钨带灯的稳定性判据试验

我们通过对国产ＢＷ—１４００型真空钨带灯的稳定性判据进行研究，发现通过钨带灯的电流达到稳定的时间很短（小于５分钟），而钨带灯的灯电阻需要经过２０分钟后才能达到稳定，因此，用电流稳定性作为钨带灯的热平衡判据是不够的，更可靠的判据还应看灯电阻是否达到平衡。     

MS界面稳定性判据新探

给出了定向凝固平界面稳定性新的判据,（ｌ＋３ｋ／ｙ０）ξ ＋［１＋（１＋ ｋ）ｙ０／４ｋ］≥１其中Ａ为无量纲速度,ξ≡ＧＬＳ／ｍＧｃ,ｙ０是有关Ａ和ξ的一个二次方程的根．新判据的最大特点是可直接由凝固参数推断界面的稳定性,不用解高次方程．发现ＭＳ绝对稳定性速度Ｖａ仅在加权温度梯度ＧＬＳ→０时才是界面稳定性的临界速度．当 ＧＬＳ＞０时,Ｖａ大于实际的临界速度．给出了一个新的绝对稳定性梯度条件,并求出了最小的绝对稳定性无量纲临界梯度．     

块体非晶合金玻璃形成能力的新判据

基于合金熔体的液相稳定性和抗晶化能力分析,提出了一个评估非晶合金玻璃形成能力(GFA)的新判据:ω=Tg/Tx-2Tg/(Tg+Tl),其中,Tg为玻璃转变温度,Tx为晶化开始温度,Tl为液相线温度。利用报道的金属玻璃实验数据对ω、Trg(=Tg/Tl)、ΔTx(=Tx-Tg)、γ(=Tx/(Tg+Tl))、γm(=(2Tx-Tg)/Tl)、α(=Tx/Tl)、β(=(Tx/Tg+Tg/Tl)、δ(=Tx/(Tl-Tg)、φ(=Trg(ΔTx/Tg)0.143)和2β(=Tx×Tg/(Tl-Tx)2)判据与GFA相关性进行了统计分析。结果表明:ω与临界冷却速率(Rc),1/ω与形成非晶的最大直径(Dmax)都具有最强的线性相关性。     

AgX光色玻璃退色动力学模型

以ＡｇＸ光色玻璃中的胶体Ａｇ^０转化为Ａｇ^＋的转化几率ｂ为基础,推导了ＡｇＸ光色玻璃的退色动力学模型：Ｔ＝１—Ｂ—ｋＣ_０exp（－ｂｔ）,并结合实测的退色动力学参数给出了这一模型的数学解法,并将根据该理论模型绘制的退色动力学曲线与实测的退色动力学曲线进行了对比．结果表明：根据ＡｇＸ光色玻璃中的转化几率ｂ所推导出的退色动力学模型,较好地解释了ＡｇＸ光色玻璃的退色过程,转化几率ｂ较准确地表征了退包动力学的退色速度,理论计算的退色动力学曲线与实测的退色动力学曲线完全吻合．这进一步证明了本文提出的退色动力学模型及其所依赖的理论基础的正确性．     

异相型AgX光色玻璃的聚类分析研究

本文运用聚类分析方法,用Ｆｏｘｐｒｏ２．６编制光功能玻璃数据库及处理程序,对异相型ＡｇＸ光色玻璃进行了聚合分类,并讨论了组成和温度对Ｔ_ｏ、Ｔ_ｄ和忧的影响．结果表明：根据不同样本的Ｔ_ｏ２５、Ｔ_ｄ２５、Ｔ_ｆ２５的相似程度,将异相型ＡｇＸ光色玻璃分成七个相互独立的类别．经过对七类光色玻璃分析认为;Ａｇ、Ｃｕ等元素对光色性质产生较大的影响,而Ｍｎ、Ｎｉ等发色元素则大大降低了玻璃的透过率．分析结果还表明：与在２５下相比较,在４０时的Ｔ_ｏ几乎没有变化,而Ｔ_ｄ、Ｔ_ｆ显著增加．     

抗菌玻璃化学稳定性影响因素研究

采用硼硅酸盐玻璃作为载体,以银离子为有效抗菌成分,制备了载银型可溶性抗菌玻璃材料;着重研究玻璃氧化物组成、热历史、侵蚀液pH值和侵蚀时间对抗菌玻璃化学稳定性的影响。     

PbI2—PbBr2二组份玻璃的化学稳定性研究

本文获得了ＰｂＩ２－ＰｂＢｒ２二组份玻璃，并且在２５℃的恒定温度下，研究了组成为７０ＰｂＩ２３０ＰｂＢｒ２（ｍｏｌ％）的玻璃在静态去离子中的侵蚀过程，在去离子水中，玻璃中的各组份以分子形式溶解，这是一个选择性溶解过程。，溶解度较高的玻璃组份将优先溶解。由于ＰｂＸ２（Ｘ＝Ｉ，Ｂｒ）的水解，溶液的ＰＨ经历一个由快速下降到逐渐稳定的变化过程，通过比较发现，所得玻璃的化学稳定性与氟锆酸盐玻璃处于同一数量级     

Popov频率判据的简化

本文用自变量取值范围为有限区间的频率特性曲线来代替原来的Ｐｏｐｏｖ频率特性曲线，从而改进和简化了ＰｏＰｏｖ频率判据。     

硼硅酸盐包层玻璃化学稳定性的研究与结构分析

研究了紫外光纤用包层玻璃组分的变化以及外掺ZrO2对光纤包层玻璃化学稳定性的影响.结果表明,通过改变SiO2/B2O3、B2O3/Al2O3、B2O3/(K2O Na2O)的值,以及适当增加外掺ZrO2含量,可以明显提高碱硼硅酸盐玻璃化学稳定性.核磁共振和红外光谱分析表明玻璃化学稳定性提高的主要原因在于Zr4 的加入促进了玻璃内部的[BO3]层状结构逐渐转变为[BO4]网络状结构.     

BaO-Al2O3-SiO2系微晶玻璃析晶机理研究

利用烧结法制备化学计量比和高Ba含量的两组BaO-Al₂O₃-SiO₂(BAS)系微晶玻璃, 采用等转化率法计算玻璃粉的活化能随析晶过程的变化, 利用线性回归的方法确定最概然析晶机理函数, 进而对比研究添加ZrO₂和提高Ba含量对BAS系微晶玻璃析晶过程的影响. 结果表明, 4种成分的BAS系玻璃的最概然析晶机理函数均为SB(m, n)函数, 析晶过程中存在自催化的相变机制. 在化学计量比的BAS系玻璃中添加ZrO₂或者提高Ba含量, 对六方钡长石的析出表现为促进作用, 并且随着温度的降低或者析晶过程的进行, 促进效果更加明显. 在高Ba含量的BAS系玻璃中添加ZrO₂对六方钡长石的析出表现为抑制作用, 并且随着温度的升高抑制效果更加明显.     

Zr-Al-Ni-Cu块体非晶合金的制备及其耐蚀性能

块体非晶合金的耐蚀性能与合金元素本身的特性及合金成分密切相关.采用铜模吸铸法制备了Zr_(55)Al_(10)Ni_5Cu_(30)块体非晶合金,用X射线衍射(XRD)、差示扫描量热分析法(DSC)和差热分析法(DTA)考察了合金的非晶特性和热力学属性,通过电化学极化试验和盐雾腐蚀试验测试了合金的耐蚀性.结果表明,制备的Zr_(55)Al_(10)Ni_5Cu_(30)合金为完全的非晶相,且具有较大玻璃形成能力和热稳定性;腐蚀电流密度仅为12.6 nA/cm~2,经144 h盐雾试验无质量变化,表明合金具有优异的耐腐蚀性能.     

中温SOFC密封玻璃热稳定性研究

研究了一种热稳定性好的中温固体氧化物燃料电池密封玻璃. 研究表明, 此密封玻璃的热膨胀系数(室温～631℃)为9.8×10^-6/K, 与8YSZ电解质的热膨胀系数10.0×10^-6/K(室温～631℃)接近, 并且在700℃热处理300h后, 该密封玻璃的热膨胀系数几乎没有变化. 粘度实验表明, 玻璃在700℃下具有足够的刚性, 适合于运行温度在700℃左右SOFC的密封. 化学相容性的研究显示, 在700℃下与8YSZ反应300h后没有发现显著的界面反应.     

掺C60磷酸盐玻璃的显微结构特征

本文报道了掺Ｃ６０磷酸盐玻璃显微结构特征的研究结果。透射电子显微镜观察表明：在玻璃介质中，Ｃ６０分子晶体能以结晶固体的形式稳定存在。     

Investigation on a thermoacoustically driven pulse tube cooler working at 80 K

The pulse tube cooler (PTC) driven by a thermoacoustic engine can completely eliminate mechanical moving parts, and then achieves a simpler and more reliable device. A Stirling thermoacoustic heat engine has been constructed and tested. The heat engine can generate a maximal pressure ratio of 1.19, which makes it possible to drive a PTC and get good performance. Frequency is one of the key operating parameters, not only for the heat engine but also for the PTC. In order to adapt to the relatively low design frequency of the PTC, the operating frequency of the thermoacoustic heat engine was regulated by varying the length of the resonance tube. Driven by the thermoacoustic engine, a single stage double-inlet PTC obtained the lowest refrigeration temperature of 80.9 K with an operating frequency of 45 Hz, which is regarded as a new record for the reported thermoacoustically driven refrigerators.     

应变能密度比准则在块体非晶合金中的应用

由于块体非晶合金独特的原子排列结构,导致其具有独特的力学行为。多年来,国内外研究人员对块体非晶合金的断裂行为进行了一系列的研究,并取得了一定的成果。本文简单介绍了近年来国内外针对块体非晶合金断裂准则的研究状况,随后比较全面地介绍了应变能密度比失效准则,并推导了遵循该准则时断裂角θT(载荷方向与断裂面的夹角)与α(断裂面剪应力与正应力的比值)应满足的关系,最后利用Zr41.2Ti13.8Cu10.0Ni12.5Be22.5块体非晶合金的拉伸实验和已有的实验结果,证实了块体非晶合金遵循应变能密度比失效准则。     

Comparative test on two kinds of new compliant foil bearing for small cryogenic turbo-expander

Two kinds of new compliant foil journal bearing for a small cryogenic turbo-expander used in the Brayton cycle cryocooler are presented in this paper. The foil of bearings is supported with copper wires and elastic material respectively, so the bearings are much simpler in structure than previous compliant foil bearing. The performances of the bearings are studied under the same experiment conditions. The results indicate that both bearings have better damp performance and the foil bearing supported with elastic material has preferable stability to the one supported with copper wires.     

High-Entropy Alloy-Induced Metallic Glass Transformation: Challenges Posed by in situ Alloying via Additive Manufacturing

In situ alloying and fabricating glassy structures through a layer-by-layer fashion approach are challenging but have high potential to develop novel-graded materials. For the first time, this cost-effective approach is applied to additive manufacturing (AM) of a Zr-based bulk metallic glass (BMG) from high-entropy alloys (HEAs). A newly developed composition of Zr₄₀Al₂₀Cu₂₀Ti₂₀ is fabricated through laser powder bed fusion (LPBF). Process parameters are optimized within a wide range of laser power (50–200 W) as well as scanning speed (50–800 mm s⁻¹). In all printed samples, microscopic and compositional examinations reveal no glass formation, but very fine grains and CuTi and AlTi nanocrystals. Some glassy transitions at the interfaces may be encouraged to occur with proper melting and mixing. However, the main reason for not obtaining a glassy matrix is the substantial proportion of unmelted Zr raw powder throughout the structure as spherical particles. Consequently, glass formation can be hindered by a considerable amount of compositional deviation. During LPBF, in situ alloying poses significant challenges to developing BMGs. Hence, the various stages of the process, including raw material specifications, laser settings, and process parameters, should be investigated further.     

埋地管道爆破振动安全允许判据试验探究

为了探究埋地管道的爆破振动安全允许判据而进行现场监测试验,试验利用TC-4850N测振仪和DH3820应变测试系统对埋地管道的爆破振动和管道应变分别进行监测。首先通过不同主振频率下的管道最大轴向应变分析发现最大应变主要集中在35 Hz以下,然后将主振频率小于35 Hz和大于35 Hz的峰值振速统计量分别拟合分析。结果表明:不同频率段的相关参数和萨氏公式有所不同,因此应在一定频率范围内分别确定爆破振动安全允许峰值振速。实际施工过程中应结合具体情况确定爆破施工方案,而不能仅根据模糊的法律规范条款简单决定爆破施工方案。     

A capacitance based axial position sensor for cryocoolers

The recent development of a Stirling cryocooler designed to operate with a body temperature of less than 220 K required an axial motor position sensor which could operate over this temperature range. Although linear variable differential transformers (LVDTs), have traditionally been used, these are temperature dependent and would have required development due to integrated electronics, which could not be used at these low temperatures. A sensor was therefore developed based on the principle of measuring the capacitance between static and moving concentric rings. The design is presented along with the signal conditioning circuit. Experimental results show that the sensor had suitable bandwidth with a temperature independent gain between room temperature and 220 K. Future developments are described including a similar sensor to measure the radial motion of a motor during operation.