Universal Material Testing Machine Research Articles

Synthesis and Characterization of a Novel Aqueous Glycidyl Azide Polymer Emulsion.

The current domestic and foreign research on azide polymers such as glycidyl azide polymers (GAP) mainly focuses on the design, synthesis, modification, and performance of elastomers; it is difficult to prepare the GAP/NC (nitrocellulose) blends, and they have poor mechanical properties. Here, we developed a green and safe strategy for the blending and compounding of azide binder and NC by blending the emulsion with NC in water and demulsifying. Considering the structural characteristics of GAP, a novel energetic aqueous GAP-E (energetic elastomer) emulsion was prepared by anionic self-emulsion polymerization using 2,2-dimethylol propionic acid as the hydrophilic chain extender, 1,4-butanediol as the chain extender, and triethylamine as a neutralizer. Furthermore, the GAP-E emulsion/triethylene glycol dinitrate/nitrocellulose blends (GAP-E/TEGN/NC) with different proportions were prepared in aqueous phase by the precipitation method. The related properties of the emulsion were studied by gel permeation chromatography, Fourier transform infrared, universal material testing machine, dynamic mechanical analyzer, thermogravimetric analysis, and scanning electron microscopy (SEM). Our results indicated the emulsion exhibited good stability with the number average molecular weight of 76,600. The GAP-E film showed a tensile strength of 17.8 MPa, elongation at break of 415%, glass transition temperature of −28.5 °C, and initial degradation temperature of 242 °C. The GAP-E emulsion and TEGN/NC can be blended in the aqueous phase by the demulsification method to prepare a homogeneous GAP-E/TEGN/NC blend. Fourier transform infrared spectroscopy (FTIR) showed that there was a certain hydrogen bond interaction between GAP-E and TEGN/NC molecules, which was conducive to the improvement of the mechanical properties. The results of SEM indicated that GAP-E could obviously soften the rigid fiber structure of TEGN/GN, and the blends were well mixed with good interfacial compatibility between the GAP-E (5%) and TEGN/NC. When the mass fraction of GAP-E was 5%, the tensile strength and the elongation at break of the blend reached up to 32.1 MPa and 54.4%, which were improved by 33 and 46% compared to those of the TEGN/NC blend system, respectively. The transition temperature remained at −21.6 °C with obvious enhancement on the mechanical properties.

Mechanical Properties and a Constitutive Model of 3D-Printed Copper Powder-Filled PLA Material.

Three-dimensional printing is becoming increasingly popular because of its extensive applicability. However, printing materials remain limited. To determine the mechanical properties of polylactic acid (PLA) and copper powder-filled polylactic acid (PLA-Cu) materials subjected to static and dynamic loading, stress–strain curves were obtained under the conditions of different strain rates using a universal material testing machine and a separated Hopkinson pressure bar experimental device. Scanning electron microscopy (SEM) was used to analyze the micro-morphology of the quasi-static compression fracture and dynamic impact sections. The results revealed that the yield stress and elastic modulus of the two materials increased with increasing strain rate. When the strain rate reached a critical point of 0.033 s−1, the rate of crack propagation in the PLA samples increased, resulting in the material undergoing a change from ductile to brittle. The strength of the material subjected to dynamic loading was significantly higher than that subjected to quasi-static loading. The SEM image of the PLA-Cu material revealed that copper powder was evenly distributed throughout the 3D-printed sample and that stress initially began to concentrate at the defect site corresponding to the interface between the copper powder and PLA matrix; this resulted in comparatively lower toughness. This finding was consistent with the photographs captured via high-speed photography, which confirmed that the destruction of the specimen was accompanied by an explosive crushing process. Additionally, a Zhu–Wang–Tang constitutive model was used to fit the experimental results and establish a viscoelastic constitutive model of the material. By comparing the dynamic stress–strain curve to the theoretically predicted curve, we found that the established constitutive model could predict the mechanical properties of the PLA-Cu material with reasonable accuracy when the strain was below 7%.

Bending Resistance of Polylactic Acid Absorbable Root Canal Pile after Repairing Residual Roots

As we all know, tooth growth is very important for children. Whether it is the growth of new teeth or the loss of deciduous teeth, the residual roots of deciduous teeth will affect the physiological replacement of permanent teeth, and the repair of non-absorbable retention posts will also participate. Therefore, the purpose of this article is to explore the polylactic acid can absorb the bending resistance of the root canal pile after repairing the residual root. The method adopted in this paper is to randomly select 24 isolated mandibular premolars to ensure the morphological similarity of the sample as much as possible. After routine root canal treatment and filling, the crown is removed, and the sample is divided into 3 groups on average.. Respectively, polylactic acid absorbable root canal post, fiberglass post and composite resin short post retention, to perform post-core resin crown repair. Subsequently, the electronic universal material testing machine and formula were used to calculate the bending resistance of each material in the fracture mode, and then LSD two-sided inspection was used for comprehensive comparison. Corresponding conclusions are drawn through data comparison. The research results show that the bending strength of the polylactic acid absorbable root canal pile group is 1031.44±359.78N, the bending strength of the glass fiber pile group is 1121.34±193.50N, and the composite resin short pile The group was 1581.36±677.20N, and the differences were statistically significant (P<0.05). The three groups of samples in the experiment are all favorable tooth creases. Therefore, it can be concluded from the experimental results that the bending resistance of the polylactic acid absorbable root canal pile after restoring the residual root is lower than that of the composite resin short pile, which can also meet the clinical needs.

Effects of hollow glass microspheres on the polybenzoxazine thermosets: Mechanical, thermal, heat insulation, and morphological properties

AbstractThe growing need for high thermal and mechanical resistant lightweight syntactic foams demands the designing of new materials. Herein, we report the successful fabrication of lightweight and high thermal resistance syntactic foams with excellent thermal and good mechanical properties. For this end, 10–50 wt% hollow glass microsphere (HGMS) containing polybenzoxazine based syntactic foams were prepared by using bisphenol‐A‐aniline (BA‐a) and phenol‐diaminodiphenylmethane (P‐ddm) benzoxazine via curing at 10 MPa compression molding. The curing behavior, tensile, flexural, compressive, and impact strength, thermal properties, and fracture morphology of the syntactic foams were studied by DSC, universal material testing machine, and drop hammer impact testing machine, TGA, and SEM, respectively. The curing temperatures of BA‐a and P‐ddm benzoxazine resins were slightly increased after blending the HGMS. The highest decline (59%) in the density and highest void contains (13.17%) was recorded for the poly(P‐ddm/HGMS50) sample. The excellent specific mechanical properties of the syntactic foams were observed on the 30 wt% HGMS loading. The thermal conductivity of the foams was gradually decreased and the lowest values of 0.106 and 0.0985 W/m.K were observed for poly(BA‐a/HMGS50) and poly(P‐ddm/HGMS50) sample, respectively. Furthermore, a gradual improvement in the thermal properties was observed as the loading of HGMS increased.

Self-lubricating interpenetrating polymer networks with functionalized nanoparticles enhancement for quasi-static and dynamic antifouling

Biofouling is an exasperating problem in medical engineering and marine equipment fields resulting in great economic losses and adverse effect. In marine protection, quasi-static and dynamic antifouling techniques are the mainstreams of protection strategies for the long-term application. Inspired by the aquatic biology skins, a series of interpenetrating polymer networks (IPNs) equipped with autocrine property were developed by free radical polymerization, which contained zwitterionic nanoparticles and lubricant. These two components leaded to quasi-static antifouling and dynamic fouling releases characters guaranteeing their broad-spectrum application. Their mechanical properties, surface morphology, and the self-leakage behavior of lubricant were inspected using an electrical universal material testing machine, an optical microscope and SEM. The protein adsorption and algae adhesion to IPNs were also tested. The results indicated that the zwitterion modified nanoparticles not only promoted the mechanical properties of IPNs, but also improved their static antifouling properties with above 95% fouling resistance efficiency. Meanwhile, a good fouling release ability (above 60%–80% fouling release efficiency) and prominent self-renewal character of IPNs interface were obtained because of the embedded lubricant component, which indicated a weak interfacial adhesion for biomass. It is expected that the polymer networks combining quasi-static and dynamic antifouling property will be translated into marine antifouling applications due to the simplicity of preparation and superior antifouling capacity.

Synthesis of a novel UV-curable prepolymer 1,3-bis[(3-ethyl-3-methoxyoxetane)propyl]tetramethyldisiloxane and study on its UV-curing properties

Abstract Precursor 3-ethyl-3-hydroxymethyloxetane was synthesized with trihydroxypropane and diethyl carbonate as the main raw materials. Intermediate 3-ethyl-3-allylmethoxyoxetane was synthesized with 3-ethyl-3-hydroxymethyloxetane and allyl bromide. Prepolymer 1,3-bis[(3-ethyl-3-methoxyoxetane)propyl]tetramethyldisiloxane was synthesized with 3-ethyl-3-allylmethoxyoxetane and 1,1,3,3-tetramethyldisiloxane. Cationic photoinitiator triarylsulfonium hexafluoroantimonate of 3 wt% was added to the prepolymer, and a novel kind of photosensitive resin was prepared. Structures of the compounds obtained at individual stages of the synthesis were analyzed and characterized by FTIR and 1H-NMR. Photo-DSC analysis showed that the prepolymer had excellent photosensitivity. Thermogravimetric analysis (TG) revealed that the ultraviolet (UV)-cured samples owned excellent thermal stabilities of up to 405°C. And the mechanical properties of the UV-cured samples were tested by the universal material testing machine, giving 25.95 MPa of tensile strength, 2,935.15 MPa of elastic modulus, and 4.09% of elongation at break.

Preparation of Bis[(3-ethyl-3-methoxyoxetane)propyl]diphenylsilane and Investigation of Its Cationic UV-Curing Material Properties.

Precusor EHO(3-ethyl-3-hydroxymethyloxetane) was synthesized with diethyl carbonate and trihydroxypropane as the main raw materials. Intermediate AllyEHO(3-ethyl-3-allylmethoxyoxetane) was synthesized with 3-ethyl-3-hydroxymethyloxetane and allyl bromide as the main raw materials. Prepolymer bis[(3-ethyl-3-methoxyoxetane)propyl]diphenylsilane was synthesized with 3-ethyl-3-methoxyoxetane)propyl and diphenylsilane. Photoinitiator triarylsulfonium hexafluoroantimonate of 3% was added to the prepolymer, and a novel kind of the photosensitive resin was prepared. They were analyzed and characterized with FTIR and 1H-NMR. Photo-DSC examination revealed that the bis[(3-ethyl-3-methoxyoxetane)propyl]diphenylsilane has great photosensitivity. The thermal properties and mechanical properties of the photosensitive resin were examined by TGA and a microcomputer-controlled universal material testing machine, with thermal stabilities of up to 446 °C. The tensile strength was 75.5 MPa and the bending strength was 49.5 MPa. The light transmittance remained above 98%.

Fracture Stregnth of Endodontically Treated Teeth with Minimally Invasive Access Cavity Desgins Versus Conventional One (An In Vitro Study)

Aim: Assess the fracture strength of endodntically treated teeth with minimally invasive access cavitydesign versus conventional one.Methods: Forty four extracted molars were assigned to 4 groups. Conservative Access Cavity, Ninja AccessCavity, Truss Access Cavity, Traditional Access Cavity (n = 11/group/type). Teeth in the Traditional groupwere prepared following the principles of traditional endodontic cavities. Conservative access prepared byusing 2 periapical radiographs to determine canals location. Ninja access scans were plotted on cone beamcomputed tomographic images for localization of root canal orifices and Truss group were scanned, andmerged with cone beam computed tomography, for fabrication of an endodontic guide.The 44 specimenswere loaded to fracture in a universal material testing machine. The maximum load at which the teethfractured and fracture pattern (restorable or unrestorable) were recorded.Results: Regarding the fracture strength, results showed that there was a significant difference betweenNinja, Conservative,Truss and traditional access groups with (p < 0.001) and no significant differencebetween Conservative and Truss groups. Regarding restorability, there was no statistical difference observedbetween the four groups with (p < 0.001).Conclusion: Teeth with traditional access showed lower fracture strength than the ones prepared withConservative, Ninja and Truss.

Porous matrix nanometric scaffold repairs rabbit tibia injury by promoting bone marrow mesenchymal stem cell osteogenic differentiation and up-regulating type I and II collagen content

To explore the effect of porous matrix nanometer scaffold on Bone marrow mesenchymal stem cell osteogenic differentiation and type I and II collagen content in rabbit tibial injury. 22 rabbits, weighing 2.20–3.10 kg, were equally divided into model and treatment groups. Von Kossa was used to detect osteogenic differentiation, while Western blot detected type I and type II collagen. The bone density meter measurement software was used to assess tibial bone density. Universal material testing machine was used to detect biomechanical indicators level, while HE staining detected bone morphology. Adherent Cells growth were observed in a week; where cells clusters appeared and continued to grow 2 weeks later, and the number of osteoblasts and mineralized nodules increased significantly 3 weeks later. The collagen level in the treatment group was significantly higher than that in model group (P < 0.05). The tibia bone mineral density in model group was significantly lower at the sixth and twelfth weeks after surgery (P < 0.05). The maximum bending load and bending stiffness of model group were significantly lower than those of treatment group with higher damage degree (P < 0.05). Treatment increased the bone tissue and osteoblasts, leading to production of trabecular bone structure. No clustered regenerated bone-like tissues in model group were observed. The porous matrix nanometer scaffold can repair rabbit tibia injury possibly by promoting Bone marrow mesenchymal stem cell osteogenic differentiation and increasing type I and type II collagen level.

Research on Parameters of Wire-Filling Laser Welding and Quenching Process for Joints Microstructure and Mechanical Property of BR1500HS Steel

With the aim to investigate the effect of parameters and the quenching process on the joint microstructure and mechanical properties of hot stamping steel by laser welding, BR1500HS boron steel was welded by wire-filling laser welding with ER70-G welding wire under different parameters. The welded specimens were heated to 900 °C and held for 5 min before water quenching. A universal material test machine, optical microscope, Vickers hardness tester, scanning electron microscope, and electron backscatter diffraction (EBSD) were used to characterize. The results show that the heat input should be greater than 1040 J/cm and the optimal wire-feeding speed is between 160 cm/min and 180 cm/min. The tensile strength of the quenched joint can reach greater than 1601.9 MPa at compatible parameters. More retained austenite distributes in the fusion zone (FZ) and fine grain zone (FGZ) than the coarse grain zone (CGZ) before quenching. However, the retained austenite in FZ and heat-affected zone (HAZ) decreases clearly and distributes uniformly after quenching. The grain diameter in FZ before quenching is not uniform and there are some coarse grains with the diameter greater than 40 μm. After quenching, the grains are refined and grain diameter is more uniform in the joint. With the increase in heat input, the microhardness of FZ and HAZ before quenching decreases from 500 HV to 450 HV. However, if the wire-feeding speed increases, the microhardness of FZ and HAZ before quenching increases from 450 HV to 500 HV. After quenching, the joint microhardness of all samples is between 450 HV and 550 HV. The fracture morphology of the joint before quenching consists of a large number of dimples and little river patterns. After quenching, the fracture morphology consists of a large amount of river patterns and cleavage facets due to the generation of martensite.

Effect of Sintering Factors on Properties of Al-Rich PTFE/Al/TiH2 Active Materials.

Sintering process is an important part of the specimen preparation process, which directly affects the properties of materials. In order to obtain the best sintering control factors of Al-rich PTFE/Al/TiH2 active materials, Al-rich PTFE/Al/TiH2 active specimens with different sintering control factors were prepared using a mold pressing sintering method. A quasi-static compression experiment was carried out on a universal material testing machine, and a real stress-strain curve was obtained. The effects of sintering control factors on the properties of Al-rich PTFE/Al/TiH2 active materials were analyzed by means of mechanical parameters such as compressive strength, failure strain and toughness. SEM and XRD were used to analyze the microstructure and phase of the sintered samples. The results show that: (1) With the increase of cooling rate, the density, yield strength, strain hardening modulus, compressive strength and toughness of Al-rich Al/PTFE/TiH2 specimens decrease gradually, while the failure strain and pores of the specimens increase gradually. (2) With the increase of sintering temperature, the density, maximum true strain and toughness of the specimens first increase and then decrease, and the failure strain of the specimens gradually increases. When the sintering temperature is 360 °C, the PTFE matrix and particles inside the specimen are closely combined, a small number of particles are exposed on the PTFE matrix and there are a small number of voids. (3) With the increase of holding time at 360 °C, the strength and toughness of the material first decrease and then increase. When the holding time is 6 h, the interface between particles and matrix inside the specimen is the strongest, and the crack propagation inside the specimen is less. (4) When the sintering time increased from 1 h to 4 h at 315 °C, the compressive strength of the specimen increased by 1.62%, the toughness of the specimen decreased by 0.55% and the failure strain of the specimen decreased by 0.54%. The interface between PTFE matrix and particles is the strongest and the crack propagation is less in the specimen with a holding time of 4 h. (5) Above all, the optimum sintering parameters of Al-rich Al/PTFE/TiH2 materials are cooling rate of 25 °C/h, sintering temperature of 360 °C, holding time of 6 h and holding time of 4 h at 315 °C. (6) The reactivity of Al-rich Al/PTFE/TiH2 specimens with 10% content of TiH2 under static compression is not significantly affected by sintering parameters.

Design and parameters optimization of root cutting tool based on garlic numerical simulation model

AbstractTo obtain the best tool parameters for garlic root cutting to reduce the root cutting force and improve efficiency, a linkage occlusion‐cutting mechanism was designed for a garlic root cutting force test. The physical and mechanical properties of garlic meat and garlic skin were measured and calculated by using a universal material testing machine. A plastic follow‐up model (MAT‐3) in the LS‐DYNA material library was used as a simulated garlic material model. A three‐dimensional model of the garlic and the tool was established and imported into ANSYS/LS‐DYNA to establish a garlic root cutting simulation model. The model was used for numerical calculation and analysis. The simulation parameters were optimized according to the actual cutting force change curve, and a reliable simulation model was obtained. The error between simulated result and actual measurement was 3.5%. Based on this reliable model, the effects of tool parameters on the root cutting force were explored. The optimal blade edge angle was 11°, the optimal blade back angle was 13°, and the cutting root force was reduced by 14.94%. The reliable model and optimal tool parameters provide a reference for the design and development of garlic root cutting equipment.Practical ApplicationsGarlic is popular worldwide because of its high nutritional value and unique flavor. A reliable numerical simulation model for garlic will encourage researchers to design garlic‐processing equipment. The optimal tool parameters also provide a reference for garlic root cutting equipment.

Influence of Cold Rolling on the Recrystallization Texture and Ridging of AISI 430 Type Ferritic Stainless Steel

The effect of cold rolling on the recrystallization texture and ridging of AISI 430 type ferritic stainless steel is investigated. For comparison, the steel was cold-rolled under different reductions, two-stage rolled, and cross-rolled, respectively, and the recrystallization texture was determined by EBSD and microstructure was characterized by SEM, and the uniaxial deformation was conducted on MTS electronic universal material testing machine. The results show that in the one-stage cold rolling and annealing process, γ-fiber texture component increases with the rolling reduction, and the maximum orientation density of which appears at {334} orientation with a slight deviation from {111} . The intensity of {100} texture decreases and the other main texture components remain unchangeable. After two-stage cold rolling, the recrystallization texture returns to the γ-fiber texture that is of the feature of the ordinary bcc metals, while cross-rolling results in a recrystallization texture of mainly {100} and {111} components. It is indicated that intermediate annealing obviously improves the deviation of orientation from γ-fiber texture, which is beneficial for the steel obtaining the typical texture of bcc metals. By one-stage cold rolling and annealing process, AISI 430 type ferritic stainless steel possesses a microstructure with the texture components of {100} , {211} , {111} and {111} , with clusters of {111} , {hkl} and {hkl} grains, which deteriorates the ridging resistance, while in the two-stage rolling and annealing process, the microstructure of dispersed oriented grains shows a much better surface ridging resistance.

A Comparative Study of the Mechanical Properties of Basalt Fiber and Basalt Grille Reinforced Concrete Composites and Theoretical Prediction

ABSTRACT In this study, the chopped basalt fiber (CBF) with different content and basalt fiber grilles (BFG) with different layers were composed with concrete matrix, respectively. The compressive, splitting tensile and flexural properties of concrete composites were studied by universal material testing machine. The cracks evolution law of specimens was analyzed to reveal the reinforcement mechanism of CBF and BFG. Results showed that under the same fiber volume ratio, BFG were better than CBF to reinforce mechanical properties of concrete. The three kinds of mechanical properties of BFG reinforced concrete were improved highest by 41.46%, 28.26% and 46.13%, respectively. BFG can play a crucial role in stress transmission, bearing load and absorbing energy during the loading process of the specimens. Based on the equivalent stress rectangle theory, an analytic model to predict the ultimate flexural capacity of BFG reinforced concrete was proposed. The experimental results from the flexural test were compared with the predicted values, and a good accuracy of the analytic model was obtained.

Preparation and characterization of basalt fabrics coated with zirconia obtained by sol-gel method for textile reinforced concrete

The poor alkali resistance of basalt fabric greatly affects the mechanical properties of textile reinforced concrete. In this study, dense zirconia coating obtained by sol-gel method was coated on the basalt fabrics surface as additional sizing to improve the alkali resistance of basalt fabrics. The morphology, wettability and phase composition of the fabric surfaces was characterized by scanning electron microscopy (SEM), static water contact angle (SWCA), X-ray powder diffraction (XRD), fourier transform infrared spectra (FI-IR), X-ray photoelectron spectroscopy (XPS) and Raman. The tensile properties of various basalt fabrics immersed in alkaline solution for different time and the mechanical property of concrete composites were examined by universal material testing machine. Results showed that a protective membrane was formed on the surface of basalt fabrics to prevent the diffusion of hydroxide ions. The final strength retention ratio of BF-c-ZrO2 (Basalt fabric-coated-Zirconia) fabrics could maintain at 89.92% compared with that of pristine basalt fabrics, which reached below 40%. The compressive strength and flexural strength of BF-c-ZrO2 fabrics reinforced concrete increased by 10.15% and 19.0% compared with that of pristine basalt fabrics reinforced concrete. A theoretical model was proposed to predict the ultimate flexural bearing capacity of BF-c-ZrO2 fabric reinforced concrete based on the equivalent stress rectangle theory. The corresponding predicted value compared with experimental result indicated a good coincidence and a reasonable accuracy, which was less than 5% of their discrepancy.

A novel and efficient surgical knotting technique for high-tension closures.

BackgroundThe closure of high-tension incisions without any assistance can be difficult and challenging for surgeons. A common practice is to fix the first knot with a clamp and then tie a reverse locking knot; however, this practice has certain disadvantages. The aim of this study was to introduce a novel and efficient surgical knotting technique with various advantages.MethodsThe two knotting methods used in this study were the absorbable braided suture where the first suture was fixed with a clamp (with assistance) and the SH-9Hospital knotting technique (without assistance) applied on the smooth surface of a cylinder. Mechanical testing was performed using a universal material testing machine. The load-elongation curve and ultimate tensile load (UTL) were recorded.ResultsThe mean knotting time was 36.40±1.50 s (range, 32–41 s) and 24.80±1.16 s (range, 21–28 s) in the clamp and SH-9Hosptial groups, respectively. The mean UTL was 120.8±10.14 N (range, 81.11–136.55 N)and 126.5±6.29 N (range, 104.88–139.56 N) in the clamp and SH-9Hospital groups, respectively. The knot strength of the SH-9Hospital technique was not inferior to traditional clinical practice.ConclusionsThe SH-9Hospital knotting technique was a secure, convenient, and efficient method for high-tension closure.

Fabrication and electrochemical behavior of halloysite/ graphene-polyaniline three-dimensional hybrid aerogel loaded with iron oxide

Great progress had been made in the synthesis and application of graphene, graphene oxide (GO) aerogels, and reduced graphene oxide (rGO). However, most of the reported graphene hybrid aerogels reduced the mechanical properties of the obtained materials because of their wide pore size distribution, which limited the recycling of aerogels. Therefore, it was urgent to prepare graphene hybrid aerogels with uniform mesopores or micropores to enhance the structural stability of aerogels. Meanwhile, the mechanical and electrical properties of graphene hybrid aerogels could be further improved. In this paper, halloysite/graphene-polyaniline three-dimensional hybrid aerogel loaded with Fe3O4(HGA-PANI) was fabricated. The microstructure, mechanical properties, and electrochemical properties of HGA-PANI were characterized by scanning electron microscope (SEM), X-ray Photoelectron Spectroscopy (XPS), N2 adsorption-desorption tests, universal material testing machine, electrochemical workstation, and so on. Halloysite nanotubes (HNT) were fixed on the surface of graphene sheets or intercalated between graphene nanosheets. The three-dimensional network structure was formed, which reduced the agglomeration between graphene sheets. The hybrid of HNT and graphene sheet increased the graphene's specific surface area and constructed a three-dimensional network porous structure. Through Cyclic voltammetry (CV), Galvanostatic charge-discharge (GCD), Electrochemical impedance spectroscopy (EIS), and cycle stability tests, HGA-PANI had acceptable electrical properties, large capacitance, thin internal resistance, and amazing cyclical stability.

Fabrication and Characterization of the Core-Shell Structure of Poly(3-Hydroxybutyrate-4-Hydroxybutyrate) Nanofiber Scaffolds.

Tissue engineering scaffolds with nanofibrous structures provide positive support for cell proliferation and differentiation in biomedical fields. These scaffolds are widely used for defective tissue repair and drug delivery. However, the degradation performance and mechanical properties of scaffolds are often unsatisfactory. Here, we successfully prepared a novel poly(3-hydroxybutyrate-4-hydroxybutyrate)/polypyrrole (P34HB-PPy) core-shell nanofiber structure scaffold with electrospinning and in situ surface polymerization technology. The obtained composite scaffold showed good mechanical properties, hydrophilicity, and thermal stability based on the universal material testing machine, contact angle measuring system, thermogravimetric analyzer, and other methods. The results of the in vitro bone marrow-derived mesenchymal stem cells (BMSCs) culture showed that the P34HB-PPy composite scaffold effectively mimicked the extracellular matrix (ECM) and exhibited good cell retention and proliferative capacity. More importantly, P34HB is a controllable degradable polyester material, and its degradation product 3-hydroxybutyric acid (3-HB) is an energy metabolite that can promote cell growth and proliferation. These results strongly support the application potential of P34HB-PPy composite scaffolds in biomedical fields, such as tissue engineering and soft tissue repair.

Study on the Strength Evolution Characteristics of Cemented Tailings Backfill from the Perspective of Porosity

At present, the filling mining method is widely used. To study strength evolution laws of cemented tailings backfill (CTB) under different curing ages, in the experiment, mine tailings were used as aggregates, ordinary Portland cement (PC32.5) was used as cementing materials, and different additives (lime and fly ash) were added to make filling samples with the solids mass concentration at 74% and the cement-sand ratios 1:4, 1:6 and 1:8. Based on the nuclear magnetic resonance (NMR) technology, the porosity test of filling samples with curing ages of 3 d, 7 d and 28 d was carried out, and the uniaxial compressive strength test was carried out on the servo universal material testing machine. The relationship between the uniaxial compressive strength and porosity of backfills and the curing age in the three groups was studied, and change laws of the porosity variation and strength growth rate of backfills were analyzed. Based on the variation in porosity, the strength evolution model of the CTB under different curing ages was established, and the model was fitted and verified with test data. Results show that the uniaxial compressive strength, porosity, porosity variation, and strength growth rate of the three groups of backfills gradually increase with the increase of the curing age, the porosity of backfill basically increases with the decrease of the cement–sand ratio, and the porosity of backfill decreases with the increase of the curing age. Porosity variations and relative strength values of the three groups of backfills under different cement-sand ratios obey an exponential function, and the two have a good correlation, indicating that the established filling strength evolution model can well reflect strength evolution laws of the CTB with the change of curing age.

Investigation of Thermal Gradient Mechanical Fatigue Test Methods for Nickel-based Superalloys

Temperature gradients significantly affect the material fatigue process. A reliable and robust test procedure is needed for quantifying the effects of temperature gradients on the evolution of fatigue damage in nickel-based superalloys. The present study aims to develop a radiation heating system for universal material testing machine for simulating thermal gradient mechanical fatigue in turbines. The developed heating system mainly consists of halogen lamps, reflectors, cooling subsystems, and control units. Based on extensive experimental and computational investigations, a thermal model is developed for accurate thermo-mechanical fatigue testing under given temperature gradients in the heating system, and it is applied to variable temperature fatigue tests. The detail procedure for determining heat transfer coefficients is presented based on experimental and computational results. TGMF tests are successfully performed with the developed radiation heating system. The temperature gradients are found to reduce the TGMF life significantly in comparison to that of the TMF life. It is confirmed that the developed thermal gradient mechanical fatigue methodology can be applied to different thermo-mechanical fatigue tests with various temperature gradients.