Strong metal–support interaction boosts the electrocatalytic hydrogen evolution capability of Ru nanoparticles supported on titanium nitride

Ruthenium(Ru)has been regarded as one of the most promising alternatives to substitute Pt for catalyzing alkaline hydrogen evolution reaction(HER),owing to its inherent high activity and being the cheapest platinum-group metal.Herein,based on the idea of strong metal–support interaction(SMSI)regulation,Ru/TiN catalysts with different degrees of TiN overlayer over Ru nanoparticles were fabricated,which were applied to the alkaline electrolytic water.Characterizations reveal that the TiN overlayer would gradually encapsulate the Ru nanoparticles and induce more electron transfer from Ru nanoparticles to TiN support by the Ru–N–Ti bond as the SMSI degree increased.Further study shows that the exposed Ru–TiN interfaces greatly promote the H_(2) desorption capacity.Thus,the Ru/TiN-300 with a moderate SMSI degree exhibits excellent HER performance,with an overpotential of 38 mV at 10 mA cm^(−2).Also,due to the encapsulation role of TiN overlayer on Ru nanoparticles,it displays super long-term stability with a very slight potential change after 24 h.This study provides a deep insight into the influence of the SMSI effect between Ru and TiN on HER and offers a novel approach for preparing efficient and stable HER electrocatalysts through SMSI engineering.

COMPARISON OF SURFACE PROPERTIES OF Ti-6Al-4V COATED WITH TITANIUM NITRIDE, TiN+TiC+Ti(C,N)/DLC, TiN/DLC AND TiC/DLC FILMS BY PLASMA-BASED ION IMPLANTATION

The surface properties of Ti-6Al-4V alloy coated with titanium nitride, TiN+TiC+Ti(C,N)/DLC (diamond like carbon), TiN/DLC and TiC/DLC films by plasma-based ion implantation (PBII) with nitrogen, PBII with nitrogen then acetylene, PBII with nitrogen then glow discharge deposition with acetylene plus hydrogen and PBII with acetylene then glow discharge deposition with acetylene plus hydrogen respectively were studied. The corresponding films are found getting dimmer, showing light gold or gold, smoky color (uneven), light red in black (uneven), and graphite black separately. The corresponding film resistivities are given. Antioxidation ability of the titanium nitride film is poor, while the existence of carbon (or carbide) improves the antioxidation ability of the films. Having undergone excellent intermediate transitional region of nitrogen and carbon implantation, the top DLC layer of the TiN+TiC+Ti(C,N)/DLC multilayer are formed after the carbon implantation has the best adhesion with the substrate among all the multilayers. Although microhardness of the samples increases in the order of coatings of titanium nitride, TiN/DLC, TiN+TiC+Ti(C,N)/DLC and TiC/DLC, the TiN/DLC and TiC/DLC multilayers have greater brittleness as compared with other films.

High performance corrosion and wear resistant composite titanium nitride layers produced on the AZ91D magnesium alloy by a hybrid method

Composite,diffusive titanium nitride layers formed on a titanium and aluminum sub-layer were produced on the AZ91D magnesium alloy.The layers were obtained using a hybrid method which combined the PVD processes with the final sealing by a hydrothermal treatment.The microstructure,resistance to corrosion,mechanical damage,and frictional wear of the layers were examined.The properties of the AZ91D alloy covered with these layers were compared with those of the untreated alloy and of some engineering materials such as 316L stainless steel,100Cr6 bearing steel,and the AZ91D alloy subjected to commercial anodizing.It has been found that the composite diffusive nitride layer produced on the AZ91D alloy and then sealed by the hydrothermal treatment ensures the corrosion resistance comparable with that of 316L stainless steel.The layers are characterized by higher electrochemical durability which is due to the surface being overbuilt with the titanium oxides formed,as shown by the XPS examinations,from titanium nitride during the hydrothermal treatment.The composite titanium nitride layers exhibit high resistance to mechanical damage and wear,including frictional wear which is comparable with that of 100Cr6 bearing steel.The performance properties of the AZ91D magnesium alloy covered with the composite titanium nitride coating are substantially superior to those of the alloy subjected to commercial anodizing which is the dominant technique employed in industrial practice.

Theoretical study of the elastic properties of titanium nitride

The equilibrium lattice parameter, relative volume V/V0, elastic constants Cij, and bulk modulus of titanium nitride are successfully obtained using the ab initio planewave pseudopotential （PW-PP） method within the framework of density functional theory. The quasi-harmonic Debye model, using a set of total energy vs molar volume obtained with the PW-PP method, is applied to the study of the elastic properties and vibrational effects. We analyze the relationship between the bulk modulus and temperature up to 2000 K and obtain the relationship between bulk modulus B and pressure at different temperatures. It is found that the bulk modulus B increases monotonously with increasing pressure and decreases with increasing temperature. Moreover, the Debye temperature is determined from the non-equilibrium Gibbs functions.

Preparation of Titanium Nitride Nanoparticles from a Novel Refluxing Derived Precursor

Titanium nitride （TiN） nanoparticles were prepared from a novel refluxing-derived precursor.The organic/inorganic hybrid precursor was prepared by a two-stage refluxing method using hydrous TiO2 as titania source and n-dodecane as carbon source.The precursor was heat-treated to 1 200 °C in flowing ammonia （NH3） to get TiN nanoparticles.The phase and chemical compositions were investigated by means of XRD,Raman spectroscopy and XPS.Samples microstructure was studied by means of SEM,TEM and SEAD.XRD pattern indicated that the product was face-centered cubic TiN with a lattice constant a = 4.236 · and average crystallite sizes of 35.2 nm.Raman spectra indicated that long time refluxing results in Alkane dehydrogenation and the formation of coke on TiO2 nanoparticles.Oxygen presence in TiN lattice was confirmed by XPS investigation.The particle size that was showed by Electron microscopy photographs ranged from 20 to 60 nm.

Pt Supported on Plasma-Chemical Titanium Nitride for Efficient Room-Temperature CO Oxidation

Catalysts of carbon monoxide oxidation were synthesized by deposition of platinum on titanium nitride (TiN). Two substrates with an average particle size of 18 and 36 nm were obtained by hydrogen reduction of titanium tetrachloride in a stream of microwave plasma of nitrogen. The surface of the catalysts was studied by X-ray photoelectron spectroscopy (XPS). The data obtained by us in the present work indicate the presence of oxynitride as a transition layer between nitride and oxide. It was found that the CO oxidation rate on the 9 - 15 wt.% Pt loaded TiN catalysts is 120 times higher than that on the platinum black with a specific surface of 30 m2/g. Increase in the reaction rate of CO oxidation on Pt/TiN catalysts as compared to platinum black can be associated with both an increase in the concentration of CO molecules adsorbed and a decrease in the activation energy of the reaction. Catalysts are promising for use in catalytic air purification systems.

Flexible regulation engineering of titanium nitride nanofibrous membranes for efficient electromagnetic microwave absorption in wide temperature spectrum

Simultaneous development of well impedance matching and strong loss capability has become a mainstream method for achieving outstanding electromagnetic microwave absorption(EMWA)performances over wide temperature range.However,it is difficult to pursue both due to the mutual restraint of relationship between impedance matching and loss capability about temperature.Here,we propose a flexible regulation engineering of titanium nitride(TiN)nanofibrous membranes(NMs,TNMs),which could be distributed uniformly in the polydimethylsiloxane(PDMS)matrix and contributed to the formation of abundant local conductive networks,generating the local conductive loss and enhancing the loss ability of EMWs.Moreover,when the TNMs are used as functional units and dispersed in the matrix,the corresponding composites exhibit an outstanding anti-reflection effect on microwaves.As hoped,under the precondition of good impedance matching,local conductive loss and polarization loss together improve the loss capacity at room temperature,and polarization loss can compensate the local conductive loss to acquire effective dielectric response at elevated temperature.Benefiting from the reasonably synergistic loss ability caused by flexible regulation engineering,the corresponding composites exhibit the perfect EMWA performances in a wide temperature range from 298 to 573 K.This work not only elaborates the ponderable insights of independent membrane in the composition-structure-function connection,but also provides a feasible tactic for resolving coexistence of well impedance matching and strong loss capability issues in wide temperature spectrum.

Titanium nitride nanorod array/carbon cloth as flexible integrated host for highly stable lithium-sulfur batteries

Lithium-sulfur(Li-S)batteries have been regarded as promising energy-storage systems,due to their high theoretical capacity and energy density.However,the carbonaceous sulfur hosts suffer from weak binding force between the hosts and polysulfides,restricting the cyclic stability of sulfur electrode.Meantime,the presence of binder and conductive agent in the traditional electrode reduces its energy density.This study demonstrates that titanium nitride(TiN)nanorod array on carbon cloth(CC)is employed as a flexible host for highly stable Li-S batteries via solvothermal synthesis-nitridation strategy.On the one hand,the flexible integrated network composed of three-dimensional TiN nanorod array and CC significantly improves the conductivity,increases the electron transport and electrolyte penetration of cathode.On the other hand,the 3D structure of TiN/CC and the enhanced polarity of TiN effectively strengthen the physical and chemical double adsorption for polysulfides.As a result,the combination of TiN nanorod array and CC synergistic ally promotes sulfur utilization and electrochemical performances of S@TiN/CC cathode.A discharge capacity of1015.2 mAh·g^(-1)at 0.5C after 250 cycles and 604.1mAh·g^(-1)at 3C after 250 cycles is realized.Under a larger current density of 5C,the resulting S@TiN/CC cathode maintains a high discharge capacity of 666.6 mAh·g^(-1)and the Coulombic efficiency of about 100%.

Defect-rich titanium nitride nanoparticle with high microwaveacoustic conversion efficiency for thermoacoustic imaging-guided deep tumor therapy

Pulse microwave excite thermoacoustic(TA)shockwave to destroy tumor cells in situ.This has promising applications for precise tumor therapy in deep tissue.Nanoparticle(NP)with high microwave-acoustic conversion is the key to enhance the efficiency of therapy.In this study,we firstly developed defect-rich titanium nitride nanoparticles(TiN NPs)for pulse microwave excited thermoacoustic(MTA)therapy.Due to a large number of local structural defects and charge carriers,TiN NPs exhibit excellent electromagnetic absorption through the dual mechanisms of dielectric loss and resistive loss.With pulsed microwave irradiation,it efficiently converts the microwave energy into shockwave via thermocavitation effect,achieving localized mechanical damage of mitochondria in the tumor cell and yielding a precise antitumor effect.In addition to the therapeutic function,the NP-mediated TA process also generates images that provide valuable information,including tumor size,shape,and location for treatment planning and monitoring.The experimental results showed that the TiN NPs could be efficiently accumulated in the tumor via intravenous infusion.With the deep tissue penetration characteristics of microwave,the proposed TiN-mediated MTA therapy effectively and precisely cures tumors in deep tissue without any detectable side effects.The results indicated that defect-rich TiN NPs are promising candidates for tumor therapy.

Precipitation behavior of titanium nitride on a primary inclusion particle during solidification of bearing steel

Titanium nitride precipitation on a primary inclusion particle during solidification of bearing steel has been tracked by varying temperature in a confocal scanning violet laser microscope.Upon precipitation,an obvious growth of titanium nitride on a primary inclusion particle was observed due to the rapid solute diffusion in liquid steel.The onset of titanium nitride precipitation did not change with primary inclusion particle size,but the time of growth was greater for a smaller primary inclusion particle.Meanwhile,the particle size displayed little influence on the total precipitated amount of titanium nitride on it under the same conditions.At the later period of solidification,almost no change occurred in inclusion size,but the inclusion shape varied from circle to almost square in two-dimension,or cubic in three-dimension,to attain the equilibrium with steel.

Fabrication of titanium nitride nanoparticles onto carbon nanotubes by atomic layer deposition for utilization as Pt electrocatalyst supports

Because of its good stability and conductivity,titanium nitride(TiN)is considered to be a very promising alternative support for Pt catalyst;however,the preparation of TiN supports is still challenging.In this work,atomic layer deposition was facilely adopted to fabricate TiN nanoparticles onto carbon nanotubes(CNTs),and then the prepared TiN/CNTs hybrid was used as a support of Pt catalyst.The resulting TiN/CNTs-supported Pt nanoparticles(Pt@TiN/CNTs)nanocomposite showed higher catalytic activity and long-term stability toward the oxygen reduction reaction than the commercial Pt/C,which should be due to the high conductivity and high stability of TiN support,as well as the favorable Pt-TiN strong interaction.

Roles of titanium-rich precipitates as inoculants during solidification in low carbon steel

The effect of titanium on the as-cast structure and the growth form of titanium precipitates, and the effect of cooling rate on the size and distribution of titanium precipitates were studied. It is shown that Ti-rich precipitates acting as heterogeneous nucleation sites play an important role in refining the grain size and increasing the equiaxed grain ratio. Cooling rate has a great effect on the size and distribution of precipitates. The number of precipitates increases and the size decreases with the increase of cooling rate. Ti-rich particles acting as het- erogeneous nucleation sites at the onset of solidification are observed in the experiment. This result suggests that TiN nucleated on Ti2O3 is an effective inoculant for δ-ferrite during solidification in low carbon steel.

Effects of alloying elements on nitrogen diffusion behavior around TiN/Ti interface α region in as-cast titanium alloys

To characterize the effects of alloying elements on inclusion dissolution of titanium nitride, the content profiles of elements around TiN/Ti boundary α phase regions in liquid titanium alloys have been experimentally carried out. Four kinds of commercial alloys of CpTi, Ti64, Ti17 and Ti6242 containing different α stabilizing or β stabilizing elements are examined through artificially embedding the TiN sponge particle into liquid alloys in VAR conditions. The content profiles of nitrogen and alloying elements around TiN/Ti boundary were measured by WDX and microprobe for as cast samples. The content profiles of nitrogen and alloying elements around N containing solid in α Ti region of these alloys show a common features of a steep change. In particular, the content profiles of elements for Ti6242 demonstrate unique change of a more gentle change tendency and further deeper into the alloy matrix. The experiment results show that, the differences among composite effects of alloying elements in different alloys within nitrogen induced diffusion α region result in different dissolution and diffusion behaviors to overcome the α phase region barriers.

The microstructural characterization of the nitrided layers prepared by direct current nitrogen arc

The characteristics of nitrided layers prepared on commercially pure titanium substrates by direct current nitrogen arc are presented by scanning electron microscopy （SEM） and transmission electron microscopy （TEM） micrographs as well as X-ray diffraction （ XRD ）. The titanium nitride （ TiN ） dendrites were fully developed with interconnected cellular morphologies at the top surface but grew almost perpendicular to the integrace with coarser arms in the middle area. Also less TiN was found near the interface. The energy inputs had an obvious effect on the microstructures and the hardness of the nitrided layers. The maximum micro-hardness was 2 500 HV at the top surface which was over 9 times higher than that of the substrate.

Influences of Technological Parameters on Carbothermal Reduction and Nitridation of Titanium Dioxide

The particle size of starting materials, the homogeneity of the carbon/oxide mixtures, and the carbon content are important parameters for a rapid reaction. The influences of technological parameters（carbon particle size, oxide particle size, mixing method, carbon content） on the reaction rate of carbothermal reduction and nitridation of titanium dioxide （TiO2 ） were investigated by a continuous thermo-gravimetric analyzer for large size specimen. The carbon particle size is the most impor tant parameter for a rapid reaction, but carbon particle may have no influence on the morphology of titanium nitride （TiN） powder. Oxide particles are the precursors of TiN powder, but the TiO2 particles size has very little influence on the reaction rate. The carbon content not only influences the reaction rate to some degree, but also influences the purity of TiN powder. The mixing method of the specimen has very little influence on the reaction rate. These results are suitable for other nitrides and carbides prepared by carbothermal reduction method.

Mechanical Properties and Electrical Conductivity of TiN-Al_2O_3 Composites

TiN- Al2O3 composite powders with different TiN contents （0, 10 vol%, 20 vol%, 30 vol% and 40 vol% ）were prepared with micrometer TiN and α-Al2O3 powder （ their purities were 99% ） as starting materials by wet ball milling for 5 h. TiN-Al2O3 composite were then prepared by pressing the above composite powders, drying at 200 ℃ for 12 h and firing at 1 800 ℃ for 3 h in nitrogen atmosphere in hot-pressing furnace. The influences of TiN content on mechanical properties and electrical conductivity of TiN -Al2O3 composites were studied. The results showed that the mechanical properties of the composite increased with TiN content increasing, while the resistivity of composites decreased. A composite with 40% TiN had 498 MPa ben- ding strength, 4. 285 MPa· m1/2 fracture toughness, 1.34×10^-3 Ω· cm resistivity. The SEM analysis showed that the fine TiN crystals distributed among the crystal boundary of Al2O3 matrix. They bonded together forming a net-like structure which played a role of restraining Al2O3 grains from growing up, toughening and strengthening, so the mechanical properties of TiN -Al2O3 composite were enhanced.

In situ observation of austenite grain growth behavior in the simulated coarse-grained heat-affected zone of Ti-microalloyed steels

The austenite grain growth behavior in a simulated coarse-grained heat-affected zone during thermal cycling was investigated via in situ observation. Austenite grains nucleated at ferrite grain boundaries and then grew in different directions through movement of grain boundaries into the ferrite phase. Subsequently, the adjacent austenite grains impinged against each other during the α→γtransformation. After the α→γ transformation, austenite grains coarsened via the coalescence of small grains and via boundary migration between grains. The growth process of austenite grains was a continuous process during heating, isothermal holding, and cooling in simulated thermal cycling. Abundant finely dispersed nanoscale TiN particles in a steel specimen containing 0.012wt% Ti effectively retarded the grain boundary migration, which resulted in refined austenite grains. When the Ti concentration in the steel was increased, the number of TiN particles de- creased and their size coarsened. The big particles were not effective in pinning the austenite grain boundary movement and resulted in coarse austenite grains.

Control of the precipitation of TiN inclusions in gear steels

In the 20CrMnTi steel production process, the nitrogen content increased by 19 × 10^-6 and 29 × 10^-6, respectively, during ladle furnace（LF） refining and during the casting process from ladle to tundish. The protective casting is the key to decrease the N content. The results of thermodynamic calculations and a growth kinetics investigation show that TiN formation occurs only when the solidification fraction is greater than 0.533 under the controlled conditions used in this study for the manufacture of 20CrMnTi steel; the radius of TiN particles decreases as the Ti and N contents decrease and as the cooling rate increases. Furthermore, the theory of austenite grains controlled by second-phase particles was analyzed. The elemental analysis results showed that the Ti content was controlled at 0.04wt%–0.06wt% and the N content decreased to 0.005wt%, which satisfy the requirements for grain refinement but can also effectively prevent the precipitation of TiN inclusions in 20CrMnTi steel.

Particular properties of Ti_2O and TiN_x nanoparticles prepared by thermal decomposition

Particular properties of Ti2O and TiNx prepared by thermal decomposition were introduced. A precursor prepared by titanium powder reacting with oxalate acid was thermally decomposed in nitrogen atmosphere at 840℃ for 15 min, and relatively pure Ti2O was then obtained. Conductive TiNx was also prepared after altering reaction conditions. Samples were characterized by resistivity, X-ray powder diffraction, transmission electron microscope, Ultraviolet-Visible diffuse reflection, and electromagnetic shielding efficiency. The results indicate that both Ti2O and TiNx have good conductivity. Moreover, Ti2O shows a better solar photocatalytic activity and TiNx does well in the electromagnetic shield.

Thermodynamic Analysis for Carbothermal Reduction and Nitridation of TiO_2

The diagrams of stability relations（namely,Predominance area phase diagram,PAPD）of nitride,carbide and oxides in Ti-C-N-O system were plotted by thermodynamic calculation.The optimum conditions and main influence factors for the synthesis of titanium nitride and titanium carbide by carbothermal reduction in nitrogen atmosphere were discussed.