MICROSTRUCTURE AND PROPERTY OF Al/TiC COMPOSITES PREPARED BY REACTION SYNTHESIS

A novel in-situ process-Reaction Synthesis has been used to fabricate Al/TiC compos-ites,the phase constitute,microstructure and mechanical property of the Al/TiC composite have been investigated by the use of XRD and SEM.It has been shown that the reaction synthesized TiC particu-late is submicron in size(about 0.1~0.8μpm),spherical in shape and smooth in surface.In macrostruc-ture the distribution of the TiC particulate in matrix is homogeneous,but in micostructure there is micro-segregation of the TiC particulate at the intergrannular.The cast structure become fine because of the existence of the TiC particulate.In addition«with the increasing of weight percentage of TiC partic-ulate in alloy,the yield strength and ultimate tensile strength of the composite increase significantly«e.g.at 15%TiC,117% and 103% increase respectively,in the same time the elongation of the composite is still more than 4.5%.In the end,the analysis has been done by SEM on the fracture morphology of the composite.The results show that the fracture is ductility,and mainly because of the cluster of TiC particulate to intergrannular and the synthesis of bar morphology Al_(3)Ti.

Effect of Pressure and Temperature on Phase Transformation and Properties of Titanium Aluminide Obtained through Reaction Synthesis

Reaction synthesis process has been used to develop γ titanium aluminide using elemental powders. Powder mixture of Ti-48 at. pct AI was prepared in ball mill and reaction synthesis was carried out in hot press with varying temperature and pressure. Titanium aluminide synthesized under high pressure and temperature resulted in better properties with respect to densification, homogenization response, mechanical properties and oxidation resistance as compared to that synthesized under low pressure and temperature. AI rich phases were observed in as-synthesized condition in all the experiments. However, some Ti rich phases were also found in high pressure-temperature synthesized samples. Density, hardness and tensile strength have been correlated with applied pressure through empirical relations. Variation in density with pressure is found to be logarithmic whereas hardness and tensile strength variation with pressure is polynomial.

PHASES AND STRUCTURE OF PREFORM DURING PREPARING PROCESS OF Al／TiCp COMPOSITES BY DIRECT REACTION SYNTHESIS

Direct reaction synthesis(DRS), based on the principle of self-propagating hightemperature synthesis (SHS), is a new method for preparing particulate metal matrix composites (PMMCs). The effects of the temperature of the aluminum melt and the aluminum content in the preform on the phases and structure of the reacted preform have been investigated by X-ray diffraction and scanning electron microscopy.It has been shown that TiC phase is prone to be synthesized with the increasing of the temperature of the aluminum melt and the decreasing of the aluminum powder content in the preform, and that the size of TiC particle becomes fine with the increasing of the temperature and the decreasing of the aluminum powder content.

Reaction Mechanism,Synthesis and Characterization of Urea-glyoxal(UG) Resin

The reaction mechanism of glyoxal （G） with urea （U） under weak acid condition was theoretically investigated at PW91/DNP/COSMO of quantum chemistry using density functional theory （DFT） method. The results show that the addition reaction of G with U under the conditions mainly involves the reactions of U with protonated glyoxal （p-G）, protonated 2,2-dihy- droxyacetaldehyde （p-G 1） and protonated bis-hemdiol （p-G2） to form two important carbocation reactive intermediates of C-p-UG and C-p-UG1, and two important hydroxyl compounds of UG and UG1. These compounds play important roles in the formation of UG resin. According to the result of quantum chemical calculation, UG resin was synthesized successfully under weak acid conditions. The UG resin was characterized by matrix assisted laser desorption ionization time of flight mass spectrometry （MALDI-TOF-MS）, ultraviolet and visible spectroscopy （UV-vis）, Fourier transform infrared spectroscopy （FT1R） and nuclear magnetic resonance spectroscopy （13CNMR and 1HNMR）. These instrumental analytical results agree with each other and further confirm the addition reaction pathway of glyoxal with urea proposed by quantum chemical calculation.

Use of Magic Angle Spinning ~1H NMR Spectroscopy to Monitor Reactions in Solid-Phase Synthesis

Proton NMR-spectra of Wang resin bound compounds were obtained using the magic angle spinning 1HNMR technique with standard equipment. It was possible to analyse the spectra to evaluate their utility in solid-phase chernistry. A typical example was presented, which could directly monitor solid-phase reactions

NEW HETEROCYCLIC SYSTEM SYNTHESIS H THE REACTION OF 2,3-DIHYDRO-1,5-BENZOTHIAZEPINES WITH DICHLOROCARBENE

The reaction of two series of 2,3-dihydro-1,5-henzothiazepines Ⅰ with dichloro- carbene,gave azirino[2,1-d][1,5]benzothiazepines Ⅷ,azirino[2,1-e][1,6]benzothiazocines Ⅸ, pyrrolo[2,1-b][1,3]benzothiazoles Ⅹ,substituted-cyclopropanes Ⅺ and 2H-1,4-benzothiazin-2-ones Ⅻ.The structures of these products were confirmed by the analytical and spectral data.Compound Ⅷ and Ⅸ are two new ring systems.

Zeolite-Catalyzed Acetalization Ⅰ. Synthesis of Some Acetals and Ketals through Reaction of Carbonyl Compounds with Ethanediol

The acetalization of a series of carbonyl compounds with ethanediolwas performed over two self-steaxned HY zeolle catalpsts' The acetal and ketaiproducts were obtained with high ytelds Espectw, the HY zeollte with highfraxnework Si/A1 ratio was proven to be suitable cataipst for the acetabotion ofunsaturated carbonyl compounds, during which the C =C double bond was notperturbed

Al/TiO_(2) SELF-COMBUSTION SYNTHESIS REACTION

Al/TiO_(2) self-combustion synthesis reaction has been studied,including the effect of initial conditions of reactants on combustion temperature,combustion velocity and combustion stability etc.The reaction mechanism of Al/TiO_(2) self-combustion synthesis has been studied emphatically and the dynamic reaction model has been created.

NATURAL PRODUCTS SYNTHESIS BY RETRO-DIELS-ALDER REACTION Ⅷ~1 A CONCISE STEREOSPECIFIC FORMAL SYNTHESIS OF TETRAHYDROCHLOROVULONE

A potent antineoplastic tetrahydrochlorovulone 3 was synthesized with retro-Diels Alder reaction as a key step.

SYNTHESIS AND CARBON TRANSFER REACTIONS OF 12-DIMETHYL-3-ARYLSULFONYL (ARYL=p-TOLYL PHENYL)-△~2-IMIDAZOLINIUM IODIDE

As models of 5, 10-methenyl-tetrahydrofolate coenaymes imidazolinium salts 6a. b were synthesized and their carbon transfer reactions with several types of nucleophiles were studied.

A New One-Pot Synthesis of Macroheterocycles Using Mannich Reaction

Three N,N-heterylmethyl derivates of diaza-18-crown-6(I) are readily prepared by the reaction of (I) with paraformaldehyde and heterocyclic compounds in dry benzene.

REACTION OF ORGAINIC-TELLURONIUM YLIDE XI.A FACILE SYNTHESIS OF DERIVATIVES OF BISCYCLOPROPANE

Some telluronium salts react easily with 1,4-bis(3-substituted phenyl-3-oxo-1-propenyl)benzene and 1,5-disubstituted phenyl-1,4-pentadien-3 -one to afford derivatives of biscyclopropanes in 61.8-88.8% yield.

A FACILE SYNTHESIS OF 2-TRIFLUOROMETHYLPYRROLE VIA 1,3-DIPOLAR CYCLOADDITION REACTION OF 2-TRIFLUOROMETHYLOXAZOLONE AND THE ACTIVATED CARBON-CARBON MULTIPLE BOND

The 1.3-dipolar cycloaddition reaction of 2-trifluoromethyl- oxazolone and the activated carbon-carbon multiple bond was studied and gave a convenient way to synthesize 2-trifluoromethylpyrrole derivatives.

Research on development of in situ titanium matrix composites and in situ reaction thermodynamics of the reaction systems

The in situ synthesis method for titanium matrix composites （TMCs） has obvious technical and economical advantages over other traditional methods. Ultrafine reinforcement particles were formed in situ by chemical reaction between elements or between elements and compounds. Using the approach, contamination at the composite matrix/reinforcement particle interface did not occur, interface bonding was good, and the reinforcement particle was thermodynamically stable. The stage of development of the preparation process for in situ TMCs as well as the thermodynamic analysis of the possible in situ reaction systems was described.

Solid-state synthesis of Sr-and Co-doped LaMnO_3 perovskites

The synthesis process for La 1- x Sr x Mn 1- y Co y O 3- δ ( x = 0.2, 0.3; y = 0.2, 0.8, designated as LSMC below) perovskite oxides prepared by solid state reaction was investigated using DSC/TG, XRD, EPMA and particle size analysis methods. It was found that LSMCs were all of single phase and the synthesis process might be divided into three stages: the decomposition of reactants, the formation of LaMn(Co)O 3 based oxides, and the formation of LSMC solid solution. Typical average and the peak value of particle size, and the specific surface area are 14.65?μm, 16.4?μm and 1.38?m 2/mL, respectively, for mixed reactants and are 23.81?μm, 32.11?μm and 0.5?m 2/mL, respectively, for powder synthesized at 1?200?℃ for 8?h in air.

Synthesis and Crystal Structure of 2-Ethoxy-3-n-butyl-benzofuro [2,3-d]pyrimidin-4(3H)-one

The crystal structure of the new title compound 2-ethoxy-3-n-butyl- benzofuro[2,3d]pyrimidin-4（3H）-one （C16H18N2O3, Mr = 286.32） has been prepared and determined by singlecrystal X-ray diffraction. The crystal is of monoclinic, space group P21/c with a = 13.7167（14）, b = 13.113（1）, c = 8.378（1） A, β = 98.992（2）^o, V = 1488.4（3） A^3, Z = 4, Dc = 1.278, F（000） = 608, μ = 0.089 mm^-1, MoKa radiation （2 = 0.71073）, R = 0.0498, wR = 0.1238 for 2336 observed reflections with I 〉 2σ（I）. X-ray diffraction analysis reveals that all ring atoms in the benzo[4, 5]furo [2,3-d] pyrimi- dinone moieties are almost coplanar.

Synthesis of condensed polynuclear aromatic resin from furfural extract oil of reduced-pressure route Ⅱ

As an industrial byproduct of oil refining,furfural extract oil from reduced-pressure route Ⅱ with high aromatic content was used to prepare heat-resistant condensed polynuclear aromatic（COPNA） resin for the first time.The basic properties of furfural extract oil and the resultant COPNA resin were characterized by infrared spectroscopy（FT-IR）,nuclear magnetic resonance spectroscopy（1H-NMR）,thermogravimetric analysis（TGA） and elemental analysis（EA）.The result showed that heat treated furfural extract oil was successfully used for the synthesis of heat-resistant COPNA resin.The average structural parameters of raw materials and prepared resin were calculated by the improved Brown-Ladner method,and the averaged molecular structure of the resin was obtained.The reaction mechanism for the synthesis of COPNA resin was suggested as an acid-catalyzed positive ion type polymerization.

Synthesis and Electrical Properties of La_ 0.8Sr_(0.2)-x Ca_xCo_(0.9)Fe_ 0.1O_3-δ

Effects of small amount of Ca doping in La site in LaCoO 3-based oxide on th e synthesis and electrical conductivity were investigated by using X-ray diffra ction (XRD), differential scanning calorimetry and thermogravimetry (DSC/TG), or dinary four-probe dc measurement methods. La 0.8Sr 0.2-xCa x Co 0.9Fe 0.1O 3-δ (LSCCF, 0≤x≤0.1) prepared by solid r eact ion synthesis is all of a single phase and the calcined process may be divided i nt o three stages: (1) decomposition of reactants; (2) formation of LaCoO 3-based oxides; and (3) formation of LSCCF solid solution. The maximum of electrical co nductivity of the LSCCF composites is above 100 S·cm -1 and the co nduction me chanism is attributed to the adiabatic-hopping of p-type small polarons.

Synthesis Mechanism and High Temperature Chemical Stability of CaZrO3

CaZrO3 powder was prepared using CaO,CaCO3 and Ca(OH)2 as calcium source,nano m-ZrO2 powder,micron m-ZrO2 powder,micron CaO partially stabilized ZrO2(Ca-PSZ)powder as zircon source,through high temperature solid reaction.Effect of the calcination temperature(800,900,1000,1100,1200,1300,1400,1500,and 1600℃)and the holding time(3,4,and 5 h)on the phase composition change was studied to research the synthesis mechanism.The synthesized CaZrO3 powder was mixed with CaO,MgO,Al2O3,Cr2O3,SiO2,and ZrO2 powder separately and fired at 1500℃for 3 h to prepare specimens to research the high temperature chemical stability of CaZrO3 with different reaction mediums.The results show that during the synthesis process,the CaZrO3 content does not always increase with the increasing calcination temperature or the prolonging holding time,CaZrO3 decomposes resulting from the diffusion of Ca2+and O2-in CaZrO3 to m-ZrO2 or c-ZrO2.At high temperatures,when CaZrO3 is in alkaline environment(such as environment containing CaO or MgO),the high temperature chemical stability is high,but when CaZrO3 is not in alkaline environment(such as environment containing Al2O3,Cr2O3,SiO2 or ZrO2),the high temperature chemical stability is low.

Efficient Synthesis,Crystal Structure and Antibacterial Activity of Two Novel Thieno[2,3-d]pyrimidin-4(3H)-one Derivatives

Two new thieno[2,3-d]pyrimidin-4（3H）-one derivatives,C24H22 Cl N3O2S（5a） and C25H25N3O2S（5b）,have been synthesized via a tandem aza-Wittig reaction.This tandem reaction has many attractive aspects such as easily accessible and versatile starting materials,mild conditions and high yields.Both compounds have been characterized by elemental analysis,HR-MS,IR,NMR spectra and X-ray single-crystal diffraction.Compound 5a crystallizes in monoclinic,space group P21/c with a = 9.986（3）,b = 14.263（4）,c = 15.530（5）A,β = 93.806（5）o,V = 2207.1（11） A^3,Mr = 451.96,Z = 4,Dc = 1.360 g/cm3,F（000） = 944,μ = 0.294 mm-1,Mo Kα radiation（λ = 0.71073 A）,the final R = 0.0444 and w R = 0.1219 for 3407 observed reflections with I 〉 2σ（I）.Compound 5bcrystallizes in triclinic,space group P1 with a = 8.974（4）,b = 10.766（5）,c = 12.260（6） A,β = 93.047（7）o,V = 1122.1（9） A^3,Mr = 431.54,Z = 2,Dc = 1.277 g/cm3,F（000） = 456,μ = 0.170 mm-1,Mo Kα radiation（λ = 0.71073 A）,the final R = 0.0378 and w R = 0.1072 for 3806 observed reflections with I 〉 2σ（I）.The preliminary antibacterial activities of 5a and 5b were investigated.Compound 5a showed 71.3% and 79.2% in vitro inhibition against Fusarium oxysporium and Rhizoctonia solani,respectively.Compound 5b showed 75.3% in vitro inhibition against Rhizoctonia solani.