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Effect of plastic deformation on the martensitic transformations in TiNi alloy

  • Belyaev, Fedor S.;Evard, Margarita E.;Volkov, Aleksandr E.
    • Smart Structures and Systems
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    • v.29 no.2
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    • pp.311-319
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    • 2022
  • A model of plastic deformation of the shape memory alloys which describes dislocation slip at the microlevel is developed. A condition similar to the Schmid law was adopted for the determination of dislocation slip onset. A description of the interaction of plastic deformation and martensitic transformations by taking into account the densities of deformation defects is proposed. It is shown that the model can correctly describe the effect of plastic strain on the shape memory effect. The proposed model is also capable of describing the two-way shape memory effect.

Limitations of Structural Behavior Response Performance Evaluation for Waterproofing Materials Under Non-Constrained Conditions and Suggestions for Future Improvement Measures (방수재료의 거동대응성능 시험시 비 구속조건에서의 구조물 거동 대응성능 평가의 한계와 향후 개선 방안 제안)

  • An, Ki-Won;Oh, Gyu-Hwan;Kim, Soo-Yeon;Oh, Sang-Keun
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2021.11a
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    • pp.212-213
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    • 2021
  • As structure and the waterproofing material are compressed through the backfilling process after the waterproofing material is installed on the underground structure at the actual site, there is a difference between the behavioral response force of the waterproofing material in the compressed state and the behavioral response force in the non-constrained state. In this regard, we will analyze the limitations of the current structural behavioral response evaluation and suggest an improvement plan so that the future test and evaluation environment can be evaluated under conditions similar to the field.

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Analysis of The Properties of Materials for Utilizing Fine Aggregates for Concrete for Coal Gasification Slag (석탄 가스화 용융 슬래그를 콘크리트용 잔골재로 활용하기 위한 재료 특성 분석)

  • Kim, Su-Hoo;Lim, Gun-Su;Han, Jun-Hui;Hyun, Seung-Yong;Kim, Jung;Han, Min-Cheol
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2021.11a
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    • pp.170-171
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    • 2021
  • This study compared the characteristics of the newly established JISA 5011-5 coal gasification slag fine aggregate with the characteristics of CGS generated in Korean IGCC through microscopic analysis. As a result of the study, similar results to K_CGS and J_CGS were found

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Turning and Metalic Characterization for CAM Shaft Materials of Diessel Engine (디젤 엔진용 캠축 소재의 금속적 특성 및 선삭 가공 특성에 관한 연구)

  • Chae, W.S.;Kim, K.W.;Kim, D.H.
    • Journal of the Korean Society for Precision Engineering
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    • v.14 no.7
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    • pp.22-28
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    • 1997
  • In this paper, We have studied internal quality incluiding chemical compositions, microscopic structure and nonmetalic inclusion of test material. We have analyzed dynamic characteristics of cutting resistence and compared chip treatment of the test material. In analyzing internal quality, all of the test material have typical ferrite+pearlite structure. But, nonmetallic inclusion has oxide and sulfide inclusion has oxide and sulfide inclusion in medium carbon steel, mainly sulfide inclusion is existed in S-free cutting steel. In Ca+S-free cutting steel, calcium aluminate and sulfide complex inclusion, had low-melting point, as deformation of sulfide and oxide inclusion is existed. Machining characteristics, cutting resistence is maximum in medium carbon steel. Chip treatement are excellent in S-free cutting steel, similar to the Ca+S free cutting steel and medium carbon steel.

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A review of chromatographic analysis for rare-earth elements with focus on Ln resin

  • Jihye Kim;Kihwan Choi
    • Analytical Science and Technology
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    • v.36 no.6
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    • pp.259-266
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    • 2023
  • The demand for rare-earth elements (REEs) is increasing owing to their significance as prominent materials in electronics, high-tech industries, geological research, nuclear forensics, and environmental monitoring. In general, the utilization of REEs in various applications requires the use of chromatographic techniques to separate individual elements. However, REEs have similar physicochemical properties, which makes them difficult to separate. Recently, several studies have examined the separation of REEs using LN resin as the stationary phase and aqueous nitric acid and hydrochloric acid solutions as eluents. Using this method, light REEs have been separated using dilute acid solutions as the eluent, whereas heavy REEs are separated using solutions with high acid concentrations. To increase the separation resolution between different REEs, either the column length or resin size is changed. In addition, the suggested methods are implemented to decrease the analysis time. This review presents technical information on the chromatographic separation of REEs using the LN resin and discusses the optimal experimental conditions.

Clinical Applications of Dual-Energy CT

  • Saira Hamid;Muhammad Umer Nasir;Aaron So;Gordon Andrews;Savvas Nicolaou;Sadia Raheez Qamar
    • Korean Journal of Radiology
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    • v.22 no.6
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    • pp.970-982
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    • 2021
  • Dual-energy CT (DECT) provides insights into the material properties of tissues and can differentiate between tissues with similar attenuation on conventional single-energy imaging. In the conventional CT scanner, differences in the X-ray attenuation between adjacent structures are dependent on the atomic number of the materials involved, whereas in DECT, the difference in the attenuation is dependent on both the atomic number and electron density. The basic principle of DECT is to obtain two datasets with different X-ray energy levels from the same anatomic region and material decomposition based on attenuation differences at different energy levels. In this article, we discuss the clinical applications of DECT and its potential robust improvements in performance and postprocessing capabilities.

Fabrication of a custom polyetherketoneketone post-and-core with digital technology

  • Ju-Hyoung Lee;Gyu-Heon Lee
    • Journal of Technologic Dentistry
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    • v.46 no.1
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    • pp.15-19
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    • 2024
  • An ideal post material should have physical properties similar to those of dentin. Post materials with high elastic moduli may cause root fractures. This clinical report describes the treatment of a severely damaged tooth using a recently introduced material. Polyetherketoneketone (PEKK) is a semicrystalline high-performance thermoplastic polymer. PEKK is a promising material for custom post-and-core fabrication because of its elasticity close to that of dentin, good shock absorbance, machinability, and low cost. A laboratory scanner was used to digitize the conventional impression of a severely damaged maxillary right first molar. A custom PEKK post-and-core was designed and milled using computer-aided design and computer-aided manufacturing technology. Using the proposed technique, a custom PEKK post-and-core was fabricated accurately and human error was reduced. Restoration was luted with resin cement. Custom PEKK post-and-core restorations are a viable alternative for treating severely damaged teeth.

Epoxy/BaTiO3 (SrTiO3) composite films and pastes for high dielectric constant and low tolerance embedded capacitors fabrication in organic substrates

  • Paik Kyung-Wook;Hyun Jin-Gul;Lee Sangyong;Jang Kyung-Woon
    • Proceedings of the International Microelectronics And Packaging Society Conference
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    • 2005.09a
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    • pp.201-212
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    • 2005
  • [ $Epoxy/BaTiO_3$ ] composite embedded capacitor films (ECFs) were newly designed fur high dielectric constant and low tolerance (less than ${\pm}15\%$) embedded capacitor fabrication for organic substrates. In terms of material formulation, ECFs are composed of specially formulated epoxy resin and latent curing agent, and in terms of coating process, a comma roll coating method is used for uniform film thickness in large area. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ composite ECF is measured with MIM capacitor at 100 kHz using LCR meter. Dielectric constant of $BaTiO_3$ ECF is bigger than that of $SrTiO_3$ ECF, and it is due to difference of permittivity of $BaTiO_3\;and\;SrTiO_3$ particles. Dielectric constant of $BaTiO_3\;&\;SrTiO_3$ ECF in high frequency range $(0.5\~10GHz)$ is measured using cavity resonance method. In order to estimate dielectric constant, the reflection coefficient is measured with a network analyzer. Dielectric constant is calculated by observing the frequencies of the resonant cavity modes. About both powders, calculated dielectric constants in this frequency range are about 3/4 of the dielectric constants at 1 MHz. This difference is due to the decrease of the dielectric constant of epoxy matrix. For $BaTiO_3$ ECF, there is the dielectric relaxation at $5\~9GHz$. It is due to changing of polarization mode of $BaTiO_3$ powder. In the case of $SrTiO_3$ ECF, there is no relaxation up to 10GHz. Alternative material for embedded capacitor fabrication is $epoxy/BaTiO_3$ composite embedded capacitor paste (ECP). It uses similar materials formulation like ECF and a screen printing method for film coating. The screen printing method has the advantage of forming capacitor partially in desired part. But the screen printing makes surface irregularity during mask peel-off, Surface flatness is significantly improved by adding some additives and by applying pressure during curing. As a result, dielectric layer with improved thickness uniformity is successfully demonstrated. Using $epoxy/BaTiO_3$ composite ECP, dielectric constant of 63 and specific capacitance of 5.1nF/cm2 were achieved.

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Solution processed inverted organic solar cells with hybrid inorganic/organic cathode interlayers

  • Lee, Jung Suk;Cha, Myoung Joo;Park, Yu Jung;Kim, Jin Young;Seo, Jung Hwa;Walker, Bright
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.154.2-154.2
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    • 2016
  • In this work, we introduce a solution-processed CdS interlayer for use in inverted bulk heterojunction (BHJ) solar cells, and compare this material to a series of standard organic and inorganic cathode interlayers. Different combinations of solution-processed CdS, ZnO and conjugated polyelectrolyte (CPE) layers were compared as cathode interlayers on ITO substrates to construct inverted solar cells based on $PTB7:PC_{71}BM$ and a $P3HT:PC_{61}BM$ as photoactive layers. Introduction of a CdS interlayer significantly improved the power conversion efficiency (PCE) of inverted $PTB7:PC_{71}BM$ devices from 2.0% to 4.9%, however, this efficiency was still fairly low compared to benchmark ZnO or CPE interlayers due to a low open circuit voltage ($V_{OC}$), stemming from the deep conduction band energy of CdS. The $V_{OC}$ was greatly improved by introducing an interfacial dipole (CPE) layer on top of the CdS layer, yielding outstanding diode characteristics and a PCE of 6.8%. The best performing interlayer, however, was a single CPE layer alone, which yielded a $V_{OC}$ of 0.727 V, a FF of 63.2%, and a PCE of 7.89%. Using $P3HT:PC_{61}BM$ as an active layer, similar trends were observed. Solar cells without the cathode interlayer yielded a PCE of 0.46% with a poor $V_{OC}$ of 0.197 V and FF of 34.3%. In contrast, the use of hybrid ZnO/CPE layer as the cathode interlayer considerably improved the $V_{OC}$ of 0.599 V and FF of 53.3%, resulting the PCE of 2.99%. Our results indicate that the CdS layer yields excellent diode characteristics, however, performs slightly worse than benchmark ZnO and CPE layers in solar cell devices due to parasitic absorption below 550 nm. These results suggest that the hybrid inorganic/organic interlayer materials are promising candidates as cathode interlayers for high efficiency inverted solar cells through the modification of interface contacts.

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Evaluation of Bioactivity of Titanium Implant Treated with H2O2/HCl Solution (H2O2/HCl 처리한 Ti 임플란트의 생체활성 평가)

  • Yue J. S.;Kwon O. S.;Lee O. Y.;Lee M. H.;Song K. H.
    • Korean Journal of Materials Research
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    • v.15 no.5
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    • pp.353-360
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    • 2005
  • Surface treatment play an important role in nucleating calcium phosphate deposition on surgical Ti implant. Therefore, the purpose of this study is to examine whether the precipitation of apatite on cp-Ti and Ti alloys are affected by surface modification in HCl and $H_2O_2$ solution. Specimens were then chemically treated with a solution containing 0.1 M HCl and 8.8M $H_2O_2$ at $80^{\circ}C$ for 30 mins, and subsequently heat-treated at $400^{\circ}C$ for 1 hour. All specimens were immersed in the HBSS with pH 7.4 at $36.5^{\circ}C$ for 15 days, and the surface was examined with XRD, SEM, EDX ana XPS. Also, pure Ti, Ti-6Al-4V and Ti-6Al-7Nb alloy specimens with and without surface treatment were implanted in the abdominal connective tissue of mice for 4 weeks. All specimens chemically treated with HCl and $H_2O_2$ solution have the ability to form a apatite layer in the HBSS which has inorganic ion composition similar to human blood plasma. The average thickness of the fibrous capsule surrounding the specimens implanted in the connective tissue was $38.57\;{\mu}m,\;62.27\;{\mu}m\;and\;45.64\;{\mu}m$ in the cp-Ti, Ti-6Al-4V ana Ti-6Al-7Nb alloy specimens with the chemical treatment respectively, and $52.20\;{\mu}m,\;75.62\;{\mu}m\;and\;66.56\;{\mu}m$ in the commercial specimens of cp-Ti, Ti-6Al-4V and Ti-6Al-7Nb without any treatment respectively. The results of this evaluation indicate that the chemically treated cp-Ti, Ti-6Al-4V ana Ti-6Al-7Nb alloys have better bioactivity and biocompatibility compared to the other metals tested.