ZrO2对CaO-Al2O3-SiO2系统微晶玻璃烧结过程的影响研究

CaO-Al2O3-SiO2系统微晶玻璃作为微晶玻璃中的一个新品种,具有非常鲜明的特点.本文讨论了在CaO-Al2O3-SiO2系统微晶玻璃中加入ZrO2,研究了ZrO2对CaO-Al2O3-SiO2系统微晶玻璃烧结的影响.随着ZrO2加入量的增加,玻璃颗粒的烧结收缩率下降,说明ZrO2的加入对玻璃颗粒的烧结收缩有一定的阻碍作用.ZrO2的加入对CaO-Al2O3-SiO2系统微晶玻璃中的主晶相(β-硅灰石晶体)的析出没有大的影响.     

利用配合料氧化还原数控制玻璃瓶色泽

通过计算配合料的氧化还原数(Redox),调整有关原料的用量,控制配合料的氧化还原程度,使玻璃熔体具有满足形成所需色泽的条件,达到控制玻璃瓶色泽的目的。     

R_2O-CaO-SiO_2-Al_2O_3-F系微晶玻璃析晶动力学

以熔融法制备的R_2O-CaO-SiO_2-Al_2O_3-F(RCSAF)系微晶玻璃为研究对象,利用热重分析、X射线衍射等手段分析微晶玻璃的形核和晶体生长动力学。借助Gaussian拟合,获得了微晶玻璃的形核和晶体生长动力学函数。并绘制了非等温加热条件下R_2O-CaO-SiO_2-Al_2O_3-F系微晶玻璃的温度–时间–转变(T–T–T)曲线,获得了微晶玻璃形核和晶体生长动力学Gaussian拟合函数关系模型。通过无模式函数模型计算得知微晶玻璃的析晶活化能Ea=357.74 k J/mol,析晶指数n=3.13,微晶玻璃以整体析晶的方式析出晶体。确立了时间、温度和析出晶相对R_2O-CaO-SiO_2-Al_2O_3-F系微晶玻璃析晶率曲线的影响规律。微晶玻璃析出的CaF_2晶体颗粒均匀弥散的分布于硅碱钙石和α-硅碱钙石中,扫描电子显微镜照片呈现的典型晶体结构进一步验证了RCSAF系微晶玻璃的晶体析出过程。     

多孔微晶玻璃的烧结及其弹性模量研究

以具有快速结晶特性的玻璃粉末为原料,用烧结法制备了多孔微晶玻璃,测量了玻璃,微昌玻璃和多孔微晶玻璃的整体密度,孔隙率,弹性模量和Ｐｏｉｓｓｏｎ比,在粘滞流动机理的基础上,描述了多孔微昌玻璃的烧结动力学过程;在烧结温度下,颗粒大小恒定量,孔隙率随烧结时间呈线性减小;烧结时间恒定时,孔隙率随颗粒的减小而降低。     

先驱体转化法制备SiOC多孔木质陶瓷

用杉木木粉浸渍高分子先驱体有机硅树脂,改变烧结温度和保温时间制备 SiOC 多孔木质陶瓷。用 X 射线衍射、扫描电子显微镜、红外光谱及热分析对样品的物相及微观结构进行了表征,并用四探针法测试样品的电学性能。结果表明：样品由 SiOC 玻璃相、α-石英和自由碳组成,化学结构主要含有 Si—O,Si—O—R,Si—C,C=C 和 C—H2。α-石英颗粒呈球状分布在样品的孔洞表面。样品在 Ar 中具有较好的热稳定性。但由于 SiOC 玻璃相和自由碳的氧化反应,样品在 O2中的质量损失较大。当烧结温度达 1200 ℃,保温 1h 时,样品具有较低的体积电阻率（0.03 ·cm）。     

6Bi_2O_3·SiO_2熔体析晶行为的实时观察

在6Bi2O3·Si O2熔体冷却过程中熔体表面会析出枝晶,其形貌呈现出高度有序的畴结构特征。原位实时观察了枝晶的生长发育过程,并分析总结了枝晶的结构、形貌特征及其在冷却过程中的生长规律。当6Bi2O3·Si O2熔体降温到1070℃时,熔体中部分区域会析出结晶性能较好的六方双锥形Si O2单晶颗粒,尺寸范围5~80μm。分析了6Bi2O3·Si O2熔体析晶机理。6Bi2O3·Si O2熔体冷却后进行线扫描,得出在所扫描区域上会出现偏析现象。采用红外光谱分析了不同温度下极冷熔体样品的微观结构,从而探讨了6Bi2O3·Si O2熔体分相的机理。熔体出现各向异性结构的原因可能由于熔体中的[Bi2O2]基元层、[Bi O6]基团和[Si O4]基团共同作用造成的。     

利用工业废渣制作β-CaCO_3/Cr_2O_3双相微晶玻璃

以冶金铬渣、花岗岩尾矿、玻纤废丝等工业废渣为主要原料,经制备配合料、熔制玻璃液、成型、晶化处理制成β-CaCO_3/Cr_2O_3双相微晶玻璃,再以差热分析、x射线衍射分析等手段,研究制成双相微晶玻璃的规律。研究表明,以工业废渣为原料熔制成的玻璃,经四段恒温,可制备β-CaCO_3和Cr_2O_3两种主晶相共存的双相微晶玻璃,并且两种晶相形成过程互相促进。     

Li2O-ZnO-SiO2系微晶玻璃结构和性能的研究

介绍了利用传统熔体冷却方法制得以P2O5为晶核剂的Li2O-ZnO-SiO2系玻璃,并探索了该系统微晶玻璃的制备工艺,用XRD、SEM和FT-IR以及膨胀系数测定仪对微晶玻璃的结构和性能进行了研究,表明了该微晶玻璃可望作为镍、镍合金及1010钢等金属的封接材料.     

ZrH2颗粒热分解行为及对泡沫铝元素分布的影响

利用程序升温热重法研究了ZrH2颗粒在铝熔体中的热分解行为,考察了升温速率对其分解的影响,分析了分解过程中的动力学与热力学特征及发泡气体与铝熔体之间可能存在的反应,制备出了平均孔径1.3 mm的泡沫铝产品,研究了ZrH2颗粒在熔体中的分散对泡沫铝元素分布的影响. 结果表明,ZrH2于500℃出现较小的吸热峰,750℃时出现尖锐吸热峰;升温速率较低时,ZrH2的氧化符合化学反应控制模式,升温速率较高时,符合固体产物层扩散控制模式. Zr和Ca元素在泡沫铝中的分布有明显差别,气泡集体上浮是主要原因.     

Na2O-CaO-SiO2-MgO-Al2O3-ZnO微晶玻璃制备及晶化行为的研究

本文设计了Na2O-CaO-SiO2-MgO-Al2O3-ZnO体系,采用熔融法制备了以磷渣为主要原料的微晶玻璃,磷渣在微晶玻璃中的使用率达到67～75%,并利用XRD,SEM等确定了玻璃的最佳热处理制度,研究了Na2O对微晶玻璃析晶及特征的影响.结果发现经过 750 ℃核化4 h,850 ℃晶化2 h,得到主晶相为硅灰石(CaSiO3)和菱硅钙钠石(Na2Ca2Si3O9)的微晶玻璃.玻璃中表面析晶和整体析晶同时存在,其中Na2O可促进整体析晶和菱硅钙钠石的析出.     

Formation of closed pore structure in CaO-MgO-Al2O3-SiO2 (CMAS) porous glass-ceramics via Fe2O3 modified foaming for thermal insulation

Due to the low density, low thermal conductivity and low water absorption, porous glass-ceramics have demonstrated excellent performance for thermal insulation. Closed pore structure can greatly reduce the thermal conductivity and convection as well as achieve high mechanical strength. However, yet it is difficult to realize closed pore structure due to the critical preparation condition. Here we use Fe₂O₃, which is the by-product of copper tailings, to optimize the pores structures of the porous glass-ceramics and facilitate the formation of uniform closed pore structure. The porous glass-ceramics were prepared by melting-quenching method, followed by sufficiently foaming through powder sintering route with SiC powders as foaming agent. The foaming process, micro structure, pore structure and thermal insulation performance were directly observed by heating microscope, scanning electron microscope (SEM), X-ray computed tomography and infrared thermal imager. The results show that the addition of Fe₂O₃ modified the depolymerization degree of the glass network and increased the numbers of non-bridged oxygen, decreasing the foaming temperature. The resultant closed pore structure showed a better thermal insulating performance than open pore structure. Accordingly, we achieved a low thermal conductivity of 0.19 W·m^?1·K^?1 with the highest specific strength of 19.55 MPa·g^?1·cm^?3 based on closed pore structure.     

Na2O—CaO—TiO2—P2O5系统多孔微晶玻璃的制备

自1934年，H·P·Hood等人发明了Vyocr glass 以来，用于制备多孔玻璃的基础玻     

Sinterability,microstructure and compressive strength of porous glass-ceramics from metallurgical silicon slag and waste glass

Porous glass-ceramics have been prepared by the direct sintering of powder mixtures of metallurgical silicon slag and waste glass. The thermal behavior of silicon slag was examined by differential thermal analysis and thermogravimetry to clarify the foaming mechanism of porous glass-ceramics. The mass loss of silicon slag below 700 °C was attributed to the oxidation of amorphous carbon from residual metallurgical coke in the silicon slag, and the mass gain above 800 °C to the passive oxidation of silicon carbide. The porosity of sintered glass-ceramics was characterized in terms of the apparent density and pore size. By simply adjusting the content of waste glass and sintering parameters (i.e. temperature, time and heating rate), the apparent density changed from 0.4 g/cm³ to 0.5 g/cm³, and the pore size from 0.7 mm to 1.4 mm. In addition to the existing crystalline phases in the silicon slag, the gehlenite phase appeared in the sintered glass-ceramics. The compressive strength of porous glass-ceramics firstly increased and then decreased with the sintering temperature, reaching a maximal value of 1.8 MPa at 750 °C. The mechanical strength was primarily influenced by the crystallinity of glass-ceramics and the interfaces between the crystalline phases and the glassy matrix. These sintered porous glass-ceramics exhibit superior properties such as light-weight, heat-insulation and sound-absorption, and could found their potential applications in the construction decoration.     

载体孔结构对银基催化剂性能影响

乙烯氧化制环氧乙烷银催化剂所用载体为大孔惰性α-Al2 O3.载体孔道结构对金属银的分布有调控作用,通过选择适宜的孔道结构,采用银胺溶液浸渍,热分解可以获得特定尺寸分布的负载银催化剂.以不同粒度和晶相的氧化铝复配,添加不同的扩孔剂,制备了孔结构不同的三种载体负载银制得银催化剂.对银催化剂进行TGA和SEM分析,并考察其...     

Pore structure and thermal oxidation curing behavior of porous polymer derived ceramics with superhigh porosity fabricated by freeze casting

Porous ceramics with porosity up to 92.5 % have been successfully fabricated by freeze casting of polycarbosilane (PCS) solution. The effect of PCS concentration and thermal oxidation curing on the pore structure and compressive properties was investigated. Curing mechanism and thermodynamics were illuminated through analyzing the molecular structure, curing activation energy, and curing degree. Porous ceramics, mainly composed of SiC and a small amount of SiO₂, have dendritic pore structure which well replicates the solidification morphology of camphene solvent. Results of FT-IR and Gaussian computation of PCS electron density show that Si–H and Si–CH₃ bonds play a dominant role in thermal oxidation curing reaction. Both curing degree and ceramic yield increase with the increase in curing temperature and time. The curing degree of Si–H bond is close to 52 % and the corresponding ceramic yield is about 83 % when the porous PCS was cured at 200 °C for 90 min. Both polymer concentration and curing time have influences on the compressive strength of porous ceramics.     

Study on the effect of micro geometric structure on heat conduction in porous media subjected to pulse laser

Based on fractal theory, different two-dimensional fractal structures were constructed to simulate the practical porous media. Effective thermal conductivity for porous media was calculated by means of the finite volume method. Theoretical analysis of thermal response in the porous media under various heating conditions was performed with a multi-layer hyperbolic heat conduction model with volumetric heat generation. The results obtained in this paper indicate that pore size and micro distribution have a far-reaching impact on the heat conduction in porous media. If we assumed that both the thermal conductivity and the heat capacity of the solid phase is larger than those of liquid phase, decreasing the pore size and porosity is helpful to enhance the heat transfer in porous media and the peak of temperature increases with pore size and porosity. With the same pore size and porosity, the effect of the pore micro-geometric distribution on heat conduction in porous media is obvious. The method presented in this paper may suggest a valuable approach to theoretically evaluate the effect of pore micro-geometric structure on heat conduction in porous media.     

孔隙分布对多孔介质内流动和传热的影响

采用Sierpinski地毯分形技术建立多孔介质内流动和传热模型,通过改变固体基质位置研究了孔隙分布结构对多孔介质内流动特性和热效率的影响,3种孔隙分布为每分形一次固体基质分布在中心位置(A)、分布在中上方(B)和分布在右上方(C),当流体稳定流过多孔介质时,不同的孔隙分布表现出不同流动和传热特性. 结果表明,孔隙分布是影响多孔介质传输特性和传热效率的重要因素,无量纲渗透率k*C>k*B>k*A,多孔介质孔隙率大于0.8时更明显;流体流过不同孔隙分布的多孔介质时,相同孔隙率时与流体接触的固体基质面积A>B>C,传热效果A最佳、C最差. 孔隙分布影响了无量纲局部熵产率,在3种孔隙分布下用Be表示的热传导引起的熵产率占主导.     

沸石补强硅酮建筑密封胶的应用研究

详述了用沸石和焙烧沸石作为补强剂用于制备硅酮建筑密封胶的工艺过程,分析了粉体用量对密封胶热稳定性、拉伸强度、断裂伸长率、干燥时间的影响;用扫描电镜（SEM）、X射线衍射（XRD）、氮气吸附—脱附等温测试（BET）和脱附孔径测试（BJH）方法对沸石和焙烧沸石的微观形貌、物相、比表面积、孔容和孔径进行了表征;研究结果表明它们是一种具有多孔结构的铝硅酸盐矿物,主要成分KNa2Ca2(Si29Al7)O72和K(Si3Al)O8,孔径分别为10nm和14nm,孔体积0.4655cc/g和0.5871cc/g,比表面积153.6m2/g和191.4m2/g,孔径分布宽、孔体积和比表面积大有利于补强,焙烧沸石的补强性优于沸石,揭示了它们的补强作用是硅烷偶联剂表面改性、孔道效应和锚固效应共同作用的结果。     

沸石补强硅酮建筑密封胶的应用

考察了用沸石和焙烧沸石作为补强剂用于制备硅酮建筑密封胶的工艺过程,分析了粉体用量对密封胶热稳定性、拉伸强度、断裂伸长率、干燥时间的影响;用扫描电镜(SEM)、X射线衍射(XRD)、氮气吸-脱附等温测试(BET)和脱附孔径测试(BJH)方法对沸石和焙烧沸石的微观形貌、物相、比表面积、孔容和孔径进行了表征;研究结果表明,它们是一种具有多孔结构的铝硅酸盐矿物,主要成分分别为KNa2Ca2(Si29Al7)O72和K(Si3Al)O8,孔径分别为10.68 nm和14.02 nm,孔体积分别为0.465 5 mL/g和0.587 1 mL/g,比表面积分别为153.6 m2/g和191.4 m2/g,孔径分布宽、孔体积和比表面积大有利于补强,焙烧沸石的补强性优于沸石,揭示了它们的补强作用是硅烷偶联剂表面改性、孔道效应和锚固效应共同作用的结果。     

The thermal,electrical and mechanical properties of porous α-SiC ceramics bonded with Ti3SiC2 and β-SiC via low temperature in-situ reaction sintering

Porous SiC ceramics have recently attracted wide attention for their applications in the electrically heatable filter. Further improvement of the thermal and electrical conductivity without sacrificing permeability is a critical parameter for such applications. In the present work, porous SiC/Ti₃SiC₂ ceramic composites with Ti₃SiC₂ and micro/nano SiC have been prepared from TiC/Si/α-SiC mixtures at a low sintering temperature (1400 °C). Nano-laminated Ti₃SiC₂ enhanced the electrical conductivity, while the good thermal conductivity was achieved through in-situ formed nano β-SiC and raw coarse α-SiC in the porous ceramics. Along with the increase of initial α-SiC particle size from 0.76 to 16.13 μm, the permeability, thermal and electrical conductivity improved due to the decreased porosity and increased pore size in porous SiC/Ti₃SiC₂ ceramics. The results suggested that the decoupling of the electrical conductivity from the thermal conductivity could be tuned by adjusting the initial α-SiC particle size.