Herbert A. McKinstry

Structural model for thermal expansion in MZr2P3O12 (M=Li, Na, K, Rb, Cs)

A structural model is proposed to describe the highly anisotropic thermal expansion in the sodium zirconium phosphate NaZr2P3O12 structure as a result of the thermal motion of the polyhedra in the structure. In the proposed model the rotations of the phosphate tetrahedra are coupled to the rotation of the zirconium octahedra. Of the two versions considered, the first one allows angular distortions to occur only in the ZrO6 octahedra; the second one permits all polyhedra to be distorted.

Low thermal expansion of alkali-zirconium phosphates

Abstract The thermal expansion of all the alkali members of the [NZP] family has been studied using high-temperature x-ray measurements at the back diffraction angles and dilatometry. The discrepancy between the results obtained with both methods is discussed. Some of the phases studied showed very low thermal expansion coefficients (

Thermal expansion behaviour of M′Ti2P3O12 (M′=Li, Na, K, Cs) and M″Ti4P6O24 (M″=Mg, Ca, Sr, Ba) compounds

The [NZP] family has been attracting considerable attention because of its potential in thermal shock-resistant applications. The compounds M′Ti2P3O12 (M″=Li, Na, K, Cs) and M″Ti4P6O24 (M″=Mg, Ca, Sr, Ba) belong to this new family of low-expansion materials. The results of a systematic study undertaken to investigate the thermal expansion behaviour of these materials are reported. A correlation between the ionic size and lattice expansion was also attempted, and compounds possessing lowest bulk thermal and low anisotropy were identified.

Ultra low thermal expansion phases: Substituted ‘PMN’ perovskites

Abstract Among different principles which can be utilized in a structure to exhibit anomalously low thermal expansion, a ‘distributed’ phase transition is a candidate. Pb(Mg 1 3 Nb 2 3 ) 3 is a well known relaxor ferroelectric material in which such a transition occurs. The change in thermal expansion of PMN ceramics caused by partially substituting various ions at the B-site has been studied in order to see any new low expansion materials with good electrostriction properties exist. Partial ionic substitution of Ni 2+ , Co 2+ , Zn 2+ , Mn 2+ , Cd 2+ , Fe 3+ , Sc 3+ , Ti 4+ , Sn 4+ , Hf 4+ , Zr 4+ , and W 6+ was made at B-site. The sintering temperature was kept at 1250° for 1 hour. Thermal expansion data and their interpretations are presented.

New [NZP] materials for protection coatings. Tailoring of thermal expansion

Abstract[NZP] (the NaZr2P3O12-Family) materials can be selected for synthesizing new thermal shock resistant ceramic coatings with a thermal expansion that can be tailored to match that of the substrate, and to possess a low thermal expansion anisotropy. The tailoring technique will involve the selection of a suitable pair of compositions which, upon being mixed to form a crystalline solution, will possess the desired thermal expansion coefficient and will have negligible thermal expansion anisotropy. This can be done when the axial thermal expansion for one end member is larger in the a-direction than in the c-direction and vice versa for the other end member.

Synthesis and thermal expansion behavior of Ba 1+x Zr 4 P 6−2x Si 2x O 24 and Sr 1+x Zr 4 P 6−2x Si 2x O 24 systems

NaZr 2 P 3 O 12 (NZP) is emerging as an important family of a large number of isostractural compounds in which several members have demonstrated very low thermal expansion characteristics. Ba 1+x Zr 4 P 6−2x Si 2x O 24 and Sr 1+x Zr 4 P 6−2x Si 2x O 24 crystalline solutions are two such systems belonging to the NZP family. Here, we report the bulk thermal expansion and axial thermal expansion behavior of various compositions in these systems. The low expansion behavior of these materials is attributed to their unique crystal structure, which is framework open structure, and can accommodate numerous ionic substitutions at various lattice sites.

Microstructure and microcracking behaviour of barium zirconium phosphate (BaZr4P6O24) ceramics

Barium zirconium phosphate (BaZr4P6O24), a member of a new family of low-thermal-expansion materials known as NZP, was synthesized by the solution sol-gel method, and sintered ceramics were prepared at 1100–1600 °C. The effect of sintering parameters such as time and temperature on the microstructure and phase composition was studied. BaZr4P6O24 is known to possess anisotropy in its axial thermal expansions, which usually causes microcracking in the sintered bodies when cooled. The microcracking activity of the sintered samples was examined by acoustic emission measurements.

Computer processing of SEM images by contour analyses

Abstract Techniques involving the computer processing of scanning electron microscope (SEM) images using a contour approach have been developed. For each picture from one to six different SEM signals are converted from analog to digital form and recorded on magnetic tape for subsequent computer analysis. A program finds and analyzes coordinate arrays representing the reconstructed computer picture. Least squares fitting of the contour arrays to ellipses provides measurements of the aspect ratios and orientations of the picture fields. Line integration techniques produce areas and perimeters. Computer plotting enables both the visual comparison of the reconstructed picture with a photograph of the image on the cathode ray tube of the SEM and an estimate of the accuracy of the ellipse fits.

A simple laser speckle dilatometer for thermal expansion measurements

Abstract A simple laser speckle method utilizing a 4 mW HeNe laser for thermal expansion measurements is described. The method utilizes the rotation of a probe kept on the sample and reference rods. For 5 cm long sample and reference rods kept 0.5 cm apart, a measurement sensitivity of 5 × 10−6 for ΔL L can easily be obtained.

Effect of vehicle size and engine displacement on automobile fuel consumption

Analysis of EPA data on 1977 automobiles shows that rate of fuel consumption increases roughly linearly with automobile weight. This is largely the consequence of engine size that is proportional, on the average, to the 1.8th power of the weight. However, increased consumption due to larger engine size is partially offset by a specific engine efficiency that improves linearly with increasing engine size. The specific consumption, measured as gal/(in 3-lb/mi), is inversely proportional to engine displacement. It is suggested that sacrifice of body size (i.e. weight) to obtain improved overall fuel consumption is only one possible trade-off; an alternative might be sacrifice of performance while retaining size which might be more acceptable to one section of the market. (a) (TRRL)