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为了增强界面传热效果,将镓基液态金属(Ga_(68.5)In_(21.5)Sn_(10))及氮化铝作为导热填料填充到甲基硅油中制备了一种新型复合的热界面材料,并利用扫描电子显微镜(SEM)和能谱仪(EDS)检测材料的微观结构和化学成分以研究其导热原理。合成的AlN掺杂的镓基液态金属硅脂导热率可达5.014 W/m·K,分别高于液态金属/甲基硅油二元复合材料和现售高端的导热硅脂产品(x-23-7762)约5%和20%。同时,接触热阻减少了约20%和50%,粘度保持在适当的范围内降低了使用过程中的溢出风险。CPU的实测结果表明新合成的AlN掺杂的镓基液态金属硅脂可以显著降低笔记本核心的工作温度,分析其导热机理后提出传热过程的协同效应原理。实验结果表明该产品是一种理想的导热界面材料且具有广泛的应用前景。 相似文献
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高导热高绝缘导热硅脂的制备及性能表征 总被引:1,自引:0,他引:1
高导热硅脂作为一种热界面材料,可以显著地减小因接触空隙而产生的热阻,提高散热效果。通过采用自制的氮化硅、氮化铝、氧化铝等陶瓷粉体来代替传统的金属粉体作为导热填料,制备出高绝缘高导热的导热硅脂。研究了陶瓷粉体种类、添加量以及表面改性剂对导热硅脂热导率的影响规律。采用热阻测试仪、AMD、Inter主板测试平台、耐压测试仪等表征了导热硅脂的导热和绝缘性能。并对实验结果进行了理论分析。 相似文献
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采用液态金属冷却工艺,对大尺寸定向凝固镍基高温合金铸件的显微组织分布、变化规律进行研究。结果表明:随铸件远离冷却盘,冷却速率逐步降低;利用二次枝晶间距与冷却速率之间的定量关系,经计算得出距离冷却盘10 mm、100 mm、200 mm和300 mm位置的冷却速率分别为2 K/s、1 K/s、0.42 K/s和0.26 K/s。冷却速率的降低导致铸件不同位置的显微组织发生变化,包括枝晶组织发生粗化,MC碳化物由规则八面体形貌发展为汉字体形貌,显微缩松含量增加。冷却速率对枝晶组织的变化产生直接影响,而MC碳化物形貌和显微缩松含量变化主要由枝晶间距的变化而引起。 相似文献
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金属材料在液态和液固转变过程中磁化率变化的测量方法和装置 总被引:1,自引:0,他引:1
提出一种基于电磁感应原理的测量液态金属材料磁化率变化的方法并开发相应装置,分析该装置的基本工作原理。使用该装置测量CuSn合金在温度变化时磁化率的变化情况。实验结果表明,样品在相变点处其磁化率有明显的变化。液态CuSn合金的磁化率的倒数与温度成线性关系,但在925℃附近,其斜率有明显的变化。通过液态合金的粘度实验证实,Cu75Sn25合金的结构在925℃时发生了相应的变化。 相似文献
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An analytical model for simulation of heat flow in plasma-sprayed thermal barrier coatings 总被引:1,自引:0,他引:1
Numerical (finite difference) and analytical models have been developed for the simulation of heat flow through plasma-sprayed
coatings, allowing the effective thermal conductivity to be predicted as a function of microstructural parameters. The structure
is assumed to be composed of lamellar material (splats), separated by (thin) pores, within which there are areas of contact
(bridges). The analytical model is based on dividing the material into two regimes, within which the heat flow occurs either
by unidirectional serial flow through lamellae and pores or by being funneled through the regions of the lamellae above and
below the bridges. The validity of this model is demonstrated by a comparison of the predictions obtained from it and those
obtained from the numerical model. The effects of pore geometry on conductive and radiative heat transfer within the coating
have been investigated over a range of temperatures and gas pressures. It is shown that the main factor controlling the conductivity
is the intersplat bridge area. Comparisons are also presented with experimental conductivity data, for cases in which some
attempt has been made to characterize the key microstructural features. The study is oriented toward thermal barrier coatings,
based on zirconiayttria top coats. It is noted that the effect of microstructural sintering, which tends to occur in these
coatings under service conditions, can be predicted using this model. 相似文献
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M.M. Franke R.M. Hilbinger A. Lohmüller R.F. Singer 《Journal of Materials Processing Technology》2013,213(12):2081-2088
Numerical methods were used to examine the influence of casting and baffle geometry, mold thickness as well as withdrawal speed on solidification conditions and resulting microstructure. Achievable thermal gradients, stability limits and primary dendrite arm spacings for Liquid Metal Cooling (LMC) and High Rate Solidification (HRS) process are reported. Calculations were compared with experimental results from the literature and good agreement was found. A thermal gradient almost 1.8 times higher was observed for the use of LMC in the case of simple cylindrical castings. In contrast, a thermal gradient up to three times higher was calculated with LMC compared to HRS for large section size castings. The numerical investigations indicate that the nature of the baffle has a stronger effect than the different mechanism of heat dissipation when HRS and LMC are compared. 相似文献
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目的优化化学镀铜氮化铝(AlN)基板的综合性能,掌握热处理对其镀层致密度、界面结合强度和热导率的作用机理,并对划痕膜层失效行为进行分析。方法采用化学镀铜法实现AlN陶瓷基板表面金属化,对其进行200~500℃热处理。利用X射线衍射仪、扫描电镜、激光导热仪,对Cu-AlN基板的物相结构、显微形貌、热学性能进行分析。采用划痕法对镀层结合力进行评价,并通过划痕形貌对膜层失效行为进行分析。结果未热处理的Cu-AlN基板表面存在鼓泡现象,结合强度为24.7 N,热导率为156.8 W/(m K)。热处理消除了Cu-AlN基板的鼓泡现象,300℃热处理的Cu-AlN基板综合性能优异,表面Cu颗粒分布均匀,结构较为致密,结合强度为32.6 N,热导率达163.8 W/(m K);当500℃热处理时,Cu-AlN基板表面存在氧化现象,形成CuO,结合强度急剧降低为18.5 N,热导率为161.2 W/(m K)。Cu-AlN基板的基膜失效方式为点剥离,随着载荷的增加,点剥离增多,膜层开裂,AlN逐渐裸露,Cu膜层磨损形貌宏观上表现为由塑性变形引起的犁沟磨损,芯部发生拉伸变形,边界呈现卷曲变形。结论对Cu-AlN进行合理热处理,可改善镀层表面组织与致密度,提高结合强度和导热性能。 相似文献
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将纳米粒子团聚大颗粒进行抽象处理,提出以理想堆垛结构为假设的纳米团聚颗粒模型。以ANSYS有限元软件为平台,模拟Al2O3-13%TiO2(质量分数)团聚纳米颗粒在热喷涂环境下的传热过程,分析传热时间、团聚颗粒直径和孔隙率等对传热的影响,并分析团聚颗粒在热喷涂传热后的组织结构差异。结果表明:在一定传热条件下,纳米团聚颗粒可以保持部分纳米粒子或长大为亚微米晶形态,且团聚颗粒直径越大,这类组织就越容易形成,而团聚颗粒孔隙率在0.48以下时,对组织形态的影响较弱。 相似文献
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采用有限差分法建立了高温钢板连续喷水冷却过程中一维非稳态传热条件下冷却水换热系数的计算模型,将试验测量到的数据应用该模型计算出了试验过程中冷却水与高温钢板间的换热系数[h。]分析结果表明:在流量一定的情况下,压力对换热系数的影响较明显,而在压力一定的情况下,流量对换热系数的影响较小,冷却水的换热系数随喷水密度的增加而增大,随钢板表面的温降呈先增加后减小的趋势。总结出了钢板表面温度为400~1 000 ℃,喷水密度为90~180 L/(m2·min)的条件下,喷水冷却换热系数[h]的经验计算公式。 相似文献
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一种铝合金水冷界面换热系数反求方法的研究 总被引:1,自引:0,他引:1
针对水冷金属界面换热系数影响因素多,测量与求解难的问题,以温度场数学模型为基础,以实测温度曲线为基准,通过数值模拟迭代计算和自动寻优,实现了铝合金水冷界面换热系数随温度变化定量关系的反求.反求得到的铝合金换热系数结果表明:在浸入式水冷过程中,铝合金界面换热系数随表面温度由低到高呈现出先升后降的单峰形状特征,降低冷却水的温度会使换热系数的峰值点升高,但不会改变峰值点出现的温度范围,换热系数的最大值出现在200~230℃.金属与冷却水之间热交换的强度主要取决于界面温度,将界面温度控制在200~230℃会使强化传热效果达到最佳. 相似文献
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讨论了连铸传热数学模型中等效导热系数对模拟结果的影响,结论表明,采用等效导热系数法可以较为准确的预测铸坯表面温度及凝固终点,但等效导热系数越大,凝固前期的铸坯坯壳厚度越薄;等效导热系数的取值对铸坯两相区将产生较大影响,等效导热系数越大,某一厚度处钢液越早进入两相区,相应地,两相区厚度越大、两相区内温度梯度越小,局部凝固时间越大;采用计算获得的二次枝晶间距与实测值强制拟合的方法可以获得对流等效因子[(m)]的合理取值;对于铸机,在液相穴中强制对流区取[m=7、]强制对流与自然对流的过渡区取[m=5、]自然对流区取[m=3、]静滞区取[m=1]计算,可以获得较为准确的模拟结果。 相似文献
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Effect of heat treatment on the thermal conductivity of plasma-sprayed thermal barrier coatings 总被引:1,自引:0,他引:1
Rollie Dutton Robert Wheeler K. S. Ravichandran K. An 《Journal of Thermal Spray Technology》2000,9(2):204-209
The effect of heat treatment on the thermal conductivity of plasma-sprayed Y2O3 stabilized ZrO2 (YSZ) and Al2O3 coatings was investigated. A heat treatment of 1300 °C in flowing argon for 50 h was found to significantly increase the
thermal conductivity of the coatings when compared to measurements in the assprayed condition. Transmission electron microscopy
(TEM) examination of the microstructures of the coatings in the as-sprayed and heat-treated conditions revealed that sintering
of microcracks at the splat interfaces was the main cause for the increase in thermal conductivity. In the YSZ coatings, complete
closure of microcracks was frequently observed. In contrast, microcrack closure in the Al2O3 coatings was characterized by the isolated necking of particles across a microcrack rather than complete closure. A model
for thermal conductivity in a solid containing oriented penny-shaped cracks was used to explain the observed increase in thermal
conductivity after heat treatment. 相似文献
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H. Ramamurthy S. Ramadhyani R. Viskanta 《Journal of Materials Engineering and Performance》1995,4(5):519-531
A thermal system mathematical model developed for a gas-fired radiant-tube continuous reheating furnace is discussed. The
mathematical model of the furnace integrates submodels for combustion and heat transfer within the radiant tube with models
for the furnace enclosure. The transport processes occurring in the radiant tube are treated using a one-dimensional scheme,
and the radiation exchange between the load, the radiant-tube surfaces, and the furnace refractories are analyzed using the
radiosity method. The continuous furnace operation is simulated under steady-state conditions. Model simulations of load surface
temperature variation compare well with measurements in an industrial galvannealing furnace. The scope and flexibility of
the model are assessed by performing extensive parametric studies using furnace geometry, material properties, and operating
conditions as input parameters in the model and predicting the thermal performance of the furnace. The various parameters
studied include the effects of load and refractory emissivities, load velocities, properties of the stock material, and variations
in the radiant-tube designs. 相似文献
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本文基于化学气相沉积(CVD)金刚石膜的超高热导率,设计并搭建了一套实验系统,分析其对于小空间高热流密度电子元件的散热效果。通过测量加热器及材料表面的温度值可知,相同工况下,金刚石膜温度梯度小,温度分布均匀性好,表面最大温差仅为铜的一半且加热面温度相比于铜更低。实验结果说明CVD金刚石膜的散热性能明显优于传统散热材料铜。实验验证了经过Ti-Ni-Au金属化处理的CVD金刚石薄膜具有可焊性。在实验基础上,利用Flotherm软件对系统进行仿真建模,进一步探讨了材料厚度、热导率及接触热阻对加热面温度和最大热流密度的影响。 相似文献