In this paper, we presented a hybrid composite of graphene quantum dots (GQDs)-modified three-dimensional graphene nanoribbons (3D GNRs) composite linked by Fe3O4 and CoO nanoparticles through reflux and ultrasonic treatment with GQDs, denoted as 3D GQDs-Fe3O4/CoO@GNRs (3D GFCG). In this hybrid, the 3D GNRs framework strengthened the electrical conductivity and the synergistic effects between GQDs and 3D GFCG enhanced the oxygen reduction reaction (ORR) activity of the nanocomposite. The results imply that decorating GQDs with other electro-catalysts is an effective strategy to synergistically improve their ORR activity.

A Cu-15Ag-5P filler metal (BCuP-5) is fabricated on a Ag substrate using a high-velocity oxygen fuel (HVOF) thermal spray process, followed by post-heat treatment (300oC for 1 h and 400oC for 1 h) of the HVOF coating layers to control its microstructure and mechanical properties. Additionally, the microstructure and mechanical properties are evaluated according to the post-heat treatment conditions. The porosity of the heat-treated coating layers are significantly reduced to less than half those of the as-sprayed coating layer, and the pore shape changes to a spherical shape. The constituent phases of the coating layers are Cu, Ag, and Cu-Ag-Cu3P eutectic, which is identical to the initial powder feedstock. A more uniform microstructure is obtained as the heat-treatment temperature increases. The hardness of the coating layer is 154.6 Hv (as-sprayed), 161.2 Hv (300oC for 1 h), and 167.0 Hv (400oC for 1 h), which increases with increasing heat-treatment temperature, and is 2.35 times higher than that of the conventional cast alloy. As a result of the pull-out test, loss or separation of the coating layer rarely occurs in the heat-treated coating layer.

In this study, a new manufacturing process for a multilayer-clad electrical contact material is suggested. A thin and dense BCuP-5 (Cu-15Ag-5P filler metal) coating layer is fabricated on a Ag plate using a high-velocity oxygen-fuel (HVOF) process. Subsequently, the microstructure and bonding properties of the HVOF BCuP-5 coating layer are evaluated. The thickness of the HVOF BCuP-5 coating layer is determined as 34.8 μm, and the surface fluctuation is measured as approximately 3.2 μm. The microstructure of the coating layer is composed of Cu, Ag, and Cu-Ag-Cu3P ternary eutectic phases, similar to the initial BCuP-5 powder feedstock. The average hardness of the coating layer is 154.6 HV, which is confirmed to be higher than that of the conventional BCuP-5 alloy. The pull-off strength of the Ag/BCup-5 layer is determined as 21.6 MPa. Thus, the possibility of manufacturing a multilayer-clad electrical contact material using the HVOF process is also discussed.

Metal–organic frameworks (MOFs) are widely used as supports for single-atom catalysts (SACs) owing to their high specific surface area, porosity, and ordered metal–ligand structure. Their activity can be increased by increasing the number of electrochemically accessible active sites via the formation of atomically dispersed metal catalysts (M–Nx) that coordinate with nitrogen atoms on the MOF. Herein, we introduce the relationship between the size of the MOF as a starting material and the catalytic activity for the oxygen reduction reaction in alkaline media. The morphology and features of the MOFs are critically dependent on their size. Remarkably, cage-like MOFs below 33 nm are converted into collapsed structures and are connected between each MOF, even carbon fiber- or tube-like features, after carbonization. SACs derived from medium-sized MOFs exhibit excellent activity and are comparable to commercial Pt/C catalysts owing to their porous structure. Therefore, we believed that controlling the size of MOFs containing active atoms is an effective method of modulating the morphological properties of the support and even the number of active sites that are closely related to the activity.

Nitrogen (N)-doped ordered mesoporous carbons (OMCs) with a dual transition metal system were synthesized as non-Pt catalysts for the ORR. The highly nitrogen doped OMCs were prepared by the precursor of ionic liquid (3-methyl-1-butylpyridine dicyanamide) for N/C species and a mesoporous silica template for the physical structure. Mostly, N-doped carbons are promoted by a single transition metal to improve catalytic activity for ORR in PEMFCs. In this study, our N-doped mesoporous carbons were promoted by the dual transition metals of iron and cobalt (Fe, Co), which were incorporated into the N-doped carbons lattice by subsequently heat treatments. All the prepared carbons were characterized by via transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). To evaluate the activities of synthesized doped carbons, linear sweep was recorded in an acidic solution to compare the ORR catalytic activities values for the use in the PEMFC system. The dual transition metal promotion improved the ORR activity compared with the single transition metal promotion, due to the increase in the quaternary nitrogen species from the structural change by the dual metals. The effect of different ratio of the dual metals into the N doped carbon were examined to evaluate the activities of the oxygen reduction reaction.

Mechanical properties of metal injection molded titanium and titanium alloy parts were investigated in this study. Material powders with low oxygen content and spherical shape were obtained by electrode induction-melting gas atomization which could melt and atomize titanium and titanium alloy bars with no touch on crucible or tundish. Tensile specimens were fabricated from obtained powders by metal injection molding process. Tensile strength of the specimens increases with increasing oxygen content. This result corresponds to a tendency of wrought metal.

Novel N2O2 tetradentate ligands, H-3BPD and H-2BPD were synthesized. Hydrochloric acid salts of Br-3BPD, Cl-3BPD, Br-2BPD and Cl-2BPD having Br and Cl substituents at the para position of the phenol hydroxyl group, were synthesized. The ligands were characterized by C. H. N atomic analysis, 1H NMR, 13C NMR, UV-visible, and mass spectra. The proton dissociation constants (logKn H) of the phenol hydroxyl group and secondary amine of the synthesized N2O2 ligands were shown by four step wise values. The orders of the calculated overall proton dissociation constants (logβp) were Br-3BPD < Cl-3BPD < H-3BPD in case of 3BPD and Br-2BPD < Cl-2BPD < H-2BPD in case of 2BPD respectively. The order agreed well with that of para Hammett substituent constants(δp). The stability constants(logKML) of the complexes between the synthesized ligands and transition metal(II) ions agreed with the order of logβp of the ligands. The order of the logKML value of the each transition metal (II) ion was Co(Ⅱ) < Ni(Ⅱ) < Cu(Ⅱ) > Zn(Ⅱ) > Cd(Ⅱ) > Pb(Ⅱ), which agreed well with that of Iriving-Williams series.

new N3-O2 pentadentate ligand, H-BHPT, was synthesized. Hydrochloric acid salts of Br-BHPT, Cl-BHPT, CH3O-BHPT and CH3-BHPT, having Br-, Cl-, CH3- and CH3O- substituents at the para position of the phenol hydroxyl group of H-BHPT were synthesized. Hydrochloric acid salts of 3OH-BHPT and 4OH-BHPT, having different position of the phenol hydroxyl group of H-BHPT were also synthesized. The synthesis of each ligand was confirmed by C. H. N. atomic analysis and 1H NMR, 13C NMR, UV-visible, and mass spectra. The calculated proton dissociation constants (logKn H) of the phenol hydroxyl group and secondary amine group of the synthesized N3-O2 ligands showed five steps of the proton dissociations. The order of the overall proton dissociation constants (logβp) of the ligands was Br-BHPT < Cl-BHPT < H-BHPT < CH3O-BHPT < CH3-BHPT. The order agreed with that of Hammett substituent constants (δp). However, dissociation steps of 3OH-BHPT were four and that of 4OH-BHPT was three. The calculated stability constants (logKML) between the ligands and transition metal ions agreed with the order of logβp values of the ligands. The order of the stability constants between the transition metal ions with the synthesized ligands was Co(Ⅱ) < Ni(Ⅱ) < Cu(Ⅱ) > Zn(Ⅱ) > Cd(Ⅱ) > Pb(Ⅱ). The order agreed well with that of the Iriving-Williams.

A new N3O2 pentadentate ligand, N,N'-Bis(2-hydroxybenzyl)-ethylenetriamine(H-BHET․3HCl) was synthesized. The hydrochloric acid salts of Br-BHET․3HCl, Cl-BHET․3HCl, CH3O-BHET․3HCl and CH3-BHET․3HCl containing Br-, Cl-, H-, CH3O- and CH3- groups at the para-site of the phenol group of the H-BHEP were synthesized. The structures of the ligands were confirmed by C. H. N. atomic analysis and 1H NMR, 13C NMR, UV-visible and mass spectra. The calculated stepwise protonation constants(logKnH) of the synthesized N3O2 ligands showed six steps of the proton dissociation. The orders of the overall protonation constants(logβp) of the ligands were Br-BHET < Cl-BHET < H-BHET < CH3O-BHET < CH3-BHET. The orders agreed well with that of para Hammett substituent constants(δp). The calculated stability constants(logKML) between the ligands and heavy metal ions (Co(Ⅱ) , Ni(Ⅱ), Cu(Ⅱ), Zn(Ⅱ), Cd(Ⅱ) and Pb(Ⅱ)) agreed well with the order of the overall proton dissociation constants of the ligands but they showed a reverse order in para Hammestt substituent constants(δp). The order of the stability constants between the heavy metal ions with the synthesized ligands were Co(Ⅱ) < Ni(Ⅱ) < Cu(Ⅱ) > Zn(Ⅱ) > Cd(Ⅱ) > Pb(Ⅱ).

Hydrochloric acid salt of a new N2O3 pentadentate ligand, N,N'-Bis(2-Hydroxybenzyl)-1,3-diamino-2-propanol(H-BHDP․2HCl) was synthesized. Br-BHDP․2HCl, Cl-BHDP․2HCl, CH3-BHDP․2HCl and CH3O- BHDP․2HCl having Br, Cl, CH3 and CH3O substituents at 5-position of the phenol group of H-BHDP․2HCl were also synthesized. The potentiometry study in aqueous solution revealed that the proton dissociations of the synthesized ligands occurred in four steps and their order of the calculated overall proton dissociation constants(logβp) was Br-BHDP〈 Cl-BHDP〈 H-BHDP〈 CH3O-BHDP〈 CH3-BHDP. The order showed a similar trend to that of Hammett substituent constants(δp). The order of the stability constants(logKML) was Co(Ⅱ)〈 Ni(Ⅱ)〈 Cu(Ⅱ)〈 Zn(Ⅱ)〈 Cd(Ⅱ)〈 Pb(Ⅱ). The order in their stability constants (logKML) of each transition metal complex agreed with that of the overall proton dissociation constants (logβp).