Synthesis of Ordered Biosilica Materials

Biogenic silica with amazing diversity of nanostructure shells,fibers and granules in diatoms and sponges is mediated by proteins and polysaccharides and forms at ambient pressure and temperatures.Chemical synthetic methods,in contrast,have to rely on extreme pH and /or surfactants to induce the condensation of silica precurors into specific patterns.One kind of benign synthesis method through plant cell wall template-directed ordered biosilica materials under ambient conditions in intriguing in this context.Organized silica materials in intercellular spaces of epidermal cells of tall fescue leaves were synthesized through molecular recognition between Si-OH and polysaccharide-OH or glycoprotein-OH of main components of plant cell walls and cellular processing as well when Si(OEt)4 was supplied rather than monosilicic acid.The biosynthesis of structural silica in tall fescue plant was correlated with the Si species applied,reflecting the slower condensation from tetraethoxysilane (TEOS) and thus providing greater opportunities for structural control by the underlying matrix of cell walls.The composition was estimated by energy dispersive X-ray(EDX) spectra on a scanning electron microscope.All organized structures showed carbon,oxygen and silicon peaks,indication that their formations differ from natural siliceous process.     

The Research of Biomedical Intelligent Polymer Materials

The properties of biomedical intelligent polymer materials can be changed obviously when there is a little physical or chemical change caused by external condition. They are in the forms of solids, solutions and the polymers on the surface of carrier, and include water solution of hydrophilic polymers, cross-linking hydrophilic polymers(i.e. hydrogels) and the polymers on the surface of carrier. The environmental stimulating factors are temperature, pH value, composition of solution, ionic int…     

Comparison of Different Crucible Materials for the Growth of AIN Crystals

Choice of crucible material is a key issue during the growth of AIN crystal. The stabilities at high temperature and life-spans of boron nitride （BN） crucible, tantalum （Ta） crucible and tungsten （W） crucible were compared. Tantalum crucible behaved worse at high temperature and life-span was shortened as compared with the other two crucible materials. It was very crisp and easy to crack. In contrast, self-seeded AIN crystals with different morphologies could be obtained at different high temperatures using BN crucible. The boron nitride crucible was stable below 2200 ℃, above which it would decompose. Thus it was unsuitable for the bulky AIN crystal growth. Tungsten crucible could endure the temperatures higher than 2200℃. Unfortunately we could only get AIN polycrystallines using tungsten crucible. After 50- 100 hours＇ run, the crucible was destroyed completely due to the multiple deep cracks. XRD results of destroyed tungsten crucible indicated that the main phases are tungsten carbide and tungsten nitride.     

Morphology – Property Correlations of PP Materials by Means of Microhardness

The present work deals with the influence of crystallization temperature, cooling rate and annealing conditions on microhardness, indentation modulus and creep behaviour of ethylene/propylene (E/P) random copolymers with 4, 6 and 8 mol% ethylene as well as α- and β-spherulites in a homopolymer and an E/P random copolymer. The materials are unnucleated, the formation of β-spherulites occurs sporadically. Additionally the indentation creep behaviour of α- and β-nucleated PP is investigated. A nearly linear correlation between hardness as well as indentation modulus and crystallintity of the E/P copolymers can be proved. An increasing cooling rate leads to decreasing hardness and modulus values due to the hindered crystallization. For the investigation of the α- and β-phases different crystallization and annealing temperatures are used. Independent of these conditions, microhardness and modulus determined by indentation testing are lower for the β-phase in both materials. Increasing crystallization temperature and annealing lead to an increasing hardness and modulus in both phases. However, an effective annealing effect takes place only at short times and elevated temperatures above 100 °C. The increasing of microhardness and modulus is correlated with an increasing in lamellae thicknesses. Additionally, indentation creep experiments were carried out on nucleated materials that show the stronger creep tendency of the β-phase PP and the stronger influence of annealing on this phase.     

Synthesis of New Squarains Used as Organic Electroluminescent Materials

SinceC.W.Tangetal[1],developedtwo-layerthinfilmorganicelectroluminescentdiodes(ELD)in1987successfully,organicELDshaveattractedmuchinterestfortheirsimplestruc-tures,lowdrivenvoltages,highluminescentefficiencyandtunablelight-emittingwavelength-es.Subsequently,researchesonorganicELmaterialsanddeviceswerecarriedoutrapidlyallovertheworldandwasrecognizedasoneofthemostadvancedandpromisingtechno1ogy.Or-ganicELDshavejustbeenputintoapplicationnow,therearestillsomedefectswhichneedtobeperfected.Thek…     

Preparation of Nano-porous Materials( Ⅱ） by Cross-linking of Amphiphilic Self-assemblies

Amphiphilic block copolymers can exhibit rich and complex morphologies in aqueous solutions but these structures are usually delicate,easily disturbed by composition change or temperature change.In this work,the use of different methods to cross-link block copolymer self-assemblies in the presence of a selective solvent and to stabilize the structures is reviewed.In addition,the cross-linking reaction kinetics of block copolymer amphiphilic self-assemblies is briefly discussed.     

Compatibility Testing of Energetic Materials,Which Technique?

Compatibility is an important safety aspect related to the production and storage of energetic materials. To test different combinations of materials a simple test method with clear criteria is advisable. At the last ESTAC the use of microcalorimetry and the vacuum stability test for the compatibility testing of propellants were presented. This paper presents DSC, DTA/TG and (pressure) vacuum stability test results for the same combination. For three polymers (PMMA, PVC and CA) the results for all tests are the same. Only Nylon-6/6 gives a variable result for the different test methods. This revised version was published online in August 2006 with corrections to the Cover Date.     

Degradation of Engineering Materials – Implications to Regenerative Medicine

Summary: Materials in general, to some degree are susceptible to environmental degradation. The degradation of biomaterials is one of the most relevant issues in the field of regenerative medicine. In industrial practice, the degradation is always a negative phenomenon. In bioengineering, the degradation may be undesirable (e.g. corrosion of metallic implants, wear of artificial joint implant) or desirable (biodegradable devices and tissue engineering). In both cases, the knowledge of the kinetics of degradation is crucial for safe use of biocomponents. The methods for predicting remaining life commonly used in industrial practice will be presented in the context of biomaterials. Non destructive techniques for monitoring degradation will be discussed and some ideas about their application to bio-environments proposed.     

Synthesis and Characterization of Fully-Functionalized Polysilanes for Photorefractive Materials

Photorefractive (PR) polymers have attracted much interest since 1991 1. Furthermore,because fully-functionalized polymeric systems can overcome the shortcomings such asphase-separation and composite sublimation in composite systems they have gainedespecial attention.Polysilanes can be used as novel photoconductors because of a-electionsdelocalization in the polymeric backbone2. Silence3 and Nishida4 have stUdied thepolysilane composite photorefractive materials and found that the response t…     

Preparation of Nano-porous Materials( Ⅰ）by Polymerization of Amphiphile Self-assemblies

The polymerizatioin of amplhiphilic self-assemblies is a promising method to synthesize nano-structured materials with novel properties.These materials have many attractive features for their application in biomedical area and materials science.Such as catalysis.separtion,surface modification,and therapeutics areas.A general review on the polymerization of lipids and surfactant self-assemblies to amplhiphilic self-assemblies is given in this paper with 49 references,The polymerization and the subsequently resulted structure of lipids in different morphologies are summarized.The polymerization of polymerizable surfactants (surfmers)in emulsion and liquid crystalline phases are also discussed.The potential application of new nano-porous materials is briefly described.     

Synthesis of OMS Materials and Investigation of Their Acceptor–Donor Characteristics

Three ordered mesoporous siliceous (OMS) materials known as MCM41s—unmodified MCM-41C16 (“C16”), and two MCM41s with different surface functionalities: MCM-41C16-SH (“C16-SH”) and MCM-41C16-NH₂ (“C16-NH₂”)—were synthesized and studied by inverse gas chromatography in order to determine their acceptor–donor properties. The specific retention volumes of nonpolar and polar probes that were chromatographed on these ordered mesoporous silica adsorbents were evaluated under infinite dilution conditions. Two methods were employed to calculate the standard free energy of adsorption, ΔG _ads, of each chromatographed probe on the basis its specific retention volume. These ΔG _ads values were then employed to estimate the van der Waals contribution and the specific contribution of the free surface energy for each MCM41. DN values (donor numbers, based on the Gutmann scale) and AN* values (acceptor numbers, based on the Riddle–Fowkes scale) were employed to determine the values of parameters that characterize the ability of the MCM41s to act as electron acceptors (parameter: K _A) and donors (parameter: K _D). Considering the different compositions of the probes, each of which has different acceptor–donor properties, a new chromatographic test to supplement the Grob test is suggested.     

Synthesis of Pyrazolines Used as Blue Organic Electroluminescence Materials

SinceTangetaldevelopedanoveltWo-layerorganicelectr0luminescentdevice(OELD)inl987successfully',OELDhasattractedmuchinterestall0verthew0rId.ltisregardedas"havingbr0ughtthethirdrev0luti0ntoflatpaneldisplay"',becauseithass0manyadvantagessuperiort0CathodeRayTube(CRT)andLiquidCrystalDevice(LCD).Ithasl0wdrivenvoltage(lO0,000cd/m=),highluminescentefficiency(l5lIn/w),goodstability(50,000h),andithassimplestructureandiseasytofabricate'.ComparedtoinorganicELD,OELDiseasie…     

Studies on Fragrance Raw Materials of α-Terpineol Analogues

Thirty four α-substituted or α, α-disubstituted-( 1-methylcyclohexen-4-yl )methanols and α-substituted or α,α-disubstituted-(4-methylcyclohexyl) methanols weresynthesized. Thirty two of them are new compounds. 1H NMR and IR spectra of allthe compounds were determined, MS spectra of some of them were obtained as well.The characteristic odors were evaluated.Keywords Fragrance raw materials,α-Terpineol analogues, Synthesis, Structuredetermination     

Towards a Rational Synthesis of Large-Pore Zeolite-Type Materials?

A range of novel structures , such as the metalloaluminosilicate UCSB-8 (depicted schematically), are accessible by synthetic strategies that could provide the basis for the rational design of other large-pore zeolites and zeolite-type materials. The combination of experimental approaches with computational methods, for example host–guest shape analysis, may provide further breakthroughs in this field.     

Synthesis and Structure of Binary Complexes of Platinum Group Metals — Precursors of Metallic Materials

This paper reviews the results of structural studies of binary complexes whose cationic part contains cobalt, rhodium, iridium, ruthenium, and chromium chloropentammne. The structure of these compounds is discussed in the light of the design of new multicomponent precursor compounds. Data are given on the chemical and phase compositions of the polymetallic powders resulting from the thermal decomposition of the compounds studied.     

New Materials Designed by Coordination Polymerization of ω-undecenyl Macromonomers

The major part of the present paper discusses the ability of well-defined ω-undecenyl polystyrene, polyisoprene or poly(styrene-block-isoprene) macromonomers to undergo coordination homopolymerization in the presence of selected titanium catalysts. Special emphasis is given to the influence of the nature of the catalyst, the polymerization temperature and the macromonomer molar mass and concentration on homopolymerization yield and average degree of homopolymerization (DP_n). Titanium-based catalytic systems such as CpTiCl₃/MAO and Cp*TiCl₃/MAO only yielded dimers. The use of the homogeneous metallocene catalyst with constrained ligand geometry (CGC-Ti/MAO) having an open active site, significantly improved the degree of polymerization. Increasing macromonomer molar mass, causes only a slight decrease of DP_n whereas conversion increased moderately. The final section briefly discusses the copolymerization of ω-undecenyl polystyrene macromonomers with ethylene in the presence of Versipol™ catalysts.     

Sorption Characteristics of “Food Fibers” in Secondary Products of Processing of Vegetable Raw Materials

Some structural-sorption characteristics of a series of secondary products (wastes) obtained in processing of vegetable raw materials, such as wheat straw, buckwheat peel, sunflower husk, and beet pulp, containing fibrous cellulose skeleton (food fibers), were determined. The effect of chemical and mechano-chemical modification of these products on the characteristics of their pore structure and sorption activity with respect to organic substances, heavy metal ions, and ⁹⁰Sr radionuclides was studied.     

Effects of Doped Elements on Electrochemical Performance of Ni（OH）2 Materials

High energy ball milling(HEBM)method was applied to synthesize Ni(OH)2 with different doped elements substitution for Ni2 .The morphology,structure and electrochemical behavior of prepared powders were studied.The results reveal that all the synthesized Ni(OH)2 particles were in sub-micron sizes and greatly agglomerated.Co-,Mg-,Fe-or Mn-doped Ni(OH)2 was of β-phase with 0.400-0.500 nm crystal interlayer distance,while Al-and Zn-doped products displayed α-phase with larger crystal interlayer spaces.The electrochemical mechanisms of synthesized Ni(OH)2 electrodes were discussed by EIS spectra.The specific capacity of Co-doped Ni(OH)2 is 245 mA·h·g-1,i.e.,60 mA·h·g-1 higher than that of Al-doped electrode,which has the highest discharging platform of a mid-voltage of 1.30 V.     

Evaluation of the Surface Referencing Technique in Depth‐Sensing Indentation of Soft Materials

Abstract

Thermal drift is an important consideration for reliable nanoindentation measurements. The surface‐referencing technique for eliminating thermal drift effects is critically assessed in this work. When applied to soft materials such as polymers and low‐melting metals, the surface‐referencing technique is found to cause a serious and problematic artificial drift due to the creep of the sample under the pressure exerted by the reference ring. A possible solution is proposed here to overcome this problem.     

Promises and Problems of Mesoscale Materials Chemistry or Why Meso?

Manipulation and control of chemical structures on the mesoscale has recently developed to a very promising and also aesthetically appealing area of chemistry. This concept article tries to integrate the views of two experts to delineate the specific principles, approaches, and the novel opportunities for chemistry that arise from the rational control of matter and functionality on that scale.