One-step Heat Treatment Research Articles

Fast mineralization of densely packed hydroxyapatite layers in the presence of overexpressed recombinant amelogenin

Learning from the process of biominerals formation provides tremendous ideas for developing advanced synthesis techniques. According to the structure formation of tooth enamel, a recombinant amelogenin his-AmelX was designed and constructed. The protein was over-expressed and could be conveniently purified in one-step heat treatment. The mineralization process of hydroxyapatite was initiated by enzyme AP and regulated by the recombinant amelogenin. Effects of solution pH value and mineralization duration were studied. It was demonstrated that his-AmelX could induce the nucleation of apatite and quicken the growth rate at pH 7.0-7.4, while impeded hydroxyapatite growth at pH 6.8. Moreover, a much denser layer of hydroxyapatite was achieved with the addition of his-AmelX. The present study may not only provide insight into the formation of natural biomaterials but also open a new path to prepare materials under environmentally benign conditions.

Split Sn-Cu Alloys on Carbon Nanofibers by One-step Heat Treatment for Long-Lifespan Lithium-Ion Batteries

To develop next-generation lithium-ion batteries (LIBs) with novel designs, reconsidering traditional materials with enhanced cycle stability and excellent rate performance is crucial. We herein report the successful preparation of three-dimensional (3D) composites in which spilt Sn–Cu alloys are uniformly dispersed in an amorphous carbon nanofiber matrix (Sn–Cu–CNFs) via one-step carbonization-alloying reactions. The spilt Sn–Cu alloys consist of active Cu6Sn5 and inactive Cu3Sn, and are controllable by optimization of the carbonization-alloying reaction temperature. The 3D carbon nanofiber framework allowed the Sn–Cu–CNFs to be used directly as anodes in lithium-ion batteries without the requirement for polymer binders or electrical conductors. These composite electrodes exhibited a stable cyclability with a discharge capacity of 400mA h g−1 at a high current density of 1.0Ag−1 after 1200 cycles, as well as an excellent rate capability, which could be attributed to the improved electrochemical properties of the Sn–Cu–CNFs provided by the buffering effect of Cu3Sn and the 3D carbon nanofiber framework. This one-step synthesis is expected to be widely applicable in the targeted structural design of traditional tin-based anode materials.

One-step self-assembled epoxide-containing nanodots as an enzyme-immobilized platform for biosensing

3-Glycidoxypropyl trimethoxysilane-containing self-assembled SiOx nanodots (GPS-SANDs) bearing epoxide functional groups were successfully fabricated via a facile one-step heat treatment process. The GPS-SANDs possessed spherical-like particles with an average diameter of 3.1±0.3nm. This material exhibited a broad band, and a multicolor. Glucose oxidase (GOx) enzyme was further immobilized on GPS-SANDs via aminolysis of the epoxide groups to detect glucose using photoluminescence (PL) spectroscopy. The PL intensity changed inversely with the glucose concentration. The glucose detection limit of GOx-immobilized GPS-SANDs was determined to be 100μM. Therefore, GPS-SANDs provide a promising GOx-immobilized platform for the design of optical glucose biosensors with high sensitivity. In addition, this platform may allow for the further development of enzyme biosensing systems through conjugations between GPS-SANDs and a target enzyme.

Catalytic decoloration of commercial azo dyes by copper-carbon composites derived from metal organic frameworks

Porous copper-carbon composites were synthesized via one-step heat treatment of copper-based metal organic frameworks (MOFs), MOF-199. The prepared composites,Cu-CC-550 and Cu-CC-650, were applied as catalysts for catalytic decoloration of two commercial azo dyes, methylene blue (MB) and rhodamine B (RB) in the presence of NaBH4. The composites were characterized by a series of spectroscopic instruments and a surface analyzer. The characterization confirmed the presence of Cu2O and Cu in the amorphous carbon network with high porosity. The composites were very active in decolorizing MB, RB, and their mixture. In particular, Cu-CC-550exhibited a great reusability to complete five consecutive MB reduction cycles with a minimal loss of catalytic capability and structural integrity. The prepared Cu-CC composite can be considered as a promising material for catalytic decoloration of dyes as well as a potential alternative to replace noble metal-based catalysts.

Nanoporous polyimide film from poly(ethylene glycol-co-imide) using a one-step heat calcination process

ABSTRACTPolyamic acid (PAA) made from 3,3, 4,4-biphenyltetracarboxylic dianhydride and 4,4-diaminodiphenyl ether was synthesized and used as the backbone of nanoporous polyimide. Thermally labile polyethylene glycol (PEG) at 10, 20 or 30 wt% was introduced to the end group of PAA. Self-assembled PAA-b-PEG micelle-like nanoparticles could be formed as a result of amphiphilic characteristics of hydrophobic PAA and hydrophilic PEG. Thermal imidization and degradation of spin-coated amphiphilic PAA-b-PEG film were performed sequentially through one-step heat treatment to obtain polyimide film with nanopores. Pore sizes decreased with increasing amount of PEG block and their dielectric constants decreased from 2.71 ± 0.13 to 2.38 ± 0.11.

Glass-ceramics one-step crystallization accomplished by building Ca2+ and Mg2+ fast diffusion layer around diopside crystal

CaOMgOSiO2 (CMS) glass-ceramics preparation normally needs two-step heat treatment (nucleation and crystal growth). In this work, CMS glass-ceramics are successfully produced by one-step heat treatment by building Ca2+ and Mg2+ fast diffusion layer between the residual glass and diopside crystal. High-temperature X-ray diffraction (HTXRD) shows that diopside crystals formed during the crystallization of CMS glass. At the glass layer between diopside crystal and residual glass, an enrichment of Na+ is observed by energy dispersive spectroscopy line scanning (EDSLS), which increases the SiONa bonds that promote Ca2+ and Mg2+ ions diffusion. This layer eventually promotes further growth or ripening of the diopside crystals. Thus, nucleation and crystal growth of the CMS glass proceed continuously at the crystallization peak temperature (Tnc), detected by differential scanning calorimetry. Thereby, one-step crystallization of the CMS glass-ceramics becomes possible and practical.

Synthesis of fine ZrB2 powders by new borothermal reduction of coarse ZrO2 powders

Effects of ZrO2 particle size (~50nm and ~2µm) on synthesis of ZrB2 powders via conventional or new borothermal reduction were investigated. The conventional process was a one-step heat treatment at 1600°C in vacuum. The newly developed process consisted of two-step heat treatment (first-step at 1000°C and second-step at 1600°C) plus intermediate step of water washing. Micron-sized ZrB2 powders were prepared by conventional process, independent of initial ZrO2 particle size. Based on new process, submicrometric ZrB2 powders were synthesized using nano-size ZrO2. However, submicrometric ZrB2 could also be synthesized using micron-size ZrO2 by prolonging the holding time during first-step heat treatment. Therefore, results of present study suggested that fine ZrB2 powders could be synthesized by controlling the time of first-step heat treatment of the new borothermal reduction process by converting ZrO2 as completely as possible independent of initial particle size.

Eco-Friendly Fabricated Porous Carbon Nanofibers Decorated with Nanosized SnOx as High-Performance Lithium-Ion Battery Anodes

In this work, one-dimensional polyvinylpyrrolidone-derived porous carbon nanofibers decorated with SnOx nanoparticles (denoted as SnOx@PCNFs) were prepared by an electrospinning technique, followed by a simple one-step heat treatment and a postetching process. The structural evolution of SnOx and the morphological change of the carbon nanofiber webs during the heat treatment are investigated by varying the content of the SnOx precursor in the electrospinning solutions. The highly interconnected pores, created by etching off the in situ generated SiO2 template in the carbon nanofibers, are beneficial for the easy penetration of Li+-carrying electrolyte into the nanocomposites and thus enable the direct contact between embedded SnOx nanoparticles and electrolyte. When tested as anode materials for lithium-ion batteries, SnOx@PCNFs with optimal SnOx component show outstanding initial reversible capacity of 1057 mA h g–1 at 0.2 A g–1, long cycling capability (511 mA h g–1 at 1 A g–1 after 900 cycles), and goo...

One-step synthesis of shell/core structural boron and nitrogen co-doped graphitic carbon/nanodiamond as efficient electrocatalyst for the oxygen reduction reaction in alkaline media

Shell/core structural boron and nitrogen co-doped graphitic carbon/nanodiamond (BN-C/ND) non-noble metal catalyst has been synthesized by a simple one-step heat-treatment of the mixture with nanodiamond, melamine, boric acid and FeCl3. In the process of the surface graphitization of nanodiamond with catalysis by FeCl3, B and N atoms from the decomposition of boric acid and melamine were directly introduced into the graphite lattice to form B, N co-doped graphitic carbon shell, while the core still retained the diamond structure. Electrochemical measurements of the BN-C/ND catalyst show much higher electrocatalytic activities towards oxygen reduction reaction (ORR) in alkaline medium than its analogues doped with B or N alone (B-C/ND or N-C/ND). The high catalytic activity of BN-C/ND is attributed to the synergetic effect caused by co-doping of C/ND with B and N. Meanwhile, the BN-C/ND exhibits an excellent electrochemical stability due to the special shell/core structure. There is almost no alteration occurred in the cyclic voltammetry measurements for BN-C/ND before and after 5000 cycles. All experimental results prove that the BN-C/ND may be exploited as a potentially efficient and inexpensive non-noble metal cathode catalyst for ORR to substitute Pt-based catalysts in fuel cells.

Formation Mechanism of alpha-Fe2O3 Nanotubes via Electrospinning and Their Adsorption Characteristics of BSA and DNA.

The alpha-Fe2O3 nanotubes with diameters of 400-700 nm have been prepared via the sol-gel assisted electrospinning and subsequent one-step heat treatment with ferric nitrate, ethanol and poly(vinyl pyrrolidone) as starting regents. The resultant alpha-Fe2O3 nanotubes were characterized by XRD, SEM, TEM, and VSM techniques. The hollow structure is mainly influenced by the water content in the gel precursor and the heating rate, and the hollow formation mechanism of alpha-Fe2O9 nanotubes is discussed. Adsorption of BSA onto the as-prepared alpha-Fe2O3 nanotubes exhibits a good capacity of 56.5 mg/g with the initial BSA concentration of 1.0 mg/mL, which demonstrates their feasibility in delivery of biomacromolecules. Subsequently, the adsorption characteristics of DNA onto the alpha-Fe2O3 nanotubes were investigated, and the adsorbance of DNA can achieve a maximum value of 4.19 microg/g when the initial DNA concentration is 50 microg/mL. The adsorption process of DNA onto alpha-Fe2O3 nanotubes can be described well by the pseudo-first-order kinetic model at room temperature according to the correlation coefficient R2 = 0.9978.

Astridia velutina-like S, N-codoped hierarchical porous carbon from silk cocoon for superior oxygen reduction reaction

Astridia velutina-like S, N-codoped micro–mesoporous carbon was synthesized by one-step heat treatment of silk cocoon, illustrating an onset potential of 0.853 V (vs. RHE) and current density of 4.5 mA cm−2 at 0 V in alkaline electrolyte.

CeO2 nanocrystallines ensemble-on-nitrogen-doped graphene nanocomposites: one-pot, rapid synthesis and excellent electrocatalytic activity for enzymatic biosensing

Ceria nanomaterials for heterogeneous catalysis have attracted much attention due to their excellent properties and have been extensively applied in recent years. But the poor electron conductivity and the aggregation behavior severely affect their electrocatalytic performances. In this paper, we prepared a novel catalyst based on CeO2 nanocrystallines (CeO2 NCs) ensemble-on-nitrogen-doped graphene (CeO2–NG) nanocomposites through a one-step heat-treatment without the need of the precursor. The results confirmed that the high dispersion of CeO2 NCs with the uniform size distribution of about 5nm on the surface of nitrogen-doped graphene (NG) sheets could be easily obtained via the one-step procedure and the resultant CeO2–NG nanocomposites were an excellent electrode material possessing outstanding electrochemical features for electron transfer. Luminol, an important electroactive substance, was further chosen to inspect the electrocatalytic properties of the as-prepared CeO2–NG nanocomposites. The studies showed that the presence of the NG in CeO2–NG nanocomposites could facilitate the electrochemical redox process of luminol. Compared with pristine CeO2 NCs, the synthesized CeO2–NG nanocomposites can enhance the electrochemiluminescence (ECL) intensity by 3.3-fold and decrease the onset ECL potential for about 72mV in the neutral condition. Employing above superiority, selecting cholesterol oxidase (ChOx) as the model oxidase, a facile ECL method for cholesterol detection with the CeO2–NG nanocomposites as the matrix to immobilize enzyme ChOx was developed. The results demonstrated CeO2–NG nanocomposites exhibited excellent performances in terms of sensitivity and catalytic activities, indicating that NG-based nanomaterials have great promise in electrocatalytic and enzymatic biosensing fields.

Self-organized formation of spherical porous granules only by one-step heat-treatment in MgO–Fe2O3–Nb2O5 system

In this letter, a new process to obtain spherical porous granules (SPGs) is presented, namely self-organized formation only by a one-step heat-treatment. Commercial MgCO3 (basic), α-Fe2O3 and Nb2O5 powders of Mg:Fe:Nb=1:1:1 in mole fraction were wet-ball milled, and were heat-treated in air at 800–1350°C. The samples heated at ≥1100°C, most of the samples became SPGs with the diameter of ∼50–100μm, containing 3-D network structure. The main constituent phase of porous spheres was pseudobrookite-type MgFeNbO5. The formation mechanism of porous microspheres was discussed by using SEM observation and high-temperature XRD analysis.

Kilogram-scale synthesis of Pd-loaded quintuple-shelled Co3O4 microreactors and their application to ultrasensitive and ultraselective detection of methylbenzenes.

We report the kilogram-scale, simple, and cost-effective synthesis of Pd-loaded quintuple-shelled Co3O4 microreactors by spray drying of aqueous droplets containing cobalt nitrate, palladium nitrate, citric acid, and ethylene glycol and subsequent heat treatment. Highly viscous gel spheres containing Co and Pd salts were successfully converted into multi thin-shelled Co3O4 reactors uniformly loaded with Pd catalysts by the sequential combustion of carbon and decomposition of the metal salts from the outer to the inner regions during one-step heat treatment. The responses (resistance ratio) of the Pd-loaded quintuple-shelled Co3O4 microreactors to 5 ppm toluene and p-xylene were 30.8 and 64.2, respectively, and the selectivity values to toluene and p-xylene against ethanol interference (response ratio) were 14.5 and 30.1, respectively. The unprecedented high response and selectivity were attributed to the effective dissociation of less reactive methylbenzenes into more active smaller species assisted both by catalytic Co3O4 and Pd during the prolonged retention within the microreactors. Kilogram-scale preparation of noble metal-loaded multishelled microreactors and their unique gas-sensing characteristics based on a novel microreactor concept can pave a new way to design of high-performance gas sensors for practical applications.

Nanocrystalline Bi2O3–B2O3– (MoO3 or V2O5) glass-ceramic systems for organic pollutants degradation

Fixation of photocatalyst in glass matrix would solve the problem of photocatalyst recovery. In this study, the system 30 Bi2O3, 20 B2O3 and 50 (MoO3 or V2O5), was used for the preparation and stabilization of the photoactive phases of both bismuth molybdate β-Bi2Mo2O9 and monoclinic–scheelite BiVO4 in a glassy matrix. Proper heat-treatment schedule, based on differential thermal analysis (DTA) results, has been applied to improve the crystallinity of the prepared glass–ceramics. The applied heat-treatment program showed a significant effect on the size of the formed crystals, especially in samples with molybdenum content. For instance, one-step heat-treatment (500°C/2h) improves the crystallinity of the material than two-step heat-treatment (355°C/1h+400°C/2h). It was also noticed that the amount of glassy matrix relative to crystalline part in case of vanadium-contained samples is much more than that in the corresponding molybdenum-contained samples. The prepared samples were used for the degradation of Red SPD Cotton dye in order to assess their photocatalytic activity. All molybdenum contained samples showed a promising photocatalytic activity. On contrary, vanadium-contained samples were inactive suggesting that most of photoactive crystals are in the bulk of materials.

Low-cost electrospun WC/C composite nanofiber as a powerful platinum-free counter electrode for dye sensitized solar cell

Tungsten carbide/carbon (WC/C) composite nanofibers were successfully prepared through electrospinning followed by a one-step heat treatment using in-situ carburization. The WC/C nanofibers were applied to low-cost and platinum-free counter electrodes for dye sensitized solar cells (DSSCs), and their catalytic activities were investigated and compared to platinum (Pt) CEs for triiodide/iodide (I3−/I−) as well as organic disulfide/thiolate (T2/T−) electrolytes. When WC/C nanofibers are used as the CE catalyst in iodine electrolytes, the DSSCs exhibited a power conversion efficiency (PCE) of 7.77%, corresponding to 96% of that of Pt CEs. In the case of T2/T− redox couples, the DSSCs based on WC/C nanofibers achieved PCE of 5.85%, which is almost twice that of Pt (3.07%). The high catalytic activities of WC/C nanofibers are attributed to synergetic effects from the combination of catalytically active WC and one-dimensional (1D) conductive carbon acting as an efficient charge transport pathway. In addition, spray-coated WC/C nanofiber CE films have a three-dimensional porous network, enhancing the permeation of the electrolyte into the CE film and the diffusion of redox couples. The electrospinning process used for the synthesis of the WC/C nanofibers is facile and scalable and is therefore promising for the commercialization of DSSCs.

Electrochemical Characterization of Li2s-P2S5 Glass-Ceramic Solid Electrolyte/Li Metal Electrode Interface

Introduction All solid-state Li rechargeable batteries are considered as promising candidates for post Li-ion batteries because non-flammability of inorganic solid electrolyte enhances their safety and reliability and Li metal can be used for a negative electrode. Sulfide-based solid electrolytes like Li2S-P2S5 showed high lithium ion conductivity of about 10-4 S cm-1 at 25 °C. In general, glass crystallization results in lower conductivities. However, 70Li2S-30P2S5 glass-ceramic obtained by crystallization of the glass showed conductivity of about 10-3 S cm-1 at room temperature because enhancement of the conductivity of the glass-ceramic came from the precipitation of superionic Li7P3S11 crystal in the glass-ceramic.1 Previously, we investigated the charge transfer reaction at the sulfide-based solid electrolyte/Li metal electrode interface and organic liquid electrolyte/Li interface by electrochemical methods with microelectrodes to evaluate activation energy (Ea ) of each process in charging. For the liquid electrolyte, the Ea for charge transfer reaction was much higher than that for ionic conduction. This suggests that the desolvation step of solvated Li+ has a large barrier. On the other hand, for the sulfide-based glass electrolyte, the Ea for charge transfer was comparable to that for ionic conduction due to the lacking of the desolvation step.2 In this study, the Ea for charge transfer reaction at the 70Li2S-30P2S5 glass-ceramic/Li metal electrode interface was evaluated, and it was compared with the Ea for the charge transfer at the Li2S-P2S5glass/Li metal electrode interface. Experimental 70Li2S-30P2S5 glass was prepared by mechanical milling of Li2S and P2S5 mixed powders for 12h. 70Li2S-30P2S5 glass-ceramics were prepared using one-step heat treatment 280 °C for 2h. 1 For electrochemical measurements, a two-electrode cell was fabricated. The glass-ceramic electrolyte powder was pelletized and sandwiched with Ni microelectrode (Φ50 μm) as working electrode and Li disk (Φ8 mm) attached on the stainless steel current collector as counter and reference electrode. All procedure was executed in Ar-filled glove box. Li was deposited on the working electrode at -150 mV (vs. Li/Li+) and the potential was stepped to -10, +10, -20, +20 mV (vs. OCV) until it reached ±150 mV. Each potential was held for 2 s. All measurements were performed at various temperatures. Results and Discussion To evaluate i0 , the steady-state current (i) measured at each overpotential (η) by potential step method was inserted into Allen-Hickling equation.Fig. 1 shows Allen-Hickling plots by the potential step method at various temperatures. All plots exhibited a linear relationship in the η range from -80 to +80 mV. From the intercept of each plot, i0 was evaluated and then i0 was plotted against the reciprocal of absolute temperature to calculate Ea using Arrhenius equation.Fig. 2 shows the Arrhenius plot of i0 obtained from potential step method. We successfully measured the Ea of charge transfer reaction at the interface between glass ceramic electrolyte and Li metal electrode. The Ea for the charge transfer was larger than that for ionic conduction, suggesting that the mechanism of charge transfer reaction at glass-ceramic/Li metal electrode interface is different from that for glass/Li metal electrode interface. Reference 1) K. Minami, A. Hayashi, M. Tatsumisago, J. Am. Ceram. Soc., 94, 1779 (2011).2) M. Chiku, W. Tsujiwaki, E. Higuchi, H. Inoue Electrochemistry, 80, 740 (2012).

Creep-Fatigue Interaction in Eurofer 3 Electron Beam Welds

In future nuclear fusion reactors, structural materials will undergo a large thermal cycling due to pulsed operation and the occurrence of several maintenance periods. Therefore, the investigation of the combined role of creep and fatigue loading is of major importance. In this study, we focused on Eurofer 3 electron beam welds. Two different post-welding heat treatments were carried out: a two-step heat treatment (30 minutes at 980°C followed by 2 hours at 750°C) and a one-step heat treatment (2 hours at 750°C). Fatigue, creep and creep-fatigue tests were performed. A 550°C test temperature was chosen, corresponding to the upper operation temperature currently foreseen for this material. Creep-fatigue experiments were achieved by interrupting a fatigue test and then applying a creep loading until the fracture of the specimen. Several fatigue pre-stress conditions were studied. The post-weld heat treatment influence was analyzed. The damage contributions of fatigue and creep were studied using electron microscopy. The results were compared to previous results obtained on base material.

High-performance supercapacitor electrodes based on porous flexible carbon nanofiber paper treated by surface chemical etching

Abstract Carbon nanofiber paper with high surface area was prepared by surface chemical etching of electrospun phenolic-based nanofiber paper with KOH. KOH was coated on the surface of nanofibers and chemical etching was performed by one-step heat treatment. The specific surface area, pore volume and surface oxygen-containing functionality of the resultant carbon paper are increased significantly with the increase of the KOH uptake on the phenolic-based nanofiber paper. The obtained porous carbon paper have a maximal surface area of 1317 m 2 g −1 , pore volume of 0.699 cm 3 g −1 and surface oxygen species of 15.1 at.%. The carbon paper was used as binder-free electrode for supercapacitor and the electrochemical performance was investigated in aqueous electrolyte (6 M KOH solution) and organic electrolyte (1 M (C 2 H 5 ) 4 NBF 4 /PC). Supercapacitor based on this flexible carbon paper high specific capacitance (362 F g −1 ), ultra-high rate handling capacity (209 F g −1 at 20 A g −1 ) and high energy density (7.1 W h kg −1 in aqueous electrolyte, 27.9 W h kg −1 in organic electrolyte), which is due to efficient charge accommodation in micropores, considerable pseudocapacitance provided by surface active species and fast ion response derived from short pore channel. These features make the porous carbon nanofiber paper a quite promising alternative for the next generation of high-performance supercapacitors.

Biotemplated Fabrication of Sn@C Anode Materials Based on the Unique Metal Biosorption Behavior of Microalgae

Biotemplating is an effective strategy to obtain morphology-controllable materials with structural specificity, complexity, and corresponding unique functions. Different from traditional biotemplating strategies replicating the morphology and using biogenic elements of biomaterials (e.g., C, Si, N, Fe, P, S), we take advantage of the unique heavy-metal-ion biosorption behavior of microalgae to fabricate tin-decorated carbon (Sn@C) anode materials for lithium-ion batteries. Microalgae Spirulina platensis is used as the biotemplate, the renewable carbon source, and the biosorbent. After a facile one-step heat treatment, Sn@C with tin particles (20-30 nm) dispersing into the porous carbon matrix can be obtained. Fourier transform infrared spectra reveal that metal-ion biosorption results from the complexation reactions between Sn(4+) ions and the hydroxyl groups associated with alginate. The Sn@C anode shows a discharge capacity of 520 mAh g(-1) after 100 cycles, as well as excellent cycle stability and high coulombic efficiency (approximately 100%), exhibiting fascinating electrochemical performance. This facile, green, and economical strategy not only will extend the scope of biotemplating synthesis of functional materials but also will provide reference for environmental protection and water purification.