bluuebunny/crossref_metadata_2025 huggingface dataset:
Eco-Friendly Approach for the Construction of Superhydrophobic Coating on Stainless Steel Metal Based on Biological Metal–Organic Framework and Its Corrosion Resistance Performance
Authors: Almufarij Rasmiah Saad , Fetouh El Sayed Howida Abouel , Mohamed Mohamed Elshahat
Published: July 2023

In this paper, we present a sustainable approach for the creation of superhydrophobic (SP) coating on a stainless-steel substrate based on a biological metal–organic framework (MOF). The MOF was synthesized using aspartic acid as a linker and copper ions as a core metal. Two SP coatings were well constructed on stainless steel utilizing electrodeposition of nickel (Ni) and nickel altered by MOF (Ni@Bio-MOF) coatings followed by soaking in a solution of stearic acid in ethanol. The results of Fourier transform infrared spectroscopy demonstrate that the stearic acid-grafted nickel coating (Ni@SA) and the stearic acid-grafted Ni@Bio-MOF composite (Ni@Bio-MOF@SA), were effectively deposited on the stainless steel. The wettability findings displayed that the water contact angle of Ni@SA and Ni@Cu-As MOF@SA are 160° ± 1.1°, and 168° ± 1.2°, respectively. The prepared SP coating was also found to be chemically and mechanically stable. The results show that the Ni@SA coating maintains SP characteristics in a pH range of 3–11 while the Ni@Cu-As MOF@SA coating retained SP characteristics in a pH range of 1–13. Additionally, the superhydrophobic Ni@SA coating demonstrated SP characteristics up to a length of abrasion equal to 1300 mm, while the Ni@Cu-As MOF@SA coating exhibited SP characteristics up to a length of abrasion equal to 2700 mm. Furthermore, the Ni@SA and Ni@Cu-As MOF@SA coatings exhibited significantly improved corrosion protection in a 0.5 M NaCl solution compared with bare stainless steel, with protection efficiencies of approximately 94% and 99%, respectively. The results of this study demonstrate that the proposed approach is a promising method for the fabrication of eco-friendly and corrosion-resistant SP coatings on stainless steel substrate.
Development of Photo-Polymerization-Type 3D Printer for High-Viscosity Ceramic Resin Using CNN-Based Surface Defect Detection
Authors: Chung Jin-Kyo , Im Jeong-Seon , Park Min-Soo
Published: July 2023

Due to the high hardness and brittleness of ceramic materials, conventional cutting methods result in poor quality and machining difficulties. Additive manufacturing has also been tried in various ways, but it has many limitations. This study aims to propose a system to monitor surface defects that occur during the printing process based on high-viscosity composite resin that maximizes ceramic powder content in real time using image processing and convolutional neural network (CNN) algorithms. To do so, defects mainly observed on the surface were classified into four types by form: pore, minor, critical, and error, and the effect of each defect on the printed structure was tested. In order to improve the classification efficiency and accuracy of normal and defective states, preprocessing of images obtained based on cropping, dimensionality reduction, and RGB pixel standardization was performed. After training and testing the preprocessed images based on the DenseNet algorithm, a high classification accuracy of 98% was obtained. Additionally, for pore and minor defects, experiments confirmed that the defect surfaces can be improved through the reblading process. Therefore, this study presented a defect detection system as well as a feedback system for process modifications based on classified defects.
Recent Progress in Testing and Characterization of Hardenability of Aluminum Alloys: A Review
Authors: Gao Chang , Liu Xin , Zhao Dong , Guo Yiming , Chen Shaohua , Gao Fantao , Liu Tianle , Cai Zhenyang , Liu Danyang , Li Jinfeng
Published: July 2023

In this paper, the progress of the test methods and characterization approaches of aluminum alloys hardenability was reviewed in detail. The test method mainly included the traditional end-quenching method and the modified method. While the characterization approaches of alloy hardenability consist mainly of ageing hardness curves, solid solution conductivity curves, ageing tensile curves, time temperature transformation (TTT) curves, time temperature properties (TTP) curves, continuous cooling transformation (CCT) curves, and advanced theoretical derivation method have appeared in recent years. The hardenability testing equipment for different tested samples with different material natures, engineering applications properties, and measurement sizes was introduced. Meanwhile, the improvement programmed proposed for shortcomings in the traditional hardenability testing process and the current deficiencies during the overall hardenability testing process were also presented. In addition, the influence factors from the view of composition design applied to the hardenability behaviors of Aluminum alloys were summarized. Among them, the combined addition of micro-alloying elements is considered to be a better method for improving the hardenability of high-strength aluminum alloys.
Highly Sensitive Detection of Microstructure Variation Using a Thickness Resonant Transducer and Pulse-Echo Third Harmonic Generation
Authors: Jeong Hyunjo , Shin Hyojeong , Zhang Shuzeng , Li Xiongbing
Published: July 2023

In nonlinear ultrasound testing, the relative nonlinear parameter is conveniently measured as a sensitive means of detecting and imaging overall variation of microstructures and damages. Compared to the quadratic nonlinear parameter (β′), the cubic nonlinear parameter (γ′), calculated as the third harmonic amplitude divided by the cube of the fundamental amplitude, has generally a higher value, providing better sensitivity in nonlinear parameter mapping. Since the third harmonic amplitude is about two orders of magnitude lower than the fundamental amplitude, efficient excitation and highly sensitive reception of third harmonic is very important. In this paper, we explore an odd harmonic thickness resonant transducer that meets the requirements for pulse-echo third harmonic generation (THG) measurements. We also address the problem of source nonlinearity that may be present in the measured amplitude of the third harmonic and propose a method to properly correct it. First, we measure γ′ for a series of aluminum specimens using the through-transmission method to observe the behavior of γ′ as a function of specimen thickness and input voltage, and examine the effects of various corrections such as attenuation, diffraction and source nonlinearity. Next, we apply the odd harmonic resonant transducer to pulse-echo THG measurements of precipitation heat-treated specimens. It is shown that such transducer is very effective in generation and detection of fundamental and third harmonics under finite amplitude toneburst excitation. The highly sensitive detectability of γ′ are presented as a function of aging time, and the sensitivity of γ′ is compared with that of β′ and β′2.
Study on the Mechanical Properties of Continuous Composite Beams under Coupled Slip and Creep
Authors: Nan Hongliang , Wang Peng , Zhang Qinmin , Meng Dayao , Lei Qinan
Published: July 2023

Steel–concrete continuous composite beams are widely used in buildings and bridges and have many economic benefits. Slip has always existed in composite beams and will reduce the stiffness of composite beams. The effect of creep under a long-term load will also be harmful. Many scholars ignore the combined effects of slip and creep. In order to more accurately study the mechanical properties of steel–concrete continuous composite beams under long-term loads, this paper will consider the combined actions of slip and creep. By combining the elastic theory and the age-adjusted effective modulus method, the differential equation of the composite beam is derived via the energy variational method. The analytical solutions of axial force, deflection and slip under a uniform load are obtained by substituting the relevant boundary conditions. The creep equation is used to simulate the behavior of concrete with time in ANSYS. The analytical solution is verified by establishing a finite element model of continuous composite beams considering slip and creep. The results suggest the following: the analytical solution is consistent with the finite element simulation results, which verifies the correctness of the analytical solution. Considering the slip and creep effects will increase the deflection of the composite beam and the bending moment of the steel beam, reduce the bending moment of the concrete slab and have a significant impact on the structural performance of the continuous composite beam. The research results considering the coupling effect of slip and creep on continuous composite beams can provide a theoretical basis for related problems.
Simplified Evaluation of Shear Stiffness Degradation of Diagonally Cracked Reinforced Concrete Beams
Authors: Zheng Kaiqi , Zhou Siyuan , Zhang Yaohui , Wei Yang , Wang Jiaqing , Wang Yuxi , Qin Xiaochuan
Published: July 2023

Shear cracking in concrete box-girder bridges, which could cause excessive deflection during the serviceability limit state, cannot be effectively avoided by code-guided design. While elastic shear deformation only accounts for a small proportion of total deformation for un-cracked reinforced concrete (RC) beams, the magnitude of after-cracking shear deformation becomes comparable to flexural deformation for RC beams. However, there is still a lack of practical models to predict the after-cracking shear deformation of RC beams. First, six thin-webbed I beams were tested to investigate the shear stiffness degradation mechanism and the decrease ratio. Then, a very simple truss strut angle formula, which is the crucial parameter for shear stiffness, was established. Furthermore, a stiffness degradation rule for partially cracked beams was proposed considering the influence of concrete tension stiffening, which is essential for predicting the development process of after-cracking shear deformation. Finally, directly measured shear strains were used to validate the proposed shear stiffness model. The results showed that the shear stiffness drops to about 30~40% of the original stiffness after the first diagonal crack, and the remaining shear stiffness is only about 10% of the original one when the stirrup yields. Increasing the stirrup ratio is a more effective method to control shear stiffness degradation for diagonally cracked RC beams. Also, the proposed shear stiffness model well captures the main features of the shear stiffness degradation, and it provides a relatively accurate prediction of the equivalent shear stiffness at the post-cracking stage.
Travelling through the Natural Hierarchies of Type I Collagen with X-rays: From Tendons of Cattle, Horses, Sheep and Pigs
Authors: Terzi Alberta , Gallo Nunzia , Sibillano Teresa , Altamura Davide , Masi Annalia , Lassandro Rocco , Sannino Alessandro , Salvatore Luca , Bunk Oliver , Giannini Cinzia , De Caro Liberato
Published: July 2023

Type I collagen physiological scaffold for tissue regeneration is considered one of the widely used biomaterials for tissue engineering and medical applications. It is hierarchically organized: five laterally staggered molecules are packed within fibrils, arranged into fascicles and bundles. The structural organization is correlated to the direction and intensity of the forces which can be loaded onto the tissue. For a tissue-specific regeneration, the required macro- and microstructure of a suitable biomaterial has been largely investigated. Conversely, the function of multiscale structural integrity has been much less explored but is crucial for scaffold design and application. In this work, collagen was extracted from different animal sources with protocols that alter its structure. Collagen of tendon shreds excised from cattle, horse, sheep and pig was structurally investigated by wide- and small-angle X-ray scattering techniques, at both molecular and supramolecular scales, and thermo-mechanically with thermal and load-bearing tests. Tendons were selected because of their resistance to chemical degradation and mechanical stresses. The multiscale structural integrity of tendons’ collagen was studied in relation to the animal source, anatomic location and source for collagen extraction.
Synergistic Effect of Nano-Silica and Intumescent Flame Retardant on the Fire Reaction Properties of Polypropylene Composites
Authors: Wang Yongliang , Liu Baoqiang , Chen Ruiyang , Wang Yunfei , Han Zhidong , Wang Chunfeng , Weng Ling
Published: July 2023

Silica nanoparticles (nano-silica) were used as synergistic agents with ammonium polyphosphate (APP) and pentaerythritol (PER) to enhance flame retardancy of polypropylene (PP) in this research. The composites were prepared using a melt-mixing method. The influences of nano-silica on the fire performance of composites were thoroughly discussed, which promotes understanding of nano-silica on the flame-retardant performance of polypropylene composite. Scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS) results indicated that the nano-silica with a diameter of about 95 ± 3.9 nm were dispersed favorably in the composite matrix, which might elevate its synergistic effect with intumescent flame retardant and improve the flame retardancy of polypropylene composite. The synergistic effects between nano-silica and intumescent flame retardant on PP composites were studied using the limiting oxygen index (LOI), UL-94 test, and cone calorimeter test (CCT). The total amount of flame retardant was maintained at 30%. When the dosage of nano-silica was 1 wt.%, the LOI value of PP/IFR/Si1.0 composite reached 27.3% and its UL-94 classification reached V-1. Based on the parameters of the CCT, the introduction of nano-silica induced composites with depressed heat release rate (HRR) and peak heat release rate (PHRR). The PHRR of PP/IFR/Si0.5 was only 295.8 kW/m2, which was 17% lower than that of PP/IFR. Moreover, the time to PHRR of PP/IFR/Si0.5 was delayed to 396 s, which was about 36 s later than that without nano-silica. EDS was used to quantitatively analyze the distribution of silica in charred residue. The EDS results indicated that the silica tended to accumulate on the surface during the fire. The surface accumulation characteristic of silica endows it with the enhanced flame-retardant properties of polypropylene composite at a very small dosage (as low as 1 wt.%).
The Influence of Heat and Cryogenic Treatment on Microstructure Evolution and Mechanical Properties of Laser-Welded AZ31B
Authors: Xu Yulang , Qian Peng , Qiao Yanxin , Yin Wujia , Jiang Zhiwei , Li Jingyong
Published: July 2023

The pores and coarse lamellar Mg17Al12 that inevitably occur in the weld zone are the major challenge for laser-welded magnesium (Mg) alloys including AZ31B. In order to improve microstructure uniformity and eliminate welding defects, a new process assisted with combination of heat and cryogenic treatment was applied in this study. The results showed that after solution treatment, the number and size of precipitates decreased and the uniformity of the microstructure improved. After cryogenic treatment, the lamellar Mg17Al12 was cracked into particles, and the grain size was refined. After solution + cryogenic treatment, Al8Mn5 substituted the lamellar Mg17Al12. Through studying the changes in microhardness, precipitates, and microstructure under different treatments, it was found that the conversation of Mg17Al12 from lamellar state into particle-like state as well as the appearance of dispersed Al8Mn5 particles played a second-phase strengthening role in improving the mechanical properties of Mg alloy laser-welded joint, and the tensile strength (258.60 MPa) and elongation (10.90%) of the sample were 4.4% and 32.6% higher than those of the as-welded joint.
Wrinkling and Strengthening Behaviors in the Two-Layer-Sheet Hot-Forming–Quenching Integrated Process for an Al–Cu–Mg-Alloy Thin-Walled Curved-Surface Shell
Authors: Fan Xiaobo , Sun Baoshan , Qu Wenliang , Chen Xianshuo , Wang Xugang
Published: July 2023

The thin-walled curved-surface component is an important structural element in aerospace. Wrinkling, springback and thermal distortion occur easily when forming these components. To form thin-walled components with high precision and strength, a two-layer-sheet hot-forming–quenching integrated process was proposed, in which wrinkling is prevented by thickening the upper sheet and springback is reduced by solution and die quenching. Selecting an appropriate upper sheet is crucial to suppress wrinkling and accomplish effective die quenching. The effect of the upper sheet on the wrinkling and strengthening behaviors of an Al–Cu–Mg-alloy melon-petal shell was thus studied in detail. The anti-wrinkle mechanism was analyzed through numerical simulation. The forming quality, including forming precision, deformation uniformity and strength, were further evaluated. The wrinkle gradually decreased with the increasing thickness of the upper sheet, resulting from the depressed compressive stress at the edge of the target sheet. A defect-free specimen with a smooth surface was finally formed when the thickness of the upper sheet reached three times that of the target sheet. The profile deviation was ±0.5 mm. Excellent thickness uniformity in a specimen can be obtained with a maximum thinning rate of 6%. The full strength, ranging from 455 to 466 MPa, can be obtained in all regions of the specimen, indicating that effective strengthening can be accomplished with the two-layer-sheet die quenching. The results indicated that high forming quality and full strength can be obtained in a two-layer-sheet hot-forming–quenching integrated process. This research has great potential for engineering applications using aluminum-alloy curved-surface thin-walled components.
Development of a Two-Stage Hydrometallurgical Process for Gold–Antimony Concentrate Treatment from the Olimpiadinskoe Deposit
Authors: Rusalev Rostislav , Rogozhnikov Denis , Dizer Oleg , Golovkin Dmitry , Karimov Kirill
Published: July 2023

An integrated two-stage metallurgical process has been developed to process concentrates from the Olimpiadinskoe deposit, which contain high levels of antimony and arsenic. The optimal parameters for the alkaline sulfide leaching process of the initial concentrate from the Olimpiadinskoe deposit were determined to achieve the maximum extraction of antimony at a 99% level. The recommended parameters include an L:S ratio of 4.5:1, a sodium sulfide concentration of 61 g/L, a sodium hydroxide concentration of 16.5 g/L, a duration of 3 h, and a temperature of 50 °C. A synergistic effect of co-processing alkaline sulfide leach cakes with sulfuric and nitric acids was observed. The pre-treatment step reduced the nitric acid composition by converting carbonates into gypsum and increased the arsenic extraction by 15% during subsequent nitric acid leaching. The laboratory research on the nitric acid leaching of decarbonized cake established the key parameters for the maximum iron and arsenic extraction in solution (92% and 98%, respectively), including an L:S ratio of 9:1, a nitric acid concentration of 6 mol/L, and a time of 90 min. Full polynomial equations for the iron and arsenic extraction from the decarbonized cake were derived. The model demonstrated a high relevance, as evidenced by the determination coefficients (R2) of 96.7% for iron and 93.2% for arsenic. The technology also achieved a high gold recovery rate of 95% from the two-stage alkaline sulfide and nitric acid leach cake. Furthermore, the maximum deposition of arsenic from the nitrate leach solution in the form of insoluble As2S3 was determined to be 99.9%. A basic technological flow sheet diagram for processing the flotation gold–antimony concentrate from the Olimpiadinskoe deposit was developed, including two stages: the production of metallic antimony and the gold extraction from the nitric leach cake.
Calculation Method for the Cracking Resistance and Bearing Performance of SFRAC Beams
Authors: Zhu Qian , Liu Jie
Published: July 2023

The utilization of recycled aggregate (RCA) in preparing recycled concrete (RAC) is an effective measure to solve the increase in construction waste. Furthermore, applying RAC to flexural members is a viable practice. The addition of steel fiber to RAC to prepare steel fiber recycled concrete (SFRAC) solves the performance deterioration caused by the recycled aggregate, so it is necessary to study the effects of the recycled aggregate replacement rate and fiber–volume ratio on the crack resistance and bending performance of SFRAC beams. In this study, 13 beams were designed and manufactured, with the water–cement ratio, recycled aggregate replacement rate, and fiber–volume ratio as the primary variables, and the cracking moment and ultimate moment of the SFRAC beams were systematically studied. The results show that the cracking and ultimate moments of the SFRAC beams increased with decreases in the water–cement ratio or with increases in the fiber–volume ratio and were unaffected by the replacement rate of recycled aggregates. Based on the experimental results and theoretical analysis, a calculation model and formula for the cracking moment were established. The ultimate bearing capacity of SFRAC beams can be accurately determined using the ACI 318 and ACI 544 standards. The research results serve as a valuable reference for the design of SFRAC beams, effectively address the issue of performance degradation in RAC structural members, and promote the use of green building materials.
An Inverse Optimization Method for the Parameter Determination of the High-Temperature Damage Model and High-Temperature Damage Graph of Ti6Al4V Alloy
Authors: Chen Xuewen , Yang Zhen , Zhang Bo , Sun Jiawei , Su Zhiyi , Mao Yiran
Published: July 2023

Ti6AL4V alloy is widely used in the biomedical and energy vehicle industries, among others. Ti6Al4V alloy cannot be fabricated at ambient temperatures; hence, it requires hot forming. However, this method is susceptible to crack defects. The crack defect problem of Ti6AL4V alloy in the hot-forming process cannot be ignored, so we must develop a precise hot-forming damage prediction model. In this study, three high-temperature damage models of Ti6Al4V alloy were developed, considering the temperature and strain rate. These models were derived from the normalized Cockcroft and Latham (NCL), Oyane, and Rice and Tracey (RT) damage models. The damage parameters of the models were identified using a genetic algorithm combined with finite element simulation. The force accumulation error of the Ti6AL4V alloy specimen, which was obtained from a simulated thermal tensile test and an actual test, was used as an optimization target function. Then, the damage parameters were optimized using the genetic algorithm until the target function reached the minimum value. Finally, the optimal damage model parameter was obtained. Through program development, the three high-temperature damage models established in this paper were embedded into Forge® NxT 2.1 finite element software. The simulated thermal tensile test of Ti6AL4V alloy was performed at a temperature of 800–1000 °C and a strain rate of 0.01–5 s−1. The simulated and actual fracture displacements of the tensile specimens were compared. The correlation coefficients (R) were calculated, which were 0.997, 0.951, and 0.912. Of the high-temperature damage models, the normalized Cockcroft and Latham high-temperature damage model had higher accuracy in predicting crack defects of Ti6Al4V alloy during the hot-forming process. Finally, a fracture strain graph and a high-temperature damage graph of Ti6Al4V alloy were constructed. The Ti6Al4V alloy damage evolution and thermal formability were analyzed in relation to the temperature and strain rate.
Gold Nanoparticles AuNP Decorated on Fused Graphene-like Materials for Application in a Hydrogen Generation
Authors: Biehler Erik , Quach Qui , Abdel-Fattah Tarek M.
Published: July 2023

The search for a sustainable, alternative fuel source to replace fossil fuels has led to an increased interest in hydrogen fuel. This combustible gas is not only clean-burning but can readily be produced via the hydrolysis of sodium borohydride. The main drawback of this reaction is that the reaction occurs relatively slowly and requires a catalyst to improve efficiency. This study explored a novel composite material made by combining gold nanoparticles and fused graphene-like materials (AuFGLM) as a catalyst for generating hydrogen via sodium borohydride. The novel fused graphene-like material (FGLM) was made with a sustainable dextrose solution and by using a pressure-processing method. Imaging techniques showed that FGLM appears to be an effective support template for nanoparticles. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and Raman spectroscopy were used to characterize and determine the size, shape, and structure of nanoparticles and composites. The TEM study characterized the fused carbon backbone as it began to take on a rounder shape. The TEM images also revealed that the average diameter of the gold nanoparticle was roughly 23 nm. The FTIR study confirmed O-H, C-C, and C=O as functional groups in the materials. The EDS analysis showed that the composite contained approximately 6.3% gold by weight. The crystal structures of FGLM and AuFGLM were identified via P-XRD analysis. Various reaction conditions were used to test the catalytic ability of AuFGLM, including various solution pHs, temperatures, and doses of NaBH4. It was observed that optimal reaction conditions included high temperature, an acidic solution pH, and a higher dose of NaBH4. The activation energy of the reaction was determined to be 45.5 kJ mol−1, and it was found that the catalyst could be used multiple times in a row with an increased volume of hydrogen produced in ensuing trials. The activation energy of this novel catalyst is competitive compared to similar catalysts and its ability to produce hydrogen over multiple uses makes the material an exciting choice for catalyzing the hydrolysis of NaBH4 for use as a hydrogen fuel source.
Effect of Shielding Gas Arc Welding Process on Cavitation Resistance of Welded Joints of AlMg4.5Mn Alloy
Authors: Dojčinović Marina , Prokić Cvetković Radica , Sedmak Aleksandar , Popović Olivera , Cvetković Ivana , Radu Dorin
Published: July 2023

The effect of the shielding gas arc welding process on the cavitation resistance of the three-component aluminum alloy AlMg4.5Mn and its welded joints was investigated. Welding was performed using the GTAW and GMAW processes in a shielded atmosphere of pure argon. After the welding, metallographic tests were performed, and the hardness distribution in the welded joints was determined. The ultrasonic vibration method was used to evaluate the base metal’s and weld metal’s resistance to cavitation. The change in mass was monitored to determine the cavitation rates. The morphology of the surface damage of the base metal and weld metal due to cavitation was monitored using scanning electron microscopy to explain the effect of the shielding gas arc welding process on their resistance to cavitation.
Effect of Sandblasting Parameters and the Type and Hardness of the Material on the Number of Embedded Al2O3 Grains
Authors: Śmielak Beata , Klimek Leszek , Krześniak Kamil
Published: July 2023

Background: Is abrasive blasting accompanied by the phenomenon of driving abrasive particles into the conditioned material? Methods: Three hundred and fifteen cylindrical disks of three types of metal alloy (chromium/cobalt, chromium/nickel, titanium, and sintered zirconium dioxide) were divided into four groups (n = 35) and sandblasted at pressures of 0.2, 0.4, or 0.6 MPa with aluminum oxide (Al2O3), grain size 50, 110, or 250 μm. Then, the surface topography was examined using a scanning microscope, and the amount of embedded grain was measured using quantitative metallography. For each group, five samples were randomly selected and subjected to Vickers hardness testing. In the statistical analyses, a three-factor analysis of variance was carried out, considering the type of material, the size of gradation of the abrasive, and the amount of pressure. Results: The smallest amounts of embedded abrasive (2.62) were observed in the ZrO2 treatment, and the largest (38.19) occurred in the treatment of the Ti alloy. An increase in the gradation and the pressure were a systematic increase in the amount of embedded grain. Conclusions: After abrasive blasting, abrasive particles were found on the surface of the materials. The amount of driven abrasive depends on the hardness of the processed material.
Effect of Y Content on Precipitation Behavior, Oxidation and Mechanical Properties of As-Cast High-Temperature Titanium Alloys
Authors: Shen Jiafeng , Fu Binguo , Wang Yufeng , Dong Tianshun , Li Jingkun , Li Guolu , Liu Jinhai
Published: July 2023

To improve the heat resistance of titanium alloys, the effects of Y content on the precipitation behavior, oxidation resistance and high-temperature mechanical properties of as-cast Ti-5Al-2.75Sn-3Zr-1.5Mo-0.45Si-1W-2Nb-xY (x = 0.1, 0.2, 0.4) alloys were systematically investigated. The microstructures, phase evolution and oxidation scales were characterized by XRD, Laser Raman, XPS, SEM and TEM. The properties were studied by cyclic oxidation as well as room- and high-temperature tensile testing. The results show that the microstructures of the alloys are of the widmanstätten structure with typical basket weave features, and the prior β grain size and α lamellar spacing are refined with the increase of Y content. The precipitates in the alloys mainly include Y2O3 and (TiZr)6Si3 silicide phases. The Y2O3 phase has specific orientation relationships with the α-Ti phase: (002)Y2O3 // (1¯1¯20)α-Ti, [110]Y2O3 // [4¯401]α-Ti. (TiZr)6Si3 has an orientation relationship with the β-Ti phase: (022¯1¯)(TiZr)6Si3 // (011)β-Ti, [1¯21¯6](TiZr)6Si3 // [044¯]β-Ti. The 0.1 wt.% Y composition alloy has the best high-temperature oxidation resistance at different temperatures. The oxidation behaviors of the alloys follow the linear-parabolic law, and the oxidation products of the alloys are composed of rutile-TiO2, anatase-TiO2, Y2O3 and Al2O3. The room-temperature and 700 °C UTS of the alloys decreases first and then increases with the increase of Y content; the 0.1 wt.% Y composition alloy has the best room-temperature mechanical properties with a UTS of 1012 MPa and elongation of 1.0%. The 700 °C UTS and elongation of the alloy with 0.1 wt.% Y is 694 MPa and 9.8%, showing an optimal comprehensive performance. The UTS and elongation of the alloys at 750 °C increase first and then decrease with the increase of Y content. The optimal UTS and elongation of the alloy is 556 MPa and 10.1% obtained in 0.2 wt.% Y composition alloy. The cleavage and dimples fractures are the primary fracture mode for the room- and high-temperature tensile fracture, respectively.
Tensile Deformation and Fracture of Unreinforced AZ91 and Reinforced AZ91-C at Temperatures up to 300 °C
Authors: Alrasheedi Nashmi H. , Ataya Sabbah , El-Sayed Seleman Mohamed M. , Ahmed Mohamed M. Z.
Published: July 2023

Magnesium alloys are still attractive materials for applications that necessitate light weight due to their low density, moderate strength, and good corrosion resistance. AZ91 is one of the widely applied magnesium alloys due to its very good castability and strength. However, one of the drawbacks of magnesium alloys is the low elastic modulus. So, reinforcing AZ91 with carbon short fibers with the aim of further increasing the strength and improving the elastic modulus is investigated in this study. Squeeze cast AZ91-23 vol.% carbon short carbon (AZ91-C) and the unreinforced AZ91 are deeply examined by tensile testing at different temperatures (20, 100, 150, 200, 250, and 300 °C). Tensile stress–strain curves are measured and the tensile parameters (yield stress, ultimate tensile strength and strain) are defined and presented against the test temperature. Yield stress of AZ91 at 20 °C (109 MPa) is doubled (226 MPa) in the reinforced AZ91-C. Yield stress is found to slightly decrease with increasing the test temperature. Ultimate tensile strength of AZ91 at 20 °C (198 MPa) is increased (262 MPa) in the reinforced AZ91-C. The improvement of the ultimate tensile strength due to reinforcing increases with increasing the test temperature. Flow curves are determined and described by a modified Mecking–Kocks relationship and the flow parameters are determined and described as a function of the test temperature. Microstructure investigation was undertaken of the fractured tensile specimens at the grain boundaries rich in eutectic structure formed at the grain boundaries. Mixed brittle/ductile fracture mode is detected on the fracture surface of unreinforced AZ91, while the SEM investigations show matrix/carbon fiber detachment and fiber fracture as main fracture modes.
The Influence of the Molecular Weight of Poly(Ethylene Oxide) on the Hydrolytic Degradation and Physical Properties of Polycaprolactone Binary Blends
Authors: Dalton Maurice , Ebrahimi Farnoosh , Xu Han , Gong Ke , Fehrenbach Gustavo , Fuenmayor Evert , Murphy Emma J. , Major Ian
Published: July 2023

The use of biodegradable polymers in tissue engineering has been widely researched due to their ability to degrade and release their components in a controlled manner, allowing for the potential regeneration of tissues. Melt blending is a common method for controlling the degradation rate of these polymers, which involves combining these materials in a molten state to create a homogenous mixture with tailored properties. In this study, polycaprolactone (PCL) was melt blended with hydrophilic poly (ethylene oxide) (PEO) of different molecular weights to assess its effect on PCL material performance. Hydrolytic degradation, thermal and viscoelastic properties, and surface hydrophilicity were performed to contrast the properties of the blends. DSC, DMA, and FTIR were performed on selected degraded PCL/PEO specimens following mass loss studies. The results showed that adding PEO to PCL reduced its melt viscosity-torque and melt temperature while increasing its hydrophilicity, optimizing PCL/PEO blend for soft tissue engineering applications and could contribute to the development of more effective and biocompatible materials for soft tissue regeneration.
Calculation Method and Application of Time-Varying Transmission Rate via Data-Driven Approach
Authors: Sun Yuqing , Zhang Zhonghua , Sun Yulin
Published: July 2023

Most research about compartmental models of infection disease often consider the transmission rate as a constant, which is not ideal for the dynamic surveillance of infectious diseases. This study fully utilized continuously updated real-time epidemiological data and proposed a SEAIUHR model incorporating asymptomatic and symptomatic infectiousness, reported and unreported cases, inpatient and non-inpatient cases, and vaccine inoculation. This study proposed a novel approach based on our model to calculate the time-varying transmission rate with an under-report rate, vaccination efficiency, and relaxation of social distancing behavior. The proposed method was evaluated based on epidemiological data from the United States. The results suggest that using this approach to combine epidemiological data can provide a clearer understanding of the spread rule of epidemic, offering data support for subsequent related research.
A Review of Treatment Methods Focusing on Human Induced Pluripotent Stem Cell-Derived Neural Stem/Progenitor Cell Transplantation for Chronic Spinal Cord Injury
Authors: Shibata Takahiro , Tashiro Syoichi , Nakamura Masaya , Okano Hideyuki , Nagoshi Narihito
Published: July 2023

Cell transplantation therapy using human induced pluripotent stem cell-derived neural stem/progenitor cells (hiPSC-NS/PCs) has attracted attention as a regenerative therapy for spinal cord injury (SCI), and its efficacy in treating the subacute phase of SCI has been reported in numerous studies. However, few studies have focused on treatment in the chronic phase, which accounts for many patients, suggesting that there are factors that are difficult to overcome in the treatment of chronic SCI. The search for therapeutic strategies that focus on chronic SCI is fraught with challenges, and the combination of different therapies is thought to be the key to a solution. In addition, many issues remain to be addressed, including the investigation of therapeutic approaches for more severe injury models of chronic SCI and the acquisition of practical motor function. This review summarizes the current progress in regenerative therapy for SCI and discusses the prospects for regenerative medicine, particularly in animal models of chronic SCI.
Tobacco Smoking Is a Strong Predictor of Failure of Conservative Treatment in Hinchey IIa and IIb Acute Diverticulitis—A Retrospective Single-Center Cohort Study
Authors: Murzi Valentina , Locci Eleonora , Carta Alessandro , Pilia Tiziana , Frongia Federica , Gessa Emanuela , Podda Mauro , Pisanu Adolfo
Published: July 2023

Background and Objectives: Therapeutic management of patients with complicated acute diverticulitis remains debatable. The primary objective of this study is to identify predictive factors for the failure of conservative treatment of Hinchey IIa and IIb diverticular abscesses. Materials and Methods: This is a retrospective cohort study that included patients hospitalized from 1 January 2014 to 31 December 2022 at the Emergency Surgery Department of the Cagliari University Hospital (Italy), diagnosed with acute diverticulitis complicated by Hinchey grade IIa and IIb abscesses. The collected variables included the patient’s baseline characteristics, clinical variables on hospital admission, abscess characteristics at the contrast-enhanced CT scan, clinical outcomes of the conservative therapy, and follow-up results. Univariable and multivariable logistic regression models were used to identify prognostic factors of conservative treatment failure and success. Results: Two hundred and fifty-two patients diagnosed with acute diverticulitis were identified from the database search, and once the selection criteria were applied, 71 patients were considered eligible. Conservative treatment failed in 25 cases (35.2%). Univariable analysis showed that tobacco smoking was the most significant predictor of failure of conservative treatment (p = 0.007, OR 7.33, 95%CI 1.55; 34.70). Age (p = 0.056, MD 6.96, 95%CI −0.18; 0.99), alcohol drinking (p = 0.071, OR 4.770, 95%CI 0.79; 28.70), platelets level (p = 0.087, MD −32.11, 95%CI −0.93; 0.06), Hinchey stage IIa/IIb (p = 0.081, OR 0.376, 95%CI 0.12; 1.11), the presence of retroperitoneal air bubbles (p = 0.025, OR 13.300, 95%CI 1.61; 291.0), and the presence of extraluminal free air at a distance (p = 0.043, OR 4.480, 95%CI 1.96; 20.91) were the other variables possibly associated with the risk of failure. In the multivariable logistic regression analysis, only tobacco smoking was confirmed to be an independent predictor of conservative treatment failure (p = 0.006; adjusted OR 32.693; 95%CI 2.69; 397.27). Conclusion: The role of tobacco smoking as a predictor of failure of conservative therapy of diverticular abscess scenarios highlights the importance of prevention and the necessity to reduce exposure to modifiable risk factors.
Flame-Resistant Poly(vinyl alcohol) Composites with Improved Ionic Conductivity
Authors: Serbezeanu Diana , Hamciuc Corneliu , Vlad-Bubulac Tăchiță , Ipate Alina-Mirela , Lisa Gabriela , Turcan Ina , Olariu Marius Andrei , Anghel Ion , Preda Dana Maria
Published: July 2023

Flame-resistant polymer composites were prepared based on polyvinyl alcohol (PVA) as a polymer matrix and a polyphosphonate as flame retardant. Oxalic acid was used as crosslinking agent. LiClO4, BaTiO3, and graphene oxide were also incorporated into PVA matrix to increase the ionic conductivity. The obtained film composites were investigated by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry and microscale combustion tests. Incorporating fire retardant (PFRV), BaTiO3, and graphene oxide (GO) into a material results in increased resistance to fire when compared to the control sample. A thermogravimetric analysis revealed that, as a general trend, the presence of PFRV and BaTiO3 nanoparticles enhances the residue quantity at a temperature of 700 °C from 7.9 wt% to 23.6 wt%. Their dielectric properties were evaluated with Broad Band Dielectric Spectroscopy. The electrical conductivity of the samples was determined and discussed in relation to the LiClO4 content. The electrical properties, including permittivity and conductivity, are being enhanced by the use of LiClO4. Additionally, a relaxation peak has been observed in the dielectric losses at frequencies exceeding 103 Hz. The electrical properties, including permittivity and conductivity, are being enhanced by the use of LiClO4. Additionally, a relaxation peak has been observed in the dielectric losses at frequencies exceeding 103 Hz. Out of the various composites tested, the composite containing 35 wt% of LiClO4 exhibits the highest alternating current (AC) conductivity, with a measured value of 2.46 × 10−3 S/m. Taking into consideration all the aspects discussed, these improved composites are intended for utilization in the manufacturing of Li-Ion batteries.
Effect of Polydopamine/Sodium Dodecyl Sulfate Modified Halloysite on the Microstructure and Permeability of a Polyamide Forward Osmosis Membrane
Authors: Yu Jie , Jing Weiqi , Liu Eryong , Du Shuangming , Cai Hui , Du Huiling , Wang Jinlei
Published: July 2023

Mine water cannot be directly consumed by trapped people when a mine collapses, so it is difficult for people to carry out emergency rescues to ensure their safety. Therefore, a water bag made of a forward osmosis (FO) membrane has been designed that can efficiently filter coal mine water to meet the urgent needs of emergency rescue. Before interfacial polymerization (IP), sodium-dodecyl-sulfate-modified halloysite (SDS−HNT) was added to an MPD aqueous solution to prepare an SDS−HNT polyamide active layer, and then the prepared membrane was placed into a polydopamine (PDA) solution formed by the self-polymerization of dopamine and a PDA/SDS−HNT composite film was prepared. The results showed that the original ridge−valley structure of the polyamide membrane was transformed to a rod-, circular-, and blade-like structure by the addition of SDS−HNTs. Subsequently, a dense PDA nanoparticle layer was formed on the modified membrane. The polyamide/polysulfone forward osmosis membrane modified by co-doping of PDA and SDS−HNTs displayed both the best water flux and rejection rate, confirming the synergistic effect of compound modification. Therefore, the high-performance permeability of the polyamide membrane modified by SDS−HNTs and PDA provides great convenience for the emergency filtration of coal mine water, and also has potential applications in wastewater treatment and seawater desalination.
The Association between Maternal Urinary Phthalate Concentrations and Blood Pressure in Pregnancy: A Systematic Review and Meta-Analysis
Authors: Zhang Mengyue , Qiao Jianchao , Xie Pinpeng , Li Zhuoyan , Hu Chengyang , Li Fei
Published: July 2023

Phthalates are commonly found in a wide range of environments and have been linked to several negative health outcomes. While earlier research indicated a potential connection between phthalate exposure and blood pressure (BP) during pregnancy, the results of these studies remain inconclusive. The objective of this meta-analysis was to elucidate the relationship between phthalate exposure and BP in pregnancy. A comprehensive literature search was carried out with PubMed, EMBASE, and Web of Science, and pertinent studies published up until 5 March 2023 were reviewed. Random-effects models were utilized to consolidate the findings of continuous outcomes, such as diastolic and systolic BP, as well as the binary outcomes of hypertensive disorders of pregnancy (HDP). The present study included a total of 10 studies. First-trimester MBP exposure exhibited a positive association with mean systolic and diastolic BP during both the second and third trimesters (β = 1.05, 95% CI: 0.27, 1.83, I2 = 93%; β = 0.40, 95% CI: 0.05, 0.74, I2 = 71%, respectively). Second-trimester monobenzyl phthalate (MBzP) exposure was positively associated with systolic and diastolic BP in the third trimester (β = 0.57, 95% CI: 0.01, 1.13, I2 = 0; β = 0.70, 95% CI: 0.27, 1.13, I2 = 0, respectively). Conversely, first-trimester mono-2-ethylhexyl phthalate (MEHP) exposure demonstrated a negative association with mean systolic and diastolic BP during the second and third trimesters (β = −0.32, 95% CI: −0.60, −0.05, I2 = 0; β = −0.32, 95% CI: −0.60, −0.05, I2 = 0, respectively). Additionally, monoethyl phthalate (MEP) exposure was found to be associated with an increased risk of HDP (OR = 1.12, 95% CI: 1.02, 1.23, I2 = 26%). Our study found that several phthalate metabolites were associated with increased systolic and diastolic BP, as well as the risk of HDP across pregnancies. Nevertheless, given the limited number of studies analyzed, additional research is essential to corroborate these findings and elucidate the molecular mechanisms linking phthalates to BP changes during pregnancy.
A Non-Sacrificial 3D Printing Process for Fabricating Integrated Micro/Mesoscale Molds
Authors: Ghaznavi Amirreza , Xu Jie , Hara Seth A.
Published: July 2023

Three-dimensional printing technology has been implemented in microfluidic mold fabrication due to its freedom of design, speed, and low-cost fabrication. To facilitate mold fabrication processes and avoid the complexities of the soft lithography technique, we offer a non-sacrificial approach to fabricate microscale features along with mesoscale features using Stereolithography (SLA) printers to assemble a modular microfluidic mold. This helps with addressing an existing limitation with fabricating complex and time-consuming micro/mesoscale devices. The process flow, optimization of print time and feature resolution, alignments of modular devices, and the advantages and limitations with the offered technique are discussed in this paper.
Cu-Cu Thermocompression Bonding with a Self-Assembled Monolayer as Oxidation Protection for 3D/2.5D System Integration
Authors: Lykova Maria , Panchenko Iuliana , Schneider-Ramelow Martin , Suga Tadatomo , Mu Fengwen , Buschbeck Roy
Published: July 2023

Cu-Cu direct interconnects are highly desirable for the microelectronic industry as they allow for significant reductions in the size and spacing of microcontacts. The main challenge associated with using Cu is its tendency to rapidly oxidize in air. This research paper describes a method of Cu passivation using a self-assembled monolayer (SAM) to protect the surface against oxidation. However, this approach faces two main challenges: the degradation of the SAM at room temperature in the ambient atmosphere and the monolayer desorption technique prior to Cu-Cu bonding. In this paper, the systematic investigation of these challenges and their possible solutions are presented. The methods used in this study include thermocompression (TC) bonding, X-ray photoelectron spectroscopy (XPS), shear strength testing, scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The results indicate nearly no Cu oxidation (4 at.%) for samples with SAM passivation in contrast to the bare Cu surface (27 at.%) after the storage at −18 °C in a conventional freezer for three weeks. Significant improvement was observed in the TC bonding with SAM after storage. The mean shear strength of the passivated samples reached 65.5 MPa without storage. The average shear strength values before and after the storage tests were 43% greater for samples with SAM than for the bare Cu surface. In conclusion, this study shows that Cu-Cu bonding technology can be improved by using SAM as an oxidation inhibitor, leading to a higher interconnect quality.