Effect of Nucleating Agents and Heat Treatments on the Crystallization of Magnesium Aluminosilicate Transparent Glass-ceramics

The crystallization behavior and transparent property of MgO-A1203-SiO2 （MAS） glasses with TiO2 and TiO2＋ZrO2 as nucleating agents were discussed by differential thermal analysis, X-ray diffraction, field emission-environment scanning electron microscope, energy dispersive spectrum and UV-VIS-NIR scanning spectrophotometer. It was found that the glass crystallized at 950 ℃ with ZrO2 less than 3% could obtain transparent glass ceramic, which presented purple to colorless. With the nucleating agent additives （5% TIO2＋3% ZrO2）, the colorless transparent glass-ceramics with spinel as the main crystal phase could be prepared, and the transmittance reached about 80%. As the crystallized temperature increase to 1 000 ℃, besides spinel（MgA1204）, sapphirine （Mg3.5A19Si1.5O20） and ZrTiO4 precipitated from matrix glass, and the transmitance of glass-ceramic decreased.

THERMODYNAMIC STUDY OF NUCLEATION PROPERTY OF NUCLEATING AGENT

It is deduced from thermodynamic relations and confirmed by experiment results that the nucleation rate and nucleation temperature of nucleating agents in the glass are dependent upon their melting entropy Delta S//m melting temperature T//m and crystal - type transition in terms of some mathematical expressions. (Author abstract) 10 Refs.

MELTING BEHAVIOR OF LOW ETHYLENE CONTENT POLYPROPYLENE COPOLYMERS WITH AND WITHOUT NUCLEATING AGENTS

The melting behavior of polypropylene (PP) and low ethylene content polypropylenecopolymer with and without nucleating agent samples crystallized under both isothermal and non-isothermal conditions were studied by Differential Scanning Calorimeter (DSC) and X-raydiffraction. Multiple melting behavior were observed depending on the existence of nucleatingagent and crystallization conditions. The observed phenomena have been discussed by the effect ofnucleating agent on perfection of crystal and the melting and recrystallization of imperfect crystalto a more perfect crystal during the heating process of samples.

Effect of a Novel Nucleating Agent on Isothermal Crystallization of Poly（L-lactic acid）

The effect of a novel active nucleating agent(TBC8-eb) on the isothermal crystallization of poly(L-lactic acid) (PLLA) was studied by differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(FTIR) . The analysis on kinetics demonstrates that TBC8-eb can not only accelerate the crystallization rate but also transform most of the original spherulite crystals of PLLA into sheaf-like crystals. Furthermore,the free energy of folding(σe) of PLLA and PLLA with TBC8-eb is 0.15 and 0.06 J·m-2,respectively,which suggests that the addition of TBC8-eb favors the regular folding of molecule chains in the crystallization of PLLA,improv-ing its crystallization rate. The FTIR results show that TBC8-eb can accelerate the conformational ordering of PLLA in the isothermal crystallization. The conformational ordering of PLLA nucleated with TBC8-eb begins with the interchain interaction of CH3,and then a short helix emerges where a couple of CH3 groups interact.

Effect of Nucleating Agent on the Crystallization of Tailings Glass Ceramics Prepared by One-time Sintering

Glass ceramics was made by the one-time sintering method using the main raw material of iron tailings. On the basis of quaternary system of CaO-MgO-Al2O3-SiO2, using DTA, XRD and SEM, the effects of different nucleating agents and mixing amounts as well as heat treatment on the crystallization of railings glass ceramics were studied. The experimental results show that, nucleating agent and heat treatment are two necessary conditions for one-time sintering preparation of tailings glass ceramics namely, only adding nucleating agent or experiencing heat treatment, the quaternary system can not crystallize. The composite nucleating agent consisting of Cr2O3 and TiO2 can further lead to the crystallization of the CaO-MgO-A1203-SiO2 quaternary system at the lower temperature, with the major phase of diopside. In the range of mass content, 0%-4%, crystal intensity and crystal content grow. But when mass content is more than 4%, the crystal size will become coarser and the crystal distribution will be less regular. Different heat treatment regimes do not change the composition of the crystalline major phase in the glass ceramics crystallization of CaO-MgO-Al2O3-SiO2 system. In the range of 30-60 minutes, with the extension of nucleation and crystallization, crystallization degree enhanced, but if the holding time surpasses 60 minutes, the crystallization is worse.

Influence of Nucleating Agent on the Formation of C_4A_3S

The reference test methods are carried out parallelly, by means of chemical analysis, X-ray diffraction, differential scanning calorimetry-thermogravimetry, scanning electron microscopy and polarized optical microscope to study the formation of C4A3S in the presence and absence of nucleating agent. The results show that nucleating agent with high calcium and low heat consumption as tricalcium silicate （C3S） promotes the formation of C4A3S and increases desulfurization degree obviously. During calcining raw meals doped with C3S, the grain sizes of C4A3S are larger compared with that without C3S. And at the same calcining level, the mass loss and the heat consumption belonged to CaCO3 decomposition is reduced.

Effects of Nucleating Agents on Crystallization of Arc-Molten Slag from Incinerator Fly Ash

Glass-ceramics obtained from the electric arc furnace molten slag of incinerator fly ash was produced by applying nucleation and crystallization through heat treatment process. The effects of nucleating agent(TiO2and Cr2O3)on the crystallization kinetics and heat treatment schedule of the slag were investigated. The results show that the nucleating agents changed the crystallization phase and morphology of the obtained glass-ceramics. The optimum heat treatment schedule of the glass with TiO2 was determined as nucleation at 952 K for 1.5 h and crystal growth at 1258 K for 1.5 h, while those values with Cr2O3 were estimated at 971 K for 2 h and at 1 238 K for 2 h. TiO2 acting as nucleating agent could decrease the activation energy of the slag and shorten the total thermal treatment time in comparison with Cr2O3. The glass-ceramics obtained under the optimum heat treatment condition was environmentfriendly and had remarkable physical/mechanical properties and chemical durability.

Enhanced Crystallization of Poly(butylene adipate-co-terephthalate)by a Self-assembly Nucleating Agent

Poly(butylene adipate-co-terephthalate)(PBAT)is a promising biodegradable flexible polymer but suffers from slow crystallization rate,making it less attractive for some applications like the injection-molded products in comparison with low-density polyethylene(LDPE).This work aimed to accelerate the crystallization of PBAT by adding a self-assembly nucleating agent octamethylenedicarboxylic dibenzoylhydrazide(OMBH).PBAT/OMBH composites with various OMBH contents(0 wt%,0.5 wt%,0.7 wt%,1 wt%,2 wt%,3 wt%and 5 wt%)were prepared through melt-mixing.The effect of OMBH on the crystallization behavior,morphologies and mechanical properties of PBAT was investigated.The highest nucleation efficiency value of 59.6%was achieved for PBAT with 0.7 wt%OMBH,much higher than that of 22.7%for PBAT with 0.7 wt%talc.Atomic force microscopy results showed that OMBH formed fine fibers and induced the formation of transcrystalline layers of PBAT.Fourier transform infrared spectroscopy(FTIR)combined with two-dimensional correlation spectra suggested that the intermolecular dipole-dipole N—H…O=C interactions but not hydrogen bond between OMBH and PBAT promoted the crystallization of PBAT in the initial period of crystallization.The presence of OMBH did not change the crystal form of PBAT but had positive contribution in enhancing its crystallinity and mechanical properties.This work is essential for preparing PBAT with high crystallization rate,enhancing its potential applications in injection-molded products.

Lightweight,Strong and High Heat-Resistant Poly(lactide acid)Foams via Microcellular Injection Molding with Self-Assembly Nucleating Agent

Poly(lactide acid)(PLA)foams have shown considerable promise as eco-friendly alternatives to nondegradable plastic foams,such as polystyrene(PS)foams.Nevertheless,PLA foam typically suffers from low heat-resistance and poor cellular structure stemming from its inherent slow crystallization rate and low melt strength.In this study,a high-performance PLA foam with well-defined cell morphology,exceptional strength and enhanced heat-resistance was successfully fabricated via a core-back microcellular injection molding(MIM)process.Differential scanning calorimetry(DSC)results revealed that the added hydrazine-based nucleating agent(HNA)significantly increased the crystallization temperature and accelerated the crystallization process of PLA.Remarkably,the addition of a 1.5 wt%of HNA led to a significant reduction in PLA’s cell size,from 43.5µm to 2.87µm,and a remarkable increase in cell density,from 1.08×10^(7)cells/cm^(3)to 2.15×10^(10)cells/cm^(3).This enhancement resulted in a final crystallinity of approximately 55.7%for the PLA blend foam,a marked improvement compared to the pure PLA foam.Furthermore,at 1.5 wt%HNA concentration,the tensile strength and tensile toughness of PLA blend foams demonstrated remarkable improvements of 136%and 463%,respectively.Additionally,the Vicat softening temperature of PLA blend foam increased significantly to 134.8°C,whereas the pure PLA foam exhibited only about 59.7℃.These findings underscore the potential for the preparation of lightweight injection-molded PLA foam with enhanced toughness and heat-resistance,which offers a viable approach for the production of high-performance PLA foams suitable for large-scale applications.

Influence of Nucleation Agents Concentration on Crystallization Structure and Properties of Glass-ceramics

Deep color glass-ceramics is prepared by using gold tailings as the main raw material, and Cr2O3 is added as nucleation agent. Influence of different Cr2O3 additions on crystallization structure and properties of CaO-MgO-Al2O3-SiO2 glass-ceramics has been discussed so as to select optimum additions. DTA is employed to determine optimum crystallization and nucleation temperatures; XRD and SEM are used to characterize microstructure of each sample; and performance indexes, such as water absorption, bulk density, flexural strength and so on, are also determined. Experimental results show that when 3wt% Cr2O3 is introduced, fine glass-ceramics with diopside as the main crystal and Ca-Fe diopside as the second-crystal is obtained, and its corresponding performance indexes are as follows： water absorption 0.12%, bulk density 2.56 g/cm^3, and flexural strength 70.01 Mpa.

Highly Reversible Zn Metal Anodes Enabled by Increased Nucleation Overpotential

Dendrite formation severely compromises further development of zinc ion batteries. Increasing the nucleation overpotential plays a crucial role in achieving uniform deposition of metal ions. However, this strategy has not yet attracted enough attention from researchers to our knowledge. Here, we propose that thermodynamic nucleation overpotential of Zn deposition can be boosted through complexing agent and select sodium L-tartrate(Na-L) as example. Theoretical and experimental characterization reveals L-tartrate anion can partially replace H_(2)O in the solvation sheath of Zn^(2+), increasing de-solvation energy. Concurrently, the Na^(+) could absorb on the surface of Zn anode preferentially to inhibit the deposition of Zn^(2+) aggregation. In consequence, the overpotential of Zn deposition could increase from 32.2 to 45.1 mV with the help of Na-L. The Zn-Zn cell could achieve a Zn utilization rate of 80% at areal capacity of 20 mAh cm^(-2). Zn-LiMn_(2)O_(4) full cell with Na-L additive delivers improved stability than that with blank electrolyte. This study also provides insight into the regulation of nucleation overpotential to achieve homogeneous Zn deposition.

EFFECTS OF NUCLEATION AGENTS ON EFFICIENCY OF BORON EXTRACTION FROM MgO－B_2O_3－SiO_2 SLAGS

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聚丙烯/蒙脱土纳米复合材料的制备与力学性能预测

本文采用熔融挤出法制备了β成核聚丙烯/蒙脱土纳米复合材料,考察了蒙脱土、β成核剂及增容剂用量对复合材料缺口冲击强度和弯曲强度的影响,并用BP神经网络进行预测。结果表明,增加蒙脱土用量有助于复合材料强度的提高但对韧性不利;随β成核剂用量的增加,复合材料的缺口冲击强度略有增加,而弯曲强度存在最优值,即添加β成核剂0.1%时,弯曲强度达到最大值35.06MPa,较不添加时增加了13.68%;随增容剂用量的增加,复合材料的韧性显著增大而强度有所降低,添加30%增容剂,复合材料的缺口冲击强度较不添加时增加了约3倍,而弯曲强度仅降低了28.39%;BP神经网络预测结果表明,该模型能够比较精确的预测该复合材料的力学性能。该研究对于优化聚丙烯基纳米复合材料制备及改进力学性能预测具有借鉴意义。

利用废岩棉制备高性能泡沫玻璃陶瓷的实验研究

以工业垃圾废岩棉和废玻璃为原料,以CaCO_(3)为发泡剂制备出高强度泡沫玻璃陶瓷。研究了废岩棉和废玻璃的添加量及烧结温度对泡沫玻璃陶瓷材料性能的影响。结果表明:随着废岩棉添加量的增加和烧结温度的提高,熔体黏度会降低,不利于气泡结构的稳定;在废岩棉添加量为40%、750℃烧结温度下得到的样品容重为0.54 g/cm^(3)、孔隙率为62.5%、抗压强度为4.76 MPa;样品主晶相为亚硅酸钙和石英晶相,加入TiO_(2)作为晶核剂后主晶相改变为榍石;TiO_(2)掺量为10%时,在750℃烧结20 min更经济,所得样品容重为0.82 g/cm^(3)、孔隙率为50%、抗压强度为7.76 MPa。

无规共聚透明聚丙烯的研发

研究了不同成核剂种类和用量对无规共聚聚丙烯(PP)RP210M透明性的影响。通过优化复合助剂配方,成功工业化生产了无规共聚透明PP产品(PP-E800),综合性能好于对标产品。

β成核聚丙烯/蒙脱土纳米复合材料的结构与力学性能

本文使用双螺杆挤出机制备了β成核聚丙烯(β-PP)/有机蒙脱土(OMMT)纳米复合材料。采用FTIR、XRD和SEM分析了复合材料的微观结构与形貌特征,考察了OMMT、β成核剂(β-NA)及增容剂用量对复合材料冲击强度和弯曲强度的影响,并对比研究了标准BP神经网络模型和LM-BP神经网络模型对力学性能的预测能力。结果表明,增容剂与OMMT表面形成了强相互作用,提高了复合体系的相容性,黏土片以插层结构分散在β-PP基体内。OMMT、β-NA及增容剂用量对复合材料的力学性能均产生了一定影响,其中添加30%增容剂时复合材料的冲击强度约为不添加时的4倍,而弯曲强度仅降低了28.39%。此外,与标准BP神经网络模型相比,LM-BP神经网络模型具有更快的收敛速度和更高的预测精度。该研究为优化PP基纳米复合材料的制备及力学性能预测提供了参考。

酰肼成核剂对聚乳酸结晶和力学性能的影响

为提高聚乳酸结晶度、改善韧性,采用熔融共混向聚乳酸(PLA)中分别加入了成核剂己二酸二苯基二酰肼(SDA210)和癸二酸二苯基二酰肼(SDA356),通过差示扫描量热仪、X射线衍射仪、偏光显微镜等表征手段测试研究了两种成核剂含量对聚乳酸结晶和力学性能的影响。研究结果表明:SDA210和SDA356都是PLA的有效成核剂。当SDA210添加量为1.0%时,对PLA成核效果达到最佳,其结晶度较纯PLA提高了10.21%;而SDA356添加量为0.8%时成核效果最好,其结晶度较纯PLA提高了12.57%。两种成核剂的加入都可以提高聚乳酸复合材料的冲击性能。PLA/0.8%SDA356的无缺口冲击强度最好,达到170.08 J/M,与纯PLA相比增加了31.3%。在相同添加量的情况下,成核剂SDA356的成核效果和增韧效果均优于SDA210。

Li_(2)O-Al_(2)O_(3)-SiO_(2)系微晶玻璃的研究进展

Li_(2)O-Al_(2)O_(3)-SiO_(2)(LAS)系微晶玻璃由于具有热膨胀系数低、透明度高、力学性能优良等特点,被广泛应用于国防、建筑、化工、生物医药等多个领域,近年来受到研究者的广泛关注。本文综述了LAS系微晶玻璃的研究现状,介绍了LAS晶相体系及相关玻璃产品,对比分析了LAS系微晶玻璃各制备工艺的特点,并讨论了LAS系微晶玻璃晶核剂的种类及成核机理,最后总结了LAS系微晶玻璃性能、应用以及相应表征技术和测试手段,并指出了LAS系微晶玻璃存在的问题及未来的发展方向。

酰肼类成核剂己二酸二苯基二酰肼对PBS复合材料性能的影响

聚丁二酸丁二酯(PBS)是近些年兴起的一类绿色环保高分子材料,具有良好的生物可降解性和生物相容性,是最具发展潜力的环境友好材料之一。然而PBS冲击强度较低,结晶性能较差,限制了其进一步的发展和应用。针对以上不足,采用酰肼类成核剂己二酸二苯基二酰肼(TMC-306)对PBS树脂进行改性,研究了酰肼类成核剂的添加量对PBS复合材料力学性能、结晶性能、加工性能以及微观形貌的影响。结果表明,TMC-306的引入明显改善了PBS/TMC-306复合材料的力学性能和结晶性能,当TMC-306添加量为15份时,PBS复合材料的冲击强度从41 J/m提高至102 J/m,提升了149%,结晶度从48.40%提高至62.01%,提升了28.12%。X射线衍射测试结果表明,成核剂TMC-306使复合材料晶面的衍射峰面积略微增大,与纯PBS晶型基本一致。流变测试结果发现,随着成核剂添加量的增加,PBS复合材料的储能模量、损耗模量和复数黏度均逐步增大,熔体强度得到了提高,这说明成核剂同时也改善了复合材料的加工性能。扫描电子显微镜测试结果表明,随着TMC-306的增加,PBS复合材料的断面由平整光滑变为“阶梯”式结构,且在添加量为15份时最为明显,这与力学测试结果相一致。

大分子成核剂对PBA型水性聚氨酯结晶行为的影响

以聚己二酸1,4-丁二醇酯(PBA)、六亚甲基二异氰酸酯(HDI)、2,2-二羟甲基丙酸(DMPA)等为主要原料制备了数均分子量9 270的水性聚氨酯(WPU),将其作为大分子成核剂加入到PBA型水性聚氨酯(以PBA、HDI、异佛尔酮二异氰酸酯(IPDI)、DMPA等为主要原料制备,数均分子量28 700)中,研究了成核剂加入量对WPU结晶性能的影响。研究表明,大分子成核剂本身具有较高的热结晶温度,它的加入提高了WPU的热结晶温度、结晶速率和结晶度,增强了WPU胶膜的力学性能。当大分子成核剂乳液加入量为3 g即20%时,WPU中PBA热结晶温度为19.6℃,结晶度为47.7%,胶膜拉伸断裂强度为11.7 MPa。