Synthesis of tritium-labeled 5-fluorouracil and 5-fluorocytosine

The effect of various catalysts and temperature on the solid-phase isotope exchange of 5-fluorouracil and 5-fluorocytosine with tritium was studied. The isotope exchange yielding the desired compounds is accompanied by dehalogenation and hydrogenation of the 5,6-double bond of the pyrimidine ring. Performing the reaction at a temperature below 160°C allowed the process to be carried out selectively, i.e., with the preservation of the functional groups and double bond in the starting compound. The yields of various products formed in the reactions of tritium with the above compounds were estimated. Synthesis conditions were found, and tritium-labeled 5-fluorouracil and 5-fluorocytosine were prepared with the molar radioactivity of 0.45 Ci mmol⁻¹ (16.7 TBq mol⁻¹) and 4.4 Ci mmol⁻¹ (0.16 PBq mol⁻¹), respectively, and with the purity exceeding 98%.     

纳米氯化银溶胶的制备及其热稳定性研究

在表面活性剂(聚乙烯吡咯烷酮、木质纤维素、聚乙二醇)的保护下,制备了纳米级的氯化银溶胶,借助于分光光度计和TEM分析仪研究了纳米氯化银在不同温度条件下的稳定性,同时对纳米氯化银的变色进行研究,用X射线衍射研究了纳米氯化银溶胶变色以后溶胶体系的变化。     

羟基磷灰石合成及高温稳定性的研究

以Ca(NO₃)₂·4H₂O和(NH₃)₂HPO₄为原料,用沉淀法合成羟基磷灰石(HA)。在合成过程中添加明胶,考察明胶对HA成核、生长、粉末形态及热稳定性的影响。研究表明:当明胶加入量超过4wt％时,将阻碍HA的成核和生长;加4wt％明胶合成的粉末,经900℃煅烧,其平均颗粒尺寸为40nm,明显小于未加明胶的HA粉末,但热稳定性较差;在1000℃煅烧便有部分羟基磷灰石分解,生成β-磷酸钙。此β-磷酸钙煅烧至1500℃呈熔融态,仍没有相变为α-磷酸钙,具有很好的热稳定性。     

MgNiSi非晶的制备及其热稳定性和腐蚀性能研究

通过机械球磨的方法成功制得Mg55Ni35Si10非晶粉末,并采用X射线衍射(XRD)对其非晶形成过程进行研究,发现Mg55Ni35Si10粉末样品在球料比为20:1、转速为600r/min的条件下,经过54h球磨后开始形成完全的非晶结构.还采用差示扫描量热仪(DSC)对Mg55Ni35Si10非晶粉末的热稳定性进行了研究,通过Kissinger方程得到样品开始晶化的表观激活能为(280.6±44.5)kJ/mol,与文献中报道的Mg65Cu25Gd10的激活能((285.2±27.6)kJ/mol)相近,说明样品具有较好的热稳定性.此外,还对Mg55Ni35Si10非晶在NaCl溶液中的腐蚀行为进行了研究,发现该样品的腐蚀电位远远正于AZ31和AZ61镁合金,表明Mg55Ni35Si10非晶具有较好的耐腐蚀性能.     

Synthesis and Thermal Oxidation Stability of Nanocrystalline Niobium Diboride

Inorganic Materials - A method has been developed for the synthesis of nanocrystalline NbB2 powder with an average particle size of 65 nm. The material has been prepared by reacting Nb and...     

硼酸酯水解稳定性研究与应用

对硼酸酯水解稳定性的本质及研究现状进行了概括，目前解决硼酸酯水解稳定性差的最佳途径是合成含氮硼酸酯，并对硼酸酯在润滑油添加剂、汽车制动液、光热引发剂、偶联剂等方面的应用进行了综述。     

一种葛根素大分子前药的合成与表征

葛根素(Puerarin)临床应用广泛,但是其水溶性低,影响疗效的更好发挥.将葛根素键合到具有良好生物相容性、可降解的水溶性聚天冬酰胺衍生物(PDHEA)上,合成了葛根素前药(PDHEA-P),并通过FT-IR、1H-NMR 验证了目标产物.研究表明,葛根素前药的水溶性大大提高,所得前药的缓释性能良好.     

纳米Mg_2Si块体的制备及其热稳定性的研究

采用机械球磨和真空热压相结合的方法,在1.5GPa压力下于400℃热压1h制得纳米晶Mg2Si金属间化合物块体.纳米晶Mg2Si块体晶粒度为30nm,致密度为91.45%.采用原位高温XRD对纳米Mg2Si块体的热稳定性进行了研究.纳米晶Mg2Si块体在700℃、800℃和900℃时晶粒的生长指数分别为6、5和4,说明其具有良好的热稳定性.     

BaTiO3纳米晶热稳定性的研究

采用硬脂酸盐（ＳＡＧ）法合成了ＢａＴｉＯ３纳米晶材料，对其粒子尺寸和性能随着温度和时间的变化进行了详细的测试，并与溶胶凝胶（Ｓｏｌｇｅｌ）法合成的ＢａＴｉＯ３纳米晶进行了对比，结果表明：ＳＡＧ法合成的ＢａＴｉＯ３纳米晶具有良好的热稳定性。产生这种特殊性能的原因可能是ＢａＴｉＯ３纳米晶晶粒表面富Ｂａ引起的。     

共沉淀法制备硅酸锆包裹炭黑及其高温稳定性

以正硅酸乙酯和氧氯化锆为原料, 采用溶胶共沉淀法制备了硅酸锆包裹炭黑复合粉体。利用XRD、SEM、色度计和粒度分析仪等手段对样品进行了表征。采用正交试验考察了前驱体pH值、煅烧温度、矿化剂种类和用量等工艺条件对复合粉体高温稳定性的影响。结果表明, 矿化剂和煅烧温度是最重要的影响因素。最佳的工艺条件是前驱溶液pH为5、矿化剂为5wt%LiF、煅烧温度为1150℃。该工艺条件下形成的球形镶嵌结构能够有效防止炭黑被氧化。获得的硅酸锆包裹炭黑粉体具有较好的高温稳定性, 粒度分布符合陶瓷色料的要求。该粉体用于熔块釉中, 1000℃烧成仍然具有较好的发色效果。     

钛酸铝材料的结构、热膨胀及热稳定性

详细回顾了关于铁酸铝材料结构、热膨胀和热稳定性的研究。A12TiO5属于正交晶系假板钛矿结构。其晶格热膨胀各向异性行为，导致多晶铁酸铝陶瓷材料的微裂纹化，从而具有低膨胀、低热导率和优良的抗热震性等特性。但Al2TiO5低温下属于动力学稳定态，当温度低于1280℃易于分解为α-A12O3和金红石型TiO2。引入异质同构的化合物MgTi2O5或Fe2TiO5固熔于A12TiO5晶格，可以降低热力学分解温度和增加结构熵，有效地抑制Al2TiO5的分解。Al2TiO5在还原气氛下的分解机理上不明确，需要进一步的研究。     

Magnetic Properties and Thermal Stability of Pr_(1-x)La_xCo_(5-y)Alloys

Pr1-xLaxCo5-y (x=0, 0.15. 0.25, 0.35,1.0, y=0.5, 0.7, 0.9, 1.0) alloys were investigated. The effect of the variation of x and y on magnetic properties and thermal stability of the alloys were studied. The magnetic properties for the Pr0.85La0.15Co4.3 and Pr0.75La0.25Co4.1 magnets are iHc=368 kA/m, Br=0.91 T, (BH)max=145.6 kJ/m3, αBr=-0.03%/℃ and iHc=568 kA/m,Br=0.8 T, (BH)max=127.2 kJ/m3,αBr,=-0.06%/℃, respectively The phase structures of as-cast alloys and magnets were investigated     

Hydrolytic Stability of Y2.5Nd0.5Al5O12-Based Garnet Ceramics under Hydrothermal Conditions

Inorganic Materials - We have studied the hydrolytic stability of Y2.5Nd0.5Al5O12-based garnet ceramics produced by spark plasma sintering. The ceramics have been tested under hydrothermal...     

不同气氛下类石墨相氮化碳的合成及热稳定性能

本研究以三聚氰胺为原料,采用热聚合法分别在空气气氛和氩气气氛下进行不同温度的热处理,制备片层状类石墨相氮化碳(g-C3 N4).运用XRD、SEM、TEM、FT-IR和Raman等对产物进行了表征分析,采用TG-DSC对三聚氰胺的热解行为和生成的g-C3 N4的热稳定性能进行了分析.结果表明:通过热聚合法可以将三聚氰胺合成高聚合度、具有片层状结构的纯相g-C3 N4.氩气气氛下热聚合生成的g-C3 N4表面光滑,片层状g-C3 N4紧密堆积程度较空气气氛下热聚合生成的g-C3 N4更高.热处理温度是影响g-C3 N4的重要因素,500℃热处理即能生成片层状g-C3 N4,且在700℃仍能稳定存在.氩气气氛下合成的g-C3 N4的热稳定性能比空气气氛下合成的g-C3 N4更好.     

Ba3BPO7的合成及其水解、热稳定性和稀土掺杂发光性能的研究

采用多种高温固相反应途径合成了纯相Ba₃BPO₇并研究了Ba₃BPO₇的水解和热稳定性能.研究表明:Ba₃BPO₇遇水水解,生成Ba₃(PO₄)₂、Ba₅(PO₄)₃OH和Ba(OH)₂;TG-DTA表明它是一致熔化合物,熔点在1353℃左右;同时,初步研究了X射线激发Ba₃BPO₇:RE(RE=Eu³⁺、Sm³⁺)的发光性能,表明基质Ba₃BPO₇与稀土离子之间存在着能量传递.     

Preparation,Thermal Stability and Electrochemical Properties of LiODFB

Lithium oxalyldifluoroborate (LiODFB) was synthesized in dimethyl carbonate solvent and purified by the method of solvent-out crystallization. The structure characterization and thermal stability of LiODFB were performed by Fourier transform infrared (FTIR) spectrometry, nuclear magnetic resonance (NMR) spectrometry and thermogravimetric analyzer (TGA). LiODFB was exposed to 50% humid air at 25 C for different time, then dried at 80 C for 12 h, and the electrochemical properties of the cells using 1 mol/L dried LiODFB in ethylene carbonate + dimethyl carbonate + ethyl(methyl)carbonate were investigated. The results showed that, pure crystallization LiODFB was obtained; it had good thermal stability with a thermal decomposition temperature of 248 C; when it was exposed to humid air, it was firstly converted into LiODFB·H2O; with increasing exposure time, more and stronger impurity peaks in the X-ray diffraction (XRD) patterns of LiODFB were observed, and both the discharge specific capacity and the capacity retention decreased gradually.     

球磨法制备Mg基非晶合金及其热稳定性

采用机械合金化法制备了Mg65Cu25Gd10非晶粉末,并研究了球磨的转速、球料比和球磨时间等工艺参数对非晶形成的影响.研究表明当球料比为20∶1,转速为200r/min时较为合适,形成非晶所需的最短时间为40h.采用差示扫描量热仪(DSC)研究了球磨得到的非晶粉末的热稳定性,得到了热力学参数玻璃转化温度Tg、开始晶化温度Tx,过冷液相区宽度ΔTx和晶化焓ΔH等,并将其与熔炼法获得的样品进行对比,发现其热力学参数不受工艺过程的影响,仍然具有很好的热稳定性.同时,用Kissinger方程式对非晶粉末的晶化动力学进行了计算,得到了Tg和Tx的表观激活能.     

Fluorinated Phosphorene: Electrochemical Synthesis,Atomistic Fluorination,and Enhanced Stability

Phosphorene has attracted great interest due to its unique electronic and optoelectronic properties owing to its tunable direct and moderate band‐gap in association with high carrier mobility. However, its intrinsic instability in air seriously hinders its practical applications, and problems of technical complexity and in‐process degradation exist in currently proposed stabilization strategies. A facile pathway in obtaining and stabilizing phosphorene through a one‐step, ionic liquid‐assisted electrochemical exfoliation and synchronous fluorination process is reported in this study. This strategy enables fluorinated phosphorene (FP) to be discovered and large‐scale, highly selective few‐layer FP (3?6 atomic layers) to be obtained. The synthesized FP is found to exhibit unique morphological and optical characteristics. Possible atomistic fluorination configurations of FP are revealed by core‐level binding energy shift calculations in combination with spectroscopic measurements, and the results indicate that electrolyte concentration significantly modulates the fluorination configurations. Furthermore, FP is found to exhibit enhanced air stability thanks to the antioxidation and antihydration effects of the introduced fluorine adatoms, and demonstrate excellent photothermal stability during a week of air exposure. These findings pave the way toward real applications of phosphorene‐based nanophotonics.     

Buccal bioadhesive delivery system of 5-fluorouracil: optimization and characterization

The objective of this work was to apply the response surface approach in the development of buccal bioadhesive tablets of 5-fluorouracil (5-FU). Experiments were performed according to a 3(2) factorial design to evaluate the effects of two polymers, Gantrez MS-955 (X(1)) and hydroxypropylmethyl cellulose (HPMC) K15M (X(2)) on the bioadhesive force, percentage drug release in 8 h (Rel(8 h)), time taken for 50% drug release (t(50%)), and diffusion coefficient (n). The effect of the two independent variables on the response variables was studied by response surface plots and contour plots generated by the Design Expert software. The compatibility between 5-FU and the tablet excipients was confirmed by differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) studies. Both the polymers were found to have synergistic effect on bioadhesion but the effect of Gantrez was more pronounced. A nonlinear twisted relationship was obtained for Rel(8 h) at the intermediate and high levels of the polymers, which indicated an interaction between them at the corresponding factor levels. Kinetic treatment to the dissolution profiles revealed that the drug release ranged from Fickian to anomalous transport, which was mainly dependent on both the independent variables. The desirability function was used to optimize the response variables, and the observed responses were in agreement with the experimental values.     

2,6-二氨基-3,5-二硝基吡嗪-1-氧化物的热安全特性分析

采用差示扫描量热仪(DSC)对2,6-二氨基-3,5-二硝基吡嗪-1-氧化物(LLM-105)进行线性升温实验,分析其热分解特性。通过Kissinger和Friedman模型对DSC曲线进行动力学计算,并结合热平衡方程计算其绝热诱导期(TMRad)及自加速分解温度(θ_sad)。结果表明:LLM-105的初始分解温度、最高分解温度、分解完成温度均随着升温速率的增加而向高温方向移动,平均分解热为718.7 J/g。通过Kissinger模型计算得到的表观活化能为358.2 kJ/mol;而通过Friedman模型的计算曲线可知,LLM-105在不同反应阶段中具有不同反应。当绝热诱导期为2.0、4.0、8.0 h时,对应温度分别为296.8、290.7、284.7 ℃。当质量分别取5.0、15.0、25.0、50.0 kg时,自加速分解温度分别为267.0、265.0、262.0、259.0 ℃。随着包装质量的增加,分解放出的热量交换到周围环境中的难度就会越大,安全性也进一步降低。因此,在储存LLM-105时,必须控制一定的药品尺寸及良好的通风条件,以保证其储存安全。