• Title/Summary/Keyword: orthorhombic phase

Search Result 177, Processing Time 0.021 seconds

Structure Analysis of Liquid Crystal Emulsions Using X-ray Scattering Analysis (X선 산란분석법을 이용한 액정에멀젼 구조분석)

  • Park, So Hyun;Kim, Su Ji;Noh, Min Joo;Lee, Jun Bae;Park, Soo Nam
    • Journal of the Society of Cosmetic Scientists of Korea
    • /
    • v.42 no.3
    • /
    • pp.297-302
    • /
    • 2016
  • In this study, we prepared liquid crystal emulsions composed of $C_{12-20}$ alkyl glucoside, $C_{14-22}$ alcohol, and behenyl alcohol and performed structure analysis using various analytical equipment. First, as an important characteristic of liquid crystal emulsions, maltese cross patterns and multi-layer structure were observed by a polarized microscope and cryo-SEM. Also, formation of liquid crystal phase was confirmed by DSC and multi-layer lamellar structure having an interlayer spacing approximately $305{\AA}$ was confirmed by small angle x-ray scattering (SAXS). The alkyl chain arrangement formed orthorhombic structure of a lamellar structure of the liquid crystal emulsion was confirmed by wide angle x-ray scattering (WAXS). These results suggest that information on the various physical properties obtained through the research of liquid crystal emulsion structure is expected to be widely used in cosmetics development in the future.

Effects of Ta Substitution on Dielectric and Piezoelectric Properties of Pb-free (Na0.53K0.47)(Nb1-xTax)O3 Ceramics (Ta 치환에 따른 비납계 (Na0.53K0.47)(Nb1-xTax)O3 세라믹의 압전 및 유전 특성)

  • Lee, Jung-Hoon;Ryu, Gyung-Hyun;Sung, Yeon-Soo;Cho, Jong-Ho;Song, Tae-Kwon;Kim, Myong-Ho
    • Journal of the Korean Ceramic Society
    • /
    • v.48 no.5
    • /
    • pp.467-470
    • /
    • 2011
  • Pb(Zr,Ti)$O_3$ (PZT) based ceramics with superior piezoelectric properties have been extensively used in various domestic and industrial appliances. However, PZT ceramics causing environmental contamination and health problems need to be eventually replaced by any of Pb-free materials. $(Na_{0.53}K_{0.47})(Nb_{1-x}Ta_x)O_3$ (NKNT), one of Pb-free piezoelectric ceramics, has long been known but its properties are not fully understood and developed. In this study, dielectric and piezoelectric properties of Pb-free NKNT ceramics were studied with Ta substitution for B-site at x = 0~0.6. It was found that polymorphic phase transition (PPT) between orthorhombic and tetragonal phases was notably influenced by Ta substitution. The highest piezoelectric coefficient ($d_{33}$) of 284 pC/N was occurred at x = 0.45.

Double magnetic entropy change peaks and high refrigerant capacity in Gd1-xHoxNi compounds in the melt-spun form

  • Jiang, Jun-fan;Ying, Hao;Feng, Tang-fu;Sun, Ren-bing;Li, Xie;Wang, Fang
    • Current Applied Physics
    • /
    • v.18 no.12
    • /
    • pp.1605-1608
    • /
    • 2018
  • $Gd_{1-x}Ho_xNi$ melt-spun ribbons were fabricated by a single-roller melt spinning method. All the compounds crystallize in an orthorhombic CrB-type structure. The Curie temperature ($T_C$) was tuned between 46 and 99 K by varying the concentration of Gd and Ho. A spin reorientation (SRO) transition is observed around 13 K. Different from $T_C$, the SRO transition temperature is almost invariable for all compounds. Two peaks of magnetic entropy change (${\Delta}S_M$) were found. One at the higher temperature range was originated from the paramagnet-ferromagnet phase transition and the other at the lower temperature range was caused by the SRO transition. The maximum of ${\Delta}S_M$ around $T_C$ is almost same. The other maximum of ${\Delta}S_M$ around SRO transition, however, had significantly positive relationship with x. It reached a maximum about $8.2J\;kg^{-1}\;K^{-1}$ for x = 0.8. Thus double large ${\Delta}S_M$ peaks were obtained in $Gd_{1-x}Ho_xNi$ melt-spun ribbons with the high Ho concentration. And the refrigerant capacity power reached a maximum of $622J\;kg^{-1}$ for x = 0.6. $Gd_{1-x}Ho_xNi$ ribbons could be good candidate for magnetic refrigerant working in the low temperature especially near the liquid nitrogen temperature range.

Optical and Structural Analysis of BaSi2O2N2:Eu Green Phosphor for High-Color-Rendering Lighting (고연색 백색 광원용 BaSi2O2N2:Eu 형광체의 광학·구조 특성 분석)

  • Lee, Sunghoon;Kang, Taewook;Kang, Hyeonwoo;Jeong, Yongseok;Kim, Jongsu;Heo, Hoon
    • Korean Journal of Materials Research
    • /
    • v.29 no.7
    • /
    • pp.437-442
    • /
    • 2019
  • Green $BaSi_2O_2N_2:0.02Eu^{2+}$ phosphor is synthesized through a two-step solid state reaction method. The first firing is for crystallization, and the second firing is for reduction of $Eu^{3+}$ into $Eu^{2+}$ and growth of crystal grains. By thermal analysis, the three-time endothermic reaction is confirmed: pyrolysis reaction of $BaCO_3$ at $900^{\circ}C$ and phase transitions at $1,300^{\circ}C$ and $1,400^{\circ}C$. By structural analysis, it is confirmed that single phase [$BaSi_2O_2N_2$] is obtained with Cmcm space group of orthorhombic structure. After the first firing the morphology is rod-like type and, after the second firing, the morphology becomes round. Our phosphor shows a green emission with a peak position of 495 nm and a peak width of 32 nm due to the $4f^65d^1{\rightarrow}4f^7$ transition of $Eu^{2+}$ ion. An LED package (chip size $5.6{\times}3.0mm$) is fabricated with a mixture of our green $BaSi_2O_2N_2$, and yellow $Y_3Al_5O_{12}$ and red $Sr_2Si_5N_8$ phosphors. The color rendering index (90) is higher than that of the mixture without our green phosphor (82), which indicates that this is an excellent green candidate for white LEDs with a deluxe color rendering index.

Furnace Annealing Effect on Ferroelectric Hf0.5Zr0.5O2 Thin Films (강유전체 Hf0.5Zr0.5O2 박막의 퍼니스 어닐링 효과 연구)

  • Min Kwan Cho;Jeong Gyu Yoo;Hye Ryeon Park;Jong Mook Kang;Taeho Gong;Yong Chan Jung;Jiyoung Kim;Si Joon Kim
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.36 no.1
    • /
    • pp.88-92
    • /
    • 2023
  • The ferroelectricity in Hf0.5Zr0.5O2 (HZO) thin films is one of the most interesting topics for next-generation nonvolatile memory applications. It is known that a crystallization process is required at a temperature of 400℃ or higher to form an orthorhombic phase that results in the ferroelectric properties of the HZO film. However, to realize the integration of ferroelectric HZO films in the back-end-of-line, it is necessary to reduce the annealing temperature below 400℃. This study aims to comprehensively analyze the ferroelectric properties according to the annealing temperature (350-500℃) and time (1-5 h) using a furnace as a crystallization method for HZO films. As a result, the ferroelectric behaviors of the HZO films were achieved at a temperature of 400℃ or higher regardless of the annealing time. At the annealing temperature of 350℃, the ferroelectric properties appeared only when the annealing time was sufficiently increased (4 h or more). Based on these results, it was experimentally confirmed that the optimization of the annealing temperature and time is very important for the ferroelectric phase crystallization of HZO films and the improvement of their ferroelectric properties.

Development of environmentally friendly inorganic fluorescent pigments, A3V5O14 (A = K and Rb) and Cs2V4O11: Crystal structure, optical and color properties (친환경 무기 형광 안료 A3V5O14 (A = K and Rb) and Cs2V4O11 개발: 결정구조, 광학적 특성 및 착색 특성)

  • Jeong, Gyu Jin;Kim, Jin Ho;Lee, Younki;Hwang, Jonghee;Toda, Kenji;Bae, Byoungseo;Kim, Sun Woog
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.30 no.2
    • /
    • pp.47-54
    • /
    • 2020
  • To develop the bright-vivid red- and yellow-inorganic fluorescent pigments with high luminescence properties, A3V5O14 (A = K and Rb) and Cs2V4O11 inorganic pigments were synthesized by a water assisted solid state reaction (WASSR) method and a conventional solid state reaction method. Although impurity peaks corresponding to the AVO3 and AV3O8 (A = K, Rb, and Cs) were observed in all samples prepared, the trigonal structure A3V5O14 (A = K and Rb) and orthorhombic structure Cs2V4O11 were successfully obtained as a main phase. These inorganic pigments showed the broad absorption band (under 550 nm) originated from CT transitions of VO4 polyhedron, and the strong broad red- and green-emission bands due to 3T21A1 and 3T11A1 transitions of the [VO4]3- group. The A3V5O14 (A = K and Rb) and Cs2V4O11 pigments showed a bright-vivid red- and yellow-body color, where the a* values of the A3V5O14 (A = K and Rb) were +35.5 and +45.9, respectively, and b* value of Cs2V4O11 pigments was +50.3. The L* values of the A3V5O14 (A = K and Rb) and Cs2V4O11 inorganic pigments were over +45. These results indicate that the A3V5O14 (A = K and Rb) and Cs2V4O11 inorganic pigments could be an attractive candidate as a bright-vivid red- and yellow inorganic pigments.

The Role of H2O as PCA and the Precipitation Behavior in Mechanically Alloyed Ni-20Cr-20Fe-5Nb Alloy (기계적합금화로 제조된 Ni-20Cr-20Fe-5Nb 합금에서 PCA로서 H2O의 역할과 시효석출거동)

  • Kim Il-Ho;Kwun S.I.;Lee Won-Sik;Chae S.W.;Hwang S.K.;Kim M.H.
    • Journal of Powder Materials
    • /
    • v.13 no.3 s.56
    • /
    • pp.178-186
    • /
    • 2006
  • The effect of use of $H_2O$ as PCA(process control agent) to prevent the carbon contamination during mechanical alloying process and the precipitation behavior in Ni-20Cr-20Fe-5Nb bulk alloy after aging were investigated. NbC and $Cr_2O_3$ were formed during mechanical alloying and consolidation processes in the Ni-20Cr-20Fe-5Nb alloy in which methanol($CH_3OH$) was added as PCA. Formation of NbC in this alloy decreased the amount of Nb dissolved in the Ni matrix. The use of $H_2O$ as PCA in Ni-20Cr-20Fe-5Nb alloy prevented the formation of NbC and increased the hardness. The increase of hardness in this alloy was attributed to the increased amount of Nb dissolved in the Ni matrix. After aging treatment for 20 hours at $600^{\circ}C\;and\;720^{\circ}C$ of Ni-20Cr-20Fe-5Nb bulk alloy in which $H_2O$ added as PCA, ${\gamma}"$$(Ni_3Nb,\;tetragonal)\;and\;{\delta}\;(Ni_3Nb,\;orthorhombic)$ precipitates were formed, respectively. The precipitation temperatures of ${\gamma}"$ and ${\delta}$ in this bulk alloy were lower than those in commercial IN 718 alloy. It seemed that the lower precipitation temperatures for ${\gamma}"$ and ${\delta}$ in this bulk alloy than in commercial IN 718 alloy were due to severe plastic deformation during mechanical alloying.