We displayed that the low-cost natural zeolite with molecular sieve structure can be used as the carrier of sulfur in lithium-sulfur batteries. Meanwhile, a simple salt-washing method was implemented on zeolite for dredging the internal microchannel to improve the ability of adsorption, ion exchange and sulfur loading. The experimental results show that the first specific discharge capacities of zeolite/S and salt-washed zeolite/S cathode under 0.2 C current density are 950.7 and 1 116.8 mAh/g, respectively, and corresponding discharge capacities remain at 350.6 and 604.2 mAh/g after 300 cycles. The first specific discharge capacity of salt-washed zeolite/S composite is 17.5% higher than that sample without salt-washing, and the corresponding ionic conductivity is improved.
A series of heteropoly acid (HPA) based Al2O3 catalysts with three-dimensional ordered (3DOM) structure were synthesized by colloidal crystal template method. Interconnected macropores (250 nm) could be clearly observed by scanning electron microscope (SEM) and transmission electron microscope (TEM). Mesopores could be detected by N2 adsorption-desorption isotherms which further confirmed the 3DOM structural characteristics of catalyst. Moreover, Keggin-type HPW was highly dispersed in the Al2O3 framework, which suggested by powder X-ray diffraction (XRD) and Fourier transform infrared spectra (FT-IR) results. The oxidation desulfurization (ODS) performance of 3DOM H3PW12O40/Al2O3 of refractory sulphur compounds was evaluated in the presence of hydrogen peroxide. It oxidized 98.5% of dibenzothiophene (DBT) into corresponding sulfone within 3 h, which exhibited superior ODS performance than corresponding mesoporous and microporous H3PW12O40/Al2O3 catalyst. The enhancement of ODS efficiency is related to the improvement of mass transfer of DBT in the pore channel resulting from the interconnected 3DOM structure. Furthermore, the as-prepared catalyst still demonstrates outstanding cycle performance after 6 runs, which could be easily recovered from the model fuel.
We fabricated the nanofiber composite membranes by impregnating Nafion into the modified polyvinylidene fluoride(PVDF) electrospinning nanofiber mat for proton exchange membrane fuel cells applications. The hydrophobic PVDF nanofibers mat became to the hydrophilic state by alkali treatment for the full embedding of Nafion into the PVDF network. The fabricated composite membranes exhibit significantly enhanced thermal stabilities, swelling resistance, and observably improved mechanical property compared to the pristine Nafion membrane. When the content of PVDF nanofiber mat is 15.1wt% in the membrane, the proton conductivity of the nanofiber composite membrane is nearly equal to that of pristine Nafion membrane with the same condition. The experimental results show that the prepared composite membrane can be used as a promising polyelectrolyte membrane for fuel cell applications.
Different heating treatments with the variation of heating rates, holding temperatures and holding time were used to simulate the LTPS procedure. The experimental results show that the reheating shrinkage rates of glass substrates are rarely changed with increasing the heating rate, but strongly enhanced by raising the holding temperature and time, which shows that the reheating shrinkage of glass is closely related to heat treatment and structural relaxation. The production process of glass is critical to the reheating shrinkage of glass.
A temperature stable Li2Zn0.95(Sr xCa1−x)0.05Ti3O8 (0⩽x⩽1) ceramics were fabricated using a conventional solid-state route sintered at 1100 °C for 4 h. The XRD results indicate that the main phase Li2ZnTi3O8 and secondary phase including Sr1Ca1−xTiO3 (0⩽x⩽1) solid solution and TiO2 co-exist in composite and form a stable composite system when the (Ca xSr1−x) (0⩽x⩽1) substitutes for Zn of Li2ZnTi3O8 ceramic. As x is increased from 0 to 1, the relative permittivity (ε r) increases from 26.65 to 27.12, and the quality factor (Q×f) increases from 63 300 to 66 600 GHz. With the increased of x, the temperature coefficient of resonant frequency (τ f) increases from 0.27 to 8.23 ppm/°C, and then decreases to 3.51 ppm/°C. On the whole, the Li2Zn0.95(Sr xCa1−x)0.05Ti3O8 (0⩽x⩽1) ceramics show excellent comprehensive properties of middle ε r = 25–27, higher Q×f ⩾ 60000 GHz and τ f ⩽±8.5 ppm/°C.
To investigate the acoustic emission (AE) characteristics of quasi-brittle materials like rock and concrete, and to further analyze their damage and failure mechanism under seismic and other dynamic loads, the uniaxial tension test of granite cylinder specimens within the strain rate range of 10−7-10−4 s−1 was monitored by AE technology, and the typical AE characteristic parameters were analyzed using statistical and correlation analysis. The experimental results show that, with the increase of strain rate, the peak of AE hit rate appears earlier and increases; the proportion of AE hits with higher duration or amplitude increases significantly, the b-value shows a decreasing trend, and the distribution of AE frequency-amplitude is increasingly discrete. In addition, the obvious characteristic of double dominant frequency bands was observed in AE waveforms by using spectrum analysis, with the increase of strain rate, the percentage of A-type waveforms corresponding to low dominant frequency band increases, while that of D-type waveforms corresponding to high ones decreases accordingly, which is significance for the further study of the damage and failure mechanism of quasi-brittle materials.
In order to develop high-performance diamond wheels, the vitrified bond with different contents of Li2O addition and corresponding diamond composites were prepared. The experimental results show that the addition of a small content of Li2O leads the formation of the mullite phase in vitrified bond. When the Li2O content is 3wt%, the mullite content in the vitrified bond reaches the maximum. Whereas, the vitrified bond turns into a pure glass phase when the Li2O content further increases to 5wt%. The softening temperature of vitrified bond, wetting angle between the vitrified bond and the diamond film decrease with the increasing of the Li2O content. The softening point of the vitrified bond with 5wt% Li2O is 537 °C and the contact angle is 32°, which are 44 °C and 44° lower than those of the sample without Li2O. The CTE (coefficient of thermal expansion), the flexural strength and hardness of the diamond composite sample first increase and then decrease with the increasing of the Li2O content. When the Li2O addition is 3wt%, the flexural strength and hardness of the composites reaches the maximum values of 93 MPa and 98 HRB, respectively, which are 43.1% and 12.6% higher than those of the sample without Li2O.
We reported a low cost, high efficiency hydrogen generation method from NaBH4 hydrolysis promoted by oxalic acid. NaBH4 and H2C2O4 were premixed and hydrogen generation was initiated by adding water into the solid mixture. H2C2O4 was selected as the acid promotor due to its solid state and low mass per proton. The effect of reactant ratio on the hydrogen yield and hydrogen storage density was investigated. With optimized reactant ratio, high gravimetric hydrogen storage up to 4.4wt% based on all the reactants can be achieved with excellent hydrogen generation kinetics.
The adventitious carbon located at 284.8 eV was used to calibrate samples without the carbon themselves. When the carbon is as a major part of the inorganic material, the adventitious carbon should be identified and used as the reference. There is no adventitious carbon on the surfaces of the polymer materials, so using C1s of the carbon in the polymer itself to calibrate the charging effect is reasonable. Furthermore, compared with gold and argon, a more practical and convenient method based on C1s is proposed to get the right positions for binding energy peaks.
The SnO2 quantum dots (SnO2QDs)/ZnS nanosheets (ZnSNs) heterojunction was fabricated via an in-situ synthetic method at room temperature. Rhodamine B, potassium dichromate, and tetracycline were used to discuss the photocatalytic activities of the as-prepared samples under the visible light illumination. The photocatalytic mechanism of the as-prepared samples was also proposed. The experimental results indicate that the degradation efficiency of the as-prepared SnO2QDs/ZnSNs heterojunction first increases and then decreases with increasing the usage of ZnSNs. When the mass ratio of SnO2QDs to ZnSNs is 1: 2 in 180 min, the asprepared samples have the highest degradation efficiency of 89.1% for rhodamine B, 97.7% for potassium dichromate, and 83.8% for tetracycline, which are much higher than 51.7%, 26.8%, and 0.9% of pure SnO2QDs as well as 37.9%, 87.1%, and 19.1% of pure ZnSNs, respectively. After it is repeatedly degraded for 3 times, it possesses the degradation efficiency of 62.5% for rhodamine B, which increases by 200.5% in comparison with 20.8% of the pure SnO2QDs. Moreover, the enhanced photocatalytic performances of the as-prepared hybrids are attributed to the formation of heterojunction between the SnO2QDs and ZnSNs. In addition, hydroxyl radicals and superoxide anion radicals play major roles during the photocatalytic degradation process, while holes play a minor role.
A niobate/titanat nanoflakes (Nb/TiNFs) composite was synthesized via the hydrothermal method and used to remove Pb(II) from water. XRD, TEM, and SEM results indicate that Nb/TiNFs appear as nanoflakes, of which the primary crystal phase is tri-titanate. Nb/TiNFs show rapid adsorption kinetics and the result fits well with the pseudo-second order model. The key mechanism of adsorption is ion-exchange between metal and -ONa/H. According to the Langmuir isotherm model, the maximum capacity of Pb(II) is 488.323 mg·g−1. The relatively low R L values indicate that Nb/TiNFs exhibit favorable adsorption of Pb(II). Nb/TiNFs indicate high adsorption capacity over a broad pH range. Co-existing inorganic ions (Na+ and Ca2+) have a slight inhibition effect on adsorption, and HA moderately inhibits the adsorption of Pb(II) on Nb/TiNFs. Because of the simple method of synthesis and high removal efficiency for heavy metals, Nb/TiNFs are a promising material in remediation of heavy metal polluted water.
The influences of new, scrap, and five modified Mo fibers on interface bonding strength of fiber-matrix and mechanical strength of RMC were studied. Typical specimens with different fibers and mass ratio of resin and hardener were prepared to verify the above assumptions. Theoretical analysis and experimental results prove that, compared with ordinary new Mo fibers, scrap Mo fibers can perform better in improving interface bonding strength and mechanical properties of RMC because many discharge pits randomly distribute on the surface of scrap fibers. For five modified Mo fibers, interface bonding strength and the reinforcing effect on RMC have been improved obviously. Wherein, comprehensive mechanical properties of RMC are optimal with the addition of M6 fibers which have undergone combined surface treatment including acidification, gasphase oxidation and coupling treatment. And interface bonding strength between M6 fiber and matrix is the maximum.
A novel fiber optic sensor based on optical composite oxygen-sensitive film was developed for determination of 2,4-dichlorophenol (DCP). The optical composite oxygen-sensitive film consists of tris(2,2′-bipyridyl) dichloro ruthenium(II) hexahydrate (Ru(bpy)3Cl2) as the fluorescence indicator and iron(III) tetrasulfophthalocyanine (Fe(III)PcTs) as bionic enzyme. A lock-in amplifier was used for detecting the lifetime of the composite oxygen-sensitive film by measuring the phase delay of the sensor head. The different variables affecting the sensor performance were evaluated and optimized. Under the optimal conditions (i e, pH 6.0, 25 °C, Fe(III)PcTs concentration of 5.0·10−5 mol/L), the linear detection range, detection limit and response time of the fiber optic sensor are 3.0×10−7–9.0×10−5 mol/L, 4.8×10−8 mol/L(S/N=3), and 220 s, respectively. The sensor displays high selectivity, good repeatability and stability, which have good potentials in analyzing DCP concentration in practical water samples.
Amine-functionalized imidazolium-based poly(ionic liquid) brushes on mesoporous silica were synthesized via “grafting through” technique and were applied as model sorbents to understand physisorption and chemisorption of carbon dioxide molecules. The experimental results reveal that the total adsorption capacity of model sorbents derived from temperature programmed desorption (TPD) approach reaches 1.72 mmol·g−1 that is much higher than the sum of adsorption capacity of bare mesoporous silica and free polymers at 25 °C under carbon dioxide partial pressure of 0.2 bar. The proposed physical adsorption and chemical adsorption of carbon dioxide molecules in TPD response curves were validated by volumetric desorption measurement. It is also observed that physical adsorption is completely reversible and chemical adsorption is irreversible. The results demonstrate that the temperature programmed desorption technique is an effective approach to differentiate chemisorption and physisorption of gaseous species on solid sorbents, which is beneficial for understanding of adsorption mechanism and materials design.
We introduced a parameter r s (the radius of the pores where the meniscus forms), which is composed of two factors, i e, water loss and cumulative pore size distribution (PSD), to provide a better explanation of the influence of superplasticizers(SPs) on early-age drying shrinkage. In our experiments, it is found that the addition of three types of SPs leads to a significant increase in the early-age drying shrinkage of cement paste, and drying shrinkage increases with the dosage of SPs. Based on the results above, we further studied the mechanism of the effects of SPs on the early-age drying shrinkage of cement paste by PSD and water loss, which are two components of r s. The experimental results indicate that r s can be a better index for the early-age drying shrinkage of cement-based materials with SPs than a single factor. In addition, the effects of SPs on other factors such as hydration degree and elastic modulus were also investigated and discussed.
Cement mortar with carbon fiber (CFc) and resin-cement mortar with carbon fiber (CFrc) were used as inner and outer cores of smart aggregate with Z shape, respectively, which was used as the basic perception units to prepare smart concrete aggregate with a mosaic structure (SAMS). The hydroxpropyl methylcellulose (HPMC) was taken into consideration to improve the properties of mortar; by using HPMC, the structure of SAMS was optimized and its mechanical and electrical properties were evaluated. The experimental results show that the toughness of mortar could be improved by the complex that formed by epoxy resin, and the effect of HPMC on the flexibility of CFc was greater than that on the flexibility of CFrc; the feasible designing indicates that the CFc-Z core and CFrc-Z core could be used as inner and outer cores of SAMS. When the proposed dosages of HPMC in inner and outer cores are 0.35wt% and 0.2wt%, respectively, it could give an effective prediction for the damage of concrete during the loading process.
Kinetics and mechanism of oxidation induced contraction of MgAl2O4 spinel carbon composites reinforced by Al4C3 in situ reaction were researched in air using vertical high temperature thermal dilatometer from 25 °C to 1 400 °C. It is shown that oxidation induced contraction of MgAl2O4 spinel carbon composites reinforced Al4C3 in situ reaction is the common logarithm of oxidation time t and the oxygen partial pressure P inside MgAl2O4 spinel carbon composites reinforced by Al4C3 in situ reaction in air at 1 400 °C is as follows: P=F(−2.75×10−4 A+2.13×10−3) lnt. The nonsteady diffusion kinetic equation of O2 at 1 400 °C inside the composites is as follows: J=D e lnt. Acceleration of the total diffusional flux of oxygen inside the composites at 1 400 °C is in inverse proportion to the oxidation time. The nonsteady state effective diffusion coefficient D e of O2(g) inside the composites decreases in direct proportional to the increase of the amount of metallic aluminium. The method of preventing the oxidation induced contraction of MgAl2O4 spinel carbon composites reinforced by Al4C3 in situ reaction is to increase the amount of Al. The slag erosion index of MgO-Al2O3 spinel carbon composite reinforced by Al4C3 in situ reaction is 0.47 times that of MgO-CaO brick used in the lining above slag line area of a VOD stainless steel-making vessel. HMOR of MgO-Al2O3 spinel carbon composite reinforced by Al4C3 in situ reaction is 26.7 MPa, HMOR of the composite is 3.6 times the same as that of MgO-CaO brick used in the lining above slag line area of a VOD vessel. Its service life is two times as many as that of MgO-CaO brick.
Autoclaved aerated concrete waste (AACW) was used as a raw material to prepare nucleation seed for acceleration of Portland cement. Nano AACW seed with median particle size of 324 nm was prepared by wet grinding method. Both the electrical conductivity and pH value of nano AACW suspension were obviously improved. Both the setting times and intensity of the main hydration heat peak were promoted by nano AACW, indicating the possibility of AACW suspension as nucleation seed. The early age compressive strength before 3 days was also clearly improved by nano AACW, with no negative effect on the late age strength. Furthermore, the reduced CH content with dosage of nano AACW indicates that nano AACW not only plays a role of nucleation seed in cement hydration, but also has a certain pozzolanic reaction.
The dynamic corrosion behaviors of Ti-6Al-4V alloy in acid artificial saliva containing fluoride ion were traced using electrochemical techniques, optical microscope, scanning electron microscopy, energy dispersive spectrometer and roughness tester. The experimental results indicate that a negative shift of corrosion potential as well as a continuous decrease in impedance for the alloy exists with increasing immersion time, and the degradation rate of the alloy presents the trend of first increase then decrease following the dissolution of passivation film and the formation of corrosion products. The accumulated fluoride ion on the alloy surface accelerates the fracture of passivation film, and the occurrence and development of corrosion of alloy are mainly located at the sites where the formation and shedding of white particles are composed of fluoride compounds, resulting in the decrease of corrosion resisting property of the alloy. A possible model is proposed to elaborate the dynamic corrosion behavior of the alloy.
Mg/Ni hybrid foams were fabricated by the electroless method. The Ni-P (Nickel-Phosphorous) coatings were deposited on the surface of closed-cell Mg alloy foams. The composition, microstructure and phases of the Ni-P coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The compressive tests were performed on the Mg/Ni hybrid foams at 400 °C using the Mg alloy foams as a reference. The experimental results show that the yield strength, plateau stress and energy absorption capacity of the closed-cell Mg alloy foams at high temperature were improved by the Ni-P coating. And there are four main modes for the Mg/Ni hybrid foam failure at 400 °C, i e, shearing in cell wall, bending in cell edge, shedding and cracking in Ni-P coating.
Co30Cr8W1.6C3Ni1.4Si coatings were fabricated on Ti6Al4V alloy using a laser thermal spraying (LTS). The surface and cross-section morphologies, phases and bonding strength of obtained coatings were investigated using scanning electronic microscopy (SEM), X-ray diffraction (XRD), and scratch test, respectively. The effects of laser power on the coefficients of friction (COFs) and corrosive-wear behaviors of Co30Cr8W1.6C3Ni1.4Si coatings were investigated using a wear tester in 3.5% NaCl solution, and the electrochemical corrosion performance was analyzed using an electrochemical workstation. The experimental results show that the Co30Cr8W1.6C3Ni1.4Si coating is bonded with the substrate in the metallurgical form, and the bonding strengths of Co30Cr8W1.6C3Ni1.4Si coatings fabricated at the laser power of 1 000, 1 200, and 1 400 W are 76.5, 56.5, and 55.6 N, respectively. The average COFs of Co30Cr8W1.6C3Ni1.4Si coatings fabricated at the laser power of 1 000, 1 200, and 1 400 W are 0.769, 0.893, and 0.941, respectively; and the corresponding wear rates are 0.267 × 105, 0.3 1 78 × 105, and 0.325 × 105 µm /Nm, respectively, which increases with the increase of laser power, the wear mechanism is primarily abrasive wear. The corrosion potential of Co30Cr8W1.6C3Ni1.4Si coatings fabricated at the laser power of 1 000, 1 200, and 1 400 W is −0.05, −0.25, and −0.31 V, respectively, higher than −0.45 V of substrate which enhances the electrochemical corrosion resistance of substrate.
A plasma cladding experiment was carried out to investigate the characteristics(surface hardness, microstructure, friction, wear properties from different substrates to the cladding layer and the bond strength) of plasma cladding Fe-Cr-Nb-Si-Mo alloy cladding layers on different substrates. In order to improve the abrasion resistance of the scraper middle trough, the plasma cladding technique was used to clad the alloy ceramic powder Ig7 on the surface of the middle trough NM450, WH60A, Hardox450, and Weartuf450 to create Fe/Cr/Nb/Mo/V cladding layer. Based on the experiment results, the microstructure, friction and wear properties of the four cladding layers were analyzed, and the bond strength between the cladding layer and the substrate was also tested. The experimental results show that the main phases of the four cladding layers are martensite and all kinds of metal carbides ((Nb, Mo)C, VC, and Cr7C3). WH60A surface cladding layer has shown good friction and wear properties.
The starch/polyvinyl alcohol (PVA)/microfibrillated cellulose (MFC) composite films were prepared using solution casting method after adding MFC into starch/PVA blend matrix. The effects of MFC content on the mechanical properties of starch/PVA composite films were investigated. As MFC content increases, the elongation at break and tensile strength increase firstly and then decrease. When the content of MFC is 2wt%, the tensile strength is 26.6 MPa and reaches the maximum. Through Fourier transform infrared (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), good dispersion of MFC in starch/PVA matrix at the loading of 2wt%, lower crystallinity of the starch/PVA/MFC films in comparison with starch/PVA blend and the effect of glass transition temperature increasing with MFC content from 0.5wt% to 4wt% can be found observed. And, incorporating MFC does not change the composition and crystal structure of the starch/PVA composite films. Thus, the reinforcing mechanism for the improvement of mechanical properties is attributed to the homogeneous dispersion of MFC with large aspect ratio, good compatibility and interfacial interactions between starch/PVA blend matrix and MFC.
Castor oil-based cationic waterborne polyurethane (CWPU) was synthesized by pre-polymer process using castor oil (CO), poly(adipic acid-1,4-succinate diol) (PBA), isophorone diisocyanate (IPDI), and N-methyldiethanolamine (MDEA). The influences of the content of CO and MDEA on comprehensive performance and finished fabric properties of cationic waterborne polyurethane was investigated, especially the antibacterial properties of finished fabric. The CWPU latex particle size and its distribution decrease as the content of CO increased from 0wt% to 16.8wt%, and increases afterwards. The CWPU films show much higher thermal stability than cationic waterborne polyurethane without CO. The surface of fabrics was characterized by scanning electron microscope (SEM). The finished fabric surface is much smoother. In addition, the finished fabric with CWPU emulsion has better antibacterial property against E. coli and S. aureus. When MDEA content is 8%, the antibacterial rates of the two kinds of bacteria are 77.3% and 82.2%, respectively.