• 한국분말재료학회지
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• 제13권5호
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• pp.340-350
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• 2006

Nanostructured materials exhibit attractive mechanical properties that are often superior to the performance of their coarse-grained counterparts. However, one major drawback is their low ductility, which limits their potential applications. In this paper, different strategies to obtain both high strength and enhanced ductility in nanostructured materials are reported for Ti-base and Zr-base alloys. The first approach consists of designing an in-situ composite microstructure containing ductile bcc or hop dendrites that are homogeneously dispersed in a nanostructured matrix. The second approach is related to refining the eutectic structure of a Ti-Fe-Sn alloy. For all these materials, the microstructure, mechanical properties, deformation and fracture mechanisms will be discussed.

• 열처리공학회지
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• 제23권1호
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• pp.3-9
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• 2010

Titanium and its alloys were brazed in the range of $850-950^{\circ}C$ within 10 min. of brazing time using expensive infra red or other heating methods. However, brazing time needs to be extended to get temperature-uniformity for mass production by using continuous belt type furnace or high vacuum furnace with low heating rate. This study examined effects of holding temperature for 60 min, on microstructure and mechanical properties of titanium alloys. Mechanical properties of titanium alloys were drastically deteriorated with increasing holding temperature followed by grain growth. Maximum holding temperatures for CP (commercial pure) titanium and Ti-6Al-4V were confirmed as $800^{\circ}C$ and $850^{\circ}C$, respectively. Both titanium alloys were successfully brazed at $800^{\circ}C$ for 60 min. with the level of base metal strengths by using Zr based filler metal, $Zr_{54}Ti_{22}Ni_{16}Cu_8$.

• Imaging Science in Dentistry
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• 제52권3호
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• pp.267-273
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• 2022

Purpose: The aim of this study was to assess the influence of kilovoltage- peak (kVp) and the metal artifact reduction (MAR) tool on the detection of buccal and lingual peri-implant dehiscence in the presence of titanium-zirconia (Ti-Zr) and zirconia (Zr) implants in cone-beam computed tomography (CBCT) images. Materials and Methods: Twenty implant sites were created in the posterior region of human mandibles, including control sites (without dehiscence) and experimental sites (with dehiscence). Individually, a Ti-Zr or Zr implant was placed in each implant site. CBCT scans were performed using a Picasso Trio device, with variation in the kVp setting (70 or 90 kVp) and whether the MAR tool was used. Three oral radiologists scored the detection of dehiscence using a 5-point scale. The area under the receiver operating characteristic (ROC) curve, sensitivity, and specificity were calculated and compared by multi-way analysis of variance (α=0.05). Results: The kVp, cortical plate involved (buccal or lingual cortices), and MAR did not influence any diagnostic values (P>0.05). The material of the implant did not influence the ROC curve values(P>0.05). In contrast, the sensitivity and specificity were statistically significantly influenced by the implant material (P<0.05) with Zr implants showing higher sensitivity values and lower specificity values than Ti-Zr implants. Conclusion: The detection of peri-implant dehiscence was not influenced by kVp, use of the MAR tool, or the cortical plate. Greater sensitivity and lower specificity were shown for the detection of peri-implant dehiscence in the presence of a Zr implant.

• 한국재료학회지
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• 제14권4호
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• pp.293-299
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• 2004

Transition metal ions doped $TiO_2$ nanostructured powders were prepared with simply heating aqueous $TiOCl_2$ solutions, contained various metal ions (Ni, Al, Fe, Zr, and Nb) of 1.47 mol% added as metal-chlorides, at $100^{\circ}C$ for 4 hrs by homogeneous precipitation process under suppressing conditions of water vaporization. The characterizations for prepared $TiO_2$ powders were carried out to observe doping of metal ions, their concentrations and microstructures using XRD, UV-VIS (DRS), XPS, SEM, TEM and ICP. Also, photo-oxidative abilities were evaluated by decomposition of 4-chlorophenol (4CP) under ultraviolet light irradiations. No secondary oxide phases were formed in all the $VTiO_2$ powders, showing doping with various transition metal ions. When adding ions ($Ni^{2+}$ or$ Al^{3+ }$ and $Zr^{4+}$ ) having valance states or ionic radii greatly different from those of $Ti^{4+}$ , the $TiO_2$ powders of mixed anatase and rutile phases were formed, whereas in the case of additions of $^Fe{3+ }$ and $Nb^{ 5+}$ as well as no addition of metal ion the powders with pure rutile phase alone were formed. Among the prepared $TiO_2$ powders, Ni$^{2+}$ doped $TiO_2$ powders, containing a small amount of anatase phase, showed excellent photo-oxidative ability in 4CP decomposition because of relative decreases in electron-hole recombination and poisoning of $TiO_2$ surface during the photoreaction.n.

• 한국세라믹학회지
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• 제50권2호
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• pp.157-162
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• 2013

The need for lead-free piezoceramics has caused a renewal of interest in $BaTiO_3$-based systems. Recently, it was found that ceramics in the $(Ba,Ca)(Zr,Ti)O_3$ system have properties comparable to those of $Pb(Zr,Ti)O_3$. However, these ceramics require rather high sintering temperatures of $1450-1550^{\circ}C$. In this work, the effect of $TiO_2$ and CuO addition on the sintering behavior, microstructure, dielectric and piezoelectric properties of $(Ba_{0.85}Ca_{0.15})(Zr_{0.1}Ti_{0.9})O_3$ (BCTZ) ceramics will be discussed. BCTZ ceramics were prepared by the mixed oxide route and 1 mol % of $TiO_2$ or CuO was added. Undoped and doped ceramics were sintered at $1350^{\circ}C$ for 1-5 h. CuO was found to be a very effective sintering aid, with samples sintered for 1 h at $1350^{\circ}C$ having a bulk density of 95% theoretical density; however the piezoelectric properties were greatly reduced, probably due to the small grain size.

• 공업화학
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• 제9권5호
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• pp.654-660
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• 1998

수열합성법을 이용한 PSZT제조시 출발물질의 첨가량과 광화제가 입자의 결정성과 입자크기 분포 및 소결체의 유전율에 미치는 영향을 조사하였다. Pb와 Sr의 비 및 Zr과 Ti의 비를 변화시킨 0.5 M의 혼합용액에 광화제로 KOH를 2~20 wt % 첨가한 후 $120{\sim}200^{\circ}C$에서 2시간 동안 수열반응을 통해 $0.3{\sim}15{\mu}m$의 평균입자 크기를 갖는 입방체모양의 PSZT분말을 제조하였다. 또한 제조된 분말을 $1150^{\circ}C$에서 2시간 동안 소결반응하여 1000~3000의 유전율을 갖는 소결체를 제조하였다. 실험결과 광화제의 농도는 10 wt %, Sr/(Sr+Ti)은 0.05, Zr/(Zr+Ti)은 0.52일 때 PSZT분말의 평균입자크기가 $0.5{\mu}m$로 작았으며, 이를 소결한 소결체의 유전율도 2900으로 높았다. 한편, 광화제의 농도를 증가시켜 입자의 평균입경을 작고 균일하게 제어할 수 있었으나 광화제를 과도하게 첨가하면 응집이 유발되어 입경이 커졌다. 입자의 결정성에 영향을 미치지 않을 정도로 Sr을 소량 첨가하여 소결체의 유전율을 증가시킬 수 있었다. 또한, Zr을 첨가함으로써 주요 결정상을 정방정에서 능면정으로 전이시킬 수 있었다.

• 한국세라믹학회지
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• 제28권8호
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• pp.654-660
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• 1991

Stabilized Zirconia (3 mol % Yttria, 3Y-TZP) was joined with intermetallic compound NiTi which has similar thermal expansion coefficient. The optimum bonding condition was determined by the Taguchi Method. Under the optimum bonding condition, the 4-point bending strength was as high as 400 MPa. bonding interfaces were examined by optical microscope, SEM, and TEM; reaction products were identified by XRD and TEM, The relationship between products and strength was examined.

• 한국재료학회지
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• 제15권12호
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• pp.814-817
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• 2005

In order to enhance energy efficiency in high electric conversion devices such as Power transformers, which need to have high power properties, an alloy design approach in $Pb(Zr,Ti)O_3(PZT)$ base ceramic system was attempted $0.03Pb(Sb_{0.5}Nb_{0.5})O_3-0.03Pb(Mn_{1/3}Nb_{2/3})O_3-(0.94-x)PbTiO_3-xPbZrO_3$[PSN-PMN- PZT] ceramics were synthesized by conventional bulk ceramic processing technique. To improve power properties, the various Zr/Ti ratio was varied ]lear their morphotropic phase boundary (MPB) composition of PSN-PMN-PZT system and their effects on subsequent piezoelectric and dielectric properties for the transformer application at high power were systematically investigated using an impedance analyzer. Microstructure and phase information were characterized using X-ray diffractometer (XRD), a scanning electron microscope (SEM) and others. When the Zr/Ti ratio was 0.415/0.465, the value of $Q_m\;and\;k_p$ were shown to reach to the maximum, indicating that this alloy design can be a feasible composition :or high power transformer.

• E2M - 전기 전자와 첨단 소재
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• 제7권5호
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• pp.369-375
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• 1994

In this study, ferroelectric thin films of PZT with different Zr/Ti ratio were prepared by sol-get processing and annealed by rapid thermal annealing at >$500^{\circ}C$>$-700^{\circ}C$ for 10 sec. -1 min. Structures of the annealed films were examined by X-ray diffraction and SEM. Thin films of PZT with perovskite structure have been obtained by annealing at >$600^{\circ}C$ or above and for 20 seconds or longer. Maximum remnant polarization of 10.24.mu.C/cm$^{2}$ and minimum coercive field of 20.06 kV/cm were obtained from the 56/44 and 65/35 Zr/Ti composition films, respectively. Dielectric constant, .epsilon.$_{r}$ of 500-1300 and dielectric loss, tan .delta., of 0.01-0.035 were obtained from the films.s.

• Bulletin of the Korean Chemical Society
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• 제16권10호
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• pp.908-911
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• 1995

The EPR spectra of Cu-or Zr-doped BaTiO3 ceramics exhibited absorption signals with g∥=2.380 and g⊥=2.063 which are assigned to Ba1+(Ba2+ + e'→Ba1+) ion reduced by an electron that was produced from the oxygen vacancy (VO..). The intensity of these signals decreased as the temperature increased indicating that Ba1+ was changed to Ba2+ as the temperature increased. These ceramics also showed the EPR signal with g=1.997 around TC which arises from ionized Ba-vacancies, VBa'(VBa + e'→VBa'. In the orthorhombic and tetragonal phase region g=1.997 signal was not seen. The electrons generating from the oxidation of Ba1+ and ionized Ba-vacancies may contribute to a space charge which is responsible for a dielectric relaxation of these samples.