With the presentation of a theory of liquid alloys, we have now assembled all the necessary tools for the ab initio construction of an alloy phase diagram.

Alloy Phase Diagrams

In this paper, oxygen permeable membrane used in membrane reactor for selective oxidation of alkanes will be discussed in detail. The recent developments for the membrane materials will be presented, and the strategy for the selection of the membrane materials will be outlined. The main applications of oxygen permeable membrane in selective oxidation of light alkanes will be summarized, which includes partial oxidation of methane (POM) to syngas and partial oxidation of heptane (POH) to produce H2, oxidative coupling of methane (OCM) to C2, oxidative dehydrogenation of ethane (ODE) to ethylene and oxidative dehydrogenation of propane (ODP) to propylene. Achievements for the membrane material developments and selective oxidation of light alkanes in membrane reactor in our group are highlighted.

Development and application of oxygen permeable membrane in selective oxidation of light alkanes

Functionally graded material (FGM) is a heterogeneous composite material including a number of constituents that exhibit a compositional gradient from one surface of the material to the other subsequently, resulting in a material with continuously varying properties in the thickness direction. FGMs are gaining attention for biomedical applications, especially for implants, owing to their reported superior composition. Dental implants can be functionally graded to create an optimized mechanical behavior and achieve the intended biocompatibility and osseointegration improvement. This review presents a comprehensive summary of biomaterials and manufacturing techniques researchers employ throughout the world. Generally, FGM and FGM porous biomaterials are more difficult to fabricate than uniform or homogenous biomaterials. Therefore, our discussion is intended to give the readers about successful and obstacles fabrication of FGM and porous FGM in dental implants that will bring state-of-the-art technology to the bedside and develop quality of life and present standards of care.

Dental implants from functionally graded materials

The layered ternary and quaternary carbides in Zr-Al(Si)-C and Hf-Al(Si)-C systems with general formulae of ( T C) n Al 3 C 2 , ( T C) n Al 4 C 3 and (TC) n [Al(Si)] 4 C 3 (where T  = Zr or Hf, n  = 1, 2, 3…) have attracted increasing attentions due to their fascinating properties such as high specific stiffness, high strength and fracture toughness, refractory, machinability by electrical discharge method, thermal shock resistance, as well as high-temperature and ultrahigh-temperature oxidation resistance. The combination of these properties makes them promising as structural components or coatings for high- and ultrahigh-temperature applications. In this review, the progresses on processing, and structure–property relationships of the novel layered carbides are comprehensively outlined. The crystal structure characteristics are introduced first. Then, methods for processing powders and bulk samples are summarized. The third section focuses on the multi-scale structure–property relationships. Finally, the potential applications and further trends in tailoring the properties and developing low cost processing methods are highlighted.

Synthesis and structure-property relationships of a new family of layered carbides in Zr-Al(Si)-C and Hf-Al(Si)-C systems

The Ti-ZrO2 nanocomposites were fabricated by powder metallurgy route. The influence of ZrO2 additions on the microstructure and properties of the Ti-based composites were examined by X-ray diffraction, scanning electron microscopy, microhardness and wear properties tests. The result showed that spread of ZrO2 nanoparticles in the Ti matrix. XRD refers to no new phase are formed between Ti and ZrO2 during the sintering process. In addition, a good microstructure is achieved. The densification behavior of the sintered nanocomposites is increased with increasing ZrO2 percent. The highest microhardness was measured as 570 HV for titanium matrix nanocomposites fabricated by using 10%wt of ZrO2 nanoparticles content. 290 HV was obtained for the titanium matrix. Results showed that the sliding wear rate increase with increasing the normal load and decrease via increasing the addition of ZrO2 nanoparticles. In addition, the friction coefficient decreases with increasing the normal load and via increasing the addition of ZrO2 nanoparticles. The microstructure refines due to ZrO2 addendums illustrated a considerable function in the wear behavior of the Ti matrix.

Effects of ZrO2 nanoparticle content on microstructure and wear behavior of titanium matrix composite

Zirconia–titanium (ZrO2–Ti) composites have been considered potential thermal barrier graded materials for applications in the aerospace industry. Powder mixtures of Ti and 3 mol% Y2O3 partially stabilized ZrO2 in various ratios were sintered at 15001C for 1 h in argon. The microstructures of the as-sintered composites were characterized by X-ray diffraction and transmission electron microscopy/energy-dispersive spectroscopy. Ti reacted with and was mutually soluble in ZrO2, resulting in the formation of a-Ti(O, Zr), Ti2ZrO, and/or TiO. These oxygencontaining phases extracted oxygen ions from ZrO2, whereby oxygen-deficient ZrO2 was generated. For relatively small Ti/ ZrO2 ratios, specimens with r30 mol% Ti, TiO were formed as oxygen could be sufficiently supplied by excess ZrO2. For the specimens with � 50 mol% Ti, lamellar Ti2ZrO was precipitated in a-Ti(Zr, O), with no TiO being found. Both m-ZrO2� x and tZrO2� x were found in specimens with r50 mol% Ti; however, only c-ZrO2� x was formed in the specimen with 70 mol% Ti. As ZrO2 was gradually dissolved into Ti, yttria was retained in ZrO2 because of the very limited solubility of yttria in a-Ti(O, Zr) or TiO. The concentration of retained yttria and the degree of oxygen deficiency in ZrO2 increased with the Ti content. The complete dissolution of ZrO2 into Ti was followed by the precipitation of Y2Ti2O7 in the specimen with 90 mol% Ti.

https://ir.nctu.edu.tw:443/bitstream/11536/10656/1/000247756500039.pdf

Reaction Between Titanium and Zirconia Powders During Sintering at 1500°C

Two basic oxidation modes of silicon carbide/zirconia/mullite (SiC/ZrO2/mullite) composites were defined based on the plotted curve of the gradient of the silica (SiO2) layer thickness (formed on individual SiC particles) versus depth. Mode I, where oxygen diffusivity was much slower in the matrix than in the SiO2 layer, exhibited a relatively large gradient and limited oxidation depth. Mode II, where oxygen diffusivity was much faster in the matrix than in the SiO2 layer, displayed a relatively small gradient and an extensive oxidation depth. When the volume fraction of ZrO2 was below a threshold limit, the composites exhibited Mode I behavior; otherwise, Mode II behavior was observed. For composites with a ZrO2 content above the threshold limit, the formation of zircon (ZrSiO4), as a result of the reaction between ZrO2 and the oxidation product (i.e., SiO2), might change the oxidation behavior from Mode II to Mode I.

https://ir.nctu.edu.tw:443/bitstream/11536/31738/1/000077588000012.pdf

Dependence of Oxidation Modes on Zirconia Content in Silicon Carbide/Zirconia/Mullite Composites

ZrO2 samples with various CaO contents were fabricated by hot pressing, whereby CaO was dissolved by and/or reacted with ZrO2 to form a solid solution and/or CaZr4O9, respectively. After a reaction with Ti at 1550°C for 6 h in argon, the interfacial microstructures were characterized using X-ray diffraction and analytical electron microscopy. Experimental results were very different from those found previously in the Y2O3–ZrO2 system. The 5 mol% CaO–ZrO2 sample was relatively stable due to the formation of a thin TiO layer acting as a diffusion barrier phase. However, α-Ti(O), β′-Ti (Zr, O), and/or Ti2ZrO were found in 9 or 17 mol% CaO–ZrO2 due to extensive interdiffusion of Ti, O, and Zr with a much thinner (β′-Ti+α-Ti) layer in 17 mol% CaO–ZrO2 than in 9 mol% CaO–ZrO2. Because CaO was hardly dissolved into Ti, it fully remained in the residual ZrO2, leading to the formation of spherical CaZrO3 in 9 mol% CaO–ZrO2 and columnar CaZrO3 in 17 mol% CaO–ZrO2. In the region far from the original interface, abundant intergranular α-Zr was formed in 5 or 9 mol% CaO–ZrO2. Scattered α-Zr and CaZrO3 were found in 17 mol% CaO–ZrO2 because a high concentration of extrinsic oxygen vacancies, which were created by the substitution of Ca+2 for Zr+4, effectively retarded the reduction of zirconia.

https://ir.nctu.edu.tw:443/bitstream/11536/31980/1/000283987400069.pdf

Compositional dependence of phase formation mechanisms at the interface between titanium and calcia-stabilized zirconia at 1550°C

In this study, 3 mol% Y2O3-stabilized zirconia (3Y–ZrO2) and commercially pure titanium (cp-Ti) joints were fabricated with an Ag68.8Cu26.7Ti4.5 interlayer (Ticusil) at 900 °C for various brazing periods. After brazing at 900 °C/0.1 h, Ti2Cu, TiCu, Ti3Cu4, and TiCu4 layers were present at the Ti/Ticusil interface, while TiCu and TiO layers were observed at the Ticusil/3Y–ZrO2 interface. In the residual interlayer, clumpy TiCu4 was formed along with the Ag solid phase. After brazing at 900 °C/1 h, Ti3Cu3O and Ti2O layers were formed at the interlayer/ZrO2 interface, while Cu2O was precipitated in the residual interlayer with ${\left[ {111} \right]_{{\rm{C}}{{\rm{u}}_2}{\rm{O}}}}//{\left[ {111} \right]_{{\rm{Ag}}}}$
 and ${\left( {20\overline 2 } \right)_{{\rm{C}}{{\rm{u}}_2}{\rm{O}}}}//{\left( {20\overline 2 } \right)_{{\rm{Ag}}}}$
 . After brazing at 900 °C/6 h, a two-phase (α-Ti + Ti2Cu) region was observed on the Ti side with ${\left[ {2\overline 1 \overline 1 0} \right]_{{\rm{\alpha }} - {\rm{Ti}}}}//{\left[ {100} \right]_{{\rm{T}}{{\rm{i}}_2}{\rm{Cu}}}}$
 and ${\left( {0002} \right)_{{\rm{\alpha }} - {\rm{Ti}}}}//{\left( {0\overline 1 3} \right)_{{\rm{T}}{{\rm{i}}_2}{\rm{Cu}}}}$
 , while the TiCu layer grew at the expense of Ti3Cu4 and TiCu4. The bonding mechanisms and diffusion paths were explored with the aid of Ag–Cu–Ti and Ti–Cu–O ternary phase diagrams.

https://ir.nctu.edu.tw:443/bitstream/11536/24758/1/000337189900010.pdf

Microstructural evolution and bonding mechanisms of the brazed Ti/ZrO2 joint using an Ag68.8Cu26.7Ti4.5 interlayer at 900 °C

The interfaces between 3-mol%-yttria-partially-stabilized zirconia and commercially pure titanium after reaction at 1750°C were analyzed with a scanning electron microscope and an analytical transmission microscope. Zirconia was reduced to oxygen-deficient zirconia (ZrO2-x) with an O/Zr ratio as low as 1.53, causing the evolution of oxygen. Part of the oxygen could accumulate at grain boundaries, the remainder being dissolved in titanium as alpha-Ti(O). An ordered titanium suboxide (Ti3O) could be formed from a solid solution of alpha-Ti(O) during cooling. A fine crystalline ZrO2-x phase (O/Zr similar/congruent 2) was also found along with alpha-Zr near the interface on the zirconia side. The alpha-Zr was twinned with one of the twin planes being indexed as {1012}. The yttria stabilizer was excluded from zirconia as the reaction was progressing, existing as oxygen-deficient yttria. Extensive dissolution of zirconia in titanium gave rise to the formation of alpha-Ti(Zr,O) solid solution. On cooling, lamellae of Ti2ZrO precipitated from alpha-Ti(Zr,O) with an orientation relationship of {110}Ti2ZrO//{100}alpha-Ti and Ti2ZrO// alpha-Ti.

/pdf/transmission-electron-microscope-investigation-of-the-pn2f8l1s5r.pdf

Chien-Cheng Lin

Papers

Reaction Between Titanium and Zirconia Powders During Sintering at 1500°C

Dependence of Oxidation Modes on Zirconia Content in Silicon Carbide/Zirconia/Mullite Composites

Compositional dependence of phase formation mechanisms at the interface between titanium and calcia-stabilized zirconia at 1550°C

Microstructural evolution and bonding mechanisms of the brazed Ti/ZrO2 joint using an Ag68.8Cu26.7Ti4.5 interlayer at 900 °C

Transmission Electron Microscope Investigation of the Interface between Titanium and Zirconia