Synthesis of one-dimensional potassium tungsten bronze with excellent near-infrared absorption property

Potassium tungsten oxide nanofibers were successfully synthesized via a facile hydrothermal reaction route in the presence of sulfate. After reduction under a reductive atmosphere of H(2)(5 vol %)/N(2), the potassium tungsten oxide transformed to potassium tungsten bronze. Because of the lack of free electrons, the potassium tungsten oxide (K(x)WO(3+x/2)) showed no NIR shielding performance; however, the potassium tungsten bronze (K(x)WO(3)) showed promising optical characteristics such as high transmittance for visible light, as well as high shielding performance for near-infrared lights, indicating its potential application as a solar filter. Meanwhile, the potassium tungsten bronze (K(x)WO(3)) showed strong absorption of near-infrared light and instantaneous conversion of photoenergy to heat.     

介孔碳材料的制备及对胆红素的优越吸附特性

以MCM-48为模板,利用模板碳化法制备了有序介孔碳材料.运用小角X射线衍射(XRD)、透射电镜(TEM)、紫外可见光谱(UV-vis)等测试方法对介孔碳材料的孔结构参数及对胆红素的吸附特性进行了表征.研究结果表明,介孔碳材料结构高度有序,为立方相Ia3d型,具有高比表面积(1438m2 g-1)、大的孔容(0.98c...     

磷酸钙骨水泥化学活性及机械性能研究

在研究磷酸四钙制备方法的基础上,讨论其化学活性,发现该物质在高温时热稳定性不好,易于向能量更低的羟基磷灰石转化;在室温下又容易吸附空气中的水分子,发生缓慢水解.因此最好真空保存.     

Dynamic fracture of a functionally gradient material having discrete property variation

A functionally gradient material (FGM) with discrete property variation is prepared, and the dynamic fracture in this material is studied using the technique of photoelasticity combined with high-speed photography. Transparent sheets required for the study are made by casting a polyester resin mixed with varying amounts of plasticizer. The mechanical (quasi-static and dynamic) and optical properties of the material are evaluated as a function of the plasticizer content. Results of material characterization show that the fracture toughness increases with increasing plasticizer content, whereas the Young's modulus decreases. The material fringe constant and the dynamic modulus are observed to be relatively insensitive to plasticizer content. The FGM is then prepared by casting together thin strips having different plasticizer content. The dynamic crack propagation phenomenon is studied for four different property variations along the crack propagation direction, and the effects of these property variations on crack speed, crack jump distance and dynamic stress intensity factor are investigated. Results of this investigation show that increasing the toughness in the direction of crack growth reduces the crack jump distance as compared to on increasing-decreasing toughness variation for the same initial energy.     

Preparation and characterization of PI/PVDF composite films with excellent dielectric property

All-organic polyimide (PI)/poly(vinylidene fluoride) (PVDF) composite materials with high dielectric constant and low dielectric loss were fabricated via solution blending. The dielectric, mechanical, and thermal properties of the PI/PVDF composite films were studied. Results indicated that the dielectric properties of the composites were highly reinforced through the introduction of PVDF, and the composites exhibited excellent thermal stability. When the mass fraction of PVDF was adjusted to 30 wt%, the specimen demonstrated excellent thermal properties, superior mechanical properties, high dielectric constant (5.7, 1 kHz), and low dielectric loss (0.009, 1 kHz). Moreover, the dependence of the dielectric constant and dielectric loss on frequency was investigated. The composite presented stable dielectric constant and dielectric loss that were less than 0.04 within the testing frequency range of 100 Hz–10 MHz. This study demonstrated that the PI/PVDF composites were potential dielectric materials in the field of electronics.     

Consequence of cement constituents, mix composition and curing conditions for self-desiccation in concrete

This article outlines an experimental and analytical expression study on the consequence of cement constituents, mix composition and curing conditions as regards self-desiccation in concrete. For this purpose nine concretes with three values of w/c (0.32, 0.38 and 0.50), based on two types of Portland Cement, were manufactured. Five per cent silica fume was used in one third of the concretes as calculated on the basis of the cement content. The measurements were done at 1 and 6 months' age. An analysis of the conditions of the measurements was performed. Parallel tests were performed on strength. The results indicated high influence of w/c, age and cement type on self-desiccation. The curing conditions only influenced internal relative humidity and strength. The study was performed at Lund Institute of Technology 1997–1998.     

PVA复合磷酸钙骨水泥的制备和性能研究

将含有不同质量分数聚乙烯醇(PVA)的PVA-KH2PO4-Na2HPO4体系缓冲溶液作为骨水泥的调和液,将其与磷酸钙骨水泥粉末混合后成型。将试样在接近生理条件(相对湿度100%,温度(37±1)℃)下养护24h,发现PVA掺入量为1%时的抗压强度达到31.71MPa,比未掺入的提高了将近70%。     

Mechanical property and in vitro biocompatibility of brushite cement modified by polyethylene glycol

Brushite (dicalcium phosphate dihydrate, DCPD) cement, owing to its high solubility in physiological condition and ability to guide new bone formation, is widely used to treat bone defects. In the present study, we have evaluated the effects of poly ethylene glycol (PEG) addition on the setting time, compressive strength and in vitro biocompatibility of brushite cement. The brushite cements were prepared by mixing β-tricalcium phosphate [β-TCP, Ca₃(PO₄)₂] and monocalcium phosphate monohydrate [MCPM, Ca(H₂PO₄)₂ ? H₂O]. PEG was introduced at 2.0 and 5.0 wt% with the liquid. Introduction of PEG resulted in marginal increase in both initial and final setting time, however, significantly affected the compressive strength. Effects of PEG incorporation on in vitro biocompatibility of brushite cements were studied by using human fetal osteoblast cells (hFOB) cells. Field emission scanning electron microscope (FESEM) images and immunohistochemical analysis indicated that pure and PEG incorporated brushite cement facilitates cell adhesion, proliferation and differentiation. Fewer cells expressed vinculin protein with increased PEG content in the cement. Cell proliferation was found to decrease with increased PEG concentration while the cell differentiation increased with PEG content. Our results provide a better understanding of in vitro biocompatibility of PEG added brushite cements that can be used to customize the cement compositions based on application need.     

高铁粉煤灰对水泥基材料吸波特性的影响

采用X射线衍射(XRD)、扫描电子显微镜(SEM)、能量色散谱仪(EDS)分析粉煤灰中铁组分矿物组成和分布形态,对高铁粉煤灰颗粒电磁参数及复合高铁粉煤灰水泥浆体的吸波性能进行了试验研究.结果表明,粉煤灰中富集在球形颗粒表面的各种微细氧化铁晶体,是高铁粉煤灰产生电磁损耗的物质基础;高铁粉煤灰颗粒具有较高的介电常数和一定的磁导率,是以介电损耗型为主的电磁波有效损耗介质;高铁粉煤灰水泥基复合材料在2～8GHz波段范围内具有吸波性能,其最小反射率为-13.01dB,同时吸波能力可能与材料电导率有关.     

Relation between cement composition and compressive strength of pure pastes

In Europe, cement paste compressive strength models are frequently described by a power law similar to that of Féret. The French LCPC has also adopted this mathematical approach in its recent concrete mixture proportioning model. However the coefficient k and exponent b of the adopted power law were calibrated with only one Portland cement clinker, starting from pure pastes with various concentrations. These parameters do not take into account the chemical properties of the clinker. The purpose of this work was to check if the clinker chemical nature had an influence on the mechanical performances of the pastes (at 28 days). Complementary tests with eight cements coming from six different cement plants were then carried out. The mathematical treatment of the results made it possible to connect coefficient k to the silica content of the clinkers and more particularly to their C₃S rates. It is linked to the strength of hydrated cement paste. Thus, the suggested approach significantly improves the accuracy of paste strength calculation. These results can be used to calculate concrete strength.     

水中高度分散的纳米羟基磷灰石分散剂的选择

采用粒度分析和测定zeta电位的方法研究了三种分散剂,包括十二烷基硫酸钠(DSS)、聚乙烯醇(PEG)和六偏磷酸钠(NaP)对纳米羟基磷灰石(HA)在水中分散行为的影响.结果显示,使用六偏磷酸钠作为分散剂可以使纳米羟基磷灰石在水中高度分散,形成溶胶.当NaP/HA=12.5(重量比)时,溶胶含有88%粒径在65-86nm之间的纳米粒子,可以用作给药系统中的药物载体.     

Mechano-chemical aspects of the processing/property/structure interactions in a macro-defect-free cement

Relationships between mixing conditions, relaxation properties of the formed paste, and the morphology and flexural strength of hardened composites have been studied for a macro-defect-free cement (MDF). Torque and temperature were monitored in a Banbury-type mixer as a function of temperature and mixing rate. The behavior of the torque-time curves as well as activation energies derived from the temperature dependence of the mixing time suggest that a mechano-chemical crosslinking takes place between the polymer and cement phases during mixing. The viscoelastic relaxation characteristics of MDF pastes processed to varying degrees were determined using a biaxial squeeze flow device. Relaxation times and their trends with mixing are consistent with the formation of an increasingly dense network structure in the paste. Flexural strengths of the hardened material display a behavior with mixing conditions which suggests that an optimal structure forms during that portion of the mixing process preceding breakdown of the paste. This conclusion is supported by the evidence of scanning electron micrographs which show the structure formation for a given set of mixing conditions.     

高温环境下聚合物水泥复合填缝料性能研究

针对聚合物水泥复合填缝料(PCCJS)耐久性研究不足的问题,对经过60℃高温处理后的PCCJS进行定伸、拉伸和剪切试验,研究高温作用对PCCJS定伸粘结性能、力学性能的影响,不同高温作用时间(1d、7d、15d、30d)对PCCJS性能的影响规律。通过扫描电镜和压汞测孔试验,分析了高温环境对PCCJS性能影响的微观机制。结果表明：高温环境下,PCCJS内部的聚合物大分子降解断裂,分子间间隙变大,导致PCCJS拉伸力学性能和剪切力学性能下降,且随高温作用时间的延长而不断降低。PCCJS在60℃环境下作用15d后,尚未发生内聚破坏或粘结破坏,呈现出良好的定伸粘结性能。     

PMMA brush-containing two-solution bone cement: preparation, characterization, and influence of composition on cement properties

Two-solution bone cement consisting of poly (methyl methacrylate) (PMMA) brushes in methyl methacrylate has been developed as an alternative to the traditional two-solution (TSBC) and powder-liquid cements. It was hypothesized that the substitution of brushes, for the entire pre-polymer phase of the cement, would permit a decrease in solution viscosity at higher polymer fractions, and allow for physical entanglements with the cement matrix. Consequently, improved cement exothermal and mechanical properties could be expected with brush addition. PMMA brushes were grafted on the surface of cross-linked PMMA nanospheres following a multi-stage synthetic strategy. Brushes exhibiting optimal molecular weight for preparation of TSBC were used for characterization of cement viscosity, flexural and compressive mechanical properties, exothermal properties and residual monomer content. Interactions between grafts and free polymer formed during free radical polymerization of the cement were evaluated based on molecular weight measurements of the cement matrix and brushes. Brush-containing cements exhibited lower viscosity at significantly higher polymer fractions in comparison to TSBC. Cements with PMMA brushes had significantly lower polymerization temperatures and residual monomer content. Measurements of molecular weight revealed the existence of a dry brush regime when using the brush compositions selected in this study, which led to a reduction in the mechanical properties of some of the compositions tested. The optimal cement viscosity and maintenance of other important cement properties achieved with addition of PMMA brushes is expected to expand the use of the two-solution cements in a range of applications.     

声波水泥胶结测井中岩性对地层波影响研究及资料应用

针对砂泥岩地层,数值研究了套管井中高密度和低密度水泥完全胶结时短源距声波测井全波波形特性,通过地层孔隙度和泥质含量的变化,分析了水泥特性和地层岩性对地层波幅度的影响。结果表明水泥特性对地层波幅度影响很小,但地层孔隙度和泥质含量对地层波幅度影响很大,并给出了地层波岩性影响的校正图版。根据理论结果结合实际测井记录的波形特点,研究了波形信息提取方法,得到了第一、第二界面胶结指数等参数,用以评价固井质量。这种方法在西北油田固井质量评价中获得了较好的结果。     

Pore solution composition and chloride binding capacity of silica-fume cement pastes

Samples of the capillary pore solution, associated with hardened cement pastes containing various proportions of silica-fume and sodium chloride, have been expressed at different stages of curing and analysed to determine concentrations of dissolved ions. The results indicate that partial replacement of Portland cement by increasing percentages of silica-fume causes a regular decrease in alkalinity of the pore solution and a reduction in the chloride-binding capacity of the material. Possible implications regarding the level of corrosion protection afforded to embedded steel are considered.

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Résumé On a préparé des échantillons de pates de ciment Portland mélangé dans diverses proportions de poids à de la poudre de silice (0–30%) avec une proportion constante d'eau, équivalente à 50% des poids combinés du ciment et de la poudre de silice. Dans certains cas, l'eau du mélange contenait du chlorure de sodium en quantités qui correspondaient à 0,4 ou 1% d'ions de chlorure, exprimés en pourcentages des poids combinés du ciment et de la poudre de silice. On a traité les pates dans des récipients scellés pendant des périodes allant jusqu'à 84 jours, puis on les a transférées dans une enceinte en acier spécial, dans laquelle la pression a été appliquée à des niveaux permettant d'exprimer en millimètres les solutions interstitielles capillaires et de les recueillir. On a effectué l'analyse par des méthodes de routine pour déterminer les concentrations dissoutes de Na⁺, K⁺, Ca²⁺, OH⁻, Cl⁻, SO ₄ ²⁻ . On a aussi évalué les quantités d'eau non évaporable dans des échantillons, afin de calculer les proportions du contenu total de chlorure dans les matériaux qui sont restés dissous. Les résultats ont indiqué que le remplacement partiel du ciment Portland par des pourcentages croissants de poudre de silice causait une diminution régulière de l'alcalinité des solutions interstitielles et une réduction de la capacité du matériau servant à lier le chlorure. On a attribué ce dernier effet à l'influence du pH de la solution sur la solubilité de 3CaO.Al₂O₃.CaCl₂.1OH₂O et on a démontré la validité de point de vue au moyen de l'analyse thermale. On a considéré la signification des résultats vis-à-vis du degré de protection de l'armature contre la corrosion et on a constaté qu'un certain nombre de questions demandait de nouvelles recherches.

     

埋置深度对黄麻纤维束与水泥基体粘结性能的影响

为了探究埋置深度对黄麻纤维束与水泥基体粘结性能的影响,利用C43电子式万能试验机进行了水泥基中黄麻纤维束的拔出试验,获得了拔出刚度、最大拔出力、等效粘结强度和拔出功随埋置深度的变化规律。试验在6 mm/min恒定试验速率下进行,测试了4组不同埋置深度（20 mm、40 mm、60 mm和80 mm）的试件。试验结果表明：随着埋置深度的增大,拔出刚度整体呈减小趋势但局部有波动;最大拔出力持续增大,并在埋置深度为60 mm时趋于稳定;等效粘结强度持续减小;拔出功初始增大,在埋置深度为60 mm处出现转折,而后迅速减小。为了进一步分析这种变化产生的具体作用机制,对不同埋置深度的破坏试件进行了观察,获得了试件破坏模式随埋置深度的变化规律。     

一种陶瓷分散剂的合成工艺及应用性能

利用碱木质素代替部分苯酚合成了改性氨基磺酸系分散剂LMA,并考察了不同工艺条件下LMA对墙地砖陶瓷浆料应用性能的影响。结果表明,LMA的最优化反应条件为m(A):m(P):m(L):m(F)=1.00:0.29:0.68:0.84,其中碱木质素代替苯酚的替代率为70%,反应体系pH值10.5,缩合温度95℃,缩合时间3.0 h。对最优条件下合成的改性氨基磺酸系分散剂LMAY进行红外分析,证实碱木质素已成功引入。当陶瓷浆料固含量为68%时,LMAY最佳掺量为0.4%,此掺量下陶瓷浆料的流出时间为37.13 s,厚化度为1.25,优于无机盐分散剂。     

钢纤维水泥基材料吸波性能实验与隐身效能分析

采用远场雷达散射截面法测试的功率反射率为表征吸波性能的指标,研究了素砂浆的吸波性能以及钢纤维长度、钢纤维掺量、复掺铁氧体、表面处理、温度和湿度等因素对钢纤维砂浆吸波性能的影响;同时根据所推导的隐身效能评价公式计算了钢纤维砂浆的隐身能力.研究表明:掺入钢纤维可以提高砂浆的低、高频吸波性能;合适的纤维长度和体积掺量是提高砂浆吸波性能的决定性因素;温、湿度升高,钢纤维砂浆的吸波性能下降;复掺的铁氧体分布在试件表层时,钢纤维砂浆的吸波性能下降,而分布在整个试件内时,可提高低频段的吸波性能;表面开浅槽可以在较宽的频段内提高吸波性能,表面开深槽可使低频吸波效果明显提高;吸波效果较好的钢纤维砂浆在2.6～4GHz的频段内,其雷达最大探测距离可降低到素砂浆的84%～89%.