Nano Ti Research Articles

Effect of Processing Routes on Physical and Mechanical Properties of Advanced Cermet System

The present research focuses on the effects of different processing routes on the physical and mechanical properties of nano Ti(CN)-based cermets with metallic binders. Tungsten carbide (WC) is added as a secondary carbide and Ni-Co is added as a metallic binder to nano Ti(CN)-based cermet processed via conventional and spark plasma sintering (SPS). A systematic comparison of the composition and sintering conditions for different cermets’ systems was carried out to design novel composition and sintering conditions. Nano TiCN powder was prepared by 30 h of ball milling. The highest density of >98.5% was achieved for the SPS-processed cermets sintered at 1200 °C and 1250 °C for 3 min at 60 MPa of pressure in comparison to the conventionally sintered cermets at 1400 °C for 1 h with a two-stage compaction process—uniaxially at 150 MPa and isostatically at 300 MPa of pressure. Comparative X-ray diffraction (XRD) analysis of the milled powders at different time intervals was performed to understand the characteristics of the as-received and milled powders. Peak broadening was observed after 5 h of ball milling, and it increased to 30 hr. Also, peak broadening and a refined carbide size was observed in the XRD and scanning electron microscope (SEM) micrographs of the SPS-processed cermet. Transmission electron microscope (TEM) analysis of the milled powder showed that its internal structure had a regular periodic arrangement of planes. SEM base scattered electron (BSE) images of all the cermets primarily showed three major microstructural phases of the core–rim–binder with black, grey, and white contrast, respectively. With the present sintering conditions, a high hardness of ~16 GPa and a fracture toughness of ~9 MPa m1/2 were obtained for SPS-processed cermets sintered at higher temperatures.

Investigation on the interface bonding and reinforcement mechanism of nano Ti/AZ31 magnesium matrix composites

In this study, nano Ti/AZ31 composites were successfully prepared by powder metallurgy method, and the strength and plasticity of the composites were improved in both directions. The SEM shows that the Ti particles were evenly distributed at the grain boundary in the sintered composite, and the Ti particles pin the grain boundary to make the grain of the composite significantly refined. EBSD shows that the addition of nano Ti particles significantly reduces the texture strength of the composite and increases the starting probability of the slip system. TEM shows that nano Ti and AZ31 matrix formed stable Al3Ti and MgO phases at the interface, and shows a strong coherent relationship. The nanoindentation test shows that the Ti/AZ31 interface of the composite was stable, the interface bonding energy and interface fracture toughness were gradiently distributed, and the bonding energy and fracture toughness of the interface bonding area were better than those of the matrix. Tensile test shows that the 1.5 wt%Ti/AZ31 composite obtained the best comprehensive mechanical properties with yield strength, ultimate tensile strength and elongation of 143 MPa, 243 MPa and 11.5%, respectively, obviously higher than those of AZ31 alloys. The increased strength was mainly due to the grain refinement and strengthening at grain boundaries. The improved ductility was the result of weakened texture, increase of slip system start-up probability and strong interfacial bonding between Ti particles and AZ31 matrix.

Achieving well-balanced mechanical properties and oxidation resistance of an oxide dispersion strengthened nickel-based alloy via in-situ solid-state reaction

An oxide dispersion strengthened nickel-based alloy with balanced mechanical strength, ductility and oxidation resistance was prepared. Ni20Cr3Al and nano Ti powders were mechanically milled in an atmosphere of Ar+20%Air. Ti powder was partly oxidized to be TiO2 during the milling and spark plasma sintering. The others are dissolved into the nickel-based alloy and form coherent intermetallic phase of Ni3Ti. Owing to the higher affinity of Al than Ti to O, most TiO2 particles were transformed to be in-situ nano Al2O3 dispersoids with good coherency to the alloy matrix as well. Grain refinement and precipitates strengthening contribute largely to the greatly improvement of mechanical strength of the NiCrAl–2Ti alloy, of which the yield strength reaches 884 MPa and ductility is 10.72%. Besides, the refined grains promote the selective oxidation of Al, ensuring an extremely high oxidation resistance. Its oxidation rate constant (kp) is as low as 9.7 × 10−8 mg2 cm−4 s−1 at 900 °C.

Trace nano-Ti addition for graphene nanoplatelets/copper composites to simultaneously enhance strength-ductility and wear resistance

Graphene nanoplatelets (GNPs)/copper composites containing nano-Ti addition were prepared using the vacuum hot-pressing sintering process. The effect of Nano-Ti on microstructure and mechanical properties of GNPs/copper composite was investigated. Before the sintering of the composite powders, the massive nano-Ti particles decorated on the GNPs surface. The GNPs/Ti chemical reaction occurred during the sintering, and then formed abundant TiC particles. Hardness and strength of bulk GNPs/copper composites were enhanced evidently by nano-Ti addition, which increased with nano-Ti increasing. The nano-Ti addition achieved simultaneous strength-ductility enhancement of GNPs/copper composites. The hardness, tensile yield strength, ultimate tensile strength and tensile elongation of the composite with 3.0 wt% nano-Ti addition demonstrated respectively 128.2 %, 199.6 %, 125.9 %, and 30.6 % enhancement comparing with no nano-Ti added sample. The nano Ti addition can effectively improve the wear resistance of GNPs/copper composites. The relevant structural formation, strengthening-toughening and wear mechanisms of GNPs/copper composites with nano-Ti addition were discussed.

Enhanced thermoelectric performance of Sr0.875La0.1TiO3-δ based composites through Bi-rich inclusions in internal and external reduction environments

The electrical transport performance of bulk SrTiO3 thermoelectric materials can be optimized by incorporating uniformly dispersed conductive inclusions. Herein, the impact of Bi2O3 addition on the thermoelectric properties of La-doped strontium titanate composite nano Ti powder (Sr0.875La0.1TiO3-δ/20 wt% Ti) has been examined. During the sintering process, Bi2O3 gradually transforms into a liquid phase to facilitate Redox reactions with nano Ti and mass transfer, followed by reduction and transformation into Bi–Bi2O3 particles that precipitate at grain boundaries. The presence of nanoscale Bi-rich phases reduces carrier transport barriers at grain boundaries and enhances phonon relaxation time associated with grain boundary scattering. Ultimately, the sample containing 10 wt% bismuth oxide exhibits the lowest lattice thermal conductivity and the highest weighted mobility. This led to a maximum power factor of 498 μW/mK2 at 873 K and a maximum ZT value of 0.188 at 1073 K. This study presents a novel approach to decouple electroacoustic transport through the utilization of Redox reactions between multiple phases, offering valuable insights for the development of high-performance thermoelectric oxide composites.

Efficient degradation of dye wastewater by catalytic ozonation reactive ceramic membrane with facile spraying of nano Ti[sbnd]Mn oxides: A pilot scale attempt

The traditional treatments of dye wastewater exist obvious drawbacks of low efficiency but high energy consumption. To solve this problem, based on the concept of combining degradation and separation, an integrated process of TiMn oxides catalytic ozonation and ceramic membranes (CM) was proposed to degrade dye wastewater in this paper. Specifically, TiO2/MnO2 hybrid catalysts were loaded on the surface of CM with a spraying printing method to prepare a reactive ceramic membrane (TiO2/MnO2-CM). The degradation efficiency and permeate flux of the TiO2/MnO2-CM + O3 system on Rhodamine B (RhB) were investigated. The SEM results illustrated that the catalyst was successfully loaded on the surface of CM. Additionally, the degradation efficiency of RhB was 100 % in 40 min under the conditions of catalyst spray layers 12, ozone concentration 2.5 g/cm3, and initial concentration of RhB 20 mg/L, and the permeate flux of TiO2/γ-MnO2-CM was as high as 125.399 kg/ (m2·h). Supplementarily, the study revealed that TiO2/γ-MnO2-CM could increase the concentration of ozone in water and catalyze ozone to produce more hydroxyl radicals (•OH), and the concentration of dissolved ozone was 0.7545 mg/L, •OH 68.16 μmol/L respectively. Eventually, the catalytic ozonation TiO2/γ-MnO2-CM device was scaled up, which treated 96 L RhB with a degradation efficiency of 100 % in 50 min. The work gives a solid foundation and scientific value for the industrial application of reactive CM in water or wastewater treatment.

Solute segregation and nanoparticle dispersion induced super high stability in a bulk nanocrystalline W-based alloy

Improvement of the stability of nanocrystalline (NC) materials is always a challenge. In this paper, the high thermal stability is achieved in a representative NC W alloy by combining nano-segregation of Ti solute to W grain boundary (GBs), and in-situ formation of nano Ti–Zr–O particles, which provide both thermodynamic and kinetic stabilization effects through solute dragging and particle pinning. The recrystallization temperature of this bulk NC W alloy reaches up to 1600 °C, and these nanometric microstructures maintain stable under a long-time and high-temperature ordeal up to 1200 °C for 120 h. And its microhardness and micro-compressive yield strength are ∼17.0 and 5.14 GPa, respectively. In addition, this bulk NC W alloy has high irradiation stability due to the high densities of stabled GBs and phase boundaries. This work demonstrates the possibility of attaining high-stability bulk NC materials in terms of segregation of solutes at GBs and in-situ formation of ultrafine nanoparticles with a coherent interface with the W matrix.

Improving high-temperature wear resistance of NiCr matrix self-lubricating composites by controlling oxidation and surface texturing

• NiCr matrix composites with WS 2 as lubricant suffer severer wear degradation at high temperatures • NiCr-WS 2 -Ti composite with heterostructure is prepared by spark plasma sintering. • The composite NiCr-WS 2 -Ti exhibits low friction coefficient and high wear resistance at elevated temperatures • Ti is preferentially oxidized, forming abundant TiO 2 protrusions and constructing in situ a special surface texture. • By controlling oxidation and surface texturing, a protective glaze layer formed at surface, leading to excellent tribological properties Self-lubricating composites (SLCs) are widely used in the fields of aerospace and marine, but the conventional NiCr matrix SLCs with sulfide as solid lubricant often suffer from low wear resistance at high temperatures. In view of its high affinity with oxygen and also the high oxidation rate, appropriate amount of nano Ti was added to NiCr-WS 2 composites prepared by spark plasma sintering (SPS) to adjust the oxidation behavior and surface texture. When exposed to high temperature, Ti was preferentially oxidized in comparison to Ni and Cr, resulting in abundant TiO 2 protrusions and microdimples on the surface, i.e. in situ surface texturing. Besides, TiO 2 was of high chemical activity and readily to react with other oxide debris during high temperature sliding process to form compounds of NiTiO 3 and CrTi 2 O 5 . The high chemical activity of oxide debris that was conducive to sintering, combining with the special surface texture that stores as many wear debris as possible, promoted the rapid formation of a protective glaze layer on the sliding surface. The NiCr-WS 2 -Ti composite exhibited low friction coefficient but high wear resistance at elevated temperatures. Especially at 800 °C, it presented a wear rate of as low as (2.1±0.3) × 10 −5 mm 3 N −1 m −1 , accounting for only 2.7% of that of NiCr-WS 2 composite.

Effects of physical and chemical factors on the suppressant enhanced explosion parameter (SEEP) in flame propagation of metal dust layers

Adding solid inertants to metal dust is an effective means of reducing the risk of dust fires and explosions. However, inertants that can effectively suppress the metal dust deflagration could somehow violently enhance the fire hazard of the same metal dust layer. This severe risk has not been well recognized and discussed in depth. To investigate the physical and chemical factors that cause the SEEP phenomenon, flame propagation experiments on mixed dust layers were performed using three common metal dusts (Mg, micro Ti, nano Ti) and five commonly used inertants (NH4H2PO4, NaHCO3, CaCO3, SiO2, CaO). The results indicate that the physical factors were the vaporization of metal dust and the destruction of the oxide layer by the gas from the decomposition of inertants. The chemical factors behind SEEP were the exothermic chemical reaction of metal dust with inertants, and the combustion of the gases released by the decomposition of inertants. Both factors significantly increased the severity of a fire in the dust layers, and in some cases, the chemical factors increased the likelihood of an explosion. Regardless of physical or chemical factors, the mass percentage of inertants in the mixed dust layers that lead to SEEP has a relatively wide range. Therefore, research on the use of solid inertant technology to prevent or mitigate dust explosions should fully consider the physicochemical properties of metal dust. The results are supposed to be used as a comprehensive guide for selecting suitable inertants for metal dust to prevent fire and explosion incidents.

The Effect of the Parameters on Al 7075 Coated with MAO Method by Adding Nano Ti-Powder

Coating processes are carried out in many areas of industry to improve the surface properties of materials such as wear and corrosion resistance or appearance. One of these coating processes is ceramic-based surface coatings. In order to obtain harder, denser and more uniform coatings, the substrate material is coated with a ceramic-based material at the desired thickness. In this study, 7075 series aluminum was coated with nano Ti powder and non-additive micro arc oxidation (MAO) method in a solution consisting of KOH, NaAlO2 and Na3PO4, and the effects of process parameters on coating thickness and wear behavior were experimentally investigated and the results were analyzed. According to the results obtained, it was observed that as the coating voltage, frequency and coating time increased, the wear rate decreased and a harder structure against wear is obtained. In addition, it was determined that the samples with nano titanium powder were less worn than the non-additive samples. According to SEM, EDX and XRD analyses, Al2O3 phase was observed in the coatings made without adding titanium particles; It has been observed that in addition to the Al2O3 main phase, TiO2 and SiO phases are also formed in titanium doped coatings.

Corrosion behaviour of biomedical Ti under simulated inflammation: Exploring the relevance of grain refinement and crystallographic texture

This study provides an insight into the separate and combined effects of nanostructure and crystallographic texture on time-dependent Ti corrosion resistance under simulated inflammatory conditions. In order to achieve this objective, the following Ti products were fabricated by differential large plastic deformation methods: (i) nano Ti materials with virtually the same grain size but distinct crystallographic textures, and (ii) Ti materials with different microstructures but similar crystallographic textures. Overall, electrochemical and XPS studies revealed that the development of a basal texture component provides the most advantageous corrosion properties in terms of prolonged immersion in a simulated inflammatory environment.

Effect of space holder percent on the porosity biocompatibility of nano Ti foam by PM technique

Powder metallurgy (PM) approach was utilized for the preparation of Ti porous material mixed mechanically with different percentages of sodium chloride salt from 10 to 40 % with stirring speed 100 rpm and ball to powder ratio 10:1 for milling time 24 h. The Ti –NaCl mixed samples were compacted under 600Mpa, then sintered at 1450 ᴼC for 90 min in a vacuum furnace. The phase composition and microstructure of Ti samples are investigated through X-ray diffraction analysis and scanning electron microscope (SEM). All the prepared samples were characterized by measuring the porosity percentage, Vickers hardness, and compression strength. Microstructure indicated that porosity was found to increase with increasing salt percent while the highest hardness (380) and the compression strength (45MPa) were recorded for the lowest ratio of salt (10%NaCl). Biocompatibility test was estimated for the prepared samples, which exhibited the high viability for cell with good growth of the life cells on the sample’s surface, and low adhesion.

Interface design of lead-free free-cutting titanium reinforced graphite brass composites and its effect on mechanical properties and cutting performance

Graphite (Gr) is used as a substitute element for lead to avoid environmental pollution and human hazards due to its solid lubrication and chip breaking similar to lead in brass. However, the mechanical properties of brass would be reduced due to non-wetting and weak interfacial bonding between Gr and brass matrix. Based on the preparation of graphite brass composites by powder metallurgy (P/M), the strength of the matrix is expected to be enhanced by solution and precipitation strengthening of titanium (Ti), and the interface bonding between Gr and brass matrix is improved by interfacial reaction of Ti with Cu and Gr to form intermetallic compounds. The results show that the addition of Gr can significantly improve the cutting performance of brass, but it is at the expense of mechanical properties. With the introduction of Ti, the formation of submicron Cu2Ti4O particles and nano Ti clusters effectively improves the mechanical properties of brass matrix. Meanwhile, TiC reaction layer formed on the interface significantly strengthens the interfacial bonding between graphite and the matrix, which is the basis of ensuring the good cutting performance of brass. The original graphite/brass non-reactive interface is transformed into graphite/reaction layer/brass and brass/precipitates/brass dual-interface structure. This study lays a research foundation for the development of lead-free free-cutting brass composites.

A Catalytic Tar Reduction Methodology Gaseous Fuels

The exploitation of fossil fuels has led to the emerging of gaseous fuel for the automobile engines. The researchers are in the search of producer gas from forest woods. In the process of bio gasification, tar is the major obstacle to produce high efficiency gaseous fuel. In this research work, a catalytic tar mitigation process is framed with nickel (Ni) based catalyst. The Ni based nano Si and Ti catalysts are synthesized using deposition-precipitation method. The synthesized Ni-Si and Ni-Ti catalysts are characterized using scanning electron microscope (SEM) and transmission electron microscope(TEM). The surface area and pore volume are calculated by Brunauer-Emmett-Teller and Barrett-Joyner- Halenda methods to justify the catalytic active surface. A design of experiments (DoE) is framed with L12 design table for the 2 level factors (catalyst, catalyst weight, bed temperature and gas feed rate) for the tar concentration response. The signal to noise (SN) ratio and mean of the factors are analysed to identify the significance. As the outcome of the statistical analysis, it is concluded that the minimum tar concentration of 0.47(mg/Nm3) is attained for the 10% of Ni-Si catalyst with the bed temperature of 800ï‚°C and gas feed rate of 0.01 l/s.

Titanium enhanced ignition and combustion of Al/I2O5 mesoparticle composites

Aluminum (Al) is widely used in thermites, and iodine pentoxide (I2O5) is a strong oxidizer that can release gas phase iodine. The result is a potentially very powerful and effective energetic composite with biocidal properties. However, the alumina coating on the Al presents a diffusion barrier that increases the ignition temperature. In this paper, nano titanium powders (nTi) were added at various mass ratios to Al/I2O5 and a composite mesoparticle was assembled by electrospray. Combustion studies showed that nano Ti can enhance the reactivity of Al/I2O5 thermites significantly with increases in pressure, pressurization rate and dramatic decreases in burn time. Part of this behavior can likely be attributed to less sintering enhancing the completeness of reaction in the Ti added cases. Addition of titanium to aluminum was found to have a significant impact on ignition and when Al is replaced with Ti, the ignition temperature was ∼300 °C below that of the corresponding aluminum thermite. These results show that titanium can be used as a fuel to tune energetic behavior and iodine release temperature and in some ways superior to aluminum.

Effect of solid inertants and sample inclination angle on fire hazard of metallic powder layers

Compared to non-metallic powders, metallic powders usually have a greater layer fire hazard because of high flame temperatures. In this paper, the effects of solid inertants and sample inclination angle on the fire hazard of three metallic powder (iron, titanium, and magnesium) layers were investigated. Flame spread velocity (FSV) was mainly dependent on the particle size and enthalpy of combustion of metallic powders. For example, FSV of iron powders jumped from 0.4 to 4.7mm/s when the particle size decreased from micro scale to nano scale. The FSV of micro Ti powder layers reached 12.8mm/s, which was much higher than the value (1.7mm/s) for micro Mg powder with similar particle size. Inclination angle significantly influenced the FSV of nano Ti powder because of a long flame length resulting from a predominantly homogeneous reaction. For other tested powders, sample inclination angle had little effect on FSV because of a short flame length resulting from a predominantly heterogeneous reaction. Addition of small amounts of solid inertant decreased the layer fire hazard of iron and titanium powder with high melting points, while increasing the fire hazard of magnesium powder because of its low melting point. The melting characteristics of metallic powders should be considered when preventing or mitigating fire hazard using solid inertant technology.

Development of High Performance (Mechanical and Wear Properties) of AA 6061-Hybrid Nano Composites Via Liquid Metallurgy Route

This research is devoted to study the influence of different weight percent concerning to the additions of Ti and Cu on mechanical and tribological properties of AA6061. The composite materials consist of different weight percentage of Ti (0.2, 0.4, and 0.6) wt% and constant weight percentage of Cu (0.2) wt% which were fabricated by liquid metallurgy route technique. Microstructural characterization and phases have been examined by using SEM (scanning electron microscopic).SEM examination showed uniform distribution of nano Ti and Cu in AA6061. The consequences of mechanical tests demonstrated clear enhancement in mechanical properties, such as ultimate tensile strength, yield strength, young modulus, ductility% and hardness at additive percentage of 0.4% Ti+0.2%Cu nano particles incorporated into molten AA6061. Percentage of enhancement ultimate tensile strength is about 73.3%, yield strength about 82.7%, young modulus is about 21.2%, the Vickers hardness about 42.6% and the decreasing in ductility was about 25.2% compared with the metal matrix (AA6061). The wear rate test was performed by using pin on disc rig for both hybrid nano composite and base metal (AA6061) under various loads (10,15and 20) N with sliding speed (1.282) m/sec at a (10) min’s time. The results showed a decrease in wear rate at 0.4%Ti+0.2%Cu compared with the base metal (AA6061). Improvement percentage of wear rate is about 105% at 20 N load.

Kinetics and evolved gas analysis of the thermo-oxidative decomposition for neat PPS fiber and nano Ti–SiO2 modified PPS fiber

Using isoconversional methods and model-fitting methods, the non-isothermal thermo-oxidative decomposition kinetics of the nano Ti–SiO2 modified PPS fiber (AO-PPS) and neat PPS fiber are investigated. Decomposition processes of both PPS fibers can be differentiated into two stages with totally different mechanisms. Using the Málek method combined with residual sum of squares, the most probable mechanism model of the first stage is derived, which belongs to the deceleration α-t curve and the integral form is g(α) = (1-α)−1-1. Thermo-oxidative decomposition processes of the second stage are the aggregation of many complicated reactions, which cannot be expressed through the simple, single kinetic mechanism. Evolved gas analysis of both PPS fibers gives an insight of the mechanism of the thermo-oxidative decomposition processes. The main reactions of the first stage involve the breaking of the phenyl-S bonds and the cross-linking of remaining molecules. The multiple complex reactions in the second stage verify the kinetic analysis of the mechanisms.

Ignition hazard of titanium powder clouds exposed to hotspots

Hotspots (overheated contact components) generated by machinery malfunction serve as an effective ignition source, contributing to almost 12% of dust explosion accidents worldwide, and pose a significant hazard for metallic powder manufacturing. The minimum ignition temperature of hotspots (MITH) of micro and nano Ti powder was only 586 °C and 225 °C, respectively. Admixing of TiO2 powder decreased the ignition hazard of micro Ti powder exposed to hotspots, but was less effective for solid inerting of nano Ti powder. Even with 80% nano TiO2 powder, the MITH of nano Ti/TiO2 mixtures was still less than 500 °C. Mixtures containing nano TiO2 powder prolonged the ignition delay time of micro Ti powder. Upon ignition by hotspots, pulsating flames occurred for micro or nano Ti powder clouds, and the flame spread velocity (FSV) of nano Ti powder was far greater than that of micro Ti powder. A small amount (e.g., 10%) of TiO2 increased the dispersibility of micro and nano Ti powders, thereby enhancing FSV values. Nano TiO2 percentages of at least 50% and 90% were required to completely suppress propagation of micro and nano Ti flames, respectively.

Microwave synthesis of nano Ti(C, N)-Ni powders in air from melamine

Ti(C, N)–Ni cermet powders were rapidly synthesized, primarily from anatase-TiO2 and melamine, by microwave assisted carbothermal reduction-nitridation (MWCRN) at a low temperature in air. The phase evolution of the MWCRN reaction was investigated using X-ray diffraction (XRD) and the microstructure of the produced powders was observed using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystal structure of Ti(C, N)–Ni cermet powders was analyzed by transmission electron microscopy (TEM). Ti(C, N) began to form in the product, and NiO was reduced to Ni at 1000 °C. During the reaction process, Ti(C, N) was formed in the sequence of TiO2, Ti3O5 and Ti(C, N). With melamine as a nitrogen source and a component of the carbon source, the decomposition temperature is low and the reaction process is fast. The nitrogen atmosphere in which it is pyrolyzed also acts as a protective atmosphere to ensure orderly progress of the reactions. In summary, pure Ti(C, N)–Ni cermet powders, with a grain size of less than 100 nm, were synthesized from metal oxides and melamine by the MWCRN reaction at 1400 °C for 10 min in air.