Red Phosphorus Particles Research Articles

Red phosphorus infiltrated into porous C/SiOx derived from rice husks to improve its initial Coulomb efficiency in lithium-ion batteries

To overcome the poor initial Coulombic efficiency (ICE) of C/SiOx anode materials of lithium-ion batteries (LIBs) and promote its industrial application, porous C/SiOx materials have been fabricated by carbonization and activation of rice husks with H3PO4 as an activator. Then, red phosphorus (RP) is infiltrated on the surface and pore inner wall of porous C/SiOx to synthesize RP@C/SiOx using the evaporation-condensation method. In the RP@C/SiOx composite, SiP2 and SiP2O7 generated by the reaction between RP and SiOx particles successfully decrease the formation of inert Li2O and Li4SiO4 during the first Li+ intercalation process. Meanwhile, RP connects with C skeleton to form P-O and P-C bonds during the preparation process, which are conducive to the production of a thin dense solid electrolyte interphase layer. All of these are beneficial to enhance the ICE of C/SiOx. After infiltration of RP, the reversible capacity of porous C/SiOx increased from 435.2 mAh/g to 1147.4 mAh/g at 0.1 A/g, with an ameliorative ICE of 73.6% (51.02% for porous C/SiOx). Even at a higher current density of 2.0 A/g, the considerable specific capacity of 630.0 mAh/g can be obtained after 738.0 cycles.

Reactivity passivation of red phosphorus with thin plasma-deposited carbon coating

Red phosphorus, when exposed to humid environments in air, breaks down into toxic phosphine gas and acidic phosphorus species, presenting a challenge for many applications, such as flame retardants or pyrotechnic obscurants. We have developed and characterized a method of plasma-deposited carbon to form a nanometer-thick, chemically stable carbon layer on red phosphorus particles to suppress phosphine and acidic phosphorus production. Using a combination of XPS surface analysis and a novel IR headspace analysis method, we developed and quantified an understanding of the reaction of red phosphorus with water vapor and the suppression of decomposition products using plasma-deposited carbon coatings. Phosphine production, quantified by IR, was accompanied by the formation of surface POx species produced as the particles react with water vapor. Increasing plasma deposition time increased thickness and uniformity of graphitic carbon coating, corresponding to a marked decrease in phosphine generation and formation of surface POx species.

Scalable method for preparing multi-walled carbon nanotube supported red phosphorus nanoparticles as anode material in lithium-ion batteries

Nanoscale red phosphorus (RP) has attracted plenty of interest as an anode material for lithium-ion batteries (LIBs). However, current methods for preparing RP nanocomposite are energy intensive and dangerous. Here, we report a scalable method for preparing multi-walled carbon nanotube supported RP nanoparticles (RP NPs/MWNT) composite. RP lump is dissolved in ethylenediamine. Then RP NPs were generated after adding HCl. Through this environmentally safe and low energy-consumption method, uniform RP NPs (5 nm) are deposited on MWNT, forming RP NPs/MWNT composite. Such small RP particles buffer volume expansion and MWNT accelerates electron transfer during cycling, therefore enabling RP NPs/MWNT to deliver a high initial reversible capacity of 1780.2 mAh g−1 and a high capacity retention of 88.6% at 200 mA g−1 after 100 cycles. Our method can be applied to synthesizing various RP nanocomposites for LIBs and is easy to set up, inexpensive, rapid, accessible to factory.

Experimental Research in to the Expected Degree of Purification of Gas and Dust Emissions from Red Phosphorus Particles at the Laboratory Foam Filtration Plant

Experimental Research in to the Expected Degree of Purification of Gas and Dust Emissions from Red Phosphorus Particles at the Laboratory Foam Filtration Plant

A red phosphorus-graphite composite as anode material for potassium-ion batteries

Red phosphorus (RP) is a promising anode material for potassium-ion batteries because of its theoretical capacity of 865 mAh/g delivered at an average potential of 0.5 V vs. K+/K. However, its alloy reaction to form KP entails a volume expansion of 162% resulting in severe stresses that lead to SEI and electrode fracture, loss of electric contact, and ultimately reduced cycle life. Moreover, its low electronic conductivity (10−14 S/cm) limits rate capability. Here, we report an RP-graphite composite prepared by a two-step ball-milling procedure to control particle size and optimize carbon coating. Raman operando on graphite in the composite suggests that the carbon coating reversibly expands and contracts due to the volume expansion of RP particles. Electrodes prepared with the composite achieve high capacity (723 mAh/gP) at C/20 and retaining 75% at 5C. It also shows very good cycling stability, retaining more than 96% of the capacity after 100 cycles at 1C.

Low-Cost Electrocatalytic Layers for Hydrogen Evolution Reaction Based on Nickel and Cobalt Phosphides: Fabrication Via Codeposition-Annealing Route and XPS Characterization

In an attempt to mitigate the effects of climate changes, modern societies are facing a revolution in energy supply. Future economy will be increasingly dominated by carbon-free and renewable energy sources. In this context, hydrogen will play a fundamental role in the energy transition from fossil to green sources. It offers the possibility to smooth the intermittency typical of many renewable energy sources and it constitutes an ideal complement for batteries in the transport sector. Hydrogen can be easily produced employing water electrolysis, stored in large amounts and subsequently re-electrified in fuel cells. Efficient water electrolysis, however, makes use of noble metal electrocatalysts to lower the overpotential required for the Hydrogen Evolution Reaction (HER) to take place. Due to the limited availability and consequent high cost of noble metals, research is currently focusing on the development of low-cost alternative catalytic materials. One of the most studied electrocatalytic compounds are transition metal phosphides [1]. These materials present remarkable advantages over commonly used Pt based catalysts: comparable performances, lower cost, high abundancy and ease of manufacturing.In the present work, transition metal phosphides were fabricated through a simple and costless codeposition-annealing process. Amorphous Ni-P and Co-P alloys were codeposited with red phosphorus particles and subsequently annealed [2]. The annealing step was applied to promote the formation of intermetallics through interdiffusion between pure phosphorus particles and the metallic matrix. As a result, different phase pure metal phosphides were obtained. The most important advantage of this methodology is the possibility to overcome the compositional limit typical of electrodeposited phosphorus-based alloys. Elemental phosphorus codeposition allows to reach P concentrations higher than 50 % at., whereas simple Ni-P solid solution electrodeposition is compositionally limited to 25 % at. Enhancing P content is fundamental to obtain phosphorus rich compounds like Ni2P and Co2P, which are characterized by high catalytic activities for HER [3]. Furthermore, the technique allows to confine elemental P inside the coating during the annealing step. This peculiarity strongly optimizes material usage and it limits the presence of gaseous phosphorus, which is typical of many phosphorization processes used in literature to obtain metal phosphides [4] and it can result into the formation of the unstable white P allotrope.Obtained nickel and cobalt phosphides were characterized with different techniques (SEM, XRD, EDS) to assess their morphology, phase structure and chemical composition. A special emphasis was placed on XPS characterization. Thanks to its ability to analyze the first superficial layers of the coatings, XPS was employed to determine the chemical state of the elements present on the surface of the electrocatalysts. Being electrocatalysis an interfacial phenomenon, this allowed to link material surface properties with observed electrocatalytic performances.The electrocatalytic HER activity and stability of the different transition metal phosphides were tested in 0.5 M H2SO4. In all cases, remarkable results were obtained, with the lowest overpotential obtained in the case of Co-P/P codeposition and subsequent annealing at 290 °C: 62 mV vs. RHE at a current density of 10 mA/cm2 in 0.5 M H2SO4 solution. This result is in line with the literature available on cobalt phosphides as electrocatalysts [5].[1] P. Xiao et al., Adv. Energy Mater. 5, 1500985 (2015)[2] R. Bernasconi et al., ACS Appl. Energy Mater. 3(7), 6525–6535 (2020)[3] A. R. J. Kucernak et al., J. Mater. Chem. A 2, 17435 (2014)[4] X. Wang et al., Angew. Chem. 54(28), 8188 (2015)[5] Saadi et al., J. Phys. Chem. C 118(50), 29294–29300 (2014)

Nickel and Cobalt Phosphides Fabricated through a Codeposition-Annealing Technique As Low-Cost Electrocatalytic Layers for Efficient Hydrogen Evolution Reaction

In the perspective of sustainable development, future economy will be increasingly dominated by carbon-free and renewable energy sources. In this context, hydrogen will play a fundamental role in the energy transition from fossil to green sources. Hydrogen can be easily produced employing water electrolysis, stored in large amounts and subsequently re-electrified in fuel cells. It offers the possibility to smooth the intermittency typical of many renewable energy sources and it constitutes an ideal complement for batteries in the transport sector. Efficient water electrolysis, however, makes use of noble metal electrocatalysts to lower the overpotential required for the Hydrogen Evolution Reaction (HER) to take place. Due to the limited availability and consequent high cost of noble metals, research is currently focusing on the development of low-cost alternative catalytic materials. One of the most studied electrocatalytic compounds are transition metal phosphides [1]. These materials present remarkable advantages over commonly used Pt based catalysts: lower cost, high abundancy and ease of manufacturing. In many cases, phosphides offer performances comparable to the noble metal electrocatalysts.In the present work, transition metal phosphides were fabricated through a simple and costless codeposition-annealing process. Amorphous Ni-P and Co-P alloys were codeposited with red phosphorus particles and subsequently annealed. The annealing step was applied to promote the formation of intermetallics and the interdiffusion between pure phosphorus particles and the metallic matrix. As a result, different phase pure metal phosphides were obtained. The most important advantage of this methodology is the possibility to overcome the compositional limit typical of electrodeposited phosphorus-based alloys [2]. Elemental phosphorus codeposition allows to reach P concentrations higher than 50 % at., whereas simple Ni-P solid solution electrodeposition is compositionally limited to 25 % at. Enhancing P content is fundamental to obtain phosphorus rich compounds like Ni2P and Co2P, which are characterized by high catalytic activities for HER [3]. Another interesting benefit of the technique presented is the confinement of elemental P inside the coating during the annealing step. This peculiarity strongly optimizes material usage and it limits the presence of gaseous phosphorus, which is typical of many phosphorization processes used in literature to obtain metal phosphides [4] and it can result into the formation of the unstable white P allotrope.Specifically, Ni-P and Co-P were codeposited with red P particles and process conditions were optimized to maximize elemental P particles concentration. Annealing temperature and duration were varied to investigate their influence on final electrocatalytic perfrormances. Characterization techniques like XRD, SEM, EDS, cross-sectional analysis and XPS were used to determine phase composition of the materials obtained and to characterize their morphology. The electrocatalytic HER activity and stability of the different transition metal phosphides were tested in 0.5 M H2SO4. In all the cases, remarkable results were obtained, which matched up well with present existing literature where similar electrocatalysts have been fabricated through different methods [5]. The lowest overpotential was obtained in the case of Co-P/P codeposition and subsequent annealing at 290 °C: 62 mV vs. RHE at a current density of 10 mA/cm2 in 0.5 M H2SO4 solution.[1] P. Xiao et al., Adv. Energy Mater. 5, 1500985 (2015)[2] R. L. Zeller and U. Landau, J. Electrochem. Soc. 139(12), 3464 (1992)[3] A. R. J. Kucernak et al., J. Mater. Chem. A 2, 17435 (2014)[4] X. Wang et al., Angew. Chem. 54(28), 8188 (2015)[5] Z. Pu et al., Chem.Mater. 26(15), 4326 (2014)

Electrochemo-Mechanical Properties of Red Phosphorus Anodes in Lithium, Sodium, and Potassium Ion Batteries

Summary Red phosphorus (RP) is a promising anode material for alkali-ion batteries due to a high theoretical capacity at low potentials when alloying with lithium, sodium, and potassium. Most alloy anode materials display large volume changes during cycling, which can lead to particle fracturing, low Coulombic efficiency, loss of electrical contact, and ultimately poor cycle life. In this paper we outline, through comprehensive electrochemo-mechanical characterization and modeling of the cycling stresses, why RP can be cycled at high current densities without fracture. Application of in situ nanoindentation and powder compression allows for measurement of the elastic, plastic, and fracture properties of RP. In situ transmission electron microscopy observation with extreme conditions (anisotropic ion diffusion and high current density) was used to validate the model, observing no catastrophic failure of RP particles. Electrochemo-mechanical characterization with geometry and stress modeling allows for predictions to be made for application of RP in alkali-ion batteries.

Electrochemomechanical Properties of Red Phosphorus with Lithium, Sodium and Potassium

Red phosphorus is a promising anode material thanks to its ability to form alloys with lithium, sodium and potassium, thus achieving high theoretical capacity (2596 mAh g-1 with Li and Na and 865 mAh g-1 with K). However, it suffers from its low electronic conductivity and a huge volume expansion that leads to the formation of stress with consequent fracture and pulverization of the particle. In this work, red phosphorus particles have been analyzed with in-situ TEM techniques in order to study the mechanism of the crack formation during the volume expansion with lithium, sodium and potassium. This experiment is coupled with computational modelling of the particles and the simulation of the diffusion of the ions through the particles to understand the development of stresses that can lead to the nucleation of the crack and the failure of the particle.

Novel Synthesis of Red Phosphorus Nanodot/Ti3C2Tx MXenes from Low-Cost Ti3SiC2 MAX Phases for Superior Lithium- and Sodium-Ion Batteries.

MXenes, synthesized from MAX, have emerged as new energy-storage materials for a good combination of metallic conductivity and rich surface chemistry. The reported MXenes are synthesized mostly from Al-based MAX. It is still a big challenge to synthesize MXenes from abundant Si-based MAX because of its strong Ti-Si bonds. Here, we report for the first time a high-energy ultrasonic cell-crushing extraction method to successfully prepare Ti3C2Tx MXenes from Si-based MAX using a single low-concentration etchant. This novel strategy for preparing MXenes has a high extraction efficiency and is a fast preparation process of less than 2 h for selective etching of Si. Furthermore, through the high-energy ball-milling technology, unique P-O-Ti bonded red phosphorus nanodot/Ti3C2Tx (PTCT) composites were successfully prepared, which enable superior electrochemical performance in lithium- and sodium-ion batteries because of the double-morphology structure, where the amorphous nano red phosphorus particles were strongly absorbed to Ti3C2Tx MXene sheets, facilitating the transport of alkali ions during cycling processes. This novel synthesis method of Ti3C2Tx MXenes from Si-based MAX and unique P-O-Ti bonded PTCT composites opens a new door for preparing high-performance MXene-based materials and facilitating the development of low-cost MXenes and other two-dimensional materials for next-generation energy storage.

Vapor Deposition Red Phosphorus to Prepare Nitrogen-Doped Ti3C2Tx MXenes Composites for Lithium-Ion Batteries.

MXenes have great application prospect in energy storage fields due to a series of special physicochemical properties. However, the application of MXenes is greatly limited due to low intrinsic capacity. Here, through spray drying and vapor deposition methods, N-doped Ti3C2Tx and phosphorus composites (N-Ti3C2Tx/P) were prepared for the first time. The red phosphorus particles were absorbed to a walnut-like N-Ti3C2Tx matrix, facilitating the transport of Li+ and electrons. When used as anodes for lithium-ion batteries, the battery can cycle up to 1040 cycles with a high stable capacity of 801 mAh/g at 500 mA/g. Impressively, there is an obvious increase of capacity in the subsequent cycles at higher current density due to the increment of interlayer spacing of Ti3C2Tx nanosheets. XPS measurements confirm that the Ti-O-P bond was formed in the composites, granting the robust structure of the composites and leading to superior performances during cycling. The facile synthesis method of red phosphorus by vapor deposition will facilitate the development of other 2D materials combined with high-capacity red phosphorus for energy storage.

Effect of the Particle-Size Distribution on the Electrochemical Performance of a Red Phosphorus-Carbon Composite Anode for Sodium-Ion Batteries

Sodium-ion batteries will have an important role as a complement to lithium-ion in a future where lithium or cobalt, two critical elements for lithium-ion batteries, become scarce or prohibitively expensive. Red phosphorus (RP) is a promising candidate as an anode for sodium-ion batteries because of its low potential and high specific capacity. Its main disadvantage is its 490% volumetric expansion during sodiation. This leads to particle pulverization and substantial reduction of the cycle life. Furthermore, RP has an extremely low electronic conductivity of 10-14 S cm-1. Both issues have been previously addressed by ball milling RP with a carbon matrix. This decreases the RP particle size and also forms a more electronically conductive composite. However, it is challenging to determine the RP particle size independent of the size of the composite particles. Consequently, little is known about how much the RP particle size must be reduced to improve anode performance. We quantified the relationship between the RP particle-size distribution and its cycle life for the first time by separating the ball milling process into two steps. An initial wet ball milling is used to control the RP particle-size distribution, which is measured via dynamic light scattering. This is followed by a dry milling step to produce RP-graphite composites. We found that wet milling breaks apart the largest RP particles in the range of 2 to 10 µm decreases the Dv90 from 1.85 to 1.26 µm and significantly increases the cycle life of the RP. The RP with a Dv90 of 0.79 µm mixed with graphite for 48h delivered 1,354 mA h g-1 with high coulombic efficiency (>99%) and cyclability (88% capacity retention after 100 cycles). Furthermore, we determined that the length of time of the second milling step affects the uniformity of the carbon distribution in the composite. Photoelectron spectroscopy and transmission electron microscopy confirms the successful formation of a carbon coating, thus improving the performance of the resulting material. These results are an important step in the development of cyclable, high-capacity anodes for sodium-ion batteries. Figure 1

Effect of the Particle-Size Distribution on the Electrochemical Performance of a Red Phosphorus-Carbon Composite Anode for Sodium-Ion Batteries.

Red phosphorus (RP) is a promising candidate as an anode for sodium-ion batteries because of its low potential and high specific capacity. It has two main disadvantages. First, it experiences 490% volumetric expansion during sodiation, which leads to particle pulverization and substantial reduction of the cycle life. Second, it has an extremely low electronic conductivity of 10–14 S cm–1. Both issues can be addressed by ball milling RP with a carbon matrix to form a composite of electronically conductive carbon and small RP particles, less susceptible to pulverization. Through this procedure, however, the resulting particle-size distribution of the RP particles is difficult to determine because of the presence of the carbon particles. Here, we quantify the relationship between the RP particle-size distribution and its cycle life for the first time by separating the ball-milling process into two steps. The RP is first wet-milled to reduce the particle size, and then the particle-size distribution is measured via dynamic light scattering. This is followed by a dry-milling step to produce RP–graphite composites. We found that wet milling breaks apart the largest RP particles in the range of 2–10 μm, decreases the Dv90 from 1.85 to 1.26 μm, and significantly increases the cycle life of the RP. Photoelectron spectroscopy and transmission electron microscopy confirm the successful formation of a carbon coating, with longer milling times leading to more uniform carbon coatings. The RP with a Dv90 of 0.79 μm mixed with graphite for 48 h delivered 1354 mA h g–1 with high coulombic efficiency (>99%) and cyclability (88% capacity retention after 100 cycles). These results are an important step in the development of cyclable, high-capacity anodes for sodium-ion batteries.

Fabrication of graphene-modified nano-sized red phosphorus for enhanced photocatalytic performance

In this present paper, nano-sized red phosphorus particles (NRP) were prepared through a mechanical milling and ultrasonic flotation method. The as-prepared red phosphorus nano particles were loaded on the surface of graphene. The residual oxidative bonds on the surfaces of the red phosphorus and graphene were carried out to form effective interface contact. The present results indicated that comparing with large size commercial red phosphorus particles, NRP possesses higher specific surface area and photocatalytic activity. The NRP/graphene composite shows a great adsorption capacity for rhodamine (RhB). Meanwhile, its visible-light-driven decolorization performance for RhB was 5 times higher than that of pure NRP, which can decolorize of RhB completely in only 3min. So, NRP/graphene composite photocatalyst possess great potential in the area of environment organic pollution purge. Electrochemical impedance spectra (EIS) and Mott-Schottky spectra results of these samples indicated that a downward bend of the conduction band of NRP was formed when it contacted with graphene, resulting in a rapid electron injection into the graphene. Therefore, the probability of recombination of photogenerated carriers was inhibited effectively, thus enhanced the overall photocatalytic performance of the composite material.

Carbothermic reduction synthesis of red phosphorus-filled 3D carbon material as a high-capacity anode for sodium ion batteries

Phosphorus is an attractive negative electrode material for sodium ion batteries due to its high theoretical specific capacity of 2596mAhg−1. However, it suffers poor conductivity (10−12Sm−1), slow reaction dynamics, and large volume expansion (~440%) during the sodiation process, leading to rapid capacity decay upon cycling. Great attention has been devoted to improving the electrical conductivity via mixing phosphorus particles with conductive carbon materials, yet little emphasis has been placed on addressing the volume expansion issue, which may leads to the loss of electrical contact between the active material and the current collector, and the sequent deterioration of the overall electrochemical performance. Here, we demonstrate a carbothermic reduction method to fabricate ultrafine red phosphorus particles (~10nm) embedded in a three-dimensional carbon framework, in which numerous interconnected nanopores are generated accompanied by the carbonization of polyethylene glycol. During discharge/charge processes, nanosized phosphorus particles accommodate the large stress without cracking, and decrease the diffusion length, as well as connect strongly with carbon framework, resulting in an improved conductivity, a reversible specific capacity of 1027mAhg−1 (at 0.2C) and high capacity retention of 88% over 160 cycles.

Chemically Bonded Phosphorus/Graphene Hybrid As a High-Performance Anode for Lithium- and Sodium-Ion Batteries

We report a red phosphorus-graphene nanosheet (P-G) hybrid as an anode material for lithium- and sodium-ion batteries. The hybrid was synthesized through a facile ball milling method where graphene stacks are exfoliated into graphene nanosheets and hybridized with red phosphorus particles during the process. The graphene nanosheets function as the conductive matrix in the hybrid and P-O-C chemical bonds are found between phosphorus and carbon in the hybrid, both of which facilitate creating robust and intimate contact between the graphene nanosheets and phosphorus and thus preventing loss of electrical contact by phosphorus particles during cycling. Benefiting from this structure, the P-G hybrid anode in lithium ion battery exhibits a high initial specific capacity of 2517 mAh/g at a current density of 130 mA/g and excellent cycling stability at ambient temperature. Moreover, even at elevated temperature of 60 oC, the hybrid anode delivers a high initial capacity of 2362 mAh/g at a current density of 260 mA/g and exhibits much better capacity retention of 74% after 200 cycles than conventional phosphorus-carbon additive hybrid. Also, the hybrid, used as anode for sodium-ion battery, delivers a high reversible capacity of 2077 mAh/g with excellent cycling stability (1700 mAh/g after 60 cycles) and high Coulombic efficiency (>98%). The attractive cycling stability at a wide range of temperature and its straightforward preparation approach of the new P-G hybrid make it a promising anode candidate for lithium- and sodium-ion batteries.We report a red phosphorus-graphene nanosheet (P-G) hybrid as an anode material for lithium- and sodium-ion batteries. The hybrid was synthesized through a facile ball milling method where graphene stacks are exfoliated into graphene nanosheets and hybridized with red phosphorus particles during the process. The graphene nanosheets function as the conductive matrix in the hybrid and P-O-C chemical bonds are found between phosphorus and carbon in the hybrid, both of which facilitate creating robust and intimate contact between the graphene nanosheets and phosphorus and thus preventing loss of electrical contact by phosphorus particles during lithiation/delithiation. Benefiting from this structure, the P-G hybrid anode in lithium ion battery exhibits a high initial specific capacity of 2517 mAh/g at a current density of 130 mA/g and excellent cycling stability at ambient temperature. Moreover, even at elevated temperature of 60 oC, the hybrid anode delivers a high initial capacity of 2362 mAh/g at a current density of 260 mA/g and exhibits much better capacity retention of 74% after 200 cycles than conventional phosphorus-carbon additive hybrid. Also, the hybrid, used as anode for sodium-ion battery, delivers a high reversible capacity of 2077 mAh/g with excellent cycling stability (1700 mAh/g after 60 cycles) and high Coulombic efficiency (>98%). The attractive cycling stability at a wide range of temperature and its straightforward preparation approach of the new P-G hybrid make it a promising anode candidate for lithium- and sodium-ion battery.

Phosphorus‐Based Nanothermites: A New Generation of Pyrotechnics Illustrated by the Example of n‐CuO/Red P Mixtures

AbstractThe use of aluminium nanoparticles (e.g. Al 50P) with various metallic oxides to prepare superthermites was reported in numerous recent papers. These compositions have exceptional energetic performances, but their fabrication cannot be scaled up due to the difficulty in producing or supplying aluminium nanopowders. The use of red phosphorus as an alternative reducing agent in nanothermite compositions was found to be very promising. Surprisingly, although this substance is a component of many explosive compositions, it was never tested with metallic oxide nanoparticles. In a preliminarily study, the reactivity of different metallic oxides with red phosphorus was screened. These tests led to classify the oxides according to their combustion potential, by ascending order: NiO<Fe2O3 $\rm{ \ll }$ CuO $\rm{ \ll }$ PbO2. The CuO/P mixture possesses an impressive reactivity, and its combustion residues are less hazardous than those formed with PbO2 insofar as lead derivatives are generally more toxic than their copper counterparts. CuO‐based P‐nanothermites were prepared by physically mixing copper(II) oxide nanoparticles with micrometre‐sized red phosphorus particles. The phosphorus content was varied from 16 to 50 wt.‐% in order to investigate the effect of the mass ratio on the reactivity of CuO/P materials. The impact sensitivity of CuO/P nanothermites is moderate (27–39 J), but their friction (<5–8 J) and electrostatic discharge sensitivities (<0.12–0.21 mJ) are extremely high. The combustion of P‐nanothermites (P‐NT) gives droplets of molten copper with a typical fractal structure after cooling down.

Design and characteristic analysis of a new nozzle for preparing microencapsulated particles by RESS

A new nozzle was designed for the technology of making microencapsulated particles by rapid expansion of supercritical solution (RESS). The design is based on the theory of gas dynamics in which the potential energy of high stagnation pressure is converted totally into effective velocity energy. Therefore, a high momentum of the exit jet can be obtained for improving the capability of removing molten debris quickly. Furthermore, the microencapsulated red phosphorus particles were prepared by RESS with the new nozzle, and the structure and property of the microencapsulated red phosphorus particles were characterized by the SEM images, droplet concentration distributions, and moisture absorption ratio. The results show that the process can effectively encapsulate the red phosphorus particles with the paraffin.

Fabrication of fine microcapsulated red phosphorus particles by SCF-RESS with a new structure nozzle

A novel process of preparing microencapsulated red phosphorus particles by rapid expansion of supercritical fluids (RESS) was tested, in which a new kind of nozzle and supercritical CO2 as a solvent were used. The structure of the microencapsulated red phosphorus particles were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). These results show that red phosphorus particles can be effectively encapsulated with paraffin by using the method. At the same time, how the moisture absorption ratio of microencapsulated red phosphorus particles was dependent on the experimental conditions was further investigated. The results suggest that paraffin-microencapsulated red phosphorus particles show a lower moisture absorption ratio within the experimental conditions of the extraction column and nozzle temperature of 120°C, extraction column pressure of more than 16 MPa, and a mass flow of core particles (0.5 g/min).

ChemInform Abstract: Suspension Electrodeposition of Phosphorus and Copper.

AbstractThe electrodeposition of red phosphorus particles and Cu from a suspension of red phosphorus in a CuSO4/H2SO4 aqueous solution is studied as a function of suspension concentration, current density, temp., solution additives, and particle size.