다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

Freedom of design, mass customisation, waste minimisation and the ability to manufacture complex structures, as well as fast prototyping, are the main benefits of additive manufacturing (AM) or 3D printing. A comprehensive review of the main 3D printing methods, materials and their development in trending applications was carried out. In particular, the revolutionary applications of AM in biomedical, aerospace, buildings and protective structures were discussed. The current state of materials development, including metal alloys, polymer composites, ceramics and concrete, was presented. In addition, this paper discussed the main processing challenges with void formation, anisotropic behaviour, the limitation of computer design and layer-by-layer appearance. Overall, this paper gives an overview of 3D printing, including a survey on its benefits and drawbacks as a benchmark for future research and development.

Additive manufacturing (3D printing): A review of materials, methods, applications and challenges

Recently a new, large family of two-dimensional (2D) early transition metal carbides and carbonitrides, called MXenes, was discovered. MXenes are produced by selective etching of the A element from the MAX phases, which are metallically conductive, layered solids connected by strong metallic, ionic, and covalent bonds, such as Ti2AlC, Ti3AlC2, and Ta4AlC3. MXenes ­combine the metallic conductivity of transition metal carbides with the hydrophilic nature of their hydroxyl or oxygen terminated surfaces. In essence, they behave as “conductive clays”. This article reviews progress—both ­experimental and theoretical—on their synthesis, structure, properties, intercalation, delamination, and potential applications. MXenes are expected to be good candidates for a host of applications. They have already shown promising performance in electrochemical energy storage systems. A detailed outlook for future research on MXenes is also presented.

25th Anniversary Article: MXenes: A New Family of Two‐Dimensional Materials

Since the discovery of mechanically exfoliated graphene in 2004, research on ultrathin two-dimensional (2D) nanomaterials has grown exponentially in the fields of condensed matter physics, material science, chemistry, and nanotechnology. Highlighting their compelling physical, chemical, electronic, and optical properties, as well as their various potential applications, in this Review, we summarize the state-of-art progress on the ultrathin 2D nanomaterials with a particular emphasis on their recent advances. First, we introduce the unique advances on ultrathin 2D nanomaterials, followed by the description of their composition and crystal structures. The assortments of their synthetic methods are then summarized, including insights on their advantages and limitations, alongside some recommendations on suitable characterization techniques. We also discuss in detail the utilization of these ultrathin 2D nanomaterials for wide ranges of potential applications among the electronics/optoelectronics, electrocat...

Recent Advances in Ultrathin Two-Dimensional Nanomaterials

1 M LiPF6 dissolved in oligo(ethylene glycol) dimethyl ether with a molecular weight, 500 g mol−1 (OEGDME500, 1 M LiPF6), was investigated as an electrolyte in experimental Al–Li/LiFePO4 cells. More than 60 cycles were achieved using this electrolyte in a Li-ion cell with an Al–Li alloy as an anode sandwiched between two Li
 x
 FePO4 electrodes (cathodes). Charging efficiencies of 96–100% and energy efficiencies of 86–89% were maintained during 60 cycles at low current densities. A theoretical investigation revealed that the specific energy can be increased up to 15% if conventional LiC6 anodes are replaced by Al–Li alloy electrodes. The specific energy and the energy density were calculated as a function of the active mass per electrode surface (charge density). The results reveal that for a charge density of 4 mAh cm−2 about 160 mWh g−1 can be reached with Al–Li/LiFePO4 batteries. Power limiting diffusion processes are discussed, and the power capability of Al–Li/LiFePO4 cells was experimentally evaluated using conventional electrolytes.

Electrochemical investigation of Al–Li/LixFePO4 cells in oligo(ethylene glycol) dimethyl ether/LiPF6

Phospholipid reinforced P(AAm-co-AAc)/Fe3+ hydrogel with ultrahigh strength and superior tribological performance

The invention discloses a method for making a personalized degradable metal stent or an internal fixing device based on 3D printing. This method includes the following steps: (1) Obtain the corresponding size parameters of the lesion in the human body through the QCA technology, and obtain the structure of the blood vessel stent, other metal stents or internal fixation devices through the three-dimensional reconstruction; (2) Build the 3D models for wax prototypes including blood vessel stents, other metal stents, or internal fixation devices in the computer, and decompose the 3D model into a series of two dimensional thin-film models; (3) Use 3D printing technology to make wax prototypes; (4) introduce plaster to the wax prototypes. After the plaster is hardened, bake it to completely evaporate the wax model prototype, and then the alloy melt is cast. After the casting is completed, the plaster shell is broken to obtain a metal stent or internal fixing device. The invention can be customized according to the patient's diseased blood vessels, and the obtained metal stent or internal fixation device is degradable, with high precision, good mechanical properties as well as good corrosion properties. Drawings Figure 1 Figure Figure 3 Page 1 of 2

Method for preparing personalized degradable metal stent or internal fixation device based on 3D printing

A biodegradable Mg-4Zn-0.6Zr alloy with different content of strontium (Sr) was prepared and studied for orthopedic applications biomaterials. The effects of Sr on the microstructure and corrosion degradation of the as-cast Mg-4Zn-0.6Zr-xSr (ZK40xSr) alloys were investigated. The optical micrograph (OM) observation, energy-dispersive spectrometer (EDS), X-ray diffractometer (XRD) and immersion test were used. The grain size of Mg-4Zn-0.6Zr alloys was reduced obviously with the addition of Sr. The excess of Sr would lead to grain size increasing and grain boundaries widening. The possible presence of the following constituent phases in the grain boundaries: α-Mg, Mg17Sr2, MgZn, ZnxSry binary and MgxZnySrz ternary phase. The formation of ZnxSry and MgxZnySrz phase owed to the larger difference of electronegativity values of Zn and Sr. The immersion tests indicated that the average corrosion rate of the as-cast ZK40xSr alloys increased with the increase of Sr content. It contributed to the micro-galvanic corrosion between the α-Mg with the continuous distribution of grain boundaries precipitates.

A Study on Corrosion Behaviour of Magnesium Alloys

The LiNi0.5Mn1.5O4(LMNO) spinel, has a redox potential of 4.7 V and a theoretical capacity of 147 mAh/g, and is therefore one of the most promising high-voltage cathodes for Li-ion batteries. The nanostructured morphology, in one hand, may benefit this material in delivering high power density and long cycling life; but the high surface side reaction may negatively affect the electrochemical performance. Fundamental understanding of the electronic structural changes of this material during cycling will provide useful information for further development of it. In this study, high-resolution transmission electron microscopy (HRTEM) and electron energy-loss spectroscopy (EELS) are used to probe the local atomic and electronic structures of the electrodes and their change through cycling, especially in the near-surface region. The x-ray absorption spectroscopy (XAS), is also carried out in-situ to monitor the structural changes of the whole electrodes during the charge/discharge cycling. The LMNO materials were synthesized via a nanospray combustion chemical-vapor condensation process, followed by post-annealing at 800C for 3 hours as described in the literature. The samples obtained have a spinel (Fd3m) structure with high phase purity confirmed by XRD. The nanostructure morphology was obtained with average particle size about 100 nm, with facets and smooth surface, as shown in Fig. 2(b). Electrochemical studies were carried through an Arbin cycler in 2025 cells using lithium foil as anode. HRTEM images and EELS spectra of the Li-K, O-K, Mn-L23 and Ni-L23, edges were measured in the JEOL2100F TEM equipped a Gatan imaging filter (GIF). X-ray absorption spectra of Mn-K and Ni-K edges were measured both ex-situ and in-situ, at the beam line X18A in NSLS. Figure 1 shows the Mn Kand Ni K-edge spectra measured in-situ during the first charge. Very little change of the Mn K-edge was observed over the whole charge. There is no change of the Ni K-edge in the first part (below 4.7 V); but a gradual shift to higher energy positions can be clearly observed in the 2 part, which is attributed to the oxidation of Ni from Ni to Ni, leading to a long plateaus at about 4.7 V. Spectra of the O Kand Mn L23-edges, across a single particle, from the surface towards the center, are shown in Figure 2. The near-edge fine structures, such as the prepeak of the O-K edge, and the crystal field splitting, i.e., t2g and eg, of the Mn L3, are characteristic features of Mn at low oxidation state, i.e. Mn in the near-surface region, and Mn in the bulk. We also noticed the low concentration of Ni in the near-surface region. The EELS measurements are consistent with the local structures measured by HRTEM image (Fig. 3a), in which a different phase, the Rhombohedral Li(NixMn)O2, rather than the spinel, was identified in the near-surface region (Fig. 3b). The measurements of local atomic and electronic structure by TEM and EELS are important for understanding the oxidation of Mn from Mn to Mn that occurs only locally in the near-surface region, which further explains the small plateau at 4.2 V in the charge curve (Fig. 1b); while no significant change of the Mn Kedge was detected by the XAS measurements. More importantly, the local analysis enables us to explore the surface change due to the direct reaction with electrolyte resulting in a structural evolution over cycling, which is critical to understanding the degradation of LNMO electrodes during cycling. We are also working towards better understanding of the correlation of the XANES of Ni K-edge with the immediate environment, i.e. bonding and coordination by DFT calculations; some of the results will be discussed.

http://ma.ecsdl.org/content/MA2011-02/12/663.full.pdf

Xiaojian Wang

Papers

Electrochemical investigation of Al–Li/LixFePO4 cells in oligo(ethylene glycol) dimethyl ether/LiPF6

Phospholipid reinforced P(AAm-co-AAc)/Fe3+ hydrogel with ultrahigh strength and superior tribological performance

Method for preparing personalized degradable metal stent or internal fixation device based on 3D printing

A Study on Corrosion Behaviour of Magnesium Alloys

Investigation of the Electrochemical Behavior of Nano LiNi0.5Mn1.5O4-δ by TEM,EELS and XAS