负热膨胀系数材料的研究现状与展望

本文从负热膨胀材料的发展概况、负热膨胀产生机理、负热膨胀材料分类出发,着重介绍了化学通式为A2M3O12的负热膨胀材料.通过几种A2M3O12型负热膨胀材料的性质、制备方法和晶体结构的归纳和总结,对这一系列的负热膨胀材料未来研究方向进行了展望.     

先进负热膨胀材料的最新研究进展

简要介绍了目前所发现的负热膨胀材料种类以及各类材料的结构特征,论述了不同材料的负热膨胀机理以及其应用前景,提出了研究发现负膨胀性材料的重要意义.     

负热膨胀材料制造方法和用途

本发明公开了负热膨胀材料的制造方法和用途：所述材料可用作负热膨胀基片(如用作光纤光栅的基片)等。例如该负热膨胀基片用于光纤光栅中，光纤附着在基片上的两个位置，并且该光纤的中间段用低模量阻尼材料进行衬垫。     

ZrV_2O_7的热膨胀和非简谐振动(英文)

因零膨胀材料在工程上的潜在应用,近10多年来,对材料的热膨胀特性得以深入了解.本文对ZrW2O8的负热膨胀现象的研究进展进行了简要回顾,并特别指出理解非简谐振动的重要性.讨论了ZrV2O7的声了特性和非简谐振动,其负热膨胀的高温相和具有正的热膨胀的低温相特征. 此外,还比较了ZrV2O7和ZrW2O8的热膨胀特性.     

反钙钛矿Mn_3AN(C)化合物中的负热膨胀与磁相转变（英文）

负热膨胀材料在诸多工业领域拥有广阔应用价值,在此类材料中,锰基反钙钛矿化合物近年来被广泛研究。本工作对具有负膨胀效应的Mn3AN(C)(A=主族或过渡族元素)化合物进行了综述与评论。讨论了该化合物特殊热膨胀行为及与磁结构和磁相转变的关系,指出其特殊磁结构是Mn3AN(C)化合物中产生磁容积效应的重要因素,Fermi能级处的电子态密度与磁相转变具有强关联性。由负热膨胀材料Mn3AN与金属铜组成的金属基复合材料显示有低热膨胀和近零热膨胀行为,可通过改变Mn3Cu0.5A0.5N(A=Ni,Sn)的混合含量,调控金属铜的热膨胀系数。     

先进负热膨胀材料(英文)

钨酸锆因其具有各向同性的负热膨胀性能,自1996年发现以来即获得极大关注.目前一些新发现的具有比钨酸锆更大负热膨胀性的材料,如:碳氮键化合物、铁电陶瓷、反钙钛矿结构的锰氮化合物和纳米粒子也同样备受注目.这些化合物的负热膨胀机理或因其具有振动结构,或因其具有磁性或电学性能的转变.这些具有更大负热膨胀特性的材料在制备不受环境温度变化影响的复合材料方面具有潜在的应用价值.     

框架结构化合物的热膨胀和相变特性(英文)

在现代精密器件中,因存在热梯度,材料的热膨胀成为一个重要的影响因素.通常材料受热后因化学键的伸长而产生膨胀,而仍有一些材料显示异常的(低的或负的)热膨胀特性,这些特性值得深入研究.并以期设计具有应用可能的热膨胀系数uI控的材料.众所刷知,材料的异常热膨胀特性与框架构造化合物中的晶体结构常存在密切关系.近年来,人们对AMo2O8,APO4,A2Mo3O12炎系列框架构造化合物进行了研究,以了解晶体结构对其热膨胀特性和相转变过程的影响.本文综合评述了影响这类材料热膨胀特性和相转变过程相关的结晶学研究结果.     

负热膨胀材料钨酸锆研究进展

ZrW2O8是由0.3K至分解温度1050K都具有各向同性的负热膨胀化合物,但由于其窄的热稳定范围反应合成相当困难。本文综述了该材料的各种合成技术以及该材料的负热膨胀的机理,讨论了ZrW2O8的特性,介绍了其潜在的应用。     

反钙钛矿结构锰氮化合物奇特的热膨胀性质(英文)

通过变温X射线衍射技术研究了反钙钛结构Mn3XN(X=Ga,Zn,Sn,Cu)化合物的热膨胀性质.随着温度的升高,此类材料在磁相变附近有时会伴随人的品格收缩,即负热膨胀效应.尽管如此,晶格收缩并不总是发生,如:Mn3ZnN,Mn3CuN,Mn3SnN.对这种独特的热膨胀性质与X位 置元素价电子数之间的关系进行了讨论.结果表明:3价元素更有利于此类化合物产生负热膨胀效应.通过X位置无素掺杂,可调控此类材料的负热膨胀系数和温区.Mn3Zn0.5Ge0.5N的负热膨胀系数可达-7.15×10-6/K,温区扩展到100K左右.此外,还发现Mn3GaN和Mn3Zn0.7Sn0.3N在室温附近, 晶胞常数随温度的升高几乎保持不变,显示为近零膨胀.     

若干材料的微裂纹、相变和各向异性与负膨胀关系的研究

对陶瓷材料的微裂纹、相变和各向异性与负膨胀关系作了研究，以实验结果为依据，列举了一些具有负膨胀性能的材料。实验结果表明，陶瓷材料的这些性能对它的热膨胀有一定的影响     

P‐V‐T measurements on PMMA : PbTiO3 polymer‐ceramic composites with tunable thermal expansion

Results of Pressure‐Volume‐Temperature measurement on Poly(methyl methacrylate) : Lead Titanate, PMMA : PbTiO₃, composite system in the pressure and temperature range 0–200 MPa and 300–473 K, respectively, are presented. The thermal expansion coefficient in PMMA : PbTiO₃ composite is expected to be quite complex because the polymer has positive thermal expansion coefficient, whereas the filler has a negative thermal expansion coefficient. In this present article, the effect of pressure on the volumetric thermal expansion coefficient in PMMA : PbTiO₃ composite system is presented. It is shown that thermal expansion coefficient of the polymer can be tailored by adding filler which has negative thermal expansion coefficient. Theoretically, a simple additive rule is formulated which can predict the variation of expansion coefficient in the PMMA : PbTiO₃ composite system. The limitation of the additive rule is also discussed. It is also shown that the glass transition temperature depends on filler concentration and also has strong pressure dependence. The reasons for large pressure dependence are discussed. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of thermal stress on non-collinear antiferromagnetic phase transitions in antiperovskite Mn3GaN compounds with Mn3SbN inclusions

In the designed (1-x)Mn₃GaN-xMn₃SbN (0.2 ≤ x ≤ 0.8) heterogeneous system, modulating the non-collinear antiferromagnetic (AFM) phase transitions of antiperovskite Mn₃GaN using thermal stress is realized for the first time. With growing the Mn₃SbN secondary phase, the Neel temperature (T_N) of Mn₃GaN phase shifts down by 40 K and then disappears, but another magnetic transition below T_N appears and shifts up by 125 K. The neutron powder diffraction (NPD) results of the sample with x = 0.6 show that the magnetic transition below T_N ascribed to the decreasing Mn–Mn distance (d_Mn–Mn) and spin re-orientation from Γ^5g to a new non-collinear M₂ AFM phase. By the NPD analysis, the d_Mn–Mn of the Mn₃GaN phase decreases from 2.75527(4) Å to 2.73925(3) Å, and the angles of the spin rotations for Mn1/Mn2, Mn3-1, and Mn3-2 atoms in M₂ AFM during the spin re-orientation process are 90°, 60°, and 60°, respectively. Negative thermal expansion behaviors and caloric effects associated with Γ^5g phase transitions are investigated systematically. Further, the thermal stress could be regulated by adjusting the proportion of Mn₃GaN and Mn₃SbN phases with mismatched thermal expansion, which could be estimated even up to GPa according to Clausius–Clapeyron relation.     

Xanthohumol-Induced Rat Glioma C6 Cells Death by Triggering Mitochondrial Stress

AIM: To investigate the underlying mechanisms of xanthohumol (XN) on the proliferation inhibition and death of C6 glioma cells. METHODS: To determine the effects of XN on C6 cells, cell proliferation and mortality after XN treatment were assessed by SRB assay and trypan blue assay respectively. Apoptotic rates were evaluated by flowcytometry after Annexin V-FITC/PI double staining. The influence of XN on the activity of caspase-3 was determined by Western blot (WB); and nuclear transposition of apoptosis-inducing factor (AIF) was tested by immunocytochemistry and WB. By MitoSOX^TM staining, the mitochondrial ROS were detected. Mitochondrial function was also tested by MTT assay (content of succinic dehydrogenase), flow cytometry (mitochondrial membrane potential (MMP)—JC-1 staining; mitochondrial abundance—mito-Tracker green), immunofluorescence (MMP—JC-1 staining; mitochondrial morphology—mito-Tracker green), WB (mitochondrial fusion-fission protein—OPA1, mfn2, and DRP1; mitophagy-related proteins—Pink1, Parkin, LC3B, and P62), and high-performance liquid chromatography (HPLC) (energy charge). Finally, mitochondrial protein homeostasis of C6 cells after XN treatment with and without LONP1 inhibitor bortezomib was investigated by trypan blue assay (proliferative activity and mortality) and WB (mitochondrial protease LONP1). All cell morphology images were taken by a Leica Microsystems microscope. RESULTS: XN could lead to proliferation inhibition and death of C6 cells in a time- and dose-dependent manner and induce apoptosis of C6 cells through the AIF pathway. After long incubation of XN, mitochondria of C6 cells were seriously impaired, and mitochondria had a diffuse morphology and mitochondrial ROS were increased. The content of succinic dehydrogenase per cell was significantly decreased after XN insults of 24, 48, and 72 h. The energy charge was weakened after XN insult of 24 h. Furthermore, the MMP and mitochondrial abundance were significantly decreased; the protein expression levels of OPA1, mfn2, and DRP1 were down-regulated; and the protein expression levels of Pink1, Parkin, LC3B-II/LC3B-I, and p62 were up-regulated in long XN incubation times (24, 48, and 72 h). XN incubation with bortezomib for 48 h resulted in lower proliferative activity and higher mortality of C6 cells and caused the cell to have visible vacuoles. Moreover, the protein expression levels of LONP1 was up-regulated gradually as XN treatment time increased. CONCLUSION: These data supported that XN could induce AIF pathway apoptosis of the rat glioma C6 cells by affecting the mitochondria.     

La2/3Sr1/3MnO3(La1.4Sr1.6Mn2O7)/Ce0.8Gd0.2O2-δ复合阴极的微观结构及热膨胀性能

采用固相反应法制备La2/3Sr1/3MnO3(LSMO3)粉体,用溶胶-凝胶法分别制备La1 4Sr1 6Mn2O7(LSMO7)和Ce0.8Gd0.2O2-δ(CGO)粉体.分别将LSMO3和LSMO7粉体与CGO粉体以1∶1的质量比均匀混合,在300MPa下冷等静压成型,并在1 500℃烧结2 h,制备了LSMO3/CGO和LSMO7/CGO复合阴极材料.研究了2种复合阴极材料的微观结构和热膨胀性能.结果表明:LSMO3/CGO与LSMO7/CGO烧结体在150～1 000℃温度范围内的平均线性热膨胀系数分别为1.52×10-5/K和1.53×10-5/K,与CGO固体电解质具有相近的热膨胀性能.烧结体断面形貌分析表明:LSMO3/CGO复合阴极具有与CGO相似的断面显微结构.     

MnO/MnO2对磷酸盐低熔玻璃性能的影响

;制备了含锰ZnO-Sb2O3-P2O5系统无铅低熔玻璃,其组成的配比(摩尔分数)为40.7%P2O5·36%ZNO-10%Sb2O3·2%Li2O·4%Na2O·3.3?O·4?O.借助红外光谱及差热分析考察了0～8%(摩尔分数)MaO及MaO2替代ZnO后对玻璃耐水性和低熔性的影响,借助紫外-可见光谱分析了锰离子在玻璃中的价态.结果表明:MaO/MnO2的引入改善了玻璃的耐水性,且以MaO2的作用更为显著;此外,锰的引入未明显提高玻璃的转变温度和软化温度,对密度及膨胀系数的影响也很小.玻璃中锰离子的价态主要与其在原料中的价态一致,同时存在有少量的Mn3 .在制备磷酸盐低熔玻璃时,MnO2是非常具有实用价值的一种组分.     

Understanding thermal expansion of pressurized silica glass using topological pruning of ring structures

We investigate the structural origin of the large thermal expansion coefficient of hot-compressed silica glass upon heating to a threshold temperature using molecular dynamics (MD) simulations. While the simulated thermal expansion at low temperature correlates well with the elongation of the average interatomic separation distance of the Si–O or Si–Si pair, the excess thermal expansion due to hot compression mainly results from change in medium range order, including a decrease in the population of large rings upon heating, without significant modification of the small ring population and without changing the short range ordering, such as the Si-O coordination number. The reduction in the characteristic ring size can be connected to the high thermal expansion through the topological pruning mechanism. Such large thermal expansion is suppressed when the silica glasses are held at their respective quench pressures. The suppression of this excess thermal expansion is consistent with the pressure stabilization of the large ring structures.     

Enhanced aging behaviors and electric thermal stabilities in 0.75BiFeO3–0.25BaTiO3 piezoceramics by Mn modifications

Lead-free 0.75BiFeO₃–0.25BaTiO₃ (0.75BF–0.25BT) ceramics have been extensively studied because of their high Curie temperature. The aging behavior and thermal stability of piezoceramics play decisive roles in their device applications. In this work, effects of Mn doping on the phase structure, aging behavior, and thermal stability of 0.75BF–0.25BT ceramics were characterized and related mechanisms were investigated. With the increase in Mn content, the typical rhombohedral phase of 0.75BF–0.25BT ceramics changed to the coexistence of pseudo-cubic and rhombohedral phases. Mn modification enhanced the aging behavior and thermal stability of ceramics obviously. The aging rates of d₃₃ and k_p for 0.75BF-0.25BT ceramics with 1.0 mol% Mn are 1.3% and 1.1%, respectively, which are only 1/4 those values for the undoped ceramics. The variation of ε_r of 0.75BF-0.25BT ceramics with 1.0 mol% Mn is half of undoped ceramics under 500℃. The depoling temperature of 0.75BF-0.25BT ceramics with 1.0 mol% Mn was 450℃, which is about 200℃ higher than that of undoped ceramics. The enhanced aging behavior results from the decreased defect concentrations, and the better thermal stability is owing to the significantly improved poling state due to the enhanced resistivity, large grain size, and decreased crystal distortion by Mn modification. These results reflect that a proper amount of Mn doping is an effective way to enhance the aging behavior and electric thermal stability.     

Large recoverable energy density with excellent thermal stability in Mn‐modified NaNbO3‐CaZrO3 lead‐free thin films

Effect of Mn dopant on energy storage properties in lead‐free NaNbO₃?0.04CaZrO₃ (NNCZ) thin films was investigated. The leakage current was largely suppressed, whereas dielectric constant, breakdown fields, and the difference between maximum polarization and remnant polarization were improved significantly by Mn doping, resulting in a large enhancement of energy storage performance. A large recoverable energy storage density of ~19.64 J/cm³ and an excellent thermal stability (from 30 to 160°C) were simultaneously achieved in the NNCZ thin film with 1 mol% Mn addition. Our results ascertain the great potential of NNCZ lead‐free thin films for the applications in energy storage devices over a wide temperature range.