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A series of stress relaxation tests on foamed high-alumina cement pastes with different relative densities under various temperatures and imposed fixed strains were conducted to study the effects of relative density and imposed strain on the stress relaxation rates of foamed high-alumina cement pastes. At the same time, the activation energy for stress relaxation of foamed high-alumina cement paste was determined from experimental results. Experimental results on the stress relaxation rates of foamed high-alumina cement pastes are also compared to a theoretical expression obtained from a cell-edge relaxation-bending model. Consequently, the microstructural coefficients included in the theoretical expression for describing the stress relaxation rates of foamed high-alumina cement pastes are found. Furthermore, the stress relaxation rates of foamed high-alumina cement pastes can be predicted from the theoretical expression once their relative density and the imposed strain are known. 相似文献
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《Ceramics International》2022,48(10):14273-14280
We develop the direct laser melting of ceramic paste technology for application in ceramic additive manufacturing (AM). The Al2O3 ceramic paste, which is a homogeneous mixture of DI-water and Al2O3 ceramic powders, was deposited on an Al2O3 substrate using free-forming extrusion (FFE), and subsequently melted by a CO2 laser. To better control the laser melting process, the flow behavior of the laser-melted Al2O3 was investigated by evaluating the microstructure of the laser-melted Al2O3 single tracks. When the laser scanning speed increased from 1 to 3.5 mm/s at a fixed laser power, the permeation of the molten Al2O3 into the surrounding porous paste was reduced, resulting in the improvement of the surface uniformity of the laser-melted Al2O3 tracks. Through optimizing the laser scanning strategy, a fully-dense Al2O3 layer with smooth surface was achieved. The phase composition and density of the laser-melted Al2O3 layers were evaluated to study their properties. The thickness of the dense Al2O3 layer varied from ~90 μm to ~120 μm periodically due to the line-by-line scanning of the Gaussian laser beam. In addition, the relationship between the melting thickness and the laser scanning speed was also investigated to further improve the controllability of the laser melting process. This direct laser melting of ceramic paste technology is promising for applications in ceramic AM, such as 3D printing of ceramic components and high-temperature ceramic welding. 相似文献
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笔者已设计的陶瓷厂单层厂房、变电所、办公楼、仓库等都已投入了使用,并且反映良好。近几年,砖壁柱H钢梁结构的厂房,由于空间大、造价低、施工方便,在陶瓷建厂设计得到广泛应用。砖围墙轻钢梁排架结构厂房的静力计算,根据房屋的空间工作性能分为刚性方案、刚弹性方案、弹性方案。下面根据实例说明这3种方案的计算过程。1弹性方案工程概况:某陶瓷厂单层工业厂房(如图1所示),厂房长60 m,跨度12 m,柱距6 m,屋面焊接工字钢梁、C型钢檩条、夹芯保温屋面板,砖壁柱的计算高度H0为6.05 m,砖砌体采用MU10粘土砖,±0.000以上采用M5混合砂浆,±0.00… 相似文献
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When a saturated rod of a porous material is deflected in three-point bending, two types of time-dependent relaxation processes occur simultaneously: hydrodynamic relaxation, caused by the flow of liquid in the porous body, and viscoelastic (VE) relaxation of the solid network. By measuring the decrease in the force required to sustain a constant deflection, it is possible to obtain the permeability from the hydrodynamic relaxation function, in addition to the VE stress relaxation function of the sample. We report the early-age evolution of permeability, elastic modulus, and stress relaxation function for Type III Portland cement paste with water–cement (w/c) ratios of 0.45, 0.50, and 0.55. The stress relaxation function is shown to preserve its shape during aging; that function is numerically transformed into the creep function. 相似文献
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A method is proposed for designing the charge composition of a two-component clay paste for production of rough wall ceramic
based on acid loams and nontraditional semiacid clay additive with a high iron oxide content.
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Translated from Steklo i Keramika, No. 1, pp. 14–15, January, 2007. 相似文献
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磷铝酸盐水泥浆体的抗冻性研究 总被引:1,自引:0,他引:1
抗冻性是砼耐久性的重要方面,尤其影响北方地区砼工程的使用寿命。引气能提高砼的抗冻性,但同时又存在气泡的稳定性问题和砼其他性能的受损问题。若能提高砼中水泥浆体的抗冻性,则对提高砼耐久性更有意义。作者从宏观和微观两方面研究了磷铝酸盐水泥浆体的抗冻性,同时与硅酸盐水泥、硫铝酸盐水泥浆体进行了比较;采用压汞测孔方法测试了三种水泥浆体冻融前后的孔结构,并用分形理论分析了各自特征。结果证实:磷铝酸盐水泥具有优越的抗冻融性能,其自身优良的水化特性以及体系的低碱度是良好抗冻性的内在原因。 相似文献
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Sarguna Ramaiyan Mahadevan Sridharan Varadarajan Anand Mohan Awasthi Subramanian Natarajan 《Journal of the American Ceramic Society》2017,100(6):2596-2603
Dielectric study over a broadband was carried out from 10 to 70 K on ceramic Gd1?xYxMnO3 (x=0.2, 0.3 and 0.4). For all the compositions, a prominent sharp peak about ~18 K was observed in the temperature dependence of both ε′(T) and ε″(T) at all frequencies, indicating a long‐range ferroelectric (FE) transition. Using Cole‐Cole fit to the permittivity data, the relaxation time τ and the dielectric strength ?ε were estimated. Temperature variation of τ(T) in the Arrhenius representation is found to be nonlinear (non‐Debyean relaxation), with increasing barrier‐activation energy over successive temperature‐windows. Interestingly, for all the compositions, we witness a jump in τ(T) about the ferroelectric transition temperature, concurred by a broad‐maximum in ?ε(T),signifying the critical slow down of relaxations near long‐range FE‐correlations. 相似文献
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以氧化淀粉为例,建立氧化淀粉糊液泡沫的制备方法,并提出一种淀粉泡沫糊液粘附性能的测试方法,实现了淀粉糊液泡沫粘附性的客观表征。讨论了浆料配方、发泡剂浓度和烘燥方式对浆液粘附力的影响。结果表明,泡沫浆液对纤维须条的润湿、铺展和吸附是形成粘合的基础;内聚破坏和界面破坏是决定粘合破坏的关键因素;与单组分氧化淀粉相比,氧化淀粉和固体聚乙烯酰胺复配后糊液泡沫粘附力增加;发泡剂浓度在临界胶束浓度时,淀粉糊液泡沫的起泡能力、泡沫的稳定性和粘附力最好;相比于热风烘燥,真空冷冻干燥法可以有效提高淀粉糊液泡沫对纤维须条的粘附性。 相似文献
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文中对新型陶瓷分散剂进行了研究,合成了不同配比的有机配位基甲基丙烯酸的铝锆偶联型分散剂。利用红外光谱对其结构进行表征及分析,通过扫描电镜、黏度测量等方法对分散效果进行了检测,并对分散剂的作用原理进行了理论分析。结果表明当分散剂加入质量分数为1.5%时,降黏幅度达到92.3%,沉降速度明显减慢,分散效果好。加入质量分数超过1.5%后,体系黏度,沉降速度趋于稳定值。此分散剂对硅酸锆具有较好的降黏效果,分散微粒的表面覆盖及包封效果优于其他分散剂,有望作为新型陶瓷分散剂应用于坯料和釉料的制备过程。 相似文献
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E. I. Suzdal’tsev D. V. Kharitonov A. A. Anashkina 《Refractories and Industrial Ceramics》2012,52(5):340-348
Results are presented for a study of functional coating application, for example with increased blackness coefficient, on
ceramic and glass ceramic materials. Various methods for coating application used currently are considered. A coating is proposed
based on methyl phenyl spirocyloxane polymer (product MFSS-8). 相似文献
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Eshwar Reddy Cholleti Jonathan Stringer Piaras Kelly Chris Bowen Kean Aw 《Polymer Engineering and Science》2020,60(12):3086-3094
The stress relaxation behavior of barium titanate (BTO)-elastomer (Ecoflex) composites, as used in large strain sensors, is studied using the generalized Maxwell-Wiechert model. In this article, we examine the stress relaxation behavior of ceramic polymer composites by conducting stress relaxation tests on samples prepared with varying the particle loading by 0, 10, 20, 30, and 40 wt% of 100 and 200 nm BTO ceramic particles embedded in a Ecoflex silicone-based hyperelastic elastomer. The influence of BTO on the Maxwell-Wiechert model parameters was studied through the stress relaxation results. While a pristine Ecoflex silicone elastomer is predominantly a hyperelastic material, the addition of BTO made the composite behave as a visco-hyperelastic material. However, this behavior was shown to have a negligible effect on the electrical sensing performance of the large strain sensor. 相似文献
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Mewin Vincent Vasanthakumari Kalarickal Gopalakrishnan Susanth Sivanandan Thankappan Radhika 《应用陶瓷进展》2019,118(3):106-113
The rheological properties of silver thick film paste are influenced by the particle size, morphology of silver particles and by the nature of the filler. Rheological properties in-turn influence the multilayer processing parameters and properties. Silver particles, synthesised with gum Arabic (Ag/GA) as the dispersant resulted in agglomerated particles with irregular morphology. Ag/GA-based thick film paste exhibited thixotropic characteristics. Silver powder synthesised with polyvinyl alcohol (Ag/PVA) as the dispersant resulted in well-dispersed, spherical, free-flowing powder with narrow particle size distribution and exhibited pseudoplastic behaviour. The rheological characteristics of Ag/GA-based thick film paste are not influenced by the filler addition. Influence of filler addition is distinctly noted in the rheological characteristics of Ag/PVA-based thick film paste. The homogeneous mixing of Ag/PVA particles with filler and reproducible rheological characteristics of the corresponding thick film paste resulted in excellent printability with good edge-definition and repeatable properties. 相似文献
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High-performance concrete (HPC) is a type of new concrete materials developed in the recent 10 years. Compared with normal strength concrete (NSC), HPC is made with lower water-binder ratio (W/B), larger dosage of superplasticizer and addition of different types of mineral admixtures. The objective of the article was to evaluate the effect of W/B, superplasticizer and mineral admixtures on the hydration heat of the binder paste in HPC. The testing results showed that the hydration heat reduced with the decrease of W/B of the binder paste. The total hydration heat did not decrease with the incorporation of superplasticizer containing retarding component, however, the hydration exothermic process was delayed. Mineral admixtures greatly reduced the hydration heat and the exothermic rate and prolonged the arrival time of the highest temperature, particularly when two or three types of mineral admixtures were added at the same time (double adding and triple adding). The influence of these three factors on hydration heat may counteract the deficiency of high hydration heat at early stage due to high cement content and high-strength cement usually used in HPC. This way, the influence of temperature stress is alleviated and the durability of concrete is enhanced. 相似文献