others fixed in ethanol stained with papnicolaou stain, Cytokeratin 8/18, Epithelial Membrane Antigen (EMA) and Calretinin. Morphometric analysis was performed using software Image Pro Plus Version 6.3 on a minimum of 20 positive and negative stained cells on IHC stained smears. Results: The sensitivity and specificity of CK 8/18 in diagnosing benign, atypical and malignant cases were 91.89% and 89.5% respectively. The sensitivity and specificity of EMA was 90.5% and 86.6% respectively. Calretinin had 97% sensitivity for mesothelial cells. The 3 negative cases did not express CK 8/18 and EMA also. Thus, Calretinin can be accepted as a technique control to decide that immunocytochemical staining is working in a given case because mesothelial cells are generally present in benign as well as malignant effusions as native exfoliated cells. Nuclear area, cytoplasmic area and N:C ratio of mesothelial cells in benign effusions were 56.2 ± 2.03 um2, 182.41 ± 4.61 um2 and 0.31 ± 0.01 um2 and in malignant effusions were 63.15 ± 2.44 um2, 185.67 ± 2.15 um2 and 0.34 ± 0.01 um2 respectively. Using ROC (Receiver Operating Characteristic) curve nuclear area 88.30 μm2 area [sensitivity (98.6%) and specificity (94%)] cytoplasmic area 200.55 μm2 area [sensitivity (100%) and specificity (90%)] and N:C ratio 0.345 [sensitivity (93%) and specificity (94%)] considered as cut off values. So, we can use this value to discriminate between reactive mesothelial proliferations from malignant cells. Conclusion: IHC can be easily performed on cytospin preparation without requiring antigen retrieval and is extremely useful in differentiating metastasis from reactive mesothelial proliferation. The results of morphometric analysis were useful adjunct.

Highly-filled hybrid composites prepared using centrifugal deposition

Abstract Natural composites of high filler content, such as nacre, a composite comprised of 95–99% w/w aragonite layers, have been of interest due to their hardness, strength and toughness. High filler content composites have been prepared synthetically, although due to viscosity and processing requirements, the filler content was limited compared with natural systems. In this paper we describe hybrid high filler content composites prepared to be biomimetic of nacre. Development of processing conditions increased the filler content from 50% w/w using a laboratory stirrer to obtain hybrid composites with 77–86% w/w filler content, prepared by centrifugal deposition and hot compression molding techniques. Both methods were very different from natural formation from layer-by-layer (LBL) construction, however, the composites formed were of high filler content approaching the level in nature. The composites exhibited high modulus and strength, although deformation at break was low, consistent with highly filled materials. Glass transition of the resin phase was increased slightly, while damping was decreased by filler content. Surface morphology of the fractured composite showed a layered structure of well dispersed fillers with minute voids scattered evenly, indicating that the composite was effectively compacted.

The Fabrication and the Properties of Gradient Porous Titanium by Centrifugal Deposition and Sintering

Gradient-porous Titanium alloys can be applied to manufacturing implants for bone replacement, due to their good biological and mechanical compatibility. In this work, the feasibility of fabricating gradient-porous Titanium by centrifugal deposition and vacuum sintering was investigated. The apparent porosity of the gradient-porous Ti examined by Archimedes method is 56%. And the open pores occupy 89%. The pore structure was observed by an optical microscope. And its porosities at different radius were calculated by image software based on optical microscopic images. In addition, a nanoindentation was employed to characterize the mechanical properties at different radius. The results showed that the porosity of the sample increased with increasing of radius. Besides, both the elastic modulus and hardness changed alone radius with a same trend.

Fabrication of Bi<sub>2-x</sub>Sb<sub>x</sub>Te<sub>3</sub> (x=0-1.5) Thick Film by Centrifugal Deposition

A Bi2-xSbxTe3(x=0-1.5) thick film thermoelectric element was fabricated using centrifugal deposition and its Sb content-dependent thermoelectric properties were investigated. When the Sb content was low (x=0.5), two types of fine structure along the direction of the thickness were observed. Pole figure measurements revealed that the vicinity of the film surface was composed of single crystal layers oriented along the c-axis and the vicinity of the interface with the substrate was composed of randomly orientated layers. As the content of Sb increased, the degree of orientation improved, and at x=1.5 the entire film was close to a single crystal. A Bi0.5Sb1.5Te3 thick film showed p-type thermoelectric properties and a thermoelectric power factor of 3.5 ×10-3W/mK2. It was thus demonstrated that centrifugal deposition can be used to fabricate thermoelectric elements with high efficiency.

Effects of Preparation Processing on Mechanical Properties of TiAl Intermetallic

Mechanical properties of the TiAl alloy produced by centrifugal spray deposition (CSD), compared to that produced by ingot metallurgy (IM), were investigated at different temperatures from 293 to 973K. The result shows that the ultimate strength, yield strength and plasticity of the CSD TiAl alloys, with excellent compression properties and plasticity, are higher than those of as-cast TiAl alloys at room temperature as well as at high temperature. There exists a critical temperature of 873K in the relationship between strength and temperature, in which strength increases with increasing temperature above 873K. The effects of CSD on mechanical properties of the TiAl alloy are discussed, and the higher strength with moderate ductility achieved is because of the finer lamellar structure got in the CSD processing, and this structure is also believed to be beneficial to ductility.

An efficient biomimetic process for fabrication of artificial nacre with ordered-nanostructure

The authors developed an efficient biomimetic process to fabricate inorganic/organic nanocomposites with clay nano-platelets being the mineral and polyimide being the organic constituency. Samples with thickness of 10–200 μm were produced in a very short time using a centrifugal deposition process. This process resulted in an ordered nanostructure with alternating organic and inorganic layers. The mechanical properties were comparable to that of lamella bones, with a tensile strength of 70–80 MPa, Young's modulus of 8–9 GPa and hardness of about 1–2 GPa. The composite films could be lifted from the substrate and stacked to form bulk material for biomedical applications such as bioactive dental materials or bone replacements. This approach represents a milestone in the development of bulk-form layered inorganic/organic nanocomposites.

Effects of Forming Processing on Mechanical Properties of Ti-48Al-2Mn-2Nb Intermetallics

Ti-48Al-2Mn-2Nb alloy was produced by “centrifugal spray deposition” (CSD), and then hot isostatic pressing (HIP) was employed to remove the porosity formed by CSD. The effects of CSD and HIP processing on the mechanical properties and microstructure of the TiAl alloy were investigated. The results show that the CSD and HIP processing can both improve the strength, plasticity of the TiAl alloy, and the tensile elongation values of the CSD or HIP samples are around 3%, which are better than those of as-cast TiAl alloys in room temperature. Especially, they show more excellent compressive properties at ambient temperature with a compressive ratio of 33.8% and compressive strength of 2210MPa for the CSD samples, and a compressive ratio of 37.8% and compressive strength of 2348MPa for the HIP samples. The CSD processing also improves the fracture toughness of TiAl alloy, which is much higher than that of the HIP processing, while the HIP processing seems to be beneficial the ductility and plasticity as having a duplex structure. The effects of CSD and HIP processing on microstructure and properties of TiAl alloys are discussed to understand the deformation and fracture process of the alloy.

The microstructure and properties of IN718 rings produced by centrifugal spray deposition

Centrifugal spray deposition (CSD) is explored as an alternative route for manufacturing ring-shaped pre-forms for casings in gas turbines. CSD offers metallurgical and economic benefits compared with conventional routes. Research centred on optimising CSD processing to produce nickel alloy rings suitable for thermo-mechanical processing. Alterations to the mass flow-rate and substrate motion produced microstructures characteristic of hot and cold deposits. Hot deposits contained coarse inter-dendritic microstructures and solidification shrinkage. Cold deposits had a banded equiaxed grained microstructure comprising layering, prior droplet boundaries, and inter-splat porosity. Intermediate mass flow-rates created microstructures common to both deposition conditions. Increasing reciprocation speed led to more layering and inter-splat porosity. Slowing reciprocation produced a near optimised microstructure of equiaxed grains, some layering adjacent to the substrate and minimal porosity (≤1.0%). Following thermo-mechanical treatments, tensile properties consistent with commercial specifications were achieved. Improvements in mechanical performance are expected through future process optimisation.