Frontiers of Materials Science


ISSN 2095-025X (Print)
ISSN 2095-0268 (Online)
CN 11-5985/TB
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Influence of service temperature on tribological characteristics of self-lubricant coatings: A review
Jun-Feng YANG, Yan JIANG, Jens HARDELL, Braham PRAKASH, Qian-Feng FANG
Front Mater Sci    2013, 7 (1): 28-39.
Abstract   HTML   PDF (408KB)

Self-lubricating coatings have been widely used to reduce friction in moving machine assemblies. However, the tribological performance of these coatings is strongly dependent on the service temperature. In this paper, an extensive review pertaining to the influence of operating service temperature on tribological performance of self-lubricating coatings has been carried out. Based on the effective lubricating temperature range, the self-lubricating coatings developed in the past have been divided into three groups: low temperature lubricant coating (from--200°C to room temperature), moderate temperature lubricant coating (from room temperature to 500°C) and high temperature lubricant coating (>500°C). Ideas concerning possible ways to extend the operating temperature range of self-lubricating coatings have been presented as follows: hybridized tribological coating, adaptive tribological coatings, and diffusion rate limited solid lubricant coating. In addition, a new self-lubricating coating formulation for potential application at a wide operating temperature range has been proposed.

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Microstructural stability of 9--12%Cr ferrite/martensite heat-resistant steels
Front Mater Sci    2013, 7 (1): 1-27.
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The microstructural evolutions of advanced 9--12%Cr ferrite/martensite heat-resistant steels used for power generation plants are reviewed in this article. Despite of the small differences in chemical compositions, the steels share the same microstructure of the as-tempered martensite. It is the thermal stability of the initial microstructure that matters the creep behavior of these heat-resistant steels. The microstructural evolutions involved? in? 9--12%Cr ?ferrite ?heat-resistant ?steels ?are ?elabo- rated, including (1) martensitic lath widening, (2) disappearance of prior austenite grain boundary, (3) emergence of subgrains, (4) coarsening of precipitates, and (5) formation of new precipitates, such as Laves-phase and Z-phase. The former three microstructural evolutions could be retarded by properly disposing the latter two. Namely improving the stability of precipitates and optimizing their size distribution can effectively exert the beneficial influence of precipitates on microstructures. In this sense, the microstructural stability of the tempered martensite is in fact the stability of precipitates during the creep. Many attempts have been carried out to improve the microstructural stability of 9--12%Cr steels and several promising heat-resistant steels have been developed.

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A study on the in vitro degradation of poly(L-lactide)/chitosan microspheres scaffolds
Ning ZHU, David COOPER, Xiong-Biao CHEN, Catherine Hui NIU
Front Mater Sci    2013, 7 (1): 76-82.
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Recent research shows that the addition of chitosan microspheres (CMs) to poly(L-lactide) (PLLA) can result in a composite scaffold material with improved biocompatibility and mechanical properties for tissue engineering applications. However, research regarding the influence of CMs on scaffold degradation is absent in the literature. This paper presents a study on the in vitro degradation of scaffolds made from PLLA with CMs. In this study, the PLLA/CMs scaffolds with a 25% ratio of CMs to PLLA were immersed in phosphate-buffered saline (PBS) solution at 37°C for 8 weeks. The in vitro degradation of the scaffolds was investigated using micro-computed tomography (μCT), weight loss analysis, Raman spectroscopy, and differential scanning calorimetry (DSC). Microstructure changes during degradation were monitored using μCT. The μCT results were consistent with the results obtained from Raman spectra and DSC analysis, which reflected that adding CMs into PLLA can decrease the degradation rate compared with pure PLLA scaffolds. The results suggest that PLLA/CMs scaffold degradation can be regulated and controlled to meet requirements imposed a given tissue engineering application.

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Scaffolds for central nervous system tissue engineering
Jin HE, Xiu-Mei WANG, Myron SPECTOR, Fu-Zhai CUI
Front Mater Sci    2012, 6 (1): 1-25.
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Traumatic injuries to the brain and spinal cord of the central nervous system (CNS) lead to severe and permanent neurological deficits and to date there is no universally accepted treatment. Owing to the profound impact, extensive studies have been carried out aiming at reducing inflammatory responses and overcoming the inhibitory environment in the CNS after injury so as to enhance regeneration. Artificial scaffolds may provide a suitable environment for axonal regeneration and functional recovery, and are of particular importance in cases in which the injury has resulted in a cavitary defect. In this review we discuss development of scaffolds for CNS tissue engineering, focusing on mechanism of CNS injuries, various biomaterials that have been used in studies, and current strategies for designing and fabricating scaffolds.

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Calcium carbonate crystallization controlled by functional groups: A mini-review
Hua DENG, Xing-Can SHEN, Xiu-Mei WANG, Chang DU
Front Mater Sci    2013, 7 (1): 62-68.
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Various functional groups have been suggested to play essential roles on biomineralization of calcium carbonate (CaCO3) in natural system. 2D and 3D models of regularly arranged functional groups have been established to investigate their effect on CaCO3 crystallization. This mini-review summarizes the recent progress and the future development is prospected.

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Recent research situation in tin dioxide nanomaterials: synthesis, microstructures, and properties
Zhi-Wen CHEN, Chan-Hung SHEK, C. M. Lawrence WU, Joseph K. L. LAI
Front Mater Sci    2013, 7 (3): 203-226.
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This review article summarizes the new research in solid-state physical chemistry understanding of the microstructure characteristics of semiconductor tin oxide thin films made in the last years in our group. The work mainly focuses on the fabrication technology of semiconductor tin oxides thin films by using pulsed laser deposition (PLD) as well as the application of this technology on new micro- and nanostructured materials. It is an interdisciplinary work that integrates the areas of physics, chemistry and materials science.

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A general synthesis strategy for the multifunctional 3D polypyrrole foam of thin 2D nanosheets
Jiangli XUE, Maosong MO, Zhuming LIU, Dapeng YE, Zhihua CHENG, Tong XU, Liangti QU
Front. Mater. Sci.    2018, 12 (2): 105-117.
Abstract   HTML   PDF (600KB)

A 3D macroporous conductive polymer foam of thin 2D polypyrrole (PPy) nanosheets is developed by adopting a novel intercalation of guest (monomer Py) between the layers of the lamellar host (3D vanadium oxide foam) template-replication strategy. The 3D PPy foam of thin 2D nanosheets exhibits diverse functions including reversible compressibility, shape memory, absorption/adsorption and mechanically deformable supercapacitor characteristics. The as-prepared 3D PPy foam of thin nanosheets is highly light weight with a density of 12 mg·cm−3 which can bear the large compressive strain up to 80% whether in wet or dry states; and can absorb organic solutions or extract dye molecules fast and efficiently. In particular, the PPy nanosheet-based foam as a mechanically deformable electrode material for supercapacitors exhibits high specific capacitance of 70 F·g−1 at a fast charge–discharge rate of 50 mA·g−1, superior to that of any other typical pure PPy-based capacitor. We envision that the strategy presented here should be applicable to fabrication of a wide variety of organic polymer foams and hydrogels of low-dimensional nanostructures and even inorganic foams and hydrogels of low-dimensional nanostructures, and thus allow for exploration of their advanced physical and chemical properties.

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Circular dichroism of graphene oxide: the chiral structure model
Jing CAO, Hua-Jie YIN, Rui SONG
Front Mater Sci    2013, 7 (1): 83-90.
Abstract   HTML   PDF (691KB)

We have observed the circular dichroism signal of dilute graphene oxide (GO), then systematically investigated the chirality of GO and established a probable chiral unit model. This study may open up a new field for understanding the structure of GO and lay the foundation for fabrication of GO-based materials.

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Electrical and non-linear optical studies on electrospun ZnO/BaO composite nanofibers
Front Mater Sci    2012, 6 (1): 69-78.
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Nanocapacitors and nonvolatile ferroelectric random access memories require nanoscale thin film coatings with ferroelectric properties. One dimensional ferroelectric nanofibers are used in ferroelectric memory devices owing to the fact that decrease of the dimensionality of the memory device elements will reduce the addressing and appreciably increase the storage capacity. Novel ZnO/BaO nanocomposite fibers exhibiting ferroelectric properties have been prepared in the form of non-woven mesh by electrospinning the sol derived from the sol-gel route. Thin cylindrical nanofibers of average diameter 100 nm have been obtained and their morphology is confirmed by SEM and AFM images. In the electrospinning process, the effect of the working distance on the fiber morphology was studied and it showed that working distance between 11 and 15 cm can produce fibers without beads and the decrease in working distance in this range increases the fiber diameter. Powder XRD was used to identify the phases and EDX analysis confirmed the presence of ZnO/BaO. Dielectric and non-linear optical properties have also been studied. The dielectric studies showed that ZnO/BaO composite nanofibers undergo a phase transition from ferroelectric to paraelectric at 323 K.

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Preparation of poly(N-isopropylacrylamide) brush grafted silica particles via surface-initiated atom transfer radical polymerization used for aqueous chromatography
Zong-Jian LIU, Yan-Li LIANG, Fang-Fang GENG, Fang LV, Rong-Ji DAI, Yu-Kui ZHANG, Yu-Lin DENG
Front Mater Sci    2012, 6 (1): 60-68.
Abstract   HTML   PDF (214KB)

Thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) brushes were densely grafted onto silica surface via surface-initiated atom transfer radical polymerization (SI-ATRP). The grafting reaction started from the surfaces of 2-bromoisobutyrate-functionalized silica particles in 2-propanol aqueous solution at ambient temperature using CuCl/CuCl2/N,N,N′,N′,N″-pentamethyldiethylenetriamine (PMDETA) as the catalytic system. Based on thermogravimetric analysis (TGA) results, the grafting amount and grafting density of PNIPAM chains on the surface of silica were calculated to be 1.29 mg/m2 and 0.0215 chains/nm2, respectively. The gel permeation chromatography (GPC) result showed the relatively narrow molecular weight distribution (Mw/Mn=1.21) of the grafted PNIPAAm. The modified silica particles were applied as high-performance liquid chromatography (HPLC) packing materials to successfully separate three aromatic compounds using water as mobile phase by changing column temperature. Temperature-dependent hydrophilic/hydrophobic property alteration of PNIPAAm brushes grafted on silica particles was determined with chromatographic interaction between stationary phase and analytes. Retention time was prolonged and resolution was improved with increasing temperature. Baseline separation with high resolution at relatively low temperatures was observed, demonstrating dense PNIPAAm brushes were grafted on silica surfaces.

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Li-ion storage performance and electrochemically induced phase evolution of layer-structured Li[Li0.2Mn0.54Ni0.13Co0.13]O2 cathode material
Ying WANG,Hong ZHANG,Zhiyuan MA,Gaomin WANG,Zhicheng LI
Front. Mater. Sci.    2016, 10 (2): 187-196.
Abstract   HTML   PDF (1131KB)

Li-rich Li[Li0.2Mn0.54Ni0.13Co0.13]O2 (LMNC) powders were synthesized by a gel-combustion method. The related microstructure, electrochemical performance and electrochemically induced phase evolution were characterized. The 900°C calcined powders have a hexagonal layered structure with high ordered degree and low cationic mixing level. The calcined materials as cathode electrode for Li-ion battery deliver the high electrochemical properties with an initial discharge capacity of 243.5 mA·h·g1 at 25 mA·g1 and 249.2 mA·h·g1 even after 50 cycles. The electrochemically induced phase evolution investigated by a transmission electron microscopy indicates that Li+ ions deintercalated first from the LiMO2 (M= Mn, Co, Ni) component and then from Li2MnO3 component in the LMNC during the charge process, while Li+ ions intercalated into Li1xMO2 component followed by into MnO2 component during the discharge process.

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Cobalt-based layered double hydroxides as oxygen evolving electrocatalysts in neutral eletrolyte
Hong LIN, Ye ZHANG, Gang WANG, Jian-Bao LI
Front Mater Sci    2012, 6 (2): 142-148.
Abstract   HTML   PDF (379KB)

Co–M (M= Co, Ni, Fe, Mn) layered double hydroxides (LDHs) were successfully fabricated by a hexamethylenetetramine (HMT) pyrolysis method. Composite electrodes were made using a self-assembly fashion at inorganic/organic surface binder-free and were used to catalyze oxygen evolution reaction. Water oxidation can take place in neutral electrolyte operating with modest overpotential. The doping of other transitional metal cations affords mix valences and thus more intimate electronic interactions for reversible chemisorption of dioxygen molecules. The application of employing LDH materials in water oxidation process bodes well to facilitate future hydrogen utilization.

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Carbon nanomaterials: controlled growth and field-effect transistor biosensors
Xiao-Na WANG, Ping-An HU
Front Mater Sci    2012, 6 (1): 26-46.
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Carbon nanostructures, including carbon nanotubes (CNTs) and graphene, have been studied extensively due to their special structures, excellent electrical properties and high chemical stability. With the development of nanotechnology and nanoscience, various methods have been developed to synthesize CNTs/graphene and to assemble them into microelectronic/sensor devices. In this review, we mainly demonstrate the latest progress in synthesis of CNTs and graphene and their applications in field-effect transistors (FETs) for biological sensors.

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Magnetic motive, ordered mesoporous carbons with partially graphitized framework and controllable surface wettability: preparation, characterization and their selective adsorption of organic pollutants in water
Bin ZHANG,Chen LIU,Weiping KONG,Chenze QI
Front. Mater. Sci.    2016, 10 (2): 147-156.
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Magnetically active, ordered and stable mesoporous carbons with partially graphitized networks and controllable surface wettability (PR-Fe-P123-800 and PR-Ni-P123-800) have been synthesized through direct carbonization of Fe or Ni functionalized, and ordered mesoporous polymers at 800°C, which could be synthesized from self assembly of resol (phenol/formaldehyde) with block copolymer template (P123) in presence of Fe3+ or Ni2+, and hydrothermal treatment at 200°C. PR-Fe-P123-800 and PR-Ni-P123-800 possess ordered and uniform mesopores, large BET surface areas, good stabilities, controllable surface wettability and partially graphitized framework. The above structural characteristics result in their enhanced selective adsorption property and good reusability for organic pollutants such as RhB, p-nitrophenol and n-heptane in water, which could be easily regenerated through separation under constant magnetic fields and washing with ethanol solvent. The unique magnetically active and adsorptive property found in PR-Fe-P123-800 and PR-Ni-P123-800 will be very important for them to be used as efficient absorbents for removal of various organic pollutants in water.

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Maintenance and induction of murine embryonic stem cell differentiation using E-cadherin-Fc substrata without colony formation
Qing-Yuan MENG, Toshihiro AKAIKE
Front Mater Sci    2013, 7 (1): 51-61.
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Induced embryonic stem (ES) cells are expected to be promising cell resources for the observation of the cell behaviors in developmental biology as well as the implantation in cell treatments in human diseases. A recombinant E-cadherin substratum was developed as a cell recognizable substratum to maintain the ES cells’ self-renewal and pluripotency at single cell level. Furthermore, the generation of various cell lineages in different germ layers, including hepatic or neural cells, was achieved on the chimeric protein layer precisely and effectively. The induction and isolation of specific cell population was carried out with the enhancing effect of other artificial extracellular matrices (ECMs) in enzyme-free process. The murine ES cell-derived cells showed highly morphological similarities and functional expressions to matured hepatocytes or neural progenitor cells.

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The multifunctional wound dressing with core–shell structured fibers prepared by coaxial electrospinning
Qilin WEI,Feiyang XU,Xingjian XU,Xue GENG,Lin YE,Aiying ZHANG,Zengguo FENG
Front. Mater. Sci.    2016, 10 (2): 113-121.
Abstract   HTML   PDF (672KB)

The non-woven wound dressing with core–shell structured fibers was prepared by coaxial electrospinning. The polycaprolactone (PCL) was electrospun as the fiber’s core to provide mechanical strength whereas collagen was fabricated into the shell in order to utilize its good biocompatibility. Simultaneously, the silver nanoparticles (Ag-NPs) as anti-bacterial agent were loaded in the shell whereas the vitamin A palmitate (VA) as healing-promoting drug was encapsulated in the core. Resulting from the fiber’s core–shell structure, the VA released from the core and Ag-NPs present in the shell can endow the dressing both heal-promoting and anti-bacteria ability simultaneously, which can greatly enhance the dressing’s clinical therapeutic effect. The dressing can maintain high swelling ratio of 190% for 3 d indicating its potential application as wet dressing. Furthermore, the dressing’s anti-bacteria ability against Staphylococcus aureus was proved by in vitro anti-bacteria test. The in vitro drug release test showed the sustainable release of VA within 72 h, while the cell attachment showed L929 cells can well attach on the dressing indicating its good biocompatibility. In conclusion, the fabricated nanofibrous dressing possesses multiple functions to benefit wound healing and shows promising potential for clinical application.

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Effect of electrochemical etching current on prepared perforated silicon structures for neutron detectors
Xiao-Qiang FAN, Yong JIANG, Chang-Yong ZHAN, Yu ZOU, Jian-Chun WU, Ning-Kang HUANG
Front Mater Sci    2013, 7 (1): 96-101.
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Neutron detector based on perforated silicon structures backfilled with neutron converting materials could be operated at a low voltage and improves the detection efficiency of thermal neutron. It is found that the intrinsic detection efficiency of thermal neutron is affected by a lot of factors such as the geometry, size, and depth of the perforation and so on. In this study, the perforated silicon was prepared by electrochemical etching. Effect of etching current on geometry, size, and depth of the perforated silicon structures for neutron detectors was also reported.

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Hydrothermal synthesis of blue-emitting YPO4:Yb3+ nanophosphor
Guangfa WANG,Linhui GAO,Hongliang ZHU,Weijie ZHOU
Front. Mater. Sci.    2016, 10 (2): 197-202.
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The blue-emitting YPO4 phosphors doped with Yb3+ were prepared by a simple hydrothermal method. All the products were characterized by XRD and TEM, which revealed that they were zircon structure with leaf-like morphology. According to the analysis of photoluminescence spectra, upon ultraviolet (275 nm) excitation, the Yb3+ doped YPO4 phosphor showed an intense blue emission composed of two main bands at 420 and 620 nm assigned to charge transfer state (CTS) → 2F5/2 and CTS → 2F7/2, respectively. Moreover, the optimum doping concentration of Yb3+ in YPO4 phosphor was 1%, which exhibited the maximum emission intensity. The possible physical mechanism of concentration quenching was discussed, and the critical transfer distance determined to be 23.889 ?. In particular, the color purity of the as-synthesized Yb3+ doped YPO4 phosphor was as high as 83%, which made it an excellent candidate for blue-emitting materials.

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Multifunctional nanoparticle systems for combined chemo- and photothermal cancer therapy
Hai WANG, Yu-Liang ZHAO, Guang-Jun NIE
Front Mater Sci    2013, 7 (2): 118-128.
Abstract   HTML   PDF (473KB)

Hyperthermia has long been considered as an adjuvant therapy for treating various diseases. Cancer treatment exploiting hyperthermia shows great clinical potential for a wide range of tumors. Importantly, the efficacy of hyperthermal therapy has recently been enhanced by the development of functional nanomaterials. The unique physicochemical properties of nanomaterials afford the specific localization of hyperthermia to primary tumors and early-stage cancers. In particular, due to their high rate of light-to-heat conversion and their capacity to be activated by tissue-penetrating electromagnetic radiation, near-infrared (NIR) light-absorbing plasmonic nanomaterials have attracted considerable attention as candidates for noninvasive photothermal therapy. The purpose of this article is to provide a overview on the current development in multifunctional nanomaterials capable of combined hyperthermia-chemotherapy delivery.

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Shaped gold and silver nanoparticles
Yugang SUN, Changhua AN
Front Mater Sci    2011, 5 (1): 1-24.
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Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticle shape and its internal crystalline structures. According to the relationship, the nanoparticles with well-defined shapes are classified into three categories: nanoparticles with single crystallinity, nanoparticles with angular twins, and nanoparticles with parallel twins. Discussion and analysis on the classical methods for the synthesis of shaped nanoparticles in each category are also included and personal perspectives on the future research directions in the synthesis of shaped metal nanoparticles are briefly summarized. This review is expected to provide a guideline in designing the strategy for the synthesis of shaped nanoparticles and analyzing the corresponding growth mechanism.

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Synthesis, characterization, antibacterial and photocatalytic performance of Ag/AgI/TiO2 hollow sphere composites
Zhihong JING, Xiue LIU, Yan DU, Yuanchun HE, Tingjiang YAN, Wenliang WANG, Wenjuan LI
Front. Mater. Sci.    2020, 14 (1): 1-13.
Abstract   HTML   PDF (3445KB)

Dispersed TiO2 hollow spheres were successfully prepared which was obtained via Ostwald ripening under solvothermal conditions without any templates or surfactants. Then, the AgI/TiO2 was synthesized by the deposition−precipitation process. Finally, Ag/AgI/TiO2 was obtained by a photocatalytic reduction way. Their characteristics were analyzed by XRD, SEM, HRTEM, N2 adsorption−desorption measurements and UV-vis absorption spectra. To demonstrate the potential applications of such composites, their antibacterial activity against Escherichia coli (E. coli) was studied by microcalorimetry for the first time, and their photocatalytic performance for degradation of different organic dyes under simulated UV and visible light was discussed. The results indicated that Ag/AgI/TiO2 hollow spheres revealed elevated antibacterial and photocatalytic activity because of their unique morphology, hollow structure and high surface area. The mechanism of the excellent antibacterial and photocatalytic activity of Ag/AgI/TiO2 hollow spheres are discussed which are attributed to the synergetic effect of Ag, AgI and TiO2. It suggested that the new Ag/AgI/TiO2 photocatalyst has broad application prospects in solar cell, sensor, antibacterial, catalysis and nanotechnology.

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The role of crystallinity on differential attachment/proliferation of osteoblasts and fibroblasts on poly(caprolactone-co-glycolide) polymeric surfaces
Helen CUI, Patrick J. SINKO
Front Mater Sci    2012, 6 (1): 47-59.
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The objective of the present study is to systematically evaluate the role of polymer crystallinity on fibroblast and osteoblast adhesion and proliferation using a series of poly(caprolactone-co-glycolide) (PCL/PGA) polymers. PCL/PGA polymers were selected since they reflect both highly crystalline and amorphous materials. PCL/PGA polymeric materials were fabricated by compression molding into thin films. Five compositions, from PCL or PGA to intermediate copolymeric compositions of PCL/PGA in ratios of 25:75, 35:65 and 45:55, were studied. Pure PCL and PGA represented the crystalline materials while the copolymers were amorphous. The polymers/copolymers were characterized using DSC to assess crystallinity, contact angle measurement for hydrophobicity, and AFM for nanotopography. The PCL/PGA films demonstrated similar hydrophobicity and nanotopography whereas they differed significantly in crystallinity. Cell adhesion to and proliferation on PCL/PGA films and proliferation studies were performed using osteoblasts and NIH-3T3 fibroblasts. It was observed that highly crystalline and rigid PCL and PGA surfaces were significantly more efficient in supporting fibroblast growth, whereas amorphous/flexible PCL/PGA 35:65 was significantly more efficient in supporting growth of osteoblasts. This study demonstrated that while chemical composition, hydrophobicity and surface roughness of PCL/PGA polymers were held constant, crystallinity and rigidity of PCL/PGA played major roles in determining cell responses.

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Characterization of decellularized scaffold derived from porcine meniscus for tissue engineering applications
Shuang GAO,Zhiguo YUAN,Tingfei XI,Xiaojuan WEI,Quanyi GUO
Front. Mater. Sci.    2016, 10 (2): 101-112.
Abstract   HTML   PDF (4166KB)

Menisci are fundamental fibrocartilaginous organs in knee joints. The injury in meniscus can impair normal knee function and predisposes patients to osteoarthritis. This study prepared decellularized meniscus scaffolds using a 1% (w/w) sodium dodecyl sulfate solution and sufficient rinsing steps. Complete cell removal was verified by hematoxylin and eosin staining and DNA content assay. Decellularized menisci had accordant tension properties to intact ones, but with declined compression properties. This occurred because the collagen fiber was not damaged but glycosaminoglycans was significantly lost during the decellularization process, which was confirmed by biochemical assay and histology staining. In vitro cytotoxicity assay demonstrated that decellularized meniscus scaffolds have no toxicity on L929 murine fibroblasts and porcine chondrocytes. Further experiment showed that porcine chondrocytes could adhere and proliferate on the scaffold surface, and some cells even could infiltrate into the scaffold. All results showed the potential of this decellularized meniscus to be the scaffolds in tissue engineering.

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Numerical calculations of effective thermal conductivity of porous ceramics by image-based finite element method
Yan-Hao DONG, Chang-An WANG, Liang-Fa HU, Jun ZHOU
Front Mater Sci    2012, 6 (1): 79-86.
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The effective thermal conductivity of heterogeneous or composite materials is an essential physical parameter of materials selection and design for specific functions in science and engineering. The effective thermal conductivity is heavily relied on the fraction and spatial distribution of each phase. In this work, image-based finite element method (FEM) was used to calculate the effective thermal conductivity of porous ceramics with different pore structures. Compared with former theoretical models such as effective media theory (EMT) equation and parallel model, image-based FEM can be applied to a large variety of material systems with a relatively steady deviation. The deviation of image-based FEM computation mainly comes from the difference between the two dimensional (2D) image and the three dimensional (3D) structure of the real system, and an experiment was carried out to confirm this assumption. Factors influencing 2D and 3D effective thermal conductivities were studied by FEM to illustrate the accuracy and application conditions of image-based FEM.

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Study on the mechanism of NH3-selective catalytic reduction over CuCexZr1--<?Pub Caret?>x/TiO2
Xujuan CHEN,Xiaoliang SUN,Cairong GONG,Gang LV,Chonglin SONG
Front. Mater. Sci.    2016, 10 (2): 211-223.
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Copper--cerium--zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction (SCR) of NOx. The reaction mechanism was proposed on the basis of results from in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH3 is introduced, ammonia bonded to Lewis acid sites is more stable over CuCe0.25Zr0.75/TiO2 at high temperature, while Br?nsted acid sites are more important than Lewis acid sites at low temperature. For the NH3+NO+O2 co-adsorption, NH3 species occupy most of activity sites on CuCe0.25Zr0.75/TiO2 catalyst, and mainly exist in the forms of NH4+ (at low temperature) and NH3 coordinated (at high temperature), playing a crucial role in the NH3-SCR process. Two different reaction routes, the L-H mechanism at low temperature (<200°C) and the E-R mechanism at high temperature (>200°C), are presented for the SCR reaction over CuCe0.25Zr0.75/TiO2 catalyst.

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Tailoring properties of reticulated vitreous carbon foams with tunable density
Front. Mater. Sci.    2016, 10 (2): 157-167.
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Reticulated vitreous carbon (RVC) foams were manufactured by multiple replications of a polyurethane foam template structure using ethanolic solutions of phenolic resin. The aims were to create an algorithm of fine tuning the precursor foam density and ensure an open-cell reticulated porous structure in a wide density range. The precursor foams were pyrolyzed in inert atmospheres at 700°C, 1100°C and 2000°C, and RVC foams with fully open cells and tunable bulk densities within 0.09–0.42 g/cm3 were synthesized. The foams were characterized in terms of porous structure, carbon lattice parameters, mechanical properties, thermal conductivity, electric conductivity, and corrosive resistance. The reported manufacturing approach is suitable for designing the foam microstructure, including the strut design with a graded microstructure.

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Silicate-doped hydroxyapatite and its promotive effect on bone mineralization
Zhi-Ye QIU, In-Sup NOH, Sheng-Min ZHANG
Front Mater Sci    2013, 7 (1): 40-50.
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Bone defect is one of the most common diseases in clinic. Existing therapeutic approaches have encountered many problems, such as lack of autogenous allogeneic bone and immunological rejection to allogeneic implant. Synthetic hydroxyapatite (HA) provided solutions for bone repair, since the HA is the main inorganic component of animals’ bone. However, HA has good biocompatibility, but does not possess osteogenic capability, which is of significance for modern bone repair materials. Si is an essential trace element in bone tissue, and it has been demonstrated to be able to promote bone formation. Therefore, silicate-doped hydroxyapatite (Si--HA) may serve as a promising material for bone repair, and promote bone regeneration in the repair. The current review discusses development of Si--HA, focusing on its preparation and characterization, in vitro and in vivo evaluations of the material, positive effect of Si--HA on promoting bone formation in clinical applications, and molecular mechanism investigation of such promotive effect.

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Bio-inspired supramolecular self-assembly towards soft nanomaterials
Yiyang LIN, Chuanbin MAO
Front Mater Sci    2011, 5 (3): 247-265.
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Supramolecular self-assembly has proven to be a reliable approach towards versatile nanomaterials based on multiple weak intermolecular forces. In this review, the development of bio-inspired supramolecular self-assembly into soft materials and their applications are summarized. Molecular systems used in bio-inspired “bottom-up self-assembly” involve small organic molecules, peptides or proteins, nucleic acids, and viruses. Self-assembled soft nanomaterials have been exploited in various applications such as inorganic nanomaterial synthesis, drug or gene delivery, tissue engineering, and so on.

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Internal friction study of ambient aging behaviors of irradiated tungsten by Si/H ions
Jing HU, Xian-Ping WANG, Qian-Feng FANG, Zi-Qiang ZHAO, Yan-Wen ZHANG, Chang-Song LIU
Front Mater Sci    2013, 7 (1): 91-95.
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The aging behaviors of irradiated tungsten by high energy Si3+ and H+ ions are mainly investigated using internal friction (IF) method combined with SEM technology. The SEM analysis indicates that more severe irradiation damage appears in the surface of simultaneous dual Si3+ + H+ irradiated specimen than that in the sequential dual Si3+ + H+ irradiated specimen or the single Si3+ irradiated specimens because of the synergistic effect of Si and H irradiation. The IF background of the irradiated sample is about one order of magnitude higher than that of the unirradiated sample owing to the existence of high density fresh dislocations induced by Si/H irradiation. In the sequential dual Si3+ and H+ irradiated specimen, the hydrogen Snoek-Kê-K?ster (SKK) peak associated with the movement of dislocations dragging hydrogen atoms is observed and its height decreases with aging time at room temperature. As for the simultaneous dual Si3+ + H+ irradiated specimen, however, there is no such hydrogen SKK peak. The reason can be explained as hydrogen diffusion and pinning effect of dislocations.

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Temperature and anion responsive self-assembly of ionic liquid block copolymers coating gold nanoparticles
Junbo LI,Jianlong ZHAO,Wenlan WU,Ju LIANG,Jinwu GUO,Huiyun ZHOU,Lijuan LIANG
Front. Mater. Sci.    2016, 10 (2): 178-186.
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In this paper, double hydrophilic ionic liquid block copolymers (ILBCs), poly poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine)]-block-(N-isopropylacrylamide) (PMMPImB-b-PNIPAAm) was first synthesized by reversible addition-fragmentation chain transfer (RAFT) and then attached on the surface of gold nanoparticles (Au NPs) via a strong gold-sulfur bonding for preparing hybrid nanoparticles (PMMPImB-b-PNIPAAm-@-Au NPs). The hybrid NPs had a three layers micelle-like structure, including a gold core, thermo-responsive inner shell and anion responsive outer corona. The self-assembling behavior of thermal- and anion-response from shell and corona were respectively investigated by change of temperature and addition of (CF3SO2)2N-. The results showed the hybrid NPs retained a stable dispersion beyond the lower critical solution temperature (LCST) because of the space or electrostatic protecting by outer PMMPImB. However, with increasing concentration of (CF3SO2)2N-, the micellization of self-assembling PMMPImB-b-PNIPAAm-@-Au NPs was induced to form micellar structure containing the core with hydrophobic PMMPImB-(CF3SO2)2N- surrounded by composite shell of Au NPs-PNIPAAm via the anion-responsive properties of ILBCs. These results indicated that the block copolymers protected plasmonic nanoparticles remain self-assembling properties of block copolymers when phase transition from outer corona polymer.

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