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Mg-Al-NO_3层状双金属氢氧化物电性质研究 总被引:1,自引:0,他引:1
采用电泳法和电势滴定法测定出不同电解质(LiCl,NaCl和KCl)溶液中Mg-Al- NO_3层状双金属氢氧化物(Mg-Al-NO_3LDH)颗粒的ξ电位、等电点、永久电荷密 度以及零电荷点等电化学物理量,探讨了电解质、pH和样品化学组成对Mg-Al- NO_3LDH电性质的影响,研究发现一价阳离子Li~+,Na~+,K~+对Mg-Al-NO_3LDH颗粒 的等电点有影响,电荷点依次增大,而等电点依次降低。 相似文献
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Zn-Al类水滑石零净电荷点及等电点研究 总被引:1,自引:0,他引:1
用非均相共沉淀法合成了系列Zn-Al类水滑石(HTlc)样品,研究发现A1/(Zn Al)摩尔比(x)在0.31~0.52范围内可得到纯类水滑石相.用电势滴定法和显微电泳法分别测定了5个纯Zn-Al HTic样品的零净电荷点(PZNC)和等电点(IEP),以考察结构电荷对PZNC和IEP的影响.研究发现随结构正电荷密度的增加,PZNC和IEP均降低;IEP高于PZNC,且随结构正电荷密度的降低,IEP与PZNC的差值也降低,表明IEP与PZNC的差异来自结构电荷的影响.结构正电荷对HTlc的IEP与PZNC相对大小的影响与高价阳离子特性吸附的影响一致.初步探讨了结构电荷对PZNC和IEP的影响机理. 相似文献
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H. Wan-Guo S. De-Jun H. Shu-Hua Z. Chun-Guang W. Guo-Ting 《Colloid and polymer science》1998,276(3):274-277
In this paper, the thixotropy of the aqueous suspension consisting of aluminum magnesium hydroxide (AMH) possessing permanent
positive charges and Na-montmorillonite possessing permanent negative charges was studied. Besides positive thixotropy and
negative thixotropy, a novel thixotropic phenomenon was found, i.e., a given system studied may display, early and late, positive
M28.8nthixotropic character and negative thixotropic character, we describe it as “complex thixotropy”. The content of the
suspension and electrolyte may influence the forms of thixotropy of the suspension studied.
Received: 4 February 1997 Accepted: 15 October 1997 相似文献
5.
Montmorillonite dispersions were completely coagulated ¶by magnesium aluminum hydroxide when the hydroxide mass fraction, χ, was 0.2 or greater. The hydroxide dispersion required only a montmorillonite mass fraction of 0.06 for total coagulation. Thus, heterocoagulates were formed for 0.2<χ<0.94. At an excess of montmorillonite, network formation between the oppositely charged particles led to maxima of the yield value and the storage modulus at 0.4<χ<0.5. At higher hydroxide contents, χ>0.5, both properties decreased steeply, indicating the reduced mechanical stability of the network. Divalent anions at concentrations above 1 mmol/l acted as liquefying agents for the dispersed heterocoagulates. The specific surface area of the freeze-dried dispersions increased to a maximum value at χ = 0.65. The pore size distributions revealed that montmorillonite lamellae and hydroxide particles were not homogeneously distributed. 相似文献
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DongXiangLI WanGuoHOU ShuPingLI MingTuHAO GaoYongZHANG 《中国化学快报》2004,15(2):224-227
The relation of the isoelectric point (IEP) and the point of zero net charge (PZNC) of the hydrotalcite-like compounds was discussed. It was found that the IEP does not equal to the PZNC and the IEP is higher than the PZNC. The structural positive charges existing in the HTlc,which cause the difference between the IEP and the PZNC. The effects of the structural positive charges of the HTlc on its IEP and PZNC are the same as the specific adsorption of metal cations. 相似文献
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Suspension of a Tunisian purified smectite and American montmorillonite are studied by acid-base potentiometric and mass titrations.
These experimental methods are used to determine the point of zero net proton charge (PZNPC). A very good agreement is observed
between the two kinds of experiments. The two Namontmorillonites, studied at different ionic strengths, present proton adsorption
vs. pH curves with a common crossing point. The PZNPC of the edge sites are 8.02 for Tunisian purified smectite and 8.11 for
pure American montmorillonite. By analyzing the proton adsorption or desorption (H+ vs. pH) curves, one may assume the presence of four active sites at the surface. The montmorillonite surface undergoes two
successive protonations and two successive deprotonations. Below pH < PZNPC and in acidic range, the cation exchange at layer
sites and protonation of edge sites (>A1OH groups) occur simultaneously. For pH > PZNPC and in alkaline pH range, deprotonation
of surface hydroxyl groups exposed at the edge sites (>SiOH, and >A1OH at high pH) of montmorillonite platelets causes an
overall negative charge.
Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 2, pp. 175–187.
The text was submitted by the authors in English. 相似文献
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S. I. Pechenyuk 《Russian Chemical Bulletin》1999,48(6):1017-1023
The modern theoretical views on the point of zero charge of the oxide hydroxide surface are considered. Methods for determination
of the pH of the point of zero charge and the use of this value to characterize the properties of oxide hydroxides are described.
Examples of using the pH of the point of zero charge in studies of oxide anodes and amorphous oxide hydroxide sorbents are
presented.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1029–1035, June, 1999. 相似文献
10.
Study on the preparation and structure of positive sol composed of mixed metal hydroxide 总被引:3,自引:0,他引:3
S. -H. Han C. -G. Zhang W. -G. Hou D. -J. Sun G. -T. Wang 《Colloid and polymer science》1996,274(9):860-865
Using precipitation method mixed metal hydroxide (MMH) positive sol was prepared. The preparation process and the properties of the sol were studied with powder XRD, TEM, particle size distribution determination system and microelectrophoresis instrument.The preparation of MMH was made as follows: Diluted ammonia water was added to the mixed solution of aluminum and magnesium chlorides which was prepared in the molar ratio of 1 1 or 1 2, or 1 3; then the pH values of the suspension at different amounts of ammonia water were measured. After that, the precipitate was aged for 5 h in the mother solution at room temperature, and washed after filtering. Finally, the filter cake was peptized at constant temperature of 333 K.The results showed that 1) preparation reaction was completed in three steps, 2) pH value was decisive factor, and 3) both the contents of magnesium and the -potential of MMH sol particles increased with pH values and finally remained constant. The mechanism of the reaction was that magnesium ions intercalated Al(OH)3 crystal lattice, forming mixed metal hydroxide. The results also showed that positively charged MMH colloidal particle belonged to hexagonal system and three-layer superposition structure. 相似文献
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Suspensions of illite clay minerals samples of three different origins (American illite from Montana, It(Mo), Tunisian glauconite from Gafsa, It(Ga), and Tunisian illite — chlorite mixed layer from El Hamma, It(Ha)) were prepared. The Fourier Transform Infrared (FTIR) spectroscopy, X-ray Diffractometry (XRD), Electron Scanning Microscopy (SEM) and surface area measurements were used to characterize the three illite samples having different extent of isomorphic substitution. The layers have a permanent negative charge due to isomorphic substitutions and pH dependent charges on the surface hydroxyls on the edges. Surface speciation of these samples was investigated using continuous potentiometric titration and mass titration curves between pH 4 and 11 at 0.001 M, 0.01 M, and 0.1 M NaCl solutions at ambient temperature. The two methods revealed point of zero charge (PZC) of the amphoteric edges sites approximately similar to the purified samples, in the range ~7.5–8.5, ~8.2–8.7, and ~ 9.0–9.3 for It(Mo), It(Ha) and It(Ga), respectively. The PZCs of freshly prepared dispersions are higher than those reported in the literature indicating basic character of these samples (pH of equilibrium suspensions in distilled water were ~7.9–9). In the present study, the focus was on the surface charge characteristics. A simple SCM model approach is presented to explain the illite H+ adsorption data. Surface weak acidic sites and surface ionization constants were calculated from titration data using regression methods. Sites with pKa 1 int values of 6–6.7; 5.4–5.8; 6.1–6.6 and sites at pKa 2 int values of 9.2–9.9; 10.2–10.4; 9.3–10 for It(Mo), It(Ga) and It(Ha), respectively, were assigned to amphoteric Al-OH and/or Fe-OH and Si-OH groups on the edges of illite samples. 相似文献
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Magnesium aluminum hydroxide, the most important member of layered double hydroxides, was peptized by intense washing. The
particle diameter, 70–130 nm, depended on the temperature of aging the parent material. The electrophoretic mobility of the
particles decreased with increasing pH, from 3.7 × 10−8 m2/Vs at pH 5 to 0.5 × 10−8 m2/Vs at pH 12.3. An isoelectric point at pH∼7 was reached with the addition of 87 mmol/l NaSCN, 3 mmol/l Na2SO4 and Na2CO3, and 0.7 mmol/l Na2HPO4. The critical coagulation concentration for the 2% (w/w) dispersion was 88 mmol/l NaCl, 1.8 mmol/l Na2CO3, 1.4 mmol/l Na2SO4, and 1.2 mmol/l Na2HPO4 at pH∼7. The 2% dispersion at pH∼7 showed an almost Newtonian flow behavior. Yield values were developed after salt addition.
The 2% dispersion reached a yield value of 2 Pa at 100 mmol/l NaCl, 3 Pa at 100 mmol/l Na2SO4, and 5 Pa at 100 mmol/l Na2CO3. Sodium phosphate in comparison with the other salts showed a liquefying effect. The yield value increased to 3 Pa at 1–10 mmol/l
Na2HPO4 and decreased to 0.5 Pa at 100 mmol/l Na2HPO4.
Received: 28 February 2001 Accepted: 8 March 2001 相似文献
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The effects of temperature (373–1373 K) on the point of zero charge (PZC) and isoelectric point (IEP) of a red soil rich in kaolinite and iron minerals were studied. PZC values of the soil treated at 373 and 573 K indicated the presence of iron oxide. The soil calcined between 773 and 1173 K shows a PZC almost coincident with the respective values of kaolinite. At 1373 K, the PZC of the soil is nearer to the value of iron oxide. In the entire temperature range studied the PZC values were lower than the IEP values. An approach of PZC and IEP values was observed after a partial removal of iron oxide by the dithionite-citrate-bicarbonate (DCB) method. The analyses of the PZC and IEP values, of electron probe micro analysis (EPMA) data and of specific surface areas evidence a specific adsorption of iron oxide on kaolinite. Finally, the dissolution sequence of iron and aluminium contained in soil was determined using hydrochloric acid. 相似文献
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Hao‐Kai Peng XiaoXiao Wang Ting‐Ting Li Ching‐Wen Lou YanTing Wang Jia‐Horng Lin 《先进技术聚合物》2019,30(8):2045-2055
Isocyanate, polyether polyol, a flame retardant (10 wt%), and aluminum hydroxide/magnesium hydroxide (0, 5, 10, 15, and 20 wt%) are used to form the rigid polyurethane (PU) foam, while nylon nonwoven fabrics and a polyester aluminum foil are combined to serve as the panel. The rigid PU foam and panel are combined to form the rigid foam composites. The cell structure, compressive stress, combustion resistance, thermal stability, sound absorption, and electromagnetic interference shielding effectiveness (EMI SE) of the rigid foam composites are evaluated, examining the effects of using aluminum hydroxide and magnesium hydroxide. Compared with magnesium hydroxide, aluminum hydroxide exhibits superior performance to the rigid foam composites. When aluminum hydroxide is 20 wt%, the rigid foam composite has an optimal density of 0.153 g/cm3, an average cell size of 0.2466 mm, a maximum compressive stress of 546.44 Kpa, an optimal limiting oxygen index (LOI) of 29.5%, an optimal EMI SE of 40 dB, and excellent thermal stability and sound absorption. 相似文献
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Influence of pH on the thixotropy of magnesium aluminum hydroxide-kaolinite suspension 总被引:1,自引:0,他引:1
The influence of pH on the thixotropy of pure kaolinite suspension and magnesium aluminum hydroxide (Mg-AI-MMH)-kaolinite suspension was studied. The results show that the thixotropic type of pure kaolinite suspension was not affected by pH studied in the range of 3.60-12.00. The thixotropic type of Mg-AI-MMH-kaolinite suspension with mass ratio (R) value of MMH to kaolinite 0.029 transformed from complex thixotropy into positive thixotropy with increasing of pH in the range of pH 3.83-12.00, and the type of thixotropy of Mg-AI-MMH-kaolinite suspension with R = 0.129 transformed from positive thixotropy into complex thixotropy with increasing of pH in the range of pH 3.70-11.96. 相似文献
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Muhammad ShafiqTariq Yasin 《Radiation Physics and Chemistry》2012,81(1):52-56
Radiation crosslinking is generally used to improve the thermo-mechanical properties of the composites. A study has been carried out to investigate the effect of gamma radiation on the thermo-mechanical properties of linear low density polyethylene containing magnesium hydroxide (MH) and sepiolite (SP) as non-halogenated flame retardant additives. The developed composites are irradiated at different doses upto maximum of 150 kGy. Infrared spectra of the irradiated composites reveal the reduction in the intensity of O-H band with increase in the absorbed doses, thus indicates a distinct structural change in MH at higher doses. The thermogravimetric analysis results of unirradiated and composites irradiated at low doses (≤75 kGy) show two steps weight loss, which is changed to single step at higher doses with lower thermal stability. The melting temperature (Tm) and crystallization temperature (Tc) of irradiated composites are lowered with irradiation whereas Vicat softening temperature (VST) is increased. The increasing trend in gel content with increase in the absorbed dose confirms the presence of crosslinked network. The mechanical properties, results show significant improvement in the modulus of irradiated composites. The results also confirm that MH gradually loses its OH functionality with irradiation. 相似文献
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Dongmin An Lili Wang Yunhui Zheng Shuang Guan Xiaoyan Gao Yumei Tian Hongxi Zhang Zichen Wang Yanhua Liu 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,348(1-3):9-13
Hydrophobic magnesium hydroxide (Mg(OH)2) nanoparticles were successfully synthesized via a one-step solution precipitation method with octadecyl dihydrogen phosphate (n-C18H37OPO3H2, ODP) as a surface modifier. The ODP was used to control the growth of crystal in the c direction (direction perpendicular to the layers) and to modify the surface property of the Mg(OH)2 particles produced from the precipitation. Measurements of relative contact angle and active ratio indicated that Mg(OH)2 samples were hydrophobic. The samples were characterized by using field emission scanning electron microscope (SEM), X-ray diffraction (XRD), infrared analysis (IR). The mechanism of influence of ODP on the surface property and morphology of Mg(OH)2 was discussed. Furthermore, from the results of the thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) tests, it was confirmed that small amount of magnesium alkyl phosphate on the surface of Mg(OH)2 particles enhanced the thermal stability of the low density polyethylene(LDPE)/Mg(OH)2. 相似文献
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氢氧化镁分解动力学的研究 总被引:1,自引:0,他引:1
以硼泥为原料与硫酸反应制备出七水硫酸镁,以氢氧化钠为沉淀剂制备出符合标准HG/T 3607-2000的氢氧化镁.利用XRD,SEM和TEM对氢氧化镁进行了表征,DTA-TG对氢氧化镁的热分解动力学进行了研究.XRD结果表明:制备粉体为单一Mg(OH)2.SEM和TEM结果表明:样品为片状或针状纤维,片直径大小不一,在20~50 nm之间,针状纤维形状不规则,大小不一致,长度在20~100 nm之间.利用Kissinger法和Ozawa法计算出的氢氧化镁热分解反应活化能分别为135.14和141.61 kJ·mol-1.利用Coats-Redfern法和Dolye法判断氢氧化镁热分解反应机理函数为A1.5. 相似文献
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Functional polymers such as polyethylene grafted glycidyl methacrylate (PE-g-GMA) and ethylene-methyl acrylate-glycidyl methacrylate terpolymer (E/MA/GMA) were used as compatibilizers in the preparation of highly filled composites of polyethylene/magnesium hydroxide(PE/MH). Comparative studies were performed on the effect of magnesium hydroxide and stearic acid on the interface within polymer and magnesium hydroxide composites. The effect of polymeric compatibilizers on the properties of the composites was studied using tensile and impact tests, torque rheological analysis, differential scanning calorimetry and environmental scanning electron microscopy (ESEM). The microstructure of highly filled PE/MH composites changed after the addition of functional polymers. The mechanical properties of the composite material increased after compatibilization. The compatibilization processes of PE-g-GMA and E/MA/GMA were different. The grafted polymer was more compatible with polyethylene, which led to a polar polymer phase. In contrast, the tercopolymer tended to adhere to the surface of MH particles. 相似文献