Oxygen In Solid Solution Research Articles

Novel nano-thin amorphous Ta-coating on 3D-printed porous TC4 implant: Microstructure and enhanced biological effects

Bone defects caused by tumors, trauma, or other bone diseases are common in clinical practice. Titanium alloy (TC4) and tantalum (Ta) are the primary metallic materials for bone repair. However, TC4 frequently suffers from poor osseointegration and implant loosening, while the high cost of Ta limits its widespread use for reconstructing large bone defects. To address this issue, this research employs magnetron sputtering (MSP) to deposit a nano-thin amorphous Ta-coating on the 3D-printed TC4 implant. SEM examinations of compressed samples show robust interfacial bonding without shedding, while the presence of Ta within the porous structure indicates high coverage. High-resolution TEM analysis first reveals a distinct multilayer amorphous zone consisting of surface TaOx, Ta-coating, and hybrid TaOx and TiOx, along with an impact-refinement nanocrystalline TC4 zone. Insufficient energy leads to the formation of amorphous layers. Meanwhile, interfacial bonding is strengthened through the solid solution of oxygen and interfacial densification of amorphous-crystalline bonding and impact compression. Biological evaluations demonstrate that the Ta-coating exhibits superior cell proliferation and bone ingrowth effects compared to TC4 and pure Ta implants, primarily attributed to the amorphous oxide composition on the surface. This study offers novel, cost-efficient, and excellent biological performance materials for bone defect implants.

On the Microstructure and Properties of Complex Concentrated bcc Solid Solution and Tetragonal D8m M5Si3 Silicide Phases in a Refractory Complex Concentrated Alloy

In this work, the refractory complex concentrated alloy (RCCA) 3.5Al–4Cr–6Ge–1Hf–5Mo–36Nb–22Si–1.5Sn–20Ti–1W (at.%) was studied in the as cast and heat treated conditions (100 h or 200 h at 1500 °C). There was strong macrosegregation of Si in the 0.6 kg button/ingot of the cast alloy, in which A2 solid solution, D8m βNb5Si3, C14-NbCr2 Laves phase and Tiss and a ternary eutectic of the A2, D8m and C14 phases were formed. The partitioning of Ti in the as cast and heat treated microstructure and its relationships with other solutes was shown to be important for the properties of the A2 solid solution and the D8m βNb5Si3, which were the stable phases at 1500 °C. The near surface microstructure of the alloy was contaminated with oxygen after heat treatment under flowing Ar. For the aforementioned phases, it was shown, for the first time, that there are relationships between solutes, between solutes and the parameters VEC, Δχ and δ, between the said parameters, and between parameters and phase properties. For the contaminated with oxygen solid solution and silicide, trends in relationships between solutes, between solutes and oxygen content and between the aforementioned parameters and oxygen content also were shown for the first time. The nano-hardness and Young’s modulus of the A2 solid solution and the D8m βNb5Si3 of the as cast and heat-treated alloy were measured using nanoindentation. Changes of nano-hardness and Young’s modulus of the A2 solid solution and D8m βNb5Si3 per solute addition for this multiphase RCCA were discussed. The nano-hardness and Young’s modulus of the solid solution and the βNb5Si3, respectively, were 9.5 ± 0.2 GPa and 177.4 ± 5.5 GPa, and 17.55 ± 0.5 GPa and 250.27 ± 6.3 GPa after 200 h at 1500 °C. The aforementioned relationships and properties of the two phases demonstrated the importance of synergy and entanglement of solutes, parameters and phases in the microstructure and properties of the RCCA. Implications of synergy and entanglement for the design of metallic ultra-high temperature materials were emphasised.

Optimized mechanical properties of titanium-oxygen alloys by powder metallurgy

Oxygen solid solution-strengthened titanium-oxygen (Ti–O) alloys with ultrahigh yield strength and large ductility were designed and synthesized via high-energy ball milling (BM) combined with spark plasma sintering (SPS) in compression. The morphology, dispersion state, and solid solution microstructure of the Ti–O alloys were optimized by regulating the mixing method, sintering temperature, and added oxygen content. Outstanding properties that include a compressive yield strength of 1220 MPa and large ductility of 36.3% were achieved after 1 h high-energy BM and 1000 °C SPS with the addition of about 1.8 at% oxygen. The grain refinement and oxygen solid solution strengthening indicate that the dense morphology, refined grain size, and oxygen solid solute atoms are responsible for the balance between the superior strength and ductility of the titanium alloys.

Enhancing strength and ductility of pure titanium by interstitial oxygen atoms

Pure titanium is an ideal material for tissue replacements and implant materials for its superior biocompatibility and corrosion resistance, but its limited strength remains a major obstacle to its wide applications. A promising strategy for enhancing the strength is to alloy the pure titanium with oxygen. Herein, we reported an oxygen solid solution strengthening for pure titanium by achieving a titanium-oxygen (Ti–O) alloy using ball milling (BM) and spark plasma sintering (SPS). The effect of oxygen contents, ranging from 0.33 to 2.08 wt%, on the mechanical properties of pure titanium was systematically investigated. Experimental results indicate that the Ti–O alloy with the oxygen content of 1.95 wt% reached an ultrahigh yield strength of 2026 MPa and showed a large ductility of 11.2% in compression. According to the quantified analysis of strengthening mechanisms, solid solute oxygen atoms are responsible for the balance of superior yield strength and ductility of the Ti–O alloys.

Microstructure regulation of titanium-oxygen alloy with high strength and excellent ductility for biomedical applications

Oxygen solid solution reinforced Ti–O alloys with high strengths and good ductility were designed and synthesized via mechanical milling and spark plasma sintering (SPS) processes. The grain size and dispersion state of the Ti–O alloys were optimized by regulating the milling time of the composite powders. Outstanding properties were achieved by 4 h milling with a yield strength of 1082 MPa, 100% higher than that of commercially pure titanium (CP–Ti). According to the quantified results of the strengthening mechanism, fine grains are responsible for the balance of superior strength and ductility of the Ti–O alloy.

Decomposition behavior of yttria-stabilized zirconia and its effect on directed energy deposited Ti-based composite material

• The present study focuses on the rule of YSZ nanoparticles in the refined both α and β grains and increased strength of additively manufactured Ti-6Al-4 V (Ti64). • The YSZ nanoparticles decomposed during the deposition process and led to the formation of Y 2 O 3 and some excess oxygen in the Ti64 matrix. • The decrease in the sizes of the prior β grains could be attributed to the increasing amount of dissolved oxygen and yttrium, which promoted constitutional supercooling. • The reduction in the size of the α grains could be ascribed to a shift of the onset of the β → α+β transformation to a higher temperature and shorter time with increasing concentration of dissolved oxygen. • The contributions of the underlying strengthening mechanisms (α grain size, oxygen solid solution, Y 2 O 3 precipitate) for the as-deposited specimens were quantitatively determined. We report on the microstructure and the strengthening mechanisms of additively manufactured parts fabricated by directed energy deposition of Ti-6Al-4V (Ti64) powders blended with yttria-stabilized zirconia (YSZ) nanoparticles. These specimens showed refined microstructures as compared to bare as-deposited Ti64, where the α and columnar prior β grain sizes decreased with increasing YSZ content. The YSZ nanoparticles decomposed during the deposition process and led to the formation of yttrium oxide and some excess oxygen in the Ti64 matrix. The decrease in the sizes of the prior β grains could be attributed to the increasing amount of dissolved oxygen and yttrium, which promoted constitutional supercooling. Furthermore, the reduction in the size of the α grains could be ascribed to a shift of the onset of the β → α+β transformation to a higher temperature and shorter time with increasing concentration of dissolved oxygen. Finally, the contributions of the underlying strengthening mechanisms for the as-deposited specimens were quantitatively determined.

Intergranular erosion corrosion of pure copper tube in flowing NaCl solution

We investigated the erosion corrosion behavior of a commercial copper tube in 1 wt% NaCl solution using a self-built loop apparatus, and revealed effects of flow velocity on corrosion layer evolution that explains the flow velocity dependent corrosion rate of copper tubes in application. Furthermore, the intergranular erosion corrosion forms the detached and partially oxidized copper grains with nut structure. From core to shell, the compositions are supposed to be copper, copper-based oxygen solid solution, Cu2O with oxygen vacancies, Cu2O, and Cu2O with copper vacancies. These findings provide deepened understanding of erosion corrosion behavior of copper and copper alloys.

Ductility improvement of high-strength Ti–O material upon heteromicrostructure formation

Oxygen solid solutions are well known to impose a strong hardening effect on Ti and its alloys, but induce the undesirable embrittlement behavior. In order to improve the ductility of Ti materials with high oxygen content, Ti(O), herein, a heteromicrostructure consisting of two phases with different oxygen contents was synthesized by redistributing the oxygen solutes through heat treatment over the dual (α + β) phase temperature range, followed by water quenching. The heteromicrostructure formation and plastic deformation mechanisms were investigated by erectron backscattered diffraction (EBSD) analysis of the quenched Ti(O) material under tensile deformation coupled with SEM. It was found that the elongation at break of the sintered Ti-0.94 mass% O alloy remarkably recovered from 6% to 19% owing to the above-mentioned heat treatment and water quenching process. The quenched Ti(O) material consisted of equiaxed grains with high oxygen content, fine α' phase grains, and misorientation regions in the equiaxed grains with low oxygen content. The high and low oxygen content phases were derived from the α and β phases, respectively. The β phase was responsible for plastic deformation, which improved the tensile elongation of the Ti(O) material.

Quantitative Strengthening Evaluation of Powder Metallurgy Titanium Alloys with Substitutional Zr and Interstitial O Solutes via Homogenization Heat Treatment.

The decomposition behavior of ZrO2 particles and uniform distribution of Zr and O solutes were investigated by employing in situ scanning electron microscope-electron backscatter diffraction (SEM-EBSD) analysis and thermogravimetric-differential thermal analysis (TG-DTA) to optimize the process conditions in preparing Ti-Zr-O alloys from the pre-mixed pure Ti powder and ZrO2 particles. The extruded Ti-Zr-O alloys via homogenization and water-quenching treatment were found to have a uniform distribution of Zr and O solutes in the matrix and also showed a remarkable improvement in the mechanical properties, for example, the yield stress of Ti-3 wt.% ZrO2 sample (1144.5 MPa) is about 2.5 times more than the amount of yield stress of pure Ti (471.4 MPa). Furthermore, the oxygen solid-solution was dominant in the yield stress increment, and the experimental data agreed well with the calculation results estimated using the Hall-Petch equation and Labusch model.

Influence of oxygen and plastic deformation on the microstructure and the hardness of a Ti–Nb–Ta–Zr–O Gum Metal

In this paper, the Gum Metal Ti–29Nb–13Ta-4.6Zr-xO with two different oxygen contents (2200 and 4600 ppm) was prepared by high-pressure torsion (HPT) and their microstructural evolution, thermal stability, physical and mechanical properties were investigated for specimens prepared under different processing conditions. An increase in the β-phase stability at the expense of αʺ, as well as in the hardness was observed with the combined effect of oxygen addition and HPT processing. The increase in hardness was attributed to the microstructural refinement, to the creation of a high density of defects, and to the stress-induced ω-phase formation, which were all obtained due to the severe plastic deformation. Besides that, oxygen solid solution hardening provides a great increase in hardness. Vickers microhardness of approximately 400 HV was obtained for samples with higher oxygen content and deformed by HPT. The elastic modulus did not change significantly for the different oxygen levels, with values of 53–66 GPa. The typical Gum Metal properties were attained in the present paper, and they are directly related to its deformation mechanisms such as slip, stress-induced αʺ-martensite as well as reverse martensitic transformation (αʺ → β). The unique Gum Metal properties combined with the obtained increase in hardness make these two alloys very well suited for biomedical applications such as implants.

Study of titanium oxidation kinetics at temperature above polymorphic transformation

The object of research is the analytical description of the phenomena in the near-surface layer, which are caused by the interaction of titanium with oxygen at high temperatures. These are temperatures that exceed the polymorphic transformation of the metal. High-temperature oxidation gives titanium products unique performance properties. Of course, such characteristics are determined, first of all, by the state of the near-surface layer. Therefore, an understanding of oxidation processes will make it possible to predict the state of the near-surface layer after heat treatment. However, to date, no unified approach has been created to describe the mechanism and kinetics of high-temperature oxidation of titanium in the near-surface layer. Indeed, most of the existing approaches make it possible to predict the nature of oxidation in the bulk of the metal. Some scientific papers describe the kinetics of oxidation, taking into account only the formation and growth of oxide layers. However, simultaneously with oxide formation, a diffusion zone is formed, which significantly affects the kinetics. Therefore, today one of the most problematic areas of high-temperature titanium oxidation is the description of the processes that take place in the near-surface layer. In this work, to describe the kinetics of high-temperature oxidation of titanium, in addition to the formation and growth of the oxide layer, the formation and growth of the diffusion zone is taken into account. In the diffusion zone, under the influence of structural phase transformations, solid solutions of oxygen are formed in the alpha and beta phases. This approach made it possible to take into account additional factors and thereby more accurately describe the processes of high-temperature oxidation of titanium. As a result of the calculations, the thickness of the oxide layer of the diffusion zone is given depending on the oxygen concentration and the duration of treatment. And also the dependences of the kinetics of displacement of the boundary of the oxide-diffusion layer are given and a system of equations for calculating the ratio of the formed phase components is developed. Thanks to the proposed analytical approach, it will be possible to calculate the sizes of interphase boundaries on the basis of temperature-time parameters and oxygen concentration and thereby form a hardened near-surface layer with certain functional properties

Lithium-Ion Conductivity of Mixed-Anion Chloride Solid Electrolyte

Lithium-ion batteries are required to have high energy density, high cycle characteristics, and safety to be used for electric vehicles. Current lithium-ion batteries use a flammable organic electrolyte as electrolyte suffers from safety issues. All-solid-state batteries using non-flammable solid electrolytes are attracting attention because they can improve safety and energy density. The practical use of all-solid-state batteries requires solid electrolytes having higher conductivity, atmospheric stability, electrochemical stability, and moldability than conventional liquid electrolytes. However, no material that combines everything has been found at present.Solid electrolytes are divided into two main types: oxide-based and sulfide-based materials. As oxide-based solid electrolytes, garnet-type Li7La3Zr2O12, which shows the room-temperature ionic conductivity is 5.1 × 10-4 S / cm, has been developed [1]. Generally, oxide-based materials have high atmospheric stability and are stable to oxide-based cathode materials, but the ionic conductivity is lower than sulfide-based materials, and a high-temperature process is required for synthesis. As sulfide-based solid electrolytes, crystalline Li10GeP2S12, which shows the room-temperature ionic conductivity is 1.2 × 10-2 S / cm, has been developed [2]. Sulfide-based materials have a relatively higher ionic conductivity than oxide-based materials. Moreover, sulfide-based materials have high moldability and can be synthesized at a lower temperature than oxide-based materials. However, sulfide-based materials have the disadvantages of low atmospheric stability, are at risk of reacting with water to generate H2S, and have low stability to oxide-based cathode materials.High ionic conductivity solid electrolytes have been discovered mainly in oxide-based and sulfide-based materials. In addition, recently, it has been reported that lithium conductive solid electrolytes of halide-based materials have high ionic conductivity, and the material-searching region is expanding. Halide-based materials are considered to have high ionic conductivity due to the properties of halogen anions. Since the monovalent halogen anion has a weaker interaction with lithium ions than the divalent sulfur and oxygen anions, high-speed transport of lithium ions can be expected. In addition, the ionic radius of the halogen anion is relatively large, and the halogen anion has high polarizability. Li3YCl6, Li3YBr6 and Li3InCl6, which show the room-temperature ionic conductivity is 10-3 S / cm have been reported as lithium halide solid electrolyte materials [3], [4].Most of these lithium halide solid electrolyte materials are single-anion compounds, and little research has been conducted on mixed-anion compounds as lithium-ion conductors. In this study, we focused on the chloride-based solid electrolyte Li3InCl6, which is reported to have high lithium-ion conductivity comparable to oxide and sulfide-based materials and is expected to have higher chemical stability than sulfide-based materials. The characteristics of the solid electrolyte when Li3InCl6 was doped with a group 16 element were investigated. A composite anion compound in which oxygen, sulfur, and selenium, which have higher polarizabilities than chlorine, were dissolved was synthesized, and the conductivity characteristics were analyzed by electrochemical measurement. Li3InCl6, Li3InCl5.4O0.3, Li3In0.9Cl5.4O0.15, Li3In0.82Cl5.4O0.03, Li3InCl5.4S0.3, Li3InCl5.4S0.6 and Li3InCl5.4Se0.6 samples were synthesized by mechanochemical method and solid-phase reaction in an argon atmosphere. The crystal structure of the synthesized samples was characterized by X-ray diffraction (XRD), and the ionic conductivity was measured by AC impedance measurements. Comparing the XRD patterns of the Li3InCl6 sample and each sample, a peak of impurities was confirmed for the oxygen solid solution sample, and a decrease in crystallinity was confirmed for the sulfur and selenium solid solution samples. The conductivity of each sample decreased in the order of Li3InCl6> Li3In0.82Cl5.4O0.03 > Li3In0.9Cl5.4O0.15 > Li3InCl5.4O0.3 > Li3InCl5.4S0.3 > Li3InCl5.4Se0.6 > Li3InCl5.4S0.6. In conclusion, addition of mixed anion to the chloride-based solid electrolytes causes negative effects for the lithium-ion conduction. From these results, it is considered that if a divalent anion is dissolved in a crystal constituting a sublattice by the monovalent anion, an increase in Coulomb interaction has a greater effect on lithium-ion conductivity than an action due to polarizability, decreasing conductivity.[1] R. Murugan, V. Thangadurai, W. Weppner, Angew. Chem 46, 7778(2007)[2] N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kamiyama, Y. Kato, S. Hama, K. Kawamoto, A. Mitsui, Nature Materials 10, 686(2011)[3] T. Asano, A. Sakai, S. Ouchi, M. Sakaida, A. Miyazaki, S. Hasegawa, Adv. Mater. 30, 1803075(2018)[4] X. L, J. Liang, J. Luo, M. N. Banis, C. Wang, W. Li, S. Deng, C. Yu, F. Zhao, Y. Hu, T. Sham, L. Zhang, S. Zhao, S. Lu, H. Huang, R. Li, K. R. Adair, X. Sun, Energy Environ. Sci. 12, 2665(2019)

Oxygen injection during fast vs slow passivation in aqueous solution

The typical defect reactions at the metal/oxide interface, which explain the growth and breakdown of passive oxide films in corrosion, include creating metal and oxygen vacancies. While the creation and coalescence of metal vacancies are well documented, there are relatively few observations on the nanoscale details of oxygen transport near the metal/oxide interface. We report here a new mechanism of oxygen injection into the metal. Fast and slow passivation (i.e., corrosion involving both oxide film growth and direct dissolution) of NiCr and NiCrMo alloys was performed by galvanostat experiments in 0.1 M NaCl (pH 4) deaerated solution. Localized regions of an unexpected nonequilibrium metal-based oxygen solid solution were observed beneath the outer (externally formed) oxides, and the saturated oxygen atoms distorted the fcc metallic lattices. Oxygen injection into the metal is more significant at a fast growth rate due to a large passivation current density for the NiCr alloy. In this case, there is a high volume of rock salt Ni(Cr)O nanocrystals in the O-rich Ni(Cr) substrate, which is consistent with greater susceptibility to chloride-induced breakdown found in potentiostat experiments. The addition of Mo promotes the formation of the corundum phase in the outer oxide layer for NiCrMo, which changes the transport mechanism as well as the diffusivity of oxygen through the oxide film and across the metal/oxide interface.

Mechanisms of tensile strengthening and oxygen solid solution in single β-phase Ti-35 at.%Ta+O alloys

Single β phase titanium alloys are used for fabricating biomedical devices, and it is desirable to improve the strength of these alloys. In this study, the tensile strength of Ti-35 at.% Ta alloys with a single β phase was improved using oxygen solid solution and the strengthening mechanism was also investigated. The lattice constants of these alloys calculated from X-ray diffraction data increased with an increase in the oxygen content. This result suggests that oxygen atoms formed solutes in the alloys, which was supported by results obtained from first-principles calculations. Microstructural analyses of the alloys indicate that Ti, Ta, and O were homogeneously distributed. Tensile tests were conducted for the alloys, and the 0.2%YS increased with the increase in the O content of the alloy. The increments of 0.2%YS which was determined experimentally correspond well with the theoretically determined trend, and this observation is a result of the effect of the change in grain size and O solid solution. The contribution of the grain refinement was negligibly small compared with that of the O solid solution, and the latter is the major reason for the observed increase in the 0.2%YS of the Ti-35 at.% Ta alloys.

Oxygen Solid Solution Strengthening of Titanium Materials Fabricated by Selective Laser Melting Process

Oxygen Solid Solution Strengthening of Titanium Materials Fabricated by Selective Laser Melting Process

An in-situ study on deformation and cracking initiation in oxygen-doped commercial purity titanium

Oxygen solid solution has been long known as a double-edge sword to Ti alloys, where, on the one hand, it has a strong strengthening effect while, on the other hand, it also embrittles the alloys. In the present work, in-situ observations using SEM and EBSD were carried out under tension to explore the mechanism that controls those effects. The results suggest that, by increasing oxygen content, the 〈a+c〉 type slip becomes more favorable than the 〈a〉 type, other than suppressing deformation twinning. As a result, the crack nucleation sites transit from grain boundaries (especially at triple junctions) into grain interior with a planar shape, which finally leads to easy cleavage. Comprehensive analysis and discussion suggest that the transition of fracture mode is due to the presence of oxygen solutes that modify the local stress state of geometrically necessary dislocation (GND) pile-ups, which then interfere with the condition for {112¯2¯} twin nucleation and turn to the activation of {112¯2}〈a+c〉 slips.

Концентрационные и диффузионные характеристики атомов внедрения (C, O, N) и модули упругости в ванадии и сплавах V – 4 Cr – 4 Ti, V – W – Cr, V – Ta – Cr – Zr

The elastic (Young’s) modulus and relaxation properties (amplitude-independent internal friction) of bcc metals and alloys (vanadium, V–4Cr–4Ti, V–W–Cr, and V–Ta–Cr—Zr alloys) have been studied in the temperature range of 25–400°С by means of dynamic mechanical spectroscopy within a low-frequency range (0.5–30.0 Hz). No carbon in vanadium and V–W–Cr alloy in solid-solution state is revealed. In the case of vanadium and V–W–Cr alloy, the solid-solution concentrations of oxygen and nitrogen and the diffusion characteristics thereof (diffusion activation energy, characteristic relaxation time, and the preexponential factor in the diffusion equation) have been determined. In the case of V–4Cr–4Ti alloy, carbon, oxygen, and nitrogen solid solutions have not been observed. In V–Ta–Cr–Zr alloy, the solid-solution concentrations of interstitial atoms (C, O, N) are substantially lower than those in vanadium and V–W–Cr alloy. The values of elastic modulus in vanadium alloys can be either higher or lower than the elastic modulus inherent in vanadium depending on type of alloy (alloying) and on temperature. The V–4Ti–4Cr alloy exhibits the smallest value of the elastic modulus among all the materials under study. The temperature curves of the elastic (Young’s) modulus for the studied materials exhibit no features, except for a slight local relaxation of the Young’s modulus in the case of vanadium and V–W–Cr alloy in the temperature range of the relaxation peaks.

Regularities of microdefect formation in silicon during heat treatment for internal getter synthesis

Gettering is defined as a process by which metal impurities in the device region are reduced by localizing them in predetermined, passive regions of the silicon wafer. Internal or intrinsic gettering is an effective way to reduce the contamination in active regions. The generation of internal getters is based on the decomposition of the supersaturated oxygen solid solution in silicon, which favours the formation of a complex defect system in silicon that consists of various precipitate/dislocation agglomerates. Regularities of microdefect formation during oxygen solid solution decomposition in silicon have been studied. We show that actual solid solution supersaturation, temperature and heat treatment duration determine the structure of the solid solution. Combining these factors, including heat treatment parameters, one can control solid solution decomposition rate and SiOx precipitate sizes and quantity. The methods of X-ray diffuse scattering and transmission electron microscopy have shown high efficiency for studying the effect of heat treatment in crystals. For annealing at 450 °C, solid solution decomposition occurs at high supersaturation degrees, and concentration inhomogeneity regions may form at an early decomposition stage over the actual annealing time (up to 40 h). With an increase in the temperature of subsequent annealing to 650 °C, local regions with above-average oxygen supersaturation degrees increase the efficiency of oxygen solid solution decomposition. Further, an increase in annealing temperature to T > 1000 °С results in a more intense generation of the largest precipitates at the expense of the smaller ones. Once the precipitate sizes become sufficiently large, the elastic stresses start to relax, leading to partial incoherence and the generation of dislocations around the particles. This type of defect structure seems to be the most efficient getter.

Strengthening Mechanisms of Powder Metallurgy Extruded CP Titanium Materials with Zirconium and Oxygen Solid Solution via Decomposition of ZrO<sub>2</sub> Additives in Sintering

Strengthening Mechanisms of Powder Metallurgy Extruded CP Titanium Materials with Zirconium and Oxygen Solid Solution via Decomposition of ZrO<sub>2</sub> Additives in Sintering

Getters in silicon

Gettering of rapidly diffusing metallic impurities and structural defects in silicon which is the main material for IC fabrication, high-power high-voltage devices and neutron doped silicon has been studied. Structural defect based getters and gas phase getters based on chlorine containing compounds have been analyzed. Formation of structural defect based getters requires producing intrinsic sources of dislocation generation and precipitate/dislocation agglomerate formation. We show that dislocations are generated at microcrack mouths and form a low-mobility dislocation network at inactive wafer sides. In the latter case the defects are generated in the wafer region adjacent to the active layer of the electronic component. The generation of intrinsic getters is based on the decomposition of the supersaturated oxygen solid solution in silicon which favors the formation of a complex defect system in silicon that consists of various precipitate/dislocation agglomerates. Stacking faults also form, i.e., oxide precipitates with Frank’s dislocation loop clouds. Two intrinsic getter formation methods have been considered: one is related to oxygen impurity drain from the wafer surface region and the other implies accurate control of vacancy distribution over wafer thickness. We have analyzed the effect of getters as defect structures on the reduction of the mechanical stress required for dislocation generation onset which may eventually determine the mechanical strength of silicon wafers. The mechanism of impurity and defect gettering by gas phase medium with chlorine-containing compound additions has been considered. We show that silicon atom interaction with chlorine in the surface wafer region at high temperatures may cause the formation of vacancies which may penetrate to the specimen bulk with some probability. This leads to the case ∆Сv > 0 and ∆Ci ≤ 0, which changes the composition and density of the microdefects. Examples have been given for practical use of heat treatment of silicon wafers in a chlorine-containing atmosphere during oxide film application with the aim to dissolve microdefects, drain rapidly diffusing impurities from crystal bulk and prevent the formation of generation/recombination centers during device fabrication and silicon neutron doping.