Short Hole Research Articles

Machining Characteristics During Short Hole Drilling of Titanium Alloy Ti10V2Fe3Al

The single-phase titanium ß-alloy Ti10V2Fe3Al (Ti-1023) has been widely used in the aerospace industry due to its unique mechanical properties, which include high fatigue strength and fracture toughness, as well as high corrosion resistance. On the other hand, these unique properties significantly hinder the cutting processes of this material, especially those characterized by a closed machining process area, such as drilling. This paper is devoted to the study of the short hole drilling process of the above-mentioned titanium alloy using direct measurements and numerical modeling. Measurements of the cutting force components in the drilling process and determination of the resultant cutting force and total cutting power were performed. The macro- and microstructure of chips generated during drilling were analyzed, and the dependence of the chip compression ratio and the distance between neighboring segments of serrated chips on cutting speed and drill feed was determined. Experimental studies were supplemented by determining the temperature on the lateral clearance face of the drill’s outer cutting insert in dependence on the cutting modes. For the modeling of the drilling process using the finite element model, the parameters of the triad of component submodels of the numerical model were determined: the machined material model, the model of contact interaction between the tool and the machined material, and the fracture model of the machined material. The determination of these parameters was performed through the DOE sensitivity analysis. The target values for performing this analysis were the total cutting power and the distance between neighboring chip segments. The maximum deviation between the simulated and experimentally determined values of the resulting cutting force is no more than 25%. At the same time, the maximum deviation between the measured values of the temperature on the lateral clearance face of the drill’s outer cutting insert and the corresponding simulated values is 26.1%.

Fe2O3 Nanoflakes - WS2 Nanosheets Heterojunctions for Multi-Fold Enhancement in Photoelectrochemical Solar Energy Conversion.

Fe2O3-based photoanodes show great potential in photoelectrochemical water splitting due to their excellent stability, moderate band gap, and abundance. However, a short hole diffusion length limits its photocurrent density. Here, a multi-fold enhancement in photocurrent density from Fe2O3 nanoflakes - WS2 nanosheets heterojunction is reported. The heterojunction exhibits a synergistic photocurrent density of 0.52mA cm-2 at 1.3V (versus RHE) under AM 1.5G simulated sunlight, which is 2.23 times higher than pristine Fe2O3 nanoflakes. The Mott-Schottky and Nyquist plots indicate a higher charge density with lower charge transfer resistance at the semiconductor-electrolyte junction. The density functional theory (DFT) -based first-principles calculations are performed by designing a heterostructure between Fe2O3(110) and WS2(001) similar to the experimentally found arrangement of crystal planes. Free energy analysis and relative band extrema positions, obtained from DFT calculations and valence band spectroscopy, indicate the formation of type II heterojunction with partial oxygen terminated surface of Fe2O3. The type-II band alignment with a charge transfer of 4.8 × 10-4 e per interfacial WS2 to Fe2O3, helps in easy separation of photogenerated charges. The work establishes both an experimental design and a theoretical framework of highly crystalline nanoflakes-nanosheet heterojunctions for efficient photoelectrochemical solar energy conversion.

Synthesis, characterization and photoelectrochemical performance of Bi2Fe4O9 thin films

Mullite-type Bi2Fe4O9 has been little explored in thin film form as a photoanode for photoelectrochemical water splitting. In this study, Bi2Fe4O9 thin films have been prepared using the sol-gel technique from a simple precursor solution based on the corresponding metal salts, acetic acid, and polyvinyl alcohol. The films were deposited by dip-coating onto fluorine-doped tin oxide substrates and dried at 350 °C, repeating the dipping-drying cycle six times, and finally sintered at 600 °C. The films were characterized by GIXRD, revealing the formation of the material in its orthorhombic phase. Raman spectroscopy showed the Ag and B1g vibrational modes, validating the formation of the bismuth iron oxide. UV–Vis transmittance measurements revealed that the material exhibits two optical transitions: a direct band gap of 2.86 eV and an indirect band gap of 1.98 eV. FESEM micrographs and AFM images showed a uniform nanostructured surface morphology. The photoelectrochemical properties of the Bi2Fe4O9 films were studied using cyclic voltammetry and chronoamperometry with front side illumination, demonstrating the stability of the material in aqueous media and the generation of photocurrent in the presence of H2O2. Furthermore, results from intensity-modulated photocurrent spectroscopy (IMPS) revealed that the photocurrent is limited by both bulk and surface recombination and a short hole diffusion length.

Interaction of Mechanical Characteristics in Workpiece Subsurface Layers with Drilling Process Energy Characteristics

The performance properties of various types of parts are predominantly determined by the subsurface layer forming methods of these parts. In this regard, cutting processes, which are the final stage in the manufacturing process of these parts and, of course, their subsurface layers, play a critical role in the formation of the performance properties of these parts. Such cutting processes undoubtedly include the drilling process, the effect of which on the mechanical characteristics of the drill holes subsurface layers is evaluated in this study. This effect was evaluated by analyzing the coincidence of the energy characteristics of the short hole drilling process with the mechanical characteristics of the drilled holes’ subsurface layers. The energy characteristics of the short-hole drilling process were the total drilling power and the cutting work in the tertiary cutting zone, which is predominantly responsible for the generation of mechanical characteristics in the subsurface layers. As mechanical characteristics of the drill holes’ subsurface layers were used, the microhardness of machined surfaces and total indenter penetration work determined by the instrumented nanoindentation method, as well as maximal indenter penetration depth, were determined by the sclerometry method. Through an analysis of the coincidence between the energy characteristics of the drilling process and the mechanical characteristics of the subsurface layers, patterns of the effect of drilling process modes, drill feed, and cutting speed, which essentially determine these energy characteristics, on the studied mechanical characteristics have been established. At the same time, the increase in the energy characteristics of the short-hole drilling process leads to a decrease in the total indenter penetration work and the maximum indenter penetration depth simultaneously with an increase in the microhardness of the drilled holes’ subsurface layers.

BiVO4 Photoanode with NiV2O6 Back Contact Interfacial Layer for Improved Hole-Diffusion Length and Photoelectrochemical Water Oxidation Activity.

The short hole diffusion length (HDL) and high interfacial recombination are among the main drawbacks of semiconductor-based solar energy systems. Surface passivation and introducing an interfacial layer are recognized for enhancing HDL and charge carrier separation. Herein, we introduced a facile recipe to design a pinholes-free BiVO4 photoanode with a NiV2O6 back contact interfacial (BCI) layer, marking a significant advancement in the HDL and photoelectrochemical activity. The fabricated BiVO4 photoanode with NiV2O6 BCI layer exhibits a 2-fold increase in the HDL compared to pristine BiVO4. Despite this improvement, we found that the front surface recombination still hinders the water oxidation process, as revealed by photoelectrochemical (PEC) studies employing Na2SO3 electron donors and by intensity-modulated photocurrent spectroscopy measurements. To address this limitation, the surface of the NiV2O6/BiVO4 photoanode was passivated with a cobalt phosphate electrocatalyst, resulting in a dramatic enhancement in the PEC performance. The optimized photoanode achieved a stable photocurrent density of 4.8 mA cm-2 at 1.23 VRHE, which is 12-fold higher than that of the pristine BiVO4 photoanode. Density Functional Theory (DFT) simulations revealed an abrupt electrostatic potential transition at the NiV2O6/BiVO4 interface with BiVO4 being more negative than NiV2O6. A strong built-in electric field is thus generated at the interface and drifts photogenerated electrons toward the NiV2O6 BCI layer and photogenerated holes toward the BiVO4 top layer. As a result, the back-surface recombination is minimized, and ultimately, the HDL is extended in agreement with the experimental findings.

Combined effects of annealing treatment and compounding with FeOOH cocatalyst on efficiency and stability of BiVO4/Ag3PO4 photoanode

Bismuth vanadate (BiVO4) is a promising metal oxide photoabsorber for photoanode applications but is limited by its relatively short hole diffusion length resulting in severe charge complexation and limited performance. Herein, Ag3PO4 was compounded on BiVO4 through photodeposition of Ag followed by solution oxidation. The annealing of the composite BiVO4/Ag3PO4 heterojunction at 400 °C precipitated some Ag from Ag3PO4 on BiVO4/Ag3PO4 to form a new ternary photoanode BiVO4/Ag3PO4/Ag. Compared to the unannealed sample, the light trapping and crystal quality enhanced, resulting in increased photocurrent density of the annealed BiVO4/Ag3PO4 photoanode (4.46 mA cm−2) by 59.9 % when compared to the unannealed photoanode (2.79 mA cm−2). To further optimize the photoanode, co-catalyst iron hydroxyl oxide (FeOOH) was deposited to yield BiVO4/Ag3PO4/Ag/FeOOH photoanode with maximum photocurrent density of 4.71 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode, VRHE), equivalent to about 3.7-fold the value of BiVO4 photoanode. The photoanode maintained 90.8 % of its initial current density after 3 h stability tests. Besides, the photoelectrocatalytic degradation of Rhodamine B pollutant by BiVO4/Ag3PO4/Ag and BiVO4/Ag3PO4/Ag/FeOOH photoanode showed performance enhancement when compared to BiVO4/Ag3PO4. Overall, the proposed strategy looks very promising for the rational fabrication of high-efficiency heterojunction photoanodes.

Decoupled Crystallization and Particle Growth of BiVO4 via Rapid Thermal Process for Enhanced Charge Separation

AbstractBiVO4 is one of the most promising candidates for photoelectrochemical water oxidation. However, the poor crystallinity and short hole diffusion length limit its charge separation. One bottleneck stems from the contradiction between high crystallinity and small particles via conventional furnace heating processes. This paper describes the design and fabrication of BiVO4 photoanodes via rapid thermal process (RTP), rather than furnace heating, to decouple the constraints between nucleation, crystallization, and growth processes of BiVO4. The higher heating ramp rate of RTP compared with furnace heating promotes the fast diffusion of reactant molecules, which elevates the nucleation rate above the particle growth rate of BiVO4, leading to small particles with high crystallinity. Moreover, the ultra‐high heating temperature makes it possible to crystallize the small BiVO4 particle within a short time. Thus, a high crystallinity can be obtained for the RTP‐treated BiVO4 while maintaining small particle size, achieving a charge separation efficiency of up to 82%, 30% higher than that of furnace‐treated BiVO4 photoanode.

Electrochemical deposition of hydrothermally pretreated TiO2 on aluminium substrate through the formation of peroxotitanium complex and their application towards visible light assisted photocurrent generation

Herein, we report a novel method for the electrochemical deposition of TiO2 on Al substrate through the formation of peroxotitanium complex without any post heat treatment process. The alkaline treated titanium precursors were used as an electrolyte and TiO2 was deposited onto aluminium substrate by both cathodic reduction and electrophoretic deposition through the formation of peroxotitanium complex. The electrodeposition process was optimized by varying the pH, concentration of the electrolyte, deposition voltage, time and area of the electrode respectively. The optimized condition to obtain a maximum yield is as follows: voltage (4.5 V), time (2.5 h), pH (5) and area of the electrode 3 × 3 cm2. The deposits were then characterized using various material characterization techniques such as high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and Raman spectroscopy respectively. The morphological analysis showed the deposition of nanocrystalline TiO2 with irregular morphology on Al substrate. The AFM revealed a non-uniform deposition of TiO2 with high surface roughness (average roughness: 44.60 nm). The XRD pattern and Raman spectrum confirmed the presence of anatase phase of TiO2. The obtained TiO2 were then subjected to photoelectrochemical studies by coating over an ITO electrode. The nanocrystalline TiO2 showed excellent photocurrent response which could be due to the short hole retrieval and fast electron transport across the electrode-electrolyte interface. The proposed method can be promising towards the industrial application for the extraction and recovery of TiO2 from the mineral ore residues and spent mining waste.

Numerical Modeling of Cutting Characteristics during Short Hole Drilling: Part 2—Modeling of Thermal Characteristics

The modeling of machining process characteristics and, in particular, of various cutting processes occupies a significant part of modern research. Determining the thermal characteristics in short hole drilling processes by numerical simulation is the object of the present study. For different contact conditions of the workpiece with the drill cutting inserts, the thermal properties of the machined material were determined. The above-mentioned properties and parameters of the model components were established using a three-dimensional finite element model of orthogonal cutting. Determination of the generalized values of the machined material thermal properties was performed by finding the set intersection of individual properties values using a previously developed software algorithm. A comparison of experimental and simulated values of cutting temperature in the workpiece points located at different distances from the drilled hole surface and on the lateral clearance face of the drill outer cutting insert shows the validity of the developed numerical model for drilling short holes. The difference between simulated and measured temperature values did not exceed 22.4% in the whole range of the studied cutting modes.

Hematite (α-Fe2O3) with Oxygen Defects: The Effect of Heating Rate for Photocatalytic Performance.

Hematite (α-Fe2O3) emerges as an enticing material for visible-light-driven photocatalysis owing to its remarkable stability, low toxicity, and abundance. However, its inherent shortcomings, such as a short hole diffusion length and high recombination rate, hinder its practical application. Recently, oxygen vacancies (Vo) within hematite have been demonstrated to modulate its photocatalytic attributes. The effects of Vo can be broadly categorized into two opposing aspects: (1) acting as electron donors, enhancing carrier conductivity, and improving photocatalytic performance and (2) acting as surface carrier traps, accelerating excited carrier recombination, and deteriorating performance. Critically, the generation rate, distribution, role, and behavior of Vo significantly differ for synthesis methods due to differences in formation mechanisms and oxygen diffusion. This complexity hampers simplified discussions of Vo, necessitating careful investigation and nuanced discussion tailored to the specific method and conditions employed. Among various approaches, hydrothermal synthesis offers a simple and cost-effective route. Here, we demonstrate a hydrothermal synthesis method for Vo introduction to hematite using a carbon source, where variations in the heating rate have not been previously explored in terms of their influence on Vo generation. The analyses revealed that the concentration of Vo was maximized at a heating rate of 16 °C/min, indicative of a high density of surface defects. With regard to photocatalytic performance, elevated heating rates (16 °C/min) fostered the formation of Vo primarily on the hematite surface. The photocatalytic activity was 7.1 times greater than that of the sample prepared at a low heating rate (2 °C/min). These findings highlight the crucial role of surface defects, as opposed to bulk defects, in promoting hematite photocatalysis. Furthermore, the facile control over Vo concentration achievable via manipulating the heating rate underscores the promising potential of this approach for optimizing hematite photocatalysts.

Designing the edges of holes (with bias flow) to maximise acoustic damping

Circular holes with a mean bias flow passing through them can amplify or damp acoustic energy and this property is relevant for many industrial applications. In this work, we propose a methodology to design the edges of such holes so that the acoustic damping is maximised. The approach relies on a Bayesian optimisation framework and is illustrated in a short circular hole with a mean laminar bias flow. The acoustic response of the perforation is characterised numerically using a two-step approach where, first, a steady mean flow is computed as the solution of the incompressible Navier–Stokes equations. Second, small-amplitude acoustic perturbations are superimposed on this mean flow and their dynamics are obtained as the solution of the linearised compressible Navier–Stokes equations. Both the upstream and downstream edges of the hole are modified with 45°chamfers. The sizes of these two chamfers are the control parameters optimised to maximise the acoustic absorption coefficient. The results of this letter show that the careful design of the edges can dramatically increase the acoustic energy that holes can damp: the hole investigated here goes from one generating 55% more acoustic energy than incident upon it at a given frequency to one that damps 46% of this acoustic energy.

Experimental study on seismic performance of two-segment replaceable link with separated splicing plates

Traditional I-beam sections connected with end plates face challenges related to end bolts and excessive residual deformation. In response to these challenges, this study introduces an innovative concept: two-segment replaceable links with separated splicing plates. Two variations of replaceable links have been designed - one with separated splicing plates featuring standard bolt holes, and another with short slotted bolt holes. Cyclic loading tests has been conducted to study their seismic performance. The test results reveal that the failure modes of the links include flange buckling and tearing at the welds connecting the flange and end plate. The hysteresis curves of the specimens are complete and stable. The average overstrength coefficient of the links is 1.75, meeting the specified limit requirement for an overstrength coefficient greater than 1.5 for the link. The ultimate plastic rotation reaches up to 0.19 rad. Notably, specimens with short slotted bolt holes exhibit a relatively significant energy dissipation ratio due to bolts slip during test and they demonstrate optimal replaceability in terms of minimized replacement time and residual shear rotation. Furthermore, the two-stage design method for high-strength bolts in splicing plate is proposed considering bolts slip.

Preparation of NiMoO4/CdS and its Application as a Photocatalyst in H2 Evolution Reaction

AbstractThe construction of heterojunction is considered to be an effective strategy for achieving efficient photocatalyst. The pure CdS shows low hydrogen production activity, for the low charges separation efficiency and the short electron and hole lifetime, which greatly limit its practical application. Therefore, we constructed heterojunction photocatalysts of NiMoO4/CdS by a simple solvothermal method. The photocatalytic hydrogen production activity of CdS was obviously improved by NiMoO4 loaded. The NiMoO4/CdS‐2 sample shows the highest H2 generation rate, which could reach 5830.49 μmolg−1 h−1, which is 122.3 times higher than that of pure CdS. The construction of heterojunction between CdS and NiMoO4 inhibits the recombination of photogenerated charges, prolongs the lifetime of photogenerated charges and improves photocatalytic hydrogen production performance. This work is important for the construction of an efficient catalytic system for the photocatalytic H2 evolution from water splitting.

Integration of surficial oxygen vacancies and interfacial two-dimensional NiFe-layered double hydroxide nanosheets onto bismuth vanadate photoanode for boosted photoelectrochemical water splitting

Considering its outstanding cost-to-efficiency ratio, N-type bismuth vanadate (BiVO4) is an ideal photoanode for photoelectrochemical (PEC) water splitting. Nevertheless, the widespread application of BiVO4 is being hindered commercially by innate challenges such as its poor carrier mobility, short hole diffusion length, and sluggish oxidation chemistry. Herein, we report the unique integration of surficial oxygen vacancies (Ovac) in conjunction with two-dimensional (2D) nickel-iron (NiFe) layered double hydroxide (LDH) nanosheets onto pristine BiVO4 photoanode to tweak the charge transfer kinetics during water splitting. The introduction of oxygen vacancies efficiently modulates band energetics, amplifies light absorption, and augments the carrier density. Concurrently, the 2D NiFe-LDH nanosheets play a dual role by facilitating interfacial hole transfer, thereby reducing excessive defect states, and serving as a protective layer against photocorrosion, ultimately resulting in a notable improvement in solar-driven water oxidation efficiency. The results of PEC water-splitting experiments demonstrate that the BiVO4 photoanode enriched with surficial oxygen vacancies and NiFe-LDH (BiVO4:Ovac/NiFe-LDH) achieved a photocurrent density of 2.92 mA cm−2 with ∼3-fold enhancement compared with a pristine BiVO4 photoanode. The engineered BiVO4 system yielded an impressive photoconversion efficiency of 1.29 %, charge separation efficiency (ηsep) > 40 %, and charge transport efficiency (ηtrans) > 35 %, clearly evidencing a boost in the charge dynamics of pristine BiVO4. Furthermore, during long-term stability testing, BiVO4:Ovac/NiFe-LDH retained 91 % of its initial photocurrent density for ∼20 h without any significant deterioration. This work sheds light on the role of integrating surface and interface engineering tactics for enhancing photo-induced charge transport in BiVO4, thereby providing efficient and stable PEC water splitting.

Numerical Modeling of Cutting Characteristics during Short Hole Drilling: Modeling of Kinetic Characteristics

Analyzing the cutting process characteristics opens up significant opportunities to improve various material machining processes. Numerical modeling is a well-established, powerful technique for determining various characteristics of cutting processes. The developed spatial finite element model of short hole drilling is used to determine the kinetic characteristics of the machining process, in particular, the components of cutting force and cutting power. To determine the component model parameters for the numerical model of drilling, the constitutive equation parameters, and the parameters of the contact interaction between the drill and the machined material on the example of AISI 1045 steel machining, the orthogonal cutting process was used. These parameters are determined using the inverse method. The DOE (Design of Experiment) sensitivity analysis was applied as a procedure for determining the component models parameters, which is realized by multiple simulations using the developed spatial FEM model of orthogonal cutting and the subsequent determination of generalized values of the required parameters by finding the intersection of the individual value sets of these parameters. The target values for the DOE analysis were experimentally determined kinetic characteristics of the orthogonal cutting process. The constitutive equation and contact interaction parameters were used to simulate the short hole drilling process. The comparison of experimentally determined and simulated values of the kinetic characteristics of the drilling process for a significant range of cutting speed and drill feed changes has established their satisfactory coincidence. The simulated value deviation from the corresponding measured characteristics in the whole range of cutting speed and drill feed variation did not exceed 23%.

A Review: Research Progress on Photoelectric Catalytic Water Splitting of α-Fe2O3

Abstract: Photoelectric catalytic water splitting for hydrogen production is considered a promising method for hydrogen production, which can convert clean and renewable solar energy into sustainable and pollution-free hydrogen energy. An in-depth understanding of the relationship between the properties and functions of photocatalytic materials can help design and prepare efficient photodegradable water systems. Among them, α-Fe2O3 has a suitable band gap, can absorb visible light below 600 nm, and has the advantages of abundant raw materials high stability, and has become one of the most promising photoelectrode materials. However, as a photoelectrode material, α-Fe2O3 has the shortcomings of short photogenerated hole diffusion distance, low oxidation kinetics, poor conductivity, ease to be corroding, and so on, resulting in a very low photoelectric conversion efficiency, which limits its application in the field of photoelectric catalysis. This paper reviews the research progress of α-Fe2O3 as a photoanode. Firstly, the principle of photoelectric catalytic water splitting for hydrogen production and the main preparation methods of α-Fe2O3 photoanode is described; Secondly, the research work on modification of α- Fe2O3 photoanode by morphology control, element doping, construction of the heterojunction, surface modification and thermal excitation assisted effect in recent years is introduced. The photochemical performance of α-Fe2O3 photoanode is enhanced by improving the photocurrent density and the transfer of photo-generated carriers.

Aerothermal characteristics of thin double-wall effusion cooling systems with novel slot holes and cellular architectures for gas turbines

Double-wall effusion cooling system is a promising cooling solution for next-generation gas turbines. Thinning the blade wall can bring the coolant closer to the hot stream, thereby enhancing overall cooling effectiveness. However, a thin blade wall creates film cooling holes with a short length-to-diameter ratio, which increases jet-crossflow mixing and reduces coolant attachment, inevitably degrading film cooling performance. Herein, we constructed a new thin double-wall effusion cooling system by integrating novel short slot holes for better coolant attachment and triply periodic minimal surface (TPMS) based cellular architectures for improved internal heat transfer. The effects of wall thickness, film hole shape, and internal turbulators configurations were numerically studied. Adiabatic and overall film cooling effectiveness, vortex structures, and aerodynamics loss were comprehensively assessed. The results demonstrate that the novel slot hole significantly improves the overall film cooling effectiveness under thin wall conditions by enhancing the attachment of kidney vortices to walls. Notably, compared to the short fan-shaped hole (scheme B), the novel slot hole (scheme C) shows an improvement in the averaged overall cooling effectiveness of over 20% and a reduction in the total pressure loss coefficient by 60%. Furthermore, three TPMS-based cellular architectures produce similar overall film cooling effectiveness and reduction of total pressure loss coefficient in the range of 0.57-0.81 and 23%-53%, respectively. This work provides guidance for designing thin double-wall effusion cooling systems for next-generation gas turbines.

Doping with Rare Earth Elements and Loading Cocatalysts to Improve the Solar Water Splitting Performance of BiVO4

BiVO4 is a highly promising material for Photoelectrochemical (PEC) water splitting photoanodes due to its narrow band gap value (~2.4 eV) and its ability to efficiently absorb visible light. However, the short hole migration distance, severe surface complexation, and low carrier separation efficiency limit its application. Therefore, in this paper, BiVO4 was modified by loading CoOOH cocatalyst on the rare earth element Nd-doped BiVO4 (Nd-BiVO4) photoanode. The physical characterization and electrochemical test results showed that Nd doping will cause lattice distortion of BiVO4 and introduce impurity energy levels to capture electrons to increase carrier concentration, thereby improving carrier separation efficiency. Further loading of surface CoOOH cocatalyst can accelerate charge separation and inhibit electron–hole recombination. Ultimately, the prepared target photoanode (CoOOH-Nd-BiVO4) exhibits an excellent photocurrent density (2.4 mAcm−2) at 1.23 V versus reversible hydrogen electrode potential (vs. RHE), which is 2.67 times higher than that of pure BiVO4 (0.9 mA cm−2), and the onset potential is negatively shifted by 214 mV. The formation of the internal energy states of rare earth metal elements can reduce the photoexcited electron–hole pair recombination, so as to achieve efficient photochemical water decomposition ability. CoOOH is an efficient and suitable oxygen evolution cocatalyst (OEC), and OEC decoration of BiVO4 surface is of great significance for inhibiting surface charge recombination. This work provides a new strategy for achieving effective PEC water oxidation of BiVO4.

Effect of thermal damage on dynamic and static mechanical properties of CFRP short pulse laser hole cutting

Carbon fiber reinforced polymer (CFRP) composites are widely used in the aerospace field because of their outstanding performance. Short pulse laser is an effective means for efficient and high-quality cutting of CFRP. However, the inevitable thermal effect of laser processing results in damage such as heat-affected zone, and the exposed area of fiber loses the ability to transmit force, which weakens the mechanical properties of CFRP. However, the effect of thermal damage on mechanical properties is complex. In this paper, the dynamic and static mechanical behavior of short pulse laser cutting CFRP is studied, and the effect of cutting damage on the mechanical properties is explored. The mechanical properties of CFRP plate hole laser cutting is similar to those of mechanical drilling but are lower than those of material without hole due to the existence of holes. Matrix cracking exists in the tensile fatigue of laser cutting holes, while surface cracks occur in the stress-concentrated area due to the not smooth cutting edge of mechanical drilling. Compared with small laser cutting damage, the tensile and bending strength of the CFRP plate were weakened by 11.5% and 6.2%, respectively. The tensile fatigue crack propagation and fiber protrusion are aggravated by large damage. The damage always starts at both sides of the vertical direction of the hole under 0° laying, resulting in cracks along the fiber axis until fracture. The failure mode and fracture cross-section morphology are mainly fiber tears and delamination, and the section of the 90° laying specimen surface is tidier than that of the 0° laying specimen. The mechanical properties under thermal damage studied in this paper will help to lay a foundation for damage suppression and improvement of material mechanical properties.

α-Fe2O3 mediated periodate activation for selective degradation of phenolic compounds via electron transfer pathway under visible irradiation

Periodate (PI)-photoactivated advanced oxidation process (AOP) has recently received increasing attention for the removal of micropollutants from water. However, periodate is mainly driven by high-energy ultraviolet light (UV) in most cases, and few studies have extended it to the visible range. Herein, we proposed a new PI visible light activation system employing α-Fe2O3 as catalyst. It is completely different from traditional PI-AOP based on hydroxyl radicals (•OH) and iodine radical (•IO3). The vis-α-Fe2O3/PI system can selectively degrade the phenolic compounds via non-radical pathway under the visible range. Notably, the designed system not only shows a well pH tolerance and environmental stability, but also exhibits a strong substrate-dependent reactivity. Both quenching experiments and electron paramagnetic resonance (EPR) experiments demonstrate that photogenerated holes are the main active species in this system. Moreover, a series of photoelectrochemical experiments reveal that PI can effectively inhibit the carrier recombination on the α-Fe2O3 surface, thereby improving the utilization of photogenerated charges and increasing the number of photogenerated holes, which effectively reacts with 4-CP through electron transfer way. In a word, this work proposes a cost-effective, green and mild mean to activate PI, and provides a facile way to solve the fatal shortcomings (i.e., inappropriate band edge position, rapid charge recombination and short hole diffusion length) of traditional iron oxide semiconductor photocatalysts.