Ceramic Emitter Research Articles

Development of an Electron Emitter via Seamless Shaping of a 3D‐Printed Ceramic Cone With Carbon Nanotube Mesh Film as an Alternative to Polymer‐Based Materials

AbstractThis paper focuses on electron emitters formed using seamless hybrid shaping of the ceramic 3D‐printed cone (as a supporting structure) and a conductive emitting film obtained from the suspension of dispersed carbon nanotubes (CNT). The ceramic cone is post‐process fired to achieve a pure ceramic cone that is coated with emitting CNT mesh film. Meanwhile, a cone‐based polymer emitter is evaluated. The resulting emitter exhibits non‐linear current‐voltage characteristics reaching maximum 0.6 mA anode current with a turn‐on‐field voltage below 1 Vµm−1 and minimal current fluctuation over time. Additionally, the ceramic emitter arrays fabricated using the same technique are demonstrated: if the tip angle and shape in a microscale have tunability in emission is confirmed, meanwhile, the type of volatile gases released during the emission is confirmed using a residual gas analyzer (RGA). The motivation and challenge are to use 3D printing to enable freedom in designing and forming the emitter tip shape and angle and to present the perspective and challenges to use the 3D printing technique combined with the seamless shaping for the CNT mesh film to tune the emitter performance. Especially as this technique and 3D‐printed materials have not been previously employed for electron emitters.

Determining clogging threshold of ceramic emitters to promote wolfberry production in Northwest China

Drip irrigation is a worldwide water-saving irrigation technology and benefits crop production. Yet, the emitter clogging is still a crucial problem for application. Recently, ceramic emitter (CE) with porous flow path was proposed as an alternative to the plastic drip emitter for continuous irrigation. However, there is still a gap in the estimation of the CE clogging degree. To address this, we conducted the field experiment in Tongxin, Yinchuan and Qinghai with the aim of the determination of the suitable discharge ratio variation (Dra) threshold of CEs under different climate conditions by using the AquaCrop model and segmented linear regressions. The results showed that there was a determined Dra threshold for soil water content (SWC), wolfberry canopy cover, biomass and yield in three experimental sites by 53.55 % - 54.62 %, 57.11 % - 65.94 %, 55.58 % - 64.30 % and 51.76 % - 61.23 %, respectively. Moreover, the Dra thresholds decreased with the precipitation increased in different climate conditions. Furthermore, we determined the Dra threshold of CEs was 56.1±5.3 % for wolfberry production, which was remarkably lower than the international standard of emitter clogging level by 75 %. Our study provides scientific insight to determine the clogging thresholds of CEs and further generalizes this technique in the irrigation science area.

Effects of algal organic matters on microporous ceramic emitters clogging in agricultural water distribution systems: Experiment and molecular simulation investigations

The mechanism by which algal organic matter (AOM) affects the clogging of ceramic emitters remains unclear, which partially reduces the operational life of agricultural water distribution systems. This paper systematically investigated the clogging phenomenon of ceramic emitters under three different AOM concentrations. The results of irrigation tests revealed that the AOM significantly affects the degree of clogging of ceramic emitters, with higher AOM concentrations leading to faster flow reduction. By analyzing the original irrigation water and effluent and characterizing the clogged emitter surface, it was demonstrated that AOM was intercepted by the ceramic emitter, forming a dense biofilm. Infrared spectroscopy analysis revealed that polysaccharides and humic substances were the main clogging components. The clogging kinetics showed that as the AOM concentration increased, the clogging of the filter cake layer gradually become dominant. Further, the mechanism of interaction between AOM and silica ceramic emitters was explored from a microscopic perspective using molecular dynamics (MD) simulation with bovine serum albumin (BSA), sodium alginate (SA), and humic acid (HA) as model clogging substances in AOM. The simulation results indicated a strong interaction between AOM molecules and silica molecules dominated by electrostatic attraction, with the strength of the interaction as SA > HA > BSA. It was hypothesized that early clogging was mainly formed by polysaccharides and humic substances combining with silica molecules, while BSA was retained later by combining with organics on the clogging layer or through size exclusion. This study provides insights into bio-clogging in microporous ceramic emitters and may offer a theoretical basis for developing measures to control emitter clogging.

A new subsurface ceramic emitter for smallholders without pumps: design, hydraulic performance, and field application

A new subsurface ceramic emitter for smallholders without pumps: design, hydraulic performance, and field application

Optimization algorithm for determining working water head of subsurface irrigation with ceramic emitters based on soil wetting patterns

Appropriate working water head of subsurface irrigation systems with ceramic emitters (SICE) is crucial for providing a stable and suitable soil water environment to promote crop production and save water resources in intensive agriculture. However, working water head optimization of SICE is hindered by the uncertainties of the soil physic properties, increasing the risk of irrational irrigation. To effectively address this challenge, this study presented an optimization algorithm for optimizing the working water head of SICE based on soil wetting patterns, considering taking into account soil physical variables and management variables, and then the reliability of the algorithm was verified by three case studies. The results of three case studies showed that the relative error between the actual irrigation amount of SICE using the optimization algorithm, and the recommended irrigation amount was lower than 5%. In three case studies, the sand-based ceramic emitter and working water head of 40 cm, 30 cm, and 70 cm were recommended parameters for SICE. The crop yield under SICE with appropriate working water head for three case studies was 109.2 × 103 kg ha−1, 5643.3 kg ha−1, and 3182.6 kg ha−1, which were 8.01%, 30.56%, and 16.90% higher than that of subsurface drip irrigation, respectively. Our findings revealed that SICE with the appropriate working water head might be an efficient subsurface irrigation method for intensification agriculture with the goal of high crop production.

Reduction of pathogenic bacteria from irrigation water through a copper-loaded porous ceramic emitter

The increasing pathogenic bacteria threat in irrigation water has become a worldwide concern, prompting efforts to discover a new cost-effective method for pathogenic bacteria eradication, different than those currently in use. In this study, a novel copper-loaded porous ceramic emitter (CPCE) was developed via molded sintering method to kill bacteria from irrigation water. The material performance and hydraulic properties of CPCE are discussed herein, and the antibacterial effect against Escherichia coli (E. coli) and Staphylococcusaureus (S. aureus) was evaluated. The incremental copper content in CPCE improved flexural strength and pore size, which was conducive to enhancing CPCE discharge. Moreover, antibacterial tests showed that CPCE displayed efficient antimicrobial activity, killing 99.99% and more than 70% of S. aureus and E. coli, respectively. The results reveal that CPCE, with both irrigation and sterilization functions, can provide a low-cost and effective solution for bacterial removal from irrigation water.

A new small-scale system of rainwater harvesting combined with irrigation for afforestation in mine area: Optimizing design and application

Afforestation plays a crucial role in the remission of water and soil erosion, adsorption of heavy metals, and protection of soil microbial community structure for mining areas. However, soil drought, the variability of precipitation, and low rainwater use efficiency severely limit the early survival rate of trees. A new small-scale system of rainwater harvesting combined with irrigation (RWHI) for afforestation in mining areas was established, which consisted of a rainwater catching board, storage tanks, and ceramic emitters. A daily water balance model under variable water supply was presented and experimentally verified to confirm the optimum catchment area, the storage capacity of tanks, and the rated discharge of ceramic emitters. Taking the Wuda mining area in Wuhai, China, as a case study, three representative years, including dry, normal, and wet years were selected by analysing local rainfall features. The results showed that the soil water content in the root zone maintained a suitable range (between field capacity and wilting coefficient) using the RWHI system. With the aim of the maximum system operating reliability for various weather conditions and tree species, it was recommended that the rated discharge of the ceramic emitter of 6 ml h−1, storage tanks of 25 L, the catchment area of 1 m2, and filling water schedule of twice a year were employed. A generalised equation for the estimation of the filling water amount was given. The vegetation coverage of the mine was significantly improved, and the survival rate of trees (Murraya paniculate) exceeded 90% using the RWHI system. It was indicated that the RWHI system has a broad application prospect in the afforestation of the mining areas.

Simplified method for estimating discharge of microporous ceramic emitters for drip irrigation

Emitter discharge is an essential index in the hydraulic design, operation, and management of drip irrigation systems. Previous studies on the calculation of discharge have focused on traditional plastic emitters with labyrinth channels. Here, water flow in the pores of microporous ceramic emitter was analysed. A simplified method for calculating the discharge of microporous ceramic emitters was presented in the form of a model that took into account pore structure, water temperature, ceramic types, and emitter structural parameters, and was experimentally verified. Emitter structure was optimised with the goal of minimising material cost. The results showed that the discharge from microporous ceramic emitters varied significantly in different seasons due to water temperature change, and the higher water temperature was associated with a higher discharge. Discharge was increased by 39.10% when the water temperature changed from 20 °C to 35 °C. Discharge can be stabilised by adjusting operating pressure for different seasons. Discharge increased linearly with increasing operating pressure at the same water temperature. Compared with the sand-based microporous ceramic emitters, the clay-based microporous ceramic emitter had a relatively low discharge due to the fine particle size of its construction material.

Clogging formation and an anti-clogging method in subsurface irrigation system with porous ceramic emitter

Emitter clogging negatively affects the performance of subsurface drip irrigation systems. The porous ceramic emitters of a subsurface irrigation system were investigated to identify the reasons for emitters clogging. Using 2-year operational data in an apple orchard, the soil water content and the emitters discharge were measured, the position and composition of the clogging substance were investigated, and the thickness of the adhesion layer in the channel of the emitter was calculated. Further, a flushing experiment using acid water with a pH of 6 was carried out to assess emitter clogging. The primary reason for the emitter clogging was substances precipitated at the inlet of the emitter, resulting in reducing the discharge of the emitter. At the same time, the water flow was affected by the clogging substance inside the micropore close to the channels. The main compounds of the clogging substances were SiO2, CaCO3, and MgAl2O4. Fe, Cl and K were also observed. Bacteria, fungus and microalgae secreted PLFAs to form biofilm. We have tested 4 flushing times (3 min, 10 min, 15 min, 20 min) and found that when the flushing time lasted 15 min, the corresponding emitter discharge were 0.046 L h−1 and 0.136 L h−1 under the working pressure of 2 kPa and 5 kPa, and discharge recovery rate were 51.11% and 75.56%, respectively. However, when the flushing time increased to 20 min, the discharge recovery was similar to that of 15 min. Therefore, it is recommended to flush with an acid solution for 15 min at flushing pressure of 100 kPa pressure to minimize the emitter clogging.

Effectiveness of a subsurface irrigation system with ceramic emitters under low-pressure conditions

A subsurface irrigation system with ceramic emitters (SICE) without a pump has been developed to limit energy consumption and reduce greenhouse gas emissions. Yet whether SICE can be used in low-pressure conditions has not been tested; moreover, there is no index for evaluating the irrigation quality of SICE. Laboratory experiments, with six treatments, were conducted to study ceramic emitter hydraulic characteristics in the air and soil under different working pressure heads and emitter types. The results indicated that when H increased, the emitter discharge increased linearly, and the discharge deviation decreased in the air. With increased H in the soil, the emitter discharge, soil water content, and soil water content uniformity increased, and the discharge deviation decreased. When H was greater than or equal to 20 cm, the discharge deviation in the soil was less than that in the air, and the soil water content uniformity was higher than 80 %. The soil water content uniformity could be used in the evaluation of the irrigation quality of SICE based on the reliability and convenience of observation. To make the best use of soil water potential on the outflow of the emitter, reduce the discharge deviation, and improve soil water content uniformity, the working pressure head of SICE should be higher than 20 cm.

Characterization of an ionic liquid electrospray thruster with a porous ceramic emitter

An ionic liquid (IL) electrospray thruster was developed for application in micro-nano satellites or gravitational wave detectors. The thruster employed a porous ceramic emitter with seven emitter strips located on its emission surface. Without any liquid-supply device, IL was delivered through porous media to emitter strips via capillary effect. Multiple emission sites then formed at the tip of each strip. A charged beam of up to 350 μA (with a current density of 540 μA cm−2) was stably produced in the negative mode. However, in the positive mode, a corona was observed which could prevent the thruster from emitting larger current. A time-of-flight mass spectrometer with significantly improved signal-to-noise ratio was built, which was used to obtain the mass distribution of the beam of the thruster. A retarding potential analysis was also performed. The test results showed that the thruster worked in the pure-ion regime, and delivered a maximum thrust of 67.1 μN with specific impulses of 3952 s and 3117 s in the positive and negative modes, respectively.

The Clogging Rules of Ceramic Emitter in Irrigation Using Saline Water with Different EC

Infiltration irrigation with saline water is a more effective method than drip irrigation to alleviate water scarcity worldwide, but so far, no report has discussed the clogging rules of ceramic emitters, a major component of infiltration irrigation system. To explore the clogging mechanism of ceramic emitter in saline water infiltration irrigation system, we used four kinds of saline water sources with electrical conductivity (EC) of 0.18, 1.74, 3.78, and 7.74 ds/m, respectively. In addition, we specifically investigated the law of discharge ratio variation (Dra) of ceramic emitters, as well as the composition and growth process of clogging substance. The results indicated that the Dra of ceramic emitters decreased in the process of saline water irrigation, and the higher the EC, the more obvious the decrease. The calcium carbonate (CaCO3) was the main component of the clogging substance in the inner wall of ceramic emitters. The clogging part was a layer on the inner wall of the emitters rather than the pores in the walls, and the clogging did not occur suddenly. Instead, it was caused by the long–term accumulation of the clogging substance. Moreover, with the increase of EC, the flocculation between the clogging particles in the water was enhanced and thus promoted the formation of stable and compact aggregates, which fundamentally led to the clogging acceleration of ceramic emitters. This clogging mechanism of ceramic emitters can provide some theoretical reference for the establishment of anti-clogging strategy.

Study of PET Spectral Absorbance in Designing Infrared Heating Control of Vacuum Forming Machine

Heating process is the first step in vacuum forming that transforms the plastic sheet from its glassy state to rubbery state, pliable enough to be formed to mold’s shape. Infrared ceramic heaters with zoning control are commonly used in thermoforming industry, in which temperature distribution and its consistency throughout processing time become very important in determining the thickness and properties of manufactured parts. Compared to other thermoplastics, Polyethylene Terephthalate (PET) with its crystallization characteristics is known to have narrower process window. Slight uneven temperature distribution and overheating will degrade PET as well as cause visible defects in final product. In order to obtain proper parameter setting of infrared ceramic heater in PET vacuum forming, a numerical approach that considers PET spectral absorbance was deployed and two methods to control temperature were compared. The experiment resulted in a reliable temperature distribution by means of voltage potentiometer control for pre-heating and implanted thermocouple inside ceramic emitter for main heating in PET vacuum forming machine.

Prediction of flow characteristics and risk assessment of deep percolation by ceramic emitters in loam

Emitter discharge is one of the most important parameters considered in the design, operation, and management of subsurface irrigation systems. The emitter discharge, if properly chosen, can eliminate surface runoff and minimize deep percolation water losses. The discharge from a ceramic emitter depends on the working pressure head and the ceramic hydraulic conductivity, so it is important to determine the optimal working levels for these two design parameters. In this work, it is confirmed that the HYDRUS-2D predictions of the cumulative infiltration and the horizontal wetting front are in good agreement with experimental results, and that the Hydrus-2D model can be used to accurately simulate soil water movement under subsurface irrigation with ceramic emitters. Additional simulations with HYDRUS-2D were used to study the effects of various design parameters (i.e. working pressure head and ceramic hydraulic conductivity) on emitter discharges in soils, deep percolation and soil wetting fronts. Results show that both the working pressure head and ceramic hydraulic conductivity have significant impact on the discharge of emitters in soil, and the deep percolation water losses. The emitter discharge in soil decreases with time and finally stabilizes. When the working pressure head and ceramic hydraulic conductivity are higher, the stable discharge (emitter discharge in soil at 120 h) is greater, and this situation may increase the risk of deep percolation. The relationship between the working pressure head, ceramic hydraulic conductivity, and stable discharge is developed as a power function. To satisfy the water requirements of trees with an active layer of root systems down to about 0–100 cm in the Loess Plateau in China and reduce the risk of deep percolation, it is recommended that the working pressure head should be 20–50 cm of water and the ceramic hydraulic conductivity should be between 0.1 and 1.9 cm h−1.

Emittance-controlled Ceramic Emitter for a Thermophotovoltaic

Emittance-controlled Ceramic Emitter for a Thermophotovoltaic

Simulation of soil water movement under subsurface irrigation with porous ceramic emitter

Subsurface irrigation has been achieved by using ceramic emitters, pitchers, pots and ceramic tubes, which have gained a certain degree of interest in arid regions due to their efficient use of water. Research on the formation of wetting patterns around the ceramic emitter is essential for the design of irrigation system. In this study, numerical simulations were carried out to investigate the effects of emitter installation method, emitter buried depth, emitter structural parameters, irrigation doses and initial soil water content on the wetting patterns in clay loam with Hydrus-2D. Finally, two field application experiments were conducted to test the practicality and reliability of simulation results. The simulation results were in good agreement with the experimental data. Results showed, emitter installation method had the least effect on the wetting pattern. A 25cm buried depth would be suit for irrigating vegetables, a 45cm deep buried depth would suit for irrigating fruit trees. The structure parameters had a significant effect on cumulative fluxes and horizontal wetting front, the structural parameters (emitter length is 7.00cm, emitter external diameter is 1.25cm, and emitter inner diameter is 0.60cm) would be a better fabricate parameters for ceramic emitter. Wetting front increased with increasing irrigation doses and initial water content. To prevent percolation, when the initial water content was high, it should be better to cut down the irrigation duration of ceramic emitter. The field results indicated that Hydrus-2D could be used to investigate the suitable parameters for ceramic emitter in subsurface irrigation systems and determine the suitable arrangement and operation mode of ceramic emitter.

Ceramic IR Emitter with Spectral Match to GaSb PV Cells for TPV

ABSTRACTA high temperature ceramic selective emitter for thermophotovoltaic (TPV) electric generators is described with a spectral match to GaSb IR cells. While solar cells generate electricity quietly and are lightweight, traditional solar cells are used with sunlight and only generate electricity during the day. Workers at JX Crystals invented the GaSb IR cell as a booster cell to demonstrate a solar cell conversion efficiency of 35%. JX Crystals now makes these IR cells. In TPV, these cells can potentially be used with flame heated ceramic emitters to generate electricity quietly day and night. One of the most important requirements for TPV is a good spectral match between the ceramic IR emitted and the IR PV cells. The first problem is to find, demonstrate, and integrate a doped ceramic IR emitter with a spectral match to these GaSb cells. Recently, nickel oxide and cobalt oxide doped MgO-based ceramics have been shown experimentally and theoretically to have spectral selectivity but no attempts have been made to integrate these ceramic IR emitters into a fully operational TPV generator. Herein, we review the history of TPV and note that a key to future progress will be the integration of an appropriate ceramic emitter with cells and a burner to demonstrate an operational TPV generator. Integrating TPV into a residential boiler is discussed as a potential future large volume commercial market.

Study of the hydroacoustic emitter based on the antisymmetric lamb wave in a piezoelectric ceramic plate

acteristics of the above waves that propagate in the piezoelectric ceramic plates in contact with liquid are well studied. However, note the absence of reliable data on the directional patterns of such emitters in liq� uid. This work is devoted to the analysis of the piezo� electric ceramic emitter based on the А 0 wave that propagates in the TsTS�19 piezoelectric ceramic material with the interdigital transducer at a central frequency of 98 kHz. To choose the optimal characteristics of the emit� ter, we theoretically study the parameters of the А0 wave in the system consisting of the TsTS�19 piezo� electric ceramic material and water.

Spectral Analysis of Transition Metal-Doped MgO "Matched Emitters" for Thermophotovoltaic Energy Conversion

A new, thermally excited Co/Ni-doped MgO ceramic emitter for TPV energy conversion is described in this work, and termed the “matched emitter” because its emissive power spectrum is very efficiently matched with the portion of the electromagnetic spectrum that can be converted directly into electrical energy by infrared responding GaSb photovoltaic cells. Ligand Field Theory calculations are used to estimate the crystal field splitting energies at high temperatures for Co and Ni-doped MgO matched emitters. Experimental measurements of the high temperature (1300–1400°C) emissive power spectrums for Co and Ni-doped MgO emitters are compared with predictions obtained from ligand field calculations for what is believed to be the first time. It was found that crystal field splitting energies of 10 Dq = 9070 cm−1 represented the “best fit” for the Co-doped MgO high temperature emissive power spectrum, and 10 Dq = 7950 cm−1 for the Ni-doped MgO spectrum. These values are only slightly lower than values reported for corresponding single crystal, transition metal doped laser materials that were measured at or well below room temperature.