Non-metallic Materials Research Articles

Застосування титану у вигляді фольги для натирання неметалевих матеріалів з метою їх змочування і паяння металевими припоями

Activation of filler metal alloys for brazing non-metals by introducing chemically active elements such as titanium, zirconium, etc. is a technically challenging task. This paper discusses some methods of brazing non-metallic materials with filler metal alloys. A brief review of publications on the metallisation of non-metallic materials by titanium friction for further brazing with filler metal alloys is given. Two types of titanium foil tools for friction coatings on non-metallic materials have been proposed and used, which, in comparison with friction with compact titanium, significantly reduce the destruction of the ceramic surface and facilitate their application. Samples of high-alumina ceramics A995 and WK94-1, were metallized by the proposed method. The wetting of ceramics coated with PSr72 filler alloy (copper-silver eutectic) was studied, brazed joints were obtained, and the microstructure of the metal-nonmetal contact zone was studied The main purpose of such a coating for brazing processes is to activate the filler metal alloys melt to wet the ceramic. The surface roughness of non-metals affects the microstructure of the applied coating. As the roughness decreases, the density of the coating increases. Studies of the microstructure of the brazed joint have shown that the PSr72 melt penetrates the titanium coating, saturates it with titanium and wets the ceramic. This means that such metallisation accelerates the saturation of the melt with titanium. The brazing modes of this method practically coincide with the brazing modes of titanium-containing filler metal alloys Using the method of friction the metallization layer reduces the cost of the brazing process. Keywords: rubbing with metals, titanium foil, soldering of ceramics, metal solders, microstructure.

Technology Focus: Production and Facilities (December 2023)

It seems that it has been a very productive period for production and facilities. I reviewed a significant number of abstracts on such an interesting variety of topics—new technology developments down- and midstream, improvements in corrosion detection and prediction, new systems for emulsion monitoring, and even downhole drones, as well as several optimization works using artificial intelligence and machine learning, for quality and control. In the materials-science aspect, composite and nonmetallic materials continue to be significantly researched, as well as additive manufacturing for fast replacement of parts. I also reviewed abstracts on new materials development for downstream applications, such as dielectric sealants and dissolvable rubbers. Some fundamental research on emulsion stability was also present, as well as new emulsion monitoring systems based on microwave, acoustic, and capacitance measurements. In the area of equipment reliability, a common trend is using digital methods on historical data for prediction of equipment failure or corrosion vulnerability. There were also inspection developments such as the use of chemical tracers to identify the location of equipment failure downstream. A couple of works in this area are suggested in paper SPE 205687, which provides an example of deep learning used for intelligent identification of equipment status, and paper SPE 205056, which is a more-fundamental work on corrosion-prediction models. My attention was particularly drawn to environmentally oriented submissions this year. Energy integration continues to be a topic of interest, with geothermal and even green hydrogen being considered for energy generation in production facilities, especially in remote locations. An example of an interesting energy integration viability study can be found in paper SPE 204551. Another relevant aspect addressed was waste management, with submissions regarding abandoned wells management and waste disposal. A very thorough review on how to deal with produced solids can be found in paper SPE 210003, which clearly explains all stages of handling, from separation to disposal, with case studies as examples. An interesting work, paper SPE 213000, combines two issues: the disposal of wind-turbine waste and the use of abandoned wells. Because of the toxicity of wind-turbine blades, abandoned wells and cement coprocessing are considered as disposal options. It is quite interesting how costs and emissions were carefully analyzed in this study. Paper SPE 211932 caught my attention for its social and economic impact. This work presents the use of modular refineries as an alternative, cheaper solution to increase refining capabilities. Many developing nations produce more oil than their internal market consumes but still need to import large quantities of refined products. This work points this out as an anomaly. While some refining companies may profit from this, deep social impacts are caused by the increased gas prices in nations that are petroleum-rich. It is nice to see developments in our field that can contribute to less social inequality in the world. Recommended additional reading at OnePetro: www.onepetro.org. SPE 205056 Possible Missing Link in CO2 Corrosion Prediction by Yves Gunaltun, Retired SPE 205687 A Deep-Learning Model To Intelligently Identify the Working Status of Screw Pumps for Oil Well Lifting by Zhen Wang, Luming Oil and Gas Exploration and Development, et al. SPE 204551 Challenges and Opportunities for Green Hydrogen Power Supply in Oil and Gas Remote Facilities by Salvador Alejandro Ruvalcaba Velarde, Heriot-Watt University

Polymeric Hydrogels for Intervertebral Disc Replacement/Integration: Playing with the Chemical Composition for Tuning Shear Behavior and Hydrophilicity.

Damages to the intervertebral disc (IVD) due to improper loading or degeneration result in back pain, which is a common disease affecting an increasing number of patients. Different strategies for IVD remediation have been developed, from surgical treatment to disc replacement, by using both metallic and non-metallic materials. Hydrogels are very attractive materials due to their ability to simulate the properties of many soft tissues; moreover, their chemical composition can be varied in order to assure performances similar to the natural disc. In particular, for the replacement of the IVD outer ring, namely, the anulus fibrosus, the shear properties are of paramount importance. In this work, we produced hydrogels through the photo-induced crosslinking of different mixtures composed of two hydrophilic monofunctional and difunctional polymers, namely, poly(ethyleneglycol) methyl ether methacrylate (PEGMEMA) and poly(ethyleneglycol) dimethacrylate (PEGDMA), together with a hydrophobic molecule, i.e., tert-butyl acrylate (tBA). By changing the ratio among the precursors, we demonstrated the tunability of both the shear properties and hydrophilicity. The structural properties of hydrogels were studied by solid-state nuclear magnetic resonance (NMR). These experiments provided insights on both the structure and molecular dynamics of polymeric networks and, together with information obtained by differential scanning calorimetry (DSC), allowed for correlating the physical properties of the hydrogels with their chemical composition.

Effect of Heat Treatment on the Structure of Self-Assembled Undecenyl Phosphonic Acid Layers Developed on Different Stainless Steel Surfaces

Deterioration caused by corrosion is well known, which can destroy metallic and non-metallic materials alike. Dissolved inhibitors of bionic micro- and nanocoatings can decrease the degree of undesirable corrosion in various ways. In this paper, a self-assembled molecular layer formed from undecenyl phosphonic acid developed on two different steel surfaces was the subject of our experiments. The influence of the metal composition, layer-forming conditions and post-heat treatment was documented by wettability measurements as well as surface roughness parameters; the change in surface morphology caused by the formation of a layer in addition to post-heat treatment was visualized by an atomic force microscope (AFM); and infrared spectroscopy elucidated the bindings of the amphiphilic molecules involved in the self-assembled layer to the metal surface as well as to each other. Over the course of the self-assembling process, the –P(O)(OH)2 head groups can fix the amphiphilic molecule to the solid surface through the metal oxide-hydroxide layer. The hydrophobic alkenyl chains remain together as a result of special forces, namely hydrogen bonds and van der Waals forces, between them. The double bond at the end of the alkenyl chain disturbs how well the layer is ordered. To improve the homogeneity of the molecular layer and increase its level of compactness, the self-assembled molecular (SAM) layer was heat treated to achieve a more compact molecular film that can perfectly cover the metal surface.

Development of an impact based pyroshock test setup using finite element and response surface methods

In this study, a simulation and test-based procedure is created and applied to develop mechanical pyroshock test setup. In order to build an effective design, preliminary input parameters are defined with finite element simulations. The agreement between impact simulations and experimental data was achieved for resonant plate, metallic anvil plate and gun system. The obtained Shock Response Spectrum (SRS) curves are not well fitted to explicit finite element simulations for nonmetallic anvil plate materials, such as felt, which also have significant contribution to results. Therefore, further improvement is established by using test-based Response Surface Method (RSM). After validating the relationship statistically, response optimizer was used to find the best combination of design parameters to achieve target SRS curve. Finally, the prediction was checked experimentally to show the effectiveness of the developed methodology.

Quantification of MRI Artifacts in Carbon Fiber Reinforced Polyetheretherketone Thoracolumbar Pedicle Screw Constructs prior to Spinal Stereotactic Radiosurgery

Carbon fiber reinforced polyetheretherketone (CFRP) is a nonmetallic material that is a subject of growing interest in the field of spinal instrumentation manufacturing. The radiolucency and low magnetic susceptibility of CFRP has potential to create less interference with diagnostic imaging compared with titanium implants. However, an objective comparison of the image artifact produced by titanium and CFRP implants has not been described. Spinal oncology, particularly after resection of spinal tumors and at the time of spinal stereotactic radiosurgery planning, relies heavily on imaging interpretation for evaluating resection, adjuvant treatment planning, and surveillance. We present a study comparing measurements of postoperative magnetic resonance imaging artifacts between titanium and CFRP pedicle screw constructs in the setting of separation surgery for metastatic disease. The diameter of the signal drop around the screws (pedicle screw artifact) and the diameter of the spinal canal free from artifacts (canal visualization) were measured in consecutive patients who had spinal instrumentation followed by spinal stereotactic radiosurgery in the June 2019 to May 2022 timeframe. The spinal cord presented a shift at the screw level in sagittal images which was also measured (Sagittal Distortion, SagD). Fifty patients, corresponding to 356 screws and 183 vertebral levels, were evaluated overall. CFRP produced less artifacts in all the 3 parameters compared with titanium: mean pedicle screw artifact (CFRP = 5.8 mm, Ti = 13.2 mm), canal visualization (CFRP = 19.2 mm, Ti = 15.5 mm), and SagD (CFRP = .5 mm, Ti = 1.9 mm), all P < .001. In practice, these findings translate into better-quality magnetic resonance imaging. The initial perceived advantages are easier evaluation of postoperative imaging, facilitating radiation treatment planning, recurrence detection, and avoidance in repeating a suboptimal computed tomography myelogram. Further clinical studies analyzing long-term outcomes of patients treated with CFRP implants are necessary.

Enhancement of plasmonic coupling on Si metallized with intense femtosecond laser pulses

Using a pump–probe technique, the reflectivity of a silicon grating surface irradiated with intense femtosecond (fs) laser pulses was measured as a function of the incidence angle and the delay time between pulses. After irradiating the surface with an intense s-polarized, 400 nm, 300 fs laser pulse, the reflectivity measured with a weak p-polarized, 800 nm, 100 fs laser pulse exhibited an abrupt decrease for an incidence angle of ~ 24°. The depth of the dip was greatest for a delay time of 0.6–10 ps, for which the reflectivity around the dip was highest. The surface was also found to be ablated most strongly for the conditions causing the deepest dip for a delay time of 5–10 ps. Surface plasmon polaritons (SPPs) on silicon metallized by the intense pulse are resonantly excited by the subsequent pulse, and the strong coherent coupling between the subsequent pulse and SPPs excited on the molten Si surface produced by high-density free electrons induces strong surface ablation due to the intense plasmonic near-field. The results clearly show that fs pulses can be used to significantly modulate the nature of nonmetallic materials and could possibly serve as a basic tool for the excitation of SPPs on nonmetallic materials using ultrafast laser–matter interactions.

Spectral pyrometry of non-metallic materials at plasma heating, melting and cooling (Tomsk)

Spectral pyrometry of non-metallic materials under plasma heating, melting and cooling is used in nanotechnology, medicine, energy, metallurgy and other industries, where accurate temperature control is required during processing various materials. Purpose: The aim of this work is to create new spectral pyrometry technique for temperature measurement in difficult conditions of material processing and synthesis, such as plasma heating, melting and cooling of non-metallic materials. Methodology/approach: Small-sized spectrometers for diagnostics of heating, melting and cooling of the quartz target using the plasma jet. HPCS300 Mini Spectrometer with the wavelength range of 380 to 780 nm is used to determine the color temperature of the reference radiation source and for fiber optic calibration. The STS-VIS Microspectrometer based on a 1024×1 element CCD photodetector array with the wavelength range of 350 to 800 nm is used to record the emission spectrum of the object. Research findings: Improvement of production processes, fuel and material cost reduction, increase in the efficiency of plants and equipment, reliability and quality improvement of the final product. Value: During the plasma jet and quartz target interaction, three stages are observed: surface deformation, stable temperature of heating, and cooling of the condensed material with phase-transition points of liquid–pyroplastic–solid states.

Exploring density and strength variations in asteroid 16 Psyche’s composition with 3D hydrocode modeling of its deepest impact structure

Asteroid 16 Psyche is the largest metallic Main Belt Asteroid and is the subject of a forthcoming NASA mission. The composition of Psyche is still unknown and subject of recent debate. In particular, how much porosity is within Psyche, along with how much of Psyche consists of non-metallic versus metallic materials, are central questions to the issue of Psyche’s composition. If Psyche is indeed predominantly composed of metallic materials, it would need to have considerable porosity (∼ 30%–50%) for a composition consistent with its expected bulk density (∼ 3.7–4.1 g/cm3). In this work, we vary the density and strength of Psyche by including uniform and layered fields of pseudo-microporosity, in addition to investigating the presence of macroscopic voids, i.e., spaces larger than the size of the simulation’s mesh cells, in rubble-pile configurations. All configurations result in bulk densities within the uncertainties of measured values, however the strength of Psyche and the distribution of pseudo-pores are varied. Through 3D computational models of Psyche’s deepest impact structure, we show that Psyche’s composition is unlikely to contain only pseudo-microporosity. Rather, rubble pile structures, which include macroscopic voids, are shown to match the crater’s measured aspect ratio better than simulations of structures that included only pseudo-microporosity.

Optimizing Energy Efficiency of Dielectric Materials’ Electrodischarge Dispersion as One Sustainable Development Green Trend

Increasing the energy efficiency of production processes is closely related to minimizing the impact on the environment and is one of the priorities of the concept of sustainable development. Electric discharge is an effective tool for multilevel grinding of non-metallic materials in various working fluids and obtaining coarse and fine suspensions. We introduce the technique for calculating the electrotechnological parameters necessary for energy-efficient electric discharge dispersion. This technique considers the strength characteristics of the crushed material (dispersed phase) and the electrical conductivity of the working fluid (dispersed medium). It is also essential to consider the energy stored in the capacitor bank, the energy criterion, the critical value of the working fluid’s electrical strength, the radius of the high-voltage electrode point, and the distance from the discharge channel axis to the disintegration object. All this allows obtaining a given granulometric composition of the dispersed phase with minimal energy consumption. Experiments confirmed the validity of the proposed calculation technique. We obtained the water-brown coal suspension with a given dispersion two times faster and consumed four times less energy in comparison with the known methods that did not take into account the electrical conductivity of the working liquid and the mechanical strength of the crushed material.

High surface area g-C3N4 nanosheets as superior solar-light photocatalyst for the degradation of parabens

The rational design and development of highly-active photocatalytic materials for the degradation of dangerous chemical compounds, such as parabens, is one of the main research pillars in the field of photocatalysis. Graphitic carbon nitride (g-C3N4) is a 2D non-metal material and is considered one of the most promising photocatalysts, because of its peculiar physicochemical properties. In this work, porous g-C3N4 nanosheets (CNNs) were successfully prepared via thermal exfoliation of bulk g-C3N4 (CNB). A thorough physicochemical characterization analysis before and after the exfoliation process was performed, revealing the improved textural characteristics (surface area of 212 m2/g), chemical stability, and optical properties (wide band gap of 2.91 eV) of CNNs compared to the CNB. Then, both CNB and CNNs were comparatively assessed as photocatalysts for the degradation of methyl-, ethyl- and propylparaben (MP, EP, and PP), as well as of their mixture. CNNs with high surface area display superior photocatalytic performance under solar irradiation, offering > 95% degradation efficiency to all parabens, in contrast to the much inferior performance of CNB (< 30%). Several experimental parameters, involving catalyst concentration, initial concentration of parabens, and irradiation type were thoroughly investigated for the degradation of MP over CNNs. Moreover, various scavengers were employed to discriminate the role of different reactive species, revealing that superoxide anion radicals (·O2–) play a pivotal role in the degradation process, in contrast to hydroxyl radicals (·OH). The present results pave the way towards the facile synthesis of high surface area CNNs with improved textural and electronic characteristics, which can be applied in various environmental applications.

Novel communication system for buried water pipe monitoring using acoustic signal propagation along the pipe

PurposeWireless sensor networks (WSN), as a solution for buried water pipe monitoring, face a new set of challenges compared to traditional application for above-ground infrastructure monitoring. One of the main challenges for underground WSN deployment is the limited range (less than 3 m) at which reliable wireless underground communication can be achieved using radio signal propagation through the soil. To overcome this challenge, the purpose of this paper is to investigate a new approach for wireless underground communication using acoustic signal propagation along a buried water pipe.Design/methodology/approachAn acoustic communication system was developed based on the requirements of low cost (tens of pounds at most), low power supply capacity (in the order of 1 W-h) and miniature (centimetre scale) size for a wireless communication node. The developed system was further tested along a buried steel pipe in poorly graded SAND and a buried medium density polyethylene (MDPE) pipe in well graded SAND.FindingsWith predicted acoustic attenuation of 1.3 dB/m and 2.1 dB/m along the buried steel and MDPE pipes, respectively, reliable acoustic communication is possible up to 17 m for the buried steel pipe and 11 m for the buried MDPE pipe.Research limitations/implicationsAlthough an important first step, more research is needed to validate the acoustic communication system along a wider water distribution pipe network.Originality/valueThis paper shows the possibility of achieving reliable wireless underground communication along a buried water pipe (especially non-metallic material ones) using low-frequency acoustic propagation along the pipe wall.

Triboelectric nanogenerators: theoretical calculations, materials, and applications in net-zero emissions

Triboelectric nanogenerators (TENGs) have shown great potential in converting discrete mechanical energy in the environment into electricity without producing any greenhouse gases in the process, and they have been regarded as one of the most powerful methods to achieve zero carbon emissions. It has been confirmed that the output performance is the main factor limiting the real-world applications of the TENGs. Establishing universal standards for quantity analysis TENGs’ outputs and seeking advanced dielectric materials to improve the charge density are the two priorities for boosting TENG outputs. Here, the working mechanisms of TENG and the quantitative analysis of TENG output performance are introduced to reveal the relationships of Q–V–I–x (charge-voltage-current-displacement) and the energy conversion efficiencies. Selecting suitable triboelectric materials is the key to enhancing the performance of TENG. Materials used as advanced friction or dielectric layers are elaborated, including metals, inorganic non-metallic materials, polymers, and composites. Moreover, the influences of performance improvement methods, such as ionization injection, intermediate layer, surface modification, and charge-excitation strategy, are discussed accordingly. Finally, applications to achieving the goal of net zero and future challenges of TENGs are presented. This review provides strategies for guiding the further development of TENGs toward higher performances and promoting the commercialization of TENG net-zero systems.

A comparative analysis of the regulations, codes and standards for on-board high-pressure hydrogen storage cylinders

Hydrogen storage cylinder is an important component in high-pressure gaseous hydrogen (HPGH2) storage system, and plays a key role in hydrogen-powered transportation including land vehicles, ships and aircrafts. Over the past decade, the number of hydrogen fuel cell vehicles (HFCVs) has rapidly increased worldwide. In order to promote the application of hydrogen storage cylinder, guide its design, manufacture, inspection and testing, a series of regulations, codes and standards have been issued. The Chinese national standard, GB/T 42612, for type IV hydrogen storage cylinders has also been issued. This paper first gives a brief overview to these regulations, codes and standards. Furthermore, the specifications including scope, category, filling cycles, service life, materials, design, manufacture, qualification tests and periodic inspections are analyzed and compared. Issues about evaluation method for hydrogen compatibility of non-metallic materials, welded joints of plastic liner, joint between boss and liner are also discussed. Notably, the performance requirements in GB/T 42612 are generally in accordance with the international ones, but the requirements of materials, design and manufacture are more detailed.

Restoration of the orientation distribution function for materials with low lattice and sample symmetry using the harmonic method

A lot of the properties polycrystalline materials depend on their crystallographic texture. The most complete information about the texture can be obtained from the orientation distribution function (ODF). We present the results of recovering ODF using series expansion technique for materials with low crystal and sample symmetry. The technique of ODF restoration is based on its Fourier series expansion with symmetrical spherical harmonic functions. Real spherical harmonics which are linear combinations of general spherical harmonics were used. The model single-component texture as well as the real texture of magnesium alloy sample subjected to equal-channel angular pressing have been studied. Textures are characterized by hexagonal crystal symmetry and triclinic sample symmetry. In both cases RP-factors and ODF calculation errors that were used as reliability criteria of ODF reconstruction showed good agreement between the calculated and experimental data. It was also revealed that the ODF of a magnesium alloy sample subjected to equal-channel angular pressing contains two texture components (1216)[1211] and (1216)[1211] with maximum intensity values of 13.81 and 2.23, respectively. The results obtained can be used for texture studies of ceramics, rocks and other non-metallic materials characterized by a lower symmetry.

TECHNOLOGICAL SUPPORT OF CONTOUR POLISHING IN THE RESTORATION OF PAINT COATINGS OF COMPLEX SURFACES

The article considers the cluster model for describing the polishing of non-metallic materials in relation to paint coatings applied to surfaces of complex geometry. In particular, technical means of contour polishing of coatings of non-metallic layers of car body elements with the use of mechatronic modules from CNC are proposed, which reproduce the movements and modes of polishing that were previously performed manually. On the basis of consideration of the problem of destruction of paint coatings of car bodies and analysis of the literature on the study of physical and mechanical processes of forming parts from non-metallic materials with a tool using polishing pastes and studying the laws of this process, the polishing ability of various polishing pastes was investigated. The geometric criteria of the quality of self-polishing of paint coatings with a formalized provision of the interrelationship of the width of the artificial scratch applied by a diamond tetrahedral pyramid with the depth and shape of the artificial scratch before and after polishing are proposed. A wide range of speed, power, and rheological factors of polishing body surfaces with double curvature were considered, but thermal and mechano-chemical processes were not established. Data on the effectiveness of polishing pastes and the quality of restored paint coatings of the car were obtained as a result of the performance of a scientific service commissioned by the Kherson PE "InterSklad" enterprise. Samples of polishing pastes of the abrasive fraction and the composition of the solvent were determined, which should meet the conditions of manual polishing, and the corresponding auto cosmetic products were put into production. A test methodology has been developed that allows you to determine in a short time the effectiveness and modes of polishing mixtures for the elimination of mechanical damage to the paintwork of cars.

Rigid but nonmetallic cranioplasty after pterional craniotomy: Technical note.

Given the popularity of pterional craniotomy, numerous modifications have been made to prevent postoperative deformities. With the advent of titanium plates, fixation has become both simple and excellent. However, titanium plates can cause skin problems, infection, or cause skull growth to fail. To develop a simple, cost-effective, and esthetically satisfactory fixation method, without the use of non-metallic materials, six young and older patients underwent pterional craniotomy. CranioFix Absorbable clamps were used to fix the bone flap in the frontal and temporal regions such that the frontal part was in close contact with the skull. After fixation, the bone chips and bone dust were placed in the bone gap and fixed with fibrin glue. We measured the computed tomography values of the reconstructed area and thickness of the temporal profiles postoperatively over time. Bone fusion was achieved in all patients by 1 year after surgery. Both the thickness of the temporalis muscle and the thickness of the temporal profile had changed within 2 mm as compared with the preoperative state. Our simple craniotomy technique, gentle tissue handling, and osteoplastic cranioplasty yielded satisfactory esthetic results and rigidness in pterional craniotomy.

Photocathodic protection performance of a nonmetal ternary heterojunction for 304 stainless steel

Photocatalytic materials are important in extensive applications including photocathodic protection. Herein, we report a nonmetal ternary photocatalyst graphitic carbon nitride/reduced graphene oxide/polypyrrole (g-C3N4/rGO/PPy) fabricated by thermal polymerization. Transmission electron microscope (TEM), X-ray diffractometer (XRD), Fourier transform infrared (FTIR), and photoluminescence spectra (PL) were used to analysis the microstructures, crystalline structures, chemical constitutions, and electronic structures of the g-C3N4, g-C3N4/rGO, and g-C3N4/rGO/PPy. The ternary photocatalyst exhibits superior photocathodic protection performance compared with that of the pristine and binary photocatalyst. These results will be pivotal to progress in photocathodic protection employing nonmetal photocatalyst materials.

Porous B3C3N2 matrix-based electrochemical sensor for sensitive determination of trace cadmium in environmental and tobacco samples

Ternary B3C3N2 nanomaterials were prepared by the hard-template method using melamine (N and C source) and tetraethyl silicate (SiO2 source) as templates, with Cs2[B12H12] as a dopant. The B3C3N2 composite material can synthesise the functional groups of the BCN substrate and the porosity of the acid-etched template, thereby achieving the selective electrochemical detection of Cd(II). Under optimal conditions, the peak current was well linearized with the Cd(II) concentration between 1 and 310 μg/L, while the theoretical detection limit was 0.32 μg/L. The B3C3N2-Nafion sensor exhibits excellent electrode stability and anti-interference ability in addition to being non-toxic and simple to produce. Our research not only bridges the preparation of nonmetallic atom-doped carbon-based materials and in situ etching strategies but also provides a novel demonstration for the detection and application of the heavy metal Cd(II).

Progress in the application of novel nano-materials to the safety analysis of agricultural products

The quality and safety of agricultural products are strongly related to human livelihood. Thus, the government and consumers have recently paid increased attention to the quality and safety of agricultural products. The development of efficient, rapid, and sensitive analytical methods for detecting pesticides, veterinary drugs, heavy metals, mycotoxins, and environmental pollutants in agricultural products is of great significance. Owing to the complexity of many sample matrices and the low concentration of pollutants in a typical sample, appropriate sample pretreatment steps are necessary to enrich pollutants in agricultural products. Solid-phase extraction (SPE) is the most widely used sample pretreatment technology; in this technique, the adsorbent generally determines the selectivity and efficiency of the extraction process. An increasing number of novel materials have been used as SPE adsorbents. The extraction efficiency, extraction selectivity, and analytical throughput of SPE could be greatly improved by combining these novel materials with various extraction modes (e. g., solid-phase microextraction, dispersed SPE, and magnetic SPE (MSPE)) during sample preparation. Because of their large specific surface area and high affinity toward target analytes, nanomaterials are often used as SPE adsorbents, thereby greatly improving the selectivity and sensitivity of the analytical technology. More importantly, these materials have become a priority area of research on preconcentration technologies for trace compounds in agricultural products. This paper summarizes the adsorption characteristics of several new nanomaterials, including magnetic materials, carbon-based materials, metal nanomaterials (MNs), metal oxide nanomaterials (MONs), metal organic frameworks (MOFs), and covalent organic frameworks (COFs). These nanomaterials present numerous advantages, such as large specific surface areas, high adsorption capacities, and tailorable structural designs. MSPE employs magnetic materials as sorbents to afford fast dispersion and efficient recycling when applied to complex sample matrices under an external magnetic field. The use of MSPE can avoid several typical problems associated with SPE such as poor adsorbent packing and high pressure, thereby greatly simplifying the pretreatment process and providing a high flux for sample analysis. Carbon-based materials are powdered or bulk nonmetallic solid materials with carbon as the main component; carbon and nitrogen materials, mesoporous carbon, carbon nanotubes, and graphene are some examples of these materials. These materials provide large specific surface areas, abundant pore structures, good thermal stability, high mechanical strength and adsorption capacity, and controllable morphology. Pure and modified carbon nanomaterials have been successfully used to purify target analytes from agricultural products. Given their unique physical and chemical properties, MNs and MONs have attracted significant interest for use in sample preparation. MNs and MONs with excellent thermal and mechanical stabilities show good resistance to a wide pH range and diverse organic solvents, which is crucial in adsorbent-based extraction methods. The surface of these materials can be easily modified with various ligands to improve their selectivity. MOFs and COFs present many advantages such as large specific surface areas, high porosity, adjustable pore performance, and good thermal stability. Several methods that employ novel adsorbent materials to analyze pollutants in a variety of agricultural products, such as chromatography, spectroscopy, mass spectrometry, and other detection technologies, have been established. This paper also reviews the application of adsorbent materials in the analysis of agricultural product quality and safety, and discusses the future development trends of these sorbents in sample preparation for the safety analysis of agricultural products.