High Collection Efficiency Research Articles

Synthesis of modified polystyrene nanoparticles and their application in fine cassiterite flotation

To solve the problem of the low flotation efficiency of fine cassiterite, we synthesised a novel high-efficiency collector comprising modified polystyrene nanoparticles (MPNs) by introducing 2-butenohydroxamic acid in emulsion polymerization. The particle size, surface potential, chemical structure and surface morphology of the collector were studied. The results showed that the collector comprised 20–100 nm cationic spherical nanoparticles with hydroxamic acid groups on the surface. The pure mineral micro-flotation experiment results revealed that fine cassiterite and calcite can be effectively separated using the MPNs as collector, which indicates the collecting capability and selectivity of MPNs for cassiterite. The selective adsorption mechanism of MPNs on the surface of cassiterite was further confirmed through Fourier transform infrared spectroscopy, zeta potential and scanning electron microscopy analysis.

Sparse SiPM Pixel Arrangement for a TOF-PET Detector Design that Achieves 100 ps Coincidence Time Resolution

Coupling silicon photomultipliers (SiPMs) to the side of a long and narrow scintillation crystal elements offers near-complete light extraction efficiency, independent of 511 keV photon interaction depth, and reduced scintillation light transit time jitter in its path toward the photodetector. With these advantages, significant improvements in PET detector coincidence time resolution (CTR) can be achieved compared to the traditional scintillation light readout configuration where an SiPM is coupled on the narrow end of crystals. Moreover, the arrangement of photosensors along the crystal’s side intrinsically provides a three-dimensional position sensing detector. One consideration for the side readout approach is the increase in the number of SiPMs required to read each crystal element. In this work, we investigate the achievable CTR when the number of SiPM elements coupled to the side of crystals is parametrically varied, including different crystal lengths and reflector configurations. A simulation model for CTR was validated against measurements with 3-20 mm length crystals employing side readout of scintillation light. The validated simulation model was used to parametrically investigate twenty-seven configurations of SiPMs arranged along the side of crystal elements. Reflector and sensor placement was parametrically varied to find configurations that optimize light collection efficiency, energy resolution, and CTR. One configuration achieved 101±1 ps FWHM CTR, while maintaining high light collection efficiency and good energy performance with a 33% reduction in photosensor area.

Bright Source of Purcell‐Enhanced, Triggered, Single Photons in the Telecom C‐Band

AbstractSeveral emission features mark semiconductor quantum dots as promising non‐classical light sources for prospective quantum implementations. For long‐distance transmission and Si‐based on‐chip processing, the possibility to match the telecom C‐band is decisive, while source brightness and high single‐photon purity are key features in virtually any quantum implementation. An InAs/InGaAs/GaAs quantum dot emitting in the telecom C‐band coupled to a circular Bragg grating is presented here. This cavity structure stands out due to its high broadband collection efficiency and high attainable Purcell factors. Here, simultaneously high brightness with a fiber‐coupled single‐photon count rate of 13.9 MHz for an excitation repetition rate of 228 MHz (first‐lens single‐photon collection efficiency ≈17% for NA = 0.6), while maintaining a low multi‐photon contribution of is demonstrated. Moreover, the compatibility with temperatures of up to 40 K attainable with compact cryo coolers, further underlines the suitability for out‐of‐the‐lab implementations.

Beetle-like structured microfibers for rapid water harvesting

Water harvesting in arid and semi-arid areas gains increasing attention, and harvesting water from the atmosphere are one of the effective ways to solve this problem. This work provides a structured microfiber coated with a beetle-like coating to obtain highly efficient water harvesting through self-induced drops jumping, drops sweeping and droplets collision. Then, the water collection efficiency of the beetle-like fiber is ∼4.7 times that of the lotus-like fiber and ∼4 times that of the initial fiber. Further more, the beetle-like harp structure exhibits a high water collection rate up to ∼2.6 × 104 g/m2/h, and the beetle-like network with a high water collection efficiency of ∼6.5 × 104 g/m2/h. These findings are considered instrumental in the further design and implementation of bionic microfiber for cost-efficient atmospheric water harvesting, industrial vapor recovery and seawater desalination, etc.

Study on sediment erosion generated by a deep-sea polymetallic-nodule collector based on double-row jet

The hydraulic double-row jet collector is widely used due to its high collection efficiency. Deep-sea sediments are usually characterized by high water content and semi-fluid dynamics, and there are few studies on the erosion properties of such sediments under jets. Resulting in the failure to accurately assess the efficiency and disturbance of a two-row jet collector. In this paper, the flow field characteristics are simulated for different double-row jet parameters (jet outlet pressure, nozzle-to-seabed height, target distance and number of nozzles). The erosion of a high water content, semi-fluid dynamic sediment layer (similar to the deep sea) under a double-row jet is experimentally investigated. According to the results from study, the jet flow field had a powerful central flow field, and decayed to both sides gradually. The formulas of flow field attenuation distribution in the upper jet zone and the maximum axial pressure are proposed. Moreover, the experiments showed that the erosion holes on the surface layer was mainly a "bowl" shape with a flat bottom and concave side, which had self-similarity. The erosion depth grew with the increase of jet outlet pressure, decreased with the increase of the nozzle height to the seabed. With the increase of target distance, the erosion depth first increased and then decreased. A new model of the erosion depth-time and erosion depth prediction are proposed. These results can provide theoretical reference for flow field calculation in nodule mining operation with double-row jet collector. It may have potential benefits on melioration of the collection efficiency and reduction of the jet disturbance.

Scalable, solvent-free transparent film-based air filter with high particulate matter 2.5 filtration efficiency

Over the course of the COVID-19 pandemic, people have realized the importance of wearing a mask. However, conventional nanofiber-based face masks impede communication between people because of their opacity. Moreover, it remains challenging to achieve both high filtration performance and transparency through fibrous mask filters without using harmful solvents. Herein, scalable transparent film-based filters with high transparency and collection efficiency are fabricated in a facile manner by means of corona discharging and punch stamping. Both methods improve the surface potential of the film while the punch stamping procedure generates micropores in the film, which enhances the electrostatic force between the film and particulate matter (PM), thereby improving the collection efficiency of the film. Moreover, the suggested fabrication method involves no nanofibers and harmful solvents, which mitigates the generation of microplastics and potential risks for the human body. The film-based filter provides a high PM2.5 collection efficiency of 99.9 % while maintaining a transparency of 52 % at the wavelength of 550 nm. This enables people to distinguish the facial expressions of a person wearing a mask composed of the proposed film-based filter. Moreover, the results of durability experiments indicate that the developed film-based filter is anti-fouling, liquid-resistant, microplastic-free and foldability.

Numerical simulation of the enhancing effect of micro–nano protrusions on electrostatic fog harvesting

Fog harvesting is one potential approach to provide supplementary water resources in arid areas. Considerable research has been devoted to electrostatic fog harvesting technology, but there are still some problems, such as high voltage, complex structures and expensive cost. Decorating micro–nano protrusions on the electrode is an effective method to lower the operating voltage and improve fog harvesting efficiency, and the enhancement effect of protrusions has already been experimentally demonstrated. However, the enhancement mechanism at the microscopic level is less reported. This manuscript tries to explain why micro–nano protrusions can enhance the discharge and electrostatic fog harvesting, via numerical simulation. Three key processes of corona discharge, fog droplet migration and fog harvesting efficiency are discussed in detail, especially the influence of droplet size, the tip radius of the protrusion, the protrusion–protrusion angle and so on. The numerical simulation results show that the inception voltage of the barbed electrode decreases from 7 kV to 3 kV (a decrease of 57%), and the current increases significantly (e.g. by 68% at 15 kV). At 15 kV, the fog harvesting efficiency of the barbed electrode is higher (29.8%) than that of the smooth wire (25.7%), even with a less-effective collection area. The collection efficiency increases with the droplet size, and there is an optimized ratio (∼1‰) of the protrusion tip radius and wire radius to gain high collection efficiency. These research results are beneficial for understanding the microscopic mechanism of protrusions that enhance electrostatic fog harvesting, and provide guidance for further fog harvesting equipment improvement.

Fresnel-type solid immersion lens for efficient light collection from quantum defects in diamond.

Quantum defects in diamonds have been studied as a promising resource for quantum science. The subtractive fabrication process for improving photon collection efficiency often require excessive milling time that can adversely affect the fabrication accuracy. We designed and fabricated a Fresnel-type solid immersion lens using the focused ion beam. For a 5.8 µm-deep Nitrogen-vacancy (NV-) center, the milling time was highly reduced (1/3 compared to a hemispherical structure), while retaining high photon collection efficiency (> 2.24 compared to a flat surface). In numerical simulation, this benefit of the proposed structure is expected for a wide range of milling depths.

Electrostatic Precipitator Design Optimization for the Removal of Aerosol and Airborne Viruses

In the midst of the COVID-19 pandemic, new requirements for clean air supply are introduced for heating, ventilation, and air conditioning (HVAC) systems. One way for HVAC systems to efficiently remove airborne viruses is by filtering them. Unlike disposable filters that require repeated purchases of consumables, the electrostatic precipitator (ESP) is an alternative option without the drawback of reduced dust collection efficiency in high-efficiency particulate air (HEPA) filters due to dust buildup. The majority of viruses have a diameter ranging from 0.1 μm to 5 μm. This study proposed a two-stage ESP, which charged airborne viruses and particles via positive electrode ionization wire and collected them on a collecting plate with high voltage. Numerical simulations were conducted and revealed a continuous decrease in collection efficiencies between 0.1 μm and 0.5 μm, followed by a consistent increase from 0.5 μm to 1 μm. For particles larger than 1 μm, collection efficiencies exceeding 90% were easily achieved with the equipment used in this study. Previous studies have demonstrated that the collection efficiency of suspended particles is influenced by both the ESP voltage and turbulent flow at this stage. To improve the collection efficiency of aerosols ranging from 0.1 μm to 1 μm, this study used a multi-objective genetic algorithm (MOGA) in combination with numerical simulations to obtain the optimal parameter combination of ionization voltage and flow speed. The particle collection performance of the ESP was examined under the Japan Electrical Manufacturers’ Association (JEMA) standards and showed consistent collection performance throughout the experiment. Moreover, after its design was optimized, the precipitator collected aerosols ranging from 0.1 μm to 3 μm, demonstrating an efficiency of over 95%. With such high collection efficiency, the proposed ESP can effectively filter airborne particles as efficiently as an N95 respirator, eliminating the need to wear a mask in a building and preventing the spread of droplet infectious diseases such as COVID-19 (0.08 μm–0.16 μm).

All fabric and flexible wearable sensors for simultaneous sweat metabolite detection and high-efficiency collection

Wearable sweat electrochemical sensors have attracted wide attention due to their advantages of non-invasive, portable, real-time monitoring, etc. However, existing sensors still have some problems with efficient sweat collection. Microfluidic channel technology and electrospinning technology are commonly used to collect sweat efficiently, but there are some limitations such as complex channel design and multiple spinning parameters. Besides, existing sensors are mostly based on flexible polymers, such as, PET, PDMS, PI and PI, which have limited wearability and permeability. Based on the above, all fabric and dual-function flexible wearable sweat electrochemical sensor is proposed in this paper. This sensor uses fabric as the raw material to implement the directional transport of sweat and the multi-component integrated detection dual functions. Meanwhile, the high-efficiency collection of sweat is obtained by a Janus fabric, wherein one side of the selected silk is superhydrophobic graft treated and the other side is hydrophilic plasma treated. Therefore, the resulting Janus fabric can effectively transfer sweat from the skin side to the electrode, and the minimum sweat droplet can reach 0.2 μL to achieve micro-volume collection. Besides, the patterned sensor, made of silk-based carbon cloth, is fabricated using a simple laser engraving, which could detect Na+, pH, and glucose instantaneously. As a result, these proposed sensors can achieve good sensing performance and high-efficiency sweat collection dual functionality; moreover, it has good flexibility and comfortable wearability.

Contribution of ammonia in xanthates adsorption onto copper oxide mineral surface in high-alkaline solution

Ammonia is a useful modifier for enhancing surface sulfurization in copper oxide ore flotation using xanthate as a collector. However, its potential role in the reaction of sulfhydryl collector with sulfurized copper oxide mineral in a complex pulp has been neglected. This work investigates the contribution of ammonia to xanthate adsorption on the sulfurized malachite surface, independent of its effect on sulfurization. Zeta potential measurements indicate that NH3·H2O increases the surface potential of malachite and enhances the proximity of xanthate to the malachite surface in a strong-alkaline solution. Adsorption tests and time-of-flight secondary ion mass spectrometry analysis demonstrate that NH3·H2O can increase the xanthate adsorption density. Spectroscopic analysis reveals copper(I) xanthate and dixanthogen as the primary xanthate products, with their quantities increasing upon NH3·H2O treatment. Thermodynamic analysis of the reaction of malachite, HS−, and xanthate to form copper(I) xanthate and dixanthogen shows that NH3·H2O treatment enhances the stability of the reaction compared to its absence. Thus, NH3·H2O treatment increased the recovery of sulfurized malachite by over 10%. This study offers a comprehensive understanding of ammonia modification for enhancing sulfurization–xanthate flotation of copper oxide minerals and provides a scientific basis for developing high-efficiency collectors.

Study on the influence of electrodes on the collection efficiency during the treatment of welding fume in electrostatic precipitators

Welding fume is hazardous to the environment and human health and is purified using an electrostatic precipitator (ESP). Electrostatic precipitators are widely used in waste gas treatment processes in thermal power plants, cement plants and other factories. The use of electrostatic precipitators to treat welding fumes requires further research. Corona discharge occurs at the electrostatic precipitator, the primary condition for particle charging. The components and physical parameters of the treated particles should be considered in the numerical simulation. This paper investigates the effects of polygonal electrode form, deflection angle, and spacing on the electric field distribution and collection efficiency. The physical quantities in the vicinity of the electrodes vary greatly. Therefore, the focus is on the vicinity of the electrode, and curves describing the trend. It is shown that the maximum velocity did not vary monotonically with increasing the number of tips and that the highest collection efficiency is obtained with a triangle electrode. Furthermore, it is shown that the variation of interelectrode distance leads to variations in the inter-electrode shielding effect.

Load-responsive bionic kirigami structures for high-efficient fog harvesting

Harvesting fog is a charming approach to alleviating the global water shortage crisis. However, it is extremely challenging to design fog collectors with high efficiency due to the scarce geometric driving structures. Herein, we develop a 3D kirigami structure inspired by the new corrugated driving structures in the Bird's Nest Fern, which can be fabricated by simple shearing and stretching. Its water collection ratio increases with the external load, forming the unique load responsiveness. The kirigami structure owns a 3D array configuration to enhance flow velocity for the efficient droplet condensation rate and has geometric and wetting gradients to transport condensate droplets spontaneously and quickly, contributing to a high water collection efficiency. The water collection ratio can reach 3.45 times that of a pure iron sheet by only changing the geometric structure, and the highest ratio can even reach 4.58 times with the assistance of wetting gradients.

Design and Evaluation of ACFC—An Automatic Cloud/Fog Collector

Cloud and fog droplets are essential in atmospheric chemistry since they affect the distribution and chemical transformation of pollutants. Collecting sufficient volumes using cloud/fog samplers is the premise of cloud fog chemical studies. Accurate identification of fog events and high collection efficiency are the basic principles of sampler design. Therefore, an automatic cloud/fog collector (ACFC) has been designed, fabricated, and extensively tested for collecting samples of cloud/fog water. The control box and standard sensors for air temperature, relative humidity, and instantaneous rainfall were used to ensure sampling automation. Airflow measurement was used to guarantee the stability of the airspeed on the inlet section, and the airspeed is 7.5 m s−1. Moreover, the median collection rate of ACFC was 160–220 mL h−1, which was tested via a simulation experiment. To evaluate the actual performance of the device in the field, we obtained eight samples of cloud fog water from Shanghuang Observatory in eastern China from the summer through the fall of 2022. Collection rates varied from 62 to 169 mL h−1. For a cloud/fog sampler equipped with multiple sensors, the ACFC has excellent sampling efficiency in thick fog, sufficient cloud fog water samples can be collected in weak fog, and it can precisely identify fog mingled with rain.

Development of Particle Collection Technique by Using Bubble Breakup Phenomenon in Venturi Tube

In decommissioning Fukushima Daiichi nuclear power station, the issue is confinement of radioactive aerosols in the primary containment vessel. Although a HEPA (High Efficiency Particulate Air) filter is used to collect the aerosol particles, pretreatment equipment such as a scrubber may be applied to reduce the load of HEPA filters. In the scrubber, the aerosol particles are removed by moving from gas to liquid through gas-liquid interface. Since the CE (collection efficiency) depends on gas-liquid interfacial area, fine bubbles are necessary to obtain high collection efficiency. JAEA (Japan Atomic Energy Agency) developed a new particle removal technique by using bubble breakup phenomenon in a Venturi tube. To confirm usefulness of the technique, we performed the CE measurements and observed gas-liquid two-phase flow in the Venturi tube. In comparison with a straight pipe type, the Venturi type can have removed particles more 1,000 than it. The CE is almost the same as a HEPA filter. In addition, the Venturi type has the enough CE as the pretreatment equipment for various materials of particles such as Kanto loam, SUS and oil. Besides, we clarified that the CE of the Venturi type depended on the gas and liquid flow rates. The CE increases with the increase of the liquid flow rate but decreases with the increase of the gas flow rate. This is because the CE is affected by the bubble breakup phenomenon in the Venturi tube. In the experiment, we confirmed that cavitation number which is the parameter of the bubble breakup was related to the CE of the Venturi type.

PPWD-SDEP-IC monitoring system for atmospheric precursor inorganic gases and PM2.5 water-soluble ions

To resolve the potential evaporation loss of about 14% NH4+ in the particle into liquid sampler (PILS), a novel two-stage semi-dry electrostatic precipitator (SDEP) was developed successfully for monitoring atmospheric PM2.5 water-soluble inorganic ions (WSIIs) with the high collection efficiency and good accuracy. The number-based collection efficiency was >95% for particle sizes ranging from 14 nm to 11 μm, and the mass-based collection efficiency for PM2.5 was also as high as 94.4–98.1%. With an efficient pulse water jet system, the SDEP had a high ion recovery rate of 93 ± 10% for Na+, 103 ± 15% for NH4+, 92 ± 5.6% for SO42−, and 96 ± 8% for NO3−, respectively. The SDEP was coupled with the parallel plate wet denuder (PPWD) and ion chromatography (IC) as the PPWD-SDEP-IC semi-automatic monitoring system for the hourly precursor gases and PM2.5 WSII concentrations. The field comparison test for three-month measurements showed that the daily average results of the PPWD-SDEP-IC had a good agreement with those of the porous-metal denuder sampler (PDS), showing the linear regression slopes of 0.99–1.05 and 0.98–1.05, respectively, for precursor gases (NH3, HONO, SO2 and HNO3) and PM2.5 WSIIs (Na+, NH4+, K+, F−, Cl−, NO3− and SO42−) with high R2 values of 0.92–0.99 and 0.96–0.99, respectively. Moreover, the results of the hourly concentration comparison between the PPWD-SDEP-IC and the PPWD-PILS-IC showed linear regression slopes of 0.90–0.99 and 0.84–0.97 for precursor gases and WSIIs with high R2 values of 0.93–0.96 and 0.90–0.96, respectively. The PILS showed an underestimation of NH4+ concentration by about 15.6 ± 6.3% when compared to NH4+ from the SDEP owing to the volatilization loss of NH4+ caused by the mixing of aerosols with high-temperature steam in the PILS. Thus, the current PPWD-SDEP-IC system can be a viable tool for accurate semi-continuous monitoring of precursor gases and PM2.5 WSII concentrations.

Sr-Doping All-Inorganic CsPbBr3 Perovskite Thick Film for Self-Powered X-ray Detectors.

The all-inorganic perovskite cesium lead bromine (CsPbBr3) has attracted much attention in the field of X-ray detectors because of its high X-ray absorption coefficient, high carrier collection efficiency, and easy solution preparation. The low-cost anti-solvent method is the main method to prepare CsPbBr3; during this process, solvent volatilization will bring a large number of holes to the film, leading to the increase of defects. Based on the heteroatomic doping strategy, we propose that Pb2+ should be partially replaced by Sr2+ to prepare leadless all-inorganic perovskite. The introduction of Sr2+ promoted the ordered growth of CsPbBr3 in the vertical direction, increased the density and uniformity of the thick film, and achieved the goal of CsPbBr3 thick film repairing. In addition, the prepared CsPbBr3 and CsPbBr3:Sr X-ray detectors were self-powered without external bias, maintaining a stable response during on and off states at different X-ray dose rates. Furthermore, the detector base on 160 µm CsPbBr3:Sr had a sensitivity of 517.02 µC Gyair-1 cm-3 at zero bias under the dose rate of 0.955 µGy ms-1 and it obtained a fast response speed of 0.053-0.148 s. Our work provides a new opportunity to produce cost-effective and highly efficient self-powered perovskite X-ray detectors in a sustainable way.

InGaN nanowire array photocathode with high electron harvesting capability

With the rise of III-V semiconductor materials, InGaN materials began to be widely concerned. Nanowire arrays have excellent light trapping ability and generate a large number of photogenerated electrons. However, the adjacent nanowires will absorb these electrons twice, so the quantum efficiency cannot perfectly measure the emission performance of the nanowire array photocathode. We introduce the collection efficiency to evaluate the photoemission performance. It is based on this background that we study the photoemission performance of InGaN nanowire array under the assistance of height, incident light Angle and applied electric field. Finite-difference time-domain (FDTD) method is used to compare the quantum efficiency and collection efficiency of InGaN nanowire. We find that when the height of the nanowire is 600 nm, the angle of incident light is 65°, and the electric field strength is 0.6V/μm, InGaN nanowire arrays have the highest collection efficiency, with the collection efficiency up to 34% and the collection ratio up to 71%. The collection efficiency is 66% higher than that without external electric field. Therefore, the research in this paper can provide a theoretical reference for the preparation and performance improvement of InGaN nanowire array photocathode.

Efficient removal of condensate droplets from the surface with microgroove composite structures

Due to the increasing scarcity of global water resources, water collection based on structural functional materials has become one of most potential ways to relieve the crisis. However, water collection functional surface with the high efficiency still encounters a bottleneck. In this paper, we constructed a rough surface with micro groove and nano grass composite structures on the copper substrate, and studied the influence of micro groove spacing on the falling radius of condensate droplets. The results show that the micro groove structure increases the nucleation of droplets, and the nano needle accelerates the removal of condensate droplets. The composite structure reduces the droplet shedding diameter, and the droplet nucleation first occurs at the edge of the micro groove. Therefore, reducing the tank spacing is conducive to the condensation and removal of droplets. In addition, the water collection experiment shows that the surface with micro/nano composite structures has higher collection efficiency than the smooth surface. These findings are useful for designing condensate collection systems with high performance.

Design and performance of a double-solenoid magnetic bottle photoelectron spectrometer for attosecond metrology.

The design and performance of an in-house developed double-solenoid magnetic bottle (MB) time-of-flight photoelectron spectrograph are presented. A combination of a strong permanent magnet (Sm2Co17) with a soft iron cone and a double-solenoid geometry is used to generate MB configuration. The first solenoid (length ∼150mm) is placed inside the vacuum, and the second solenoid (length ∼1m) is placed outside the vacuum. The double-solenoid geometry improves the effective conductance and reduces overall material outgassing. Due to this, an ultra-high vacuum (∼5 × 10-8mbar) desirable for the working of the spectrograph was achieved using a small capacity (300 lps) turbo-molecular pump. An optimization of solenoid current generates a smooth magnetic field variation in MB, which keeps the adiabaticity parameter ∼0.6 at ∼25eV photoelectron energy. The double-solenoid geometry also provides high collection efficiency as well as high energy resolution of the spectrograph. The experimentally measured energy resolution (ΔE) of the spectrograph is better than ∼60meV at ∼15eV photoelectron energy. The collection efficiency is estimated to be ∼25% under optimum conditions as compared with ∼10-4 in field-free configuration. The calibrated MB spectrograph is used for the characterization of the attosecond pulse train using a cross-correlation "RABBITT" technique. The attosecond pulse train is generated from 15th to 25th odd high-harmonic orders, in argon filled cell. Attosecond pulses of average duration ∼260 as (FWHM) have been measured. The proposed MB electron spectrograph design provides a compact experimental setup for attosecond metrology and pump-probe studies with a relaxed requirement on vacuum pump capacity.