Bulk Ti Research Articles

Fabrication of aqueous colloids of TixO2x-1 and Ag composite nanostructures by means of pulsed laser processing

Pulsed laser ablation in liquids is utilized for preparation of composite nanostructures on the basis of TixO2x-1 and Ag. Plates of bulk Ti and Ag immersed in the corresponding liquid serve as targets in the ablation procedure. A nanosecond Nd:YAG pulsed laser is employed as a source of irradiation. Its fundamental wavelength and the third and fourths harmonic are used both to fabricate and to change the chemical composition and the morphology of the nanostructures considered. The procedure for synthesis of complex nanostructures is performed following a specific sequence, namely, the consecutive laser ablation of the selected targets is followed by a post-ablation irradiation of the colloid obtained of the complex nanostructures. The changes in the characteristics of the complex nanostructures are indirectly evaluated based on the profile of the optical transmission spectra of the as-obtained colloids. The colloids’ properties are controlled by varying the laser beam parameters. Transmission electron microscopy (TEM) is applied for direct visualization of their shape. The chemical composition and the morphology were assessed by high-resolution TEM and SAED analyses.

Dynamically-generated TiO2 active site on MXene Ti3C2: Boosting reactive desulfurization

• Designed a mild reactive desulfurization system based on MXene. • Dynamically generated TiO 2 on MXene plays a key role in the catalytic oxidation. • The catalytic system shows high catalytic activity and durability. • The mechanism of oxygen activation and free radical reaction was revealed. Ti 3 C 2 MXene with dynamically-generated TiO 2 active site for boosting catalytic oxidative desulfurization has been researched. The two-dimensional Ti 3 C 2 MXene, with abundant interface engineering and loosely layered structure, was synthesized through selectively etching of aluminum (Al) layer in Ti 3 AlC 2 MAX. The desulfurization activity of Ti 3 C 2 MXene is higher than that of bulk Ti 3 AlC 2 MAX. Compared with Ti 3 AlC 2 MAX, the expanded slit layer provides more pores and cavities to accelerate the mass transfer of the reaction. Also, the excellent dispersion and interfacial affinity are conducive to the further access of MXene with the substrate in diesel. More than 87% of sulfides in real diesel can be removed with Ti 3 C 2 MXene as the catalyst. Specifically, the dynamically-generated active sites originate from the continuous activation of molecular oxygen and Ti 3 C 2 MXene, which favors the enhance of catalytic activity. Meanwhile, by detecting and analyzing the oxidizing products of various aromatic sulfides, the results show that the MXene interlayers serve as a reaction micro-cavity and are beneficial to the adsorption and removal of the sulfone. This work not only illustrates that MXene can be used in thermally excited catalytic systems, but also provides an example around the construction of dynamically generated active sites to extend the life of the catalyst.

Light emission signatures from ballistic impact of reactive metal projectiles

The light emission signatures generated following the impact of small cylindrical bulk Al, Ti, and Zr projectiles with an aluminum oxide target at supersonic speeds in the range of 0.4 – 1.1 km/s are investigated in air, argon, and vacuum using a suite of optical diagnostics, including a high-speed video camera, a three-colour optical pyrometer, a fast-response avalanche photodetector, and a low temporal resolution spectrometer. The history of the light emission in air may be divided into two distinct stages with different timescales. The first stage lasts up to 10 µs and is associated with the primary impact event. Within this stage the primary contribution to the light emission comes from projectile kinetic energy being converted into thermal energy. A second light emission stage, that lasts from hundreds of microseconds to a few milliseconds, is associated with the emission from the diffusion-limited combustion of metal fragments ignited upon impact. In contrast with the impact of Ti and Zr projectiles, for Al projectiles the second combustion stage was only observed above a threshold impact velocity of about 0.7 km/s. The low thermal conductivity, specific heat, and brittleness of Ti and Zr are believed to facilitate the formation of hot spots on the surface of fragments which contributes to ready fragment ignition.

Microstructural evolution and mechanical properties of bulk and porous low-cost Ti–Mo–Fe alloys produced by powder metallurgy

A series of low-cost Ti–10Mo-xFe (x = 1, 5, 9 wt%) alloys were fabricated using conventional press and sinter powder metallurgy to investigate the effect of Fe content on their phase stability, sintering response, microstructure and mechanical properties. Phase analyses indicated that all alloys were composed of α, β and intermetallic phases. However, Fe additions increased the proportion of β and intermetallic phases and reduced the propensity of the alloy system to form α phase during slow furnace cooling. Densification of the Ti–10Mo-xFe alloys was subjected to two contradicting effects; a strong sintering response caused by the fast diffusion rate of Fe atoms which promotes densification and formation of Kirkendall pores related to the fast diffusion rate of Fe atoms in conjunction with comparatively slower diffusion of Ti and Mo. Nonetheless, the porosity level of the alloys was less than that of the sintered CP-Ti. Depending on the content of α, β and intermetallic phases, the alloys exhibited varied mechanical properties. It was found that Ti–10Mo–5Fe presented the best combination of mechanical properties including the highest compressive strength (2392 MPa) and strain (43%) and low elastic modulus (91 GPa) superior to the corresponding ones for the commonly used CP-Ti and some other Ti-based alloys. Porous Ti–10Mo–5Fe alloy was also fabricated by addition of 30 and 60 vol% ammonium hydrogen carbonate (NH4HCO3) space holder which generated sintered scaffolds with 25% and 52% porosity, respectively, with an increased effective pore size at higher porosity. This reduced the compressive strengths to 649 MPa and 168 MPa and the elastic moduli to 34 GPa and 16 GPa, respectively. This study demonstrates that Ti–Mo–Fe alloys offer significant savings on raw materials compared to current commercial and many recently developed biomedical Ti alloys. It also shows that porous Ti–10Mo–5Fe scaffolds are promising for hard tissue engineering applications offering mechanical properties which closely match with the human bone and optimal pore sizes essential for bone ingrowth.

Crystal Structure Evolution, Microstructure Formation, and Properties of Mechanically Alloyed Ultrafine-Grained Ti-Zr-Nb Alloys at 36≤Ti≤70 (at. %).

Titanium β-type alloys are preferred biomaterials for hard tissue replacements due to the low Young modulus and limitation of harmful aluminum and vanadium present in the commercially available Ti6Al4V alloy. The aim of this study was to develop a new ternary Ti-Zr-Nb system at 36 ≤ Ti ≤ 70 (at. %). The technical viability of preparing Ti-Zr-Nb alloys by high-energy ball-milling in a SPEX 8000 mill has been studied. These materials were prepared by the combination of mechanical alloying and powder metallurgy approach with cold powder compaction and sintering. Changes in the crystal structure as a function of the milling time were investigated using X-ray diffraction. Our study has shown that mechanical alloying supported by cold pressing and sintering at the temperature below α→β transus (600 °C) can be applied to synthesize single-phase, ultrafine-grained, bulk Ti(β)-type Ti30Zr17Nb, Ti23Zr25Nb, Ti30Zr26Nb, Ti22Zr34Nb, and Ti30Zr34Nb alloys. Alloys with lower content of Zr and Nb need higher sintering temperatures to have them fully recrystallized. The properties of developed materials are also engrossing in terms of their biomedical use with Young modulus significantly lower than that of pure titanium.

Ohmic contact in graphene/SnSe2 Van Der Waals heterostructures and its device performance from ab initio simulation

Van der Waals (vdW) type metallic/semiconducting heterostructures have attracted much attention for applications like nanoelectronics. The electronic properties of graphene/SnSe2 vdW heterostructure are investigated by the first-principles calculation. The band dispersions of both the graphene and SnSe2 layers are well preserved in the graphene/SnSe2 vdW heterostructure. Notably, n-type Ohmic contact is found at the graphene/SnSe2 vdW interface so that graphene is a fantastic electrode for the SnSe2 Schottky barrier field-effect transistor (SBFET). The on-state current of the 10-nm-gate-long ML SnSe2 SBFET with graphene electrode is 1535 µA/µm for high-performance (HP) application, which is twice that of the ML MoS2 SBFET with bulk Ti electrode and exceeds the requirement of the International Technology Roadmap for Semiconductors for HP devices.

The High-Temperature Mechanical Properties of EN 1.4509 Stainless Steel Cast Using Investment Casting

The high-temperature (600-900 °C) mechanical properties of EN 1.4509 stainless steel made by investment casting were studied by changing the Nb content based on this stainless steel composition standard. The results indicate that with an increase in tensile temperature, the high-temperature strength shows a downward trend and the high-temperature plasticity increases. The results also indicate that with an increase in Nb content, the high-temperature strength rises continually and the high-temperature plasticity decreases; for example, the tensile strengths at 900 °C of Steel A, Steel B and Steel C are 21, 25 and 31 MPa, respectively, and the yield strengths are 15, 20 and 22 MPa, respectively, and the elongations are 97.7, 85.3 and 73.7%, respectively. The high-temperature tensile strength of the investment casting EN 1.4509 stainless steel sample is closely related to the bulk (Ti, Nb) (C, N) and the Laves phase (Fe2Nb) at the ferritic grain boundaries and in the ferritic grains. These are the main factors for improvement in the high-temperature strength of the tested steels; additionally, the coarse ferritic grains also play a certain role in improving the mechanical properties. The Nb content of the investment casting EN 1.4509 stainless steel can be reduced to 0.25 wt.%, and at this content, a combination of good high-temperature mechanical properties and higher room-temperature plasticity is obtained.

Nanotube Formation And Surface Evolution On Hydrothermally Treated Ti In Alkali Solution

The present study intends to check which nanotube formation mechanism match the surface evolution on bulk Ti surface after soaked in hydrothermal treatment. Polished cp-Ti disks were hydrothermally immersed in various concentration NaOH for 1h, 2h, and 4h at 220°C. The SEM observations and XRD studies showed a sequence transformation from polished Ti surface into titanium oxide with plate shape and leave-like structure in the beginning. Bigger plates or leaves oxide then evolved into sodium titanate nanorods that finally became nanotubes as the immersing time lengthened. Apparently self-assembly and partial dissolution were the most applied mechanism to explained the sodium titanate formation. Plate and leaves-like oxide mainly formed by dissolution of Ti metal followed by precipitation of TiO6 in self-assemble manner as the resultant of reaction between Ti(OH)3+ and OH−. While, nanorod and nanotube structure were produced by partial dissolution of leaves structure followed precipitation of sodium titanate by reaction of Na+ with HTiO3− generated from OH-reaction with Ti metal and TiO6.

The Electrochemical and Mechanical Behavior of Bulk and Porous Superelastic Ti‒Zr-Based Alloys for Biomedical Applications.

Titanium alloys are well recognized as appropriate materials for biomedical implants. These devices are designed to operate in quite aggressive human body media, so it is important to study the corrosion and electrochemical behavior of the novel materials alongside the underlying chemical and structural features. In the present study, the prospective Ti‒Zr-based superelastic alloys (Ti-18Zr-14Nb, Ti-18Zr-15Nb, Ti-18Zr-13Nb-1Ta, atom %) were analyzed in terms of their phase composition, functional mechanical properties, the composition and structure of surface oxide films, and the corresponding corrosion and electrochemical behavior in Hanks’ simulated biological solution. The electrochemical parameters of the Ti-18Zr-14Nb material in bulk and foam states were also compared. The results show a significant difference in the functional performance of the studied materials, with different composition and structure states. In particular, the positive effect of the thermomechanical treatment regime, leading to the formation of a favorable microstructure on the corrosion resistance, has been revealed. In general, the Ti-18Zr-15Nb alloy exhibits the optimum combination of functional characteristics in Hanks’ solution, while the Ti-18Zr-13Nb-1Ta alloy shows the highest resistance to the corrosion environment. The Ti-18Zr-14Nb-based foam material exhibits slightly lower passivation kinetics as compared to its bulk equivalent.

Compressive properties and micro-structural characteristics of Ti–6Al–4V fabricated by electron beam melting and selective laser melting

Bulk Ti–6Al–4V material and its lattice structures with rhombic dodecahedron unit cells are fabricated by electron beam melting (EBM) and selective laser melting (SLM) method respectively. The effect of part size on the compressive properties and failure modes of the material is taken into consideration. Electronic universal testing machine and Split Hopkinson pressure bar (SHPB) system are adopted for experiments, and the compressive behavior of the additively manufactured materials is investigated accordingly. Meanwhile, multiscale observations are conducted to reveal the macro- and microscopic deformation mechanism. The results showed that the mechanical response of the dense struts as well as micro-lattice structures manufactured by the two processes are quite different. The geometric imperfections are considered to reduce the strength of the undersized struts prepared by EBM. The specimens fabricated by both of the two approaches exhibit elastic-plastic deformation. Besides, the SLM made material is found to be more sensitive to strain rate especially for that below 1000/s than the EBM parts.

Deposition and phase transformation behaviors of Ti–Ni-Hf-Cu quaternary shape memory alloy thin films

In the present study, Ti–Ni-Hf-Cu thin films were successfully fabricated by magnetron sputtering process. Moreover, the effects of various factors on the quality of Ti–Ni-Hf-Cu thin film were investigated and the optimal processing parameters were determined. The results reveal that the composition and quality of Ti–Ni-Hf-Cu thin film can be mainly tailored by changing the sputtering power and Ar pressure. The amorphous Ti–Ni-Hf-Cu thin films with the high-quality can be obtained at the following condition: sputtering power = 150 W; Ar pressure = 0.6 Pa; sputtering time = 6 h. The annealed Ti–Ni-Hf-Cu thin film consisted of monoclinic B19′ martensite phase and nano-scale (Ti,Hf)2Ni type precipitate. Compared with the bulk Ti–Ni-Hf-Cu alloy, the annealed Ti–Ni-Hf-Cu thin film showed the lower martensitic transformation temperature. Nevertheless, the forward martensitic transformation starting temperature of the annealed Ti–Ni-Hf-Cu thin film was still higher than 100 °C, which can meet the requirement of the high temperature application field.

Two-step doping approach releasing the piezoelectric response of BiFeO3 bulk ceramics co-doped with titanium and samarium

The conventional solid state processing of bulk Ti,Sm co-doped BiFeO3 ceramics typically produces a complex micro-nanostructure which exhibits an effective decrease of the leakage conductivity. This same nanostructured configuration however confines the mobility of the ferroelectric domains and in this way the potential piezoelectric response of the formulated composition remains restrained. Hereby, a two-step doping strategy based on a simple surface modification approach is proposed which eventually allows for suitably engineering the microstructural development of the material, leading to a coarsened configuration where the conductivity is kept in low levels while the piezoelectric response is satisfactorily released for practical purposes.

Biocompatible Two-Dimensional Titanium Nanosheets for Multimodal Imaging-Guided Cancer Theranostics

Photothermal therapy (PTT) based on two-dimensional (2D) nanomaterials has shown significant potential in cancer treatment. However, developing 2D nanomaterial-based theranostic agents with good biocompatibility and high therapeutic efficiency remains a key challenge. Bulk titanium (Ti) has been widely used as biomedical materials for their reputable biocompatibility, whereas nanosized Ti with a biological function remains unexplored. In this work, the 2D Ti nanosheets (NSs) are successfully exfoliated from nonlayer bulk Ti and utilized as an efficient theranostic nanoplatform for dual-modal computed tomography/photoacoustic (CT/PA) imaging-navigated PTT. Besides the excellent biocompatibility obtained by TiNSs as expected, they are found to show strong absorption ability with an extinction coefficient of 20.8 L g-1 cm-1 and high photothermal conversion ability with an efficiency of 61.5% owing to localized surface plasmon resonances, which exceeds most of other well-known photothermal agents, making it quite promising for PTT against cancer. Furthermore, the metallic property and light-heat-acoustic transformation endow 2D Ti with the strong CT/PA imaging signal and efficient cancer therapy, simultaneously. This work highlights the enormous potential of nanosized Ti in both the diagnosis and treatment of cancer. As a paradigm, this study also paves a new avenue for the elemental transition-metal-based cancer theranostics.

Bulk titanium–graphene nanocomposites fabricated by selective laser melting

Abstract

Bulk Ti–Pd Alloys as Easily Recyclable and Preactivation-Free Heterogeneous Catalysts for Cross-Coupling Reactions

Abstract Ti–Pd alloys have been found to be novel heterogeneous palladium catalysts for organic cross-coupling reactions. Catalyst preactivation is not necessary, resulting in facile recovery and reuse of the catalysts. Palladium is not leached into the reaction solution and the catalysts can be recycled several times without losing their catalytic activity.

Fabrication of high-quality Ti joint with ultrafine grains using submerged friction stirring technology and its microstructural evolution mechanism

It is rather challenging to obtain high-quality Ti joints by conventional friction stir welding because of the problem of over-heating. The welding process and final microstructures and properties of the joints are controlled by both plastic deformation and recrystallization. However, for a long time, studies have only focused on recrystallization mechanisms but ignored deformation modes. In this study, a defect-free ultrafine-grained Ti joint with a joint efficiency of 100% was for the first time produced by submerged friction stirring (SFS) technology. We utilized transmission electron microscopy with a two-beam diffraction technique and electron backscatter diffraction to systematically investigate the deformation mode versus the grain refinement mechanism. The finite element method was utilized to simulate the temperature field throughout the joint for the microstructural explanation. During the whole SFS, prismatic slip occurred, and the other dominant deformation mechanisms changed from {101¯2} twinning and basal slip to pyramidal <a + c> slip. The variation of slip modes was largely dependent on the twinning and temperature rise. The ultrafine-grained microstructure was attributed to the successive refinement effect of the twin-dislocation interaction, dislocation absorption, dynamic grain boundary migration and texture-induced grain convergence. The effect of the temperature, strain and strain rate on the microstructural evolution mechanisms was discussed. Based on our work, we expect the wide application of SFS in producing ultrafine-grained bulk Ti materials and high-quality joints.

Bulk Ti nitride prepared from rutile TiO2 for its application as stimulation electrode in neuroscience

Bulk titanium nitride (TiN) was synthesized by nitridation of TiO2 rutile substrates. TiN pellets were successfully achieved at 1100 °C in ammonia stream; these materials were characterized by the evaluation of their microstructure, surface, chemical composition and electrical and electrochemical properties, concluding that the synthesis promotes the creation of a TiNxOy surface, which shows high metallic conductivity (close to 102 S/cm) and a microstructure with micro- and nano-features. Electrochemical studies reveal high storage capacities which are delivered through an injection mechanism that involves the double charge layer and EIS show a high capacitive contribution to the mechanism. Neuron cell cultures assessed the biocompatibility of the sample prepared and put forward this material as a promising candidate for implantable stimulation electrode in neuroscience.

New series of bulk amorphous/crystal bimetal composites of Vit1-clad Ti alloy

A series of bulk amorphous/crystal bimetal composites (BCs) were designed and prepared to utilize the advantages of bulk amorphous alloys and resolve the limitation of critical size on its applications. The typical bulk amorphousVit1 alloy and Ti alloys (pure Ti, TZ20, and TZ51 alloys) were used to prepare bulk amorphous/crystal BCs of Vit1-clad Ti alloy (Vit1/Ti alloy). Phase composition, microstructure, and hardness of Vit1-clad Ti alloy BCs were examined. Results revealed that the cladding layer of Vit1/Ti and Vit1/TZ20 is in a fully amorphous state. By contrast, partial crystallization occurs in the cladding layer of Vit1/TZ51. The prepared bulk amorphous/crystal BCs maintain the advantages of Vit1 bulk amorphous alloy while requiring minimally critical size.

Local structure of stoichiometric and oxygen-deficient A2Ti6O13 (A = Li, Na, and K) studied by X-ray absorption spectroscopy and first-principles calculations

Oxygen vacancy defects (VO) in Ti-based oxides play important roles in catalytic processes despite limited knowledge regarding their formation and characterization. Here, we demonstrate the use of X-ray absorption spectroscopy (XAS) measurements to compare the relative proportion of VO defects in as-grown alkali hexatitanate A2Ti6O13 (A = Li, Na, K). Both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) regions were studied. The similarity of measured XANES spectra of Ti K-edge in all samples indicates the presence of (Ti4+)O6 units in good agreement with reported X-ray diffraction results. The small influence of cations A at the tunnel was observed and can be well reproduced in the simulated spectra. In addition, we present a semi-quantitative approach to intuitively determine the content of VO defects in oxygen-deficient K2Ti6O13-x by in situ time-resolved XAS measurements under reducing conditions (10%H2/Ar, 50-650 °C). The in situ XANES measurements indicate that the oxidation state of bulk Ti remains the same as the as-grown sample, i.e., 4+, at elevated temperatures. By in situ EXAFS measurements, the relative number of VO defects is highest at a reduction temperature of ∼550 °C and slightly decreases after that. To confirm the formation of VO defects, first-principles calculations were independently carried out using a 126-atom K2Ti6O13 supercell with VO at various positions. Based on calculated EXAFS, the removal of the oxygen atom nearest to the tunnel, which is the lowest energy structure, provides a good match to the experimental spectra.

A Novel Synthetic Method for N Doped TiO2 Nanoparticles Through Plasma-Assisted Electrolysis and Photocatalytic Activity in the Visible Region.

Nitrogen doped TiO2 (N-TiO2) nanoparticles were synthesized via a novel plasma enhanced electrolysis method using bulk titanium (Ti) as a source material and nitric acid as the nitrogen dopant. This method possesses remarkable merits with regard to the direct-metal synthesis of nanoparticles with its one-step process, eco-friendliness, and its ability to be mass produced. The nanoparticles were synthesized from bulk Ti metal and dipped in 5–15 mmol of a nitric acid electrolyte under the application of AC 500 V, the minimum range of voltage to generate plasma. By controlling the electrolyte concentration, the nanoparticle size distribution could be tuned between 12.1 and 24.7 nm using repulsion forces via variations in pH. The prepared N-TiO2 nanoparticles were calcined at between 100 and 300°C to determine their photocatalytic efficiency within the visible-light region, which depended on their crystal structure and N doping content. Analysis showed that the temperature treatment yielded an anatase TiO2 crystalline structure when the N doping content was varied from 0.4 to 0.54 at.%. In particular, the 0.4 at.% N doped TiO2 catalyst exhibited the highest catalytic performance with quadruple efficiency compared to the P-25 standard TiO2 nanoparticles, which featured a 91% degradation of methyl orange organic dye within 300 min. This solid-liquid reaction based on plasma enhanced electrolysis could open new pathways with regard to high purity mass producible ceramic nanoparticles with advanced properties.