Preparation and Characterization of ZnO-CuO-Bi_(2)O_(3)-B_(2)O_(3)-SiO_(2)System Low Melting Sealing Glasses

Lead-free low melting glasses,ZnO-CuO-Bi_(2)O_(3)-B_(2)O_(3)-SiO_(2)system,with fixed contents of 15 mol%CuO and 20 mol%Bi_(2)O_(3),were prepared by using melt cooling method.Structure and thermal properties of the glasses were studied by using X-ray diffractometer(XRD),infrared spectrometer(FIT-IR),thermal dilatometer and differential thermal analyzer(DTA).Chemical durability of the glasses was studied by using dissolution rate method.Wettability of glasses on substrate was tested by using button sintering experiment.It is found that alkaline resistance of the glass solders is lower than that of plate glass and the water resistance is comparable with that of plate glass.The sealing temperatures are Ts=445-490℃,while the average thermal expansion coefficient from room temperature to 300℃is in the range of(65-82)×10^(−7)℃^(−1).At sealing temperature,the glass solders have good wettability on plate glass or alumina substrate.They are not crystallized even sintered at the sealing temperature for 30 min.The solder glasses are suitable for sealing plate glass,alumina and other inorganic non-metallic materials.

Thermal stability,crystallization behavior,Vickers hardness and magnetic properties of Fe-Co-Ni-Cr-Mo-C-B-Y bulk metallic glasses

Thermal stability,crystallization behavior,Vickers hardness and magnetic properties of the Fe41Co7-xNixCr15Mo14C15B6Y2（x=0,1,3,5） bulk metallic glasses were investigated.The Fe41Co7-xNixCr15Mo14C15B6Y2（x=0,1,3,5） metallic glasses were fabricated by copper mold casting method.The thermal stability and crystallization behavior of the metallic glass rods were investigated by differential scanning calorimetry and isothermal experiments.Hardness measurements for samples annealed at different temperatures for different time were carried out at room temperature by the Vickers hardness tester,and magnetic measurements were performed at different temperatures by the vibrating sample magnetometer.It is shown that the addition of Ni does not play a positive role for enlarging ΔTx and GFA from parameter γ（=Tx/（Tg＋Tl））,and it can,however,increase the activation energy in the initial stage of crystallization by changing the initial crystallization behavior.The minor addition of Ni can refine the crystal grain obtained from the full crystallization experiment.The primary crystallization causes the decrease of hardness in these alloys,and as the crystallization continues,the hardness in all samples increases instead due to the precipitation of carbide and boride.The annealing temperature has an obvious effect on magnetic properties of these alloys,and the minor addition of Ni can effectively prevent the alloy annealed at high temperature to transform from paramagnetic to ferromagnetic state.

聚丙烯酰胺的合成及性能

以丙烯酰胺(AM)为单体,(NH_4)_2S_2O_8,NaHSO_3为氧化还原引发体系,采用水溶液聚合法制备聚丙烯酰胺(PAM)。研究了PAM的结构、性能和相对分子质量,同时考察了反应温度及单体、引发剂和链转移剂的质量分数对聚合反应转化率及PAM相对分子质量的影响。傅里叶变换红外光谱谱图中998 cm^(-1)处C=C双键的伸缩振动吸收峰消失以及在X射线衍射谱图中衍射角为20°～23°出现PAM特征弥散衍射峰,表明AM聚合生成了PAM。PAM热分解分3个阶段进行,其玻璃化转变温度随相对分子质量增大而升高。提高反应温度、增大引发剂和单体质量分数都可以提高单体转化率。升高反应温度、降低单体质量分数、增加引发剂和链转移剂质量分数均可以降低PAM的相对分子质量。

Thermal stability and Judd-Ofelt analysis of optical properties of Er^(3+)-doped tellurite glasses

Er3＋-doped TeO2-ZnO-Na2O-B2O3-GeO2 （TZNBG） glasses were prepared by melt-quenching method. Differential scanning calorimetry （DSC） and thermal mechanical analysis （TMA） were used to calculate thermal parameters： crystallization temperature （Tx）, glass transition temperature （Tg） and thermal expansion （α）. Besides, Judd-Ofelt theory is applied to analyzing absorption spectra. Intensity parameters -λ （λ=2, 4, 6）, transition probabilities Aed, radiative lifetime τi, and branching ratios β of Er3＋ transitions were obtained. Emission cross-section σemis of 4I13/2→4I15/2 transition of Er3＋ was calculated according to the theory of McCumber. All of the parameters indicate that the thermal stability and optical properties of Er3＋-doped TZNBG glasses are improved effectively.

GeO_2含量对掺铒锗碲酸盐玻璃物性和光谱特性的影响

本文研究了xGeO2-(70-x)TeO2-5K2O-5Na2O-10Nb2O5-10ZnO-0·2Er2O3(x=0,10,25,50,70(摩尔百分数))玻璃的物性和光谱特性,讨论GeO2含量对锗碲酸盐玻璃物性和光谱特性的影响.研究发现:GeO2的加入提高了碲酸盐玻璃热稳定性,并且使玻璃的最大声子能量略微增加;随GeO2的增加,掺Er3+锗碲酸盐玻璃的Judd-Ofelt强度参量Ω2和Ω6逐渐增大,但玻璃受激发射截面有减小的趋势;由McCumber理论,计算了掺铒锗碲酸盐玻璃在1·53μm处最大受激发射截面为9·92×10-21cm2,Er3+离子4I13/2→4I15/2发射谱的最大荧光半高宽为52nm,同时,实验发现,在977nmLD抽运下,掺铒锗碲酸盐玻璃存在较强的荧光上转换现象,随GeO2含量的增加,上转换荧光强度呈降低的趋势.

Improving plasticity of the Zr46Cu46Al8 bulk metallic glass via thermal rejuvenation

In this paper, effects of cryogenic thermal cycling on deformation behavior and thermal stability of the Zr46Cu46AI8 bulk metallic glass （BMG） were studied. The results show that with the increase of the number of cryogenic thermal cycles （CTC）, thermal stability remains almost unchanged, while the plasticity is increased, indicating that the cryogenic thermal cyclic treatment is an effective way to improve plasticity of metallic glasses without distinctly deteriorating thermal stability. Our analysis suggests that the increase in the defect density resulted from the cryogenic thermal treatments are responsible for the plasticity increment. Variation of yield strength can be well interpreted from microstructural percolation which affected by both density and characteristic volume of the defect sites.

Effect of thermal cycling on the mechanical properties of Zr_(41)Ti_(14)Cu_(12.5)Ni_(10)Be_(22.5) alloy

The effect of thermal cycling treatment on mechanical properties and thermal stability of a Zr41Ti14Cu12.5Ni10Be22.5 bulk metallic glass is investigated.The metallic glassy samples are sealed into quartz tubes under high vacuum condition,and liquid nitrogen together with electric furnace are used to control a periodical temperature variation between 196℃ and 150℃.The structure and properties of the tested samples for different thermal cycles have been examined by X-ray diffraction analysis,mechanical properties measurement and thermal analysis.It has been found that the structure and properties of the samples do not show a significant change even after 200 cycles,which suggests Zr41Ti14Cu12.5Ni10Be22.5 alloy as having potential in aerospace environment.

Effects of Cu,Fe and Co addition on the glass-forming ability and mechanical properties of Zr-Al-Ni bulk metallic glasses

The thermal stability,glass-forming ability(GFA) and mechanical properties of Zr60Al15Ni25xTMx(TM = Cu,Fe and Co,x = 0-10) bulk metallic glasses(BMGs) were systematically investigated.Additional 5-10 at.% Cu greatly enhances the thermal stability and GFA of the base alloy.Zr60Al15Ni15Cu10 BMG exhibits the largest supercooled liquid region of 104 K and critical diameter of 18 mm.However,addition of 5-10 at.% Fe or Co decrease the thermal stability and GFA.In addition,the plasticity of the BMG can be improved by adding of Cu,while the strength is decreased slightly.Zr60Al15Ni20Cu5 BMG has the largest plastic strain of 5.5% with a yield stress of 1755 MPa and Young's modulus of 83 GPa.Addition of Co brings an increase of strength but a lower of plasticity,and additional Fe reduces the strength and plasticity simultaneously.