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Additively manufactured TiAl alloys present alternating dendritic grain (DG) and fully lamellar colony (FLC) microstructure, which is detrimental to mechanical properties. This work proposes a novel strategy for eliminating alternating DG and FLC and in-situ obtaining fine FLC by performing arc rescanning (AR) on each deposition layer to increase its thermal cycling number during additive manufacturing. The AR can not only eliminate its mechanical anisotropy, but enhance its mechanical properties by tailoring fine FLC microstructure. [ABSTRACT FROM AUTHOR]

In the process of directed energy deposition-arc (DED-arc), the geometrical shape of weld bead in arc-striking (AS) and arc-extinguishing (AE) areas are usually inconsistent with that in the middle section, which directly affects the forming accuracy of component thus needs to be optimized. In this paper, high-speed photography is used to observe the molten pool behavior of nickel aluminum bronze (NAB) bead deposition, and the causes of abnormal bead shape in the AS and AE areas are analyzed. On that basis, an optimization method for AS and AE is put forward. In the AS area, the welding current and travel speed are increased. And after the arc strikes, a hovering time is used during which the torch hovers at the AS point. In the AE area, the welding current is gradually reduced while the torch keeps hovering at the AE point. Then, the optimization effect of AS parameters on the bead shape are explained through factorial experiments, and the optimization effects of AE parameters are explained through orthogonal experiments. At the same time, the optimal parameter combination of AS and AE is obtained. With the proposed method and the optimal parameters, the height and width deviation of the deposited single bead are controlled within 5%. After adopting the optimization method, the effective height ratio of the DED-arc–manufactured NAB thin wall is increased from 67.5% to 91.5% under the unidirectional deposition path, which is also increased from 88.9% to 98.3% under the bidirectional deposition path. [ABSTRACT FROM AUTHOR]

To investigate the performance of graphene (Gra) modified with ethoxycarbonyl ionic liquid (IL), chain mobility and crystallization kinetics of poly(L-lactic acid) (PLLA), a series of PLLA nanocomposites have been prepared using solution-cast method. IL can improve the dispersion of Gra in PLLA matrix and the samples containing IL have higher growth rate of PLLA spherulite than neat PLLA does. PLLA/IL/Gra and PLLA/2Gra exhibit the same relaxation strength and time of αN relaxation that corresponds to the longest normal mode motion at 110−140 °C. PLLA/IL/Gra shows a faster crystallization rate than PLLA/2Gra does, which might be attributed to the Gra-imidazolium cation interaction in IL modified Gra, the significant dispersion effect of IL at Gra surface, and the increase of nuclei density of PLLA/IL/Gra. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF) based nanocomposites with γ-oxo-pyrenebutyric acid-noncovalent modified multiwalled carbon nanotubes (denoted as PACNTs) and stearic acid-covalent modified MWCNTs (SACNTs) as nanofillers, were fabricated using solution-blending method and their dielectric properties were carefully investigated. γ-Oxo-pyrenebutyric acid (PA) or stearic acid (SA) can improve the dispersion of MWCNTs in PVDF matrix because of strong physical π-π interaction and the surface of MWCNTs grafted with SA respectively. The values of percolation threshold for PVDF/PACNTs and PVDF/SACNTs were determined to be 5.7 and 6.3 vol%, respectively. Higher dielectric permittivity and lower loss tangent of PVDF/PACNTs originates from remarkable interfacial polarization because PA have more contact area with MWCNTs and can reduce leakage current compared with SA. [ABSTRACT FROM AUTHOR]

The effect of basic and rare earth metal oxides on the stability of nickel-based catalysts for the CO reforming of CH has been studied. The addition of metal oxides increased the stability of Ni-based catalysts and reversed the values of the reaction orders with respect to both CH and CO. In the presence of metal oxides, the values of the reaction orders with respect to CO partial pressure followed the same trend of catalyst stability. [ABSTRACT FROM AUTHOR]

A Cu/CrO catalyst was prepared by co-precipitation method, studied in methanol dehydrocoupling to methyl formate in different gas streams and characterized by BET, XRD, TPR, TPD of NH and CO, etc. The results demonstrate that the catalyst can catalyze the dehydrocoupling of methanol to methyl formate in high efficiency, e. g. 99% selectivity to methyl formate at 48% conversion of methanol. The results further indicate that metallic copper might be the active species for the formation of methyl formate [ABSTRACT FROM AUTHOR]

The precision of the yield measurement of the Higgs boson decaying into a pair of Z bosons process at the Circular Electron Positron Collider is evaluated. Including the recoil Z boson associated with the Higgs production (Higgsstrahlung) a total of three Z bosons are involved for this channel, from which final states characterized by the presence of a pair of leptons, quarks, and neutrinos are chosen for the signal. Two analysis approaches are compared and the final statistical precision of σ ZH · BR( H → Z Z ∗ ) is estimated to be 6.9% using a multivariate analysis technique, based on boosted decision trees. The relative precision of the Higgs boson width, using this H → Z Z ∗ decay topology, is estimated by combining the obtained result with the precision of the inclusive ZH cross section measurement. [ABSTRACT FROM AUTHOR]

D,L-lactide was prepared from D,L-lactic acid by means of polymerization and depolymerization at low vacuum level. Morpholine-2,5-dione (MD) was synthesized from the cyclization of chloroacetyl glycine which was made from chloroacetyl chloride and glycine in the basic condition. A novel copolymer (PLAMD) with D,L-lactide ( D,L-LA) and morpholine-2,5-dione (MD) was synthesized using stannous octoate as initiator, and characterized with FT-IR and HNMR. The biocompatibility of PLAMD and PLA was investigated by MTT and microscope. The results show that amino acid is introduced into PDLLA main chain. PLAMD has better cell affinity than PLA, so it is a promising biomaterial. [ABSTRACT FROM AUTHOR]