Stress relaxation of foamed high-alumina cement paste

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.     

Direct laser melting of Al2O3 ceramic paste for application in ceramic additive manufacturing

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.     

浅谈陶瓷工厂设计中的静力计算

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…     

PVC糊树脂的结构性能研究

通过对不同工艺PVC糊树脂的微观结构、粒径分布、凝胶化过程、脱膜性能的研究，确定了微悬浮和种子乳液法糊树脂的特性。     

Measuring permeability and stress relaxation of young cement paste by beam bending

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.     

Method of calculating the composition of ceramic paste based on acid loams with semiacid clay additive

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. __________ Translated from Steklo i Keramika, No. 1, pp. 14–15, January, 2007.     

磷铝酸盐水泥浆体的抗冻性研究

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。     

新型陶瓷换热器材料的实验研究

从多组实验配方中找出了一种耐热冲击性强、热膨胀性小、烧结致密的最佳配方。研究了几种主要陶瓷成分对陶瓷换热器抗热震性能的影响。     

Studies on dielectric relaxation in ceramic multiferroic Gd1−xYxMnO3

Dielectric study over a broadband was carried out from 10 to 70 K on ceramic Gd_1?xY_xMnO₃ (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.     

淀粉糊液泡沫的制备与粘附性研究

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。     

淀粉糊液泡沫的制备与粘附性研究

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。     

多孔氧化铝支撑体制备工艺的研究

本文研究了多孔氧化铝支撑体的制备工艺对其性能的影响,发现原料粉体的粒度、物料的成型方法、坯体的干燥环境及坯体的焙烧制度对支撑体的性能有重要影响。在研究的基础上制定了本实验所采用的各种工艺条件,并由此制备出了性能优越的多孔氧化铝支撑体。     

陶瓷玩具设计研究

中国玩具有着广阔玩具市场,市面上各种材质的玩具星罗棋布.但整个玩具产业,陶瓷玩具出现较少.陶瓷作为我国一种特色的材料,应该深入挖掘,但是国内对陶瓷玩具的研究也非常的浅显,并且传播力度不大.其实陶瓷玩具本身有非常大的实验和创作空间,本文通过对陶瓷玩具产品进行调研,总结了陶瓷玩具设计的特点,为陶瓷玩具设计提供思路.     

水泥浆体早期收缩的试验研究

开发了一套采用高精度LVDT位移传感器测定水泥浆体长度变化的仪器,并用该仪器对不同水灰比和不同混合材的水泥浆体的收缩行为进行了研究。结果表明,该仪器能够准确、连续地测量水泥浆体终凝后的自收缩和干燥收缩的发展过程。早期自收缩和干燥收缩随着水灰比降低而明显增加,在20℃相对湿度50%的环境下,水泥浆体的自收缩占干燥收缩的10%左右;掺粉煤灰可以少量降低水泥浆体的自收缩和干燥收缩,而掺入石灰石和矿渣则不同程度的增大了水泥浆体早期收缩率。     

有机金属偶联型陶瓷分散剂的研究

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。     

Study of functional coating preparation on ceramic materials

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).     

The effect of barium titanate ceramic loading on the stress relaxation behavior of barium titanate-silicone elastomer composites

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.     

Factors influencing rheological characteristics of silver thick film paste and its correlation to multilayer ceramic processing

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.     

三乙胺法废铅膏脱硫工艺研究

以三乙胺浸出废铅膏中硫酸铅,经过反应得到易于分解的氢氧化铅,实现铅的回收。分析三乙胺与废铅膏中硫酸铅物质的量比、液固质量比、反应温度、反应时间对脱硫率的影响。研究表明：当三乙胺与废铅膏中硫酸铅物质的量比为10、液固质量比为10、反应温度为60 ℃、反应时间为6 h时,脱硫率可达到86.77%。对原铅膏和最佳条件下的脱硫铅膏进行XRD和SEM分析。脱硫铅膏中出现许多氢氧化铅的特征峰,硫酸铅的特征峰大量减少;得到的氢氧化铅的形状为表面光滑的杆状。     

Study on the hydration heat of binder paste in high-performance concrete

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.