VARIATIONS IN PYROMETRIC CONE EQUIVALENTS OF SILICA CEMENTS AND FIRE CLAYS1

In order to determine what variations might occur due to the method of preparing the sample for the pyrometric cone equivalent test a series of 100 silica cements and five fire clays were tested using the cement “as received,” ground to pass a 65-mesh Tyler screen, and after calcining a t 1400°C grinding to pass a 65-mesh Tyler screen. The pyrometric cone equivalent values were obtained by two operators, the cones being made by one operator. It was found that testing of silica cements “as received” gave closer checks than ground samples. The grinding of the sample lowers the pyrometric cone equivalent 1^1/2to 2 cones in general.     

A NOTE ON COMPARISON OF ENGLISH VS. ORTON PYROMETRIC CONES1

The English made pyrometric cones from 10–32 inclusive were compared to Orton cones for fusion values. The results are expressed in Orton cones. The work was done in a pot furnace and the comparison was intended to give values for this type of work. A drawing shows the position of English as to that of Orton cones.     

A COMPARISON OF THE SOFTENING POINTS OF SOME FOREIGN AND AMERICAN PYROMETRIC CONES1

This paper is a report of results obtained from a study of the softening points of pyrometric cones as made in England, France, Germany, and America. The results are briefly discussed and are also shown photographically so that interested readers can best obtain the specific information they desire from a study of these photographs. The data obtained further indicate that the temperature at which the cones most used in the trade (Nos. 1 to 20) soften can be determined with an accuracy of ±15°C in laboratory kilns of the gas-fired type, provided good pyrometric equipment is used and reasonable precautions are taken to maintain definite rates of heating. Errors of as much as ±25° can be expected in the determination of temperatures at which cones less refractory than No. 1 or more refractory than No. 20 soften. In the case of more refractory cones this is due principally to the difficulty of maintaining definite rates of heating while, in the case of the less refractory cones Nos. 022 to 01 inclusive, inaccuracies can be attributed both to difficulty of maintaining definite heating rates and to the sensitiveness of the softening behavior of the cones to furnace atmospheres. This is particularly true of the “red series” (cones 010 to 01) the softening points of which are materially affected by changes of a few per cent in the CO₂ and SO₂ content of furnace gases.     

POTASH–SODA–LIME FELDSPAR EUTECTIC STUDY*

An investigation was made of the fusion behavior of the potash feldspar, soda feldspar, and soda-lime feldspar system, all materials being of commercial grade. The potash feldspar had a pyrometric cone equivalent of cone 9½, the soda feldspar, cone 6½, and the soda-lime feldspar deformed at cone 11½. Mixtures varying according to the triaxial diagram were made in the form of pyrometric cones. These were fired in groups along with standard Orton cones. The 30% commercial potash feldspar-70% commercial soda feldspar mixture reached 6 o'clock deformation when standard Orton cone 6 showed 2 o'clock deformation. The mixture of 62½% commercial potash feldspar with 37½% soda-lime feldspar reached 6 o'clock deformation when cone 7 showed 1 o'clock deformation, the deformation of the cone 9½ potash feldspar being reduced 3 cones by the addition of the proper percentage of the cone 11½ soda-lime feldspar. There was an increase in deformation temperatures (no indication of eutectic) in the plagioclase series, soda feldspar to soda-lime feldspar. The mixture of 30% commercial potash feldspar, 60% commercial soda feldspar, 10% soda-lime feldspar showed 6 o'clock deformation when cone 6 showed 1 o'clock deformation, this being the lowest temperature at which any member of the system showed 6 o'clock deformation.     

冷冻解冻法破除液体石蜡W/O乳状液

冷冻解冻法是一种新型的破除W/O乳状液的物理破乳方法.为了揭示冷冻解冻破乳作用机制,本文以稳定性好的液体石蜡W/O乳状液为研究对象,采用差热扫描量热仪（DSC）与显微镜,研究了高黏度连续相液体石蜡体系的W/O乳状液的冷冻解冻破乳过程.结果表明：该破乳过程是一个渐进过程.当乳珠粒径均匀细小,小于5.5 μm时,乳珠在冷冻解冻循环中逐渐长大,经多次冷冻解冻后完成破乳;然而当乳珠粒径较大时,如51 μm,乳状液体系仅需单次冷冻解冻循环就可破乳较完全,破乳率超过90%.此外,乳状液含水量的增加有利于提高破乳效率.乳状液水相的凝固点受乳珠尺度的影响,但受含水量的影响不显著.当乳珠粒径较大时,水相凝固点随乳珠粒径的减小而降低;但是当乳珠粒径降至5.5 μm时,乳珠粒径的改变对其影响已不明显.     

Influence of Freezing Temperature on Product Parameters of Solid Dosage Forms Prepared via the Freeze‐Casting Technique

The freeze‐casting technique was used to formulate porous solid bodies containing theophylline as an active pharmaceutical ingredient, potato starch as a filler and citric acid or saccharose as binding agents. Aqueous suspensions of the ingredients were frozen at three different temperatures. The aim of this work was to investigate the influence of the freezing temperature on the ice crystal growth rate of the suspensions and the resulting porosity of the freeze‐casted samples. The impact of the freezing temperature on the solidification of the suspensions was analyzed via contact angle measurements. The rate of ice crystal growth was expressed as an overall linear growth rate. The porosity of the freeze‐casted bodies was determined by high‐pressure mercury porosimetry. A close correlation was found between the freezing temperature and the investigated product parameters. Lower cooling temperatures resulted in higher final porosities. The lowest temperature, at which final product properties could be regulated by varying the cooling regimes, was –30 °C. The influence of the freezing temperature and the impact of the additives were not remarkable at a freezing temperature lower than –30 °C. Therefore, it can be concluded that the optimum freezing temperature of the suspensions investigated in this study is in the temperature range between –20 °C and –30 °C.     

高浓度尿素废水泠冻浓缩极限

冷冻浓缩技术是处理尿素厂废水和尿液等高浓度尿素废水的有效方法之一,浓缩极限的确定则是预测和评价该工艺最高水回收率和工作效率的必要条件.以尿素溶液为研究对象,采用差示扫描量热技术分析了溶液在冷冻过程中的相态变化规律,通过冷冻试验确定了溶液发生尿素共晶析出时的浓度;以尿液为对象,研究了确定高浓度尿素废水冷冻浓缩极限的方法.研究结果表明：尿素废水在达到浓缩极限之前,当尿素浓度高于26.3%时,继冰晶析出之后会共晶析出尿素;尿素废水在浓缩极限处呈玻璃态,由差示扫描量热分析可确定废水玻璃化转变温度、推算冷冻浓缩工艺最高水回收率;尿液的玻璃化转变温度为-108.33 ℃,相应的溶液浓度为57.92%,冷冻浓缩可达到的最高水回收率为97.75%.     

Study of cryostructuration of polymer systems. XXI. Cryotropic gel formation of the water–maltodextrin systems

The freeze–thaw behavior of water solutions containing dissolved maltodextrin (MD; enzymatically converted potato starch derivative with MW of 8000 Da) over a wide range of MD concentration (0.1–15 g/dL) and freezing temperatures from ?24 to ?6°C was studied. Cryogenic treatment of these systems resulted in the formation of precipitates or gels, whose yield and thermal characteristics (fusion temperature and enthalpy) depended on the initial polymer concentration and conditions of freezing, frozen storage, and thawing. There appeared to be at least two stages to this process: (i) a rapid stage, when partial insolubilization occurred while the system was freezing, and (ii) a slower stage, the rate of which was dependent mainly on the thawing regimes used or the duration of storage at subzero temperatures. In this respect, the cryostructuration of MD was very similar to the freeze–thaw behavior of amylopectin/amylose and locust bean gum water solutions studied earlier. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1658–1667, 2002     

Calibration of Pyrometric Cones

Pyrometric cones produced by the Standard Pyrometric Cone Company (now known as The Edward Orton, Jr., Ceramic Foundation) were calibrated at the National Bureau of Standards in 1926. Cones available from the 1926 calibration were recalibrated, and new working standards were obtained by calibrating specimens of present production from the Orton Foundation. Heating rates of 150° and 60°C. per hour were used in determining the end points of a series of large cones, whereas a rate of 300°C. per hour was employed for the small cones through cone 12. The pyrometric cone equivalent (P.C.E.) series was calibrated and extended down to cone 12
.     

PYROMETRIC PROPERTIES OF SPODUMENE-FELDSPAR MIXTURES *

An experimental study is reported on pyrometric properties of mixtures of potash feldspar, soda feldspar, and spodumene. Numerical and graphic data show that the addition of spodumene to the feldspars up to 20% lowers the P.C.E. of the mixtures very rapidly. As spodumene is increased above 40%, the P.C.E. of the mixtures increases rapidly. By means of a triaxial diagram a considerable area is shown with P.C.E. values six to seven cones below those of the feldspars.     

冻融环境下GFRP管混凝土柱轴压性能试验研究

通过对21个玻璃纤维增强聚合物（GFRP）管混凝土柱和21个素混凝土柱分别在水溶液和质量分数为3.5 %的氯化钠（NaCl）溶液中进行冻融循环试验及轴压试验，且对冻融后的GFRP管混凝土柱进行了超声波检测，研究冻融环境下不同冻融介质和冻融循环次数对GFRP管混凝土柱轴压性能的影响。结果表明，冻融介质相同的情况下，随着冻融循环次数的增加，质量损失率增大，相对动弹性模量降低，GFRP管混凝土柱内异常点增多，承载力下降，极限应变下降；冻融次数相同的情况下，经盐冻作用的GFRP管混凝土柱轴压极限承载力降低更为明显。GFRP管混凝土柱盐冻循环150次后极限承载力下降了29.45 %，下降量是相同条件下水冻结果的2.19倍。盐冻循环后的GFRP管混凝土柱极限应变小于相同条件下的水冻循环极限应变。     

TEMPERATURE MEASURING CONES *

A series of pyrometric cones that measure temperature independent of the rate of heating has been developed. These cones are mixtures of inorganic salts and melt congruently. Melting-point data are presented for the three binary systems MgSO₄-Li₂SO₄, K₂SO₄-KBr, and Na₂SO₄-NaBr.     

Freeze Drying of Aluminum Nanoflakes from Cyclohexane Suspensions

Hydrophobic aluminum nanoflake slurries were freeze dried using varying freezing conditions, aluminum concentrations, and shelf temperatures. The effectiveness of using cyclohexane as a carrier to produce dry, de-agglomerated aluminum powders was determined from light scattering measurements. Significantly less aggregation was observed in the dried aluminum powders when cyclohexane was used as opposed to water, with most aggregation being prevented by freeze drying dilute aluminum slurries at low shelf temperatures. A significant increase in the primary rate of freeze drying was also observed when particles were dried from cyclohexane compared to particles dried from water.     

Freeze-cast honeycomb structures via gravity-enhanced convection

The effect of gravity on directional solidification was investigated in solution-based freeze casting. A preceramic siloxane-based polymer was freeze-cast with a cyclohexene solvent from two different directions: that against the direction of the gravitational force and that in concert with the gravitational force. Because the density of preceramic polymer is higher than the solvent, the segregated polymer creates a denser solution ahead of the freezing front than the underlying solution when the freezing direction is the same as the gravity direction. This results in convective flow in the liquid phase. This convective flow influences constitutional supercooling, which changes not only the pore size of freeze-cast structure but also the pore morphology from dendritic to cellular pores.     

EXERGY ANALYSIS FOR THE FREEZING STAGE OF THE FREEZE DRYING PROCESS

The mathematical expressions for exergy and the exergy analysis of the freezing stage of the freeze drying process are presented. The exergy analysis indicates that very substantial reductions in the magnitudes of the total exergy loss and of the exergy input due to the heat that must be removed during the freezing stage, can be obtained when the freezing stage is operated through the use of a rational distribution in the magnitude of the temperature of the cooling source. The rational distribution in the magnitude of the temperature of the cooling source should provide significant savings in the utilization of energy during the freezing stage of the freeze drying process as well as satisfactory freezing rates that form ice crystals that are continuous and highly connected and their shape and size are such that the pores of the porous matrix of the dried layer generated by sublimation during the primary drying stage, have a pore size distribution, pore shape, and pore connectivity that are appropriate to allow high rates for mass and heat transfer during the primary and secondary drying stages of the lyophilization process.     

Differential scanning calorimetry investigation of formation of poly(ethylene glycol) hydrate with controlled freeze–thawing of aqueous protein solution

The formation of poly(ethylene glycol) (PEG) hydrate during freeze–thawing of dilute lactate dehydrogenase solutions with the addition of 0.05–160 mg/mL PEG 6000 is investigated by differential scanning calorimetry and modulated temperature differential scanning calorimetry. The freeze–thawing process is performed with a controlled temperature history. A moderate cooling rate to a low freezing temperature in combination with a low heating rate seems to create the most stable PEG hydrate. The maximum amount and the most stable hydrate phase are obtained when the freezing temperature is at or below ?60°C. The enthalpy of melting for the hydrate at ?15°C is dependent on the heating rate but not on the cooling rate if the freezing temperature is ?60°C. The effect of the addition of reduced form nicotinamide adenine dinucleotide to the PEG and protein solution indicates that competing interactions with the protein can increase the stability of the PEG hydrate. The amount of bound water in the PEG hydrate can be calculated directly from the melting enthalpy of the hydrate if an adequate temperature history is used. For solutions with >10 mg/mL PEG there are 1.7–2.7 water molecules bound per PEG unit. The PEG protection of the protein at freeze–thawing can be an effect of the amount of available PEG hydrate in relation to the amount of ice surface. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1626–1634, 2004     

Durability of wood flour‐plastic composites exposed to accelerated freeze–thaw cycling. Part I. Rigid PVC matrix

This study examined the effects of accelerated freeze–thaw actions on the durability of wood fiber‐plastic composites. Rigid PVC formulations filled with various concentrations of wood flour (both pine and maple) were processed in a counterrotating twin‐screw extruder and exposed to cyclic freeze–thaw actions according to ASTM Standard D6662. Freeze–thaw cycling was also modified by omitting portions of the test (either the water or freezing) to verify whether or not moisture was the primary cause for property loss. The durability of exposed samples was assessed in terms of flexural properties, density, and dimensional stability. Scanning electron micrographs of unexposed and freeze–thaw‐exposed samples were taken to qualitatively evaluate the interfacial adhesion between the wood flour and PVC matrix. The experimental results indicated that the density was not affected by freeze–thaw cycling. The dimensional stability was also relatively unaffected, although greater wood flour content exhibited greater dimensional change. The loss in stiffness of the composites was statistically significant after only two freeze–thaw cycles, regardless of both the wood species and content. Conversely, the strength of the composites was not significantly affected by five freeze–thaw cycles at lower wood flour contents (50 and 75 phr). The deleterious effects of the freeze–thaw actions on the strength of the composites became apparent at higher wood flour content (100 phr) after only two freeze–thaw cycles for maple flour and five freeze–thaw cycles for pine flour. The property loss was attributed primarily to the water portion of the cycling, which appears to have led to the decreased interfacial adhesion between the wood flour and the rigid PVC matrix. J. VINYL. ADDIT. TECHNOL. 11:1–8, 2005. © 2005 Society of Plastics Engineers.     

Preparation of Silver Nanopowder by Freeze-Drying Procedure

A freeze-drying procedure is developed for manufacturing silver nanopowder with regular shape and uniform diameter. The procedure includes four steps: preparing the precursor solution, freezing the solution, drying the congelation, and calcining the drying product. The starting substances are silver nitrate and caustic soda and the precursor is diammine silver solution. Three freezing styles including direct freezing, vacuum evaporation freezing, and spray freezing are adopted to freeze the precursor solution. In the drying stage, two heating styles for the frozen solution are compared. X-ray diffraction (XRD) and energy disperse spectroscopy (EDS) spectrograms show that the products of freeze drying are pure amorphous silver nanopowder without hard agglomerations. Silver cubic nanocrystals are subsequently obtained by calcination. The chemical fundamentals and the drying curves of freeze drying are given. The processes of preparing silver nanopowder are described in detail. The effect of freezing and heating on characteristics of the powder are discussed. The mechanism of grain forming and growing up is analyzed according to the observation results. The characteristics of powder freeze drying and its feasibility for volume production are presented.     

Microstructural Evolution of Nanoparticle Aqueous Colloidal Suspensions During Freeze Casting

This study is focused on the microstructural evolution of Al₂O₃ nanoparticle aqueous suspension during freeze casting. Freeze casting aid glycerol plays an important role in avoiding large cleavage-type fracture while undesirably lowering nanoparticle packing for freeze-cast samples. "Fines" effect influences freeze-cast surface nanoparticle packing. Trapped air bubbles in the suspension result in porous bulk microstructures if not allowed to escape from the suspension before freezing by prerest. Maintaining relatively open surface nanoparticle packing before freezing is critical in removing the air bubbles and achieving dense microstructures after freeze casting.     

预冻在冻干过程中的作用简

预冻环节中降温速度、冻结温度、冻结时间都是重要的工艺参数,它们互相作用,影响着冻结体的结晶情况,最终会对冻干过程形成决定性的影响。本文通过实例,介绍了预冻过程中冻结速率对冻干结果的影响。说明适当的预冻参数可大大提高冻干效率和产品质量。