Effects of ZrO₂-La₂O₃ co-addition on the microstructural and optical properties of transparent Y₂O₃ ceramics

Zhu, Lin-Lin,Park, Young-Jo,Gan, Lin,Go, Shin-Il,Kim, Ha-Neul,Kim, Jin-Myung,Ko, Jae-Woong Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.11

<P><B>Abstract</B></P> <P>Commercial Y<SUB>2</SUB>O<SUB>3</SUB> powder was used to fabricate Y<SUB>2</SUB>O<SUB>3</SUB> ceramics sintered at 1600°C and 1800°C with concurrent addition of ZrO<SUB>2</SUB> and La<SUB>2</SUB>O<SUB>3</SUB> as sintering aids. One group with different contents of La<SUB>2</SUB>O<SUB>3</SUB> (0–10mol%) with a fixed amount of 1mol% ZrO<SUB>2</SUB> and another group with various contents of ZrO<SUB>2</SUB> (0–7mol%) with a fixed amount of 10mol% La<SUB>2</SUB>O<SUB>3</SUB> were compared to investigate the effects of co-doping on the microstructural and optical properties of Y<SUB>2</SUB>O<SUB>3</SUB> ceramics. At low sintering temperature of 1600°C, the sample single doped with 10mol% La<SUB>2</SUB>O<SUB>3</SUB> exhibits much denser microstructure with a few small intragranular pores while the samples with ZrO<SUB>2</SUB> and La<SUB>2</SUB>O<SUB>3</SUB> co-doping features a lot of large intergranular pores leading to lower density. When the sintering temperature increases to 1800°C, samples using composite sintering aids exhibit finer microstructures and better optical properties than those of both ZrO<SUB>2</SUB> and La<SUB>2</SUB>O<SUB>3</SUB> single-doped samples. It was proved that the grain growth suppression caused by ZrO<SUB>2</SUB> overwhelms the acceleration by La<SUB>2</SUB>O<SUB>3</SUB>. Meanwhile, 1mol% ZrO<SUB>2</SUB> acts as a very important inflection point with regard to the influence of additive concentration on the transmittance, pore structure and grain size. The highest in-line transmittance of Y<SUB>2</SUB>O<SUB>3</SUB> ceramic (1.2mm in thickness) with 3mol% of ZrO<SUB>2</SUB> and 10mol% of La<SUB>2</SUB>O<SUB>3</SUB> sintered at 1800°C for 16h is 81.9% at a wavelength of 1100nm, with an average grain size of 11.2µm.</P>

Fabrication and characterization of highly transparent Er:Y₂O₃ ceramics with ZrO₂ and La₂O₃ additives

Zhu, Lin-Lin,Park, Young-Jo,Gan, Lin,Go, Shin-Il,Kim, Ha-Neul,Kim, Jin-Myung,Ko, Jae-Woong Elsevier 2017 CERAMICS INTERNATIONAL Vol.43 No.16

<P><B>Abstract</B></P> <P>In this study, we report highly transparent Er:Y<SUB>2</SUB>O<SUB>3</SUB> ceramics (0–10at% Er) fabricated by a vacuum sintering method using compound sintering additives of ZrO<SUB>2</SUB> and La<SUB>2</SUB>O<SUB>3</SUB>. The transmittance, microstructure, thermal conductivity and mechanical properties of the Er:Y<SUB>2</SUB>O<SUB>3</SUB> ceramics were evaluated. The in-line transmittance of all of the Er:Y<SUB>2</SUB>O<SUB>3</SUB> ceramics (1.2mm thick) exceeds 83% at 1100nm and 81% at 600nm. With an increase in the Er doping concentration from 0 to 10at%, the average grain size, microhardness and fracture toughness remain nearly unchanged, while the thermal conductivity decreases slightly from 5.55 to 4.89W/mK. A nearly homogeneous doping level of the laser activator Er up to 10at% in macro-and nanoscale was measured along the radial direction from the center to the edge of a disk specimen, which is the prominent advantage of polycrystalline over single-crystal materials. Based on the finding of excellent optical and mechanical properties, the compound sintering additives of ZrO<SUB>2</SUB> and La<SUB>2</SUB>O<SUB>3</SUB> are demonstrated to be effective for the fabrication of transparent Y<SUB>2</SUB>O<SUB>3</SUB> ceramics. These results may provide a guideline for the application of transparent Er:Y<SUB>2</SUB>O<SUB>3</SUB> laser ceramics.</P>

Enhancement of the thermal shock resistance of transparent Y₂O₃ ceramics by reducing the content of sintering additive

Zhu, Lin-Lin,Park, Young-Jo,Gan, Lin,Kim, Ha-Neul,Ko, Jae-Woong,Lee, Jae-Wook,Kim, Hai-Doo Elsevier 2018 Ceramics international Vol.44 No.14

<P><B>Abstract</B></P> <P>It is known that 1.0 at.% is the lowest amount of ZrO<SUB>2</SUB> which can be used for the sintering of well-balanced Y<SUB>2</SUB>O<SUB>3</SUB> ceramics to ensure both transparency and strength. In this work, a highly transparent Y<SUB>2</SUB>O<SUB>3</SUB> ceramic material doped with a reduced amount of ZrO<SUB>2</SUB> (0.5 at.%) was fabricated by means of a hot-press sintering method at a temperature as low as 1600°C using commercial powders. The in-line transmittance of the 0.5 at.% ZrO<SUB>2</SUB>-doped Y<SUB>2</SUB>O<SUB>3</SUB> sample (2 mm thick) is 80.8% at 1100 nm and 72.2% at 400 nm with an average grain size of 1.06 μm. By reducing the ZrO<SUB>2</SUB> content from 1.0 to 0.5 at.%, the thermal conductivity is increased by 18.2% with only a slight decline in the strength and the band gap becomes broader. Consequently, the Hasselman mild-thermal-shock figure of merit of the developed specimen increases by 13.0% overall. These results indicate that this Y<SUB>2</SUB>O<SUB>3</SUB> ceramic has potential for use as a laser host or an infrared window material used on Mach-speed applications.</P>

Fabrication of transparent Y₂O₃ ceramics with record-high thermal shock resistance

Zhu, Lin-Lin,Park, Young-Jo,Gan, Lin,Kim, Ha-Neul,Ko, Jae-Woong,Kim, Hai-Doo Elsevier 2018 Journal of the European Ceramic Society Vol.38 No.11

<P><B>Abstract</B></P> <P>Sintering-additive-free fine-grained highly transparent Y<SUB>2</SUB>O<SUB>3</SUB> ceramics featuring record-high thermal shock resistance were fabricated using commercial powders via vacuum pre-sintering (1375–1550 °C) followed by hot-isostatic pressing (1450 °C). The sample pre-sintered at 1450 °C provides the optimum microstructure for post HIPing, which resulted in a grain size of 0.64 μm. The transmittance, microhardness and fracture toughness of the thus HIPed sample are 80.8% at 1100 nm and 65.5% at 400 nm (1.2 mm thick), 8.0 ± 0.02 GPa and 1.00 ± 0.06 MPa m<SUP>1/2</SUP>, respectively. The thermal conductivity increases from 13.1 to 16.5 W/m/K with increasing vacuum pre-sinterin Proc. SPIE-Int. Soc. Opt g temperature from 1450 to 1550 °C. This hybrid sintering method realized high thermal conductivity and high strength simultaneously. Consequently, the thermal shock resistance of the HIPed specimen vacuum pre-sintered at 1450 °C in this work is the highest ever reported to the best of our knowledge, which makes the developed material a promising candidate for high-power laser host and IR dome.</P>

Fabrication and characterization of highly transparent Y₂O₃ ceramics by hybrid sintering: A combination of hot pressing and a subsequent HIP treatment

Zhu, Lin-Lin,Park, Young-Jo,Gan, Lin,Kim, Ha-Neul,Ko, Jae-Woong,Kim, Hai-Doo Elsevier 2018 Journal of the European Ceramic Society Vol.38 No.9

<P><B>Abstract</B></P> <P>We succeeded in the optimization of highly transparent Y<SUB>2</SUB>O<SUB>3</SUB> ceramics with a submicrometer grain size approximately 0.6 μm by hot pressing (1300–1550 °C) and a subsequent HIP (1450 °C) treatment using commercial Y<SUB>2</SUB>O<SUB>3</SUB> powders as starting powders and ZrO<SUB>2</SUB> as a sintering additive. The optimum microstructure for the HIP treatment was prepared by hot pressing at a temperature as low as 1400 °C for 3 h with a relative density of 99.3%. The thus HIP-treated specimen showed the best transmittance (2 mm thick) ever reported of 83.4% and 78.3% at 1100 and 400 nm, respectively. Specifically, the transmittance using this hybrid sintering method improved substantially in the visible range compared to that of the counterpart using hot pressing only. A simulation of the transmittance based on the Beer-Lambert law and Mie scattering theory has proved that this improvement is mainly due to the elimination of nanopores below 15 nm in size.</P>

Fabrication of transparent MgAl₂O₄ from commercial nanopowders by hot-pressing without sintering additive

Zhu, Lin-Lin,Park, Young-Jo,Gan, Lin,Go, Shin-Il,Kim, Ha-Neul,Kim, Jin-Myung,Ko, Jae-Woong North-Holland 2018 Materials letters Vol.219 No.-

<P><B>Abstract</B></P> <P>Transparent magnesium aluminate spinel (MgAl<SUB>2</SUB>O<SUB>4</SUB>) ceramics were successfully fabricated for the first time using commercially available nanopowders without sintering additive by a single hot-press step process. This method does not involve all the complexity of powder, green body pre-treatment and post-treatment, which are commonly used in the fabricating process. Effects of holding time (3–12 h) at the sintering temperature 1500 °C on the transmittance, microstructure and Vickers microhardness are investigated. The highest transmittance is achieved for the sample hot pressed at 1500 °C for 12 h, which exhibits 80.2% at the wavelength of 1100 nm. These results may provide a guide for understanding the microstructural development of transparent spinel without sintering additive.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pure MgAl<SUB>2</SUB>O<SUB>4</SUB> transparent ceramic was prepared by a single hot-press step. </LI> <LI> The transmittance of the sample at 1500 °C for 12 h reached 80.2% at 1100 nm. </LI> <LI> The Vickers microhardness decreases from 15.1 to 12.5 GPa with holding time from 3 to 12 h. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Implementation of the Adaptive CSMA-CA Algorithm Based on Traffic Load

Lin Zhu,Guangming Li,Wei Liu 보안공학연구지원센터 2014 International Journal of Future Generation Communi Vol.7 No.4

Application of Non-certificate Multi-level Proxy Digital Signature Scheme in Online Banking Transaction

Lin Zhu 보안공학연구지원센터 2016 International Journal of Security and Its Applicat Vol.10 No.10

In order to resist to active attacks, Chen Jiaqi has proposed an authenticated noncertificate three-party key negotiation protocol in 2010, but this key protocol cannot resist to passive attacks or meet the requirements for some security attributes mentioned in his paper. In order to solve the above problems, He De-biao has proposed a new authenticated non-certificate three-party key negotiation protocol on the basis of noncertificate two-party key negotiation protocol. The results of the security analysis and the efficiency analysis of the new protocol show that the new protocol can meet the security requirements of the authenticated non-certificate three-party key negotiation protocol. Compared with the protocol proposed by Chen Jiaqi, the new protocol has less bilinear pairings and higher calculation efficiency.

Thermal Stability and Fracture Toughness of Epoxy Resins Modified with Epoxidized Castor Oil and Al2O3 Nanoparticles

Lin Zhu,Fan-Long Jin,박수진 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.8

This study examined the effects of the epoxidized castor oil (ECO) and Al2O3 content on the thermal stability and fracture toughness of the diglycidylether of bisphenol-A (DGEBA)/ECO/Al2O3 ternary composites using a range of techniques. The thermal stability of the composites was decreased by the addition of ECO and Al2O3 nanoparticles. The fracture toughness of the composites was improved significantly by the addition of ECO and Al2O3 nanoparticles. The composite containing 3 wt % Al2O3 nanoparticles showed the maximum flexural strength. Scanning electron microscopy (SEM) revealed tortuous cracks in the DGEBA/ECO/Al2O3 composites, which prevented deformation and crack propagation.

NAD(P)H: Quinone Oxidoreductase 1 (NQO1) C609T Gene Polymorphism Association with Digestive Tract Cancer: A Meta-analysis

Zhu, Cheng-Lin,Huang, Qiang,Liu, Chen-Hai,Lin, Xian-Sheng,Xie, Fang,Shao, Feng Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.4

NAD(P)H: quinone oxidoreductase 1 (NQO1) C609T gene polymorphisms have been reported to influence the risk for digestive tract cancer (DTC) in many studies; however, the results remain controversial and ambiguous. We therefore carried out a meta-analysis of published case-control studies to derive a more precise estimation of any associations. Electronic searches were conducted on links between this variant and DTC in several databases through April 2012. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were calculated to estimate the strength of associations in fixed or random effect models. Heterogeneity and publication bias were also assessed. A total of 21 case-control studies were identified, including 6,198 cases and 7,583 controls. Overall, there was a statistically significant association between the NQO1 C609T polymorphism and DTC risk (TT vs. CC: OR=1.224, 95%CI=1.055-1.421; TT/CT vs. CC: OR=1.195, 95%CI=1.073-1.330; TT vs. CT/CC: OR=1.183, 95%CI=1.029-1.359; T vs. C: OR=1.180, 95%CI=1.080-1.290). When stratified for tumor location, the results based on all studies showed the variant allele 609T might have a significantly increased risk of upper digest tract cancer (UGIC), but not colorectal cancer. In the subgroup analysis by ethnicity, we observed a significantly risk for DTC in Caucasians. For esophageal and gastric cancer, a significantly risk was found in both populations, and for colorectal, a weak risk was observed in Caucasians, but not Asians. This meta-analysis suggested that the NQO1 C609T polymorphism may increase the risk of DTC, especially in the upper gastric tract.