Macro-defect free cements: a future oriented polymer composite materials for construction industries

Abstract

An overview of Macro-defect free cements (MDFCs) formed by the interaction between polymer and cement hydration phases at very low w/c ratios is presented. As strength is a basic demand of every construction to make more durable infrastructure. Therefore, these materials have received a lot of attention due to their very high flexural and tensile strength properties. The effect of various constituents materials such as alumina content of cement, molecular weight and degree of hydrolysis of polymers on MDFCs along with their hardened properties by using different instrumentation techniques such as- X-ray diffraction (XRD), Scanning electron microscope (SEM), Dynamic mechanical analysis (DMA), Thermal studies, Hydration studies etc. have been studied by various researches and some of them are discussed in the presented review article. Therefore, this review describes the parameters, which influences the properties of MDFCs, enhances their properties and also provide a foot print for future scope after analysing all the necessary parameters. These materials can be used as a best future oriented construction materials in comparison to other conventional materials by improving their desired properties.     

Potential of fullerene-based materials for the utilization of solar energy

This paper reviews the prospects of fullerene-based materials for photovoltaics. The device structure and parameters of inorganic and organic fullerene-based solar cells are presented. An additional promising direction of solar energy utilization—the production of fullerenes and carbon nanotubes by concentrated sun-light—is also discussed.     

Improved quantification of alite and belite in anhydrous Portland cements by Si MAS NMR: Effects of paramagnetic ions

The applicability, reliability, and repeatability of ²⁹Si MAS NMR for determination of the quantities of alite (Ca₃SiO₅) and belite (Ca₂SiO₄) in anhydrous Portland cement was investigated in detail for 11 commercial Portland cements and the results compared with phase quantifications based on powder X-ray diffraction combined with Rietveld analysis and with Taylor–Bogue calculations. The effects from paramagnetic ions (Fe³⁺) on the spinning sideband intensities, originating from dipolar couplings between ²⁹Si and the spins of the paramagnetic electrons, were considered and analyzed in spectra recorded at four magnetic fields (4.7–14.1 T) and this has led to an improved quantification of alite and belite from ²⁹Si MAS NMR spectra recorded at “high” spinning speeds of ν_R=12.0–13.0 kHz using 4 or 5 mm rotors. Furthermore, the impact of Fe³⁺ ions on the spin-lattice relaxation was studied by inversion-recovery experiments and it was found that the relaxation is overwhelmingly dominated by the Fe³⁺ ions incorporated as guest-ions in alite and belite rather than the Fe³⁺ sites present in the intimately mixed ferrite phase (Ca₂Al_xFe_2−xO₅).     

Potential electrical characteristics of interference transistors made from various materials

A theoretical analysis of the electrical characteristics of GaAs, InAs, InSb, and Si quantum interference T transistors is performed with consideration of the dependence of the effective masses on the quantum wire dimensions. It is shown for extremely small wire dimensions that none of the materials has significant advantages over the others with respect to the frequency characteristics of the transistors investigated. Zh. Tekh. Fiz. 69, 130–131 (November 1999)     

Potential models for quarkonia

In this paper I discuss what we can learn about quarkonium dissociation from lattice-potential based models. Special emphasis is given to results obtained in agreement by different models, and to the relevance of lattice QCD for potential models. Future directions are also discussed.     

Ab initio materials design for transparent-conducting-oxide-based new-functional materials

Based upon ab initio electronic structure calculations for delafossite CuAlO₂ and ZnO, we report on the design of new-functional materials for transparent conducting oxides (TCO), such as (i) low-resistive p-type ZnO and CuAlO₂ by co-doping, (ii) high-efficiency thermoelectric power in CuAlO₂ (ZT>3) by p-type doping, (iii) half-metallic ferromagnetism in transition-metal-impurity doped CuAlO₂ and ZnO-based diluted magnetic semiconductors, and (iv) CaO, MgO, SrO and BaO based DMS without transition metal impurities. We also discuss the implementation of the self-interaction correction to our materials design method. PACS 61.72.Bb; 61.72.Jj; 71.15.Mb; 72.15.Jf; 82.75.-d     

Investigating the CO2 laser cutting parameters of MDF wood composite material

Laser cutting of medium density fibreboard (MDF) is a complicated process and the selection of the process parameters combinations is essential to get the highest quality cut section. This paper presents a means for selecting the process parameters for laser cutting of MDF based on the design of experiments (DOE) approach. A CO₂ laser was used to cut three thicknesses, 4, 6 and 9 mm, of MDF panels. The process factors investigated are: laser power, cutting speed, air pressure and focal point position. In this work, cutting quality was evaluated by measuring the upper kerf width, the lower kerf width, the ratio between the upper kerf width to the lower kerf width, the cut section roughness and the operating cost. The effect of each factor on the quality measures was determined. The optimal cutting combinations were presented in favours of high quality process output and in favours of low cutting cost.     

Solution of Klein-Gordon Equation for Pseudo-Coulomb Potential Plus a New Ring-Shaped Potential

Under the condition of an equal mixing of vector and scalar potentials, exact solutions of bound states of the Klein-Gordon equation with pseudo-Coulomb potential plus a new ring-shaped potential are presented. Simultaneously, energy spectrum equations are also obtained. It is shown that the radial equation and angular wave functions are expressed by confluent hypergeogetric and hypergeogetric functions respectively.     

Preparation of fluoride substituted apatite cements as the building blocks for tooth enamel restoration

Fluoride substituted apatite cement (fs-AC) was synthesized by using the cement powders of tetracalcium phosphate (TTCP) and sodium fluoride (NaF), and the cement powders were mixed with diluted phosphoric acid (H₃PO₄) as cement liquid to form fs-AC paste. The fs-AC paste could be directly filled into the carious cavities to repair damaged dental enamel. The results indicated that the fs-AC paste was changed into fluorapatite crystals with the atom molar ratio for calcium to phosphorus of 1.66 and the F ion amount of 3 wt% after self-hardening for 2 days. The solubility of fs-AC in Tris-HCl solution (pH 6) was slightly lower than hydroxyapatite cement (HAC) that was similar to the apatite in enamel, indicating the fs-AC was much insensitive to the weakly acidic solution than the apatite in enamel. The fs-AC was tightly combined with the enamel surface because of the chemical reaction between the fs-AC and the apatite in enamel after the caries cavities was filled with fs-AC. The extracts of fs-AC caused no cytotoxicity on L929 cells, which satisfied the relevant criterion on dental biomaterials, revealing good cytocompatibility. The fs-AC had potential prospect for the reconstitution of carious lesion of dental enamel.     

六角密堆结构钇的解析型键序作用势

为了构建拟合势需要的数据库,采用密度泛函理论方法计算了六角密堆结构钇(hcp-Y)的晶格参数、弹性常数、内聚能、结构能差以及相关的点、面缺陷性质. 基于解析型键序作用势,构建了hcp-Y的多体作用势模型. hcp-Y势模型是通过拟合Y的晶格参数、弹性常数、体弹模量、内聚能、空位形成能和不同相之间的结构能差而构建.分析发现,所得到的势模型能够很好地描述hcp-Y的自填隙原子形成能、空位形成能、双空位键能以及其它体性质,同时,构建的势模型用来研究Y的热动力学性质的相关结果也比较理想.     

Oscillator Representation for Pseudoharmonic Potential

Oscillator representation method is applied to obtain the bound state energy eigenvalues and the corresponding eigenfunctions of the n-dimensional Schrödinger equation for the pseudoharmonic potential with arbitrary angular momentum.     

Sensitive Probe for Symmetry Potential

Based on both very obvious isospin effect of the neutron-proton number ratio of nucleon emissions （n/p）nud on symmetry potential and （n/p）nucl＇s sensitive dependence on symmetry potential in the nuclear reactions induced by halo-neutron projectiles, compared to the same mass stable projectile, probing symmetry potential is investigated within the isospin-dependent quantum molecular dynamics with isospin and momentum-dependent interactions for different symmetry potentials U;ym and U2^sym. It is found that the neutron-halo projectile induces very obvious increase of （n/p）nucl and strengthens the dependence of （n/p） l on the symmetry potential for all the beam energies and impact parameters, compared to the same mass stable projectile under the same incident channel condition. Therefore （n/p）nucl induced by the neutron-halo projectile is a more favourable probe than the normal neutron-rich and neutron-poor projectiles for extracting the symmetry potential.     

Development of new materials for spintronics

This article presents a review of the state of the art of materials used in spintronics. It is devoted to materials exhibiting novel and exciting electronic properties: manganites, double perovskites, spinel ferrites and diluted magnetic semiconductors. We present the main features of these classes of materials as well as the most important solid state physics results obtained from them in the field of spintronics. To cite this article: J. Cibert et al., C. R. Physique 6 (2005).     

Potential of amorphous silicon for solar cells

This paper reviews recent developments in the field of amorphous-silicon-based thin-film solar cells and discusses potentials for further improvements. Creative efforts in materials research, device physics, and process engineering have led to highly efficient solar cells based on amorphous hydrogenated silicon. Sophisticated multijunction solar cell designs make use of its unique material properties and strongly suppress light induced degradation. Texture-etching of sputtered ZnO:Al films is presented as a novel technique to design optimized light trapping schemes for silicon thin-film solar cells in both p-i-n and n-i-p device structure. Necessary efforts will be discussed to close the efficiency gap between the highest stabilized efficiencies demonstrated on lab scale and efficiencies achieved in production. In case of a-Si:H/a-Si:H stacked cells prepared on glass substrates, significant reduction of process-related losses and the development of superior TCO substrates on large areas promise distinctly higher module efficiencies. A discussion of future perspectives comprises the potential of new deposition techniques and concepts combining the advantages of amorphous and crystalline silicon thin-film solar cells. Received: 1 March 1999 / Accepted: 28 March 1999 / Published online: 14 June 1999     

Searching for better plasmonic materials

Plasmonics is a research area merging the fields of optics and nanoelectronics by confining light with relatively large free‐space wavelength to the nanometer scale ‐ thereby enabling a family of novel devices. Current plasmonic devices at telecommunication and optical frequencies face significant challenges due to losses encountered in the constituent plasmonic materials. These large losses seriously limit the practicality of these metals for many novel applications. This paper provides an overview of alternative plasmonic materials along with motivation for each material choice and important aspects of fabrication. A comparative study of various materials including metals, metal alloys and heavily doped semiconductors is presented. The performance of each material is evaluated based on quality factors defined for each class of plasmonic devices. Most importantly, this paper outlines an approach for realizing optimal plasmonic material properties for specific frequencies and applications, thereby providing a reference for those searching for better plasmonic materials.     

Plasma-facing materials for fusion devices

In a future D/T fusion reactor the walls of the vessel containing the magnetically confined hot plasma have to stand simultaneously very high power, particle and neutron loads. In today’s high temperature plasma experiments at the areas of the highest load, i.e. the divertor and the limiters, W, Mo and Carbon (CFC) are used and Be, W, Mo, Inconel and stainless steel are at the other wall areas. These materials are also envisaged for future bigger fusion experiments, such as ITER [1–3]. The resistance of these materials to the different expected higher loads in a fusion reactor is only partly known and more investigations are needed with respect to find better materials and/or a modification of the divertor.     

New nanohybrid materials for biophotonics

Hybrid nanomaterials were prepared by one- and two-step procedures in the absence of water. Femtosecond laser ablation of a ZnO target in absolute ethanol afforded a colloidal ZnO solution. Dye molecules were grafted onto the ZnO nanoparticle surface by mixing the ZnO solution with an ethanol solution of tetramethylrhodamine B isothiocyanate or rhodamine B. Formation of strongly facetted nanohybrid particles with the average size of 21 nm was observed by HRTEM measurements. Ablation of ZnO in the presence of the dyes afforded nanohybrids with the average size of 12 nm. The occurrence of energy transfer from the ZnO nanoparticles towards the attached dye molecules was demonstrated by photoluminescence spectroscopy of the nanohybrids after single and multi-photon excitations. In particular, two-photon absorption of the nanohybrids ZnO core gave rise to emission of the grafted dyes. PACS 81.07.Bc; 81.07.Nb; 78.67.Bf; 78.55.Et; 81.15.Fg     

Topometry for locally changing materials

Three-dimensional topometry is supplemented with ellipsometric measurements on the same pixel raster for calculation of the phase of the reflected waves and correction of the height fields. Lateral resolution is <1mum . The ellipsometric angles are determined by phase shifting and contrast evaluation. Three-dimensional fields of the ellipsometric angles, the real and the imaginary parts of the refractive index, and the corrected topography of the heights are presented.     

New materials for optical cooling

Well-characterized solid-state laser materials are evaluated for performance in optical refrigeration as well as radiation-balanced laser systems. New figures-of-merit are developed and applied to ytterbium-doped materials. Superior performance is predicted for high-cross-section tungstate materials. Photothermal deflection experiments on samples of Yb³⁺-doped KGd(WO₄)₂ confirm anti-Stokes fluorescence cooling. This is the first observation of optical cooling in a crystal. Received: 1 February 2000 / Revised version: 15 June 2000 / Published online: 13 September 2000