TiN Dendrites Research Articles

A sequential template electrodeposition anodization and in situ aniline electropolymerization-based facile electrochemical synthesis strategy

Herein, we propose a facile continuous electrochemical synthesis strategy to build 3D hierarchical hybrid conductive networks based on sequential template electrodeposition-anodization and in-situ aniline electropolymerization. It was implemented in a tin system to prepare a 3D tin skeleton with micron-scale features using the hydrogen bubble dynamic template method, followed by electrochemical anodization to achieve nanoscale modulation. This well-designed 3D hierarchical metal oxide framework was used for the in-situ electropolymerization of aniline, preserving the hierarchical morphological features while establishing large conductive networks for ultrafast electron transport and enhancing the structural stability of tin dendrites. Regulation of the hierarchical morphologies promotes material surface reactivity, increases the electrochemically active sites, and improves the ion diffusion kinetics, thus solving the “dead surface” problem in the energy storage process. Such multifaceted synergistic strategies of structural modulation and functional hybridization have opened up new ways to design efficient binder-free hybrid electrode materials.

The control of morphology and structure of galvanostatically produced tin dendrites by analysis of chronopotentiometry response

The control of morphology and structure of galvanostatically produced tin dendrites by analysis of chronopotentiometry response

ELECTROCHEMICAL MIGRATION FAILURE OF PURE TIN UNDER BROMIDE-POLLUTED THIN ELECTROLYTE LAYER

The electrochemical migration (ECM) time to failure (TTF) tests for pure tin in the bromide-containing environment were carried out using the thin electrolyte layer (TEL) method. In-situ electrochemical measurement was made to monitor the ECM behavior while the changes of surface morphology and localized pH during the ECM process were real-time observed using the 3D optical digital microscope. Microstructure and composition of products obtained after the ECM tests were characterized using the scanning electron microscope, energy-dispersive spectrometer and X-ray diffractometer. Results indicated that the growth rate of dendrite increased with bromide ion concentration at low bromide concentration levels, and it decreased at medium concentration levels. Tree-like tin dendrites covered with white precipitates are formed after the ECM tests. As for the high bromide ion concentration condition, no dendrite can be found and a thick layer of precipitate is formed between the twin electrodes. This precipitate layer has a higher thickness than the electrolyte layer, which can act as a barrier layer retarding ionic migration and thus inhibiting the ECM failure. Relevant mechanism has been proposed to clarify the effect of bromide ions on the ECM of pure tin under the thin electrolyte layer.

The microstructure and cavitation erosion resistance of Ti6Al4V alloy treated by laser gas nitriding with scanning galvanometer

In this study, the nitrided layer was prepared on Ti6Al4V alloy by laser gas nitriding using the scanning galvanometer (G-LGN). Its typical features were investigated in comparison to that using the diode laser with robot (D-LGN) under the same energy density and treated area. In order to reveal the connections between the cavitation resistance (CE) and characteristics of the nitrided layer, the samples were characterized by OM, SEM, XRD, XPS, laser scanning microscopy, and microhardness tester. Due to using the scanner, the G-LGN method is given a smaller laser spot size (micrometer scale), higher scanning speed, and remelting brought by successive overlapping during processing. Those cause it different from the D-LGN method in the microstructure and CE resistance of the nitrided layer. The results show that the G-LGN sample has a more uniform surface with a lower average surface roughness (Sa = 3.043 μm) compared with the D-LGN sample. Moreover, the TiN dendrites with smaller sizes and an amount of TiN0.3 phase are formed in its nitrided layer. It is interesting that the TiN0.3 phases in the G-LGN sample result in a lower surface hardness (about 700–800 HV) with respect to the D-LGN sample, but a more uniform hardness distribution through the depth direction can be detected. According to the results of the CE test, the G-LGN sample exhibits the lowest cumulative mass loss and mean erosion rate during the whole erosion time in comparison to the substrate and D-LGN sample, suggesting the best CE resistance. Therefore, the G-LGN method will provide competitive advantages over the D-LGN method for the CE protection of the titanium components owing to the improvement in the quality and performance of the nitrided layer as well as the superiority of the scanning galvanometer.

The microstructures and mechanical properties of martensite Ti and TiN phases in a Ti6Al4V laser-assisted nitriding layer

A fiber laser assisted the preparation of a nitride layer on the Ti6Al4V surface in a pure nitrogen atmosphere. Through SEM, XRD, and XPS analyses, the nitride layer is found to be mainly composed of dendritic TiN phase and an interdendritic α′-Ti phase. Not only the true crystal structure of the two main phases (TiN and α′-Ti) were directly characterized using TEM, but also the mechanical properties were tested by micro-indentation and nano-indentation methods for the first time.It is found that the nano-hardness of the TiN phase is 2609 HV, and the elastic modulus is 208 GPa. During the TiN dendritic fracture process, the primary dendrites undergo near ductile fracture along the growth direction of the secondary dendrites, and microcracks, bifurcations, deflection, etc. occur to form a crack-toughening mechanism. The nano-hardness of α′-Ti is 632 HV, and the elastic modulus is 142.8 GPa. The entanglement of two sets of parallel dislocations in α′-Ti crystals forms subgrain boundaries, which exert a positive influence on work hardening and fine-grain strengthening. • A large number of parallel dislocation groups in the generated TiN. • TiN dendrites not only have near ductile fracture, but also have crack toughening; • A large number of parallel dislocation groups and subgrain boundaries in the α′-Ti.

Effect of aging on microstructure and wear resistance of Ti-55511/BN composite coating

ABSTRACT In situ synthesized TiN and TiB reinforced metal matrix composite coating was fabricated on Ti-55511 by laser cladding with Ti-55511/BN powder mixture (2 wt-% BN). Results indicated that coating was mainly composed of TiB, dendrite TiN and α phase. The diameter of small-sized hollow tubular TiB was less than 400 nm, and the width of the other rod-shaped TiB was less than 1 μm. The flower-like structure formed during solidification consisted of TiN dendrite in centre and rod-shaped or hollow tubular TiB at edge. Coating had high hardness (540 HV) due to formation of TiB and TiN. After direct aging (600°C/5 h/AC), the hardness of coating and HAZ increased to 660 and 450 HV respectively because of nano-scaled α phase precipitation. In the friction and wear test, the weight loss of the coating was only 62% of that of substrate, which further reduced to 47% after aging.

Microstructure and microhardness of a novel TiZrAlV alloy by laser gas nitriding at different laser powers

The Ti–20Zr–6.5Al–4V (T20Z, wt%) alloy surface was treated by the process of laser surface nitriding. The evolution of microstructures and microhardness has been investigated by changing the laser power parameter from 120 to 240 W. All laser-treated T20Z samples show two regions with distinctly different microstructural features, as compared with the untreated substrate: dense TiN dendrites and (α + β) − Ti (remelting zone, RMZ), nanoscale α laths doped with part of β phase (heat-affected zone, HAZ). The formation of TiN dendrites can be analyzed by a series of complex reactions during the process of melting and solidification. The increase in laser power results in the increase in content of TiN dendrite which is mainly due to the increase in energy input. In HAZ, the self-quenching effect leads to the formation of nanoscale α laths and the residue of β phase. Microhardness profile of different regions was measured from the surface to the interior, and the highest microhardness was obtained (~ HV 916.8) in the RMZ, as the laser power was set to 240 W. In the present study, we explained various microstructural characteristics induced by laser surface nitriding treatment.

In situ selective laser gas nitriding for composite TiN/Ti-6Al-4V fabrication via laser powder bed fusion

Laser-assisted gas nitriding of selective Ti-6Al-4 V surfaces has been achieved during laser powder bed fusion fabrication by exchanging the argon build gas environment with nitrogen. Systematic variation of processing parameters allowed microdendritic TiN surface coatings to be formed having thicknesses ranging from a few tens of microns to several hundred microns, with TiN dendrite microstructure volume fractions ranging from 0.6 to 0.75; and corresponding Vickers microindentation hardness values ranging from ∼ 7.5 GPa–9.5 GPa. Embedded TiN hard layers ranging from 50 μm to 150 μm thick were also fabricated in the laser-beam additively manufactured Ti-6Al-4 V alloy producing prototype, hybrid, planar composites having alternating, ductile Ti-6Al-4 V layers with a hardness of ∼ 4.5 GPa and a stiff, TiN layer with a hardness of ∼8.5 GPa. The results demonstrate prospects for fabricating novel, additively manufactured components having selective, hard, wear and corrosion resistant coatings along with periodic, planar or complex metal matrix composite regimes exhibiting superior toughness and related mechanical properties.

Effect of Organic Acids on the Electrochemical Migration of Tin in Thin Electrolyte Layer

Background and Objective: The effects of representative solder flux residue weak organic acids on electrochemical migration (ECM) of tin in thin electrolyte layer were studied using a technique based on the coupling of in situ electrochemical measurements and optical observations, as well as ex situ characterizations. Methods and Results: The results showed that the increasing amount of weak organic acid decreased the probability of ECM and dendrites formed were mainly composed of metallic tin. Tin ions reacted with organic compound ions from hydrolysis of weak organic acids to form complexes with electronegativity, which retarded the transfer of tin ions. Some complexes can be oxidized to the insoluble tin oxides on the anode surface and blocked the dissolution of anode during tin ECM. Conclusion: The growth rate of tin dendrite was found to be limited by the dissociation of complexes. Mechanisms involved were proposed to explain the role of weak organic acid in the tin ECM.

Analysis of Dendrite Images Formed by Electrochemical Migration in a Semiconductor Sensor

Dendrites were observed in the failure of semiconductor sensor devices. EDX analysis showed that the dendrites grown from bare sensor dice consisted of tin metal. The tin dendrites exhibited massive and dense branches. Dendrites grown from mechanically decapped parts consisted of silver. The silver dendrites exhibited delicate, lace-like structure. Binary and grey scale images of dendrites were analyzed for fractal dimension number and branch density. The tin dendrites had a higher, statistically significant branch density number than silver, due to tin’s more intricate branching pattern. Fractal numbers can be used to differentiate between tin and silver dendrites, even in the absence of EDX analysis equipment.

Rapid surface nitriding of titanium alloy by a nanosecond fiber laser under atmospheric conditions

A modified surface layer using a Yb nanosecond fiber laser beam under atmospheric conditions was fabricated by applying a surface nitriding process on disc-shaped Ti–6Al–4V samples. On the generated surface, a melt layer comprising a TiN dendrite structure and a heat affected zone containing a needle-like α phase were detected. The modified layer exhibited optimal characteristics with the treatment at a laser output power of 12W, resulting in a hardness of 12GPa. The results of friction wear evaluation tests revealed that the layer exhibited superior abrasion resistance compared with an untreated Ti–6Al–4V substrate.

Enhanced Urea Activity of Oxidation on Nickel‐Deposited Tin Dendrites

AbstractUrea oxidation has gained tremendous research interest, owing to its application in direct urea fuel cells and urea electrolyzers. In this work, the electrochemical oxidation of urea on a Ni/Sn dendrites catalyst is investigated. Ni and Ni/Sn dendrites are synthesized through electrodeposition on porous Toray© carbon paper. The prepared catalysts were characterized by scanning electron microscopy, X‐ray diffraction, and inductively coupled plasma−optical emission spectroscopy. The Ni/Sn dendrites oxidized 0.33 M urea in alkaline solution at an onset potential of 0.34 V vs. Ag/AgCl with a current density of 44 mA cm−2@0.55 V, which is higher than that of electrodeposited Ni/TC (31 mA cm−2 @0.55 V). In situ Raman spectroscopic measurements indicate that urea oxidation on Ni/Sn dendrites is initiated by Ni(III)OOH species. Electrochemical impedance spectroscopy patterns of Ni/Sn dendrites in the presence of urea displayed a single depressed semicircle at potentials of 325 mV and two semicircles above 325 mV with a decreased total charge‐transfer resistance. The Ni/Sn dendrites electrode shows lower resistance at the tested potentials, indicative of faster urea oxidation kinetics.

Influence of atmospheric water uptake on the hydrolysis of stannous chloride in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate

Abstract In this paper we report on the influence of water uptake on the hydrolysis of anhydrous stannous chloride in the ionic liquid 1-butyl-1-methylpyrrolidinium trifluoromethylsulfonate ([Py 1,4 ]TfO) under ambient atmosphere. The effect of water uptake on the electrodeposition of tin in the employed ionic liquid containing 0.1 M SnCl 2 was also demonstrated. The hydrolysis products as well as the Sn electrodeposits were characterized by different techniques comprising; scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results show that the employed ionic liquid electrolyte strongly absorbs water under ambient conditions. Colloidal particles were formed in the electrolyte after an exposure time of about 4 weeks as a result of the hydrolysis of Sn(II) species. The electrochemical behaviour of the employed electrolyte and the morphology of tin electrodeposits were significantly influenced by the presence of water. Tin dendrites were obtained from IL-electrolyte exposed to air for one month, whereas dendrite free deposits were formed in the freshly prepared electrolyte.

Mechanistic Prediction of the Effect of Microstructural Coarsening on Creep Response of SnAgCu Solder Joints

Mechanistic microstructural models have been developed to capture the effect of isothermal aging on time dependent viscoplastic response of Sn3.0Ag0.5Cu (SAC305) solders. SnAgCu (SAC) solders undergo continuous microstructural coarsening during both storage and service because of their high homologous temperature. The microstructures of these low melting point alloys continuously evolve during service. This results in evolution of creep properties of the joint over time, thereby influencing the long term reliability of microelectronic packages. It is well documented that isothermal aging degrades the creep resistance of SAC solder. SAC305 alloy is aged for (24–1000) h at (25–100)°C (~0.6–0.8 × Tmelt). Cross-sectioning and image processing techniques were used to periodically quantify the effect of isothermal aging on phase coarsening and evolution. The parameters monitored during isothermal aging include size, area fraction, and inter-particle spacing of nanoscale Ag3Sn intermetallic compounds (IMCs) and the volume fraction of micronscale Cu6Sn5 IMCs, as well as the area fraction of pure tin dendrites. Effects of microstructural evolution on secondary creep constitutive response of SAC305 solder joints were then modeled using a mechanistic multiscale creep model. The mechanistic phenomena modeled include: (1) dispersion strengthening by coarsened nanoscale Ag3Sn IMCs in the eutectic phase; and (2) load sharing between pro-eutectic Sn dendrites and the surrounding coarsened eutectic Sn-Ag phase and microscale Cu6Sn5 IMCs. The coarse-grained polycrystalline Sn microstructure in SAC305 solder was not captured in the above model because isothermal aging does not cause any significant change in the initial grain size and orientation of SAC305 solder joints. The above mechanistic model can successfully capture the drop in creep resistance due to the influence of isothermal aging on SAC305 single crystals. Contribution of grain boundary sliding to the creep strain of coarse grained joints has not been modeled in this study.

Magneto-electro deposition of tin dendrites

The magnetic strength and number of electrons in tin magneto-electro deposition can induce the limiting current by increasing the mass transport of electro active species. The presence of the magnetic field can lead to the eventual increase of the electrolytic current by means of convective movement of the electro active species. In this paper, the growth of tin dendrites under the magnetic field is reported. The results show that the deposited mass (coating) and fractal dimension increase in the presence of the magnetic field from a simulation (based on the diffusion limited aggregation) and an experiment.

Titanium Matrix Composite Ti/TiN Produced by Diode Laser Gas Nitriding

A high power direct diode laser, emitting in the range of near infrared radiation at wavelength 808–940 nm, was applied to produce a titanium matrix composite on a surface layer of titanium alloy Ti6Al4V by laser surface gas nitriding. The nitrided surface layers were produced as single stringer beads at different heat inputs, different scanning speeds, and different powers of laser beam. The influence of laser nitriding parameters on the quality, shape, and morphology of the surface layers was investigated. It was found that the nitrided surface layers consist of titanium nitride precipitations mainly in the form of dendrites embedded in the titanium alloy matrix. The titanium nitrides are produced as a result of the reaction between molten Ti and gaseous nitrogen. Solidification and subsequent growth of the TiN dendrites takes place to a large extent at the interface of the molten Ti and the nitrogen gas atmosphere. The direction of TiN dendrites growth is perpendicular to the surface of molten Ti. The roughness of the surface layers depends strongly on the heat input of laser nitriding and can be precisely controlled. In spite of high microhardness up to 2400 HV0.2, the surface layers are crack free.

Cover Image, Volume 98, Issue 1

The inserted image shows an optical micrograph of the transverse cross‐section of a titanium nitride coating on a commercially pure titanium (CP‐Ti) sample. The titanium nitride coating was deposited by scanning the CP‐Ti specimen multiple times in the presence of a nitrogen plasma sustained by a CO2 laser and a coaxial flow of nitrogen. The cross section shows TiN dendrites, the heat affected zone and the base metal. Crack formation can be observed in some areas of the coating. Micrograph courtesy of Amar M. Kamat, The Pennsylvania State University.image

Microstructure and wear resistance of one-step in-situ synthesized TiN/Al composite coatings on Ti6Al4V alloy by a laser nitriding process

Abstract The aim of this paper was to develop a one-step in situ method to synthesize the TiN reinforced Al metallic matrix composite coatings on Ti6Al4V alloy. In this method, the Al powder and nitrogen gas were simultaneously fed into feeding nozzle during a laser nitriding process. The microstructure, microhardness and sliding wear resistance of TiN/Al coatings synthesized at different laser powers in laser nitriding were investigated. Results showed that the crack- and pore-free coatings can be made through the proposed method. However, the morphologies and distribution of TiN dendrites and wear resistance of coatings were strongly dependent on laser power used in nitriding. With increasing the laser power, the amount and density of massive TiN dendritic structure in the coating decreased and the elongated and narrow dendrites increased, leading to the increment of wear resistance of coating. When the laser power is high, the convectional flow pattern of the melt pool can be seen near the bottom of pool.

Mechanism of Laser Surface Modification of the Ti-6Al-4V Alloy in Nitrogen Atmosphere Using a High Power Diode Laser

The influence of the nitrogen content in argon/nitrogen gas mixture on mechanism of titanium nitrides formation during laser surface processing of titanium alloy Ti6Al4V with high power diode laser was investigated. The phase composition and microhardness on cross-section of surface layers were analyzed and described. It was found that the nucleation of TiN dendrites in nitrogen rich atmosphere (at least 75 % of N2) takes place on the liquid/gas boundary as a result of the reaction between molten titanium and gaseous nitrogen. The subsequent growth of titanium nitride dendrites (crystallization) proceeds into the liquid metal (weld pool), perpendicularly to the top surface. High length of the titanium nitride dendrites up to 180÷250 μm in the surface layer produced in pure nitrogen atmosphere indicates also very rapid rate of dendrites growth in the molten titanium. The tendency to form titanium nitrides during laser surface processing of the investigated titanium alloy falls dawn with the decrease of nitrogen content in the gas mixture.

A Comparative Study on the Electrodeposition of Tin from Two Different Ionic Liquids: Influence of the Anion on the Morphology of the Tin Deposits

AbstractThe electrodeposition of tin from two ionic liquids (ILs) containing the 1‐butyl‐1‐methylpyrrolidinium cation ([Py1,4]+) and the trifluoromethylsulfonate (TfO−) or dicyanamide (DCA−) anion is investigated by cyclic voltammetry, scanning electron microscopy (SEM), infrared (IR) spectroscopy and X‐ray diffraction. Cyclic voltammetry is employed to evaluate the electrochemical behaviour of SnCl2 in the two ILs, and IR spectroscopy is used to study the difference in the complexation of SnCl2 in the two ILs. The electrodeposition of tin is also studied in [EMIm]DCA ([EMIm]+=1‐ethyl‐3‐methylimidazolium), for the purpose of comparison. The morphology of the electrodeposited tin from the different ILs is investigated by SEM, which shows that the morphology of the tin deposits changes upon changing the IL. Agglomerated tin deposits are obtained on gold and copper from [Py1,4]TfO. Tin dendrites were obtained both from [Py1,4]DCA and [EMIm]DCA. This study reveals that a change in the ionic composition (anion) of the IL can influence the morphology of electrodeposits of tin and presumably of other elements and compounds.