Deposition Efficiency Research Articles

Introducing TiO2 to design high-reflectivity AlN composite substrates to synthesize green/white converters for high-brightness reflective laser illumination☆

Phosphor-in-glass (PiG) has been prepared into various types of phosphor films owing to its simplicity process, exceptional color purity, and convenient color adjustability. Nevertheless, existing reflective PiGs films have encountered limitations in terms of stability and feasibility as reliable color converters, mainly attributed to issues related to thermal deposition and insufficient optical efficiency. Herein, we propose to use AlN substrate with superior thermal conductivity to coat the TiO2 layer to obtain TiO2–AlN (TA), which enhances the reflectivity of blue light to facilitate the light conversion process. By incorporating highly thermally stable LuAG:Ce-PiGs on a TA substrate, the LuAG:Ce-PiTA converter exhibits a luminous flux of 1102 lm@6.4 W, and maintains a relative intensity of 94.6% at 473 K benefiting from the high thermal conductivity of 34.1 W/(m·K). The addition of CASN3:Eu to the color converter 50 L&10C-PiTA enables an impressive CRI of 90.7. Relative luminescence intensities of LuAG:Ce-PiTA and 50 L&10C-PiTA only decrease by 5.35% and 3.28%, respectively, in the 24 h illumination aging decay test of the reflective laser module. The results confirm the suitability of the optimally designed TA substrate for LuAG:Ce color converter applications in high-power reflective laser illumination.

The Potential of High-Velocity Air-Fuel Spraying (HVAF) to Manufacture Bond Coats for Thermal Barrier Coating Systems

Driven by the search for an optimum combination of particle velocity and process temperature to achieve dense hard metal coatings at high deposition efficiencies and powder feed rates, the high-velocity air-fuel spraying process (HVAF) was developed. In terms of achievable particle velocities and temperatures, this process can be classified between high-velocity oxy-fuel spraying (HVOF) and cold gas spraying (CGS). The particular advantages of HVAF regarding moderate process temperatures, high particle velocities as well as high productivity and efficiency suggest that the application of HVAF should be also investigated for the manufacture of MCrAlY (M = Co and/or Ni) bond coats (BCs) in thermal barrier coating (TBC) systems. In this work, corresponding HVAF spray parameters were developed based on detailed process analyses. Different diagnostics were carried out to characterize the working gas jet and the particles in flight. The coatings were investigated with respect to their microstructure, surface roughness and oxygen content. The spray process was assessed for its effectiveness. Process diagnostics as well as calculations of the gas flow in the jet and the particle acceleration and heating were applied to explain the governing mechanisms on the coating characteristics. The results show that HVAF is a promising alternative manufacturing process.

Review on Microfluidic Technology Based Synthesis of Fe-based Nanoparticles for Catalyst in Fuel Cell

Conventional combustion based energy generations, reliant on fossil fuels, poses significant environmental harm. In contrast, fuel cells offer an efficient and eco-friendly energy conversion method, capable of integrating with renewable sources and contemporary energy carriers to support sustainable development and energy security. Consequently, fuel cells are considered the promising energy conversion devices of the future. However, extensive research reveals that the cost of catalysts constitutes the most substantial portion of the overall fuel cell cost. To tackle this cost constraint, considerable advancements have been achieved in the development of cost-effective, precious metal-free electrocatalysts. Common methods for the preparation of metal nanomaterials (NPs) have more stringent requirements, lower deposition efficiency and higher costs. In addition, conventional preparation methods without precisely control of reagent concentration, mixing and temperature during the preparation process, makes it difficult to obtain the same results with poor reproducibility, restricting the industrial fabrication of high performance nanomaterials. Microfluidic reactors have advantages of efficient mixing, high heat and mass transfer, low reagent consumption, precise control of reactant components, residence time, reaction temperature and other parameters. They can also be coupled with multi-step reactions, greatly reducing the preparation time while obtaining composite nanomaterials with excellent dimensional homogeneity. In this review, we mainly discuss the microfluidic technology-based synthesis of PGM-free catalyst used in fuel cell.

Energy-efficient electrochemical recovery of gold enabled by a thiourea-based electrolyte system

The application of non-cyanide baths in electroplating for gold recovery has drawn significant attention due to their clear benefits on the environment and human health. Among these alternatives, thiourea has emerged as a promising non-cyanide bath, and yet high energy and reagent consumption has impeded its widespread adoption. Herein, an energy-efficient gold recovery process via electroplating was developed to reduce bath depletion. The redox potentials of gold deposition using thiourea electrolyte were examined through linear sweep voltammetry, and the consumed energy during the electrochemical plating of gold was quantified. The gold deposition was achieved in the two-electrode system enabling a 97% recovery under 0.3 V of the cell voltage. The proposed system exhibited a significant reduction in energy consumption to 0.129 kWh∙kg−1, implying that the oxidation of free thiourea on the anode mainly contributed to the decrease in the applied voltage and energy. Furthermore, the suppression of the bath consumption was evaluated compared with electroless plating, another reliable deposition process, throughout monitoring gold desorption and deposition efficiencies during the cyclic use of thiourea. The retardation of the sorbent consumption was observed in the electroplating during the consecutive cycles, which inferred that the reduction of its oxidized form, formamidine disulfide, led to the regeneration of the agent on the cathode. Thus, the suggested electroplating process with a gold-thiourea bath shows great potential as a workable means of gold recovery from an economic standpoint with its low energy and sorbent consumption to realize the commercialization of urban mining in the electronic industry.

High performance tin-based Babbitt coatings deposited by high-pressure cold spraying

Tin-based Babbitt alloys are widely used as sliding bearing materials due to their excellent tribological properties such as good friction reduction, friction resistance and embeddedness. In this study, for the first time, tin-based Babbitt coatings (SnSb11Cu6) were deposited on 40Cr steel substrates by a high-pressure cold spraying system with dual downstream injection as a preliminary investigation of anti-friction coatings for sliding bearings. The effects of process parameters on deposition efficiency, microstructure, microhardness, bond strength and tribological properties of cold sprayed SnSb11Cu6 coatings were systematically investigated. Results showed that with the optimization of process parameters, deposition efficiency tends to increase first and then decrease, and the optimal deposition efficiency achieved is 53 %. The coating prepared at the gas pressure of 1.5 MPa and gas temperature of 450 °C has the highest density, and the best overall mechanical and tribological properties. XRD results showed that no phase change and oxidation occurred for coatings under all cold spraying conditions. The highest microhardness of cold sprayed SnSb11Cu6 coatings is 28.8 HV0.05, higher than that of as-cast alloy (~22.5 HV0.05). The bond strength between SnSb11Cu6 coatings and the steel was significantly increased by using bond coat and is highest as 21 ± 3 MPa. The lowest coefficient of friction and wear rate of the SnSb11Cu6 coatings is 0.23 and 7.99 × 10−5 mm3/N·m, respectively (pair: GCr15 ball, 3 N). The deposition mechanisms and wear mechanisms of cold sprayed SnSb11Cu6 coatings were also analyzed. With the optimization of process parameters, the particle physical state transits from semi-molten to fully-molten, and the bonding mechanism is mainly mechanical interlocking. The wear mechanisms of cold sprayed SnSb11Cu6 coatings are abrasive wear and adhesive wear, and abrasive wear dominates.

Effect of pole piece structure on magnetic lens electrospinning system: Experimental and simulation study

Magnetic lenses can effectively reduce the fiber diameter and whipping-circle width to control the random behavior of electrospinning. Although the axisymmetric magnetic lens for electrostatic spinning have several potential applications, the effect of its pole-piece structure on the electrostatic spinning process has not been adequately discussed. In this study, we explored the influence of changing the pole piece structure of the magnetic lens on the electrospinning process using experimental and numerical simulation methods. The results showed that for a 12 wt% polyacrylonitrile (PAN) solution, when the applied voltage was 15 kV, the feed rate was 1 mL/h, and current of the magnetic lens was 1 A, the gap width of the magnetic lens had a notable effect on the fiber deposition efficiency of the electrostatic spinning range of the magnetic lens. Appropriately reducing the gap width in the range of 1–10 mm can effectively reduce the deposition range of the fibers and improve fiber film thickness. Furthermore, when the angle of α is 45°, it exerts the most significant effect on the electrostatic spinning spray range and deposition efficiency, and the fiber film thickness and average fiber diameter attain their highest values. When the angle of α increases or decreases from 45°, the fiber film thickness and fiber diameter both show a decreasing trend. A change in the magnetic lens structure can effectively change the ejection range and fiber diameter during electrostatic spinning, which shows great potential in the field of nanofiber production.

Microstructure, mechanical properties, and tribological properties of laser assisted cold sprayed CuCrZr coatings: Influences of laser power and laser position

CuCrZr has good conductivity, thermal conductivity and high strength and is widely used in the production of continuous casting mold. In this study, for the first time, high-performance CuCrZr coatings were successfully deposited on the surface of CuCrZr mold by laser assisted cold spray (LACS) method as a preliminary trial to validate LACS a repair technique of worn mold surfaces. This study systematically characterizes the microstructure, microhardness, bonding strength, electrical conductivity, wear performance, and thermal shock performance of CS, concentric LACS and eccentric LACS coatings. The results show that compared to CS, LACS shows great improvements in coating density, bond strength, friction and wear performance, and electrical conductivity, thus exhibiting significant prospects in the repair of mold. In particular, eccentric LACS CuCrZr coatings feature higher bonding strength and deposition efficiency, while concentric LACS coatings have better wear, hardness, and electrical conductivity. The best overall coating performance is achieved at eccentric LACS-4 kW-5.5 mm CuCrZr coating which exhibits a porosity of 0.49 %, a grain size of 1.06 µm, a microhardness of 200 HV0.3, a bond strength of 205 MPa (on CuCrZr substrates), a friction coefficient of 0.48 and a wear rate of 1.55 × 10-5 mm3/N·m (counterbody: GCr15 balls, 15 N load), an electrical conductivity of 63.50 % IACS, and a thermal shock resistance of > 120 cycles under 650 ℃. The mechanisms associated with microstructural formation and mechanical performances of LACS coatings are also analyzed. There was no obvious phase change within the coating, while a heat affected zone is formed at the coating-substrate interface with the formation of CuxZry phases and slight oxides. The grain characteristics of LACS coatings include deformed grains, recovered grains, recrystallized grains. The wear mechanisms of LACS coatings are combined adhesive wear and abrasive wear.

Preparation of highly dense Ti-based coatings with enhanced corrosion protection performance via cold spray

In the current study, relatively large TC4 powder (D50: 35.1 μm) were blended with Ti powder (D50: 24.2 μm) in different mixing fractions (0, 10, 30, 50, 100 vol%) to prepare corrosion protection Ti-based coatings on 1045 steel substrates via cold spray under moderate ‘intensity’ deposition condition. The idea is to utilize the strong hammering effect of hard TC4 particles to significantly densify the originally loose Ti layer, while the inclusion of TC4 particles after deposition will not cause severe galvanic problem with Ti due to similar free potential in corrosive medium, which avoids the deterioration of the corrosion resistance of Ti-based coating. Results show that cold sprayed Ti-based coating with high density (99.8 %) was achieved when the mixed powder contains 30 vol% TC4 particles. Moreover, only a slight decrease trend in deposition efficiency of the mixed powder is shown with the increase of TC4 content. Electrochemical tests and cross-sectional microstructural observations indicate that this coating is not permeable during the entire 24 h immersion in 10 wt% HCl solution, thus provided excellent corrosion protection for the substrate. The present method of cold spraying Ti and TC4 mixed powders exhibits great potential for economical and effective preparations of Ti-based corrosion protection coatings.

Degradable PDA@PNIPAM-TA Nanocomposites for Temperature- and NIR light-Controlled Pesticide Release.

Controlled pesticide delivery systems offer many distinctive advantages over conventional pesticide formulations. In this work, degradable poly(N-isopropylacrylamide) (PNIPAM)-tannic acid (TA) microgels and multifunctional PDA@PNIPAM-TA nanocomposites were prepared in a high-gravity rotating packed bed reactor (RPB) for smart pesticide delivery and release. The as-prepared microgels and nanocomposites showed reversible temperature-dependent swelling/deswelling behavior and irreversible pH-induced degradation. A dynamic contact angle test suggested that the introduction of TA and PDA into the PNIPAM matrix could enhance foliar adhesion and deposition efficiency. The nanocomposites were further used for the encapsulation and delivery of imidacloprid (IMI) to protect it from rapid photolysis and improve its pest-control efficiency. Their thermoresponsive behavior as well as pesticide loading capacity could be tuned by tailoring the PNIPAM-TA shell thickness, which could be varied by the NIPAM amount. The release rate of IMI from the core/shell nanocomposites was positively correlated with environmental temperature and near-infrared (NIR) light, which was adaptive to the positive temperature-dependent toxicity correlation of IMI and the increasing trend of pests under high temperature. The cumulative release of IMI was 23.5% at 25 °C, while it was 81.2% at 40 °C after 24 h of incubation, and the release rate was greatly enhanced under NIR irradiation. The results indicated that the facile control of pesticide release could be realized by regulating environmental conditions. This work also provides an idea for using high-gravity technology to conveniently construct a smart, effective, and environmentally friendly pesticide delivery system for sustainable crop protection.

Development and evaluation of precision liquid pollinator for kiwifruit

Cultivation of kiwifruit heavily relies on assisted pollination, and sufficient pollination can enhance fruit quality. A precision liquid pollinator for kiwifruit robotic pollination was developed as part of the research, and it was optimized with the aim of improving pollination quality while saving pollen usage. The pollinator employs a grating ruler to measure the stroke of a pneumatic hydraulic cylinder to achieve precise control of pollen suspension dosage, and uses an internal mixing air-assisted nozzles to spray pollen suspension for pollination. Through experiments of optimizing pollen suspension volume control, constructing of pollination distance prediction model, and measuring droplet size distribution, a working range of air pressure and liquid pressure was established. Eight sets of air–liquid pressure parameters were selected to evaluate the planar pollen deposition of the pollination device, and the optimal parameters were applied to pollinate kiwifruit flowers. The results indicated that reducing droplet size enhanced the overall pollen deposition rate.. In a windless laboratory environment, the developed pollinator achieved a pollen deposition efficiency of 21.15% under an air pressure of 0.15 MPa and liquid pressure of 0.25 MPa. This precision liquid pollination device is advantageous for precise control under high pressure and low flow conditions, suitable for the end effector of autonomous pollination robots. The optimization and evaluation methods established within this study provide reference for the development of precision pollination devices.

Microstructure and mechanical properties of 2319 aluminum alloy deposited by laser and cold metal transfer hybrid additive manufacturing

Wire and arc additively manufactured aluminum alloys are prone to porosity, leading to poor mechanical properties in samples, which hinders their broad industrial application. Laser and arc hybrid processes have garnered increasing attention for their potential to reduce porosity, stabilize the arc, and enhance deposition efficiency. This paper investigates the porosity, element distribution, microstructure evolution, and mechanical properties of 2319 aluminum alloy produced through the laser and cold metal transfer (laser-CMT) hybrid additive manufacturing process. In comparison with the as-deposited samples, the laser-CMT hybrid process decreases porosity, enhances element distribution, mitigates Cu element segregation, and results in increased θ′′ phase precipitation. Following T6 heat treatment, the ultimate tensile strength (UTS), yield strength (YS), and elongation of the x-direction specimens from the laser-CMT hybrid process are 450.0 MPa, 318.1 MPa, and 10.0%, respectively. These values are 11.27%, 7.03%, and 36.65% higher than those of the as-deposited samples. To validate the findings, a large-scale load-carrying frame for a commercial aircraft was fabricated, demonstrating the efficacy of the process. The paper also presents a detailed analysis of the strengthening mechanism. Samples deposited using the laser-CMT method exhibit reduced porosity and excellent mechanical properties, making this process promising for a wide range of applications.

Bonding probabilities in cold spray deposition of composite blends

Cold gas spraying of metal alloys using single feedstock powder is well described in terms of impact conditions and critical velocities for bonding of similar particles. In contrast, the mechanism of layer build-up in cold spraying of dissimilar powder blends, especially where the particles have significantly different thermomechanical properties, is far from being fully established and has remained an open question.We explore this question by taking W-Cu and Mo-Cu as example blends of significantly dissimilar materials, with potential applications in thermal management systems. The current study aims mainly to provide a comprehensive overview of the electrical, mechanical and microstructural characteristics of the deposits formed under varied feedstock compositions.The experimental data are further interpreted in view of a statistical model for deposition, considering the different deformation behavior as well as the possibly even repulsive chemical interaction of the dissimilar particles. In this way, the model supplies a quantitative description of the observed deposition efficiency as a function of powder size and composition. The paper also discusses the scope of application of the findings and the model to other cold-sprayed composites or single alloy systems.

Oxidative potential and source apportionment of size-resolved particles from indoor environments: Dithiothreitol (DTT) consumption and ROS production

Oxidation potential (OP) is an emerging index to measure the toxicity of atmospheric particulate matter (PM), but little research data on indoor PM OP are available. This study focuses on the size-resolved particle OP and source apportionment of PM from indoor environments. Different-size PM samples were gathered from March 6, 2022, to April 18, 2022, from offices, canteens, dormitories, and laboratories using Anderson samplers. Particles from these indoor environments were separated into nine size fractions, and the chemical components (including transition metals, ions, and water-soluble organic carbon (WSOC)) were measured. The water-soluble OP (OPws) of the investigated PM was highest in the dormitory (61.02 nmol min−1 μg−1) and lowest in the canteen (25.58 nmol min−1 μg−1), varying by factors of up to 2.38. Additionally, the particulate Mn (r2 = 0.94), Fe (r2 = 0.93), and Zn (r2 = 0.92) concentrations were closely related to OPws. The OPws distribution in indoor PM samples featured a single peak from 0.7 to 3.2 μm. ROS (·OH) showed the same trend (1.1–3.2 μm) as PM OP, which shows that PM3.2 is the main contributor to adverse health effects among all size fractions of PM due to the strengthened oxidative ability of PM3.2 compared to PM > 3.2. The source apportionment results showed that secondary sources (52.3%), construction sources (28%), vehicle emissions (18.5%), and dust sources (1.2%) were the main sources of indoor PM OP. Multiple path particle dosimetry (MPPD) model tests evidenced that PM3.2 control the lung OPws and ROS (accounting for >71.49% and 68.07%, respectively) deposition because of the high deposition efficiency and metal concentration in the alveolar region. The experimental trend of OP was closely related to that of ROS. Overall, since OPws is directly associated with diverse health effects for PM OP, special attention to PM3.2 impact.

Optimization of Segmented Thermal Barrier Coatings (s-TBCs) for High-Temperature Applications

AbstractHot section components of stationary gas turbines, such as turbine blades and vanes, are coated with thermal barrier coatings (TBCs) to increase the component life. TBCs provide thermal insulation to the metallic components from hot gas in the gas turbines. The TBCs represent high-performance ceramics and are mainly composed of yttria-stabilized zirconia (YSZ) to fulfill the thermal insulation function. The microstructure of the TBCs should be porous to decrease heat conduction. Besides the porous TBCs, the subsequently developed vertically segmented thermal barrier coatings (s-TBCs) feature outstanding thermal durability. For the formation of this segmented coating microstructure, the YSZ should be deposited under high thermal tensile stress during the coating process. Therefore, substrates are heated just before the coating by plasma or in an oven in recent research. In this work, the development of process parameters for s-TBCs produced by atmospheric plasma spray (APS) without pre-heating is presented. Within the experiments, the relevant process parameters, such as plasma gases, powder feed rate, surface speed, and pathway strategy, have been optimized to achieve the segmented coating microstructure with high deposition efficiency by a conventional plasma torch. Furthermore, YSZ powders used in this study are characterized, and the effect of powder characteristics on the coating microstructure is investigated. The coating microstructure in this work aims to achieve the formation of a high number of vertical cracks with a combination of low internal residual stress and high adhesive tensile strength for the s-TBCs.

Enhancing the flexural properties of CFRP with vacuum-assisted deposition of cellulose microfibrils to create a multiscale reinforcement network

ABSTRACT Carbon fiber (CF) was coated with micro-fibrillated cellulose (MFC) using vacuum-assisted deposition in aqueous suspensions at concentrations of 0.1%, 0.2%, and 0.4%. The impact of distribution mesh configurations (DM arrangements) and fabric layer configuration on cellulose deposition was examined. Multiscale CF-MFC-Epoxy composites were created using resin infusion under flexible tooling, forming a 3D network of MFC between CFs that transferred stress and acted as a node at the intersection of 0–90 bundles. The addition of 0.1% MFC suspensions improved flexural properties, using no distribution media enhanced deposition and penetration efficiency, and drying stacked layers of CF fabrics improved load transference between them. This combination of parameters resulted in composites with a 16% increase in flexural modulus and 45% increase in flexural strength.

Fabrication of High-Entropy Alloys Using a Combination of Detonation Spraying and Spark Plasma Sintering: A Case Study Using the Al-Fe-Co-Ni-Cu System

The use of pre-alloyed powders as high-entropy alloy (HEA) coating precursors ensures a predetermined (unaltered) elemental composition of the coating with regard to the feedstock powder. At the same time, it is interesting to tackle a more challenging task: to form alloy coatings from powder blends (not previously alloyed). The powder-blend-based route of coating formation eliminates the need to use atomization or ball milling equipment for powder preparation and allows for the introduction of additives into the material in a flexible manner. In this work, for the first time, a HEA was obtained using detonation spraying (DS) followed by spark plasma sintering (SPS). A powder mixture with a nominal composition of 10Al-22.5Fe-22.5Co-22.5Ni-22.5Cu (at.%) was detonation-sprayed to form a multicomponent metallic coating on a steel substrate. The elemental composition of the deposited layer was (9 ± 1)Al-(10 ± 1)Fe-(20 ± 1)Co-(34 ± 1)Ni-(27 ± 1)Cu (at.%), which is different from that of the feedstock powder because of the differences in the deposition efficiencies of the metals during DS. Despite the compositional deviations, the deposited layer was still suitable as a precursor for a HEA with a configurational entropy of ~1.5R, where R is the universal gas constant. The subsequent SPS treatment of the substrate/coating assembly was carried out at 800–1000 °C at a uniaxial pressure of 40 MPa. The SPS treatment of the deposited layer at 1000 °C for 20 min was sufficient to produce an alloy with a single-phase face-centered cubic structure and a porosity of <1%. Interestingly, the hardness values of the as-sprayed and SPS-treated coatings were close to each other (~320 HV0.3). The hardness of the coatings measured in two perpendicular directions did not differ significantly. The features of the DS–SPS route of the formation of HEA coatings and its potential applications are discussed.

Numerical analysis of airflow and particle deposition in multi-fidelity designs of nasal replicas following nasal administration

Background and ObjectiveAn improved understanding of flow behaviour and particle deposition in the human nasal airway is useful for optimising drug delivery and assessing the implications of pollutants and toxin inhalation. The geometry of the human nasal cavity is inherently complex and presents challenges and manufacturing constraints in creating a geometrically realistic replica. Understanding how anatomical structures of the nasal airway affect flow will shed light on the mechanics underpinning flow regulation in the nasal pharynx and provide a means to interpret flow and particle deposition data conducted in a nasal replica or model that has reduced complexity in terms of their geometries. This study aims to elucidate the effects of sinus and reduced turbinate length on nasal flow and particle deposition efficiencies. MethodsA complete nasal airway with maxillary sinus was first reconstructed using magnetic resonance imaging (MRI) scans obtained from a healthy human volunteer. The basic model was then modified to produce a model without the sinus, and another with reduced turbinate length. Computational fluid dynamics (CFD) was used to simulate flow in the nasal cavity using transient flow profiles with peak flow rates of 15 L/min, 35 L/min and 55 L/min. Particle deposition was investigated using discrete phase modelling (DPM). ResultsResults from this study show that simplifying the nasal cavity by removing the maxillary sinus and curved sections of the meatus only has a minor effect on airflow. By mapping the spatial distribution of monodisperse particles (10 μm) in the three models using a grid map that consists of 30 grids, this work highlights the specific nasal airway locations where deposition efficiencies are highest, as observed within a single grid. It also shows that lower peak flow rates result in higher deposition differences in terms of location and deposition quantity, among the models. The highest difference in particle deposition among the three nasal models is ∼10%, and this is observed at the beginning of the middle meatus and the end of the pharynx, but is only limited to the 15 L/min peak flow rate case. Further work demonstrating how the outcome may be affected by a wider range of particle sizes, less specific to the pharmaceutical industries, is warranted. ConclusionA physical replica manufactured without sections of the middle meatus could still be adequate in producing useful data on the deposition efficiencies associated with an intranasal drug formulation and its delivery device.

Lattice distortion of PtCo nanoparticles encapsulated in TiO2 nanotubes boosts methanol oxidation

Exploring highly efficient, CO-tolerant and stability catalyst, such as Pt-based bimetallic catalyst for methanol oxidation reaction (MOR) is pressingly demanded towards commercialization of direct methanol fuel cells (DMFCs). Herein, the PtCo nanoparticles are encapsulated in bamboo-like highly ordered TiO2 nanotubes (PtCo/TNTs/Ti) by a facile electrochemical method. The obtained PtCo/TNTs/Ti electrode exhibits a large electrochemical active area of 1220.4 cm2/mgpt. Its mass activity reaches to 1148 mA/mgPt, which is 3.6 times and 7.5 times than that of Pt/TNTs/Ti and PtC, respectively. The lattice spacing of (111) and (200) faces are respectively reduced by 3.5% and 7.1%, caused by Co incorporated into Pt lattice. The lattice strain is an important reason for improving catalytic performance. In addition, an insight into growth mechanism is proposed according to the first-principle calculations. Co atoms that alloyed with Pt on the surface provide active sites for the following reduction of Pt, promoting the deposition efficiency. The obtained PtCo/TNTs/Ti is expected as the candidate electrode to output high power density in DMFCs.

Dry Powder Formulations for Inhalation Require a Smaller Aerodynamic Diameter for Usage at High Altitude

BackgroundHigh Altitude Pulmonary Edema (HAPE) seriously threatens the health of people at high altitudes. There are drug treatments for HAPE, and dry powder formulations (DPFs) represent a rapid and accessible delivery vehicle for these drugs. However, there are presently no reports on the inhalability of DPFs in low-pressure environments. Given the reduced atmospheric pressure typical at high altitudes, conventional DPFs might not be suitable for inhalation. Therefore, it is necessary to elucidate the deposition behaviors of dry powder in the respiratory tract at low pressure, as well as to improve their pulmonary deposition efficiency via adjustments to their formulation and design. MethodsThe effect of air pressure, inspiratory velocity, and particle properties (such as size, density, and aerodynamic diameter) on pulmonary deposition of DPFs was calculated by a computational fluid dynamics (CFD)-coupled discrete phase model. DPFs of various aerodynamic diameters were prepared by spray drying, and the inhalability of these DPFs in a low-pressure environment was evaluated in mice. Finally, a mouse model of HAPE was established, and the treatment of HAPE by nifedipine-loaded DPFs with small aerodynamic diameter was validated. ResultsCFD results showed that low pressure decreased the deposition of DPFs in the lungs. At 0.5 standard atmosphere, DPFs with aerodynamic diameter of ∼2.0 μm could not enter the lower respiratory tract; however, a decrease in the physical diameter, density, and, consequently, the aerodynamic diameter of the DPFs was able to enhance pulmonary deposition of these powders. To validate the CFD results, three kinds of dry powder with aerodynamic diameters of 0.66, 0.98, and 2.00 μm were prepared by spray drying. Powders with smaller aerodynamic diameter could be inhaled into the lungs of mice more effectively, and, consequently could ameliorate the progression of HAPE more effectively than conventional powders. These results were consistent with the CFD results. ConclusionsLow atmospheric pressure can prevent the pulmonary deposition of DPFs at high altitudes. Compared with conventional DPFs, powders with smaller aerodynamic diameter can be effectively inhaled at these pressures and thus might be more suitable for the treatment the HAPE.

High-efficiency localized electrochemical deposition based on ultrafast laser surface modification

Localized electrochemical deposition is a promising technology that allows for additive manufacturing of micro-nano structures in designated areas with high precision and controllability. However, ultra-low printing speed of current localized electrochemical deposition hinders its practical applications, especially the manufacturing of large-scale and complex devices. Here we propose a strategy combining ultrafast laser surface modification with traditional electrochemical deposition to achieve high-efficiency and large-scale printing. With using a focused ultrafast laser, arbitrary large-scale patterned structure can be efficiently scratched on substrate surface. Since the laser scratched region has formed nano-sized surface relief structures which experience local field enhancement when subjected to a voltage, the electrochemical deposition rate in the laser scratched region can be significantly improved, resulting in equivalent localized electrochemical deposition under traditional electrochemical deposition conditions. Such parallel electrochemical deposition can significantly shorten the printing time for large-scale devices. As for the processing of microstructure arrays with a size of 16 mm2, the printing time is compressed within 10 min, among which the electrochemical deposition process is compressed to 10 s. The results demonstrate the potential for improving the efficiency and scalability of localized electrochemical deposition through this combined approach.