Post-treatment Process Research Articles

Manipulation of the In Situ Nitrogen‐Vacancy Doping Efficiency in CVD‐Grown Diamond

Herein, the in situ generation of nitrogen‐vacancy (NV) centers in diamond during chemical vapor deposition (CVD) is investigated depending on the electric‐field strength at the sample position. The alteration of the electric‐field strength is induced by changing the resonance conditions within the resonator cavity while keeping the growth input variables constant. The electric‐field strength distribution is obtained by simulation results. During the growth experiments, optical‐emission spectroscopy data is collected, which shows the impact of the electric‐field strength on the radical concentrations within the plasma and the gas temperature. Through the reduction of the electric‐field strength, the synthesis of thick, high‐quality, nitrogen‐doped diamond without the formation of a polycrystalline rim around the sample edges and the twinning‐induced growth of polycrystalline grains was accomplished. Therefore, a reduced internal and more homogeneous stress distribution is achieved. Furthermore, significant influences on the in situ NV doping are discovered. In addition to a considerable gain of the in situ NV generation, also a major enhancement of the in situ incorporation efficiency of NV centers in comparison to centers up to almost 3% is observed. Depending on the application, this makes posttreatment processes for additional NV generation dispensable.

A template-free I2-assisted pyrolysis strategy to synthesize coral-like nitrogen-doped carbon with a regulated hierarchical porous structure toward efficient oxygen reduction

Construction of hierarchical porous structures in N-doped carbon (N/C) catalysts is of great significance to promote the reaction kinetics during the electrocatalysis. However, many existing template methods used to synthesize porous carbon networks are usually complicated in operation and might undermine the catalytic active sites of N/C in the post-treatment processes (e.g., templates removal under caustic conditions). Herein, a template-free I2-assisted pyrolysis strategy is developed to regulate the morphology and porous structure of N/C thermally derived from zeolitic imidazolate frameworks. Gas-phase I2 is controllably adsorbed (by adjusting the adsorption temperature) into the porous structure of the zeolitic imidazolate frameworks and then corrodes the frameworks during the pyrolysis. The as-synthesized N/C without any post-treatment features a coral-like morphology, a large pore volume, and a meso/macropore-dominated porous structure, rendering excellent electrocatalytic performance toward oxygen reduction reaction with a half-wave potential of 0.868 V vs. RHE due to the effective exposure of active sites and enhanced mass-transfer capability. A Mg-air battery assembled with the as-synthesized coral-like N/C as the cathode catalyst exhibits an excellent peak power density of 123 mW cm−2 at 0.73 V. This I2-assisted pyrolysis strategy could be widely applicable for regulating the porous structure and morphology of carbon materials derived from different porous precursors for energy conversion and storage applications.

Fundamental and recent progress on the strengthening strategies for fabrication of polyacrylonitrile (PAN)-derived electrospun CNFs: Precursors, spinning and collection, and post-treatments

Thus far, polyacrylonitrile (PAN)-derived electrospun CNFs with smooth and uniform cross-sections with various morphologies and structures were massively fabricated. There is no denying the fact that the mechanical strength of CNFs is restricted which has been the main obstacle toward being highly applicable for a broad range of applications. Based on recent fundings, these limitations can be simply overcome over different synthesis stages consisting of the precursor strategy, spinning and collection methods, post-treatment processes such as stretching and aligning, and complex post-thermal procedures like stabilization and carbonization. This paper aims to fundamentally review the mechanical characteristics of CNF nanocomposites and systematically summarize the possible strengthening strategies for further development over every stage of the fabrication procedure.

Production and Upgrading of Recovered Carbon Black from the Pyrolysis of End-of-Life Tires

Increasing awareness regarding fossil fuel dependence, waste valorization, and greenhouse gas emissions have prompted the emergence of new solutions for numerous markets over the last decades. The tire industry is no exception to this, with a global production of more than 1.5 billion tires per year raising environmental concerns about their end-of-life recycling or disposal. Pyrolysis enables the recovery of both energy and material from end-of-life tires, yielding valuable gas, liquid, and solid fractions. The latter, known as recovered carbon black (rCB), has been extensively researched in the last few years to ensure its quality for market applications. These studies have shown that rCB quality depends on the feedstock composition and pyrolysis conditions such as type of reactor, temperature range, heating rate, and residence time. Recent developments of activation and demineralization techniques target the production of rCB with specific chemical, physical, and morphological properties for singular applications. The automotive industry, which is the highest consumer of carbon black, has set specific targets to incorporate recycled materials (such as rCB) following the principles of sustainability and a circular economy. This review summarizes the pyrolysis of end-of-life tires for the production of syngas, oil, and rCB, focusing on the process conditions and product yield and composition. A further analysis of the characteristics of the solid material is performed, including their influence on the rCB application as a substitute of commercial CB in the tire industry. Purification and modification post-treatment processes for rCB upgrading are also inspected.

Temperature-Controlled Selectivity of Hydrogenation and Hydrodeoxygenation of Biomass by Superhydrophilic Nitrogen/Oxygen Co-Doped Porous Carbon Nanosphere Supported Pd Nanoparticles.

Selective hydrogenation and hydrodeoxygenation (HDO) of biomass to value-added products play a crucial role in the development of renewable energy resources. However, achieving a temperature-controlled selectivity within one catalytic system while retaining excellent hydrogenation and HDO performance remains a great challenge. Here, nitrogen/oxygen (N/O) co-doped porous carbon nanosphere derived from resin polymer spheres is synthesized as the host matrix to in situ encapsulate highly dispersed Pd nanoparticles (NPs). Through N/O co-doping, the defects on the surface of carbon structure can serve as active sites to promote substrate adsorption. After a facile H2 O2 post-treatment process, the presence of abundant carboxyl groups on the porous carbon nanospheres can act as acidic sites to replace the use of acidic additives in the HDO process. Additionally, the increased surface oxygen-containing groups improve hydrophilicity to disperse catalysts in aqueous solutions. Owing to the unique highly dispersed Pd NPs and abundant surface defects, the Pd@APF-H2 O2 (2.3nm) catalysts exhibit excellent catalytic activity and temperature-controlled selectivity for hydrogenation and HDO products of biomass-derived vanillin.

Insight into Factors Influencing Thermal Oxidation of Iridium Oxide Electrode: Thermostatic Post-Treatment Temperature

pH detection of strict environments such as deep sea environment, extremely acid or alkaline environment etc. put forward high requirements for pH monitoring electrode. In this paper, the IrOx electrodes prepared by cyclic thermal oxidation and quenching process (CHQ) went through thermostatic posttreatment process, i.e., heat treatment at the temperature of 400 °C, 500 °C, 600 °C for 0.5 h with furnace cooling to room temperature further. Aiming at filtrating an optimal posttreatment process and improving the comprehensive properties of the IrOx electrodes, the E-pH relationship, potential-time dependence tests, and long-term stability tests were carried out. Further characterizations including surface morphologies, surface roughness, surface crystal qualities, and surface compositions were examined through advanced detection methods. The results indicate that the IrOx electrode went through thermostatic posttreatment at 400 °C has larger surface roughness and relatively smaller cracks, implying the increasement in active surface area for electrode reaction. Optimal percentage of Ir4+and Ir3+ revealed by the X-ray photoelectron spectroscopy (XPS), better crystal quality shown by Raman spectroscopy, relief of tensile stress in the surface film demonstrated by (X-ray diffraction) XRD and Raman could account for the excellent performance of the posttreatment IrOx electrode.

Surface treatment of magnetron-sputtered tantalum pentoxide coatings and its effect on the phenotype and function of immune cells in vitro

The effect was analyzed of surface treatment by argon ions and electron beam on the properties of tantalum pentoxide coatings deposited by reactive magnetron sputtering and the treatment’s correlation with immune cells response. The characteristics of the coatings were determined by means of energy dispersive X-ray (EDX) scanning electron microscopy (SEM), X-ray photoemission spectroscopy (XPS), and atomic force microscopy (AFM). The results demonstrate that the electron-irradiation post-treatment process stimulates the adhesive potential and phagocytic activity of antigen-presenting cells.

Research and applications of additive manufacturing technology of SiC ceramics

<p indent="0mm">Silicon carbide (SiC) ceramic material shows significant application prospects in engineering and technical fields, such as aerospace, nuclear energy, and automobile industry engineering, due to its excellent mechanical, thermal, and optical properties. It is also key to the breakthrough of national scientific research and important strategic equipment. In recent years, the requirement of high-performance SiC ceramic components with complicated shapes, such as lightweight space optical mirrors, is becoming increasingly stringent, pushing the need for ceramic processing techniques. Traditional manufacturing techniques for SiC ceramic components include slip casting, isostatic pressing, and injection molding, etc. However, these processing methods have certain restrictions, including the requirement of molds and tools, time-consuming steps, high cost, and incapability to prepare SiC ceramic parts with complex shapes and arbitrary geometries. Additive manufacturing (AM) technology has provided a new development direction for the preparation of SiC ceramic. Different from the conventional processing methods, AM is performed in a layer-by-layer fashion to fabricate the components from a computer-aided design model. It theoretically allows the production of complex-shaped SiC ceramic parts without the requirement of molds, thus overcoming the shortcomings of the conventional methods in fabricating complicated ceramic components. The AM technique has become an effective way to achieve lightweight SiC ceramic formation and integration of complex SiC ceramic components. Currently, the AM of SiC ceramics has become a research hotspot in this field. In this review, the recent advances in the research and applications of SiC ceramics prepared by AM are systematically summarized and discussed, including the material design and fabrication methods, processes and equipment, post-processing technology, finite element simulation, performance evaluation, and desired applications. After briefly introducing the general research ideas and expected results of SiC ceramics via additive manufacturing, the design and preparation methods of AM-based SiC materials, including SiC powder, slurry/paste, filament, and laminate, are described in detail. Subsequently, the common AM process of SiC ceramics is introduced, including selective laser sintering, three-dimensional printing, stereolithography, direct ink writing, fused deposition modeling, and laminated object manufacturing. Further, post-treatment processes of the green body for AM-based SiC ceramics are presented, including carbonization, liquid/gas silicon infiltration, chemical vapor infiltration, and precursor impregnation and pyrolysis. In addition, this paper summarizes the finite element simulation of AM and post-treatment process for SiC ceramics and illustrates the performance evaluation methods of SiC ceramic components, including their mechanical, thermal, and optical performances. Typical applications of AM-based SiC ceramic components are elaborated as well. Finally, the outstanding challenges, future directions, and potential perspectives related to AM-prepared SiC ceramics are proposed. In the future, the AM-prepared SiC components will develop toward the advanced directions, such as the SiC ceramics with micro- or macroscale structures, lightweight SiC ceramics, the application of SiC composite material, and the material-structure-function combination for SiC ceramics. The purpose of this paper is to provide a significant reference for the research of complex SiC ceramic components fabricated via AM.

Effect of UV Irradiation on Optical Properties of Water-Based Synthetic Zinc Selenide Quantum Dots

ZnSe quantum-dots were synthesized in an aqueous system and UV irradiation was introduced as a post-treatment process. The synthesis temperature was varied from 25 oC to 90 oC, and the surface of the nano powder was stabilized using different ligands such as glutathione (GSH), 3-mercaptopropionic acid (MPA) and thioglycolic acid (TGA). Then, the effect of UV irradiation on the structure and the absorption/ emission properties of the nano powder were investigated. As the UV light was irradiated, the PL intensity of the quantum dots increased. UV irradiation for 16 h increased the PL intensity of the synthesized quantum dots at room temperature to the level of those at 90 oC. Particle aggregation was not found with UV irradiation of at least 24 h. XRD patterns confirmed that the UV irradiation released sulfur from the GSH, inducing the formation of the ZnSe/ZnS composite-typed nano powders. The luminescence characteristics of the GSH or TGA-added quantum dots were enhanced by UV irradiation regardless of temperature, while MPA-added quantum dots were not significantly affected by UV irradiation. The post-treatment process with UV irradiation showed the possibility that even ZnSe quantum dots, which are synthesized at low temperature and have low luminescence intensity, can have luminescence characteristics comparable to those of high-temperature synthesis.

Recycling chains for lithium-ion batteries: A critical examination of current challenges, opportunities and process dependencies.

Lithium-ion batteries (LIBs) show high energy densities and are therefore used in a wide range of applications: from portable electronics to stationary energy storage systems and traction batteries used for e-mobility. Considering the projected increase in global demand for this energy storage technology, driven primarily by growth in e-vehicles, and looking at the criticality of some raw materials used in LIBs, the need for an efficient recycling strategy emerges. In this study, current state-of-the-art technologies for LIB recycling are reviewed and future opportunities and challenges, in particular to recover critical raw materials such as lithium or cobalt, are derived. Special attention is paid to the interrelationships between mechanical or thermal pre-treatment and hydro- or pyrometallurgical post-treatment processes. Thus, the unique approach of the article is to link processes beyond individual stages within the recycling chain. It was shown that influencing the physicochemical properties of intermediate products can lead to reduced recycling rates or even the exclusion of certain process options at the end of the recycling chain. More efforts are needed to improve information and data sharing on the exact composition of feedstock for recycling as well as on the processing history of intermediates to enable closed loop LIB recycling. The technical understanding of the interrelationships between different process combinations, such as pyrolytic or mechanical pre-treatment for LIB deactivation and metal separation, respectively, followed by hydrometallurgical treatment, is of crucial importance to increase recovery rates of cathodic metals such as cobalt, nickel, and lithium, but also of other battery components.

Influence of Al2O3 platelets addition on ceramic slurry and local flow induced platelets alignment in ceramic mask stereolithography process

Ceramic mask stereolithography can fabricate ceramic parts with complex macrostructures and specific microstructures. Adding the two-dimensional material of alumina platelet crystal to the slurry make this technology possible to print the nacre like “brick-mortar” bionic microstructure ceramics or textured ceramics. However, how the curable ceramic slurry added with the platelets affects the ceramic mask stereolithography process, and how to directly and effectively orient the platelets in the slurry are still needed to be analyzed and solved. This investigation found that without relying on the shear force generated by the slurry scraper, the platelets in the slurry can be directly oriented by the gradient shear stress induced by the local slurry laminar flow during the positioning of the platform. With the increase of the platelets content, the viscosity of the slurries decreased. Since the platelets had fewer scattering effects on ultraviolet light, the increase of the platelets content could increase the curing thickness. In the post-treatment process, compared with the green part without platelets, the shrinkage in the X-Y direction of the green part with oriented platelets was reduced, and the shrinkage in the Z direction was increased. The 50 vol% total solid content slurry with the platelets content of 5 vol% – 20 vol% could be printed through mask stereolithography. The local flow induced alignment effect of the platelets decreased as the solid content of the platelets increased.

Tunable thermoresponsive UCST-type alkylimidazolium ionic liquids as a draw solution in the forward osmosis process

Recently, forward osmosis (FO) has been attracting attention as a new energy-saving water treatment technology. To put the FO process to practical use, it is indispensable to develop the optimum draw solution (DS) and construct its low energy regeneration process. In this study, various types of alkylimidazolium tetrafuluoroborate salts were synthesized, and their capabilities as novel thermoresponsive DSs for the FO desalination process were assessed using solution parameters such as phase diagram and osmotic pressure. The carbon number of a cation tunables the upper critical solution temperature (UCST)-point of alkylimidazolium-based ionic liquids' phase transition temperature. Considering the effect on the membrane material, the cooling temperature according to the climate, and the temperature range of low-grade waste heat in FO process, the ionic liquids having UCST points in the range of 25 °C to 50 °C, 1-pentyl-3-methylimidazolium tetrafluoroborate ([C5mim][BF4]), 1-pentyl-2,3-dimethylimidazolium tetrafluoroborate ([C5dmim][BF4]), 1-butyl-3-ethylimidazolium tetrafluoroborate ([C4eim][BF4]) and 1,3-dipropylidazolium tetrafluoroborate ([C3pim][BF4]), were judged to be suitable. The osmolalities of its water mixture varied with temperature, with a larger value at 50 °C than at 25 °C, with ILs with a lower UCST point exhibiting higher osmolality. The concentrated phase of [C4eim][BF4], which was phase-separated at 25 °C, had an osmotic pressure at 50 °C that was 1.6 times that of seawater, implying that it might be used as a DS in the FO seawater desalination process. Moreover, the osmolality at 25 °C dilutive phases of the [C5mim][BF4], [C5dmim][BF4], and [C4eim][BF4] aqueous solutions were all extremely low, these indicating that the osmotic resistance in the post-treatment membrane process can be minimized. The tunable thermoresponsive materials enabled a flexible process design, depending on the environmental and waste heat temperatures. Further, they can be used in various reaction solvents, extraction solvents, and other ingredients of the process.

Reduction of NOx Emission from the Cement Industry in South Korea: A Review

As climates change around the world, concern regarding environmental pollutants emitted into the atmosphere is increasing. The cement industry consistently produces more than 4000 million metric tons of cement per year. However, the problem of air pollutants being emitted from the calcination process is becoming more critical because their amount increases proportionally with cement production. Each country has established regulatory standards for pollutant emission. Accordingly, the cement industry is equipped with facilities to reduce air pollutants, one of which is the NOx removal process. NOx reduction processes under combustion conditions are modified to minimize NOx generation, and the generated NOx is removed through post-treatment. In terms of NOx removal efficiency, the post-treatment process effectively changes the combustion conditions during calcination. Selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) processes are post-treatment environmental facilities for NOx reduction. Accordingly, considering the stringent NOx emission standards in the cement industry, SNCR is essential, and SCR is selectively applied. Therefore, this paper introduces nitrogen oxide among air pollutants emitted from the South Korean cement industry and summarizes the technologies adapted to mitigate the emission of NOx by cement companies in South Korea.

Improving Surface Functionality, Hydrophilicity, and Interfacial Adhesion Properties of High-Density Polyethylene with Activated Peroxides.

Polyolefins have had limited application in advanced technologies due to their low surface energy, hydrophobicity, and weak interfacial adhesion with polar coatings. Herein, we propose the use of transition metals at their lowest oxidation state and inorganic peroxides to improve the functionality, surface free energy, hydrophilicity, and adhesion properties of high-density polyethylene (HDPE). Among the nine combinations of transition metals and peroxides used in this study, the combination of Co(II) and peroxymonosulfate (PMS) peroxide was the most effective for surface modification of HDPE, followed closely by the combination of Ru(III) and PMS. After chemical treatment, HDPE's surface functionality, composition, and energy were analyzed via Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements. Hydroxyl, carbonyl, and carboxylic acid functional groups were detected on the surface, which explained the improved hydrophilicity of the modified HDPE surface; the contact angle of HDPE with DI water decreased from 94.31 to 51.95° after surface treatment. To investigate the effect of HDPE's surface functionality on its interfacial properties, its adhesion to a commercial epoxy coating was measured via pull-off strength test according to ASTM D54541. After only 20 min of surface treatment with Co(II)/PMS solution, the adhesion strength at the interface of HDPE and the epoxy coating increased by 193%, confirming the importance of polyolefins' surface functionality on their interfacial adhesion properties. The method outlined herein can improve HDPE's surface functionality by introducing sulfate radicals. It improves HDPE's hydrophilicity and adhesion properties without requiring strong acids or time-consuming pre- or post-treatment processes. This process has the potential to increase the use of polyolefins in various industries, such as for protective coatings, high performance lithium-ion battery separators, and acoustic sensors.

A shift from chemical oxygen demand to total organic carbon for stringent industrial wastewater regulations: Utilization of organic matter characteristics

From 2022, industrial wastewater discharge regulations in South Korea will replace chemical oxygen demand (CODMn) with total organic carbon (TOC). A shift from CODMn to TOC is a pioneering change in protecting water bodies from organic contaminants. However, several industries are struggling to meet these TOC requirements even though their effluents met the CODMn limits. Effluent CODMn/TOC ratios (1.28 ± 0.64) found in our study were lower than the CODMn/TOC coefficients (1.33–1.80) suggested by the Ministry of Environment in South Korea. Aliphatic and particulate organic matter contents in effluents likely influenced the CODMn/TOC ratio. Regardless of the industrial category, dissolved organic carbon often consists of low molecular weight neutrals, hydrophobic organic carbon, and protein-like substances in raw and treated industrial wastewaters. The present study also revealed that TOC and CODMn represented different organic matter fractions in the paper mill and oil refinery wastewater, whereas the industrial park wastewater showed similar dissolved organic matter characteristics. Specifically, CODMn was effective in the determination of humic content in paper mill wastewater but was underestimated in oil refinery wastewater. Additionally, only paper mill effluents exceeded the TOC requirements (4 of 6 samples) and required an additional post-treatment process owing to higher organic loads.

Direct growth and post-treatment of zeolitic imidazolate framework-67 on carbon paper: an effective and stable electrode system for electrocatalytic reactions

Co-based MOFs are directly grown using an electrodeposited layer of Co(OH)2 on carbon paper and converted to cobalt sulfide (CoxSy) through a post-treatment process. The final electrode system exhibits remarkable oxygen evolution reaction performance.

A review of reverse osmosis process for seawater desalination

The freshwater availability in many regions of the world has been a rising concern for the last few decades due to disturbing increase in population, urbanization, and industrial advancement. As water consumption is increasing year by year, the obvious solution to the freshwater shortage is to increase its supply. Desalination has been a prominent process to produce fresh water in numerous water-stressed regions to counteract the water shortage issues. Amongst the various desalination methods, the reverse osmosis method is used for generating fresh water from saline or brackish water by removing salts to make it suitable for human utilization, agriculture, and industrial purposes. In the present study, a systematic review of the seawater reverse osmosis process is presented to address the developments in the pretreatment, membrane, and post-treatment processes of reverse osmosis.

High Thermoelectric Performance of Spray-Coated Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) Films Enabled by Two-Step Post-Treatment Process

High Thermoelectric Performance of Spray-Coated Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) Films Enabled by Two-Step Post-Treatment Process

In situpassivation of Pb0traps by fluoride acid-based ionic liquids enables enhanced emission and stability of CsPbBr3nanocrystals for efficient white light-emitting diodes

A great hurdle restricting the optoelectronic applications of cesium lead halide perovskite (CsPbX3) nanocrystals (NCs) is due to the uncoordinated lead atoms (Pb0) on the surface, where most attempts to address the challenges in the literature depend on complicated post-treatment processes. Here we report a simple in situ surface engineering strategy to obtain highly fluorescent and stable perovskite NCs, wherein the introduction of the multifunctional additive 1-butyl-3-methyl-imidazolium tetrafluoroborate ([Bmim]BF4) can significantly eliminate the Pb0 traps. The photoluminescence quantum yield (PLQY) of the as-synthesized NCs was improved from 63.82% to 94.63% due to the good passivation of the surface defects. We also confirm the universality of this in situ passivation pathway to remove Pb0 deep traps by using fluoride acid-based ionic liquids (ILs). Due to the high hydrophobicity of the cations of ILs, the as-prepared CsPbBr3 NCs exhibit robust water resistance stability, maintaining 67.5% of the initial photoluminescence (PL) intensity after immersion in water for 21 days. A white light emitting diode (LED), assembled by mixing the as-synthesized CsPbBr3 NCs and red K2SiF6:Mn4+ phosphors onto a blue chip, exhibits high luminous efficiency (100.07 lm W-1) and wide color gamut (140.64% of the National Television System Committee (NTSC) standard). This work provides a promising and facile technique to eliminate the Pb0 traps and improve the optical performance and stability of halide perovskite NCs, facilitating their applications in optoelectronic fields.

Post-treatment of 351 nm SiO2 antireflective coatings for high power laser systems prepared by the sol-gel method

Different post-treatment processes involving the use of ammonia and hexamethyldisilazane (HMDS) were explored for application to 351 nm third harmonic generation SiO2 antireflective (3ωSiO2 AR) coatings for high power laser systems prepared by the sol-gel method. According to experimental analysis, the 3ωSiO2 AR coatings that were successively post-treated with ammonia and HMDS at 150°C for 48 h and again heat-treated at 180°C for 2 h (N/H 150 + 180 AR) were relatively better. There were relatively fewer changes in the optical properties of the N/H 150 + 180 AR coating under a humid and polluted environment, and the increase in defect density was slow in high humidity environments. The laser-induced damage threshold of the N/H 150 + 180 AR coating reached 15.83 J/cm2 (355 nm, 6.8 ns), a value that meets the basic requirements of high power laser systems.