The influence of additives on the rheological and sensory properties of nonfat yogurt

In this work, response surface methodology was applied to a study of the effects of the addition of skim milk powder and stabilizers on the apparent viscosity and sensory attributes of nonfat yogurt. The addition of stabilizers has been shown to produce a significant effect on sensory attributes, while high concentrations of xanthan and guar gum are seen to decrease the overall acceptability of the yogurt, with gelatin producing the higher apparent viscosity and consistency. The correlation among apparent viscosity, which is an instrumental measurement, and consistency, which is a sensory evaluation, was 0.72.     

Polymorphism of Tricalcium Silicate and Its Solid Solutions

In tricalcium silicate and its solid solutions six modifications were established: one rhombohedral ( R ), two monoclinic ( M _I, M _II), and three triclinic ( T _I, T _II, T _III). All these forms are rhombohedral or pseudorhombohedral and extremely similar; the variations in the X-ray diagrams and the transformation enthalpies are minute. Only three of the five transitions were observed by both X rays and DTA: T _I- T _II (600°), T _III– M _I (980°), and M _I– M _II (990°); one was established by DTA ( T _II– T _III, 920°) and one by X rays only ( M _II– R , 1050°C). This scheme of polymorphism is compared critically with results of other authors, and the nature of the various displacive transformations is discussed. X-ray and DTA investigations of solid solutions of Ca₃SiO₅ with Al₂O₃ and ZnO established the phase relations as functions of temperature and composition. With Al₂O₃, two modifications ( T _I and T _II) were stabilized; and with ZnO, five polymorphs ( T _I T _II, M_I, M _II, and R ). With both pure C₃S and the solid solutions, the results are consistent and have a close bearing on the constitution of alites in portland cement clinker.     

A Ce-Nb-(Al) Oxide Porous Glass-Ceramic

Substitution of the end-member oxides in the ternary sodium borosilicate system diagram was studied. Replacing SiO₂ in this ternary system with a combination of CeO₂ and Nb₂O₅ was found to produce glasses which, after heat treatment, decomposed into two immiscible microphases of which one is water-soluble. The mode of phase decomposition is sensitive to impurities. The importance of crucible selection, e.g. Al₂O₃ or Pt/Rh, is demonstrated by differences in pore size, surface area, heat resistance, and structure of the insoluble phase for a series of Ce₂O₃-Nb₂O₅ and Ce₂O₃−Nb₂O₅−Al₂O₃ glass-ceramics. These new materials have a specific surface area of up to 217 m²/g and a pore radius of between 1.1 and 54.5 nm.     

高沉积率激光金属沉积Inconel 718的孔隙率控制

为降低高沉积率激光金属沉积(Laser Metal Deposition,LMD)工艺中材料的孔隙率,研究了以镍基高温合金Inconel 718(IN718)为粉末沉积材料的高沉积率LMD工艺中主要工艺参数对材料孔隙率的影响,以及通过调整工艺参数降低材料孔隙率的方法。以目标沉积率为2kg/h的LMD工艺为基础,通过参数固化和分离的手段开展了高沉积率LMD的镀层实验,研究了主要工艺参数即激光功率、扫描速度及送粉量对LMD镀层材料孔隙率的影响,分析了不同参数下各镀层的横截面孔隙率及镀层孔隙率。实验显示:当激光功率从1 440 W增加到4 214 W时,镀层材料的孔隙率从约1.5%降低至0.02%左右;当扫描速度为500mm/min至5 000mm/min时,镀层材料孔隙率始终保持为0.07%至0.18%左右;当送粉量从0.64kg/h增加至6.48kg/h时,镀层材料孔隙率从约0.01%增加至0.84%左右。可见在高沉积率LMD工艺中,扫描速度对材料孔隙率无明显影响,而提高激光功率、限制送粉量均可有效降低LMD材料孔隙率,提高横截面孔隙率的一致性。