用吹气法研究脱脂乳粉的结块特性

为了研究脱脂乳粉的结块特性,建立了一套测试粉体结块特性的吹气动力学实验装置,对脱脂乳粉和混合添加剂的脱脂乳粉的结块特性进行了实验研究,应用非晶态粉体玻璃化转变理论分析实验数据,确定脱脂乳粉结块的影响因素和结块特征。正交实验及方差分析结果表明,相对湿度和温度是影响脱脂乳粉的两个主要因素;得到了相对湿度、温度、时间,以及添加剂种类及用量对脱脂乳粉结块指数的影响规律。     

聚丙烯玻璃化转变温度的分子动力学模拟

对等规、间规、无规三种不同聚丙烯(PP)的玻璃化转变温度进行了分子动力学模拟。用分子动力学模拟来获得不同构型聚丙烯在不同温度下的特征体积,通过对模拟得到的体积-温度(V-T)作图,求得玻璃化转变温度,其模拟结果与实验值吻合得较好。同时分析了聚丙烯主链柔顺性、立构规整度和力场能量项对PP玻璃化转变温度的影响,模拟结果表明,二面角扭转能和非键能在玻璃化转变温度附近出现拐点,这是高分子出现玻璃化转变的主要根源。     

粉体产品的结块及预防

粉体结块是粉体力学中一个比较复杂且尚未得到很好解决的难题 ,也是粉体加工和处理行业亟待解决的问题。本文中介绍了粉体结块的现象与机理 ,重点介绍了非晶态粉体结块动力学及预防结块的原理和措施     

润湿促进剂对粉末涂料玻璃化转变温度的影响研究

研究了影响粉末涂料用润湿促进剂玻璃化转变温度的主要因素,探讨了润湿促进剂对粉末涂料玻璃化转变温度的影响规律。结果表明,不同厂家生产的润湿促进剂,其玻璃化转变温度差异明显,通过调节润湿促进剂的分子量及共聚硬单体的种类可以调节其玻璃化转变温度。同时,润湿促进剂自身的玻璃化转变温度及添加量对粉末涂料的玻璃化转变温度均有影响。     

离聚体的微观链运动与玻璃化转变温度

本文用动态力学谱和~(13)C NMR方法分别测定了丙烯酸-1,1,5-三氢全氟戊酯与丙烯酸共聚物为基础的离聚体的玻璃化转变温度T_s和~(13)C自旋-自旋驰豫时间t_2,用描述高分子主链链段运动的VJGM模型计算了所测样品的链段运动活性。结果表明,离聚体样品的玻璃化转变温度与离聚体大分子链运动活性密切相关,大分子的微观链段运动越困难,玻璃化转变温度越高。     

N—取代马来酰亚胺型高分子耐热改性剂的研究进展

高分子材料的玻璃化温度是塑料在使用过程中的重要问题。用高分子耐热改性剂来提高其玻璃化温度是当前先进的改性方法。本文对Ｎ－取代马来酰亚胺型高分子耐热改性剂的制备以及它与基体树脂共混的研究进展进行综述和分析，提出一些对制备耐热变形材料具有参考性的建议。     

聚醚醚酮/聚醚酰亚胺合金的热学性能与力学性能

通过熔融共混和注塑成型的方法制备了不同质量比的聚醚醚酮/聚醚酰亚胺（PEEK/PEI）合金,确定了各种质量比下时的最佳加工温度。采用热重分析、差示扫描量热分析、动态力学热分析和拉伸、三点弯曲的性能表征方法,研究了PEEK/PEI共混合金的热学和力学性能随PEEK/PEI质量比的变化趋势。结果表明,各组分比的PEEK/PEI合金均具有良好的热稳定性;随着PEEK含量增加,合金结晶度呈现上升的趋势,而玻璃化转变温度不断下降;室温时,PEEK含量对PEEK/PEI共混物的力学性能影响较弱;当测试温度稍低于PEEK玻璃化转变温度时,其力学性能随着PEEK含量的增加表现出降低的趋势;当测试温度在PEEK与PEI玻璃化转变温度之间时,合金的力学性能随着PEEK含量的增加先下降再上升。最后,基于随机森林法量化了合金质量比及热性能参数对PEEK/PEI合金力学性能的贡献程度。     

聚氯乙烯/蒙脱土纳米复合材料的开发及研究

利用DSC的方法研究了纳米复合材料的玻璃化转变温度 ,测试了复合材料的力学性能 ,研究发现复合材料的力学性能与其玻璃化转变温度成线性关系 ,并随玻璃化转变温度的降低其力学性能提高。对复合材料进行热处理后 ,发现有机蒙脱土对聚氯乙烯的热降解引起的力学性能下降具有一定的抑制作用。     

低温保护剂溶液固化性质的DSC研究

利用差示扫描量热仪,研究了乙二醇、丙三醇、1,3丙二醇、1,3丁二醇和2,3丁二醇水溶液的水合性质、玻璃化转变温度和反玻璃化转变温度,得出了这些性质与溶液浓度的关系.研究发现未冻水含量在低浓度时没有明显的规律性,而在中高浓度则随着溶液浓度的增大而增大.对于玻璃化转变,中低浓度区溶液形成的是部分晶体的玻璃态,紧接着在高浓度区溶液形成完全的玻璃态.部分玻璃化的温度不随浓度变化,而玻璃化的温度随浓度增大而升高.形成反玻璃化的浓度范围比较小,反玻璃化的温度随浓度增大而升高.保护剂在玻璃化转变温度和反玻璃化转变温度的明显差异,则反映它们在玻璃化能力方面的强与弱.     

基于工业级原料FeMoPC块体非晶态合金的制备

通过Fluxing提纯技术和J-quenching快速凝固技术相结合的方法,成功制备了基于工业级原料的Fe80-xMoxP13C7(x=0,4,8,12)块体非晶态合金。结果表明,少量的Mo置换Fe能够提高Fe80P13C7合金的玻璃化形成能力,当Mo的替换量为8%时,合金的玻璃化形成临界尺寸达到4mm,然而Mo含量的进一步增加则使合金的玻璃化形成能力降低。随着Mo含量的增加,FeMoPC块体非晶态合金的玻璃转变温度(T_g)和起始晶化温度(T_x)单调增加,而冷液相区宽度(ΔT_x=T_x-T_g)先增大后减小。压缩测试结果显示,随着Mo含量的增加,FeMoPC块体非晶态合金的压缩断裂强度(σ_f)和塑性应变(ε_p)都先增大后减小,当Mo含量为8%时,合金的σ_f和ε_p都分别达到了最大值3.6GPa和4.6%。磁性测试结果表明,随着Mo含量从0%增加到12%,FeMoPC块体非晶态合金的饱和磁化强度从1.42T降为0.33T,这可能是由于Mo与Fe原子间反铁磁耦合造成的。     

Stable amorphous danazol nanostructured powders with rapid dissolution rates produced by spray freezing into liquid

The objective of this study was to produce, by spray freezing into liquid (SFL) technology, high-potency, high glass transition temperature (T_g) danazol/polymer powders that remain amorphous and exhibit high dissolution rates after 6 months. Three polymers were investigated, including polyvinylpyrrolidone (PVP) K-15, poloxamer 407, and PEG 8000. The physicochemical properties of SFL powders were characterized by X-ray diffraction (XRD), scanning electron microscopy, particle size distribution, surface area analysis, moisture content, and dissolution rate. The influence of moisture content, drug potency, and excipient type on T_g of SFL powders was investigated using modulated differential scanning calorimetry (mDSC). XRD results indicated that danazol was amorphous for each added excipient. The surface area of danazol/PVP K-15 powders (89.8 m²/g) was higher than that of danazol/PEG 8000 (12.0 m²/g) and danazol/poloxamer 407 (5.49 m²/g). The SFL powders with the various excipient types exhibited similar and significantly enhanced dissolution rates relative to micronized bulk danazol. As the potency of danazol in the SFL danazol/PVP K-15 powders was increased from 33% to 91%, the T_g decreased from 126°C to 104°C. The SFL powders, which were packaged in sealed 30-mL glass vials with a desiccant, were physically stable when stored at 25°C for 6 months, based on dissolution rates and mDSC and XRD measurements. SFL danazol/PVP K-15 powders with high surface areas and high glass transition temperatures remain amorphous and exhibit rapid dissolution rates after 6 months' storage.     

Structural evolution during mechanical milling and subsequent annealing of Cu–Ni–Al–Co–Cr–Fe–Ti alloys

This study reports the structural evolution of high-entropy alloys from elemental materials to amorphous phases during mechanical alloying, and further, to equilibrium phases during subsequent thermal annealing. Four alloys from quaternary Cu_0.5NiAlCo to septenary Cu_0.5NiAlCoCrFeTi were analyzed. Microstructure examinations reveal that during mechanical alloying, Cu and Ni first formed a solid solution, and then other elements gradually dissolved into the solid solution which was finally transformed into amorphous structures after prolonged milling. During thermal annealing, recovery of the amorphous powders begins at 100 °C, crystallization occurs at 250–280 °C, and precipitation and grain growth of equilibrium phases occur at higher temperatures. The glass transition temperature usually observed in bulk amorphous alloys was not observed in the present amorphous phases. These structural evolution reveal three physical significances for high-entropy alloys: (1) the annealed state of amorphous powders produces simple equilibrium solid solution phases instead of complex phases, confirming the high-entropy effect; (2) amorphization caused by mechanical milling still meets the minimum criterion for amorphization based on topological instability proposed by Egami; and (3) the nonexistence of a glass transition temperature suggests that Inoue's rules for bulk amorphous alloys are still crucial for the existence of glass transition for a high-entropy amorphous alloy.     

放电等离子烧结技术制备Fe78Si13B9块体非晶纳米晶磁性材料

通过高能球磨技术制备了Fe₇₈Si₁₃B₉磁性非晶合金粉体,采用XRD和DSC分析了Fe₇₈Si₁₃B₉非晶合金粉体的相组成、玻璃转变温度T_g、开始晶化温度 T_x 和晶化峰温度T_p;利用放电等离子烧结（SPS）技术在不同烧结温度下制备了块体磁性非晶纳米晶合金试样,利用XRD、SEM、Gleeble3500、VSM等分析了不同烧结温度下烧结块体试样的相转变特性、微观形貌、力学性能和磁学性能。结果表明,在500 MPa的烧结压力下,随着烧结温度的升高,烧结试样中的非晶相开始逐渐晶化,烧结试样的致密度、抗压强度、微观硬度、饱和磁化强度均显著提高;在500 MPa的烧结压力和823.15 K的烧结温度下,获得了密度为6.6 g/cm³,抗压强度为1500 MPa,饱和磁化强度为1.3864 T的非晶纳米晶磁性材料。     

高能球磨技术制备Fe_(78-x)MxSi_(13)B_9磁性材料

采用高能球磨技术制备Fe78-xMxSi13B9软磁非晶合金粉体,利用X射线衍射仪、差示扫描量热分析仪、扫描电镜和振动样品磁强计分析过渡金属元素M(Zr、Nb、Mo)的添加对合金粉体微观组织结构、热稳定性及软磁性能的影响。结果表明,Zr、Nb的添加有利于Fe-Si-B系合金的非晶转变,其最大过冷液相区ΔTx为70.62 K,玻璃转变温度Tg和开始晶化温度Tx分别为785.05、855.67 K;饱和磁化强度Ms为111 emu/g,矫顽力Hc约为2 028.443 A/m。     

Frustration, connectivity, and the glass transition

The concepts of connectivity, localization, and frustration are explored in relation to glass formation in amorphous materials. First, the concept of eigenclusters to geometrically characterize correlations in amorphous materials is introduced, and discussed in detail for both the Ising ferromagnet and Ising spin glass models. Second, a new, glass-forming percolation model that contains frustration as the essential ingredient, and exhibits two percolation transitions, is discussed. This new model gives new insights into frustrated systems, and applications to the Ising spin glass model and other glass-forming systems are discussed. In particular, we propose the possibility that the occurrence of a percolation-type transition at temperatures above the glass transition temperature may be a general feature of glass-forming systems. The important role of computer simulations in probing the mechanism of glass formation is emphasized.     

大尺寸La2O3-TiO2-ZrO2非晶塑性烧结行为

La₂O₃-TiO₂-ZrO₂玻璃具有很高的折射率, 在镜头材料和上转换发光基质材料等领域表现出良好的应用前景, 但其玻璃形成能力低, 通常只能采用快速冷却的方法制备, 因此难以获得大尺寸材料。为了获得大尺寸La₂O₃-TiO₂-ZrO₂玻璃, 本研究采用La₂O₃-TiO₂-ZrO₂非晶粉末为原料, 利用非晶在玻璃转变温度以上的塑性行为, 在温度动力学窗口ΔT内进行热压烧结制备了大尺寸La₂O₃-TiO₂-ZrO₂玻璃, 在保持非晶的前提下实现了La₂O₃-TiO₂-ZrO₂粉末的完全致密化。采用SEM、XRD等方法研究了样品的显微结构和相组成。研究发现, 当烧结温度高于910 ℃时, 烧结过程中会析出La₄Ti₉O₂₄晶相; 当烧结温度低于900 ℃时, 样品保持良好的非晶性, 并随着烧结温度的增加, 样品的致密度有所升高。烧结压力也会影响烧结过程, 样品的致密度随着烧结压力升高而增加。大尺寸La₂O₃-TiO₂-ZrO₂非晶材料具有很高的折射率, 在587.6 nm处折射率可达到2.33。在La₂O₃-TiO₂-ZrO₂非晶粉末烧结过程中, 塑性流动是其主要的传质机理。     

CRYSTALLIZATION, MORPHOLOGY, AND DYNAMIC MECHANICAL BEHAVIOR OF SUPRAMOLECULAR [60]FULLERENE-CONTAINING POLY(ETHYLENE-co-ACRYLIC ACID)

A multifunctional [60]fullerene derivative AEAF was melt-mixed with poly(ethylene-co-acrylic acid) (PEAA20). The strong interaction between AEAF and PEAA20, as shown by x-ray photoelectron spectroscopy, enables AEAF to be well dispersed in the amorphous phase of PEAA20. WAXD revealed that the crystallinity of PEAA20 is reduced and the crystallites are deformed by the addition of AEAF. The storage modulus and dynamic glass transition temperature of the polymer increase upon the incorporation of AEAF. Unlike C₆₀ and a monofunctional C₆₀ derivative, AEAF is able to sustain its reinforcing effect in the glass-rubber transition region.     

The entropy theory of glass formation after 40 years

It is argued that an equilibrium theory of the glass transition is required before a full understanding of the glass transition, as observed kinetically, can be obtained. The lattice model provides a basis for such a theory and predicts that vitrification occurs as the configurational entropy S_c approaches zero. Comparison with nine different classes of polymer experiments shows semiquantitative agreement in each case. An important aspect of glass formation in polymers is that the crystal phase is not ubiquitous so that amorphous polymer material exists necessarily at low temperatures. A low-temperature equilibrium theory for these materials is required. Using equilibrium theory as a base, a kinetic theory is developed and an equation for the relaxation function is derived which predicts the proper temperature dependence of the viscosity and shows stretched exponential-like behavior for the relaxation.     

Reentrant glass transition leading to ultrastable metallic glass

Polyamorphs are often observed in amorphous matters, and a representative example is the reentrant glass transition in colloid systems. For metallic amorphous alloys, however, the cases reported so far are limited to metallic glasses (MGs) that undergo electronic transitions under gigapascal applied pressure, or the presence of two liquids at the same composition. Here we report the first observation of a reentrant glass transition in MGs. This unusual reentrant glass transition transforms an MG from its as-quenched state (Glass I) to an ultrastable state (Glass II), mediated by the supercooled liquid of Glass I. Specifically, upon heating to above its glass transition temperature under ambient pressure, Glass I first transitions into its supercooled liquid, which then transforms into a new Glass II, accompanied by an exothermic peak in calorimetric scan, together with a precipitous drop in volume, electrical resistance and specific heat, as well as clear evidence of local structural ordering on the short-to-medium-range scale revealed via in-situ synchrotron X-ray scattering. Atomistic simulations indicate enhanced ordering of locally favored motifs to establish correlations in the medium range that resemble those in equilibrium crystalline compounds. The resulting lower-energy Glass II has its own glass transition temperature higher than that of Glass I by as much as 50 degrees. This route thus delivers a thermodynamically and kinetically ultrastable MG that can be easily retained to ambient conditions.