Investigation of grafted mesoporous silicon sponge using hyperpolarized ¹²⁹Xe NMR spectroscopy

Mao, Yougang,Kim, Dokyoung,Hopson, Russell,Sailor, Michael J.,Wang, Li-Qiong Cambridge University Press (Materials Research Soc 2018 Journal of materials research Vol.33 No.17

<▼1><B>Abstract</B><P/></▼1><▼2><P>Temperature-dependent (173-373 K) hyperpolarized <SUP>129</SUP>Xe nuclear magnetic resonance (<SUP>129</SUP>Xe NMR) analyses along with transmission electron microscopy and N2 adsorption measurements have been applied to understand pore structure and interconnectivity of bare and grafted mesoporous silicon sponge (MSS) materials. The Xe NMR chemical shift data indicate the existence of micropores inside the larger mesopore channels and the effects of grafting on the pore surfaces. The grafted layer estimated at 2 nm in thickness blocks the micropores on the surfaces of mesoporous channels. Partitioning of Xe between the micropores and the mesopores in the MSS materials is temperature-dependent, with Xe principally occupying the micropores at lower temperatures. In addition, the temperature-dependent Xe peak shift of MSS materials verifies the increased uniformity and interconnectivity of mesopores after surface grafting. The results from this study provide useful information for design and development of novel materials.</P></▼2>

Theranostic applications of organic nanoparticles for cancer treatment

Yhee, Ji Young,Son, Sohee,Kim, Namho,Choi, Kuiwon,Kwon, Ick Chan Cambridge University Press (Materials Research Soc 2014 MRS bulletin Vol.39 No.3

<▼1><B>Abstract</B><P/></▼1><▼2><P>Research in nanotechnology-based molecular imaging and targeted drug delivery has resulted in a noticeable progress in cancer theranosis, the simultaneous application of cancer therapy and diagnosis. Theranostic nanoparticles (NPs) have been developed using diverse base materials, and organic materials are of major interest in the synthesis and preparation of these NPs. A variety of organic NPs have their own advantages, depending on the physiochemical and biological properties of the base materials. This article reviews recent developments in organic NPs, which are grouped into four major kinds of base materials: lipids, polysaccharides, peptides/proteins, and synthetic polymers. The advantageous properties of frequently used base materials and practical performance of the various organic NPs <I>in vivo</I> are discussed. These theranostic NPs offer new opportunities for effective cancer treatment.</P></▼2>

A spherical indentation technique for property evaluation of hyperelastic rubber

Hyun, Hong Chul,Lee, Jin Haeng,Kim, Minsoo,Lee, Hyungyil Cambridge University Press (Materials Research Soc 2012 Journal of materials research Vol.27 No.20

<▼1><B>Abstract</B><P/></▼1><▼2><P>The numerical approach of Lee et al. [<I>Trans. Korean Soc. Mech. Eng., A</I>28, 816-825 (2004)] to spherical indentation technique for property evaluation of hyperelastic rubber is enhanced. The Yeoh model is adopted as the constitutive form of rubber material because it can express well large deformation and cover various deformation modes with a simple form. We first determine the friction coefficient between a rubber specimen and a spherical indenter in a practical viewpoint and perform finite element simulations for a deeper indentation depth than that selected by Lee et al. [<I>Trans. Korean Soc. Mech. Eng., A</I>28, 816-825 (2004)]. An optimal data acquisition spot is selected, which features sufficiently large strain energy density and negligible frictional effect. We improve then two normalized functions mapping an indentation load-displacement curve onto a strain energy density-invariant curve, the latter of which gives the Yeoh model constants. The enhanced spherical indentation approach successfully produces the rubber material properties with an average error of less than 5%. The validity of our developed approach is verified by experimental evaluation of material properties with three kinds of rubber materials.</P></▼2>

Plasticity in the nanoscale Cu/Nb single-crystal multilayers as revealed by synchrotron Laue x-ray microdiffraction

Budiman, Arief Suriadi,Han, Seung-Min,Li, Nan,Wei, Qiang-Min,Dickerson, Patricia,Tamura, Nobumichi,Kunz, Martin,Misra, Amit Cambridge University Press (Materials Research Soc 2012 Journal of materials research Vol.27 No.3

<▼1><B>Abstract</B><P/></▼1><▼2><P>There is much interest in the recent years in the nanoscale metallic multilayered composite materials due to their unusual mechanical properties, such as very high flow strength and stable plastic flow to large strains. These unique mechanical properties have been proposed to result from the interface-dominated plasticity mechanisms in nanoscale composite materials. Studying how the dislocation configurations and densities evolve during deformation will be crucial in understanding the yield, work hardening, and recovery mechanisms in the nanolayered materials. In an effort to shed light on these topics, uniaxial compression experiments on nanoscale Cu/Nb single-crystal multilayer pillars using ex situ synchrotron-based Laue x-ray microdiffraction technique were conducted. Using this approach, we studied the nanoscale Cu/Nb multilayer pillars before and after uniaxial compression to about 14% of plastic strain and found significant Laue peak broadening in the Cu phase, which indicates storage of statistically stored dislocations, while no significant Laue peak broadening was observed in the Nb phase in the nanoscale multilayers. These observations suggest that at 14% plastic strain of the nanolayered pillars, the deformation was dominated by plasticity in the Cu nanolayers and elasticity or possibly a zero net plasticity (due to the possibility of annihilation of interface dislocations) in the Nb nanolayers.</P></▼2>

Three-dimensionally printed cellular architecture materials: perspectives on fabrication, material advances, and applications

Kaur, Manpreet,Han, Seung Min,Kim, Woo Soo Cambridge University Press (Materials Research Soc 2017 MRS Communications Vol.7 No.1

<▼1><B>Abstract</B><P/></▼1><▼2><P>Three-dimensional (3D) printing generates cellular architected metamaterials with complex geometries by introducing controlled porosity. Their ordered architecture, imitative from the hierarchical high-strength structure in nature, defines the mechanical properties that can be coupled with other properties such as the acoustic, thermal, or biologic response. Recent progress in the field of 3D architecture materials have advanced that enables for design of lightweight materials with high strength and stiffness at low densities. Applications of these materials have been identified in the fields of ultra-lightweight structures, thermal management, electrochemical devices, and high absorption capacity.</P></▼2>

Surface modification and fabrication of 3D nanostructures by atomic layer deposition

Bae, Changdeuck,Shin, Hyunjung,Nielsch, Kornelius Cambridge University Press (Materials Research Soc 2011 MRS bulletin Vol.36 No.11

<▼1><B>Abstract</B><P/></▼1><▼2><P>Atomic layer deposition (ALD) not only presents a direct way to prepare nanomaterials when combined with templates, but also allows surface engineering to fine-tune the properties of the material. Here, we review recent progress in the field of nanostructured materials and devices that have been fabricated by ALD. Various materials, including semiconducting, magnetic, noble metallic, and insulating materials, can be used to form three-dimensional (3D), complex nanostructures with controlled composition and physical properties. We begin this review with ALD nanomaterials that can be prepared from porous templates with a 2D pore arrangement, such as anodic aluminum oxide, and advance toward opal structures with a 3D pore arrangement. We also discuss surface engineering by ALD on existing nanowires/nanotubes, devices, and chemical patterns that has the potential for application in high-performance transistors, sensors, and green energy conversion. Finally, we provide perspectives for future device applications that could arise from ALD nanomaterials.</P></▼2>

Electrochemical and ex-situ analysis on manganese oxide/graphene hybrid anode for lithium rechargeable batteries

Kim, Haegyeom,Kim, Sung-Wook,Hong, Jihyun,Park, Young-Uk,Kang, Kisuk Cambridge University Press (Materials Research Soc 2011 Journal of materials research Vol.26 No.20

<▼1><B>Abstract</B><P/></▼1><▼2><P>A Mn3O4/graphene hybrid material is fabricated using a facile and simple in-situ reduction process and shown to be a promising anode for lithium rechargeable batteries. The hybrid material retains a high capacity with a good cycle life of up to 990 mAh g<SUP>−1</SUP> after 30 cycles. The excellent electrochemical performance is attributable to the unique nanostructure of the hybrid material. Highly crystalline Mn3O4 particles (20-30 nm) are uniformly dispersed on graphene whose high electronic conductivity and high surface area provide a conductive percolating network throughout the electrode in the hybrid material. The conductive graphene networks enhance an electron transfer in the electrode and promote the electrochemical activity of the crystalline Mn3O4.</P></▼2>

An efficient way of extracting creep properties from short-time spherical indentation tests

Rickhey, Felix,Lee, Jin Haeng,Lee, Hyungyil Cambridge University Press (Materials Research Soc 2015 Journal of materials research Vol.30 No.22

<▼1><B>Abstract</B><P/></▼1><▼2><P>Indentation as a means to extract creep properties has the advantage that it can be applied directly to micro/nano-structures. Many studies on indentation creep reported at least partially poor agreement with creep parameters derived from uniaxial test. One important reason for the incompatibility is the neglect of transient creep. Another one is the choice of equivalent stress and strain measures to relate the different material responses. Applying a material model that accounts for transient creep effects we propose an efficient method for deriving creep properties from short-time spherical indentation tests. We first determine a subsurface point where the material response is very close to that observed in uniaxial tests. We then map the load-displacement data to the material response, expressed in terms of two dimensionless variables, at this point. Converting the dimensionless variables data to stress, strain, and strain rate data, we finally determine the material's creep coefficient and exponent.</P></▼2>

Developing high-capacity hydrogen storage materials via quantum simulations

Jhi, Seung-Hoon,Ihm, Jisoon Cambridge University Press (Materials Research Soc 2011 MRS bulletin Vol.36 No.3

<▼1><B>Abstract</B><P/></▼1><▼2><P>Hydrogen is considered by some to be a promising non-CO2-emitting energy carrier for the future. However, to realize a hydrogen economy, there are several technological barriers to overcome. Currently, safe and efficient storage of hydrogen is a bottleneck in the practical usage of hydrogen for fuels. In this article, we present a review on the first-principles computational approach in designing hydrogen storage materials with an emphasis on molecular hydrogen storage in nanostructured materials. Given the limitation of pristine nanostructures for room-temperature hydrogen storage, the strategy of decorating the backbone structure of the nanostructure with transition metal atoms in order to enhance the hydrogen adsorption energy is addressed, and the interplay between the Coulomb interactions and the so-called Kubas interaction (nondissociative weak chemisorption via electron donation and back-donation channels) has been studied. The influence of electron spin on the hydrogen binding energy, problems of metal clustering and oxidation, and the structural instability that may arise during hydrogen sorption are also discussed. We address the limitations and challenges in the development of high-capacity hydrogen storage materials and provide perspectives for how computational materials design can help cope with those problems.</P></▼2>

Ultrafast electron energy-loss spectroscopy in transmission electron microscopy

Pomarico, Enrico,Kim, Ye-Jin,Garcí,a de Abajo, F. Javier,Kwon, Oh-Hoon,Carbone, Fabrizio,van der Veen, Renske M. Cambridge University Press (Materials Research Soc 2018 MRS bulletin Vol.43 No.7

<▼1><B>Abstract</B><P/></▼1><▼2><P>In the quest for dynamic multimodal probing of a material’s structure and functionality, it is critical to be able to quantify the chemical state on the atomic-/nanoscale using element-specific electronic and structurally sensitive tools such as electron energy-loss spectroscopy (EELS). Ultrafast EELS, with combined energy, time, and spatial resolution in a transmission electron microscope, has recently enabled transformative studies of photoexcited nanostructure evolution and mapping of evanescent electromagnetic fields. This article aims to describe state-of-the-art experimental techniques in this emerging field and its major uses and future applications.</P></▼2>