用Bridgman-Stockbarger技术多坩埚生长氟化钙晶体的研究

用Bridgman-Stockbarger技术多坩埚生长氟化钙晶体,在合理的温场条件下,成功地生长出质优量多的不同直径的晶体。成品率高于单坩埚生长,达70%。对批量生产,缩短生长周期,提高经济效益,具有明显的价值。(利用多坩埚可以生长不同形状的异形体晶体)     

熔铝坩埚的研制

通过对熔铝坩埚成分的选择和工艺合理制订,生产出了高质量的熔铝坩埚,实践证明,该材质坩埚寿命提高1～2倍.     

多孔预制体对SiC/Al复合材料孔隙率的影响

采用无压浸渗法制备了SiC含量较高的SiC/Al复合材料,分析了造孔剂添加量对多孔预制体孔隙率的影响,利用铝液浸渗多孔体理论分析了多孔顸制体孔隙结构对复合材料孔隙率的影响.结果表明:通过添加造孔剂可以调节多孔预制体的孔隙结构,使预制体的孔隙率增加;多孔预制体的孔隙结构的变化可以调节复合材料的孔隙率.多孔预制体的孔隙率越高、孔隙尺寸越大,则铝液浸渗畅通,复合材料的孔隙率越小.     

高效强化换热技术—大空隙率绕花丝多孔体

本文对水蒸汽和水在大空隙率多孔体绕花丝等多孔介质管内的对流换热进行了系统的实验研究，发现采用大孔率多孔体绕花线可以使管内流体在很低的流速下（Ｒｅ≤２５０）由于弥散产应提前由层流向湍流的转化，从而使换热得到了显著的增强，本文通过流型照片的分析对换热强化的进行了讨论，并给出了换热的研究结果已在工业实践中应用，运行结果与实验数据符合很好。     

激光聚焦线扫描法测量KDP晶体坯片的体缺陷

为了快速准确测量磷酸二氢钾(KDP)晶体坯片的体缺陷,提出了高速激光聚焦线扫描散射成像方法,并建立了相应的测量系统。研究了该系统的测量原理和图像采集、图像处理和体缺陷信息提取方法。基于激光散射技术,结合高速运动装置对晶体坯片内部进行三维扫描,用线阵CCD探测器接收气泡、包裹物等体缺陷产生的散射光。然后利用折射率匹配液消除粗糙表面带来的不利影响。最后结合数字图像处理技术,对采集的图像进行实时处理。通过去除背景后与设定阈值比较得到具有体缺陷特征的图像,再对其进行二值化处理,提取得到体缺陷的位置和尺寸信息。利用该检测装置对KDP晶体坯片体缺陷进行了测量,结果显示其检测分辨率优于40μm,能够为晶体坯片的精确切割和最大程度的利用提供依据,从而节省了大量成本。     

掺杂AgCl晶体的生长与应用

介绍了采用埚坩下降法生长掺杂AgCl晶体的工艺,得到了尺寸为φ20×60mm的AgCl晶体棒;对掺杂AgCl电极晶体的性质、测试数据及应用作了报导。     

镁合金熔炉坩埚瞬态传热与热应力分析

针对镁合金熔炉坩埚使用寿命较短,坩埚各接合处易变形开裂而失效,采用有限元分析方法,对镁合金熔炉坩埚升温过程进行了瞬态传热模拟分析,得到了其升温过程曲线和温度场分布云图,并与实验采集的数据进行对比;在此基础上进行热—结构耦合分析,计算得出了升温结束时坩埚各接合处的热应力分布情况。分析结果显示:坩埚瞬态传热分析结果与实验数据吻合良好,说明瞬态传热分析真实可靠;坩埚各接合处热应力波动较大且局部有应力集中现象。     

Machinability of single crystal calcium fluoride by applying elliptical vibration diamond cutting

Functional micro/nano structures are promising for enhancing the performance of CaF₂-based devices. However, it is still a challenge to precisely manufacture CaF₂ micro/nano structures due to their brittleness. In the present work, we demonstrated the machinability of ductile-mode diamond cutting of CaF₂ and the ability to sculpture sophisticated micro/nano structures on CaF₂ by applying elliptical vibration cutting. Firstly, the nanoindentation of CaF₂ reveals the crystal orientation-dependent interaction between dislocation slip and crack propagation, thus obtaining the optimal crystal orientation for plasticity. Subsequently, the grooving tests were conducted along the crystal orientation of (111)$\left[\bar{1}2\bar{1}\right]$. With elliptical vibration cutting, the critical depth of cut from ductile-to-brittle transition is increased by 42 times as compared with ordinary cutting. Furthermore, considering the instantaneous uncut chip thickness in each vibration cycle, the influence of vibration amplitude on the ductile machinability of CaF₂ is discussed in detail. Finally, based on these fundamental results, ultra-precision hexagonal microlenses were successfully sculptured on CaF₂ by applying the amplitude-controlled sculpturing method in elliptical vibration cutting.     

Experimental study of crystal anisotropy based on ultra-precision cylindrical turning of single-crystal calcium fluoride

To realize ultimately efficient signal processing, it is necessary to replace electrical signal processing circuits with optical ones. The optical micro-resonator, which localizes light at a certain spot, is an essential component in optical signal processing. Single-crystal calcium fluoride (CaF₂) is the most suitable material for a highly efficient optical micro-resonator. The CaF₂ resonator can only be manufactured by ultra-precision machining processes, because its crystal anisotropy does not allow the application of chemical etching. However, the optical micro-resonator's performance depends definitely on the surface integrity.This study investigated the relationship between surface quality after ultra-precision machining and crystal anisotropy. Firstly, crack initiation was investigated on the (1 0 0), (1 1 0), and (1 1 1) planes using the micro-Vickers hardness test. Secondly, brittle-ductile transition was investigated by orthogonal cutting tests. Finally, cutting performance of cylindrical turning was evaluated, which could be a suitable method for manufacturing the CaF₂ resonator. The most difficult point in cylindrical turning of CaF₂ is that the crystalline plane and cutting direction vary continuously. In order to manufacture the CaF₂ optical micro-resonator more efficiently, analysis was conducted on crack initiation and surface quality of all crystallographic orientations from the perspective of slip system and cleavage.     

炉室上升式BS法单晶炉的设计

这里介绍了炉室上升式BS法单晶炉的设计思路及工作原理，结合晶体生长的特殊工艺要求，分析了其主要结构及特点。     

磺酸钙基脂晶型转化反应机理探讨

探讨了磺酸钙基脂晶型转化的反应机理,分析了不同活性氢物质作转化剂对晶型转化的影响。结果表明:磺酸钙基脂的极压性能由碳酸钙的晶型种类决定;小分子有机酸作为转化剂时形成的润滑脂综合性能最佳。     

Ultrastructural evaluation of enamel after dental bleaching associated with fluoride

This study evaluated the effects on human enamel after two bleaching procedures: with a fluoridated bleaching agent and with topical fluoride application postbleaching. It used 43 enamel blocks (3 mm(2) ) that were ground flat (600-2,000 grit) and polished with polishing paste (one and one-fourth). Specimens were randomly divided into three groups according to the bleaching procedure: (1) control group, (2) hydrogen peroxide 35% (HPF) and topical application of fluoride 1.23%, and (3) HP 38% (OP) with fluoride in its composition. Bleaching agents were used according to the manufacturer's instructions. Three methodologies were used: nanoindentation, to observe surface hardness and elastic modulus; atomic force microscopy, to observe surface roughness (R(a) - R(z)); and scanning electron microscopy, to observe the enamel surface effects. Group OP had a decrease in the elastic modulus after bleaching, which was recovered at 14 days. An increased roughness (R(a); 32%) was observed on group HPF and had an increased erosion on enamel surface (67%). It was concluded that topical application of fluoride, after using the nonfluoridated whitening agent, increased the roughness values and erosion of enamel.     

单晶蓝宝石的延性研磨加工

为实现单晶蓝宝石的延性研磨加工,采用纳米压痕和划痕法测试并分析了单晶蓝宝石(0001)面的微纳力学特性,建立了单颗圆锥状磨粒的压入模型并计算了延性研磨加工的受力临界条件,分析了金刚石磨粒嵌入合成锡研磨盘表面的效果.对单晶蓝宝石进行了延性研磨加工试验,采用NT9800白光干涉仪、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等方法分析了单晶蓝宝石的延性研磨表面特征.试验结果表明:采用纳米压痕和划痕法可以为单晶蓝宝石的延性研磨加工提供工艺参数,单晶蓝宝石的延性堆积的极限深度为100 nm,金刚石磨粒的嵌入及在适当载荷下可以实现蓝宝石的延性研磨加工,实验条件下的最佳载荷为21 kPa,延性研磨后单晶蓝宝石表面划痕深度的分布情况较好,分散性小,研磨后的表面发生了位错滑移变形.     

FDTD方法在光子晶体光纤中的应用

光子晶体光纤是近年来研究的热点,提出时域有限差分法在光子晶体光纤理论分析中应用的具体方法。通过实例计算,得到了光子晶体光纤的有效折射率等传播参量。     

几种氟化物薄膜材料的光学特性

为了进一步明确氟化薄膜材料在紫外(UV)-真空紫外(VUV)波段的光学常数,研究了真空紫外领域常用的基底材料和6种大带隙的氟化物薄膜材料的光学特性.分别在熔石英(JGS1)基底和氟化镁单晶基底上用热舟蒸发法以不同的沉积速率和不同的基底温度镀制了3种高折射率材料薄膜LaF3、NdF3、GdF3和3种低折射率材料薄膜MgF2、AlF3、Na3AlF6;在国家同步辐射真空紫外实验站测定了它们120～300 nm的透射光谱曲线,用商用lambda900光谱仪测量了它们190～500 nm的透射光谱曲线,两者相结合标定了透射率的准确值.用包络法和模拟退火相结合研究了它们在120～500 nm的折射率和消光系数,给出了6种氟化物材料的光谱色散曲线.结果显示,3种高折射率薄膜的折射率在157 nm处约为1.77～1.89,而3种低折射率薄膜的折射率在157 nm处约为1.44～1.48;研究表明,选用折射率相差较大的高、低折射率氟化物薄膜,可在膜系设计中组成高低折射率材料对,用于设计各种实用的薄膜器件.