石灰石晶形结构对煅烧石灰活性的影响

以具有不同晶形结构的两种石灰石原矿为研究对象,通过改变煅烧温度和保温时间获得不同活度的煅烧产物,借助X射线衍射分析煅烧产物的物相组成,依靠扫描电子显微镜观测其微观形貌,以酸碱滴定法测量其活度,考察原矿中石灰石结晶形貌对石灰石分解的影响。结果表明:层状结构的石灰石比颗粒状结构的石灰石具有更高的热分解温度,且分解速率较慢;在相同的煅烧条件下,前者的煅烧产物较后者具备更高的活性。在相同的煅烧温度下保温60 min时,Ca O晶体具有疏松的多孔结构并且存在大量的缺陷,此时的活度最高,活度值达到328.6 m L。

TiO_2形态结构与光催化活性关系的研究

本文介绍了 Ti O2 多相光催化剂的作用机理及其结构特性对光催化活性的影响 ,并对 Ti O2 的晶相组成、晶粒尺寸、比表面积、表面形态与光催化活性的关系作了综述。

聚丙烯-蒙脱土纳米复合材料性能的研究

采用熔融插层法制备了聚丙烯-蒙脱土纳米复合材料,并对复合材料的力学性能及晶形结构进行研究。结果表明:添加少量的纳米蒙脱土(<5%,质量分数),能够明显改善PP/MMT纳米复合材料的力学性能,当其质量分数达到4%～5%时,复合材料的冲击强度、断裂伸长率、拉伸强度及弹性模量均达最佳值。同时,随着蒙脱土含量的增加,聚丙烯的晶形结构会发生转变,其晶体尺寸呈不断减小趋势。

氧化锌溶胶的制备及防紫外线性能的研究

采用溶胶-凝胶法制备了氧化锌溶胶,探讨了溶剂、反应物浓度对溶胶稳定性、粒径的影响,及焙烘温度、焙烘时间、溶胶浓度对织物防紫外线性能的影响,并对织物进行了水热化处理。结果表明,以甲醇为溶剂制备的氧化锌溶胶平均粒径为86.2 nm,具有较好的稳定性;氧化锌溶胶整理织物最佳条件为:氧化锌溶胶浓度0.025 mol/L,浸渍5 min,焙烘温度为150℃,焙烘时间为10 min,处理后织物具有较好的防紫外线性能;氧化锌溶胶整理织物后经水热化处理,织物表面的氧化锌形成了晶形结构,防紫外线性能明显提升。

皂石矿物的合成工艺和性能简介

综述了皂石的合成方法,以及合成条件对皂石结构、性质的影响。合成方法包括水热合成法、微波辅助合成法以及非水热合成法。皂石的晶形、性质、形貌、纯度受原料和合成条件,比如温度、时间、初始p H以及聚合物的加入等因素影响。皂石的合成为粘土类矿物的形成机理,理化性质和相关的应用提供了更好的理解。

Effect of hot deformation conditions on grain structure and properties of 7085 aluminum alloy

The influences of deformation conditions on grain structure and properties of 7085 aluminum alloy were investigated by optical microscopy and transmission electron microscopy in combination with tensile and fracture toughness tests. The results show that the volume fraction of dynamic recrystallization increased with the decrease of Zener-Hollomon （Z） parameter, and the volume fraction of static recrystallization increased with the increasing of Z parameter. The strength and fracture toughness of the alloy after solution and aging treatment first increased and then decreased with the increase of Z parameter. The microstructure map was established on the basis of microstructure evolution during deformation and solution heat treatment. The optimization deformation conditions were acquired under Z parameters of 1.2×10^10-9.1×10^12.

Cooling rate dependence of polymorph selection during rapid solidification of liquid metal zinc

The polymorph selection during rapid solidification of zinc melt was investigated by molecular dynamics simulation. Several methods including g（r）, energy, CNS, basic cluster and visualization were used to analyze the results. The results reveal that the cooling rate has no observable effect on the microstructure as TTc（Tc is the onset temperature of crystallization）; and at the first stage of crystallization, although microstructures are different, the morphologies of nucleus are similar, which are composed of HCP and FCC layers; the polymorph selection of cooling rate finally takes place at the second stage of crystallization： at a high cooling rate, the rapid increase of FCC atoms leads to a FCC crystal mixed with less HCP structures; while at a low cooling rate, HCP atoms grow at the expense of FCC atoms, resulting in an almost perfect HCP phase. The results reveal that the cooling rate is one of the important factors for polymorph selection.

Hot deformation behavior and processing map of Cu-Ni-Si-P alloy

The high-temperature deformation behavior of Cu-Ni-Si-P alloy was investigated by using the hot compression test in the temperature range of 600-800 ℃ and strain rate of 0.01-5 s-1. The hot deformation activation energy, Q, was calculated and the hot compression constitutive equation was established. The processing maps of the alloy were constructed based on the experiment data and the forging process parameters were then optimized based on the generated maps for forging process determination. The flow behavior and the microstructural mechanism of the alloy were studied. The flow stress of the Cu-Ni-Si-P alloy increases with increasing strain rate and decreasing deformation temperature, and the dynamic recrystallization temperature of alloy is around 700 ℃. The hot deformation activation energy for dynamic recrystallization is determined as 485.6 kJ/mol. The processing maps for the alloy obtained at strains of 0.3 and 0.5 were used to predict the instability regimes occurring at the strain rate more than 1 s-1 and low temperature （〈650 ℃）. The optimum range for the alloy hot deformation processing in the safe domain obtained from the processing map is 750-800 ℃ at the strain rate of 0.01-0.1 s i The characteristic microstructures predicted from the processing map agree well with the results of microstructural observations.

Microstructure and texture evolution in titanium subjected to friction roll surface processing and subsequent annealing

Commercial purity and high purity titanium sheets were initially strained by a new technique, named as friction roll surface processing （FRSP）. Severe strain was imposed into the surface layer and strain gradient was formed through the thickness of the sheet. The microstructure and texture in as-strained state were investigated by optical microscopy and X-ray diffraction technique On the surface of the sheets, ultra-fine grains were found to have a sharp texture with a preferred orientation strongly related to the FRSP direction. The evolution of microstructure and crystallographic texture of FRSPed samples during recrystallization were also studied by electron back-scattered diffraction （EBSD） technique after being annealed at selected temperatures and time. The results indicated that the preferred orientations resulting from FRSP and annealing in the surface layer were formed during rolling and its recrystallization textures were reduced by FRSP. In addition, the texture evolved stably without change in main components during the annealing.

Effects of melt overheating degree on undercooling degree and amorphous forming of Nd_9Fe_(85-x)Ti_4C_2B_x(x=10, 12) magnetic alloys

The effectsof melt overheating degree on the undercooling degree and resultant solidification structures of Nd9Fe85-xTi4C2Bx（x=10, 12） glass-forming alloyswerestudied by differential thermal analysis combining with solidification structure analysis. The results indicate that the undercooling degree of Nd9Fe85-xTi4C2Bx（x=10, 12） alloys significantly increaseswith the rise of melt overheating degree, and two overheating degree thresholds corresponding to the drastic increase of the mean undercooling degree are found for each of the alloys. The existence of two turning points of the mean undercooling degreescan be linked to the structure transitions inside the overheated melts, which result in the evident increase of volume fraction of amorphous phasein the solidified structures.

Formation mechanism and crystal simulation of Na_2O-doped calcium aluminate compounds

Calcium aluminate clinkers doped with Na2O were synthesized using analytically pure reagents CaCO3, Al2O3, SiO2 and Na2CO3. The effects of Na2O-doping on the formation mechanism of calcium aluminate compounds and the crystal property of 12CaO·7Al2O3 (C12A7) cell were studied. The results show that the minerals containing Na2O mainly include 2Na2O·3CaO·5Al2O3 and Na2O·Al2O3, when the Na2O content in clinkers is less than 4.26% (mass fraction). The rest of Na2O is mainly doped in 12CaO·7Al2O3, which results in the decrease of the crystallinity of 12CaO·7Al2O3. The crystallinity of 2Na2O·3CaO·5Al2O3 is also inversely proportional to the Na2O content in clinkers. The formation processes of 2Na2O·3CaO·5Al2O3 and 12CaO·7Al2O3 can be divided into two ways, which are the direct reactions of raw materials and the transformation of CaO·Al2O3, respectively. The simulation shows that the covalency of O-Na bond in Na2O-doped 12CaO·7Al2O3 cell is weaker than those of O-Ca and O-Al bonds. The free energy of the unit cell increases because of Na2O doping, which results in the improvement of chemical activity of 12CaO·7Al2O3. The leaching efficiency of Al2O3 in clinker is improved from 34.81% to 88.17% when the Na2O content in clinkers increases from 0 to 4.26%.

Deformation characteristics and strain-compensated constitutive equation for AA5083 aluminum alloy under hot compression

The hot deformation behavior of AA5083 aluminum alloy was studied using isothermal compression tests with a Gleeble 3500 thermal simulator at strain rate of 0.0110 s 1 and at temperature of 300500°C.The experimental results indicate that dynamic recrystallization(DRX)tends to occur at high strain rates and temperatures,and therefore the flow stress is decreased.To predict the flow behavior under different deformation conditions,a strain-compensated constitutive equation based on Arrhenius-type equation and Zener Hollomon parameters was proposed.The flow stresses obtained from the constitutive equation are consistent with the experimental results.The average absolute relative error is only 4.52%over the entire experimental range,indicating that the proposed constitutive equation exhibits high prediction precision for the hot deformation behavior of AA5083 aluminum alloy.

Structural characteristics of spherical Ni(OH)_2 and its charge/discharge process mechanism

Spherical Ni（OH）2 particles were prepared by an aqueous solution precipitation route. The structure of spherical Ni（OH）2 was investigated by scanning electron microscopy and transmission electron microscopy and compared with that of traditional Ni（OH）2. The results show that the spherical nickel hydroxide consists of （Ni（OH）2） spheres with a reticulate structure of platelet-like, which is almost arranged radially and the crystalline grains intervene and connect with each other to form a three-dimensional net. The spherical Ni（OH）2 particle is full of pores, crannies between cleave planes. It is supposed that this structure is beneficial to the structural stability for the spherical particles during the charge/discharge processes and can improve the cycle life of the electrode; the pores and the crannies in spherical particles can shorten the proton diffusion distance and speed its velocity, which may result in that the local polarization is lowered. The electrochemical performances of the spherical Ni（OH）2 are improved by enhancing the conducting properties of the crystalline lattice due to its quick proton diffusion.

Crystal Growth,Structure and Morphology of Rifapentine Methanol Solvate

Rifapentine, an important antibiotic, was crystallized from methanol solvent in the form of its methanol solvate. The crystal structure of rifapentine methanol solvate belongs to monoclinic, space group P21, with the unit cell parameters of a = 1.2278（3） nm, b = 1.9768（4） rim, c = 1.2473（3） nm, Z= 2, and β = 112.35（3）. The parallelepiped.morphology was also predicted by Materials Studio simulation program.. The influence of intermolecular in-teraction was taken into account in the attachment energy model. The crystal shape fits the calculated morphology well, which was performed on the potential energy minimized model using a generic DREIDING 2.21 force fieldand developed minimization protocol with derived＇partial charges.

Microstructure evolution and hot deformation behavior of Cu–3Ti–0.1Zr alloy with ultra-high strength

The hot compression deformation behavior of Cu−3Ti−0.1Zr alloy with the ultra-high strength and good electrical conductivity was investigated on a Gleeble−3500 thermal-mechanical simulator at temperatures from 700 to 850℃ with the strain rates between 0.001 and 1 s^−1.The results show that work hardening,dynamic recovery and dynamic recrystallization occur in the alloy during hot deformation.The hot compression constitutive equation at a true strain of 0.8 is constructed and the apparent activation energy of hot compression deformation Q is about 319.56 kJ/mol.The theoretic flow stress calculated by the constructed constitutive equation is consistent with the experimental result,and the hot processing maps are established based on the dynamic material model.The optimal hot deformation temperature range is between 775 and 850℃ and the strain rate range is between 0.001 and 0.01 s^−1.

Effects of deformation parameters on microstructure and texture of Mg−Zn−Ce alloy

Compression tests were performed on the Mg−6Zn−0.5Ce(wt.%)alloy using a Gleeble−1500 thermomechanical simulator testing system at temperatures of 250,300,350℃ and strain rates of 0.001,0.01,0.1 s^−1.The microstructure and texture evolution of the Mg−6Zn−0.5Ce alloy during hot compression were investigated by optical microscopy(OM)and electron backscattered diffraction(EBSD).The results showed that Zener−Hollomon parameters obtained from the deformation processes had a significant effect on the dynamic recrystallization and texture of the Mg−6Zn−0.5Ce alloy.The fraction of undynamically recrystallized(unDRXed)regions increased,and the dynamically recrystallized(DRXed)grain size decreased with increasing the Zener−Hollomon parameters.The texture intensity of the DRXed regions was weaker compared with that in the unDRXed regions,which resulted in a sharper texture intensity in the samples deformed with higher Zener−Hollomon parameters.The increase in recrystallized texture intensity was related to preferred grain growth.

Microstructure and mechanical properties of TA15/TC11 graded structural material by wire arc additive manufacturing process

A graded structural material(GSM)with a material transition from TA15 to TC11 was fabricated by wire arc additive manufacturing(WAAM)method.The grain morphology,chemical composition,microstructure and mechanical properties of the as-deposited GSM were all characterized to investigate their variations along the deposition direction.The results indicate that from TA15 to TC11,the grain size decreases and a transition from columnar grains to equiaxed grains occurs.The content of alloy element alters greatly within a short distance,and the width of the mutation zone is 800μm.Both TA15 and TC11 regions exhibit basketweave microstructure withα-phase andβ-phase.However,during the transition from TA15 to TC11,theα-lath becomes fine,which leads to an increase in microhardness.The tensile test shows that the bonding strength at the interface is higher than the longitudinal strength of TA15,and the lateral elongation at the interface is higher than that of TA15 and TC11.

Rice Husk Ash:A New Silicon Source for Preparing SAPO-34 Catalysts Used in the Methanol-to-Olefins Reaction

SAPO-34 molecular sieves were synthesized directly by hydrothermal method with rice husk ash(RHA)used as the silicon source.The crystal structure,composition,surface morphology and acidity of the synthesized products weresieves had a high crystallinity,without any impure phase.Compared with the SAPO-34 prepared by the silica sol,RHA-SAPO-34 had similar acid properties in strength.The methanol to olefins(MTO)experiments showed that the SAPO-34molecular sieve synthesized from RHA exhibited both a good catalytic activity and ethylene selectivity.

FE-based coupling simulation of Ti60 alloy in isothermal upsetting process

A constitutive equation was proposed to describe the effect of grain size on the deformation behavior.And a coupling simulation of deformation with heat transfer and microstructure was carried out in isothermal upsetting process of Ti60 alloy.The effects of processing parameters on the equivalent strain,the equivalent stress,the temperature rise and the grain size distribution in isothermal upsetting process of Ti60 alloy were analyzed.It is concluded that the uniformity of equivalent strain and equivalent stress increases with the increase of deformation temperature.However,the temperature rise and the grain size decreases with the increase of deformation temperature.The non-uniformity of equivalent strain,equivalent stress,temperature field and grain size increases with the increase of height reduction.And the calculated grain size using simulation is in good agreement with the experimental one.

EBSD characterization of Al7075/graphene nanoplates/carbon nanotubes composites processed through post-deformation annealing

The effects of the post-deformation annealing on the microstructural evolution of hot rolled Al7075 matrix composites reinforced with CNTs and GNPs were investigated.The multi-pass hot rolling was applied on the stir cast samples.Annealing was then applied to the composites at 450℃ for 4 h.Microstructural evolution was examined by SEM,EDS,and EBSD techniques.EBSD data showed that the addition of 0.87 vol.%(GNPs+CNTs)significantly inhibited the occurrence of recrystallization.Also,in the composite with 0.96 vol.%CNTs,recrystallization was partially inhibited.Whereas,in composites with 0.92 vol.%of GNPs,the occurrence of recrystallization through particle stimulated nucleation(PSN)mechanism was significantly accelerated.The volume fraction of recrystallized grains depends significantly on the occurrence of PSN in the presence of reinforcements.The intensity and type of the main components of the texture as well as the FCC fibers depend on the type of reinforcement.