Effects of Fe-Al intermetallic compounds on interfacial bonding of clad materials

The growth of intermetallic compounds at the interface between solid Al and Fe and the effects of intermetallic compound layers on the interfacial bonding of clad materials were investigated. The results showed that the interface between the solid Fe and Al formed by heat-treatment consisted of Fe2Al5 and FeAl3 intermetallic compound layers, which deteriorated the interfacial bonding strength. Fractures occurred in the intermetallic compound layer during the shear testing. The location of the fracture depended on the defects of microcracks or voids in the intermetallic compound layers. The microcracks in the intermetallic compound layer were caused by the mismatch of thermal expansion coefficients of materials during cooling, and the voids were consistent with the Kirkendall effect. The work will lay an important foundation for welding and joining of aluminum and steel, especially for fabrication of Al-Fe clad materials.

Covalently bonded ternary photocatalyst comprising MoSe_(2)/black phosphorus nanosheet/graphitic carbon nitride for efficient moxifloxacin degradation

Covalently bonded bridging between different semiconductors is a remarkable approach to improve the transfer of charge carriers at interfaces.In this study,we designed a ternary heterojunction(MBG)combining of molybdenum diselenide(Mo Se_(2)),black phosphorus nanosheets(Bpn)and graphitic carbon nitride(GCN).Among this MBG of Mo Se_(2)/Bpn/GCN,(i)the covalently bonded bridging effect between Bpn/GCN facilitates directional charge carrier transfer,meanwhile(ii)a Z-scheme heterojunction is formed between Mo Se_(2)/GCN to enhance the separation of photogenerated carriers.Furthermore,(iii)this composite exhibits an increased absorption for visible light.Using this MBG,photocatalytic degradation of over 98%of moxifloxacin is achieved within 20 min,with O_(2)·-confirmed as the primary photocatalytic active species.These findings provide novel insights into the construction of efficient heterojunction by covalently bonded bridging.

Metal-free two-dimensional phosphorene-based electrocatalyst with covalent P-N heterointerfacial reconstruction for electrolyte-lean lithium-sulfur batteries

The use of lithium-sulfur batteries under high sulfur loading and low electrolyte concentrations is severely restricted by the detrimental shuttling behavior of polysulfides and the sluggish kinetics in redox processes.Two-dimensional(2D)few layered black phosphorus with fully exposed atoms and high sulfur affinity can be potential lithium-sulfur battery electrocatalysts,which,however,have limitations of restricted catalytic activity and poor electrochemical/chemical stability.To resolve these issues,we developed a multifunctional metal-free catalyst by covalently bonding few layered black phosphorus nanosheets with nitrogen-doped carbon-coated multiwalled carbon nanotubes(denoted c-FBP-NC).The experimental characterizations and theoretical calculations show that the formed polarized P-N covalent bonds in c-FBP-NC can efficiently regulate electron transfer from NC to FBP and significantly promote the capture and catalysis of lithium polysulfides,thus alleviating the shuttle effect.Meanwhile,the robust 1D-2D interwoven structure with large surface area and high porosity allows strong physical confinement and fast mass transfer.Impressively,with c-FBP-NC as the sulfur host,the battery shows a high areal capacity of 7.69 mAh cm^(−2) under high sulfur loading of 8.74 mg cm^(−2) and a low electrolyte/sulfur ratio of 5.7μL mg^(−1).Moreover,the assembled pouch cell with sulfur loading of 4 mg cm^(−2) and an electrolyte/sulfur ratio of 3.5μL mg^(−1) shows good rate capability and outstanding cyclability.This work proposes an interfacial and electronic structure engineering strategy for fast and durable sulfur electrochemistry,demonstrating great potential in lithium-sulfur batteries.

Direct Synthesis of α-Aminophosphonates from Amines,Alcohols,and White Phosphorus

Developing practical strategies for the synthesis of organophosphorus compounds(OPCs)from white phosphorus(P_(4))without the use of Cl_(2) and PCl_(3) remains a significant challenge.The first multicomponent oxidative α-phosphonylation of amines with P_(4) and alcohols has been developed.With the use of copper(Ⅱ)as the catalyst and air as the safe oxidant,structurally sophisticated α-aminophosphonates have been prepared in high yields.Furthermore,this method is also suitable for selective construction of P-O-P compounds.The reaction is characterized by a complete conversion of P_(4).The activation of P_(4) with transition metals often leads to formation of complexes[M_(x)P_(y)]_(n) associated with the deactivation of transition metals.This breakthrough showcases the potential of transition-metal-catalyzed reactions in elemental phosphorus chemistry.

Carbon-halogen bond activation by a structurally constrained phosphorus(Ⅲ)platform

Theσ-bond activation by main group element has received enormous attention from theoretical and experimental chemists.Here,the reaction of C-X(X=Cl,Br,I)bonds in benzyl and allyl halides with a pincer-type phosphorus(Ⅲ)species was reported.A series of structurally robust phosphorus(Ⅴ)compounds were formed via the formal oxidative addition reactions of C-X bonds to the phosphorus(Ⅲ)center.Density functional theory calculations show that the nucleophilic addition process is more favorable than the direct oxidative addition mechanism.Isomerization of bent structures of phosphorus(Ⅲ)compound to poorly nucleophilic compounds to undergo further C-X bond activation can be rationalized by frontier molecule orbital analysis.This study not only provides a deep understanding of the reactivity of phosphorus(Ⅲ)species but also demonstrates a potential of main group elements for the small-molecule activation.

Synthesis and Molecular Structure of Phosphorus-Sulfur Hybrid Atom Ligand and Their Palladium Complexes With the Studies on the C—H Bond Activation and Photochemical Carbonylation Reaction of Benzene

In this paper, a novel and ideal synthetic method of the phosphorus and sulfur hybrid atom ligand is reported. The speciality of this method is that the by-products of some reactions could be used circularly as starting materials in the synthetic route. Further, we synthesized a series of organopalladium complexes containing these hybrid atom chelate ligands, among them the molecular structures of novelorganopalladium complexes Pd((i-Pr)_2-P(CH_2)_2SEt)Cl_2, Pd(Et_2P(CH_2)_2SEt)Cl_2 and Pd(Ph_2P(CH_2)_2SEt)Cl_2 were determined by using the X-ray single crystal diffraction method. We first used the organotransition metal complexes containing phosphorus and sulfur hybrid atom ligands to activate the σ-C—H bond, and researched the catalytic activity, i.e. the photochemical carbonylation of benzene was catalyzed by these palladium complexes.

The role of 3d orbitals in the bonding of phosphorus compounds

Ab initio LCAO-MO-SCF calculations for several typical molecules containing phosphorus have been undertaken to study the role of phosphorus 3d orbitals in the bonding.It is emphasized that the discussion about the 3d orbital participation in bonding should be based on a reasonable choice of basis sets and it seems suitable to choose the atomic orbitals in proper molecular environment as the basis set.As an approximation,the optimized minimal STO-NG basis sets have been adopted in the present paper.The results obtained well exhibit the model of 3d orbital participation in bonding. It is shown that under the influence of highly electronegative ligands the phosphorus 3d orbitals con- tract greatly,their energy levels drop considerably,and thus they can effectively participate in bond- ing.The presence of highly electronegative ligands seems necessary.The contribution of 3d orbitals to bonding is achieved mainly through the concertedformation of σ bonds and p-d backbonds,though the contribution to σ bonding is minor.The three-center,four-electron bond modelis only approxi- mately correct.The results of the present paper demonstrate that the model of 3d orbital participation in bonding favoured by experimental chemists is reasonable and possesses sound ground.

Phosphafluorenyl lithiums:direct synthesis from white phosphorus,structure and diversified synthons

While rich chemistry of phospholyl anions is discovered,phosphafluorenyl anions are only proposed as the critical intermediates for the synthesis of phosphafluorenes.In this article,we reported the direct synthesis of phosphafluorenyl lithiums from white phosphorus(P_(4))through direct P-C bond formation.The reaction between P4 and biphenyl dilithio reagents efficiently afforded phosphafluorenyl lithiums,which were further used to synthesize different kinds of organophosphorus compounds.The aggregation states of phosphafluorenyl lithiums were investigated for the first time.Mechanistic studies by DFT calculations revealed a cooperative nucleophilic attack of two C−Li bonds on P_(4)molecule.

Are Sc-C and Sc-P Bonds Reactive in Scandium Phosphinoalkylidene Complex？ Insights on a Versatile Reactivity

The peculiar electronic structure of scandium phosphinoalkylidene complex [LSc{C（SiMe3）PPh2}THF] （L=[MeC（NDIPP）CHC（NDIPP）Me]-）, DIPP= 2,6-（Pr）2C6H3） leads to an interesting versatile reactivity, which is demonstrated both experimentally and computationally. The complex undergoes [2＋2] cycloaddition reactions with alkynes, and easily activates various X-O bonds such as C-O of propylene oxide, N-O of 3,5-dimethylisoxazole, B-O of pinacolborane and Si-O of triethoxysilane. These reactions occur on the Sc-C bond of the phosphinoalkylidene complex. Interestingly, the Sc-P bond can also be activated as the presence of a Sc-C-P three center π interaction in the complex allows performing C-F activation of 2,6-difluoro- pyridine and 1,2 addition with imine or ketone. The complex also reacts with metal complexes, [（COD）RhCl]2 and （Ph3P）AuCl, to form structural intriguing heterobimetallic complexes.

Introducing Covalent Metal-Phosphorus Bonds into Intermetallic Platinum-Based Catalysts for High-Performance Fuel Cells

The inadequate performance of oxygen reduction reaction(ORR)catalysts hampers the development of proton exchange membrane fuel cells(PEMFCs).Herein,we proposed an approach to tackle this problem by modulating the chemical bond type of intermetallic Pt-based catalysts,using phosphorus(P)doped L1_(0)-PtFeGa_(0.1)/C(P-L1_(0)-PtFeGa_(0.1)/C)as a proof of concept.X-ray absorption spectroscopy(XAS)demonstrated that the doped P transferred electrons to Pt,and thus,modified the electronic structure of Pt,weakening the adsorption strength with oxygen-containing species.Therefore P-L1_(0)-PtFeGa_(0.1)/C showed 13 times mass activity(MA)compared with commercial Pt/C,with a decay of only 28%after 100,000 potential cycles.When equipped in the membrane electrode assembly,the P-L1_(0)-PtFeGa_(0.1)/C catalyst also exhibited a remarkable activity(MA=0.84 A mgPt^(−1)at 0.9 V)and stability(MA retention=72%and voltage loss=9 mVat 0.8 A cm^(−2)after 30,000 cycles),making it one of the best performers among recorded Pt-based catalysts.Theoretical studies demonstrated that the doping of P optimized the adsorption energy between Pt and oxygen intermediates through sp-d orbital interactions and prevented metal dissolution by forming stronger Pt-P covalent bonds compared with Pt–Pt bonds.

Reduction of Carbon-bearing Pellets of Oolitic Hematite in a Shaft Furnace

When carbon-bearing pellets of oolitic hematite are treated in a shaft furnace,some problems are typically encountered：the metallization ratio of the metal pellets is low;the carbon-bearing pellets bond with each other at high temperatures;and the separation of phosphorus from iron is difficult.To solve these problems,experiments were conducted on oolitic hematite reduction in a resistance furnace and semi-industrial test shaft furnace.The results showed that the metallization rate reached 90% or greater under the conditions of a reduction temperature of 1 150℃,an atmosphere of simulated flue gas,and a reduction time between 1.5and 2.0h.The problem of high-temperature bonding among pellets can be solved by increasing the strength of the pellets,coating their surface with a surface transfer agent and maintaining an even temperature inside the shaft furnace.The basicity of the ore blend exerted no obvious effect on the magnetic concentrate and phosphorus content.The phosphorus content in the magnetic concentrate can be further reduced by improving the grinding capacity of the ball mills used in the experiments.On the basis of the experimental results related to oolitic hematite reduction with carbon-bearing pellets in a shaft furnace,the experimental requirements were satisfied with an average 88.27%total Fe content and 0.581% P content in the pellets.

THE SYNTHESIS AND SPECTRAL PROPERTIES OF TRIAZOPHOSPHOLENE(Ⅴ)

The first series of fused tricydotriazophospholene, 1-phenyl-5-N, N-dialkylaminobenzothiazolo-（2, 3, c）-△2-1, 2, 4, 5-triazophospholenes （Ⅰ）, has been obtained by the reaction of 2-（N2-phenyl）hydrazinobenzothiazole with tris（dialkylamino）-phosphines:

Visible-light-induced synthesis of phosphorylated N-heterocycles through proton-coupled electron transfer

Phosphorus-containing organic compounds are important feedstock for the synthesis of value-added bioactive molecules.Therefore,the development of highly efficient synthetic methods for the construction of phosphorus-element bonds has drawn huge attention in the past decades[1].Particularly,the formation of P–C bonds from phosphoruscentered radicals has been demonstrated to be one of the most efficient and convenient strategies,which has been widely applied for the synthesis of organic phosphorus compounds in recent years.