In Situ Reaction Strengthening and Toughening of B_(4)C/TiSi_(2)Ceramics

B_(4)C-SiC-TiB_(2)ceramics were prepared by in situ reactive hot-pressing sintering with TiSi_(2)as an additive.The reaction pathways of TiSi_(2)and B_(4)C were investigated.The sintering was found to be a multistep process.The reaction started at approximately 1000℃,and TiB_(2)was formed first.Part of Si and C started to react at 1300℃,and the unreacted Si melted at 1400℃to form a liquid phase.TiSi_(2)predominantly affected the intermediate sintering process of B_(4)C and increased the sintering rate.Due to the unique reaction process of TiSi_(2)and B_(4)C,a large number of aggregates composed of SiC and TiB_(2)were generated.The results showed that composite ceramics with the optimal flexural strength of 807 MPa,fracture toughness of 3.2 MPa·m1/2,and hardness of 32 GPa,were obtained when the TiSi_(2)content was 10 wt%.

Reaction procedure of a graphite fiber reinforced Ti-Al composite produced by squeeze casting-in situ reaction

The in situ reaction procedure and microstructure evolution of a graphite fiber reinforced Ti-Al composite （Grf/Ti-Al） was investigated, and the stability of TiAl3 at high temperature was discussed. As-cast material was prepared by pressing molten pure aluminum into a preform, which was composed of titanium particles and graphite fibers. The in situ reaction procedure of the as-cast material was investigated by differential scanning calorimetry （DSC）, and phases in the products were detected by X-ray diffraction （XRD）. Experimental results showed that TiAl3 was formed first. With an increase in temperature, TiC and Al4C3 were observed, but TiAl3 decreased. In the final product, Al2O3 and TiO2 were observed. It was considered that the previous forming TiAl3 decomposed, then TiC precipitated, and subsequently, oxidation resulted in the formation of Al2O3 and TiO2.

Kinetics and Mechanism of Oxidation Induced Contraction of MgAl2O4 Spinel Carbon Composites Reinforced by Al4C3 in situ Reaction

Kinetics and mechanism of oxidation induced contraction of MgAl2O4 spinel carbon composites reinforced by Al4C3 in situ reaction were researched in air using vertical high temperature thermal dilatometer from 25℃to 1400℃.It is shown that oxidation induced contraction of MgAl2O4 spinel carbon composites reinforced Al4C3 in situ reaction is the common logarithm of oxidation time t and the oxygen partial pressure P inside MgAl2O4 spinel carbon composites reinforced by Al4C3 in situ reaction in air at 1400℃is as follows:P=F(-2.75×10^-4A+2.13×10^-3)lnt.The nonsteady diffusion kinetic equation of O2 at 1400℃inside the composites is as follows:J=De lnt.Acceleration of the total diffusional?flux of oxygen inside the composites at 1400℃is in inverse proportion to the oxidation time.The nonsteady state effective diffusion coefficient De of O2(g)inside the composites decreases in direct proportional to the increase of the amount of metallic aluminium.The method of preventing the oxidation induced contraction of MgAl2O4 spinel carbon composites reinforced by Al4C3 in situ reaction is to increase the amount of Al.The slag erosion index of MgO-Al2O3 spinel carbon composite reinforced by Al4C3 in situ reaction is 0.47 times that of MgO-CaO brick used in the lining above slag line area of a VOD stainless steel-making vessel.HMOR of MgO-Al2O3 spinel carbon composite reinforced by Al4C3 in situ reaction is 26.7 MPa,HMOR of the composite is 3.6 times the same as that of MgO-CaO brick used in the lining above slag line area of a VOD vessel.Its service life is two times as many as that of MgO-CaO brick.

ANALYSIS OF THE GROWTH MECHANISM OF TiAl_3 WHISKERS PREPARED BY IN SITU REACTION IN MOLTEN ALUMINUM

Some TiAl3 whiskers are found to be produced simultaneously during the formation process of TiB2 Particulates fabricated by in situ reaction in molten aluminum. The thec t of temperature of molten aluminum on the morphologies of the TiAl3 whiskers and the growth mechanism of the whiskers are studied in this paper. The results show that the aspect rutio of the TiAl3 whiskers decreases with the increase of the temperoture. The growth of the whiskers is proved to be controlled by a Vapor-LiquidSoltd (VLS) mechanism. The titanium and aluminum atoms in the catalytic droplet,however, have been coofrmed to react with each othen which is dtherent from other whlskcrs growing by a VLS mcchanism where the compostion in the catalytic droplet is a constant.

Combination of a reaction cell and an ultra-high vacuum system for the in situ preparation and characterization of a model catalyst

An in-depth understanding of the structure-activity relationship between the surface structure,chemical composition,adsorption and desorption of molecules,and their reaction activity and selectivity is necessary for the rational design of high-performance catalysts.Herein,we present a method for studying catalytic mechanisms using a combination of in situ reaction cells and surface science techniques.The proposed system consists of four parts:preparation chamber,temperatureprogrammed desorption(TPD)chamber,quick load-lock chamber,and in situ reaction cell.The preparation chamber was equipped with setups based on the surface science techniques used for standard sample preparation and characterization,including an Ar+sputter gun,Auger electron spectrometer,and a low-energy electron diffractometer.After a well-defined model catalyst was prepared,the sample was transferred to a TPD chamber to investigate the adsorption and desorption of the probe molecule,or to the reaction cell,to measure the catalytic activity.A thermal desorption experiment for methanol on a clean Cu(111)surface was conducted to demonstrate the functionality of the preparation and TPD chambers.Moreover,the repeatability of the in situ reaction cell experiment was verified by CO_(2) hydrogenation on the Ni(110)surface.At a reaction pressure of 800 Torr at 673 K,turnover frequencies for the methanation reaction and reverse water-gas shift reaction were 0.15 and 7.55 Ni atom^(-1) s^(-1),respectively.

Al-Si/Al_2O_3 in situ composite prepared by displacement reaction of CuO/Al system

Al2O3 particle-reinforced ZL109 composite was prepared by in situ reaction between CuO and Al2O3 . The microstructure was observed by means of OM, SEM and TEM. The Al2O3 particles in sub-micron sizes distribute uniformly in the matrix, and the Cu displaced from the in situ reaction forms net-like alloy phases with other alloy elements. The hardness and the tensile strength of the composites at room temperature have a slight increase as compared to that of the matrix. However, the tensile strength at 350℃ has reached 90.23 MPa, or 16.92 MPa higher than that of the matrix. The mechanism of the reaction in the CuO/AI system was studied by using of differential scanning calorimetry（DSC） and thermodynamic calculation. The reaction between CuO and Al involves two steps. First, CuO reacts with Al to form Cu20 and Al2O3 at the melting temperature of the matrix alloy, and second, Cu20 reacts with Al to form Cu and Al2O3 at a higher temperature. At ZL109 casting temperature of 750- 780 ℃, the second step can also take place because of the effect of exothermic reaction of the first step.

Microstructure and mechanism of in-situ Al_2O_(3(p))/Al nano-composites synthesized by sonochemistry melt reaction

The Al2O3（p）/Al nano-composites were fabricated from Al-K2ZrF6-Na2B4O7 system by sonochemistry in situ reaction. The fabrication mechanisms, including high intensity ultrasonic influence on microstructures and reinforcement particles-aluminum matrix interface, were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The XRD results show that the component of the as-prepared composites is Al2O3 reinforcement. The SEM analysis results indicate that Al2O3 particles are uniformly distributed in the aluminum matrix. The TEM results show that the morphologies of Al2O3 particles present in nearly sphere-shape, the sizes are in the range of 20-100 nm, and the interfaces are net and no interfacial outgrowth is observed. Analysis with secondary development Image-J software shows that Al2O3 recoveries are firstly improved and then decreased with increasing ultrasonic power. When the power is 0.4 kW, the distribution is the best, and a maximum number of particles are obtained. The reaction mechanisms were investigated.

Synthesis of C_f/TiAl_3 Composite by Infiltration-In Situ Reaction

Infiltration-in situ reaction synthesis of Cf/TiAl3 composite was investigated. The as-cast material was obtained by titanium particles, carbon fibers and pure aluminum. Titanium particles and carbon fibers were mixed and pressed to form a preform firstly, and then molten pure aluminum was pressed into the preform, subsequently, cooled rapidly. In situ reaction samples were obtained by heating the as-cast material from 600 to 1000℃ for I h. The microstructural evolution of in situ reaction samples was analyzed by scanning electron microscopy and energy dispersive X-ray. In addition, the phase composition of products was inspected by X-ray diffraction. Experimental results showed that the dominant product of TiAl3 and a small amount of Al4C3 were formed at low temperature. While TiAl3 was not stable at high temperature, along with its decrease, TiC phase became favorable. In the final products, TiAl3, TiC and Al4C3 were detected. Thus, the in situ reaction for Ti-Al-C system composite proceeded a formed-decomposed-precipitated mechanism.

Effect of Ti/B Additions on the Formation of Al_3 Ti of in situ TiB_2/Al Composites

A novel technique for fabricating TiB_2/Al composites in molten aluminum was introduced. The formation mechanism of brittleAl,Ti particulates up to 30 m in size produced in the composites was studied and a method of eliminating them was proposed. The resultsshow that (l) the brittle Al,Ti particulates are always present in the composites when the molar ratio of Ti to B 'T,:nB is l:2; and (2) theformation of the brittle Al,Ti phase can be avoided entirely from the final product by using a proper 'T,:nB of l:4 in the Ti-B-Al preforms.In the former case, the tensile elongation of the composite is only 4%, much lower than the value of pure aluminum (20%). In the latercase, the tensile elongation of this composite is 10%, higher than the value of the composite with a lot ofAl,Ti (4%), whereas the ultimatetensile stfength of the former is nearly that of the later.

Syntheses, Structures and Interactions with DNA of Two in situ Generated Palladium(Ⅱ) Complexes

Two new complexes [Pd（L-phe）2·2H2O] （1） and [Pd（4,4＇-dcbpy）（en）·H2O] （2） （L-phe = L-phenylalanine, 4,4＇-dcbpy = 2,2＇-bipyridyl-4,4＇-dicarboxylate, en = ethylenediamine） were synthesized and characterized. L-phenylalanine was in situ formed via the hydrolysis of N-（tert-butoxycarbonyl）-L-phenylalanine, and ethylenediamine came from the in situ reaction of piperazine （pip） under hydrothermal conditions. The single-crystal X-ray structure analyses reveal that the Pd（Ⅱ） ion constructs a square planer coordination geometry in complexes 1 and 2, respectively. Complex 1 extends into a 2D layered structure via H-bond interactions and complex 2 connects into a 3D network through hydrogen bonds and 7r-tr stacking interactions. The interactions of 1 and 2 with fish sperm DNA （FS-DNA） were examined via UV-Vis absorption spectra and fluorescence spectroscopy. The cleavage reaction for plasmid DNA has been assayed by agarose gel electrophoresis. The results indicate that two complexes interact with DNA and the insertion is the main binding mode.

Preparation of Poly ( L-lactic acid ) / Vermiculites Composites by in situ Copolymerization of Lactic Acid and Hydroxylic Vermiculites

L-lactic acid (L-LA) based copolymer/hydroxylation vermiculites composites (PLLA-co-bis A/HVMTs) were prepared by in situ reaction among L-LA, adipic acid, and hydroxylation lamellar vermiculites (HVMTs) using bisphenol-A epoxy resin as chain extending agent. HVMTs were obtained by sulfuric acid-leaching of lamellar vermiculites (VMTs). The effects of sulfuric acid leaching on the VMTs structure were characterized by X-ray diffraction (XRD), 29Si magic-angle spinning nuclear magnetic resonance(29Si NMR), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TGA). FTIR, FE-SEM, and TGA were used to characterize the reaction activity of HVMTs. The results indicated that VMTs with increased hydroxyl groups had been successfully obtained and could react with -COOH of the reaction system. The amount of L-LA based copolymer grafted on the surface of HVMTs was more than 22%. The onset decomposition temperature of L-LA based copolymer grafted on the surface of HVMTs was 30℃ higher than that of free L-LA based copolymer.

Microstructures and Mechanism of Al_2O_3/Al Composites Fabricated by the Reaction between SiO_2 and Molten Aluminum

Al 2O 3/Al composite was fabricated by the reaction between SiO 2 and molten aluminum.The microstructures of the composite obtained under different reaction conditions were analyzed. The formation mechanism of the composite microstructure was discussed. Results show that the reaction kinetics is influenced remarkably by the reaction temperature, reaction time and the quantity of SiO 2.The morphologies of Al 2O 3 have different features,depending on the reaction temperature.The composite has equiaxed Al 2O 3 grains when materials reacted below 1200℃,and the composite is composed of a large number of fine Al 2O 3 grains and aluminum.The composite has a frame shaped Al 2O 3 microstructure at the reaction temperature of above 1250℃.

In Situ High-Temperature Reaction-Induced Local Structural Dynamic Evolution of Single-Atom Pt on Oxide Support

The dynamic evolution of active site coordination structure during a high-temperature reaction is critically significant but often difficult for the research of efficient single-atom catalysts(SACs).Herein,we for the first time report the in situ activation behaviors of the local coordination structure of Pt single atoms(Pt_(1))during the high-temperature oxidation of light alkanes.The distinctly enhanced activity of the catalyst is attributed to the in situ evolved Pt_(1)−oxygen vacancy(Pt_(1)−OV)combination ensemble as an efficient and stable active site.Theoretical calculations reveal that the lattice oxygen adjacent to Pt_(1)and the H dissociated from CH4 constitute the lattice hydroxyl,which is the initial step in the formation of the Pt_(1)−OV combination.Pt_(1)and nearby unsaturated Mn can donate the charge back to O−O to promote the dissociation of O_(2).This work provides molecular-level insight into the in situ reaction-induced evolution of a single-atom coordination environment for designing efficient SACs under harsh conditions.

Competitive precipitation behavior of hybrid reinforcements in copper matrix composites fabricated by powder metallurgy

Copper matrix composites reinforced by in situ-formed hybrid titanium boride whiskers(TiB_(w))and titanium diboride particles(TiB_(2p))were fabricated by powder metallurgy.Microstructural observations showed competitive precipitation behavior between TiB_(w) and TiB_(2p),where the relative contents of the two reinforcements varied with sintering temperature.Based on thermodynamic and kinetic assessments,the precipitation mechanisms of the hybrid reinforcements were discussed,and the formation of both TiB_(w) and TiB_(2p) from the local melting zone was thermodynamically favored.The precipitation kinetics were mainly controlled by a solid-state diffusion of B atoms.By forming a compact compound layer,in situ reactions were divided into two stages,where Zener growth and Dybkov growth prevailed,respectively.Accordingly,the competitive precipitation behavior was attributed to the transition of the growth model during the reaction process.

Syntheses and Crystal Structures of Cd(Ⅱ) and Ni(Ⅱ) Complexes Containing Flexible Sulfide and Nitrogen Heterocyclic Ligands

Two new coordination polymers [Cd（EBLA）（ip）（H2O）] （1） and [Ni（EBSA） （im）2（H2O）], （2） were synthesized by hydrothermal and solution methods using 2,2＇-dithio- salicylicacid （EBSA）, lH-imidazo[4,5-f][1,10]phenanthroline （ip）, imidazole （im）, Cd（NO3）2-4H2O and Ni（NOa）z＇6H20. The complexes were characterized by elemental analysis and FT-IR. Meanwhile, the crystal structures, fluorescence properties of complex 1 and thermogravimetrie analysis of complex 2 have been studied. In complex 1, 2,2＇-dicarboxydiphenylthioether （EBLA） was prepared with 2,2＇-dithiosalicylicacid （EBSA） in situ reaction by hydrothermal method. Complex 1 is a dinuclear structure and Cd2＋ is five-coordinated in a distorted trigonal bipyramidal geometry. Complex 2 is a one-dimensional infinite linear chain and Ni2＋ is six-coordinated to form a distorted octahedral geometry. Hydrogen bonding and π-π interactions are observed in these complexes.

Syntheses, Structures and Fluorescent Property of Two Cd(Ⅱ) 3D Coordination Polymers with Mixed Ligands of Azide and Piperazine Derivatives

Two new coordination polymers, [Cd（N3）2（Baep）l/2]n （1） and [Cd2（N3）4（CH3OH）（Bapp）I/.2]n （2） （Baep = 1,4-bis（2-aminoethyl）piperazine, Bapp = 1,4-bis（3-aminopropyl）piperazine） were synthesized. The crystal of 1 is of monoclinic system, space group P21/c with a = 9.341（7）, b = 11.677（9）, c = 8.195（6） A, fl = 93.925（13）, V= 891.8（11） A3, Z= 4, μ（MoKa） = 2.42 mm-1, Mr = 280.58, Dc = 2.090 g/cm3, the final R = 0.0297 and wR = 0.0720. The crystal of 2 is of triclinic system, space group PI with a = 9.121（5）, b = 9.666（5）, c = 10.250（6） A, a = 72.91（2）, β= 77.10（2）, V = 73.95（2）°, V = 820.0（8）°, Z = 2,μ（MoKa） = 2.62 mm-1, Mr= 522.10, Dc = 2.114 g/cm3, the final R = 0.0251 and wR = 0.0632. Single-crystal X-ray diffraction studies reveal that 1 is a 3D structure based on a dinuclear unit {Cd2（N3）a（Baep）}, in which the Baep ligands formed in situ display two different bridging modes. Compound 2 also has a 3D structure based on a tetranuclear cluster {Cda（N3）8（CH3OH）2（Bapp）}, in which the azido anions exhibit four different bridging modes （μ-1,1, μ-1,3, μ-l,l,1 and μ-1,1,3）. The thermal stability and fluorescent property of 1 and 2 have also been investigated.

MECHANISM OF TiC FORMATION IN LIQUID ALUMINIUM

The mechanism of in situ formation of TiC phase in liquid aluminium during the contact reaction was studied in the present work. The results show that TiC phase forms through two reactions, i.e., 3Al＋Ti→Al3 Ti and Al3 Ti＋C→TiC＋3Al. Itis proposed that aluminium acts as a catalyst activating the reaction of TiC formation.

Reaction Processes of the Titanium Matrix Composites Fabricated from Ti-Al-B2O3 System

Titanium matrix composites reinforced with a-Al2O3 and TiB2 particles were fabricated by in situ synthesis from a Ti-Al-B2O3 system. The reaction processes and microstructure were analyzed by using differential scanning calorimetry（DSC）, scanning electron microscopy（SEM） and X-ray diffraction（XRD）. The results showed that the reactions in the Ti-Al-B2O3 system can occur spontaneously and consist of three steps： 1） 15 Al ＋ 7B2O3 → 7α-Al2O3 ＋ AlB12 ＋ 2B; 2） 14 B ＋ 2Al → AlB12 ＋ AlB2 and 3） 7Ti ＋ AlB（12） ＋ AlB2 → 7TiB2 ＋ 2Al. The final reinforcements were composed of α-Al2O3 and TiB2 particles, which were uniformly distributed in the titanium matrix.

Hepatitis C and B Virus Infection in Chinese Patients with Extrahepatic Bile Duct Carcinoma

Objective In China, the incidence of extrahepatic bile duct carcinoma (EBDC) tends to increase over the past decades. The etiology of the noted increase in EBDC is not identified. Approximately, in a half of the overall Chinese patients with EBDC, the causative factors in the development of EBDC have not been demonstrated.There is a high prevalence of hepatitis C virus (HCV) or hepatitis B virus (HBV) in China, both of which can induce malignant transformation of infected cells and strongly associated with hepatocellular carcinoma (HCC). In this study, EBDC tissues from Chinese patients were examined for the presence of HCV and HBV infection to investigate further the potential causes of EBDC.Methods HCV NS5 protein and HBsAg were detected by labeled streptavidin biotin (LSAB) method; HCV RNA and HBV DNA were detected by in situ polymerase chain reaction (IS-PCR) in formalin fixed, paraffin embedded specimens from 51 Chinese patients with EBDC. HCV RNA and HBV DNA were detected by IS-PCR in 34 Chinese patients with specimens of benign lesions of hepatobiliary tract (control group) .Results In 51 case tissue sections of EBDC, NS5 protein was detected in 14 (27.5%), and HBsAg in 5 (9.8%), HCV RNA in 18 (35.4%) and HBV DNA in 8 (15.9%) .respectively, of which HCV and HBV co-infection was detected in 2 (3.9%). In 34 case tissue sections of the control group, HCV RNA was detected in 2 (5.9 % ), and HBV DNA in 3 (8.8%).Conclusion In this study using standard histochemical and PCR techniques, HCV and HBV genomes and their encoding proteins were detected in the tissues of EBDC. The data show that there is a higher than expected incidence of HCV and HBV presence in EBDC tissues than would be expected on serologic grounds. The detectable rate of HCV RNA in EBDC tissues was significantly higher than in control group (x2 = 9.808, P = 0.002). As a result, this study indicates that there is a correlation between the presence of HCV infection and EBDC, and HCV infection has possible etiologic significance in the development of EBDC in China. While HBV DNA was detected in EBDC tissues with the difference in the detectable rate of HBV, DNA being not significance between EBDC tissues and the control group (x2 = 0.853, P = 0.356) . Further research is necessary to determine the presence of a causal relationship between HCV/HBV infection and the development of EBDC.

Investigation on Hepatitis C and B Virus Infection in Carcinoma of the extrahepatic bile duct in CHINA

Objective: The incidence of carcinoma of extrahepatic bile duct tends to increase during recent decade in China, but its cause is unclear. This study is to investigate the hepatitis C virus (HCV) and Hepatitis B virus (HBV) infection in the tissues of carcinoma of extrahepatic bile duct and study their correlation. Methods: HCV RNA and HBV DNA was detected by in situ polymerase chain reaction (IS-PCR) in sections of 51 cases of carcinoma of extrahepatic bile duct and 34 cases of control group. Results: Of 51 carcinoma of extrahepatic bile duct, HCV RNA was detected in 18 (35.4%), HBV DNA in 8 (15.9%). In 34 cases of control group, HCV RNA was detected in 2 (5.9%), and HBV DNA in 3 (8.8%). Conclusion:The prevalence of hepatitis C and B viralinfection in the tissues of carcinoma of extrahepatic bile duct was significantly higher than in control group. The findings suggest a correlation between HCV, HBV infection and carcinoma of extrahepatic bile duct, inferring HCV and HBV might be involved in the development of carcinoma of extrahepatic bile duct.