Titanium Powder Research Articles

Research on structure and technological parameters of multi-channel cold spraying nozzle

Cold spraying technology is a method to obtain coating by the high-speed collision of particles with the substrate through supersonic (300–1200 m/s) propulsion gas. The deposition process is mainly mechanical bonding, which has attracted more and more attention in engineering applications. The critical component of a cold spraying system is the nozzle. The performance of the nozzle directly affects the quality of the material surface coating. Therefore, the discussion of the nozzle is of great significance. At present, there are many examples of cold spraying single-channel nozzles in engineering, but there are few reports about multi-channel cold spraying nozzles. This paper explores and studies the multi-channel cold spraying nozzle, designs a special three internal channel nozzle, and adopts a 90° angle in the divergent section of the nozzle. When spraying in a small area, the nozzle with angle has apparent advantages for spraying more areas. The powder injection pressure, particle size, recovery coefficient, and internal channel position are analyzed, which affect the particle trajectory. Combined with these factors, the multi-channel nozzle is optimized and improved to solve the problem of particle collision with the inner wall of the nozzle. Finally, the technological parameters of aluminum, titanium, copper, nickel, magnesium, and zinc powders are preliminarily studied using the multi-channel nozzle. The results show that the multi-channel nozzle meets the critical velocity requirements of copper, magnesium, and zinc powder spraying in the homogeneous (powder and matrix are the same material) and aluminum powder spraying in the case of heterogeneous (powder and matrix are different materials), the multi-channel nozzle has a sound engineering application prospect and provides a specific reference for relevant technicians.

Discrete One-Stage Mechanochemical Synthesis of Titanium-Nitride in a High-Energy Mill

Discrete (discontinuous) mechanochemical synthesis of titanium nitride was experimentally investigated. The experimental results show that mechanical activation intensifies the chemical conversion in the Ti-N system, and the discrete synthesis of the final product is conducted under “soft” controlled conditions without high heat release. The new theory of mechanochemical synthesis and the mathematical model based on it were used for theoretical evaluation of the dynamics of titanium activation in the nitrogen medium. It was found that the discrete mode of synthesis includes two factors accelerating mechanochemical reactions in the Ti-N synthesis: structural (grinding of metallic reagent and formation of interfacial areas) and kinetic (accumulation of excess energy stored in the formed structural defects in metallic reagent). The kinetic constants of the process were found using experimental data and the inverse problem method. The diagrams defining the controlled modes of obtaining titanium nitride particles with the given characteristics were constructed. A mathematical model for theoretical estimation of the dynamics of activation of titanium powder in the nitrogen medium was developed using a new macrokinetic theory of mechanochemical synthesis.

Laser Surface Modification of Powder Metallurgy-Processed Ti-Graphite Composite Which Can Enhance Cells' Osteo-Differentiation.

The paper examines the surface functionalization of a new type of Ti-graphite composite, a dental biomaterial prepared by vacuum low-temperature extrusion of hydrogenated-dehydrogenated titanium powder mixed with graphite flakes. Two experimental surfaces were prepared by laser micromachining applying different levels of incident energy of the fiber nanosecond laser working at 1064 nm wavelength. The surface integrity of the machined surfaces was evaluated, including surface roughness parameters measurement by contact profilometry and confocal laser scanning microscopy. The chemical and phase composition were comprehensively evaluated by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analyses. Finally, the in vitro tests using human mesenchymal stem cells were conducted to compare the influence of the laser processing parameters used on the cell’s cultivation and osteo-differentiation. The bioactivity results confirmed that the surface profile with positive kurtosis, platykurtic distribution curve and higher value of peaks spacing exhibited better bioactivity compared to the surface profile with negative kurtosis coefficient, leptokurtic distribution curve and lower peaks spacing.

The effect of functionalized titanium dioxide nanotube reinforcement on the water sorption and water solubility properties of flowable bulk-fill composite resins

The aim of this study was to investigate the effects of titanium dioxide nanotube addition on the water sorption and water solubility values of different composite resins. Titanium dioxide nanotubes were synthesized from titanium dioxide powder in anatase form and in 13nm diameter by hydrothermal process and then functionalized with methacrylic acid. Characterization of the nanotubes was performed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction and Fourier transform infrared spectroscopy. A flowable composite resin (Filtek Ultimate Flowable) and four flowable bulk-fill composite resins (Filtek Bulk Fill Flowable, SDR Bulk Fill Flowable, Venus Bulk Fill, X-tra Base) were tested. Two groups of each composite resin were prepared: groups of the resins without nanotubes; groups of the resins reinforced with 1.0 wt% functionalized titanium dioxide nanotube. Sorption and solubility in water were assessed according to ISO 4049 standards after 1, 7, 14, 21days immersion periods. Data were analyzed using Mann-Whitney U and Kruskal-Wallis H tests (p < 0.05). Long cylindrical tubular structures with a diameter of 41.09-72.49nm were observed in electron microscopy analysis. The band at 1636cm - 1 showed the existence of the vinyl (C=C) bond of methacrylic acid coordinated to the nanotubes in Fourier transform infrared spectroscopy analysis. None of the materials tested in this study exceeded the maximum sorption and solubility values established by ISO. Regarding the water solubility, negative values were obtained. TiO2 nanotube reinforcement decreased the water sorption and solubility values significantly at different evaluation periods in all composite resins except for Venus (p < 0.05).

Effects of nano-sized titanium dioxide powder and ultraviolet light on superficial veins in a rabbit model.

Titanium dioxide (TiO2) is widely used in many fields such as food, cosmetics, and paper industries. Studies on the photocatalytic properties of TiO2 on living tissue are limited. To examine the histopathological effects of TiO2 solution on the marginal veins of rabbit ears under ultraviolet (UV) light. In this study, 4 groups of rabbits (8 rabbits per group) were used: the 1st group was the control group, the 2nd group received 20% of nano-TiO2 only, the 3rd group received UV light only, and the 4th group received nano-TiO2 and UV light, simultaneously. The study lasted for 14 days and samples were taken from the marginal ear vein on the 15th day. The ear tissues of rabbits in the control and TiO2 groups showed a normal histological appearance. In the UV group, the results showed severe chronic inflammation due to mononuclear cells around the hair follicles and perivascular areas. However, these findings decreased in the UV/nano-TiO2 group. The method applied in this study can be used in the treatment of telangiectasia in the future. However, this study investigating the effects of nano-TiO2 on vascular structures under UV light had a predominantly histological and observational nature. Further studies involving genetic, cytogenetic, biochemical, histochemical, and immunohistochemical analyses need to be performed to test the theories we proposed.

Numerical and experimental determination of optical properties and thermal conductivity of ceramic composites based on fumed silica and silica fiber

The thermal insulation material composed of fiber-reinforced fumed silica (in the raw and opacified with silicon carbide, zirconia or titania powders) was produced and analyzed. Optical properties (scattering and absorption coefficients) were experimentally examined in the spectral range of 0.9 – 4.7 µm by the solution of the inverse problem of radiative transfer. The inverse problem was based on the invariant embedding equation and the measured spectral directional-hemispherical reflectance. The effect of silicon carbide opacifier addition on the optical properties, effective and radiative thermal conductivity was estimated. The calculated radiative thermal conductivity of thermal insulations with various volume fractions of SiC opacifier was compared to the one deduced from the effective thermal conductivity using the calorimetric technique of conductive and radiative components separation. The effective thermal conductivity was measured by the quasi-stationary technique in the temperature range of 373 – 1173 K. The results of the inverse problem solution were compared to the calculations based on the Mie theory and the measured size distribution of silicon carbide particles. The experimental scattering coefficient was shown to be smaller than the calculated one. At the same time, absorption coefficients demonstrated mutual consent. Possible uncertainties in SiC powder size and the complex refractive index of the basic material were considered as a probable explanation of the obtained results. The size distribution of SiC opacifier was numerically optimized to obtain as low Rosseland mean radiative thermal conductivity as possible. The influence of the opacifier chemical composition was analyzed by collating radiative thermal conductivity deduced from the measured effective thermal conductivity to ones calculated using Mie theory. Finally, the effect of Fe2O3, Si3N4, TiO2, graphite, ZrO2, TiN, TiC, AlN opacifiers was numerically analyzed using Mie theory. Compounds based on titanium and an iron sesquioxide were shown to be promising opacifiers for high temperature applications.

Effect of powder loading on plasma spheroidization of hydride-dehydride titanium powders

Spherical titanium particles have been produced from hydride-dehydride titanium raw powders using an inductively coupled plasma spray system. Taking into account the variously modified particle morphologies with different plasma conditions, the effect of powder loading on spheroidization was quantified and evaluated in terms of the altered particle heating capabilities. The averaged particle heat transfer coefficient was found to vary with powder feeding rate and associated strongly with Ar–H2 gas thermal conductivity. Furthermore, there observed a most efficient particle heating condition for each powder feeding rate, but the efficient heating condition tends to vaporize small raw powders and increase the overall oxygen content unintentionally as a result of the attachment of satellites nanoparticles on spherical particles. It is therefore important that the plasma input power is optimally controlled with particular attention to the altered degree of heat transfer especially for the case of small powder injection.

Analyzing coarsening versus densification phenomenon present in partial sintering of Al2O3/TiO2 composites

Alumina–titania (Al2O3/TiO2) composites are well-known for their physical and microstructural properties, which allow several engineering applications. However, these properties change when different sintering temperatures are used, due to the existence of two antagonistic phenomena (grain coarsening versus densification) that occurs during sintering process. The aim of this study was to evaluate the microstructural and physical properties of the alumina–titania composites and to understand these two antagonistic phenomena when different partial sintering temperatures are used. The composites were prepared from alumina and titania powders by uniaxial pressing and sintered at different temperatures (1100–1400 °C). The structural analysis showed that in addition to expected phases (α-Al2O3 and rutile), the alumina–titania composite sintered at 1100 °C presents anatase phase, while those obtained at 1300 and 1400 °C present tialite phase. The morphology analysis revealed a random distribution of grains with irregularly shaped pores. According to the Archimedes-based immersion test, all composites have a relative bulk density ranging 60.43–73.59%, showing that none of them reached the final sintering stage. Statistical analysis revealed that the average grain size of the matrix ranges from 3.62 to 5.24 μm. Moreover, the statistical analysis also showed that the grain coarsening predominates over densification for the composites sintered from 1100 to 1150 °C. The densification predominates over grain coarsening for the composites sintered from 1150 to 1200 °C, and from 1250 to 1400 °C. The two phenomena coexist only for the composites sintered from 1200 to 1250 °C.

Study on the effect and mechanism of Ca(H2PO4)2 and CaCO3 powders on inhibiting the explosion of titanium powder

In this paper, the experiment of titanium powder explosion was carried out by using Hartmann and 20-L spherical explosion tank. The inhibition effect of different proportions of Ca(H2PO4)2 and CaCO3 powders on titanium powder explosion was studied, and the inhibition mechanism of inhibitor on titanium powder explosion was analyzed. The experimental results show that with the increase of the proportion of inhibitors, the flame brightness becomes darker, the propagation velocity and distance decrease gradually, and the Pex and (dp/dt)ex decrease gradually. When 80% Ca(H2PO4)2 and CaCO3 were added, the average flame propagation speed decreased to 0.59 m/s and 1.08 m/s, respectively, and decreased by 87.7% and 77.4%; the Pex decreased to 0.152 MPa and 0.206 MPa, respectively, and decreased by 80% and 72.9%. The results show that both Ca(H2PO4)2 and CaCO3 have certain inhibition effect on titanium powder explosion, and the inhibition effect of Ca(H2PO4)2 is better.

Role of Ti3AlC2 MAX phase on characteristics of in-situ synthesized TiAl intermetallics. Part I: sintering and densification

Five TiAl–Ti3AlC2 composite samples containing (10, 15, 20, 25 and 30 wt% Ti3AlC2 MAX phase) were prepared by spark plasma sintering technique at 900 °C for 7 min under 40 MPa. For this purpose, metallic titanium and aluminum powders (aiming at the in-situ formation of the TiAl matrix phase) were ball-milled with predetermined contents of Ti3AlC2 MAX phase, which already was synthesized using the same metallic powders as well as graphite flakes. Displacement-time-temperature variations during the heating and sintering steps, displacement rate versus temperature, displacement rate versus time, and densification behavior were studied. Two sharp changes were detected in the diagrams: the first one, ~16 min after the start of the heating process due to the melting of Al, and the second one, after ~35 min because of the sintering progression and the applied final pressure. The highest relative densities were measured for the samples doped with 20 and 25 wt% Ti3AlC2 additives. More Ti3AlC2 addition resulted in decreased relative density because of the agglomeration of MAX phase particles.

Experimental and Numerical Investigations of Titanium Deposition for Cold Spray Additive Manufacturing as a Function of Standoff Distance

In this research, the cold spray process as an additive manufacturing method was applied to deposit thick titanium coatings onto 7075 aluminium alloy. An analysis of changes in the microstructure and mechanical properties of the coatings depending on the standoff distance was carried out to obtain the maximum deposition efficiency. The process parameters were selected in such a way as to ensure the spraying of irregular titanium powder at the highest velocity and temperature and changing the standoff distance from 20 to 100 mm. Experimental studies demonstrated that the standoff distance had a significant effect on the microstructure of the coatings and their adhesion. Moreover, its rise significantly increased the deposition efficiency. The standoff distance also significantly affected the coating microstructure and their adhesion to the substrate, but did not cause any changes in their phase composition. The standoff distance also influenced the coating porosity, which first decreased to a minimum level of 0.2% and then increased significantly to 9.8%. At the same time, the hardness of the coatings increased by 30%. Numerical simulations confirmed the results of the tests.

Accuracy of a titanium maxillary complete denture baseplate fabricated by using the electron beam melting technique: An in vitro study

Statement of problemElectron beam melting (EBM) is a promising additive manufacturing technique for fabricating denture baseplates; however, studies evaluating its accuracy are sparse. PurposeThe purpose of this in vitro study was to compare the fit accuracy of titanium maxillary complete denture baseplates fabricated by using the EBM technique with those fabricated by using the conventional casting technique and to evaluate the dimensional accuracy of the EBM baseplate by using a 3-dimensional inspection software program. Material and methodsDefinitive casts of an edentulous maxilla were prepared. After the casts were optically scanned, computer-aided designs for the EBM baseplate were created by using a software program for standard tessellation language file editing. The EBM baseplates were fabricated with an EBM machine by using a Grade II titanium powder as the raw material. The cast baseplates were fabricated with a lost-wax casting technique by using refractory casts duplicated from the definitive casts. After fitting the EBM and cast baseplates to their corresponding definitive cast, they were embedded in a Type IV stone. The embedded baseplates on the casts were sectioned at 3 regions: posterior palatal seal, molar, and premolar. The maximum gaps between the baseplate and definitive cast were measured in these 3 regions. The virtual casts obtained by scanning the EBM baseplate were superimposed on the computer-aided design to evaluate the dimensional accuracy. Distribution color maps were then generated, and the mean absolute deviations and root mean square deviations were calculated. One-way analysis of variance and t tests were used for statistical analysis (α=.05). ResultsNo significant differences in the maximum gaps among the 3 regions were found in the cast or EBM baseplate groups (P>.05). The EBM baseplate group showed significantly lower values than the cast baseplate group in all regions (premolar: P=.008; molar: P=.003; posterior palatal seal: P=.004). The mean maximum gap for the 3 regions in the cast baseplates was 168.0 μm and that in the EBM baseplates was 60.7 μm. The distribution color map of the EBM baseplate showed a favorable dimensional accuracy. The mean absolute deviation value was 19.7 μm, and the root mean square deviation value was 25.1 μm. ConclusionsThe EBM baseplates had a significantly higher fit accuracy than the cast baseplates. Thus, the fit accuracy of the EBM technique is suitable for fabricating metal baseplates.

Influence of high-temperature annealing on structure of titanium aluminide materials obtained by combustion and high-temperature shear deformation

A compact material based on initial powders of titanium and aluminum (porosity <1%) was obtained by unrestricted SHS-compression. This method combines combustion processes in the mode of self-propagating high-temperature synthesis (combustion temperature – 1460 °C, combustion front propagation – 3.7 mm/s) and high-temperature shear deformation. The obtained material structure and phase composition were studied. The high-temperature shear deformation was shown to lead to textured structure of the material which consisted of alternating intermetallic phases in the following sequence: α2-Ti3Al, γ-TiAl, TiAl2 и TiAl3. Influence of high-temperature annealing at T = 1000 °C during 0.5–4 h on the material structure and phase composition was studied.

Effect of mechanical activation and combustion parameters on titanium carbide SHS compaction

The paper presents the results of a study on the dense titanium carbide production by SHS compaction. It is shown that the use of a mechanically activated reaction mixture of titanium and carbon black powders makes it possible to obtain titanium carbide samples with a maximum relative density of 95 %. A feature of this research is that the mechanical activation of components and Ti + C mixture stirring were carried out in a ball mill. The study covers the influence of process parameters on the combustion properties and structure of the consolidated titanium carbide. It was found that the high-speed reaction mixture combustion is an essential condition for dense titanium carbide production. It was shown that the burning rate and temperature strongly depend on the size, mass and density of charge compacts. With an increase in the diameter (20–58 mm) and weight (10–70 g) of compacts made of mixtures with activated reagents, the burning rate varied from 10 to 100 cm/s, and the burning temperature varied from 2200 to 3100 °C. An influence of the pre-pressing pressure (applied at the combustion stage) on the burning rate and temperature was shown: the burning rate sharply decreases from 100 to 10 cm/s at pressures between 0 and 10 MPa, and the combustion temperature decreases monotonically from 3000 to 2000 °C at pressures between 0 and 40 MPa. A high-speed combustion mechanism was proposed for the titanium and carbon black reaction mixture where the formation of radial (longitudinal) cracks in compacts pressed from the mechanically activated mixture is an important factor. These cracks ensure the propagation of incandescent impurity gases and the exothermic reaction initiation in the sample volume.

ANTIMICROBIAL BIODEGRADABLE PACKAGING FOR SLICED BAKERY

In the modern minds of the advanced ecology and safety of food products control, it is relevant the development of antimicrobial biodegradable packaging. The article presents the results of the antagonistic action of nanodispersed titanium dioxide powder (TiO2) at the warehouse of biodegradable packaging for bakery products on the living of microorganisms (Escherichia сoli, Bacillus subtilis, Candida albicans, Aspergillus niger). It is known there are developments on the use of antimicrobial substances of both organic and inorganic origin, the microbiological action of the substances used have an effect on pathogenic, opportunistic, fungi, gram-negative and gram-positive bacteria. We found that the introduction of 1% TiO2 r into the molding solution allows to give the package antibacterial properties, as it inhibits the development of Escherichia coli and Bacillus subtilis, as there is a delay in the growth of their colonies compared to the sample without packaging with TiO2. According to the results of provocative testing, biodegradable packaging with a content of 1% TiO2 has an inhibitory effect on Bacillus subtilis. In addition to antimicrobial properties, the package under study must also have barrier properties, so the vapor permeability of the presented package was determined. The study results show that the addition of 1% TiO2 slightly reduces the vapor permeability, but the increase in the concentration 2–5% of TiO2 causes an increase in vapor permeability from 4.7 to 5.2 mg / (m∙h∙kPa). The vapor permeability of the presented biodegradable antimicrobial packaging is due to the presence of pores, the number and size of which were determined experimentally. Thus, nanodispersed TiO2 in the amount of 1% in the molding solution of the biodegradable coating is an effective antimicrobial component for antimicrobial coatings, which does not impair their barrier properties.

Evaluation and parameter analysis of compaction equations applied to titanium powder

ABSTRACT Titanium is widely used in the fields of medicine, industry, and biological science due to its excellent properties. In addition, titanium powder metallurgy (PM) is widely used in production because it could considerably reduce the cost. The most critical step in PM is powder compaction. Thus, the compaction equation is highly important in the prediction and analysis of powder compaction process. In this paper, the experimental data of titanium hydride powder and hydrogenated-dehydrogenated titanium powder were fitted using different compaction equations, and all the equations could obtain a high fitting degree (R 2 > 0.99) and a small error. The linear compaction equation could distinguish the powder type and different particle size distribution forms in the same type of powder through fitting parameters. The nonlinear compaction fitting equation could also analyse the contribution of powder densification mechanism through parameter calculation.

Synthesis of Ti Powder from the Reduction of TiCl4 with Metal Hydrides in the H2 Atmosphere: Thermodynamic and Techno-Economic Analyses

Titanium hydride (TiH2) is one of the basic materials for titanium (Ti) powder metallurgy. A novel method was proposed to produce TiH2 from the reduction of titanium tetrachloride (TiCl4) with magnesium hydride (MgH2) in the hydrogen (H2) atmosphere. The primary approach of this process is to produce TiH2 at a low-temperature range through an efficient and energy-saving process for further titanium powder production. In this study, the thermodynamic assessment and technoeconomic analysis of the process were investigated. The results show that the formation of TiH2 is feasible at low temperatures, and the molar ratio between TiCl4 and metal hydride as a reductant material has a critical role in its formation. Moreover, it was found that the yield of TiH2 is slightly higher when CaH2 is used as a reductant agent. The calculated equilibrium composition diagrams show that when the molar ratio between TiCl4 and metal hydrides is greater than the stoichiometric amount, the TiCl3 phase also forms. With a further increase in this ratio to greater than 4, no TiH2 was formed, and TiCl3 was the dominant product. Furthermore, the technoeconomic study revealed that the highest return on investment was achieved for the production scale of 5 t/batch of Ti powder production, with a payback time of 2.54 years. The analysis shows that the application of metal hydrides for TiH2 production from TiCl4 is technically feasible and economically viable.

Optical properties degradation of wollastonite powders under the electron irradiation in vacuum

The study on grain size distribution, phase composition, diffuse-reflectance spectra (ρλ), and integral absorption coefficient has been provided. In addition, the properties of wollastonite powders were examined after the irradiation with 30 keV electrons with recording ρλ spectra before and after each irradiation period in vacuum at the irradiation site (in situ). High powder reflectance has been determined, which provides a small value of absorption coefficient (аs = 0.11). It has been shown that optical properties degradation is determined mainly by UV radiation absorbing defects, the most probable among them being anionic vacancies. ρλ spectra are modified to a smaller extent while irradiating in the visible spectrum. The powder under analysis exceeds titanium dioxide powders, which are widely used as pigments for dyes and spacecraft reflective coatings, by the value of initial optical properties and their post-irradiation changes.

Tuning Ligand-Coordinated Single Metal Atoms on TiO2 and their Dynamic Response during Hydrogenation Catalysis.

Invited for this month's cover is the group of Steven Tait at Indiana University. The image shows single metal atoms stabilized by small molecules on a titanium dioxide powder support that are active in catalyzing ethylene hydrogenation. The Full Paper itself is available at 10.1002/cssc.202100208.

Multiphysics Modeling of Thermal Behavior of Commercial Pure Titanium Powder During Selective Laser Melting

Multiphysics Modeling of Thermal Behavior of Commercial Pure Titanium Powder During Selective Laser Melting