InP quantum dots (QDs) have attracted researchers’ interest due to their applicability in quantum dot light-emitting displays (QLED) or biomarkers for detecting cancers or viruses. The surface or interface control of InP QD core/ shell has substantially increased quantum efficiency, with a quantum yield of 100% reached by introducing HF to inhibit oxide generation. In this study, we focused on the control of bandgap energy of quantum dots by changing the Zn/(In+Zn) ratio in the In(Zn)P core. Zinc incorporation can change the photoluminescent light colors of green, yellow, orange, and red. Diluting a solution of as-synthesized QDs by more than 100 times did not show any quenching effects by the Förster resonance energy transfer phenomenon between neighboring QDs.

Amorphous In-Ga-Zn-O (a-IGZO) thin film transistors (TFTs) with a coplanar structure were fabricated to investigate the feasibility of their potential application in large size organic light emitting diodes (OLEDs). Drain currents, used as functions of the gate voltages for the TFTs, showed the output currents had slight differences in the saturation region, just as the output currents of the etch stopper TFTs did. The maximum difference in the threshold voltages of the In-Ga-Zn-O (a-IGZO) TFTs was as small as approximately 0.57 V. After the application of a positive bias voltage stress for 50,000 s, the values of the threshold voltage of the coplanar structure TFTs were only slightly shifted, by 0.18 V, indicative of their stability. The coplanar structure TFTs were embedded in OLEDs and exhibited a maximum luminance as large as 500 nits, and their color gamut satisfied 99 % of the digital cinema initiatives, confirming their suitability for large size and high resolution OLEDs. Further, the image density of large-size OLEDs embedded with the coplanar structure TFTs was significantly enhanced compared with OLEDs embedded with conventional TFTs.

Lead-free perovskite ceramics, which have excellent energy storage capabilities, are attracting attention owing to their high power density and rapid charge-discharge speed. Given that the energy-storage properties of perovskite ceramic capacitors are significantly improved by doping with various elements, modifying their chemical compositions is a fundamental strategy. This study investigated the effect of Zn doping on the microstructure and energy storage performance of potassium sodium niobate (KNN)-based ceramics. Two types of powders and their corresponding ceramics with compositions of (1-x)(K,Na)NbO3-xBi(Ni2/3Ta1/3)O3 (KNN-BNT) and (1-x)(K,Na)NbO3-xBi(Ni1/3Zn1/3Ta1/3) O3 (KNN-BNZT) were prepared via solid-state reactions. The results indicate that Zn doping retards grain growth, resulting in smaller grain sizes in Zn-doped KNN-BNZT than in KNN-BNT ceramics. Moreover, the Zn-doped KNNBNZT ceramics exhibited superior energy storage density and efficiency across all x values. Notably, 0.9KNN-0.1BNZT ceramics demonstrate an energy storage density and efficiency of 0.24 J/cm3 and 96%, respectively. These ceramics also exhibited excellent temperature and frequency stability. This study provides valuable insights into the design of KNNbased ceramic capacitors with enhanced energy storage capabilities through doping strategies.

The effects of annealing on the microstructure and mechanical properties of Al–Zn–Mg–Cu–Si alloys fabricated by high-energy ball milling (HEBM) and spark plasma sintering (SPS) were investigated. The HEBM-free sintered alloy primarily contained Mg2Si, Q-AlCuMgSi, and Si phases. Meanwhile, the HEBM-sintered alloy contains Mg-free Si and θ-Al2Cu phases due to the formation of MgO, which causes Mg depletion in the Al matrix. Annealing without and with HEBM at 500oC causes partial dissolution and coarsening of the Q-AlCuMgSi and Mg2Si phases in the alloy and dissolution of the θ-Al2Cu phase in the alloy, respectively. In both alloys, a thermally stable α-AlFeSi phase was formed after long-term heat treatment. The grain size of the sintered alloys with and without HEBM increased from 0.5 to 1.0 μm and from 2.9 to 6.3 μm, respectively. The hardness of the sintered alloy increases after annealing for 1 h but decreases significantly after 24 h of annealing. Extending the annealing time to 168 h improved the hardness of the alloy without HEBM but had little effect on the alloy with HEBM. The relationship between the microstructural factors and the hardness of the sintered and annealed alloys is discussed.

The Mn-Zn ferrite powders were prepared by high energy ball milling, then compacted and sintered at various temperatures to assess their sintering behavior and magnetic properties. The initial ferrite powders were spherical in shape with the size of approximately 70 m. After 3 h of ball milling at 300 rpm, aggregated powders ~230 nm in size and composed of ~15 nm nanoparticles were formed. The milled powders had a density of ~70 % when compacted at 490 MPa for 3 min. In the samples subsequently sintered at 1,273 K ~ 1,673 K for 3 h, the MnZnFe2O4 phase was detected. The density of the sintered samples had a tendency to increase with increasing sintering temperature up to 1,473 K, which produced the highest density of 98 %. On the other hand, the sample sintered at 1,373 K had the highest micro-hardness of approximately 610 Hv, which is due to much finer grains.

In the flux used in the batch galvanizing process, the effect of the component ratio of NH₄Cl to ZnCl₂ on the microstructure, coating adhesion, and corrosion resistance of Zn-Mg-Al ternary alloy-coated steel is evaluated. Many defects such as cracks and bare spots are formed inside the Zn-Mg-Al coating layer during treatment with the flux composition generally used for Zn coating. Deterioration of the coating property is due to the formation of AlClx mixture generated by the reaction of Al element and chloride in the flux. The coatability of the Zn-Mg-Al alloy coating is improved by increasing the content of ZnCl2 in the flux to reduce the amount of chlorine reacting with Al while maintaining the flux effect and the coating adhesion is improved as the component ratio of NH4Cl to ZnCl2 decreases. Zn-Mg-Al alloy-coated steel products treated with the optimized flux composition of NH₄Cl•3ZnCl₂ show superior corrosion resistance compared to Zn-coated steel products, even with a coating weight of 60 %.

본 연구에서는 방사성동위원소 추적자 실험을 통해서 산화아연 또는 두 종류의 은나노물질로 오염시킨 토양에서 지렁이 (Eisenia fetida)의 금속축적과 제거율을 비교하였고, 이들을 이온상의 Ag와 Zn으로 처리한 대조구와 비교하였다. 추가적으로 토양의 금속을 다단계추출법 (sequential extraction method)을 이용하여 금속의 결합 형태로부터 생물이용도 (bioavailability)를 예측하고 실제 생물축적 (BAF, bioaccumulation factor)과 비교하였다. ZnO 처리구의 BAF (0.06)는 아연이온 처리구 BAF (1.86)보다 31배 낮았는데, 이는 토양에서 ZnO의 생물전이가 매우 낮음을 제시해 준다. 한편, 은의 BAF는 금속의 오염 형태에에 무관 하게 0.11~0.17의 범위를 보였다. 다단계추출법을 통해서 아연이온 처리구의 아연은 토양에 비교적 약한 결합을 하 는 형태 (mobile fraction)에 35% 분포하여 아연이온처리구 값 (<20%)보다 높았고, 이는 전자의 더 높은 BAF와 일치 한다. 하지만, ZnO 처리구의 다단계추출은 생물이용도나 BAF를 잘 예측하지 못했으며 이는 ZnO가 토양에서 아연 이온과 지화학적으로 다른 거동을 하기 때문으로 추정된다. 지렁이 체내에 축적된 은의 제거율 (3.2~3.8% d-1)은 아연의 제거율 (1.2~1.7% d-1)보다 2~3배 더 높았다

Effects of Sc addition on microstructure, electrical conductivity, thermal conductivity and mechanical properties of the as-cast and as-extruded Al-2Zn-1Cu-0.3Mg-xSc (x = 0, 0.25, 0.5 wt%) alloys are investigated. The average grain size of the as-cast Al-2Zn-1Cu-0.3Mg alloy is 2,334 μm; however, this value drops to 914 and 529 μm with addition of Sc element at 0.25 wt% and 0.5 wt%, respectively. This grain refinement is due to primary Al3Sc phase forming during solidification. The as-extruded Al-2Zn-1Cu-0.3Mg alloy has a recrystallization structure consisting of almost equiaxed grains. However, the asextruded Sc-containing alloys consist of grains that are extremely elongated in the extrusion direction. In addition, it is found that the proportion of low-angle grain boundaries below 15 degree is dominant. This is because the addition of Sc results in the formation of coherent and nano-scale Al3Sc phases during hot extrusion, inhibiting the process of recrystallization and improving the strength by pinning of dislocations and the formation of subgrain boundaries. The maximum values of the yield and tensile strength are 126 MPa and 215 MPa for the as-extruded Al-2Zn-1Cu-0.3Mg-0.25Sc alloy, respectively. The increase in strength is probably due to the existence of nano-scale Al3Sc precipitates and dense Al2Cu phases. Thermal conductivity of the as-cast Al-2Zn-1Cu-0.3Mg-xSc alloy is reduced to 204, 187 and 183 W/MK by additions of elemental Sc of 0, 0.25 and 0.5 wt%, respectively. On the other hand, the thermal conductivity of the as-extruded Al-2Zn-1Cu-0.3Mg-xSc alloy is about 200 W/Mk regardless of the content of Sc. This is because of the formation of coherent Al3Sc phase, which decreases Sc content and causes extremely high electrical resistivity.

Metal–organic frameworks (MOFs) are network-like frameworks composed of transition metals and organic ligands containing oxygen or nitrogen. Because of its highly controllable composition and ordered porous structure, it has broad application prospects in the field of material synthesis. In this work, Zn4( PYDC)4(DMF)2∙3DMF (ZPD) was synthesized via a hydrothermal method. Self-doped nitrogen porous carbon ZPDC-T was then prepared by one-step carbonization. The results show that the self-doped nitrogen porous carbon ZPDC-850 has a micro/mesoporous structure with a specific surface area of 1520 m2 g− 1 and a nitrogen content of 6.47%. When a current density is 1.0 A g− 1, its specific capacitance is 265.1 F g− 1. After 5000 times of constant current charging and discharging, the capacitance retention rate was 79.2%. Thus, self-doped nitrogen porous carbon ZPDC-850 exhibits excellent electrochemical properties and good cyclic stability. Therefore, the self-doped nitrogen porous carbon derived from MOFs can be a promising electrode material for supercapacitors.

The annealing characteristics of cold-rolled Al-6.5Mg-1.5Zn-0.5Fe-0.5Mn alloy, newly designed as an automobile material, are investigated in detail, and compared with those of other aluminum alloys. Using multi-pass rolling at room temperature, the ingot aluminum alloy is cut to a thickness of 4 mm, width of 30 mm, and length of 100 mm to reduce the thickness to 1 mm (r = 75 %). Annealing after rolling is performed at various temperatures ranging from 200 to 500 oC for 1 hour. The specimens annealed at temperatures up to 300 oC show a deformation structure; however, from 350 oC they have a recrystallization structure consisting of almost equiaxed grains. The hardness distribution in the thickness direction of the annealed specimens is homogeneous at all annealing temperatures, and their average hardness decreases with increasing annealing temperature. The tensile strength of the as-rolled specimen shows a high value of 496 MPa; however, this value decreases with increasing annealing temperature and becomes 338MPa after annealing at 400 oC. These mechanical properties of the specimens are compared with those of other aluminum alloys, including commercial 5xxx system alloys.

Synthesis of composite powders for the Fe2O3-Zn system by mechanical alloying (MA) has been investigated at room temperature. Optimal milling and heat treatment conditions to obtain soft magnetic composite with fine microstructure were investigated by X-ray diffraction, differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM) measurement. It is found that α-Fe/ZnO composite powders in which ZnO is dispersed in α-Fe matrix can be obtained by MA of Fe2O3 with Zn for 4 hours. The change in magnetization and coercivity also reflects the details of the solid-state reduction process of hematite by pure metal of Zn during MA. Densification of the MA powders was performed in a spark plasma sintering (SPS) machine at 900 ~ 1,000 ℃ under 60 MPa. Shrinkage change after SPS of sample MA'ed for 5 hrs was significant above 300 ℃ and gradually increased with increasing temperature up to 800 ℃. X-ray diffraction results show that the average grain size of α-Fe in the α-Fe/ZnO composite sintered at 900 ℃ is in the range of 110 nm.

인간의 인위적 활동으로 인해 발생하는 중금속 중 카드 뮴 (Cd)과 아연 (Zn)은 다양한 경로를 통해 하천으로 유입 되어 서식생물에게 유해 영향을 준다. 본 연구에서는 도심 하천에서 우점하는 장수깔따구 (Chironomus plumosus)를 이용하여 Cd와 Zn 노출에 따른 생태독성학적 반응을 연구 하였다. 생활사를 고려하여, 생존율, 성장율, 우화율, 성비와 하순기절 기형을 관찰하였다. 장수깔따구 생존율은 Cd 와 Zn 노출에 따라 시간, 농도의존적인 경향을 나타냈다. 성장율은 Cd 노출 후 Day 4와 Day 7, 농도의존적인 감소를 보였으며, 고농도인 50 mg L-1에서 대조군에 비해 급격한 감소를 나타냈다. 또한, 우화율은 10, 50 mg L-1 Cd에서 대조군에 비해 감소함을 관찰하였다. 성비 변화는 100 mg L-1 Zn에서 암컷의 비율이 증가였으나 농도가 높아짐에 따라 수컷의 비율이 높아짐을 보이며 성비불균형이 관찰되었다. 게다가, 장수깔따구의 하순기절에서는 대조군에 비해 Cd와 Zn 노출된 장수깔따구에서 기형이 관찰되었다. 이와 같은 결과는 수생태계로 유입되는 중금속이 하천의 하상저층에 서식하는 저서무척추동물에게 유해한 영향을 주며, 중금속 노출에 따른 생물학적 분석을 위한 현장 지표 종으로서의 가능성을 보여주었다.

ZnO crystals with different morphologies are synthesized through thermal evaporation of the mixture of Zn and Cu powder in air at atmospheric pressure. ZnO crystals with wire shape are synthesized when the process is performed at 1,000 oC, while tetrapod-shaped ZnO crystals begin to form at 1,100 oC. The wire-shaped ZnO crystals form even at 1,000 oC, indicating that Cu acts as a reducing agent. As the temperature increases to 1,200 oC, a large quantity of tetrapod-shaped ZnO crystals form and their size also increases. In addition to the tetrapods, rod-shaped ZnO crystals are observed. The atomic ratio of Zn and O in the ZnO crystals is approximately 1:1 with an increasing process temperature from 1,000 oC to 1,200 oC. For the ZnO crystals synthesized at 1,000 oC, no luminescence spectrum is observed. A weak visible luminescence is detected for the ZnO crystals prepared at 1,100 oC. Ultraviolet and visible luminescence peaks with strong intensities are observed in the luminescence spectrum of the ZnO crystals formed at 1,200 oC.

Hot-press forming(HPF) steel can be applied successfully to auto parts because of its superior mechanical properties. However, its resistances to aqueous corrosion and the subsequent hydrogen embrittlement(HE) decrease significantly when the steel is exposed to corrosive environments. Considering that the resistances are greatly dependent on the properties of coating materials formed on the steel surface, the characteristics of the corrosion and hydrogen diffusion behaviors regarding the types of coating material should be clearly understood. Electrochemical polarization and impedance measurements reveal a higher corrosion potential and polarization resistance and a lower corrosion current of the Al-coating compared with Zn-coating. Furthermore, it was expected that the diffusion kinetics of the hydrogen atoms would be much slower in the Al-coating, and this would be due mainly to the much lower diffusion coefficient of hydrogen in the Al-coating with a face-centered cubic structure. The superior surface inhibiting effect of the Al-coating, however, is degraded by the formation of local cracks in the coated layer under severe stress conditions, and therefore further study will be necessary to gain a clearer understanding of the effect of cracks formed on the coated layer on the subsequent corrosion and hydrogen diffusion behaviors.

The cold rolling workability and mechanical properties of two new alloys, designed and cast Al-5.5Mg-2.9Si and Al-7Mg-0.9Zn alloys, were investigated in detail. The two alloy sheets of 4 mm thickness, 30 mm width and 100 mm length were reduced to a thickness of 1 mm by multi-pass rolling at ambient temperature. The rolling workability was better for the Al-7Mg-0.9Zn alloy than for the Al-5.5Mg-2.9Si alloy; in case of the former alloy, edge cracks began to occur at 50% rolling reduction, and their number and length increased with rolling reduction; however, in the latter alloy, the sheets did not have any cracks even at higher rolling reduction. The mechanical properties of tensile strength and elongation were also better in the Al-7Mg-0.9Zn alloy than in Al-5.5Mg-2.9Si alloy. Work hardening ability after cold rolling was also higher in the Al-7Mg- 0.9Zn alloy than in the Al-5.5Mg-2.9Si alloy. At the same time, the texture development was very similar for both alloys; typical rolling texture developed in both alloys. These differences in the two alloys can primarily be explained by the existence of precipitates of Mg2Si. It is concluded that the Al-7Mg-0.9Zn alloy is better than the Al-5.5Mg-2.9Si alloy in terms of mechanical properties.

본 연구는 구리 아연 금속합금의 산화 환원 반응과 합성 알루미늄 실리케이트의 흡착 반응을 이용한 폐수 중 중금속 처리에 관한 연구이다. 극세사 형태로 제조된 구리 아연 금속합금이 수용액 중에 서 산화 환원반응에 의해 아연보다 이온화 경향이 작은 중금속은 환원 처리되고, 이온화 된 아연 및 미 반응 중금속은 흡착 처리하여 제거하는 연구이다. 극세사 형태로 제조된 금속합금 물질은 표면적이 커서 1회 처리만으로도 반응 평형에 도달하게 하여 효율이 높은 것으로 나타났다. 크롬(Cr+3)은 redox 반응 1 회 처리만으로도 100.0 % 제거 되었으며, 수은은 98.0 %, 주석 92.0 %, 구리는 91.4 % 정도 제거되었 다. 카드뮴, 니켈, 납도 각각 40.0 %, 50.0 %, 58.0 %가 제거 되었다. 크롬(Cr+3)은 아연과 이온화 경향 차이가 거의 없지만 제거 효율이 높은 것으로 나타났는데 이는 3가 크롬은 이온 상태로 존재하면 redox 반응에서 발생한 OH- 이온과 결합하여 수산화물 침전을 형성하는 것으로 판단된다. Redox 반응 후 증 가한 아연 및 미반응 중금속 농도를 알루미늄실리케이트를 1회 통과하여 거의 100.0 % 제거할 수 있었 다. 이는 합성 알루미늄 실리케이트의 비표면적이 크고 금속 이온의 흡착능력이 우수한 것으로 나타났으 며, 반응 후 알루미늄 이온은 증가하지 않는 것으로 보아 이온 교환이 아닌 흡착으로 아연 및 중금속 이 온들을 제거할 수 있는 것으로 나타났다.

The effect of adding Ca on the microstructural and mechanical properties of as-cast Mg-11Li-3Zn-1Sn(wt%) alloys were investigated. Mg-11Li-3Zn-1Sn-0.4Mn with different Ca additions (0.4, 0.8, 1.2 wt%) were cast under an SF6 and Co2 atmosphere at 720 oC. The cast billets were homogenized at 400 oC for 12h and extruded at 200 oC. The microstructural and mechanical properties were analyzed by OM, XRD, SEM, and tensile tests. The addition of Ca to the Mg-11Li-3Zn-1Sn-0.4Mn alloy resulted in the formation of Ca2Mg6Zn3, MgSnCa intermetallic compound. By increasing Ca addition, the volume fraction and size of Ca2Mg6Zn3 with needle shape were increased. This Ca2Mg6Zn3 intermetallic compound was elongated to the extrusion direction and refined to fine particles due to severe deformation during hot extrusion. The elongation of the 0.8 wt% Ca containing alloy improved remarkably without reduction strength due to the formation of fine grain and Ca2Mg6Zn3 intermetallic compounds by Ca addition. It is probable that fine and homogeneous Ca2Mg6Zn3 intermetallic compounds played a significant role in the increase of mechanical properties.

ZnO micro/nanocrystals at large scale were synthesized through the thermal evaporation of Al-Zn mixtures under air atmosphere. The effect of synthetic temperature and time on the morphology of the micro/nanocrystals was examined. It was found that the temperature and time affected the morphology of the ZnO crystals. At temperatures below 900 oC, no crystals were synthesized. At a temperature of 1000 oC, ZnO crystals with a rod shape were synthesized. With an increase in temperature from 1000 oC to 1100 oC, the morphology of the crystals changed from rod shape to wire and granular shapes. As the time increased from 2 h to 3 h at 1000 oC, tetrapod-shaped ZnO crystals started to form. XRD patterns showed that the ZnO crystals had a hexagonal wurtzite structure. EDX analysis revealed that the ZnO crystals had high purity. It is believed that the ZnO nanowires were grown via a vapor-solid mechanism because no catalyst particles were observed at the tips of the micro/nanocrystals in the SEM images.