Chemical States of Lanthanum in Carbonized La_2O_3-Mo Thermionic Cathode Materials

The chemical reaction between lanthanum oxide and molybdenum carbide was studied by thermodynamic calculation, thermal analysis and in situ X ray Photoelectron Spectroscopy. The theoretical results show that at the environment allowing for the evaporation of lanthanum, such as in high vacuum, La 2O 3 in the La 2O 3 Mo materials can be reduced to metallic lanthanum by molybdenum carbide (Mo 2C). To confirm the conclusion, many analysis methods such as XRD, SPS, and TG DTA were taken. The experimental results show that the chemical state of lanthanum changes during heating. It was proved, for the first time, that reacted metallic lanthanum appears at the surface of this kind of material at high temperature.

XPS Studies of Chemical States of NiO/NiFe Interface

Ta/NTiO/NiFe/Ta multilayers were prepared by radio frequency reactive and dc magnetron sputtering. The exchange coupling field between NiO and NiFe reached 9.6 x 10(3) A/m. The compositions and chemical states at the interface region of NiO/NiFe were studied using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique, The results show that there are two thermodynamically favorable reactions at NiO/NiFe interface: NiO+Fe = Ni + FeO and 3NiO+2Fe =3 Ni+Fe2O3. The thickness of the chemical reaction area estimated by angle-resolved XPS was about 1-1.5 nm. These interface reaction products appear magnetic defects, and the exchange coupling field H-ex and the coereivity H-c of NiO/NiFe are affected by these defects.

Carbon nanotube supported PtOx nanoparticles with hybrid chemical states for efficient hydrogen evolution

Efficient electrocatalysts for hydrogen evolution reaction(HER) in alkaline solution are highly required for water splitting.Here we design an ultra-small PtOx nanoparticle with hybrid Pt chemical states on carbon nanotubes as highly efficient alkaline HER catalyst,which shows a low overpotential of 19.4 mV at 10 mA cm^(-2),a high mass activity of 5.56 A mg_(Pt)^(-1) at 0.1 V, and a stable durability for at least 20 h.The HER performance is better than that of the benchmark 20 wt% Pt/C while the Pt content in the catalyst is only about one tenth of that in Pt/C.It also represents one of the best catalysts ever reported for HER in alkaline solution.Synchrotron radiation X-ray absorption spectroscopy reveals that the efficient and stable alkaline HER performance can be attributed to the favorable design of hybrid chemical states of Pt with carbon nanotubes,which exhibits abundant surface Pt-O as active catalytic sites and forms stable Pt-C interfacial interaction to both anchor the NPs and improve the synergistic effect between catalyst and substrate.

Phase and chemical state tuning of FeNi oxides for oxygen evolution reaction

Advancing and deploying the Fe Ni-based catalyst,the state-of-the-art pre-electrocatalysts,for oxygen evolution reactions(OER)still suffer from unclear chemical state correlation to the catalytic ability,as evidenced by the variedly reported performance for the different Fe Ni structures.Herein,we contributed the phase and redox chemical states tuning of Fe Ni oxides by the surface microenvironment regulation for the OER catalysis that was realized by the urea-assisted pyrolysis and molybdenum-doping technique by integrating molybdenum into the iron–nickel metal-organic precursor.Driven by the complicated and compromised atmosphere,namely,the oxidation state driven by the Mo doping and reduction ability induced by the urea-assisted pyrolysis,could transfer confined Fe Ni oxides to hybrid phases of Fe_(2)O_(3)and FeNi_(3)alloy,and the resultant compromised chemical states by the charge redistribution imparted very high electrocatalytic performance for OER compared with the control samples.The insitu Raman spectroscopy and post-XPS analysis confirmed the facile Fe/Ni oxyhydroxide active phase formation resulting from the proper phase and chemical states,and theoretical analysis disclosed the microenvironment regulation resulting in the charge redistribution forming the electron accumulation and depletion sites to accelerate the oxygen-species to oxyhydroxide-species transformation and enhance the electronic state density near the Fermi level by significantly reducing the energy barrier.The work not only showed the importance of surface chemical state tunning that can basically answer the varied performance of Fe Ni catalysts but also revealed an effective approach for fine-tuning their catalytic properties.

Variations in surface functional groups, carbon chemical state and graphitization degree during thermal deactivation of diesel soot particles

The thermal deactivation of diesel soot particles exerts a significant influence on the control strategy for the regeneration of diesel particulate filters(DPFs).This work focused on the changes in the surface functional groups,carbon chemical state,and graphitization degree during thermal treatment in an inert gas environment at intermediate temperatures of 600℃,800℃,and 1000℃ and explore the chemical species that were desorbed from the diesel soot surface during thermal treatment using a thermogravimetric analyser coupled with a gas-chromatograph mass spectrometer(TGA-GC/MS).The surface functional groups and carbon chemical statewere characterized using Fourier transform infrared spectroscopy(FT-IR)and X-ray photoelectron spectroscopy(XPS).The graphitization degree was evaluated by means of Raman spectroscopy(RS).The concentrations of aliphatic C–H,C–OH,C=O,and O–C=O groups are reduced for diesel soot and carbon black when increasing the thermal treatment temperature,while the sp^(2)/sp^(3) hybridized ratio and graphitization degree enhance.These results provide comprehensive evidence of the decreased reactivity of soot samples.Among oxygenated functional groups,the percentage reduction during thermal treatment is the largest for the O–C=O groups owing to its worst thermodynamic stability.TGA-GC/MS results show that the aliphatic and aromatic chains and oxygenated species would be desorbed from the soot surface during 1000℃ thermal treatment of diesel soot.

Functional Optical Fiber Sensors Detecting Imperceptible Physical/Chemical Changes for Smart Batteries

The battery technology progress has been a contradictory process in which performance improvement and hidden risks coexist.Now the battery is still a“black box”,thus requiring a deep understanding of its internal state.The battery should“sense its internal physical/chemical conditions”,which puts strict requirements on embedded sensing parts.This paper summarizes the application of advanced optical fiber sensors in lithium-ion batteries and energy storage technologies that may be mass deployed,focuses on the insights of advanced optical fiber sensors into the processes of one-dimensional nano-micro-level battery material structural phase transition,electrolyte degradation,electrode-electrolyte interface dynamics to three-dimensional macro-safety evolution.The paper contributes to understanding how to use optical fiber sensors to achieve“real”and“embedded”monitoring.Through the inherent advantages of the advanced optical fiber sensor,it helps clarify the battery internal state and reaction mechanism,aiding in the establishment of more detailed models.These advancements can promote the development of smart batteries,with significant importance lying in essentially promoting the improvement of system consistency.Furthermore,with the help of smart batteries in the future,the importance of consistency can be weakened or even eliminated.The application of advanced optical fiber sensors helps comprehensively improve the battery quality,reliability,and life.

Surface Carbon Chemical States of Ion Implanted AISI 440C Martensitic Stainless Steel

Carbon atoms segregate in the surface region for polished AISI 440C stainless steel After ion implanta tion, the surface carbon atoms exist in different forms. To elucidate their existence, surface structures and carbon chemical states o[ unimplanted, N~ implanted, Ti＋ implanted and N＋/Ti＋ co-implanted samples were analyzed by X-ray diffraction （XRD）, transmission electron microscopy （TEM） and X-ray photoelectron spectroscopy （XPS）. The results indicated that various phases form in the surface or subsurface region after ion implantation, while the surface topography of the samples remains intact. For polished unimplanted sample, besides some Fe3 C phase and C- C phase, Cr, Cs phase dominates its surface region. Little change of carbon chemical states occurs after N＋ ion im- plantation. For Ti＋ implanted sample, besides some metal oxycarbide phases, most carbon amorphous phases form in surface region. Concerning N＋/Ti＋ co-implantation, CrrCs compound as well as Fe^C phase dominates the sur face region while no C-C phase is found. In addition, compared with single ion implantation, N＋/Ti＋ co-implanta tion would increase the ion implantation depth significantly. The formed phases of the carbon atoms play an impor- tant role in affecting the surface properties of AISI 440C stainless steel.

CO catalytic oxidation over Pd/CeO2 with different chemical states of Pd

Three Pd/CeO2 catalysts were,respectively,prepared by reduction-deposition and impregnation method(IMP)to investigate the effect of chemical state of Pd on CO oxidation.Two kinds of surface Pd species,namely PdO and Pdδ+(2<δ≤4)in PdxCe1-xO2,were identified in all Pd/CeO2 samples although their relative ratios in each sample were different.Surface PdxCe1-xO2 species were found to be very active for CO oxidation,and it could act as a channel by which active oxygen species can be transferred from CeO2 to Pd species for CO oxidation.Our results reveal that the preparation method can severely influence the chemical state of Pd which can further determine the activity for CO oxidation.

NON-EQUILIBRIUM STATIONARY STATE IN CHEMICAL REACTION OF SiO_2/Fe AT INTERFACE OF SLAG/METAL AND ITS STABILITY DURING ARC WELDING

For characteristics of open and far from thermodynamic equilibrium in welding chemical reaction, a new kind of quantitative method, which is used to analyze direction and extent for chemical reaction of SiO2/Fe during quasi-steady state period, is introduced with the concept of non-equilibrium stationary state. The main idea is based on thermodynamic driving forces, which result in non-zero thermodynamic fluxes and lead to chemical reaction far away from thermodynamic equilibrium. There exists certain dynamic equilibrium relationship between rates of diffusion fluxes in liquid phase of reactants or products and the rate equation of chemical reaction when welding is in quasi-steady state. As result of this, a group of non-linear equations containing concentrations of all substances at interface of slag/liquid-metal may be established. Moreover the stability of this non-equilibrium stationary state is discussed using dissipative structure theory and it is concluded theoretically that this non-equilibrium stationary state for welding chemical reaction is of stability.

Chemical Kinetic Aspects of Solid State Reaction Producing Wollastonite from Rice Husk Silica and Limestone

An industrial mineral wollastonite (CaSiO3) was produced under solid state conditions from rice husk silica and limestone. Reaction was carried out at 900'C to 1300'C for 1 h. The product batches were subjected to XRD and chemical analysis techniques specific for wollastonite. Mole fractions of different product batches were calculated on the basis of accumulated data to study the kinetics. Specific rate constants and reaction rate were also found out. Various probable models of mechanism for reaction were considered and testified with the laid down criterion for suggesting the suitable one. The resulting data were treated with Arrhenius equation as well and activation energy was calculated--therefrom. In addition to finding it's value from the slope of Arrhenius curve, an alternate method was also applied for this purpose. Both of the values were observed to be comparable. The activation energy required for performed reaction was found to be almost one third of that reported for synthesizing CaSiO3 by using quartz. This referred to the economical preparation of wollastonite by using rice husk as a source of silica instead of quartz.

Effect of Complexants on Nano-La_2O_3 Prepared by Solid State Chemical Reaction

Precursors were prepared by solid state chemical reaction between LaCl_3 and C_2H_2O_4·2H_2O or NH_4HCO_3 at ambient temperature. Differential temperature analysis (DTA) and thermogravimetric analysis (TGA) were used to determine the decomposing temperature. Oxide (La_2O_3) was obtained by decomposing the precursor for about 2.5 h. X-ray diffraction (XRD), scanning electronic microscope (SEM) and ZETA potentiometer were respectively used to analyze the composition, morphology and size distribution of the products. The results show that La_2O_3 prepared by LaCl_3 and C_2H_2O_4·2H_2O is of ball-like shape and the diameter of particles (95%) is below 50 nm, while La_2O_3 prepared by LaCl_3 and NH_4HCO_3 is net-like.

Chemical stability of La_2O_3 in La_2O_3-Mo cathode materials

Chemical stability of La 2O 3 in carbonized and uncarbonized La 2O 3 Mo cathodes was studied by in situ XPS analysis. Experimental results show that chemical stability of La 2O 3 is not good enough. In vacuum and at high temperature, oxygen can be dissociated from the lattice of La 2O 3 in the uncarbonized La 2O 3 Mo cathode. Binding energy shifts of La?3d5/2 and La?3d3/2 core peaks, and obvious decrease of satellite peak intensity in La?3d doublet with increasing temperature show that metallic La appears at carbonized La 2O 3 Mo cathode surface at high temperature.

Design principles in MOF-derived electromagnetic wave absorption materials:Review and perspective

At present,metal-organic framework(MOF)-derived nano-micro architectures are actively explored for electromagnetic(EM)wave absorption owing to their flexible composition and structural manipulation that enhance dielectric and magnetic attenuations.However,the basic design principles in MOF-derived microwave absorption materials have not been summarized.This review is devoted to analyzing design principles in MOF-derived microwave absorption materials from the following perspectives:diverse monomers(ligands and ions of MOFs),topologies,chemical states,and physical properties.The derived essential information regarding the EM wave absorption mechanism and the structural-functional dependency is also comprehensively summarized.Finally,a clear insight into the challenges and perspectives of the industrial revolution upgrading in this promising field is proposed.

EXPERIMENTAL AND THEORETICAL RESEARCH OF ELECTRON EMISSION MECHANISM OF M-TYPE CATHODES

With the most advanced Synchronous Radiation Photoelectron Spectrum(SRPS),the emission mechanism of M-type cathodes has been investigated from the perspective of chemical state.Based on the experimental results of SRPS analysis,a new model of the electron emission mechanism for M-type cathode is discussed.The main topics in this paper include the research status of electron emission mechanism of M-type cathodes;the advantages of SRPS technology;the distribution of oxygen chemical state on the cathode surface and the evolvement of oxygen chemical state during activation process;the relation between barium chemical state and osmium(Os)-coating;surplus barium and its formula;the characteristics of Os,and other noble metal coatings;the relation between film characteristics and emission performance of cathodes,the inhibition effects to the emission for Platinum(Pt)-coated cathode,etc.At the end of this paper,electron emission mechanism of M-type cathode is summarized and foreseen.

Surface Characterization of Ni_(64)P_(20)Fe_(16)Amorphous Alloy by X-ray Photoelectron Spectroscopy and Auger Electron Spectroscopy

The nature of the native oxides formed on the surface layer of amorphous alloy Ni_(64)P_(20)Fe_(16)has been studied by X-ray photoelectron spectroscopy (XPS)and Auger electron spectroscopy(AES)with depth profiling by ion bombardment.There are great distinctions in compositions and chemical states between the surface layer and the bulk.The main constituents Ni,P and Fe are lower in the sur- face layer,and they are mostly in oxidized states, whereas C,O and N are enriched in the surface lay- er.The thickness of surface oxide layer is approximately 20 nm,this layer was assumed to be of great significance to various properties of amor- phous alloy Ni_(64)P_(20)Fe_(16),expecially to the chemical and catalytic properties.Experiments proved that transitional element Fe cannot improve oxidation resistance of the amorphous Ni-P system.

Preparation of silicon carbide nitride films on Si substrate by pulsed high-energy density plasma

Thin films of silicon carbide nitride （SiCN） were prepared on （111） oriented silicon substrates by pulsed high-energy density plasma （PHEDP）. The evolution of the chemical bonding states between silicon, nitrogen and carbon was investigated as a function of discharge voltage using X-ray photoelectron spectroscopy. With an increase in discharge voltage both the C 1s and N 1s spectra shift to lower binding energy due to the formation of C--Si and N--Si bonds. The Si--C--N bonds were observed in the deconvolved C ls and N ls spectra. The X-ray diffractometer （XRD） results show that there were no crystals in the films. The thickness of the films was approximately 1-2 μm with scanning electron microscopy （SEM）.