Universal Material Testing Machine Research Articles

Effect of the synergistic interaction of zinc adipate, hydrotalcite and ethylene propylene rubber on the performances of polypropylene

Polypropylene (PP) is widely used in a range of areas due to its excellent physical and chemical properties, but its low-temperature brittleness and low-impact resistance largely limits its application. Hence, this study investigated the changes in mechanical and thermal properties of isotactic polypropylene (iPP) modified by the addition of the β-nucleating agent zinc adipate (ZnAA), the inorganic rigid particle hydrotalcite (HT), and the rubber elastomer bipropylene rubber (EPR). The structure and properties of modified PP were investigated by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), electronic universal material testing machine, and simple-beam impact testing machine. At last, the non-isothermal crystallization kinetics of iPP was investigated by the Caze method. It was found that with the addition of EPR reached 30 wt%, the notched impact strength of iPP was 34.74 kJ/m2, which was 542.43 % higher than that of pure iPP, and more than twice as high as that of ZnAA and HT modification, and the relative crystallinity ( K β) value of the β-crystalline form reached 79.66 % when 10 wt% EPR was added to the iPP. The addition of ZnAA, HT and EPR could significantly increase the crystallisation peak temperature ( T c), shorten the half-crystallisation time ( t 1/2) and increase the crystallisation activation energy ( ΔE) of iPP.

Effects of Carbon Fiber Content on the Crystallization and Rheological Properties of Carbon Fiber-Reinforced Polyamide 6.

Carbon fiber (CF)-reinforced polyamide 6 (PA6) composites have an excellent performance, attributed to properties such as light quality, high strength, and vibration reduction, and they are widely used in fields such as aerospace and transportation. Four kinds of carbon fiber-reinforced polyamide 6 (CF/PA6) composite pellets with carbon fiber contents of 20, 30, 40, and 50 wt.% were prepared using twin screw extrusion. The results were characterized using a simultaneous thermal analyzer, capillary rheometer, electronic universal material testing machine, and scanning electron microscope (SEM); their crystallization, rheological behavior, mechanical properties, surface structure, etc., were studied. DSC results indicate that an increase in carbon fiber content enhances the thermal stability of CF/PA6 and narrows the crystallization window but has a minor effect on the molecular chain diffusion time. The crystallinity reaches its maximum at a carbon fiber content of 40 wt.%, reaching 55.16%. The steady-state rheological behavior reveals that CF/PA6 behaves as a pseudoplastic fluid, exhibiting shear-thinning behavior. When the carbon fiber content is 40 wt.%, the power law exponent (n) reaches its maximum, and the consistency coefficient (K) decreases by 300 Pa⋅sn compared to the 30 wt.% content. With increasing temperature, n increases while K decreases. SEM observations reveal that samples with carbon fiber contents of 20 wt.% and 40 wt.% exhibit better fiber dispersion and orientation. However, the interfacial bonding strength is superior in the 40 wt.% sample. When the carbon fiber content reaches 50 wt.%, significant injection molding defects occur at the clamping end, leading to extensive matrix tearing during tension testing.

Superior load-to-failure in an all-suture anchor system for all-inside meniscal repair compared to a PEEK-cage anchor system in an experimental cadaveric test setting.

The purpose of this study was to compare the biomechanical properties of a latest generation all-suture anchor repair device (ASARD) for meniscal repair with that of a latest generation PEEK-cage anchor repair device (PCARD) in an experimental setting using cadaveric menisci. Twenty-six menisci were obtained from the knees of fresh body donors. Artificially created meniscal lesions were treated randomly, using a single stitch with either an ASARD or a PCARD. Cyclic biomechanical testing, utilising a universal material testing machine and following an established protocol, was carried out and load-to-failure (LTF), displacement, stiffness, and mode-of-failure (MOF) reported. Mean LTF was found to be 61% higher in the ASARD group at 107.10 N (standard deviation [SD], 42.34), compared to 65.86 N (SD, 27.42) in the PCARD group with statistical significance (p = 0.022). The ASARD exhibited a trend towards higher stiffness (10.35 N; SD, 3.92 versus 7.78 N; SD; 3.59) and higher displacement at cycles one, 100, and 499 (1.64, 3.27, and 4.17 mm versus 0.93, 2.19, and 2.83 mm) compared to the PCARD. Cheese wiring was the most common mode-of-failure in both groups (76.9%). This study demonstrates that an ASARD shows a higher mean LTF than a PCARD when compared in an experimental biomechanical setting. Level III.

Preliminary study on the preparation of antler powder/chitosan/β-glycerophosphate sodium/polyvinyl alcohol porous hydrogel scaffolds and their osteogenic effects.

Introduction: The production of bone-like structural scaffolds through bone tissue engineering technology is a promising method for bone regeneration to repair bone defects. Deer antler, an easily harvested and abundantly sourced initial bone tissue structure, resembles the composition and structure of human cancellous bone and can serve as a new material for allogeneic bone transplantation. Methods: This study involved the preparation and characterization of antler powder/chitosan/β-glycerophosphate sodium/polyvinyl alcohol (AP/CS/β-GP/PVA) porous hydrogel scaffolds to verify their material properties and osteogenic mechanisms. The microstructure, hydrophilicity, and mechanical properties of the scaffolds were studied using Scanning Electron Microscopy (SEM), contact angle measurement, and a universal material testing machine. The interactions between the various components were investigated using Fourier-Transform Infrared Spectroscopy (FTIR). Biocompatibility, osteogenic properties, and expression of osteogenesis-related proteins of the scaffolds were evaluated through Cell Counting Kit-8 (CCK-8) assays, alkaline phosphatase staining, Alizarin Red staining, live/dead cell staining, and Western blot analysis. Results: The results showed that as the content of deer antler powder increased, both the hydrophilicity and mechanical properties of the scaffold materials improved, while the porosity slightly decreased with an increase in deer antler powder content. Cell culture experiments demonstrated that scaffolds with a higher proportion of deer antler powder were beneficial for the proliferation and differentiation of mouse pre-osteoblast (MC3T3-E1) cells, with the scaffolds containing 10% and 8% deer antler powder showing the best effects. The upregulation of RUNX2, OCN, OSX, and OPN protein expression may promote differentiation. Discussion: Therefore, the AP/CS/β-GP/PVA hydrogel scaffolds have the potential to become a promising biomaterial for bone tissue engineering.

Study on the Shear and Bending Mechanical Properties of Millet Stem

To determine the patterns and influencing factors of the mechanical properties of millet stems from different varieties during the maturity period, this study employed a complete block experiment method and conducted shearing and bending tests on millet stems using the INSTRON5544 electronic universal material testing machine. The research investigated the variation in the shear strength, specific shear energy, bending strength, elastic modulus, and bending stiffness at different internode positions of the stems of Changza 466, Zhangza 16, and Jingu 21 during their maturity period. The results indicated that the variety had a significant impact on the mechanical properties of millet stems: from largest to smallest, the order of shear and bending forces was Jingu 21, Zhangza 16, and Changza 466. The shear strength and bending strength of Jingu 21 were the greatest among the three stem samples. The internode position significantly affected the shear mechanical properties of the millet stems, showing a general trend of decreasing shear strength with ascending internode position. The effect of the internode position on the bending stiffness was highly significant, whereas its impact on the bending strength and elastic modulus was not significant. The shear strength of the millet stems ranged from 3.866 ± 1.086 to 6.953 ± 2.208 MPa, significantly lower than the bending strength, which ranged from 18.934 ± 4.374 to 34.286 ± 6.875 MPa. The lowest shear strength and specific shearing energy, recorded at the fifth internode, were 4.028 ± 1.918 MPa and 15.097 ± 12.633 MJ/mm2, respectively. Jingu 21 and Changza 466 exhibit better lodging resistance than Zhangza 16. It is recommended to use a cutting-type platform for harvesting millet stems, with the cutting height set at the fifth internode position. This study provides a theoretical basis for the design of millet harvesting machinery and the selection of harvest parameters.

Synthesis of [2-(3,4-epoxycyclohexyl) ethyl] triphenylsilane and study on its amine curing properties

Abstract [2-(3,4-epoxycyclohexyl) ethyl] triphenylsilane was synthesized, using triphenylsilane and 1,2-epoxy-4-vinylcyclohexane as the main raw materials. When the molar ratio of triphenylsilane to 1,2-epoxy-4-vinylcyclohexane was 1.0:1.2, the content of Wilkinson catalyst was 0.4%, the reaction temperature was 90°C, and the reaction time was 6 hours, the yield of [2-(3,4-epoxycyclohexyl) ethyl] triphenylsilane could reach 95.21%. The structure of the synthesized product was analyzed and characterized using FT-IR and 1H-NMR. The synthesized product was added to a bisphenol A-type epoxy resin (E-51) and a modified amine (593 amine) to prepare an adhesive. Then, the adhesive was poured into the mold and cured at 35°C for 8 hours. The cured sample exhibited the best performance when the ECETPS: E-51:593 amine molar ratio was 0.8:7.2:2. Thermal gravimetric analysis (TG) showed that the thermal stability of the cured samples increased relative to pure E-51 amine-cured samples with the synthesized product added. The mechanical properties of the samples were tested using a universal material testing machine, and the results showed a tensile strength of 37.95 MPa and a bending strength of 39.10 MPa.

Effect of Printing Orientation on the Mechanical Properties of 3D-Printed Cu–10Sn Alloys by Laser Powder Bed Fusion Technology

This article focuses on investigating the effect of printing direction on the mechanical properties of Cu–10Sn alloys prepared by laser powder bed fusion (LPBF) technology. Specimens with different forming angles (0°, 15°, 30°, 45°, 60°, 75°, and 90°) were fabricated using LPBF technology, and their mechanical properties were systematically tested. During the testing process, we used an Instron 5985 electronic universal material testing machine to accurately evaluate the mechanical properties of the material at a constant strain rate of 10−3/s. The experimental results showed that the mechanical properties of the specimens were the best when the test direction was perpendicular to the growth direction (i.e., the 0° direction). As the angle between the test direction and the growth direction increased, the mechanical properties of the material exhibited a trend of first decreasing, then increasing, and then decreasing again, which was consistent with the direction of the microtexture of the specimens. The root cause of this trend lies in the significant change in the stress direction borne by the columnar crystals under different load directions. Specifically, as the load direction gradually transitions from being parallel to the columnar crystals to perpendicular to them, the stress direction of the columnar crystals also shifts from the radial direction to the axial direction. Due to the differences in the number and strength of grain boundaries in different stress directions, this directly leads to changes in mechanical properties. In particular, when the specimen is loaded in the radial direction of the columnar crystals, the grain boundary density is higher, and these grain boundaries provide greater resistance during dislocation migration, thus significantly hindering tensile deformation and enabling the material to exhibit superior tensile properties. Among all the tested angles, the laser powder bed fusion specimen with a forming angle of 0° exhibited the best mechanical properties, with a tensile strength of 723 MPa, a yield strength of 386 MPa, and an elongation of 33%. In contrast, the specimen with a forming angle of 90° performed the worst in terms of tensile properties. These findings provide important insights for us to deeply understand the mechanical properties of Cu–10Sn alloys prepared by LPBF.

Assessing the Influence of Thermocycling on Compressive Strength, Flexural Strength, and Microhardness in Green-Mediated Nanocomposite-Enhanced Glass Ionomer Cement Compared to Traditional Glass Ionomer Cement.

Background and objective Glass ionomer cement (GIC), also known as polyalkenoate cement, has been extensively used in dentistry for both luting and restorative purposes. Despite being the first choice for aesthetic restorations due to their chemical bonding ability to teeth, GICs have faced challenges such as low mechanical properties, abrasion resistance, and sensitivity to moisture, leading to the search for improved materials. This study aims to assess the effects of thermocycling on the compressive, flexural strength, and microhardness of green-mediated nanocomposite-modified GIC in comparison to traditional GIC. Methodology Green-mediated nanoparticles, consisting of chitosan, titanium, zirconia, and hydroxyapatite (Ch-Ti-Zr-HA), were synthesized using a one-pot synthesis technique to form nanocomposites. These nanocomposites were then incorporated intoGICspecimens in varying concentrations (3%, 5%, and 10%), denoted as Group I, Group II, and Group III, respectively. Group IV served as the control, consisting of conventional GIC. To assess the performance of the novel restorative materials over an extended period, compressive strength, flexural strength, and microhardness were measured before and after thermocycling using a universal material testing machine. Furthermore, scanning electron microscopy (SEM) analysis was carried out following the thermocycling process. The collected data were subjected to statistical analysis through one-way analysis of variance (ANOVA) and paired t-tests. Results The findings demonstrated that, in comparison to the control group, both the mean compressive strength and flexural strength, as well as hardness, were notably higher for the 10% and 5% nanocomposite-modified GIC specimens before and after thermocycling (P< 0.05). Notably, there was no notable difference observed between the 5% and 10% concentrations (P > 0.05). These results suggest that incorporating green-mediated nanocomposites (Ch-Ti-Zr-HA) modified GIC at either 5% or 10% concentration levels leads to improved mechanical properties, indicating their potential as promising alternatives in dental restorative materials. Conclusions Based on our findings, it can be inferred that the 10% and 5% concentrations of green-mediated (Ch-Ti-Zr-HA) modified GIC exhibit superior compressive and flexural strength compared to conventional GIC. Additionally, analysis of the scanning electron microscope (SEM) morphology revealed that green-mediated GIC displays smoother surface characteristics in contrast to conventional GIC. These results underscore the potential advantages of utilizing green-mediated nanocomposite-modified GIC in dental applications, suggesting enhanced mechanical properties and surface quality over conventional.

Mechanism for formation of porcine blood hydrogels used as additives in the mortar of traditional Chinese architectural painting

Ancient Chinese architecture drawing is a unique form of ancient Chinese art. Porcine blood hydrogels are distinctive ingredients used to prepare the composite material of the substrate layer for architecture drawing. This investigation was focused on the mechanism for porcine blood hydrogel formation. Based on the traditional Chinese recipe for the preparation of porcine blood-lime mortar, samples with different ratios of porcine blood and lime water were prepared, and the molecular-scale interactions between the lime water and proteins in the porcine blood were examined with FTIR spectroscopy, Raman spectroscopy, XRD, XPS, fluorescence spectroscopy, contact angle and rheology studies. The mechanical properties and morphological features of the samples were detected with a rheometer, universal material testing machine and SEM. The results indicated that an appropriate amount of lime water was required for gelation of the porcine blood. With the appropriate alkalinity, sufficient carboxyl groups on the fibrin chains were deprotonated, and coordination with Ca2+ ions formed enough cross-links for support networks within the structure of the porcine blood hydrogel. Complexation of deprotonated carboxyl groups on the fibrin chains with Ca2+ ions led to the formation of a hydrophobic surface due alterations of the fibrin conformation and increased the adhesive properties of the hydrogel. With the hydrogel used as an ingredient in the preparation of a substrate layer composite, it is suggested that the hydrophobic surface of the hydrogel facilitated mixing with hydrophobic tung oil during preparation of the composite material, and strong adhesion of the hydrogel increased the mechanical strength and crack resistance of the substrate layer.

Effect of sintering temperature on the microstructure and properties of Al–7.5Cu–1Si alloy

With increasing requirements for environmental protection and energy conservation, Al–Cu powder alloys play an important role in machine weight reduction. During the preparation of the Al–Cu powder alloy, an appropriate sintering temperature helps improve the comprehensive performance of the alloys. In this study, powder metallurgy was used to prepare Al–7.5Cu–1Si alloys, and the effects of different sintering temperatures on their relative sintering density, hardness, and tensile strength were studied. The microstructure and phase composition of the alloy were observed and analyzed by scanning electron microscopy and x-ray diffraction, and the mechanical properties of the alloy were studied using a Brinell hardness tester and a universal material testing machine. By analyzing the microstructural changes of the alloys at different sintering temperatures, the optimal sintering temperature of the alloy was determined to obtain the best properties. The results demonstrated that the sintering temperature significantly affected the diffusion and migration of the metal particles inside the alloy. When the temperature was low, numerous pores were present in the alloy, and the degree of bonding between the metal particles was poor. As the temperature increased, the number of pores in the alloy decreased, and good metallurgical bonding occurred between the particles. The relative densities and mechanical properties of the alloys were significantly affected by the sintering temperature. When the temperature was below 570 °C, the relative density and mechanical properties were low. At 590 °C, the alloy underwent deformation and was in an over-sintered state. The best sintering temperature was 570 °C. This is because at this temperature, the relative sintering density, hardness, and tensile strength of the alloy all reached maximum values, which were 98.6%, 71 HB, and 153 MPa, respectively.

Achieving synchronous compression-shear loading on SHPB by utilizing mechanical metamaterial

Materials in service often experience complex stress states, such as a combination of shear and compression or tension. Therefore, it is crucial to experimentally measure the mechanical responses of materials under complex stress states before designing structures, as these responses differ from those under uniaxial loading. However, conducting combined loading experiments, especially under dynamic impact, is challenging and usually requires complex and costly equipment. In the present work, by employing compression-torsion coupling metamaterials, an easy method is proposed for the first time to achieve synchronous dynamic compression-shear loading on 1D Split Hopkinson Pression Bar (SHPB), which is also feasible for quasi-static experiments on universal material testing machine. The compression-torsion coupling metamaterial can convert a compression wave into combined waves of compression and torsion, and ensures the two waves naturally synchronously act on the thin-walled cylinder specimen. Since the compression-shear dynamic loading experiment can be performed on a traditional 1-D SHPB, it is a cost-effective, convenient, and easily implementable method. Both the dynamic and quasi-static mechanical properties of 1060 Al were measured under various shear-compression ratios, and a well von-Mises yield surface was obtained with strain rate insensitivity, confirming the validity of the proposed experimental methods.

Influence of Dilution on the Mechanical Properties and Microstructure of Polyurethane-Cement Based Composite Surface Coating.

Polyurethane-cement composite are widely used in modern civil engineering, and the method of adding diluent is often used to adjust the construction process to adapt to the engineering environment. Studies have shown that the addition of diluent impacts the performance of polyurethane-cement based composite surface coatings, but there have been few reports on the influence of diluent content on the mechanical properties and microstructure of the coatings. To address this, polyurethane coatings with different diluent contents were prepared, and positron annihilation lifetime spectroscopy was used to test the microstructure of the coatings. The tensile strength and elongation at rupture were tested using a universal material testing machine, and the fracture interface morphology of each coating was observed by scanning electron microscopy. Finally, the correlation between the microstructure parameters and the mechanical properties of the coating was analyzed using grey relation theory. The results demonstrated that with the increase in diluent content, (i) the average radius of the free volume hole (R) and the free volume fraction (FV) of the coating both showed a trend of first decreasing and then increasing. The value of R was between 3.04 and 3.24 Å, and the value of FV was between 2.08 and 2.84%. (ii) The tensile strength of the coating increased first and then decreased, while the elongation at rupture decreased first and then increased. Among them, the value of tensile strength was between 3.23 and 4.02 MPa, and the value of elongation at fracture was between 49.34 and 63.04%. In addition, the free volume in polymers plays a crucial role in facilitating the migration of molecular chain segments and is closely related to the macroscopic mechanical properties of polymers. A correlation analysis showed that the R value of the coating had the greatest influence on its tensile strength, while FV showed a higher correlation with the elongation at rupture.

Constitutive modeling and simulation of polyethylene foam under quasi-static and impact loading

In this paper, quasi-static and dynamic compression experiments were carried out on polyethylene foam by a universal material testing machine and a drop tower impact device. The mechanical response characteristics and energy absorption capacity of polyethylene foam under quasi-static and moderate strain rate (4 × 10−3–102s−1) loading conditions were obtained. An improved constitutive model of strain-rate term coupling strain and strain rate was established based on the Sherwood–Frost phenomenological constitutive model and Johnson–Cook constitutive model. Low Density Foam model combined in the finite element software ABAQUS with the improved constitutive model was used as the parameter definition of polyethylene foam material in the simulation. The drop-tower impact tests at different heights were simulated, and the simulation results were compared with the actual drop tower impact test results. The results showed that the peak acceleration errors between simulation and experiment were less than 7.1%, verifying the accuracy of the constitutive model. This study provides a method of constitutive models and finite element simulation to the performance of polymer foams.

Dynamic mechanical properties and constitutive model establishment of QSTE420 steel

The uniaxial tensile tests of QSTE420 steel under different strain rates were carried out using an electronic universal material testing machine, a high-speed tensile testing machine and a split Hopkinson tension bar (SHTB) device, the engineering stress-strain curves of steel within the range of 0.001– 1000 s−1 were obtained and the mechanical properties of steel at different strain rates were analyzed. The results show that in the static strain rate range of 10−3– 10−2 s−1, the yield strength and tensile strength of QSTE420 steel exhibit minimal variation, fluctuating between 430– 434 MPa and 507– 515 MPa, respectively; while the uniform elongation and elongation at break remain approximately at 12% and 35%, respectively. In the high strain rate range of 10−1– 103 s−1, both yield strength and tensile strength exhibit a consistent increase in direct correlation with the tensile rate. Specifically, the yield strength increases from 444 to 607 MPa and the tensile strength increases from 523 to 640 MPa as the strain rate escalates from 10−1 to 103 s−1. Moreover, the elongation at break demonstrates a general increasing trend and reaches its peak value of 45.65% at 100 s−1. The morphology of fracture surfaces under different strain rates are observed by Scanning Electron Microscopy (SEM). The fracture appearance analysis reveals numerous dimples in the fracture, indicating a ductile fracture. Furthermore, the comparison demonstrates that steel exhibits enhanced plasticity at a strain rate of 100 s−1. Based on the experimental results, the Johnson-Cook constitutive model was established and modified. The modified Johnson-Cook model exhibits a higher determination coefficient (R2) compared to the original version, signifying an improved fitting accuracy.

A comparative study of cyanoacrylate-based tissue adhesive and surgical sutures on marginal flap stability following coronally advanced flap

IntroductionThe present study evaluated the biomechanical characteristics of cyanoacrylate-based tissue adhesive (TA) compared to surgical sutures in coronally advanced flap (CAF) procedures using an ex-vivo model.Material and methodsThirty-six half-pig mandibles were divided into three groups, n=12 each: (I) CAF fixed with sutures (sling and tag suture technique), (II) CAF fixed with TA, and (III) CAF fixed with sutures and TA. At mandibular premolars, gingival recession defects extending 3 mm apical to the cemento-enamel junction (CEJ) were created. CAF procedures were performed using a split-full-split approach, with coronal advancement of the flap to 1 mm above the marked CEJ and stabilization according to the respective groups I–III. Marginal flap stability against pull-of forces (maximum tensile force) was measured with a universal material testing machine until the CEJ became visible.ResultsThe comparison between groups I–III demonstrated a significantly increased maximum tensile force for the TA (II) compared to the suture group (I) (p<0.001). A significantly increased maximum tensile force was found for the suture and TA (III) compared to the suture group (I) (p<0.001). There was also a significantly increased maximum tensile force in the suture and TA (III) compared to the TA group (II) (p<0.001).ConclusionThe results suggest that cyanoacrylate-based TA can increase marginal flap stability compared to sutures in CAF procedures.Clinical relevanceCyanoacrylate-based TA can be considered a useful and valuable adjunct to conventional suturing techniques in periodontal plastic surgery, especially in cases where high flap stability is required. The results of this ex-vivo study can only be transferred to the clinical situation with limitations. Clinical long-term follow-up data must be generated.

Ionic liquids modified MXene as a flame retardant synergist for the unsaturated polyester resin

AbstractI‐MXene with excellent dispersibility was successfully prepared using the chemical grafting method with 1‐butyl‐3‐methylimidazole hexafluorophosphate ([BMIM]PF6) onto MXene. It was characterized by X‐ray diffraction (XRD) and transmission electron microscopy (TEM), which was added to unsaturated polyester resin (UPR) as a synergistic agent, combined with ammonium polyphosphate (APP) to improve the flame retardancy of composites. Tensile strength of the composites was measured using the electronic universal material testing machine. The results showed that the incorporation of I‐MXene was able to increase the tensile strength and elongation at break of the composites. The flame retardancy and thermal stability of the composites were investigated through limiting oxygen index (LOI), cone calorimeter test (CCT), TG and Fourier‐infrared spectroscopy (FT‐IR). The experimental data showed that the LOI values of I‐MXene/APP/UPR composites increased to 29.1%, complying with UL‐94V‐0 rating. Its peak heat release rate (pHRR) and total heat release (THR) were 19.35% and 16.35% lower than those of APP/UPR composites, and the total smoke production (TSP) was reduced by 10.78%. When heated to 800°C, the amount of residual carbon increased by 7.71%. The catalytic effect of I‐MXene contributed to the formation of a compact and expanded carbon layer, resulting in further suppression of heat and smoke release.Highlights A new type of modified MXene is obtained. It has good dispersivity and synergistic effects. It has good flame retardancy and smoke suppression effects.

Effects of spark plasma sintering parameters on properties of Fe-based bulk amorphous alloys

Fe-based bulk amorphous alloys were prepared by spark plasma sintering (SPS) with different parameters. The thermal stability of Fe-based bulk amorphous alloys was characterized by differential scanning calorimetry (DSC) to determine the thermodynamic characteristic temperature, such as glass transition temperature (Tg) and crystallization temperature (Tx). X-ray diffraction (XRD), Archimedes drainage method, universal material testing machine, Electrochemical workstation and scanning electron microscope (SEM) were utilized to analyze the phase composition, relative density, compressive strength, corrosion performance, and fracture morphology and corrosion morphology of Fe based bulk amorphous alloys. This experiment show that Fe-based amorphous powder can be made into Fe-based bulk amorphous alloy with the size of φ12 × 9 mm by SPS technology. Meanwhile, the sample prepared with the parameters of sintering temperature of 560 ℃, sintering pressure of 550 MPa and the holding time of 1 min basically maintains the amorphous structure, and it has good compressive strength of 678 MPa, Microhardness of 1351.2 HV, density of 94.4 %, and perfect corrosion resistance.

Preparation and Properties of Multifunctional Nanocellulose-Reinforced PVA Ionic Hydrogel

In this paper, polyvinyl alcohol (PVA), nanocellulose crystals (CNC), glycerol, and aluminum chloride hexahydrate (AlCl3·6H2O) were used to prepare PVA-CNC ionic conductive hydrogels by a one-pot freeze-thaw method. The microscopic morphology and internal structure of the hydrogel were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spec-troscopy (FTIR). The mechanical properties, electrical conductivity, and sensing properties of the hydrogel were tested by a universal material testing machine and LCR digital bridge, and the anti-freezing performance and water retention performance of the hydrogel were analyzed and compared. The results show that different concentrations of nanocellulose can significantly affect the mechanical strength of the hydrogel. When the content of CNC is 2%, the hydrogel has high tensile properties (elongation at break 384.29%) and firmness (up to 1.92 MPa). The open-circuit voltage of the hydrogel-based self-powered device can reach 0.815 V. In the bending sensing test, it was monitored that the resistance of the hydrogel changes rapidly at different bending angles, indicating that the hydrogel has good strain sensitivity. The addition of glycerol makes the hydrogel have high water retention rate, good mechanical properties and certain conductivity at −20 °C. The ionic conductive hydrogels prepared in this work have certain application potential in sensors, human-computer interaction, and flexible wearable devices.

Effects of blood flow restriction training on bone turnover markers, microstructure, and biomechanics in rats.

The present study aimed to investigate the effects of blood flow restriction training on muscle strength, bone tissue structure material, and biomechanical properties in rats applying various exercise interventions and to analyze the process by identifying the bone turnover markers, it provides a theoretical basis for the application of BFRT in clinical rehabilitation. A total of 24, 3-month-old male SD (Sprague Dawley) rats were randomly divided into pressurized control group (CON, n=6), low-intensity training group (LIRT, n=6), high-intensity training group (HIRT, n=6), and blood flow restriction training group (LIBFR, n=6) for 8-week ladder-climbing exercises. The pressured control group were given only ischemia treatments and did not undertake any burden. The low-intensity training group was allowed to climb the ladder with 30% of the maximum voluntary carrying capacity (MVCC). The rats in the high-intensity training group were allowed to climb the ladder with 70% MVCC. The blood flow restriction training group climbed the ladder with 30% MVCC while imposing blood flow restriction. Before sampling, the final MVCC was measured using a ladder-climbing protocol with progressively increasing weight loading. The serum, muscle, and bone were removed for sampling. The concentrations of the bone turnover markers PINP, BGP, and CTX in the serum were measured using ELISA. The bone mineral density and microstructure of femur bones were measured using micro-CT. Three-point bending and torsion tests were performed by a universal testing machine to measure the material mechanics and structural mechanics indexes of the femur bone. The results of maximum strength test showed that the MVCC in LIRT, HIRT, and LIBFR groups was significantly greater than in the CON group, while the MVCC in the HIRT group was significantly higher than that in the LIRT group (P<0.05). According to the results of the bone turnover marker test, the concentrations of bone formation indexes PINP (amino-terminal extension peptide of type I procollagen) and BGP (bone gla protein) were significantly lower in the CON group than in the HIRT group (P<0.01), while those were significantly higher in the LIRT group compared to the HIRT group (P<0.01). In terms of bone resorption indexes, significant differences were identified only between the HIRT and other groups (P<0.05). The micro-CT examination revealed that the HIRT group had significantly greater bone density index values than the CON and LIRT groups (P<0.05). The results of three-point bending and torsion test by the universal material testing machine showed that the elastic modulus and maximum load indexes of the HIRT group were significantly smaller than those of the LIBFR group (P<0.05). The fracture load indexes in the HIRT group were significantly smaller than in the LIBFR group (P<0.05). 1. LIRT, HIRT, LIBFR, and CON all have significant differences, and this training helps to improve maximum strength, with HIRT being the most effective. 2. Blood flow restriction training can improve the expression of bone turnover markers, such as PINP and BGP, which promote bone tissue formation. 3. Blood flow restriction training can improve muscle strength and increase the positive development of bone turnover markers, thereby improving bone biomechanical properties such as bone elastic modulus and maximum load.

Study on preparation and properties of PVDF/CB composite films

Carbon black was often used as a UV stabilizer, due to its ability to absorb high-energy ultraviolet radiation. In this study, carbon black was added to PVDF resin, and PVDF film with carbon black (PVDF/CB composite film) was fabricated using a precision co-extrusion casting mechanism. The properties of the films were characterized by differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), field emission scanning electron microscope (FESEM), water contact angle (WCA), and universal material testing machine. Furthermore, the DSC results suggested that the melting temperature (Tm) of PVDF/CB composite film was 168.7°C. The TGA results showed that the initial decomposition temperature (Td) of PVDF/CB composite film was 358.9°C. The FESEM observation showed that the surface of the PVDF/CB composite film was smooth without obvious defects. The WCA results indicated that PVDF/CB composite film had good hydrophobicity. In addition, the UV transmittance results presented that PVDF/CB composite film had higher UV aging resistance than that PVDF film.