Non-metallic Materials Research Articles

THE RELATIONSHIP BETWEEN THE MECHANICAL PROPERTIES OF ARMOR STEEL AND ITS BALLISTIC RESISTANCE (overview)

The relevance of the work. Today the industry is actively developing in the field of manufacturing means for protection of all types of armored vehicles against fire damage by small arms and artillery weapons. At present, ensuring high dynamic resistance of armor against modern weapons without increasing its thickness and, accordingly, the mass of the structure as a whole is achieved due to the use of various non-metallic materials (armor ceramics, high-strength fabrics, etc.) as part of compositions with traditional steel armor. The development and design of workable materials and structures of armor protection is a complex scientific and technical problem. To ensure high stability and survivability of armor, it is necessary to establish a relationship between the mechanical properties of armor steel and its ballistic characteristics. Purpose. Based on the analysis of literary sources, determine the relationship between the mechanical properties of steel armor and its ballistic characteristics. Methodology. The method of scientific and technical literature analysis regarding the requirements for armored obstacles is applied. The results. Analytical investigations of the relationship between the main mechanical properties of steel armor and its ballistic characteristics are conducted in the work, which will allow predicting the optimal combination of mechanical properties’ values that will ensure high ballistic resistance. Increasing the hardness of armor steel usually reduces the impact toughness of steels. It is noted that the ballistic characteristics of structural and armor steels are correlated with the tensile strength limit. The existence of a correlation between the strength properties of materials and their resistance to crack propagation under high-speed (explosive) loading is shown. For a number of materials, there is a close relationship between predicted and measured ballistic characteristics at high deformations associated with ballistic impact, when compressive flow stress is used as a measure of material strength. Increasing impact toughness, especially in high and ultra-high hardness classes, is an important task in the development of armor steel. Hardness limits are therefore set for specific grades of steel armor to control impact toughness during production and reduce the risk of fracture or other brittle damage for specific steel compositions and applications.

INCREASING THE ACCURACY OF DEFECTOSCOPY BY THE METHOD OF ACTIVE THERMOGRAPHY OF PRODUCTS MADE OF NON-METALLIC HETEROGENEOUS MATERIALS AND USED IN ENGINEERING

Nowadays, non-metallic heterogeneous materials are widely used in mechanical engineering, which is primarily due to their unique properties, such as strength, light weight, corrosion resistance, and high vibration, sound, and heat insulation characteristics. At the same time, non-destructive control methods that would allow to obtain the most complete picture of the defective state of products made of such materials are of great importance. The main task of the work is the development of optimal algorithms for determining each defect of a product made of non-metallic heterogeneous material with the establishment of its exact location, including the depth of occurrence, as well as its geometric parameters. The method of thermal non-destructive testing is considered promising. Studies of the accuracy of determining the parameters of defects in non-metallic heterogeneous materials by the specified method have been carried out.

Algae-derived metal-free boron-doped biochar acts as a catalyst for the activation of peroxymonosulfate toward the degradation of diclofenac

In this study, plain seaweed biochar (SW) and boron-doped seaweed biochar (BSW) were prepared through a simple pyrolysis process using Undaria pinnatifida (algae biomass) and boric acid. The BSW catalyst was utilized to degrade organic pollutants in aqueous environments by activating peroxymonosulfate (PMS). Surface characterization of the BSW demonstrated successful doping of boron into the biochar materials. BSW600 exhibited greater catalytic activity than SW600, as evidenced by the former's maximum adsorption capacity of diclofenac (DCF) onto BSW600 (qmax = 30.01 mg g−1) and the activation of PMS. Complete degradation of DCF was achieved in 30 min using 100 mg L−1 BSW600, 0.5 mM PMS, and 6.5 initial solution pH as critical parameters. The pseudo-first-order kinetic model accurately described the DCF degradation kinetics. The scavenger experiment displayed that radical and non-radical reactive oxygen species (ROS) formed in the BSW600/PMS system. Furthermore, the generation of ROS in the BSW600/PMS system was confirmed by electron spin resonance spectroscopy (ESR). The percentage contribution of ROS was assessed to be 12.3, 45.0, and 42.7% for HO•, SO4•–, and 1O2, respectively. Additionally, the electron transfer pathway was also confirmed by electrochemical analysis. Moreover, the influence of water matrics on the BSW600/PMS system was demonstrated. The co-existence of anions and humic acid (HA) did not affect the catalytic activity of the BSW600/PMS system. The recyclability of BSW600 was assessed by DCF removal (86.3%) after three cycles. Ecological structure-activity relationships software was used to assess by-product toxicity. This study demonstrates the efficacy of non-metallic heteroatom-doped biochar materials as eco-friendly catalysts in groundwater applications.

Visualization of Micro Damage in SOFC Using Terahertz Waves

SOFC effective area for power generation is reduced when delamination occurs. Hence, non-destructive evaluation methods for detecting delamination of SOFC are required. We focused on Terahertz-Time Domain Spectroscopy (THz-TDS) as a SOFCs’ non-destructive evaluation method. THz-TDS has been used as an effective and safe method for non-destructive evaluation of non-metal materials. However, THz-TDS generates a huge amount of measurement data for one batch test. In this study, we propose a THz-TDS based method to visualize the internal damage of SOFC by using machine learning. Each waveform was discretely vectorized, and a Self -Organizing Map (SOM) was utilized to examine for its similarity. Therefore, we found that the waveforms have been changed because of the wave interference induced by the generation of air layer associated with the occurrence of delamination.

Defect-rich selenium doped graphitic carbon nitride for high-efficiency hydrogen evolution photocatalysis

Graphitic carbon nitride (g-C3N4) has been demonstrated as a promising non-metal material for photocatalytic hydrogen evolution (PHE), while its photocatalytic activity is greatly limited due to the narrow visible light response-ability and the intrinsic severe charge deep trapping and recombination effects. Herein, a co-functionalized g-C3N4 system by Se doping and nitrogen vacancies modification is developed through a Se vapor-assisted-chemical vapor deposition synthetic strategy. Advanced characterization results revealed that Se dopants promote the visible-light absorption ability of g-C3N4, while nitrogen defects-induced shallow trap states are constructive to improving charge separation/transportation efficiency by effectively retarding the detrimental charge deep trapping and recombination. As a result, the synergistic effect of the Se dopants and nitrogen defects leads to a highly efficient PHE performance of g-C3N4. The integrated engineering strategy and mechanism understanding provided in this work may offer new insights into developing other novel photocatalysts for various applications.

The Fundamental Mechanisms of Laser Cleaning Technology and Its Typical Applications in Industry

Laser cleaning is an advanced surface-cleaning technology that can lead to the instant evaporation and stripping of the attachments found on a substrate’s surface, such as contaminants, rust, and coatings; it uses a high-energy laser beam to irradiate the components’ surface. Compared with common surface-cleaning technologies, laser cleaning has the advantages of precision, efficiency, and controllability. In this paper, the fundamental mechanisms of laser cleaning technology are summarized in detail; these include the laser thermal ablation mechanism, the laser thermal stress mechanism, and the plasma shock wave mechanism. The operational principles, characteristics, and application range of each mechanism are discussed. Their typical applications in industry are outlined according to the differences in the substrate materials used, including metallic materials, nonmetallic materials, and semiconductor elements. This study provides a significant reference and guiding basis for researchers to further explore the fundamental mechanisms of laser cleaning, as well as various aspects of the typical industrial applications of laser cleaning.

Molten-Salt Synthesis of Triazine-Based Carbon Nitride and Its Photocatalytic Degradation Mechanism Investigation by In Situ NMR

Carbon nitride-based catalysts are nonmetallic materials with efficient photocatalysis for water splitting, degradation of organic dyes, and CO2 reduction. In this paper, a one-step molten salt method was employed for the synthesis of ionic doped carbon nitride materials named CNs (carbon nitride catalysts), which exhibited excellent adsorption performance and photocatalytic activity. The adulteration of Zn2+ ions created a unique nanosheet stack morphology, leading to more effective active sites and better electron transfer efficiency. Additionally, the degradation mechanism was investigated by the quasi-in situ NMR method. The reaction products and photocatalytic process were fully discussed, providing a new degradative pathway of methylene blue (MB) by such CN-based catalysts.

Mechanistic Insights into Radical-Induced Selective Oxidation of Methane over Nonmetallic Boron Nitride Catalysts

Boron-based nonmetallic materials (such as B2O3 and BN) emerge as promising catalysts for selective oxidation of light alkanes by O2 to form value-added products, resulting from their unique advantage in suppressing CO2 formation. However, the site requirements and reaction mechanism of these boron-based catalysts are still in vigorous debate, especially for methane (the most stable and abundant alkane). Here, we show that hexagonal BN (h-BN) exhibits high selectivities to formaldehyde and CO in catalyzing aerobic oxidation of methane, similar to Al2O3-supported B2O3 catalysts, while h-BN requires an extra induction period to reach a steady state. According to various structural characterizations, we find that active boron oxide species are gradually formed in situ on the surface of h-BN, which accounts for the observed induction period. Unexpectedly, kinetic studies on the effects of void space, catalyst loading, and methane conversion all indicate that h-BN merely acts as a radical generator to induce gas-phase radical reactions of methane oxidation, in contrast to the predominant surface reactions on B2O3/Al2O3 catalysts. Consequently, a revised kinetic model is developed to accurately describe the gas-phase radical feature of methane oxidation over h-BN. With the aid of in situ synchrotron vacuum ultraviolet photoionization mass spectroscopy, the methyl radical (CH3•) is further verified as the primary reactive species that triggers the gas-phase methane oxidation network. Theoretical calculations elucidate that the moderate H-abstraction ability of predominant CH3• and CH3OO• radicals renders an easier control of the methane oxidation selectivity compared to other oxygen-containing radicals generally proposed for such processes, bringing deeper understanding of the excellent anti-overoxidation ability of boron-based catalysts.

Twin thickness-dependent tensile deformation mechanism on strengthening-softening of Si nanowires

Twin thickness-dependent deformation and the transition from strengthening to softening in twinned silicon nanowires are investigated using molecular dynamics simulations with cylindrical and hexagonal cross sections. The results show that the transition from strengthening to softening occurs at critical twin thicknesses of 8.1 nm (11.0 TB s) with cylindrical cross section and 11.0 nm (8 TBs) with hexagonal cross section with decreasing twin thickness, and that the strongest twin thickness originates from a transition in the initial plasticity mechanism from full dislocation nucleation and interaction with the TBs to partial dislocation nucleation and gliding parallel to the TBs. Moreover, it is found that the relationship between peak stress and twin thickness can be divided into two regions. Several full and partial dislocations are formed in the regions with strengthening twin thickness range. The accumulation and pile-up of these dislocations and their interaction with the TBs at high density cause the Hall-Petch strengthening behavior. In contrast, few full and partial dislocations are formed with softening twin thickness range. These dislocations are nucleated and propagate parallel to the TBs, resulting in TB migration that causes inverse Hall-Petch softening behavior. Our simulation results provide sufficient insight into the mechanical behavior of twinned silicon nanowires with cylindrical and hexagonal cross sections. The study will be helpful to the further understanding of CTB-related mechanical behaviors of non-metallic materials and non-metallic system.

WS2–TiO2 hetero-photocatalysts for efficient hydrogen evolution via plasmon-induced resonance energy transfer

Lowering the cost and increasing the efficiency of photocatalysts for hydrogen (H2) evolution remain challenging, especially with eco-friendly materials. With these goals in mind, in this study we adopted tungsten disulfide (WS2) nanosheets, a nonmetallic surface plasmon resonance (SPR) material covering P25 TiO2, for plasmon-induced resonance energy transfer (PIRET) to improve the photocarrier response of H2 evolution. Under simulated solar light irradiation, the optimized 2.4W heterostructure provided a durable and outstanding H2 evolution rate (321 μmol g−1 h−1) that was approximately 55.3 times higher than that of TiO2. Raman spectra revealed the presence of dipole–dipole interactions within the WS2–TiO2 heterostructure, while UV–Vis optical absorption spectra indicated that the WS2 absorption range overlaid the band gap of TiO2. Under irradiation with light, the SPR of the WS2 nanosheets underwent near-field dipole-dipole coupling with the excitons of TiO2 to increase the number of excitons and inhibit charge recombination. This study suggests the possibility of using nonmetallic SPR materials for efficient solar energy conversion.

Comparative analysis of compressed hydrogen losses during its transportation through the pipelines from different materials

The authors estimate possible losses of transported compressed hydrogen (P = 10 MPa) due to diffusion through the pipe wall applying Sieverts law and Arrhenius equation and using tabular data on the coefficients of permeability and solubility. The calculation was carried out for pipelines made of various metallic and non-metallic materials at room and elevated temperatures. It is shown that the volume of the diffused gas at T = 298°K (25°С) is only fractions of a percent of the pumped hydrogen volume. At the same time, the biggest loss occurs in a pipeline made of polyethylene (~0.03%), and the most insignificant one in austenitic steels (~10-6%). For carbon and low-alloy steels, the main materials of gas pipelines, these losses are at the level of 10-4–10-5 %. When the temperature rises to 683°K (410°C), the losses in steel pipelines increase to 0.25%, in polymer pipelines to 20%.

One-step synthesis of S, N dual-element doped rGO as an efficient electrocatalyst for ORR

The commercial application of oxygen reduction reaction (ORR) technology challenges the development of new electrocatalysts with excellent performance, high stability and low cost. Non-metallic materials, especially graphene-based catalysts, have become potential electrocatalysts for ORR due to their source richness and good stability. Here, we report a simple one-step hydrothermal method to synthesize S, N dual-element doped reduced graphene oxide (S, N-rGO) for ORR using graphene oxide as carbon source, thiourea as both sulfur-nitrogen source and reducing agent. The ORR performance is effectively enhanced by heteroatoms doping that increases the active sites of edge defects, introduces new S and N active sites, and adjusts the electronic structure of rGO. The 0.05-S, N-rGO catalyst shows the optimal ORR activity under alkaline conditions with the onset potential of 0.793 V vs RHE, good stability and anti-tolerance toward methanol. The calculated electron transfer number of about 3.1 ± 0.1 suggests that both the two-electron and four-electron processes occur on the catalyst.

Time-resolved plasma diagnostics of cathodic cage plasma nitriding system with variable pulsed duty cycle and surface modification of plain carbon steel

Cathodic cage plasma nitriding (CCPN) is an efficient technique to improve the surface properties of metallic and non-metallic materials, including steels. Usually, CCPN is powered by pulsed voltage sources due to additional control of the nitrided layer's thickness and composition as well as the discharge transition to the arc region can be controlled by varying the pulsed duty cycle. As the behavior of pulsed plasma varies with time, it is important to monitor variation in plasma parameters by using time-resolved plasma diagnostics. Unfortunately, the fundamental time-resolved diagnostics of such discharges are still very limited. Here, we report time-resolved measurements of current, voltage, plasma emission, space, and time-resolved emission from a single hole in the cathode as a function of pulsed duty cycle (15–75 %) at constant total current. The results show that the electron temperature is higher if a higher peak current and the shortest 15 % pulsed duty cycle are used. The results obtained from plasma diagnostics are confirmed by treatment of plain carbon steel samples in identical conditions and found that the best hardness, wear, and corrosion resistance is obtained at the lowest pulsed duty cycle. The study suggests that plasma generated at a low pulsed duty cycle and a higher peak discharge current exhibits higher electron temperature and less fluctuations in plasma emission which are more efficient in attaining high surface hardness, better wear, and corrosion resistance to nitride plain carbon steel.

Fire Resistance Test of Geopolymer Coatings on Non-Metallic Underlying Substrates

This article summarizes the results from the fire resistance test of geopolymer suspensions in the form of coatings on non-metallic substrates. Their heat resistance was evaluated based on the burn-through time compared to the uncoated substrate. Non-metallic substrate materials, extruded polystyrene (XPS) and chipboard (DTD) were chosen as the underlying substrates for GP suspension research. Parameters from the fire resistance test as fire test duration of geopolymer coatings and percentage increase in burn time of geopolymer coatings on an XPS and DTD substrates compared to an uncoated substrate were evaluated. One of the discussed point was also the addition of CaCO3 and Al(OH)3 for studding flame retardancy effect.

Design and testing of an electromechanical engine for a small solid-propellant rocket using non-metal materials

In this paper an engine prototype of 2 degrees of freedom from a work still in progress that helps a solid fuel rocket to stay vertical during motor operation is presented. One of the philosophies of this paper consists in using cheap and accessible materials, as well as avoiding the use of industrial machinery for its manufacture. This paper describes the procedure to generate solid fuel from a mixture of sugar and potassium nitrate. Subsequently, the design of the engine and tests conserning reusability with the prototype are presented. The design is based solely on obtaining the torques required to keep the prototype rocket moving in a vertical direction. The corresponding equations are written and after linearization, the transfer function is presented and the system is simulated using a PID control. The electromechanical system (ES) as well as the solid fuel motor were manufactured, and even though the ES is not coupled to the motor so the control actions are not evaluated, the performance of the rocket motor is measured using different design options and the propulsion times were evaluated. To measure the orientation and position the BMP280 and MPU6050 sensors were selected, and their stabilization time after turning them on was evaluated. It was found that the materials can be reused at least once for tests up to 23 grams of solid fuel, and that the selected electronic devices must have a stabilization time before ignition.

New Patterns of Polishing Surfaces of Parts Made of Nonmetallic Materials

New Patterns of Polishing Surfaces of Parts Made of Nonmetallic Materials

Editorial

Editorial

Effect of Adding Al2O3 on the Macrostructure of Friction Stir Welding Polypropylene Sheet

In this study, an experimental investigation has been carried out to determine the effect of alumina (Al2O3) addition in joining polypropylene. Polypropylene is a thermoplastic material used most as a non-metallic material. One of the joining methods that can be applied in Polypropylene is Friction Stir Welding (FSW). The use of Al2O3 as a filler is to modify the polypropylene matrix's properties to improve the joint's quality. The Al2O3 powder with 99 9% purity was inserted along the polypropylene plates in the groove. This research analyzed the role of adding Al2O3 and tool rotation speed concerning the joints' quality. The experiment was performed under different values of tool speed rotation (204 rpm, 356 rpm, 620 rpm, and 1140 rpm) and the presence or absence of the addition of alumina powder. Then, the joint's quality is visually observed by optical macroscopy at the top and cross-section view. From macroscopic observations, adding alumina could make the visual of the joint look better and result in minimum defects than the joint without alumina addition. Instead, the increasing tool speed rotation helped the distribution of alumina during the welding process.

Achieving purple light excitable high-efficiency temperature-responsive dual- and single-mode afterglow in carbon dots

Afterglow materials including thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) have inspired extensive attention and research in anti-counterfeiting and sensing application prospects. However, a critical challenge currently remains within this afterglow materials only exhibit single-mode phosphorescence or delayed fluorescence with a persistent luminescence but low quantum yield. In this study, carbon dots composites with long-lived afterglow and ultra-high afterglow quantum yields of 193.5 ms and 35.07% were obtained by embedding the luminescent centers of ciprofloxacin into the formed rigid boric acid matrix by a one-step hydrothermal with purple light as the excitation wavelength. It is worth mentioning that the constructed composites exhibit dual-mode afterglow (DF and RTP) features at room temperature. Moreover, the carbon dots composites have distinctive temperature-responsive color-tunable properties and represent afterglow emission dominated by delayed fluorescence or phosphorescence at different temperatures. Based on the extraordinary temperature sensitivity, a single-mode ultra-long phosphorescence with a lifetime of up to 1.11 s is achieved at low temperatures. Additionally, as-prepared carbon dots composites exhibit the afterglow quantum yield of 40.97% in CB-VII, which is an ultra-high value for inorganic non-metallic materials. Furthermore, the resultant composites of carbon dots with new potential materials of encryption technology are designed for advanced information encryption and anti-counterfeiting applications.

PENGGUNAAN MATERIAL LOGAM DI BERBAGAI INDUSTRI MANUFAKTUR INDONESIA: SISTEMATIK KAJIAN LITERATUR

Material processing techniques in the manufacturing industry in Indonesia are more dominant in using metal applications as the main raw material in product design in the form of machines. The use of metal materials needs to be studied because before they are used in the industry, their designation must be known first so that these materials can be optimized in their use. The process of processing metal materials must pay attention to their type and properties in advance, especially in the process of forming and behavior during use. So that in its application it can be following the specifications of raw materials in a product that is produced. This study aims to find out and identify how important the role of metal materials is in their application in the world of the Indonesian manufacturing industry. This research method uses a systematic literature review method by collecting 20 articles related to the use of metal materials in various manufacturing industries from several national journals on the Google Scholar database. This research found several dominant articles published in 2020 and focused on the alloy casting industry. The results obtained from the collected data are that the use of metal materials plays an important role in the manufacturing industry in Indonesia. Metal materials are still very much needed as one of the main raw materials in the manufacturing industry because these materials have unique properties that non-metallic materials do not have