南邮材料化学MC2016-Chapter5-b
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第四章材料化学热力学Chapter 4 Chemical Thermodynamics of Materials1. Cs熔体的标准吉布斯自由能(单位为J)与温度T(单位为K)的关系为=2100-6.95T, 求Cs的熔点。
Relationship between the standard Gibbs free ΔG om, Csenergy (in units of J) of Cs melt and temperature T (K) is shown as ΔG o m,=2100-6.95T, please determine the melting point of Cs.Cs解:根据热力学定律,当ΔG<0时,反应可以自发进行,因此ΔG=0时对应的平衡反应(即Cs由固相转变为液相的反应)的温度即为Cs的熔点。
由ΔG o m, Cs=2100-6.95T=0,可得T =302K,所以Cs的熔点为302K。
Answer: A ccording to the laws of thermodynamics, when ΔG <0, t he reaction can be spontaneous. Therefore, ΔG = 0 corresponding to the equilibrium reaction of Cs change from solid phase into liquid phase, the temperature corresponding to the melting point of Cs. From ΔG o m, Cs=2100-6.95T=0, we can get T=302K, so the melting point of Cs is 302K.2.通过埃灵罕姆图解释为何碳在高温下可以用作金属氧化物的还原剂。
According to the Ellingham diagram, please explain why the carbon can be used as a reductant of the metal oxides at high temperature.答:根据埃灵罕姆图,ΔG o-T曲线越在下方,氧化物的ΔG o负值越大,其稳定性就越高。
第三章材料的性能Chapter 3 Properties of material1、用固体能带理论说明什么是导体、半导体、绝缘体?Please explain what is a conductor, semiconductor, and insulator with band theory of solids.答: 1)固体能带理论是关于晶体的量子理论,是研究固体中电子运动规律的一种近似理论。
其中,分子轨道理论认为,两原子间相应的原子轨道可以组合成相同数目的分子轨道。
在金属晶体中,金属原子靠得很近,可以通过原子轨道组合成分子轨道,以使能量降低。
金属晶体中通常包含数目极多的原子,这些原子轨道可组成极多的分子轨道,随着数量的增多,各相邻分子轨道实际上连成一片,构成了具有一定能量宽度的能带。
2)固体通常含有不同的能带。
已充满电子的能带叫满带,其中的电子无法自由流动、跃迁。
在此之上,能量较高的能带,可以是部分充填电子或全空的能带,叫做空带,空带获得电子后可以参与导电过程,又叫导带。
价电子所填充的能带称为价带。
3)固体的导电性质由其能带结构决定。
导体的能带特点是价带是未满带,或价带是满带,而禁带宽度为零,价带与较高的空带相交叠,满带中的电子能占据空带,因此这两种情况都能导电。
半导体和绝缘体的能带结构相似,价带为满带,价带与空带间存在禁带。
当禁带宽度为0.1~3eV时,呈现半导体性质;禁带宽度大于5eV时则为绝缘体。
Answer: 1) Band theory of solids is quantum theory of crystal, is an approximate theory for studying laws of electron motion in solids. Among them, molecular orbital theory considers that atomic orbitals between two atoms can combine to the molecular orbitals with the same number. In metal crystals, metal atoms are very close, they can form molecular orbitals by combining the atomic orbitals in order to reduce the energy. Metal crystals usually contain a very large number of atoms, these atomic orbitals can form a number of molecular orbitals. With the increase of the molecular orbital, in fact, they form a whole band with certain energy width. 2) Solids usually contain different bands. Bands filled with electrons are called full band, in which electrons can not flow and transit freely. Bands with higher energy are on the top of full band, they may be partially filled with electrons or empty, they are called empty band. When the empty band gain electrons they will participate in conductive process, also known as conduction band. Bands filled with valence electron are called valence band. 3) Conductive nature of solids is determined by its band structure. Band of conductor is characterized by the partially full or full valence band, and widthof forbidden band is zero. Valence band overlap with higher empty band, electrons in full band can occupy the empty band, so in these cases, solids can be conductive. Semiconductor and insulator have the similar band structure, their valence band is filled band, and there exist forbidden band bewteen valence band and empty band. When the forbidden band is 0.1 ~ 3eV, it exhibit semiconductor nature; when the forbidden band is greater than 5eV, it exhibit insulate nature.2、有一根长为5 m,直径3 mm的铝线,已知铝的弹性模量为70 GPa,求在200 N的拉力作用下,此线的总长度。
第46卷第2期2024年3月沈 阳 工 业 大 学 学 报JournalofShenyangUniversityofTechnologyVol 46No 2Mar 2024收稿日期:2023-10-24基金项目:国家自然科学基金项目(62305175);江苏省前沿引领技术基础研究专项(BK20222002);江苏省高等学校基础科学(自然科学)研究项目(1020231538);江苏省双创博士专项资金项目(CZ032SC210506);东南大学生物电子学国家重点实验室开放研究基金项目(SKLB2022 K08);南京邮电大学引进人才科研启动基金项目(XK0320920167)。
作者简介:田育糰(1990—),男,山西怀仁人,工程师,硕士,主要从事生物图像处理等方面的研究。
檪檪檪檪檪檪檪檪檪檪殏殏殏殏电气工程 DOI:10.7688/j.issn.1000-1646.2024.02.04基于超导的小型化磁粒子成像系统仿真构建田育糰1,马少华1,王程松2,范 霖2,3,4(1 沈阳工业大学电气工程学院,辽宁沈阳110870;2 南京邮电大学集成电路科学与工程学院,江苏南京210023;3 南京大学医学院,江苏南京210093;4 东南大学生物电子学国家重点实验室,江苏南京210096)摘 要:针对磁粒子成像技术尚停留在实验室鼠用设备阶段,传统线材线圈过大,无法在可接受的设备体量内达到临床人体检测所需磁场强度的问题,提出了一种基于超导技术构建高场强、小型化磁粒子成像设备的方法。
采用高温超导MgB2线圈替代传统铜线圈,构建磁粒子成像选择场与驱动场。
结果表明,在达到相同磁通量的情况下,超导磁粒子成像系统可将两组功能区总质量降低为0 01kg,设备体积缩小至7L。
在此基础上,采用超导线圈构建梯度磁场还能够获得更高的变化斜率,使零磁扫描区边缘更为清晰规则,移动过程中形态更为稳定,平均直径缩小近二分之一。
关 键 词:磁粒子成像;小型化设备;梯度磁场;零磁区;高温超导;MgB2线圈;选择场;驱动场中图分类号:TM937 文献标志码:A 文章编号:1000-1646(2024)02-0138-06SimulatedconstructionofminiaturizedmagneticparticleimagingsystembasedonsuperconductorTIANYushen1,MAShaohua1,WANGChengsong2,FANLin2,3,4(1.SchoolofElectricalEngineering,ShenyangUniversityofTechnology,Shenyang110870,Liaoning,China;2.SchoolofIntegratedCircuitScienceandEngineering,NanjingUniversityofPostsandTelecommunications,Nanjing210023,Jiangsu,China;3.MedicalSchool,NanjingUniversity,Nanjing210093,Jiangsu,China;4.StateKeyLaboratoryofBioelectronics,SoutheastUniversity,Nanjing210096,Jiangsu,China)Abstract:Aimingattheproblemthatmagneticparticleimaging(MPI)hasbeenstayedinthelaboratorymouse scalestage,duetotheconventionalcoilsbeingincapableofconstructingahigh strengthgradientmagneticfieldforhumanusewithinanacceptablesize,amethodbasedonsuperconductorwasproposedtodevelopminiaturizedMPIsystemwithahigh strengthmagneticfield.High temperaturesuperconductorMgB2coilswereemployedtoreplacetheconventionalcoppercoilstoconstructselectionanddrivefieldsofmagneticparticles.Theresultsshowthatundertheconditionofachievingthesameorderofmagneticflux,thetotalweightoftwofunctionalmodulesdecreasesto0 01kg,andtheequipmentvolumedecreasesto7LduetothesuperconductorMPI.Onthisbasis,thesuperconductorcoilscanprovideagradientmagneticfieldwithasteeperslopeofchange,contributingtoaclearandregularboundariesoffield freescanningregionandmorestableshapeduringthemovingprocesswithanaveragediameternarrowsbyabout50%.Keywords:magneticparticleimaging;miniaturizedequipment;gradientmagneticfield;fieldfreeregion;high temperaturesuperconductor;MgB2coil;selectionfield;drivefield 磁粒子成像(MPI)是一种新近提出的生物医学样本检测成像技术[1-2],与核磁共振成像(MRI)[3-5]类似,磁粒子成像同样通过构建梯度磁场获取响应信号[6]。