Material Pixel-based Process Planning for Layered Manufacturing of Heterogeneous Objects

Kim, Hong Seok,Shin, Ki-Hoon Korean Society for Precision Engineering 2014 International Journal of Precision Engineering and Vol.15 No.11

Layered manufacturing (LM) is emerging as a feasible technology that enables the fabrication of three dimensional heterogeneous objects such as multi-materials or functionally graded materials (FGMs). In this paper, we present a new material pixel-based processing planning method that takes into account not only the geometry, but also material variation along the build direction. The continuous material distribution on each 2D slice is first approximated by a set of material pixels. Iso-material regions for tool path planning are then computed by applying marching square algorithm to these material pixels. Next, the layer thickness at the current z-height is adaptively determined by calculating both the geometry-dependent and the material-dependent layer thicknesses. Once the slicing is done by repeating the previous steps (calculation of material pixels, iso-material regions, and layer thickness) for each slice, extra contours serving as support structures are added to each slice to obtain a complete LM model. We first introduce the representation scheme for heterogeneous objects and the new process planning method is then described in detail. Examples are shown to illustrate the overall procedure.

이중 기공구조를 갖는 다공질체의 제조

윤중열,김해두,박천홍,Yun, Jung-Yeul,Kim, Hai-Doo,Park, Chun-Hong 한국세라믹학회 2002 한국세라믹학회지 Vol.39 No.10

표면층과 내부간의 기공구조가 다른 다공질체를 제조하기 위해 입자크기가 다른 두 종류의 분체를 이용하여 다공질 성형체를 제조하였다. 두 층간의 소결 수축율을 동일하게 제어하기 위해 성형밀도 변화에 따른 소결밀도 변화를 예측할 수 있는 Ford's equation을 도입하여 소결 수축율을 동일한 조건을 구하였다. 제조된 다공질체는 미세구조와 통기도를 조사함으로서 기공의 이중 구조화 여부를 평가하였다. SEM 관찰결과 기공크기가 다른 두 층으로 구성되어 있는 것을 확인하였다. 각 층의 통기도는 출발 입자크기와 기공율이 클수록 증가하였으며, 이중 기공구조를 갖는 시편의 통기도는 기공크기가 작은 층의 특성에 의존하였다. In order to fabricate double-layered porous materials powders of different particle sizes were pressed stepwise. Ford's equation which predicts the fired density with the change in pressed density was employed in order to adjust the difference in sintering shrinkage of the green body with double-layered porous structure. Double-layered porous materials were characterized by investigating microstructures and permeability. SEM micrographs showed the distinct difference in pore sizes of double-layered porous material. Permeability of single-layered porous material increased by increasing the starting particle sizes and porosity as well. Permeability of the double-layered porous material depends largely on the layer of small pore diameter.

Antiglare and antireflective coating of layer-by-layer SiO₂ and TiZrO₂ on surface-modified glass

Hudaya, Chairul,Jeon, Bup Ju,Verdianto, Ariono,Lee, Joong Kee,Sung, Yung-Eun Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.490 No.-

<P><B>Abstract</B></P> <P>Antiglare and antireflection materials take considerable research attention due to its important role in transparent optical materials for various purposes. In this study, we employed layer-by-layer coating materials consist of SiO<SUB>2</SUB> and TiZrO<SUB>2</SUB> deposited on etched-surface glass substrate using dual electron beam evaporator system. The surface morphology investigated by using scanning electron microscopy (SEM) exhibited the microstructure patterns of glass surface. The cross-sectional image of transmission electron microscopy (TEM) showed uniformly layer-by-layer coating materials with the thickness of ~20–80 nm. The Auger electron spectroscopy (AES) revealed the depth profiles of elemental composition of surface layer-by-layer coating, confirming the presence of elements of SiO<SUB>2</SUB> and TiZrO<SUB>2</SUB> layers. In addition, the layer-by-layer coated glass surface performed the hydrophobic properties with contact angle of 69°. The microstructure surface treatment and layer-by-layer coating have successfully decreased the reflectance (~3%) and increased the transmittance of the treated glass (~91%), opening the possibility for the applications of any optical devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Layer-by-layer deposition of SiO<SUB>2</SUB> and TiZrO<SUB>2</SUB> as antiglare and antireflection </LI> <LI> Multilayer thin film coating with increased transmittance </LI> <LI> Microstructure patterns through surface etching with hydrophobic capability </LI> <LI> Homogeneous coating materials through dual electron beam evaporator </LI> <LI> Potential applications for PV panel, laser, optical lenses and display devices </LI> </UL> </P>

Piezo/triboelectric nanogenerators based on 2-dimensional layered structure materials

Han, Sang A,Lee, Jaewoo,Lin, Jianjian,Kim, Sang-Woo,Kim, Jung Ho Elsevier 2019 Nano energy Vol.57 No.-

<P><B>Abstract</B></P> <P>Recently, research on energy harvesting has attracted great attention as a solution to energy depletion and environmental problems due to the use of fossil fuels such as coal, natural gas, and oil. To be precise, harvesting technology converts the energy sources around us such as solar, heat, and mechanical energy into electrical energy. It has the advantage of being able to supply and sustain energy on a permanent basis, rather than being non-renewable, and it is also eco-friendly. Among the various energy harvesting techniques, nanogenerators based on piezoelectric and triboelectric phenomena can generate electrical energy based on mechanical energy sources, which are usually ubiquitous, there are no restrictions due to weather, time, or space, and this technology is also user-friendly. Recently, two-dimensional (2D) materials have been chosen for implementing piezo/triboelectric nanogenerators. The 2D materials have transparency, flexibility, and a high surface-to-volume ratio. Owing to the very low thickness of the atomic unit, a stacking structure using 2D materials can be also made to form a very thin device, which is applicable for insertion into the body or wearable electronic devices. In this review, we summarize the characteristics and research results on piezo/triboelectric energy harvesters based on 2D layered structure materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The characteristics of 2D materials are transparency, flexibility, and high surface-to-volume ratio. </LI> <LI> With these advantages, 2D materials with piezo/triboelectric potential can be applied as various electronic devices. </LI> <LI> We summarize the research results on piezo/triboelectric energy harvester based on 2D layered structure materials. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Research Trends in Hybrid Cross-Laminated Timber (CLT) to Enhance the Rolling Shear Strength of CLT(CLT의 rolling shear 향상을 위한 hybrid cross laminated timber 연구 동향)

( Seung Min YANG ),( Hwa Hyung LEE ),( Seog Goo KANG ) 한국목재공학회 2021 목재공학 Vol.49 No.4

In this study, hybrid CLT research and development trends were analyzed to improve the low rolling shear strength of CLT, a large wooden panel used in high-rise wooden buildings. Through this, basic data that can be used in research and development directions for localization of CLT were prepared. As a way to improve the low rolling shear strength, the use of hardwood lamina, the change of the lamina arrangement angle, and the use of structural composite materials are mainly used. Rolling shear strength and shear modulus of hardwood lamina are more than twice as high as softwood lamina. It confirmed that hardwoods can be used and unused species can be used. Rolling shear strength 1.5 times, shear modulus 8.3 times, bending stiffness 4.1 times improved according to the change of the layer arrangement angle, and the CLT strength was confirmed by reducing the layer arrangement angle. Structural wood-based materials have been improved by up to 1.35 times MOR, 1.5 times MOE, and 1.59 times rolling shear strength when used as laminas. Block shear strength between the layer materials was also secured by 7.0 N/㎟,which is the standard for block shear strength. Through the results of previous studies, it was confirmed that the strength performance was improved when a structural wood based materials having a flexural performance of MOE 7.0 GPa and MOR 40.0 MPa or more was used. This was determined based on the strength of layered materials in structural wood-based materials. The optimal method for improving rolling shear strength is judged to be the most advantageous application of structural wood based materials with strength values according to existing specifications. However, additional research is needed on the orientation of CLT lamina arrangement according to the fiber arrangement of structural wood-based materials, and the block shear strength between lamina materials.

Atomic-layer-deposited buffer layers for thin film solar cells using earth-abundant absorber materials: A review

Sinha, Soumyadeep,Nandi, Dip K.,Kim, Soo-Hyun,Heo, Jaeyeong North-Holland 2018 Solar Energy Materials and Solar Cells Vol. No.

<P><B>Abstract</B></P> <P>Atomic layer deposition (ALD) is not just a thin film deposition technology limited to the semiconductor IC industries to grow high-<I>k</I> gate dielectric or a Cu diffusion barrier layer. In recent times, it has found plenty of applications in the field of renewable energy due to its precise thickness control up to few angstroms and its unique feature of conformal and uniform coating on any randomly shaped 3D structure. ALD has far-reaching applications in this field, including electrochemical storage, fuel cells, solar photovoltaics (PV), and catalysis for water splitting to produce H<SUB>2</SUB> as a green fuel. In solar PV technology, ALD is now being extensively used as an efficient tool to deposit surface passivation layers, absorber or sensitizer, transparent conducting oxide, and barrier and buffer layers in several kinds of solar cells. Out of all the different layers associated with a solar cell, ALD is majorly used for the development of a very thin <I>n-</I>type buffer layer. This review article presents a systematic chronological study on such ALD-grown buffer layers for thin film solar cells (TSFCs). The study is carried out in detail based on different earth-abundant absorber materials, such as Cu<SUB>2</SUB>ZnSn(S,Se)<SUB>4</SUB> (CZTSSe), Cu<SUB>2</SUB>O and SnS, for which ALD is successfully used to deposit the buffer layer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> ALD buffer layers for TFSCs based on emerging absorbers are reviewed. </LI> <LI> Correlation between cell performance and ALD process parameters is investigated. </LI> <LI> Progress on the efficiency of the TFSCs based on ALD buffers is reported. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Pillar Host Material로써 Layered(Mg/Al) Double Hydroxide의 물리화학적 특성화

형경우,이용석 한국세라믹학회 1998 한국세라믹학회지 Vol.35 No.5

Layered double hydroxides(LDHs) [{{{{ {Mg }_{1-x } }}{{{{ {Al }_{x } }}({{{{ {OH}_{2 } }})]ζ+({{{{ {CO }`_{3 } ^{2- } ){ }_{x/2 } }}$.${{{{ { yH}_{2 }O }} wioth variation of layer charge densitywere synthesized by co-precipitation methdo since their charge densities have a very important role to be det-ermined the physicochemical properties of layered materials. The XRD IR and thermal studies of them were discussed and the kinetic study for the decarbonation reaction was also carried out. From the results of XRD analysis we found that the lattice parameter and the unit cell volume were linearly decreased with the amount of Al substituents(x) in the vicinity of x=2∼10${\times}$1/3${\times}$10-1 but they had nearly constant values when the x are far from these vicinit. The activation energies for the decarbonation reaction of x=6.8, 10${\times}$1/3${\times}${{{{ { 10}^{-1 } }} were estimated to be 47.0, 37.6, 39.3 kcal/mol The specific surface areas(90-120 m2/g) of stable hy-drotalcite-type LDHs were dractically decreased with increasing of layer charge density.

Functionalization of graphene layers and advancements in device applications

Nandanapalli, Koteeswara Reddy,Mudusu, Devika,Lee, Sungwon Elsevier 2019 Carbon Vol.152 No.-

<P><B>Abstract</B></P> <P>The invention of graphene, as a two-dimensional (2D) atomic layered material, has created enormous scientific revolutions in materials science. As a result, there are a variety of 2D materials came into limelight and intervening the existing technology. Today, one of the focusing issues in graphene technology is the development of functionalized (doped) graphene monolayers since the pristine graphene is chemically inert, hydrophobic and zero band gap material. As a result, the potential applications of graphene are limited to a few fields of science and technology. Surface functionalization, one of the typical approaches, is well-adopted for the development of functionalized graphene layers. In this scenario, we reviewed the latest advancements exclusively in the development of functionalized graphene layers, and exciting breakthroughs in graphene's science and technology. A brief history along with intrinsic properties of graphene is discussed in the introduction. Then, the methods adopted for the realization of functionalized graphene layers, and the impact of surface modification on their physical and chemical properties along with device performances are elaborately discussed. Finally, the review is summarized and outlined the perspectives of functionalized graphene layers in view of the development of multifunctional high-quality graphene layers for next-generation device applications.</P> <P><B>Graphical abstract</B></P> <P>This review discusses the importance of graphene functionalization, typical methodologies adopted for functionalizing the graphene layers or sheets, and advancements in the performance of graphene-based devices.</P> <P>[DISPLAY OMISSION]</P>

원자층 증착법을 이용한 열전 소재 연구 동향

이승혁,박태주,김성근 한국분말재료학회 2022 한국분말재료학회지 (KPMI) Vol.29 No.1

Atomic layer deposition (ALD) is a promising technology for the uniform deposition of thin films. ALD is based on a self-limiting mechanism, which can effectively deposit thin films on the surfaces of powders of various sizes. Numerous studies are underway to improve the performance of thermoelectric materials by forming core-shell structures in which various materials are deposited on the powder surface using ALD. Thermoelectric materials are especially relevant as clean energy storage materials due to their ability to interconvert between thermal and electrical energy by the Seebeck and Peltier effects. Herein, we introduce a surface and interface modification strategy based on ALD to control the performance of thermoelectric materials. We also discuss the properties of the interface between various deposition materials and thermoelectric materials.

Enhanced Power Conversion Efficiency of Dye-Sensitized Solar Cells Assisted with Phosphor Materials

이용민,김동인,황기환,남상훈,부진효 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.4

Theoretically dye-sensitized solar cells (DSSCs) are high efficiency solar cells. However,DSSCs have lower power conversion efficiency (PCE) than silicon based solar cells. In thisstudy, we use scattering layer and phosphor materials, such as ZrO2 and Zn2SiO4:Mn(Green), to enhance the PCE of DSSCs. The scattering layer and phosphor materials wereprepared and used as an effective scattering layer on the transparent TiO2 photoelectrodethrough the doctor blade method. We confirmed that the scattering layer improves the PCEand Jsc due to the enhancement of light harvesting by increasing the scattering andabsorbance in the visible range. Under sun illumination AM 1.5 conditions, the PCE of themesoporous TiO2 based DSSCs was 5.18%. The PCE of the DSSCs with ZrO2 scatteringlayer was 5.61% and Zn2SiO4:Mn as the scattering layer was enhanced to 5.72%. In order tocompare the change in optical properties, DSSCs were measured by EQE, reflectance andPCE. At the same time, FE-SEM and XRD were used to confirm the structural changes ineach layer.