盐卤硼酸盐化学 Ⅹ.MgO·2B2O3-MgCL2-H2O浓盐溶液在20℃时硼酸盐的结晶动力学研究

配制MgO·2B_2O—MgCl_2—H_2O浓盐溶液在20℃恒温静置过程中,第一阶段析出MgO·3B_2O_3·7H_2O,第二阶段析出2MgO·2B_2O_3·MgCl_2·14H_2O。采用一级和二级混合反应速率模型,用计算机对结晶动力学C_B—t实验曲线进行拟合,给出结晶动力学速率方程-r=-dC/dt-k(C-C_(平衡))~2+k’(C-C(平衡))。基于高硼浓盐溶液中硼氧配阴离子是以多粒子共存的设想,提出了这两种水合硼酸镁盐结晶反应过程的机制,结晶过程中溶液pH变化的测定结果证实了这一解释。     

盐卤硼酸盐化学 ⅩⅢ.2MgO·2B_2O_3·MgCl_2·14H_2O结晶动力学研究

对MgO-B_2O_3-MgCl_2-H_2O浓盐溶液结晶析出氯柱硼镁石(2MgO·2B_2O_3·MgCl_2·14H_2O)的动力学过程进行了研究。利用单纯形优化法配合Runge-Kutta微分方程组数值解法对实验数据进行处理,给出了结晶动力学方程。并对硼在溶液中的存在形式进行了讨论,提出了结晶反应机理,同时考察了温度和氯化镁浓度对结晶速率的影响。     

盐卤硼酸盐化学XIII;2MgO.2B2O3. Mgcl2.14H2O结晶动力学研究

本发明对MgO-B2O-MgCl2-H2O浓盐溶液结晶析出氯柱硼镁石(αMgO,αB2O3MgCl.14H2O)的动力学过程进行了研究, 利用单纯形优化法配合Runge-Kutta微分方程组数值解法对实验数据进行处理, 给出了结晶动力学方程, 并对硼在溶液中的存在形式进行了讨论, 提出了结晶反应机理, 同时考察了温度和氯化镁浓度对结晶速率的影响。     

盐卤硼酸盐化学XIII;2MgO.2B2O3. Mgcl2.14H2O结晶动力学研究

本发明对MgO-B2O-MgCl2-H2O浓盐溶液结晶析出氯柱硼镁石(αMgO,αB2O3MgCl.14H2O)的动力学过程进行了研究, 利用单纯形优化法配合Runge-Kutta微分方程组数值解法对实验数据进行处理, 给出了结晶动力学方程, 并对硼在溶液中的存在形式进行了讨论, 提出了结晶反应机理, 同时考察了温度和氯化镁浓度对结晶速率的影响。     

MgO·3B2O3·3.5H2O的合成、表征及其溶液Raman光谱分析

硼是具有独特化学行为的稀有亲氧元素，在自然界中主要是以无机硼氧酸和硼氧酸盐形式存在。在硼酸盐晶体中，硼以聚合硼氧配阴离子形式存在，其中配位数为３和４的硼原子比可以有所不同，这使得硼酸盐种类繁多，结构复杂多样。至今，人们在自然界和实验室已发现了４种六硼酸镁盐犤１，２犦：MgO·３B２O３·nH２O（n＝７．５，７，６，５），它们的分子结构中都含有犤B６O７（OH）６犦２－基团。最近，我们在硼酸盐化学系列研究中，利用复盐氯柱硼镁石在沸点温度下的硼酸溶液中的相转化，合成了一种新的六硼酸镁盐MgO·３B２O３·３．…     

盐卤硼酸盐化学V:合硼浓缩盐卤稀释过程中硼酸盐的行为

经日晒蒸发制得的高含硼浓缩卤水加水稀释时, 溶液的pH随稀释度增大而明显上升. 不同稀释度卤水在室温放置过程中,有不同的硼酸镁水合盐结晶析出. 采用加水稀释法已经从含硼浓缩卤水中得到多水硼镁石(2MgO.3B2O3.15H2O), 章氏硼镁石(MgO.2B2O3.9H3O), 六硼酸镁(MgO.3B2O3.7H2O)和氯柱硼镁石(2MgO.2B2O3.MgCl2.14H2O).     

盐卤硼酸盐化学 Ⅴ.含硼浓缩盐卤稀释过程中硼酸盐的行为

经日晒蒸发制得的高含硼浓缩卤水加水稀释时,溶液的pH随稀释度增大而明显上升.不同稀释度卤水在室温放置过程中,有不同的硼酸镁水合盐结晶析出.采用加水稀释法已经从含硼浓缩卤水中得到多水硼镁石(2MgO·3B_2O_3·15H_2O),章氏硼镁石(MgO·2B_2O_3·9H_2O),六硼酸镁(MgO·3B_2O_3·7H_2O)和氯柱硼镁石(2MgO·2B_2O_3·MgCl_2·14H_2O).     

MgSO4-H3BO3-H2O体系水热条件下结晶动力学

自然界中硼铁矿属于多元素(Ｆｅ、Ｂ、Ｍｇ)共生矿,使用价值很高,是我国未来硼资源的主要来源.根据我国硼铁矿品位低的特点,东北大学提出了硼铁矿高炉铁硼分离生产含硼生铁及富硼渣、富硼渣硫酸浸出一步法生产硼酸的火法工艺路线[1],矿石中的镁以硫酸镁的形式存在于母液中.母液经浓缩、过滤,主要成分为硫酸镁和硼酸水溶液,母液中硫酸镁和硼酸分离是目前急需解决的问题.当温度高于80℃时,硫酸镁在水中的溶解度随温度的升高而降低,硼酸的溶解度随温度的升高而增加[2].根据硫酸镁和硼酸的溶解度特点,在常温下将两者分离是不可能的,通过高温结晶…     

硼特效树脂吸附硼的动力学研究

采用动边界模型对硼特效树脂XSC-800吸附模拟废水中硼酸根离子的动力学进行了描述.采用有限浴方法考察了体系温度、搅拌速度、树脂粒径及溶液中硼酸根离子浓度对交换过程的影响,并得到了交换动力学总方程.确定了硼酸根离子的交换过程属颗粒扩散控制,交换过程的表现活化能为20.38kJ/mol,表观反应级数为1.661.     

盐卤硼酸盐化学 Ⅻ.MgO·3B_2O_3·7H_2O的热行为和脱水动力学

通过对合成MgO·3B__2O_3·7H_2O的热分析研究确定热脱水反应的阶段、温度和产物,给出脱水过程的热化学反应方程式.利用甲醇、水与三氧化二硼之间的酯化反应进行相分离,确定该化合物高温结晶化产物的物相组成为晶态六硼酸镁(2MgO·3B_2O_3)和无定形B_2O_3.对该化合物的TG和DTG数据进行处理结果,给出了相应的非等温热脱水反应动力学方程.     

盐卤硼酸盐化学XXX-MgO·2B2O3-18%MgCl2-H2O过饱和溶液结晶动力学

对ＭｇＯ．２Ｂ２Ｏ３－１８％ＭｇＣｌ２－Ｈ２Ｏ过饱和和溶液在不同温度条件下的结晶动力学过程进行测定,给出结晶动力学方程析出固相采用Ｘ－射线粉末衍射、红外光谱和热分析进行物相鉴定,提出使用结晶法合成章氏硼镁石的新方法。     

盐卤硼酸盐化学XXX-MgO·2B_2O_3-18%MgCl_2-H_2O过饱和溶液结晶动力学

对ＭｇＯ·２Ｂ_２Ｏ_３－１８％ＭｇＣｌ_２－Ｈ_２Ｏ过饱和溶液在不同温度条件下的结晶动力学过程进行测定,给出结晶动力学方程。析出固相采用Ｘ－射线粉末衍射、红外光谱和热分析进行物相鉴定。提出使用结晶法合成章氏硼镁石的新方法。     

Non-isothermal crystallization kinetics of poly(trimethylene terephthalate)/poly(ethylene 2,6-naphthalate) blends

The glass-transition temperature and non-isothermal crystallization of poly(trimethylene terephthalate)/poly(ethylene 2,6-naphthalate) (PTT/PEN) blends were investigated by using differential scanning calorimeter (DSC). The results suggested that the binary blends showed different crystallization and melting behaviors due to their different component of PTT and PEN. All of the samples exhibited a single glass-transition temperature, indicating that the component PTT and PEN were miscible in amorphous phase. The value of T_g predicted well by Gordon-Taylor equation decreased gradually with increasing of PTT content. The commonly used Avrami equation modified by Jeziorny, Ozawa theory and the method developed by Mo were used, respectively, to fit the primary stage of non-isothermal crystallization. The kinetic parameters suggested that the PTT content improved the crystallization of PEN in the binary blend. The crystallization growth dimension, crystallization rate and the degree of crystallinity of the blends were increased with the increasing content of PTT. The effective activation energy calculated by the advanced iso-conversional method developed by Vyazovkin also concluded that the value of E_a depended not only on the system but also on temperature, that is, the binary blend with more PTT component had higher crystallization ability and the crystallization ability is increased with increasing temperature. The kinetic parameters U^* and K_g were also determined, respectively, by the Hoffman-Lauritzen theory.     

Demarcation of reaction effects on laminar burning velocities of diluted syngas–air mixtures at elevated temperatures

Laminar burning velocities of CO₂/N₂ (60%, 70%) diluted H₂/CO/air mixtures were measured at elevated temperatures using the externally heated diverging channel method. The computed burning velocities using the two reaction mechanisms (Davis et al., Proc. Combust. Inst. 2005;30(1):1283–1292; FFCM-1, http://nanoenergy.stanford.edu/ffcm1 ) are compared with the experimentally determined burning velocities. The accuracy of the chemical kinetic mechanisms at high dilution rates and elevated temperatures was investigated for various hydrogen fractions in the fuel composition. The burning velocity is observed to increase at high temperatures due to higher mixture enthalpy. The dilution effect on the variation of laminar burning velocity was stronger for the CO₂ dilution case compared to N₂ dilution. A comparison between the FFCM-1 mechanism and experimental measurements shows an accurate depiction of the reaction chemistry regarding the prediction of laminar burning velocities. The role of third-body reactions and direct inhibiting effect of N₂ and CO₂ molecules on burning velocity of diluted syngas–air mixtures is analyzed in detail. Detailed kinetic analysis revealed that the use of GRI 3.0 collision efficiency factors in the Davis mechanism helps in accurately predicting the burning velocities at elevated temperatures and high CO₂ dilution rates. The thermal effect dominates the reduction in laminar burning velocity for N₂ dilution case. The FFCM-1 mechanism agrees well with the experiments for syngas flames diluted with N₂ compared to the Davis mechanism. The addition of third-body efficiency of N₂ in the FFCM-1 mechanism improved the predictions of laminar burning velocities for the N₂ dilution case.     

Ti基化学镀Ni-P和Ni-P-Cg镀层晶化动力学

利用化学镀技术在Ti基体材料表面制备了Ni-P合金镀层和Ni-P-Cg复合镀层。利用SEM、XRD和EDS等分析了镀层的晶化过程,用差热分析仪研究了Ni-P合金镀层和复合镀层的晶化动力学,运用Ozawa、Freeman-Carroll、Achar和Coats-Redfern方法对非等温动力学数据进行了分析和比较。结果发现,复合镀层的特征温度T_m和晶化激活能E均高于Ni-P合金镀层,而热焓值｜ΔH｜却低于Ni-P镀层;计算出Ni-P合金镀层和Ni-P-Cg复合镀层晶化激活能分别为308.9 kJ·mol^-1和412.99 kJ·mol^-1、指前因子A分别为58.03 s^-1和77.84 s^-1,确定了Ni-P合金镀层和复合镀层晶化动力学方程。     

MgO•3B2O3-18％MgSO4-H2O过饱和溶液结晶动力学

针对我国盐湖硼资源的特点,模拟合成MgO•3B2O3-18％MgSO4-H2O过饱和溶液,在20 ℃恒温静置,跟踪结晶动力学过程.析出固相采用X射线粉末衍射、红外光谱和热分析进行物相鉴定.拟合并给出结晶动力学方程,同时对结晶机制进行了探讨.结果表明,该结晶过程分两个阶段,第一阶段析出三方硼镁石（MgO•3B2O3•7.5H2O）,第二阶段结晶析出章氏硼镁石（MgO•2B2O3•9H2O）.     

Nonisothermal crystallization kinetics of isotactic polypropylene nucleated with a novel supported β-nucleating agent

The introduction of β-nucleating agent into isotactic polypropylene (iPP) is the most effective method to prepare β-iPP. In this paper, iPP nucleated with a novel highly efficient supported β-nucleating agent (NA100), calcium pimelate (CaHA) supported on the surface of nano-CaCO₃, was prepared and its nonisothermal crystallization kinetic, melting characteristic, and crystallization activation energy are investigated and compared with those of pure iPP, nano-CaCO₃ filled iPP, and β-nucleating agent CaHA nucleated iPP. The results indicate that addition of nano-CaCO₃ increases the crystallization temperature of iPP and has no influence on the crystal form of iPP. iPP and nano-CaCO₃ filled iPP mainly crystallize in the form of α-crystal. Although NA100 and CaHA induce iPP to mainly form β-crystal, NA100 nucleated iPP shows higher crystallization temperature, melting temperature, and β-phase content than that nucleated with CaHA without supports. Nonisothermal crystallization kinetic is well described by the equations of Avrami and Mo, and the crystallization activation energy was calculated from Kissinger’s method. It was found that the decreased crystallization activation energy is favorable to increase the crystallization rate and the content of β-crystal. Although the content of CaHA in 5 wt% NA100 nucleated iPP was less than that in 0.1 wt% CaHA nucleated iPP, the former formed more β-iPP than the latter, indicating that the β-nucleating agent CaHA supported on the surface of nano-CaCO₃ exhibits higher efficiency for preparation of β-iPP than pure CaHA powder.     

Chemistry of borate in salt lake brine (XXXIV)

The crystallization processes of hydrated Mg-borates, boric, magnesium hydroxide and Mg-oxychloride from MgO-B₂O₃-18%MgCl₂-H₂O supersaturated solution at 20°C have been studied by kinetic method. The crystallization solid phases were characterized by X-ray powder diffraction, IR spectra, thermal analysis and chemical analysis. The liquid-solid phase diagram of thermodynamic nonequilibrium state has been given. In this phase diagram, there exist eight crystallization fields, boric acid(H₃BO₃), trigomagneborite(MgO · 3B₂O₃ · 7.5H₂O, MgO · 3B₂O₃ · 7H₂O), hungchaoite(MgO · 2B₂O₃ · 9H₂O), inderite(2MgO · 3B₂O₃ · 15H₂O), chloropinnoite(2MgO · 2B₂O₃ · MgCl₂ · 14H₂O), magnesium hydroxide(Mg(OH)₂) and magnesium oxychloride (5Mg(OH)₂ · MgCl₂ · 8H₂O).     

Kinetics of nonisothermal crystallization of Cs2O–Fe2O3–P2O5 glasses

The crystallization kinetics of Cs₂O–Fe₂O₃–P₂O₅ glasses containing 12.5–27 mol% Cs₂O were studied by using differential scanning calorimetry under nonisothermal conditions. Strong dependence of activation energy with temperature was observed, indicating the complex nature of the crystallization process. The various crystallization products were identified by X-ray diffraction technique. CsFeP₂O₇ was found to be the major crystalline phase in all cases. The overall activation energy obtained by classical model-free kinetic method was compared with that of isoconversional method; and from the results, the dependence of activation energy on extent of reaction and average temperature was delineated.     

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION OF POLY (ETHYLENE TEREPHTHALATE) MODIFIED BY POLY (ETHYLENE GLYCOL)

The non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) modified by poly (ethlene glycol) (PEG) were determined by DSC. The dual linear regression method was used to evaluate the relationship between the reciprocal of t 1/2 ( the half life of crystallization) and the appropriate temperature variable. The parameters such as the activation energy (Ed) for transport, the equilibrium melting temperature (T_m~0),the nucleation parameter (ψ),themaximum crystallization temperature (T_(e, max)), and the kinetic crystallizability (G) for the copolyesters were obtained. The influence of the PEG content in PET chains on the parameters characterizing crystallization kinetics and crystallization thermodynamics was discussed.