Effects of B2O3 on Crystallization,Structure, and Heat Transfer of CaO-Al2O3-Based Mold Fluxes

Metallurgical and Materials Transactions B - The reaction between traditional CaO-SiO2-based mold fluxes and high-Al steel inevitably changes flux composition, and, consequently, flux properties....     

Properties of Boron Suboxide B13O2

We describe for the first time a method for synthesis of boron suboxide under vacuum from a B₂O₃ + B mixture. We show that at 1420°C, under vacuum a boron suboxide phase of composition B₁₃O₂ is formed. The product is a highly disperse powder which, according to electron microscopy and crystal optics analysis, consists of agglomerates of various sizes with single-crystal particles mainly no larger than 2 m. We have used differential thermal analysis for the first time to study the reaction of crystalline boron with boric anhydride under vacuum and also in helium. We have shown that the temperature of onset of the reaction (B + B₂O₃) depends on the heating rate of the reagent mixture, and is practically independent of the reaction medium (1420°C). Compared with the original boron, the B₁₃O₂ powder has higher chemical stability in liquid reagents and thermal stability in air for isothermal and nonisothermal heating conditions. We wetted hot-pressed B₁₃O₂ samples with iron, nickel, copper, and tin melts. We have shown that B₁₃O₂ is readily wetted by iron and nickel at temperatures of 1200-1300°C, while it is practically unwetted by copper and tin at 1200°C and 900°C.     

Structure,strength, and wear resistance of materials of the system B4C-Al2O3

Translated from Poroshkovaya Metallurgiya, No. 6(318), pp. 89–95, June, 1989.     

The thermodynamic activity of MnO in melts containing SiO2, B2O3, and TiO2

The activity of MnO in the systems MnO-Ti₂ and MnO-B₂O₃, and in pseudobinary sections in the systems MnO-TiO₂-SiO₂, MnO-TiO₂-B₂O₃ and MnO-SiO₂-B₂O₃ have been measured at temperatures in the range of 1400 to 1550 °C by means of the technique in which equilibrium is established between the melt, a gaseous atmosphere of fixed oxygen pressure and a Pt-Mn foil immersed in the melt. The excess free energies of melts in the system MnO-TiO₂ at 1500 and 1550 °C are closely represented by the regular solution formalism withG _xs = −55280N _MnO ·N _{TiO 2} J, and the form of the variation ofa _MnO, within the narrow composition range amenable to study at 1400 °C in the system MnO-B₂O₃, is characteristic of a system of polyanions. The negative deviations ofa _MnO from a proposed model behavior, observed in melts in the systems MnO-SiO₂-TiO₂ and MnO-B₂O₃-TiO₂, are explained in terms of the influence of preferred ionic interactions between Ti₄₊ and O₂ and between Mn₂₊ and the O₋ groups on the polysilicate or polyborate anions. The activity of MnO is independent of composition in the system 2MnO · SiO₂−3MnO · B₂O₃ and the thermodynamics of mixing are calculated from application of polymer theory. The influence of B₂O₃ and TiO₂ on the activity of MnO in manganese silicates is discussed with reference to the proposed use of B₂O₃ and/or TiO₂ as substitutes for CaF₂ as the flux for steelmaking slags.     

Mechanical degradation and viscous dissipation in B2O3

CT often plays an important role in the evaluation of abdominal aortic aneurysms. Many vascular surgeons consider it an integral part of the preoperative assessment of aneurysms. CT is also used to examine symptomatic patients with possible aneurysmal ruptures when the diagnosis is unclear and to study patients with aortic grafts in whom potentially lethal complications, such as graft infection, aortoenteric fistulas, and anastomotic pseudoaneurysms, are clinically suspected. This paper reviews the current role of CT in the assessment of patients with abdominal aortic aneurysms.     

Synthesis,Luminescence and Magnetic Properties of YGa_(3-x)Cr_xB_4O_(12)

Ｓｙｎｔｈｅｓｉｓ，ＬｕｍｉｎｅｓｃｅｎｃｅａｎｄＭａｇｎｅｔｉｃＰｒｏｐｅｒｔｉｅｓｏｆＹＧａ３－ｘＣｒｘＢ４Ｏ１２ＹａｎｇＪｉａｎｍｅｉ（杨健美），ＳｕＱｉａｎｇ（苏锵）（ＬａｂｏｒａｔｏｒｙｏｆＲａｒｅＥａｒｔｈＣｈｅｍｉｓｔｒｙａｎｄＰｈｙ...     

B2O3在CaO-BaO-SiO2-Al2O3-CaF2精炼渣中的作用

选择w（CaO）=46％,w（BaO）=10％,w（SiO2）=11．2％,w（Al2O3）=11．6％的渣作基础渣系,将B2q作助熔剂替代CaF2,发现B2q和CaF2的助熔效果相当,B2q可用作环保型助熔剂。将CaO-SiO2-BaO-Al2O3-CaF2作基础渣系,B2O3作酸性氧化物,在碱度（m（CaO＋BaO）／m（SiO2＋B2O3））为2．5和2．8时,研究B2O3替代SiO2后精炼渣的熔化性能。结果表明,B2O3替代25％的SiO2后就可大幅度降低粘度,并且发现富硼精炼渣的高温熔化性能稳定,粘度值稳定在0．3～0．5Pa·s。在碱度为2．8wt进行脱硫工艺实验,当w（SiO2）=20．6％时渣剂脱硫率为80％,当w（SiO2）=10．3％,w（B2O3）=10．3％时渣剂脱硫率为91．3％,主要原因是熔化性能良好的熔渣有助于提高传质速率。     

Tailoring effect of Y2O3 on water resistance of Na2O-ZnO-Al2O3-B2O3 glasses

To explore the improving effect of Y₂O₃ on the water resistance of xY₂O₃-(100-x)(0.05 Al₂O₃-0.15 ZnO-0.15 Na₂O-0.65 B₂O₃)(x=0,0.7 mol%,1.4 mol%,2.1 mol%,2.8 mol%) glasses,glass structure and ion migration characteristics were respectively characterized by an infrared spectrometer and an electrochemical workstation.X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive Xray spect...     

X射线荧光光谱法测定Dy_2O_3及其杂质Eu_2O_3,Gd_2O_3,Tb_4O_7,Ho_2O_3,Er_2O_3和Y_2O_3

当前稀土应用范围越来越广,尤其Dy2O3和金属Dy其出口量不断增大．Dy2O3中所含杂质总量通常在0．1％～5％之间,该范围内的测定方法以XRFR为合适,快速、准确、无破坏．1实验部分1．l原理本法采用粉末直接压片法制样,在各元素分析线峰位上测量X射线强度,根据待测元素的X射线荧光光谱强度与含量的定量关系,选择相应的数学模型,由计算机自动计算出待测成份含量．1．2仪器和试剂荷兰飞利浦PW—1400顺序式X射线荧光光谱仪;康柏486计算机;电动小型油压机;万分之一精度分析天平．DyZO399．999％;EnD3,GdD3,ThAn,HoAn,ErD3…     

转炉终点氧含量预报模型

建立了两种转炉炼钢终点氧预报模型。即数学统计模型和神经网络模型。数学模型采用多元线性回归方法建模,该模型简单、可视,但预报效果不理想,预报误差小于80×10-6,命中率仅为72.7%。神经网络模型在选取适当输入参数的基础上,通过对现场生产数据进行训练,求得合理优化的网络权重,可对转炉终点氧含量进行离线预报,该模型的预报结果较好,预报误差小于80×10-6时,预报命中率超过86.4%。     

基于正交试验的环形炉炉温制度优化研究

建立了环形加热炉管坯加热过程数学模型,使用VB语言编写离线加热程序,并通过"黑匣子"试验验证该程序的准确性;然后,针对某钢厂低碳钢种(Φ=270 mm),加热时间为180 min,采用13因素3水平多目标的正交试验设计方法,对环形加热炉的炉温制度进行分析,并利用综合平衡法对试验结果进行权衡分析;最后,在满足工艺要求的前提下,给出了最佳炉温制度组合,经验证,在此炉温制度下,出炉管坯能满足工艺要求,并降低能耗0.6%左右。     

X射线荧光光谱法测定矾土中硅、铁、钾、钙、钛、锰、铝、镁、磷等氧化物含量

建立了X射线荧光光谱法测定矾土中硅、铁、钾、钙、钛、锰、铝、镁、磷等氧化物的方法。以四硼酸锂做熔剂、溴化锂做脱模剂制备玻璃熔片 ,以标准物质和高纯试剂制备标准片做校正曲线 ,并对吸收增强效应和光谱重叠做出校正。通过测定标准样品进行比较 ,本法没有显著性差异。回收率为 86.7%～ 10 6.2 %。     

Hepatitis B virus infection, hepatitis B vaccine, and hepatitis B immune globulin

Hepatitis B virus (HBV) infection is a major health problem in the United States; in 1995, approximately 128,000 cases occurred. Transmission of HBV occurs primarily by blood exchange (eg, by shared needles during injection drug use) and by sexual contact. Persons infected early in life are much more likely to become chronically infected than those infected during adulthood: as many as 90% of infants infected perinatally develop chronic infection and up to 25% will die of HBV-related chronic liver disease as adults. Clinical signs of acute hepatitis occur in about 50% of infected adults but in only 5% of infected preschool-aged children. In the United States, hepatitis B vaccine is currently made by recombinant DNA technology using baker's yeast. Preexposure vaccination results in protective antibody levels in almost all infants and children (> 95%) and healthy adults younger than 40 years of age (> 90%). The most common adverse event following administration of hepatitis B vaccine is pain at the injection site, which occurs in 13% to 29% of adult and 3% to 9% of children. A comprehensive hepatitis B vaccination policy is now recommended that includes (1) routine infant vaccination; (2) catch-up vaccination of 11- to 12-year-olds who were not previously vaccinated; (3) catch-up vaccination of young children at high risk for infection; (4) vaccination of adolescents and adults based on lifestyle or environmental, medical, and occupational situations that place them at risk; and (5) prevention of perinatal HBV infection.