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1.
研究了热压烧结B4C陶瓷的室温和高温力学强度。结果表明:气流粉碎B4C粉末(中位粒径为3.85pm)在2150℃热压烧结10min后,烧结体密度达到理论密度的91.6%,平均晶粒尺寸为7μm,室温抗弯强度和抗压强度分别为280和1463MPa;振动球磨B4C粉末(0.35μm)在相同条件下的热压烧结密度达到理论密度的99.7%,室温抗弯强度和抗压强度分别为515和2780MPa。随着温度升高,两种热压烧结B4C陶瓷的抗弯强度均缓慢降低,低于600℃,抗压强度快速降低,随后则降低缓慢。对两种热压烧结B4C陶瓷的力学强度与温度、气孔率等参数之间的关系进行了讨论。  相似文献   

2.
进行了气流粉碎B4C粉末(比表面积2.53 m2/g)的掺碳烧结实验,研究了掺碳剂种类、掺碳量、烧结温度等对B4C烧结密度的影响.结果表明:掺碳显著促进B4C的烧结;在炭黑、葡萄糖和酚醛树酯3种掺碳剂中,掺入酚醛树酯可获得最高的烧结密度.B4C+3%(酚醛树脂)分别经2 200和2 250 ℃烧结后的相对密度为92.1%和94.4%,而纯B4C在相同温度下的相对密度仅分别为78.6%和82.5%.  相似文献   

3.
气流粉碎B4C粉末的活化烧结研究   总被引:1,自引:0,他引:1  
《原子能科学技术》2003,37(Z1):70-72
进行了气流粉碎B4C粉末(比表面积2.53 m2/g)的掺碳烧结实验,研究了掺碳剂种类、掺碳量、烧结温度等对B4C烧结密度的影响.结果表明掺碳显著促进B4C的烧结;在炭黑、葡萄糖和酚醛树酯3种掺碳剂中,掺入酚醛树酯可获得最高的烧结密度.B4C+3%(酚醛树脂)分别经2 200和2 250 ℃烧结后的相对密度为92.1%和94.4%,而纯B4C在相同温度下的相对密度仅分别为78.6%和82.5%.  相似文献   

4.
分别采用热压烧结与无压烧结工艺制备了掺杂5%~20%多壁碳纳米管(MWNTs)的UO2复合燃料芯块,分析了芯块的性能。结果表明:乙醇湿法球磨可将MWNTs均匀分散到UO2基体中;热压烧结芯块随MWNTs含量的增加,芯块密度逐渐下降,MWNTs含量为5%的芯块密度为96.7%TD;无压烧结芯块随MWNTs含量的增加,芯块密度先升高后降低,MWNTs含量为12.5%的芯块密度最高,为97.2%TD;1 400℃、50 MPa热压烧结工艺,MWNTs与UO2基体未发生反应;1 750℃无压烧结工艺,MWNTs与UO2基体产生微弱反应生成少量UC相;SEM显示,MWNTs在UO2基体以沿晶和穿晶状态分布;在250℃,热压烧结UO2-10%MWNTs芯块热导率为6.76 W/(m·K),提高了20.28%;无压烧结UO2-12.5%MWNTs芯块热导率为6.65 W/(m·K),提高了18.33%。  相似文献   

5.
以氧化钆、十水草酸铈和磷酸二氢铵为原料,采用热压烧结制备掺钆铈独居石陶瓷固化体,借助X射线衍射(XRD)、场发射扫描电镜(FESEM)、能谱(EDS)和电感耦合等离子体发射光谱-质谱(ICP-MS)等分析手段,研究掺钆铈独居石陶瓷固化体的热压烧结及固化体在热-水-力-化学(THMC)耦合作用下的化学稳定性。结果表明,采用热压烧结技术,实现了单相Ce0.9Gd0.1PO4陶瓷固化体的低温(1150~1200 ℃)、快速(2 h)烧结,固化体的相对密度达99.62%;在THMC耦合作用下(温度为90~200 ℃(0.101~1.554 MPa),pH=5~9),固化体具有优异的化学稳定性,浸出时间为42 d时,模拟次锕系核素Gd的归一化浸出率在10-6~10-5 g/(m2•d)数量级;温度和pH值对Ce的归一化浸出率影响较小;温度对Gd的归一化浸出率没有影响;与弱碱性(pH=9)水溶液相比,在弱酸性(pH=5)和中性(pH=7)水溶液中,Gd的归一化浸出率相对较高。  相似文献   

6.
UN燃料具有铀密度高、熔点高、热导率高、热膨胀系数低、辐照稳定性好等优点,是未来空间核电源、核火箭、快堆和ADS的重要候选燃料。本文采用金属铀粉与氮气在300~400℃直接发生化合反应,制得单相U2N3粉末。粒度为38.3 μm的U2N3粉末在1 600 ℃真空热压烧结,制得相对密度为93.5%、存在少量金属铀相的UN陶瓷;而18.1 μm的U2N3粉末在1 550 ℃真空热压烧结,制得相对密度为96.1%、不残留金属铀相的UN陶瓷,U与N的总质量分数为99.57%,每个金属杂质含量均低于50 μg/g,氧含量为1 048 μg/g,碳含量为502 μg/g。U2N3在1 027 ℃以上将会完全分解成UN,UN在1 627 ℃以上也会发生分解。  相似文献   

7.
研制了一种药盒 ,能简单、快速、有效地制备188Re -硫化铼混悬液制剂。药盒由A、B、C 3瓶 (10mL/瓶 )组成 ,在无菌环境下 ,配制各种试剂。A瓶加入mol比为 70 :1的Na2 S2 O3 和KReO4溶液 1mL ,再加入一定量的赋形剂 ;B瓶加入 5mol/L的盐酸溶液 1mL ;C瓶加入摩尔比为 10 0 0 :1的PVP和NaOH溶液 1.5mL。B瓶加盖密封 ;A瓶和C瓶在冷冻干燥后 ,压盖密封。无菌、细菌内毒素及安全性检验均合格。常温下放置 ,制备188Re -硫化铼混悬液 ,在两个月内始终保持很高的标记率 (>98% ) ,颗粒度为 1— 5 μm(6 0 .1± 12 .7) % ;5— 10 μm(30 .9± 8.1) % ;>10 μm(9.0±4 .7) %。制备的188Re -硫化铼混悬液在 5天内非常稳定 ,放化纯度 >98% ,颗粒度为 1— 5 μm(49.9± 4 .4 ) % ;5— 10 μm(41.1± 5 .4 ) % ;>10 μm(9.0± 3.3) %。  相似文献   

8.
铅/碳化硼/硼酚醛树脂(Pb/B4C/BPR)是一种新型屏蔽复合材料,具有较好的耐高温性能,在辐射屏蔽领域有重要应用。本文系统研究了该复合材料中Pb粉添加量(体积分数)、Pb粉粒径、Pb粉表面处理(SiO2包覆)对其线膨胀系数和力学性能的影响规律。结果表明:Pb粉添加量为36%、粒径为38 μm时,复合材料具有最小的线膨胀系数与优异的综合力学性能;Pb粉表面包覆适量的SiO2可有效减小Pb粉颗粒和B4C颗粒之间的密度差异,不仅显著降低了复合材料的线膨胀系数,还提高了其拉伸强度、弯曲强度和冲击韧性,但Pb粉表面包覆过多SiO2将导致复合材料的线膨胀系数增加,拉伸强度、弯曲强度和冲击韧性降低。  相似文献   

9.
将快堆控制棒模拟样品置于高温热对流钠回路中 ,于 550℃下进行B4 C/Na/S .S .三元体系化学相容性试验 ,研究相容时间及钠中氧含量对相互作用特性的影响。结果表明 :试验后的B4 C芯块完整 ,无掉角、龟裂或破碎 ;包壳管内表面渗B ,渗B量与相容时间的平方根成正比 ,渗B深度不随相容时间变化 ;包壳管内表面显微硬度明显升高 ,其升高幅度随相容时间增长略有增大 ,不同相容时间下的硬化层深度均约为 4 0 μm ;相容时间从 80d增加到 4 0 0d ,包壳管内表面相继出现反应产物Cr2 B ,Na4 B10 O17,B6Fe2 3,CrB和NiB ,NiB12 ;B向包壳管内表面的扩散与温度、相容时间及钠中氧含量有关 ,氧对B的扩散起促进作用。  相似文献   

10.
W/Cu和W/C涂层的循环热负荷实验   总被引:1,自引:0,他引:1  
用等离子体喷涂和热压方法制作了W /Cu梯度功能材料和W /C涂层 ,其中W/C涂层具有多层的钨 (W )、铼 (Re)扩散阻挡势垒。为了试验这些复合材料能否经受聚变等离子体破裂时的高热负荷 ,用大功率ND :YAG激光进行了模拟实验。结果表明 :在 1 0 0~ 4 0 0MW /m2 的瞬时 (脉冲宽度为 4ms)热负荷作用下 ,经过 2 0 0~ 70 0次热循环 ,未发现W /Cu复合体的开裂。其中在 1 2 3MW /m2 的功率密度下作用70 0次后 ,发现等离子体喷涂试样表面的再结晶现象和严重的晶界腐蚀 ,由于激光的冷效应 ,晶粒生长的趋势并不明显 ,再结晶层的晶粒呈垂直于表面的柱状结构。W/C试样的退火实验表明 ,钨涂层的再结晶温度稍高于 1 4 0 0℃。在更高的功率密度下 (3 98MW /m2 )出现了明显的腐蚀坑 ,坑内呈疏松的蜂窝结构 ,坑的边缘形成了沉积区 ,能谱分析表明沉积区集聚了大量的金属杂质。等离子体喷涂试样比热压试样更易产生晶界的断裂和裂纹。在同等的热负荷条件下 ,W /CuFGM的质量损失低于石墨材料  相似文献   

11.
This paper introduces the injection and extraction control system design for SSRF,which is a distributed control system aimed at stability and reliability of the pulse power supplies,PPS(Personnel Protection System)and MPS(Machine Protection System).The hardware environment is mainly based on PLC(Programmable Logic Con- troller),and ARM(Advanced RISC Machine)is also applied for studying stability of the power supplies.WinCC and EPICS(Experimental Physics and Industrial Control System)have been selected as the platforms of SCADA(Super- visory Control and Data Acquisition).For unifying the interfacing to the control computer,all front-end equipments are connected via Industrial Ethemet.  相似文献   

12.
Food irradiation is gaining popularity worldwide and this technology is important to improve quality and reduce the post harvest losses of food. Because of the rapid commercialization of irradiated foods throughout the world, compliance of different regulations relating to use of technology in different countries and demand of consumers for clear labelling of irradiated foods, there is need for the development of analytical methods to detect radiation treatment of food. Among several methods studied so far, thermoluminescence (TL) is an important method that can be used to find out the irradiation history of food that contain even a very minute amount of dust particles. In this study, the irradiated and unirradiated wheat and rice samples were analyzed using the TL method. The samples were purchased from the local market of Peshawar and irradiated to radiation doses of 0.5 and 1.0 kGy using Co-60 gamma irradiator at the Nuclear Institute for Food and Agriculture (NIFA), Peshawar. The mineral contaminants were isolated by jet water, ultrasonic treatment, and density gradient. TL glow curves of the isolated minerals from irradiated and unirradiated samples were recorded between the temperature ranges of 50-500℃ using a TL reader. Generally, the glow curves for irradiated samples showed much higher TL intensities (TL1) than the unirradiated samples. The results were normalized by rerradiation of mineral samples to gamma-ray dose of 1.0 kGy followed by determination of the second glow curves (TL2). The ratio of the area of first glow curve to that of second glow curve (TL1/TL2) was calculated for selected temperature intervals and compared with the recommended values for unirradiated and irradiated samples. Finally, the shapes of the glow curves for irradiated and unirradiated samples were also analyzed. On the basis of these results (comparison of TL-intensities, TL1/TL2 ratios and shapes of the glow curves), all the irradiated and unirradiated samples of wheat and rice were unequivocally identified.  相似文献   

13.
Zn-doped TiO2 catalysts were prepared using a sol-gel method and characterized by XPS,UV-Vis, BET, XRD in this study. Under the irradiation of simulant sunlight, the photocatalytic activity for the degradation of p-nitrophenol was studied too. After irradiation for 2.5 h, the degradation percentage of p-nitrophenol could rise to more than 80 %. The results showed that the spectrum absorption band edge of Zn/TiO2 powder does not broaden obviously comparing with pure TiO2 powder. Zinc exists as Zn (11). When calcined at 973 K, there is a new phase as ZnTiO3 in Zn/TiO2 catalyst. The order of photocatalytic activity of Zn/TiO2 catalysts calcined at different temperatures for p-nitrophenol is 773 K 〉 673 K 〉 873 K 〉 573 K 〉 973 K and the photocatalytic activity of Zn/TiO2 catalyst calcined at 773 K is better than TiO2 catalysts heated at the same temperature, and outclasses that of commercial TiO2 catalyst. It also showed that the photocatalytic degradation of p-nitrophenol follows first-order kinetics under the irradiation of simulant sunlight.  相似文献   

14.
Radiotherapy for the treatment of prostate cancer has been extensively explored in the past. Along with the comprehensive understanding of the biology of prostate cancer and rapid advances in terms of technology, the out- come of treatment for the patients with prostate cancer has improved. The authors review radiotherapy as the primary treatment for the disease, with particular emphasis on the technological advances from both the radiobiological and radiophysics aspects. Nonconventional fractionated irradiation like hyper- or hypo-fractionation has been imple- mented in the clinic, the final results still need to be confirmed in the future. Technological advances like IMRT, IGRT, in the last two decades have significantly improved the delivery of external radiotherapy to the prostate. This has re- sulted in an overall increase in the total dose that can be safely delivered to the prostate, which has led to modest im- provements in the biochemical outcome. However, establishing the standard therapy for prostate cancer remains con- troversial. It is hoped that the next decades will bring continued advances in the development of biologicals that will further improve current clinical outcomes.  相似文献   

15.
Pulsed photo-stimulated luminescence (PPSL) is a simple screening method that can be employed qualitatively at the spot for the detection of eggs treated with ionizing radiation.Due to the variations in the results during storage,the eggs of ostrich,duck,hen,and quail were irradiated to doses of 0,1,2,and 3 kGy.Most of the samples were incorrectly identified during storage after four months of irradiation.Thermoluminescence (TL) technique was also tried by using egg shells in order to confirm the irradiation treatment in eggs.TL glow curves were recorded between the temperatures 50℃to 400℃at the rate of 5°/s for all the control and irradiated samples.On the basis of integrated areas of first glow curves (TL1),the glow curve ratios (TL1/TL2) and the shapes of maxima of TL1, the irradiation treatment of all the eggs was confirmed.Furthermore,the presence of calcite and aragonite minerals that cause the TL signal in the egg shells were studied using X-ray diffraction spectrometry.  相似文献   

16.
Monitoring results of gamma dose rate level in 1992~2004 in the ambient environment of the Qinshan Nuclear Power Plants(QNPP)Base,the northeast of Zhejiang Province,are reported in this paper.It is shown that the gamma dose rate of five monitoring sites of 2.5 km to QNPP Base is 84~113 nGy/h,with an average of 96 nGy/h in the 13 years.The average value is close to the background level of 93 nGy/h prior to operation of the QNPP Base,and is lower than the monitoring result of 101 nGy/h at the reference site in Hangzhou City.Within 50 km from the QNPP Base,the cumulative dose rate of the thermoluminescent dosimeter(TLD)is 90 nGy/h,which is lower than the back- ground level of 111 nGy/h.  相似文献   

17.
为对自制的活性面积高达1 000 cm2的大面积源进行表面发射率定值,同时作为现有2πα、2πβ表面发射率标准装置能力的扩充,研制了一套内置式大面积2π多丝正比计数器测量系统,并利用活性区直径为8 mm的241Am点源及活性区面积为10 cm×15 cm的大面积241Am和90Sr-90Y源对其进行计量学性能测试。结果表明:计数器内计数响应均匀性优于±0.4%,有效探测面积达1 400 cm2;所得241Am源高压坪曲线的坪长为1 400 V,坪斜为0.27%/100 V,坪区内计数变化为0.87%;90Sr-90Y源高压坪曲线的坪长为300 V,坪斜为0.75%/100 V,坪区内计数变化为0.80%;10次测量重复性好于0.4%,8 h内短期稳定性好于0.3%,1 a内长期稳定性好于0.8%。  相似文献   

18.
为研究含空气蒸汽在水平管内强制对流冷凝换热特性,基于对传热传质过程的分析,建立了管内为环状流与波状流条件下的流动冷凝换热模型。从潜热、显热和液膜3个环节对整个换热过程进行建模,最终得到计算局部冷凝换热系数的理论关系式。模型预测结果与实验数据的对比表明,二者相对偏差在±20%以内,验证了该换热模型的准确性与适用性。通过进一步的研究发现:从换热管入口至出口,随着冷凝的进行,管内换热主要热阻由液膜热阻向气液界面的凝结热阻转变;主流气体对流换热过程基本可忽略。  相似文献   

19.
<正>1.NUCLEAR SCIENCE AND TECHNIQUES(NST),a bimonthly journal,is devoted to all aspects of nuclear science and technology,theoretical or experimental.Its special interest lies in the subjects of synchrotron radiation science and technology;low energy accelerators,radiation technology and appli-  相似文献   

20.
<正>1.NUCLEAR SCIENCE AND TECHNIQUES(NST),a bimonthly journal,is devoted to all aspects of nuclear science and technology,theoretical or experimental.Its special interest lies in the subjects of synchrotron radiation science and technology;low energy accelerators,radiation technology and applications;radiochemistry,radiopharmaceuticals and nuclear medicine;nuclear electronics and instrumentation;interdisciplinary studies of  相似文献   

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