One-pot synthesis of the highly efficient bifunctional Ni-SAPO-11 catalyst

Hydroisomerization of linear alkanes to branched isomers is an important petrochemical process for production of gasoline with high octane number.Non-noble metal bifunctional catalysts used in this process always suffer from low metal dispersion and poor metal-acid synergy.Herein,a facile one-pot synthesis method was used to simultaneously regulate metal particle sizes and acidity of the Ni-SAPO-11 hydroisomerization catalyst.The physicochemical properties are investigated using XANES,EXAFS,TEM/STEM,FT-1R,XPS,UV-vis and NH3-TPD.Apart from the highly dispersed nickel nanoparticles with an average diameter of 8 nm,the framework Ni2+ions are generated via substituting framework Al3+ions of the SAPO-11.The formed NiP-OH structures have lower deprotonation energy(DPE)than the SiAl-OH ones,contributing more and stronger acid sites to the Ni-SAPO-11 catalyst.The great metal-acid synergy including high metal to acid sites ratio(nNi/nA)and close intimacy is obtained for the Ni-SAPO-11 catalyst.The Ni-SAPO-11 catalyst outperforms the counterpart prepared by the impregnation method and exhibits comparable activity and isomers selectivity to the Pt/SAPO-11 catalyst in the n-hexane hydroisomerization.     

Effect of post heat-treatment on the microstructure and high-temperature oxidation behavior of precipitation hardened IN738LC superalloy fabricated by selective laser melting

The present study investigated the effect of as-built and post heat-treated microstructures of IN738LC alloy fabricated via selective laser melting process on high temperature oxidation behavior.The as-built microstructure showed fine cell and columnar structure due to high cooling rate.Ti element segrega-tion was observed in inter-cell/inter-columnar area.After post heat-treatment,the initially-observed cell structure disappeared,instead bimodal Ni3(Al,Ti)particles formed.High temperature(1273 K and 1373 K)oxidation test results showed parabolic oxidation curves regardless of temperature and initial microstructure.The as-built IN738LC fabricated via the selective laser melting process displayed oxida-tion resistance similar to or slightly better than that of IN738LC fabricated via wrought or cast process.Heat-treated SLM IN738LC,although had similar oxidation weight-gain values to those of the SLM as-built material at 1273 K,showed relatively better oxidation resistance at 1373 K.Bimodal Ni3(Al,Ti)precipitate formed in the post heat treatment changed the local chemical composition,thereby led to changes in alumina former/chromia former location and fraction on the alloy surface.It was concluded that in heat-treated IN738LC increased alumina former fraction was found,and this resulted in excellent oxidation resistance and relatively low weight-gain.     

Amelioration of weld-crack resistance of the M951 superalloy by engineering grain boundaries

Fusion weld is a portable and economical joining and repairing method of metals.However,weld cracks often occur during the fusion weld of Ni-base superalloys,which hinder the applications of fusion weld on this kind of materials.In this work,the effects of microstructures of grain boundaries(GBs)of the prototype M951 superalloy on its weldability were investigated.The precipitated phases,the elemental segregations on GBs,and the morphologies of GBs can be largely altered by regulating the cooling rates of pre-weld heat treatments.With decreasing the cooling rate,chain-like M23X6 phase precipitates along the GBs,accompanying segregations of B,and GBs becomes more serrated in morphology.During fusion weld,the engineered GBs in the M951 superalloy with a low cooling rate favor the formation of the continuous liquid films on GBs,which together with the serrated GB morphology significantly prevents the formation of weld cracks.Our findings imply that the weld-crack resistance of the superalloys can be ameliorated by engineering GBs.     

Plasma spraying of zirconia-reinforced hydroxyapatite composite coatings on titanium: Part II Dissolution behaviour in simulated body fluid and bonding degradation

The change of phase, morphology and bond strength of plasma sprayed hydroxyapatite (HA) coating and ZrO2/HA composite coatings immersed in simulated body fluid (SBF) for various periods of time was studied. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were used to identify the phase and observe the morphology of the coating surface before and after immersion. In addition, inductively coupled plasma emission spectroscopy (ICP) was used to measure the ion release rate of coatings in SBF for various periods of time. Observation of the morphology by SEM shows that the composite coating with the addition of ZrO2 in HA significantly reduced the dissolution rate of impurity phases in simulated body fluid. The argument was supported by measurement of Ca2+ ion concentration in SBF. During plasma spraying, less OH- ions were lost in a ZrO2-containing composite coating. This factor, together with the reduced effective surface of the ZrO2-containing HA coating, were attributed to the reduced dissolution rate of the composite coatings. All the plasma sprayed coatings degraded after immersion in SBF owing to dissolution of constituents in the coating, however, the addition of ZrO2 in HA improved the bonding strength of HA coating after immersion in SBF.     

Improvement of the uniformity and dipole ferromagnetism in Co nanodots assemblies on Pb/Si(111) via step tuned dimensionality variation

We fabricated quasi-one-dimensional Co nanochain assemblies and two-dimensional Co nanodot assemblies on Pb/Si(111) substrates by step decoration. The morphology and magnetic properties of these two kinds of Co nanodot assemblies were investigated by in situ scanning tunneling microscopy and magneto-optical Kerr effect measurements. It was found that the steps cannot only improve the uniformity of the Co nanodots, but also increase the critical temperature T(c). Monte Carlo simulation indicates that the ferromagnetism mainly originates from the dipolar interactions and the critical temperature T(c) can be enhanced by introducing an in-plane uniaxial magnetic anisotropy via the step tuned dimensionality variation of the nanodot assemblies.     

Synthesis of calcium zincate powders by a chemical Co-precipitation method and their electrochemical performances

Calcium zincate powders used as active materials for a secondary Zn electrode were prepared by a chemical precipitation (CP) method. The characteristic properties of calcium zincate powders were examined by thermal gravimetric analysis (TGA), X-ray diffraction (XRD) analysis, Brunauer-Emmett-Teller (BET) measurement, Transmission electron microscope (TEM) and micro-Raman spectroscopy. For comparison, the secondary Zn electrodes using CP-calcium zincate powders, so-called the CP-ZnCa, were obtained and examined. The electrochemical performances of the secondary Zn electrodes were investigated by galvanostatic charge/discharge measurements. As a result, the best performance of the CP-ZnCa powders were synthesized at pH 12 with a mole ratio of Zn:Ca = 2.5:1. The experimental results indicated that the secondary Zn electrode based on the CP-ZnCa powders exhibited better charge/discharge reversibility and longer cycle-life performance.     

Nanoparticle syntheses using non-porous and porous polyelectrolyte multilayers for biological applications

Polyelectrolyte multilayers comprised of poly(allylamine hydrochloride) and poly(acrylic acid) were assembled by layer-by-layer technique for metal nanoparticle syntheses. Using weak polyelectrolytes in LbL process, it is readily available to tune the deposited film properties by simple changing of the dipping solution pH. The PAH/PAA multilayer systems exhibit different surface morphologies and functionalities depending on the assembly conditions. We have studied two distinctive PAH/PAA multilayer films to utilize them for nanoparticle synthesis. The reactive functional groups of the polyelectrolytes within the films were remained after the film deposition or reactivated by a simple pH stimulus, and therefore they were allowed to undergo further chemical reactions to synthesize Pd and Au nanoparticles. Synthesized metal nanoparticles were easily characterized by their optical properties including surface plasmon absorption. These metal nanoparticle-embedded multilayers may have great potentials for biomolecule sensing or catalytically active coatings.     

Effect of MWCNTs Additive on Desorption Properties of Zn（BH4）2 Composite Prepared by Mechanical Alloying

In this study,the effect of multi-walled carbon nanotubes（MWCNTs） additive on the dehydriding properties of the Zn（BH₄）₂/NaCI composite prepared by high energy ball milling were investigated.X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FTIR） results demonstrated that Zn（BH₄）₂ was produced from mechanochemical reaction between ZnCI₂ and NaBH₄.Compared with the undoped sample,10 wt% MWCNTs effectively lowered the decomposition temperature of Zn（BH₄）₂ by 15℃.The complex released 3.6 wt%hydrogen within 250 s at 100℃and totally released 4.5 wt%hydrogen within 2500 s,indicating it has a considerable potential as a hydrogen storage material.     

Periodic mesoporous organosilica as a multifunctional nanodevice for large-scale characterization of membrane proteins

A versatile protocol has been developed for large-scale characterization of hydrophobic membrane proteins based on the periodic mesoporous organosilica (PMO) acting as both an extractor for hydrophobic substrate capture and a nanoreactor for efficient in situ digestion. With introduction of organic groups in the pore frameworks and the presence of hydrophilic silanol groups on the surface, PMO can be well-dispersed into not only an organic solution to concentrate the dissolved membrane proteins but also an aqueous solution containing enzymes for sequential rapid proteolysis in the nanopores. The unique amphiphilic property of PMO ensures a facile switch in different solutions to realize the processes of substrate dissolution, enrichment, and digestion effectively. Furthermore, this novel PMO-assisted protocol has been successfully applied for identification of complex membrane proteins extracted from mouse liver as proof of general applicability.     

The precursor compound of two types of ZnSe magic-sized clusters

Precursor compounds(PCs)link quantum dots(QDs)and magic-sized clusters(MSCs),which is pivotal in the conversion between QDs and MSCs.Here,for the first time,we report the transformation,synthesis,and composition of a type of ZnSe PCs.ZnSe PCs can be directly transformed to two different MSCs with the assistance of octylamine and acetic acid at room temperature.The two types of MSCs exhibit sharp absorption peaks at 299 and 328 nm which are denoted as MSC-299 and MSC-328.In the preparation of ZnSe PCs,diphenylphosphine(DPP)as an additive plays a key role which not only inhibits the thermal decomposition of Zn precursor,but also acts as a reducing agent to reduce the by-products produced in the reaction.The composition was explored by X-ray photoelectron spectroscopy,energy dispersive spectrometer,matrix-assisted laser desorption/ionization time-of-flight mass spectra with ZnSe PC powder appeared as white powder after purifying by toluene(Tol)and methanol(MeOH).The results indicate that the molar ratio of Zn/Se is 2:1 with a molecular of?3,350 Da.Therefore,we propose that the molecular formula of ZnSe PCs is Zn₃₂Se₁₆.In addition,at the molecular level,the covalent bond of Zn-Se is formed in ZnSe PCs.This study offers a deeper understanding of the transformation from PCs to MSCs and for the first time proposes the composition of PCs.Meanwhile,this research provides us with a new understanding of the role of DPP in the synthesis of colloidal semiconductor nanoparticles.